Adirondack Astronomy Retreat
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Adirondack Astronomy Retreat 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% 8% 6% 5% 5% 5% 5% 6% 30%	16466
	Night	17% 8% 6% 5% 5% 5% 6% 31%	16468
Cloud Cover	Day	15% 8% 5% 7% 6% 6% 5% 5% 7% 28%	16476
	Night	16% 9% 7% 6% 5% 5% 6% 30%	16487
Transparency	Day	12% 16% 20% 9%	12367
	Night	11% 15% 22% 9%	12401
Seeing	Day	46% 15% 14% 8%	1098
	Night	50% 17% 13% 5%	5087

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% 8% 5% 8% 8% 7% 5% 25%	979
	Night	15% 11% 5% 10% 7% 5% 5% 6% 23%	1720
February	Day	9% 12% 8% 9% 8% 5% 6% 6% 25%	1040
	Night	11% 11% 6% 8% 6% 8% 5% 6% 5% 25%	1367
March	Day	14% 8% 5% 6% 5% 36%	1318
	Night	16% 7% 6% 7% 6% 5% 5% 34%	1359
April	Day	21% 9% 6% 6% 33%	1447
	Night	21% 7% 6% 5% 5% 5% 6% 32%	1157
May	Day	21% 5% 5% 5% 5% 5% 6% 32%	1704
	Night	19% 5% 5% 5% 6% 37%	1009
June	Day	22% 5% 5% 6% 7% 6% 6% 9% 24%	1663
	Night	21% 5% 6% 6% 5% 7% 32%	956
July	Day	15% 6% 6% 6% 8% 6% 6% 7% 28%	1716
	Night	17% 5% 5% 6% 8% 8% 34%	974
August	Day	12% 6% 5% 6% 7% 6% 7% 36%	1581
	Night	10% 6% 5% 6% 6% 45%	1133
September	Day	16% 6% 5% 7% 43%	1363
	Night	16% 5% 7% 46%	1241
October	Day	19% 9% 5% 6% 5% 6% 7% 28%	1191
	Night	22% 8% 6% 5% 5% 30%	1503
November	Day	18% 12% 7% 5% 5% 5% 27%	1247
	Night	20% 9% 7% 6% 6% 26%	1923
December	Day	17% 21% 9% 7% 6% 17%	1217
	Night	19% 15% 6% 7% 6% 5% 22%	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% 10% 9% 8% 7% 23%	977
	Night	14% 11% 6% 10% 7% 6% 5% 6% 22%	1721
February	Day	8% 12% 8% 9% 8% 5% 5% 5% 5% 7% 23%	1038
	Night	10% 11% 5% 11% 7% 8% 6% 6% 5% 23%	1358
March	Day	13% 8% 5% 7% 5% 5% 5% 34%	1339
	Night	14% 8% 6% 8% 6% 6% 5% 32%	1383
April	Day	20% 8% 5% 8% 5% 33%	1446
	Night	19% 8% 7% 5% 5% 6% 6% 31%	1157
May	Day	19% 6% 5% 5% 6% 5% 5% 7% 31%	1698
	Night	17% 7% 6% 5% 7% 36%	1003
June	Day	19% 6% 6% 5% 7% 6% 6% 9% 23%	1672
	Night	19% 6% 5% 7% 7% 30%	958
July	Day	13% 6% 7% 5% 8% 6% 6% 8% 26%	1716
	Night	16% 5% 6% 6% 9% 9% 32%	975
August	Day	9% 6% 7% 6% 6% 6% 7% 8% 34%	1575
	Night	9% 5% 7% 5% 5% 5% 45%	1135
September	Day	15% 5% 5% 5% 8% 41%	1362
	Night	14% 5% 5% 5% 7% 45%	1242
October	Day	17% 9% 5% 7% 5% 7% 6% 28%	1191
	Night	20% 9% 6% 6% 5% 5% 29%	1503
November	Day	16% 11% 5% 8% 5% 5% 5% 6% 26%	1245
	Night	19% 9% 5% 8% 6% 6% 5% 25%	1922
December	Day	16% 20% 9% 9% 6% 6% 16%	1217
	Night	17% 15% 6% 9% 6% 5% 20%	2130

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	13% 17% 19% 6%	676
	Night	17% 13% 18% 8%	1169
February	Day	15% 18% 17% 5%	742
	Night	13% 18% 17% 5%	972
March	Day	10% 17% 22% 13%	963
	Night	8% 15% 28% 9%	1000
April	Day	9% 11% 21% 14% 7%	986
	Night	9% 13% 21% 18%	793
May	Day	9% 17% 20% 13%	1247
	Night	8% 15% 25% 16%	745
June	Day	15% 21% 17% 5%	1192
	Night	14% 22% 27%	693
July	Day	13% 18% 16% 8%	1112
	Night	16% 18% 27% 5%	661
August	Day	12% 14% 22% 10%	1424
	Night	11% 16% 26% 14%	1007
September	Day	9% 13% 29% 14%	1186
	Night	7% 16% 34% 12%	1071
October	Day	11% 13% 18% 9%	1030
	Night	10% 13% 17% 9%	1282
November	Day	12% 16% 18% 8%	928
	Night	11% 14% 15% 7%	1454
December	Day	12% 13% 14%	881
	Night	11% 14% 15%	1554

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	58% 20% 10%	491
February	Day	58% 15% 11% 8%	60
	Night	59% 15% 10%	430
March	Day	61% 6% 13%	124
	Night	62% 13% 9%	495
April	Day	58% 14% 8% 7%	119
	Night	59% 14% 12%	445
May	Day	56% 17% 11%	122
	Night	57% 20% 10%	268
June	Day	52% 20% 8% 7%	113
	Night	51% 13% 18% 5%	228
July	Day	50% 10% 20% 10%	110
	Night	46% 13% 21% 6%	220
August	Day	32% 18% 17% 13% 8%	121
	Night	30% 19% 24% 13%	381
September	Day	31% 13% 14% 11% 12%	116
	Night	32% 18% 20% 14%	463
October	Day	30% 19% 20% 8%	121
	Night	37% 18% 18% 5%	487
November	Day	41% 19% 15% 7%	92
	Night	49% 20% 10% 7%	573
December	Night	55% 19% 8%	606

Page generated at 2009-12-30 05:20:37. Version ab11