Revall's Coyote Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Revall's Coyote Creek Observatory clear sky chart from 2005-11-06 to 2026-04-17.

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	13% 9% 3 8% 5% 5% 5% 4 6% 7% 36%	131623
	Night	13% 10% 3 8% 5% 5% 4 4 5% 7% 37%	130834
Transparency	Day	45% 6% 12% 23% 12% 1	135078
	Night	46% 6% 13% 23% 12% 1	135466
Seeing	Day	18% 15% 32% 22% 10% 3	17941
	Night	18% 10% 33% 29% 10% 1	27970

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	9% 13% 4 11% 5% 6% 6% 5% 5% 7% 29%	4691
	11th to 20th	Day	10% 13% 5% 11% 6% 5% 5% 4 6% 7% 29%	4679
	21st to end	Day	9% 11% 5% 12% 6% 5% 5% 4 6% 7% 30%	5156
February	1st to 10th	Day	9% 12% 4 10% 5% 5% 5% 4 6% 6% 34%	1784
	11th to 20th	Day	10% 11% 4 10% 6% 5% 5% 3 6% 6% 34%	2009
	21st to end	Day	13% 13% 5% 9% 6% 4 4 4 5% 7% 31%	1730
March	1st to 10th	Day	12% 10% 2 5% 4 3 4 4 5% 7% 43%	4578
	11th to 20th	Day	11% 10% 3 10% 6% 6% 6% 4 6% 7% 32%	4763
	21st to end	Day	23% 13% 4 10% 5% 4 4 3 4 4 27%	6101
April	1st to 10th	Day	17% 13% 4 9% 6% 4 4 3 5% 6% 27%	2520
	11th to 20th	Day	20% 10% 3 7% 4 5% 4 3 6% 6% 32%	2460
	21st to end	Day	18% 9% 3 8% 5% 4 5% 4 5% 7% 33%	2600
May	1st to 10th	Day	12% 7% 2 7% 5% 4 4 3 5% 6% 45%	6062
	11th to 20th	Day	11% 7% 3 7% 5% 5% 5% 3 6% 7% 41%	6319
	21st to end	Day	13% 8% 3 7% 5% 5% 5% 4 6% 8% 37%	6949
June	1st to 10th	Day	12% 6% 2 5% 5% 5% 5% 4 6% 8% 42%	2800
	11th to 20th	Day	14% 7% 2 8% 5% 5% 5% 4 5% 8% 38%	2800
	21st to end	Day	12% 7% 2 6% 5% 5% 5% 4 7% 10% 37%	2800
July	1st to 10th	Day	12% 5% 2 6% 4 4 5% 4 6% 9% 42%	6359
	11th to 20th	Day	7% 5% 2 5% 4 5% 5% 4 6% 8% 48%	6360
	21st to end	Day	8% 6% 2 6% 4 4 5% 4 6% 9% 45%	6926
August	1st to 10th	Day	8% 6% 2 8% 5% 6% 6% 5% 7% 9% 38%	4563
	11th to 20th	Day	12% 6% 2 5% 4 4 4 4 5% 6% 47%	4170
	21st to end	Day	13% 7% 2 7% 4 5% 5% 4 5% 7% 42%	4312
September	1st to 10th	Day	12% 6% 2 6% 5% 4 4 4 5% 8% 43%	2400
	11th to 20th	Day	12% 4 2 6% 5% 5% 5% 4 7% 9% 42%	2270
	21st to end	Day	12% 6% 3 8% 5% 5% 5% 4 7% 8% 37%	2200
October	1st to 10th	Day	16% 6% 3 7% 4 4 4 4 6% 8% 38%	2130
	11th to 20th	Day	20% 9% 4 9% 6% 5% 5% 4 6% 6% 27%	1905
	21st to end	Day	19% 9% 4 9% 5% 5% 4 3 5% 6% 29%	1980
November	1st to 10th	Day	14% 10% 3 7% 4 5% 4 4 6% 7% 36%	1852
	11th to 20th	Day	15% 12% 4 9% 6% 5% 5% 4 7% 7% 26%	1871
	21st to end	Day	15% 12% 4 9% 5% 5% 5% 4 6% 7% 27%	1680
December	1st to 10th	Day	10% 13% 5% 11% 6% 6% 6% 4 6% 7% 25%	2690
	11th to 20th	Day	13% 17% 4 10% 5% 5% 5% 5% 5% 5% 26%	3084
	21st to end	Day	23% 21% 5% 10% 4 4 4 3 4 4 18%	4070
January	1st to 10th	Night	11% 12% 5% 11% 6% 5% 4 3 5% 6% 32%	8233
	11th to 20th	Night	8% 14% 6% 14% 8% 6% 5% 4 5% 6% 23%	8236
	21st to end	Night	7% 11% 5% 11% 6% 6% 6% 4 5% 7% 32%	9058
February	1st to 10th	Night	10% 13% 5% 10% 6% 5% 4 4 5% 6% 32%	2835
	11th to 20th	Night	10% 11% 4 9% 5% 5% 4 4 6% 7% 35%	2496
