Re: More APPM Results -- Can Someone Help Me Understand This?

Ray Gralak

BTW, at that image scale you should probably by using the UCAC4 catalog, if your plate solver can use it.


-----Original Message-----
From: [] On Behalf Of mjb87 via
Sent: Tuesday, April 20, 2021 6:55 PM
Subject: [ap-gto] More APPM Results -- Can Someone Help Me Understand This?

Running an APPM session with a f/10 (native f/15 with 0.67 focal reducer) Cassegrain on an 1100 using an
ASI1600MC-Cool. Image scale is 0.26 but because this is a OSC at Ray's suggestion I used 0.52 for both X
and Y scale. Other settings were generally standard except the max catalog magnitude was reduced to 12.
(This seems to avoid a lot of checkpoint timing errors.) This was during a half-moon almost directly overhead.
Not ideal conditions. A bit of wind. I can't figure out how to manually set temperature, pressure and humidity so
the default of 10 was used when it was closer to 18.

The run on the east side made sense. Most errors with a couple of dozen arcminutes.

Things went crazy on the west side, reporting pointing errors of 10 or 15 degrees!

I installed this model and then pointed in the west and did a plate-solve and recal and got an error telling me
the platesolve-based correction of 15 degrees was more than the maximum allowed. So something is wrong

The physical setup of the telescope on the mount seems appropriate -- for sure no 15 degree misalignment in
orthogonality. The primary mirror is fixed. Collimation is good -- checked a week ago. The polar alignment is
good -- ran a session with Polemaster yesterday and checked with RAPAS today.

Am I missing something obvious here?


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