At this point, you can also buy the tube, and the altitude bearings. Before the introduction of the Dobsonian by John Dobson, the vast majority of amateur telescopes consisted of small telescopes with primitive mechanics - barely enough to see the polar caps of Mars or the rings of Saturn. At that price it is hard to justify building one. Unfortunately, the standard sizes are 1 and 2 meters in length. If you can find a scrap … Who would ever have thought ten years ago you could buy a 300mm (12 inch)Truss Tube telescope for around the $1200.00? No telescope type has changed the hobby quite as much as the Dobsonian. It is now very cheap to purchase Dobsonian telescopes off the shelf, and fully equipped with lenses and finder scopes. $450 will buy a new 150mm (6 inch) telescope. Pioneered by John Dobson in the 1960s, the instrument combines a Newtonian reflector telescope with a unique two-axis movable base. This is a Generation II telescope.All updates have been performed on this telescope. For this telescope, you need a PVC drain tube. Orion SkyQuest XX12" f/4.9 Truss-Tube Dobsonian Reflector Telescope w/ parabolic primary optics 9-point flotation primary mirror cell with spring loaded thumbscrew collimation adjustments 70mm minor-axis secondary mirror on 4-vaned (0.7mm thick vanes) secondary holder 4 groups of two-pole rotatable truss assemblies with captive assembly knobs Dobsonian telescopes are popular with amateur telescope makers for their ease of design and construction, portability, and their use of large optical mirrors. Plans/drawings for truss Dobsonian. - posted in ATM, Optics and DIY Forum: Anyone got any plans on how to make a truss Dobsonian?I dont really want to buy the books out there and Ive seen some beautiful and simple looking home made Dobs.Thanks,Mark If you have a 150 mm F8 mirror, a 200 mm OD tube is needed.