Black Kettle National Grasslands
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Black Kettle National Grasslands clear sky chart from 2005-11-06 to 2024-12-09.

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	6% 5% 2 4 3 3 4 3 5% 7% 58%	105302
	Night	6% 4 2 4 3 3 3 3 5% 7% 59%	103118
Transparency	Day	27% 3 8% 25% 27% 10%	105068
	Night	26% 3 8% 24% 27% 12%	102941
Seeing	Day	9% 9% 29% 32% 18% 4	15480
	Night	9% 9% 35% 35% 11% 1	25433

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	6% 7% 2 6% 4 4 4 3 4 5% 56%	2847
	11th to 20th	Day	5% 5% 2 4 3 4 4 2 4 6% 63%	2850
	21st to end	Day	11% 9% 2 5% 3 3 3 2 4 5% 53%	3213
February	1st to 10th	Day	7% 7% 2 6% 3 3 2 2 4 7% 55%	1900
	11th to 20th	Day	6% 6% 2 5% 3 3 3 2 4 6% 59%	1849
	21st to end	Day	5% 6% 2 4 3 3 2 3 4 6% 60%	1570
March	1st to 10th	Day	7% 5% 2 4 2 2 3 3 4 6% 63%	3156
	11th to 20th	Day	7% 5% 2 4 3 3 3 3 4 6% 59%	3480
	21st to end	Day	8% 8% 3 7% 4 4 4 4 5% 6% 47%	3814
April	1st to 10th	Day	8% 4 1 3 3 2 3 3 5% 7% 61%	2204
	11th to 20th	Day	11% 5% 2 5% 3 4 4 3 4 6% 52%	2251
	21st to end	Day	10% 4 2 4 3 4 3 3 5% 6% 56%	2437
May	1st to 10th	Day	12% 6% 2 5% 4 4 3 3 4 6% 51%	4120
	11th to 20th	Day	9% 5% 2 5% 4 3 3 4 5% 7% 54%	4082
	21st to end	Day	9% 6% 2 5% 4 4 3 3 5% 6% 54%	4489
June	1st to 10th	Day	6% 3 2 4 3 4 5% 5% 7% 9% 52%	2470
	11th to 20th	Day	4 4 2 4 3 4 3 3 5% 9% 59%	2470
	21st to end	Day	5% 4 1 3 4 4 4 4 6% 7% 59%	2470
July	1st to 10th	Day	7% 5% 2 5% 5% 4 5% 5% 7% 8% 48%	4120
	11th to 20th	Day	3 3 1 4 4 4 4 4 6% 9% 58%	4120
	21st to end	Day	2 3 1 3 3 3 4 4 6% 10% 61%	4466
August	1st to 10th	Day	5% 3 2 5% 4 4 4 4 6% 8% 56%	4103
	11th to 20th	Day	4 3 1 4 3 3 3 4 6% 8% 60%	3803
	21st to end	Day	4 3 1 3 3 3 3 3 6% 9% 63%	4180
September	1st to 10th	Day	8% 4 1 4 4 3 4 3 4 6% 58%	2162
	11th to 20th	Day	8% 5% 2 5% 3 4 5% 3 6% 6% 54%	2090
	21st to end	Day	6% 3 1 4 3 3 4 3 5% 6% 63%	2090
October	1st to 10th	Day	6% 3 1 3 2 2 2 1 3 5% 73%	3480
	11th to 20th	Day	5% 3 1 3 2 3 3 2 4 6% 69%	3283
	21st to end	Day	5% 3 1 3 2 2 2 2 4 6% 70%	3292
November	1st to 10th	Day	6% 4 1 4 2 2 2 2 4 6% 67%	1763
	11th to 20th	Day	4 4 2 4 3 2 2 3 4 5% 69%	1800
	21st to end	Day	8% 5% 2 3 3 2 3 2 4 6% 62%	1800
December	1st to 10th	Day	6% 4 2 5% 3 3 3 3 5% 6% 61%	1782
	11th to 20th	Day	7% 6% 2 4 4 3 4 3 4 5% 58%	2161
	21st to end	Day	6% 8% 3 7% 5% 5% 5% 3 5% 6% 47%	3135
January	1st to 10th	Night	7% 6% 2 6% 4 4 4 3 5% 5% 54%	4108
	11th to 20th	Night	3 4 1 4 3 3 4 3 5% 7% 62%	4120
	21st to end	Night	11% 11% 2 5% 3 2 2 2 4 5% 53%	4468
February	1st to 10th	Night	8% 8% 3 6% 3 3 3 2 3 6% 55%	2280
	11th to 20th	Night	8% 6% 2 5% 3 4 3 2 4 6% 56%	2218
	21st to end	Night	6% 6% 2 5% 4 2 3 4 5% 6% 57%	1884
March	1st to 10th	Night	4 5% 2 5% 4 3 3 2 5% 6% 62%	3706
