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Old 06-11-2019, 08:31 AM
Quercus is offline
Join Date: Dec 2000
Location: temperate forest
Posts: 7,123
Originally Posted by brossa View Post
It would probably be of value to do a seconds count to see how long it takes the Sun to rise completely, from first sighting to fully above the horizon. Say this is 200 seconds. So now you know that when the sun is setting, from the time it grazes the horizon until it vanishes completely will also be about 200 seconds. This lets you time your phone call so that it will overlap that vanishing point; once you think the Sun is touching the horizon, wait 170 seconds and place your call. It's easier to say when the Sun has disappeared than to say with certainty when it is 100% risen. The Sun takes from 2 to 5 minutes to rise and set depending on latitude and time of year, and it would be a waste to place your phone call too soon or late to capture the moment of disappearance.
I don't think we need that much accuracy. If we're off by one minute for the sunrise time, that's a maximum error of 16 miles or so (less away from the equator). Since the island is the only possible correct location within multiple miles, it wouldn't take long to correct that kind of error.