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 2024-12-24.

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%	101960
	Night	14% 10% 4 8% 5% 4 4 3 5% 6% 37%	98299
Transparency	Day	45% 7% 13% 22% 12% 1	105432
	Night	46% 6% 13% 23% 11% 1	102915
Seeing	Day	18% 15% 32% 23% 10% 3	16175
	Night	18% 10% 32% 29% 10% 1	26126

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% 13% 5% 10% 5% 6% 6% 5% 5% 6% 26%	2527
	11th to 20th	Day	13% 13% 4 12% 5% 6% 5% 4 7% 7% 24%	2530
	21st to end	Day	14% 17% 8% 12% 6% 5% 5% 4 5% 5% 20%	2783
February	1st to 10th	Day	9% 12% 4 10% 5% 5% 5% 4 6% 6% 34%	1614
	11th to 20th	Day	10% 12% 4 10% 7% 5% 5% 3 6% 6% 33%	1812
	21st to end	Day	13% 14% 5% 8% 6% 5% 4 4 5% 7% 31%	1570
March	1st to 10th	Day	11% 11% 3 7% 4 3 4 4 5% 6% 42%	3118
	11th to 20th	Day	8% 10% 4 11% 7% 5% 5% 4 5% 7% 34%	3259
	21st to end	Day	19% 14% 4 11% 6% 5% 4 3 4 5% 26%	4165
April	1st to 10th	Day	17% 14% 4 8% 6% 4 4 3 5% 6% 27%	2280
	11th to 20th	Day	20% 10% 3 7% 4 5% 4 3 6% 6% 32%	2267
	21st to end	Day	18% 9% 3 8% 5% 4 5% 4 5% 7% 33%	2470
May	1st to 10th	Day	14% 8% 2 8% 6% 4 4 3 5% 6% 39%	4226
	11th to 20th	Day	13% 6% 3 7% 4 5% 5% 4 6% 8% 41%	4399
	21st to end	Day	13% 7% 2 7% 5% 5% 5% 4 6% 8% 38%	4837
June	1st to 10th	Day	12% 5% 2 5% 5% 5% 5% 4 6% 8% 42%	2660
	11th to 20th	Day	13% 6% 2 7% 5% 5% 5% 4 5% 7% 39%	2660
	21st to end	Day	12% 7% 2 6% 5% 5% 5% 4 6% 10% 38%	2660
July	1st to 10th	Day	14% 5% 2 6% 5% 5% 5% 4 7% 9% 38%	4440
	11th to 20th	Day	5% 4 1 5% 4 5% 6% 5% 7% 9% 49%	4440
	21st to end	Day	8% 5% 2 5% 4 4 5% 4 6% 8% 47%	4814
August	1st to 10th	Day	8% 6% 2 8% 5% 6% 6% 5% 8% 9% 38%	4423
	11th to 20th	Day	12% 5% 2 5% 4 4 4 4 5% 6% 48%	4039
	21st to end	Day	13% 7% 2 7% 4 5% 5% 4 5% 7% 41%	4180
September	1st to 10th	Day	12% 6% 2 6% 5% 4 4 4 5% 8% 44%	2280
	11th to 20th	Day	11% 4 2 6% 4 4 5% 4 7% 9% 42%	2157
	21st to end	Day	12% 6% 3 8% 5% 5% 5% 5% 6% 8% 37%	2090
October	1st to 10th	Day	16% 6% 3 7% 4 4 4 4 6% 8% 38%	2024
	11th to 20th	Day	21% 10% 4 9% 6% 5% 4 3 6% 6% 27%	1810
	21st to end	Day	20% 10% 4 9% 6% 5% 5% 3 5% 6% 28%	1881
November	1st to 10th	Day	14% 10% 3 7% 4 4 4 4 6% 7% 36%	1762
	11th to 20th	Day	15% 12% 4 9% 6% 5% 5% 4 7% 7% 26%	1782
	21st to end	Day	15% 11% 4 9% 5% 4 5% 4 7% 8% 28%	1600
December	1st to 10th	Day	12% 12% 4 9% 6% 5% 6% 4 6% 8% 29%	1600
	11th to 20th	Day	14% 16% 4 9% 6% 5% 5% 5% 5% 6% 25%	1994
	21st to end	Day	23% 22% 4 10% 5% 4 4 3 4 4 18%	2807
January	1st to 10th	Night	13% 14% 6% 11% 5% 4 4 3 4 5% 32%	4428
	11th to 20th	Night	11% 15% 5% 12% 7% 6% 6% 4 5% 6% 23%	4440
	21st to end	Night	12% 17% 7% 12% 6% 5% 4 3 5% 6% 23%	4884
February	1st to 10th	Night	10% 13% 5% 10% 6% 5% 4 4 5% 6% 32%	2565
	11th to 20th	Night	10% 11% 4 9% 5% 5% 4 4 6% 7% 35%	2253
	21st to end	Night	14% 13% 4 9% 6% 4 4 3 5% 6% 32%	1884
