Beiträge von Acrab

Dear Wolgang,
Only Terry could clarify this matter, I'm sure it has a logical explanation of where those numbers come out. The fact is that he never post in the forums, including Cloudy Nights in EEUU, which also touched on the subject:
http://www.cloudynights.com/ubbthreads/showflat.php?Cat=&Board=atm&Number=4004876&Forum=f67&Words=&Searchpage=0&Limit=25&Main=3998758&Search=true&where=bodysub&Name=22994&daterange=1&newerval=1&newertype=y&olderval=&oldertype=&bodyprev=#Post4004876
How I said before, in EEUU his reputation is impeccable, I have not found a single post in any forum where someone says that one of his mirrors is mediocre, on the contrary, always labeled as premium mirror.
Anyway I have to say that I don't understand very much about of optical theory, although I always tried to find the reason of things, but I can assure that the Ostahowski mirror, tested under the eyepiece, is simply excellent, and I have almost 20 years of visual observer.
Víctor

Mi question is:
And then the numbers that appear in the quick fringe test report, have they been invented directly?

Wolfgang,
Sorry, I do not understand optics. Terry has an impeccable reputation in the U.S., but then where those numbers come out?.

Hello Mr. Wolfgang,
Terry Ostahowski mail me some time ago with this answer about this. I'm sorry is in english:
Hey Victor,
I had three 16" f/5 mirrors up for sale at one time (made all of them in a group) and they all were very consistent with one another, though, every optic has subtle differences.
I read the Cloudynights forum, though I never post to them, and it is pleasing to see that those who understand the difficulty in making an optic look this good with interferometry (especially one of this size) are hands down in agreement that it is a superb mirror, thank you.
The idea of the P-V being different is not a new discussion as we are talking about the two worst points of data. As I understand it, OMI no longer provides P-V data on their optics (please verify this) just because of this exact subject. I hope I do not have to do the same as I have always posted very reasonable numbers on my primaries. Your primary is an exceptional one but most of mine are in the .20 to .25 P-V range. I believe this is a fair way to market a primary mirror despite the competition using P-V numbers that are 1/50 wave or better (without interferometry). It is a hard sell for me but I know it is an honest one and I'm okay with that. I have always said (for many years now) that I would buy a mirror with an interferogram (forget the numbers-just show me a fringe picture) versus a mirror that has a "certified" book of numbers.
For the record, all my mirrors are corrected by double pass auto collimation as it is the null test configuration for a parabola. I have been using this same test set up for more than 20 years. The Interferometry is done only after I have figured it as close to a null as I possibly can (or think I can), then I test it to see where it can be improved upon, if at all. For those who really want or must know, I can do Interferometry both by double pass and single pass. I have just learned to appreciate the quicker set up time (much easier to collimate a single pass!) associated with the RN interferometer. All reference elements are tested/made at Zygo for those who wish to cast doubt when the opportunity presents itself.
Victor, you have my permission to post any or all of this message.
Enjoy your telescope.

Terry