Sommers-Bausch Observatory - University of Colorado



Illuminated Fraction of the Lunar Face - Year 2015


Data courtesy the

US Naval Observatory Astronomical Applications



The fraction (or percent) of the Moon's face that is illuminated is a more thorough description of its phase than merely specifying "days since new moon" or the nearest quarter phase.

0.00 = New Moon (0% illuminated)
0.50 = First Quarter Moon (following the New Moon)
1.00 = Full Moon (100% illuminated)
0.50 = Third Quarter Moon (following the Full Moon)

Waxing Moon = Period between New Moon and Full Moon
Waning Moon = Period between Full Moon and New Moon

Crescent Moon = Fraction illuminated is more than 0.00 (0%) and less than 0.50 (50%)
Gibbous Moon = Fraction illuminated is more than 0.50 (50%) and less than 1.00 (100%)


                                    Fraction of the Moon Illuminated, 2015           Astron. Applications Dept.
                                                  at Midnight                        U. S. Naval Observatory   
                                            Mountain Standard Time                   Washington, DC 20392-5420 
                                                                                                               
                                                                                                               
 Day    Jan.     Feb.     Mar.     Apr.     May      June     July     Aug.     Sep.     Oct.     Nov.     Dec.
                                                                                                               
 01     0.85     0.93     0.83     0.91     0.92     0.98     0.99     0.99     0.91     0.86     0.72     0.69
 02     0.91     0.97     0.90     0.96     0.97     1.00     1.00     0.95     0.83     0.77     0.62     0.60
 03     0.96     0.99     0.95     0.99     0.99     0.99     0.98     0.89     0.73     0.67     0.52     0.50
 04     0.99     1.00     0.98     1.00     1.00     0.97     0.94     0.80     0.62     0.56     0.43     0.41
 05     1.00     0.98     1.00     0.99     0.99     0.92     0.87     0.70     0.51     0.46     0.33     0.32
 06     0.99     0.95     1.00     0.97     0.95     0.85     0.78     0.59     0.41     0.36     0.25     0.24
 07     0.96     0.90     0.98     0.93     0.90     0.76     0.68     0.48     0.31     0.27     0.17     0.16
 08     0.91     0.84     0.94     0.87     0.82     0.65     0.57     0.37     0.22     0.19     0.11     0.10
 09     0.85     0.77     0.89     0.79     0.73     0.54     0.45     0.27     0.14     0.12     0.05     0.05
 10     0.78     0.68     0.82     0.70     0.63     0.43     0.34     0.18     0.08     0.06     0.02     0.02
 11     0.70     0.59     0.74     0.60     0.52     0.32     0.24     0.11     0.04     0.03     0.00     0.00
 12     0.61     0.49     0.65     0.49     0.40     0.22     0.15     0.05     0.01     0.00     0.00     0.01
 13     0.51     0.38     0.55     0.37     0.29     0.13     0.08     0.02     0.00     0.00     0.03     0.04
 14     0.41     0.28     0.44     0.27     0.19     0.06     0.04     0.00     0.01     0.02     0.07     0.09
 15     0.32     0.19     0.33     0.17     0.11     0.02     0.01     0.00     0.04     0.05     0.12     0.16
 16     0.22     0.11     0.23     0.09     0.05     0.00     0.00     0.03     0.08     0.10     0.20     0.25
 17     0.14     0.05     0.14     0.03     0.01     0.01     0.02     0.06     0.14     0.16     0.29     0.35
 18     0.07     0.01     0.07     0.00     0.00     0.03     0.05     0.12     0.21     0.25     0.39     0.46
 19     0.02     0.00     0.02     0.00     0.02     0.08     0.10     0.19     0.30     0.34     0.50     0.58
 20     0.00     0.03     0.00     0.03     0.06     0.14     0.16     0.27     0.39     0.44     0.62     0.69
 21     0.01     0.08     0.01     0.08     0.12     0.22     0.24     0.35     0.49     0.55     0.72     0.79
 22     0.05     0.15     0.05     0.16     0.19     0.30     0.33     0.45     0.60     0.66     0.82     0.87
 23     0.11     0.25     0.12     0.24     0.27     0.39     0.42     0.55     0.70     0.76     0.90     0.94
 24     0.19     0.35     0.20     0.33     0.37     0.49     0.51     0.65     0.80     0.85     0.96     0.98
 25     0.29     0.46     0.30     0.43     0.46     0.58     0.61     0.75     0.88     0.93     0.99     1.00
 26     0.40     0.56     0.40     0.53     0.56     0.67     0.70     0.84     0.95     0.98     1.00     0.99
 27     0.51     0.66     0.50     0.62     0.65     0.76     0.79     0.91     0.99     1.00     0.97     0.96
 28     0.62     0.75     0.60     0.71     0.74     0.84     0.87     0.97     1.00     0.99     0.93     0.91
 29     0.72              0.69     0.79     0.81     0.91     0.94     1.00     0.98     0.95     0.86     0.84
 30     0.80              0.77     0.87     0.88     0.96     0.98     1.00     0.93     0.89     0.78     0.77
 31     0.88              0.85              0.94              1.00     0.97              0.81              0.68