Ridgway Nature & Science Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ridgway Nature & Science Center clear sky chart from 2005-11-06 to 2025-05-26.

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	3 6% 3 7% 5% 4 5% 4 6% 7% 50%	118169
	Night	2 6% 3 6% 4 4 4 4 5% 7% 56%	120059
Transparency	Day	33% 9% 9% 19% 21% 8%	117929
	Night	28% 7% 10% 22% 23% 9%	119888
Seeing	Day	10% 22% 32% 24% 10% 2	15989
	Night	6% 12% 29% 32% 17% 3	26227

By Month

Percentage Cloud Cover SW (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	1 8% 5% 15% 7% 4 4 3 5% 6% 42%	3983
	11th to 20th	Day	1 8% 4 11% 7% 5% 4 4 6% 6% 44%	4100
	21st to end	Day	1 8% 4 9% 4 4 4 3 6% 6% 51%	4510
February	1st to 10th	Day	2 12% 5% 10% 5% 4 5% 4 6% 6% 43%	1800
	11th to 20th	Day	2 10% 4 9% 6% 5% 4 4 6% 7% 43%	1795
	21st to end	Day	1 10% 6% 10% 6% 5% 4 4 5% 5% 45%	1650
March	1st to 10th	Day	1 9% 4 10% 5% 4 4 3 5% 7% 48%	4951
	11th to 20th	Day	1 12% 5% 10% 5% 5% 5% 5% 7% 9% 36%	5000
	21st to end	Day	1 8% 4 9% 6% 6% 6% 5% 7% 9% 40%	5502
April	1st to 10th	Day	3 10% 2 7% 5% 4 4 5% 6% 7% 48%	2400
	11th to 20th	Day	2 11% 4 8% 4 5% 5% 5% 6% 7% 43%	2371
	21st to end	Day	3 11% 3 6% 5% 5% 4 3 5% 8% 46%	2400
May	1st to 10th	Day	3 8% 3 7% 5% 5% 6% 4 6% 7% 46%	4165
	11th to 20th	Day	3 6% 2 7% 6% 5% 6% 6% 8% 9% 44%	4249
	21st to end	Day	3 5% 2 6% 5% 5% 5% 5% 6% 8% 50%	4897
June	1st to 10th	Day	2 3 2 4 4 5% 5% 4 5% 8% 57%	2660
	11th to 20th	Day	3 2 1 4 4 3 4 4 5% 7% 62%	2660
	21st to end	Day	3 4 2 4 4 5% 4 4 6% 8% 57%	2660
July	1st to 10th	Day	3 2 1 4 4 3 4 4 5% 5% 65%	4401
	11th to 20th	Day	3 3 1 4 5% 6% 8% 7% 11% 11% 41%	4110
	21st to end	Day	5% 4 2 5% 4 5% 6% 4 6% 7% 50%	4454
August	1st to 10th	Day	6% 4 2 6% 6% 7% 8% 6% 10% 12% 33%	4092
	11th to 20th	Day	5% 4 2 6% 6% 6% 6% 6% 7% 8% 44%	3909
	21st to end	Day	3 3 2 7% 6% 6% 6% 5% 8% 12% 43%	4180
September	1st to 10th	Day	6% 5% 2 7% 5% 5% 4 3 5% 8% 49%	2280
	11th to 20th	Day	6% 4 2 5% 5% 4 4 4 6% 7% 53%	2268
	21st to end	Day	5% 4 2 6% 3 4 3 3 4 6% 61%	2005
October	1st to 10th	Day	3 3 1 3 2 2 2 2 4 7% 70%	3170
	11th to 20th	Day	4 5% 2 5% 4 4 6% 4 6% 8% 53%	3150
	21st to end	Day	3 6% 1 3 2 2 3 3 3 5% 69%	3438
November	1st to 10th	Day	1 5% 2 5% 3 2 2 2 5% 6% 66%	1934
