Date   

Re: Adjust CP4 Clock Frequency

Craig Young
 

The ATrack design is very similar to DONUTS, introduced in 2013: https://www.jstor.org/stable/10.1086/670940?seq=1#metadata_info_tab_contents

For high precision photometry it is very important that the image remain centered on the same pixel over the cadence run of several hours.  Dithering is not used.  Given that there can be random drift corrections during the run, the accumulated error can move the target off a pixel, which is why careful re-centering is required in addition to drift correction.

I will find a more precise method for measuring the actual sidereal tracking rate of the mount instead of using a piece of tape, which is not precise enough to yield the metric needed to correct it.  I still don't see why reporting the pulse count from the encoder is proprietary.  I can see "what you do with the pulses in an algorithm" would be proprietary but I don't see why reporting the pulse count is proprietary.  I will find another way then.

Craig


Re: Adjust CP4 Clock Frequency

Roland Christen
 


Craig's posts bring up significant points that are quite relevant and should be considered seriously.
Which points did he bring up that are significant to you.? You realize that tracking to sub-arc sec levels is quite possible and has been possible for many years. In your opinion, what are we missing?

Roland


-----Original Message-----
From: Steven Steven <steven447@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Wed, May 6, 2020 3:53 pm
Subject: Re: [ap-gto] Adjust CP4 Clock Frequency

Ray, 
Many AP clients doing photometry REQUIRE that kind of 1 arc-sec precision and it seems achievable with the right approach. A number of us would like to know more about how to achieve it. Dithering is not an option in photometry. Craig's posts bring up significant points that are quite relevant and should be considered seriously.

Steve


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Ray Gralak <groups3@...>
Sent: Wednesday, 6 May 2020 10:50 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Adjust CP4 Clock Frequency
 
Hi Craig,

> So if I understand correctly, using your scope, unguided, and with APCC corrective tracking, you can plate solve
> your first image, three hours later plate solve your last image and the difference in plate solutions is less than 1
> arc-sec?

No, I'm not saying that at all, although I'm sure under some conditions that would be possible.

What I'm saying is most people would not want to do that. Most want to randomly dither the telescope position between images to average out differences in pixel sensitivity and noise when stacking images. Dithering obviously will change the image center between images.  And cases where low pixel resolution (e.g. camera lens) dithering can be used to increase effective detail in an image.

So acceptable unguided performance is needed only for the duration of the longest exposure. There's little advantage for tracking to be better than that, but it's great that you are able to do that via a closed loop process.

Anyway, hopefully you can try Roland's test so you can validate your mount's sidereal tracking rate.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3:  https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

> -----Original Message-----
> From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Craig Young
> Sent: Wednesday, May 6, 2020 7:02 AM
> To: main@ap-gto.groups.io
> Subject: Re: [ap-gto] Adjust CP4 Clock Frequency
>
> Ray,
> So if I understand correctly, using your scope, unguided, and with APCC corrective tracking, you can plate solve
> your first image, three hours later plate solve your last image and the difference in plate solutions is less than 1
> arc-sec?
>
> Craig
>





Re: Adjust CP4 Clock Frequency

Steven
 

Ray, 
Many AP clients doing photometry REQUIRE that kind of 1 arc-sec precision and it seems achievable with the right approach. A number of us would like to know more about how to achieve it. Dithering is not an option in photometry. Craig's posts bring up significant points that are quite relevant and should be considered seriously.

Steve


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Ray Gralak <groups3@...>
Sent: Wednesday, 6 May 2020 10:50 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Adjust CP4 Clock Frequency
 
Hi Craig,

> So if I understand correctly, using your scope, unguided, and with APCC corrective tracking, you can plate solve
> your first image, three hours later plate solve your last image and the difference in plate solutions is less than 1
> arc-sec?

No, I'm not saying that at all, although I'm sure under some conditions that would be possible.

What I'm saying is most people would not want to do that. Most want to randomly dither the telescope position between images to average out differences in pixel sensitivity and noise when stacking images. Dithering obviously will change the image center between images.  And cases where low pixel resolution (e.g. camera lens) dithering can be used to increase effective detail in an image.

