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Interferograms for Four High Quality Telescopes and Two Commercial Telescopes
Some of you might be might be interested in photos and a brief analysis
added to Roland Christen's essays: http://voltaire.csun.edu/roland/interfer.html Ed T. |
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Interferograms for Four High Quality Telescopes and Two Commercial Telescopes
"Edward" wrote Some of you might be might be interested in photos and a brief analysis added to Roland Christen's essays: http://voltaire.csun.edu/roland/interfer.html Ed, Interesting stuff! I recently purchased a used Obsession 20-inch Newt. The Torus mirror had been re-figured at the request of the owner, even though the specs show it to be "OK", but not "spectacular". Torus now posts on their website interferograms of each mirror and re-figured mirror that they do. On the mirror I have, the re-figured mirror is not as good peak-to-valley, but it has a better RMS and Strehl ratio. In fact it is better than the figures on my 10-inch RC Cass, and a 20-inch RC Cass that I use a lot. Torus also provides figures that are the average of 20 interferogram tests, plus a Ronchi grating image. They average results of many tests because they claim that there is too much variation between test runs. They were having problems with producing a few turned-down edges and missing them with just an interferogram test, so they concluded that they also had to do the Ronchi test as the best way to detect a turned edge. George Normandin |
#3
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Interferograms for Four High Quality Telescopes and Two Commercial Telescopes
"Edward" wrote Some of you might be might be interested in photos and a brief analysis added to Roland Christen's essays: http://voltaire.csun.edu/roland/interfer.html Ed, Interesting stuff! I recently purchased a used Obsession 20-inch Newt. The Torus mirror had been re-figured at the request of the owner, even though the specs show it to be "OK", but not "spectacular". Torus now posts on their website interferograms of each mirror and re-figured mirror that they do. On the mirror I have, the re-figured mirror is not as good peak-to-valley, but it has a better RMS and Strehl ratio. In fact it is better than the figures on my 10-inch RC Cass, and a 20-inch RC Cass that I use a lot. Torus also provides figures that are the average of 20 interferogram tests, plus a Ronchi grating image. They average results of many tests because they claim that there is too much variation between test runs. They were having problems with producing a few turned-down edges and missing them with just an interferogram test, so they concluded that they also had to do the Ronchi test as the best way to detect a turned edge. George Normandin |
#4
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Interferograms for Four High Quality Telescopes and Two Commercial Telescopes
"Edward" wrote Some of you might be might be interested in photos and a brief analysis added to Roland Christen's essays: http://voltaire.csun.edu/roland/interfer.html Ed, Interesting stuff! I recently purchased a used Obsession 20-inch Newt. The Torus mirror had been re-figured at the request of the owner, even though the specs show it to be "OK", but not "spectacular". Torus now posts on their website interferograms of each mirror and re-figured mirror that they do. On the mirror I have, the re-figured mirror is not as good peak-to-valley, but it has a better RMS and Strehl ratio. In fact it is better than the figures on my 10-inch RC Cass, and a 20-inch RC Cass that I use a lot. Torus also provides figures that are the average of 20 interferogram tests, plus a Ronchi grating image. They average results of many tests because they claim that there is too much variation between test runs. They were having problems with producing a few turned-down edges and missing them with just an interferogram test, so they concluded that they also had to do the Ronchi test as the best way to detect a turned edge. George Normandin |
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