[ATM] first light on a Lurie-Houghton

[Guy Brandenburg]

I think I have finally finished the Lurie-Houghton that Nagesh Kanvindeh and I started about three years ago. Looked at a couple of nearby rooftops this afternoon, then adjusted a few things; still need to move the primary back a little bit; went back to the lathe to make the lens cell fit better into the tube, made a little shield to go on the front out of some thin metal and duct tape. This is a HEAVY telescope all right!
Will be heading up to the Almost Heaven Star Party right next to Spruce Knob, WV tomorrow to see if it really works on the stars and stuff. I hope all of the work has been worth it.
One interesting thing that I discovered was that surface #2 and surface #4, which are supposed to be identical but opposite and have extremely long radii of curvature (one's convex, the other concave) were really difficult to figure. The concave one gave me the willies. Finally got it. Then when I did monochromatic interference testing of that surface against #2, which is supposed to be identical, I was really upset because there were about 80 concentric interference rings. Well, I did some calculations from first principles and also using the new WillBell book on making a refractor, and calculated that the difference in ROC of the 2 surfaces worked out to about 1.4 inches, which didn't mean squat according to my maneuvering on OSLO LT. 
Evidently, this is a very forgiving design.
I forget where it's possible to upload pictures to. 
This is a GREEN telescope, by the way.



Guy Brandenburg, Washington, DC
My home page on astronomy, mathematics, education:
http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
or else 
http://tinyurl.com/r6fh2

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