March	1st to 10th	Night	12% 9% 3 7% 4 4 3 3 5% 7% 43%	3722
	11th to 20th	Night	9% 10% 4 9% 5% 5% 5% 4 5% 7% 37%	3717
	21st to end	Night	17% 10% 4 9% 6% 6% 5% 4 5% 6% 27%	3476
April	1st to 10th	Night	19% 10% 3 9% 4 5% 4 3 6% 5% 30%	1900
	11th to 20th	Night	21% 8% 3 6% 4 4 3 4 4 6% 38%	1861
	21st to end	Night	17% 8% 3 8% 5% 4 4 3 5% 8% 35%	1710
May	1st to 10th	Night	17% 8% 3 6% 4 4 4 3 6% 6% 39%	2715
	11th to 20th	Night	12% 8% 3 6% 6% 4 5% 4 5% 6% 41%	2506
	21st to end	Night	17% 7% 2 5% 5% 5% 5% 4 5% 7% 39%	2750
June	1st to 10th	Night	11% 7% 1 6% 4 4 5% 4 5% 7% 45%	1520
	11th to 20th	Night	13% 8% 3 7% 4 4 4 4 6% 7% 39%	1520
	21st to end	Night	14% 5% 2 5% 3 4 4 5% 6% 9% 43%	1520
July	1st to 10th	Night	14% 5% 2 6% 4 5% 5% 5% 5% 8% 42%	2530
	11th to 20th	Night	6% 3 2 4 3 3 4 3 5% 8% 58%	2530
	21st to end	Night	9% 5% 2 6% 4 4 4 3 5% 7% 52%	2750
August	1st to 10th	Night	10% 6% 2 7% 4 4 5% 3 5% 8% 45%	2517
	11th to 20th	Night	12% 4 2 5% 4 4 4 3 5% 7% 51%	2786
	21st to end	Night	11% 6% 2 6% 5% 4 4 3 5% 6% 48%	3476
September	1st to 10th	Night	9% 6% 2 6% 4 3 4 3 5% 7% 53%	1900
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 5% 6% 51%	2004
	21st to end	Night	14% 7% 2 7% 4 4 4 3 4 7% 43%	2090
October	1st to 10th	Night	16% 5% 2 6% 4 3 3 3 5% 8% 44%	2152
	11th to 20th	Night	16% 10% 3 7% 5% 4 4 4 5% 7% 35%	2369
	21st to end	Night	18% 11% 3 8% 4 4 5% 3 5% 6% 33%	2717
November	1st to 10th	Night	15% 9% 3 7% 4 4 4 3 5% 7% 38%	2536
	11th to 20th	Night	15% 11% 3 8% 5% 5% 5% 4 5% 7% 32%	2615
	21st to end	Night	14% 11% 4 9% 6% 5% 5% 4 5% 7% 31%	2800
December	1st to 10th	Night	13% 13% 5% 8% 5% 5% 4 3 5% 7% 31%	2800
	11th to 20th	Night	13% 13% 5% 10% 6% 5% 5% 4 5% 5% 29%	3423
	21st to end	Night	24% 19% 6% 9% 5% 3 3 3 3 4 21%	4933

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	56% 7% 13% 16% 7% 1	2528
	11th to 20th	Day	56% 8% 14% 16% 6%	2530
	21st to end	Day	63% 7% 12% 13% 4 1	2783
February	1st to 10th	Day	49% 7% 12% 19% 12% 1	1614
	11th to 20th	Day	49% 6% 14% 20% 10% 2	1822
	21st to end	Day	51% 7% 11% 19% 11% 2	1570
March	1st to 10th	Day	41% 6% 13% 21% 17% 2	3120
	11th to 20th	Day	47% 7% 14% 21% 9% 1	3259
	21st to end	Day	60% 7% 8% 16% 9%	4165
April	1st to 10th	Day	55% 6% 11% 18% 9% 1	2280
	11th to 20th	Day	52% 6% 9% 21% 11% 2	2267
	21st to end	Day	50% 6% 9% 18% 14% 2	2470
May	1st to 10th	Day	43% 7% 10% 24% 15% 1	4238
	11th to 20th	Day	39% 7% 12% 27% 13% 1	4403
	21st to end	Day	42% 8% 11% 19% 17% 3	4837
June	1st to 10th	Day	37% 8% 13% 26% 14% 2	2660
	11th to 20th	Day	43% 6% 13% 20% 16% 1	2660
	21st to end	Day	40% 9% 13% 24% 13% 1	2660
July	1st to 10th	Day	41% 7% 15% 24% 12% 1	4371
	11th to 20th	Day	28% 8% 12% 36% 14% 2	4365
	21st to end	Day	33% 7% 11% 30% 18% 1	4662
August	1st to 10th	Day	39% 8% 15% 25% 12% 1	4408
	11th to 20th	Day	35% 7% 17% 28% 13%	4078
