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Main
Date: 15 Nov 2006 17:55:37
From: Uncle Bob
Subject: Celestron C 9-1/4 alignment issues
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Greets--
I have just reassembled my Losmandy GM8 mount, which was shipped from
the factory with .011" end play in the RA axis. In due course, I had to
have a new shaft machined (from 303 stainless, instead of the aluminum
Losmandy uses), and it was machined to fit with .0005" end play on the
RA (polar axis), Needless to say, this helps pointing accuracy and
tracking, removing a wild non-periodic error that it took a while to
hunt down. Now the mount behaves more like an AP mount. ;-)
So,..
I'm fitting my Celestron 9.25" SCT to this mount using a standard
Losmandy dovetail plate...and looking at the OTA, I notice that the
casting to which the radius blocks attach on the Primary end of the scope
is noticeably thinner than the ring which encircles the corrector plate.
The primary end casting is 33" in diameter, the corrector plate ring is
33.25" in diameter. Unless these differences are accounted for in mounting
the OTA to the mounting rail or plate, you are going to have fun getting
this scope to point consistently. I believe it will get very confused when
you move it from one part of the sky to another, especially if your
targets are on different sides of the meridian. To achieve any degree of
pointing accuracy, you have to eliminate cone error. WTF were they
thinking? They could have just machined a little flat on the corrector
ring and this problem wouldn't exist...is that too expensive to implement?
My solution is to shim the radius block on the primary end as required. I
plan on using McMaster-Carr laminated aluminum shim stock, which is very
cool, because you can peel off layers of the shim in .002" increments
until it is the correct thickness. This should get me close to true
orthogonality.
This kind of stuff makes me weary.
Uncle Bob
Fairfax, CA
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Date: 16 Nov 2006 11:48:10
From: Kai
Subject: Re: A.C.L.U./Anti-Christian Liberal Union
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In article <Xns987CBD6B38C45rrfkwrantispamattbic@216.196.97.136 >
Perseid <eidpers@anti-spam.comcast.net > wrote:
>
> After Much Chewing of Cud and Cogitation, Ivdeo-Xian Star Logician
> <anon@comments.header> Spat the Words
>
> > Liberal Union/God-hating, Family-hating and Country-hating
> > terminally-Rabid Liberal Atheist butt-buddies. :D
>
> The Democrats swept Congress in a landslide. Get over it, get
> used to it. We The People Spoke. Republicans Suck !
>
Amen!
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