Quote: I have a question- How many who are touting the acceptability of such poor mirrors with high strehl as being "acceptable" have actually seen what the imaging capability (specifically, contrast) of such a piece actually is? And can they describe it meaningfully to back up such assessment?
Quote:he talks enough about his own mess ups or returns, so you don't have to be so judgemental.
Quote: Also theoretically: why would a surface roughness of RMS 100nm be worse than, let's say, spherical abberation of the same amount?The latter will direct more light from Airy disk to the rings surrounding this. The roughness would probably just enlarge the Airy disk itself, but I expect not further than that ring?
20 inch f8 Chief Ed Jones designed and a 17 f9 Zanbuto Wide Band Chief Mike Jones designed .Both unobstructed telescopes .
Ed Jones ........... The best data is an interferogram, the best analysis is from an honest optician.
Quote: I am not being judgmental.
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Quote:You guys should have a mirror contest .
Quote:So, a 2mm roughness in 200mm mirror would spread (too tiny to notice) energy in a halo about 100 times the Airy disc diameter.
Quote:Mark, My point is that on the Igram the surface roughness is quantified and in other methods it is not. The KE shows roughness but what is good and what isn't? Carl seems to be throwing IF under the bus so to speak but yet he uses IF to test his flats. Surface roughness on a flat is just as damaging as in the primary. Sure, good mirrors can be made without IF but don't bash IF for the sake of self promotion.
7x50 tasco binoculars, 60 mm tasco refractor, 10" f/6 dob, (4" f/14 newtonian)
Quote:Im confused,I dont know anything about mirror making, or testing.Was planing on ordering a 14"from Zambuto, but after hearing what MKV is saying it sounds like maybe I would be better of looking elsewhere.Would Discovery be a better choice, they use interferometer testing?
Homemade 14.5" f4.3 Truss Dobsonian
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Quote: It is a good time for people who appreciate fine optics.
Quote:Quote:So, a 2mm roughness in 200mm mirror would spread (too tiny to notice) energy in a halo about 100 times the Airy disc diameter.Did you mean to say 2 nm, not mm?
Quote:you don't need IF to know this needs work...
Quote:But I am still looking for answers, so please answer these three simple questions
Quote:(1) do you think Vla's statement was "wrong and groundless"?
Quote:(2) do you know how wide is a virtual "slit" in a slitless tester (and therefore how sensitive is the test), and how do you determine that width?
Quote:(3) do you think it's okay to throw interferometry under the bus?
Mike Lockwood - Owner, Lockwood Custom Optics. 20" F/3 MX Starmaster, 14.5" F/2.55 self-built Newt., nine self-built scopes, 4.25" to 30" http://www.Loptics.com/
Quote:Quote:you don't need IF to know this needs work...You don't nee the Foucualt test either.
Quote:you don't need IF to know this needs work...
Quote:Also theoretically: why would a surface roughness of RMS 100nm be worse than, let's say, spherical abberation of the same amount? The latter will direct more light from Airy disk to the rings surrounding this. The roughness would probably just enlarge the Airy disk itself, but I expect not further than that ring?
Quote:Quote:and the slitless version had no slit at all on the source...
Mark, the slitless test forms a virtual" slit. The width of that slit is determined by the lateral position of the k-e.
Quote:and the slitless version had no slit at all on the source...
John Hayes, Ph.D.
Adjunct Research Professor
College of Optical Sciences
University of Arizona
I wonder how they test for smoothness on small scales in large mirrors like the 8 meter mirrors at Steward if you can't do it with an interferometer?
Tak FC100 Tak FS152 10" f/6 Zambuto dob 24" f/3.3 Starstructure
Quote: The first mirror interferogram given in Carl Zambuto's site has an rms of .008 wave, and the wavelength used is 632.8 nm, so it looks like the surface roughness is 50.6 Angstroms RMS - correct?Would it be correct to say that a 10-20 Angstroms RMS mirror by IF would be basically a functionally perfect mirror for visual observing if it's Strehl were also high( eg >0.96) ?
Celestron 8SE Dobstuff 13.1": Swayze refigured Coulter mirror, 6 pt mirror cell (2 pt edge support) and CF focuser board made by me StarBlast 4.5 ST80/PortaMount II Zhumell 20x80/Oberwerk 15x70 on a Seronik-style tripod boom mount Hubble Optics 18 inch F/4 mirror.
12.5" Home built F-4.8 Eq Newt. Lightholder Optics mirror 12'x12' roll-off roof observatory 6" Home built f-6 Newt. w/Dick Wessling mirror on CG-5 Eq. mount. 4.5" Orion Starblast My equipment philosophy... If it ain't broke, fix it anyway.
Quote:I don't see anywhere where the mirror in question is called a pc of junk by Zambuto.
Quote:Ok, but my question remains. :Then ask someone with a solid theoretical and practical experience in optics, what level necessary to consider polishing a mirror like quality. I'm very interested in this issue because I always used the Lyot test.Would test Lyot sufficient to evaluate next to these indices certificates?