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Bear Branch Nature Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bear Branch Nature Center clear sky chart from 2005-11-05 to 2008-11-10.

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% 5% 5% 5% 5% 7% 39%	12103
	Night	15% 5% 5% 5% 8% 38%	11930
Cloud Cover	Day	13% 5% 5% 5% 5% 7% 39%	12122
	Night	15% 5% 5% 5% 8% 38%	11953
Transparency	Day	7% 18% 27% 18%	8758
	Night	7% 18% 27% 18%	8658
Seeing	Day	11% 28% 24% 19% 6%	751
	Night	16% 32% 29% 11%	3461

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	14% 7% 5% 5% 7% 6% 8% 33%	802
	Night	18% 5% 5% 5% 9% 34%	1238
February	Day	15% 8% 5% 5% 39%	764
	Night	14% 7% 5% 5% 5% 6% 6% 36%	1027
March	Day	13% 5% 6% 5% 5% 6% 41%	996
	Night	13% 5% 6% 5% 7% 5% 9% 35%	1001
April	Day	16% 6% 6% 5% 5% 6% 5% 36%	1078
	Night	19% 5% 5% 5% 6% 7% 34%	899
May	Day	12% 5% 5% 7% 9% 40%	1262
	Night	8% 5% 7% 5% 9% 45%	785
June	Day	12% 7% 5% 7% 10% 39%	1251
	Night	11% 6% 7% 7% 8% 42%	718
July	Day	9% 6% 8% 6% 6% 8% 37%	1266
	Night	9% 5% 5% 7% 5% 9% 10% 36%	774
August	Day	11% 5% 5% 6% 5% 7% 42%	1152
	Night	13% 5% 5% 5% 5% 5% 7% 42%	880
September	Day	18% 5% 8% 46%	1035
	Night	14% 6% 51%	941
October	Day	12% 5% 5% 5% 49%	923
	Night	17% 5% 7% 45%	1111
November	Day	17% 10% 5% 5% 7% 32%	830
	Night	20% 5% 5% 5% 6% 7% 32%	1259
December	Day	15% 7% 5% 5% 6% 5% 7% 36%	744
	Night	17% 6% 6% 5% 9% 34%	1297

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	14% 7% 5% 5% 6% 7% 8% 33%	801
	Night	18% 5% 5% 5% 5% 9% 35%	1239
February	Day	13% 8% 6% 5% 5% 5% 39%	762
	Night	13% 7% 5% 5% 5% 5% 6% 36%	1018
March	Day	11% 5% 6% 6% 5% 6% 5% 6% 40%	1019
	Night	13% 5% 5% 5% 7% 5% 9% 34%	1023
April	Day	16% 6% 6% 6% 6% 5% 5% 36%	1077
	Night	18% 6% 5% 5% 6% 7% 34%	899
May	Day	11% 5% 5% 7% 9% 40%	1261
	Night	8% 5% 6% 5% 9% 44%	785
June	Day	11% 7% 5% 7% 10% 39%	1260
	Night	10% 5% 6% 7% 9% 41%	720
July	Day	9% 6% 8% 6% 6% 9% 36%	1266
	Night	8% 5% 5% 8% 6% 8% 11% 34%	775
August	Day	10% 5% 5% 6% 5% 6% 7% 40%	1147
	Night	13% 5% 5% 5% 5% 8% 42%	882
September	Day	18% 5% 5% 8% 45%	1034
	Night	14% 5% 6% 50%	942
October	Day	12% 7% 48%	923
	Night	16% 7% 45%	1111
November	Day	16% 10% 5% 5% 7% 32%	828
	Night	20% 6% 5% 5% 6% 5% 6% 32%	1258
December	Day	15% 7% 5% 5% 5% 7% 35%	744
	Night	16% 6% 5% 6% 5% 8% 34%	1301

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	7% 21% 32% 15%	525
	Night	5% 22% 31% 18%	825
February	Day	5% 23% 29% 11%	552
	Night	5% 24% 24% 19%	729
March	Day	5% 23% 29% 16%	721
	Night	10% 19% 29% 15%	700
April	Day	6% 18% 18% 21% 8%	734
	Night	5% 21% 18% 18% 10%	619
May	Day	6% 16% 32% 20%	961
	Night	8% 16% 32% 22%	600
June	Day	13% 27% 33% 13%	858
	Night	12% 26% 35% 14%	496
July	Day	12% 18% 24% 16%	678
	Night	12% 21% 23% 14%	425
August	Day	7% 14% 24% 20%	989
	Night	5% 14% 24% 20%	757
September	Day	6% 9% 28% 29%	824
	Night	5% 9% 26% 29% 6%	783
October	Day	5% 12% 27% 25%	797
	Night	6% 9% 27% 26%	935
November	Day	8% 22% 24% 10%	583
	Night	8% 16% 30% 12%	857
December	Day	10% 25% 22% 13%	536
	Night	7% 24% 28% 12%	932

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	28% 40% 22%	318
February	Day	33% 40% 16%	30
	Night	31% 36% 21%	278
March	Day	22% 36% 27%	85
	Night	24% 44% 20%	333
April	Day	17% 38% 13% 13%	81
	Night	18% 38% 22% 8%	322
May	Day	8% 32% 24% 22% 6%	87
	Night	10% 31% 36% 14%	221
June	Day	5% 26% 32% 26% 6%	79
	Night	27% 43% 23%	158
July	Day	5% 23% 29% 27% 7%	77
	Night	21% 43% 25%	188
August	Day	19% 30% 21% 13%	88
	Night	16% 42% 21%	303
September	Day	9% 14% 19% 32% 14%	83
	Night	5% 19% 37% 27%	329
October	Day	16% 20% 29% 18%	87
	Night	13% 24% 31% 16%	341
November	Day	7% 42% 16% 9%	54
	Night	20% 32% 25% 7%	334
December	Night	17% 43% 23%	336

Page generated at 2008-11-11 07:54:39. Version ab11