[ATM] Focal Ratio for a Fast 24"
peter at kitgear.com
Mon Mar 14 09:04:19 JST 2011
Thanks Lance for the advice about the BVC and I'll keep an eye on the
laminations. The mirror already has an f/5 curve and it looks good so far.
You may remember that we met a few times at Starfest.
Mel thank you for your nice reply. I have to say that after reading your
message and associated links I'm really excited about this project. My
biggest concern now has to do with the exit pupil size relative to my aging
eyes. I'm turning 50 this year and if I interpret your chart properly I'm
already in the 5.5 mm range so I would lose light at a 6mm exit pupil. Do
you know if the chart assumes complete dark adaption or normal skies for
astronomy? Perhaps there is not difference.
I'll appreciate guidance during final figuring to make sure I meet the
extremely tight tolerances of an f/3.3 figure. I'll l have to think more
Other than a star test which other testing methods were you referring to?
Today I started grinding so here are a few pictures of the mirror. I'll add
more pics as I get further along. I'm using a 10" tool to hog out the
remaining 0.150". The BVC glass seems soft but still I'm only able to cut
0.010" per hour of grinding. I have a 75% tool ready to take over once I get
close to the ROC.
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