Date   

Re: Is Yahoo Groups moderating every messages?

Gregory <fyrframe@...>
 

Yes, "I use the email delivery system for message posts, rather than using a browser and group login. Perhaps THAT method makes a difference."

I'm thinking Yahoo has finally started to rise up out of the it's own ashes.

As if this morning, all of my email are starting to show up in the respective forums in a timely fashion. No delays. Man, that feels good.

Gregory


On 2/1/2018 9:30 PM, 'Joseph Zeglinski' J.Zeglinski@... [ap-gto] wrote:
 

Greg,
 
    Is the problem just Yahoo Groups, or Yahoo email system in general?
Have you tried including your own email address when you email out to Yahoo groups, to compare how long a direct email comes right back, versus popping up in the Group’s new email arrival box? If there is a dual problem with posting to Yahoo Groups, and another forum based at  RIT University, then it may not be the fault of either destination server, but your ISP server between them and your PC.
 
    I wonder if there is some over active spam checker in play at your ISP. They can trigger on the most “innocuous” words. Perhaps the ISP webmaster has tweaked its SPAM-checking criteria tighter, recently.
 
    Except for that recent  2-day Yahoo hiatus period, my emails to Yahoo groups have, as usual,  arrived back to my own INBOX, from any of my  groups,  in a matter of minutes, if not seconds – and this is  all the way from Canada.
 
    However, I would have appreciated an explanation, if not an apology from Yahoo, for the recent service down time.
I can say that generally, Yahoo Group emails have had excellent turn around times for my posts. I use the email delivery system for message posts, rather than using a browser and group login. Perhaps THAT method makes a difference.
 
    Since I have been getting several repeats of Rolando’s recent post from last weekend  -  about (Fwd: AP Mount Encoder Tests - what do AP encoders really do?) ...  I assume the current Yahoo Groups service crisis is over, and we can resume normal postings.
 
    Anyway, I’m glad to see that Yahoo is now back to business as usual ...  although ... I have been expecting Google to buy them out for some time now.
Joe


Re: Guiding AP mounts with PHD

W Hilmo
 

I don’t think that is what guide software is doing.

 

It assumes a two dimensional object, where each pixel has equivalent weight.  I think that what’s really needed is a calculation where the calculation is weighted by pixel intensity.  One way to do this is to use a center or mass calculation.  See the below for a reference:

 

https://www.lost-infinity.com/night-sky-image-processing-part-4-calculate-the-star-centroid-with-sub-pixel-accuracy/

 

If the star is saturated, then the center of mass calculation is incorrect, leading to an inaccurate centroid.

 

It would be interesting to see how accurate it would be to do a two dimensional centroid calculation on only the saturated pixels in a saturated star.  I suppose that this could be tested by calculating the centroid of an unsaturated star using the method in the above article, and then clipping the pixels at some lower level to simulate saturation and comparing the two dimensional centroid calculation to the unsaturated result.  You could even do the comparison many times, clipping the pixels at different levels.  You would want to repeat the experiment with the common aberrations that occur off axis in different telescopes (I have a small Ritchey-Chrétien where the stars have so much coma and astigmatism in the OAG, that they look like little T shapes, and the guide software needs to work with data like that, too.)

 

If that experiment shows that it’s possible to get an accurate result on a saturated star, then the guide software could use different methods, depending on whether the star is saturated, and possibly by how much.  That might be the most resilient way to do it.

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, February 2, 2018 11:45 PM
To: ap-gto@...
Subject: AW: [ap-gto] Guiding AP mounts with PHD

 

 

>> I don’t know of any way to calculate an accurate centroid on a saturated star, since you have no actual data on any saturated pixels.

You would actually use the generic formula for a centroid:

https://en.wikipedia.org/wiki/Centroid#By_integral_formula

In our case, the characteristic function g(x) is the (normalized) intensity of a pixel. For saturated pixels, the normalized g(x) = 1. This is then the trivial problem of computing the centroid of a 2D figure.

Kind regards,

Horia

Von: ap-gto@... [mailto:ap-gto@...]
Gesendet: Freitag, 2. Februar 2018 19:18
An: ap-gto@...
Betreff: RE: [ap-gto] Guiding AP mounts with PHD

I don’t know of any way to calculate an accurate centroid on a saturated star, since you have no actual data on any saturated pixels. I was making an assumption that on a longer exposure, you would need to select an appropriately dim star as the guide star. I also understand the challenges of guiding in declination with any backlash at all.

I actually use Maxim for guiding and am happy with the results I’ve been getting. Almost all of my imaging is automated, so I am rarely present to see what it’s doing and don’t generally have the opportunity to do a test run to determine the seeing. I just have Maxim’s parameters set to handle my typical conditions. If we ever get any more clear nights, I am going to kind of relearn the best practices for my own gear. I just added absolute encoders to my AP1600GTO and am changing my polar alignment routine per your recommendations for minimum drift at the zenith. That, along with a good APCC tracking model, will likely change the way that I think about guiding. I use SCTs fairly often, so I don’t think that I can get away from guiding completely, just to deal with mirror shift and non-repeatable flexure.

I do a fair amount of helping other folks to image, though, and have worked with PHD and PHD2 quite a few times. I’m thinking about putting together a second imaging laptop, built around PHD2, and maybe SGP, since that is what all the cool kids seem to be using and I want to understand it well. I really appreciate your posting all of this information so far, and I will be able to use it. I just wanted to follow up on the recommendation for short exposures, because it was unexpected and goes a bit against what I’ve always understood and recommended.

Thanks,

-Wade

From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, February 2, 2018 8:00 AM
To: ap-gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD

Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.

First, long exposures in PHD result in saturated stars which the program apparently can't handle, or can't calculate a proper centroid.

Second, it may be stable for a period of time until there is just one single excursion outside the envelope. The software will then send a move command which may not fully reverse the axis, so the guide star stays outside the envelope for another guide cycle until finally it gets pushed back down. This may then start an oscillation in the other direction, but even if not, the correcting signals are few and far between time-wise, so the RMS error gets larger. With faster guide exposures, the mount gets faster correction signals and the guide star spends less time in the wrong place.

All I'm saying is to try this method with PHD Guiding and see if it improves your results. It is not a hard and fast rule, just a suggestion of where to start setting the parameters. You are welcome to experiment and post your results here. We all can learn.

I have PHD now and will experiment further. I may try to add a tiny bit of backlash compensation in Dec to see what effect that has and whether that will reduce the back and forth oscillation or make it worse.

Rolando

-----Original Message-----
From: 'Wade Hilmo' y.groups@... <mailto:y.groups@...> [ap-gto] <ap-gto@... > >
To: ap-gto <
ap-gto@... > >
Sent: Thu, Feb 1, 2018 7:50 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

If you are taking 10 second guide exposures, doesn’t that mean that the star will have bounced around randomly for the whole 10 seconds? As I understand it, the conventional wisdom is that longer guide exposures will have larger stars due to the atmospheric effects, but that the correct star position is likely to be near the center of the blob. Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.

I suppose that this gets down to the effectiveness of the centroid calculation. If it’s just looking for the brightest single pixel, then I can see where longer guide exposures might not be helpful. But I thought that the calculations were more sophisticated than that, and would look at the stellar profile to determine the centroid. Perhaps not, I guess? And perhaps it varies with the guide software.

-Wade

From:
ap-gto@yahoogroups..com <mailto:gto@...> [mailto:ap-gto@... ]
Sent: Thursday, February 1, 2018 1:47 PM
To:
ap-gto@... <mailto:gto@...>
Subject: Re: [ap-gto] Guiding AP mounts with PHD

I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

In this case it was because of poor seeing, not so much drift. When you get instances of poor seeing that move the guide star back and forth erratically, then you end up with many instances of guider corrections being sent to the mount. If you take a 10 second exposure and it shows the guide star at +1.5 arc second location, the mount will receive a command to move -1.5 arc seconds. But chances are that this +1.5 position occurred sometime before the end of the exposure, and at the exact time the move command is sent (after the fact), that star could already be at the opposite extreme, -1.5 arc sec position. The net result is that the guider software moves the guide star to -3 arc sec position for the next exposure. It's quite possible that the next guider pulse sent to the mount will have to be be +3 arc seconds, and you will see oscillations back and forth for a while until the seeing steadies up momentarily.

This is also complicated by any slight delay in Dec reversal that may exist in the mount which will require more than 1 pulse the do a full reversal.

In order to avoid this scenario, I would suggest setting a no-response limit around zero where the guider does not send any guide pulses, and just let the guide star bobble around in there. As soon as it steps outside this limit, the mount will get an instant reverse command. If the mount needs to reverse in Dec, then the necessary pulses will be sent quickly, perhaps 2 or 3 needed for full reversal. If you have long 10 second delays between each guide pulse, it may take 20, 30 or more seconds to get the guide star to move back to zero point.

Rolando

-----Original Message-----
From: 'Ray Gralak (Groups)' groups3@... <mailto:groups3@...> [ap-gto] <ap-gto@yahoogroups..com > >
To: ap-gto <
ap-gto@... > >
Sent: Thu, Feb 1, 2018 1:40 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

Hi Wade,

I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

If good-quality tracking rate correction can be used then I think that
autoguider exposures could be increased significantly. Otherwise, how could
doing unguided exposures using tracking rate correction work! :-)

Best regards,

-Ray Gralak
Author of APCC (Astro-Physics Command Center):
http://www.astro-physics.com/index.htm?products/accessories/software/apcc/ap
cc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma

> -----Original Message-----
> From: ap-gto@... <mailto:gto@...> <mailto:gto@... > > [mailto:ap-gto@... ?> ]
> Sent: Thursday, February 1, 2018 10:39 AM
> To: ap-gto@... <mailto:gto@...> <mailto:gto@... > >
> Subject: RE: [ap-gto] Guiding AP mounts with PHD
>
>
>
> I am curious about this result, especially the part at the end where you
say
> that 1 second exposures worked well, but longer exposures "became more and
> more sluggish and less accurate".
>
> It's my understanding that the mount is going to track well, assuming that
> PEM is programmed correctly and enabled, and that guiding should basically
> be correcting any drift due to slight polar misalignment, refraction,
> flexure, etc. If my understanding is correct, it would seem that longer
> exposures (within reason) would be just as effective as shorter exposures
-
> perhaps more effective, since longer exposures would tend to average out
> seeing distortion in the individual guider subs. If you were getting
better
> results at 1 second, that would suggest that you were chasing seeing with
> some success.
>
> Do you understand why it worked the way that it did for you? Was it
> correcting for slower seeing effects? Is there some other reason?
>
> Thanks,
>
> -Wade
>
> From:
ap-gto@... <mailto:gto@...> <mailto:gto@... > > [mailto:ap-gto@... ?> ]
> Sent: Thursday, February 1, 2018 9:36 AM
> To: ap-gto@... <mailto:gto@...> <mailto:gto@... > >
> Subject: Re: [ap-gto] Guiding AP mounts with PHD
>
> Great info. A few questions:
>
> - You mention that you set the MinMo to 0.8 arc-secs. I believe MinMo in
the
> PHD interface is shown in pixels. So if you set the MinMo to 0.8 it would
> have been 0.8 pixels. Did you guys just do the math to figure out the
> correct pixel value?
>
> - Were these changes made on both axis in PHD2? MinMo and Aggressiveness
> can
> be configured per axis.
>
> The rest of this looks very interesting and as soon as the weather gets
> better I plan to test this and see how my guiding performs.
>
> _____
>
> From:
ap-gto@... <mailto:gto@...> <mailto:gto@... > > <ap-gto@... > <mailto:gto@... > > > on behalf of
>
chris1011@... <mailto:chris1011@...> <mailto:chris1011@... > > [ap-gto] <ap-gto@... > <mailto:gto@... <mailto:gto@...?> > >
> Sent: Wednesday, January 31, 2018 4:51 PM
> To: ap-gto@... <mailto:gto@...> <mailto:gto@... > > ; ap-ug@... <mailto:ug@...> <mailto:ug@... > >
> Subject: [ap-gto] Guiding AP mounts with PHD
>
> Howdy,
>
> Howard and I had a chance to log in to a customer's Mach1 mount last night
> to help him with some guiding issues using PHD. He had sent his
calibration
> graph and it looked quite good, but he was having some problems guiding.
> After doing some mechanical tests we set up parameters in PHD to get the
> mount to track and respond accurately. Since PHD is somewhat different
from
> MaximDL, which I use, we had to approach the settings a bit differently.
>
> The first step is to do a quick 2 - 3 minute Unguided run using 1 second
> guide exposures, and look at the guider graph to see what the maximum
> excursions are in Declination. The guide star will bounce around a certain
> amount and this peak error will be the seeing that you cannot guide out
with
> normal guide software. This P-V value, which in our case was between +-0.5
> and +-0.8 arc seconds is what I call the Guide Star "Bobble" limit. Trying
> to correct for that with guide moves to the mount is impossible (only a
fast
> acting AO system can chase that seeing error).
>
> So, knowing that the minimum seeing error is +-0..8 arc seconds, you will
> want to set the initial Min Move setting in PHD to be approximately this
> value as a starting value. We set the Min Move to 0.8 arc sec, the guide
> rate at 1x and the aggressiveness to 100%. This means that no correction
> pulses are sent to the mount while the guide star is bobbling within that
> envelope, but once it exceeds even slightly, the mount gets a full
> correction command (-0.8 arc sec) to bring it back toward the zero
position.
> We turned guiding on and the result was that the mount responded quickly
> whenever the error exceeded the bobble limits and overall guiding was
tight,
> accurate and almost the same RMS value, ~0.35 arc sec, for both axes. An
> exposure with the main camera showed tight round stars..
>
> So, as a starting point:
> Determine the amount of guide star bobble above and below the axis
> Set the Min Move to that value
> Set Guide rate to 1x sidereal
> Set the guide star exposure rate to 1 second
> Set Aggressiveness to 100%
> Begin guiding and note the RMS value for both axes.
>
> You can then change any of the parameters to see if you can tune the RMS
to
> a lower value. We tried longer guide star exposures, but found that the
> response to tracking errors became more and more sluggish and less
accurate.
> So for these seeing conditions a faster guide rate of 1 per second
resulted
> in the lowest RMS error on both axes. In pristine seeing it might allow
> longer guide exposures, at least that is what we found using PHD Guiding.
>
> Rolando
>
> [Non-text portions of this message have been removed]
>
>
>
>