	21st to end	Day	41% 6% 16% 22% 14% 1	4179
September	1st to 10th	Day	38% 8% 13% 27% 13%	2280
	11th to 20th	Day	35% 9% 19% 28% 8%	2157
	21st to end	Day	42% 9% 14% 26% 9%	2090
October	1st to 10th	Day	31% 5% 13% 29% 21%	3362
	11th to 20th	Day	51% 5% 10% 22% 12%	2987
	21st to end	Day	52% 6% 14% 21% 6%	3081
November	1st to 10th	Day	46% 7% 12% 24% 11%	1762
	11th to 20th	Day	55% 7% 14% 15% 9% 1	1782
	21st to end	Day	52% 8% 16% 18% 5% 1	1600
December	1st to 10th	Day	53% 7% 13% 21% 6%	1600
	11th to 20th	Day	57% 7% 13% 14% 8% 1	1995
	21st to end	Day	69% 6% 8% 12% 5%	2807
January	1st to 10th	Night	54% 6% 11% 20% 8% 1	4428
	11th to 20th	Night	59% 7% 13% 17% 5%	4440
	21st to end	Night	61% 6% 13% 14% 5%	4884
February	1st to 10th	Night	52% 6% 9% 21% 11% 2	2565
	11th to 20th	Night	46% 6% 13% 22% 10% 2	2254
	21st to end	Night	53% 5% 12% 20% 9% 1	1884
March	1st to 10th	Night	41% 5% 19% 24% 10% 1	3733
	11th to 20th	Night	44% 6% 12% 25% 11% 1	3718
	21st to end	Night	54% 7% 11% 16% 9% 1	3476
April	1st to 10th	Night	53% 7% 9% 16% 14% 1	1900
	11th to 20th	Night	47% 5% 11% 22% 12% 3	1861
	21st to end	Night	47% 6% 11% 21% 13% 2	1710
May	1st to 10th	Night	43% 6% 12% 25% 13% 1	2722
	11th to 20th	Night	41% 8% 12% 25% 13% 1	2507
	21st to end	Night	43% 8% 13% 18% 11% 7%	2751
June	1st to 10th	Night	36% 8% 12% 28% 15% 2	1520
	11th to 20th	Night	41% 7% 14% 21% 16% 2	1520
	21st to end	Night	36% 8% 15% 27% 14% 2	1520
July	1st to 10th	Night	40% 7% 14% 23% 13% 3	2490
	11th to 20th	Night	22% 6% 18% 37% 15% 2	2482
	21st to end	Night	32% 6% 13% 26% 21% 1	2662
August	1st to 10th	Night	37% 6% 14% 24% 17% 2	2508
	11th to 20th	Night	33% 7% 14% 32% 13% 2	2813
	21st to end	Night	36% 7% 13% 25% 17% 2	3476
September	1st to 10th	Night	31% 6% 14% 33% 16% 1	1900
	11th to 20th	Night	33% 6% 15% 35% 11%	2004
	21st to end	Night	39% 6% 16% 27% 10% 1	2090
October	1st to 10th	Night	32% 5% 10% 36% 15% 1	3594
	11th to 20th	Night	40% 5% 13% 26% 15%	3931
	21st to end	Night	50% 5% 12% 24% 10%	4467
November	1st to 10th	Night	44% 7% 13% 25% 11% 1	2536
	11th to 20th	Night	51% 6% 14% 18% 11%	2615
	21st to end	Night	52% 7% 15% 20% 5% 1	2800
December	1st to 10th	Night	52% 7% 15% 19% 7%	2800
	11th to 20th	Night	56% 7% 11% 19% 7%	3421
	21st to end	Night	67% 6% 8% 14% 5%	4933

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% 14% 38% 21% 9%	270
	11th to 20th	Day	23% 17% 35% 19% 5% 1	270
	21st to end	Day	24% 13% 38% 21% 4	297
February	1st to 10th	Day	16% 21% 41% 16% 6% 1	270
	11th to 20th	Day	17% 26% 34% 18% 4	270
	21st to end	Day	23% 24% 41% 11% 1	225
March	1st to 10th	Day	16% 25% 44% 12% 4	270
	11th to 20th	Day	20% 19% 36% 19% 6% 1	312
	21st to end	Day	27% 16% 29% 19% 8% 1	506
April	1st to 10th	Day	26% 16% 32% 20% 5% 1	460
	11th to 20th	Day	27% 18% 28% 19% 7% 2	452
