ATM project around a Coulter 17.5" mirror COMPLETE with Intelliscope C.O.L Apogee 6" F8 refractor, CG-5 mount, Coronado P.S.T Criterion 4" F12 Dynascope
Quote:Hi Guys,MessiTom: If only it were that easy and if primary mirrors were super thin this would be possible but as Gary Seronik has pointed out, the thick glass used even in todays thinner mirrors acts as a heat battery. It radiates heat long into the night, and Id suspect in many cases it never truly reaches ambient air temperature all the way through ever [outside of a stable lab environment control]. The upshot here is the mirror is never temperature equal all the way through. A rear blowing fan still leaves the otherside of the glass warmer than the fan facing side and hence a bubbling boundary layer of heat. Turn the fans off and the interior heat that was never gotten rid of radiates back to the surface. A side blowing boundary fan never cools this interior temp to the ambient air but it blows the boundary layer physically off the optic and cools the surface as well helping to keep the layer from reforming - so long as the side fan is running ofcourse. Switch it off and the layer returns literally in seconds.Tom a rear fan is a great thing but theres no doubt removing the boundary layer is beneficial too. For deepsky, it can mean tighter stars and/or galactic cores which in term can potentially mean success in reaching your faint magnitude limit. After seeing Europa tighten up due to fan cooling Ive got every confidence this can boost my faint magnitude limit
15" Obsession #1603 AstroTech AT66
C10NGT, Z8, 150 Rumak, XLT 150, C6, C5, SW5 Newt, 4.5 Ball, C102GT, C90, ST80, A70LF; 15x70, 25x100; Burgess BV; Paracorr II; T6 2.5, XO 2.58/5.1, Ethos-SX 3.7, Delos 4.5, TV Plossl 7.4-26, BCO 10, Hutech HC 12.5, Sterling 12.5-25, ES100 14, CZJ H 16/25, CZJ O 16, M5k UWA 24, T5 31, Ultrascopic 35, Titan-II 40; Bino Pairs M5k UWA 6.7, Baader Zoom 8-24, M5k SWA 24, TV Plossl 26, RKE 28.7; Zooms NZ 2-4, NZ 3-6, Leica ASPH 8.9-17.8, Baader 8-24; Baader Zoom Barlow, VIP Barlow
Quote: I kept seeing a circular motion in defocused planet images in that scope.
"I have been paddling in the shallows of a great ocean of knowledge." - Sir Isaac Newton * * 15" F4.55 Starsplitter Dob & a Denk II binoviewer * * http://peaceofsky.wordpress.com/ Pacheco State Park Fremont Peak
Quote: Or possibly could it actually help disrupt the boundary layer?
150mm MCT f/13, 31% CO
"People say I'm in denial. I disagree."
Quote: So, it might work to pull the boundary layer from the top of the Dob tube.
Quote:Simply induce additional suggestion to its natural inclination.
Quote: Next thermal project:
Quote:I don't think air tight is good if it allows vibrations to disturb the image.
10" F/4.7 Modified Skywatcher Reflector, 38mm Orion Q70, 17mm Modified Ultima LX, 10mm TeleVue Delos, 7mm Pentax XL.
Quote:For the road I am going to use 2 C cell 4 cell holders and wire them together for 12v.
Quote: From all that I have read the side mounted fans are not really needed on 10" and less mirrors although it has been done.
Quote:Don, so your side fans are really for cooling due to vibration. Have you tried some vibration suppression material? I thought of mounting them on a neoprene sheet (with a hole in it, of course.) Let the neoprene absorb the vibration sparing the rigid tube of that task.
Quote:Agreed on the vibration. One idea is to use a piece if sheet rubber if you can find some. Fly to Hong Kong, they have venders with anything you could ever think of.
Quote: Rubber bands are the same idea. Maybe they work well enough, dunno. Anyway, if you can isolate or dampen the vibration to nil, no vibration should make it's way to the tube.
Quote: My idea was using a rubber sheet as an air tight seal across the back end of the tube. But, with a fan or two in the middle of it, I was concerned it might budge out with the fans blowing full force. (YIKE) Smaller is better, it seems, mounted on a more rigid thingy.
Quote:As I understand the thread I posted above he had the fan blowing on the primary and up the tube. I will try both directions it's easy enough. Happy new year