Walter Nissen wrote: >"How far North do you have to be to see more planes simultaneously?". For a minimum satellite elevation of 10° you would have to be higher than latitude 75° to see all Iridium planes simultaneously. For a minumum elevation of 20° it would be 80.5°. The northernmost town with a daily scheduled air service (I think) is Longyearbyen in Svalbard (Spitsbergen) at 78.15° which offers you 15° minimum elevation on all Iridium planes. But except for very bright Iridium flares you would not see much during the summer time due to the midnight sun. Up there the time to do your observations would be winter. Taking this site (which by the way is about as far North as McMurdo in Antarctica is South) and doing a few calculations I found that even in mid-winter there are certain times of the day when illuminated satellites from all six planes would be high enough in the sky simultanously to be observed (in different directions, of course, and with binoculars as most of them would not flare at the time). In fact, you could see every single satellite of the Iridium constellation within a 100 minute period! At other times of the day the section visible from the observation site of one or the other plane might not be illuminated. An observer directly at the Pole could see satellites from all planes all the time throughout the day. Gerhard HOLTKAMP Darmstadt, Germany ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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