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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Old style lunar
From: Fred Hebard
Date: 2004 Dec 9, 22:47 -0500
From: Fred Hebard
Date: 2004 Dec 9, 22:47 -0500
On Dec 9, 2004, at 8:35 PM, Frank Reed wrote: > Alex wrote: > "Perhaps Frank can also tell us what accuracy can be expected > from his lunar "predictions" for 200 years ago." > > +/- 1 arcsecond or better. > > Here's a specific sample from the 1778 Nautical Almanac (N.A.) > compared with my online lunars predictions (modern ephemeris). Angles > in degrees, minutes, and seconds, dd.mm.ss: > Noon, March 20, 1778 > Sun-Moon distance from N.A.: 65.19.52 > Modern ephemeris: 65.19.58 > Noon, June 18, 1778 > Sun-Moon distance from N.A.: 84.02.18 > Modern ephemeris: 84.02.04 > Noon, August 25, 1778 > Sun-Moon distance from N.A.: 39.49.12 > Modern ephemeris: 39.49.17 > Noon, November 14, 1778 > Sun-Moon distance from N.A.: 52.37.19 > Modern ephemeris: 52.37.44 Frank, The only one that's somewhat serious is Nov 14, 1778, and that's out by 25" of arc. This can't explain discrepancies of 1 degree of arc! Fred
