Coyote Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coyote Observatory clear sky chart from 2005-11-06 to 2026-02-16.

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	15% 10% 4 9% 5% 5% 5% 4 5% 6% 32%	131181
	Night	15% 12% 4 9% 6% 5% 5% 4 5% 6% 30%	129642
Transparency	Day	51% 7% 12% 20% 10% 1	134672
	Night	53% 7% 11% 19% 10% 1	134238
Seeing	Day	22% 17% 31% 19% 8% 3	15941
	Night	22% 14% 30% 24% 9% 1	25208

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	12% 16% 6% 13% 8% 7% 5% 3 5% 6% 20%	4661
	11th to 20th	Day	11% 18% 7% 16% 8% 5% 4 3 5% 4 18%	4650
	21st to end	Day	8% 16% 7% 17% 9% 7% 5% 3 4 5% 19%	5464
February	1st to 10th	Day	12% 16% 5% 12% 9% 5% 5% 4 4 4 24%	1890
	11th to 20th	Day	10% 15% 6% 12% 7% 6% 4 4 5% 6% 27%	1798
	21st to end	Day	19% 13% 3 10% 7% 5% 5% 4 4 4 25%	1623
March	1st to 10th	Day	18% 13% 6% 12% 5% 4 4 3 4 5% 26%	4565
	11th to 20th	Day	10% 12% 5% 10% 6% 5% 5% 4 5% 6% 29%	4980
	21st to end	Day	15% 12% 4 7% 5% 4 3 3 4 5% 37%	5708
April	1st to 10th	Day	21% 13% 3 7% 5% 4 4 4 4 6% 31%	2400
	11th to 20th	Day	21% 11% 3 6% 4 4 4 3 4 4 36%	2374
	21st to end	Day	21% 10% 3 8% 5% 4 4 3 4 6% 32%	2546
May	1st to 10th	Day	22% 10% 3 8% 4 4 5% 4 5% 6% 29%	6346
	11th to 20th	Day	15% 9% 3 9% 5% 5% 5% 4 6% 8% 31%	6318
	21st to end	Day	20% 8% 2 7% 4 4 5% 4 5% 6% 35%	6949
June	1st to 10th	Day	19% 10% 3 7% 6% 5% 4 4 6% 6% 31%	2800
	11th to 20th	Day	14% 6% 3 6% 5% 5% 5% 5% 6% 7% 40%	2800
	21st to end	Day	17% 8% 3 6% 5% 5% 5% 4 7% 7% 33%	2800
July	1st to 10th	Day	13% 7% 3 7% 5% 5% 6% 4 7% 9% 34%	6360
	11th to 20th	Day	9% 5% 2 7% 5% 5% 5% 5% 7% 8% 43%	6360
	21st to end	Day	9% 5% 2 6% 4 4 4 5% 6% 10% 46%	6926
August	1st to 10th	Day	14% 7% 3 8% 5% 4 5% 4 6% 7% 37%	4411
	11th to 20th	Day	16% 6% 2 7% 5% 4 5% 4 5% 7% 38%	4174
	21st to end	Day	11% 5% 2 6% 4 4 5% 5% 7% 9% 40%	4314
September	1st to 10th	Day	13% 6% 2 6% 5% 5% 4 4 5% 8% 42%	2400
	11th to 20th	Day	12% 5% 2 6% 4 4 5% 4 5% 8% 47%	2400
	21st to end	Day	17% 7% 3 6% 4 4 4 4 6% 6% 40%	2120
October	1st to 10th	Day	19% 8% 3 7% 4 4 5% 4 4 6% 36%	2000
	11th to 20th	Day	20% 10% 3 7% 5% 6% 5% 4 5% 7% 29%	2000
	21st to end	Day	24% 11% 3 8% 4 4 5% 3 4 5% 27%	2071
November	1st to 10th	Day	15% 11% 4 8% 5% 4 6% 4 5% 6% 34%	1819
	11th to 20th	Day	16% 13% 4 10% 6% 6% 4 4 5% 6% 27%	1680
	21st to end	Day	20% 15% 5% 11% 6% 6% 4 3 4 6% 20%	1680
December	1st to 10th	Day	20% 20% 6% 13% 6% 5% 4 3 4 5% 12%	2680
	11th to 20th	Day	15% 16% 6% 12% 7% 5% 4 3 4 5% 24%	3066
	21st to end	Day	22% 16% 5% 15% 6% 4 3 3 3 4 19%	4048
January	1st to 10th	Night	12% 17% 8% 15% 7% 5% 5% 4 4 5% 18%	8234
	11th to 20th	Night	11% 16% 6% 15% 8% 6% 5% 4 4 5% 19%	8235
	21st to end	Night	10% 16% 6% 12% 7% 7% 6% 4 5% 5% 22%	8702
February	1st to 10th	Night	11% 15% 6% 11% 8% 6% 4 4 6% 6% 23%	2730
	11th to 20th	Night	12% 14% 5% 11% 7% 5% 5% 3 4 5% 28%	2599
