400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform Skywatcher 130mm f/5 BlackLine (finder, widefield scope and solar continuum scope) Sumerian 250mm f/4.8 Alkaid (as travelscope without platform and on Tom O. platform above).
woody a parsec farther out...
12.5" f/4.8 custom truss dob, EQ platform
I think you're worth a double serving of happiness!Tal-200K (#199) with JMI NGF-Mini2M focuser on GEM3 • Astro-Tech AT80ED • Orion Sirius EQ-G with wireless EQDIRECT • Astro-Tech Voyager • Celestron Regal LX 10x42 • Helios 15x70 ATM projects: 14" f/5 truss Dobson: first light Jul 1, 2011 - currently in 'tweak & widget' mode
Home made 16" f5 Terry Ostahowski optics - ArgoNavis/ServoCAT
ES 30 mm, Ethos 21, 13 and 10 mm, Paracorr II, Antares Barlow 2" 1.6X
2" DGM NPB filter
2" Catseye Cheshire/Sight tube - 2" Howie Glatter laser + Tublug
Quote:Thanks for reporting your test results Alexis!
I think I am set now with my fan configuration: 1 big fan at the back + a couple cheapies to the side for initial cooling.
Every week I do something new to reduce light pollution. Eyes on the Sky is at 650,000+ views so far; more views = more awareness. Please consider sharing with others.
Quote:and the secondary may need a heater to avoid dew problems.
20x90 Bino 12" Lightbridge + Stellarvue F50 TV Ethos, Pentax XW, Meade UWA 5k, ES 82°, Hyperion, AT Titan
Quote:Sixela, I assume your dob has a square layout of the rocker box similar to Mauro's, hasn't it?.
Do you think it will be any different when you have a round one (e.g. like the Lightbridge)?
The Cheapest Astronomer in the World gets excited by Jupiter. Builds dob, builds eq platform, arranges to borrow webcam...
"A craftsman relies on science when knowledge allows it, tradition and experience when it does not, and makes art whenever he can." 14 built scopes from 4.25 to 18" and a 24" in (perpetual) progress. 15 ATM awards. Co-mounted CPC 1100 EdgeHD/TAK FS-102/Orion ED80T on a trash-cart for when I'm feeling lazy. "Simple minds discuss people. Good minds discuss events. Great minds discuss telescopes." http://stardazed.com/
But what about initial cooldown?
Quote: My guess is that the higher-velocity blast from a back-pusher would remove heat from the mirror much faster than the gentler pull of the pull-fan at the same cfm.
Quote:How about a fan mounted on magnets that we can easily reverse?
Quote:Thanks for well reasoned report, Sixela. With a mirror as large as yours perhaps it's a small detail, but the exactly-mirror-sized baffle will cause some degree of vignetting.
Quote:This looks like a nice clear result: a back pulling fan does a better job of sweeping up convecting air in the light path,
A 60mm department store refractor started it all....
I read your post with great interest. You have a very shallow mirror box 16CM.... I am in the design phase of starting rebuild number 4 or 5 on my 16" F4.5...... Each time learning more and more...
One of the design decisions I have been struggling with is baffling, for light that comes in at a shallow angle to the optical axes of the scope, which easily makes its way to the eyepiece.
My plans for the latest rebuild, to address this as they stand now, include a circular mirror box liner 1.5" off of the mirror (19 inch ID) to eliminate mirror box currents, and to extend this circular liner up about 500mm above the mirror to cut down on stray light from this source... Do you think the Mario di Lauro baffle would work in this configuration?
Jeff Morgan - Wile E. Coyote School of Telescope Making
Johnny FS152 15" Obsession Classic w/ 14.5" f/4.65 Zambuto