So acceptable unguided performance is needed only for the duration of the longest exposure. There's little advantage for tracking to be better than that, but it's great that you are able to do that via a closed loop process.

Anyway, hopefully you can try Roland's test so you can validate your mount's sidereal tracking rate.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3:  https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

> -----Original Message-----
> From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Craig Young
> Sent: Wednesday, May 6, 2020 7:02 AM
> To: main@ap-gto.groups.io
> Subject: Re: [ap-gto] Adjust CP4 Clock Frequency
>
> Ray,
> So if I understand correctly, using your scope, unguided, and with APCC corrective tracking, you can plate solve
> your first image, three hours later plate solve your last image and the difference in plate solutions is less than 1
> arc-sec?
>
> Craig
>





Re: Mount recommendation for TEC 180FL with FLI 16803 + FW #Mach2GTO

Michael Hambrick <mike.hambrick@...>
 

I use an 1100 mount with my Astro-Physics 180 EDT and SBIG STXL16200. The 1100 handles this setup without any problems. Here is a photo:




Best Regards

Michael Hambrick
ARLANXEO
TSR Global Manufacturing Support
PO Box 2000
Orange, TX 77631-2000
Phone: +1 (409) 882-2799
email: mike.hambrick@...


Re: Mount recommendation for TEC 180FL with FLI 16803 + FW #Mach2GTO

dvjbaja
 

It's all about the moment arm.  Long tube, weight on each end.  The Mach 2 will support the weight. But it may have the Jello effect because of the long moment arm.  



Sent via the Samsung Galaxy Note9, an AT&T 5G Evolution capable smartphone


-------- Original message --------
From: Shailesh Trivedi <strivedi@...>
Date: 5/6/20 11:44 AM (GMT-08:00)
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Mount recommendation for TEC 180FL with FLI 16803 + FW #Mach2GTO

Hi Stuart,

If I absolutely need the 1600 then that may be an option. Alternately I do have a Paramount MX (legacy) with a 90 lb payload  capacity which may or may not suffice. The TEC 180 spec says 37lbs and 44 inches lenght retracted; so by the time I add the FLI camera + FW it adds another 15lbs and focusing will add another 4-5 inches to the length easily.

That said, I am eagerly awaiting the Mach2 notification since its size/weight/encoders for the price are all quite alluring and is the closest I will get to a portable setup. As we get older, our definition of portable changes. Though for me the TEC 180 FL will be far from portable (to some it is easy).

Shailesh


Re: Mount recommendation for TEC 180FL with FLI 16803 + FW #Mach2GTO

Shailesh Trivedi
 

Hi Stuart,

If I absolutely need the 1600 then that may be an option. Alternately I do have a Paramount MX (legacy) with a 90 lb payload  capacity which may or may not suffice. The TEC 180 spec says 37lbs and 44 inches lenght retracted; so by the time I add the FLI camera + FW it adds another 15lbs and focusing will add another 4-5 inches to the length easily.

That said, I am eagerly awaiting the Mach2 notification since its size/weight/encoders for the price are all quite alluring and is the closest I will get to a portable setup. As we get older, our definition of portable changes. Though for me the TEC 180 FL will be far from portable (to some it is easy).

Shailesh


Re: Mount recommendation for TEC 180FL with FLI 16803 + FW #Mach2GTO

Stuart <stuart.j.heggie@...>
 

Is the 1600 out of reach financially? That is a big, long scope. So weight isn't the only issue.


On Wed, 6 May 2020 at 14:27, Shailesh Trivedi <strivedi@...> wrote:
Hello All,

I have two AP refractors (130GTX and Stowaway). I am also on the April 2019 list for the Mach2 GTO and on waitlist for a TEC 180FL.

I use either a SBIG ST8300M + FW or Proline FLI 16803 (heavier).

My question: I am quite sure that the Mach2 GTO will not be able to handle a TEC 180 + FLI image train from weight & length standpoint.

For such a load, are we talking AP1200 or will a AP1100 do?

