----- Original Message -----
From: "Larry Phillips" <llp41astro@cox.net>
To: <ap-gto@yahoogroups.com>
Sent: Sunday, April 27, 2008 5:42 PM
Subject: [ap-gto] Re: Focuser Backlash

Everything is working fine. After getting a series of profiles I
thought maybe I could improve things. I did not know you could
correct backlash with the software. My original question was making
a correction mechanically to the focuser. I will give your
suggestions a try.

Larry

--- In ap-gto@yahoogroups.com, "JoeMize" <jmize@...> wrote:

Larry, you can adjust your Backlash in either FMx itself or in FT's

Driver

ASCOM window. L.Webber says not to use both. Go into FMx's System

tab,

there you'll see FMx's Backlash settings. Click on Settings to

have the

ASCOM window displayed. On my AP155 using the FTF-3545 w/FT's

Digital

MicroFocuser motor I have 'both' set to Zero. Great combination.

BTW,

there's a FMx Yahoo group,

http://tech.groups.yahoo.com/group/FMaxUG/ ...joe

:)

PS: You didn't mention if you're experiencing any other problems.

Just in

case, be sure your focuser Locking knob is completely loose. The

FT Motor

holds my STL11K, A-P Field Flattener and adapters without trouble.

"May You Go Among The Imperishable Stars"
Joe Mize www.cav-sfo.com
Chiefland Astronomy Village, Fla.

----- Original Message -----
From: "Larry Phillips" <llp41astro@...>
To: <ap-gto@yahoogroups.com>
Sent: Sunday, April 27, 2008 11:40 AM
Subject: [ap-gto] Focuser Backlash

After using FocusMax with my new AP 140 4" focuser using a

FeatherTouch

motor, I am wondering if there is anyway to adjuct the focuser

backlash.

Larry


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----- Original Message -----
From: "Richard Seavey" <reseavey@verizon.net>
To: <ap-gto@yahoogroups.com>
Sent: Sunday, April 27, 2008 4:03 PM
Subject: Re: [ap-gto] Re: DEC Backlash and RA "Drift" on AP1200GTO

Joe
In paragraph 1), Roland is saying that he does a calibration at the
equator, and uses it for all other declinations. That might work OK
depending on what is causing the errors in RA to occur, but if the errors
are from something like a gust of wind, then it could take a lot of guide
cycles to correct that error. I think that correcting the RA guide speed
for declination is a better approach and is what I do. I'm sure that
Roland's technique works well if used for correcting such things as worm
periodic error.

In paragraph 2), it seems to say that one has to calibrate the guider with
the binning set to 1x1. I don't believe that is true. Maxim adjusts the
guide speed depending on how the guide chip binning is set. The confusion
might be that in the "tutorial" section of the MaxIm manual, it says to set
the binning to 1x1. I think that was just for the tutorial and not a
general statement. The detailed information in chapter 6 of the manual says
nothing about using 1x1 for calibration. Just my 2 cents.

Richard



At 02:14 AM 4/27/2008 -0400, you wrote:

Jim & Richard, I saved a post from Roland back on 02-19 in "Re: [ap-gto]
Guide star drifting in RA" thread.

At the time it made since but reading it now it's a little convoluted
without knowing went on beforehand. The important two things I saved it for
was what Roland said,

1) In his first paragraph he said don't use the Guider Tab's DEC Co-ordinate
box. I do this myself. If you're unfamiliar with this technique I'll 'try'
to explain. Set the DEC box to '0' and Uncheck the "Use Scope DEC" in the
Guider dropdown list. Then calibrate my Guider on the Equator near the
Meridian where the sky moves its fastest. The further away form the Equator
you are guiding the slower the sky moves and the smaller the deviations.
With the Calibration on the Equator the numbers generated are sufficient to
correct those larger deviations yet when deviations occur further away from
the Equator the same numbers are used to make smaller corrections. (hope
you get jist of what I'm trying to say) My Calibration lasts as long as I
don't make changes to my imaging train. The last time I Calibrated my
Guider was months ago. This method works even if you're not permanently
mounted, works great. My RMS' are usually in the lower 0.0xx's. You should
be able to do so too.

