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 2026-09-29.

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	2 5% 2 6% 4 4 5% 4 6% 8% 52%	157750
	Night	2 6% 2 6% 3 3 4 4 6% 7% 57%	151318
Transparency	Day	30% 9% 10% 20% 21% 9%	152649
	Night	26% 7% 11% 23% 23% 10%	147427
Seeing	Day	10% 21% 32% 25% 10% 2	17890
	Night	6% 12% 29% 33% 17% 3	27953

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% 6% 4 4 3 5% 7% 43%	5177
	11th to 20th	Day	1 6% 3 9% 5% 4 3 3 5% 6% 56%	5340
	21st to end	Day	1 8% 4 9% 3 3 4 3 5% 6% 54%	5844
February	1st to 10th	Day	2 11% 5% 9% 5% 4 4 3 6% 6% 44%	1890
	11th to 20th	Day	2 10% 4 9% 6% 5% 4 5% 6% 7% 42%	1887
	21st to end	Day	1 9% 6% 10% 6% 4 4 4 5% 5% 47%	1730
March	1st to 10th	Day	1 9% 4 10% 5% 4 4 3 5% 7% 49%	5061
	11th to 20th	Day	1 12% 5% 9% 5% 5% 5% 5% 7% 8% 37%	5110
	21st to end	Day	8% 4 8% 6% 6% 6% 5% 7% 9% 41%	5623
April	1st to 10th	Day	3 9% 2 7% 4 3 4 5% 5% 7% 49%	2520
	11th to 20th	Day	2 11% 4 8% 4 5% 5% 5% 6% 7% 44%	2491
	21st to end	Day	3 11% 3 6% 5% 5% 5% 3 6% 8% 45%	2520
May	1st to 10th	Day	4 6% 2 6% 5% 5% 5% 4 6% 7% 49%	7488
	11th to 20th	Day	3 5% 2 6% 5% 5% 6% 5% 7% 9% 49%	7671
	21st to end	Day	2 4 1 4 4 4 5% 4 6% 9% 56%	9026
June	1st to 10th	Day	2 3 2 4 4 5% 5% 4 6% 9% 57%	2940
	11th to 20th	Day	3 2 1 4 4 3 4 4 5% 7% 64%	2940
	21st to end	Day	3 4 1 4 4 5% 4 4 6% 7% 60%	2940
July	1st to 10th	Day	2 2 1 3 3 3 4 4 4 5% 69%	8192
	11th to 20th	Day	3 2 1 4 4 6% 7% 6% 10% 10% 47%	7650
	21st to end	Day	4 3 2 5% 4 6% 7% 5% 9% 9% 45%	8304
August	1st to 10th	Day	3 3 1 4 4 5% 6% 5% 8% 10% 52%	7549
	11th to 20th	Day	4 3 1 5% 4 5% 6% 5% 8% 11% 48%	7342
	21st to end	Day	3 3 2 6% 5% 6% 7% 6% 10% 13% 38%	7751
September	1st to 10th	Day	6% 5% 2 6% 5% 5% 4 3 6% 8% 50%	2520
	11th to 20th	Day	5% 4 2 5% 5% 4 4 4 7% 7% 53%	2506
	21st to end	Day	5% 4 2 6% 3 4 4 4 4 6% 59%	2196
October	1st to 10th	Day	3 3 1 3 2 2 2 2 4 7% 70%	3270
	11th to 20th	Day	4 5% 2 5% 4 4 6% 4 5% 8% 54%	3250
	21st to end	Day	3 5% 1 3 2 2 3 3 3 5% 70%	3548
November	1st to 10th	Day	1 5% 2 5% 3 2 2 2 5% 6% 67%	2033
	11th to 20th	Day	1 7% 2 5% 2 3 3 3 5% 5% 63%	1863
	21st to end	Day	2 6% 3 7% 3 3 4 3 3 5% 60%	1680
December	1st to 10th	Day	1 8% 4 6% 3 2 2 2 4 5% 64%	2700
	11th to 20th	Day	1 7% 3 7% 3 3 3 3 4 6% 60%	3106
	21st to end	Day	1 9% 3 8% 5% 4 4 3 6% 7% 49%	4092
January	1st to 10th	Night	9% 6% 14% 5% 4 5% 4 6% 7% 39%	7799
	11th to 20th	Night	1 8% 3 8% 4 4 3 3 4 5% 57%	7650
	21st to end	Night	1 9% 4 8% 4 3 4 3 4 5% 56%	8370
February	1st to 10th	Night	1 9% 5% 9% 4 4 4 2 4 6% 51%	2730
	11th to 20th	Night	2 8% 4 8% 5% 5% 5% 4 5% 7% 47%	2619
	21st to end	Night	1 10% 3 9% 6% 4 3 3 4 6% 49%	2076
March	1st to 10th	Night	1 9% 3 8% 5% 5% 4 4 5% 6% 51%	5050
	11th to 20th	Night	1 8% 5% 9% 4 4 4 4 5% 6% 49%	5110