	21st to end	Night	14% 12% 5% 9% 7% 5% 5% 4 5% 6% 28%	2005
March	1st to 10th	Night	20% 14% 5% 10% 6% 4 3 3 3 3 29%	5272
	11th to 20th	Night	11% 12% 4 9% 5% 5% 5% 5% 7% 8% 30%	4979
	21st to end	Night	17% 10% 4 10% 6% 4 3 3 5% 6% 32%	5223
April	1st to 10th	Night	20% 11% 3 9% 4 3 4 3 5% 6% 32%	2000
	11th to 20th	Night	20% 9% 3 8% 4 4 4 3 4 5% 36%	1975
	21st to end	Night	20% 10% 3 8% 5% 4 4 3 4 5% 33%	1870
May	1st to 10th	Night	21% 10% 4 7% 5% 4 5% 4 6% 6% 27%	3594
	11th to 20th	Night	14% 7% 2 6% 4 4 4 3 5% 8% 41%	3575
	21st to end	Night	17% 9% 3 7% 5% 4 5% 4 6% 8% 33%	3926
June	1st to 10th	Night	15% 7% 3 7% 5% 5% 4 5% 6% 9% 34%	1600
	11th to 20th	Night	13% 6% 3 6% 4 3 4 4 6% 7% 44%	1600
	21st to end	Night	16% 8% 2 6% 5% 5% 5% 4 6% 7% 37%	1600
July	1st to 10th	Night	12% 7% 3 7% 5% 5% 6% 4 6% 8% 34%	3600
	11th to 20th	Night	12% 5% 2 5% 4 4 5% 4 6% 8% 45%	3600
	21st to end	Night	8% 5% 2 6% 4 4 5% 4 6% 8% 47%	3926
August	1st to 10th	Night	11% 6% 2 7% 5% 5% 4 4 7% 8% 41%	2734
	11th to 20th	Night	13% 7% 3 6% 4 4 4 4 5% 7% 43%	2875
	21st to end	Night	12% 6% 3 6% 5% 4 5% 4 6% 8% 43%	3550
September	1st to 10th	Night	11% 6% 2 6% 5% 4 4 4 5% 6% 47%	2000
	11th to 20th	Night	13% 5% 2 4 4 4 3 3 5% 6% 51%	2000
	21st to end	Night	16% 6% 2 6% 5% 4 4 3 5% 6% 43%	2277
October	1st to 10th	Night	17% 8% 2 6% 4 4 4 3 5% 6% 40%	2400
	11th to 20th	Night	18% 10% 3 8% 5% 4 5% 4 5% 7% 31%	2400
	21st to end	Night	21% 11% 3 8% 4 4 5% 3 5% 6% 29%	2767
November	1st to 10th	Night	18% 11% 3 7% 6% 4 4 3 5% 6% 33%	2696
	11th to 20th	Night	17% 12% 4 8% 6% 4 5% 3 5% 6% 29%	2940
	21st to end	Night	20% 15% 5% 11% 6% 5% 4 3 5% 5% 22%	2940
December	1st to 10th	Night	18% 18% 5% 12% 7% 6% 5% 4 5% 6% 15%	4720
	11th to 20th	Night	20% 14% 5% 11% 6% 4 4 3 4 4 25%	5348
	21st to end	Night	25% 17% 5% 12% 5% 3 3 3 4 4 20%	7150

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	63% 8% 12% 13% 5%	4662
	11th to 20th	Day	67% 5% 8% 10% 9%	4680
	21st to end	Day	68% 5% 7% 10% 8% 1	5464
February	1st to 10th	Day	63% 5% 9% 17% 5% 1	1890
	11th to 20th	Day	58% 6% 11% 15% 9% 1	1807
	21st to end	Day	60% 7% 10% 13% 9% 2	1623
March	1st to 10th	Day	60% 5% 9% 12% 12% 2	4568
	11th to 20th	Day	51% 9% 14% 15% 9% 2	4980
	21st to end	Day	49% 5% 6% 19% 18% 3	5708
April	1st to 10th	Day	54% 5% 7% 18% 13% 3	2400
	11th to 20th	Day	50% 6% 7% 20% 15% 2	2374
	21st to end	Day	53% 5% 8% 15% 15% 4	2546
May	1st to 10th	Day	55% 6% 8% 19% 10% 3	6357
	11th to 20th	Day	48% 8% 12% 18% 12% 1	6322
	21st to end	Day	48% 7% 11% 20% 12% 1	6949
June	1st to 10th	Day	52% 8% 10% 19% 11% 1	2800
	11th to 20th	Day	41% 8% 11% 24% 13% 2	2800
	21st to end	Day	47% 9% 12% 20% 11% 1	2800
July	1st to 10th	Day	44% 7% 14% 26% 9%	6290
	11th to 20th	Day	35% 8% 14% 29% 14%	6285
	21st to end	Day	32% 7% 15% 35% 10%	6728
August	1st to 10th	Day	44% 7% 15% 23% 10%	4397
