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Yesterday I had the pleasure of finally meeting Hewitt Schlereth (we compared watches in a bar ;-) and one of his students. We shot the breeze rather than the Sun and managed to blow an entire afternoon :) His student has a visual condition called monopsia and I was wondering if this was an advantage or a handicap when using a sextant ? He sails a 35 ft. ketch and claims to have never felt seasickness even in heavy weather. Perhaps monopsia can explain this immunity to seasickness.

From Wikipedea:

"Monopsia is a medical condition in humans who cannot perceive three-dimensionally even though their two eyes are medically normal, healthy, and spaced apart in a normal way. Vision that perceives three-dimensional depth requires more than parallax. In addition, the resolution of the two disparate images, though highly similar, must be simultaneous, subconscious, and complete. (After-images and "phantom" images are symptoms of incomplete visual resolution, even though the eyes themselves exhibit remarkable acuity.) A feature article in The New Yorker magazine published in early 2006 dealt with one individual in particular, who, learning to cope with her disability, eventually learned how to see three-dimensional depth in her daily life. Medical tests are available for determining monoptic conditions in humans."

Greg Rudzinski