Badlands Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Badlands Observatory clear sky chart from 2005-11-06 to 2025-11-03.

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	8% 5% 2 5% 4 4 4 3 5% 8% 51%	135621
	Night	7% 6% 2 6% 4 4 4 4 6% 7% 50%	131836
Transparency	Day	32% 5% 14% 27% 18% 4	130365
	Night	33% 6% 14% 27% 18% 3	128099
Seeing	Day	11% 8% 28% 32% 17% 4	17314
	Night	10% 8% 33% 38% 11%	27215

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	3 8% 4 12% 7% 5% 4 4 5% 8% 39%	3638
	11th to 20th	Day	3 7% 5% 10% 6% 5% 4 3 6% 7% 44%	3640
	21st to end	Day	2 5% 2 10% 5% 4 5% 3 5% 7% 52%	4004
February	1st to 10th	Day	7% 11% 4 9% 6% 6% 5% 4 5% 6% 37%	1756
	11th to 20th	Day	6% 10% 4 7% 4 4 5% 4 6% 7% 44%	1949
	21st to end	Day	4 9% 3 8% 5% 5% 4 4 5% 6% 47%	1650
March	1st to 10th	Day	5% 8% 2 5% 4 4 4 3 4 6% 54%	4500
	11th to 20th	Day	7% 6% 2 4 3 3 3 3 5% 8% 58%	4705
	21st to end	Day	15% 10% 4 7% 4 4 4 4 5% 7% 36%	5869
April	1st to 10th	Day	12% 9% 3 5% 4 3 3 3 6% 8% 44%	2400
	11th to 20th	Day	12% 7% 2 7% 5% 5% 4 4 5% 7% 41%	2379
	21st to end	Day	14% 6% 2 6% 4 4 4 3 6% 7% 42%	2600
May	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 5% 7% 49%	5900
	11th to 20th	Day	14% 6% 2 5% 4 3 4 3 5% 8% 45%	6241
	21st to end	Day	19% 6% 2 5% 4 3 4 4 5% 6% 42%	6925
June	1st to 10th	Day	9% 5% 1 4 3 3 4 4 6% 9% 52%	2800
	11th to 20th	Day	9% 4 1 4 4 3 4 4 7% 9% 52%	2800
	21st to end	Day	5% 3 1 3 3 3 3 3 6% 9% 60%	2800
July	1st to 10th	Day	5% 3 1 5% 4 4 4 4 6% 9% 55%	6339
	11th to 20th	Day	8% 3 2 4 3 4 4 3 5% 8% 56%	6340
	21st to end	Day	7% 3 1 4 3 3 4 4 6% 8% 57%	6903
August	1st to 10th	Day	6% 4 2 5% 4 4 4 4 6% 9% 53%	6147
	11th to 20th	Day	5% 3 1 3 3 3 4 3 6% 9% 58%	5729
	21st to end	Day	9% 4 2 4 3 3 4 3 5% 8% 54%	5984
September	1st to 10th	Day	6% 4 1 4 2 3 3 2 4 7% 63%	2400
	11th to 20th	Day	8% 3 1 4 3 3 3 3 4 7% 60%	2260
	21st to end	Day	10% 3 1 3 2 2 2 2 4 7% 63%	2200
October	1st to 10th	Day	6% 3 1 3 2 2 2 2 2 4 71%	3562
	11th to 20th	Day	9% 4 1 5% 3 3 3 2 4 7% 59%	3091
	21st to end	Day	10% 6% 2 6% 4 4 4 4 6% 8% 48%	3190
November	1st to 10th	Day	6% 5% 2 5% 4 4 5% 3 5% 7% 54%	1781
	11th to 20th	Day	6% 5% 2 6% 4 4 4 4 6% 7% 53%	1800
	21st to end	Day	5% 9% 3 5% 4 3 4 4 5% 9% 49%	1689
December	1st to 10th	Day	3 6% 3 8% 5% 5% 5% 4 7% 7% 48%	2620
	11th to 20th	Day	2 4 3 8% 6% 5% 5% 4 6% 8% 50%	3026
	21st to end	Day	6% 10% 4 6% 5% 5% 4 3 5% 6% 47%	4004
January	1st to 10th	Night	6% 10% 4 12% 7% 5% 4 3 4 6% 40%	6327
	11th to 20th	Night	2 7% 3 10% 6% 6% 6% 4 5% 6% 45%	6340
	21st to end	Night	1 5% 2 7% 4 4 5% 4 5% 6% 56%	6974
February	1st to 10th	Night	8% 10% 4 9% 5% 5% 4 4 6% 7% 39%	2659
	11th to 20th	Night	4 9% 3 10% 5% 7% 4 4 6% 7% 41%	2338
	21st to end	Night	6% 7% 3 7% 4 4 4 3 6% 7% 48%	1980
March	1st to 10th	Night	9% 8% 2 5% 4 3 4 3 5% 6% 51%	5374
