A Hard Day's Work ................ is ready
The author of this program, Massimo Ricardi, Italy spent a lot of hours on the source, and
step by step, and the advices of some users of that extraordinary Fringes Analysing
Software this is the result now to solve some of the problems in analysis all kind of fringes
map. Especially for those astronomers, who want analyse Radius of Center fringes, as the
following fotos show. By the way this kind of analysing fringes is not the matter of a
Zygo, but most of the astronomers couldn't buy a new modern Zygo with all the very
expensive essentials round it. In a second step, I will show some of the calculation
problems, you have.
01. AtmosFringe - Version 2.7
The first Edition Version 1.4 was allready a very comfortable analysing programm and
Massimo startet this project more than two years ago. On Chrismas 2004 we got in
contact and so I've got every new updates for controlling and working with this - meanwhile
the best program an astronomer can get. So I will not repeat my report about V 1.4. I'll
just report of the interesting new features and implementations.
The AutoTracing of the fringes runs with great exactness, when you have a good
contrast of the fringes map and you select short dots distances. Very tricky is to put just
one point on every fringe and the program is drawing fringe by fringe in a short time. Very
important in this case is a sharp edge of the fringes map.
[Blockierte Grafik: http://rohr.aiax.de/AF-V2-7-01.jpg]
Now in this Version 2.7 it's possible to average several kind of fringes maps. So I had
to analyse a Newton mirorr 403/1803.5 in different setups, on at RoC(Radius of
Curvature) as a Zygo does, and in autokollimation or double pass setup. The four
exposures with the Bath-Interferometer and 532 nm wave show differents results, you
can't imagine them correct at the next foto.
[Blockierte Grafik: http://rohr.aiax.de/AF-V2-7-02.jpg]
But if you calculate the four RoC fringes maps, there are very different values, of course.
Now this version 2.7 calculates the averaged results on basic of the Zernike coeffitiens,
the correct way of this. An arithmetic calculation with the PV- and Strehl-value is wrong,
as some astronomers did and shows different results, as you can see.
[Blockierte Grafik: http://rohr.aiax.de/AF-V2-7-03.jpg]
This is the fringes map of the best result, number 4. For analysing this fringes map you
have to know the exact optical diameter and the exact radius, and the edge on the foto
must be sharp. It makes a big difference if the sourrounding circle is not correct and if
the radius is not correct. The longer the radius in this example the smaller the
undercorrection of this mirror. So with 3660 mm radius instead fo 3607 mm the results
become better and better.
[Blockierte Grafik: http://rohr.aiax.de/AF-V2-7-04.jpg]
One big problem of the RoC analysing is the astigmatism. At first you have to look for a
significant astigmatism, because the air movement shows artificial astigmatism. So there
is the discussion, are you allowed to deactivate astigmatism or not. Coma you can
deactivate of course. So I use this test, that shows the actual situation. I guess there is
no significant astigmatism. But the new Version 2.7 allowes you subtracting values from
each of the Zernike coeffitients, in this case a definite amount of astigmatism. But then
we have to discuss the different orders of astigmatism: Low oder high order one as this
"Zernike Zoo" shows.
[Blockierte Grafik: http://rohr.aiax.de/AF-V2-7-05.jpg]
If you have a short focus mirror f/4.5 so you get a lot of fringes on your map. For this it's
better to draw the fringes as this foto shows and you insert 2 instead of 1 at
[Blockierte Grafik: http://rohr.aiax.de/AF-V2-7-06.jpg]
The next feature of this program calculate a RoC fringes map to a null-test as the Zygo
does. So it shows in a RoC map all the errors: Coma, astigmatism, undercorrection, that
you wouldn't see with your eyes and so you can imagine much better the errors of a
[Blockierte Grafik: http://rohr.aiax.de/AF-V2-7-07.jpg]
This shows the Certification Report of the actual version 2.7. In this case the best of the
[Blockierte Grafik: http://rohr.aiax.de/AF-V2-7-08.jpg]
This foto shows the situation with Foucault or Lyot-Test, but in double pass.
[Blockierte Grafik: http://rohr.aiax.de/AF-V2-7-09.jpg]
There were a lot of questions we could check with a Zygo in my neighbourhood. And so
we noticed how important the correct supporting of a mirror is by testing it. Meanwhile I
can test with the Zygo, too. But most of the normal astronomers wouldn't pay for that.
But it would be possible.
[Blockierte Grafik: http://rohr.aiax.de/AF-V2-7-10.jpg]
The next is following later.
Prima, AtmosFringe wird immer besser wie ich sehe.
Ich würde mir noch ein wesentlich grösseres Fenster für die Streifenauswertung wünschen.
they is really very sympathetic like update, I my version impatiently waits, certainly this week. Then I would have questions about how to take photographs of fringe of good quality!!!
For the moment I use an eyepiece of camera with my webcam, the image is good but not large enough
Beautiful work, Wolfgang and Massimo!
I have a suggestion to make for next the update, it would be interessant to be able to simulate the ocultation of the secondary, for example while entering its size, the software would center it automatically, it would be simpler than with the "add circle"?
What do you think about it?
I just have the problem, to undestand your suggestion: "to simulate the ocultation of the secondary", would you explain this? Is it a way to get the sourrounding circle automatically? Could you add any drawing for that?
"Steter Tropfen höhlt den Stein..."
AtmosFringe ist das Freizeit-Vergnügen von Massimo, und ich bin äußerst froh darüber,
daß dieses Programm sich so wunderbar weiterentwickelt hat, mit unser aller Anregung
und Hilfe. Die Nanometer-Angabe war ja Deine Idee. Die Frage der Fenstergröße bewegt
mich genauso wie Du und die anderen User. Irgendwann hat das auch der Massimo
programmiert. Es muß nur noch ein paarmal angesprochen werden, besonders auch im
privaten Kontakt. AtmosFringe hat sich ja tatsächlich aus der praktischen Anwendung
heraus entwickelt und zwar ganz besonders in der für uns wichtigen RoC-Auswertung,
also der Auswertung im Krümmungsmittelpunkt einer Parabel, weil bei großen Spiegeln
der Flat fehlt, und Zygo ja aus dem Krümmungsmittelpunkt heraus auswerten kann.
Bei hinreichender Sorgfalt kann man ja tatsächlich die Zygo-Messungen mit unseren
Mitteln einstellen: http://www.astro-foren.de/showthread.php?t=6761
excuse me, I am explained, like you mentions above, with a zygo one can simulate the place of the small flat mirror in the telescope, it would be thus wise to be able to simulate its place thanks to the key "add obstruction" but that it is the software places this obstruction according to a parameter that one insert in the software.
One can oneself do it with "add obstruction" but they is less easy?!
with AtmosFringe it's also possible, to simulate one secondary flat. The first circle would be the surrounding one, the second inner circle would be the obstruction one. If there are any surface errors, so you can subtract them by the obstruction circle. But then you'll get another MTF-diagram. Many of the Germans wouldn't understand this,
they want a certificate of the full surface of the parabola - this is a special philosophy by the astronomical distributers, how they sell Newton telescopes: At that time with the term "PV" the worst argument of all. This is funny.
however same with the test of Foucault and the mask to "couder" , the center is blocked?!The central part of the mirror is never used.
The central part of the mirror is never used.<!-- / message -->
yes, that's true, but most of the Germans wants it perfect or better than perfect.
it is all with their honor, but it is more expensive