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


Andrea Lucchetti
 

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


Howard Hedlund
 

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

www.astro-physics.com

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


Andrea Lucchetti
 

Thank you Howard,
Will try this next time, I’ll let you know.
Andrea 


Sébastien Doré
 

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@...>
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

www.astro-physics.com

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


Roland Christen
 

Dec arc tracking is for doing unguided imaging on one object along the track. It really isn't intended for pointing, so it is of limited use for that. If you want both, you need to make a full sky model.

Rolando

-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Thu, Sep 30, 2021 3:21 pm
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@...>
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
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

--
Roland Christen
Astro-Physics


 

Hey Sébastien - just one thing I can comment on:

>>>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 ?

Dec Arc Tracking is a type of tracking enhancement, so you definitely need to enable tracking correction regardless of whether you use dec arc or not. Then in your case enable dec arc tracking, assuming that is your preferred approach. If you disable tracking correction, no tracking corrections are applied at all

>>>

On Thu, Sep 30, 2021 at 1:21 PM Seb@stro <sebastiendore1@...> wrote:
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@...>
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

www.astro-physics.com

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



--
Brian 



Brian Valente


Ray Gralak
 

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

www.astro-physics.com <http://www.astro-physics.com/>

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


Howard Hedlund
 

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
www.astro-physics.com
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

www.astro-physics.com <http://www.astro-physics.com/>

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


Sébastien Doré
 

Thank you Ray, Brian and Roland ! That pretty much covers the configuration part of my question. Now, does my understanding of the internal modeling "magic" seems about right ?

Also, speaking of forum étiquette in another thread, thanks to Andrea for posting this in the first place too. My apologies if I hi-jacked your post. I felt like my questions were relevant to the topic and may be complementary to yours and might be interesting to other portable imager new at modeling as well...

Clear skies,
Sébastien


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
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-----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
>
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> Please include this e-mail with your response.
>
>
>
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>
>
> 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
>
>












Max Mirot
 

I am getting poor results so far with the Dec arc tracking model on my AP1100 and AP Honders 305 combo.

First I made an all sky tracking model using 250 points.
I checked the Dec arc box and did 10 minutes.
The Image showed big ovals nearly short trails.
The standard model was nearly round at 10 minutes in the same area.

Next night I acquired new images with APPM. This was a single 15 point arc at the Dec only.
I got trailing across the entire image at 10 minutes.

APPM mapped a point near zenith in addition to the Dec arc.
I removed the zenith point from the calculation and model improved to long ovals again.

I tell ya , I get no respect. No respect at all ...

Max


Ray Gralak
 

Hi Max,

My guess is that there weren't enough points in each dec arc row near where you were trying to image. There should be at least 5 points, but more is better. A good rule of thumb is to use a 5-degree (or less) spacing for both RA and Dec to get a nice sky grid.

-Ray

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Max Mirot via groups.io
Sent: Saturday, October 9, 2021 4:15 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Dec Arc APPM mode: any l best practices for field set up

I am getting poor results so far with the Dec arc tracking model on my AP1100 and AP Honders 305 combo.

First I made an all sky tracking model using 250 points.
I checked the Dec arc box and did 10 minutes.
The Image showed big ovals nearly short trails.
The standard model was nearly round at 10 minutes in the same area.

Next night I acquired new images with APPM. This was a single 15 point arc at the Dec only.
I got trailing across the entire image at 10 minutes.

APPM mapped a point near zenith in addition to the Dec arc.
I removed the zenith point from the calculation and model improved to long ovals again.

I tell ya , I get no respect. No respect at all ...

Max


Max Mirot
 

I will try again.

Thanks