ATM Re: [CCD] Alt/Az Autoguiding

[Al Kelly <akelly@ghg.net>]

At 11:18 PM 6/14/99 -0500, you wrote:
>-----Original Message-----
>From: Tom & Lou Krajci <krajcit@3LEFTIES.COM>
>>Have you evaluated your main scope/guide scope rig for differential flexure?
>
>
>>This may be a source of trailing, even in four minute exposures (especially
>>considering the size of the main instrument), so it's worth analyzing this
>>aspect of your system's performance
>
>Hi Tom,
>
>I know the 32 does have some shifting, but I do not think its too much.  Al
Kelly might chime in and improve my thoughts on this.  The orientation of
the scope did not change too much in 4 minutes, so I am not sure the
>flexure played a big role, though it may have played "some" role.....

Hi Tom,

        Flexure is always something to worry about and the method you
described is one pretty standard way of checking it out; but, like Chuck, I
don't suspect that was the source of the minor residual translation that we
appeared to experience.  The first suspected cause is inaccuracy in the
boresighting of the autoguider FR axis with the main OTA axis (as defined by
the imaging field, which is another potential source of error, although we
have checked that out pretty well with our unguided imaging).  Given our
rather sturdy setup, I don't suspect detectable flexure in four minutes.

Regards,

Al K.
---------------------------------------------------------------
Al Kelly .... e-mail: akelly@ghg.net 
         .... web site: http://www.ghg.net/akelly/