From: "Pieter Meyer" 
To: 
Reply-To: "Pieter Meyer" 




 Hi Guys
 Being an ABSOLUTE novice atm and meddling with something totally foreign to
 me……MODAS, I am wondering if I should parabolize my mirror?
 With that said here's the facts:
 My 150mm plate glass mirror with a focal point of 980mm (?COC - where the
 sunspot is in-focus when testing with wet mirror, sun and wall). MODAS
gives
a f stop of 6.53.

Now, if I choose spherical in the easy design option it spews out these
beautiful concentric spot diagrams and with parabolized its skews things
terribly or is it terrible….?.

The thing is, even after the tutorial reading I don't know which is better
or worse and I understand about 10% of what is going on in the program.

I am in the finishing stages of polishing ( after discovering if you make
your pitch in winter [ave. 16deg. C] it doesn't work so well in summer
[ave. 35 deg. C]) and have kept a nice sphere according to Ronchi test and
will love to eliminate figuring.

Please advice
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