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


Since you already have the dial indicator, you can always make a new base
for it.  A lathe helps to make a 3 ball or ring spherometer.  I'd suggest
that you make one that is no more than 1" less in diameter than the
smallest mirror that you plan on making.  You can also do a bar type
spherometer, also called a two ball spherometer, instead,  That kind just
needs to have the indicator midway between the two balls. I do have several
spherometers that I have built and they are in the 4" range.  If
you're in the 48 states, I can ship you one that has a .0005"
indicator on for $40 if you want to go that way.  I have no more with a
secondary dial for the full scale.  They do work well for the typical
mirror focal length that most people do, the 40" to 150" ROC. Bob
May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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