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Subject: Re: vote by
By: Anonymous (
In Reply to: Anonymous ( (Original Vote)
Date: 03/17/2002 11:25:47 pm PDT
>I bought mine used with a cracked corrector plate (!!!) on EBay for $50. Fork mount and drive base work fine and are in pristine condition. I replaced the corrector plate (myself!!!) with a used Tokina 105mm multi-coated UV filter (!!!) as I was desperately trying to restore it to somewhat usable order. I figured that I would have nothing to lose if the "modification" did not work. The view turned out OK (!!!) when I pointed the scope at Mars last week - obvious undercorrection but nevertheless the Martian disk is bright and quite contrasty. After tweaking with the collimation I was able to use over 100X with acceptable results. A surprise considering the total cost ($65.00) I spent and the total lack of technical considerations that had gone into the "optical transplantation". As it turns out my little Criterion 4000 now performs pretty "healthy" in comparison to several other quality 80mm achromats my friend owns.

I also bought a used Criterion 4000, and like yours it also has
a broken corrector plate. (Being a novice, I asume the corrector plate is the glass holding the secondary mirror?)
Does this 'glass' have special coatings?? and is this why I can't seem to calibrate mine? It sounds like you may have already done what I've been trying to do...I sure could use

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