Re: [ATM] 8" F/4.2... Done?

[Jim Burrows <burrjaw@earthlink.net>]

At 2005-12-06 18:28 -0500, Jason Hissong wrote:

>Here are the ML readings...
>http://www.undermidnight.com/images/atm/12052005_figureXP_final_ml.jpg

I'm guessing the ML "readings" are really the result of a Foucault 
test.  In general, the ML plot doesn't tell you what to do next (as 
FigureXP says, "...this isn't the surface of the mirror.")

>Should I leave it as is and trust the the surface RMS error?
>
>Getting so close and I am afraid to do much else with it.   I have yet
>to do a serious star test because I don't have a center "dot" on the
>primary to collimate it properly.

A Strehl of .919 says don't touch the mirror, it's time for a star 
test.  If you want to put that off, I'd suggest another bench test, 
particularly if the last test was indeed Foucault - it's tricky at 
f/4.2.  There's several alternate tests you could try (not really "am I 
done?" tests):  caustic, LWT (Lateral Wire Test), Everest pin.

         -- Jim Burrows
         -- mailto://burrjaw@earthlink.net
         -- http://home.earthlink.net/~burrjaw
         -- Seattle N47.4723 W122.3662 (WGS84)  

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