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 2024-01-16.

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 3 4 5% 5% 8% 50%	74851
	Night	7% 6% 2 5% 5% 3 4 5% 6% 8% 49%	74969
Transparency	Day	31% 7% 15% 27% 16% 4	74555
	Night	32% 7% 14% 26% 16% 4	74787
Seeing	Day	11% 8% 28% 33% 18% 4	14751
	Night	10% 8% 33% 38% 11%	24852

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 6% 3 7% 8% 4 5% 5% 4 9% 46%	1518
	11th to 20th	Day	4 7% 4 7% 6% 4 4 4 5% 8% 48%	1480
	21st to end	Day	4 9% 3 8% 6% 3 6% 6% 5% 9% 41%	1584
February	1st to 10th	Day	7% 9% 5% 8% 7% 4 6% 6% 5% 7% 38%	1580
	11th to 20th	Day	6% 9% 4 5% 5% 4 5% 6% 6% 7% 43%	1749
	21st to end	Day	5% 9% 4 7% 7% 3 5% 6% 5% 6% 44%	1480
March	1st to 10th	Day	6% 7% 3 7% 5% 3 4 5% 5% 9% 46%	1800
	11th to 20th	Day	7% 5% 2 4 5% 3 5% 5% 5% 9% 49%	1861
	21st to end	Day	12% 9% 4 6% 6% 3 5% 6% 6% 8% 36%	2332
April	1st to 10th	Day	12% 8% 3 4 5% 3 4 4 6% 9% 44%	2160
	11th to 20th	Day	13% 7% 2 6% 6% 4 5% 5% 6% 8% 39%	2137
	21st to end	Day	13% 6% 2 5% 5% 3 5% 4 6% 8% 42%	2340
May	1st to 10th	Day	13% 5% 2 5% 4 3 5% 5% 6% 8% 44%	2340
	11th to 20th	Day	15% 6% 3 5% 4 3 5% 5% 6% 9% 40%	2447
	21st to end	Day	16% 6% 2 5% 4 3 4 5% 6% 8% 41%	2724
June	1st to 10th	Day	9% 4 1 3 4 2 4 5% 6% 9% 52%	2520
	11th to 20th	Day	9% 3 1 3 4 2 4 5% 6% 9% 53%	2520
	21st to end	Day	5% 2 2 3 4 2 3 4 5% 9% 60%	2520
July	1st to 10th	Day	5% 2 1 4 4 3 5% 5% 7% 8% 55%	2520
	11th to 20th	Day	4 2 1 2 3 2 3 4 5% 8% 66%	2520
	21st to end	Day	4 2 1 3 3 3 4 5% 6% 9% 59%	2742
August	1st to 10th	Day	6% 3 2 4 4 3 5% 6% 7% 9% 50%	2472
	11th to 20th	Day	5% 3 1 3 4 2 4 4 5% 8% 62%	2265
	21st to end	Day	5% 3 1 3 3 2 4 3 6% 8% 61%	2376
September	1st to 10th	Day	7% 4 1 4 3 2 3 3 4 7% 62%	2160
	11th to 20th	Day	8% 3 2 3 4 2 3 3 4 7% 61%	2034
	21st to end	Day	10% 3 1 2 3 2 3 3 5% 7% 61%	1980
October	1st to 10th	Day	12% 6% 2 5% 4 2 4 3 3 6% 54%	1966
	11th to 20th	Day	10% 5% 2 5% 4 2 4 4 4 7% 53%	1714
	21st to end	Day	9% 5% 2 5% 4 3 4 5% 6% 7% 51%	1782
November	1st to 10th	Day	6% 5% 2 4 4 3 4 5% 5% 7% 54%	1673
	11th to 20th	Day	6% 5% 2 5% 4 3 5% 4 6% 8% 52%	1710
	21st to end	Day	5% 8% 3 5% 4 2 5% 5% 5% 9% 50%	1605
December	1st to 10th	Day	5% 8% 3 7% 5% 3 4 6% 6% 7% 47%	1520
	11th to 20th	Day	4 4 3 6% 5% 2 5% 5% 6% 9% 52%	1926
	21st to end	Day	8% 11% 4 5% 5% 3 5% 4 5% 6% 44%	2794
January	1st to 10th	Night	4 5% 3 8% 7% 3 6% 6% 6% 7% 46%	2647
	11th to 20th	Night	4 7% 3 6% 6% 3 5% 6% 6% 9% 45%	2591
	21st to end	Night	3 9% 4 8% 5% 4 5% 7% 6% 8% 40%	2772
February	1st to 10th	Night	8% 9% 4 7% 6% 4 4 5% 6% 7% 41%	2394
	11th to 20th	Night	5% 8% 4 8% 6% 4 6% 5% 6% 7% 42%	2098
	21st to end	Night	7% 8% 3 7% 5% 3 4 4 6% 7% 46%	1776
March	1st to 10th	Night	8% 8% 3 6% 5% 3 4 5% 5% 7% 46%	2160
	11th to 20th	Night	8% 6% 3 5% 5% 3 5% 5% 7% 8% 45%	2098
