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After having paused with amateur astronomy for 15 years, the clear and
dark sky in the spanish suburb of La Coruña where I live,
inspired me 1995 to take up my hobby again. Unfortunately my former
"firstscope" a 60mm Refractor is still in Germany, so I had
to find another way of getting hold of a telescope. Since I already
got a little bored with the small Refractor 15 years ago, I thought
this might be an opportunity to get a new telescope.
Looking through some prospects of Celestron and Meade convinced me
very fast that a good commercial telescope would cost far more than I
was willing to spend at the time. So I started investigating for
possibilities to build a telescope myself. Soon I found the ATM Mailinglist , where I received a lot of
support and encouragement.
I selected a 6" Newtonian Telescope as my first project. Since I
do not know any ATM's close to the place where I live, I wanted to
start small.
After deciding that I would grind the mirror myself I ordered a
6" low expansion glass kit from the german astronomical
association VDS . I wanted to spare the second glass disk and
made a Tile on Plaster tool
.
Grinding, polishing and figuring the 6" mirror took roughly 40
hours and was completed by testing the mirror with my self-made Slitless Foucault Tester .
The next step
was to design the mount. To avoid complications, I decided to
construct Richard Berry's 6" Dobsonian mount. I liked
the look and it seemed easy to construct. I finally ended up with a
lot of modifications ,
but the basic design stayed the same.
I bought one 122x250x10 mm and one 122x250x20 mm plywood sheet. Half
of each I used for the mount.
I felt quite uncertain about the focuser and spider design, since I
had never worked with a reflector before. This uncertainty led me to
constructing them myself, because I did not want to spend money for
something, what later on might not fulfil the requirements. In the end
I decided to construct a motorized Sled-type focuser and a two vane fully
adjustable spider .
Both are almost fully made of wood.
As side bearings, I used two 18 cm PVC rings that alternately ride on ball bearings or teflon pads , depending on whether I want to use the telescope manually or guided by computer (at the moment I have not yet implemented the computer drive).
For more information about Amateur Telescope Making, you should have a look at the ATM section of my Astronomy Links page .
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