Deer Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deer Lake 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	19% 5% 5% 7% 37%	16480
	Night	20% 6% 5% 7% 37%	16451
Cloud Cover	Day	18% 5% 5% 7% 38%	16489
	Night	20% 5% 5% 7% 37%	16472
Transparency	Day	8% 18% 24% 16%	13124
	Night	7% 17% 23% 15%	13136
Seeing	Day	44% 14% 16% 8%	1177
	Night	46% 16% 15% 5%	5168

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	18% 6% 5% 7% 36%	986
	Night	19% 7% 5% 5% 6% 39%	1712
February	Day	14% 6% 5% 6% 6% 7% 36%	1071
	Night	16% 6% 7% 39%	1335
March	Day	16% 5% 5% 5% 6% 40%	1315
	Night	18% 6% 5% 6% 41%	1363
April	Day	21% 5% 5% 7% 39%	1443
	Night	21% 7% 6% 5% 5% 36%	1161
May	Day	22% 7% 36%	1664
	Night	24% 5% 6% 8% 32%	1049
June	Day	22% 6% 5% 5% 5% 6% 9% 27%	1663
	Night	23% 5% 5% 5% 5% 5% 6% 30%	956
July	Day	16% 6% 5% 5% 6% 11% 33%	1716
	Night	15% 5% 5% 7% 5% 7% 9% 28%	974
August	Day	14% 5% 5% 6% 8% 40%	1543
	Night	12% 7% 6% 5% 5% 6% 6% 7% 36%	1170
September	Day	15% 5% 6% 47%	1352
	Night	19% 6% 43%	1251
October	Day	17% 5% 6% 7% 40%	1211
	Night	19% 5% 5% 5% 5% 5% 38%	1482
November	Day	25% 5% 5% 36%	1299
	Night	25% 6% 5% 6% 34%	1873
December	Day	22% 6% 5% 7% 38%	1217
	Night	21% 6% 7% 39%	2125

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	19% 6% 5% 5% 8% 37%	984
	Night	19% 7% 5% 5% 6% 39%	1713
February	Day	15% 5% 5% 6% 6% 8% 37%	1068
	Night	17% 5% 5% 7% 40%	1327
March	Day	16% 5% 5% 5% 6% 40%	1336
	Night	18% 6% 5% 5% 5% 41%	1387
April	Day	22% 5% 7% 39%	1442
	Night	21% 7% 6% 6% 36%	1161
May	Day	22% 5% 6% 37%	1658
	Night	24% 5% 5% 8% 32%	1043
June	Day	22% 6% 5% 5% 5% 9% 28%	1672
	Night	23% 6% 5% 5% 5% 6% 30%	958
July	Day	16% 5% 5% 5% 6% 9% 36%	1716
	Night	14% 5% 6% 7% 6% 6% 10% 29%	975
August	Day	13% 5% 5% 6% 9% 40%	1537
	Night	12% 6% 5% 5% 5% 5% 6% 7% 36%	1173
September	Day	15% 5% 6% 47%	1351
	Night	19% 5% 6% 43%	1252
October	Day	16% 6% 5% 7% 41%	1211
	Night	19% 5% 6% 5% 6% 38%	1482
November	Day	25% 5% 5% 5% 36%	1297
	Night	25% 5% 5% 7% 34%	1872
December	Day	21% 6% 5% 39%	1217
	Night	21% 5% 7% 39%	2129

Transparency (when cloud cover <= 30%)
Color Meanings: Poor Below Average Average Above average Transparent
Month		Occurrence of each Forecast	Data Points
January	Day	6% 23% 26% 12%	752
	Night	6% 19% 30% 14%	1303
February	Day	9% 21% 25% 14%	866
	Night	8% 19% 26% 13%	1049
March	Day	8% 18% 26% 17%	1047
	Night	8% 17% 25% 16%	1122
April	Day	8% 18% 24% 14% 7%	1126
	Night	6% 12% 23% 18%	884
May	Day	9% 17% 20% 17%	1318
	Night	9% 13% 19% 16%	812
June	Day	13% 23% 22% 7%	1229
	Night	11% 23% 18% 11%	671
July	Day	11% 17% 26% 15%	1103
	Night	12% 16% 24% 13%	622
August	Day	8% 15% 24% 21%	1368
	Night	9% 14% 25% 15%	1027
September	Day	7% 14% 22% 27%	1200
	Night	5% 11% 21% 27%	1103
October	Day	6% 15% 26% 14%	1096
	Night	7% 15% 19% 15%	1323
November	Day	5% 16% 23% 12%	1038
	Night	6% 18% 24% 11%	1453
December	Day	6% 23% 22% 12%	981
	Night	7% 20% 22% 14%	1767

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% 18% 10%	491
February	Day	55% 24% 10%	87
	Night	56% 16% 12%	430
March	Day	58% 14% 12%	124
	Night	57% 17% 10%	495
April	Day	53% 13% 10% 8%	119
	Night	54% 12% 14%	449
May	Day	52% 12% 9% 7%	122
	Night	53% 12% 12%	309
June	Day	48% 7% 16% 9%	113
	Night	49% 8% 21% 5%	228
July	Day	46% 8% 20% 10%	110
	Night	45% 9% 26% 6%	220
August	Day	28% 7% 28% 12% 9%	121
	Night	27% 11% 27% 17%	417
September	Day	30% 17% 19% 12% 6%	116
	Night	28% 13% 25% 16%	463
October	Day	30% 22% 19% 9%	121
	Night	31% 25% 18% 6%	487
November	Day	44% 18% 14%	144
	Night	45% 19% 13%	573
December	Night	51% 19% 9%	606

Page generated at 2009-12-30 05:20:33. Version ab11