Sky Hound Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sky Hound Observatory clear sky chart from 2005-11-06 to 2026-04-02.

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	3 4 2 5% 4 4 4 4 6% 8% 57%	140248
	Night	3 5% 2 5% 3 4 4 3 5% 7% 59%	139128
Transparency	Day	22% 7% 12% 24% 22% 13%	135032
	Night	22% 6% 13% 26% 21% 11%	135349
Seeing	Day	6% 8% 23% 34% 22% 7%	17131
	Night	5% 4 23% 43% 21% 4	27486

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	2 3 2 6% 5% 5% 5% 4 6% 10% 53%	5318
	11th to 20th	Day	1 2 1 3 4 4 4 4 6% 8% 64%	5340
	21st to end	Day	1 5% 2 7% 5% 4 4 4 5% 7% 55%	5844
February	1st to 10th	Day	2 4 2 5% 3 3 6% 3 8% 8% 55%	1890
	11th to 20th	Day	3 5% 3 6% 4 4 4 4 6% 9% 52%	1845
	21st to end	Day	2 6% 2 6% 5% 4 4 5% 6% 8% 53%	1729
March	1st to 10th	Day	2 9% 3 7% 4 4 5% 4 5% 7% 49%	5064
	11th to 20th	Day	3 9% 3 6% 4 4 5% 4 6% 8% 48%	5110
	21st to end	Day	5% 10% 4 7% 5% 5% 5% 5% 6% 7% 41%	5607
April	1st to 10th	Day	3 4 2 5% 3 4 4 4 7% 8% 56%	2301
	11th to 20th	Day	3 6% 2 6% 5% 4 5% 4 5% 7% 52%	2405
	21st to end	Day	4 4 2 6% 5% 5% 5% 4 6% 7% 52%	2600
May	1st to 10th	Day	5% 5% 2 6% 3 4 4 4 7% 8% 52%	5880
	11th to 20th	Day	4 4 2 6% 5% 5% 5% 5% 7% 9% 48%	5841
	21st to end	Day	3 3 1 5% 4 5% 5% 4 7% 7% 56%	6653
June	1st to 10th	Day	4 3 1 4 4 4 5% 4 7% 9% 56%	2800
	11th to 20th	Day	4 3 1 3 3 3 4 4 5% 7% 63%	2800
	21st to end	Day	2 2 1 3 3 4 4 4 6% 7% 65%	2800
July	1st to 10th	Day	2 3 1 3 3 3 4 4 5% 6% 65%	5977
	11th to 20th	Day	2 2 1 4 4 5% 6% 6% 8% 9% 51%	5880
	21st to end	Day	2 2 1 4 3 5% 5% 4 7% 9% 58%	6401
August	1st to 10th	Day	2 2 1 3 3 4 4 4 6% 8% 63%	5779
	11th to 20th	Day	2 2 1 4 4 5% 4 5% 6% 6% 62%	5798
	21st to end	Day	4 4 2 6% 4 5% 5% 5% 7% 7% 51%	6248
September	1st to 10th	Day	4 2 1 3 3 4 3 3 5% 6% 65%	2374
	11th to 20th	Day	3 2 2 3 3 3 5% 4 5% 6% 64%	2200
	21st to end	Day	5% 2 1 3 2 2 2 2 4 7% 69%	2200
October	1st to 10th	Day	4 3 1 3 2 2 3 2 4 5% 73%	3317
	11th to 20th	Day	6% 4 2 4 2 3 3 2 5% 7% 61%	3250
	21st to end	Day	3 4 2 3 3 3 3 3 5% 6% 65%	3548
November	1st to 10th	Day	3 3 2 4 2 2 3 3 5% 7% 65%	1957
	11th to 20th	Day	2 3 1 3 3 3 2 3 5% 8% 67%	1796
	21st to end	Day	3 4 1 5% 3 4 3 3 6% 7% 61%	1680
December	1st to 10th	Day	1 2 1 3 3 2 2 3 5% 8% 69%	2700
	11th to 20th	Day	2 3 2 3 4 4 3 4 8% 12% 54%	3106
	21st to end	Day	2 6% 3 7% 6% 5% 5% 5% 7% 8% 47%	4210
January	1st to 10th	Night	2 7% 3 6% 3 3 4 3 5% 8% 56%	7605
	11th to 20th	Night	1 3 1 3 3 3 3 3 5% 5% 70%	7650
	21st to end	Night	2 6% 3 7% 4 4 4 4 6% 7% 54%	8370
February	1st to 10th	Night	2 5% 2 5% 3 3 4 4 6% 8% 58%	2730
	11th to 20th	Night	3 6% 3 6% 5% 4 4 3 6% 8% 53%	2662
	21st to end	Night	2 6% 2 5% 3 3 4 4 5% 6% 59%	2071
March	1st to 10th	Night	2 8% 3 8% 4 4 5% 4 5% 6% 52%	5050
	11th to 20th	Night	3 8% 2 6% 4 5% 5% 4 6% 8% 48%	5110