	11th to 20th	Day	43% 8% 14% 27% 8% 1	4213
	21st to end	Day	37% 7% 16% 28% 11% 1	4314
September	1st to 10th	Day	39% 8% 14% 29% 11%	2400
	11th to 20th	Day	35% 7% 13% 30% 14%	2400
	21st to end	Day	44% 8% 13% 25% 10%	2120
October	1st to 10th	Day	47% 6% 10% 29% 8%	3260
	11th to 20th	Day	46% 6% 15% 22% 11% 1	3240
	21st to end	Day	50% 6% 18% 20% 6%	3322
November	1st to 10th	Day	48% 8% 15% 22% 6% 1	1819
	11th to 20th	Day	56% 7% 13% 15% 8% 1	1680
	21st to end	Day	65% 7% 12% 9% 6% 1	1680
December	1st to 10th	Day	73% 7% 11% 8% 2	2680
	11th to 20th	Day	63% 6% 10% 13% 7%	3066
	21st to end	Day	70% 4 8% 14% 4	4048
January	1st to 10th	Night	66% 6% 10% 12% 5%	8234
	11th to 20th	Night	66% 6% 9% 12% 6%	8280
	21st to end	Night	62% 5% 8% 13% 11% 1	8702
February	1st to 10th	Night	60% 6% 11% 16% 6% 1	2730
	11th to 20th	Night	57% 6% 10% 19% 7% 1	2601
	21st to end	Night	55% 6% 10% 18% 9%	2005
March	1st to 10th	Night	60% 5% 8% 15% 10% 3	5282
	11th to 20th	Night	49% 9% 17% 16% 8% 2	4980
	21st to end	Night	50% 6% 8% 21% 11% 3	5223
April	1st to 10th	Night	52% 6% 8% 18% 13% 2	2000
	11th to 20th	Night	50% 4 8% 22% 14% 1	1975
	21st to end	Night	52% 6% 6% 17% 15% 3	1870
May	1st to 10th	Night	54% 8% 9% 18% 8% 3	3600
	11th to 20th	Night	40% 8% 15% 20% 15% 2	3576
	21st to end	Night	46% 9% 14% 16% 13% 1	3927
June	1st to 10th	Night	45% 8% 12% 23% 10% 1	1600
	11th to 20th	Night	39% 7% 12% 23% 17% 2	1600
	21st to end	Night	44% 10% 13% 19% 13% 1	1600
July	1st to 10th	Night	44% 9% 15% 19% 13% 1	3560
	11th to 20th	Night	35% 7% 14% 30% 13%	3552
	21st to end	Night	33% 8% 12% 32% 14%	3809
August	1st to 10th	Night	38% 9% 14% 26% 12% 1	2724
	11th to 20th	Night	39% 8% 15% 29% 8%	2902
	21st to end	Night	37% 8% 15% 27% 11% 2	3550
September	1st to 10th	Night	36% 7% 13% 29% 14% 1	2000
	11th to 20th	Night	32% 7% 14% 35% 11% 1	2000
	21st to end	Night	42% 6% 12% 28% 11%	2277
October	1st to 10th	Night	39% 5% 12% 30% 14%	3920
	11th to 20th	Night	45% 6% 16% 23% 9%	3899
	21st to end	Night	48% 7% 18% 20% 8%	4466
November	1st to 10th	Night	51% 6% 14% 20% 8%	2696
	11th to 20th	Night	54% 8% 11% 18% 8% 1	2940
	21st to end	Night	62% 7% 12% 15% 4	2940
December	1st to 10th	Night	69% 6% 12% 10% 2	4720
	11th to 20th	Night	63% 5% 8% 14% 10% 1	5348
	21st to end	Night	69% 5% 6% 12% 9%	7150

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	22% 21% 36% 18% 3	220
	11th to 20th	Day	29% 20% 36% 10% 5%	220
	21st to end	Day	19% 21% 39% 17% 3	305
February	1st to 10th	Day	27% 24% 32% 12% 5%	330
	11th to 20th	Day	29% 27% 37% 6% 1	315
	21st to end	Day	29% 23% 35% 12% 1	387
March	1st to 10th	Day	28% 20% 35% 15% 3	500
	11th to 20th	Day	26% 20% 34% 16% 3 1	500
	21st to end	Day	32% 21% 28% 14% 4	550
April	1st to 10th	Day	32% 21% 29% 12% 5%	500
	11th to 20th	Day	33% 21% 21% 15% 8% 2	492
	21st to end	Day	29% 19% 33% 12% 5% 1	500