	21st to end	Night	12% 9% 3 6% 6% 3 4 5% 6% 8% 39%	2021
April	1st to 10th	Night	13% 6% 3 5% 5% 3 5% 6% 6% 8% 41%	1800
	11th to 20th	Night	13% 8% 3 5% 5% 3 4 4 5% 6% 43%	1769
	21st to end	Night	13% 7% 2 5% 5% 3 4 5% 5% 9% 43%	1620
May	1st to 10th	Night	11% 6% 2 5% 5% 3 4 5% 6% 8% 44%	1620
	11th to 20th	Night	13% 6% 3 4 4 3 3 5% 6% 8% 45%	1445
	21st to end	Night	14% 5% 2 5% 5% 3 5% 5% 5% 8% 43%	1552
June	1st to 10th	Night	9% 4 2 4 4 3 4 4 6% 8% 52%	1440
	11th to 20th	Night	11% 3 2 4 5% 3 3 5% 5% 10% 49%	1440
	21st to end	Night	5% 4 1 3 3 4 4 5% 6% 8% 57%	1440
July	1st to 10th	Night	5% 3 1 4 4 3 4 6% 7% 9% 55%	1440
	11th to 20th	Night	4 2 1 3 3 2 3 4 5% 9% 63%	1440
	21st to end	Night	4 2 1 4 4 3 4 5% 6% 8% 60%	1576
August	1st to 10th	Night	5% 4 2 5% 4 3 4 6% 7% 8% 52%	1467
	11th to 20th	Night	4 3 2 5% 4 2 4 3 6% 8% 61%	1631
	21st to end	Night	4 3 1 3 4 2 4 4 5% 7% 63%	1980
September	1st to 10th	Night	7% 3 2 3 3 2 3 4 4 7% 63%	1800
	11th to 20th	Night	7% 3 2 3 3 3 3 5% 5% 7% 60%	1926
	21st to end	Night	10% 3 1 4 3 1 3 3 4 6% 61%	1980
October	1st to 10th	Night	13% 5% 2 4 4 3 4 4 5% 7% 50%	1992
	11th to 20th	Night	10% 5% 2 5% 4 2 4 4 5% 5% 55%	2227
	21st to end	Night	10% 6% 2 4 4 3 3 4 5% 8% 52%	2574
November	1st to 10th	Night	7% 5% 2 5% 5% 3 4 6% 6% 8% 49%	2405
	11th to 20th	Night	6% 6% 3 6% 5% 3 5% 5% 5% 7% 50%	2470
	21st to end	Night	5% 6% 3 5% 4 2 4 5% 5% 8% 53%	2574
December	1st to 10th	Night	5% 8% 3 6% 5% 3 5% 5% 6% 7% 48%	2660
	11th to 20th	Night	4 5% 2 5% 5% 3 4 5% 6% 8% 51%	3271
	21st to end	Night	9% 12% 3 5% 5% 3 4 4 5% 7% 44%	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	36% 7% 16% 27% 13% 1	1519
	11th to 20th	Day	35% 8% 19% 26% 10% 2	1480
	21st to end	Day	38% 9% 19% 21% 11% 2	1584
February	1st to 10th	Day	45% 8% 13% 20% 12% 2	1580
	11th to 20th	Day	38% 8% 17% 20% 13% 4	1759
	21st to end	Day	38% 8% 15% 25% 11% 3	1480
March	1st to 10th	Day	36% 7% 16% 27% 13% 2	1800
	11th to 20th	Day	31% 8% 15% 30% 15% 1	1861
	21st to end	Day	43% 10% 16% 22% 9%	2332
April	1st to 10th	Day	37% 6% 17% 28% 10% 3	2160
	11th to 20th	Day	41% 8% 15% 22% 12% 2	2140
	21st to end	Day	39% 8% 15% 28% 10%	2340
May	1st to 10th	Day	36% 7% 16% 30% 10% 1	2340
	11th to 20th	Day	40% 7% 18% 24% 10%	2451
	21st to end	Day	38% 10% 18% 23% 9% 1	2724
June	1st to 10th	Day	28% 9% 19% 28% 15% 2	2520
	11th to 20th	Day	26% 9% 18% 27% 16% 3	2520
	21st to end	Day	19% 7% 15% 31% 21% 6%	2520
July	1st to 10th	Day	23% 7% 16% 29% 20% 4	2451
	11th to 20th	Day	17% 6% 12% 26% 27% 12%	2445
	21st to end	Day	19% 7% 14% 27% 24% 9%	2590
August	1st to 10th	Day	27% 8% 15% 26% 19% 5%	2456
	11th to 20th	Day	21% 6% 14% 31% 21% 7%	2265
	21st to end	Day	21% 6% 11% 24% 27% 11%	2376
September	1st to 10th	Day	23% 4 10% 28% 26% 10%	2160