	21st to end	Night	14% 13% 4 9% 6% 4 4 3 6% 6% 31%	2076
March	1st to 10th	Night	14% 8% 2 7% 4 4 4 3 4 7% 43%	5482
	11th to 20th	Night	11% 9% 3 9% 5% 5% 5% 4 6% 8% 33%	5447
	21st to end	Night	20% 9% 3 7% 5% 5% 5% 4 5% 6% 29%	5083
April	1st to 10th	Night	19% 11% 3 8% 4 5% 4 3 6% 5% 30%	2100
	11th to 20th	Night	22% 8% 3 6% 4 3 3 4 5% 6% 37%	2020
	21st to end	Night	17% 8% 3 8% 5% 3 4 3 5% 8% 36%	1800
May	1st to 10th	Night	14% 7% 3 6% 4 4 4 3 5% 6% 45%	3883
	11th to 20th	Night	11% 10% 3 6% 6% 4 5% 3 4 6% 42%	3596
	21st to end	Night	17% 7% 2 5% 4 4 4 3 5% 7% 40%	3949
June	1st to 10th	Night	11% 7% 1 6% 4 4 5% 4 6% 7% 45%	1600
	11th to 20th	Night	14% 8% 3 8% 4 4 4 4 6% 7% 38%	1600
	21st to end	Night	15% 5% 2 5% 3 4 4 4 6% 9% 43%	1600
July	1st to 10th	Night	12% 5% 2 6% 4 5% 5% 5% 5% 8% 45%	3620
	11th to 20th	Night	8% 4 2 4 3 3 3 3 5% 8% 57%	3620
	21st to end	Night	7% 4 2 6% 4 4 4 3 6% 8% 52%	3948
August	1st to 10th	Night	10% 6% 2 7% 4 4 5% 3 5% 8% 46%	2597
	11th to 20th	Night	12% 4 2 5% 4 4 4 3 5% 7% 50%	2875
	21st to end	Night	10% 6% 2 6% 5% 4 4 3 5% 6% 49%	3586
September	1st to 10th	Night	9% 6% 2 6% 4 3 4 3 4 7% 53%	2000
	11th to 20th	Night	12% 5% 2 5% 3 4 3 3 5% 6% 50%	2110
	21st to end	Night	14% 7% 2 7% 4 4 4 3 4 7% 44%	2200
October	1st to 10th	Night	16% 5% 2 6% 4 3 4 3 5% 8% 44%	2265
	11th to 20th	Night	16% 10% 3 7% 5% 4 4 4 5% 7% 35%	2494
	21st to end	Night	18% 11% 3 7% 4 4 4 3 5% 6% 34%	2860
November	1st to 10th	Night	15% 9% 3 7% 5% 4 4 3 5% 7% 38%	2666
	11th to 20th	Night	15% 10% 3 8% 5% 5% 5% 4 5% 7% 33%	2746
	21st to end	Night	14% 11% 4 9% 6% 5% 5% 4 5% 7% 30%	2940
December	1st to 10th	Night	13% 10% 4 7% 4 5% 5% 4 6% 9% 33%	4720
	11th to 20th	Night	13% 14% 5% 12% 7% 6% 5% 3 4 4 27%	5343
	21st to end	Night	23% 16% 5% 9% 5% 4 3 3 4 5% 23%	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	53% 6% 15% 18% 8%	4692
	11th to 20th	Day	53% 6% 9% 22% 9% 1	4710
	21st to end	Day	52% 6% 11% 19% 13%	5156
February	1st to 10th	Day	48% 7% 12% 20% 12% 1	1784
	11th to 20th	Day	48% 6% 13% 21% 10% 1	2019
	21st to end	Day	52% 6% 11% 19% 11% 2	1730
March	1st to 10th	Day	39% 5% 15% 19% 17% 4	4580
	11th to 20th	Day	49% 6% 14% 20% 10% 1	4763
	21st to end	Day	61% 5% 7% 15% 11%	6101
April	1st to 10th	Day	56% 6% 11% 18% 9% 1	2520
	11th to 20th	Day	52% 5% 10% 21% 11% 2	2460
	21st to end	Day	50% 6% 9% 18% 14% 2	2600
May	1st to 10th	Day	38% 5% 10% 26% 17% 2	6071
	11th to 20th	Day	40% 7% 12% 26% 14% 1	6323
	21st to end	Day	44% 7% 10% 20% 17% 3	6949
June	1st to 10th	Day	37% 8% 13% 26% 14% 2	2800
	11th to 20th	Day	44% 6% 14% 20% 15% 1	2800
	21st to end	Day	41% 9% 14% 23% 13% 1	2800
July	1st to 10th	Day	37% 6% 15% 31% 10% 1	6291
	11th to 20th	Day	31% 6% 14% 36% 12% 1	6285
	21st to end	Day	34% 7% 12% 30% 16% 1	6728
August	1st to 10th	Day	39% 8% 15% 25% 12% 1	4548
