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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?


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:

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