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Home > Classifieds > Astromart Classifieds > Telescope Making > Classified #280465

Sale/Trade: Reference Quality flats for folding your big lens

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Fold your big achromat or APO objective lens, as I have done successfully for 4" and 6" objectives. These round flats would be perfect for an 8" or even a 6" double-fold or triple-fold:

4.375" diameter near 1/20th wave ZERODUR reference-quality optical flat, aluminized, 1" thick, ultraflat, superclean, and never used. Custom made by professional opticians, was to be the fold-mirror in my D&G 8" F12 achromat before I decided to leave it classic straight. Provided with interferogram and test report sheet demonstrating .056 waves peak-to-valley and .008 waves RMS over 4" diameter, would be even better with the focus term removed, which is what your eye would see. Very flat out to the edge, but I only had access to a 4" reference. Uncoated 1/10 wave equivalent from Edmund Optics would be $613.

$375 shipped in CONUS, PayPal encouraged, or interesting trade.


5" diameter 1/12th wave optical flat, BK7 crown glass, I used this in my folded 6" F20 D&G refractor with absolutely no visible impact on the image or temperature issues. Aluminized coating is quite usable, but somewhat cosmetically challenged with a series of minor marks, ultimately needs to be stripped and recoated. Provided with interferogram and test report sheet demonstrating .075 waves peak-to-valley and .008 waves RMS over 4" diameter, would be even better with the focus term removed, which is what your eye would see. Very flat out to the edge, but I only had access to a 4" reference.

$175 shipped in CONUS, PayPal encouraged, or interesting trade.
 

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