------------------------------------
Posted by: "Ray Gralak \(Groups\)" <
groups3@... > <mailto:groups3@... > > >
------------------------------------

To UNSUBSCRIBE, or for general information on the ap-gto list
see
http://groups.yahoo.com/group/ap-gto
------------------------------------

Yahoo Groups Links

[Non-text portions of this message have been removed]

------------------------------------
Posted by: "Wade Hilmo" <wade@... > >
------------------------------------

To UNSUBSCRIBE, or for general information on the ap-gto list
see
http://groups.yahoo.com/group/ap-gto
------------------------------------

Yahoo Groups Links

[Non-text portions of this message have been removed]


Re: Guiding AP mounts with PHD

Horia
 

I don’t know of any way to calculate an accurate centroid on a saturated star, since you have no actual data on any saturated pixels.


You would actually use the generic formula for a centroid:



https://en.wikipedia.org/wiki/Centroid#By_integral_formula



In our case, the characteristic function g(x) is the (normalized) intensity of a pixel. For saturated pixels, the normalized g(x) = 1. This is then the trivial problem of computing the centroid of a 2D figure.



Kind regards,

Horia





Von: ap-gto@... [mailto:ap-gto@...]
Gesendet: Freitag, 2. Februar 2018 19:18
An: ap-gto@...
Betreff: RE: [ap-gto] Guiding AP mounts with PHD





I don’t know of any way to calculate an accurate centroid on a saturated star, since you have no actual data on any saturated pixels. I was making an assumption that on a longer exposure, you would need to select an appropriately dim star as the guide star. I also understand the challenges of guiding in declination with any backlash at all.



I actually use Maxim for guiding and am happy with the results I’ve been getting. Almost all of my imaging is automated, so I am rarely present to see what it’s doing and don’t generally have the opportunity to do a test run to determine the seeing. I just have Maxim’s parameters set to handle my typical conditions. If we ever get any more clear nights, I am going to kind of relearn the best practices for my own gear. I just added absolute encoders to my AP1600GTO and am changing my polar alignment routine per your recommendations for minimum drift at the zenith. That, along with a good APCC tracking model, will likely change the way that I think about guiding. I use SCTs fairly often, so I don’t think that I can get away from guiding completely, just to deal with mirror shift and non-repeatable flexure.



I do a fair amount of helping other folks to image, though, and have worked with PHD and PHD2 quite a few times. I’m thinking about putting together a second imaging laptop, built around PHD2, and maybe SGP, since that is what all the cool kids seem to be using and I want to understand it well. I really appreciate your posting all of this information so far, and I will be able to use it. I just wanted to follow up on the recommendation for short exposures, because it was unexpected and goes a bit against what I’ve always understood and recommended.



Thanks,

-Wade



From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, February 2, 2018 8:00 AM
To: ap-gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD







Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.

First, long exposures in PHD result in saturated stars which the program apparently can't handle, or can't calculate a proper centroid.

Second, it may be stable for a period of time until there is just one single excursion outside the envelope. The software will then send a move command which may not fully reverse the axis, so the guide star stays outside the envelope for another guide cycle until finally it gets pushed back down. This may then start an oscillation in the other direction, but even if not, the correcting signals are few and far between time-wise, so the RMS error gets larger. With faster guide exposures, the mount gets faster correction signals and the guide star spends less time in the wrong place.

All I'm saying is to try this method with PHD Guiding and see if it improves your results. It is not a hard and fast rule, just a suggestion of where to start setting the parameters. You are welcome to experiment and post your results here. We all can learn.

I have PHD now and will experiment further. I may try to add a tiny bit of backlash compensation in Dec to see what effect that has and whether that will reduce the back and forth oscillation or make it worse.

Rolando





-----Original Message-----
From: 'Wade Hilmo' y.groups@... <mailto:y.groups@...> [ap-gto] <ap-gto@... <mailto:ap-gto@...> >
To: ap-gto <ap-gto@... <mailto:ap-gto@...> >
Sent: Thu, Feb 1, 2018 7:50 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

If you are taking 10 second guide exposures, doesn’t that mean that the star will have bounced around randomly for the whole 10 seconds? As I understand it, the conventional wisdom is that longer guide exposures will have larger stars due to the atmospheric effects, but that the correct star position is likely to be near the center of the blob. Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.



I suppose that this gets down to the effectiveness of the centroid calculation. If it’s just looking for the brightest single pixel, then I can see where longer guide exposures might not be helpful. But I thought that the calculations were more sophisticated than that, and would look at the stellar profile to determine the centroid. Perhaps not, I guess? And perhaps it varies with the guide software.



-Wade



From: ap-gto@yahoogroups..com <mailto:gto@...> [mailto:ap-gto@... <mailto:ap-gto@...?> ]
Sent: Thursday, February 1, 2018 1:47 PM
To: ap-gto@... <mailto:gto@...>
Subject: Re: [ap-gto] Guiding AP mounts with PHD







I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

In this case it was because of poor seeing, not so much drift. When you get instances of poor seeing that move the guide star back and forth erratically, then you end up with many instances of guider corrections being sent to the mount. If you take a 10 second exposure and it shows the guide star at +1.5 arc second location, the mount will receive a command to move -1.5 arc seconds. But chances are that this +1.5 position occurred sometime before the end of the exposure, and at the exact time the move command is sent (after the fact), that star could already be at the opposite extreme, -1.5 arc sec position. The net result is that the guider software moves the guide star to -3 arc sec position for the next exposure. It's quite possible that the next guider pulse sent to the mount will have to be be +3 arc seconds, and you will see oscillations back and forth for a while until the seeing steadies up momentarily.

This is also complicated by any slight delay in Dec reversal that may exist in the mount which will require more than 1 pulse the do a full reversal.

In order to avoid this scenario, I would suggest setting a no-response limit around zero where the guider does not send any guide pulses, and just let the guide star bobble around in there. As soon as it steps outside this limit, the mount will get an instant reverse command. If the mount needs to reverse in Dec, then the necessary pulses will be sent quickly, perhaps 2 or 3 needed for full reversal. If you have long 10 second delays between each guide pulse, it may take 20, 30 or more seconds to get the guide star to move back to zero point.

Rolando





-----Original Message-----
From: 'Ray Gralak (Groups)' groups3@... <mailto:groups3@...> [ap-gto] <ap-gto@yahoogroups..com <mailto:ap-gto@yahoogroups..com> >
To: ap-gto <ap-gto@... <mailto:gto@...> >
Sent: Thu, Feb 1, 2018 1:40 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

Hi Wade,

I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

If good-quality tracking rate correction can be used then I think that
autoguider exposures could be increased significantly. Otherwise, how could
doing unguided exposures using tracking rate correction work! :-)

Best regards,

-Ray Gralak
Author of APCC (Astro-Physics Command Center):
http://www.astro-physics.com/index.htm?products/accessories/software/apcc/ap
cc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma

-----Original Message-----
From: ap-gto@... <mailto:gto@...> <mailto:gto@... <mailto:gto@...?> > [mailto:ap-gto@... <mailto:ap-gto@...?> <mailto:ap-gto@... <mailto:ap-gto@...?> ?> ]
Sent: Thursday, February 1, 2018 10:39 AM
To: ap-gto@... <mailto:gto@...> <mailto:gto@... <mailto:gto@...?> >
Subject: RE: [ap-gto] Guiding AP mounts with PHD



I am curious about this result, especially the part at the end where you
say
that 1 second exposures worked well, but longer exposures "became more and
more sluggish and less accurate".

It's my understanding that the mount is going to track well, assuming that
PEM is programmed correctly and enabled, and that guiding should basically
be correcting any drift due to slight polar misalignment, refraction,
flexure, etc. If my understanding is correct, it would seem that longer
exposures (within reason) would be just as effective as shorter exposures
-
perhaps more effective, since longer exposures would tend to average out
seeing distortion in the individual guider subs. If you were getting
better
results at 1 second, that would suggest that you were chasing seeing with
some success.

Do you understand why it worked the way that it did for you? Was it
correcting for slower seeing effects? Is there some other reason?

Thanks,

-Wade

From: ap-gto@... <mailto:gto@...> <mailto:gto@... <mailto:gto@...?> > [mailto:ap-gto@... <mailto:ap-gto@...?> <mailto:ap-gto@... <mailto:ap-gto@...?> ?> ]
Sent: Thursday, February 1, 2018 9:36 AM
To: ap-gto@... <mailto:gto@...> <mailto:gto@... <mailto:gto@...?> >
Subject: Re: [ap-gto] Guiding AP mounts with PHD

Great info. A few questions:

- You mention that you set the MinMo to 0.8 arc-secs. I believe MinMo in
the
PHD interface is shown in pixels. So if you set the MinMo to 0.8 it would
have been 0.8 pixels. Did you guys just do the math to figure out the
correct pixel value?

- Were these changes made on both axis in PHD2? MinMo and Aggressiveness
can
be configured per axis.

The rest of this looks very interesting and as soon as the weather gets
better I plan to test this and see how my guiding performs.

_____

From: ap-gto@... <mailto:gto@...> <mailto:gto@... <mailto:gto@yahoogroups..com?> > <ap-gto@... <mailto:gto@...> <mailto:gto@... <mailto:gto@...?> > > on behalf of
chris1011@... <mailto:chris1011@...> <mailto:chris1011@... <mailto:chris1011@...?> > [ap-gto] <ap-gto@... <mailto:gto@...> <mailto:gto@... <mailto:gto@...?> > >
Sent: Wednesday, January 31, 2018 4:51 PM
To: ap-gto@... <mailto:gto@...> <mailto:gto@... <mailto:gto@...?> > ; ap-ug@... <mailto:ug@...> <mailto:ug@... <mailto:ug@...?> >
Subject: [ap-gto] Guiding AP mounts with PHD

Howdy,

Howard and I had a chance to log in to a customer's Mach1 mount last night
to help him with some guiding issues using PHD. He had sent his
calibration
graph and it looked quite good, but he was having some problems guiding.
After doing some mechanical tests we set up parameters in PHD to get the
mount to track and respond accurately. Since PHD is somewhat different
from
MaximDL, which I use, we had to approach the settings a bit differently.

