Re: [ATM] Ghost image

[vorblesnak@peak.org]

It has been busy, so although I have read your suggestions I have not had
a chance to test them all.  I have done some ..

I rechecked the collimation, including rotating the laser collimator in
the focuser tube.  There is a bit of slop in the tube.  The return dot
from the laser almost goes off the hole of the laser collimator, but never
completely.  So there is a bit of wobble.  It is a home made laser
collimator.

It is a sealed tube so the mirror does cool very slowly.  It has been
stormy here so I have not had it out long enough to allow the mirror to
cool in the tube.  I like the idea of opening the trap door to allow the
mirror to cool prior to viewing.

I rechecked the figure of the primary, it looks good to me.  Using Windows
Ronchi the figure looks the same as the example in the Ronchi program.  I
do not have a foucalt tester.

There is no pinching in the primary cell that I can see.  The mirror sits
on a strap that is supported above the diameter of the mirror, but flares
away from the mirror below the diameter. (does that make sense?)  There
are stops on the posts that hold the primary to keep the mirror from
tipping out, they do not touch the mirror.  The back of the mirror is
irregular but there are only three contact points and it does not look
like they touch any of the surface defects. The mirror is about 1.25
inches thick.  It is very white glass, not indication that it is Pyrex or
not.

The coating on the secondary is good.  Both mirrors are dusty but not
overtly dirty.

I adjusted the primay mirror in it's cell and tried another view.  I
looked at Saturn again.  After all of the above fiddling, and a couple of
days waitting for a sucker hole, the 'blob' was now on Saturn as opposed
to being next to it.  It appears to be the same size.  I was not able to
move around the eyepiece and find a spot where the 'blob' disappeared. 
Stars and deep sky objects do not show the blob, or it is so diminished
that I cannot see it.

When I get a clear night and some time I will try the other suggestions. 
And yes, if I can I will take an afocal picture.


David Davis
Toledo, OR 97391








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