10" f/3.5 Astrograph with Rosin focal reducer
Posted 15 November 2012 - 06:40 PM
Posted 15 November 2012 - 06:43 PM
Posted 15 November 2012 - 06:44 PM
Posted 16 November 2012 - 08:35 AM
My OSLO version says the reducer glass isn't in the catalog, and it barfs. How recent is your OSLO version?
Posted 16 November 2012 - 10:01 PM
Posted 17 November 2012 - 10:18 AM
Posted 17 November 2012 - 05:28 PM
Posted 19 November 2012 - 01:13 PM
Posted 19 November 2012 - 02:09 PM
K, there is some miniscule residual coma, but the images are still diffraction-limited for all practical purposes. Mike's Rosin corrected scope is a superb solution, both visually and photographically. It would be interesting to comapre it to Paracorr's performance.
Where can a lens be gotten ? Field aberrations? Is that coma .
The PSF images below show just what the stars images would look like under very high magnification. The image patch for each image is 25 microns wides, so you can see the images themselves are no bigger than 5-6 microns.
The corrector lenses can be ordered from professional companies, but they won't be cheap. Almost not worth it. They could be made using a small spindle but not by hand.
Mike: It would be interesting to see a tolerance analysis of the configuration. It's definitely a very advanced project - and very promising.
Posted 19 November 2012 - 03:47 PM
Posted 20 November 2012 - 04:15 AM
Depending on tolerance requirements (OSLO.edu has only limited capacity for this type of work), the corrector will probably be the priciest element of the configuration.
On the practical side, if tolerances are within amateur production capabilities (and I mean advanced amateurs!), then this project would be a lot more financially attractive - especially for big, fast mirrors!
The highly aspheric, fast, primary is another story. Making an accurate f/4 highly hyperboloidal primary requires a well tooled and experienced worker, unless custom-ordered mirrors are not a financial burden.
Speaking of tinkering on those cloudy nights, it would be interesting to do a direct theoretical comparison of this Mike I. Jones-Rosin corrected system as opposed to a 10-inch f/3.5 Newtonian with a Paracorr and a 10-inch f/3.5 Newotnian using a Wynne-type corrector (both of which are commercially available).
At any rate, seeking such solutions on cloudy nights has produced many an attractive design, and this is definitely one of them. Excellent work, Mike.
Posted 20 November 2012 - 06:49 AM
Posted 20 November 2012 - 07:16 AM
I can take a look at the tolerances on this triplet Rosin. Typically, tolerances tighten up with increasing element power, surface curvature and/or marginal ray incidence angles.
Posted 20 November 2012 - 07:25 AM
Posted 20 November 2012 - 09:35 AM
Posted 20 November 2012 - 10:48 AM
I don't think posting a list of links to the published designs would violate the TOS.
I have some saved already was not sure if the authors would be ok with me posting them .I like your idea I know You Dave And ED have alot .
Posted 20 November 2012 - 10:58 AM
Posted 20 November 2012 - 11:04 AM
Posted 20 November 2012 - 11:30 AM
Posted 20 November 2012 - 11:37 AM
Posted 20 November 2012 - 11:44 AM
as seems to be the case with Ethos. Given this precedence, I am really surprised no one has come up with a Paracorr copy. Either it's not lucrative enough, or perhaps the laws have changed since this photo was taken.