The 'Dobsonian'

To be exact it is the telescope as well as the mount. The true Dobsonian telescope includes a relatively light-weight (compared to traditional Newtonians), self ground mirror with most of his original mirrors being made from salvaged ship porthole windows.

Though the rocker box does work with heavy 10" Schmidt Newtonians!


Never heard about the portholes before!

salvaged ship porthole windows

Wow! - Really?
How did they get them to reflect evenly (parabolicly?)
Did they silver them as well?

So are these scopes easy enough to make?.....
(Hmmm...Bad weather project maybe)


Albert...
it's funny....
That is the mental picture I had of what my new 'Lidl' LXD
would end up like!

There is a saying in Engineering circles:

"The Great Engineer Simplifies things, the Bad Engineer makes things more complicated."

Nowhere is this principle more true than in the ingenius design invented by John Dobson.

Sometimes the greatest inventions look "obvious" AFTER they have been invented.

John Dobson's name will live on in the Hall of Fame of telescope designers.

One of these days I expect to be able purchase a top-quality 20" telescope which is easy set up and to use and with which gives rock steady views even at high magnifications....For LESS than the price of an old second hand banger.

Thank you John Dobson,genius.

Peter.

Quote:
salvaged ship porthole windows

Wow! - Really?
How did they get them to reflect evenly (parabolicly?)
Did they silver them as well?

To clarify, he used the glass form two porthole windows to grind and figure one into a parabolic shape that was then "silvered" by a coat of aluminum (usually).

Though the rocker box does work with heavy 10" Schmidt Newtonians!

Nice sturdy looking mount Albert. One thing I found with my first home built dobsonian was that with the focuser mounted like yours made it difficult to balance.
When pointed at the Zenith the weight of the eyepiece would cause it to creep past the zenith. I use the focuser at 45 degrees to eliminate this and moved the altitude bearings a little (10mm) above the tube center to also help balance the finder, etc.

With a longer tube or with an additional platform under the rocker box to give it more height it might be practical to have the focuser axis parallel with the azimuth access. That would cancel the balance problem.