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Subject: [M]: Re: Secondary Spinning


Anthony,
I also have an 8"LX200 and was out the other night collimating and
noticed that when I turned the hex wrench in one of the more stubborn
collimation screws, the secondary housing turned rather freely around
despite no movement by the corrector plate. I noticed that as I turned it
more counterclockwise it spun more freely and when spinning back clockwise
it tightened back up. I decided to tighten it as much as possible with my
hand and then recollimated from there. It was a strange experience but
surely not fatal to good collimation. I was able to readily get back to
perfect diffraction rings.

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This happened to my 10" as well...just about as you described. I called
Meade to determine what effect this might have and they suggested "sending
the scope in" for realignment. As the scope was long out of warrantee, I
decided to forgo the experience and try and return the secondary to it's
proper position.

I determined two factors here. First, the secondary should be centered. I
found that there was quite a bit of play - use some shims to make sure it
stays centered. I used some small thin plastic strips.

Secondly, Meade told me (after a lot of interrogation on my part), and the
rotational position is set to within 5 degrees when they do the alignment.
That is, they rotate the secondary by 5 degree increments until the image is
"optimized". The didn't tell me what that meant. Also, after alignment,
they do not put alignment marks on the secondary. I looked very closely at
the housing and the inside of the corrector hole, and found two matching
impressions that appeared to go together. I placed the corrector in the
hole at this point and tightened it up.

I have no idea if this was as critical as either I or Meade thought. The
images are fine, and everything is now tight and centered. I stopped
worrying about it a year or so ago.

Hope this helps,

John

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