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Subject: Re: optics lx200 8"
From: Rob Roy
Reply To: mapug@shore.net
Date: Sun Nov 12 08:39:12 1995

>If you made this mirror yourself, I would say masking the edge is a good
>idea. I don't think it's quite acceptable for a commercial mirror to have
>a T.D.E. On the other hand, are you certain that the edge really was bad
>? Did you ever look at the mirror with a Ronchi or Knife edge test ?
>
>-Robert
>
Hi Robert,

No, I didn't test the mirror when it was out of the scope. I didn't take
this painting of the mirror lightly, either. It was only after weeks of
star testing and communicating with others that I even decided to try the
cardboard mask. The improvement was dramatic. The next step was to remove
the offending 'limb' permanently.

I am not suggesting that everybody go and do this. In many cases it would
be unnecessary and there would inevitably be some disasters! I, too, was
VERY surprised (AND don't find it quite acceptable) that my commercial
mirror could have a turned edge. On the other hand, who am I to argue with
Dr. Suiter who, according to S&T, Mar/95, on pg. 46, says that, "The blunt
truth is that most mirrors would probably be better off with their outer
1/8" masked off." He also goes on to say that commercial mirrors suffer
from steep narrow TDE (my case, exactly,) while home-mades have wider
shallower ones. I only know that it worked in my case!

BTW, not that it was done with this goal in mind, but, I have now done
'everything.' I replaced the RA drive 2x, filed off a burr on the dec drive
worm gear, changed mother boards 2x, replaced roms 5x??, replaced fuses,
packed up scope to go back to factory 2x and have now removed primary
mirror. I think I originally got a 'citrus fruit,' {:-^) but it has been
fun and I sure know where everything is! Please don't anybody type back
suggesting that now I do some observing. I do a lot of that every chance I
get. I just want the best with which to do it. No harm in that is there?
................................................................
Rob Roy Maker of LX200 joysticks
a5817394@mcmail.cis.mcmaster.ca
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