Cooksburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cooksburg clear sky chart from 2005-11-06 to 2025-10-04.

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% 12% 4 9% 5% 4 4 4 5% 6% 29%	126435
	Night	18% 12% 5% 10% 5% 4 4 3 4 6% 29%	122938
Transparency	Day	54% 6% 11% 19% 10% 1	130031
	Night	55% 6% 10% 18% 10% 1	127411
Seeing	Day	25% 16% 27% 18% 10% 3	15827
	Night	24% 14% 27% 24% 10% 1	25328

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	16% 21% 9% 26% 4 3 3 2 2 3 12%	3758
	11th to 20th	Day	11% 21% 11% 22% 8% 7% 2 1 2 3 12%	4060
	21st to end	Day	21% 18% 8% 13% 7% 5% 5% 3 3 4 14%	4466
February	1st to 10th	Day	17% 21% 6% 13% 8% 5% 3 3 4 3 19%	1800
	11th to 20th	Day	16% 15% 7% 16% 7% 4 4 3 5% 5% 19%	1753
	21st to end	Day	20% 16% 4 12% 6% 5% 4 3 4 5% 22%	1615
March	1st to 10th	Day	18% 12% 7% 9% 5% 3 4 3 4 5% 31%	4935
	11th to 20th	Day	13% 14% 7% 8% 5% 4 4 3 4 6% 33%	4980
	21st to end	Day	17% 12% 5% 10% 5% 4 4 3 4 5% 30%	5465
April	1st to 10th	Day	19% 15% 4 7% 5% 5% 4 3 4 7% 28%	2354
	11th to 20th	Day	19% 15% 3 7% 4 4 4 4 4 4 33%	2374
	21st to end	Day	22% 10% 3 6% 4 4 3 3 5% 6% 34%	2595
May	1st to 10th	Day	24% 10% 3 8% 5% 5% 5% 3 5% 5% 26%	5862
	11th to 20th	Day	22% 9% 3 8% 5% 5% 5% 4 6% 8% 25%	6041
	21st to end	Day	21% 7% 3 6% 4 4 5% 5% 6% 7% 32%	6934
June	1st to 10th	Day	17% 7% 2 7% 6% 4 5% 4 6% 8% 33%	2800
	11th to 20th	Day	17% 7% 2 7% 6% 5% 5% 4 6% 9% 32%	2800
	21st to end	Day	17% 6% 2 6% 4 5% 4 5% 7% 8% 35%	2800
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 5% 6% 9% 39%	6360
	11th to 20th	Day	12% 7% 3 8% 5% 5% 6% 5% 7% 8% 34%	6087
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 3 5% 7% 42%	6424
August	1st to 10th	Day	19% 8% 3 8% 4 5% 5% 4 6% 8% 29%	4234
	11th to 20th	Day	14% 7% 3 7% 5% 5% 5% 5% 7% 8% 32%	4174
	21st to end	Day	12% 6% 3 7% 4 5% 6% 5% 7% 9% 37%	4396
September	1st to 10th	Day	18% 7% 2 6% 4 4 3 3 4 6% 42%	2400
	11th to 20th	Day	13% 6% 2 7% 4 5% 5% 3 6% 7% 42%	2282
	21st to end	Day	21% 9% 4 7% 5% 4 4 3 6% 7% 31%	2155
October	1st to 10th	Day	20% 7% 2 6% 5% 5% 4 3 5% 7% 36%	1930
	11th to 20th	Day	23% 10% 3 6% 4 4 4 4 4 5% 33%	1900
	21st to end	Day	24% 12% 3 7% 4 3 5% 4 4 6% 27%	2090
November	1st to 10th	Day	13% 11% 3 8% 4 4 5% 4 5% 6% 39%	1861
	11th to 20th	Day	18% 17% 4 8% 5% 3 4 4 4 5% 27%	1600
	21st to end	Day	20% 21% 5% 7% 4 5% 3 3 4 6% 21%	1600
December	1st to 10th	Day	19% 22% 12% 18% 5% 3 3 2 2 3 10%	2600
	11th to 20th	Day	21% 22% 8% 9% 4 2 3 2 3 4 22%	2990
	21st to end	Day	24% 24% 7% 10% 5% 4 3 2 4 4 13%	3960
January	1st to 10th	Night	15% 18% 9% 26% 7% 4 3 2 3 3 10%	6183
	11th to 20th	Night	13% 17% 9% 22% 9% 7% 4 3 3 3 11%	5900
	21st to end	Night	21% 17% 8% 14% 6% 5% 5% 3 3 4 15%	6490
February	1st to 10th	Night	19% 17% 6% 12% 7% 5% 5% 3 3 4 20%	2600
	11th to 20th	Night	17% 15% 6% 13% 6% 6% 5% 3 4 5% 20%	2533
