I’d like to make some corrections and additions to what has been posted here:
First, I personally owned a C22 back in the early nineties. I bought it from an industrial surplus company that had gotten it and a lot of other equipment from an aerospace company that closed their space systems division near Los Angeles back in 1989. As a professional optical engineer with many contacts in the aerospace industry, I was in the right place at the right time and with the financial resources available to acquire it. Unfortunately, I had to put it up for sale before I had chance to finish my plans to install it in a permanent observatory in a dark location here in SoCal. My wife had gotten some severe health problems (that turned out to be terminal), and we needed the funds to pay for medical bills and such. I did set up the scope on a temporary Alt-Az platform that could be dragged out to be able to check it out. Unfortunately, it had a cast iron mirror cell (the OTA seemed to weigh a ton) that took forever to stabilize. I did get the scope interferometrically tested at an optical lab. It turned out to have an optical figure of 1/5 wave peak-to-valley. Not bad for a telescope of this size and complexity. It would be pretty much seeing-limited, anyway, due to local atmospheric seeing conditions, rather than the optical figure being the limiting factor most of the time. Of course, it wasn’t meant to be a planet-killer, but a general purpose scope. Since it was going to be in a permanent observatory dedicated to astrophotography, I ordered a very high quality equatorial mount in the place of the low-quality Celestron that had to be scrapped. I ended up selling the scope and new mount to a wealthy Texan, who prefers his anonymity (he is not on the CN Forums, nor any other).
Dimitris is right in his post from a few days ago about seeing our ad for the sale of it in an issue of Sky & Tel from the early nineties!! My friend and former business partner is Bill Anderson of Diffraction Limited (no connection with Cyanogen) in Tucson, Arizona. He is, ironically, one of the very few professional opticians who fabricates Schmidt plates using the original vacuum method (as prescribed by Schmidt, himself) and became a specialist in fabrication of Schmidt systems back in the late seventies. He originally worked at the Kitt Peak Observtory Optical Shop for a number of years before starting his own business. He opened up his own shop when he got the method of fabricating Schmidt plates down to a an efficient and cost effective process, which he could use as an advantage in the fabrication of Schmidt systems to sell to amateurs and professionals, alike. Eventually the shop was closed in the early nineties during an economic recession at the time that greatly affected his business. He eventually went to work for the Univ. of Ariz. Optical Sciences Center Optics Lab for the long term (where he still works).
While he worked at his own firm, he fabricated quite a number of Schmidt systems for a variety of amateur, commercial and scientific applications. The largest Schmidt type scopes that he ever made were two different types of 20” aperture Schmidt-Cassegrain scopes (of my own design) for a university in the Middle East!! Plans were made to build a series of 24” aperture Schmidt-Cassegrain scopes, but, unfortunately, an outside investor in the project eventually pulled-out before any of the optics were completed. As a side note, Bill also became noted for the fabrication of the original SimMak scopes (Maksutov-Cassegrain scopes of unique design) that were originally designed by Mike Simmons back in the late seventies. Just for the record, Mike quit working with Bill after a short time and went to work for Jim Riffle of AstroWorks. They came out with another series of Mak-Cass scopes known as the AstroMak, which became fairly prominent back in the eighties. Later, Mike went to work for Celestron and designed the original Compustar series, for which he became famous for. After that he disappeared from the astronomy world to pursue his own interests.
Anyway, my friend Bill had fabricated the optics for a number of classic Schmidt cameras as well as a variety of Schmidt-Cass scopes (including Baker Flat-Field designs and variations of them) mostly for photographic applications with film in the 6” to 20” aperture range. Of course, now, there is little call for such systems these days, and this is just another interesting facet in the history of telescope systems for amateur and professional astronomers.
As far as knowing about other C22 scopes in use at observatories around the country, I know that the Denver Museum of Natural History originally had one installed at their observatory. But, they had it converted a number of years ago to a Ritchey-Chretien system (due to problems with the original optical system). I also know of one in a private observatory at the home of a wealthy individual, whom I understand is the president of a bank, in the foothills above Reno, Nevada. I know that he actually made arrangements with a nearby college to allow the astronomy students to occasionally use his observatory. He also has a Celestron 14” Schmidt camera piggybacked on the C22!! I have also heard of a C22 in private hands on the East coast, but know little details of it.
As has been pointed out here, Meade did make a few 20” aperture Schmidt cameras a number of years ago, but only a handful. They also did a make a few 20” aperture Schmidt-Cass scopes. Unfortunately, I never got to see them, or meet any of the owners, so I don’t know any details.
Please excuse me for being a bit long-winded here, but I wanted to present everything involved with my own experience with some of the large Schmidt systems that I have had the privilege to own and/or work with.