Re: PA Error what is acceptable for 530mm FL & 2.1arc sec/pix


Ray Gralak
 

Hi Shailesh,

I ran a 290 point APPM model last Friday and am having trouble centering to a target (I am off by several
degrees). Ray suggested "Plate Solve and Recal" in APPM, but I noticed something odd in looking at the
Model numbers. The polar elevation is -600 something arc seconds and the polar azimuth is -300 something,
see attached.
Provided polar alignment has not shifted, the model will compensate for polar alignment errors in both pointing and tracking.

I said "provided" because some people have noticed that settling in the ground can cause measurable changes in polar alignment.

-Ray

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Shailesh Trivedi
Sent: Monday, September 27, 2021 8:27 AM
To: main@ap-gto.groups.io
Subject: [ap-gto] PA Error what is acceptable for 530mm FL & 2.1arc sec/pix

Hi,

I ran a 290 point APPM model last Friday and am having trouble centering to a target (I am off by several
degrees). Ray suggested "Plate Solve and Recal" in APPM, but I noticed something odd in looking at the
Model numbers. The polar elevation is -600 something arc seconds and the polar azimuth is -300 something,
see attached.

I know that APPM is expected to correct for PA errors, but for a 530mm FL and image scale of 2.1 arc sec
per pixel, is this error too much?

I prefer to dial it down to less than 10 arc sec, but the night I did my PA with PEMPRO, I was chasing the
seeing in suburban Sacramento.



Please shed light. thanks.

Shailesh

Join main@ap-gto.groups.io to automatically receive all group messages.