Re: [ATM] Tough questions about Aperature Stops

[Mark Holm <mdholm@telerama.com>]

Mike Carambat wrote:
> Playing around with an aperature stop for my Orion
> XT10 when viewing Mars. IT REALLY WORKS WELL! Doubling
> and blurryness are gone and I'm getting very, very
> nice edges and actually quite alot of surface detail
> (dark and light areas). 

I'm with the replies that say:

1. Make sure your mirror is cooled down.

2. If those nasty image problems are still there, you have an alignment,
mirror support, secondary support, bad mirror, bad secondary, tube
current or eyeball problem.  Check alignment first.  A sight tube from
Orion will do the job along with online instructions by Nils Olof
Carlin.  Then. if the problems are still there, look for support
problems, such as mirror pinching or too tight edge clips, if present.
Our good buddy Richard Schwartz likes to make wise cracks about
tightening down edge clips with an impact wrench, but he does have a
point.  If too tight, they will definitely warp your mirror.

3. Not so certain about helping with atmospherics in this scope size
range.  Perhaps the atmospherics are really tube currents?  Do they move
around slowly?  Slowly moving doubling and blurryness sounds a fair
amount like tube currents.

4. Might be the problem is in your eyeballs.  Try the other one.
Stopping down would decrease the exit pupil of the telescope, and thus
decrease the effective entrance pupil of your eye.  Eye lens abberations
tend to decrease markedly as entrance pupil is decreased.


-- 
Mark Holm
mdholm@telerama.com

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