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Re: Coulter 13

Subject: Re: Coulter 13
From: Edward Erbeck
Date: Sun, 30 Apr 2006 17:50:47 -0700
Newsgroups: sci.astro.amateur
       Jerry Young wrote:

> Thanks for the info, guess I have about an F4.3 mirror then. The mirror
> is very thin measuring a little less than 3/4" thickness at the edge. I
> suppose the University 9 point cell would be adequate as the original
> cell supports the mirror on only three 1" circular Teflon discs. I
> would think a 12 point cell would be about the minimum for this thin of
> mirror, but can't find anything off-the-shelf like that.
> 

    No Problem - Oh yea, seeing as it's a 13.1 the F.L. Is suppose to be
58.95" so -3" results in a F.L. Of 55.95". Not that .45" really makes all
that much difference unless you're using a short travel focuser.
    
    In the "For What It's Worth" category, personally I'd go ahead and just
redo the original mount (after seeing if the "push" screws have a solid base
to push against - I've seen many of the later "Red Tube" Coulters that just
pushed against the wood and not nail heads. No kidding, that's what they
used). Reason being is if you go to a "real" Cell you are going to either
add counter weights or move the Elevation Bearings. If adding Counter
Weights remember to reinforce the Tube Base because the Tubes protection
used to be the Cell. If you move the Elevation Bearings you'll need to redo
the Rocker because the lower portion will be "longer" to correct the weight
change. 
    Just idle thoughts from someone that's been there.

            Crazy Ed 


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