Roger Hamlett wrote in message ...

"Cie" wrote in message
roups.com...
Hi,

How is the quality of the latest generation of celestron 11"
SCTs? What is the most lemon one you've received.

Cie
There was a page, showing a set of tests carried out on a C11 in Germany,
published here a few weeks ago. I'd say that this was a pretty 'fair'
example (it showed about 1/7th wave PV), with some slight surface
roughness from the machine figuring. Generally, I have not seen a 'bad'
C11, in any recent scope. My own one, is pretty comparable with the German
example, showing fairly smooth optics, with a 'best corrected' point for
SA, about 4.5" behind the rear port (slightly further than is often
quoted), and at this point, nice parallel Ronchi lines.
I'd say the quality was pretty good.

Best Wishes


that was on the Baader-Planetarium page .
Talking with some friends from Germany apparently that interferometric test
was conducted by a fellow named Wolfgang Rohr, who in some people's opinion
is less than credible due to a past test of a Chinese refractor, in which he
arrived at almost the same Strehl of 0.98 .
Later he was contradicted by other measurements and admitted (allegedly)
that he had tested the refractor only over the center 20mm of aperture ,
where it had indeed that high Strehl , then simply claimed the number for
the whole scope.
Please note that I do not have any first hand knowledge if this is the case
or not, and would be interested to learn more . Based on what I understood
from that test report, it just seems incomplete in the sense that the test
setup and method was not described, pictured or in any way specified
accurately .
Any test should be taken with a grain of salt if the test setup is not
published , especially the ones floating over the internet , which has no
peer review and anybody can mae any claims .
I would really be interested in any feedback from the German guys who read
this list which is really the case with that Celestron test. My own
experience with Celestron was along the general lines of that test , the
same surface roughness level and that weird radial pattern but really
nowhere as good a Strehl .

best regards,
matt tudor