Black Canyon of the Gunnison
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Black Canyon of the Gunnison clear sky chart from 2005-11-06 to 2024-11-03.

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	5% 8% 3 6% 4 4 4 4 6% 7% 50%	101246
	Night	6% 10% 3 6% 4 3 4 3 5% 6% 50%	98000
Transparency	Day	30% 8% 9% 21% 22% 10%	101004
	Night	33% 7% 9% 22% 21% 9%	97831
Seeing	Day	9% 12% 28% 33% 16% 2	15339
	Night	10% 6% 22% 42% 19% 1	25456

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	4 10% 4 13% 5% 5% 5% 4 6% 6% 37%	2727
	11th to 20th	Day	7% 17% 4 10% 4 3 3 4 6% 5% 36%	2860
	21st to end	Day	4 13% 5% 8% 4 3 3 2 5% 6% 48%	3146
February	1st to 10th	Day	8% 12% 5% 8% 5% 4 4 3 6% 6% 41%	1710
	11th to 20th	Day	7% 15% 5% 7% 4 3 4 3 6% 6% 40%	1697
	21st to end	Day	5% 16% 6% 10% 5% 3 4 3 5% 5% 40%	1570
March	1st to 10th	Day	5% 16% 5% 8% 4 3 4 3 6% 6% 40%	3430
	11th to 20th	Day	3 11% 4 8% 5% 4 5% 4 6% 7% 44%	3490
	21st to end	Day	5% 17% 5% 10% 6% 5% 5% 4 6% 6% 32%	3845
April	1st to 10th	Day	7% 11% 3 6% 4 4 4 4 4 7% 46%	2280
	11th to 20th	Day	7% 12% 4 7% 5% 5% 4 3 6% 6% 42%	2251
	21st to end	Day	6% 9% 3 6% 4 4 5% 4 6% 8% 45%	2280
May	1st to 10th	Day	6% 14% 3 7% 5% 5% 4 4 5% 6% 41%	4062
	11th to 20th	Day	4 5% 2 5% 4 5% 6% 5% 7% 9% 49%	4161
	21st to end	Day	6% 6% 1 4 3 4 4 4 6% 6% 55%	4825
June	1st to 10th	Day	3 4 1 3 3 3 4 4 6% 8% 60%	2660
	11th to 20th	Day	4 3 1 4 3 3 4 3 5% 6% 64%	2660
	21st to end	Day	2 3 1 4 3 4 5% 4 6% 7% 62%	2660
July	1st to 10th	Day	2 3 1 4 2 3 3 3 4 5% 69%	4430
	11th to 20th	Day	2 2 1 3 3 4 6% 6% 10% 13% 50%	4149
	21st to end	Day	3 3 1 4 4 4 5% 4 7% 8% 57%	4454
August	1st to 10th	Day	4 3 1 5% 4 5% 6% 7% 10% 12% 42%	4092
	11th to 20th	Day	4 3 1 5% 4 5% 5% 5% 7% 8% 53%	3918
	21st to end	Day	3 3 2 5% 4 4 6% 5% 8% 10% 51%	4180
September	1st to 10th	Day	5% 3 1 4 3 4 4 5% 6% 7% 58%	2280
	11th to 20th	Day	5% 4 1 4 3 3 4 4 5% 7% 60%	2273
	21st to end	Day	5% 4 1 4 3 3 3 2 4 6% 65%	2001
October	1st to 10th	Day	8% 5% 1 4 3 3 3 3 5% 6% 60%	1900
	11th to 20th	Day	5% 4 1 4 3 2 3 3 4 5% 65%	1900
	21st to end	Day	7% 7% 2 4 3 3 2 2 4 5% 61%	2090
November	1st to 10th	Day	4 6% 2 4 3 2 3 2 5% 6% 64%	1835
	11th to 20th	Day	8% 7% 2 5% 3 3 2 2 4 4 60%	1670
	21st to end	Day	5% 10% 3 8% 3 2 3 3 4 4 57%	1520
December	1st to 10th	Day	8% 13% 3 7% 4 3 2 2 3 4 50%	1520
	11th to 20th	Day	7% 13% 4 9% 4 4 4 3 4 6% 43%	1926
	21st to end	Day	5% 12% 4 9% 4 3 4 3 5% 6% 43%	2794
January	1st to 10th	Night	4 13% 8% 12% 4 4 4 3 4 4 39%	4257
	11th to 20th	Night	6% 21% 6% 7% 4 3 3 3 4 6% 37%	4110
	21st to end	Night	5% 16% 5% 9% 4 3 3 2 4 5% 44%	4521
February	1st to 10th	Night	7% 15% 3 8% 4 3 3 3 4 5% 45%	2470
	11th to 20th	Night	6% 13% 4 9% 4 3 3 4 6% 5% 44%	2369
	21st to end	Night	5% 16% 4 7% 3 4 4 3 4 5% 44%	1884
March	1st to 10th	Night	5% 18% 4 7% 5% 4 3 3 5% 4 43%	3440