	11th to 20th	Night	8% 4 1 4 3 3 4 2 4 6% 61%	3480
	21st to end	Night	7% 5% 2 6% 4 3 4 3 5% 7% 53%	3817
April	1st to 10th	Night	5% 4 2 4 2 4 3 3 5% 6% 61%	1971
	11th to 20th	Night	8% 5% 2 4 3 3 4 3 6% 7% 55%	1877
	21st to end	Night	11% 5% 1 3 3 2 3 3 6% 7% 56%	1743
May	1st to 10th	Night	14% 7% 2 5% 3 3 2 2 4 5% 53%	2850
	11th to 20th	Night	8% 5% 2 5% 4 4 4 4 5% 8% 51%	2823
	21st to end	Night	9% 4 2 4 2 2 4 3 5% 7% 58%	3098
June	1st to 10th	Night	4 3 1 3 4 4 4 5% 8% 10% 55%	1710
	11th to 20th	Night	4 3 1 3 3 3 5% 4 7% 11% 56%	1710
	21st to end	Night	4 3 1 4 2 4 4 3 7% 8% 60%	1710
July	1st to 10th	Night	7% 3 2 5% 3 4 4 4 5% 9% 55%	2850
	11th to 20th	Night	3 2 1 4 3 4 4 4 8% 12% 56%	2850
	21st to end	Night	2 2 1 4 3 3 4 3 6% 10% 63%	3097
August	1st to 10th	Night	2 2 1 4 3 4 5% 4 7% 12% 56%	2836
	11th to 20th	Night	4 3 1 4 3 4 5% 4 8% 13% 51%	3019
	21st to end	Night	3 2 1 4 3 3 4 4 6% 8% 63%	3487
September	1st to 10th	Night	7% 3 1 4 3 3 3 3 5% 7% 62%	2016
	11th to 20th	Night	10% 6% 1 4 3 3 4 3 5% 8% 53%	2090
	21st to end	Night	5% 4 2 4 3 3 2 3 4 7% 63%	2090
October	1st to 10th	Night	4 2 1 2 2 2 2 2 4 5% 73%	3480
	11th to 20th	Night	5% 2 1 3 2 2 2 2 4 6% 71%	3601
	21st to end	Night	5% 2 1 2 2 1 2 2 4 7% 73%	4245
November	1st to 10th	Night	6% 3 1 3 2 2 3 2 5% 6% 68%	2535
	11th to 20th	Night	4 3 1 3 2 3 3 2 3 5% 70%	2600
	21st to end	Night	8% 4 2 4 3 3 3 2 4 5% 63%	2600
December	1st to 10th	Night	7% 4 1 4 3 2 3 3 4 6% 63%	2581
	11th to 20th	Night	7% 6% 2 5% 4 3 3 3 4 7% 57%	3036
	21st to end	Night	8% 7% 2 5% 3 4 4 4 5% 6% 52%	4532

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	34% 1 5% 22% 30% 8%	2848
	11th to 20th	Day	25% 1 10% 24% 32% 7%	2850
	21st to end	Day	36% 1 4 24% 30% 5%	3213
February	1st to 10th	Day	31% 2 8% 26% 25% 9%	1900
	11th to 20th	Day	29% 2 6% 27% 25% 11%	1859
	21st to end	Day	26% 1 4 23% 31% 15%	1570
March	1st to 10th	Day	25% 1 7% 17% 23% 27%	3156
	11th to 20th	Day	29% 1 7% 25% 29% 10%	3480
	21st to end	Day	39% 1 7% 26% 21% 6%	3814
April	1st to 10th	Day	25% 2 8% 23% 26% 16%	2204
	11th to 20th	Day	34% 3 6% 23% 22% 13%	2254
	21st to end	Day	31% 3 9% 26% 25% 7%	2437
May	1st to 10th	Day	36% 2 9% 19% 20% 14%	4120
	11th to 20th	Day	32% 2 11% 28% 21% 6%	4086
	21st to end	Day	33% 2 9% 20% 19% 17%	4489
June	1st to 10th	Day	28% 4 16% 29% 15% 8%	2470
	11th to 20th	Day	24% 3 11% 27% 26% 9%	2470
	21st to end	Day	23% 4 11% 27% 23% 11%	2470
July	1st to 10th	Day	32% 6% 9% 29% 20% 6%	4056
	11th to 20th	Day	22% 4 11% 30% 28% 5%	4051
	21st to end	Day	18% 5% 11% 32% 30% 4	4325
August	1st to 10th	Day	26% 4 9% 27% 27% 7%	4090
	11th to 20th	Day	21% 5% 9% 27% 29% 8%	3841
	21st to end	Day	20% 4 11% 32% 28% 5%	4179
September	1st to 10th	Day	28% 3 10% 23% 23% 14%	2162
	11th to 20th	Day	30% 4 9% 23% 29% 6%	2090
