December 10, 2019

Astro-Event of the Week: September 16th-22nd: The Harvest Moon.

This months’ Full Moon is the most well known: the Harvest Moon.

Contrary to popular myth, this moon is not the largest or brightest moon visible during the year; it is merely the closest full moon to the Autumnal Equinox. In days of yore, the Harvest Moon gave farmers a few extra hours of illumination in a season of dwindling twilight to bring in their crops. Along with the Easter and Blue Moon, its one of the last remaining “Moon names” to still found in general use. I guess the Sturgeon, Egg, and Hunger Moon weren’t all that sexy. Note also that, on successive nights, the moon rises nearly at the same time. This is due to the oblique angle of the ecliptic and the moons orbit to the local horizon at this time of year. For example, the full moon occurs on Monday, September 15th, at 5:13 AM EDT local and rises that night at about 6:35 PM for mid-northern latitudes; however, the rising times on the 14th and 16th are only different by -17 minutes and +19 minutes, respectively.

This weeks’ Astro-word of the week is draconic month. This is a lunar month that is measured from the time it takes the moon to pass from one ascending node on the ecliptic to the next: its length is 27 days, 5 hours, 5 minutes, and 35.8 seconds, respectively. Also called the draconitic or nodical month, it is a precession caused by the tidal forces of the sun’s gravity on the moons orbit, causing the nodes of the moon’s orbit to advance in a complete 360 degree circle once every 18.6 years. When a full moon occurs at an ascending node, a lunar eclipse occurs. As if anomalistic, sidereal, tropical and synodic months weren’t confusing enough! Impress your friends with this one… tell them Astroguyz sent you!


  1. [...] Sunday, September 30th. Being the closest Full Moon to the September Equinox, this is known as the Harvest Moon. Note how the Moon seems to “linger” from night to night, rising less than 30 minutes apart on [...]

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