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 2024-11-02.

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 7% 3 7% 5% 5% 5% 4 6% 7% 48%	101185
	Night	2 7% 3 6% 4 4 4 4 6% 7% 53%	98039
Transparency	Day	35% 9% 9% 18% 20% 8%	100945
	Night	30% 7% 11% 22% 21% 9%	97868
Seeing	Day	10% 21% 31% 24% 11% 2	15281
	Night	7% 12% 28% 32% 18% 3	25405

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% 4 15% 7% 4 4 3 6% 6% 41%	2771
	11th to 20th	Day	2 11% 5% 10% 7% 6% 4 4 6% 7% 40%	2860
	21st to end	Day	1 11% 5% 11% 4 4 4 3 5% 5% 46%	3146
February	1st to 10th	Day	2 13% 5% 10% 5% 4 5% 4 6% 6% 41%	1710
	11th to 20th	Day	2 9% 4 9% 6% 5% 4 4 6% 7% 44%	1703
	21st to end	Day	1 10% 6% 11% 6% 5% 4 4 5% 5% 43%	1570
March	1st to 10th	Day	2 9% 4 10% 4 4 4 4 6% 7% 45%	3441
	11th to 20th	Day	1 13% 4 10% 6% 5% 5% 5% 7% 7% 36%	3490
	21st to end	Day	1 10% 6% 10% 7% 7% 7% 6% 7% 8% 32%	3841
April	1st to 10th	Day	3 10% 2 7% 5% 4 4 5% 6% 7% 48%	2280
	11th to 20th	Day	2 12% 4 8% 4 5% 5% 5% 6% 7% 42%	2251
	21st to end	Day	3 12% 3 6% 5% 5% 4 3 5% 8% 45%	2280
May	1st to 10th	Day	3 8% 3 7% 5% 5% 5% 4 6% 7% 46%	4037
	11th to 20th	Day	3 6% 2 7% 6% 5% 6% 6% 8% 9% 44%	4118
	21st to end	Day	3 5% 2 6% 5% 5% 5% 5% 6% 8% 49%	4825
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	5% 6% 1 4 4 4 4 3 6% 6% 58%	1900
	11th to 20th	Day	4 5% 2 3 3 3 3 3 4 6% 65%	1900
	21st to end	Day	3 8% 2 4 3 3 3 3 3 5% 62%	2090
November	1st to 10th	Day	2 4 2 4 3 2 2 2 5% 6% 68%	1846
	11th to 20th	Day	2 8% 2 5% 2 3 3 3 5% 5% 62%	1687
	21st to end	Day	2 6% 3 8% 3 3 4 3 3 6% 59%	1520
December	1st to 10th	Day	2 9% 4 8% 6% 3 4 3 5% 6% 50%	1520
	11th to 20th	Day	2 10% 4 11% 5% 4 4 4 5% 7% 44%	1926
	21st to end	Day	1 8% 3 10% 6% 5% 4 4 5% 6% 48%	2794
January	1st to 10th	Night	1 8% 5% 17% 6% 5% 5% 3 4 5% 41%	4211
	11th to 20th	Night	1 13% 5% 8% 6% 6% 5% 4 5% 7% 40%	4110
	21st to end	Night	1 11% 5% 11% 4 4 4 3 5% 5% 47%	4521
February	1st to 10th	Night	2 10% 5% 10% 4 4 4 2 4 6% 48%	2470
	11th to 20th	Night	2 8% 4 8% 5% 5% 5% 4 5% 7% 48%	2364
	21st to end	Night	1 11% 4 9% 6% 4 3 4 5% 6% 47%	1884
March	1st to 10th	Night	1 9% 3 8% 5% 5% 5% 4 5% 7% 48%	3430
	11th to 20th	Night	1 10% 4 8% 5% 5% 5% 5% 7% 7% 44%	3490
	21st to end	Night	1 11% 5% 9% 5% 5% 7% 6% 9% 7% 35%	3811
April	1st to 10th	Night	3 8% 3 7% 4 4 5% 4 7% 7% 48%	1900
	11th to 20th	Night	2 12% 4 6% 4 4 4 4 7% 7% 46%	1877
	21st to end	Night	4 10% 3 5% 3 3 4 5% 5% 7% 51%	1900
May	1st to 10th	Night	3 8% 2 5% 4 4 4 4 7% 7% 54%	2930
	11th to 20th	Night	3 5% 1 4 3 4 4 4 7% 10% 55%	2785
	21st to end	Night	3 3 1 3 3 4 3 3 5% 6% 67%	2762
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	4 4 1 3 3 3 3 2 4 7% 65%	2280
	11th to 20th	Night	2 3 1 3 3 1 3 3 4 6% 71%	2280
	21st to end	Night	4 7% 2 4 2 2 3 2 3 5% 65%	2508
November	1st to 10th	Night	2 5% 1 3 2 3 3 3 5% 7% 66%	2233
	11th to 20th	Night	2 8% 2 4 3 3 3 2 5% 5% 63%	2492
	21st to end	Night	2 8% 4 6% 3 3 3 3 4 6% 57%	2660
December	1st to 10th	Night	2 8% 3 6% 4 4 4 3 5% 6% 55%	2660
	11th to 20th	Night	1 9% 3 8% 5% 5% 5% 5% 6% 8% 45%	3271
	21st to end	Night	1 7% 4 11% 6% 4 4 3 5% 5% 49%	4873

