Re: APPM model how many points portable?

Linwood Ferguson

Sounds like it is more measuring the accuracy of the mount and closed loop slew than the plate solving.


I would think you want to take a FITS image and plate solve with ASTAP and compare the answer to other plate solving programs.  Except of course you would need to try a bunch of FITS images in different parts of the sky, probably at different focal lengths, with different amounts of distortion, different image scales.


Then try to figure out which plate solver is the more authoritative when they all disagree with each other.


I thought about trying it, grabbed an image and tried PI and AStAP, but I saw all the associated data (not just center coordinates and PA) and decided I wasn’t competent to compare.   L



From: [] On Behalf Of Jim Grubb via
Sent: Friday, April 23, 2021 11:03 AM
Subject: Re: [ap-gto] APPM model how many points portable?


Here is my proposed experiment to measure accuracy of different plate solvers.


1. Choose a star (A) mag ~9, plate solve, re-sync, and then slew back to it.  (in SkyX they call this closed loop plate solving)


2. Choose a second star (B), say 30ºs away, slew to it, plate solve, re-sync, and then slew back to it.


3. Slew back to star A, plate solve, re-sync, and slew back to it. Then use a tool to measure the difference between the center of the screen (reticle crosshair), and where the star actually is after the closed loop slew.


4. Repeat steps 1-3 a number of times to get an average error.


5. Repeat the experiment with each plate solver and compare the average error.


Does this sound like a sound experiment?


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