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[-=CROMAN=-]

Hey all...

I picked up a Celestron 114az for $20 tonight and I would to try to collimate it. The guy I bought it from only used it a couple of times and it is in really good condition. I noticed that the primary mirror does not have a center mark on it like I have been reading about. Do I really need to remove the mirror and mark it myself? Do I really need a collimation cap ( i cant find one yet ) or should i get a laser collimator?

[patrickm]

Congrats on the scope!!

It will likely need collimating for sure. It is NOT my forte, but here are links to the best three articles on the subject that I have found. It is one of those perennial topics on astro boards where novices express fear and bewilderment only to have experts then tell them how easy it really is (I believe Joe's words were, "It will work itself out." I still have no idea what that means!). I lean way more to the former than the latter. Good luck!

Zen and the Art of Telescope Collimation

Thierry Legault - The collimation

How do I collimate my 114LCM telescope?

Attachments:

[Chicago Astronomer - Astro Joe]

Heh...

Twenty bucks is a great deal for a starter scope, considering nothing is banged up.

The links are good and collimation is not a difficult procedure. Here are some rough quick techniques to get you started...

Point your scope on a star preferably and defocus slowly. You should see concentric circles form around the star, demonstrating that the optics are in line and you are ready to go. If you can't get a star with this cloudy weather, use some bright glinty object some distance away. If the circles are deformed to one side...then you need to collimate.

Look down the focus tube without an eyepiece and see if the primary mirror, the big heavy mirror - down at the bottom of the tube), is centered in the focus tube. You should be able to see the entire disk. ( In the above pic, the secondary is not aligned with the main mirror.)

If not, loosen the main center screw on the secondary mirror, (the smaller angled mirror near the top of the tube, (do not loosen the surrounding three adjustment screws...not yet anyway.)

See if you can center the main mirror by slightly rotating the secondary. If not, then loosen the three adjustment screws on the secondary and tighten one, loosen another until you can get the main mirror centered down the focus tube. It's will be a juggling act to manipulate all these secondary mirror tilt screws ...but you'll start to develop a sense on what screw does what and get those two mirrors aligned.

Normally, you don't have to adjust the bottom mirror until you are ready for final collimation - getting those sharp concentric circles just right..(Unless it's way off!)

With my 114mm reflector, I had the option of adjusting the three secondary mirror vanes along elongated holes through the outside of the tube, hardly ever needing to adjust the tilt screws.

A laser/Chesire collimator are good, but not entirely necessary. As long as you can get the circles around the stars concentric and sharp.

With enough delicate small adjustments....it'll work itself out... ;D

[patrickm]

From my experience, the only things that really work themselves out are erosion, oxidation, and entropy.

[-=CROMAN=-]

Thanks for all the input folks! I'll be attempting this tonight

[patrickm]

Jan 28, 2011 10:54:57 GMT -6 patrickm said:

From my experience, the only things that really work themselves out are erosion, oxidation, and entropy.

Oh, and death.