Re: [APML] Guiding far from the object

[Matt BenDaniel <matt@starmatt.com>]

At 02:13 PM 6/27/2002, Tony Hallas wrote:
>Matt,
> 
>   Jim Riffle once told me thousands of years ago that guiding on a star that was not in the central area of the imaging FOV would result in trailed stars no matter how well the scope was polar aligned. I didn't believe him... it didn't make sense... but he's right. I have taken images with a scope that was dead nuts polar aligned, but with a guide star at the edge of the FOV and sure enough... trailed stars.
>Does anyone have an explanation for this? I guess it might have to do with angular velocities... in a given time a set part of the sky will move a greater distance than another part? Like to hear what the more mathematically gifted than me can make of this.

There will be differences due to atmospheric refraction, but if you're both shooting and guiding near zenith, I don't think that's detectable.
--
Matt BenDaniel
matt@starmatt.com
http://starmatt.com


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