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Lunar distance accuracy with StarPilot
From: Paul Hirose
Date: 2025 Dec 2, 22:33 -0800
From: Paul Hirose
Date: 2025 Dec 2, 22:33 -0800
An anomaly in a lunar distance computation by StarPilot has generated some discussion in another forum. The observation is: 2025 Nov 16 12:06 UTC (approx) N46 W093 (approx) 0 height 10 C 1013 mb 9° 56.0' Spica distance from near limb 21° 53.0' Moon LL altitude 14° 02.0' Spica altitude One application gave "cleared" lunar distance 10°52.5' and UTC 12:12:20. Someone got 12:12:18 with Karl's method. My Lunar 4.4 software also says 12:12:18 UTC (cleared distance 10°52.5'), and my implementation of the Chauvenet method says 12:12:16 (cleared distance 10°52.5′). The extreme spread between the four solutions is only 4 s. Then there's StarPilot. It gives 12:15:12 according to one person, who also said, "Star Pilot, I've always thought, is the gold standard for lunars. They use an iterative approach (see Starpath.com)." I'm not familiar with the program. Any theories on the reason for the big discrepancy? I suggested a look at its lunar ephemeris accuracy. -- Paul Hirose sofajpl.com
