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


I like the test involving the appearance of the secondary shadow at
(measured) equal distances from focus.  That really nails the general
correction.  put a 33% obstruction disk on the secondary spider to make it
obvious.

Colin

-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of Rick
Maillet
Sent: Thursday, June 05, 2003 1:43 PM To: atm{at}shore.net
Subject: ATM Star Test report



Hello All,

Star test report..

10" F-6 Dob.
Target star....Polaris
Magnification....375x (4mm)
                 250x (6mm)
Two hours after setting up, began testing. First test to determane if
spider was causing stop sign shape on out of focus image..I added a piece
of wire,90 degrees to one of my three vanes to see if this would change
image....it did not, conclusion, cell is stressing mirror, need new cell.
the image in focus did change, more diffraction spikes.
removed wire and continued with testing. tube currents are still apparent(
will install fan or fans with new cell)
ok image time.... out of focus image is easier to view, inner focus image
more prone to turbulace or currents, not sure why.
outter focus image is six evenly bright rings, but the outter most ring is
slightly brighter and a bit fuzzy, not sure if it has to do with not being
at complete equalibrium or not, but other then that one ring the others
look good.
now for the inner focus image...it to has equally bright rings but the
outter most is still slightly brighter then the rest, and the ineer most
ring has(diffraction like)spikes all around it. now yes, we must take the
stop sign shape into effect, but below is a link to a sight in which you
can detect that very effect.

http://www.astunit.com/tutorials/startest.htm

if you look at these images you can notice that effect with the inner most
ring, but mine is more pronounced and can be seen out to the outter ring.

I know this is not much to go with, and I probably should wait till I build
a new cell and probably a spider too, but could any star testers out there
tell me what the problem might be,I believe I have a slight T.U.E. but is
this the reason for the bright inner ring with spikes inside focus and also
why still a brighter outter ring inside focus? I thought this would be
darker.

Thanks
                                                      Rick

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