I used to try to collimate at medium power, mainly due to inexperience and/or ignorance, and not having had much experience with SCT's. I just didn't realize the difference it makes. The other night I was observing near the Skyline Drive at about 9500 feet. I was looking at iota Cas and realized that the stars just weren't as crisp as they should be. Since I was using relatively high power, about 300x (as one must do for iota Cas) I just took a quick look at the out-of-focus image of a nearby bright star. The difference between what I could see at about 100x and what I saw at 300x was pretty dramatic. I hadn't realized that the scope was out of collimation. It wasn't much, not noticeable at lower powers, but enough that I could clearly see the off-center shadow of the secondary mirror that I hadn't seen at lower powers. With Bob's Knobs the collimation took all of about two minutes. The difference was striking. Iota Cas was the closely separated images of three pinpoints of light with perfectly concentric diffraction rings, as I remembered, and not the rather mushy appearance it had pre-collimation. Even as a veteran I have to be reminded to optimize the mechanics of my equipment to get the most out of my observing. Kim -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Monday, July 26, 2010 1:41 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Next time someone complains about collimating.. . I can't even see a diffraction pattern at low power. Who would even try such a thing? On 7/26/10, Kim <kimharch@cut.net> wrote:
Use the highest power eyepiece or eyepiece and Barlow combination that you have. The results will be much better than using a low power setup.
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