Coyle Field
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coyle Field 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	20% 6% 7% 36%	8727
	Night	21% 5% 6% 5% 6% 37%	8447
Transparency	Day	18% 14% 40% 24%	4798
	Night	17% 12% 40% 25%	4581
Seeing	Day	8% 27% 31% 20% 12%	547
	Night	11% 34% 33% 18%	2411

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	22% 6% 5% 5% 6% 33%	512
	Night	23% 5% 7% 38%	841
February	Day	18% 6% 5% 5% 42%	551
	Night	16% 6% 5% 5% 41%	703
March	Day	27% 6% 6% 7% 32%	674
	Night	25% 5% 5% 6% 7% 5% 29%	690
April	Day	22% 5% 5% 44%	720
	Night	28% 5% 5% 33%	600
May	Day	19% 7% 5% 10% 36%	837
	Night	19% 5% 5% 5% 8% 7% 33%	518
June	Day	16% 5% 5% 8% 5% 6% 9% 34%	840
	Night	18% 7% 6% 5% 5% 10% 32%	476
July	Day	17% 5% 5% 5% 7% 5% 6% 8% 32%	866
	Night	14% 6% 9% 8% 5% 10% 30%	496
August	Day	20% 5% 6% 5% 6% 6% 7% 29%	1139
	Night	21% 5% 7% 5% 6% 34%	900
September	Day	22% 5% 7% 40%	1020
	Night	22% 6% 41%	925
October	Day	25% 7% 5% 37%	612
	Night	24% 5% 5% 5% 37%	749
November	Day	20% 6% 7% 41%	470
	Night	21% 7% 5% 38%	697
December	Day	20% 6% 7% 43%	486
	Night	15% 5% 5% 8% 44%	852

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	27% 15% 39% 13%	233
	Night	22% 12% 44% 18%	392
February	Day	17% 9% 41% 28%	291
	Night	14% 8% 42% 28% 5%	383
March	Day	15% 20% 45% 17%	316
	Night	13% 17% 41% 25%	291
April	Day	11% 9% 39% 35%	398
	Night	13% 8% 42% 28% 6%	277
May	Day	28% 15% 45% 10%	480
	Night	29% 16% 41% 12%	265
June	Day	19% 10% 43% 25%	450
	Night	13% 11% 49% 25%	228
July	Day	21% 6% 41% 27%	422
	Night	23% 14% 38% 19%	244
August	Day	21% 20% 35% 21%	515
	Night	25% 14% 39% 17%	441
September	Day	10% 13% 32% 36% 8%	590
	Night	13% 9% 33% 35% 7%	513
October	Day	12% 13% 44% 28%	475
	Night	15% 12% 35% 32%	585
November	Day	15% 20% 41% 16% 6%	341
	Night	16% 16% 41% 20% 5%	455
December	Day	18% 18% 40% 21%	287
	Night	15% 12% 43% 26%	507

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	14% 58% 22%	195
February	Day	12% 63% 21%	33
	Night	10% 49% 32% 7%	195
March	Day	22% 35% 31% 11%	45
	Night	15% 56% 26%	196
April	Day	12% 40% 28% 12% 6%	49
	Night	12% 43% 32% 12%	181
May	Day	6% 26% 48% 12% 8%	50
	Night	7% 24% 49% 17%	126
June	Day	21% 41% 25% 9%	51
	Night	6% 24% 54% 13%	102
July	Day	9% 14% 35% 24% 16%	54
	Night	8% 15% 42% 31%	114
August	Day	15% 30% 33% 19%	72
	Night	7% 17% 34% 35% 5%	291
September	Day	20% 23% 26% 26%	73
	Night	8% 20% 34% 35%	297
October	Day	8% 32% 23% 20% 15%	73
	Night	13% 25% 31% 22% 7%	298
November	Day	14% 23% 34% 25%	47
	Night	13% 30% 34% 19%	205
December	Night	15% 45% 30% 8%	211

Page generated at 2008-06-05 23:07:38. Version ab11