Ernst Schoeberl's  15"  f/5 Full Carbon Scope

Pictures by Volker Gerhardt, Text by Stathis Kafalis 

Ernst build all the whole Dobsonian structure from airplane grade carbon fiber material at a weight of 6.8 kg. The secondary mirror, focuser, pointer and Nagler eyepiece add another 1.5 kg. Only due to the full thickness mirror of 15.2 kg the total weight sums up to 23.5 kg.

The cage rings, the mirror box and the rocker are made as sandwich construction: Two thin layers of carbon laminate and a sort of glass foam filling 

Even the finder tube and it's diagonal are made of carbon 

The extremely stiff mirror box as sandwich construction

The rocker weights less than 2 kg.