One Trip Dobsonian - Dimensioned Drawings

These drawings for my One Trip Dobsonian are not complete, and are guides only. You will need to spend some time with them, the article, and the pictures. Make sure you really understand how it all goes together before cutting wood.

Balance is critical with this scope. An F4 primary will work but an F5 will be dicey and probably will require counterweights. Make sure to balance it from front to back and top to bottom with your eyepieces and finder before attaching the altitude bearings.

I'm not sure how well the drum shell will scale up. Tubes are extremely strong in bending and axial loads, but not so good at side loads. When you push on the side of the telescope, you are "crushing" the tubing sideways, a direction that the side truss cannot resist. The "flat" ring more commonly used in a single ring UTA (Bruce Sayre) or a double ring UTA (Obsession) helps tie in the different truss poles for stiffness. I think an 8" would be okay, but I would expect a 10" or 12" of this design to get wobbly at high powers.

Remember that all the plywood is 1/2" appleply (which is actually .500" unlike regular plywood!) and uses 1/8" deep dadoes and rabbets.

Autocad DWG file
Autocad DXF file

These files are licensed under the GNU GPL, which means you can use them for free, modify them, and give away the new drawings.