deLOOKA wrote:Hi Laura,
I tried to answer my daughter's question but I can't.
How do you look through your telescope. And how can it fit in the van?
Seriously these are her questions.
-Isaac
The telescope is a Newtonian reflector. The big primary mirror, 18 inches across, is in the wooden housing at the bottom. It gathers light which then bounces off the secondary mirror in the "drum" housing at the top, sending it out the side to the eyepiece. See, for example,
http://en.wikipedia.org/wiki/Newtonian_telescope. When the scope is pointing high in the sky I can't reach the eyepiece, which is what the ladder (blown over by the wind) is for.
The beauty of this design is that the truss tubes between the rocker box and the secondary cage are removable. So when you take it apart for transport you have a big wooden box, the secondary cage which sits on top of it, and a pile of aluminum tubes. To make things even easier scopes in this size range have detachable wheeled handles, so you attach them and wheel it around like a wheelbarrow. That's what the things with wheels are under Gumdrop's rear bumper. It weighs nearly 150 kilos, but it's remarkably easy to move around. I made a set of loading ramps from 2x8s to get it in and out of Gumdrop.
Here is a web page from somebody who built a similar scope, with pictures of all the bits and pieces:
http://www.astrosurf.com/jwisn/20inch.htm. The mount is called a Dobsonian mount, after John Dobson, who popularized it. You can't use it for astrophotography, but it's excellent for visual observation: the scope moves with one finger, stays where you point it, and any vibrations are damped quickly by all the wood. The bearings are teflon with formica tabletop sheet material - they don't have to move very fast, but they have to be very smooth. They are. See
http://en.wikipedia.org/wiki/Dobsonian_telescope. It looks complicated, but it only takes 10 minutes to set up.
People used to make telescopes in this size range with solid tubes, often using Sonotube concrete forms. They worked well but were extremely unwieldy. One group actually used a converted school bus to haul their telescope around, and it was about the same size as mine.
...laura
