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Thread: Your opinion on this mirror

  1. #1
    Join Date
    Dec 2007
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    Question Your opinion on this mirror

    Its an 8 inch mirror on ebay for 80 bucks and the seller has good feedback, is there anything I am overlooking?

    http://cgi.ebay.com/NEW-8-INCH-PRIMA...3%3A1|294%3A50

    The f-ratio is actually 3.7, is that too low?

  2. #2
    Join Date
    Dec 2006
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    3,275
    Seems to fall into the too good to be true category. Also a claim of quarter wave accuracy with nothing more is meaningless. Without knowing how this is measured and at what frequency it could signify a very lousy mirror yet meet their claim. Personally, I'd not buy any astro products from Ebay but stick to more mainstream sources.

    Rick

  3. #3
    Join Date
    Nov 2005
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    WA state, USA - Seattle area
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    On the listing, it says 'Power = 6'. What does that mean?

  4. #4
    Join Date
    Dec 2006
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    3,275
    I took that as a clue to run. Makes no sense to me either. Shaving mirror magnification?

    Rick

  5. #5
    Join Date
    Feb 2007
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    848
    Those mirrors are a scam, they're ~f/3 spherical mirrors and very thin, too. I'd stay away.

  6. #6
    Join Date
    Sep 2006
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    302
    Quote Originally Posted by TimmySand View Post
    Its an 8 inch mirror on ebay for 80 bucks and the seller has good feedback, is there anything I am overlooking?

    http://cgi.ebay.com/NEW-8-INCH-PRIMA...3%3A1|294%3A50

    The f-ratio is actually 3.7, is that too low?
    The cleanliness of mirror is important also. I got a 10 inch mirror in 1993, installed it on my school's telescope, and tried to keep it clean all these years. But I still have a lot of dirt on it I wish I could clean.

    So it might not be clean enough, depending on its care and age

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