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Longest Lunar Month in 2014 from August 25 to September 24




The lunar month, also called a lunation or the synodic month, is the measure of time between two successive new Moons. It's no coincidence that the year's longest lunar month begins one fortnight after the year's closest and largest supermoon on August 10, 2014.


Image credit on right: NASA


The longest lunar month of 2014 - August 25 through September 24 - lasts for 29 days 16 hours and 1 minute. That's 3 hours and 17 minutes longer than the mean lunar month of 29 days 12 hours and 44 minutes.


The shortest lunar month this year happened in between the new Moons of January 30 and March 1. (There was no new Moon in February 2014.) This lunar month was only 29 days 10 hours and 21 minutes long, or 2 hours and 23 minutes shorter than the mean lunar month of 29 days 12 hours and 44 minutes.



Lengths of the Lunar Months in 2014




Successive new moons

Length of lunar month

January 1 to January 30

29 days 10 hours 24 min

January 30 to March 1

29 days 10 hours 21 min

March 1 to March 30

29 days 10 hours 45 min

March 30 to April 29

29 days 11 hours 30 min

April 29 to May 28

29 days 12 hours 26 min

May 28 to June 27

29 days 13 hours 28 min

June 27 to July 26

29 days 14 hours 33 min

July 26 to August 25

29 days 15 hours 31 min

August 25 to September 24

29 days 16 hours 01 min

September 24 to October 23

29 days 15 hours 43 min

October 23 to November 22

29 days 14 hours 36 min

November 22 to December 22

29 days 13 hours 04 min


Sources: Astropixels.com and TimeandDate.com


In 2014, the year's longest and shortest lunar months do not actually showcase great extremes. In fact, the longest and shortest lunar months in the years ahead will vary more greatly from the mean. The longest lunar month of the 21st century (2001 to 2100) happens in between the December 2017 and January 2018 new Moons. With a length of 29 days 19 hours and 47 minutes, this particular lunar month exceeds the mean by a whopping 7 hours and 3 minutes.


The century's shortest lunar month takes place in between the new Moons of June and July 2053, a period of 29 days 6 hours and 35 minutes. That's 6 hours and 9 minutes shorter than the mean.



How About The Time Period Between Successive Full Moons?


How about that we, just for the fun of it, measure the length of the lunar month by successive full Moons? In 2014, we find that the longest and shortest lunar months, as measured by successive full Moons, vary more greatly from the mean than do this year's new Moons.


Here's the story for 2014. The longest lunation occurs between the January and February 2014 full Moons: 29 days 19 hours and 1 minute. The shortest happens between the August and September full supermoons: 29 days 6 hours and 44 minutes.



Lengths of the Lunar Months (As Measured by Successive Full Moons) in 2014




Successive new moons

Length of lunar month

January 16 to February 14

29 days 19 hours 33 min

February 14 to March 16

29 days 17 hours 16 min

March 16 to April 15

29 days 14 hours 33 min

April 15 to May 14

29 days 11 hours 34 min

May 14 to June 13

29 days 08 hours 55 min

June 13 to July 12

29 days 07 hours 14 min

July 12 to August 10

29 days 06 hours 44 min

August 10 to September 9

29 days 07 hours 29 min

September 9 to October 8

29 days 09 hours 13 min

October 8 to November 6

29 days 11 hours 32 min

November 6 to December 6

29 days 14 hours 04 min



Why The Differences In The Lengths Of Lunar Months?


The lunar month, whether measured by successive new Moons or full Moons, is longer than average if the successive new (full) Moons align closely with apogee - the Moon's farthest point from Earth in its orbit. On the other hand, the lunar month is shorter than average if the successive new (full) Moons closely align with perigee - the Moon's nearest point.


The longest lunar months happen when successive new (full) Moons occur near lunar apogee - and in addition, the Earth is near perihelion (Earth's closest point to the Sun in its orbit). Because Earth is always closest to the Sun in early January, the very longest lunar months take place in between December and January new (full) Moons.


On the other hand, extremely short lunar months happen when successive new (full) Moons fall near lunar perigee - and in addition, the Earth is near aphelion (Earth's farthest point from the Sun in its orbit). Because Earth is always at aphelion in early July, the very shortest lunar months take place in between June and July new (full) Moons.



Longest And Shortest Lunar Months


During the period from 1760 to 2200, the longest new Moon lunar month happened in between the new Moons of December 1787 and January 1788: 29 days 19 hours and 58 minutes. The shortest was between the June and July new Moons of 1885: 29 days 06 hours and 34 minutes.*


During the same time period from 1760 to 2200, the longest full Moon lunar month happened in between the full Moons of December 1880 and January 1881: 29 days 19 hours and 58 minutes. The shortest was between the June and July full Moons of 1783: 29 days 06 hours and 34 minutes.*


Source: Page 13 of Mathematical Astronomy Morsels V by Jean Meeus


copyright 2014 by Bruce McClure

July 2014 Feature * Sept 2014 Feature