Coyle Field
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coyle Field clear sky chart from 2005-11-06 to 2025-11-03.

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% 7% 2 6% 4 4 4 4 6% 7% 41%	126732
	Night	15% 7% 2 6% 4 4 4 3 5% 7% 43%	123287
Transparency	Day	41% 5% 12% 23% 16% 3	130272
	Night	41% 4 11% 23% 18% 4	127834
Seeing	Day	19% 11% 29% 24% 13% 4	16379
	Night	18% 9% 30% 30% 11% 1	25560

By Month

Percentage Cloud Cover NE (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	13% 7% 2 4 3 3 3 3 4 5% 52%	3597
	11th to 20th	Day	14% 7% 2 7% 4 4 4 3 4 5% 46%	3570
	21st to end	Day	19% 9% 3 7% 4 3 3 2 4 5% 42%	4466
February	1st to 10th	Day	14% 9% 3 7% 5% 3 4 3 5% 8% 40%	1815
	11th to 20th	Day	18% 8% 2 6% 4 3 4 4 4 6% 40%	1948
	21st to end	Day	17% 9% 3 7% 4 4 3 3 4 5% 42%	1650
March	1st to 10th	Day	21% 6% 1 4 3 3 3 3 3 5% 47%	4476
	11th to 20th	Day	12% 7% 2 6% 4 4 3 3 6% 7% 45%	4842
	21st to end	Day	17% 6% 2 6% 3 4 4 3 5% 6% 44%	5878
April	1st to 10th	Day	17% 7% 2 6% 4 4 4 4 5% 6% 40%	2400
	11th to 20th	Day	14% 7% 2 6% 4 4 3 4 5% 8% 43%	2374
	21st to end	Day	16% 7% 2 6% 4 3 4 4 6% 7% 41%	2400
May	1st to 10th	Day	24% 8% 3 6% 4 4 4 4 6% 8% 29%	5830
	11th to 20th	Day	25% 8% 3 6% 3 4 3 3 4 6% 35%	6225
	21st to end	Day	19% 6% 2 6% 4 4 4 4 6% 8% 35%	6949
June	1st to 10th	Day	13% 7% 2 6% 5% 5% 5% 4 7% 8% 39%	2800
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 4 7% 9% 39%	2800
	21st to end	Day	10% 5% 2 6% 6% 5% 5% 5% 7% 9% 41%	2800
July	1st to 10th	Day	10% 5% 2 6% 5% 6% 6% 5% 8% 10% 37%	6360
	11th to 20th	Day	12% 7% 2 8% 6% 5% 7% 5% 8% 10% 30%	6360
	21st to end	Day	11% 6% 3 7% 5% 5% 6% 5% 7% 9% 38%	6926
August	1st to 10th	Day	17% 7% 3 8% 5% 5% 6% 4 7% 8% 31%	4151
	11th to 20th	Day	14% 6% 3 6% 5% 5% 5% 4 6% 8% 38%	3850
	21st to end	Day	9% 5% 2 6% 4 5% 5% 4 7% 10% 44%	4312
September	1st to 10th	Day	14% 6% 2 5% 3 5% 4 3 5% 8% 45%	2400
	11th to 20th	Day	13% 5% 2 5% 4 4 4 2 5% 7% 49%	2328
	21st to end	Day	18% 8% 2 7% 4 4 4 4 4 6% 38%	2200
October	1st to 10th	Day	19% 6% 2 5% 3 3 4 3 4 7% 45%	2070
	11th to 20th	Day	16% 5% 3 5% 2 3 3 2 4 7% 50%	2000
	21st to end	Day	16% 6% 2 5% 4 4 4 3 4 6% 47%	2085
November	1st to 10th	Day	13% 5% 2 5% 4 3 3 3 4 6% 52%	1779
	11th to 20th	Day	15% 5% 2 6% 4 3 3 3 5% 7% 48%	1800
	21st to end	Day	15% 5% 2 4 5% 4 4 4 5% 7% 46%	1745
December	1st to 10th	Day	13% 6% 2 5% 3 3 4 4 6% 8% 47%	2600
	11th to 20th	Day	21% 8% 2 5% 3 2 2 2 4 4 46%	2986
	21st to end	Day	14% 7% 2 5% 3 4 5% 4 6% 8% 43%	3960
January	1st to 10th	Night	13% 6% 2 5% 3 3 3 3 4 6% 52%	6349
	11th to 20th	Night	15% 8% 2 5% 4 3 3 3 4 5% 49%	6298
	21st to end	Night	16% 8% 2 6% 4 4 4 3 5% 6% 43%	6490
February	1st to 10th	Night	17% 9% 3 5% 4 4 4 3 4 6% 41%	2583
	11th to 20th	Night	19% 8% 2 4 4 3 4 3 5% 5% 42%	2338
	21st to end	Night	18% 6% 2 7% 4 3 3 3 4 6% 43%	1980