Thanks in advance for your advice.

Shailesh


--

Stuart
http://www.astrofoto.ca/stuartheggie/


Mount recommendation for TEC 180FL with FLI 16803 + FW #Mach2GTO

Shailesh Trivedi
 

Hello All,

I have two AP refractors (130GTX and Stowaway). I am also on the April 2019 list for the Mach2 GTO and on waitlist for a TEC 180FL.

I use either a SBIG ST8300M + FW or Proline FLI 16803 (heavier).

My question: I am quite sure that the Mach2 GTO will not be able to handle a TEC 180 + FLI image train from weight & length standpoint.

For such a load, are we talking AP1200 or will a AP1100 do?

Thanks in advance for your advice.

Shailesh


Re: Mach2 User Manual

Karen Christen
 

Hello David,

We have not released the Mach2GTO manual yet because it’s not finalized.  The first Mach2 owners all have a draft copy and are providing us with feedback regarding accuracy, completeness, and usability.  We really appreciate their help!  

Karen Christen

AP

 

From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Masera, David
Sent: Wednesday, May 6, 2020 8:38 AM
To: main@ap-gto.groups.io
Subject: [ap-gto] Mach2 User Manual

 

Hi AP,

I am fortunate to be in the current group to receive a Mach2 GTO mount in the next couple of months.  I was wondering if AP would post the user manual on their website for download.  I am new to the automated mount world and would like to learn as much as I can before the mount arrives.  It will be a steep learning curve so any help will be appreciated.  Thanks for all that your team does and stay safe. 

David Masera


--
Karen Christen
Astro-Physics


Re: Mach2 User Manual

Dean Jacobsen
 

I have been waiting for the public release version as well.

David, I was looking through the APCC Pro software manual this morning.  It does reference the GTOCP5 controller which is unique to the Mach2 so at least you can familiarize yourself with the software manual in the interim.  It document is on the Order and Download page.
--
Dean Jacobsen
http://astrophoto.net/wp/ 
Image Gallery - http://astrophoto.net/wp/image-gallery/
Astrobin - https://www.astrobin.com/users/deanjacobsen/ 


Mach2 User Manual

Masera, David
 

Hi AP,

I am fortunate to be in the current group to receive a Mach2 GTO mount in the next couple of months.  I was wondering if AP would post the user manual on their website for download.  I am new to the automated mount world and would like to learn as much as I can before the mount arrives.  It will be a steep learning curve so any help will be appreciated.  Thanks for all that your team does and stay safe. 

David Masera


Re: Adjust CP4 Clock Frequency

Ray Gralak
 

Hi Craig,

So if I understand correctly, using your scope, unguided, and with APCC corrective tracking, you can plate solve
your first image, three hours later plate solve your last image and the difference in plate solutions is less than 1
arc-sec?
No, I'm not saying that at all, although I'm sure under some conditions that would be possible.

What I'm saying is most people would not want to do that. Most want to randomly dither the telescope position between images to average out differences in pixel sensitivity and noise when stacking images. Dithering obviously will change the image center between images. And cases where low pixel resolution (e.g. camera lens) dithering can be used to increase effective detail in an image.

So acceptable unguided performance is needed only for the duration of the longest exposure. There's little advantage for tracking to be better than that, but it's great that you are able to do that via a closed loop process.

Anyway, hopefully you can try Roland's test so you can validate your mount's sidereal tracking rate.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Craig Young
Sent: Wednesday, May 6, 2020 7:02 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Adjust CP4 Clock Frequency

Ray,
So if I understand correctly, using your scope, unguided, and with APCC corrective tracking, you can plate solve
your first image, three hours later plate solve your last image and the difference in plate solutions is less than 1
arc-sec?

Craig


Re: Adjust CP4 Clock Frequency

Roland Christen
 


I do agree with you that errors in polar alignment, tube flexure, mirror shift, cables, etc can all contribute to factors that will reduce the effectiveness of using APCC for long duration unguided imaging on larger SCTs.
Right now I want to focus on whether or not the basic tracking rate of the mount is correct or not. You claim that the mount tracking rate is wrong by 0.1%, so that's what I'm trying to clear up. Everything else is peripheral right now.

