The construction of the new 30-inch f/4.0 Dobsonian telescope in 2007

In late 2006, a new 30-inch Dobsonian telescope featuring a modern design was constructed. The requirements were: tool-free assembly in 10 minutes by two observers and a reduction in weight compared to the aluminum Dobsonian model. Loading and unloading from the trailer had to be easier. All telescope components—including the ladder, finder box, and loading ramps—fit inside the trailer.

We opted for a "lowrider" design with a 20° tilt. The existing secondary mirror—measuring 6.5 inches along its minor axis—would have been slightly too small for the 30° tilt typically used with this configuration. Thanks to this design and additional measures—such as lowering the structure—the eyepiece height was reduced from the 11 feet of the old aluminum Dobsonian to 8.5 feet. The new observing ladder—a "Hailo Gangway" used for viewing at the zenith—is much more compact and comfortable.

Construction began in January 2007, proceeding from the inside out with the design and fabrication of a new mirror cell featuring 27 support points and a lateral radial support system utilizing two rocker arms.

The main structure,a T-shape with two short outriggers—was fabricated from steel. My analysis indicated that, for a 30-inch telescope, aluminum loses its weight advantage due to the thicker wall sections required; furthermore, its lower material strength compared to steel presents disadvantages. Consequently, the mirror cell's main structure was cost-effectively fabricated and welded from steel.

We received generous support from a machine shop in manufacturing the necessary steel and aluminum components.

The aluminum triangles for the truss structure were cut using a waterjet process, while the main frame was fabricated by cutting and welding steel U-channels. The axle and the steering handle for the rocker box were also made from square steel tubing based on our drawings. When I went to settle the bill, the owner, Gerhard, said: "That’s my contribution to your new telescope!"

In appreciation, the company was listed as a sponsor on the new telescope alongside John Dobson's signature. I built this telescope together with my friends Mike and Micha over the course of three joint workshop weeks in January, February, and July 2007.

All components of the new 30-inch telescope—with the exception of the existing mirror set and focuser—were newly fabricated by us at the telescope workshop in Unterweissach. Images showing the various stages of construction can be seen below.

In August 2007, the new 30-inch Dobsonian was set up outside the venue where the Backnang Stargazers hold their regular meet-up and was presented to our group. See the picture at the very bottom.

Right off the bat, during the "first light" session in front of the restaurant, the central star of the Ring Nebula (M57) was visible at 234x magnification using the old 13mm Nagler—simply sensational!

IIn October 2007, I took the new 30-inch telescope to the Emberger Alm in Carinthia for a week—but that is a story for another post in the "Travels to Dark-Sky Sites" section.