· Get a Cloudy Nights T-Shirt · Submit a Review / Article    Click here if you are having trouble logging into the forums Cloudy Nights - Official Forums of the 2009 International Year of Astronomy Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User   You are not logged in. [Login] Forum Archives · Entrance · Main Index · Search · New user · Who's Online FAQ · Calendar Equipment Discussions >> ATM, Optics and DIY Forum Previous   Index   Next   Flat   Steven Aggas sage Reged: 04/15/08 Posts: 463 Loc: Arizona Re: RTV, Glass, and Holder Material       07/07/09 05:34 PM Edit   Reply   Quote   Quick Reply:   Thanks Preston. With RTV 20+ then it's really mismatched to either glass or practically any material used for a holder, though aluminum comes the closest, and you said it gave the worst results. It's unclear to me how a good result can be had with Carbon Fiber (you) and Stainless Steel (Mark) when they are so different in CTE to each other as a holder, though they both have similar delta CTE RTV to glass (unless the aspect ratio of the two mirrors is significantly different one (you) to the other (Mark), thickness to minor axis). So maybe the holder material makes not so much apparent difference when there is sufficient aspect ratio of the glass? Additionally, just piecing the FEA data you mentioned.... Material Stack; CTE's; FEA Commented Result CF-RTV-Pyrex; 0.3-20-2; Best SS-RTV-Pyrex; 9-20-2; Next Best Al-RTV-Pyrex; 12-20-2; Worst Then, how does the mirror'ed, symetrical mismatch on both sides of RTV, seen above, give better FEA results than to an asymetrical mismatch? Two high-stressed junctions in a mirror'ed system perform better? Do stresses like that cancel, one being compressive and the other tensile? To insert the wood holder sandwich, 2 to 5-20-2, into the list above, it should give better results than SS..., but not as good as CF. (2 to 5 for wood depending on the wood chosen and results have been emirically found to be good) I know, questions - I got more where those came from.... Steven -------------------- Mr. Wizard Walking on a Dob: http://darkskyobserving.com/MtGraham.html Elements in Harmony I, an 8"f6 German Equatorial - Stellafane Winner, II a 20"f4.2 Newt-Dob - Astrofest Winner, III a 6"f3.5 Finder/Newt-Dob, and IV a 36"f4.5 Newt-Dob - "If it's up there, it's in here." Apache-Sitgreaves Center for Astrophysics www.DarkSkyObserving.com Post Extras       Entire thread Subject Posted by Posted on RTV, Glass, and Holder Material Steven Aggas 07/02/09 04:20 PM Re: RTV, Glass, and Holder Material mark cowan   07/02/09 08:33 PM Re: RTV, Glass, and Holder Material Biff   07/09/09 03:03 PM Re: RTV, Glass, and Holder Material Mark Harry   07/03/09 07:18 AM Re: RTV, Glass, and Holder Material PrestonE   07/03/09 03:36 PM Re: RTV, Glass, and Holder Material mark cowan   07/04/09 02:42 AM Re: RTV, Glass, and Holder Material PrestonE   07/04/09 04:12 PM Re: RTV, Glass, and Holder Material Steven Aggas   07/06/09 03:18 PM Re: RTV, Glass, and Holder Material PrestonE   07/06/09 08:55 PM Re: RTV, Glass, and Holder Material Steven Aggas   07/07/09 12:25 PM Re: RTV, Glass, and Holder Material PrestonE   07/07/09 04:11 PM Re: RTV, Glass, and Holder Material Steven Aggas   07/07/09 05:34 PM Re: RTV, Glass, and Holder Material mark cowan   07/07/09 09:10 PM Re: RTV, Glass, and Holder Material Steven Aggas   07/08/09 12:39 PM Re: RTV, Glass, and Holder Material PrestonE   07/10/09 02:43 PM Re: RTV, Glass, and Holder Material Steven Aggas   07/10/09 03:33 PM Re: RTV, Glass, and Holder Material PrestonE   07/11/09 11:12 PM Re: RTV, Glass, and Holder Material Steven Aggas   07/13/09 12:14 PM Re: RTV, Glass, and Holder Material PrestonE   07/15/09 05:50 PM Re: RTV, Glass, and Holder Material Steven Aggas   07/16/09 11:28 AM Re: RTV, Glass, and Holder Material PrestonE   07/17/09 10:37 AM Re: RTV, Glass, and Holder Material Steven Aggas   07/13/09 12:16 PM Re: RTV, Glass, and Holder Material Steven Aggas   07/13/09 05:06 PM Re: RTV, Glass, and Holder Material mark cowan   07/08/09 03:42 PM Re: RTV, Glass, and Holder Material Steven Aggas   07/09/09 12:28 PM Re: RTV, Glass, and Holder Material Charl   07/06/09 06:43 PM Re: RTV, Glass, and Holder Material PrestonE   07/02/09 06:13 PM Extra information 7 registered and 5 anonymous users are browsing this forum. 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