	11th to 20th	Night	6% 5% 2 5% 3 4 4 3 6% 9% 53%	5266
	21st to end	Night	13% 10% 3 8% 5% 5% 4 4 6% 8% 34%	5077
April	1st to 10th	Night	13% 7% 2 6% 4 5% 4 4 6% 8% 41%	2000
	11th to 20th	Night	12% 8% 3 6% 5% 4 4 3 5% 6% 45%	1967
	21st to end	Night	13% 7% 2 6% 4 4 4 4 5% 8% 43%	1800
May	1st to 10th	Night	9% 5% 2 6% 4 4 4 4 6% 8% 49%	4080
	11th to 20th	Night	11% 5% 2 5% 4 4 4 4 6% 8% 49%	3671
	21st to end	Night	20% 6% 2 5% 3 4 4 3 5% 6% 42%	3972
June	1st to 10th	Night	8% 4 2 4 3 4 4 4 6% 9% 52%	1600
	11th to 20th	Night	10% 4 2 5% 4 4 4 4 6% 9% 48%	1600
	21st to end	Night	6% 4 1 4 3 4 5% 3 6% 7% 57%	1600
July	1st to 10th	Night	5% 3 1 4 3 4 4 4 6% 8% 58%	3640
	11th to 20th	Night	7% 3 1 4 3 4 4 4 6% 8% 56%	3640
	21st to end	Night	6% 3 1 5% 4 4 4 5% 7% 7% 54%	3970
August	1st to 10th	Night	6% 4 2 5% 4 4 4 4 6% 9% 51%	3665
	11th to 20th	Night	5% 4 2 5% 4 4 4 4 6% 9% 54%	4115
	21st to end	Night	8% 4 2 6% 4 4 5% 4 6% 7% 50%	4993
September	1st to 10th	Night	6% 3 1 3 3 2 3 3 4 7% 64%	2000
	11th to 20th	Night	7% 3 2 4 2 3 4 4 5% 7% 58%	2140
	21st to end	Night	9% 3 1 4 3 2 3 2 4 6% 63%	2200
October	1st to 10th	Night	7% 3 1 3 2 2 2 2 3 4 70%	3617
	11th to 20th	Night	7% 4 2 5% 3 3 3 3 5% 7% 58%	4024
	21st to end	Night	10% 6% 1 5% 3 4 4 3 5% 8% 51%	4610
November	1st to 10th	Night	7% 6% 2 6% 4 3 5% 4 6% 8% 49%	2562
	11th to 20th	Night	5% 6% 2 6% 4 4 5% 3 5% 7% 51%	2600
	21st to end	Night	5% 7% 2 5% 4 3 4 4 6% 7% 52%	2710
December	1st to 10th	Night	3 6% 2 6% 4 5% 5% 5% 7% 8% 50%	4570
	11th to 20th	Night	3 5% 2 6% 6% 5% 6% 5% 7% 8% 47%	5181
	21st to end	Night	7% 11% 3 7% 4 5% 5% 3 5% 7% 43%	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	43% 6% 17% 25% 9%	3639
	11th to 20th	Day	39% 7% 15% 21% 15% 3	3640
	21st to end	Day	31% 7% 15% 32% 13% 3	4004
February	1st to 10th	Day	46% 8% 13% 19% 13% 2	1756
	11th to 20th	Day	38% 8% 17% 19% 14% 4	1959
	21st to end	Day	36% 7% 15% 26% 13% 3	1650
March	1st to 10th	Day	31% 5% 10% 27% 24% 3	4500
	11th to 20th	Day	25% 5% 14% 35% 20% 1	4705
	21st to end	Day	46% 7% 17% 20% 10%	5869
April	1st to 10th	Day	37% 6% 16% 28% 10% 2	2400
	11th to 20th	Day	40% 8% 14% 22% 15% 2	2382
	21st to end	Day	39% 8% 15% 28% 10%	2600
May	1st to 10th	Day	33% 6% 11% 29% 18% 2	5900
	11th to 20th	Day	37% 7% 14% 24% 16% 3	6245
	21st to end	Day	40% 8% 13% 24% 14% 1	6926
June	1st to 10th	Day	28% 8% 19% 28% 14% 3	2800
	11th to 20th	Day	27% 8% 18% 26% 17% 3	2800
	21st to end	Day	20% 6% 15% 31% 22% 6%	2800
July	1st to 10th	Day	26% 3 13% 33% 22% 2	6271
	11th to 20th	Day	27% 3 12% 28% 24% 6%	6265
	21st to end	Day	25% 4 13% 26% 25% 7%	6705
August	1st to 10th	Day	27% 5% 18% 23% 21% 6%	4473
	11th to 20th	Day	27% 5% 16% 28% 19% 4	4144
	21st to end	Day	22% 3 10% 26% 26% 12%	4311
September	1st to 10th	Day	22% 4 10% 29% 27% 9%	2400