	21st to end	Night	1 9% 4 7% 4 4 6% 5% 7% 7% 44%	5593
April	1st to 10th	Night	3 8% 3 7% 4 4 5% 4 7% 7% 49%	2100
	11th to 20th	Night	2 12% 4 6% 3 4 4 4 7% 8% 47%	2077
	21st to end	Night	4 9% 3 4 4 3 4 4 5% 7% 52%	2100
May	1st to 10th	Night	3 6% 2 5% 4 4 4 4 7% 8% 54%	5443
	11th to 20th	Night	3 4 1 4 3 3 4 3 6% 9% 61%	5219
	21st to end	Night	2 2 1 3 2 3 3 3 5% 7% 71%	5181
June	1st to 10th	Night	2 2 2 3 2 3 3 5% 8% 69%	1680
	11th to 20th	Night	2 2 1 2 2 3 3 3 5% 6% 72%	1680
	21st to end	Night	1 1 1 3 2 3 4 4 6% 7% 67%	1680
July	1st to 10th	Night	1 1 1 2 2 3 3 3 5% 6% 74%	4791
	11th to 20th	Night	2 2 1 4 4 4 5% 4 8% 12% 54%	5340
	21st to end	Night	2 2 1 3 3 4 5% 5% 8% 12% 55%	5805
August	1st to 10th	Night	2 1 1 2 3 3 4 4 7% 9% 63%	5273
	11th to 20th	Night	1 1 1 2 3 3 4 4 7% 11% 63%	5512
	21st to end	Night	3 2 2 4 4 4 6% 6% 9% 13% 47%	6465
September	1st to 10th	Night	3 3 1 4 3 3 4 4 6% 10% 59%	2100
	11th to 20th	Night	3 2 1 3 3 4 5% 5% 6% 7% 63%	2109
	21st to end	Night	3 4 1 4 2 2 3 2 4 6% 70%	2380
October	1st to 10th	Night	3 3 1 2 2 2 2 1 2 5% 78%	3920
	11th to 20th	Night	2 3 1 3 3 2 4 3 5% 7% 65%	3898
	21st to end	Night	3 6% 2 4 2 1 2 2 3 4 70%	4252
November	1st to 10th	Night	2 5% 1 3 2 2 3 3 5% 7% 66%	2462
	11th to 20th	Night	2 8% 2 4 3 3 3 2 5% 5% 64%	2755
	21st to end	Night	2 8% 4 6% 3 3 3 3 4 6% 58%	2940
December	1st to 10th	Night	1 6% 2 6% 3 2 2 2 4 5% 67%	4710
	11th to 20th	Night	1 6% 2 5% 3 3 3 3 5% 8% 61%	5321
	21st to end	Night	2 10% 4 10% 5% 4 4 3 5% 6% 48%	7128

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	41% 8% 11% 23% 14% 2	5180
	11th to 20th	Day	32% 5% 11% 23% 22% 7%	5340
	21st to end	Day	31% 7% 9% 23% 23% 7%	5844
February	1st to 10th	Day	43% 6% 12% 16% 16% 7%	1890
	11th to 20th	Day	43% 6% 7% 19% 18% 6%	1896
	21st to end	Day	42% 5% 6% 19% 20% 8%	1730
March	1st to 10th	Day	34% 8% 8% 19% 22% 10%	5061
	11th to 20th	Day	42% 9% 12% 22% 13% 2	5110
	21st to end	Day	42% 11% 10% 25% 11% 2	5623
April	1st to 10th	Day	37% 8% 8% 22% 19% 6%	2520
	11th to 20th	Day	40% 9% 8% 19% 20% 4	2494
	21st to end	Day	37% 9% 10% 25% 17% 2	2520
May	1st to 10th	Day	31% 10% 11% 26% 18% 3	7488
	11th to 20th	Day	28% 11% 10% 19% 28% 4	7674
	21st to end	Day	22% 9% 9% 26% 30% 5%	9027
June	1st to 10th	Day	25% 9% 10% 25% 23% 9%	2940
	11th to 20th	Day	22% 7% 7% 15% 29% 20%	2940
	21st to end	Day	26% 8% 7% 14% 24% 22%	2940
July	1st to 10th	Day	18% 6% 6% 7% 18% 45%	8124
	11th to 20th	Day	26% 13% 14% 20% 16% 11%	7581
	21st to end	Day	30% 14% 18% 12% 16% 11%	8120
August	1st to 10th	Day	31% 12% 15% 11% 18% 13%	5978
	11th to 20th	Day	34% 12% 15% 17% 16% 5%	5789
	21st to end	Day	34% 15% 16% 16% 15% 4	6078
September	1st to 10th	Day	35% 8% 9% 15% 24% 8%	2520
	11th to 20th	Day	32% 10% 9% 14% 26% 8%	2506
	21st to end	Day	30% 7% 6% 21% 28% 8%	2196
