Re: Dec Arc APPM mode: any l best practices for field set up


Bill Long
 

Awesome! Can you share some of the FITS from the testing? 


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Howard Hedlund <howard@...>
Sent: Friday, October 1, 2021 10:17 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Dec Arc APPM mode: any l best practices for field set up
 
Hi Sébastien and group,

I am starting some serious testing on Ray's latest improvements to APCC's modeled pointing and tracking using our system in Chile.  This system is a 305mm f/8 Mak Cass on a 1600GTO AE.  With 2440 mm of focal length, this should provide enough challenge to give the improved modeling, and the Dec Arc Tracking a good evaluation.

I went ahead and made a huge mapping run in APPM - 487 points.  The mapping used Dec spacing of just 4° and RA spacing of 10° to provide full dec arc coverage over the entire sky.  The mapping also included a large number of CW-up points to add to the challenge.  The mapping run was unbelievable: 485 successful plate solutions out of 487 points, so I was really happy about that.  The entire run only took a few hours which is not a bad time investment for a permanent setup.

Preliminary tests using 10 min. unguided subs in several parts of the sky are yielding excellent results with flatness measurements below 0.1 and FWHM values that were as good as we ever get with guiding. 

Stay tuned!  If the weather and the wife cooperate, I'll be collecting more data over the next couple nights.

Mag. 7 or Better Skies!

Howard Hedlund
Astro-Physics, Inc.
AP Phone: 815-282-1513
Direct Phone:  815-315-7015
https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.astro-physics.com%2F&amp;data=04%7C01%7C%7C1d8edf759ae044aa83d908d984ff575a%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637687054484212064%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=H8u8uABiDA%2BAu%2BmpTewmU71%2FdXb6M8H50AFc627xIHw%3D&amp;reserved=0
Please include this e-mail with your response.

 Consider the environment before printing this e-mail.

-----Original Message-----
From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Ray Gralak
Sent: Friday, October 1, 2021 7:35
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Dec Arc APPM mode: any l best practices for field set up

Hi Sébastien,

Two rows of sky data points will work, but Howard's suggestion for three rows of sky data points will yield even better tracking rate accuracy for a target.

> but I would like a confirmation
> that both types of corrections are not conflicting with each other,
> meaning that it is the Dec Arc algorithm that is actually the one being used to compute the tracking corrections.

As Brian previously pointed out, you must enable tracking rate corrections to use Dec Arc tracking.

> Also, would you recommend to "Enable Pointing Correction" in such a
> case? Maybe since the model is generally rather small (< 50 pts) the pointing corrections would not be accurate enough across the sky ?

The problem is not the number of sky points, but the lack of distribution of data points across the sky. The all-sky model will be much more accurate if there is a wide distribution of sky data points.

> Would it harm to keep the pointing corrections enabled anyway in case
> I would like to switch target in the same declination range for example ? What about a target outside of the "dec arc model" range?

There is no definitive answer for this, as it depends on the setup as a whole. But usually, pointing will not be as good outside of the narrow range of sky points that were collected. However, that shouldn't be a problem as many of the imaging programs have a "plate solve and re-center" feature.

-Ray



> -----Original Message-----
> From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf
> Of Seb@stro
> Sent: Thursday, September 30, 2021 1:21 PM
> To: main@ap-gto.groups.io
> Subject: Re: [ap-gto] Dec Arc APPM mode: any l best practices for
> field set up
>
> Hello Howard,
>
> I'm also trying to learn the ropes of the new Dec Arc Tracking feature
> for portable use (with a new model each night). Please keep in mind
> I'm totally new at modeling in general. At this point, I believe I
> have quite managed to understand the global idea from the a little
> experimentation (did a complete Dec Arc mapping run successfully), reading the manual and some recent posts but I'm still left with the following questions about the pointing model tab in APCC.
>
> My general understanding is that the tracking corrections will use the
> "all-sky algorithm" to compute the correction terms from the mapped
> points unless the Dec Arc Tracking is also enabled in which case
> another algorithm (taking also other variables into account) to compute more accurately the correction terms for the current declination arc. Am I getting this right ?
>
>
>
> If so, I was wondering if I should ONLY tick the "Enable Dec Arc
> Tracking" checkbox or if I do also need to tick the "Enable Tracking
> Correction" box for the Dec Arc tracking corrections to be actually
> sent to the mount ? It seems the latter is required from what I see in
> the Tracking Status window, but I would like a confirmation that both types of corrections are not conflicting with each other, meaning that it is the Dec Arc algorithm that is actually the one being used to compute the tracking corrections.
>
> Also, would you recommend to "Enable Pointing Correction" in such a
> case? Maybe since the model is generally rather small (< 50 pts) the pointing corrections would not be accurate enough across the sky ?
> Would it harm to keep the pointing corrections enabled anyway in case
> I would like to switch target in the same declination range for example ? What about a target outside of the "dec arc model" range?
>
>
> Thanks for your time,
>
> Sébastien
>
>
>
> ________________________________
>
> De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de
> Howard Hedlund <howard@astro- physics.com> Envoyé : 30 septembre 2021
> 12:50 À : main@ap-gto.groups.io <main@ap-gto.groups.io> Objet : Re:
> [ap-gto] Dec Arc APPM mode: any l best practices for field set up
>
>
> Hi Andrea, for portable setups, the APCC Dec Arc feature is amazing!  It is perfect for your situation.
>
>
>
> I would definitely run 3 arcs if you can spare the time – one right on
> the target declination, and two more – one a couple degrees north, and the other a couple degrees south of your target dec.
>
>
>
> As for the RA density, I would experiment a little.  You presently do
> 2 arcs each with 10 or so points giving 20 total.  3 arcs totaling between 25 and 30 should rock!
>
>
>
> Mag. 7 or Better Skies!
>
>
>
> Howard Hedlund
>
> Astro-Physics, Inc.
>
> AP Phone: 815-282-1513
>
> Direct Phone:  815-315-7015
>
> https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.astro-physics.com%2F&amp;data=04%7C01%7C%7C1d8edf759ae044aa83d908d984ff575a%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637687054484222024%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=Z5SDCCArwi5RAr00ZzAFQKXMJpngGrRYzcnITuLrLsc%3D&amp;reserved=0 <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.astro-physics.com%2F&amp;data=04%7C01%7C%7C1d8edf759ae044aa83d908d984ff575a%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637687054484222024%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=Z5SDCCArwi5RAr00ZzAFQKXMJpngGrRYzcnITuLrLsc%3D&amp;reserved=0>
>
> Please include this e-mail with your response.
>
>
>
> P Consider the environment before printing this e-mail.
>
>
>
> From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of
> Andrea Lucchetti
> Sent: Thursday, September 30, 2021 6:16
> To: main@ap-gto.groups.io
> Subject: [ap-gto] Dec Arc APPM mode: any l best practices for field
> set up
>
>
>
> Hi, the new functionality is now more mature and I assume some of you have some good data to share.
>
> I usually shoot one subject per night.
> Given the declination, what is the best combination of :
>
> -number of dec arcs
> -total number of points
> -RA spacing
>
> my present strategy is to run 2 arcs one degree north /south of the object declination for a total of 20 points.
> But I wonder if there is a better approach. I think I can increase the
> number of total points while still investing a reasonable amount of time.
> it is better to increase the number of points in the two arcs or may
> be have one middle arc running on the object declination?
>
> Also, Someone recommended a new feature to easily model these points:
> I think that it would be very useful for people with a nomad set up.
>
> Thank you,
> Andrea
>
>











Join main@ap-gto.groups.io to automatically receive all group messages.