Wolf Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wolf Creek Observatory clear sky chart from 2005-11-06 to 2025-09-19.

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	10% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	125815
	Night	11% 7% 2 6% 4 4 4 4 6% 8% 44%	123264
Transparency	Day	38% 5% 12% 19% 18% 7%	129640
	Night	37% 5% 11% 18% 20% 8%	127499
Seeing	Day	14% 9% 22% 25% 20% 10%	15712
	Night	14% 8% 22% 30% 22% 5%	25615

By Month

Percentage Cloud Cover SE (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	13% 8% 3 5% 3 3 3 2 5% 6% 49%	4056
	11th to 20th	Day	10% 7% 4 5% 3 3 4 4 4 6% 50%	4451
	21st to end	Day	20% 9% 3 7% 3 3 3 3 4 5% 38%	4972
February	1st to 10th	Day	16% 9% 2 7% 5% 3 5% 3 5% 6% 39%	2000
	11th to 20th	Day	16% 8% 2 6% 4 4 4 3 5% 5% 43%	1948
	21st to end	Day	16% 8% 3 6% 5% 5% 4 4 4 6% 40%	1650
March	1st to 10th	Day	16% 8% 3 7% 4 4 4 4 6% 7% 37%	4480
	11th to 20th	Day	9% 5% 2 5% 5% 4 4 3 5% 7% 51%	4783
	21st to end	Day	13% 6% 3 8% 5% 5% 4 4 5% 6% 41%	5733
April	1st to 10th	Day	12% 5% 3 5% 5% 5% 3 4 5% 7% 45%	2400
	11th to 20th	Day	11% 6% 2 7% 4 4 4 4 6% 6% 46%	2374
	21st to end	Day	7% 5% 2 5% 4 4 5% 4 5% 7% 53%	2400
May	1st to 10th	Day	13% 7% 2 7% 5% 5% 5% 3 6% 9% 38%	5625
	11th to 20th	Day	11% 6% 2 7% 4 5% 5% 5% 6% 11% 36%	5861
	21st to end	Day	7% 5% 2 6% 4 5% 5% 5% 7% 10% 44%	6433
June	1st to 10th	Day	7% 6% 2 9% 7% 6% 6% 6% 7% 10% 33%	2600
	11th to 20th	Day	5% 5% 2 6% 6% 7% 7% 6% 7% 11% 39%	2600
	21st to end	Day	6% 5% 3 8% 7% 7% 7% 7% 8% 11% 32%	2600
July	1st to 10th	Day	6% 5% 3 7% 6% 7% 8% 8% 10% 12% 28%	5900
	11th to 20th	Day	5% 4 2 6% 6% 7% 7% 6% 9% 13% 35%	5900
	21st to end	Day	5% 5% 2 8% 7% 8% 9% 7% 11% 14% 25%	6016
August	1st to 10th	Day	4 3 1 5% 5% 6% 7% 5% 8% 12% 45%	3905
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 7% 10% 48%	3849
	21st to end	Day	7% 4 2 6% 5% 5% 6% 5% 8% 12% 40%	4312
September	1st to 10th	Day	9% 6% 3 7% 6% 6% 6% 5% 6% 7% 38%	2342
	11th to 20th	Day	12% 7% 2 7% 5% 5% 5% 3 5% 7% 41%	2178
	21st to end	Day	9% 5% 2 5% 4 5% 5% 3 5% 7% 50%	2090
October	1st to 10th	Day	9% 5% 2 5% 4 4 3 3 4 7% 53%	2090
	11th to 20th	Day	11% 4 1 4 4 3 3 2 6% 7% 56%	2090
	21st to end	Day	11% 5% 1 4 4 2 3 3 4 6% 55%	2046
November	1st to 10th	Day	10% 6% 2 5% 3 4 3 2 4 5% 55%	1762
	11th to 20th	Day	12% 7% 2 5% 3 3 4 2 4 6% 52%	1800