	21st to end	Day	23% 17% 28% 21% 9% 1	460
May	1st to 10th	Day	21% 20% 31% 18% 8% 3	529
	11th to 20th	Day	17% 15% 36% 20% 9% 2	675
	21st to end	Day	18% 15% 29% 25% 9% 4	734
June	1st to 10th	Day	13% 17% 31% 27% 9% 3	680
	11th to 20th	Day	18% 11% 35% 24% 10% 3	680
	21st to end	Day	17% 11% 29% 30% 10% 4	680
July	1st to 10th	Day	9% 8% 30% 34% 14% 5%	671
	11th to 20th	Day	10% 10% 30% 30% 14% 6%	668
	21st to end	Day	8% 7% 33% 28% 18% 6%	739
August	1st to 10th	Day	10% 8% 28% 30% 17% 5%	676
	11th to 20th	Day	13% 8% 23% 27% 22% 8%	512
	21st to end	Day	16% 11% 22% 25% 20% 5%	539
September	1st to 10th	Day	15% 11% 29% 24% 16% 5%	490
	11th to 20th	Day	12% 8% 27% 33% 17% 4	490
	21st to end	Day	17% 13% 25% 27% 14% 3	490
October	1st to 10th	Day	21% 15% 30% 20% 11% 2	424
	11th to 20th	Day	24% 20% 36% 17% 3	300
	21st to end	Day	28% 20% 35% 15% 2	330
November	1st to 10th	Day	19% 18% 37% 17% 7% 1	300
	11th to 20th	Day	25% 22% 33% 15% 5% 1	300
	21st to end	Day	24% 16% 40% 14% 5%	300
December	1st to 10th	Day	19% 16% 40% 17% 6% 1	300
	11th to 20th	Day	24% 21% 35% 16% 3 1	300
	21st to end	Day	30% 18% 34% 14% 3	306
January	1st to 10th	Night	17% 10% 41% 26% 5%	950
	11th to 20th	Night	20% 13% 36% 23% 7% 1	950
	21st to end	Night	19% 8% 36% 27% 8% 1	1045
February	1st to 10th	Night	17% 11% 39% 27% 6% 1	950
	11th to 20th	Night	18% 13% 37% 26% 6% 1	778
	21st to end	Night	21% 15% 38% 22% 4	628
March	1st to 10th	Night	17% 12% 36% 26% 8%	760
	11th to 20th	Night	15% 14% 42% 22% 6%	760
	21st to end	Night	20% 9% 33% 29% 9% 1	637
April	1st to 10th	Night	24% 11% 34% 24% 7%	570
	11th to 20th	Night	25% 10% 28% 28% 7% 1	563
	21st to end	Night	21% 8% 33% 29% 9% 1	570
May	1st to 10th	Night	21% 10% 28% 32% 8% 1	570
	11th to 20th	Night	18% 9% 33% 31% 8% 1	561
	21st to end	Night	16% 5% 29% 36% 14%	617
June	1st to 10th	Night	13% 6% 30% 42% 9%	570
	11th to 20th	Night	17% 7% 27% 35% 13% 1	570
	21st to end	Night	15% 6% 23% 40% 15% 1	570
July	1st to 10th	Night	8% 3 25% 43% 21% 1	555
	11th to 20th	Night	9% 3 26% 40% 21%	552
	21st to end	Night	8% 5% 27% 38% 20% 2	624
August	1st to 10th	Night	11% 4 23% 40% 21% 1	567
	11th to 20th	Night	10% 3 18% 40% 25% 3	564
	21st to end	Night	12% 5% 23% 39% 21% 1	627
September	1st to 10th	Night	12% 4 26% 32% 22% 3	570
	11th to 20th	Night	14% 5% 27% 33% 18% 3	674
	21st to end	Night	17% 8% 27% 31% 15% 2	760
October	1st to 10th	Night	19% 9% 30% 28% 14% 1	760
	11th to 20th	Night	21% 11% 34% 26% 7%	760
	21st to end	Night	24% 11% 34% 23% 7%	836
November	1st to 10th	Night	19% 12% 36% 26% 6% 1	780
	11th to 20th	Night	21% 16% 34% 23% 6%	815
	21st to end	Night	19% 15% 34% 26% 6%	1000
December	1st to 10th	Night	21% 12% 39% 21% 6% 1	1000
	11th to 20th	Night	20% 12% 36% 24% 7% 2	1000
	21st to end	Night	28% 11% 35% 22% 4	1063

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