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	43% 7% 13% 16% 17% 4	2772
	11th to 20th	Day	45% 7% 13% 21% 11% 2	2860
	21st to end	Day	42% 6% 7% 24% 16% 4	3146
February	1st to 10th	Day	46% 6% 12% 15% 14% 6%	1710
	11th to 20th	Day	42% 6% 7% 19% 19% 7%	1712
	21st to end	Day	45% 5% 6% 18% 19% 7%	1570
March	1st to 10th	Day	38% 8% 7% 22% 20% 6%	3441
	11th to 20th	Day	46% 8% 12% 23% 9% 2	3490
	21st to end	Day	51% 10% 8% 17% 12% 2	3841
April	1st to 10th	Day	38% 8% 8% 21% 19% 6%	2280
	11th to 20th	Day	42% 9% 7% 19% 18% 4	2254
	21st to end	Day	39% 8% 9% 26% 16% 2	2280
May	1st to 10th	Day	37% 8% 8% 19% 21% 6%	4037
	11th to 20th	Day	33% 11% 10% 23% 20% 3	4121
	21st to end	Day	30% 9% 8% 21% 28% 5%	4825
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	31% 8% 7% 20% 25% 10%	1900
	11th to 20th	Day	23% 5% 5% 26% 32% 9%	1900
	21st to end	Day	27% 5% 8% 27% 27% 6%	2090
November	1st to 10th	Day	21% 5% 11% 24% 32% 7%	1846
	11th to 20th	Day	26% 3 10% 30% 25% 7%	1687
	21st to end	Day	30% 5% 9% 24% 21% 11%	1520
December	1st to 10th	Day	37% 6% 12% 24% 16% 5%	1520
	11th to 20th	Day	42% 6% 9% 19% 22% 3	1924
	21st to end	Day	35% 7% 9% 18% 21% 11%	2794
January	1st to 10th	Night	45% 5% 9% 21% 14% 6%	4211
	11th to 20th	Night	45% 7% 11% 22% 13% 3	4110
	21st to end	Night	39% 5% 8% 26% 18% 4	4521
February	1st to 10th	Night	41% 5% 11% 19% 17% 7%	2470
	11th to 20th	Night	37% 5% 9% 23% 19% 7%	2365
	21st to end	Night	39% 5% 8% 19% 22% 6%	1884
March	1st to 10th	Night	32% 7% 8% 23% 26% 4	3430
	11th to 20th	Night	36% 8% 13% 28% 13% 2	3490
	21st to end	Night	45% 11% 12% 20% 11% 2	3811
April	1st to 10th	Night	35% 8% 10% 23% 19% 5%	1900
	11th to 20th	Night	37% 8% 11% 20% 21% 4	1877
	21st to end	Night	34% 8% 10% 28% 18% 2	1900
May	1st to 10th	Night	29% 7% 9% 24% 28% 3	2930
	11th to 20th	Night	22% 8% 11% 34% 23% 1	2786
	21st to end	Night	18% 7% 9% 24% 34% 9%	2762
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	23% 5% 10% 22% 28% 12%	2280
	11th to 20th	Night	17% 6% 8% 26% 32% 11%	2280
	21st to end	Night	24% 4 8% 29% 27% 8%	2508
November	1st to 10th	Night	20% 7% 12% 24% 27% 10%	2233
	11th to 20th	Night	25% 4 10% 26% 27% 8%	2492
	21st to end	Night	30% 5% 7% 22% 24% 12%	2660
December	1st to 10th	Night	32% 5% 14% 21% 20% 7%	2660
	11th to 20th	Night	36% 7% 10% 20% 21% 6%	3272
	21st to end	Night	38% 6% 9% 15% 21% 12%	4873