	21st to end	Day	13% 5% 3 5% 4 4 4 3 5% 7% 47%	1800
December	1st to 10th	Day	14% 7% 2 5% 4 3 3 3 4 6% 49%	2930
	11th to 20th	Day	10% 8% 3 6% 3 4 3 3 4 6% 49%	3373
	21st to end	Day	15% 10% 3 6% 4 3 3 2 4 5% 45%	4466
January	1st to 10th	Night	15% 7% 4 5% 3 3 3 3 4 5% 47%	5889
	11th to 20th	Night	14% 10% 3 6% 4 3 3 3 4 6% 46%	5504
	21st to end	Night	18% 12% 2 6% 3 3 4 3 4 6% 38%	5984
February	1st to 10th	Night	14% 9% 3 7% 4 4 3 3 6% 6% 42%	2400
	11th to 20th	Night	18% 8% 3 5% 3 3 3 3 4 5% 45%	2338
	21st to end	Night	14% 7% 3 6% 4 4 4 4 6% 6% 43%	1980
March	1st to 10th	Night	20% 10% 3 6% 3 3 3 3 6% 6% 36%	5373
	11th to 20th	Night	11% 7% 2 6% 4 3 3 3 5% 6% 48%	5175
	21st to end	Night	10% 7% 3 7% 4 4 4 3 4 6% 47%	5223
April	1st to 10th	Night	10% 6% 3 6% 4 4 4 4 5% 7% 47%	2000
	11th to 20th	Night	12% 5% 2 5% 3 4 4 4 6% 7% 48%	1975
	21st to end	Night	6% 4 2 4 4 4 5% 4 5% 8% 55%	2000
May	1st to 10th	Night	11% 6% 2 7% 5% 5% 5% 4 6% 9% 39%	4267
	11th to 20th	Night	13% 7% 3 7% 5% 4 4 4 7% 9% 38%	4032
	21st to end	Night	7% 5% 2 6% 4 5% 6% 5% 7% 12% 42%	4421
June	1st to 10th	Night	7% 7% 2 7% 6% 6% 5% 6% 9% 12% 34%	1800
	11th to 20th	Night	4 4 2 5% 5% 6% 5% 6% 9% 12% 42%	1800
	21st to end	Night	4 5% 2 7% 6% 5% 6% 6% 9% 12% 39%	1800
July	1st to 10th	Night	6% 6% 3 8% 6% 7% 7% 7% 10% 13% 27%	4058
	11th to 20th	Night	4 4 2 6% 6% 6% 8% 6% 10% 16% 33%	4057
	21st to end	Night	5% 6% 3 9% 7% 7% 8% 6% 10% 12% 27%	4829
August	1st to 10th	Night	4 3 2 5% 4 5% 6% 6% 9% 14% 43%	3244
	11th to 20th	Night	4 4 2 6% 4 5% 6% 4 7% 11% 46%	3200
	21st to end	Night	5% 5% 2 5% 4 5% 7% 5% 8% 11% 43%	3586
September	1st to 10th	Night	9% 5% 2 6% 5% 6% 6% 6% 8% 8% 38%	2036
	11th to 20th	Night	12% 6% 2 6% 5% 5% 5% 5% 6% 8% 41%	2179
	21st to end	Night	8% 5% 2 6% 4 5% 6% 4 6% 7% 47%	2090
October	1st to 10th	Night	8% 6% 2 4 4 4 3 3 4 7% 56%	2090
	11th to 20th	Night	9% 5% 1 4 3 3 3 3 4 5% 60%	2090
	21st to end	Night	11% 6% 2 5% 3 3 3 2 4 5% 57%	2546
November	1st to 10th	Night	9% 4 2 5% 3 3 3 4 5% 6% 55%	2536
	11th to 20th	Night	12% 5% 2 4 3 3 3 3 4 5% 56%	2600
	21st to end	Night	13% 6% 2 5% 4 3 4 3 5% 6% 49%	2600
December	1st to 10th	Night	14% 6% 2 5% 3 2 3 3 5% 6% 51%	4250
	11th to 20th	Night	13% 6% 2 6% 4 3 3 3 4 5% 51%	4822
	21st to end	Night	16% 8% 2 6% 4 4 4 3 4 6% 45%	6490

