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exile
super member
Reged: 01/15/08
Posts: 118
Loc: Guangzhou, China
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Re: Disassemble Astro-Physics Triplet Lens Cell?
08/07/08 01:19 PM
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Hi Jono. Thanks, the photos help a lot. You might appreciate some input from someone who has just recently completed doing the very same thing with a triplet lens (but not the same as yours).
It CAN be done, but you run the risk of opening up a Pandora's Box no matter how cautious you are. When I disassembled mine I found (you might too) that the 'cemented' triplet was anything but, that there were no cell or lens collimating marks. Cleaning the lens elements will mean removal of the spacers, which HAVE to be replaced exactly as they were.
If there are any mistakes, re-collimation will mean extensive (and painfully slow) adjustments to all three elements under rigorous star testing. This is impossible using a real star, and you would have to get your hands on an artificial star to do it. I've read somewhere here that the only way to collimate a triplet properly is using an interferometer and it's probably true; the potential for error is much larger than in a two lens design.
But it IS possible, my triplet has a slightly better image than when I received it, the mould that was growing between the elements is gone, and it still gives me hours of observing pleasure. But it took a LOT of time, patience and care and I learnt a few things the 'hard' way...
In any case the scope is going to be 'off tap' for some time; this is not something you can knock off on a rainy afternoon, believe me. So maybe better for the AP guys to do it, ... they will do it RIGHT.
FWIW, the mould on my lenses did NOT appreciably affect the image quality and this appeared much worse than what I see in your photos. If the telescope works well and you enjoy what you see, forget it, be happy with what you have and don't court disaster...
--------------------
90mm Scopos f6.7 Apo Triplet on EQ2
Tak FS78 f8.1 on Vixen SP
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