Modern history


art The Moon, April 18-19, 1775

Many participants remembered that the moon was nearly full on the night of April 18-19, 1775. “The moon shone bright,” Paul Revere wrote in his deposition. His fellow captive Sanderson wrote independently, “It was a bright moon-light after the rising of the moon, and a pleasant evening” (Phinney, Lexington, 31).

These memories have been confirmed by two American astronomers, Donald W. Olson and Russell L. Doescher, who studied this subject in detail, and found that the nearest full moon occurred on April 15, 1775, and the last quarter on April 22. On the night of the midnight ride, they calculate that “there was indeed a bright waning-gibbous moon, 87 percent sunlit, in Boston on the night of April 18, 1775.” They estimate that the moon rose over Boston at approximately 9:53 p.m., local apparent solar time (approximately 25 minutes later than our modern Eastern Standard Time).

On that night Olson and Doescher reckon that the moon had a strong southern declination of -18 degrees. If Revere’s friends were rowing him across the Charles River at approximately 45 minutes after moonrise, the moon would have been very low in the southern sky—6 degrees above the horizon, on a true bearing of 121 degrees.

Revere’s course from the North End of Boston to Charlestown’s ferry landing was approximately 330 degrees. The moon was almost directly behind him, and as it was only 6 degrees above the horizon, his boat would have been shrouded in the dark moonshadow of the town’s skyline, and very difficult to see from the deck of HMS Somerset, or even from British guardboats that were patrolling the river that night.

The transit of the moon occurred at 2:42 a.m. according to the computations of two other astronomers, Jacques Vialle and Darrel Hoff. The marker in the Minute Man National Historical Park that refers to a third quarter moon is not correct.

See Donald W. Olson and Russell L. Doescher, “Astronomical Computing: Paul Revere’s Midnight Ride,” Sky and Telescope, April 1992, pp. 437-40; also Jacques Vialle and Darrel Hoff, “The Astronomy of Paul Revere’s Ride,” Astronomy 20 (1992): 13-18.

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