	11th to 20th	Day	2 8% 2 5% 2 3 3 3 5% 5% 63%	1775
	21st to end	Day	2 6% 3 7% 4 3 4 3 3 5% 60%	1600
December	1st to 10th	Day	1 7% 4 6% 3 2 3 2 4 5% 64%	2620
	11th to 20th	Day	1 7% 3 7% 3 3 3 3 4 6% 59%	3026
	21st to end	Day	1 9% 3 8% 5% 4 4 3 6% 7% 49%	4004
January	1st to 10th	Night	9% 7% 15% 5% 4 4 3 5% 6% 40%	6023
	11th to 20th	Night	1 10% 4 10% 5% 5% 4 4 4 6% 46%	5880
	21st to end	Night	1 9% 4 9% 4 4 4 4 5% 5% 52%	6468
February	1st to 10th	Night	1 10% 5% 10% 4 4 4 3 4 6% 50%	2600
	11th to 20th	Night	2 8% 4 8% 4 5% 5% 4 5% 6% 48%	2491
	21st to end	Night	1 11% 3 9% 6% 4 3 3 5% 6% 48%	1980
March	1st to 10th	Night	1 9% 3 8% 5% 5% 4 4 5% 6% 50%	4940
	11th to 20th	Night	1 8% 5% 9% 5% 4 4 4 6% 6% 48%	5000
	21st to end	Night	1 9% 4 8% 5% 4 6% 5% 7% 7% 43%	5472
April	1st to 10th	Night	3 8% 3 7% 4 4 5% 4 7% 7% 49%	2000
	11th to 20th	Night	2 12% 4 6% 3 4 4 4 7% 7% 46%	1977
	21st to end	Night	4 9% 3 4 3 3 4 4 5% 7% 52%	2000
May	1st to 10th	Night	3 8% 2 5% 4 4 4 4 7% 7% 53%	3022
	11th to 20th	Night	3 5% 1 4 3 4 4 4 6% 10% 56%	2874
	21st to end	Night	3 3 1 3 3 4 3 3 5% 6% 67%	2806
June	1st to 10th	Night	2 2 2 3 3 3 3 6% 8% 68%	1520
	11th to 20th	Night	2 2 1 2 2 3 3 3 5% 6% 71%	1520
	21st to end	Night	1 1 1 3 3 3 4 5% 7% 8% 66%	1520
July	1st to 10th	Night	1 1 1 3 2 3 3 4 5% 5% 71%	2563
	11th to 20th	Night	2 2 1 3 3 4 5% 4 9% 12% 57%	2860
	21st to end	Night	2 2 2 4 4 5% 5% 5% 7% 9% 55%	3109
August	1st to 10th	Night	3 3 1 4 4 5% 7% 7% 10% 14% 42%	2847
	11th to 20th	Night	2 2 1 3 3 4 6% 5% 8% 10% 56%	2928
	21st to end	Night	3 3 1 4 4 4 6% 5% 8% 10% 53%	3487
September	1st to 10th	Night	3 3 1 4 3 3 4 4 6% 10% 58%	1900
	11th to 20th	Night	3 2 1 3 3 4 5% 5% 5% 7% 63%	1908
	21st to end	Night	3 4 1 4 2 2 3 2 3 5% 72%	2175
October	1st to 10th	Night	3 3 1 2 2 2 2 1 2 5% 78%	3800
	11th to 20th	Night	2 3 1 4 3 2 4 4 5% 8% 65%	3778
	21st to end	Night	3 6% 2 4 2 1 3 2 3 4 70%	4120
November	1st to 10th	Night	2 5% 1 3 2 3 3 4 5% 7% 64%	2342
	11th to 20th	Night	2 9% 2 4 3 3 3 2 5% 5% 64%	2624
	21st to end	Night	2 8% 4 6% 3 3 3 3 4 6% 58%	2800
December	1st to 10th	Night	1 5% 2 6% 3 2 2 2 4 5% 67%	4570
	11th to 20th	Night	1 6% 2 5% 3 3 3 4 5% 8% 60%	5181
	21st to end	Night	2 10% 4 10% 5% 4 4 3 5% 6% 47%	6974

