----- Original Message ---- > From: music_ki <[EMAIL PROTECTED]> > > I guess what I'm almost asking, is if > there is something like a compass, but for vertical degrees, that I > could use for this kind of stuff, in order to better plan in advance.
In ancient times they called in an astrolabe. A more advanced version used by navigators to sail by the stars was called a sextant. You can make a simple astrolabe with a plastic protractor <http://www.chicos.caltech.edu/classroom/pointer/protractor.gif> (semicircular thing for measuring/drawing angles, about $1 at an office supply store, or the "school supplies" section of many stores- it's a standard implement for geometry class) Get a piece of string and a small weight to use as a plumb bob. Protractors have a small hole at the "center" (center of what would be the full circle, if you extended the semicircle). Thread the string through the hole and tie a knot in the short end, and then hang the weight from the other end. With the curved edge of the protractor aimed down, sight along the straight edge of the protractor to the "target", and read the angle where the string is hanging. Unfortunately the angles on protractors usually start at 0 along the straight edge, with 90 at the midpoint of the semicircle, so to read angles above the horizon, you'll need to subtract the protractor reading from 90. There are also "full circle" protractors, so if you start with the 0 degree line aimed down, then rotate until the 90/270 line is aimed at the target (with 270 towards the target, and 90 towards your eye), then you could read the angle directly. But it might be hard to see the 90/270 line in the dark. I once taped a straw to a protractor to use as the "sight". I recently saw a protractor with a straight plastic arm that pivoted from the "center". With that, if you hold the protractor with the curved edge up, and level the straight edge to the horizon, and then move the arm to sight the target, you could read the angle directly. -John
