Dale, thanks for responding. The mirror, when it was spherical, no large defects were noted. The edge looked good and did not show astigmatism. In the figuring...
23365
david_a_rowe
May 19, 2013 2:12 am
Hello, You might find this presentation on Interferometry of interest: http://www.atmsite.org/contrib/Rowe/bath/rtmc04/rtmc04.html The colors on the title page...
23366
atmpob
May 19, 2013 3:40 am
I don't know about your term K. However a conic constant of -1.19 is a focusing optic. It is just an over corrected paraboloid. Where a sphere would be 0 and...
23367
david_a_rowe
May 19, 2013 3:51 am
Hi Dale, It certainly makes sense to define the Strehl as the ratio of the on-axis light intensity of the actual mirror to the ideal mirror, whatever desired...
23368
atmpob
May 19, 2013 4:08 am
Aldo, That is not an easy question to answer because all errors including astig add to the overall surface error. It also depends on which criterion you want...
23369
Jan
janvangastel
May 19, 2013 5:43 am
Aldo, If this report is only based on one interferogram, the astig value (and other values) is not reliable. If you want to be sure about the astig, you need...
23370
John
a.johnw
May 19, 2013 1:29 pm
Thanks for your web pages David. I've spent some time looking at the Dall twin slit test but still aren't sure if I understand it. Some one posted a paper on...
23371
david_a_rowe
May 19, 2013 2:25 pm
Hi John, I wrote a DOS-based Foucault analysis program called Figure (ca. 1996) that became the computational heart of FigureXP, which is still in widespread ...
23372
Ed
opticsed
May 19, 2013 4:06 pm
Dave, I too have built a Bath interferometer to familiarize myself with it. The thing I like about it is that it can quantify astigmatism which is a very...
23373
John
a.johnw
May 19, 2013 4:52 pm
Given one of the persons that mentioned that Dale you could be right. Thanks for the info on the robo. Camera shadow readings interest me as I think there is a...
23374
atmpob
May 19, 2013 5:38 pm
Hi John, Ditto what Dave said for OpenFringe. Dave Rowe also wrote the heart of that section of OpenFringe as well because OF is based on his FringeXP. What I...
23375
John
a.johnw
May 19, 2013 5:43 pm
Hi Dave :-) My brain was addled. It happens when I look at too many things at once. I shouldn't have used the term best fit conic and normalising can mean all...
23376
atmpob
May 19, 2013 6:02 pm
John, The bath induced astig for that configuration with a laser of 640 nm is .061 waves on the wavefront or .03 waves on the surface. So you must have not...
23377
atmpob
May 19, 2013 6:04 pm
John, I meant to say in the last email that using a slower mirror works better for beginners. Your 8 inch mirror is already small enough. Dale...
23378
david_a_rowe
May 19, 2013 8:49 pm
Hi John, I don't know the particular software in question, but this appears to be an example of calculating the focus position that minimizes the RMS surface...
23379
atmpob
May 19, 2013 8:52 pm
Ed, The artificial null depends upon the accuracy of your measure of the diameter of the clear aperture, it's ROC and the laser wavelength. The null has a...
23380
paul valleli
pvalleli
May 19, 2013 9:20 pm
Dale, What I meant was that if one points any mirror at a star that is not a Paraboloid with K= -1.0000, it will not produce a stigmatic image. Very slight...
23381
zoran stojcevski
astrozor
4:18 am
Kevin, Â this idea is not at all bad, I already bought 2-3 months ago digital drop indicator in range 0-1 inch to measure the tester axial movement !!!! It is...
23382
John
a.johnw
10:25 am
I think that aspect relates to many of the questions I have asked over what could be several years. I have no other interest at the moment other than finishing...
23383
Vladimir
vladimirgalo...
10:50 am
I am intersted in trying to test f/2 mirror with my PSI Bath in order to find out what is possible, what are requirements for interferometer, what will be the...
23384
atmpob
2:47 pm
John, From a previous message about Bath astig you specified an 8 inch F3 mirror as your target. Now you have confused me. How is a 12 F2.8 mirror smaller and...
23385
John
a.johnw
2:53 pm
This idea may be of interest. http://home.freeuk.net/dunckx/astro/index.html Off the top of my head tilt shouldn't matter on a sphere providing what ever rolls...
23386
david_a_rowe
3:07 pm
Hi John, This page is very old, but the equations given on it are exact, and account for the radius of the balls. ...
23387
Jerry
atc322asd
3:18 pm
It takes balls to make a good spherometer. If not balls what? Sharp scratchy points? Or flats that would really complicate compensation and still put a sharp...
23388
John
a.johnw
4:05 pm
To find out which tests are actually usable Dale without a possible fruitless expedition into figuring the mirror I want to make if no test that I can use is...
23389
atmpob
4:38 pm
John, You are rambling again. I asked a very simple question. Why when I said "smaller, slower mirrors are better to learn with" did you then propose the...
23390
John
a.johnw
6:47 pm
Before I rambled if that's what you want to call a certain degree of discussion Dale I said very specifically why the already made 12in F2.8 - BECAUSE I HAVE...
23391
John
a.johnw
7:03 pm
I'll accept its as exact but can understand why some feel that the ball's addition causes some people to believe that isn't exact. It's not intuitive. I've...
23392
atmpob
7:34 pm
John, Somehow I got the impression that you had a 220 F3 that you wanted to measure. I guess you are at the stage of you would like to make one but worry that...
23393
atmpob
8:38 pm
Paul, Ok I understand. Now I'm probably getting in way over my head to explain the reason OpenFringe uses the strehl a little bit differently. It approximates...
