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.

"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

"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

"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