For more info: http://www.obsessiontelescopes.com
The HAS 12" Truss-Tube Dobsonian Project
PART I: Introduction / What is a Truss-Tube Dobsonian?
A Truss-Tube Dobsonian is based on a telescope type introduced by James Dobson in the early 70s. It usually consists of a large aperture Newtonian telescope on a simple, usually wooden, alt-azimuth construction which allows the user to simply push the scope in the desired direction (see photograph). This type of scope has become tremendously popular because it has three distinct advantages over telescopes using more traditional types of mount, such as the German equatorial:
Dobsonians are an easy design for the self-build enthusiast;
Dobsonians are very easy to transport and set up;
Dobsonians provide the biggest aperture for your money.
Although this may all seem great, Dobsonians do have a number of limitations which make them less suitable for certain purposes. Because of the lack of slow motion controls and drives, they are quite fiddly to use at high magnification and pretty much unsuitable for serious astro-photography.
However, if you are a deep space enthusiast who likes bright images of larger swathes of sky, these telescope are a great asset.
TRUSS-TUBE CONSTRUCTION
Once you pass a certain size of aperture, a closed tube construction may become very difficult to handle and transport. To overcome this problem, you can introduce an open construction using a number of thin alloy tubes that together form a rigid truss-tube (see photograph). This method is much lighter, the truss is collapsible and the entire scope fits easily in the back of a car.
The mount, and the compartment in which the mirror is housed, fit together into a box which then fits in the back of most cars.
BUILD YOUR OWN DOBSONIAN
If you are interested in building your own Dobsonian telescope, there is a very good book available called 'The Dobsonian Telescope' by Dave Kriege and Richard Berry. It should be available through Amazon, or have a look here.
