Homemade 8 inch "goto" dobsonian telescope


following several years of telescope building (15 to be correct), some searches were underway to develop something more challenging and complex.

I wanted a telescope system that was capabel of observing remotly and autonomously.

Some criteria were impossed at the start of the research phase:


The system must be completely home made, or at least as cheap as possible and without to many exterior help.

It must be possible to make the system with a good equipped machine shop, i had at home.

The system must be made out of scrap material if possible to reduce the overall cost.

I am not that good in electronics so this must be kept as simple as possible.

Same for the software, i will not be able to program something that complicated myself so i must find an alternative.


After some research i came on the very interesting telescope page of Mel Bartels.


The concept is very simple:

take two stepper drives, make some wooden structure with some axes and rollerdrives

add some bearings, make truss tube constroction for the optics

connect all motors to some home made amplifioer electronics and to the parrallel port of and old computer

spend about one year of free time, save some dollars by doing it all yourself.


Here are some pictures of my telescope and some interesting construction detail:


The base plate is made of a wooden construction: two high density plywood plates glued together.

On this plate , there is a aluminium ring (Duralumin) bolted to the plywood. Under this plywood plate, there are three nylon pads.

The exterior of the plate was milled round, centered trough the central whole in the plate on a fixed shaft attached to the table of a conventianal milling machine.

The rotational movement was don by hand.


I inversed some examples i saw in order to have all electrical components attached to the same wooden plate.

In the above picture, you can see both motors attached to the second plywood plate.

Both plates are connected with the centra shaft trought the base. 30 mm diameter. The second plate (azimuth table) has a self centering roller bearing to keep it

coaxial with the base plate.

Between both plates, we can see the rollers (three rollers spaced unevenly) They are on the same diameter and conical to have the same rotational speed over the

whole contact line. two of them are 100 degrees apart, the third is placed 130 degrees further to have more pressure on it and to reduce overal dimensions. The third

one is the one containing the worm and motor group.

Notice the conical roller mounted under the correct angle to give perfect linecontact

Also the home made wormwheel in Aluminium 82 teeth made on the lathe with an universal M24 cutting tool.


Here you can see the middel axis with self regulating bearing.


The azimut plate holds all the other components: motors, worm reducers, electronics and supporting points for the mirror cage.


Details of the home made worm reducers: see also my page on home made worm-wheels


And the mirror box with bearings and friction drive plus temporary electronics.


Close up of the electronics


close up of the encoders and their decoding box.


Also an old computer is needed to drive the electronic amplifiers trought the parrallel port output


So far all was for the goto movement

There is also a truss tube construction to hold the secondary cage and optics, focuser,...


The spiders are made from a 1.5 mm thick steel cable adjustable to all directions.


for the future , i left some space to upgrade the optics, only truss tubes and secundary cage must be changed.


Please add your comments

Back to Homepage

last update: August 29, 2010