March	1st to 10th	Night	18% 10% 2 5% 3 3 2 2 3 6% 45%	5364
	11th to 20th	Night	13% 11% 3 6% 4 4 3 2 4 4 47%	5102
	21st to end	Night	16% 8% 2 7% 4 3 4 3 4 5% 43%	5054
April	1st to 10th	Night	18% 8% 3 7% 3 4 4 4 4 6% 41%	2000
	11th to 20th	Night	14% 9% 3 6% 4 3 4 3 4 6% 43%	1975
	21st to end	Night	17% 6% 2 5% 3 4 4 3 6% 8% 43%	2000
May	1st to 10th	Night	20% 10% 3 7% 5% 4 4 4 6% 9% 28%	4110
	11th to 20th	Night	23% 9% 3 6% 4 4 3 3 5% 7% 33%	3697
	21st to end	Night	20% 8% 3 7% 4 3 3 3 5% 7% 36%	3926
June	1st to 10th	Night	14% 6% 3 6% 4 4 5% 4 5% 8% 41%	1600
	11th to 20th	Night	11% 7% 2 7% 6% 5% 4 3 6% 8% 40%	1600
	21st to end	Night	9% 6% 2 5% 4 5% 4 5% 7% 11% 41%	1600
July	1st to 10th	Night	9% 7% 3 10% 6% 5% 5% 4 7% 9% 35%	3600
	11th to 20th	Night	12% 8% 3 8% 5% 5% 5% 4 7% 10% 32%	3600
	21st to end	Night	11% 7% 3 7% 5% 4 4 4 6% 9% 40%	3926
August	1st to 10th	Night	20% 8% 2 7% 5% 4 4 4 6% 8% 32%	2961
	11th to 20th	Night	12% 6% 2 6% 4 4 4 4 5% 7% 44%	3197
	21st to end	Night	8% 5% 2 5% 4 4 4 4 6% 7% 52%	3586
September	1st to 10th	Night	13% 6% 2 6% 5% 4 4 3 5% 6% 46%	2000
	11th to 20th	Night	11% 5% 2 5% 3 3 3 3 5% 7% 51%	2070
	21st to end	Night	19% 8% 2 6% 3 3 4 3 6% 7% 39%	2200
October	1st to 10th	Night	17% 7% 2 6% 3 3 3 3 4 5% 46%	2326
	11th to 20th	Night	16% 5% 2 5% 3 3 3 3 4 6% 51%	2400
	21st to end	Night	17% 6% 2 5% 3 3 3 3 5% 5% 48%	2754
November	1st to 10th	Night	11% 5% 2 5% 3 4 4 3 5% 6% 53%	2564
	11th to 20th	Night	16% 6% 2 5% 3 3 3 3 4 5% 48%	2600
	21st to end	Night	13% 6% 2 5% 4 4 4 4 5% 6% 47%	2653
December	1st to 10th	Night	14% 6% 2 5% 3 4 4 3 5% 6% 49%	4580
	11th to 20th	Night	22% 6% 2 5% 3 3 3 2 4 6% 42%	5208
	21st to end	Night	16% 8% 3 6% 4 4 4 3 5% 6% 42%	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	34% 3 7% 27% 25% 3	3598
	11th to 20th	Day	41% 3 7% 24% 18% 6%	3600
	21st to end	Day	47% 3 8% 25% 13% 3	4466
February	1st to 10th	Day	43% 5% 12% 25% 13% 1	1815
	11th to 20th	Day	45% 4 9% 23% 16% 3	1957
	21st to end	Day	46% 4 9% 22% 15% 5%	1650
March	1st to 10th	Day	40% 3 8% 24% 16% 8%	4479
	11th to 20th	Day	38% 4 9% 27% 17% 5%	4842
	21st to end	Day	41% 4 10% 16% 23% 6%	5878
April	1st to 10th	Day	44% 5% 10% 20% 16% 6%	2400
	11th to 20th	Day	40% 6% 13% 22% 17% 3	2374
	21st to end	Day	41% 5% 11% 20% 19% 4	2400
May	1st to 10th	Day	53% 6% 14% 17% 9% 1	5841
	11th to 20th	Day	51% 4 9% 23% 12% 1	6229
	21st to end	Day	45% 6% 10% 23% 14% 1	6949
June	1st to 10th	Day	41% 8% 13% 21% 15% 2	2800
	11th to 20th	Day	40% 8% 13% 25% 12% 2	2800
	21st to end	Day	37% 10% 13% 22% 17% 1	2800
July	1st to 10th	Day	40% 9% 16% 21% 13% 1	6290
	11th to 20th	Day	48% 6% 19% 19% 8% 1	6285
	21st to end	Day	40% 6% 11% 22% 20% 1	6728
August	1st to 10th	Day	48% 6% 16% 20% 9%	4137
	11th to 20th	Day	42% 6% 13% 26% 12% 1	3886
	21st to end	Day	33% 6% 12% 29% 17% 2	4312