	21st to end	Day	23% 4 7% 23% 33% 11%	2090
October	1st to 10th	Day	17% 2 6% 14% 41% 20%	3480
	11th to 20th	Day	19% 3 9% 24% 26% 19%	3283
	21st to end	Day	18% 2 6% 25% 36% 13%	3292
November	1st to 10th	Day	21% 1 6% 25% 29% 18%	1763
	11th to 20th	Day	20% 2 5% 27% 33% 14%	1800
	21st to end	Day	26% 2 4 22% 32% 14%	1800
December	1st to 10th	Day	25% 2 9% 28% 28% 7%	1782
	11th to 20th	Day	30% 2 8% 20% 30% 11%	2159
	21st to end	Day	38% 1 6% 20% 26% 9%	3135
January	1st to 10th	Night	32% 2 6% 28% 27% 6%	4108
	11th to 20th	Night	24% 1 14% 23% 29% 8%	4120
	21st to end	Night	37% 1 6% 20% 28% 8%	4468
February	1st to 10th	Night	33% 2 6% 22% 27% 10%	2280
	11th to 20th	Night	32% 2 6% 21% 26% 12%	2218
	21st to end	Night	28% 2 4 23% 26% 18%	1884
March	1st to 10th	Night	25% 2 4 20% 24% 25%	3706
	11th to 20th	Night	27% 1 6% 28% 25% 13%	3480
	21st to end	Night	33% 2 9% 25% 21% 11%	3817
April	1st to 10th	Night	24% 3 8% 21% 26% 17%	1971
	11th to 20th	Night	30% 4 9% 24% 23% 12%	1877
	21st to end	Night	28% 3 9% 29% 24% 7%	1743
May	1st to 10th	Night	37% 3 6% 16% 21% 16%	2850
	11th to 20th	Night	34% 2 14% 26% 17% 7%	2824
	21st to end	Night	28% 4 11% 18% 17% 23%	3099
June	1st to 10th	Night	23% 5% 18% 32% 16% 6%	1710
	11th to 20th	Night	22% 5% 13% 28% 24% 7%	1710
	21st to end	Night	22% 4 12% 28% 24% 11%	1710
July	1st to 10th	Night	27% 4 11% 34% 21% 3	2805
	11th to 20th	Night	19% 4 12% 28% 30% 6%	2796
	21st to end	Night	18% 4 13% 28% 32% 6%	2999
August	1st to 10th	Night	20% 4 12% 26% 29% 8%	2826
	11th to 20th	Night	24% 5% 9% 27% 28% 6%	3046
	21st to end	Night	20% 4 13% 32% 25% 5%	3487
September	1st to 10th	Night	24% 3 12% 24% 25% 13%	2016
	11th to 20th	Night	31% 4 9% 20% 28% 8%	2090
	21st to end	Night	23% 3 7% 23% 31% 12%	2090
October	1st to 10th	Night	16% 2 5% 16% 38% 22%	3480
	11th to 20th	Night	17% 3 7% 20% 36% 17%	3601
	21st to end	Night	14% 1 4 26% 38% 16%	4245
November	1st to 10th	Night	20% 2 6% 25% 28% 18%	2535
	11th to 20th	Night	19% 2 6% 26% 33% 14%	2600
	21st to end	Night	25% 2 5% 22% 30% 16%	2600
December	1st to 10th	Night	24% 2 8% 28% 28% 10%	2581
	11th to 20th	Night	30% 2 4 23% 31% 9%	3037
	21st to end	Night	34% 1 8% 21% 26% 10%	4532

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	9% 13% 42% 25% 9% 1	270
	11th to 20th	Day	14% 17% 36% 23% 9% 1	270
	21st to end	Day	8% 14% 46% 24% 6% 1	297
February	1st to 10th	Day	9% 16% 47% 21% 6%	270
	11th to 20th	Day	11% 13% 50% 17% 7% 1	270
	21st to end	Day	8% 24% 44% 19% 5%	225
March	1st to 10th	Day	9% 13% 49% 23% 5%	270
	11th to 20th	Day	16% 16% 42% 17% 6% 2	270
	21st to end	Day	16% 16% 43% 20% 4	297
April	1st to 10th	Day	15% 20% 36% 23% 5% 1	384
	11th to 20th	Day	13% 23% 44% 18% 2	452
	21st to end	Day	13% 20% 37% 22% 7% 1	617
