Date   

Re: APCC Pro model details #APCC

Steve Reilly
 

Ray,

I'm late to this discussion and am in the process of finalizing a transfer from the roll off roof to my 12' dome. I've polar aligned using my PoleMaster but can't say I'm overly confident as I haven't used it before. So if I run a model will this verify the alignment accuracy? If so how many points should be used? Sorry if I'm behind but this project has had so many twists and turns that I'm a bit intimidated trying to get back online.

Thanks,

Steve

-----Original Message-----
From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Ray Gralak
Sent: Monday, May 30, 2022 1:16 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] APCC Pro model details

Hi Brent,

None would be essential but maybe useful. For polar alignment I should have said to verify alignment instead of refine it.
I have a permanent pier and build models (probably more often than I need to) a lot more than adjust polar alignment.
Seeing those values in the model verify that polar alignment is still reasonable.
Yes, and this is currently available. APCC shows the mount’s polar alignment error (in arc-seconds) for both pier sides.

Yes, as a tool to measure cone error.
APCC displays Cone error (in arc-seconds) in the two "Non-Perpendicularity" pointing terms. To measure the cone error for both scopes, you need to create a separate model for each scope.

Maybe I am misinterpreting, but could a model with a high RMS indicate flexure (probably not specifically)?
RMS is just a measure of how well the pointing model fits the sky data points.By itself, it does not distinguish between unmodeled behavior (e.g., complex flexure) and randomness caused by moving components (eg. Mirror flop).

-Ray


Re: APCC Pro model details #APCC

Ray Gralak
 

Hi Brent,

None would be essential but maybe useful. For polar alignment I should have said to verify alignment instead of refine it.
I have a permanent pier and build models (probably more often than I need to) a lot more than adjust polar alignment.
Seeing those values in the model verify that polar alignment is still reasonable.
Yes, and this is currently available. APCC shows the mount’s polar alignment error (in arc-seconds) for both pier sides.

Yes, as a tool to measure cone error.
APCC displays Cone error (in arc-seconds) in the two "Non-Perpendicularity" pointing terms. To measure the cone error for both scopes, you need to create a separate model for each scope.

Maybe I am misinterpreting, but could a model with a high RMS indicate flexure (probably not specifically)?
RMS is just a measure of how well the pointing model fits the sky data points.By itself, it does not distinguish between unmodeled behavior (e.g., complex flexure) and randomness caused by moving components (eg. Mirror flop).

-Ray


Re: Field Rotation

Edward Beshore
 

Hi Mike

What is the focal length of your setup? If its over 1000mm, I would definitely consider an off-axis guider. As an acquaintance of mine says (who knows) "When you are dealing with an arc sec, everything is made of rubber."

Ed


Re: Field Rotation

M Hambrick
 

Hi Ray and Hy

I was continuously guiding (via MaxIm DL) for the entire 5 hours that I was taking these images, but I am not using a model. The RMS guiding errors were averaging 0.4" to 0.5" in RA and 0.5" to 0.6" in Dec. I am using a separate guide scope in a side-by-side arrangement. Everything is well balanced.

I suspect I have some flexure going on, but I didn't think that differential flexure will cause a progressive drift like I am seeing ? I suppose it is possible. M51 was just past the meridian with the scope pointing almost vertically when I started taking images. Five hours later it is only 25 degrees above the horizon. I suppose that during this time the forces that cause differential flexure are continuously changing and likely getting worse as the orientation of the scope changes from vertical to horizontal.

I think I am going to have to switch to an off-axis guiding configuration to resolve this.

Mike


Re: [ap-ug] Happy Memorial Day - new video for total solar eclipses

thefamily90 Phillips
 

Happy Memorial Day! In remembrance of all who fought and died for the USA!

Jim 

From: main@ap-ug.groups.io <main@ap-ug.groups.io> on behalf of Harley Davidson <astrocnc@...>
Sent: Monday, May 30, 2022 7:00:15 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>; main@ap-ug.groups.io <main@ap-ug.groups.io>
Subject: [ap-ug] Happy Memorial Day - new video for total solar eclipses
 
Hello

I made a simple "flip" solar filter setup for viewing total solar eclipses. I wanted something for the eclipse upcoming on Monday,  April 8, 2024.

https://www.youtube.com/watch?v=NzYIrXdCGXk

tony



Happy Memorial Day - new video for total solar eclipses

Harley Davidson
 

Hello

I made a simple "flip" solar filter setup for viewing total solar eclipses. I wanted something for the eclipse upcoming on Monday,  April 8, 2024.

https://www.youtube.com/watch?v=NzYIrXdCGXk

tony



Re: Flashing light from usb to serial adapter

Mike Dodd
 

On 5/29/2022 10:24 PM, Yves Laroche wrote:

Electrical tape will do the job.
I Prefer black paint. Electrical tape will get gummy over time, and fall off or make a mess.

--- Mike


Re: Flashing light from usb to serial adapter

Yves Laroche
 

Hi Geoff,

Electrical tape will do the job.

