Web Cam Collimation Using 50um Artificial Star

Folks, Under non-ideal conditions, gusting wind and muddy ground due to temps >32F, I was still able to make some collimation improvements with my C11 last night. Going from a 150 to 50um pinhole required slower exposure times/more gain but the tweaking sensitivity seemed better. By using the dew shield I was able to eliminate any heat from the inside computers and power boxes from interferring, however, this required going outside the dome and reaching in to tweak the knobs. My previous attempts at collimating were mostly "inside" focus trying to center the "donuts". This time I concentrated on "outside" focus which allowed the center dot/diffraction rings more accurate feedback in my adjustments. 20sec avis were taken at f25 outside focus and f45 at focus (see attached). The best airy patterns both visually and taken by the web cam were observed. The slight "elliptical" shape (astigmatism) was likely due to the "sagging" dew shield which I noticed too late. Hopefully I can verify these improvements on some "real" objects soon...

Regards,
Steve

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Just to see, I tried to afocally capture the airy pattern at f25, however, the probability of capturing a cleanly focused shot through the turbulence was slim. Here's the best one of 10 attempts. In my opinion, the web cam method is better since it averages 200 shots.

Regards,
Steve

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Here is the page with the Turned Edge. Look at the bottom photo, does it look like what you saw?

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Folks, While the artifical star helped me obtain near perfect collimation in the horizontal direction, the gravitational forces on my optics required additional fine tuning when trying to view Mars/Saturn. My optical sag was a result of improper installation of the focuser. Once it was installed square to the visual back, there was no need for the rubber band slingshot thing. I did visually move the focuser up, down, left, right and the dount in the eyepiece did not appear much different but it did move accordingly. I was also surprised to find the polar alignment difficult recovering from my horizontal collimation work.

I used my 2nd alignment star, Aldebaran, for collimation (but actually it was too bright), then checked Mars. Although it was too low in the sky, I was able to resolve hints of detail using the barlow which I couldn't before. I then slewed to Saturn and was impressed with the view of the rings and at least 6 mooons. I took a webcam video and attached the best stacking of 300shots taken at 1/25sec. I believe the collimation can be improved further due to the "washout" in the rings.

In the end, the artifical star helped me learn how to collimate, but I'd say there's no replacement for true "in sky" collimation.

Regards,
Steve

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