I don't know about repairs - never had to. The 3/4" plywood I used was scrap CDX. If I were to do it again, I'd use marine grade plywod. Still, I sealed and painted it well before adhering the mirror, and I don't hesitate to even dip it in water to clean the mirror, which I haven't done for maybe 10 years, anyway. I think the key to easy removal of the cell, if needed, is to gap the mirror and plywood with some kind of shim when using the silicone. Then a saw blade can easily be slipped between the cell and mirror to remove it. I used three dollops of silicone, maybe 3/4" in diameter. Never regretted it. Kim -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Chuck Hards Sent: Thursday, August 19, 2010 1:37 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Items for sale My only gripe about using silicone is that it's an all-day process to remove and re-attach the mirror should cell repairs or a good cleaning be required. Three tiny edge clips are just too easy, IMO. If kept small enough, no diffraction effects are noticed. On 8/19/10, Kim <kimharch@cut.net> wrote:
Rich, I know it may be too low-tech for your project, but my full-thickness 10-inch Parks mirror has been in a plywood and silicone sealant mirror cell for more than 20 years with "stellar" performance. Never have I seen any adverse affect from this simplest of mirror cells. The silicone holds the mirror just fine (or at least it has for 20+ years) with just enough flexibility not to torque the glass from thermal expansion or other stresses. I've always wondered how well it would work with thinner mirrors, though. Anyway, good luck with your project.
Where's Kenneth Novak when you need him?
Kim
-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Richard Tenney Sent: Thursday, August 19, 2010 10:09 AM To: Utah Astronomy Subject: Re: [Utah-astronomy] Items for sale
Jealous, indeed! And of course all that stuff sounds definitely like it would be well worth a look to say the least.
Yes, I bought (and have) the Protostar tube and secondary (bought the rings and end-caps too). I'm trying to decide on a color (leaning toward metallic green) to have my son-in-law (an auto-body painter) do it justice (he brought over a book with hundreds of color samples, and now there are too many choices to make an easy decision!).
Will likely go with a Wyorock focuser (if I can get them to answer their e-mails!), and the UO mirror cell is the likely culprit unless someone can talk me into something better. Funds are tight still, but hopefully sometime in the coming few months I'll obtain the remaining parts and then with luck Mr. Hards can find some time to help me design and implement a simple mount, and put this little beast together...?
/R
--- On Wed, 8/18/10, Chuck Hards <chuck.hards@gmail.com> wrote:
From: Chuck Hards <chuck.hards@gmail.com> Subject: Re: [Utah-astronomy] Items for sale To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Date: Wednesday, August 18, 2010, 11:02 PM I've got a number of non-astronomy items that I'm looking to let go of, including WWI themed posters, as well as model kits. Any interest in such items?
Also some astronomical and Sci-Fi themed posters, books, etc., not just hardware and optics.
I have an autographed copy of Bert Willard's bio of Russell W. Porter that I may part with... the non-personalized one, I also have a first edition that Bert made out to me. :o) Yeah, I'm special, lol.
I have a first edition copy of "A Fall of Moondust" (with dust jacket) with one of Arthur C. Clarke's PERSONAL, signed bookplates tipped-in, that isnt really for sale, but if someone waved five or six grand under my nose, I'm sure beads of sweat would break-out on my brow...
And, oh, yes, I also have another of Sir Arthur's personal, signed bookplates that may be brought out for drooling purposes... but no, the letter that Sir Arthur wrote to ME, Chuck Hards, PERSONALLY, is most definitely NFS... (we bad, we bad...lol)
I'm such a stinker. ;o)
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