The first step is to do a quick 2 - 3 minute Unguided run using 1 second
guide exposures, and look at the guider graph to see what the maximum
excursions are in Declination. The guide star will bounce around a certain
amount and this peak error will be the seeing that you cannot guide out
with
normal guide software. This P-V value, which in our case was between +-0.5
and +-0.8 arc seconds is what I call the Guide Star "Bobble" limit. Trying
to correct for that with guide moves to the mount is impossible (only a
fast
acting AO system can chase that seeing error).

So, knowing that the minimum seeing error is +-0..8 arc seconds, you will
want to set the initial Min Move setting in PHD to be approximately this
value as a starting value. We set the Min Move to 0.8 arc sec, the guide
rate at 1x and the aggressiveness to 100%. This means that no correction
pulses are sent to the mount while the guide star is bobbling within that
envelope, but once it exceeds even slightly, the mount gets a full
correction command (-0.8 arc sec) to bring it back toward the zero
position.
We turned guiding on and the result was that the mount responded quickly
whenever the error exceeded the bobble limits and overall guiding was
tight,
accurate and almost the same RMS value, ~0.35 arc sec, for both axes. An
exposure with the main camera showed tight round stars..

So, as a starting point:
Determine the amount of guide star bobble above and below the axis
Set the Min Move to that value
Set Guide rate to 1x sidereal
Set the guide star exposure rate to 1 second
Set Aggressiveness to 100%
Begin guiding and note the RMS value for both axes.

You can then change any of the parameters to see if you can tune the RMS
to
a lower value. We tried longer guide star exposures, but found that the
response to tracking errors became more and more sluggish and less
accurate.
So for these seeing conditions a faster guide rate of 1 per second
resulted
in the lowest RMS error on both axes. In pristine seeing it might allow
longer guide exposures, at least that is what we found using PHD Guiding.

Rolando

[Non-text portions of this message have been removed]





------------------------------------
Posted by: "Ray Gralak &#92;(Groups&#92;)" <groups3@... <mailto:groups3@gralak..com> <mailto:groups3@... <mailto:groups3@...?> > >
------------------------------------

To UNSUBSCRIBE, or for general information on the ap-gto list
see http://groups.yahoo.com/group/ap-gto
------------------------------------

Yahoo Groups Links







[Non-text portions of this message have been removed]



------------------------------------
Posted by: "Wade Hilmo" <wade@... <mailto:wade@...> >
------------------------------------

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Re: Guiding AP mounts with PHD

Bill Long
 

I second what Peter says here. PHD2 is so widespread in use that it makes great sense to have you guys work with it and figure out the best ways for us to use PHD with AP mounts. Once the weather gets better here I plan to test out the methods you guys have outlined so far and will provide data and feedback to help the cause.




From: ap-gto@... on behalf of pnagy@... [ap-gto]
Sent: Friday, February 2, 2018 1:21 PM
To: ap-gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD
 
 

Thank you Rolando and George for using PHD2. Once you get the hang of it, you will be able to help others since PHD2 and SGP are getting very popular not because of automation but much cheaper than Maxim DL and other automation software. SGP costs only $99 and it does a full automation and unsupervised imaging so I can go to sleep.

Peter



---In ap-gto@..., wrote :


I just wanted to follow up on the recommendation for short exposures, because it was unexpected and goes a bit against what I’ve always understood and recommended.
It does indeed go against what I have used and done with MaximDL in the past, and what I've recommended. My thinking was that all guiding software was the same, which apparently is not the case. PHD has been an unknown for me so i need to have more hands-on experience.

Rolando


-----Original Message-----
From: 'Wade Hilmo' y.groups@... [ap-gto]
To: ap-gto
Sent: Fri, Feb 2, 2018 12:19 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD



I don’t know of any way to calculate an accurate centroid on a saturated star, since you have no actual data on any saturated pixels.  I was making an assumption that on a longer exposure, you would need to select an appropriately dim star as the guide star.  I also understand the challenges of guiding in declination with any backlash at all.
 
I actually use Maxim for guiding and am happy with the results I’ve been getting.  Almost all of my imaging is automated, so I am rarely present to see what it’s doing and don’t generally have the opportunity to do a test run to determine the seeing.  I just have Maxim’s parameters set to handle my typical conditions.  If we ever get any more clear nights, I am going to kind of relearn the best practices for my own gear.  I just added absolute encoders to my AP1600GTO and am changing my polar alignment routine per your recommendations for minimum drift at the zenith.  That, along with a good APCC tracking model, will likely change the way that I think about guiding.  I use SCTs fairly often, so I don’t think that I can get away from guiding completely, just to deal with mirror shift and non-repeatable flexure.
 
I do a fair amount of helping other folks to image, though, and have worked with PHD and PHD2 quite a few times.  I’m thinking about putting together a second imaging laptop, built around PHD2, and maybe SGP, since that is what all the cool kids seem to be using and I want to understand it well.  I really appreciate your posting all of this information so far, and I will be able to use it.  I just wanted to follow up on the recommendation for short exposures, because it was unexpected and goes a bit against what I’ve always understood and recommended.
 
Thanks,
-Wade
 
From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, February 2, 2018 8:00 AM
To: ap-gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD
 
 
 
Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.
First, long exposures in PHD result in saturated stars which the program apparently can't handle, or can't calculate a proper centroid.

Second, it may be stable for a period of time until there is just one single excursion outside the envelope. The software will then send a move command which may not fully reverse the axis, so the guide star stays outside the envelope for another guide cycle until finally it gets pushed back down. This may then start an oscillation in the other direction, but even if not, the correcting signals are few and far between time-wise, so the RMS error gets larger. With faster guide exposures, the mount gets faster correction signals and the guide star spends less time in the wrong place.

All I'm saying is to try this method with PHD Guiding and see if it improves your results. It is not a hard and fast rule, just a suggestion of where to start setting the parameters. You are welcome to experiment and post your results here. We all can learn.

I have PHD now and will experiment further. I may try to add a tiny bit of backlash compensation in Dec to see what effect that has and whether that will reduce the back and forth oscillation or make it worse.

Rolando
 
 
-----Original Message-----
From: 'Wade Hilmo' y.groups@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Thu, Feb 1, 2018 7:50 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

If you are taking 10 second guide exposures, doesn’t that mean that the star will have bounced around randomly for the whole 10 seconds? As I understand it, the conventional wisdom is that longer guide exposures will have larger stars due to the atmospheric effects, but that the correct star position is likely to be near the center of the blob. Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.



I suppose that this gets down to the effectiveness of the centroid calculation. If it’s just looking for the brightest single pixel, then I can see where longer guide exposures might not be helpful. But I thought that the calculations were more sophisticated than that, and would look at the stellar profile to determine the centroid. Perhaps not, I guess? And perhaps it varies with the guide software.



-Wade



From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, February 1, 2018 1:47 PM
To: ap-gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD







I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

In this case it was because of poor seeing, not so much drift. When you get instances of poor seeing that move the guide star back and forth erratically, then you end up with many instances of guider corrections being sent to the mount. If you take a 10 second exposure and it shows the guide star at +1.5 arc second location, the mount will receive a command to move -1.5 arc seconds. But chances are that this +1.5 position occurred sometime before the end of the exposure, and at the exact time the move command is sent (after the fact), that star could already be at the opposite extreme, -1.5 arc sec position. The net result is that the guider software moves the guide star to -3 arc sec position for the next exposure. It's quite possible that the next guider pulse sent to the mount will have to be be +3 arc seconds, and you will see oscillations back and forth for a while until the seeing steadies up momentarily.

This is also complicated by any slight delay in Dec reversal that may exist in the mount which will require more than 1 pulse the do a full reversal.

In order to avoid this scenario, I would suggest setting a no-response limit around zero where the guider does not send any guide pulses, and just let the guide star bobble around in there. As soon as it steps outside this limit, the mount will get an instant reverse command. If the mount needs to reverse in Dec, then the necessary pulses will be sent quickly, perhaps 2 or 3 needed for full reversal. If you have long 10 second delays between each guide pulse, it may take 20, 30 or more seconds to get the guide star to move back to zero point.

Rolando





-----Original Message-----
From: 'Ray Gralak (Groups)' groups3@... [ap-gto] <ap-gto@yahoogroups..com>
To: ap-gto gto@...>
Sent: Thu, Feb 1, 2018 1:40 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

Hi Wade,

I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

If good-quality tracking rate correction can be used then I think that
autoguider exposures could be increased significantly. Otherwise, how could
doing unguided exposures using tracking rate correction work! :-)

Best regards,

-Ray Gralak
Author of APCC (Astro-Physics Command Center):
http://www.astro-physics.com/index.htm?products/accessories/software/apcc/ap
cc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma

> -----Original Message-----
> From: ap-gto@... <mailto:gto@...> [mailto:ap-gto@... <mailto:ap-gto@...?> ]
> Sent: Thursday, February 1, 2018 10:39 AM
> To: ap-gto@... <mailto:gto@...>
> Subject: RE: [ap-gto] Guiding AP mounts with PHD
>
>
>
> I am curious about this result, especially the part at the end where you
say
> that 1 second exposures worked well, but longer exposures "became more and
> more sluggish and less accurate".
>
> It's my understanding that the mount is going to track well, assuming that
> PEM is programmed correctly and enabled, and that guiding should basically
> be correcting any drift due to slight polar misalignment, refraction,
> flexure, etc. If my understanding is correct, it would seem that longer
> exposures (within reason) would be just as effective as shorter exposures
-
> perhaps more effective, since longer exposures would tend to average out
> seeing distortion in the individual guider subs. If you were getting
better
> results at 1 second, that would suggest that you were chasing seeing with
> some success.
>
> Do you understand why it worked the way that it did for you? Was it
> correcting for slower seeing effects? Is there some other reason?
>
> Thanks,
>
> -Wade
>
> From: ap-gto@... <mailto:gto@...> [mailto:ap-gto@... <mailto:ap-gto@...?> ]
> Sent: Thursday, February 1, 2018 9:36 AM
> To: ap-gto@... <mailto:gto@...>
> Subject: Re: [ap-gto] Guiding AP mounts with PHD
>
> Great info. A few questions:
>
> - You mention that you set the MinMo to 0.8 arc-secs. I believe MinMo in
the
> PHD interface is shown in pixels. So if you set the MinMo to 0.8 it would
> have been 0.8 pixels. Did you guys just do the math to figure out the
> correct pixel value?
>
> - Were these changes made on both axis in PHD2? MinMo and Aggressiveness
> can
> be configured per axis.
>
> The rest of this looks very interesting and as soon as the weather gets
> better I plan to test this and see how my guiding performs.
>
> _____
>
> From: ap-gto@... <mailto:gto@...> gto@... <mailto:gto@...> > on behalf of
> chris1011@... <mailto:chris1011@...> [ap-gto] gto@... <mailto:gto@...> >
> Sent: Wednesday, January 31, 2018 4:51 PM
> To: ap-gto@... <mailto:gto@...> ; ap-ug@... <mailto:ug@...>
> Subject: [ap-gto] Guiding AP mounts with PHD
>
> Howdy,
>
> Howard and I had a chance to log in to a customer's Mach1 mount last night
> to help him with some guiding issues using PHD. He had sent his
calibration
> graph and it looked quite good, but he was having some problems guiding.
> After doing some mechanical tests we set up parameters in PHD to get the
> mount to track and respond accurately. Since PHD is somewhat different
from
> MaximDL, which I use, we had to approach the settings a bit differently.
>
> The first step is to do a quick 2 - 3 minute Unguided run using 1 second
> guide exposures, and look at the guider graph to see what the maximum
> excursions are in Declination. The guide star will bounce around a certain
> amount and this peak error will be the seeing that you cannot guide out
with
> normal guide software. This P-V value, which in our case was between +-0.5
> and +-0.8 arc seconds is what I call the Guide Star "Bobble" limit. Trying
> to correct for that with guide moves to the mount is impossible (only a
fast
> acting AO system can chase that seeing error).
>
> So, knowing that the minimum seeing error is +-0.8 arc seconds, you will
> want to set the initial Min Move setting in PHD to be approximately this
> value as a starting value. We set the Min Move to 0.8 arc sec, the guide
> rate at 1x and the aggressiveness to 100%.. This means that no correction
> pulses are sent to the mount while the guide star is bobbling within that
> envelope, but once it exceeds even slightly, the mount gets a full
> correction command (-0.8 arc sec) to bring it back toward the zero
position.
> We turned guiding on and the result was that the mount responded quickly
> whenever the error exceeded the bobble limits and overall guiding was
tight,
> accurate and almost the same RMS value, ~0.35 arc sec, for both axes. An
> exposure with the main camera showed tight round stars.
>
> So, as a starting point:
> Determine the amount of guide star bobble above and below the axis
> Set the Min Move to that value
> Set Guide rate to 1x sidereal
> Set the guide star exposure rate to 1 second
> Set Aggressiveness to 100%
> Begin guiding and note the RMS value for both axes.
>
> You can then change any of the parameters to see if you can tune the RMS
to
> a lower value.. We tried longer guide star exposures, but found that the
> response to tracking errors became more and more sluggish and less
accurate.
> So for these seeing conditions a faster guide rate of 1 per second
resulted
> in the lowest RMS error on both axes. In pristine seeing it might allow
> longer guide exposures, at least that is what we found using PHD Guiding.
>
> Rolando
>
> [Non-text portions of this message have been removed]
>
>
>
>



