Wilcox Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wilcox Park clear sky chart from 2003-08-01 to 2005-11-07.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	22% 5% 6% 5% 6% 33%	8738
	Night	25% 5% 6% 6% 33%	8435
Transparency	Day	20% 17% 39% 20%	4156
	Night	19% 17% 39% 20%	4069
Seeing	Day	13% 29% 29% 19% 7%	539
	Night	17% 35% 30% 14%	2268

By Month

Percentage Cloud Cover
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month		Occurrence of each Forecast	Data Points
January	Day	25% 7% 6% 5% 34%	499
	Night	27% 5% 6% 5% 33%	854
February	Day	14% 5% 5% 6% 5% 44%	549
	Night	18% 5% 5% 5% 8% 38%	705
March	Day	30% 6% 7% 28%	672
	Night	25% 6% 5% 5% 7% 29%	692
April	Day	24% 5% 43%	728
	Night	32% 6% 34%	592
May	Day	18% 7% 7% 5% 7% 31%	844
	Night	24% 7% 5% 7% 5% 6% 27%	510
June	Day	17% 5% 5% 8% 6% 5% 6% 34%	840
	Night	23% 5% 5% 6% 6% 36%	476
July	Day	20% 6% 5% 9% 7% 6% 7% 24%	866
	Night	18% 6% 5% 8% 5% 8% 30%	496
August	Day	24% 5% 5% 5% 7% 5% 6% 26%	1165
	Night	23% 5% 6% 5% 7% 9% 29%	873
September	Day	23% 6% 40%	1017
	Night	23% 6% 44%	928
October	Day	28% 6% 5% 33%	608
	Night	35% 5% 5% 5% 30%	754
November	Day	21% 5% 5% 6% 5% 8% 5% 32%	464
	Night	24% 5% 5% 6% 33%	703
December	Day	25% 6% 5% 6% 5% 5% 6% 5% 24%	486
	Night	26% 6% 6% 5% 5% 32%	852

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	29% 24% 26% 15%	222
	Night	23% 16% 44% 15%	357
February	Day	22% 8% 42% 24%	292
	Night	23% 8% 43% 18% 6%	373
March	Day	24% 23% 37% 13%	275
	Night	21% 20% 41% 16%	278
April	Day	11% 9% 33% 39% 5%	381
	Night	17% 7% 35% 35%	248
May	Day	25% 16% 47% 11%	380
	Night	23% 17% 39% 19%	206
June	Day	17% 12% 52% 15%	395
	Night	16% 9% 45% 28%	223
July	Day	23% 15% 43% 15%	332
	Night	24% 15% 37% 19%	219
August	Day	20% 27% 37% 15%	474
	Night	21% 26% 30% 19%	383
September	Day	11% 13% 35% 38%	563
	Night	9% 14% 46% 26%	509
October	Day	20% 17% 44% 17%	383
	Night	19% 17% 42% 19%	513
November	Day	31% 22% 28% 14%	270
	Night	20% 30% 32% 15%	388
December	Day	30% 15% 42% 8%	189
	Night	23% 19% 36% 18%	372

Seeing (when cloud cover <= 80%)
Color Meanings: Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month		Occurrence of each Forecast	Data Points
January	Night	36% 42% 17%	185
February	Day	15% 43% 37%	32
	Night	18% 53% 19% 8%	188
March	Day	10% 43% 32% 13%	46
	Night	23% 43% 28%	192
April	Day	17% 40% 25% 8% 8%	47
	Night	26% 35% 22% 16%	165
May	Day	16% 35% 32% 11%	53
	Night	14% 42% 33% 8%	123
June	Day	12% 37% 29% 18%	54
	Night	5% 35% 46% 13%	99
July	Day	6% 16% 34% 30% 12%	49
	Night	7% 34% 30% 27%	108
August	Day	16% 19% 26% 28% 9%	73
	Night	9% 25% 37% 24%	264
September	Day	9% 18% 24% 28% 18%	74
	Night	10% 23% 41% 23%	293
October	Day	15% 24% 28% 22% 8%	70
	Night	17% 29% 27% 22%	271
November	Day	9% 36% 34% 17%	41
	Night	19% 35% 33% 10%	195
December	Night	22% 44% 27%	185

Page generated at 2008-09-30 05:41:14. Version ab11