The mirror is pyrex, 1.125 inches thick and is supported on an 18 point flotation cell. The coating is Beral, a coating that was popular years ago, but I haven't heard much about it since. The secondary is 3.1 inches minor axis. That gives right around 1 inch fully illuminated circle. The spider is a bicycle rim and spokes with the bycycle hub holding the secondary. I believe only eight of the spokes are populated. I ground and polished the mirror with a little help from my friends. Vague recollection of the mirror accuracy is between 1/4 and 1/8 wave. I know that on the right nights planetary images were spectacular. That only happened once or twice per year as I recall. The mirror had to be in the cell just right (relatively simple), and the seeing had to be exceptional (harder to get). I always said that the 22 inch began to show objects the way they looked in photographs. The telescope is large, but was designed to go into the back of my Chevy Malibu station wagon with the tube sitting on a roof rack on top. That is why it is a 22 inch and not a 24 inch. Design of the plywood parts was done with John Dobson, and follows the design philosophy of the 24 inch he built. It is VERY stable. He provided me the tool to grind the mirror, which I broke just prior to finishing the rough grinding. I still remember sitting in his apartment in San Francisco and asking him how he ground mirrors so quickly. His response was "What takes you so long? Mirror grinding is cave man's work - eat well, sleep well, and work like hell!" The concrete form tube is very resilient. It blew off the top of my truck near Nephi one night and bounced down the freeway at 56 mph ending up in the median. The roof rack was totally destroyed, but I had a star party I had to do in Panguitch the next Friday. I bought a new roof rack but had no time to do anthing else. I transported the tube and scope to Panguitch and assembled the scope. I did not even have to change the collimation! I miss those times. From: Chuck Hards <chuck.hards@gmail.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Tuesday, October 29, 2013 9:02 AM Subject: Re: [Utah-astronomy] Journey to the 1.8 meter Brent, how thick is the mirror and what is the substrate? Is the coating standard aluminum? What is the secondary size, and do you recall the fully illuminated image diameter? You ground and figured it yourself, right? Do you recall the specifics of the figure accuracy? My mind is whirling... On Tue, Oct 29, 2013 at 8:34 AM, Brent Watson <brentjwatson@yahoo.com>wrote:
139.5 inches. That is 11.625 feet.