Technical Notes 

 0006 Oct 08    09:31     0.048   1.070     

 0006 Nov 07   04:26     0.257   0.869     

 0005 Apr 04   05:09     1.557  0.579     

77m     

 0005 Sep 27    11:19     1.374  0.298     

62m      

 0004 Mar 23    18:32    2.850    1.821    

111m  51m 

 0004 Sep 15    20:22     2.730    1.715    

109m  50m 

 0003 Mar 13    00:52     1.456    0.370     

70m     

 0003 Sep 05    11:18     1.723    0.745     

84m     

 0002 Jan 31    07:55     0.293    0.814     

 0002 Mar 02    01:18     0.126    0.983     

 0002 Jul 27    18:56     0.550   0.447     

 0002 Aug 26    03:44     0.435    0.549     

 0001 Jan 20    12:04     1.646   0.587     

82m     

 0001 Jul 17    05:25     1.880    0.829     

95m     

0000 Jan 09    23:20    2.801    1.794    

107m  50m 

0000 Jul 05   

08:49    2.537    1.448    

115m  48m 

0000 Dec 29    14:43    1.570    0.581     

76m     

0001 Jun 24    09:25    1.150    0.069     

32m     

0001 Nov 19    16:47    0.364   0.683     

0001 Dec 19    05:38    0.318    0.700     

    The first column above is the year, month, and day. The year is given using astronomical dating, where 

0001 is 

A.D.

 1; 0000 is 1 

B.C.

;  0001 is 2 

B.C.

; etc. The next column is the time in Universal Time (which uses a 

24 hour clock). The next two columns are the penumbral and umbral magnitudes of the eclipse. 

    The umbra of a lunar eclipse is the area of darkest shadow of the earth, seen on the visible disk of the moon 

during an umbral lunar eclipse. The penumbra is the area of partial shadow of the earth. The magnitude of 

each of these two types of shadows is the percentage of the visible surface of the moon covered by the shadow. 

A magnitude of 1.0 or greater means that the entire visible disk of the moon is covered by the earth's shadow 

(at the time of greatest magnitude). If the umbral magnitude is greater than or equal to 1.0, the eclipse is a total 

eclipse. If the umbral magnitude is less than 1.0 and greater than zero, the eclipse is a partial eclipse. If the 

umbral magnitude is less than zero, then the eclipse is a penumbral eclipse. If the umbral magnitude is less 

than zero and the penumbral magnitude is 1.0 or greater, the eclipse is a total penumbral eclipse. (If both the 

umbral and penumbral magnitudes are less than zero, then there is no eclipse at all.) A negative number for 

the umbral magnitude means that the umbra (the darkest part of the earth's shadow) does not affect the visible 

disk of the moon for that particular eclipse at all. Such eclipses are called penumbral eclipses. 

    The last two columns are the semi duration of the partial and total eclipses. The semi duration of the partial 

eclipse is one half the time that any portion of the umbral shadow is seen on the moon's surface. The partial 

eclipse begins when the umbral shadow is first seen on the visible disk of the moon, and ends when it is last 

seen. The semi duration of the total eclipse is one half the length of time that the visible surface of the moon is 

completely covered by the umbra. Every total lunar eclipse will have a semi duration number for both the 

partial and total phases of the eclipse. Partial lunar eclipses will only have a semi duration number for the 

partial eclipse. 

    Penumbral eclipses will not have a semi duration number at all, because semi durations refer only to the 

umbral shadow, not the penumbral shadow. Penumbral eclipses are difficult to observe and may not be 

noticeable to the casual observer at all. This is because the penumbral shadow is only a partial shadow. It is 

darkest close to the umbral shadow and progressively lighter away from the umbral shadow. For this reason, 

brief or partial penumbral eclipses would not have been noticed by observers in ancient times and would not 

be recorded by the ancient historians as lunar eclipses.  

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