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Morris County Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morris County 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	16% 5% 5% 5% 8% 37%	12259
	Night	18% 5% 8% 39%	12135
Cloud Cover	Day	15% 5% 5% 6% 5% 8% 37%	12274
	Night	17% 5% 5% 7% 38%	12161
Transparency	Day	9% 18% 25% 18%	8804
	Night	8% 19% 25% 18%	8897
Seeing	Day	12% 33% 24% 14%	773
	Night	18% 35% 25% 8%	3479

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% 5% 7% 5% 6% 7% 34%	767
	Night	21% 7% 5% 9% 36%	1273
February	Day	15% 6% 5% 5% 5% 5% 7% 39%	779
	Night	14% 6% 5% 5% 6% 7% 37%	1012
March	Day	15% 7% 7% 37%	989
	Night	15% 5% 5% 5% 8% 38%	1008
April	Day	19% 6% 5% 5% 6% 38%	1078
	Night	21% 5% 7% 5% 6% 35%	899
May	Day	16% 5% 7% 5% 9% 36%	1273
	Night	15% 7% 9% 43%	775
June	Day	17% 5% 5% 5% 6% 6% 10% 31%	1251
	Night	16% 5% 5% 6% 5% 8% 35%	718
July	Day	13% 5% 5% 5% 8% 6% 10% 30%	1301
	Night	11% 7% 6% 8% 12% 35%	740
August	Day	15% 5% 5% 5% 5% 5% 6% 7% 38%	1144
	Night	15% 6% 9% 42%	889
September	Day	16% 5% 7% 46%	1038
	Night	17% 6% 50%	938
October	Day	16% 6% 8% 43%	912
	Night	18% 5% 6% 45%	1122
November	Day	23% 7% 39%	983
	Night	26% 6% 6% 34%	1464
December	Day	15% 6% 6% 5% 6% 5% 6% 8% 33%	744
	Night	16% 6% 5% 5% 5% 7% 37%	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	16% 5% 5% 7% 5% 6% 7% 34%	766
	Night	20% 7% 5% 8% 36%	1274
February	Day	14% 5% 5% 5% 6% 40%	776
	Night	14% 5% 5% 6% 5% 7% 38%	1004
March	Day	14% 5% 5% 5% 6% 7% 37%	1010
	Night	15% 5% 5% 6% 5% 7% 38%	1032
April	Day	18% 6% 5% 6% 5% 7% 38%	1077
	Night	20% 5% 7% 5% 5% 6% 35%	899
May	Day	15% 5% 5% 7% 5% 9% 36%	1272
	Night	14% 6% 5% 9% 41%	775
June	Day	16% 5% 5% 7% 5% 6% 10% 31%	1260
	Night	15% 5% 6% 6% 5% 9% 35%	720
July	Day	12% 5% 5% 9% 6% 6% 10% 29%	1301
	Night	10% 6% 6% 8% 12% 34%	741
August	Day	14% 5% 5% 5% 7% 6% 8% 37%	1138
	Night	14% 6% 5% 5% 8% 42%	891
September	Day	16% 7% 46%	1037
	Night	16% 7% 49%	939
October	Day	15% 5% 5% 5% 7% 44%	912
	Night	17% 5% 7% 44%	1122
November	Day	23% 7% 39%	981
	Night	25% 6% 6% 34%	1463
December	Day	14% 6% 5% 6% 5% 6% 5% 6% 8% 33%	744
	Night	16% 6% 5% 7% 37%	1301

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	10% 24% 28% 12%	512
	Night	8% 22% 33% 12%	845
February	Day	11% 19% 26% 15%	573
	Night	10% 19% 25% 17%	725
March	Day	8% 18% 28% 20%	690
	Night	10% 21% 27% 18%	720
April	Day	7% 16% 20% 24% 7%	749
	Night	9% 18% 19% 21%	620
May	Day	8% 18% 27% 21%	900
	Night	9% 19% 20% 25%	576
June	Day	15% 26% 30% 7%	819
	Night	13% 27% 27% 16%	447
July	Day	12% 16% 28% 12%	675
	Night	19% 20% 22% 15%	436
August	Day	8% 13% 20% 22%	964
	Night	6% 14% 21% 24%	760
September	Day	6% 13% 23% 28%	859
	Night	5% 11% 28% 30%	790
October	Day	7% 13% 24% 19%	797
	Night	5% 15% 28% 19%	960
November	Day	5% 18% 23% 16%	753
	Night	6% 18% 25% 13%	1082
December	Day	8% 30% 20% 13%	513
	Night	10% 28% 24% 10%	936

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% 42% 16%	312
February	Day	20% 41% 23%	43
	Night	32% 39% 16%	286
March	Day	27% 37% 20% 7%	90
	Night	30% 39% 15%	343
April	Day	10% 51% 10% 12%	80
	Night	20% 40% 22% 5%	319
May	Day	13% 38% 22% 11%	84
	Night	16% 37% 28% 5%	203
June	Day	8% 32% 31% 16%	73
	Night	8% 29% 44% 13%	155
July	Day	26% 31% 27%	73
	Night	5% 29% 44% 14%	158
August	Day	7% 21% 30% 17% 8%	85
	Night	27% 34% 18%	304
September	Day	25% 23% 23% 11%	81
	Night	7% 20% 37% 20%	330
October	Day	14% 27% 27% 16%	85
	Night	12% 32% 30% 9%	341
November	Day	11% 36% 25% 6%	79
	Night	18% 35% 19% 7%	392
December	Night	21% 47% 17%	336

Page generated at 2008-11-27 13:47:49. Version ab11