	11th to 20th	Day	35% 6% 17% 29% 13%	4209
	21st to end	Day	41% 6% 16% 23% 14% 1	4311
September	1st to 10th	Day	38% 8% 14% 27% 13%	2400
	11th to 20th	Day	36% 9% 19% 28% 8%	2270
	21st to end	Day	42% 8% 14% 26% 10%	2200
October	1st to 10th	Day	31% 5% 13% 29% 21%	3468
	11th to 20th	Day	51% 5% 10% 22% 12%	3082
	21st to end	Day	51% 6% 14% 22% 7%	3180
November	1st to 10th	Day	46% 7% 12% 24% 11% 1	1852
	11th to 20th	Day	54% 7% 14% 16% 9% 1	1871
	21st to end	Day	54% 8% 16% 18% 5% 1	1680
December	1st to 10th	Day	56% 7% 14% 19% 5%	2690
	11th to 20th	Day	58% 6% 11% 13% 11% 1	3085
	21st to end	Day	68% 5% 7% 14% 6%	4070
January	1st to 10th	Night	52% 5% 9% 24% 9%	8233
	11th to 20th	Night	59% 6% 10% 14% 11%	8280
	21st to end	Night	51% 5% 10% 20% 13%	9058
February	1st to 10th	Night	52% 6% 9% 21% 11% 2	2835
	11th to 20th	Night	46% 6% 13% 21% 11% 2	2497
	21st to end	Night	52% 5% 12% 21% 8% 1	2076
March	1st to 10th	Night	41% 5% 18% 21% 14% 1	5493
	11th to 20th	Night	46% 6% 17% 19% 11% 1	5448
	21st to end	Night	54% 6% 12% 17% 10% 1	5083
April	1st to 10th	Night	53% 6% 9% 16% 14% 1	2100
	11th to 20th	Night	49% 5% 10% 22% 12% 2	2020
	21st to end	Night	47% 6% 12% 21% 13% 2	1800
May	1st to 10th	Night	39% 5% 12% 27% 14% 3	3890
	11th to 20th	Night	40% 8% 10% 24% 17% 2	3597
	21st to end	Night	43% 6% 11% 23% 12% 5%	3950
June	1st to 10th	Night	36% 8% 12% 28% 15% 2	1600
	11th to 20th	Night	43% 7% 14% 21% 15% 1	1600
	21st to end	Night	37% 7% 14% 26% 14% 2	1600
July	1st to 10th	Night	36% 6% 15% 30% 11% 2	3580
	11th to 20th	Night	25% 5% 18% 36% 14% 2	3572
	21st to end	Night	31% 6% 15% 27% 20% 1	3832
August	1st to 10th	Night	37% 6% 15% 24% 17% 2	2588
	11th to 20th	Night	34% 6% 14% 31% 13% 2	2902
	21st to end	Night	36% 7% 13% 26% 17% 2	3586
September	1st to 10th	Night	31% 6% 14% 32% 16% 1	2000
	11th to 20th	Night	34% 6% 15% 35% 11%	2110
	21st to end	Night	39% 6% 16% 28% 11% 1	2200
October	1st to 10th	Night	32% 5% 10% 36% 15% 2	3707
	11th to 20th	Night	40% 5% 13% 26% 15%	4056
	21st to end	Night	49% 5% 12% 24% 10%	4610
November	1st to 10th	Night	44% 7% 13% 25% 11% 1	2666
	11th to 20th	Night	50% 6% 14% 19% 11% 1	2746
	21st to end	Night	53% 7% 14% 20% 5% 1	2940
December	1st to 10th	Night	47% 7% 20% 19% 6%	4720
	11th to 20th	Night	60% 5% 10% 16% 9%	5341
	21st to end	Night	63% 5% 8% 15% 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	18% 15% 40% 19% 8%	330
	11th to 20th	Day	23% 18% 35% 19% 4 1	330
	21st to end	Day	22% 17% 39% 18% 4	363
February	1st to 10th	Day	15% 24% 41% 14% 5% 1	330
	11th to 20th	Day	18% 25% 38% 16% 4	330
	21st to end	Day	26% 24% 38% 10% 1	273
March	1st to 10th	Day	20% 24% 42% 11% 4	330
	11th to 20th	Day	23% 20% 34% 17% 5% 1	376
	21st to end	Day	29% 18% 28% 18% 7% 1	594
April	1st to 10th	Day	28% 17% 32% 18% 5% 1	540
	11th to 20th	Day	28% 18% 27% 18% 7% 2	516
	21st to end	Day	25% 17% 28% 20% 9% 1	500