------------------------------------
Posted by: "Ray Gralak \(Groups\)" <groups3@... <mailto:groups3@...> >
------------------------------------

To UNSUBSCRIBE, or for general information on the ap-gto list
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------------------------------------

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[Non-text portions of this message have been removed]



------------------------------------
Posted by: "Wade Hilmo" <wade@...>
------------------------------------

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Re: Guiding AP mounts with PHD

John Stiner
 

Would this suggestion regarding shorter guide exposures apply equally to absolute encoders mounts?


Re: Last Step after replacing L chip to V chip

D Sidote <dsidote@...>
 

Peter and Joel,

I hoped there would be a less expensive DIY option, but you guys are right. I am going to buy the length cable I need from Optec.

Thanks again, guys!

Dave

On Thu, Feb 1, 2018 at 1:10 PM, pnagy@... [ap-gto] <ap-gto@...> wrote:
 

Before I cut my Optec USB/serial cable, I ordered another one as a backup in case I screwed up with the original USB/serial cable. As soon as I received the second Optec USB/serial cable, I shortened the original USB/serial cable successfully. It's really easy.

Peter



---In ap-gto@..., wrote :

Dave, 
RE: making your own USB/serial cable - I tried to do this several time.  I bought what I was sure were the correct USB boards and got the pinouts from Optec to make my own cables.  I tried 3 different USB cables but for some reason I couldn't get any of them to work.  I custom made the ethernet cables to the lengths I needed and I'm comfortable crimping etc, but I just couldn't get these to work.

Bottom line, just buy another one from Optec and have them custom make the length you need.  I wish I had done that in the first place and not spent more than I needed to...live and learn.  
joel



Re: Guiding AP mounts with PHD

topboxman
 

Thank you Rolando and George for using PHD2. Once you get the hang of it, you will be able to help others since PHD2 and SGP are getting very popular not because of automation but much cheaper than Maxim DL and other automation software. SGP costs only $99 and it does a full automation and unsupervised imaging so I can go to sleep.

Peter


---In ap-gto@..., <chris1011@...> wrote :



I just wanted to follow up on the recommendation for short exposures, because it was unexpected and goes a bit against what I’ve always understood and recommended.
It does indeed go against what I have used and done with MaximDL in the past, and what I've recommended. My thinking was that all guiding software was the same, which apparently is not the case. PHD has been an unknown for me so i need to have more hands-on experience.

Rolando

-----Original Message-----
From: 'Wade Hilmo' y.groups@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Fri, Feb 2, 2018 12:19 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD



I don’t know of any way to calculate an accurate centroid on a saturated star, since you have no actual data on any saturated pixels. I was making an assumption that on a longer exposure, you would need to select an appropriately dim star as the guide star. I also understand the challenges of guiding in declination with any backlash at all.

I actually use Maxim for guiding and am happy with the results I’ve been getting. Almost all of my imaging is automated, so I am rarely present to see what it’s doing and don’t generally have the opportunity to do a test run to determine the seeing. I just have Maxim’s parameters set to handle my typical conditions. If we ever get any more clear nights, I am going to kind of relearn the best practices for my own gear. I just added absolute encoders to my AP1600GTO and am changing my polar alignment routine per your recommendations for minimum drift at the zenith. That, along with a good APCC tracking model, will likely change the way that I think about guiding. I use SCTs fairly often, so I don’t think that I can get away from guiding completely, just to deal with mirror shift and non-repeatable flexure.

I do a fair amount of helping other folks to image, though, and have worked with PHD and PHD2 quite a few times. I’m thinking about putting together a second imaging laptop, built around PHD2, and maybe SGP, since that is what all the cool kids seem to be using and I want to understand it well. I really appreciate your posting all of this information so far, and I will be able to use it. I just wanted to follow up on the recommendation for short exposures, because it was unexpected and goes a bit against what I’ve always understood and recommended.

Thanks,
-Wade

From: ap-gto@... mailto:gto@... [mailto:ap-gto@... mailto:ap-gto@...?]
Sent: Friday, February 2, 2018 8:00 AM
To: ap-gto@... mailto:gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD






Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.

First, long exposures in PHD result in saturated stars which the program apparently can't handle, or can't calculate a proper centroid.

Second, it may be stable for a period of time until there is just one single excursion outside the envelope. The software will then send a move command which may not fully reverse the axis, so the guide star stays outside the envelope for another guide cycle until finally it gets pushed back down. This may then start an oscillation in the other direction, but even if not, the correcting signals are few and far between time-wise, so the RMS error gets larger. With faster guide exposures, the mount gets faster correction signals and the guide star spends less time in the wrong place.

All I'm saying is to try this method with PHD Guiding and see if it improves your results. It is not a hard and fast rule, just a suggestion of where to start setting the parameters. You are welcome to experiment and post your results here. We all can learn.

I have PHD now and will experiment further. I may try to add a tiny bit of backlash compensation in Dec to see what effect that has and whether that will reduce the back and forth oscillation or make it worse.

Rolando





-----Original Message-----
From: 'Wade Hilmo' y.groups@... mailto:y.groups@... [ap-gto] <ap-gto@... mailto:ap-gto@...>
To: ap-gto <ap-gto@... mailto:ap-gto@...>
Sent: Thu, Feb 1, 2018 7:50 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

If you are taking 10 second guide exposures, doesn’t that mean that the star will have bounced around randomly for the whole 10 seconds? As I understand it, the conventional wisdom is that longer guide exposures will have larger stars due to the atmospheric effects, but that the correct star position is likely to be near the center of the blob. Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.



I suppose that this gets down to the effectiveness of the centroid calculation. If it’s just looking for the brightest single pixel, then I can see where longer guide exposures might not be helpful. But I thought that the calculations were more sophisticated than that, and would look at the stellar profile to determine the centroid. Perhaps not, I guess? And perhaps it varies with the guide software.



-Wade



From: ap-gto@... mailto:gto@... [mailto:ap-gto@... mailto:ap-gto@...?]
Sent: Thursday, February 1, 2018 1:47 PM
To: ap-gto@... mailto:gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD







I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

In this case it was because of poor seeing, not so much drift. When you get instances of poor seeing that move the guide star back and forth erratically, then you end up with many instances of guider corrections being sent to the mount. If you take a 10 second exposure and it shows the guide star at +1.5 arc second location, the mount will receive a command to move -1.5 arc seconds. But chances are that this +1.5 position occurred sometime before the end of the exposure, and at the exact time the move command is sent (after the fact), that star could already be at the opposite extreme, -1.5 arc sec position. The net result is that the guider software moves the guide star to -3 arc sec position for the next exposure. It's quite possible that the next guider pulse sent to the mount will have to be be +3 arc seconds, and you will see oscillations back and forth for a while until the seeing steadies up momentarily.

This is also complicated by any slight delay in Dec reversal that may exist in the mount which will require more than 1 pulse the do a full reversal.

In order to avoid this scenario, I would suggest setting a no-response limit around zero where the guider does not send any guide pulses, and just let the guide star bobble around in there. As soon as it steps outside this limit, the mount will get an instant reverse command. If the mount needs to reverse in Dec, then the necessary pulses will be sent quickly, perhaps 2 or 3 needed for full reversal. If you have long 10 second delays between each guide pulse, it may take 20, 30 or more seconds to get the guide star to move back to zero point.

Rolando





-----Original Message-----
From: 'Ray Gralak (Groups)' groups3@... mailto:groups3@... [ap-gto] <ap-gto@yahoogroups..com mailto:ap-gto@yahoogroups..com>
To: ap-gto <ap-gto@... mailto:gto@...>
Sent: Thu, Feb 1, 2018 1:40 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

Hi Wade,

I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

If good-quality tracking rate correction can be used then I think that
autoguider exposures could be increased significantly. Otherwise, how could
doing unguided exposures using tracking rate correction work! :-)

Best regards,

-Ray Gralak
Author of APCC (Astro-Physics Command Center):
http://www.astro-physics.com/index.htm?products/accessories/software/apcc/ap http://www.astro-physics.com/index.htm?products/accessories/software/apcc/ap
cc
Author of PEMPro: http://www.ccdware.com http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma http://www.gralak.com/sigma

