Re: SV: [APML]: Drive error or bad polar allignment?

[Chuck Vaughn <aa6g@aa6g.org>]

The Astro-Photography Mailing List
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Wil Milan wrote:

>The easiest way to distinguish field rotation due to polar
>misalignment from drive error is to note the direction of the
>elongation. Drive error (fast or slow drive, large periodic
>error, overshoots or overcorrection in right ascension) will
>*always* be in the celestial east-west direction. Overshoots in
>declination (rare, but can occur with bad manual guiding
>technique or improper setup of the drive or autotoguider) can
>cause north-south trailing. If the trailing is in any direction
>other than exactly north-south or east-west, and particularly if
>the trailing is more in one part of the frame than another, the
>likely cause is field rotation due to polar misalignment. 

Field rotation causes the stars to be trailed in different
directions across the frame. If you make a print and play connect-
the-dots you'll get a circle or part of a circle with the center 
on the star you guided on.

Chuck  <aa6g@aa6g.org>