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Kopernik Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kopernik Observatory clear sky chart from 2005-11-05 to 2008-11-27.

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	17% 9% 6% 7% 5% 6% 5% 7% 27%	12251
	Night	18% 9% 6% 6% 5% 6% 5% 6% 28%	12142
Cloud Cover	Day	18% 9% 5% 6% 5% 6% 5% 7% 27%	12269
	Night	19% 8% 6% 6% 5% 5% 5% 6% 29%	12166
Transparency	Day	7% 19% 22% 13%	7956
	Night	8% 20% 23% 12%	8060
Seeing	Day	12% 26% 22% 19% 5%	710
	Night	18% 32% 26% 8%	3352

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	16% 11% 7% 14% 9% 6% 17%	774
	Night	23% 13% 7% 7% 7% 5% 6% 16%	1266
February	Day	15% 11% 9% 12% 10% 6% 5% 5% 13%	765
	Night	15% 9% 8% 10% 8% 9% 5% 5% 7% 17%	1026
March	Day	18% 13% 11% 7% 5% 5% 5% 22%	992
	Night	18% 7% 9% 8% 5% 5% 28%	1005
April	Day	18% 8% 7% 5% 7% 35%	1078
	Night	19% 9% 6% 5% 6% 5% 5% 5% 31%	899
May	Day	15% 7% 6% 7% 5% 6% 34%	1289
	Night	11% 5% 5% 6% 5% 5% 5% 8% 37%	758
June	Day	16% 5% 5% 5% 7% 5% 6% 10% 29%	1251
	Night	18% 5% 6% 5% 8% 36%	718
July	Day	14% 6% 6% 7% 6% 7% 10% 27%	1300
	Night	12% 9% 5% 8% 8% 36%	741
August	Day	16% 6% 5% 5% 5% 5% 8% 35%	1153
	Night	15% 5% 7% 5% 5% 5% 6% 38%	879
September	Day	19% 8% 5% 5% 5% 35%	1040
	Night	17% 7% 5% 6% 45%	937
October	Day	17% 12% 7% 5% 5% 5% 7% 29%	913
	Night	19% 9% 5% 5% 6% 34%	1121
November	Day	21% 13% 6% 8% 5% 6% 21%	952
	Night	21% 11% 5% 6% 5% 5% 6% 24%	1495
December	Day	18% 14% 11% 11% 7% 6% 5% 14%	744
	Night	17% 11% 9% 9% 7% 6% 6% 7% 16%	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	17% 10% 8% 10% 10% 6% 5% 17%	773
	Night	24% 12% 8% 7% 6% 5% 6% 16%	1267
February	Day	15% 14% 8% 11% 10% 6% 5% 15%	763
	Night	15% 10% 8% 9% 9% 7% 5% 6% 6% 18%	1017
March	Day	19% 13% 11% 7% 5% 5% 22%	1014
	Night	20% 7% 8% 7% 7% 5% 27%	1028
April	Day	19% 8% 6% 6% 35%	1077
	Night	21% 9% 5% 5% 5% 5% 32%	899
May	Day	15% 6% 5% 5% 9% 5% 6% 34%	1288
	Night	11% 6% 6% 5% 5% 6% 5% 7% 38%	758
June	Day	18% 5% 5% 6% 6% 6% 9% 29%	1260
	Night	18% 5% 6% 5% 7% 37%	720
July	Day	15% 5% 5% 8% 7% 7% 10% 28%	1300
	Night	14% 7% 6% 8% 7% 37%	742
August	Day	17% 6% 6% 5% 5% 8% 35%	1148
	Night	16% 5% 7% 5% 5% 39%	881
September	Day	21% 6% 5% 6% 36%	1039
	Night	19% 7% 6% 46%	938
October	Day	19% 12% 5% 5% 8% 30%	913
	Night	19% 8% 6% 7% 34%	1121
November	Day	23% 13% 5% 8% 5% 5% 5% 21%	950
	Night	24% 10% 5% 5% 5% 6% 6% 24%	1494
December	Day	18% 15% 10% 10% 7% 6% 15%	744
	Night	17% 11% 9% 9% 5% 6% 5% 7% 17%	1301

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	8% 25% 18% 5%	398
	Night	9% 28% 16% 6%	646
February	Day	12% 17% 14% 8%	407
	Night	8% 25% 17% 8%	576
March	Day	7% 18% 23% 14%	552
	Night	8% 23% 25% 10%	617
April	Day	7% 16% 26% 20% 7%	679
	Night	6% 15% 19% 22% 6%	557
May	Day	8% 19% 26% 17%	884
	Night	8% 15% 27% 21%	565
June	Day	10% 27% 28% 8%	814
	Night	10% 24% 35% 8%	474
July	Day	9% 25% 25% 7%	695
	Night	9% 25% 27% 10%	415
August	Day	5% 13% 23% 18%	966
	Night	5% 13% 27% 16%	713
September	Day	5% 14% 25% 20%	795
	Night	14% 35% 17%	753
October	Day	10% 22% 18%	727
	Night	6% 16% 21% 16%	939
November	Day	22% 15% 7%	656
	Night	8% 18% 18% 8%	1050
December	Day	8% 25% 11%	383
	Night	14% 27% 14%	755

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	29% 38% 17%	291
February	Day	29% 19% 29% 6%	31
	Night	28% 40% 14%	271
March	Day	25% 30% 20% 9%	82
	Night	30% 32% 16% 5%	329
April	Day	17% 32% 20% 13%	79
	Night	23% 36% 25% 5%	307
May	Day	10% 27% 21% 27%	84
	Night	12% 36% 30% 12%	186
June	Day	5% 35% 26% 19%	71
	Night	6% 23% 48% 15%	152
July	Day	6% 25% 30% 23% 6%	72
	Night	5% 22% 50% 11%	152
August	Day	19% 19% 24% 14%	82
	Night	23% 33% 23%	290
September	Day	6% 17% 15% 30% 10%	78
	Night	9% 17% 36% 21%	323
October	Day	11% 23% 30% 16%	81
	Night	11% 29% 28% 11%	336
November	Day	20% 30% 16% 12%	50
	Night	21% 35% 20%	395
December	Night	25% 41% 19%	320

Page generated at 2008-11-27 13:47:40. Version ab11