May	1st to 10th	Day	13% 13% 39% 28% 5% 2	653
	11th to 20th	Day	13% 8% 29% 30% 17% 2	675
	21st to end	Day	12% 8% 36% 28% 15% 2	734
June	1st to 10th	Day	6% 5% 25% 38% 21% 5%	680
	11th to 20th	Day	6% 4 31% 39% 18% 2	680
	21st to end	Day	5% 3 24% 43% 21% 4	680
July	1st to 10th	Day	8% 2 13% 36% 32% 10%	671
	11th to 20th	Day	4 3 12% 43% 33% 7%	668
	21st to end	Day	4 1 8% 39% 40% 8%	739
August	1st to 10th	Day	5% 2 13% 45% 31% 5%	676
	11th to 20th	Day	6% 1 14% 42% 31% 6%	530
	21st to end	Day	5% 1 10% 42% 32% 9%	539
September	1st to 10th	Day	9% 1 12% 39% 33% 7%	372
	11th to 20th	Day	5% 2 14% 46% 26% 6%	300
	21st to end	Day	9% 5% 21% 31% 27% 6%	300
October	1st to 10th	Day	10% 5% 29% 32% 20% 4	300
	11th to 20th	Day	7% 9% 32% 36% 13% 3	300
	21st to end	Day	16% 9% 38% 22% 13% 3	330
November	1st to 10th	Day	9% 10% 38% 31% 10% 2	300
	11th to 20th	Day	7% 16% 37% 26% 11% 3	300
	21st to end	Day	15% 13% 38% 21% 10% 3	300
December	1st to 10th	Day	6% 13% 43% 28% 9% 1	294
	11th to 20th	Day	11% 11% 42% 26% 10% 1	270
	21st to end	Day	15% 21% 35% 22% 6%	297
January	1st to 10th	Night	7% 12% 39% 35% 7%	950
	11th to 20th	Night	9% 13% 36% 33% 8%	950
	21st to end	Night	8% 10% 42% 33% 6% 1	1007
February	1st to 10th	Night	12% 13% 40% 30% 5% 1	760
	11th to 20th	Night	11% 12% 45% 25% 6%	744
	21st to end	Night	11% 17% 43% 25% 4	628
March	1st to 10th	Night	7% 15% 43% 30% 4	745
	11th to 20th	Night	13% 14% 39% 29% 5%	570
	21st to end	Night	12% 17% 44% 24% 4	627
April	1st to 10th	Night	8% 16% 45% 26% 5%	570
	11th to 20th	Night	12% 15% 49% 21% 2	563
	21st to end	Night	14% 13% 40% 27% 6%	570
May	1st to 10th	Night	15% 11% 42% 29% 4	570
	11th to 20th	Night	11% 9% 38% 30% 11% 1	561
	21st to end	Night	8% 8% 38% 34% 10% 1	617
June	1st to 10th	Night	6% 5% 36% 38% 13% 1	570
	11th to 20th	Night	4 4 46% 38% 8%	570
	21st to end	Night	6% 3 32% 45% 14% 1	570
July	1st to 10th	Night	8% 1 21% 45% 24% 2	555
	11th to 20th	Night	4 1 18% 53% 22% 2	552
	21st to end	Night	4 1 12% 54% 27% 2	624
August	1st to 10th	Night	4 1 15% 53% 25% 2	567
	11th to 20th	Night	7% 2 16% 51% 24%	564
	21st to end	Night	5% 1 16% 43% 32% 2	627
September	1st to 10th	Night	8% 2 18% 48% 24% 1	570
	11th to 20th	Night	14% 2 25% 41% 18% 1	570
	21st to end	Night	8% 4 31% 36% 20% 2	570
October	1st to 10th	Night	8% 6% 27% 42% 16% 1	570
	11th to 20th	Night	9% 9% 38% 36% 7%	647
	21st to end	Night	11% 9% 36% 29% 15%	912
November	1st to 10th	Night	9% 8% 36% 36% 10% 1	975
	11th to 20th	Night	7% 11% 41% 33% 8%	1000
	21st to end	Night	11% 12% 34% 32% 10% 1	1000
December	1st to 10th	Night	9% 9% 39% 34% 8% 1	993
	11th to 20th	Night	12% 11% 43% 29% 6%	950
	21st to end	Night	12% 15% 37% 30% 6%	1045

Page generated at 2024-12-06 02:54:54. Version ac07

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