2) I believe what Roland says in his second paragraph: "...(p.s. you didn't
bin the guider by any chance?)." means when you Calibrate your Guider you
need to do so in Bin-1 scale. MaximDL says the same thing and goes further
by saying to turn off Backlash in the Guider settings while Calibrating.

The following is Roland's response. I hope I interpreted correctly.
HTH...joe :)

===

I looked at Maxim and do not see what you are talking about on the uncheck
"use Scope Dec" Is this by chance the make simultaneous corrections?

No, It's under Options. If you have an older version of the software, there
is a place for you to enter the Dec co-ordinate. Always use zero here,
otherwise the software will reduce the correction level by the cosine of the
angle
that you enter, and this is not good.

If you look in your parameters, it should tell you what te pixel scale is,
and that should be somewhere close to what you calculate for your focal
length
and pixel size (p.s. you didn't bin the guider by any chance?). If it isn't,
then indeed the software will make smaller corrections than is needed to
bring
the star back to zero.

In order for you to guide successfully, you need to know what every number
means. If you do not, you will never be able to troubleshoot the guide loop,
and
certainly I cannot do it very well for you because I have no idea what is in
your various parameter windows.

Roland Christen
===

"May You Go Among The Imperishable Stars"
Joe Mize www.cav-sfo.com
Chiefland Astronomy Village, Fla.

----- Original Message -----
From: "Richard Seavey" <<mailto:reseavey%40verizon.net>reseavey@verizon.net>
To: <<mailto:ap-gto%40yahoogroups.com>ap-gto@yahoogroups.com>
Sent: Saturday, April 26, 2008 11:03 PM
Subject: Re: [ap-gto] Re: DEC Backlash and RA "Drift" on AP1200GTO

Hi Jim
Your rms guiding errors are quite similar to what I get. I image at 0.72
arc-sec per pixel, so on nights when the seeing is 2.5 arc-sec or better,
I
need to keep the errors below about 0.3 arc-sec rms. Even more important
is
to get the same error in both axis so that the stars aren't elongated. For
me, oval stars are a lot more annoying than slightly bigger stars. I am
using MaxIm to control the guiding and usually turn on the feature that
plots the guiding errors in real time. I know I have backlash in the DEC
axis, but need to measure it again so I can compare it to what you are
getting. My sub exposures are 10 minutes and guide exposures are usually
between 2 and 6 seconds. I have been using 3 pixels of dither and my max
move is 0.13 sec. It would be very interesting to see what others are
getting for guiding errors.

Richard


At 03:06 AM 4/26/2008 +0000, you wrote:

Hi Richard,

It varies. And CCDSoft doesn't provide those numbers in a convenient
fashion, so I have to go through each 8min exposure to mine them.

Here are a couple of samples from last night. All are 8min imaging
exposures, with 4sec guide exposures. The numbers are in arc-seconds:

1. RAmax = 0.824, RArms = 0.252, DECmax = 0.705, DECrms = 0.303
2. RAmax = 1.337, RArms = 0.323, DECmax = 1.054, DECrms = 0.329
3. RAmax = 1.970, RArms = 0.666, DECmax = 1.967, DECrms = 0.524

These were: (1) the best image of the night (perhaps the best result
I've EVER seen at my site with my gear), (2) a more typical image of
the night, and (3) the worst image of the night, respectively. CCDI
says the FWHMs were 1.94", 3.07", and 4.25", for the actual images,
respectively.

To be fair, the seeing did seem to change over the course of the
night, starting and ending reasonably well but deteriorating for 45min
or so in the middle.

