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

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

Hi Steve,

Thanks for the feedback. I had seen your web site, and one of my collimation
sessions was with a printed copy of your site in hand as we were collimating
the C14. It did indeed speed the process.

I'm afraid that in my earlier post I wasn't as clear as I should have been.
The main problem I am having is that even after collimating the best I can,
the images are still bad. The fact that the 'scope loses collimation between
sessions is really a secondary effect--I can't manage to get the darn thing
to give good images in the first place!

The next time I have clear skies and I am out at the weekend house with the
'scope, I plan to check all the things that people have mentioned in replies
(mostly that the secondary, corrector plate, and secondary alignment screws
are all snug). I really appreciate everyone's feedback.

Clear skies,
Andy

-----Original Message-----
From: astro-photo-bounces@seds.org
[mailto:astro-photo-bounces@seds.org]On Behalf Of Steve Walters
Sent: Monday, November 29, 2004 8:10 AM
To: Discussion of Film Astrophotography
Subject: Re: [APML] Help! Advice on collimating a C14


Andy,

>From your description, it sounds like the secondary screws are not properly
snugged up. You have to have all 3 tight or the secondary will flop around.
It's sitting on a "cone" so it can be tilted by the 3 screws, if you tighten
one, you have to loosen the others. At least many of the newer SCTs are made
this way, older ones had springs on each of the screws.

On my website, there is a simplified procedure that may help you collimate.
It tells you which screw to turn and in which direction based on the image
seen when viewing a defocused star. It always keeps you moving in the right
direction without having to guess what to do next.

Steve...
www.StarryNights.us

----- Original Message -----
From: "Andrew Clegg" <andy@w4je.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Monday, November 29, 2004 12:29 AM
Subject: [APML] Help! Advice on collimating a C14


> Gang,
>
> 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...
>
> 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 is
> frustrating because in the reviews of the C14 CGE that I've read, they
> often
> mention that the 'scope provides some of the best lunar and planetary
> images
> the reviewers have ever seen.
>
> As I eventually want to move past piggyback astrophotos to shooting
> through
> the C14 itself, I need to find a way to get good collimation. I've tried
> collimating on stars (with the help of a friend), but the process is very
> slow, tedious, and frustrating (even with Bob's Knobs), and never ends up
> with greatly improved images. And when the 'scope is packed up for the
> night, collimation is lost, and the next observing session is once again
> spent mostly on collimation, in a vein attempt to improve the images.
> Arghh.
>
> I've read almost everything I can on the tricks of star collimation, but
> it
> just ain't working for me. So the next option is one of the specialized
> laser collimators for SCTs, which shine through the optical path of the
> SCT
> in reverse and project a scattered laser spot onto a distant target. I
> wouldn't mind trying that, but I really would like to know if anyone has
> any
> experience collimating SCTs (either with a laser or something else) before
> I
> shell out $200 for the laser collimator. Another choice would be
> collimating
> on an artificial star, but again, it would be good to hear some opinions
> before sitting down at the workbench to make one of these.
>
> Has anyone had the same trouble as me getting a large SCT collimated?
> Should
> I send the OTA back to Celestron to make sure there isn't something wrong
> with the optics? That would cost me a couple hundred bucks, but it would
> be
> worth it if that would cure my problems.
>
> Help!
>
> Clear skies,
> Andy
> www.w4je.com
>
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