Bjoern Gimle <b_gimle@usa.net> wrote- >For the 8x56, an old person uses only 8x4 or 8x5 mm = 32-40 mm >instead of 56 mm. In the case of 7x18, all healthy persons would >utilize the full 18 mm. > >For 8x56, 4.2 + 5 * log( 8) is 8.7 >For 7x18, 4.2 + 5*log(18/5) is 7.0 and 4.2+5*log(18/7) is 6.3 Is there a reasonably accurate formula for calculating the predicted magnitude for a satellite? I suspect that it would have to include the satellite's cross section area, albedo, percentage sunlit (usually either 1 or 0), and distance from observer. I would suspect that the same formula could be used to calculate the magnitude of the moon, planets, and any other objects which shine by reflected sunlight. I have the graphs from the Desmond Hele book but would like a formula which I can plug in to a spreadsheet. Philip Chien, KC4YER Earth News world (in)famous writer, science fiction fan, ham radio operator, all-around nice guy, etc.