The Truss is an architectural form that is used on larger telescopes. It adds great strength while reducing weight
There are design challenges when it comes to making large telescopes. By large I mean that it generally has a primary mirror of over 10 inches in diameter. A truss, which is often seen in bridges, is a triangular configuration with thin columns forming the triangles.
When it comes to telescopes there are advantages to using the truss set up. First, it makes for a very strong optical tube with little or no vibrational motion or slipping. This is important with telescopes because the slightest unwanted motion can ruin the image. Second, the truss set up is very light. A large telescope could weigh in excess of 100 pounds and the truss configuration will reduce the overall weight of the scope. This is a consideration when it comes to lugging it around, putting it in the car or setting it up. With a truss configuration a much larger telescope all of a sudden becomes portable.
If you are looking at truss tube telescopes then I want to congratulate you! These are some nice scopes with some serious light gathering power. You are going to get some breathtaking views of the universe.
Meade 10" LightBridge Truss-Tube Dobsonian Telescope - 1005-05-02
It's not just a big telescope. It's a big telescope that goes anywhere. New LightBridge truss-dobs from Meade take down and set up quickly. So you can take one of these massive windows on the universe out to your favorite dark sky locations with ease. LightBridge dobs give you high quality Meade optics, premium components, and ultra portability - all for about the same price as an ordinary tube dob. With a LightBridge truss-dob prepare to cross the universe.
Orion SkyQuest XX12i IntelliScope Truss-Tube Dob
If the idea of a big-aperture telescope appeals to you, but the portability issue has kept you on the fence, you can hop off it now. We've got the perfect solution - Orion's SkyQuest XX12i IntelliScope Truss Tube Dobsonian Telescope. It's a deep-sky observer's dream scope, offering jumbo 12" optics (f/4.9); a stylish, reduced-weight base outfitted with IntelliScope object location technology; and a sturdy truss tube design that disassembles in about a minute into compact, easily portable components. Finally, a deluxe, large-aperture Dobsonian telescope that fits comfortably in a compact car for transport to your favorite observing site! The eight trusses (four captive pairs) provide more-rigid support than other designs in this category. We've also outfitted the XX12i base with nothing but the best materials: EbonyStar laminate and VirginTeflon azimuth bearing surfaces provide silky smooth azimuth motion. Equipped with dual-speed (11:1) 2" Crayford focuser, large 8" altitude bearings, a full set of great accessories, a computerized database of 14,000 celestial objects -- and a price just north of a grand! -- the XX12i is one killer telescope deal. It's the big Dobsonian you've dreamed of owning, and now you can take it with you wherever dark skies beckon! Get the practical, amazingly affordable Orion SkyQuest XX12i Computerized Dobsonian telescope and hit the road to astronomical adventure. One-year limited warranty.