October	1st to 10th	Day	18% 5% 5% 17% 40% 15%	3270
	11th to 20th	Day	25% 9% 9% 26% 25% 6%	3250
	21st to end	Day	20% 6% 6% 25% 36% 7%	3548
November	1st to 10th	Day	22% 5% 11% 25% 32% 6%	2033
	11th to 20th	Day	24% 3 10% 31% 24% 8%	1863
	21st to end	Day	30% 5% 9% 25% 22% 10%	1680
December	1st to 10th	Day	26% 4 8% 36% 20% 6%	2700
	11th to 20th	Day	28% 6% 10% 26% 27% 3	3104
	21st to end	Day	33% 8% 9% 22% 20% 8%	4092
January	1st to 10th	Night	42% 8% 9% 23% 13% 4	7800
	11th to 20th	Night	30% 5% 10% 25% 21% 10%	7650
	21st to end	Night	30% 5% 8% 22% 26% 9%	8370
February	1st to 10th	Night	37% 5% 10% 20% 19% 8%	2730
	11th to 20th	Night	38% 6% 9% 22% 18% 7%	2620
	21st to end	Night	37% 6% 8% 19% 23% 7%	2076
March	1st to 10th	Night	30% 7% 7% 19% 28% 9%	5050
	11th to 20th	Night	33% 8% 11% 23% 21% 5%	5110
	21st to end	Night	39% 10% 12% 27% 10% 2	5593
April	1st to 10th	Night	34% 8% 10% 23% 19% 6%	2100
	11th to 20th	Night	35% 8% 11% 20% 21% 4	2077
	21st to end	Night	32% 8% 10% 28% 20% 2	2100
May	1st to 10th	Night	26% 8% 10% 31% 22% 2	5441
	11th to 20th	Night	19% 8% 10% 29% 31% 2	5220
	21st to end	Night	14% 6% 10% 28% 35% 8%	5182
June	1st to 10th	Night	15% 6% 11% 27% 31% 10%	1680
	11th to 20th	Night	15% 5% 7% 18% 32% 23%	1680
	21st to end	Night	15% 8% 8% 17% 29% 23%	1680
July	1st to 10th	Night	12% 6% 7% 10% 13% 52%	4751
	11th to 20th	Night	19% 8% 17% 28% 14% 13%	5286
	21st to end	Night	19% 11% 25% 16% 18% 10%	5677
August	1st to 10th	Night	21% 10% 17% 13% 21% 19%	4168
	11th to 20th	Night	19% 12% 25% 21% 15% 9%	4341
	21st to end	Night	22% 11% 22% 24% 16% 4	5069
September	1st to 10th	Night	22% 9% 12% 19% 30% 9%	2100
	11th to 20th	Night	21% 8% 11% 21% 28% 11%	2109
	21st to end	Night	17% 6% 8% 27% 32% 9%	2380
October	1st to 10th	Night	14% 3 6% 16% 42% 19%	3920
	11th to 20th	Night	16% 8% 9% 32% 28% 7%	3898
	21st to end	Night	19% 4 6% 24% 36% 11%	4252
November	1st to 10th	Night	20% 6% 11% 25% 28% 9%	2462
	11th to 20th	Night	24% 5% 9% 27% 27% 8%	2755
	21st to end	Night	30% 5% 7% 23% 24% 11%	2940
December	1st to 10th	Night	22% 4 9% 34% 26% 5%	4710
	11th to 20th	Night	23% 6% 10% 30% 24% 7%	5322
	21st to end	Night	37% 7% 9% 17% 21% 9%	7128

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	12% 20% 36% 21% 10% 1	330
	11th to 20th	Day	11% 25% 34% 22% 8% 1	330
	21st to end	Day	4 22% 41% 26% 6% 1	363
February	1st to 10th	Day	14% 35% 30% 18% 4 1	330
	11th to 20th	Day	17% 36% 32% 12% 3	330
	21st to end	Day	19% 32% 29% 16% 3	273
March	1st to 10th	Day	16% 35% 29% 16% 3 1	537
	11th to 20th	Day	12% 33% 31% 19% 5%	540
	21st to end	Day	18% 36% 28% 15% 2	594
April	1st to 10th	Day	16% 29% 33% 16% 4 2	540
	11th to 20th	Day	19% 38% 28% 11% 3	532
	21st to end	Day	15% 34% 32% 14% 4	540
May	1st to 10th	Day	14% 31% 33% 16% 5% 1	543