Regards,
Yves

Le 29 mai 2022 21 h 32, Geoff Smith <ghsmith45@...> a écrit :
I have the FTDI USB-to_serial adapter recommended by Astro-Physics. It flashes continuously when imaging--very annoying. Does anybody have a good method of dealing with this? Paint, tape or even (you never know) a software solution?
Geoff

 



Re: Flashing light from usb to serial adapter

Yves Laroche
 

Electrical tape will do the job.

Regards,
Yved

Le 29 mai 2022 21 h 32, Geoff Smith <ghsmith45@...> a écrit :
I have the FTDI USB-to_serial adapter recommended by Astro-Physics. It flashes continuously when imaging--very annoying. Does anybody have a good method of dealing with this? Paint, tape or even (you never know) a software solution?
Geoff

 



Flashing light from usb to serial adapter

Geoff Smith
 

I have the FTDI USB-to_serial adapter recommended by Astro-Physics. It flashes continuously when imaging--very annoying. Does anybody have a good method of dealing with this? Paint, tape or even (you never know) a software solution?
Geoff

 


Re: APCC Pro model details #APCC

Brent Boshart
 
Edited

Hi Ray,
None would be essential but maybe useful.  For polar alignment I should have said to verify alignment instead of refine it.  I have a permanent pier and build models (probably more often than I need to) a lot more than adjust polar alignment. Seeing those values in the model verify that polar alignment is still reasonable. The only times I need to adjust is when the frosts sets in and then spring time - it seems to nudge my pier a little. Or sometimes when I do some sort of maintenance around the pier/mount.  So I guess I'm saying not as a tool for polar alignment, but data available to verify polar alignment when doing a model anyway.
Yes, as a tool to measure cone error.  While the model corrects this, I have two OTAs and have adjusted my second OTA to reasonably match the other in terms of cone error. I can swap OTAs during a session and still have reasonably good pointing - of course I could always build a model for each OTA.
Thanks for the comments about flexure.  I believe my current setup has more flexure than it should, I want to try a few things to improve that and having a measure would be good.  Maybe I am misinterpreting, but could a model with a high RMS indicate flexure (probably not specifically)?  I recall you commenting on another post that an user's RMS appeared high for a refractor. My usual RMS with my refractor is at least as high or higher so I suspected inconsistent flexure.  Thanks.


Re: Field Rotation

Hy Murveit
 

Mike,

That movement of the image sounds like differential flexure to me (flex between your guide scope/camera vs your main scope/camera).

Hy

On Sun, May 29, 2022 at 6:06 AM M Hambrick <mhambrick563@...> wrote:
Thanks for the comments Roland and Howard.

What do you think I am seeing when the position of my images is shifting over an extended period ? Friday night I was taking images of M51 over a period of about 5 hours. I took the first image at about 10:30 pm when it was .just on the west side of the meridian. The last image was at 3:30 am. I plate solved the first and last images and measured the difference in the coordinates at the center of the two images.

The RA had shifted 7.91" and the Dec had shifted 25.5"

Can this be explained by atmospheric refraction ?

Mike


Trouble auto-connect ASCON driver following mount intialization

John Stiner
 

I have an AP1100 GTO AE-L. I connect my laptop to the CP4 via an Icron Ranger for USB over a Cat 5e/6/7 cable (not sure if that matters).   I was out of commission for 9 months awaiting camera repairs and, in the meantime, acquired a new imaging laptop with Windows 11, so I'm fairly certain this is user error due to forgetting what little I knew before.  I'm using APCC Pro v1.9.4.3 and v.5.50.03 of the ASCOM driver.  In any event, I'm trying to get everything back up and running. I initially encountered the trouble with virtual ports and so took the actions described in the post below.  I set the virtual ports to "None" in APCC's Virtual Ports tab and in the ASCOM Driver settings, I checked the "IP Address" box which showed the "APCC REST API" box, which I also checked.

New versions of APCC Standard, Pro, and AP V2 ASCOM Driver to use as an Eltima alternative (groups.io)

After powering up the amount and opening APCC, APCC now auto-initializes and, following initialization, I can click the "Connect" button for the AP V2 Driver and it connects fine.  However, despite having "Auto-Connect" box checked for the AP V2 Driver (as well as for the Mount), for whatever reason the driver never auto-connects or attempts to do so.  Rather, I have to click on the "Connect" button.  I realize there are worse problems than having to click a button but still wonder why the driver does not auto-connect.


Re: Field Rotation

Ray Gralak
 

What do you think I am seeing when the position of my images is shifting over an extended period ? Friday night I
was taking images of M51 over a period of about 5 hours. I took the first image at about 10:30 pm when it was .just
on the west side of the meridian. The last image was at 3:30 am. I plate solved the first and last images and
measured the difference in the coordinates at the center of the two images.

The RA had shifted 7.91" and the Dec had shifted 25.5"
Mike, were you autoguiding or not? Also, were you using an APCC model or not? If you were using a model, were you using Dec Arc tracking rate correction?

-Ray


Re: Field Rotation

Howard Ritter
 

That doesn’t seem quite plausible to me. Atmospheric refraction causes a difference of about 55 arcsec in apparent elevation of an object when it’s at an elevation of 45º compared to when it’s at the zenith.