	21st to end	Night	5% 8% 2 5% 3 4 4 4 5% 7% 52%	5610
April	1st to 10th	Night	3 5% 2 5% 3 4 4 4 5% 6% 58%	2121
	11th to 20th	Night	5% 5% 1 5% 4 3 4 4 7% 7% 54%	1939
	21st to end	Night	5% 5% 1 5% 4 3 4 3 5% 8% 56%	1800
May	1st to 10th	Night	8% 7% 3 7% 5% 4 4 4 5% 7% 47%	4100
	11th to 20th	Night	3 4 2 5% 4 4 4 3 5% 7% 59%	4074
	21st to end	Night	5% 4 2 5% 3 4 4 4 7% 9% 54%	4228
June	1st to 10th	Night	3 3 1 4 3 4 4 4 7% 9% 57%	1600
	11th to 20th	Night	5% 3 1 3 2 3 3 3 4 7% 65%	1600
	21st to end	Night	2 3 1 3 2 3 3 3 5% 4 71%	1600
July	1st to 10th	Night	3 2 1 5% 4 4 4 3 5% 6% 63%	3997
	11th to 20th	Night	2 3 1 5% 4 4 5% 5% 7% 10% 54%	4100
	21st to end	Night	2 2 1 5% 4 6% 5% 4 6% 7% 56%	4472
August	1st to 10th	Night	2 3 1 4 2 3 4 4 6% 8% 62%	4033
	11th to 20th	Night	3 3 2 5% 4 5% 4 4 5% 7% 59%	4051
	21st to end	Night	3 3 2 5% 4 5% 5% 4 6% 9% 55%	4729
September	1st to 10th	Night	3 3 1 4 3 2 4 3 5% 7% 65%	2023
	11th to 20th	Night	3 3 1 4 2 3 3 3 5% 6% 68%	2200
	21st to end	Night	3 3 1 4 2 2 3 2 4 5% 71%	2200
October	1st to 10th	Night	3 2 1 2 2 2 2 2 3 5% 75%	3873
	11th to 20th	Night	5% 3 1 4 3 3 3 3 4 6% 64%	3898
	21st to end	Night	3 6% 2 4 2 2 2 2 4 7% 66%	4252
November	1st to 10th	Night	3 3 1 4 3 3 3 3 5% 7% 66%	2559
	11th to 20th	Night	2 3 1 3 3 3 3 3 6% 7% 66%	2798
	21st to end	Night	3 5% 2 5% 3 3 4 3 5% 6% 62%	2940
December	1st to 10th	Night	2 3 1 3 2 2 2 2 4 6% 72%	4710
	11th to 20th	Night	2 5% 2 5% 4 3 4 3 6% 8% 57%	5321
	21st to end	Night	3 6% 2 6% 4 4 5% 4 7% 9% 50%	7052

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	25% 9% 25% 25% 15% 1	5321
	11th to 20th	Day	17% 7% 17% 34% 19% 6%	5340
	21st to end	Day	26% 8% 19% 30% 15% 3	5844
February	1st to 10th	Day	24% 8% 21% 32% 13% 3	1890
	11th to 20th	Day	27% 5% 17% 32% 16% 2	1854
	21st to end	Day	26% 8% 14% 31% 17% 4	1729
March	1st to 10th	Day	26% 10% 9% 33% 16% 6%	5064
	11th to 20th	Day	30% 7% 11% 28% 18% 5%	5110
	21st to end	Day	35% 10% 13% 28% 12% 2	5607
April	1st to 10th	Day	22% 7% 13% 28% 22% 7%	2301
	11th to 20th	Day	28% 6% 10% 25% 24% 6%	2408
	21st to end	Day	26% 8% 9% 28% 25% 4	2600
May	1st to 10th	Day	24% 8% 9% 21% 29% 9%	5880
	11th to 20th	Day	25% 8% 8% 23% 30% 7%	5844
	21st to end	Day	21% 7% 9% 25% 32% 7%	6654
June	1st to 10th	Day	20% 7% 8% 20% 32% 13%	2800
	11th to 20th	Day	19% 5% 5% 16% 27% 28%	2800
	21st to end	Day	16% 4 4 12% 29% 35%	2800
July	1st to 10th	Day	17% 5% 5% 8% 13% 51%	5914
	11th to 20th	Day	21% 7% 8% 12% 26% 26%	5811
	21st to end	Day	19% 6% 7% 13% 25% 30%	6217
August	1st to 10th	Day	21% 7% 9% 22% 20% 21%	4208
	11th to 20th	Day	21% 8% 10% 18% 25% 18%	4197
	21st to end	Day	21% 6% 9% 17% 22% 24%	4503
September	1st to 10th	Day	19% 4 7% 16% 27% 27%	2374
	11th to 20th	Day	19% 6% 7% 21% 27% 20%	2200
