Who ever the dill was, that said we were the sunburnt country, obviously
didn't own a telescope.
Whilst my 216XT is on holidays back at Meade (the subject of another
story) I've been refining my polar alignment in between clouds. That can
be pretty frustrating, as one night I can track for 10 minutes
accurately, and the next available night, 3 or four minutes only. No
amount of adjusting the mount overcame this to any great extent. Last
night (almost clear) I remembered discussions on mirror slop, something
I hadn't come across before, so I tried the following:-
Centre an east or west horizon star, give the OTA four or five sharp
raps with the fingers and watch in the reticle to see the star move.
Centre it and do the drift bit with mount adjustments. Centre a meridian
star and
rap the OTA again, the star moves up to 30 arc seconds. Centre and align
again. Seems to improve alignment.
I'm wondering if any-one else has any thoughts as to whether the mirror
would move in a predictable way on say, my 8" LX200. If it does, then it
may be necessary to rap the OTA before imaging, when the 'scope was
moved to another part of the sky.
Comments would be appreciated.

Regards,
Coffs Harbour N.S.W. Australia

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