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	37% 2 5% 22% 28% 6%	4057
	11th to 20th	Day	36% 3 5% 18% 29% 9%	4451
	21st to end	Day	49% 3 8% 13% 15% 13%	4972
February	1st to 10th	Day	46% 4 8% 14% 20% 8%	2000
	11th to 20th	Day	44% 4 5% 15% 24% 9%	1958
	21st to end	Day	45% 5% 7% 15% 17% 11%	1650
March	1st to 10th	Day	46% 3 8% 15% 20% 7%	4480
	11th to 20th	Day	34% 3 5% 16% 21% 21%	4783
	21st to end	Day	43% 3 9% 16% 19% 9%	5735
April	1st to 10th	Day	38% 5% 9% 20% 18% 10%	2400
	11th to 20th	Day	37% 5% 8% 19% 21% 10%	2374
	21st to end	Day	30% 6% 10% 23% 27% 5%	2400
May	1st to 10th	Day	43% 6% 11% 23% 15% 2	5660
	11th to 20th	Day	41% 5% 18% 22% 12% 1	5865
	21st to end	Day	34% 6% 14% 26% 18% 1	6447
June	1st to 10th	Day	44% 9% 13% 21% 11% 2	2600
	11th to 20th	Day	36% 11% 16% 22% 13% 3	2600
	21st to end	Day	41% 11% 17% 18% 10% 2	2600
July	1st to 10th	Day	44% 9% 27% 14% 6% 1	5835
	11th to 20th	Day	38% 10% 31% 19% 2	5831
	21st to end	Day	45% 11% 23% 20% 2	5843
August	1st to 10th	Day	30% 7% 14% 29% 19% 1	3893
	11th to 20th	Day	31% 8% 15% 28% 16% 1	3885
	21st to end	Day	37% 6% 20% 22% 13% 2	4311
September	1st to 10th	Day	42% 9% 15% 16% 14% 5%	2342
	11th to 20th	Day	41% 7% 12% 17% 18% 5%	2178
	21st to end	Day	34% 6% 10% 20% 23% 7%	2090
October	1st to 10th	Day	30% 3 6% 11% 25% 25%	3480
	11th to 20th	Day	18% 2 5% 16% 25% 35%	3458
	21st to end	Day	21% 2 6% 15% 41% 15%	3334
November	1st to 10th	Day	33% 3 7% 18% 26% 12%	1762
	11th to 20th	Day	34% 4 6% 15% 27% 14%	1800
	21st to end	Day	36% 5% 8% 17% 23% 11%	1800
December	1st to 10th	Day	38% 4 6% 18% 30% 4	2930
	11th to 20th	Day	39% 2 9% 20% 24% 6%	3370
	21st to end	Day	43% 2 4 22% 24% 4	4466
January	1st to 10th	Night	40% 2 5% 19% 27% 6%	5889
	11th to 20th	Night	42% 2 4 17% 25% 10%	5504
	21st to end	Night	49% 2 6% 13% 22% 8%	5984
February	1st to 10th	Night	42% 4 7% 16% 20% 11%	2400
	11th to 20th	Night	43% 4 6% 13% 22% 12%	2339
	21st to end	Night	40% 6% 8% 17% 16% 13%	1980
March	1st to 10th	Night	50% 3 6% 13% 20% 9%	5373
	11th to 20th	Night	38% 4 8% 13% 20% 18%	5175
	21st to end	Night	39% 3 9% 20% 19% 11%	5223
April	1st to 10th	Night	36% 5% 12% 15% 20% 12%	2000
	11th to 20th	Night	34% 5% 9% 17% 24% 11%	1975
	21st to end	Night	26% 7% 11% 25% 23% 8%	2000
May	1st to 10th	Night	40% 7% 16% 18% 16% 3	4297
	11th to 20th	Night	41% 6% 16% 23% 12% 2	4033
	21st to end	Night	33% 6% 16% 26% 16% 2	4429
June	1st to 10th	Night	40% 11% 17% 17% 15% 1	1800
	11th to 20th	Night	29% 10% 22% 24% 12% 3	1800
	21st to end	Night	34% 12% 21% 19% 11% 4	1800
July	1st to 10th	Night	45% 11% 26% 14% 4 1	4015
	11th to 20th	Night	36% 12% 32% 17% 2	4006
	21st to end	Night	46% 13% 19% 19% 3	4688
August	1st to 10th	Night	29% 9% 16% 30% 13% 2	3232
	11th to 20th	Night	29% 8% 20% 26% 15% 2	3230
	21st to end	Night	34% 7% 19% 21% 17% 2	3586
September	1st to 10th	Night	40% 10% 15% 15% 14% 6%	2036
	11th to 20th	Night	39% 8% 10% 19% 17% 6%	2179
	21st to end	Night	33% 8% 10% 20% 20% 9%	2090
October	1st to 10th	Night	32% 3 7% 11% 22% 25%	3480
	11th to 20th	Night	16% 2 4 15% 29% 33%	3461
	21st to end	Night	21% 2 3 16% 37% 21%	4195
November	1st to 10th	Night	30% 4 8% 17% 25% 16%	2536
	11th to 20th	Night	31% 3 5% 17% 30% 14%	2600
	21st to end	Night	36% 4 7% 19% 21% 14%	2600
December	1st to 10th	Night	35% 3 7% 21% 27% 8%	4250
	11th to 20th	Night	37% 2 7% 21% 26% 6%	4824
	21st to end	Night	41% 3 7% 18% 28% 3	6490