	11th to 20th	Day	24% 5% 12% 28% 24% 7%	2034
	21st to end	Day	24% 5% 11% 33% 26% 3	1980
October	1st to 10th	Day	33% 5% 12% 23% 23% 3	1966
	11th to 20th	Day	31% 5% 12% 28% 20% 5%	1714
	21st to end	Day	30% 7% 16% 28% 14% 5%	1782
November	1st to 10th	Day	29% 7% 14% 25% 19% 6%	1673
	11th to 20th	Day	30% 6% 12% 28% 20% 4	1710
	21st to end	Day	30% 6% 16% 29% 15% 4	1605
December	1st to 10th	Day	34% 8% 15% 26% 15% 2	1520
	11th to 20th	Day	27% 9% 20% 33% 10% 1	1924
	21st to end	Day	41% 6% 11% 30% 12% 1	2794
January	1st to 10th	Night	36% 7% 16% 27% 13% 2	2647
	11th to 20th	Night	35% 9% 18% 24% 13% 2	2591
	21st to end	Night	39% 9% 16% 24% 11% 2	2772
February	1st to 10th	Night	42% 7% 15% 23% 12% 1	2394
	11th to 20th	Night	39% 8% 14% 24% 13% 3	2098
	21st to end	Night	37% 6% 16% 24% 12% 5%	1776
March	1st to 10th	Night	36% 7% 14% 28% 13% 2	2160
	11th to 20th	Night	34% 7% 14% 25% 17% 2	2098
	21st to end	Night	42% 8% 15% 22% 11% 1	2021
April	1st to 10th	Night	39% 9% 14% 22% 13% 3	1800
	11th to 20th	Night	41% 8% 13% 22% 14% 2	1769
	21st to end	Night	38% 8% 15% 25% 13% 1	1620
May	1st to 10th	Night	35% 10% 15% 27% 11% 1	1620
	11th to 20th	Night	36% 9% 18% 27% 9%	1446
	21st to end	Night	39% 9% 16% 22% 13% 1	1552
June	1st to 10th	Night	28% 9% 18% 28% 15% 2	1440
	11th to 20th	Night	31% 9% 19% 23% 15% 3	1440
	21st to end	Night	23% 8% 15% 29% 19% 6%	1440
July	1st to 10th	Night	22% 9% 17% 27% 20% 5%	1400
	11th to 20th	Night	18% 6% 13% 26% 25% 12%	1392
	21st to end	Night	21% 6% 14% 26% 23% 10%	1488
August	1st to 10th	Night	26% 9% 14% 25% 18% 7%	1459
	11th to 20th	Night	21% 6% 12% 28% 27% 6%	1631
	21st to end	Night	19% 8% 11% 26% 26% 11%	1980
September	1st to 10th	Night	22% 5% 10% 27% 28% 9%	1800
	11th to 20th	Night	21% 7% 14% 26% 25% 6%	1926
	21st to end	Night	26% 5% 8% 30% 26% 5%	1980
October	1st to 10th	Night	34% 7% 11% 22% 21% 4	1992
	11th to 20th	Night	31% 5% 10% 27% 21% 6%	2227
	21st to end	Night	31% 6% 15% 24% 18% 6%	2574
November	1st to 10th	Night	31% 7% 14% 25% 17% 6%	2405
	11th to 20th	Night	33% 6% 13% 24% 20% 5%	2470
	21st to end	Night	28% 7% 16% 27% 18% 3	2574
December	1st to 10th	Night	34% 8% 14% 28% 14% 2	2660
	11th to 20th	Night	29% 6% 15% 34% 13% 2	3272
	21st to end	Night	39% 7% 13% 28% 11% 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	6% 6% 33% 29% 22% 4	270
	11th to 20th	Day	13% 11% 30% 32% 12% 2	255
	21st to end	Day	9% 13% 44% 27% 6% 1	264
February	1st to 10th	Day	10% 12% 40% 30% 8%	240
	11th to 20th	Day	13% 12% 36% 31% 8% 1	240
	21st to end	Day	10% 13% 40% 29% 7% 2	198
March	1st to 10th	Day	10% 13% 33% 28% 12% 4	240
	11th to 20th	Day	10% 12% 30% 30% 15% 3	240
	21st to end	Day	19% 11% 32% 22% 12% 4	418
April	1st to 10th	Day	15% 13% 35% 28% 7%	420
	11th to 20th	Day	20% 17% 31% 24% 7% 1	418