	11th to 20th	Night	4 14% 4 7% 4 4 4 4 5% 6% 45%	3490
	21st to end	Night	7% 20% 5% 8% 5% 5% 4 3 5% 5% 32%	3807
April	1st to 10th	Night	8% 13% 4 6% 6% 4 2 3 5% 5% 44%	1900
	11th to 20th	Night	8% 12% 4 8% 4 4 3 3 5% 5% 44%	1877
	21st to end	Night	11% 9% 2 5% 4 3 3 3 6% 5% 48%	1900
May	1st to 10th	Night	10% 12% 2 5% 4 4 3 4 6% 6% 43%	2905
	11th to 20th	Night	6% 5% 2 6% 4 3 5% 4 5% 8% 51%	2739
	21st to end	Night	8% 5% 1 4 3 2 3 3 4 6% 60%	2762
June	1st to 10th	Night	3 3 2 4 4 3 5% 4 5% 7% 61%	1520
	11th to 20th	Night	4 3 2 3 3 3 2 3 4 5% 67%	1520
	21st to end	Night	3 2 1 3 3 4 4 4 6% 8% 63%	1520
July	1st to 10th	Night	2 2 1 3 3 3 4 3 5% 6% 69%	2540
	11th to 20th	Night	1 2 1 4 4 4 4 5% 10% 12% 53%	2817
	21st to end	Night	2 3 2 5% 4 5% 5% 4 7% 9% 55%	3109
August	1st to 10th	Night	4 4 2 7% 5% 6% 7% 6% 9% 10% 40%	2847
	11th to 20th	Night	3 3 1 5% 4 4 6% 5% 7% 9% 53%	2921
	21st to end	Night	4 4 1 6% 5% 5% 5% 4 7% 8% 50%	3487
September	1st to 10th	Night	4 4 2 5% 3 4 4 4 6% 7% 59%	1900
	11th to 20th	Night	5% 4 1 4 4 3 4 3 5% 7% 61%	1904
	21st to end	Night	6% 3 1 4 2 3 2 2 3 5% 69%	2177
October	1st to 10th	Night	8% 5% 1 3 3 3 3 2 5% 6% 61%	2280
	11th to 20th	Night	5% 4 2 4 3 3 3 2 3 6% 66%	2280
	21st to end	Night	8% 7% 2 4 2 3 2 2 3 5% 63%	2508
November	1st to 10th	Night	5% 6% 2 3 3 2 2 3 4 5% 63%	2267
	11th to 20th	Night	8% 8% 2 3 3 2 2 3 4 5% 61%	2508
	21st to end	Night	6% 10% 3 5% 3 3 3 3 4 5% 55%	2660
December	1st to 10th	Night	9% 12% 3 6% 3 2 3 3 4 5% 51%	2660
	11th to 20th	Night	7% 14% 4 7% 5% 3 3 3 5% 8% 40%	3271
	21st to end	Night	5% 14% 6% 8% 4 3 3 2 4 6% 45%	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	40% 13% 13% 21% 12% 1	2728
	11th to 20th	Day	44% 11% 16% 19% 9% 1	2860
	21st to end	Day	36% 9% 11% 31% 10% 2	3146
February	1st to 10th	Day	45% 8% 13% 19% 12% 3	1710
	11th to 20th	Day	43% 7% 7% 24% 17% 3	1706
	21st to end	Day	46% 7% 4 21% 18% 3	1570
March	1st to 10th	Day	37% 13% 6% 23% 17% 4	3430
	11th to 20th	Day	35% 7% 10% 35% 10% 2	3490
	21st to end	Day	44% 16% 6% 20% 13% 2	3845
April	1st to 10th	Day	36% 7% 7% 23% 20% 6%	2280
	11th to 20th	Day	40% 7% 7% 21% 21% 4	2254
	21st to end	Day	35% 9% 7% 25% 22% 3	2280
May	1st to 10th	Day	36% 14% 6% 16% 23% 5%	4062
	11th to 20th	Day	27% 10% 7% 27% 25% 4	4164
	21st to end	Day	25% 10% 5% 18% 35% 7%	4825
June	1st to 10th	Day	21% 6% 6% 22% 30% 15%	2660
	11th to 20th	Day	21% 5% 5% 12% 29% 28%	2660
	21st to end	Day	19% 6% 5% 16% 27% 28%	2660
July	1st to 10th	Day	17% 5% 5% 9% 20% 43%	4361
	11th to 20th	Day	19% 7% 10% 26% 25% 12%	4078
	21st to end	Day	21% 7% 11% 19% 19% 22%	4314
August	1st to 10th	Day	26% 11% 19% 19% 14% 11%	4078
	11th to 20th	Day	26% 8% 11% 16% 26% 13%	3957
	21st to end	Day	24% 9% 11% 18% 24% 13%	4179
September	1st to 10th	Day	25% 7% 7% 14% 29% 18%	2280