	11th to 20th	Day	25% 5% 12% 29% 23% 7%	2260
	21st to end	Day	23% 4 10% 32% 27% 4	2200
October	1st to 10th	Day	20% 3 9% 22% 32% 15%	3562
	11th to 20th	Day	27% 3 12% 35% 20% 3	3091
	21st to end	Day	35% 4 13% 29% 16% 4	3190
November	1st to 10th	Day	29% 6% 14% 25% 20% 5%	1781
	11th to 20th	Day	29% 6% 12% 28% 21% 5%	1800
	21st to end	Day	31% 6% 16% 30% 14% 4	1689
December	1st to 10th	Day	34% 5% 17% 29% 15% 1	2620
	11th to 20th	Day	32% 6% 19% 30% 12% 1	3024
	21st to end	Day	39% 4 9% 35% 12% 1	4004
January	1st to 10th	Night	46% 5% 11% 26% 11% 1	6327
	11th to 20th	Night	38% 8% 14% 22% 16% 2	6340
	21st to end	Night	28% 6% 15% 30% 20% 2	6974
February	1st to 10th	Night	43% 7% 15% 21% 13% 1	2659
	11th to 20th	Night	41% 8% 13% 23% 13% 3	2338
	21st to end	Night	34% 6% 16% 26% 13% 5%	1980
March	1st to 10th	Night	32% 6% 9% 27% 23% 3	5374
	11th to 20th	Night	28% 5% 15% 30% 21% 1	5266
	21st to end	Night	45% 8% 17% 19% 10%	5077
April	1st to 10th	Night	39% 8% 14% 23% 13% 3	2000
	11th to 20th	Night	39% 7% 12% 23% 17% 2	1967
	21st to end	Night	39% 8% 14% 26% 12% 1	1800
May	1st to 10th	Night	31% 10% 12% 26% 20% 2	4080
	11th to 20th	Night	32% 7% 16% 29% 14% 2	3672
	21st to end	Night	42% 7% 10% 26% 15%	3972
June	1st to 10th	Night	28% 9% 18% 28% 16% 2	1600
	11th to 20th	Night	32% 9% 19% 22% 15% 3	1600
	21st to end	Night	24% 7% 15% 29% 20% 5%	1600
July	1st to 10th	Night	24% 4 17% 30% 22% 3	3600
	11th to 20th	Night	27% 3 13% 30% 21% 5%	3592
	21st to end	Night	28% 4 16% 28% 19% 5%	3856
August	1st to 10th	Night	30% 5% 17% 23% 19% 6%	2663
	11th to 20th	Night	30% 5% 19% 23% 19% 4	2976
	21st to end	Night	25% 5% 12% 24% 25% 8%	3597
September	1st to 10th	Night	21% 4 10% 29% 28% 8%	2000
	11th to 20th	Night	24% 6% 14% 25% 25% 6%	2140
	21st to end	Night	25% 4 8% 30% 26% 7%	2200
October	1st to 10th	Night	20% 4 7% 20% 31% 18%	3617
	11th to 20th	Night	27% 4 10% 34% 22% 4	4024
	21st to end	Night	32% 4 12% 27% 19% 7%	4610
November	1st to 10th	Night	31% 7% 13% 25% 18% 6%	2562
	11th to 20th	Night	32% 6% 13% 24% 21% 5%	2600
	21st to end	Night	29% 7% 16% 28% 18% 3	2710
December	1st to 10th	Night	31% 5% 18% 30% 15% 2	4570
	11th to 20th	Night	33% 5% 18% 31% 12% 2	5182
	21st to end	Night	41% 5% 10% 30% 13% 1	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	8% 7% 30% 29% 23% 4	300
	11th to 20th	Day	13% 10% 33% 32% 11% 2	300
	21st to end	Day	8% 13% 40% 28% 11% 1	330
February	1st to 10th	Day	11% 12% 40% 30% 7%	300
	11th to 20th	Day	12% 11% 37% 33% 7% 1	300
	21st to end	Day	9% 12% 41% 29% 8% 2	249
March	1st to 10th	Day	9% 12% 35% 27% 13% 3	300
	11th to 20th	Day	9% 12% 33% 31% 13% 2	300
	21st to end	Day	18% 13% 32% 22% 11% 3	502
April	1st to 10th	Day	16% 14% 35% 27% 7% 1	500
	11th to 20th	Day	19% 18% 30% 24% 8% 1	500
	21st to end	Day	17% 10% 24% 34% 13% 1	700