Roland Christen


-----Original Message-----
From: Craig Young <craig.young.m8@...>
To: main@ap-gto.groups.io
Sent: Tue, May 5, 2020 9:31 pm
Subject: Re: [ap-gto] Adjust CP4 Clock Frequency

Roland,
I do agree with you that errors in polar alignment, tube flexure, mirror shift, cables, etc can all contribute to factors that will reduce the effectiveness of using APCC for long duration unguided imaging on larger SCTs.  I have seen this also on Parmount mounts where ATrack is used to correct tracking over long periods of time, so it is not just an AP problem.  ATrack doesn't really care if the sidereal tracking rate is wrong or polar alignment or any other problem with the system, it is similar to using an autoguider which also corrects tracking, but in a different way.  So there is no real need to try and diagnose the system when it is not really needed.

It is best to simply accept the limitations of the system, which includes the mount, the optical train, the pier and foundation, sky conditions, etc and just plan to use an autoguider or a program like ATrack.

Craig


Re: Adjust CP4 Clock Frequency

Craig Young
 

Ray,
So if I understand correctly, using your scope, unguided, and with APCC corrective tracking, you can plate solve your first image, three hours later plate solve your last image and the difference in plate solutions is less than 1 arc-sec?

Craig


Re: Adjust CP4 Clock Frequency

Ray Gralak
 

On the other hand, if you are working on improvements to an unguided solution and need a test site I would be
glad to help. ATrack is both a correction tool but also an analysis tool. Because it gives you the exact tracking
rates required for unguided imaging, you can compare the values with a modeled approach and see where the
problems are. The goal of the model should be to provide tracking as good as ATrack or an autoguider.
But why? Using APCC Pro's modeling I have had no problem doing 20-30 minute images unguided at 1.74 arc-sec/pixel with round stars. I've posted maybe about a dozen here before. A number of users have also done unguided images.

Some scopes need closed loop guiding because they are hard to model. I think yours is one of them.

Even the concept of using drift to set the tracking rate was done long ago. My own PulseGuide did something similar over 15 years ago. You would center a star, start a timer and let the star drift. The user would re-center the star and click another button andPulseguide would set the tracking rate in both declination and right ascension. It could be used for any object too, like comets.

And what might be even more crazy is that PulseGuide could do this *before* custom tracking rates could be set in the AP control boxes. It did this by sending evenly spaced, well-timed guider pulses, thus its name, "PulseGuide". You can still download it from here: https://www.pulseguide.com.

And it's not like I don't have experience with lots of telescopes, from refractors, SCTs, MakCass's, Newts, RC's, etc. I've experience with scopes with serious flexure issues that can make dramatic changes in focus as temperature swings, like my old18-inch Newt on a 1200GTO circa 2003 (and a younger me! :-)

https://raygralak.smugmug.com/Astronomy/18-CPT/

For now, APCC hasn't been able to do miracles with your particular truss tube scope so it's necessary for you to do closed loop autoguiding. For people with solid, repeatably pointing scopes APCC Pro's tracking rate correction already sets the tracking rate well enough to do unguided imaging, and even to dither without having to do plate solves. :-)

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Craig Young
Sent: Tuesday, May 5, 2020 7:49 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Adjust CP4 Clock Frequency

Ray,
No problem, let me know if you want to discuss further offline.

But as I said above, it is not really necessary because ATrack provides excellent tracking with whatever condition
the scope/mount are in. APCC tracking is not that robust, it blindly sets the tracking rate, based on a model, with
no feedback. Given any factors not accounted for accurately in the model you should not expect a perfect
tracking solution. Both ATrack and autoguiders use feedback to correct tracking rates. So rather than try to
research the source of the tracking error it is a lot simpler to let ATrack or an autoguider correct for it and not use
a tracking model.