	11th to 20th	Day	23% 7% 8% 18% 29% 15%	2273
	21st to end	Day	22% 5% 4 18% 39% 12%	2001
October	1st to 10th	Day	26% 6% 7% 25% 26% 11%	1900
	11th to 20th	Day	22% 5% 5% 26% 34% 8%	1900
	21st to end	Day	26% 6% 8% 30% 25% 5%	2090
November	1st to 10th	Day	22% 5% 8% 26% 33% 4	1835
	11th to 20th	Day	29% 5% 8% 32% 23% 3	1670
	21st to end	Day	32% 5% 9% 27% 23% 4	1520
December	1st to 10th	Day	40% 5% 15% 22% 15% 3	1520
	11th to 20th	Day	43% 6% 8% 26% 17% 1	1924
	21st to end	Day	38% 10% 10% 16% 22% 4	2794
January	1st to 10th	Night	45% 9% 10% 21% 14% 1	4257
	11th to 20th	Night	45% 10% 15% 20% 9% 1	4110
	21st to end	Night	42% 8% 13% 25% 11% 2	4521
February	1st to 10th	Night	42% 6% 14% 21% 16% 2	2470
	11th to 20th	Night	40% 7% 9% 25% 17% 2	2370
	21st to end	Night	42% 6% 5% 24% 20% 3	1884
March	1st to 10th	Night	40% 10% 4 23% 21% 3	3440
	11th to 20th	Night	36% 8% 10% 31% 13% 2	3490
	21st to end	Night	47% 12% 8% 19% 12% 1	3807
April	1st to 10th	Night	41% 6% 6% 20% 20% 6%	1900
	11th to 20th	Night	41% 7% 6% 18% 22% 6%	1877
	21st to end	Night	36% 6% 8% 23% 24% 3	1900
May	1st to 10th	Night	35% 10% 7% 20% 24% 5%	2905
	11th to 20th	Night	27% 9% 9% 30% 22% 3	2740
	21st to end	Night	24% 7% 6% 17% 36% 11%	2762
June	1st to 10th	Night	20% 7% 6% 18% 31% 18%	1520
	11th to 20th	Night	19% 4 6% 15% 22% 34%	1520
	21st to end	Night	17% 6% 6% 17% 25% 30%	1520
July	1st to 10th	Night	17% 5% 8% 9% 18% 43%	2500
	11th to 20th	Night	19% 7% 11% 31% 15% 17%	2765
	21st to end	Night	22% 8% 14% 19% 18% 19%	3011
August	1st to 10th	Night	33% 10% 21% 14% 12% 12%	2838
	11th to 20th	Night	26% 7% 18% 13% 17% 19%	2948
	21st to end	Night	28% 8% 11% 17% 22% 14%	3487
September	1st to 10th	Night	23% 7% 8% 16% 24% 22%	1900
	11th to 20th	Night	23% 6% 10% 16% 27% 18%	1904
	21st to end	Night	20% 4 4 19% 39% 14%	2177
October	1st to 10th	Night	24% 5% 7% 24% 27% 13%	2280
	11th to 20th	Night	22% 5% 6% 23% 33% 11%	2280
	21st to end	Night	26% 5% 6% 29% 29% 5%	2508
November	1st to 10th	Night	23% 5% 8% 28% 29% 6%	2267
	11th to 20th	Night	27% 4 9% 31% 25% 4	2508
	21st to end	Night	31% 5% 6% 26% 27% 4	2660
December	1st to 10th	Night	36% 5% 14% 24% 18% 2	2660
	11th to 20th	Night	41% 6% 9% 23% 20% 1	3272
	21st to end	Night	40% 7% 9% 17% 24% 2	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	16% 8% 31% 31% 13% 1	270
	11th to 20th	Day	12% 16% 35% 27% 10%	270
	21st to end	Day	10% 7% 32% 37% 13% 1	297
February	1st to 10th	Day	13% 17% 36% 27% 5% 2	270
	11th to 20th	Day	18% 14% 38% 24% 5% 1	270
	21st to end	Day	13% 20% 38% 23% 5% 1	225
March	1st to 10th	Day	16% 20% 29% 25% 9% 1	446
	11th to 20th	Day	12% 18% 28% 29% 13%	460
	21st to end	Day	18% 23% 33% 20% 6%	506
April	1st to 10th	Day	14% 19% 32% 22% 12% 2	460
	11th to 20th	Day	16% 23% 32% 20% 8% 1	452
	21st to end	Day	15% 20% 33% 22% 9% 1	460
