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Baffled by Baffin
From: tony
Date: 2005 Nov 23, 16:56 +0000
From: tony
Date: 2005 Nov 23, 16:56 +0000
I have been reading the ?Voyages of William Baffin? (Hakluyt Society), but am having a problem with the description of his initial attempt to find his longitude on the west coast of Greenland (pp 20 & 21). Putting aside the shortcomings of the lunar culmination method, his data and description suggest that he saw the moon as outstripping the sun in its daily passage around the earth. ?Thursday, the ninth day, very early in the morning, I went on shore the island, being a faire morning, and observed till the moone came just upon the meridian. At which instant I observed the sunne?s height, and found it 8 51.? He then goes on to describe that by the use of spherical trignometry involving his latitude, the sun?s declination and the sun?s altitude, he found the sun?s local hour angle. Converting this to local time, he found the time of the observation to be 4h 17m 24s. My problem is what follows next. ?Which when I had done, I found by mine ephemerides, that the moone came to the meridian at London that morning at 4h 25m 34s which 17 minutes 24 seconds subtracted from 25minutes 34 seconds leaveth 8min 10secs of time for the difference of longitude betwixt the meridian of London (for which the ephemerides was made) and the meridian passing by this place in Groenland.? He then describes the moon?s motion that day as 48mins and 29 secs and describes it as ?the time that the moone commeth to the meridian sooner that day then she did the day before, give 360, the whole circumference of the earth; what shall 8 minutes 10 seconds give, to wit 60 degrees, 30 minutes.? Has anyone else seen this and can they offer any explanation. Baffin writes with much clarity and the problem does not arise elesewhere in his account. As his pioneering attempt to measure longitude was so very far out, I have wondered if he looked up the wrong data in Searle?s Ephemerides.