> -----Original Message-----
> From: ap-gto@... mailto:gto@... <mailto:gto@... mailto:gto@...?> [mailto:ap-gto@... mailto:ap-gto@...? <mailto:ap-gto@... mailto:ap-gto@...??> ]
> Sent: Thursday, February 1, 2018 10:39 AM
> To: ap-gto@... mailto:gto@yahoogroups..com <mailto:gto@... mailto:gto@...?>
> Subject: RE: [ap-gto] Guiding AP mounts with PHD
>
>
>
> I am curious about this result, especially the part at the end where you
say
> that 1 second exposures worked well, but longer exposures "became more and
> more sluggish and less accurate".
>
> It's my understanding that the mount is going to track well, assuming that
> PEM is programmed correctly and enabled, and that guiding should basically
> be correcting any drift due to slight polar misalignment, refraction,
> flexure, etc. If my understanding is correct, it would seem that longer
> exposures (within reason) would be just as effective as shorter exposures
-
> perhaps more effective, since longer exposures would tend to average out
> seeing distortion in the individual guider subs. If you were getting
better
> results at 1 second, that would suggest that you were chasing seeing with
> some success.
>
> Do you understand why it worked the way that it did for you? Was it
> correcting for slower seeing effects? Is there some other reason?
>
> Thanks,
>
> -Wade
>
> From: ap-gto@... mailto:gto@... <mailto:gto@... mailto:gto@...?> [mailto:ap-gto@... mailto:ap-gto@...? <mailto:ap-gto@... mailto:ap-gto@...??> ]
> Sent: Thursday, February 1, 2018 9:36 AM
> To: ap-gto@... mailto:gto@... <mailto:gto@... mailto:gto@...?>
> Subject: Re: [ap-gto] Guiding AP mounts with PHD
>
> Great info. A few questions:
>
> - You mention that you set the MinMo to 0.8 arc-secs. I believe MinMo in
the
> PHD interface is shown in pixels. So if you set the MinMo to 0.8 it would
> have been 0.8 pixels. Did you guys just do the math to figure out the
> correct pixel value?
>
> - Were these changes made on both axis in PHD2? MinMo and Aggressiveness
> can
> be configured per axis.
>
> The rest of this looks very interesting and as soon as the weather gets
> better I plan to test this and see how my guiding performs.
>
> _____
>
> From: ap-gto@... mailto:gto@... <mailto:gto@... mailto:gto@...?> <ap-gto@... mailto:gto@... <mailto:gto@... mailto:gto@...?> > on behalf of
> chris1011@... mailto:chris1011@... <mailto:chris1011@... mailto:chris1011@...?> [ap-gto] <ap-gto@... mailto:gto@... <mailto:gto@... mailto:gto@...?> >
> Sent: Wednesday, January 31, 2018 4:51 PM
> To: ap-gto@... mailto:gto@... <mailto:gto@... mailto:gto@...?> ; ap-ug@... mailto:ug@... <mailto:ug@... mailto:ug@...?>
> Subject: [ap-gto] Guiding AP mounts with PHD
>
> Howdy,
>
> Howard and I had a chance to log in to a customer's Mach1 mount last night
> to help him with some guiding issues using PHD. He had sent his
calibration
> graph and it looked quite good, but he was having some problems guiding.
> After doing some mechanical tests we set up parameters in PHD to get the
> mount to track and respond accurately. Since PHD is somewhat different
from
> MaximDL, which I use, we had to approach the settings a bit differently.
>
> The first step is to do a quick 2 - 3 minute Unguided run using 1 second
> guide exposures, and look at the guider graph to see what the maximum
> excursions are in Declination. The guide star will bounce around a certain
> amount and this peak error will be the seeing that you cannot guide out
with
> normal guide software. This P-V value, which in our case was between +-0.5
> and +-0.8 arc seconds is what I call the Guide Star "Bobble" limit. Trying
> to correct for that with guide moves to the mount is impossible (only a
fast
> acting AO system can chase that seeing error).
>
> So, knowing that the minimum seeing error is +-0.8 arc seconds, you will
> want to set the initial Min Move setting in PHD to be approximately this
> value as a starting value. We set the Min Move to 0.8 arc sec, the guide
> rate at 1x and the aggressiveness to 100%.. This means that no correction
> pulses are sent to the mount while the guide star is bobbling within that
> envelope, but once it exceeds even slightly, the mount gets a full
> correction command (-0.8 arc sec) to bring it back toward the zero
position.
> We turned guiding on and the result was that the mount responded quickly
> whenever the error exceeded the bobble limits and overall guiding was
tight,
> accurate and almost the same RMS value, ~0.35 arc sec, for both axes. An
> exposure with the main camera showed tight round stars.
>
> So, as a starting point:
> Determine the amount of guide star bobble above and below the axis
> Set the Min Move to that value
> Set Guide rate to 1x sidereal
> Set the guide star exposure rate to 1 second
> Set Aggressiveness to 100%
> Begin guiding and note the RMS value for both axes.
>
> You can then change any of the parameters to see if you can tune the RMS
to
> a lower value.. We tried longer guide star exposures, but found that the
> response to tracking errors became more and more sluggish and less
accurate.
> So for these seeing conditions a faster guide rate of 1 per second
resulted
> in the lowest RMS error on both axes. In pristine seeing it might allow
> longer guide exposures, at least that is what we found using PHD Guiding.
>
> Rolando
>
> [Non-text portions of this message have been removed]
>
>
>
>



------------------------------------
Posted by: "Ray Gralak \(Groups\)" <groups3@... mailto:groups3@... <mailto:groups3@... mailto:groups3@...?> >
------------------------------------

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------------------------------------

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[Non-text portions of this message have been removed]



------------------------------------
Posted by: "Wade Hilmo" <wade@... mailto:wade@...>
------------------------------------

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Re: Guiding AP mounts with PHD

Worsel
 

PHD2 Best Practices are a good place to start.


Bryan



---In ap-gto@..., <chris1011@...> wrote :


I just wanted to follow up on the recommendation for short exposures, because it was unexpected and goes a bit against what I’ve always understood and recommended.
It does indeed go against what I have used and done with MaximDL in the past, and what I've recommended. My thinking was that all guiding software was the same, which apparently is not the case. PHD has been an unknown for me so i need to have more hands-on experience.

Rolando



Re: Guiding AP mounts with PHD

Roland Christen
 


I just wanted to follow up on the recommendation for short exposures, because it was unexpected and goes a bit against what I’ve always understood and recommended.
It does indeed go against what I have used and done with MaximDL in the past, and what I've recommended. My thinking was that all guiding software was the same, which apparently is not the case. PHD has been an unknown for me so i need to have more hands-on experience.

Rolando


-----Original Message-----
From: 'Wade Hilmo' y.groups@... [ap-gto]
To: ap-gto
Sent: Fri, Feb 2, 2018 12:19 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD



I don’t know of any way to calculate an accurate centroid on a saturated star, since you have no actual data on any saturated pixels.  I was making an assumption that on a longer exposure, you would need to select an appropriately dim star as the guide star.  I also understand the challenges of guiding in declination with any backlash at all.
 
I actually use Maxim for guiding and am happy with the results I’ve been getting.  Almost all of my imaging is automated, so I am rarely present to see what it’s doing and don’t generally have the opportunity to do a test run to determine the seeing.  I just have Maxim’s parameters set to handle my typical conditions.  If we ever get any more clear nights, I am going to kind of relearn the best practices for my own gear.  I just added absolute encoders to my AP1600GTO and am changing my polar alignment routine per your recommendations for minimum drift at the zenith.  That, along with a good APCC tracking model, will likely change the way that I think about guiding.  I use SCTs fairly often, so I don’t think that I can get away from guiding completely, just to deal with mirror shift and non-repeatable flexure.
 
I do a fair amount of helping other folks to image, though, and have worked with PHD and PHD2 quite a few times.  I’m thinking about putting together a second imaging laptop, built around PHD2, and maybe SGP, since that is what all the cool kids seem to be using and I want to understand it well.  I really appreciate your posting all of this information so far, and I will be able to use it.  I just wanted to follow up on the recommendation for short exposures, because it was unexpected and goes a bit against what I’ve always understood and recommended.
 
Thanks,
-Wade
 
From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, February 2, 2018 8:00 AM
To: ap-gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD
 
 
 
Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.
First, long exposures in PHD result in saturated stars which the program apparently can't handle, or can't calculate a proper centroid.

Second, it may be stable for a period of time until there is just one single excursion outside the envelope. The software will then send a move command which may not fully reverse the axis, so the guide star stays outside the envelope for another guide cycle until finally it gets pushed back down. This may then start an oscillation in the other direction, but even if not, the correcting signals are few and far between time-wise, so the RMS error gets larger. With faster guide exposures, the mount gets faster correction signals and the guide star spends less time in the wrong place.

All I'm saying is to try this method with PHD Guiding and see if it improves your results. It is not a hard and fast rule, just a suggestion of where to start setting the parameters. You are welcome to experiment and post your results here. We all can learn.

I have PHD now and will experiment further. I may try to add a tiny bit of backlash compensation in Dec to see what effect that has and whether that will reduce the back and forth oscillation or make it worse.

Rolando
 
 
-----Original Message-----
From: 'Wade Hilmo' y.groups@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Thu, Feb 1, 2018 7:50 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

If you are taking 10 second guide exposures, doesn’t that mean that the star will have bounced around randomly for the whole 10 seconds? As I understand it, the conventional wisdom is that longer guide exposures will have larger stars due to the atmospheric effects, but that the correct star position is likely to be near the center of the blob. Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.



I suppose that this gets down to the effectiveness of the centroid calculation. If it’s just looking for the brightest single pixel, then I can see where longer guide exposures might not be helpful. But I thought that the calculations were more sophisticated than that, and would look at the stellar profile to determine the centroid. Perhaps not, I guess? And perhaps it varies with the guide software.



-Wade



From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, February 1, 2018 1:47 PM
To: ap-gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD







I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

In this case it was because of poor seeing, not so much drift. When you get instances of poor seeing that move the guide star back and forth erratically, then you end up with many instances of guider corrections being sent to the mount. If you take a 10 second exposure and it shows the guide star at +1.5 arc second location, the mount will receive a command to move -1.5 arc seconds. But chances are that this +1.5 position occurred sometime before the end of the exposure, and at the exact time the move command is sent (after the fact), that star could already be at the opposite extreme, -1.5 arc sec position. The net result is that the guider software moves the guide star to -3 arc sec position for the next exposure. It's quite possible that the next guider pulse sent to the mount will have to be be +3 arc seconds, and you will see oscillations back and forth for a while until the seeing steadies up momentarily.

This is also complicated by any slight delay in Dec reversal that may exist in the mount which will require more than 1 pulse the do a full reversal.

In order to avoid this scenario, I would suggest setting a no-response limit around zero where the guider does not send any guide pulses, and just let the guide star bobble around in there. As soon as it steps outside this limit, the mount will get an instant reverse command. If the mount needs to reverse in Dec, then the necessary pulses will be sent quickly, perhaps 2 or 3 needed for full reversal. If you have long 10 second delays between each guide pulse, it may take 20, 30 or more seconds to get the guide star to move back to zero point.

Rolando





-----Original Message-----
From: 'Ray Gralak (Groups)' groups3@... [ap-gto] <ap-gto@yahoogroups..com>
To: ap-gto gto@...>
Sent: Thu, Feb 1, 2018 1:40 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

Hi Wade,

I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

If good-quality tracking rate correction can be used then I think that
autoguider exposures could be increased significantly. Otherwise, how could
doing unguided exposures using tracking rate correction work! :-)

Best regards,

-Ray Gralak
Author of APCC (Astro-Physics Command Center):
http://www.astro-physics.com/index.htm?products/accessories/software/apcc/ap
cc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma

> -----Original Message-----
> From: ap-gto@... <mailto:gto@...> [mailto:ap-gto@... <mailto:ap-gto@...?> ]
> Sent: Thursday, February 1, 2018 10:39 AM
> To: ap-gto@... <mailto:gto@...>
> Subject: RE: [ap-gto] Guiding AP mounts with PHD
>
>
>
> I am curious about this result, especially the part at the end where you
say
> that 1 second exposures worked well, but longer exposures "became more and
> more sluggish and less accurate".
>
> It's my understanding that the mount is going to track well, assuming that
> PEM is programmed correctly and enabled, and that guiding should basically
> be correcting any drift due to slight polar misalignment, refraction,
> flexure, etc. If my understanding is correct, it would seem that longer
> exposures (within reason) would be just as effective as shorter exposures
-
> perhaps more effective, since longer exposures would tend to average out
> seeing distortion in the individual guider subs. If you were getting
better
> results at 1 second, that would suggest that you were chasing seeing with
> some success.
>
> Do you understand why it worked the way that it did for you? Was it
> correcting for slower seeing effects? Is there some other reason?
>
> Thanks,
>
> -Wade
>
> From: ap-gto@... <mailto:gto@...> [mailto:ap-gto@... <mailto:ap-gto@...?> ]
> Sent: Thursday, February 1, 2018 9:36 AM
> To: ap-gto@... <mailto:gto@...>
> Subject: Re: [ap-gto] Guiding AP mounts with PHD
>
> Great info. A few questions:
>
> - You mention that you set the MinMo to 0.8 arc-secs. I believe MinMo in
the
> PHD interface is shown in pixels. So if you set the MinMo to 0.8 it would
> have been 0.8 pixels. Did you guys just do the math to figure out the
> correct pixel value?
>
> - Were these changes made on both axis in PHD2? MinMo and Aggressiveness
> can
> be configured per axis.
>
> The rest of this looks very interesting and as soon as the weather gets
> better I plan to test this and see how my guiding performs.
>
> _____
>
> From: ap-gto@... <mailto:gto@...> gto@... <mailto:gto@...> > on behalf of
> chris1011@... <mailto:chris1011@...> [ap-gto] gto@... <mailto:gto@...> >
> Sent: Wednesday, January 31, 2018 4:51 PM
> To: ap-gto@... <mailto:gto@...> ; ap-ug@... <mailto:ug@...>
> Subject: [ap-gto] Guiding AP mounts with PHD
>
> Howdy,
>
> Howard and I had a chance to log in to a customer's Mach1 mount last night
> to help him with some guiding issues using PHD. He had sent his
calibration
> graph and it looked quite good, but he was having some problems guiding.
> After doing some mechanical tests we set up parameters in PHD to get the
> mount to track and respond accurately. Since PHD is somewhat different
from
> MaximDL, which I use, we had to approach the settings a bit differently.
>
> The first step is to do a quick 2 - 3 minute Unguided run using 1 second
> guide exposures, and look at the guider graph to see what the maximum
> excursions are in Declination. The guide star will bounce around a certain
> amount and this peak error will be the seeing that you cannot guide out
with
> normal guide software. This P-V value, which in our case was between +-0.5
> and +-0.8 arc seconds is what I call the Guide Star "Bobble" limit. Trying
> to correct for that with guide moves to the mount is impossible (only a
fast
> acting AO system can chase that seeing error).
>
> So, knowing that the minimum seeing error is +-0.8 arc seconds, you will
> want to set the initial Min Move setting in PHD to be approximately this
> value as a starting value. We set the Min Move to 0.8 arc sec, the guide
> rate at 1x and the aggressiveness to 100%.. This means that no correction
> pulses are sent to the mount while the guide star is bobbling within that
> envelope, but once it exceeds even slightly, the mount gets a full
> correction command (-0.8 arc sec) to bring it back toward the zero
position.
> We turned guiding on and the result was that the mount responded quickly
> whenever the error exceeded the bobble limits and overall guiding was
tight,
> accurate and almost the same RMS value, ~0.35 arc sec, for both axes. An
> exposure with the main camera showed tight round stars.
>
> So, as a starting point:
> Determine the amount of guide star bobble above and below the axis
> Set the Min Move to that value
> Set Guide rate to 1x sidereal
> Set the guide star exposure rate to 1 second
> Set Aggressiveness to 100%
> Begin guiding and note the RMS value for both axes.
>
> You can then change any of the parameters to see if you can tune the RMS
to
> a lower value.. We tried longer guide star exposures, but found that the
> response to tracking errors became more and more sluggish and less
accurate.
> So for these seeing conditions a faster guide rate of 1 per second
resulted
> in the lowest RMS error on both axes. In pristine seeing it might allow
> longer guide exposures, at least that is what we found using PHD Guiding.
>
> Rolando
>
>
>
>
>
>



