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
>




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