I don’t know what your latitude is, but at mine in Ohio, M51 is very close to just these positions at 2230 and 0330 currently. It looks like, at a latitude of 45º, the elevation vector is almost parallel to RA at the location of M51 during this interval. This means that the better part of that 55” would be projected onto the RA coordinate. And then, because of the fact that the lines of RA, like those of longitude, converge as they approach the pole, a line segment (say) 40" in length cutting across the lines of RA nearly perpendicularly would extend across more than 40” of RA – I believe it would be 40”/cos(Dec). The Dec of M51 is close to 45º, whose cos is ~0.7, so maybe a shift in RA of 60” or so, not the 8" or so that you saw. The effect on Dec would be first to increase it, then to decrease it, as the orientation of M51’s elevation vector relative to celestial coordinates changes, probably with little net effect, whereas you saw a shift of 25".

That said, I’m not an expert, of which there must be some in this group. It would be interesting to hear from them.

—howard

On May 29, 2022, at 9:06 AM, M Hambrick <mhambrick563@...> wrote:

Thanks for the comments Roland and Howard.

What do you think I am seeing when the position of my images is shifting over an extended period ? Friday night I was taking images of M51 over a period of about 5 hours. I took the first image at about 10:30 pm when it was .just on the west side of the meridian. The last image was at 3:30 am. I plate solved the first and last images and measured the difference in the coordinates at the center of the two images.

The RA had shifted 7.91" and the Dec had shifted 25.5"

Can this be explained by atmospheric refraction ?

Mike


Re: Field Rotation

ap@CaptivePhotons.com
 

On Sun, May 29, 2022 at 10:18 AM, christian viladrich wrote:
Years ago, when professionals used large Schmidt telescopes with large photographic glass plates, they change the polar elevation of the mount according the photographic field in order to minimize field rotation.
TSX with tPoint gives you a choice of places to point for polar alignment based on what kind of drift/rotation you want to minimize.  Below is the last polar alignment I ran with it.  The little table gave different adjustments (in arc seconds) to make for different purposes.

My answer is guiding.  :) 

Linwood



Re: Field Rotation

christian viladrich
 

Hello,

Years ago, when professionals used large Schmidt telescopes with large photographic glass plates, they change the polar elevation of the mount according the photographic field in order to minimize field rotation.

I think I have the calculation somewhere in a book. But not sure this is relevant now, even for 24x36 mm CCD sensor and 30 min integration time😉

Christian Viladrich


Le 28/05/2022 à 16:57, M Hambrick a écrit :

Am I correct in my thinking that field rotation is inevitable even on a perfectly polar aligned mount ? I seem to recall reading that somewhere on this forum.

Regardless, are there techniques besides good polar alignment that will minimize the amount of field rotation that occurs during a long series of guided exposures ? A couple possible things come to mind: 

  • Guide star selection (farther away from the axis of rotation)
  • Multiple star guiding
  • Having a mount with absolute encoders.
Mike


Re: APCC Pro model details #APCC

Ray Gralak
 

Hi Brent,

I have a few questions so that I may better understand your points.

* Of course the polar axis values to refine polar alignment
APCC already provides these values, so I assume you meant the conversion of the polar axis values to knob turns for the specific mount? Many other polar alignment alternatives provide faster polar alignment, so what advantage do you see in having APCC do this?

* Cone error if trying to reduce that.
Why is this important if modeling accounts for this? Do you just want a tool to measure this?

* Flexure - for troubleshooting excess flexure
I don't think there are enough samples to make a good determination of "excess flexure." There are many types of telescopes. The OTA's material, construction, diameter, and length all matter. Also affecting flexure are things like the OTA balance point, length of the OTA, the mounting plate strength, the weight of cameras, etc. There are many variables so trying to come up with a value for excess flexure for all of the variables would be difficult.

The model compensates for those items but reducing them, relying less on the model compensation seems better.
It may seem better, but these are not where you will see much gain. A more meaningful area to look into is the amount of randomness in the system. Any of the pointing terms can have a low average value but higher variance. APPM provides a way to look into this with the "5x Verify" option. APPM will run the same set of data points five times. Then, A-P staff (or I) can analyze the APPM logs for variances.

-Ray


Re: Field Rotation

M Hambrick
 

Thanks for the comments Roland and Howard.

What do you think I am seeing when the position of my images is shifting over an extended period ? Friday night I was taking images of M51 over a period of about 5 hours. I took the first image at about 10:30 pm when it was .just on the west side of the meridian. The last image was at 3:30 am. I plate solved the first and last images and measured the difference in the coordinates at the center of the two images.

The RA had shifted 7.91" and the Dec had shifted 25.5"

Can this be explained by atmospheric refraction ?

Mike


Re: APCC Pro model details #APCC

Brent Boshart
 

Some measures presented to the user would be useful:
  • Of course the polar axis values to refine polar alignment
  • Cone error if trying to reduce that.
  • Flexure - for troubleshooting excess flexure
The model compensates for those items but reducing them, relying less on the model compensation seems better.

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