	21st to end	Day	16% 4 4 24% 35% 17%	2200
October	1st to 10th	Day	15% 3 5% 20% 32% 25%	3317
	11th to 20th	Day	23% 4 7% 27% 31% 8%	3250
	21st to end	Day	19% 4 12% 34% 26% 5%	3548
November	1st to 10th	Day	18% 6% 14% 34% 22% 6%	1957
	11th to 20th	Day	16% 4 18% 40% 19% 2	1796
	21st to end	Day	22% 4 16% 36% 19% 3	1680
December	1st to 10th	Day	14% 5% 22% 44% 12% 4	2700
	11th to 20th	Day	20% 9% 28% 33% 10% 1	3104
	21st to end	Day	31% 8% 19% 23% 15% 4	4210
January	1st to 10th	Night	27% 6% 19% 30% 16% 3	7605
	11th to 20th	Night	15% 6% 16% 37% 19% 6%	7650
	21st to end	Night	26% 9% 20% 23% 18% 4	8370
February	1st to 10th	Night	23% 7% 20% 32% 14% 4	2730
	11th to 20th	Night	28% 6% 15% 29% 19% 3	2663
	21st to end	Night	22% 7% 16% 28% 23% 5%	2071
March	1st to 10th	Night	29% 6% 9% 32% 19% 6%	5050
	11th to 20th	Night	32% 6% 11% 32% 15% 5%	5110
	21st to end	Night	29% 7% 13% 30% 19% 3	5610
April	1st to 10th	Night	24% 5% 11% 28% 22% 9%	2121
	11th to 20th	Night	25% 6% 11% 26% 26% 6%	1939
	21st to end	Night	24% 7% 10% 30% 25% 5%	1800
May	1st to 10th	Night	32% 8% 9% 18% 26% 7%	4097
	11th to 20th	Night	22% 7% 7% 25% 31% 9%	4075
	21st to end	Night	22% 7% 8% 24% 34% 5%	4228
June	1st to 10th	Night	21% 5% 10% 22% 27% 16%	1600
	11th to 20th	Night	19% 4 5% 16% 24% 32%	1600
	21st to end	Night	14% 4 3 12% 26% 40%	1600
July	1st to 10th	Night	20% 4 5% 9% 12% 50%	3952
	11th to 20th	Night	20% 6% 7% 13% 23% 32%	4046
	21st to end	Night	20% 7% 8% 13% 21% 31%	4344
August	1st to 10th	Night	19% 5% 9% 23% 20% 22%	2928
	11th to 20th	Night	25% 6% 9% 17% 22% 20%	2928
	21st to end	Night	16% 6% 11% 17% 24% 27%	3405
September	1st to 10th	Night	17% 4 8% 16% 26% 29%	2023
	11th to 20th	Night	16% 5% 7% 24% 26% 22%	2200
	21st to end	Night	16% 4 5% 18% 37% 20%	2200
October	1st to 10th	Night	12% 3 5% 18% 31% 31%	3873
	11th to 20th	Night	21% 5% 7% 26% 32% 10%	3898
	21st to end	Night	19% 3 9% 36% 29% 4	4252
November	1st to 10th	Night	17% 6% 11% 35% 24% 6%	2559
	11th to 20th	Night	17% 5% 13% 42% 20% 3	2798
	21st to end	Night	22% 4 14% 36% 21% 3	2940
December	1st to 10th	Night	14% 4 18% 42% 18% 3	4710
	11th to 20th	Night	23% 7% 27% 34% 8% 1	5322
	21st to end	Night	28% 9% 20% 25% 16% 2	7052

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	7% 7% 24% 36% 19% 7%	330
	11th to 20th	Day	6% 4 21% 45% 19% 4	330
	21st to end	Day	4 2 20% 47% 22% 5%	363
February	1st to 10th	Day	5% 8% 32% 38% 13% 3	330
	11th to 20th	Day	5% 7% 32% 38% 15% 3	330
	21st to end	Day	6% 15% 32% 35% 10% 1	425
March	1st to 10th	Day	8% 13% 29% 36% 13% 2	540
	11th to 20th	Day	10% 14% 27% 32% 14% 3	540
	21st to end	Day	9% 13% 31% 33% 13% 1	594
April	1st to 10th	Day	7% 19% 26% 28% 15% 5%	505
	11th to 20th	Day	11% 17% 31% 26% 12% 3	492
	21st to end	Day	8% 16% 24% 28% 19% 4	500
May	1st to 10th	Day	8% 13% 26% 31% 17% 5%	503