I'm not sure how representative the above numbers truly are. Most
times I bother to calculate out this stuff the DEC rms errors are
actually larger than the RA rms errors (and both are generally larger
than the numbers shown above) which suggests to me that DEC errors are
going uncorrected for one reason or another, and I personally believe
that reason to be DEC backlash.

This was also shooting M81, which is pretty far north, and so the
periodic error is only 1/3 what it would be at the equator, in terms
of "true sky angle".

Cheers,
JS

--- In

<mailto:ap-gto%40yahoogroups.com><mailto:ap-gto%40yahoogroups.com>ap-gto@yahoogroups.com,
Richard

Seavey <reseavey@...> wrote:

Jim
What are your typical peak and rms guide errors in DEC and RA when your
seeing is in the 2-3 arc-sec range?

Richard

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--- In ap-gto@yahoogroups.com, "Larry Phillips" <llp41astro@...> wrote:

Have you tried precise polar aligning using other methods besides
PAM? I have had mixed results using PAM, especially if you use the
entire process. I have better success if I only reiterate the
initial 3 exposure step. Try drift align or one of AP's alignment
methods to be sure it is the alignment scope and not the alignment
procedure. Just a thought. I am usually very close after a polar
scope alignment and need to make only small adjustments with a
precision alignment technique. I have a PASILL4 which I received in
March.

Larry

At 02:14 AM 4/27/2008 -0400, you wrote:

Jim & Richard, I saved a post from Roland back on 02-19 in "Re: [ap-gto]
Guide star drifting in RA" thread.

At the time it made since but reading it now it's a little convoluted
without knowing went on beforehand. The important two things I saved it for
was what Roland said,

1) In his first paragraph he said don't use the Guider Tab's DEC Co-ordinate
box. I do this myself. If you're unfamiliar with this technique I'll 'try'
to explain. Set the DEC box to '0' and Uncheck the "Use Scope DEC" in the
Guider dropdown list. Then calibrate my Guider on the Equator near the
Meridian where the sky moves its fastest. The further away form the Equator
you are guiding the slower the sky moves and the smaller the deviations.
With the Calibration on the Equator the numbers generated are sufficient to
correct those larger deviations yet when deviations occur further away from
the Equator the same numbers are used to make smaller corrections. (hope
you get jist of what I'm trying to say) My Calibration lasts as long as I
don't make changes to my imaging train. The last time I Calibrated my
Guider was months ago. This method works even if you're not permanently
mounted, works great. My RMS' are usually in the lower 0.0xx's. You should
be able to do so too.

2) I believe what Roland says in his second paragraph: "...(p.s. you didn't
bin the guider by any chance?)." means when you Calibrate your Guider you
need to do so in Bin-1 scale. MaximDL says the same thing and goes further
by saying to turn off Backlash in the Guider settings while Calibrating.

The following is Roland's response. I hope I interpreted correctly.
HTH...joe :)

===

I looked at Maxim and do not see what you are talking about on the uncheck
"use Scope Dec" Is this by chance the make simultaneous corrections?

No, It's under Options. If you have an older version of the software, there
is a place for you to enter the Dec co-ordinate. Always use zero here,
otherwise the software will reduce the correction level by the cosine of the
angle
that you enter, and this is not good.

If you look in your parameters, it should tell you what te pixel scale is,
and that should be somewhere close to what you calculate for your focal
length
and pixel size (p.s. you didn't bin the guider by any chance?). If it isn't,
then indeed the software will make smaller corrections than is needed to
bring
the star back to zero.

In order for you to guide successfully, you need to know what every number
means. If you do not, you will never be able to troubleshoot the guide loop,
and
certainly I cannot do it very well for you because I have no idea what is in
your various parameter windows.

Roland Christen
===

"May You Go Among The Imperishable Stars"
Joe Mize www.cav-sfo.com
Chiefland Astronomy Village, Fla.