September	1st to 10th	Day	37% 6% 13% 21% 21% 3	2400
	11th to 20th	Day	35% 4 10% 25% 23% 3	2328
	21st to end	Day	47% 5% 10% 17% 18% 3	2200
October	1st to 10th	Day	36% 4 9% 20% 27% 5%	3369
	11th to 20th	Day	26% 3 8% 24% 31% 7%	3240
	21st to end	Day	27% 3 13% 26% 26% 5%	3349
November	1st to 10th	Day	34% 4 13% 27% 20% 3	1779
	11th to 20th	Day	38% 3 10% 22% 24% 3	1800
	21st to end	Day	39% 4 12% 30% 13% 3	1745
December	1st to 10th	Day	35% 4 16% 26% 17% 2	2600
	11th to 20th	Day	43% 3 10% 29% 12% 3	2986
	21st to end	Day	39% 6% 11% 23% 19% 2	3960
January	1st to 10th	Night	35% 3 7% 25% 23% 7%	6349
	11th to 20th	Night	39% 3 9% 24% 18% 7%	6343
	21st to end	Night	43% 3 8% 23% 19% 3	6490
February	1st to 10th	Night	44% 4 13% 24% 14% 2	2583
	11th to 20th	Night	44% 4 8% 21% 18% 6%	2340
	21st to end	Night	43% 3 8% 22% 18% 6%	1980
March	1st to 10th	Night	43% 3 8% 23% 14% 10%	5374
	11th to 20th	Night	42% 4 11% 24% 14% 5%	5103
	21st to end	Night	44% 4 7% 16% 24% 4	5054
April	1st to 10th	Night	45% 5% 9% 19% 18% 5%	2000
	11th to 20th	Night	43% 5% 9% 20% 20% 4	1975
	21st to end	Night	40% 5% 10% 20% 21% 5%	2000
May	1st to 10th	Night	53% 6% 13% 17% 9% 3	4116
	11th to 20th	Night	52% 4 10% 19% 14% 1	3698
	21st to end	Night	47% 5% 12% 20% 14% 1	3927
June	1st to 10th	Night	41% 7% 10% 20% 20% 1	1600
	11th to 20th	Night	41% 8% 11% 25% 13% 2	1600
	21st to end	Night	36% 7% 15% 24% 16% 2	1600
July	1st to 10th	Night	46% 7% 13% 21% 11% 1	3560
	11th to 20th	Night	47% 6% 18% 21% 7% 1	3552
	21st to end	Night	40% 5% 14% 22% 18% 1	3809
August	1st to 10th	Night	50% 6% 18% 16% 9% 1	2951
	11th to 20th	Night	39% 5% 12% 32% 11% 1	3227
	21st to end	Night	31% 5% 10% 30% 21% 2	3586
September	1st to 10th	Night	39% 6% 12% 21% 19% 3	2000
	11th to 20th	Night	33% 5% 11% 24% 23% 4	2070
	21st to end	Night	44% 5% 9% 21% 18% 2	2200
October	1st to 10th	Night	38% 3 10% 24% 22% 3	3807
	11th to 20th	Night	24% 3 10% 26% 30% 6%	3899
	21st to end	Night	27% 3 10% 31% 25% 5%	4440
November	1st to 10th	Night	34% 4 11% 25% 21% 5%	2564
	11th to 20th	Night	39% 4 8% 22% 22% 5%	2600
	21st to end	Night	37% 4 12% 26% 19% 2	2653
December	1st to 10th	Night	36% 4 11% 29% 16% 3	4580
	11th to 20th	Night	44% 3 11% 23% 15% 4	5208
	21st to end	Night	43% 4 12% 20% 18% 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	21% 22% 37% 15% 5% 1	200
	11th to 20th	Day	20% 30% 32% 15% 4	200
	21st to end	Day	25% 17% 35% 18% 5% 1	330
February	1st to 10th	Day	23% 19% 40% 14% 4	315
	11th to 20th	Day	28% 19% 39% 13% 2	496
	21st to end	Day	24% 20% 36% 17% 3	414
March	1st to 10th	Day	20% 21% 35% 19% 4 1	500
	11th to 20th	Day	17% 21% 38% 16% 5% 2	500
	21st to end	Day	23% 17% 34% 20% 5%	550
April	1st to 10th	Day	23% 17% 36% 17% 5% 1	500
	11th to 20th	Day	20% 15% 37% 20% 6% 2	492
	21st to end	Day	22% 14% 36% 19% 7% 2	500