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	14% 19% 33% 21% 12% 1	270
	11th to 20th	Day	13% 27% 31% 21% 7% 1	270
	21st to end	Day	4 21% 41% 25% 7% 1	297
February	1st to 10th	Day	14% 34% 30% 18% 3 1	270
	11th to 20th	Day	15% 36% 33% 12% 4	270
	21st to end	Day	21% 34% 28% 14% 3	225
March	1st to 10th	Day	18% 35% 28% 15% 3	457
	11th to 20th	Day	13% 32% 30% 19% 5%	460
	21st to end	Day	21% 38% 27% 12% 2	506
April	1st to 10th	Day	17% 31% 33% 14% 3 1	460
	11th to 20th	Day	21% 37% 28% 11% 3	452
	21st to end	Day	16% 33% 33% 14% 4	460
May	1st to 10th	Day	16% 33% 33% 13% 4	463
	11th to 20th	Day	12% 23% 35% 21% 7% 1	509
	21st to end	Day	12% 24% 29% 21% 10% 3	734
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	11% 31% 27% 22% 8% 1	273
	11th to 20th	Day	6% 25% 33% 22% 13% 1	270
	21st to end	Day	8% 26% 30% 23% 11% 1	270
December	1st to 10th	Day	13% 24% 31% 22% 9% 1	270
	11th to 20th	Day	12% 24% 30% 23% 10% 1	270
	21st to end	Day	18% 22% 35% 19% 6% 1	297
January	1st to 10th	Night	8% 12% 30% 31% 15% 4	822
	11th to 20th	Night	8% 14% 30% 29% 16% 3	760
	21st to end	Night	5% 13% 30% 34% 14% 4	836
February	1st to 10th	Night	8% 17% 36% 29% 9% 2	760
	11th to 20th	Night	7% 17% 38% 27% 10% 1	744
	21st to end	Night	9% 18% 42% 24% 7%	628
March	1st to 10th	Night	9% 23% 32% 25% 9% 2	760
	11th to 20th	Night	5% 15% 33% 31% 16% 1	760
	21st to end	Night	9% 22% 32% 26% 10% 1	831
April	1st to 10th	Night	10% 20% 36% 27% 6% 1	570
	11th to 20th	Night	11% 20% 33% 26% 8% 1	563
	21st to end	Night	11% 19% 30% 27% 11% 2	570
May	1st to 10th	Night	6% 15% 37% 30% 11% 1	570
	11th to 20th	Night	7% 10% 31% 32% 16% 4	561
	21st to end	Night	8% 11% 32% 29% 17% 2	617
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% 25% 32% 18% 4	745
	11th to 20th	Night	7% 13% 32% 29% 16% 3	950
	21st to end	Night	8% 17% 27% 31% 14% 3	950
December	1st to 10th	Night	9% 14% 32% 31% 12% 2	950
	11th to 20th	Night	9% 19% 31% 25% 15% 1	950
	21st to end	Night	9% 13% 37% 31% 8% 1	1045

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