----- Original Message -----
From: "Richard Seavey" <<mailto:reseavey%40verizon.net>reseavey@verizon.net>
To: <<mailto:ap-gto%40yahoogroups.com>ap-gto@yahoogroups.com>
Sent: Saturday, April 26, 2008 11:03 PM
Subject: Re: [ap-gto] Re: DEC Backlash and RA "Drift" on AP1200GTO

Hi Jim
Your rms guiding errors are quite similar to what I get. I image at 0.72
arc-sec per pixel, so on nights when the seeing is 2.5 arc-sec or better,
I
need to keep the errors below about 0.3 arc-sec rms. Even more important
is
to get the same error in both axis so that the stars aren't elongated. For
me, oval stars are a lot more annoying than slightly bigger stars. I am
using MaxIm to control the guiding and usually turn on the feature that
plots the guiding errors in real time. I know I have backlash in the DEC
axis, but need to measure it again so I can compare it to what you are
getting. My sub exposures are 10 minutes and guide exposures are usually
between 2 and 6 seconds. I have been using 3 pixels of dither and my max
move is 0.13 sec. It would be very interesting to see what others are
getting for guiding errors.

Richard


At 03:06 AM 4/26/2008 +0000, you wrote:

Hi Richard,

It varies. And CCDSoft doesn't provide those numbers in a convenient
fashion, so I have to go through each 8min exposure to mine them.

Here are a couple of samples from last night. All are 8min imaging
exposures, with 4sec guide exposures. The numbers are in arc-seconds:

1. RAmax = 0.824, RArms = 0.252, DECmax = 0.705, DECrms = 0.303
2. RAmax = 1.337, RArms = 0.323, DECmax = 1.054, DECrms = 0.329
3. RAmax = 1.970, RArms = 0.666, DECmax = 1.967, DECrms = 0.524

These were: (1) the best image of the night (perhaps the best result
I've EVER seen at my site with my gear), (2) a more typical image of
the night, and (3) the worst image of the night, respectively. CCDI
says the FWHMs were 1.94", 3.07", and 4.25", for the actual images,
respectively.

To be fair, the seeing did seem to change over the course of the
night, starting and ending reasonably well but deteriorating for 45min
or so in the middle.

I'm not sure how representative the above numbers truly are. Most
times I bother to calculate out this stuff the DEC rms errors are
actually larger than the RA rms errors (and both are generally larger
than the numbers shown above) which suggests to me that DEC errors are
going uncorrected for one reason or another, and I personally believe
that reason to be DEC backlash.

This was also shooting M81, which is pretty far north, and so the
periodic error is only 1/3 what it would be at the equator, in terms
of "true sky angle".

Cheers,
JS

--- In

<mailto:ap-gto%40yahoogroups.com><mailto:ap-gto%40yahoogroups.com>ap-gto@yahoogroups.com,
Richard

Seavey <reseavey@...> wrote:

Jim
What are your typical peak and rms guide errors in DEC and RA when your
seeing is in the 2-3 arc-sec range?

Richard

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

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

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Groups Links

----- Original Message -----
From: "Larry Phillips" <llp41astro@cox.net>
To: <ap-gto@yahoogroups.com>
Sent: Sunday, April 27, 2008 11:40 AM
Subject: [ap-gto] Focuser Backlash

After using FocusMax with my new AP 140 4" focuser using a FeatherTouch
motor, I am wondering if there is anyway to adjuct the focuser backlash.

Larry


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

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

At 03:06 AM 4/26/2008 +0000, you wrote:

Hi Richard,

It varies. And CCDSoft doesn't provide those numbers in a convenient
fashion, so I have to go through each 8min exposure to mine them.

