Re: How Much RAPAS Misalignment is Too Much ?

Roland Christen

Is the RA Correction procedure reliable enough that I should trust these results ?
It is not a reliable process for precision polar alignment. It was meant for quick setups when no other means are available.If you have any non-orthogonality in your telescope optics, then any method using your telescope will not be accurate.

When you say field rotation, over how many hours are you experiencing this? Also, how do you determine that it is field rotation? If you are seeing field rotation over a long time period, say 6 hours from beginning to end in a wide field image, that is natural because the skies do not follow an exact sidereal path due to atmospheric refraction.


-----Original Message-----
From: M Hambrick <mhambrick563@...>
Sent: Fri, Sep 24, 2021 11:10 am
Subject: [ap-gto] How Much RAPAS Misalignment is Too Much ?

I have been getting a lot of what I suspect is field rotation in my guided images so I thought I would check my polar alignment using the RA Correction method as described in the manuals. I have a portable setup with an 1100 GTO mount that I set up and take down every night, and I set my polar alignment using the RAPAS. 

At the end of the RA Correction process I checked the position of Polaris in the RAPAS and compared it to what the Polar Align App said it should be. The results are in the sketches below.

I am assuming that if I am going to adjust the RAPAS, I will need to adjust the push pull screws in the plate at the base of the RA axis where the RAPAS attaches, but before I do this I wanted to make sure that this is not an irreversible process. I am worried that if I suddenly start adjusting the push-pull screws that I will do more harm than good.

Is the RA Correction procedure reliable enough that I should trust these results ? I think that at a minimum I will repeat the alignment procedure before I start adjusting anything.

The offset as seen seems in the sketches seems excessive, and I am also wondering what could cause the RAPAS alignment to get so far off, assuming that it was correct when I first got the mount. To my knowledge I have never dropped or damaged the RAPAS or the mount.

Any comments or advice would be appreciated.


Roland Christen

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