I was just messing around with the dob, Discovery 10 inch, and noticed that even if a light source is way off to the side, you can see the wall of the tube opposite the focuser, lit up when looking through the empty focuser. The spider is pretty deep in the tube, so I figured I didn't have to worry about that. Does anyone put like a shield on their dob also? Does it make a difference? We have a street light south of us, it would be about 2 degrees below Mars in the FOV, I'm thinking it might really be messing with the contrast.
Also (oops) someone gave me a link a while back for flocking paper stuff, and I know I clicked favorites, well, I thought I did, anyway I don't have it
Ron, By all means get a light shield on the front of your dob. Gary Seronik wrote an article in the April 2001 issue of Sky and Telescope titled Newtonion Baffling Made Easy which describes in order of effectiveness the modifications which enhance contrast in Newts. It's a worthwhile read.
ANYTHING you can do to keep stray light out of that tube will make a BIG difference IF you often view from a place that has lots of scattered light around. I view from my back yard in St. Paul and there's light everywhere. So I built my 10" dob with this city-use optimization in mind. An overly-long solid tube that extends more than a foot past the eyepiece and dark cloth spray-painted ultra-flat black glued to the whole inside.