Clean everything rinsing under fresh water every time. Clean clothes . Clean hands. Clean work space , no air movement.
The ronchi screen downloaded from stellafane printed on a acetate on a laser printer works. Easiest way to start. Use the Bartels light box or a tiny tube on a stand with an led in it at centre . The auto collimation test is far too complex for the first stage of polishing.
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Originally Posted by legswilly
I will need to be more careful with the washing/cleaning after each grit. Made myself a wash stand covered in black plastic just outside the shed entrance. After my session today, I found some small scratches and a few little pits. Tomorrow I will clean everything before I start another session. Keep on going with the 800 grit until I get it right.
Another problem I have is the foucault/ronchi test. I built the autocollimation test stand as in the movie on the Stellafane site. Until I have a mirror, which I am making now, I thought I would try and do the ronchi test. They say it is easy, for me it is not obvious.I got some slides with ronchi grids, But the grids are just a small area, maybe 10mm square and one can't shine the light source through them and at the same time look through the grid. Made myself a ronchi grid out of fishing line to shine the light through and at the same time look through it. Cant see any pattern.
I bought a cheap mirror from China solely for the purpose of learning how to test a mirror. It is a 200mm mirror and the specs say it is 750mm focal length. Today I measured the saggita as 0.1325" and that works out to 742.8mm. So I am within the range of the tester set up to 1500mm. What do I do wrong?
Wish I had a telescope/mirror grinder here.
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