Coordinator, Fox Park Observatory
A 50mm Edu-Science refractor started it all...Thanks Mom and Dad!
Celestron CGEM; Various OTA's Various eyepieces; Modified Canon XS; Orion SSAG
My Astrophotos on Flickr
Quote:I have a buddy that wants to build a folded refractor but he is having trouble finding quality flat mirrors for the scope. Any thoughts on where I could direct him?
Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schiefspiegler,60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4" f/12, 4.5" f/16 & 6" f/12 Schupmann Medial refractors, 4" Celestar, 19 Stellafane awards 9 in optics Engineering = Taking what you have and making what you need.
6"f15 D&G, 6"f5 Jaegers.
TSA 102, TV60.
Docter 15x60, 10x50.
Ed "You have to grow old, you don't have to grow up."
Quote: Purchased some thick 1/10 wave mirrors from the Shed that look good. Not tested yet.
-DannyMy warehouseMy Channel
Quote: Quote: Purchased some thick 1/10 wave mirrors from the Shed that look good. Not tested yet.
I got a couple from the shed I had to send back. they do have a 10 day return policy which is nice.
I wouldn't wait to test them.
Quote:I have a lot of experience in folded refractors. You do not need 1/10 wave or anything close to that! 1 wave of flatness is perfectly fine. However, there must be no astigmatism in the flats.
Quote:Excellent surface smoothness is a requirement of any optical surface, but I repeat that 1/10 wave flatness is overkill. OSLO or ZEMAX will tell you that 1 wave of flatness is perfectly adequate. The tilt with a long refractor OG is very small, so astigmatism is not a problem. Even a Newtonian flat need not be 1/10 wave flat! If the departure from flat is elliptical in shape so that the projected error is purely spherical, you can get away with a surprising lack of flatness. It only changes the focal position very slightly. See Norman Oldham's web site on this point.
Quote:I got a couple from the shed I had to send back. they do have a 10 day return policy which is nice.