Collimation of Celestron cpc 925

[Nexus 6]

Hoping I might be able to get advice on weather i need to collimate my new scope.Never done any adjustments like this before and was advised not to attempt it on an sct.Just feel the view on stars is not as sharp as it could be.Bought this scope at the start of November not had much opportunity to use it due the weather(who has?)

[Bigwings]

It should have been set up before dispatch but they can be upset in transit by big bangs.

I think I would hold off and check it out on moon targets as well as stars in good seeing before tinkering.

[dweller25]

SCT's take a long time to cool down and will give fuzzy star images until they do.

If when you defocus the star image you see lots of wriggly worms on the circles then the scope is not cooled down enough.

Keep the scope in an unheated area if you can as it will help with the cooldown. An SCT stored in a warm house and then taken out into a winters night could take 2 hours or more to cool down.

Once the scope is cool then check the defocussed star image to see if the bright dot is central in the doughnut image and that the circles forming the doughnut are concentric.

In fact collimation is not too hard and once done it's easier the second time - just keep metal tools, rings and watches away from the corrector !!!

HTH

[Peter Drew]

SCT optics are actually some of the easiest to collimate as there is only one component that is adjustable, however, this adjustment is very sensitive and requires only fractions of a turn to make a difference. Very important to heed the previous advice re cooling down of the optics and ambient seeing conditions. SCT's can need frequent fine tuning for best results, specially if portable, the sooner you have a go at collimating when necessary, the sooner you will become comfortable with it.

[Starjumper]

Hi ajfdab,

Welcome to SGL.

John

[Talitha]

Hi and welcome to SGL, ajfdab.

Ed's Guide to SCT Collimation is the best, most informative collimation guide i've ever read. Granted, some of the techspeak flies over my head like the Shuttle, but it's good solid info. Hope it helps.

[ron.s.g]

Hi ajfdab and welcome.

regards ron.s.g

[Brinders]

I've had two SCTs and both required collimation upon receipt. After that I have found only very minor adjustments were occasionally necessary. If you store the scope either in an unheated garage, or as I do, in a plastic Kecher storage cabinet outside, cool down time should be minimal.

As has been said above, once you have had a go at collimation and gained confidence it really will be easier subsequently - just don't get too obsessive about it and enjoy your scope!

Brinders

[Nexus 6]

Hi to every one.Thanks the info on collimation.I have used my 925 three times since I bought it and have been careful to let it settle down to negate any thermal issues.There is a definite skewing off when I focus through a star.I am pretty sure I should adjust the the optics.Its heavy piece of kit and I can just about manage it on my own so I did wonder if I may be knocking the alignment out slightly when I move it.I would also like to ask if my garage is a better place to keep this scope rather than a conservatory. Hoping for a sustained clear period to get out and put this scope though its paces!

[johnh]

Welcome to the forum, with SCT the collimation has to be precise owing to the short distance of secondary to primary and the star focusing one side but not the other certainly needs a tweak. If you use a mono webcam to collimate with a barlow you get a much bigger Airy disc and can see the diffraction rings symmetry easily.

JohnH.