Update on progress:
I have almost reached the sagitta of 3mm using #100 grit. There is no noticeable astigmatism, at least not by rough measure. I say this because I can slide a series of drill bits in various directions under a straight edge and each size pushes out the same distance no matter which direction I choose. So, I feel that things are going pretty well.
BTW, I made a new tool using small pieces of 4mm glass. This works quite well. The grinding proceeds very smoothly.
The one thing that I'm not sure of this: there's still a 5mm ring all around the edge where no grinding (or at least very little) has taken place and so the edge is still flat. Otherwise, there seems to be a nice smooth curve from center out towards the edge.
Is this the normal thing?
Clears,
Joe
I have almost reached the sagitta of 3mm using #100 grit. There is no noticeable astigmatism, at least not by rough measure. I say this because I can slide a series of drill bits in various directions under a straight edge and each size pushes out the same distance no matter which direction I choose. So, I feel that things are going pretty well.
BTW, I made a new tool using small pieces of 4mm glass. This works quite well. The grinding proceeds very smoothly.
The one thing that I'm not sure of this: there's still a 5mm ring all around the edge where no grinding (or at least very little) has taken place and so the edge is still flat. Otherwise, there seems to be a nice smooth curve from center out towards the edge.
Is this the normal thing?
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