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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 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	17% 9% 5% 7% 6% 5% 5% 7% 26%	16457
	Night	17% 9% 5% 7% 6% 5% 6% 28%	16478
Cloud Cover	Day	18% 9% 5% 6% 5% 5% 5% 7% 27%	16469
	Night	18% 9% 5% 7% 5% 5% 5% 6% 28%	16496
Transparency	Day	6% 16% 20% 11%	12156
	Night	7% 17% 20% 11%	12394
Seeing	Day	11% 25% 22% 17% 5%	973
	Night	17% 30% 25% 7%	4712

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% 10% 6% 15% 9% 7% 5% 17%	1025
	Night	21% 13% 6% 9% 8% 6% 6% 16%	1674
February	Day	14% 12% 9% 12% 9% 6% 5% 16%	1028
	Night	13% 9% 7% 11% 9% 8% 5% 5% 19%	1379
March	Day	17% 12% 9% 7% 5% 5% 5% 24%	1331
	Night	18% 8% 8% 8% 5% 5% 29%	1348
April	Day	18% 10% 6% 5% 5% 7% 33%	1418
	Night	19% 9% 5% 5% 6% 5% 5% 31%	1186
May	Day	17% 7% 5% 5% 6% 5% 6% 34%	1709
	Night	15% 5% 5% 5% 6% 7% 36%	1003
June	Day	19% 6% 5% 5% 6% 5% 6% 9% 26%	1663
	Night	20% 5% 5% 6% 8% 34%	956
July	Day	15% 5% 5% 6% 7% 6% 7% 10% 28%	1714
	Night	13% 5% 8% 5% 7% 7% 37%	976
August	Day	16% 6% 5% 5% 5% 5% 8% 34%	1540
	Night	13% 5% 6% 5% 5% 7% 39%	1173
September	Day	19% 9% 6% 34%	1371
	Night	16% 6% 5% 5% 5% 45%	1232
October	Day	20% 11% 7% 5% 5% 7% 27%	1209
	Night	21% 9% 6% 5% 6% 31%	1485
November	Day	20% 14% 5% 7% 5% 6% 21%	1232
	Night	20% 11% 5% 6% 5% 5% 6% 25%	1940
December	Day	18% 15% 9% 11% 7% 5% 15%	1217
	Night	18% 11% 7% 10% 7% 5% 5% 6% 17%	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	15% 9% 7% 13% 9% 5% 6% 5% 17%	1023
	Night	21% 12% 7% 9% 7% 5% 6% 15%	1675
February	Day	15% 15% 7% 11% 9% 5% 17%	1026
	Night	14% 10% 7% 10% 9% 6% 6% 5% 5% 19%	1370
March	Day	18% 13% 9% 7% 5% 5% 6% 24%	1353
	Night	19% 8% 8% 8% 6% 5% 28%	1371
April	Day	19% 9% 6% 5% 6% 34%	1417
	Night	20% 9% 5% 5% 5% 5% 32%	1186
May	Day	17% 7% 5% 7% 7% 33%	1703
	Night	15% 6% 5% 5% 5% 5% 6% 37%	997
June	Day	21% 5% 5% 5% 6% 6% 5% 9% 27%	1672
	Night	20% 6% 5% 5% 5% 8% 35%	958
July	Day	16% 5% 5% 7% 6% 7% 10% 28%	1714
	Night	14% 6% 5% 7% 6% 38%	977
August	Day	16% 6% 7% 5% 5% 5% 8% 33%	1535
	Night	14% 6% 5% 5% 6% 40%	1175
September	Day	21% 7% 5% 35%	1370
	Night	18% 6% 6% 45%	1233
October	Day	21% 12% 5% 5% 8% 27%	1209
	Night	22% 9% 5% 5% 6% 31%	1485
November	Day	21% 13% 5% 7% 5% 6% 22%	1230
	Night	21% 11% 5% 6% 5% 6% 7% 24%	1939
December	Day	19% 15% 9% 10% 7% 15%	1217
	Night	18% 11% 8% 9% 6% 6% 5% 5% 6% 18%	2130

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	8% 22% 16%	649
	Night	7% 20% 14% 5%	1054
February	Day	8% 15% 16% 5%	670
	Night	7% 21% 16% 5%	929
March	Day	6% 15% 21% 13%	883
	Night	6% 17% 22% 10%	960
April	Day	5% 12% 24% 18% 5%	1019
	Night	5% 12% 20% 20%	841
May	Day	6% 15% 23% 15%	1304
	Night	7% 13% 22% 19%	811
June	Day	8% 21% 24% 7%	1226
	Night	9% 20% 32% 6%	712
July	Day	8% 20% 23% 8%	1109
	Night	8% 21% 28% 10%	650
August	Day	5% 13% 22% 16%	1353
	Night	6% 15% 25% 16%	1007
September	Day	5% 11% 24% 18%	1126
	Night	12% 31% 18%	1048
October	Day	5% 10% 19% 14%	1025
	Night	5% 15% 19% 13%	1303
November	Day	5% 19% 14% 8%	936
	Night	7% 16% 18% 8%	1495
December	Day	6% 18% 11%	856
	Night	10% 20% 11%	1584

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	25% 37% 20%	411
February	Day	28% 23% 21%	42
	Night	28% 39% 13%	383
March	Day	22% 29% 23% 8%	113
	Night	27% 30% 18%	453
April	Day	15% 30% 19% 13%	108
	Night	21% 35% 21% 6%	421
May	Day	10% 26% 20% 24%	113
	Night	12% 32% 31% 10%	249
June	Day	6% 32% 27% 16%	100
	Night	5% 24% 44% 11%	211
July	Day	21% 32% 21% 5%	101
	Night	20% 51% 11%	211
August	Day	18% 20% 23% 16%	113
	Night	21% 34% 23%	398
September	Day	5% 20% 15% 24% 12%	106
	Night	8% 19% 36% 18%	436
October	Day	10% 23% 29% 13%	111
	Night	12% 28% 26% 9%	456
November	Day	18% 30% 18% 15%	66
	Night	19% 32% 22%	526
December	Night	25% 35% 16%	557

Page generated at 2009-12-30 05:20:35. Version ab11