Re: [APML] Just when you think you have it all sorted out ....(a bitlong)

["John C. Mirtle" <jmirtle@shaw.ca>]

Bill;
    Another thing that can getcha is the secondary mirror. Unless it is
counterbalanced (see Wallis and Provin's sacred tome) the secondary can also
flex slightly under it's own weight.  I fought with these issues with my old
16" and all the problems promptly vanished with a Lumicon Newtonian guider.
Fortunately, the ST4 seems to be able to handle comatic star images just
fine, once you get the thing focused. I haven't worked as fast as f4 (just
f4.5 and f6) but there is always the Lumicon field flattener. It will also
tidy up the off-axis star images for the guider.

John Mirtle
Calgary, Ab. Canada

----- Original Message -----
From: "William R. Mattil" <wrmattil@ix.netcom.com>
To: <astro-photo@seds.org>
Sent: Friday, November 01, 2002 11:39 AM
Subject: [APML] Just when you think you have it all sorted out ....(a bit
long)


Hi,

I thought that I would share this with the group so that everyone could
have a bit of a chuckle and if there is anyone who hadn't run across
this (doubtful) then it might save them some trouble. I have been
moderately successful imaging with a pair of Schmidt Cameras (8in and
5.5in) using a Losmandy GM100 with the high precision RA gear. Set up
was using a DSBS and 90mm guidescope ALA Kent Kirkley (Thanks Kent).
<- snip ->


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