	21st to end	Night	21% 13% 4 14% 6% 4 4 2 4 4 23%	2011
March	1st to 10th	Night	19% 14% 6% 8% 7% 4 3 3 4 5% 29%	4918
	11th to 20th	Night	14% 13% 7% 6% 4 3 3 2 4 6% 38%	4980
	21st to end	Night	17% 11% 5% 8% 4 4 4 3 4 5% 33%	5467
April	1st to 10th	Night	19% 14% 4 8% 5% 3 4 3 5% 5% 30%	2045
	11th to 20th	Night	19% 10% 3 6% 4 4 4 4 5% 6% 36%	1975
	21st to end	Night	15% 10% 4 7% 3 3 5% 4 4 9% 35%	1822
May	1st to 10th	Night	28% 11% 3 7% 4 4 4 3 4 6% 26%	4033
	11th to 20th	Night	23% 11% 3 6% 5% 4 3 3 3 6% 34%	3850
	21st to end	Night	21% 8% 2 5% 4 4 4 3 5% 8% 35%	3920
June	1st to 10th	Night	11% 7% 3 6% 5% 5% 5% 4 6% 8% 41%	1600
	11th to 20th	Night	14% 6% 3 7% 5% 5% 5% 3 6% 8% 39%	1600
	21st to end	Night	13% 6% 3 7% 4 4 4 3 6% 9% 40%	1600
July	1st to 10th	Night	14% 7% 2 7% 5% 4 4 3 5% 8% 40%	3598
	11th to 20th	Night	13% 6% 2 6% 5% 5% 5% 4 7% 9% 38%	3865
	21st to end	Night	10% 6% 2 6% 4 4 4 4 6% 7% 47%	4427
August	1st to 10th	Night	17% 8% 3 7% 4 5% 4 3 6% 7% 37%	2915
	11th to 20th	Night	16% 7% 2 7% 5% 4 4 4 6% 6% 40%	2875
	21st to end	Night	11% 4 2 6% 4 4 5% 4 6% 8% 46%	3454
September	1st to 10th	Night	15% 6% 2 5% 3 3 5% 4 4 6% 47%	2000
	11th to 20th	Night	12% 4 2 5% 3 4 4 3 5% 8% 50%	2115
	21st to end	Night	20% 7% 3 7% 5% 4 4 3 5% 6% 36%	2245
October	1st to 10th	Night	17% 7% 2 6% 4 4 4 3 5% 7% 42%	2317
	11th to 20th	Night	20% 9% 2 7% 4 3 4 3 5% 6% 36%	2280
	21st to end	Night	23% 11% 3 6% 4 5% 4 3 5% 5% 31%	2508
November	1st to 10th	Night	14% 10% 3 5% 4 4 4 3 5% 6% 41%	2431
	11th to 20th	Night	19% 17% 3 8% 6% 4 4 3 4 5% 26%	2800
	21st to end	Night	20% 18% 6% 8% 4 4 4 3 5% 6% 23%	2800
December	1st to 10th	Night	17% 20% 11% 16% 4 5% 4 2 4 4 13%	4580
	11th to 20th	Night	23% 18% 8% 11% 5% 3 3 2 4 4 20%	5205
	21st to end	Night	22% 19% 7% 11% 5% 4 4 3 4 4 16%	6996

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	80% 3 6% 7% 3	3759
	11th to 20th	Day	81% 2 6% 7% 3 1	4060
	21st to end	Day	76% 3 7% 9% 4	4466
February	1st to 10th	Day	72% 4 7% 11% 6%	1800
	11th to 20th	Day	68% 5% 8% 13% 6%	1762
	21st to end	Day	65% 5% 10% 14% 5% 2	1615
March	1st to 10th	Day	56% 5% 12% 20% 7%	4935
	11th to 20th	Day	51% 6% 16% 20% 6% 2	4980
	21st to end	Day	55% 6% 8% 19% 12% 1	5465
April	1st to 10th	Day	57% 5% 10% 16% 12% 1	2354
	11th to 20th	Day	54% 5% 10% 18% 12% 1	2374
	21st to end	Day	51% 5% 10% 20% 12% 2	2595
May	1st to 10th	Day	57% 6% 8% 18% 8% 3	5897
	11th to 20th	Day	55% 8% 9% 18% 9% 1	6045
	21st to end	Day	48% 7% 13% 19% 11% 1	6949
June	1st to 10th	Day	46% 8% 12% 20% 13% 1	2800
	11th to 20th	Day	48% 7% 14% 18% 12% 1	2800
	21st to end	Day	43% 7% 13% 24% 12% 1	2800
July	1st to 10th	Day	40% 7% 12% 26% 14% 1	6290
	11th to 20th	Day	44% 7% 13% 24% 12%	6013
	21st to end	Day	40% 6% 9% 25% 19% 1	6240
August	1st to 10th	Day	51% 7% 13% 20% 8%	4221