------------------------------------
Posted by: "Ray Gralak \(Groups\)" <groups3@... <mailto:groups3@...> >
------------------------------------

To UNSUBSCRIBE, or for general information on the ap-gto list
see http://groups.yahoo.com/group/ap-gto
------------------------------------

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[Non-text portions of this message have been removed]



------------------------------------
Posted by: "Wade Hilmo" <wade@...>
------------------------------------

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Re: Guiding AP mounts with PHD

Worsel
 

If you let PHD2 choose the guide star, then you will not get a saturated star, regardless of the exposure.  PHD2 selects a star with sufficient SNR, but not saturated.

For those of you that are not familiar with PHD2, it offers substantial improvements over PHD.


Bryan


From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, February 2, 2018 8:00 AM
To: ap-gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD

 

 

 

First, long exposures in PHD result in saturated stars which the program apparently can't handle, or can't calculate a proper centroid.

Second, it may be stable for a period of time until there is just one single excursion outside the envelope. The software will then send a move command which may not fully reverse the axis, so the guide star stays outside the envelope for another guide cycle until finally it gets pushed back down. This may then start an oscillation in the other direction, but even if not, the correcting signals are few and far between time-wise, so the RMS error gets larger. With faster guide exposures, the mount gets faster correction signals and the guide star spends less time in the wrong place.

All I'm saying is to try this method with PHD Guiding and see if it improves your results. It is not a hard and fast rule, just a suggestion of where to start setting the parameters. You are welcome to experiment and post your results here. We all can learn.

I have PHD now and will experiment further. I may try to add a tiny bit of backlash compensation in Dec to see what effect that has and whether that will reduce the back and forth oscillation or make it worse.

Rolando

  


Re: Guiding AP mounts with PHD

W Hilmo
 

I don’t know of any way to calculate an accurate centroid on a saturated star, since you have no actual data on any saturated pixels.  I was making an assumption that on a longer exposure, you would need to select an appropriately dim star as the guide star.  I also understand the challenges of guiding in declination with any backlash at all.

 

I actually use Maxim for guiding and am happy with the results I’ve been getting.  Almost all of my imaging is automated, so I am rarely present to see what it’s doing and don’t generally have the opportunity to do a test run to determine the seeing.  I just have Maxim’s parameters set to handle my typical conditions.  If we ever get any more clear nights, I am going to kind of relearn the best practices for my own gear.  I just added absolute encoders to my AP1600GTO and am changing my polar alignment routine per your recommendations for minimum drift at the zenith.  That, along with a good APCC tracking model, will likely change the way that I think about guiding.  I use SCTs fairly often, so I don’t think that I can get away from guiding completely, just to deal with mirror shift and non-repeatable flexure.

 

I do a fair amount of helping other folks to image, though, and have worked with PHD and PHD2 quite a few times.  I’m thinking about putting together a second imaging laptop, built around PHD2, and maybe SGP, since that is what all the cool kids seem to be using and I want to understand it well.  I really appreciate your posting all of this information so far, and I will be able to use it.  I just wanted to follow up on the recommendation for short exposures, because it was unexpected and goes a bit against what I’ve always understood and recommended.

 

Thanks,

-Wade

 

From: ap-gto@... [mailto:ap-gto@...]
Sent: Friday, February 2, 2018 8:00 AM
To: ap-gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD

 

 

 

Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.

First, long exposures in PHD result in saturated stars which the program apparently can't handle, or can't calculate a proper centroid.

Second, it may be stable for a period of time until there is just one single excursion outside the envelope. The software will then send a move command which may not fully reverse the axis, so the guide star stays outside the envelope for another guide cycle until finally it gets pushed back down. This may then start an oscillation in the other direction, but even if not, the correcting signals are few and far between time-wise, so the RMS error gets larger. With faster guide exposures, the mount gets faster correction signals and the guide star spends less time in the wrong place.

All I'm saying is to try this method with PHD Guiding and see if it improves your results. It is not a hard and fast rule, just a suggestion of where to start setting the parameters. You are welcome to experiment and post your results here. We all can learn.

I have PHD now and will experiment further. I may try to add a tiny bit of backlash compensation in Dec to see what effect that has and whether that will reduce the back and forth oscillation or make it worse.

Rolando

 

 

-----Original Message-----
From: 'Wade Hilmo' y.groups@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Thu, Feb 1, 2018 7:50 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

If you are taking 10 second guide exposures, doesn’t that mean that the star will have bounced around randomly for the whole 10 seconds? As I understand it, the conventional wisdom is that longer guide exposures will have larger stars due to the atmospheric effects, but that the correct star position is likely to be near the center of the blob. Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.



I suppose that this gets down to the effectiveness of the centroid calculation. If it’s just looking for the brightest single pixel, then I can see where longer guide exposures might not be helpful. But I thought that the calculations were more sophisticated than that, and would look at the stellar profile to determine the centroid. Perhaps not, I guess? And perhaps it varies with the guide software.



-Wade



From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, February 1, 2018 1:47 PM
To: ap-gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD







I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

In this case it was because of poor seeing, not so much drift. When you get instances of poor seeing that move the guide star back and forth erratically, then you end up with many instances of guider corrections being sent to the mount. If you take a 10 second exposure and it shows the guide star at +1.5 arc second location, the mount will receive a command to move -1.5 arc seconds. But chances are that this +1.5 position occurred sometime before the end of the exposure, and at the exact time the move command is sent (after the fact), that star could already be at the opposite extreme, -1.5 arc sec position. The net result is that the guider software moves the guide star to -3 arc sec position for the next exposure. It's quite possible that the next guider pulse sent to the mount will have to be be +3 arc seconds, and you will see oscillations back and forth for a while until the seeing steadies up momentarily.

This is also complicated by any slight delay in Dec reversal that may exist in the mount which will require more than 1 pulse the do a full reversal.

In order to avoid this scenario, I would suggest setting a no-response limit around zero where the guider does not send any guide pulses, and just let the guide star bobble around in there. As soon as it steps outside this limit, the mount will get an instant reverse command. If the mount needs to reverse in Dec, then the necessary pulses will be sent quickly, perhaps 2 or 3 needed for full reversal. If you have long 10 second delays between each guide pulse, it may take 20, 30 or more seconds to get the guide star to move back to zero point.

Rolando





-----Original Message-----
From: 'Ray Gralak (Groups)' groups3@... [ap-gto] <ap-gto@yahoogroups..com>
To: ap-gto gto@...>
Sent: Thu, Feb 1, 2018 1:40 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

Hi Wade,

I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

If good-quality tracking rate correction can be used then I think that
autoguider exposures could be increased significantly. Otherwise, how could
doing unguided exposures using tracking rate correction work! :-)

Best regards,

-Ray Gralak
Author of APCC (Astro-Physics Command Center):
http://www.astro-physics.com/index.htm?products/accessories/software/apcc/ap
cc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma

> -----Original Message-----
> From: ap-gto@... <mailto:gto@...> [mailto:ap-gto@... <mailto:ap-gto@...?> ]
> Sent: Thursday, February 1, 2018 10:39 AM
> To: ap-gto@... <mailto:gto@...>
> Subject: RE: [ap-gto] Guiding AP mounts with PHD
>
>
>
> I am curious about this result, especially the part at the end where you
say
> that 1 second exposures worked well, but longer exposures "became more and
> more sluggish and less accurate".
>
> It's my understanding that the mount is going to track well, assuming that
> PEM is programmed correctly and enabled, and that guiding should basically
> be correcting any drift due to slight polar misalignment, refraction,
> flexure, etc. If my understanding is correct, it would seem that longer
> exposures (within reason) would be just as effective as shorter exposures
-
> perhaps more effective, since longer exposures would tend to average out
> seeing distortion in the individual guider subs. If you were getting
better
> results at 1 second, that would suggest that you were chasing seeing with
> some success.
>
> Do you understand why it worked the way that it did for you? Was it
> correcting for slower seeing effects? Is there some other reason?
>
> Thanks,
>
> -Wade
>
> From: ap-gto@... <mailto:gto@...> [mailto:ap-gto@... <mailto:ap-gto@...?> ]
> Sent: Thursday, February 1, 2018 9:36 AM
> To: ap-gto@... <mailto:gto@...>
> Subject: Re: [ap-gto] Guiding AP mounts with PHD
>
> Great info. A few questions:
>
> - You mention that you set the MinMo to 0.8 arc-secs. I believe MinMo in
the
> PHD interface is shown in pixels. So if you set the MinMo to 0.8 it would
> have been 0.8 pixels. Did you guys just do the math to figure out the
> correct pixel value?
>
> - Were these changes made on both axis in PHD2? MinMo and Aggressiveness
> can
> be configured per axis.
>
> The rest of this looks very interesting and as soon as the weather gets
> better I plan to test this and see how my guiding performs.
>
> _____
>
> From: ap-gto@... <mailto:gto@...> gto@... <mailto:gto@...> > on behalf of
> chris1011@... <mailto:chris1011@...> [ap-gto] gto@... <mailto:gto@...> >
> Sent: Wednesday, January 31, 2018 4:51 PM
> To: ap-gto@... <mailto:gto@...> ; ap-ug@... <mailto:ug@...>
> Subject: [ap-gto] Guiding AP mounts with PHD
>
> Howdy,
>
> Howard and I had a chance to log in to a customer's Mach1 mount last night
> to help him with some guiding issues using PHD. He had sent his
calibration
> graph and it looked quite good, but he was having some problems guiding.
> After doing some mechanical tests we set up parameters in PHD to get the
> mount to track and respond accurately. Since PHD is somewhat different
from
> MaximDL, which I use, we had to approach the settings a bit differently.
>
> The first step is to do a quick 2 - 3 minute Unguided run using 1 second
> guide exposures, and look at the guider graph to see what the maximum
> excursions are in Declination. The guide star will bounce around a certain
> amount and this peak error will be the seeing that you cannot guide out
with
> normal guide software. This P-V value, which in our case was between +-0.5
> and +-0.8 arc seconds is what I call the Guide Star "Bobble" limit. Trying
> to correct for that with guide moves to the mount is impossible (only a
fast
> acting AO system can chase that seeing error).
>
> So, knowing that the minimum seeing error is +-0.8 arc seconds, you will
> want to set the initial Min Move setting in PHD to be approximately this
> value as a starting value. We set the Min Move to 0.8 arc sec, the guide
> rate at 1x and the aggressiveness to 100%. This means that no correction
> pulses are sent to the mount while the guide star is bobbling within that
> envelope, but once it exceeds even slightly, the mount gets a full
> correction command (-0.8 arc sec) to bring it back toward the zero
position.
> We turned guiding on and the result was that the mount responded quickly
> whenever the error exceeded the bobble limits and overall guiding was
tight,
> accurate and almost the same RMS value, ~0.35 arc sec, for both axes. An
> exposure with the main camera showed tight round stars.
>
> So, as a starting point:
> Determine the amount of guide star bobble above and below the axis
> Set the Min Move to that value
> Set Guide rate to 1x sidereal
> Set the guide star exposure rate to 1 second
> Set Aggressiveness to 100%
> Begin guiding and note the RMS value for both axes.
>
> You can then change any of the parameters to see if you can tune the RMS
to
> a lower value. We tried longer guide star exposures, but found that the
> response to tracking errors became more and more sluggish and less
accurate.
> So for these seeing conditions a faster guide rate of 1 per second
resulted
> in the lowest RMS error on both axes. In pristine seeing it might allow
> longer guide exposures, at least that is what we found using PHD Guiding.
>
> Rolando
>
> [Non-text portions of this message have been removed]
>
>
>
>



