$100 6" flex scope:
My main telescope right now is a 6" f8 reflector. It is sweet and cheap.
Being a good Scott, the cheapness is an integral part to it's being
sweet, so for those of you that enjoy buying the best, please excuse my references
to price - to the thrifty out there - you will understand the reason - getting
something that works great for just a little cash is part of the fun.
The basic plan for the mount follows the Sidewalk Astronomer's dobsonian
plan - it is fast and cheap to build:
http://members.aol.com/sfsidewalk/cdobplans.htm
For the optics, I bought a small cheap 1.3 inch secondary from Orion (about
12 dollars), and a main spherical mirror ($50) and a plastic focuser ($13)
- both from Sky Instruments in Canada (best to call for info, ordering, or
catalog - they do not have a web site: 604.207.2813). I would
probably just buy one of their secondaries to save postage from Orion.
The trick of this is that turning the mirror into a flexed parabola
makes this little scope too fun to use! At Bill Kelley's advice, I
did not use the more sophisticated puller plate setup, but his original system
of gluing a bolt to the back of the mirror, and simply pull from there. Since
it is a slow mirror (f8 does fine as a spherical to begin with), the loss
of accuracy from a single point of pull is not that great. It
is also very simple: in fact I simply took a large 5/8" by 3" bolt,
filed the head smooth, and glued it into the exact center of the mirror with
a 5 minute epoxy. The pusher ring was made with a cut ring of foam
from a backpacking sleeping mat from sports chalet (another Kelley idea.)
This scope has given me very satisfying views - I can split 1.5 second doubles,
and stars appear as tiny pinpricks. I had a night of very steady seeing
and Saturn looked unbelievably sharp, contrasty, and REAL. Much like
the advice to make a 6" mirror before a 12", it may be wise to make a simple
flex scope before embarking on a more sophisticated design - once you see
how things sharpen with he turn of a nut - adjusting the optics after fabrication
is just too much fun to pass up.
Pictures to follow soon.
Gil