	11th to 20th	Day	44% 8% 13% 25% 8%	4213
	21st to end	Day	40% 8% 14% 27% 11% 1	4396
September	1st to 10th	Day	43% 6% 9% 23% 16% 2	2400
	11th to 20th	Day	40% 7% 11% 26% 15%	2282
	21st to end	Day	51% 5% 12% 19% 12%	2155
October	1st to 10th	Day	40% 5% 12% 24% 18% 1	3190
	11th to 20th	Day	46% 6% 13% 18% 13% 4	3140
	21st to end	Day	44% 4 13% 26% 12% 1	3428
November	1st to 10th	Day	45% 6% 12% 19% 15% 2	1861
	11th to 20th	Day	60% 4 10% 17% 8% 2	1600
	21st to end	Day	65% 5% 10% 15% 5% 1	1600
December	1st to 10th	Day	82% 3 7% 6% 1	2600
	11th to 20th	Day	68% 4 10% 13% 5%	2986
	21st to end	Day	76% 4 8% 8% 3	3960
January	1st to 10th	Night	80% 4 6% 8% 2	6183
	11th to 20th	Night	79% 4 8% 7% 2	5900
	21st to end	Night	74% 4 8% 9% 4 1	6490
February	1st to 10th	Night	69% 5% 8% 13% 5%	2600
	11th to 20th	Night	67% 5% 8% 14% 5%	2535
	21st to end	Night	65% 4 8% 13% 9%	2011
March	1st to 10th	Night	60% 4 10% 20% 6% 1	4918
	11th to 20th	Night	48% 5% 16% 21% 7% 3	4980
	21st to end	Night	52% 5% 9% 17% 15% 1	5467
April	1st to 10th	Night	56% 6% 9% 17% 12% 1	2045
	11th to 20th	Night	48% 7% 11% 19% 13% 2	1975
	21st to end	Night	46% 7% 11% 22% 11% 2	1822
May	1st to 10th	Night	60% 6% 8% 14% 10% 3	4060
	11th to 20th	Night	52% 7% 10% 20% 10% 1	3851
	21st to end	Night	46% 8% 11% 20% 12% 3	3927
June	1st to 10th	Night	39% 8% 12% 24% 15% 2	1600
	11th to 20th	Night	42% 10% 11% 22% 13% 1	1600
	21st to end	Night	39% 8% 14% 22% 16%	1600
July	1st to 10th	Night	42% 5% 10% 25% 16% 1	3560
	11th to 20th	Night	40% 8% 16% 25% 11% 1	3819
	21st to end	Night	35% 6% 11% 23% 25% 1	4297
August	1st to 10th	Night	45% 8% 13% 23% 10% 1	2904
	11th to 20th	Night	42% 7% 12% 29% 9% 1	2902
	21st to end	Night	34% 7% 15% 30% 12% 2	3454
September	1st to 10th	Night	37% 6% 13% 24% 17% 3	2000
	11th to 20th	Night	31% 6% 13% 28% 20% 1	2115
	21st to end	Night	49% 7% 11% 18% 14% 1	2245
October	1st to 10th	Night	39% 5% 10% 23% 21% 1	3837
	11th to 20th	Night	41% 6% 12% 20% 15% 6%	3779
	21st to end	Night	40% 4 14% 23% 17% 1	4120
November	1st to 10th	Night	43% 6% 12% 22% 14% 3	2431
	11th to 20th	Night	59% 5% 9% 17% 8% 3	2800
	21st to end	Night	62% 6% 11% 17% 4 1	2800
December	1st to 10th	Night	75% 6% 9% 7% 2	4580
	11th to 20th	Night	69% 4 10% 13% 3	5208
	21st to end	Night	71% 6% 9% 11% 3	6996

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	35% 30% 24% 9% 2	235
	11th to 20th	Day	36% 33% 24% 5% 2 1	300
	21st to end	Day	36% 27% 30% 5% 2	330
February	1st to 10th	Day	32% 33% 28% 6% 1	300
	11th to 20th	Day	41% 26% 28% 5%	300
	21st to end	Day	41% 22% 30% 6% 1	314
March	1st to 10th	Day	32% 22% 30% 13% 2	500
	11th to 20th	Day	32% 23% 31% 10% 2 1	500
	21st to end	Day	36% 23% 26% 11% 4	550
April	1st to 10th	Day	34% 22% 25% 14% 4 1	500
	11th to 20th	Day	29% 22% 26% 13% 7% 3	492
	21st to end	Day	29% 18% 31% 16% 5% 1	500
