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Fuzzy bright stars with my Celestron CPC 1100 XLT

When looking at the brighter stars I cannot focus them to a sharp image. They appear fuzzy. Image of a star test on Vega attached (taken with a Watec 120N webcam). Diffraction rings are sparse and mottled. Does not really indicate that scope needs collimation. Can you help please.?


Mike Brightmore

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  • Anonymous Dec 20, 2008


    All objects seem out of focus no matter how I adjust the focus knob.

    The images of stars look similar to your picturs. The moon's craters can be seen, but they do not have the sharp definition I was used to with other telescopes I have used. I was told that this could be an issue of the telescope needing to be collimated (sp?) correctly. I noticed that the stars are slightly tear drop shaped which leads me to believe that the optics are misaligned. How is this done? I had a reflector and the process was easy. How is it done on a Celestron Schmidt-Cassegrain?


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The image shows that the optics are not centered properly. The secondary may be tilted slightly to the 2 o'clock position. When not centered, a focused star will have an astigmatic shape, and not come to a full focus. Also check the mirror and corrector plate for dewing, that will also affect the views.

Posted on Nov 08, 2008

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I have had the same problem, but when I got used to the collimation process and which way to turn the adjuster screws life has been much easier for photographing, usung a 7.5mm eye piece for adjusting the perfice circle.

Posted on Aug 20, 2010

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