From: Rick Maillet 
To: atm{at}shore.net
Reply-To: Rick Maillet 


I did a star test on vega last night,and the result are bothering me, so I
need some input please. First off, i did not have time to leave the scope
equalize, but it was out in barn so I doubt if it was that far off,
here is what happened.... was out observing and decided to try a star test
on Vega, my highest power being 250x, telescope is a 10" F-6 dob, in
focus I see 6 spikes, believe this to be defraction from my 3 vane spider,
does this sound correct, BTW, I get this result on only the bright stars.
now in and out of focus is the concern, either way, the defraction image is
nickel shaped,mind you there was turbulance in the image but the nickel
shape was apparent.
I can tell you this,I had noticed this once before but never really thought
much of it, I had the mirror out last week and reinstalled it after
drilling holes in bottom of mount to allow air in for cooling down.. the
mirror is mounted on three layers of plywood laminated together, with 6
blobs of silicone placed according to plop,and three blobs inbetween the
posts and the mirror, the mirror is 7/8" thick.

Has anyone any idea as to why the nickel shaped image, wondering what the culprit is.
words of wisdom from those who know would be appreciated.

     Thanks

      Rick

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