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Objective doublet assembly

Hi there , ihave recently aquired a celestron firstscope 80 refractor , the objective lens although in good condition was very dirty ( the result of being kept in dusty shed with no dust covers ) having removed and cleaned objectives i have noticed that the front lens of the doublet seems to be more convex on one side compared to the other, and as a result or my stupidity and not noticing i am unsure whitch side should fit to the second element ( i.e. more convex side facing second element or facing away ) i would realy appreciate any advice u may have as i currently have a dead scope ....thank ? s alot hope u can help......

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This should help you reassemble correctly--

http://www.cloudynights.com/documents/cleaning2.pdf

Posted on May 22, 2009

  • Joe Lalumia aka TelescopeMan

    I hope there are "registration marks" on the edge of the glass so you can reassemble EXACTLY in their original positions.

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This is an old problem but I will answer it--

The rattling sound is a KNOWN ISSUE with these scopes. It actually does not affect anything. The scope is what is called an acromatic refractor. ALL ACROMATIC REFRACTORS show color fringing around bright objects. You would need to buy an APOCROMATIC refractor with 3 lenses to get true color correction. These scopes are very expensive to buy.

You can also use a "minus violet" filter to eliminate most of the color fringing in that scope. If the scope cannot be collimated it should be returned to Meade.



www.telescopeman.org
www.telescopeman.info
www.telescopeman.us

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