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Cornland Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cornland Park clear sky chart from 2005-11-05 to 2009-10-21.

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	14% 5% 5% 5% 8% 38%	15848
	Night	14% 5% 5% 5% 7% 41%	15585
Cloud Cover	Day	14% 5% 5% 5% 6% 5% 5% 7% 38%	15861
	Night	14% 5% 5% 5% 7% 41%	15602
Transparency	Day	8% 15% 24% 18%	12595
	Night	7% 14% 23% 20%	12538
Seeing	Day	10% 23% 25% 20% 7%	1055
	Night	13% 30% 31% 12%	4815

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	17% 5% 5% 41%	1085
	Night	15% 6% 5% 5% 5% 7% 41%	1613
February	Day	14% 5% 7% 46%	1047
	Night	14% 6% 7% 46%	1359
March	Day	16% 5% 5% 47%	1338
	Night	15% 5% 5% 44%	1340
April	Day	16% 5% 8% 39%	1418
	Night	17% 5% 5% 7% 42%	1186
May	Day	14% 5% 6% 7% 42%	1615
	Night	17% 5% 5% 7% 40%	1098
June	Day	12% 5% 8% 6% 7% 10% 31%	1663
	Night	10% 5% 5% 6% 7% 6% 8% 10% 32%	956
July	Day	9% 5% 7% 7% 7% 8% 9% 30%	1642
	Night	10% 5% 6% 7% 7% 9% 9% 32%	1048
August	Day	10% 5% 5% 6% 7% 6% 9% 9% 31%	1514
	Night	10% 5% 6% 6% 5% 6% 10% 38%	1200
September	Day	19% 8% 6% 5% 7% 7% 30%	1372
	Night	17% 5% 7% 40%	1231
October	Day	15% 5% 5% 6% 44%	1113
	Night	15% 6% 5% 47%	1340
November	Day	18% 5% 6% 41%	1049
	Night	16% 5% 5% 46%	1483
December	Day	16% 7% 5% 5% 8% 41%	992
	Night	15% 6% 5% 6% 42%	1731

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% 5% 5% 6% 41%	1083
	Night	15% 6% 7% 41%	1614
February	Day	14% 5% 5% 7% 46%	1044
	Night	13% 6% 5% 5% 7% 46%	1351
March	Day	15% 5% 5% 47%	1361
	Night	15% 6% 5% 6% 42%	1362
April	Day	15% 5% 7% 40%	1417
	Night	16% 6% 5% 5% 6% 42%	1186
May	Day	14% 5% 6% 7% 41%	1610
	Night	17% 5% 5% 5% 5% 5% 7% 39%	1091
June	Day	11% 6% 8% 7% 8% 10% 30%	1672
	Night	9% 5% 5% 5% 7% 6% 8% 11% 31%	958
July	Day	9% 6% 6% 9% 6% 8% 9% 30%	1642
	Night	9% 5% 6% 7% 8% 8% 8% 32%	1049
August	Day	10% 5% 5% 6% 7% 7% 9% 9% 30%	1509
	Night	9% 5% 6% 5% 5% 5% 6% 10% 38%	1202
September	Day	17% 8% 6% 5% 6% 5% 7% 29%	1371
	Night	17% 5% 5% 7% 40%	1232
October	Day	15% 6% 5% 5% 45%	1113
	Night	14% 6% 5% 47%	1340
November	Day	18% 5% 7% 41%	1047
	Night	16% 5% 6% 45%	1482
December	Day	16% 7% 5% 5% 8% 40%	992
	Night	14% 7% 5% 6% 42%	1735

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	7% 12% 25% 24%	821
	Night	5% 12% 24% 23% 7%	1226
February	Day	5% 12% 33% 22%	849
	Night	12% 26% 29%	1100
March	Day	5% 14% 27% 22%	1063
	Night	7% 12% 24% 21%	1090
April	Day	7% 13% 20% 19% 8%	1129
	Night	5% 15% 17% 23% 8%	942
May	Day	7% 14% 26% 20%	1310
	Night	10% 16% 27% 16%	881
June	Day	14% 21% 25% 10%	1246
	Night	14% 23% 23% 10%	718
July	Day	12% 19% 20% 11%	1070
	Night	15% 20% 17% 14%	698
August	Day	11% 16% 21% 12%	1325
	Night	10% 17% 25% 15%	1042
September	Day	7% 12% 14% 18%	1177
	Night	7% 13% 19% 20%	1075
October	Day	9% 25% 22%	980
	Night	6% 8% 25% 22% 5%	1192
November	Day	5% 18% 28% 17%	825
	Night	6% 16% 25% 23%	1153
December	Day	5% 18% 24% 16% 6%	800
	Night	6% 15% 19% 20% 6%	1421

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% 37% 21%	461
February	Day	26% 36% 21% 5%	60
	Night	25% 37% 21%	407
March	Day	17% 35% 20% 8%	118
	Night	19% 38% 23%	480
April	Day	16% 31% 17% 14%	113
	Night	13% 40% 24% 6%	445
May	Day	12% 29% 26% 13% 5%	115
	Night	9% 33% 37% 8%	324
June	Day	5% 19% 40% 23%	107
	Night	5% 24% 50% 14%	222
July	Day	13% 31% 34% 10%	107
	Night	18% 50% 22%	277
August	Day	11% 28% 32% 17%	117
	Night	13% 43% 28%	438
September	Day	21% 22% 17% 20%	113
	Night	20% 33% 23%	443
October	Day	13% 22% 16% 27% 6%	106
	Night	11% 25% 29% 16%	427
November	Day	18% 21% 30% 17%	99
	Night	15% 30% 32% 11%	427
December	Night	14% 35% 28% 7%	464

Page generated at 2009-10-21 19:31:50. Version ab11