------------------------------------
Posted by: "Ray Gralak \(Groups\)" <groups3@... <mailto:groups3@...> >
------------------------------------

To UNSUBSCRIBE, or for general information on the ap-gto list
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------------------------------------
Posted by: "Wade Hilmo" <wade@...>
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Re: Is Yahoo Groups moderating every messages?

Joe Zeglinski
 

Greg,
 
    Thanks for your latest clarification on the current Yahoo problems.
 
    Since the delivery lag, or even entire absence of Yahoo email service, seems to be “user,  or perhaps ISP specific”, then Yahoo must be having some difficulty with exchanging emails from certain ISP routing addresses,  or regional network trunk lines.
Glad to hear that you found that Yahoo is working on their now “known”,  (non-Group specific), problem, and may hopefully resolve it soon.
 
    This may explain why only some random users are still having such difficulty. That major Yahoo outage on the weekend might indicate the severity of “their problem”, so they had to completely shut down service to isolate the cause,  a bit better, perhaps a server virus flush at the same time.
 
Joe


Re: Is Yahoo Groups moderating every messages?

Gregory <fyrframe@...>
 

Sorry, I disagree.

>>>"Yahoo is running smooth as silk right now."

No it's not for some and yes Yahoo mail is working fine for some. My post are still kind of funcky in the way my posts return from Yahoo. Yahoo is the common denominator in all of this. My Yahoo account/profile is not functioning. I can't read any of my email on the Yahoo sever. They have a notice up (did?) that states they acknowledged they are having difficulties and are working on it. That notice has been up for quite awhile.

I have also noticed "test" posts in the many Yahoo forums I use. They are looking at some posting problem, and that introduces Yahoo. They are all testing their Yahoo forum posts. The Yahoo site itself was experiencing all kinds of problems. I too for sometime could only post by going to that forum's Yahoo site and post from there.

Only now are posts showing up in the appropriate forums. It's slowly starting to come back for me. At first, it took a couple of hours before the post would appear. Now they are starting to show up more rapidly. Yet, I still can't post to the MaxumDL forum. So it's not all silky smooth._eot

Thanks for listening.

Gregory Gig Harbor, WA.



On 2/2/2018 8:47 AM, 'Joseph Zeglinski' J.Zeglinski@... [ap-gto] wrote:
 

Mike,
 
    I got my post sent back to my Live Mail (ISP Rogers..com in Canada) ...  in “just 4 minutes” between the time I sent it and the time I received it back from this Yahoo group page.
So, Yahoo is running smooth as silk right now, and has generally been the norm, except for last weekend.  Can’t complain.
 
    You need to look elsewhere for the problem with your Groups Emails exchanges.
 
Hope this test helped.
Joe
 
From: 'Joseph Zeglinski' J.Zeglinski@... [ap-gto]
Sent: Friday, February 2, 2018 11:30 AM
To: ap-gto@...
Subject: [ap-gto] Re: Is Yahoo Groups moderating every messages?
 


Mike,
 
    It is 11:38 AM here,  and I am replying to your post using Microsoft Live Mail “directly” as you said.
– Lets see how quickly this post pops up on this group’s list strictly using emails than a browser to the Yahoo Group site.
 
    I don’t think it is a Yahoo problem, since I am handling group posts the same ... as you were, before your recent problems.
Perhaps it is something going on at the “Q.com” web handler.
 
Joe
 
From: mshade@q.com [ap-gto]
Sent: Friday, February 2, 2018 8:38 AM
To: ap-gto@...
Subject: [ap-gto] Re: Is Yahoo Groups moderating every messages?
 


I used to be able to post directly to the group, and all of my groups on Yahoo.  I cannot do this anymore but have to go to the Yahoo website and post from there.  Some of my posts will show up several days later, some will get bounced back with an undelivered message.  In looking at the useless Yahoo help forum, a number of people are all of a sudden having e-mail problems with their Yahoo accounts, similar to what I and seemingly others are experiencing.  I am having not other e-mail problems.
 
Mike


Re: Guiding AP mounts with PHD

Roland Christen
 


PHD2 implements a hysteresis algorithm where you can specify how much the next correction sent relies on the most recent sample versus the history of samples.

There are also several options which use a low pass filter to achieve a similar end.

Also you can specify a maximum move per step.  You can also tell if if is see a very large excursion (due to a dither move) it will attempt to recover more quickly than the max move you specified.
That's interesting and I'll be anxious to try it.

Rolando


-----Original Message-----
From: Michael Fulbright mike.fulbright@... [ap-gto]
To: ap-gto
Sent: Fri, Feb 2, 2018 11:07 am
Subject: Re: [ap-gto] Guiding AP mounts with PHD



PHD2 implements a hysteresis algorithm where you can specify how much the next correction sent relies on the most recent sample versus the history of samples.

There are also several options which use a low pass filter to achieve a similar end.

Also you can specify a maximum move per step.  You can also tell if if is see a very large excursion (due to a dither move) it will attempt to recover more quickly than the max move you specified.

Most is summarized here:

http://openphdguiding.org/man/Guide_algorithms.htm

I've found using long (4-6 second) exposures extremely useful when dealing with nights of poor seeing.   It is a simple experiment to incrementally increase the exposure time and watch the random scatter of samples of the DEC axis while guiding is turned off to gauge how well this works. 

If seeing conditions are so bad that you are seeing excursions more than say 1 arcsecond regularly it is probably time to shut down as that night is a lost cause.

Something to consider is there are other factors that can cause large jumps which have nothing to do with mechanical or atmospheric behavior.  For example, for a period apparently some QHY cameras with certain QHY drivers would occasionally output frames that were shifted by 1 pixel!  Imagine the consequences on guiding when using a smaller guide scope and a pixels scale of several arcseconds/pixel.

Michael Fulbright


On 2/2/2018 11:39 AM, 'Joseph Zeglinski' J.Zeglinski@... [ap-gto] wrote:
 
Rolando,
 
    On your second point ... wouldn’t it be nice if guider programs did a “limit check” and tossed out any centroid which exceeded a user set star position jump size,  and only accepted them “as real” after 2 or more samples that stayed at that new position. This might eliminate effects of sudden bursts of bad seeing, caused by major drift pockets in air temperature, even the occasional passing aircraft’s lights.
 
    Perhaps this is “already being done”,  in PemPro – if not, maybe it would be a good test vehicle for this kind of guide compensation.
 
Joe




Re: Guiding AP mounts with PHD

Roland Christen
 

There may be ways of averaging and weighting the guide data so that only drift is compensated and seeing effects are ignored. In Dec especially, drift is only in one direction, so no reason to do lots of Dec axis reversals. During a dither move the software could adjust the guide pulses to bring the guide star back to zero rapidly, and then resume an average slower drift compensation. All this requires a higher level of sophistication in the guide software, but if the software is free, then nobody pays for the labor required to develop it. Dilemma ramalamadingdong

Rolando



-----Original Message-----
From: 'Joseph Zeglinski' J.Zeglinski@... [ap-gto]
To: ap-gto
Sent: Fri, Feb 2, 2018 11:01 am
Subject: Re: [ap-gto] Guiding AP mounts with PHD



Rolando,
 
    On your second point ... wouldn’t it be nice if guider programs did a “limit check” and tossed out any centroid which exceeded a user set star position jump size,  and only accepted them “as real” after 2 or more samples that stayed at that new position. This might eliminate effects of sudden bursts of bad seeing, caused by major drift pockets in air temperature, even the occasional passing aircraft’s lights.
 
    Perhaps this is “already being done”,  in PemPro – if not, maybe it would be a good test vehicle for this kind of guide compensation.
 
Joe



Re: Guiding AP mounts with PHD

Michael Fulbright <mike.fulbright@...>
 

PHD2 implements a hysteresis algorithm where you can specify how much the next correction sent relies on the most recent sample versus the history of samples.

There are also several options which use a low pass filter to achieve a similar end.

Also you can specify a maximum move per step.  You can also tell if if is see a very large excursion (due to a dither move) it will attempt to recover more quickly than the max move you specified.

Most is summarized here:

http://openphdguiding.org/man/Guide_algorithms.htm

I've found using long (4-6 second) exposures extremely useful when dealing with nights of poor seeing.   It is a simple experiment to incrementally increase the exposure time and watch the random scatter of samples of the DEC axis while guiding is turned off to gauge how well this works. 

If seeing conditions are so bad that you are seeing excursions more than say 1 arcsecond regularly it is probably time to shut down as that night is a lost cause.

Something to consider is there are other factors that can cause large jumps which have nothing to do with mechanical or atmospheric behavior.  For example, for a period apparently some QHY cameras with certain QHY drivers would occasionally output frames that were shifted by 1 pixel!  Imagine the consequences on guiding when using a smaller guide scope and a pixels scale of several arcseconds/pixel.

Michael Fulbright


On 2/2/2018 11:39 AM, 'Joseph Zeglinski' J.Zeglinski@... [ap-gto] wrote:
 

Rolando,
 
    On your second point ... wouldn’t it be nice if guider programs did a “limit check” and tossed out any centroid which exceeded a user set star position jump size,  and only accepted them “as real” after 2 or more samples that stayed at that new position. This might eliminate effects of sudden bursts of bad seeing, caused by major drift pockets in air temperature, even the occasional passing aircraft’s lights.
 
    Perhaps this is “already being done”,  in PemPro – if not, maybe it would be a good test vehicle for this kind of guide compensation.
 
Joe


Re: Is Yahoo Groups moderating every messages?

Joe Zeglinski
 

Mike,
 
    I got my post sent back to my Live Mail (ISP Rogers.com in Canada) ...  in “just 4 minutes” between the time I sent it and the time I received it back from this Yahoo group page.
So, Yahoo is running smooth as silk right now, and has generally been the norm, except for last weekend.  Can’t complain.
 
    You need to look elsewhere for the problem with your Groups Emails exchanges.
 
Hope this test helped.
Joe
 

From: 'Joseph Zeglinski' J.Zeglinski@... [ap-gto]
Sent: Friday, February 2, 2018 11:30 AM
To: ap-gto@...
Subject: [ap-gto] Re: Is Yahoo Groups moderating every messages?
 


Mike,
 
    It is 11:38 AM here,  and I am replying to your post using Microsoft Live Mail “directly” as you said.
– Lets see how quickly this post pops up on this group’s list strictly using emails than a browser to the Yahoo Group site.
 
