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Re: Mach2 with Polar Axis Correction

Bill Long
 

Changed the subject line. 

I have been running for 3 hours tonight and no repro of the problem at all. For those using extremely wide fields like me (Field radius: 2.326 degrees) and if you know the optical train is not perfected yet -- I switched to 1/2 crop setting in APPM and it works great.


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Roland Christen via groups.io <chris1011@...>
Sent: Sunday, July 24, 2022 8:30 AM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Mach2 and Eggy Stars with Polar Axis Correction
 
I hope it's at an end because the heading makes it sound like the Mach2 makes eggy stars. And that's the one thing everybody seems focused on to the nth degree on all the astronomy newsgroups.

Rolando

-----Original Message-----
From: Greg McCall <emailgregnow@...>
To: main@ap-gto.groups.io
Sent: Sun, Jul 24, 2022 2:16 am
Subject: Re: [ap-gto] Mach2 and Eggy Stars with Polar Axis Correction

FYI - this discussion looks like it's at or almost at an end, so I wanted to highlight a point. 

thanks for all the detailed troubleshooting discussion as it helps a lot with learning some issues of platesolving when you see all these troubleshooting discussions

cheers
Greg

On Sun, Jul 24, 2022 at 5:10 PM Bill Long <bill@...> wrote:
Roland! 

You nailed it sir, the subframes solved the problem. It was the distortion you talked about that created a poor model. New model with subframes works excellent because the field is full of perfect excellent stars.

Thank you, my friend. 🙂 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Roland Christen via groups.io <chris1011=aol.com@groups.io>
Sent: Saturday, July 23, 2022 4:09 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Mach2 and Eggy Stars with Polar Axis Correction
 

Would the RA Delta in APPM be reported lower or higher than what it actually should be?
YES!

Rolando


-----Original Message-----
From: Bill Long <bill@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Sat, Jul 23, 2022 5:51 pm
Subject: Re: [ap-gto] Mach2 and Eggy Stars with Polar Axis Correction

Either way works for me, but this distortion thing is still eating at me. 😂

Let's say the field was distorted and the solver doesn't compensate for that. Would the RA Delta in APPM be reported lower or higher than what it actually should be?


From: main@ap-gto.groups.io <main@ap-gto.groups.io> on behalf of Ray Gralak <iogroups@...>
Sent: Saturday, July 23, 2022 3:46 PM
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Subject: Re: [ap-gto] Mach2 and Eggy Stars with Polar Axis Correction
 
Bill,

> Dec wasn't really all that different. RA was, about 4x different.

One way to test subframe accuracy would be to take some full frame images in different parts of the sky (you can use APPM and have
it save all the FITS images). Then, create a subframe image from each full-frame image and run both sizes through ASTAP to see how
much difference there is.

If the average of the Ra/Dec differences is minimal, then you can feel comfortable using subframes.

-Ray







--
Roland Christen
Astro-Physics

--
Roland Christen
Astro-Physics

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