From: "Dwight K. Elvey" 
To: atm{at}shore.net
Reply-To: "Dwight K. Elvey" 


>From: "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.

Hi
 What do you mean nickel shaped? A nickel is round.
Round is good.
 Three vanes will cause 6 spikes. The fact that you
only notice it on bright stars means that the vanes are good.
Dwight


>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
>
>=====
>Keep looking up,You just may see something interesting.
>
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