Thank YOU for weighing in, Brent! Your answer was succinct. People sometimes don't realize that focusing a system is just a matter of making focal planes coincide. Visually, the eyepiece focal plane must occupy the same location as the objective focal plane. In imaging, the chip or film surface must coincide with the final focal plane of the entire system, be it direct-objective or with additional lenses. A little bit of math goes a long way towards saving time and frustration under the stars. I'm sure there must be websites and apps available these days to do it, without having to take pencil to paper. But where's the fun in that? There are also off-the-shelf solutions for the mass-produced telescopes and cameras, if one does a bit of sleuthing or is lucky enough to find a salesperson who understands what they want to do and can recommend the proper hardware. On Sun, Aug 11, 2013 at 9:41 AM, Brent Watson <brentjwatson@yahoo.com>wrote:
Chuck beat me to the answer. His explanation was also better. Thanks, Chuck!