Here are a couple of samples from last night. All are 8min imaging
exposures, with 4sec guide exposures. The numbers are in arc-seconds:

1. RAmax = 0.824, RArms = 0.252, DECmax = 0.705, DECrms = 0.303
2. RAmax = 1.337, RArms = 0.323, DECmax = 1.054, DECrms = 0.329
3. RAmax = 1.970, RArms = 0.666, DECmax = 1.967, DECrms = 0.524

These were: (1) the best image of the night (perhaps the best result
I've EVER seen at my site with my gear), (2) a more typical image of
the night, and (3) the worst image of the night, respectively. CCDI
says the FWHMs were 1.94", 3.07", and 4.25", for the actual images,
respectively.

To be fair, the seeing did seem to change over the course of the
night, starting and ending reasonably well but deteriorating for 45min
or so in the middle.

I'm not sure how representative the above numbers truly are. Most
times I bother to calculate out this stuff the DEC rms errors are
actually larger than the RA rms errors (and both are generally larger
than the numbers shown above) which suggests to me that DEC errors are
going uncorrected for one reason or another, and I personally believe
that reason to be DEC backlash.

This was also shooting M81, which is pretty far north, and so the
periodic error is only 1/3 what it would be at the equator, in terms
of "true sky angle".

Cheers,
JS

--- In <mailto:ap-gto%40yahoogroups.com>ap-gto@yahoogroups.com, Richard
Seavey <reseavey@...> wrote:

Jim
What are your typical peak and rms guide errors in DEC and RA when your
seeing is in the 2-3 arc-sec range?

Richard

----- Original Message -----
From: ayiomamitis
To: ap-gto@yahoogroups.com
Sent: Saturday, April 26, 2008 2:47 AM
Subject: [ap-gto] Re: DEC Backlash and RA "Drift" on AP1200GTO


--- In ap-gto@yahoogroups.com, "JoeMize" <jmize@...> wrote:
>
> Jim, change you Max Move from 0.2sec to 2.0sec. 0.2sec limits the
> correction to a Maximum drive time of 0.2sec. Changing to 2.0sec will allow
> you to correct longer excursions and Dither moves. I actually have mine set
> to 3.0sec because of the size of my Dither moves...joe :)

Aha! Now perhaps I see why the Dither plugin for CCDSoft was hanging on my machine. I
will go back and check but this time using a purposely much higher setting for MAX.

Thanks Joe!

Anthony.

