From: "Bob May" 
To: "atmlist" 
Reply-To: "Bob May" 


A lens is  a much more complex thing than a mirror is.  I'd suggest that
you get a few mirrors under your belt first before going and grinding a
lens. The first thing I'll note with a lens is that you have to meet the
ROC values for 4 surfaces without fail. Second is that you have to attain
those curves AND make the thickness of the glass to the spec in addition.
Third is that the two surfaces on a lens have to be concenctric to each
other and centered on the glass - your basic wedge is not what you want as
that is a built-in prism.
If you go to Google and type in "mirror making" you will get
hundreds of sites describing how to make a single curved surface that will
act as a nice Newtonian mirror.  There are even a few sites describing
making flats that will be suitable for the secondary if you want to go that
far.  In addition, there are thousands of sites that describe making the
rest of the telescope. I'll also note that even before you start grinding a
lens, you have to do all kinds of calculations to find out what curves to
put on the 4 surfaces for a doublet refractor.
Bob May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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