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Oklahoma City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oklahoma City 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	13% 6% 8% 43%	8706
	Night	13% 5% 5% 7% 46%	8468
Transparency	Day	10% 16% 39% 27% 6%	5474
	Night	11% 15% 36% 28% 8%	5537
Seeing	Day	5% 21% 37% 29% 5%	534
	Night	8% 30% 37% 22%	2600

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	20% 7% 7% 5% 5% 37%	550
	Night	19% 5% 6% 5% 6% 38%	803
February	Day	22% 6% 5% 5% 6% 5% 6% 6% 28%	559
	Night	25% 5% 7% 6% 5% 6% 29%	697
March	Day	14% 5% 5% 5% 6% 44%	678
	Night	12% 5% 5% 6% 47%	686
April	Day	13% 6% 9% 51%	721
	Night	12% 5% 5% 7% 5% 5% 47%	599
May	Day	11% 5% 5% 12% 41%	803
	Night	9% 6% 8% 10% 45%	550
June	Day	9% 5% 5% 5% 11% 43%	780
	Night	6% 6% 9% 6% 6% 13% 38%	537
July	Day	7% 5% 6% 10% 48%	801
	Night	6% 5% 6% 12% 53%	558
August	Day	11% 9% 5% 7% 8% 37%	1179
	Night	7% 5% 6% 6% 10% 48%	862
September	Day	7% 6% 5% 9% 51%	970
	Night	9% 5% 5% 5% 53%	975
October	Day	15% 7% 5% 6% 41%	634
	Night	16% 5% 5% 6% 45%	726
November	Day	29% 44%	483
	Night	28% 45%	684
December	Day	7% 5% 5% 8% 54%	548
	Night	7% 7% 62%	791

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	11% 21% 36% 29%	264
	Night	12% 17% 36% 32%	408
February	Day	14% 14% 51% 17%	247
	Night	15% 14% 44% 20% 5%	300
March	Day	10% 16% 39% 29%	387
	Night	8% 17% 32% 30% 9%	414
April	Day	9% 11% 41% 31% 5%	472
	Night	12% 15% 25% 34% 11%	352
May	Day	14% 17% 40% 22% 5%	478
	Night	20% 16% 47% 13%	369
June	Day	17% 15% 33% 28% 5%	473
	Night	22% 11% 34% 27%	331
July	Day	8% 18% 41% 24% 6%	532
	Night	12% 19% 38% 23% 6%	409
August	Day	15% 20% 41% 19%	693
	Night	11% 22% 46% 16%	596
September	Day	6% 16% 39% 28% 8%	706
	Night	7% 8% 32% 36% 14%	668
October	Day	11% 10% 33% 36% 8%	544
	Night	6% 17% 29% 35% 11%	682
November	Day	6% 10% 30% 33% 18%	280
	Night	8% 11% 30% 36% 13%	419
December	Day	16% 41% 32% 7%	398
	Night	6% 8% 44% 30% 10%	589

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	12% 42% 36% 8%	255
February	Night	13% 36% 39% 11%	174
March	Night	13% 48% 34%	170
April	Day	9% 55% 28% 5%	52
	Night	13% 35% 38% 11%	160
May	Day	9% 27% 43% 18%	111
	Night	7% 29% 47% 15%	170
June	Day	24% 35% 29% 6%	110
	Night	26% 39% 26%	171
July	Day	14% 34% 42% 6%	117
	Night	12% 39% 43%	173
August	Day	8% 41% 36% 9%	144
	Night	6% 40% 46%	265
September	Night	15% 35% 39% 5%	250
October	Night	5% 29% 36% 26%	304
November	Night	17% 38% 31% 12%	223
December	Night	9% 44% 34% 10%	285

Page generated at 2008-08-27 06:51:54. Version ab11