Then there is the infamous world of military acronyms. my personal favorite is an acronym within an acronym! The GASP Program- which was the GPETE Asset ...
... This makes me curious. Why the "diameter of mirror divided by f " term in addition of focuser size? If the tube/cage edge is one focal length away from the...
... I think Rohr did a Zemax layout of the beams and it came out to 1/8 wave for 5mm seperation. People need to ask the kind of interferometer that was used in...
Ric, ... You seem to imply by this that the Bath interferometer is incapable of producing an accurate wavefront rating, because of its inherent astigmatism. I...
Nils I have interchangable focusers and to be quite honest the last factor was used for my 50mm camera field set up with an oversized diagonal for wide field...
Nils Another thing. It incited others to direct the questioner to reliable design programs which I out of curiosity downloaded for myself. As for me, I just...
First, decide how much vignetting is tolerable. If your are going to do any kind of photometery, the appropriate amount of vignetting is ZEROE over the focal...
It would help to qualify the wave rating you are specifying. PV or RMS? Surface or wave front? I have not always specified these either but I try. Mirror...
... The 1/8 wave rating I got for a 5mm seperation was from a posting Rohr made on the interferometer group .At 1/8 it better be p.v....:) ... the ... The...
Ric, The astigmatism caused by non-zero beam separation is a function of the beam-to-beam distance, the diameter of the mirror and the radius of curvature of...
Hi all, I've got a strange (to me) problem with a dob I'm trying to put together. It's a fast (f4) 8" two pole collapsing dob. Mechanically it seems fine but...
Dave, ... As you guessed, most likely it is an optical problem with the primary. Your best tool for diagnosing this in the scope is the star test. Are you...
Several ways to test. The Star Test is one way as Steve mentioned. Also there is the Ronchi grating test where you are looking for straight lines. A fine...
... Do you mean straight lines iwth one of those ronchi eyepices because other wise for an 8" F/4 the lines should be very curved in a regualr ronchi test...
Mitch, ... When the Ronchi test is done at the focal plane of a completed telescope using a star as the light source, the Ronchi lines are ideally perfectly...
Your suggestion reminded me I had an Easy Tester in the closet (duh). I used it and found that the mirror is horribly undercorrected, so badly in fact that I'm...
Has anyone seen, come up with or made "telescoping" struts for the "tube" assembly? The idea being that one could just extend the top sipder/diagonal up from...
... Yes, it has been tried before. If your "truss tubes" are parallel, there is little incintive to resist twisting due to parallelism of the system. This...
Remember that when you test on the bench, you're testing at the ROC of the mirror. Thus a parabola has curved lines as the ROC is constanly changing and the...
I'd probably more want to do the bungee cord in the middle of the rods ala the collapsing/folding rods for the lightweight tents these days. This method only...
Hi, My vision isn´t the same anymore, I´m having problems to compare the grays on the focault tester specialy with long FL mirrors. Anyone with a project for...
Ricardo Dunna I've never needed to do it but woudn't the opticle element from an eyepiece (minus the case/tube) mounted so you can focuse it on the knife-edge...
Using an eyepiece alone will not work for the Focault. A complete telescope assembly ( objective and eyepiece ) is needed with the objective just behind but...
Get with Bob May. Even with my rotten eyes, I can read a foucault test on his computer screen. It is not hard to do. ... From: atm_free@yahoogroups.com...
... grays on the focault tester specialy with long FL mirrors. ... Or as richard said you could rig up some type of camera. I have tried using my monochrome...
Ricardo, Any small, good quality finder should work fine. I use the finder from a Meade ETX-90. Another solution is to use a webcam with the finder scope, and...
FWIW, the monitor that I like to use for viewing images has a 4X amplifier on the input so that the contrast is really high. This works very nicely on...
Fellow Astronomers, I recently replaced my homemade finder scope with a neat 60mm one. Better and clearer over the cheap poorly constructed ones often found on...
