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Dave, I'm guessing you had a lot of requests to check mirrors due to the HO mirror thread .I guess these folks don't realize they could build a tester cheaper than round trip shipping would be and that they aren't hard to use. I made a tester over winter didn't even cost me $10 & using it was easy.

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yes, i tried to answer a bunch of emails and finally just started this thread. if i did not directly answer you, and just replied with this link, i was not being rude, i just had too many emails for a personal reply to everyone. sorry .


some other answers here too:


if you are never going to make a mirror and just want to "see" the roughness in your mirror or look at TDE indeed you can skip the dial indicator altogether. add one later if you feel the need.

no you dont have to use a piece of copper pipe, you can use any straight anything. take apart that old printer you have in the closet and use the rods, axles, gears make nice knobs.... old microscope stages, old linear guides from machines, aluminum tubing left from your trusses, arrow shafts. i know its "safe" to work exactly off a set of plans, but once you see how simple it is your mind will explode with ideas of what you could have used.

the razor blade needs to cut through half (or so) of the LED light. the blade is IN the path of the light.

if you paint the front of the tester a light color, it can help you adjust the return beam.


you want a bright LED for testing uncoated optics or very long focal length optics. radio shack is good or if you want really bright (you might even have to dial down bright) LEDs go to:
http://www.superbrightleds.com/leds.htm


a really nice way to test for strain:
http://bi-staff.beckman.uiuc.edu/~melockwo/mirror_making/strain/strain.html

tri-color LEDs:
http://www.superbrightleds.com/TriColor%20LED.htm

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dave bonandrini
30" f/5.2 Dobsonian
President of GCAC
Astromart Moderator

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