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Re: Baffled by Baffin
From: Frank Reed CT
Date: 2005 Dec 9, 01:18 EST
From: Frank Reed CT
Date: 2005 Dec 9, 01:18 EST
George H wrote: "What Baffin needed to know was the hour, in Apparent Time at London, at which the Moon was predicted to cross the Meridian of London, on the same day that he measured the corresponding Local Apparent Time in Greenland of the Moon crossing the meridian there." What's interesting, too, is that Baffin didn't need to know this information on the spot. Rather than using a pre-calculated ephemeris, his observations could have been rendered much more useful if he had had an accomplice (or several actually) back in England carefully observing the Moon's position as often as possible --a makeshift Royal Observatory. Then, even if the ephemerides of the era were poor, the longitude based on his observations would have been as accurate as the best observations of the era. Who knows... maybe someone even thought of that after Baffin returned home. An accurate lunar ephemeris, calculated in advance, is a necessity for "live" navigation by lunar position/lunar distances to a known destination, but it's merely a convenient luxury for surveying and exploration. For mapping the world, what's required is nearly simultaneous observations from a known longitude. The Moon can do what it will, and we don't need to have the science to predict it if our purpose is only mapping. -FER 42.0N 87.7W, or 41.4N 72.1W. www.HistoricalAtlas.com/lunars