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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 2009-12-29.

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	15% 5% 5% 5% 5% 7% 38%	16447
	Night	16% 5% 5% 5% 5% 7% 38%	16485
Cloud Cover	Day	14% 5% 5% 5% 5% 7% 38%	16461
	Night	16% 5% 5% 5% 7% 38%	16501
Transparency	Day	7% 16% 25% 16%	13097
	Night	6% 15% 26% 17%	13210
Seeing	Day	10% 26% 24% 18% 6%	1024
	Night	15% 31% 27% 10%	4903

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% 6% 6% 8% 36%	1062
	Night	17% 5% 5% 6% 8% 35%	1637
February	Day	13% 8% 5% 5% 5% 40%	1027
	Night	12% 7% 5% 5% 7% 6% 38%	1380
March	Day	14% 5% 5% 6% 5% 5% 7% 38%	1337
	Night	15% 6% 6% 5% 5% 8% 35%	1342
April	Day	18% 6% 5% 5% 5% 38%	1418
	Night	20% 5% 5% 5% 7% 35%	1186
May	Day	15% 5% 5% 5% 6% 8% 37%	1673
	Night	13% 5% 5% 5% 8% 42%	1039
June	Day	15% 6% 6% 7% 10% 37%	1663
	Night	12% 6% 6% 6% 7% 42%	956
July	Day	9% 6% 5% 8% 7% 6% 8% 36%	1671
	Night	9% 5% 5% 5% 7% 5% 8% 10% 36%	1018
August	Day	11% 5% 5% 5% 6% 7% 8% 39%	1539
	Night	13% 5% 5% 5% 5% 7% 43%	1174
September	Day	19% 7% 44%	1364
	Night	17% 5% 6% 48%	1238
October	Day	15% 6% 6% 45%	1223
	Night	20% 5% 6% 42%	1471
November	Day	18% 9% 5% 5% 5% 7% 32%	1253
	Night	20% 6% 5% 5% 5% 6% 32%	1918
December	Day	17% 5% 5% 5% 5% 5% 7% 36%	1217
	Night	18% 6% 5% 5% 5% 7% 36%	2126

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% 8% 5% 5% 5% 6% 8% 35%	1060
	Night	18% 5% 5% 5% 9% 35%	1638
February	Day	12% 8% 5% 6% 5% 6% 40%	1025
	Night	11% 7% 5% 5% 6% 7% 38%	1371
March	Day	14% 5% 5% 6% 5% 5% 5% 6% 37%	1360
	Night	15% 5% 5% 5% 6% 5% 8% 35%	1364
April	Day	18% 6% 5% 6% 5% 5% 38%	1417
	Night	19% 6% 5% 5% 5% 6% 35%	1186
May	Day	15% 6% 5% 6% 8% 37%	1668
	Night	13% 5% 5% 5% 8% 41%	1032
June	Day	14% 6% 5% 7% 9% 37%	1672
	Night	11% 5% 6% 6% 7% 41%	958
July	Day	9% 6% 5% 8% 7% 6% 9% 36%	1671
	Night	8% 5% 6% 7% 5% 7% 11% 35%	1019
August	Day	11% 6% 5% 6% 5% 7% 8% 38%	1534
	Night	12% 5% 5% 8% 43%	1176
September	Day	19% 5% 5% 7% 43%	1363
	Night	17% 5% 48%	1239
October	Day	15% 5% 7% 45%	1223
	Night	19% 6% 42%	1471
November	Day	18% 9% 5% 5% 5% 5% 6% 31%	1251
	Night	20% 6% 5% 5% 5% 6% 33%	1917
December	Day	17% 5% 5% 5% 6% 7% 36%	1217
	Night	18% 6% 5% 5% 5% 6% 37%	2130

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	5% 17% 31% 14%	785
	Night	18% 31% 16%	1224
February	Day	20% 31% 9%	815
	Night	5% 20% 29% 16%	1082
March	Day	5% 19% 24% 15%	1054
	Night	8% 17% 24% 16%	1041
April	Day	5% 13% 17% 22% 8%	1074
	Night	16% 16% 20% 9%	903
May	Day	6% 14% 25% 18%	1373
	Night	8% 14% 26% 19%	854
June	Day	11% 22% 29% 12%	1270
	Night	10% 20% 29% 16%	734
July	Day	11% 15% 25% 14%	1083
	Night	10% 18% 24% 12%	669
August	Day	8% 14% 24% 17%	1376
	Night	6% 14% 25% 19%	1051
September	Day	5% 9% 25% 26%	1153
	Night	5% 8% 25% 26% 5%	1080
October	Day	11% 25% 22%	1099
	Night	6% 9% 24% 23%	1295
November	Day	5% 15% 25% 9%	1006
	Night	6% 12% 28% 12%	1516
December	Day	7% 21% 22% 12%	1009
	Night	6% 18% 26% 13%	1761

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	26% 41% 18%	438
February	Day	41% 31% 12%	41
	Night	30% 37% 18%	390
March	Day	20% 36% 25% 5%	116
	Night	21% 42% 21%	457
April	Day	16% 30% 15% 15% 6%	110
	Night	17% 36% 22% 8%	436
May	Day	6% 30% 22% 21% 6%	116
	Night	9% 29% 34% 13%	292
June	Day	25% 28% 25%	108
	Night	29% 41% 18%	217
July	Day	21% 33% 27% 7%	106
	Night	26% 40% 22%	256
August	Day	17% 28% 21% 15%	119
	Night	17% 40% 21%	411
September	Day	8% 18% 18% 28% 13%	111
	Night	18% 34% 26%	442
October	Day	14% 19% 29% 16%	117
	Night	11% 24% 29% 14%	461
November	Day	7% 37% 20% 11%	80
	Night	17% 31% 26% 6%	530
December	Night	19% 40% 18%	573

Page generated at 2009-12-30 05:20:23. Version ab11