May	1st to 10th	Day	27% 14% 30% 18% 9% 2	503
	11th to 20th	Day	24% 9% 35% 23% 7% 2	527
	21st to end	Day	21% 6% 23% 25% 19% 5%	573
June	1st to 10th	Day	15% 7% 29% 28% 17% 3	530
	11th to 20th	Day	15% 7% 30% 31% 13% 5%	530
	21st to end	Day	12% 4 26% 34% 19% 4	530
July	1st to 10th	Day	13% 2 21% 32% 23% 9%	525
	11th to 20th	Day	9% 2 19% 36% 26% 8%	524
	21st to end	Day	12% 3 24% 34% 21% 6%	576
August	1st to 10th	Day	13% 3 24% 31% 21% 8%	526
	11th to 20th	Day	13% 3 18% 32% 26% 9%	519
	21st to end	Day	12% 4 20% 32% 21% 10%	583
September	1st to 10th	Day	17% 5% 24% 24% 18% 11%	530
	11th to 20th	Day	13% 2 24% 32% 19% 10%	530
	21st to end	Day	24% 6% 24% 26% 14% 5%	530
October	1st to 10th	Day	23% 6% 23% 24% 17% 8%	530
	11th to 20th	Day	19% 11% 28% 24% 15% 4	530
	21st to end	Day	19% 11% 31% 24% 12% 3	520
November	1st to 10th	Day	14% 10% 34% 27% 11% 3	401
	11th to 20th	Day	18% 15% 34% 26% 8%	400
	21st to end	Day	18% 15% 31% 25% 10% 2	345
December	1st to 10th	Day	24% 18% 38% 13% 8% 1	200
	11th to 20th	Day	27% 16% 36% 17% 5% 1	200
	21st to end	Day	22% 15% 31% 21% 10% 1	220
January	1st to 10th	Night	19% 16% 38% 22% 5%	800
	11th to 20th	Night	22% 15% 34% 25% 4	800
	21st to end	Night	18% 14% 41% 25% 2	880
February	1st to 10th	Night	22% 12% 38% 26% 3	800
	11th to 20th	Night	24% 18% 39% 18% 1	783
	21st to end	Night	22% 16% 36% 23% 3	660
March	1st to 10th	Night	20% 15% 37% 24% 4	800
	11th to 20th	Night	21% 12% 37% 24% 5% 1	800
	21st to end	Night	21% 8% 42% 22% 7%	880
April	1st to 10th	Night	22% 14% 37% 21% 6%	800
	11th to 20th	Night	20% 11% 34% 30% 6%	791
	21st to end	Night	19% 7% 36% 32% 6% 1	800
May	1st to 10th	Night	20% 10% 33% 28% 8% 1	630
	11th to 20th	Night	23% 8% 33% 30% 6%	451
	21st to end	Night	20% 2 19% 38% 19% 2	433
June	1st to 10th	Night	18% 4 25% 36% 16% 2	400
	11th to 20th	Night	14% 3 21% 44% 19%	400
	21st to end	Night	9% 3 22% 48% 18% 1	400
July	1st to 10th	Night	12% 3 17% 45% 21% 2	390
	11th to 20th	Night	11% 4 15% 41% 27% 3	388
	21st to end	Night	10% 1 17% 49% 21% 2	438
August	1st to 10th	Night	12% 2 13% 45% 26% 2	617
	11th to 20th	Night	13% 2 17% 39% 27% 2	790
	21st to end	Night	13% 2 15% 40% 25% 5%	880
September	1st to 10th	Night	15% 3 20% 37% 23% 4	800
	11th to 20th	Night	15% 3 15% 36% 26% 5%	800
	21st to end	Night	24% 3 19% 34% 19% 1	800
October	1st to 10th	Night	20% 5% 24% 28% 20% 4	800
	11th to 20th	Night	19% 8% 24% 34% 14% 1	800
	21st to end	Night	20% 7% 34% 28% 10% 1	880
November	1st to 10th	Night	14% 7% 34% 32% 12% 1	789
	11th to 20th	Night	19% 12% 32% 29% 8% 1	800
	21st to end	Night	15% 12% 36% 28% 9% 1	800
December	1st to 10th	Night	23% 12% 34% 22% 7% 1	800
	11th to 20th	Night	21% 10% 37% 26% 5%	800
	21st to end	Night	19% 11% 37% 29% 3	880

Page generated at 2025-10-31 02:02:42. Version ac07

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