Pointing the telescope toward a relatively dark region of the sky is not enough to ensure good results. It is important to limit the direct and indirect light that hits the instrument, since this illumination always seems to find a path to the CCD detector with disastrous results. By setting up my telescope at a suitable location on the roof I can eclipse a particularly obnoxious streetlight with a nearby chimney. Another possibility is to make a simple shield or enclosure for the telescope from cardboard or lightweight plywood. I am particularly careful to prevent extraneous light from getting into the telescope around the focuser.
Most Newtonian telescopes have openings at the focuser's base.
I sealed the openings on my scope with opaque black plastic strips made from a bag that holds photographic enlarging paper. It is also very important to use an extension hood on the front of the telescope similar to the one pictured on page 109 and in the June 1997 issue, page 84. This extension is my fundamental defense against extraneous light. The hood should be as long as possible without vignetting the CCD's field of view. It can be easily constructed from cardboard and laminated with cellophane tape to make it dew resistant.