On the other hand, if you are working on improvements to an unguided solution and need a test site I would be
glad to help. ATrack is both a correction tool but also an analysis tool. Because it gives you the exact tracking
rates required for unguided imaging, you can compare the values with a modeled approach and see where the
problems are. The goal of the model should be to provide tracking as good as ATrack or an autoguider. The
problem with an autoguider is it doesn't tell you what the tracking rates should be .. ATrack provides that.

But hopefully a model solution will be coming, and from what I have heard over the last year, it might be coming
from AP. Looking forward to it.

Craig


Re: need learning aids for astrophoto

 

>>> Some of the newer DSLRs have very low noise.  Read up on the new Canon Ra, about which Sky& Telescope and Astronomy are raving.  That said, the cooling available in many astro cameras is an advantage.

The Canon RA is $2500

you could get a very nice cooled astronomy camera for that price. shoot, you could get a very nice cooled astronomy camera for less than 1/2 that price

it's a nice camera for sure. I think it's more geared for casual astronomy users who also want to shoot terrestrial and maybe already own some canon glass. If i were starting from scratch and focused on astronomy, i don't think this direction would be my first choice.

Brian

On Tue, May 5, 2020 at 8:24 PM Worsel via groups.io <bryancashion=yahoo.com@groups.io> wrote:
I agree with Mike that a DSLR is a good option to consider.  I would offer a different take on the following.

2. IMO a DSLR is a good choice if you're just starting out. But I think buying a cooled CMOS astronomy camera is a better choice if your budget allows. Consider:

A) A CMOS camera is powered from the USB (usually USB 3.0) cable, not from an internal battery that might not last through an imaging session.

I power my DSLRs with the AC adapter, not a battery.  This works in an observatory, off 120VAC (mains) or the field, if you have a large capacity (amp-hours) battery and inverter

B) A cooled CMOS camera has lower noise than an uncooled DSLR.

Some of the newer DSLRs have very low noise.  Read up on the new Canon Ra, about which Sky& Telescope and Astronomy are raving.  That said, the cooling available in many astro cameras is an advantage.

C) ZWO offers an off-axis guider (OAG) that mounts in between the OTA and the imaging camera. A small lightweight (and inexpensive) camera screws into this OAG. You can easily add autoguiding without needing a separate guide scope and camera. (I use a separate guider for specific reasons related to my imaging goals.)

I image with an Astrodon MOAG, which sits between the camera and the scope, and a DSLR.


Bryan



--
Brian 



Brian Valente


Re: need learning aids for astrophoto

Worsel
 

I agree with Mike that a DSLR is a good option to consider.  I would offer a different take on the following.

2. IMO a DSLR is a good choice if you're just starting out. But I think buying a cooled CMOS astronomy camera is a better choice if your budget allows. Consider:

A) A CMOS camera is powered from the USB (usually USB 3.0) cable, not from an internal battery that might not last through an imaging session.

I power my DSLRs with the AC adapter, not a battery.  This works in an observatory, off 120VAC (mains) or the field, if you have a large capacity (amp-hours) battery and inverter

B) A cooled CMOS camera has lower noise than an uncooled DSLR.

Some of the newer DSLRs have very low noise.  Read up on the new Canon Ra, about which Sky& Telescope and Astronomy are raving.  That said, the cooling available in many astro cameras is an advantage.

C) ZWO offers an off-axis guider (OAG) that mounts in between the OTA and the imaging camera. A small lightweight (and inexpensive) camera screws into this OAG. You can easily add autoguiding without needing a separate guide scope and camera. (I use a separate guider for specific reasons related to my imaging goals.)

I image with an Astrodon MOAG, which sits between the camera and the scope, and a DSLR.


Bryan


Re: Adjust CP4 Clock Frequency

Craig Young
 

Ray,
No problem, let me know if you want to discuss further offline.

But as I said above, it is not really necessary because ATrack provides excellent tracking with whatever condition the scope/mount are in.  APCC tracking is not that robust, it blindly sets the tracking rate, based on a model, with no feedback.  Given any factors not accounted for accurately in the model you should not expect a perfect tracking solution.  Both ATrack and autoguiders use feedback to correct tracking rates.  So rather than try to research the source of the tracking error it is a lot simpler to let ATrack or an autoguider correct for it and not use a tracking model.

