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09/28/2015 – Ephemeris – The Harvest Moon effect

September 28, 2015

Ephemeris for Monday, September 28th.  The Sun will rise at 7:36.  It’ll be up for 11 hours and 52 minutes, setting at 7:29.   The Moon, 1 day past full, will rise at 8:00 this evening.

Yesterday’s full moon was the famous Harvest Moon, the nearest full moon to the autumnal equinox.  This is a time of the full and waning gibbous moons in the next few days rising in twilight.  In the old days before electric lights it helped farmers by effectively lengthening the hours of light to gather in the crops.  The Moon on average rises 50 minutes later each night.  The interval between tonight’s moon rise and tomorrow’s will be 38 minutes.  The interval between Tuesday and Wednesday will be 42 minutes.  This year’s harvest moon effect is spoiled a bit because the Moon was at perigee Sunday, the so-called supermoon, so it’s moving faster in its orbit than average.  Like the Sun, the Moon always appears orange or red near the horizon.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.


Path of the Harvest Moon

The positions of the Moon from September 28 to October 1, 2015. Note the path of the Moon. At Harvest Moon in northern Michigan time it makes less than a 45 degree angle with the horizon. For other latitudes it’s less than (90 – latitude). shorthand term for 90 – latitude is co-latitude. Created using Cartes du Ciel.

The closer to horizontal the Moon’s path is the shorter the difference in night-to-night rise times.

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