From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 


Good news, and you're clearly on the ball, diagnosing, asking, thinking.

The cell would give you a triangular image.

The star test for spherical is a matter of comparing the out of focus disk
images at equal distances inside and outside focus.  Figure a way to
measure this distance, such as the method by Suiter, so you don't get
variables in the test that will confuse the images.  The most information
is in the images near focus.  I don't know if the fuzzy outer ring you see
is inside or out.

Cell first, then mask the edge for a trial.


Good work,

Colin



-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of Jerry
B. Hillman
Sent: Saturday, May 31, 2003 10:54 PM To: atm{at}shore.net
Subject: ATM new star test



Hi all,
I am encouraged by tonights star test results.  It wasn't perfect but I now
have a good idea of what is wrong.
I started by doing a Ronchi test on Arcturus.  I set it to show seven
lines. Although I had to chase the image a couple of times I did see that
the ends of the lines have a slight hook. Otherwise, they seemed to be
perfectly straight and  evenly spaced. Okay, first problem identified.  I
have TDE. That, I think I can fix.
Next I did a star test using my highest power eyepiece.  3.6 mm.  This
gives me almost 500x.  I would prefer higher but, that's life.  Outside of
focus I started where I could see a fairly large image.  My secondary
shadow was nicely centered. The image itself was a bright fuzzy ring
enclosing a series of not so bright rings  Rings within rings within rings.
The entire image was almost perfectly round.  As I moved closer to focus
the image shrinked, I had fewer rings and the image became somewhat oblong.
 When I got the image down to where I had only the bright ring and about 4
or 5 inner rings the image was becoming a little triangular. I moved inside
of focus to check and it did turn 90 degrees. I moved back outside of focus
and turned my primary mirror in the cell about 1/4 of a turn.  The image
became more oblong than triangular.  I turned the mirror another 10 degrees
and I still had an oblong, but it hadn't changed position. Okay, another
problem identified.  My mirror cell definitely has to be rebuilt into a
flotation cell.  I intended to do that anyway, but didn't have time to do
it today. In the image, isn't the bright, fuzzy outer ring being caused by
the TDE?? I hope so.  If not, please, someone tell me.  I already
determined that the center zones of mirror were still a little on the
spherical side this morning with the Ronchi test.  I tweaked it a little. 
Based on the star Ronchi test, I think I better leave it alone for now, and
just worry about the edge.
Now I am going to go and just look through it and see what I can see.
Jupiter looks nice at 100x and pretty good at 200x.  I am going to see what
else I can find.
Clear skies, Jerry

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