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	42% 8% 11% 18% 17% 3	3984
	11th to 20th	Day	42% 6% 11% 16% 19% 6%	4100
	21st to end	Day	32% 9% 8% 23% 21% 6%	4510
February	1st to 10th	Day	45% 6% 13% 15% 14% 7%	1800
	11th to 20th	Day	43% 6% 7% 19% 18% 7%	1804
	21st to end	Day	43% 5% 6% 18% 20% 8%	1650
March	1st to 10th	Day	34% 8% 8% 19% 22% 10%	4951
	11th to 20th	Day	42% 9% 12% 21% 14% 2	5000
	21st to end	Day	42% 11% 10% 24% 11% 1	5502
April	1st to 10th	Day	38% 8% 8% 22% 19% 6%	2400
	11th to 20th	Day	41% 9% 7% 19% 19% 4	2374
	21st to end	Day	38% 8% 10% 25% 17% 2	2400
May	1st to 10th	Day	37% 8% 9% 20% 21% 6%	4165
	11th to 20th	Day	32% 11% 10% 23% 20% 4	4252
	21st to end	Day	29% 9% 8% 21% 28% 5%	4897
June	1st to 10th	Day	25% 9% 9% 24% 22% 10%	2660
	11th to 20th	Day	24% 7% 7% 15% 28% 19%	2660
	21st to end	Day	27% 8% 7% 15% 24% 18%	2660
July	1st to 10th	Day	24% 7% 6% 7% 16% 40%	4332
	11th to 20th	Day	31% 13% 13% 17% 17% 9%	4041
	21st to end	Day	32% 10% 10% 14% 18% 16%	4314
August	1st to 10th	Day	41% 15% 17% 12% 10% 5%	4078
	11th to 20th	Day	40% 11% 11% 10% 21% 7%	3948
	21st to end	Day	34% 13% 11% 14% 22% 6%	4179
September	1st to 10th	Day	37% 8% 9% 13% 24% 9%	2280
	11th to 20th	Day	33% 9% 9% 14% 26% 9%	2268
	21st to end	Day	28% 7% 6% 21% 29% 8%	2005
October	1st to 10th	Day	19% 5% 5% 16% 40% 15%	3170
	11th to 20th	Day	26% 9% 9% 27% 24% 5%	3150
	21st to end	Day	20% 6% 6% 25% 36% 7%	3438
November	1st to 10th	Day	23% 5% 11% 24% 31% 6%	1934
	11th to 20th	Day	25% 3 10% 29% 25% 8%	1775
	21st to end	Day	30% 5% 9% 23% 23% 11%	1600
December	1st to 10th	Day	25% 4 8% 36% 20% 6%	2620
	11th to 20th	Day	29% 5% 10% 26% 27% 3	3024
	21st to end	Day	33% 7% 9% 22% 20% 8%	4004
January	1st to 10th	Night	43% 6% 9% 22% 15% 5%	6023
	11th to 20th	Night	39% 6% 9% 18% 20% 8%	5880
	21st to end	Night	32% 5% 7% 22% 25% 8%	6468
February	1st to 10th	Night	39% 6% 10% 19% 18% 8%	2600
	11th to 20th	Night	38% 5% 9% 22% 19% 7%	2492
	21st to end	Night	38% 5% 8% 18% 23% 8%	1980
March	1st to 10th	Night	30% 6% 7% 18% 28% 9%	4940
	11th to 20th	Night	33% 8% 11% 22% 21% 5%	5000
	21st to end	Night	39% 11% 12% 26% 10% 1	5472
April	1st to 10th	Night	34% 8% 10% 24% 19% 5%	2000
	11th to 20th	Night	36% 8% 10% 20% 21% 4	1977
	21st to end	Night	33% 8% 10% 28% 20% 2	2000
May	1st to 10th	Night	29% 7% 9% 25% 28% 3	3022
	11th to 20th	Night	22% 8% 11% 34% 24% 1	2875
	21st to end	Night	18% 7% 9% 23% 35% 9%	2806
June	1st to 10th	Night	15% 6% 11% 27% 31% 9%	1520
	11th to 20th	Night	16% 5% 7% 19% 32% 21%	1520
	21st to end	Night	15% 8% 9% 18% 30% 20%	1520
July	1st to 10th	Night	16% 7% 8% 10% 15% 43%	2523
	11th to 20th	Night	18% 8% 14% 31% 17% 12%	2806
	21st to end	Night	23% 11% 15% 17% 18% 17%	3011
August	1st to 10th	Night	29% 13% 22% 15% 12% 9%	2838
	11th to 20th	Night	23% 11% 22% 14% 19% 12%	2955
	21st to end	Night	25% 10% 14% 21% 23% 6%	3487
September	1st to 10th	Night	23% 9% 12% 18% 29% 10%	1900
	11th to 20th	Night	20% 8% 12% 21% 28% 12%	1908
	21st to end	Night	17% 6% 7% 27% 33% 9%	2175
October	1st to 10th	Night	14% 3 6% 16% 42% 20%	3800
	11th to 20th	Night	16% 8% 10% 32% 27% 7%	3778
	21st to end	Night	20% 4 6% 24% 35% 11%	4120
November	1st to 10th	Night	21% 7% 12% 24% 27% 9%	2342
	11th to 20th	Night	24% 4 9% 26% 28% 9%	2624
	21st to end	Night	30% 5% 7% 21% 25% 12%	2800
December	1st to 10th	Night	22% 4 9% 34% 27% 5%	4570
	11th to 20th	Night	24% 7% 9% 30% 24% 7%	5182
	21st to end	Night	38% 7% 9% 18% 20% 9%	6974