	11th to 20th	Day	12% 24% 34% 22% 6% 2	591
	21st to end	Day	11% 23% 29% 23% 11% 3	844
June	1st to 10th	Day	5% 13% 33% 29% 16% 3	780
	11th to 20th	Day	6% 16% 37% 27% 11% 3	780
	21st to end	Day	4 17% 37% 26% 14% 3	780
July	1st to 10th	Day	3 7% 28% 39% 19% 4	753
	11th to 20th	Day	5% 5% 23% 38% 21% 7%	564
	21st to end	Day	7% 5% 27% 36% 21% 5%	619
August	1st to 10th	Day	9% 7% 31% 33% 16% 4	567
	11th to 20th	Day	7% 9% 29% 34% 16% 6%	557
	21st to end	Day	4 6% 34% 35% 15% 5%	627
September	1st to 10th	Day	8% 10% 32% 31% 16% 4	570
	11th to 20th	Day	6% 17% 40% 26% 8% 2	570
	21st to end	Day	8% 19% 29% 29% 12% 3	470
October	1st to 10th	Day	9% 23% 25% 23% 15% 4	330
	11th to 20th	Day	7% 27% 28% 26% 10% 2	330
	21st to end	Day	9% 24% 30% 27% 9% 1	363
November	1st to 10th	Day	9% 28% 29% 24% 9% 1	330
	11th to 20th	Day	7% 24% 33% 24% 12% 1	330
	21st to end	Day	8% 26% 33% 22% 9% 1	330
December	1st to 10th	Day	12% 21% 33% 24% 9% 1	330
	11th to 20th	Day	10% 23% 32% 23% 11% 1	330
	21st to end	Day	16% 23% 35% 20% 5% 1	363
January	1st to 10th	Night	8% 11% 33% 30% 14% 4	908
	11th to 20th	Night	7% 13% 32% 31% 15% 3	840
	21st to end	Night	5% 13% 33% 33% 12% 4	924
February	1st to 10th	Night	7% 18% 37% 28% 9% 2	840
	11th to 20th	Night	7% 18% 40% 25% 9% 1	824
	21st to end	Night	8% 16% 43% 25% 6%	692
March	1st to 10th	Night	8% 23% 33% 25% 9% 1	840
	11th to 20th	Night	5% 15% 35% 30% 15% 1	840
	21st to end	Night	8% 20% 35% 27% 9% 1	919
April	1st to 10th	Night	10% 19% 37% 27% 6%	630
	11th to 20th	Night	11% 21% 35% 26% 8% 1	623
	21st to end	Night	10% 17% 32% 28% 10% 2	630
May	1st to 10th	Night	6% 14% 38% 31% 11%	630
	11th to 20th	Night	7% 11% 33% 31% 15% 3	621
	21st to end	Night	7% 10% 33% 31% 16% 2	683
June	1st to 10th	Night	3 7% 29% 37% 22% 2	630
	11th to 20th	Night	3 10% 31% 37% 17% 3	630
	21st to end	Night	1 6% 24% 42% 23% 3	630
July	1st to 10th	Night	3 1 21% 41% 32% 3	615
	11th to 20th	Night	3 2 13% 41% 36% 5%	612
	21st to end	Night	3 3 9% 38% 42% 4	690
August	1st to 10th	Night	3 2 12% 42% 35% 5%	627
	11th to 20th	Night	3 2 13% 44% 33% 5%	624
	21st to end	Night	4 3 16% 43% 28% 6%	693
September	1st to 10th	Night	4 3 18% 45% 27% 3	630
	11th to 20th	Night	3 4 25% 38% 25% 4	639
	21st to end	Night	4 9% 22% 37% 20% 8%	832
October	1st to 10th	Night	6% 12% 27% 37% 16% 2	800
	11th to 20th	Night	5% 12% 28% 32% 19% 5%	800
	21st to end	Night	8% 11% 28% 31% 17% 5%	880
November	1st to 10th	Night	6% 13% 28% 33% 16% 4	822
	11th to 20th	Night	7% 12% 34% 30% 15% 3	1050
	21st to end	Night	8% 16% 28% 31% 13% 3	1050
December	1st to 10th	Night	8% 14% 33% 32% 12% 2	1050
	11th to 20th	Night	8% 18% 32% 26% 15% 1	1050
	21st to end	Night	9% 13% 38% 31% 8% 1	1155

Page generated at 2026-09-26 02:18:44. Version ac07

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