On the other hand, if you are working on improvements to an unguided solution and need a test site I would be glad to help.  ATrack is both a correction tool but also an analysis tool.  Because it gives you the exact tracking rates required for unguided imaging, you can compare the values with a modeled approach and see where the problems are.  The goal of the model should be to provide tracking as good as ATrack or an autoguider.  The problem with an autoguider is it doesn't tell you what the tracking rates should be .. ATrack provides that.

But hopefully a model solution will be coming, and from what I have heard over the last year, it might be coming from AP.  Looking forward to it.

Craig


Re: Adjust CP4 Clock Frequency

Ray Gralak
 

Craig,

So Atrack is essentially an autoguiding program. It's been done before in many different ways. Closed loop guiding is usually more accurate, so nothing new here. Wait for machine learning though and you will see improvements without closed loop responses.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Craig Young
Sent: Tuesday, May 5, 2020 7:31 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Adjust CP4 Clock Frequency

Roland,
I do agree with you that errors in polar alignment, tube flexure, mirror shift, cables, etc can all contribute to factors
that will reduce the effectiveness of using APCC for long duration unguided imaging on larger SCTs. I have seen
this also on Parmount mounts where ATrack is used to correct tracking over long periods of time, so it is not just
an AP problem. ATrack doesn't really care if the sidereal tracking rate is wrong or polar alignment or any other
problem with the system, it is similar to using an autoguider which also corrects tracking, but in a different way. So
there is no real need to try and diagnose the system when it is not really needed.

It is best to simply accept the limitations of the system, which includes the mount, the optical train, the pier and
foundation, sky conditions, etc and just plan to use an autoguider or a program like ATrack.

Craig


Re: Adjust CP4 Clock Frequency

Ray Gralak
 

Craig,

Nothing indicates an error in mount clock rate.

As I said before the tracking rate errors you are seeing in the APCC version you are using are almost certainly caused by unmodeled pointing errors in your truss tube OTA. There is a solution coming using a combination of temperature modeled pointing terms and machine learning.

No matter what the temperature is .. a warm summer night or a cold winter night .. the tracking
corrections are always the same.
Refraction and flexure changes caused by temperature don't affect tracking? I suppose your focus never shifts either with temperature?

Why don't we take this offline?

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver


-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Craig Young
Sent: Tuesday, May 5, 2020 7:08 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Adjust CP4 Clock Frequency

ATrack monitors a science images folder for new images recorded by the camera. New images are added by
Voyager/MaximDL. When a new image is detected ATrack does a plate solve and measure both drift (difference
between last image and this image) and shift (difference between a reference position or image and this image).
The drift is then used to adjust the tracking rate, the shift is used to temporarily change the motor speed for a
period of time to recenter the next image. Through an observing run of several hours ATrack will change the
tracking rate (RA, DEC) to minimize the drift rate and keep the image centered. It does this very accurately.
ATrack does not care what the cause of the drift, it simply measures it and readjusts the motor speeds to cancel it.
Through the night the changes are very small and consistent .. there is no wild jumps. It is also very repeatable,
from night to night. No matter what the temperature is .. a warm summer night or a cold winter night .. the tracking
corrections are always the same.

Now, if I turn off tracking correction on ATrack and turn on tracking correction in APCC then the stars drift away
very quickly .. pixels per minute .. about 1 arc sec a minute. This happens whether I use a 25 point model or a 200
point model. When I compare the correction rates in APCC with ATrack I see the same difference no matter
where I am pointed. East side or West side. The mount is always tracking in RA too fast and has to be slowed
down. This is consistent with ATrack which always shows the mount tracking too fast and it uses correction
values that are negative .. in other words, it tries to slow down the sidereal tracking rate.

The fact that DEC is similar would seem to indicate there is a base constant in the motor speeds that is incorrect.
DEC is always a positive number in the range 0.02000 to 0.01200 arcsec/sec and is the same in both East and
West sides.

Craig

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