May	1st to 10th	Day	27% 15% 31% 18% 7% 2	503
	11th to 20th	Day	19% 17% 32% 22% 8% 3	527
	21st to end	Day	22% 16% 30% 20% 10% 2	573
June	1st to 10th	Day	23% 14% 32% 21% 9% 1	530
	11th to 20th	Day	17% 15% 32% 23% 11% 3	530
	21st to end	Day	18% 16% 33% 20% 11% 2	530
July	1st to 10th	Day	11% 9% 32% 31% 13% 3	525
	11th to 20th	Day	10% 10% 34% 28% 14% 3	524
	21st to end	Day	13% 11% 34% 27% 12% 3	576
August	1st to 10th	Day	14% 6% 29% 33% 14% 5%	526
	11th to 20th	Day	14% 7% 26% 31% 15% 6%	519
	21st to end	Day	14% 12% 29% 26% 14% 6%	583
September	1st to 10th	Day	15% 11% 30% 22% 13% 8%	530
	11th to 20th	Day	11% 11% 22% 26% 19% 12%	530
	21st to end	Day	18% 14% 30% 20% 13% 5%	530
October	1st to 10th	Day	23% 15% 25% 21% 12% 4	530
	11th to 20th	Day	23% 22% 31% 16% 5% 2	530
	21st to end	Day	28% 21% 27% 19% 4 1	511
November	1st to 10th	Day	27% 20% 28% 18% 6% 1	393
	11th to 20th	Day	23% 23% 35% 13% 4 2	220
	21st to end	Day	32% 26% 30% 8% 3	220
December	1st to 10th	Day	30% 20% 35% 12% 2	220
	11th to 20th	Day	32% 22% 35% 7% 3	220
	21st to end	Day	28% 23% 32% 11% 4 2	242
January	1st to 10th	Night	25% 18% 36% 18% 3	840
	11th to 20th	Night	27% 20% 28% 20% 5%	840
	21st to end	Night	18% 16% 37% 24% 4	924
February	1st to 10th	Night	20% 18% 37% 21% 4	840
	11th to 20th	Night	19% 19% 39% 19% 3	804
	21st to end	Night	24% 20% 29% 23% 4	660
March	1st to 10th	Night	25% 18% 34% 21% 3	800
	11th to 20th	Night	24% 20% 33% 19% 5% 1	800
	21st to end	Night	23% 17% 31% 21% 8%	880
April	1st to 10th	Night	27% 16% 30% 22% 5%	800
	11th to 20th	Night	24% 19% 29% 20% 8% 1	791
	21st to end	Night	26% 14% 29% 23% 8% 1	670
May	1st to 10th	Night	24% 9% 31% 26% 10% 1	400
	11th to 20th	Night	21% 10% 34% 27% 7% 1	394
	21st to end	Night	14% 9% 37% 28% 11%	433
June	1st to 10th	Night	16% 9% 33% 35% 8%	400
	11th to 20th	Night	15% 9% 32% 32% 11% 1	400
	21st to end	Night	19% 9% 27% 32% 13%	400
July	1st to 10th	Night	8% 9% 28% 40% 14% 1	390
	11th to 20th	Night	11% 6% 29% 41% 13% 1	388
	21st to end	Night	9% 5% 28% 45% 12% 2	438
August	1st to 10th	Night	9% 6% 23% 41% 20% 1	481
	11th to 20th	Night	12% 3 25% 37% 21% 3	594
	21st to end	Night	13% 8% 27% 33% 17% 2	857
September	1st to 10th	Night	14% 7% 29% 30% 18% 2	800
	11th to 20th	Night	16% 6% 21% 31% 23% 4	800
	21st to end	Night	18% 10% 25% 26% 20% 2	800
October	1st to 10th	Night	22% 11% 27% 25% 14% 1	800
	11th to 20th	Night	23% 16% 32% 20% 8% 1	800
	21st to end	Night	26% 17% 28% 25% 5%	880
November	1st to 10th	Night	26% 15% 27% 24% 6%	820
	11th to 20th	Night	24% 18% 33% 16% 9%	840
	21st to end	Night	30% 19% 26% 20% 5%	840
December	1st to 10th	Night	29% 18% 32% 18% 4	840
	11th to 20th	Night	27% 20% 31% 18% 3	840
	21st to end	Night	32% 16% 31% 17% 4	924

Page generated at 2026-02-13 01:42:16. Version ac07

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