Thx Gary. I have the Ronchi screen, although I had some problems using the file accessible on the Stellafane site. When reduced to a small size, the lines get all messed up. I thought it might have something to do with the graphic card, but the same problem occurs on several computers,it also occured on the computer where I went to have the screen printed to the transparency film. So my temporary Ronchi screen is in bad shape, I'll hve to find a better solution. Apropos, I reckon the Ronchi screen is placen exactly where the knife edge is at the moment and the green light then passes through the middle of the screen at the bottom through the Ronchi screen, reflects fro the mirror and returns to meet the eye behint the screen. Anyway, I hardly wait to start playing with the device.
22" f/3.61 David Lukehurst Ultra-Portable Dobsonian, mirror set by John Nichol
Nagler 26 mm, Ethos 13 mm, Ethos 8 mm, Nagler 3.5 mm
TV Paracorr
Lumicon 2" UHC, Lumicon 1.25" H-Beta, Orion 2" ND 13% transm.
Unihedron - SQM-L
Canon EOS 350d