Joerg Peter's  14- inch f/4.5 Ultralight Travel Dobson

Pictures: Rolf Stadelmaier and Volker Gerhardt
Text: Stathis Kafalis

Joerg built a travel scope that had to fulfill the air travel carry on luggage limitations, jet be as big as possible. So, the dimensions and weight had to be kept within tight limits - of course without compromising optical and mechanical performance. When I heard of this project, I burned to make the ultrathin mirror for it. The scope was finished just in time for the Telescope Meeting at Vogelsberg / Germany (ITV) in May 2003. The prototype version tipped the scale at just 10.8 kg (24lb), but showed due to the too thin trusses, the too weak rocker and the insufficient alt bearing connecting bars too much vibrations. 

Main Mirror: 
14" f/4.5 made by Stathis of 20 mm thick Schott Borosilicate glass. The glass weights 4 kg (8.8 lb) See 14" ultrathin mirror making

All Aluminum, powder coated. It fits for air travel into a 42x40x19 cm (16"x16"x7.5") bag. The altitude bearings and Trusses are transported in the suitcase separately.

Diameter 20 mm (0,79")
Thickness: 1 mm (0.04")
Collapsible into 2 parts each

Baffling: Via a sock over the whole truss structure

Total weight: 
13.9 kg (30 lb)


The scope collected much attraction at the ITV
Welded aluminum secondary cage with eccentric spider and self made helical crayford focuser
Very large altitude bearings of 5 mm aluminum, x-cross connected with various bars, to achieve sufficient stiffness. See more pictures of the lower part here
Extremely low profile18 point mirror cell, that can be collimated by 3 thumbscrews from the side. The floating system is made with ball bearings, to provide small friction and deform the light and thin mirror as little as possible.

See more pictures of the lower part here

The unique truss clamp: A round stud is tighten with a thumbscrew against the rectangular housing. The truss is clamped in between. Is very fast and very stable.
The aluminum welded open rocker runs lateral against the 3 small wheels of  the ground triangle (instead of a central pivot). Strong, light and compact. My 24" uses the same principle.

Joerg took it as carry on luggage to Tenerife and had spectacular views of the southern sky and Mars staying high in the sky from that location.  

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