May	1st to 10th	Day	15% 19% 32% 25% 8%	463
	11th to 20th	Day	9% 13% 30% 29% 17% 2	539
	21st to end	Day	10% 16% 27% 31% 15% 2	734
June	1st to 10th	Day	5% 10% 29% 34% 21% 2	680
	11th to 20th	Day	6% 12% 34% 30% 16% 1	680
	21st to end	Day	3 11% 28% 41% 16% 1	680
July	1st to 10th	Day	3 6% 19% 47% 21% 3	671
	11th to 20th	Day	4 4 16% 44% 29% 4	508
	21st to end	Day	5% 5% 17% 39% 30% 4	531
August	1st to 10th	Day	5% 8% 21% 43% 20% 4	487
	11th to 20th	Day	5% 5% 24% 40% 24% 3	477
	21st to end	Day	4 4 21% 46% 24% 2	539
September	1st to 10th	Day	6% 6% 25% 38% 23% 3	490
	11th to 20th	Day	6% 8% 33% 39% 13% 2	490
	21st to end	Day	7% 10% 25% 34% 21% 1	401
October	1st to 10th	Day	9% 11% 22% 32% 23% 3	300
	11th to 20th	Day	5% 16% 29% 30% 18% 2	300
	21st to end	Day	10% 11% 30% 33% 15% 1	330
November	1st to 10th	Day	8% 17% 29% 30% 14% 1	276
	11th to 20th	Day	7% 11% 34% 32% 14% 2	270
	21st to end	Day	12% 11% 31% 29% 14% 2	270
December	1st to 10th	Day	10% 14% 35% 29% 10% 1	270
	11th to 20th	Day	12% 10% 32% 31% 13% 1	270
	21st to end	Day	13% 13% 37% 26% 10% 1	297
January	1st to 10th	Night	13% 7% 23% 40% 16% 1	855
	11th to 20th	Night	12% 9% 22% 41% 14% 1	760
	21st to end	Night	12% 7% 24% 43% 12% 1	836
February	1st to 10th	Night	13% 9% 28% 40% 9%	760
	11th to 20th	Night	11% 8% 28% 42% 11%	744
	21st to end	Night	14% 7% 32% 39% 7%	628
March	1st to 10th	Night	13% 9% 28% 39% 11% 1	760
	11th to 20th	Night	7% 8% 25% 42% 18%	760
	21st to end	Night	16% 9% 25% 38% 12%	827
April	1st to 10th	Night	13% 11% 28% 39% 9%	570
	11th to 20th	Night	14% 10% 24% 38% 12% 1	563
	21st to end	Night	13% 9% 25% 36% 15% 1	570
May	1st to 10th	Night	13% 7% 26% 39% 13% 1	570
	11th to 20th	Night	10% 4 24% 41% 19% 3	561
	21st to end	Night	8% 8% 26% 36% 20% 2	617
June	1st to 10th	Night	3 5% 22% 42% 26% 2	570
	11th to 20th	Night	5% 4 23% 46% 19% 2	570
	21st to end	Night	4 3 17% 46% 28% 2	570
July	1st to 10th	Night	4 1 12% 46% 33% 2	555
	11th to 20th	Night	3 1 10% 41% 41% 4	552
	21st to end	Night	4 2 10% 42% 40% 2	624
August	1st to 10th	Night	6% 3 12% 40% 37% 3	567
	11th to 20th	Night	4 3 11% 45% 34% 2	564
	21st to end	Night	6% 3 12% 42% 34% 4	627
September	1st to 10th	Night	4 4 13% 49% 29% 1	570
	11th to 20th	Night	6% 3 17% 43% 29% 2	574
	21st to end	Night	7% 4 18% 41% 26% 3	760
October	1st to 10th	Night	9% 4 20% 46% 20% 1	760
	11th to 20th	Night	6% 6% 20% 44% 21% 3	760
	21st to end	Night	12% 4 20% 41% 20% 2	836
November	1st to 10th	Night	7% 5% 23% 44% 19% 2	771
	11th to 20th	Night	11% 6% 22% 42% 18% 2	950
	21st to end	Night	11% 8% 23% 42% 16% 1	950
December	1st to 10th	Night	13% 7% 23% 44% 12% 1	950
	11th to 20th	Night	15% 9% 25% 37% 13%	950
	21st to end	Night	13% 9% 28% 41% 8%	1045

Page generated at 2024-10-31 01:39:20. Version ac07

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