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how to make a secondary

Started by BABOafrica, 08/23/2012 12:17AM
Posted 08/23/2012 12:17AM Opening Post
In one of the old ATM books I have, it explains how to make a secondary. I want to try to do that.

I got a f/4.5 17.5" primary (damaged but workable) and I was thinking of making a 3.5" secondary for it.

I was hoping I could get away with using 12mm plate glass. It's the thickest glass I can get here in Kenya.

I have more than enough grit to do whatever needs to be done, I was mainly concerned about the thickness of the glass. All the secondaries I've seen are thicker than 12mm.

Any thoughts on the matter?

Clears,
Joe

In lumine tuo videbimus lumen.

8O Home-made 10” Dob / Home-made 4” refractor

EPs: Konig 32mm (1.25") / Zhumell WF 30mm (2") / Nagler 13mm T1 / Orion Sirius Plossls 25 & 10mm / Zhumell Plossl 9 mm / Meade MA 9mm
Posted 08/23/2012 08:05AM #1
If you can hand pick the glass from a good selection of candidate blanks, you may not need to grind and polish anything:

http://www.oldham-optical.co.uk/Elliptical.htm

The traditional method (described in Texereau) involves making three flats, all worked against the others in a round-robin fashion and tested similarly.

Jim McSheehy