May	1st to 10th	Day	20% 20% 31% 18% 8% 3	573
	11th to 20th	Day	17% 16% 36% 20% 8% 2	725
	21st to end	Day	19% 15% 29% 24% 8% 4	789
June	1st to 10th	Day	13% 17% 31% 26% 9% 3	730
	11th to 20th	Day	19% 11% 35% 23% 9% 2	730
	21st to end	Day	17% 12% 30% 28% 9% 4	730
July	1st to 10th	Day	9% 8% 31% 34% 13% 5%	721
	11th to 20th	Day	10% 10% 31% 29% 14% 5%	718
	21st to end	Day	8% 8% 34% 28% 18% 6%	794
August	1st to 10th	Day	11% 9% 28% 30% 17% 6%	726
	11th to 20th	Day	13% 8% 23% 27% 21% 8%	554
	21st to end	Day	16% 10% 23% 25% 21% 5%	583
September	1st to 10th	Day	15% 12% 29% 23% 16% 5%	530
	11th to 20th	Day	12% 8% 26% 33% 18% 5%	530
	21st to end	Day	16% 13% 25% 28% 15% 3	530
October	1st to 10th	Day	20% 15% 30% 21% 12% 2	460
	11th to 20th	Day	23% 20% 37% 17% 3	330
	21st to end	Day	26% 18% 36% 16% 2 1	363
November	1st to 10th	Day	20% 19% 36% 17% 7% 1	330
	11th to 20th	Day	25% 22% 32% 14% 6% 1	330
	21st to end	Day	25% 17% 39% 13% 5%	330
December	1st to 10th	Day	18% 18% 41% 17% 6% 1	330
	11th to 20th	Day	25% 23% 35% 15% 2 1	330
	21st to end	Day	32% 17% 33% 13% 3 1	363
January	1st to 10th	Night	17% 11% 40% 26% 5%	1050
	11th to 20th	Night	20% 13% 37% 23% 6% 1	1050
	21st to end	Night	18% 10% 38% 26% 8% 1	1155
February	1st to 10th	Night	17% 12% 38% 25% 6%	1050
	11th to 20th	Night	18% 14% 37% 25% 5% 1	861
	21st to end	Night	21% 15% 38% 22% 4	692
March	1st to 10th	Night	18% 12% 36% 26% 7%	840
	11th to 20th	Night	18% 14% 41% 21% 6%	840
	21st to end	Night	20% 10% 35% 27% 8% 1	704
April	1st to 10th	Night	25% 12% 33% 24% 6%	630
	11th to 20th	Night	27% 11% 28% 27% 7% 1	611
	21st to end	Night	21% 8% 33% 29% 9% 1	600
May	1st to 10th	Night	21% 10% 28% 32% 8% 1	600
	11th to 20th	Night	18% 9% 34% 30% 8% 1	591
	21st to end	Night	16% 5% 30% 35% 13%	650
June	1st to 10th	Night	13% 6% 30% 42% 8%	600
	11th to 20th	Night	18% 7% 27% 35% 13% 1	600
	21st to end	Night	16% 6% 24% 39% 14% 1	600
July	1st to 10th	Night	8% 3 24% 44% 20% 1	585
	11th to 20th	Night	9% 3 27% 41% 20%	582
	21st to end	Night	8% 5% 28% 39% 19% 2	657
August	1st to 10th	Night	10% 4 23% 40% 22% 1	597
	11th to 20th	Night	10% 3 19% 40% 24% 3	594
	21st to end	Night	11% 5% 22% 39% 22% 1	660
September	1st to 10th	Night	12% 4 26% 32% 23% 3	600
	11th to 20th	Night	14% 5% 25% 33% 19% 3	710
	21st to end	Night	17% 8% 26% 32% 16% 2	800
October	1st to 10th	Night	18% 9% 30% 28% 14% 1	800
	11th to 20th	Night	21% 11% 34% 26% 7%	800
	21st to end	Night	24% 10% 34% 24% 8%	880
November	1st to 10th	Night	20% 12% 36% 26% 6% 1	820
	11th to 20th	Night	20% 17% 34% 23% 5%	856
	21st to end	Night	20% 16% 34% 26% 6%	1050
December	1st to 10th	Night	20% 12% 39% 22% 6% 1	1050
	11th to 20th	Night	20% 13% 36% 23% 7% 2	1050
	21st to end	Night	28% 11% 35% 21% 4	1155

Page generated at 2026-04-14 02:44:24. Version ac07

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