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Date: 16 Oct 2006 01:15:10
From: Glenn Holliday
Subject: Collimating Nexstar refractor?
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I've been looking for resources but haven't yet found
what I think I need. I suspect an expect is reading
saa ...
I have a Celestron Nexstar 102 GT refractor. It has begun
showing symptoms of a collimation problem - "comet tails"
on stars at high magnification. There are no adjustments
I can find on the objective cell, and no information in
any of the docs I can find from Celestron.
I've read this symptom on a refractor might also be caused
by a problem with the diagonal or drawtube. I've tried
a friend's diagonal, and also better brands of eyepieces,
with the same symptoms. I don't know how to check the
drawtube for misalignment.
How do I decide which adjustment this Nexstar needs and
apply it correctly? Does somebody have the procedure I
need written up somewhere?
I'll be very grateful for pointers. Thanks.
--
Glenn Holliday holliday@acm.org
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Date: 16 Oct 2006 04:46:02
From: RMOLLISE
Subject: Re: Collimating Nexstar refractor?
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Glenn Holliday wrote:
>
> I have a Celestron Nexstar 102 GT refractor. It has begun
> showing symptoms of a collimation problem - "comet tails"
> on stars at high magnification. There are no adjustments
> I can find on the objective cell, and no information in
> any of the docs I can find from Celestron.
>
> I've read this symptom on a refractor might also be caused
> by a problem with the diagonal or drawtube. I've tried
> a friend's diagonal, and also better brands of eyepieces,
> with the same symptoms. I don't know how to check the
> drawtube for misalignment.
>
> How do I decide which adjustment this Nexstar needs and
> apply it correctly? Does somebody have the procedure I
> need written up somewhere?
>
Hi:
Do you mean at the center or near the center of the field OR out toward
the field edge (as 50% or so toward the field edge)? If the latter, you
just have to live with it (or buy expensive eyepieces, which can help
some). At f/5 the field is not flat. Expect stars toward the edge to
look...uh..."icky." ;-)
If the former, these (Synta) scopes can be collimated after a fashion.
All you can do is loosen the screws on the tailpiece/focuser where it
connects to the tube and move the entire rear assembly gently in the
required direction until good collimation is achieved. I've frequently
done this with Short Tube 80s with good results, though this is
certainly not an optimum solution.
Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
and
_The Urban Astronomer's Guide_
<http://skywatch.brainiac.com/astroland/index.htm >
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers:
<http://groups.yahoo.com/group/sct-user >
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Date: 16 Oct 2006 21:43:02
From: Glenn Holliday
Subject: Re: Collimating Nexstar refractor?
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RMOLLISE wrote:
> Glenn Holliday wrote:
>> How do I decide which adjustment this Nexstar needs and
>> apply it correctly? Does somebody have the procedure I
>> need written up somewhere?
>
> Do you mean at the center or near the center of the field OR out toward
At the center.
> All you can do is loosen the screws on the tailpiece/focuser where it
> connects to the tube and move the entire rear assembly gently in the
> required direction until good collimation is achieved. I've frequently
> done this with Short Tube 80s with good results, though this is
> certainly not an optimum solution.
Thanks Rod. I'll go to work on it.
--
Glenn Holliday holliday@acm.org
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