RE: [APML] Help! Advice on collimating a C14

["Andrew Clegg" <andy@w4je.com>]

Hi Alan,

Glad to hear some people use SCTs for good astrophotos! I was beginning to
think that refractors and R-C's were the only way to go!

I don't think the mount is the problem, as the CGE mount is very solid. It
is a heavy-duty equatorial mount that doesn't use fork arms. The 'scope sits
on the mount via a dovetail. I have generally been very pleased with the CGE
mount. When properly polar aligned the thing tracks very well. However, I
take your point that this is a possible cause of image degradation if the
drive motors are in fact inducing a small-amplitude vibration that degrades
fine detail. Next time I am out with the scope I will try collimation and
observing with the drive turned completely off just to check.

I understand the magnification issue. I've been using telescope for years
and years (too many!). My image problems are very noticeable even when using
a 50mm eyepiece. It's as if I have a soft-focus filter in the optical path,
and the degradation is consistent with what happens when the optical system
is not collimated, even when I have collimated the thing the best I can.

Thanks for the feedback. By the way, your SCT pictures on your web site are
amazing. When I get the optical problems resolved, I aspire to these kind of
images!

Clear skies,
Andy

-----Original Message-----
From: astro-photo-bounces@seds.org
[mailto:astro-photo-bounces@seds.org]On Behalf Of Alan Voetsch
Sent: Monday, November 29, 2004 12:41 PM
To: Discussion of Film Astrophotography
Subject: Re: [APML] Help! Advice on collimating a C14


Hey Andy,

--- Andrew Clegg <andy@w4je.com> wrote:
> This may not be the best place to ask this question, since everyone
> seems to use RCs or refractors, but I thought I'd ask anyway...

Plenty of us use SCTs.

> I have a C14 CGE, and I am having one &$%#^ of a time getting the
> thing
> collimated. Deep sky views are spectacular, but lunar and planetary
> views
> are basically horrible (my Orion ED80 gives better views).

This tells me that you may be limited by the mount itself. There is
going to be some vibration transmitted by the drive motors through the
fork arms. Over the years I have often been disappointed by the views
through my 10" and 12" SCTs. But, they have performed admirably on long
exposures on DSOs. Once in awhile, when all steadies for a brief split
second, you get clear, sharp views through an EP, but then that is
lost.

How is your scope used? The tripod itself will also put a limit on what
you see. Putting the OTA on a steady, sold pier will probably be the
only thing you can do. My experience shows that only occaisonally will
I be able to use even a 17mm EP and get steady views. More often, I was
limited to the 26mm if I wanted sharpness. If you are expecting a stock
scope to provide crystal clear views of the moon with a 7MM EP, I think
you may be asking too much.

Just my 2 cents,
Alan






=====
SCT Astrophotography: http://www.pbase.com/avoetsch/astrophotography
FS-102 G-11/Gemini: http://www.pbase.com/avoetsch12952/tak_fs102
& http://www.pbase.com/avoetsch12952/fs102



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