With CALC-O-SCOPE, your iPhone does a lot of the calculations for you. You have the option of saving up to 4 different presets and calling them up again with a tap. Here are some features: - focal ratio - magnification -Light gathering ability - Exit pupil (with warning) - resolving power (with warning) - min. magnification - beneficial enlargement - max magnification (with warning) - moonphase (with calendar entry) - julian date - show UTC If you wish, Calc-o-scope will show you your current position and help you align the telescope with a compass. Also take a look at my calc-o-scope website (german). There you will find a way to equip your iPhone with a system-wide red filter with a triple click (no more flashed eyes if a message pops up). Have fun with calc-o-scope Udo Schmitt