6 inch/f8 Dobson
click on the images to enlarge them
Some years ago I read a book about amateur astronomy, and one chapter described how nearly anyone could grind a telescope- mirror using mainly his (or her) hands and a few simple tools.
The chance of making such an high- precision optical component fascinated me since then. After having read some books about mirror making the decision was made to grind my own mirror.
The Structure
Secondary cage and mirror box are made from 4mm Multiplex- plywood and connected to each other by 2 U- shape aluminium- profiles. The rocker is made from 8mm Multiplex plywood.
Focussing is done with a sled focuser made from 1,5mm aluminium- sheet metal, that runs in Dry-Lin guidings manufactured by IGUS
The sled focuser is moved by turning a knob with a pinion, that drives a rack fastened to the slide. The focussing range is big enough to use also a binocluar attachment. In that case the additional weight of the bino connected to the guide slide is supported against gravity force by a rotary brake manufactured by ACE. The pinion of this brake only grabs into the rack if the guiding slide has moved about half way down.
The primary mirror rests on three pads of cork which are glued to a plywood ring. This "mirror-cell" can be adjusted by three spring- loaded collimation bolts.
The balance of the entire tube referring to the axis of the altitude bearings is trimmed by an adjustable counterweight.
For easy transportation the components can be piled up inside the rocker. The whole telescope then forms a compact unit where all sensitive parts are well protected.
The performance of the telescope is much better than I dared to hope during construction. The main mirror gives excellent images and the movements of the Dobson- mount are smooth and comfortable to handle within all magnifications up to 250power.
Home
Secondary cage and mirror box are made from 4mm Multiplex- plywood and connected to each other by 2 U- shape aluminium- profiles. The rocker is made from 8mm Multiplex plywood.
Focussing is done with a sled focuser made from 1,5mm aluminium- sheet metal, that runs in Dry-Lin guidings manufactured by IGUS
The sled focuser is moved by turning a knob with a pinion, that drives a rack fastened to the slide. The focussing range is big enough to use also a binocluar attachment. In that case the additional weight of the bino connected to the guide slide is supported against gravity force by a rotary brake manufactured by ACE. The pinion of this brake only grabs into the rack if the guiding slide has moved about half way down.
The primary mirror rests on three pads of cork which are glued to a plywood ring. This "mirror-cell" can be adjusted by three spring- loaded collimation bolts.
The balance of the entire tube referring to the axis of the altitude bearings is trimmed by an adjustable counterweight.
For easy transportation the components can be piled up inside the rocker. The whole telescope then forms a compact unit where all sensitive parts are well protected.
The performance of the telescope is much better than I dared to hope during construction. The main mirror gives excellent images and the movements of the Dobson- mount are smooth and comfortable to handle within all magnifications up to 250power.
Home