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	13% 19% 34% 22% 11% 1	300
	11th to 20th	Day	12% 26% 32% 21% 8% 1	300
	21st to end	Day	4 22% 41% 26% 7% 1	330
February	1st to 10th	Day	15% 36% 30% 16% 2 1	300
	11th to 20th	Day	15% 36% 33% 12% 4	300
	21st to end	Day	19% 33% 28% 16% 4	249
March	1st to 10th	Day	17% 35% 28% 15% 3	497
	11th to 20th	Day	13% 33% 30% 19% 5%	500
	21st to end	Day	20% 36% 28% 13% 2	550
April	1st to 10th	Day	16% 29% 33% 16% 4 1	500
	11th to 20th	Day	20% 38% 28% 11% 3	492
	21st to end	Day	15% 33% 33% 15% 4	500
May	1st to 10th	Day	15% 32% 32% 16% 4 1	503
	11th to 20th	Day	13% 24% 35% 21% 6% 1	550
	21st to end	Day	12% 24% 29% 22% 10% 3	760
June	1st to 10th	Day	5% 13% 35% 29% 15% 3	680
	11th to 20th	Day	6% 17% 36% 26% 11% 3	680
	21st to end	Day	3 15% 36% 27% 16% 3	680
July	1st to 10th	Day	4 7% 27% 37% 20% 4	655
	11th to 20th	Day	6% 6% 24% 37% 21% 6%	484
	21st to end	Day	7% 6% 27% 35% 20% 4	531
August	1st to 10th	Day	11% 6% 29% 33% 16% 5%	487
	11th to 20th	Day	8% 9% 32% 32% 15% 4	477
	21st to end	Day	4 6% 35% 37% 14% 4	539
September	1st to 10th	Day	9% 10% 31% 29% 18% 3	490
	11th to 20th	Day	6% 19% 40% 24% 8% 2	490
	21st to end	Day	7% 20% 28% 30% 11% 3	405
October	1st to 10th	Day	10% 21% 26% 23% 16% 4	300
	11th to 20th	Day	6% 25% 28% 28% 11% 2	300
	21st to end	Day	9% 25% 30% 26% 9% 1	330
November	1st to 10th	Day	10% 29% 28% 23% 8% 1	300
	11th to 20th	Day	7% 25% 32% 23% 12% 1	300
	21st to end	Day	8% 26% 33% 22% 10% 1	300
December	1st to 10th	Day	12% 22% 32% 23% 10% 1	300
	11th to 20th	Day	11% 23% 32% 23% 9% 1	300
	21st to end	Day	17% 22% 35% 19% 6% 1	330
January	1st to 10th	Night	8% 12% 31% 30% 15% 4	865
	11th to 20th	Night	8% 13% 30% 31% 15% 3	800
	21st to end	Night	5% 13% 32% 34% 13% 4	880
February	1st to 10th	Night	7% 19% 37% 27% 9% 2	800
	11th to 20th	Night	7% 17% 39% 26% 10% 1	784
	21st to end	Night	9% 17% 42% 25% 7%	660
March	1st to 10th	Night	8% 23% 33% 25% 9% 2	800
	11th to 20th	Night	5% 15% 34% 30% 16% 1	800
	21st to end	Night	8% 21% 33% 26% 9% 1	875
April	1st to 10th	Night	10% 20% 37% 27% 6% 1	600
	11th to 20th	Night	11% 20% 34% 26% 8% 1	593
	21st to end	Night	10% 18% 31% 28% 11% 2	600
May	1st to 10th	Night	6% 14% 36% 32% 11% 1	600
	11th to 20th	Night	7% 11% 32% 31% 15% 4	591
	21st to end	Night	8% 11% 33% 29% 16% 2	634
June	1st to 10th	Night	2 8% 28% 36% 23% 3	570
	11th to 20th	Night	3 12% 29% 37% 18% 3	570
	21st to end	Night	1 5% 23% 42% 25% 4	570
July	1st to 10th	Night	3 20% 39% 34% 3	555
	11th to 20th	Night	3 1 13% 40% 38% 5%	552
	21st to end	Night	3 3 9% 38% 42% 5%	624
August	1st to 10th	Night	3 3 11% 40% 38% 6%	567
	11th to 20th	Night	4 2 14% 42% 34% 5%	564
	21st to end	Night	4 3 16% 43% 28% 7%	627
September	1st to 10th	Night	4 3 17% 43% 29% 4	570
	11th to 20th	Night	3 4 24% 37% 27% 4	578
	21st to end	Night	4 9% 21% 36% 21% 9%	760
October	1st to 10th	Night	7% 12% 26% 37% 17% 2	760
	11th to 20th	Night	4 11% 27% 33% 20% 5%	760
	21st to end	Night	9% 11% 27% 30% 18% 5%	836
November	1st to 10th	Night	6% 14% 26% 33% 17% 4	782
	11th to 20th	Night	7% 13% 33% 29% 15% 3	1000
	21st to end	Night	8% 17% 27% 31% 14% 3	1000
December	1st to 10th	Night	8% 14% 32% 33% 12% 2	1000
	11th to 20th	Night	8% 18% 33% 25% 15% 1	1000
	21st to end	Night	10% 13% 37% 31% 8% 1	1100

Page generated at 2025-05-23 07:21:02. Version ac07

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