1978 Flagstaff Nighttime Cloudiness Summary N.B.: Incomplete observations in some months. Nights tallied in each month as follows. June: 12; August: 18; September: 14. These months not included in the yearly averages. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric (6) 6 (5) (8) 13 8 16 62 Monthly Average: 10.8 Partial (2) 2 (0) (1) 1 1 3 10 Monthly Average: 1.8 Spectroscopic (2) 5 (5) (1) 6 5 0 24 Monthly Average: 4.0 Cloudy (2) 18 (8) (4) 11 16 12 71 Monthly Average: 14.3 -------------------------------------------------------------------------------- Clear Hours (40) 40 (35) (65) 100 85 180 545 Monthly Average: 78. Clear+Dark Hours Monthly Average: Mean Consec (3.0) 1.2 (1.7)(3.5) 2.6 1.6 3.2 Monthly Average: 2.4 Max Consec Monthly Average: -------------------------------------------------------------------------------- Definitions: Photometric - cloudfree dusk-to-dawn. Partial - at least 3 consecutive cloudfree hours during the night. Spectroscopic - less than about 1 mag. extinction throughout the night. Cloudy - cloudy. Clear+Dark Hours = photometric hours with moon absent. Mean Consec = mean number of consecutive photometric nights during the month. Max Consec = maximum number of consecutive photometric nights during the month.