I'm playing around with a CatsEye collimation system. I like this set of tools, it has a nice
intuitive feel, and you come away with your gut telling you you've got it right.
But I've noticed something odd, and think it may be not just this scope, or tools, but an across
the board issue in Dobs with heavy mirrors. BTW... this is a 12.5" f/5 with a 12 pound (I think)
conical mirror.
Using the laser (if you have a CatsEye, you know what I'm talking about)... even just a plain old
single beam laser, when the scope is near horizontal, and I elevate it up to say, 60 degrees, the
"spot" stays pretty much dead-on. But once I get close to vertical - pointing to zenith - the dot
moves off dead-center.
Now, honestly, I recall this going on with my 18" Obsession too. And I think my friends have
noticed the same thing.
I'm wondering the a mirror puts so much torque on the cell, that unless you have a major beefy
cell in back with the glass glued to it, you're going to get some "shift" when the scope is
pointed upward, and the stress is relieved?
The amount of shift is rather small, but it is there, I can see it.
Any comments, ideas, even rasberries? ;-)
Thanks,
Mark
--
GSSP Web Page updated 3/4/08: http://www.goldenstatestarparty.org
Who's observing where? - http://observers.org/OI-calendar/
Mailing list preferences: http://seds.org/mailman/listinfo/sf-bay-tac
Received on Thu Mar 13 16:19:07 2008