May	1st to 10th	Day	30% 18% 28% 16% 6% 2	503
	11th to 20th	Day	26% 15% 27% 21% 9% 3	527
	21st to end	Day	20% 12% 28% 22% 13% 5%	573
June	1st to 10th	Day	21% 14% 30% 25% 9% 2	530
	11th to 20th	Day	24% 12% 25% 23% 13% 3	530
	21st to end	Day	18% 12% 32% 25% 11% 2	530
July	1st to 10th	Day	14% 8% 24% 26% 21% 7%	525
	11th to 20th	Day	14% 8% 27% 27% 17% 7%	524
	21st to end	Day	14% 7% 30% 25% 18% 6%	576
August	1st to 10th	Day	14% 7% 24% 26% 21% 7%	526
	11th to 20th	Day	18% 6% 25% 28% 15% 9%	519
	21st to end	Day	15% 8% 25% 29% 16% 8%	583
September	1st to 10th	Day	19% 10% 19% 27% 18% 8%	530
	11th to 20th	Day	13% 5% 21% 30% 22% 10%	530
	21st to end	Day	27% 10% 25% 22% 13% 4	530
October	1st to 10th	Day	21% 12% 27% 21% 15% 5%	502
	11th to 20th	Day	28% 14% 31% 17% 8% 2	490
	21st to end	Day	32% 17% 29% 16% 6%	539
November	1st to 10th	Day	23% 19% 30% 16% 11% 2	419
	11th to 20th	Day	34% 22% 28% 12% 4 2	200
	21st to end	Day	34% 22% 34% 9% 1	200
December	1st to 10th	Day	37% 25% 27% 8% 3 2	200
	11th to 20th	Day	38% 21% 32% 8% 2 1	200
	21st to end	Day	33% 24% 32% 9% 3	220
January	1st to 10th	Night	30% 25% 31% 12% 2	800
	11th to 20th	Night	32% 22% 30% 14% 2	800
	21st to end	Night	27% 25% 31% 16% 2	880
February	1st to 10th	Night	31% 21% 29% 17% 1	800
	11th to 20th	Night	31% 24% 34% 10% 1	783
	21st to end	Night	30% 24% 31% 14% 2	660
March	1st to 10th	Night	27% 21% 34% 16% 3	800
	11th to 20th	Night	31% 19% 27% 19% 5%	800
	21st to end	Night	26% 18% 35% 17% 4 1	880
April	1st to 10th	Night	28% 17% 32% 18% 5%	800
	11th to 20th	Night	25% 16% 30% 20% 8% 1	791
	21st to end	Night	21% 12% 34% 28% 5% 1	622
May	1st to 10th	Night	26% 10% 26% 28% 10% 1	600
	11th to 20th	Night	22% 11% 28% 31% 9%	513
	21st to end	Night	15% 6% 27% 31% 19% 2	433
June	1st to 10th	Night	12% 5% 31% 37% 16%	400
	11th to 20th	Night	17% 5% 24% 42% 12%	400
	21st to end	Night	15% 5% 29% 36% 16% 1	400
July	1st to 10th	Night	12% 4 21% 41% 20% 3	390
	11th to 20th	Night	13% 3 17% 37% 27% 2	499
	21st to end	Night	12% 5% 15% 43% 23% 2	657
August	1st to 10th	Night	13% 2 15% 42% 27% 2	597
	11th to 20th	Night	14% 4 14% 38% 26% 3	594
	21st to end	Night	13% 3 20% 35% 25% 4	800
September	1st to 10th	Night	18% 6% 19% 32% 22% 3	800
	11th to 20th	Night	13% 6% 16% 34% 27% 4	800
	21st to end	Night	23% 9% 22% 25% 18% 3	800
October	1st to 10th	Night	20% 8% 23% 28% 18% 2	773
	11th to 20th	Night	27% 10% 28% 24% 9% 1	760
	21st to end	Night	29% 13% 30% 24% 5%	836
November	1st to 10th	Night	20% 14% 30% 27% 9%	780
	11th to 20th	Night	29% 16% 30% 19% 5% 1	800
	21st to end	Night	31% 18% 31% 16% 4	800
December	1st to 10th	Night	35% 21% 27% 14% 3	800
	11th to 20th	Night	30% 24% 27% 15% 3	800
	21st to end	Night	31% 20% 31% 16% 2	880

Page generated at 2025-10-01 01:39:02. Version ac07

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