May	1st to 10th	Day	15% 10% 26% 29% 17% 3	703
	11th to 20th	Day	20% 7% 22% 30% 17% 5%	725
	21st to end	Day	16% 9% 29% 27% 15% 4	789
June	1st to 10th	Day	7% 8% 23% 32% 22% 8%	730
	11th to 20th	Day	11% 6% 29% 36% 14% 3	730
	21st to end	Day	5% 6% 25% 37% 22% 3	730
July	1st to 10th	Day	5% 2 21% 40% 26% 6%	721
	11th to 20th	Day	6% 4 22% 45% 21% 2	718
	21st to end	Day	5% 2 20% 43% 26% 4	794
August	1st to 10th	Day	5% 3 22% 42% 24% 4	726
	11th to 20th	Day	7% 3 19% 39% 25% 7%	675
	21st to end	Day	5% 6% 23% 32% 26% 7%	583
September	1st to 10th	Day	6% 6% 25% 30% 26% 6%	530
	11th to 20th	Day	9% 4 19% 33% 27% 7%	390
	21st to end	Day	12% 9% 25% 29% 19% 6%	330
October	1st to 10th	Day	14% 7% 25% 25% 18% 12%	330
	11th to 20th	Day	15% 12% 34% 22% 14% 3	330
	21st to end	Day	12% 14% 33% 25% 14% 2	363
November	1st to 10th	Day	11% 9% 39% 26% 14% 2	306
	11th to 20th	Day	12% 12% 33% 28% 13% 2	300
	21st to end	Day	12% 8% 30% 35% 14% 2	300
December	1st to 10th	Day	7% 13% 42% 28% 9% 2	300
	11th to 20th	Day	9% 7% 43% 30% 9% 1	300
	21st to end	Day	10% 12% 36% 28% 12% 2	330
January	1st to 10th	Night	7% 10% 34% 37% 12% 1	1000
	11th to 20th	Night	7% 13% 36% 35% 8% 1	1000
	21st to end	Night	8% 10% 39% 35% 8%	1100
February	1st to 10th	Night	13% 9% 39% 33% 6%	897
	11th to 20th	Night	8% 8% 41% 36% 7% 1	784
	21st to end	Night	10% 8% 40% 35% 7% 1	660
March	1st to 10th	Night	11% 9% 35% 38% 7% 1	800
	11th to 20th	Night	10% 7% 33% 40% 8% 1	730
	21st to end	Night	15% 10% 31% 33% 9% 1	660
April	1st to 10th	Night	15% 9% 35% 36% 5%	600
	11th to 20th	Night	18% 11% 34% 33% 4	593
	21st to end	Night	16% 11% 29% 35% 10%	600
May	1st to 10th	Night	12% 8% 31% 36% 13% 1	600
	11th to 20th	Night	15% 8% 26% 39% 12%	591
	21st to end	Night	18% 7% 34% 29% 11%	650
June	1st to 10th	Night	8% 6% 31% 39% 16% 1	600
	11th to 20th	Night	11% 6% 36% 40% 8% 1	600
	21st to end	Night	6% 6% 30% 46% 12%	600
July	1st to 10th	Night	4 2 29% 45% 18% 1	585
	11th to 20th	Night	4 3 28% 51% 14%	582
	21st to end	Night	4 2 28% 54% 12%	657
August	1st to 10th	Night	6% 2 27% 51% 14%	597
	11th to 20th	Night	5% 2 29% 48% 16% 1	594
	21st to end	Night	5% 3 28% 48% 15%	660
September	1st to 10th	Night	7% 4 26% 47% 16% 1	600
	11th to 20th	Night	9% 3 27% 44% 16% 2	600
	21st to end	Night	10% 7% 26% 40% 16% 1	600
October	1st to 10th	Night	15% 6% 29% 33% 16%	614
	11th to 20th	Night	13% 7% 33% 35% 11% 1	875
	21st to end	Night	12% 9% 33% 35% 10% 1	1100
November	1st to 10th	Night	10% 6% 34% 41% 8%	986
	11th to 20th	Night	10% 9% 35% 38% 9%	1000
	21st to end	Night	7% 10% 35% 38% 10%	1000
December	1st to 10th	Night	8% 11% 37% 35% 8%	1000
	11th to 20th	Night	8% 8% 38% 37% 9%	1000
	21st to end	Night	13% 11% 33% 33% 10%	1100

Page generated at 2025-10-31 00:02:39. Version ac07

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