	21st to end	Day	16% 10% 24% 34% 14% 1	600
May	1st to 10th	Day	14% 10% 27% 29% 17% 3	603
	11th to 20th	Day	20% 6% 22% 30% 16% 5%	625
	21st to end	Day	16% 8% 29% 28% 15% 4	679
June	1st to 10th	Day	6% 7% 22% 32% 23% 10%	630
	11th to 20th	Day	11% 6% 30% 35% 15% 4	630
	21st to end	Day	5% 6% 24% 37% 24% 4	630
July	1st to 10th	Day	5% 2 21% 40% 27% 5%	621
	11th to 20th	Day	5% 4 23% 46% 21% 2	618
	21st to end	Day	5% 2 19% 44% 26% 3	684
August	1st to 10th	Day	5% 3 20% 43% 25% 4	626
	11th to 20th	Day	7% 3 19% 40% 25% 6%	579
	21st to end	Day	5% 6% 22% 33% 27% 8%	495
September	1st to 10th	Day	6% 6% 27% 31% 24% 6%	450
	11th to 20th	Day	10% 4 16% 34% 28% 8%	324
	21st to end	Day	14% 10% 26% 29% 17% 4	270
October	1st to 10th	Day	17% 7% 22% 25% 18% 10%	270
	11th to 20th	Day	14% 13% 33% 20% 16% 4	270
	21st to end	Day	12% 14% 32% 26% 13% 2	297
November	1st to 10th	Day	10% 10% 36% 27% 15% 2	270
	11th to 20th	Day	12% 12% 31% 29% 14% 2	270
	21st to end	Day	12% 9% 30% 34% 13% 1	270
December	1st to 10th	Day	8% 12% 41% 28% 9% 2	270
	11th to 20th	Day	9% 7% 43% 31% 9% 1	270
	21st to end	Day	10% 13% 36% 27% 13% 1	297
January	1st to 10th	Night	6% 10% 35% 37% 12% 1	950
	11th to 20th	Night	8% 13% 35% 35% 9% 1	926
	21st to end	Night	9% 10% 39% 35% 6%	990
February	1st to 10th	Night	13% 9% 39% 33% 7%	808
	11th to 20th	Night	8% 8% 42% 34% 7% 1	704
	21st to end	Night	10% 8% 39% 33% 8% 1	592
March	1st to 10th	Night	11% 9% 35% 38% 7% 1	720
	11th to 20th	Night	11% 7% 32% 39% 9% 1	658
	21st to end	Night	15% 10% 29% 34% 10% 1	594
April	1st to 10th	Night	14% 9% 35% 36% 6%	540
	11th to 20th	Night	18% 11% 33% 33% 4	533
	21st to end	Night	16% 11% 27% 35% 11%	540
May	1st to 10th	Night	12% 7% 31% 35% 13% 1	540
	11th to 20th	Night	15% 8% 25% 39% 13%	531
	21st to end	Night	17% 7% 34% 29% 12%	584
June	1st to 10th	Night	9% 5% 30% 39% 16% 1	540
	11th to 20th	Night	11% 5% 35% 40% 8% 1	540
	21st to end	Night	5% 5% 29% 48% 13%	540
July	1st to 10th	Night	4 2 30% 43% 19% 1	525
	11th to 20th	Night	3 3 29% 50% 15%	522
	21st to end	Night	3 2 26% 56% 13%	591
August	1st to 10th	Night	6% 2 26% 52% 15%	537
	11th to 20th	Night	5% 2 27% 49% 17% 1	534
	21st to end	Night	4 3 28% 48% 17%	594
September	1st to 10th	Night	8% 4 27% 44% 16% 1	540
	11th to 20th	Night	9% 3 27% 43% 17% 1	540
	21st to end	Night	11% 7% 27% 39% 15% 1	540
October	1st to 10th	Night	16% 6% 28% 34% 15%	552
	11th to 20th	Night	13% 7% 33% 35% 12% 1	787
	21st to end	Night	13% 10% 32% 35% 11% 1	990
November	1st to 10th	Night	10% 6% 34% 41% 9%	925
	11th to 20th	Night	10% 9% 34% 38% 9%	950
	21st to end	Night	7% 10% 35% 38% 10%	950
December	1st to 10th	Night	9% 10% 37% 35% 9%	950
	11th to 20th	Night	8% 8% 37% 38% 10%	950
	21st to end	Night	13% 11% 32% 33% 10%	1045

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