>
>
> "May You Go Among The Imperishable Stars"
> Joe Mize www.cav-sfo.com
> Chiefland Astronomy Village, Fla.
>
> ----- Original Message -----
> From: "Jim S." <blues_rule_solomon_1999@...>
> To: <ap-gto@yahoogroups.com>
> Sent: Friday, April 25, 2008 3:53 PM
> Subject: [ap-gto] DEC Backlash and RA "Drift" on AP1200GTO
>
>
> > Hi,
> >
> > I've got some questions about getting the best possible guiding
> > results out of my AP1200. It's performing better than any mount I've
> > ever owned, by a mile, but there might be some room for me to improve
> > my results, which is the topic of this post.
> >
> > Dec Backlash:
> >
> > First, I've measured my DEC backlash at mean = 12.55", sigma = 3.59".
> > (See below for the method I'm using.) A friend and I removed the DEC
> > cover and one of the reduction gears, and could not "feel" any
> > backlash in the worm gear to worm wheel mesh. Rather, it looked to us
> > as if all or most of that backlash was in the mesh among the reduction
> > gears, in which we could indeed feel some slop.
> >
> > DEC Backlash is causing me some grief in guiding, as I can see the
> > tell-tale signs of the DEC axis "wandering between the rails" when
> > looking at the Autoguider.log file in CCDSoft, with the result that
> > DEC errors take many guide-exposure periods to correct. Sometimes it
> > takes CCD Commander a long time to "dither" because it has to unwind
> > the backlash, and sometimes it gives up because it takes too long to
> > reach my minimum-error threshold before kicking off an exposures. And
> > in so dithering in the DEC direction, it almost always overshoots.
> >
> > I'm using the "Roland-approved" guiding parameters: guide rate = 1x
> > Sidereal, min = 0.02s, max = 0.2s, backlash compensation = OFF, and
> > calibration time = 30s, guide exposures = 4s (sometimes longer), PEC =
> > ON, Aggressiveness = 8; and my polar alignment error is VERY small,
> > well less than an arc-minute according to PAM and verified with a
> > drift. The measured calibration speeds agree with the analytical
> > computed values to within tenths of a percent, so indeed the
> > calibration results are "correct".
> >
> > My question is thus: Is it possible on the AP1200 to adjust the
> > reduction-gear mesh to trim some of this backlash? If indeed the
> > "slop" is in the reduction gears, then I don't believe "intentional
> > DEC misbalance" will help as a "solution" to this problem, though
> > perhaps intentional polar misalignment -- to induce some drift in a
> > constant direction -- might help. I think this latter case, however,
> > is inevitable when atmospheric refraction and ANY polar alignment
> > error is taken into account. And there will be an inevitable
> > "reversal" when dithering.
> >
> > RA "Drift":
> >
> > My long-term RA "drift" has an odd shape that I can't quite explain,
> > and fitting a curve to that "drift" is imperative when using PEMPro to
> > dial in an optimal PE curve. I've uploaded a chart to my web site for
> > inspection:
> >
> > http://www.SaratogaSkies.com/tmp/ra-drift.gif
> >
> > The spot data is the instantaneous RA error (with PEC off) measured by
> > PEMPro. The solid line is a "curve fit" I've done which is simply a
> > moving average of the instantaneous errors, wherein the "window" of
> > that moving average is equal to the worm period (382.95 seconds).
> >
> > Can someone explain why the "RA drift" curve has the odd shape it
> > does? I would expect it to be roughly monotonically increasing or
> > decreasing, as polar misalignment and/or atmospheric refraction affect
> > the apparent RA of the star.
> >
> > Could this be the reduction gears at work? Or perhaps flexure/sagging
> > of the camera/focuser? I'm using a 6" refractor with the FT3545
> > focuser, and an all-threaded coupling between a ST-2000XM camera and
> > the focuser, and the data was collected at DEC=0 beginning JUST west
> > of the Meridian and running for roughly 8 worm periods.
> >
> > More importantly, is this indicative of any issue with the mount? Or
> > is it just a long-term, slowly varying "drift", that I shouldn't sweat
> > because it can be easily guided out?
> >
> > Backlash Measurement Method:
> >
> > For those interested, here's how I'm measuring DEC Backlash:
> >
> > 1. Preload the DEC gear by moving (at 1x Sidereal) in the Y+ direction
> > (I use the "move" buttons in PulseGuide for this).
> > 2. Do a calibration in CCDSoft of a specified calibration time.
> > 3. Derive DEC backlash from the measured Y+ and Y- speeds.
> >
> > Note: Y+ is the first direction that CCDSoft moves in DEC, and then it
> > moves the same amount in Y-.
> >
> > I then compute the DEC Backlash as follows:
> >
> > DEC backlash = (Y+ - Y-) * Tc * Res
> >
> > where:
> >
> > o Y+ and Y- are the speeds in pixels/second measured by CCDsoft (px/s)
> > o Tc is the calibration time in seconds (s)
> > o Res is the imaging scale produced by my scope/camera combination in
> > arc-seconds/pixel ("/s)
> >
> > Is this method valid? If not, why not?
> >
> > Thanks for any help/advice you folks might be able to offer.
> >
> > Cheers,
> > Jim S.
> >
> >
> > ------------------------------------
> >
> > To UNSUBSCRIBE, or for general information on the ap-gto list
> > see http://groups.yahoo.com/group/ap-gtoYahoo! Groups Links
> >
> >
> >
> >
>

--- In ap-gto@yahoogroups.com, Richard Seavey <reseavey@...> wrote:

Jim
What are your typical peak and rms guide errors in DEC and RA when your
seeing is in the 2-3 arc-sec range?

Richard