	11th to 20th	Day	7% 12% 28% 25% 20% 8%	528
	21st to end	Day	6% 11% 21% 28% 25% 9%	673
June	1st to 10th	Day	6% 5% 21% 32% 26% 10%	730
	11th to 20th	Day	5% 8% 25% 34% 22% 5%	730
	21st to end	Day	3 5% 23% 37% 25% 7%	730
July	1st to 10th	Day	3 4 17% 34% 30% 12%	572
	11th to 20th	Day	3 3 18% 34% 31% 10%	524
	21st to end	Day	3 3 11% 35% 34% 14%	575
August	1st to 10th	Day	3 4 19% 36% 28% 11%	527
	11th to 20th	Day	4 3 15% 35% 28% 14%	517
	21st to end	Day	3 2 21% 33% 31% 11%	583
September	1st to 10th	Day	5% 4 18% 30% 28% 15%	530
	11th to 20th	Day	5% 6% 21% 38% 21% 8%	530
	21st to end	Day	6% 5% 18% 31% 31% 10%	530
October	1st to 10th	Day	7% 7% 20% 30% 22% 15%	364
	11th to 20th	Day	6% 10% 20% 34% 22% 7%	330
	21st to end	Day	7% 6% 24% 36% 24% 4	363
November	1st to 10th	Day	5% 8% 24% 37% 22% 3	330
	11th to 20th	Day	5% 7% 23% 40% 19% 6%	330
	21st to end	Day	6% 3 23% 38% 23% 7%	330
December	1st to 10th	Day	4 5% 24% 40% 21% 6%	330
	11th to 20th	Day	7% 4 21% 46% 20% 2	330
	21st to end	Day	9% 5% 24% 42% 17% 4	363
January	1st to 10th	Night	5% 4 24% 41% 22% 4	840
	11th to 20th	Night	4 3 23% 44% 20% 6%	840
	21st to end	Night	5% 2 20% 51% 17% 4	924
February	1st to 10th	Night	5% 6% 29% 43% 14% 3	840
	11th to 20th	Night	5% 5% 31% 44% 12% 3	824
	21st to end	Night	4 7% 35% 41% 12% 1	692
March	1st to 10th	Night	7% 5% 30% 41% 14% 3	840
	11th to 20th	Night	7% 5% 28% 41% 18% 2	840
	21st to end	Night	7% 6% 33% 42% 11% 1	924
April	1st to 10th	Night	6% 8% 33% 39% 12% 2	714
	11th to 20th	Night	8% 8% 33% 39% 11% 1	593
	21st to end	Night	6% 7% 32% 38% 15% 3	600
May	1st to 10th	Night	7% 6% 32% 38% 15% 3	600
	11th to 20th	Night	8% 4 19% 42% 25% 3	591
	21st to end	Night	7% 5% 26% 36% 22% 3	650
June	1st to 10th	Night	4 5% 20% 44% 26% 2	600
	11th to 20th	Night	7% 5% 28% 42% 17% 2	600
	21st to end	Night	4 2 19% 48% 25% 3	600
July	1st to 10th	Night	3 2 16% 39% 35% 5%	585
	11th to 20th	Night	3 2 11% 45% 36% 3	582
	21st to end	Night	3 2 7% 40% 42% 6%	657
August	1st to 10th	Night	4 2 12% 43% 35% 4	597
	11th to 20th	Night	4 2 9% 47% 34% 4	594
	21st to end	Night	3 1 13% 42% 35% 6%	660
September	1st to 10th	Night	4 2 14% 40% 34% 6%	623
	11th to 20th	Night	4 2 17% 43% 26% 9%	800
	21st to end	Night	4 2 17% 38% 28% 11%	800
October	1st to 10th	Night	6% 3 21% 43% 23% 5%	800
	11th to 20th	Night	4 5% 21% 42% 22% 5%	800
	21st to end	Night	4 3 22% 40% 25% 5%	880
November	1st to 10th	Night	4 2 25% 39% 24% 6%	820
	11th to 20th	Night	3 4 28% 43% 16% 5%	908
	21st to end	Night	4 5% 22% 42% 22% 4	1050
December	1st to 10th	Night	5% 4 25% 46% 18% 2	1050
	11th to 20th	Night	6% 4 22% 50% 16% 3	1050
	21st to end	Night	9% 5% 23% 46% 14% 2	1118

Page generated at 2026-03-30 00:18:42. Version ac07

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