[ATM] Star Test Interpretation

["Tony Owens" <tonyowens@shibumi-technology.com>]

Dear all,
Maybe someone more experienced can advise me about an optical test issue.
I recently acquired a nice 10" F6 planetary Newt and have been tuning it up
and putting it thru its paces.  The optics are clean with good coatings and
the primary and secondary come from very reputable US makers.  I have
collimated the scope fairly critically, using a Chesire to set the secondary
to the focuser axis, a holographic laser to align the secondary to the
primary (no center mark provided) and the laser and defocused star test to
align the primary.  Some room for improvement there, I suppose.
When I star tested the cooled scope (2 hrs in stable windless environment) I
noted that the intrafocal star image was very soft and 'wooly', unlike the
extrafocal image which was fine.  The scope has a pretty snappy focus.
There is no visible astigmatism.  On the night I did this testing, there was
a thin veil of high cloud which partially obscured the target stars I used,
dimming them by one or two magnitudes.  Am I looking at a turned edge here,
or at something related to the high cloud?  Anyone got any suggestions?
 
Many thanks
 
Tony
Wicklow, Ireland
 
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