8" F/3.9 RFT - my first mirror
Well, this was a challenge. My first mirror was sitting a box in
the closet, fine ground to about F/4. It needed to get finished.
So, I rebuilt my focault tester into a slitless model, fine
ground, polished, and figured it with a subdiameter lap. It took
about 3 months and I learned many valuable things.
The scope tube is 10" sonotube, painted Rust-Oleum Royal Blue.
The inside was sanded until the paper was rough, and then I just
poured in some primer and rotated the tube. It was then spray
painted flat black. This made a nice bumpy black interior, as you
can see in one of the pictures below. I made a three-vane offset
spider, which works okay. The focuser is a JMI NFG-3 (with fine
focus). The wood is 3/4" Poplar plywood. The tube box is
hinged and opens when the cam lever is released, allowing the tube to
be removed or to be rebalanced.
The mirror cell is a simple three point cell with Teflon pads.
Three wooden knobs pull the three corners of the cell against
springs, and allow nice control of the motion. I can reach the
knobs while looking in the focuser.
This scope usually sits on a heavy-duty wooden tripod that I built,
somewhat based on Berry's refractor tripod from "Build Your Own
This scope not only shows beautiful star fields in the milky way, but
also sharp, contrasty views of planets. It provided good views of
Mars during the 2003 opposition.