I did a query out to see what focal length a SCT operates for prime focus, such as when a Toucam with no diagonal is attached, and it seems it's pretty much...
Just learned of this tool on another forum and don't know much about it. I am intrigued by the prospects, but after looking through some of the archived...
Hi Kevin, The Strehl ratio is the ratio between the amount of light in the Airy disk for the scope and "some other number." Usually the other number is the...
Thanks John, you've been most helpful. I see in looking at the examples and tests that the software is in French. Is there a page with some translations or...
Hi Kevin, Some answers below.... ... No, we do not have an english version of the software. The Cookbook in the Files section is in english, however, and...
This is fantastic news! New version 2.0 is much more user-friendly with regard to setting thresholds and aligning the images. This is an area where people...
Good news. I did hear back from the programmer Lequevre who will try to join us here. And he mentions he is interested to make an english version also. I...
I'm interested in seeing some good data on SCT quality particularly the Celestrons. Also John B. I saw one of your old posts about testing a c14. I'm ...
Hi Greg, ... There are a few tests on Celestrons in the files area. My impression so far is that most have good glass. Though typically we see several...
Well let me know when you want to have a group chat. I would announce you. You probably don't need it. But we have enough people with web cams that we...
I'm familiar with that article. I really do wonder if all the 9.25s are that poor! After rotating the correctors they got Strehls of .83 and .88, but they...
I suspect this (i.e. 0.92 strehl isn't 1/4 wave) is more along the lines of not understanding how an optic is measured and what it means! With the rise of...
Numbers for the SCT tested here so far (converted to Strehl using ((RMS * 2 * pi) 2 -/+ ) Inv Nat Log): C11 - either 0.71 or 0.85 C8 - 0.88 C11 - 0.87 C14 -...
How could the c14 be "above" the theoretical Strehl limit? I'm still not understanding whether we are comparing "the sct to a perfectly executed theoretical...
We are using the Strehl ratio not compared to a perfect unobstructed telescope, but to a perfect telescope that has the same obstruction size as the one under...
We do need more scopes that have been interferometrically tested in order to gain more confidence with the limitations and applicability of the Roddier test....
Personal opinion here but I think that's a confusing way to do it that people are likely to take out of context. Obstruction percentages vary. To compare...
Or at least to have some term that will disambiguate. For example, "strehl-to-design" vs "strehl to unobstructed" but I guess that's not good because...
This is extremely interesting. It almost exactly matches my own ownership experience with one exception. I routinely post on Cloudy Nights that the C9.25 I...
Hi Greg, ... announce ... web ... a "seminar ... OK, I'll let you know. Probably wait a few weeks until we have more documentation on the lastest Roddier...
... that ... vary. To ... sense that ... much ... designs. ... I think for a person trying to evaluate or tweak their scope, it will be more confusing to...
A little bird pointed out to me that some folks are wondering how 8 bit webcams can achieve as good results as 16 bit cams. The number of bit resolution in A/D...
Gosh it's hard to say. My old 9.25 is now owned by another club member, and when he sets it up next to my c14 I'm always impressed with it. Not because it...
Hi Philip, Thanks for doing the test! Bravo! Yes, stacking 8-bit images will get you more bit depth. Another way at the same question, is "just how many bits...
Since the "Strehl Ratio" is the ratio between the intensity distribution across the Point Spread Function of an unaberrated, unobstructed circular aperture and...
Hi Chris, Well this may be more complicated than I thought. My copy of ZEMAX here (Feb 2005, p. 52), to quite from the manual, states "The Strehl ratio is...
John, I have used Zeemax in the past (I use a G4 Mac so cannot install it on my computer). As I recollect there is an option setting to turn off normalisation...
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