Friday, December 4, 2009

Primitive telescope making tools

I've recently restarted my 4-inch reflector telescope project at the urging of an acquaintance from dance class. About 10 years ago I had already hogged out the curve, aiming for about a 100cm focal length, which I overshot a little. I managed to find my grinding log from back then, but it includes entries only for grits #120 and #220. I skipped #320, figuring that I can just put in (much) more time at #500; I also didn't want to deepen the curve yet more. Actually I'm not sure if I did or didn't use #320; the baby food jar in which the grit lives had lost its insulation-tape seal around the rim of the lid.

My grinding station is now the bathroom table in the otherwise unused flat in my back yard. Every other waist-height surface in my home is in use. (Yes, I need to get my ass in gear and create some more surfaces.) But anyway, unused is good, as it means there aren't any random household particles landing on my work.

According to ATM canon, I should have a wooden slab and brackets to hold the mirror. But faux-poor and lazy as I am, I simply plonked the glass on a sheet of newspaper, in turn on the bare laminated tabletop, and started grinding. Here is my setup:

That black thing is a quick-and-dirty pitch polisher. I simply softened some pitch and transferred it to a pickle jar cap, then pressed it on the mirror blank to establish some contact. The pink stuff is rouge, of course. I was completely surprised by how well this polisher worked - I got specular reflections after about 5 minutes of polishing with this thing!