The mirror did not require any figuring, which was a great relief to Mike. The mirrors figure was discovered only after the mechanical part of the telescope was complete enough to put the mirror in and test it. So by then, he was very committed to the project. They did find that the central part of the mirror is not corrected, but this is not a big deal as it is in the shadow of the large secondary. Perhaps the lack of correction was due to the fact that whatever cameras/instruments were to be installed on the original spy telescope would "shade" that part of the mirror. Mat -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of William Fenton Sent: Tuesday, October 22, 2013 10:11 AM To: Utah Astronomy Subject: Re: [Utah-astronomy] 2-Meter Mike I'm reading about the 70" with great interest and showed the KSL piece to my astronomy class. Does anyone know more about the story of the mirror? How often does the government put something like that up for auction? How do you find it? How much does it cost? Did it require and figuring? Again, fascinating story, thanks for all the info so far. On Oct 22, 2013, at 8:19 AM, Chuck Hards <chuck.hards@gmail.com> wrote: Good insight, Bruce, thanks. It's my understanding that the structure breaks-down for transport, though I'm not sure yet about exactly how. I'll be seeing Mike again on the weekend and will forward your questions. He has no email and no online presence. I did not notice any flex while using it myself, though we avoided Dobson's Hole and stayed with objects below about 50-degrees altitude. Stars remained round no matter the orientation so I assume collimation wasn't lost. I wish I could use a laser collimator to check flexure, but the mirror centers are masked-off so that won't work. I'll let you all know that there is an article in the works for a major astronomy magazine, an editor has contacted me, and Mike and I are moving ahead with it. That's all I can say about it for now, stay tuned. On Mon, Oct 21, 2013 at 7:10 PM, Bruce Hugo <bruce.hugo@yahoo.com> wrote:
Wow! I'd be a bit nervous moving something of that size without sufficient support on the flatbed! Heading down the road, flexing of the truss system would most likely lead to fatigue cracks/failures eventually. Also, that's a huge chunk of glass. I'm not well versed in the properties of glass but I would assume that too would need a beefed up support (greater than 3 points as found on my itty bitty teeny weeny 10" Dob. :-)
Oh, I was wondering how much flex there is in the truss system when it is taken from straight up to a near horizon position. There will be some flex in A36 carbon steel truss system. Does he have to re-collimate with major changes in declination?
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