Here's my latest. 10" f/5.6, built around an older Orion mirror made by Discovery. Weighs 36 lbs total, eyepiece height 54" at zenith. Made everything except the focuser and the optics. Came in well under $400 (thank you astromart). Very happy with it mechanically, but I'm still waiting for first light, though I've been done for a week.
The cutouts on the mirror box were inspired by Ed Taychert's folded dob
(http://www.irony.com/Ed/astro/18inch/), and the circular cutout on the rocker, as well as the courage to use 1/2" ply on the rocker sides, from Albert Highe's designs.(http://pw2.netcom.com/~ahighe/home.html)
The holes on the rocker sides provide a very convenient hand-hold for picking up the whole thing. The cutout mirror box allows me to store the secondary cage within the confines of the mirror box sides for transport (next pic). I was afraid they would weaken the structure, but once the altitude bearings went on the whole thing stiffened up nicely. It's really quite rigid. The pole seats are 1" aluminum square tubing filled with a maple plug, drilled to accept the 3/4" truss tubes. I got away with just 1.5 lbs of counterweight (steel bars at back of mirror box), and it balances nicely with up to a pound of eyepiece. The mirror cover sits on the back of the mirror box, supported by the counterweight, to act as a dew shield when observing. Tom Simmons' suggestion resulted in a 1.25" baffle placed in the drawtube of the focuser, which I'm very happy with. Finally, a friend suggested the idea of recessing the light baffle opposite the focuser--this should prevent shallow reflections from bright targets messing up the contrast.
Next post I'll show it packed up for travel.
George
The cutouts on the mirror box were inspired by Ed Taychert's folded dob
(http://www.irony.com/Ed/astro/18inch/), and the circular cutout on the rocker, as well as the courage to use 1/2" ply on the rocker sides, from Albert Highe's designs.(http://pw2.netcom.com/~ahighe/home.html)
The holes on the rocker sides provide a very convenient hand-hold for picking up the whole thing. The cutout mirror box allows me to store the secondary cage within the confines of the mirror box sides for transport (next pic). I was afraid they would weaken the structure, but once the altitude bearings went on the whole thing stiffened up nicely. It's really quite rigid. The pole seats are 1" aluminum square tubing filled with a maple plug, drilled to accept the 3/4" truss tubes. I got away with just 1.5 lbs of counterweight (steel bars at back of mirror box), and it balances nicely with up to a pound of eyepiece. The mirror cover sits on the back of the mirror box, supported by the counterweight, to act as a dew shield when observing. Tom Simmons' suggestion resulted in a 1.25" baffle placed in the drawtube of the focuser, which I'm very happy with. Finally, a friend suggested the idea of recessing the light baffle opposite the focuser--this should prevent shallow reflections from bright targets messing up the contrast.
Next post I'll show it packed up for travel.
George
Attached Image:
George Golitzin