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	21% 25% 33% 18% 2 1	300
	11th to 20th	Day	21% 21% 33% 16% 8% 2	300
	21st to end	Day	22% 23% 38% 13% 2 1	330
February	1st to 10th	Day	27% 18% 33% 18% 4	300
	11th to 20th	Day	31% 20% 32% 15% 2	300
	21st to end	Day	20% 24% 39% 17%	249
March	1st to 10th	Day	22% 20% 40% 12% 5% 1	300
	11th to 20th	Day	20% 19% 34% 19% 6% 1	407
	21st to end	Day	20% 16% 33% 24% 6%	550
April	1st to 10th	Day	20% 15% 35% 19% 11% 1	500
	11th to 20th	Day	17% 12% 34% 24% 12% 1	492
	21st to end	Day	10% 11% 29% 29% 17% 4	500
May	1st to 10th	Day	9% 11% 29% 28% 17% 5%	503
	11th to 20th	Day	9% 6% 26% 29% 21% 9%	527
	21st to end	Day	11% 3 22% 31% 20% 13%	573
June	1st to 10th	Day	8% 4 15% 35% 25% 13%	530
	11th to 20th	Day	8% 2 14% 29% 29% 18%	530
	21st to end	Day	8% 2 12% 27% 30% 21%	530
July	1st to 10th	Day	7% 2 5% 26% 37% 23%	525
	11th to 20th	Day	5% 1 6% 23% 36% 29%	524
	21st to end	Day	5% 1 6% 25% 43% 21%	576
August	1st to 10th	Day	8% 2 7% 21% 37% 26%	526
	11th to 20th	Day	10% 1 7% 19% 37% 26%	519
	21st to end	Day	13% 1 10% 27% 28% 21%	583
September	1st to 10th	Day	9% 2 12% 30% 30% 17%	530
	11th to 20th	Day	14% 3 11% 28% 32% 11%	522
	21st to end	Day	10% 4 16% 28% 31% 12%	490
October	1st to 10th	Day	13% 4 24% 31% 23% 5%	490
	11th to 20th	Day	12% 6% 22% 30% 25% 5%	490
	21st to end	Day	18% 12% 23% 27% 17% 3	386
November	1st to 10th	Day	18% 9% 26% 32% 13% 3	300
	11th to 20th	Day	17% 13% 37% 22% 8% 2	300
	21st to end	Day	15% 17% 33% 25% 9% 1	300
December	1st to 10th	Day	20% 18% 35% 18% 7% 1	300
	11th to 20th	Day	24% 18% 35% 17% 5% 1	300
	21st to end	Day	21% 19% 32% 21% 6% 1	330
January	1st to 10th	Night	19% 17% 34% 25% 4	800
	11th to 20th	Night	20% 17% 26% 29% 8%	800
	21st to end	Night	23% 15% 35% 24% 4	880
February	1st to 10th	Night	19% 13% 32% 31% 5%	800
	11th to 20th	Night	24% 15% 31% 25% 5%	783
	21st to end	Night	17% 18% 35% 27% 3	660
March	1st to 10th	Night	16% 16% 34% 28% 6%	800
	11th to 20th	Night	14% 15% 36% 25% 10%	800
	21st to end	Night	14% 15% 33% 29% 9%	778
April	1st to 10th	Night	13% 13% 32% 30% 11% 1	600
	11th to 20th	Night	16% 8% 33% 28% 15% 2	593
	21st to end	Night	8% 9% 25% 38% 20% 1	600
May	1st to 10th	Night	10% 6% 26% 35% 20% 4	600
	11th to 20th	Night	9% 4 23% 34% 26% 5%	591
	21st to end	Night	8% 2 16% 36% 34% 4	650
June	1st to 10th	Night	10% 1 13% 35% 35% 6%	600
	11th to 20th	Night	6% 2 10% 27% 43% 13%	600
	21st to end	Night	5% 1 9% 30% 45% 11%	600
July	1st to 10th	Night	8% 1 5% 25% 45% 16%	585
	11th to 20th	Night	6% 1 5% 20% 47% 21%	582
	21st to end	Night	6% 1 5% 28% 46% 14%	657
August	1st to 10th	Night	7% 4 24% 46% 18%	597
	11th to 20th	Night	7% 2 5% 26% 46% 14%	594
	21st to end	Night	9% 2 8% 27% 38% 15%	660
September	1st to 10th	Night	11% 2 10% 28% 37% 13%	636
	11th to 20th	Night	14% 2 13% 30% 34% 7%	793
	21st to end	Night	10% 2 14% 31% 39% 5%	760
October	1st to 10th	Night	11% 2 20% 38% 25% 3	760
	11th to 20th	Night	11% 5% 21% 33% 26% 3	760
	21st to end	Night	14% 7% 20% 37% 21% 2	836
November	1st to 10th	Night	10% 6% 23% 37% 21% 3	780
	11th to 20th	Night	16% 8% 28% 34% 14% 2	800
	21st to end	Night	16% 13% 25% 33% 12% 1	800
December	1st to 10th	Night	17% 12% 26% 32% 12% 1	800
	11th to 20th	Night	19% 11% 32% 30% 9%	800
	21st to end	Night	24% 13% 28% 26% 7%	880

Page generated at 2025-09-16 00:49:14. Version ac07

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