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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Moonrise-over-Connecticut
From: Paul Hirose
Date: 2021 Nov 6, 14:28 -0700
From: Paul Hirose
Date: 2021 Nov 6, 14:28 -0700
On 2021-11-05 14:30, Peter Blaskett wrote: > Celestial Navigation Data for 2021 Nov 6 at 11 43 35 UT (GMT) > Delta T = 87.7 seconds > For Assumed Location: Longitude 0 00.0 > Latitude 0 00.0 At that time and place, with the ICE delta T, the Lunar 4.4 program gives: Moon geocentric apparent place 244°53.26' -21°54.44' equinox RA, dec 135°43.80' +58°35.81' geocentric az, el However, the correct delta T is 32.184 (a fixed value) + 37 (until the next leap second) - -0.107 (UT1-UTC from IERS Bulletin A). The sum is 69.29 s. With the correct delta T: 244°53.06' -21°54.39' equinox RA, dec 135°43.97' +58°35.99' geocentric az, el ICE altitude error is almost 0.2'. Since the ICE delta T is 18.41 s too large, the position of the Moon in its orbit is correct if we move UT1 back that much. But now Earth rotation has not carried the observer far enough east. The solution is to convert the time correction to arc and move the observer east. Result with the wrong delta T but corrected UT1 and observer longitude is practically perfect: 244°53.06' -21°54.39' equinox RA, dec 135°43.95' +58°35.98' geocentric az, el -- Paul Hirose http://sofajpl.com/