    I don’t think it is a Yahoo problem, since I am handling group posts the same ... as you were, before your recent problems.
Perhaps it is something going on at the “Q.com” web handler.
 
Joe
 
From: mshade@q.com [ap-gto]
Sent: Friday, February 2, 2018 8:38 AM
To: ap-gto@...
Subject: [ap-gto] Re: Is Yahoo Groups moderating every messages?
 


I used to be able to post directly to the group, and all of my groups on Yahoo.  I cannot do this anymore but have to go to the Yahoo website and post from there.  Some of my posts will show up several days later, some will get bounced back with an undelivered message.  In looking at the useless Yahoo help forum, a number of people are all of a sudden having e-mail problems with their Yahoo accounts, similar to what I and seemingly others are experiencing.  I am having not other e-mail problems.
 
Mike


Re: Guiding AP mounts with PHD

Joe Zeglinski
 

Rolando,
 
    On your second point ... wouldn’t it be nice if guider programs did a “limit check” and tossed out any centroid which exceeded a user set star position jump size,  and only accepted them “as real” after 2 or more samples that stayed at that new position. This might eliminate effects of sudden bursts of bad seeing, caused by major drift pockets in air temperature, even the occasional passing aircraft’s lights.
 
    Perhaps this is “already being done”,  in PemPro – if not, maybe it would be a good test vehicle for this kind of guide compensation.
 
Joe


Re: Is Yahoo Groups moderating every messages?

Joe Zeglinski
 

Mike,
 
    It is 11:38 AM here,  and I am replying to your post using Microsoft Live Mail “directly” as you said.
– Lets see how quickly this post pops up on this group’s list strictly using emails than a browser to the Yahoo Group site.
 
    I don’t think it is a Yahoo problem, since I am handling group posts the same ... as you were, before your recent problems.
Perhaps it is something going on at the “Q.com” web handler.
 
Joe
 

From: mshade@q.com [ap-gto]
Sent: Friday, February 2, 2018 8:38 AM
To: ap-gto@...
Subject: [ap-gto] Re: Is Yahoo Groups moderating every messages?
 


I used to be able to post directly to the group, and all of my groups on Yahoo.  I cannot do this anymore but have to go to the Yahoo website and post from there.  Some of my posts will show up several days later, some will get bounced back with an undelivered message.  In looking at the useless Yahoo help forum, a number of people are all of a sudden having e-mail problems with their Yahoo accounts, similar to what I and seemingly others are experiencing.  I am having not other e-mail problems.
 
Mike


Re: Guiding AP mounts with PHD

Roland Christen
 


Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.
First, long exposures in PHD result in saturated stars which the program apparently can't handle, or can't calculate a proper centroid.

Second, it may be stable for a period of time until there is just one single excursion outside the envelope. The software will then send a move command which may not fully reverse the axis, so the guide star stays outside the envelope for another guide cycle until finally it gets pushed back down. This may then start an oscillation in the other direction, but even if not, the correcting signals are few and far between time-wise, so the RMS error gets larger. With faster guide exposures, the mount gets faster correction signals and the guide star spends less time in the wrong place.

All I'm saying is to try this method with PHD Guiding and see if it improves your results. It is not a hard and fast rule, just a suggestion of where to start setting the parameters. You are welcome to experiment and post your results here. We all can learn.

I have PHD now and will experiment further. I may try to add a tiny bit of backlash compensation in Dec to see what effect that has and whether that will reduce the back and forth oscillation or make it worse.

Rolando


-----Original Message-----
From: 'Wade Hilmo' y.groups@... [ap-gto]
To: ap-gto
Sent: Thu, Feb 1, 2018 7:50 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

If you are taking 10 second guide exposures, doesn’t that mean that the star will have bounced around randomly for the whole 10 seconds? As I understand it, the conventional wisdom is that longer guide exposures will have larger stars due to the atmospheric effects, but that the correct star position is likely to be near the center of the blob. Then the centroid calculation by the guide software shouldn’t be seeing huge swings in the centroid position.



I suppose that this gets down to the effectiveness of the centroid calculation. If it’s just looking for the brightest single pixel, then I can see where longer guide exposures might not be helpful. But I thought that the calculations were more sophisticated than that, and would look at the stellar profile to determine the centroid. Perhaps not, I guess? And perhaps it varies with the guide software.



-Wade



From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, February 1, 2018 1:47 PM
To: ap-gto@...
Subject: Re: [ap-gto] Guiding AP mounts with PHD







I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

In this case it was because of poor seeing, not so much drift. When you get instances of poor seeing that move the guide star back and forth erratically, then you end up with many instances of guider corrections being sent to the mount. If you take a 10 second exposure and it shows the guide star at +1.5 arc second location, the mount will receive a command to move -1.5 arc seconds. But chances are that this +1.5 position occurred sometime before the end of the exposure, and at the exact time the move command is sent (after the fact), that star could already be at the opposite extreme, -1.5 arc sec position. The net result is that the guider software moves the guide star to -3 arc sec position for the next exposure. It's quite possible that the next guider pulse sent to the mount will have to be be +3 arc seconds, and you will see oscillations back and forth for a while until the seeing steadies up momentarily.

This is also complicated by any slight delay in Dec reversal that may exist in the mount which will require more than 1 pulse the do a full reversal.

In order to avoid this scenario, I would suggest setting a no-response limit around zero where the guider does not send any guide pulses, and just let the guide star bobble around in there. As soon as it steps outside this limit, the mount will get an instant reverse command. If the mount needs to reverse in Dec, then the necessary pulses will be sent quickly, perhaps 2 or 3 needed for full reversal. If you have long 10 second delays between each guide pulse, it may take 20, 30 or more seconds to get the guide star to move back to zero point.

Rolando





-----Original Message-----
From: 'Ray Gralak (Groups)' groups3@... [ap-gto]
To: ap-gto gto@...>
Sent: Thu, Feb 1, 2018 1:40 pm
Subject: RE: [ap-gto] Guiding AP mounts with PHD

Hi Wade,

I think that the length of the interval between guider exposures depends on
how much drift is present. A 1-second duration worked best for Howard and
Roland in their particular case probably because there was enough drift to
require a moves after 1 second.

If good-quality tracking rate correction can be used then I think that
autoguider exposures could be increased significantly. Otherwise, how could
doing unguided exposures using tracking rate correction work! :-)

Best regards,

-Ray Gralak
Author of APCC (Astro-Physics Command Center):
http://www.astro-physics.com/index.htm?products/accessories/software/apcc/ap
cc
Author of PEMPro: http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma

> -----Original Message-----
> From: ap-gto@... <mailto:gto@...> [mailto:ap-gto@... <mailto:ap-gto@...?> ]
> Sent: Thursday, February 1, 2018 10:39 AM
> To: ap-gto@... <mailto:gto@...>
> Subject: RE: [ap-gto] Guiding AP mounts with PHD
>
>
>
> I am curious about this result, especially the part at the end where you
say
> that 1 second exposures worked well, but longer exposures "became more and
> more sluggish and less accurate".
>
> It's my understanding that the mount is going to track well, assuming that
> PEM is programmed correctly and enabled, and that guiding should basically
> be correcting any drift due to slight polar misalignment, refraction,
> flexure, etc. If my understanding is correct, it would seem that longer
> exposures (within reason) would be just as effective as shorter exposures
-
> perhaps more effective, since longer exposures would tend to average out
> seeing distortion in the individual guider subs. If you were getting
better
> results at 1 second, that would suggest that you were chasing seeing with
> some success.
>
> Do you understand why it worked the way that it did for you? Was it
> correcting for slower seeing effects? Is there some other reason?
>
> Thanks,
>
> -Wade
>
> From: ap-gto@... <mailto:gto@...> [mailto:ap-gto@... <mailto:ap-gto@...?> ]
> Sent: Thursday, February 1, 2018 9:36 AM
> To: ap-gto@... <mailto:gto@...>
> Subject: Re: [ap-gto] Guiding AP mounts with PHD
>
> Great info. A few questions:
>
> - You mention that you set the MinMo to 0.8 arc-secs. I believe MinMo in
the
> PHD interface is shown in pixels. So if you set the MinMo to 0.8 it would
> have been 0.8 pixels. Did you guys just do the math to figure out the
> correct pixel value?
>
> - Were these changes made on both axis in PHD2? MinMo and Aggressiveness
> can
> be configured per axis.
>
> The rest of this looks very interesting and as soon as the weather gets
> better I plan to test this and see how my guiding performs.
>
> _____
>
> From: ap-gto@... <mailto:gto@...> gto@... <mailto:gto@...> > on behalf of
> chris1011@... <mailto:chris1011@...> [ap-gto] gto@... <mailto:gto@...> >
> Sent: Wednesday, January 31, 2018 4:51 PM
> To: ap-gto@... <mailto:gto@...> ; ap-ug@... <mailto:ug@...>
> Subject: [ap-gto] Guiding AP mounts with PHD
>
> Howdy,
>
> Howard and I had a chance to log in to a customer's Mach1 mount last night
> to help him with some guiding issues using PHD. He had sent his
calibration
> graph and it looked quite good, but he was having some problems guiding.
> After doing some mechanical tests we set up parameters in PHD to get the
> mount to track and respond accurately. Since PHD is somewhat different
from
> MaximDL, which I use, we had to approach the settings a bit differently.
>
> The first step is to do a quick 2 - 3 minute Unguided run using 1 second
> guide exposures, and look at the guider graph to see what the maximum
> excursions are in Declination. The guide star will bounce around a certain
> amount and this peak error will be the seeing that you cannot guide out
with
> normal guide software. This P-V value, which in our case was between +-0.5
> and +-0.8 arc seconds is what I call the Guide Star "Bobble" limit. Trying
> to correct for that with guide moves to the mount is impossible (only a
fast
> acting AO system can chase that seeing error).
>
> So, knowing that the minimum seeing error is +-0.8 arc seconds, you will
> want to set the initial Min Move setting in PHD to be approximately this
> value as a starting value. We set the Min Move to 0.8 arc sec, the guide
> rate at 1x and the aggressiveness to 100%. This means that no correction
> pulses are sent to the mount while the guide star is bobbling within that
> envelope, but once it exceeds even slightly, the mount gets a full
> correction command (-0.8 arc sec) to bring it back toward the zero
position.
> We turned guiding on and the result was that the mount responded quickly
> whenever the error exceeded the bobble limits and overall guiding was
tight,
> accurate and almost the same RMS value, ~0.35 arc sec, for both axes. An
> exposure with the main camera showed tight round stars.
>
> So, as a starting point:
> Determine the amount of guide star bobble above and below the axis
> Set the Min Move to that value
> Set Guide rate to 1x sidereal
> Set the guide star exposure rate to 1 second
> Set Aggressiveness to 100%
> Begin guiding and note the RMS value for both axes.
>
> You can then change any of the parameters to see if you can tune the RMS
to
> a lower value. We tried longer guide star exposures, but found that the
> response to tracking errors became more and more sluggish and less
accurate.
> So for these seeing conditions a faster guide rate of 1 per second
resulted
> in the lowest RMS error on both axes. In pristine seeing it might allow
> longer guide exposures, at least that is what we found using PHD Guiding.
>
> Rolando
>
> [Non-text portions of this message have been removed]
>
>
>
>



------------------------------------
Posted by: "Ray Gralak \(Groups\)" <groups3@... <mailto:groups3@...> >
------------------------------------

To UNSUBSCRIBE, or for general information on the ap-gto list
see http://groups.yahoo.com/group/ap-gto
------------------------------------

Yahoo Groups Links







[Non-text portions of this message have been removed]



------------------------------------
Posted by: "Wade Hilmo" <wade@...>
------------------------------------

To UNSUBSCRIBE, or for general information on the ap-gto list
see http://groups.yahoo.com/group/ap-gto
------------------------------------

Yahoo Groups Links

<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/ap-gto/

<*> Your email settings:
Individual Email | Traditional

<*> To change settings online go to:
http://groups.yahoo.com/group/ap-gto/join
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