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Northern and Southern Lunistices

Solstice Points

The sun climbs to its farthest point north of the celestial equator on the June (Northern) solstice. Then six calendar months later, the Sun reaches its southernmost point for the year on the December (Southern) solstice. This US Naval Observatory page gives you the dates and times for the solstices. The Sun shines very close to the border of the constellations Taurus and Gemini at the Northern Solstice and above the spout of the Sagittarian Teapot on the Southern solstice.
Jim Kaler's maps show you the solstice points amidst the stars. The Northern Solstice is marked as 90 degrees (on the ecliptic) on this chart, and the Southern solstice is marked as 270 degrees on this chart.

The Lunistice

Lunistice is the same idea as solstice, except that you're referring to the Moon instead of the Sun. The Sun takes about 365.25 days to travel full circle through the constellations of the zodiac, but the swifter-moving moon takes only around 27.3 days to go full circle. Wheras solstices happen twice a year, lunistices happen twice a month. Sometimes, three lunistices can fall in one calendar month, if the first lunistice occurs early enough in the month.
I've found almost no astronomical almanac that lists lunistice dates, and I couldn't even find the word 'lunistice' in the Second Edition of the Random House Webster's Unabridged Dictionary. Although people are enormously curious about the Moon and its movements, clearly the astronomical community has done little to connect the populace with the idea of lunistice. I'm happy to report, however, that Almanako.com and Derek C. Breit give the dates and times for the northern and southern lunistices.
In April 2008, the Northern lunistice falls on April 10, at 18 hours Universal Time (2 p.m. Eastern Daylight Time), and the Southern lunistice falls on April 24, at 23 hours UT (7 p.m. EDT). At this month's Northern lunistice, the moon be will a waxing crescent, about 28% illuminated by sunshine. On the April 24, 2008 Southern lunistice, it'll be a waning gibbous moon over 82% lit.

Interplay of Phases & Lunistices

Lunar phases repeat in periods of about 29.5 days, but northern or southern lunistices recur in 27.3-day cycles. That's why lunistices and the phases do not realign as the months go by. For example, the Northern lunistice in May 2008 occurs on May 8, 2 hours UT (May 7, 11 p.m. EDT). At 10% illumination, it's a thinner waxing crescent than the 28%-illuminated crescent in April 2008. The Southern lunistice on May 22, 2008 (4 hours UT) sports a 96%-illuminated waning gibbous Moon, which is fuller than at the April 2008 Southern lunistice.
Every 27.3 days, the lunistice happens in roughly the same place relative to the background stars. (You can use the Northern & Southern solstice points as a ballpark guide to the Northern & Southern lunistices.) As always, the Sun moves eastward (along the ecliptic) through the stars. Between the lunistices in April and May, the Sun moves closer to the Northern solstice point but farther away from Southern solstice point.
Therefore, in 2008, a thinner waxing crescent and a larger waning gibbous Moon accompany the lunistices in May than in April.

copyright 2008 by Bruce McClure

March 2008 Feature * May 2008 Feature