Starry Kingdom Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starry Kingdom Observatory clear sky chart from 2005-11-06 to 2026-05-02.

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	10% 5% 1 4 3 3 3 3 4 6% 59%	140718
	Night	12% 7% 2 5% 3 3 3 3 4 5% 53%	139257
Transparency	Day	28% 3 7% 20% 23% 18%	135567
	Night	34% 3 8% 18% 21% 16%	135402
Seeing	Day	15% 10% 24% 28% 17% 6%	17155
	Night	16% 5% 14% 30% 28% 7%	26431

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	23% 11% 3 7% 4 4 4 4 5% 6% 28%	5018
	11th to 20th	Day	16% 6% 2 4 2 3 3 2 3 5% 54%	5340
	21st to end	Day	18% 7% 3 6% 4 4 4 3 5% 7% 41%	5843
February	1st to 10th	Day	21% 9% 2 5% 3 3 3 3 4 6% 40%	1890
	11th to 20th	Day	18% 11% 3 7% 5% 3 3 3 6% 6% 35%	1845
	21st to end	Day	20% 11% 3 6% 3 4 4 3 5% 5% 36%	1724
March	1st to 10th	Day	23% 16% 3 6% 3 3 3 2 3 6% 31%	5062
	11th to 20th	Day	18% 10% 2 6% 4 4 3 3 4 5% 40%	5110
	21st to end	Day	22% 13% 3 7% 4 5% 5% 5% 5% 6% 26%	5607
April	1st to 10th	Day	17% 9% 2 6% 5% 3 4 5% 6% 9% 34%	2499
	11th to 20th	Day	16% 7% 2 5% 3 4 3 3 5% 6% 45%	2489
	21st to end	Day	8% 7% 2 5% 3 3 4 3 7% 8% 50%	2590
May	1st to 10th	Day	5% 4 1 3 3 3 3 3 5% 7% 63%	5894
	11th to 20th	Day	4 3 1 3 2 2 2 3 4 5% 72%	5957
	21st to end	Day	4 2 1 2 2 2 2 2 4 6% 75%	6902
June	1st to 10th	Day	7% 4 1 4 3 3 3 4 5% 6% 59%	2800
	11th to 20th	Day	3 2 2 2 2 2 2 4 5% 76%	2800
	21st to end	Day	3 2 1 2 1 2 2 2 2 3 81%	2800
July	1st to 10th	Day	1 1 1 1 1 1 1 1 3 89%	6319
	11th to 20th	Day	1 1 1 1 1 1 1 2 4 86%	5930
	21st to end	Day	1 1 1 1 2 2 3 5% 85%	6402
August	1st to 10th	Day	1 1 1 1 1 1 2 3 5% 83%	5777
	11th to 20th	Day	2 1 2 1 2 2 2 3 5% 80%	5796
	21st to end	Day	1 1 1 2 1 2 2 2 3 6% 79%	5987
September	1st to 10th	Day	1 1 2 1 2 2 2 3 5% 82%	2400
	11th to 20th	Day	3 3 1 3 2 3 3 3 4 6% 68%	2329
	21st to end	Day	4 2 1 3 1 2 2 1 3 6% 75%	2142
October	1st to 10th	Day	4 2 1 2 2 2 3 2 3 4 74%	3280
	11th to 20th	Day	8% 3 1 3 2 3 4 4 5% 7% 59%	3261
	21st to end	Day	9% 6% 2 7% 4 4 3 3 5% 7% 49%	3558
November	1st to 10th	Day	14% 7% 2 5% 4 4 4 3 6% 7% 45%	2048
	11th to 20th	Day	17% 6% 2 7% 5% 4 4 3 5% 8% 38%	1739
	21st to end	Day	15% 5% 2 5% 4 3 3 3 5% 8% 47%	1680
December	1st to 10th	Day	11% 5% 2 5% 3 3 4 3 6% 7% 50%	2700
	11th to 20th	Day	29% 10% 3 8% 4 5% 5% 4 6% 7% 19%	3108
	21st to end	Day	27% 11% 3 8% 5% 4 5% 3 6% 6% 23%	4092
January	1st to 10th	Night	26% 12% 3 6% 5% 4 4 4 5% 7% 24%	7887
	11th to 20th	Night	13% 6% 2 6% 3 4 3 3 6% 6% 48%	7650
	21st to end	Night	19% 9% 3 7% 4 4 3 3 5% 6% 37%	8371
February	1st to 10th	Night	19% 8% 3 6% 4 2 4 3 4 5% 41%	2730
	11th to 20th	Night	18% 11% 3 8% 5% 4 4 3 5% 5% 35%	2662
	21st to end	Night	19% 8% 2 6% 3 3 4 3 5% 7% 40%	2076
March	1st to 10th	Night	20% 21% 4 6% 3 3 3 3 4 5% 29%	5052
	11th to 20th	Night	19% 11% 2 5% 4 3 3 3 4 5% 42%	5110
	21st to end	Night	19% 17% 3 8% 5% 4 4 3 5% 6% 24%	5610
April	1st to 10th	Night	15% 11% 3 7% 4 3 4 4 4 7% 38%	2121
	11th to 20th	Night	10% 9% 3 7% 4 3 3 3 5% 7% 46%	2079
	21st to end	Night	9% 5% 1 4 3 3 4 3 6% 8% 54%	2027
May	1st to 10th	Night	5% 4 1 4 2 2 2 2 4 6% 69%	4109
	11th to 20th	Night	4 3 1 4 3 2 2 2 3 5% 71%	3946
	21st to end	Night	3 2 1 2 2 2 2 2 3 6% 77%	3972
June	1st to 10th	Night	5% 5% 2 4 4 3 3 3 5% 7% 60%	1600
	11th to 20th	Night	3 2 1 2 2 1 1 2 3 5% 79%	1600
	21st to end	Night	3 2 2 2 2 1 2 2 4 80%	1600
July	1st to 10th	Night	1 1 1 1 1 1 1 2 3 90%	3640
	11th to 20th	Night	1 1 2 1 1 1 1 1 2 90%	4044
	21st to end	Night	1 1 1 1 1 3 5% 85%	4472
August	1st to 10th	Night	1 1 2 1 2 1 2 3 85%	4035
	11th to 20th	Night	1 2 1 2 2 2 2 2 2 3 83%	4052
	21st to end	Night	2 1 1 1 1 1 1 3 4 83%	5010
September	1st to 10th	Night	2 1 1 1 1 1 1 3 4 85%	2000
	11th to 20th	Night	4 3 1 3 2 3 2 2 4 6% 70%	2068
	21st to end	Night	4 3 1 3 2 2 2 2 4 5% 73%	2256
October	1st to 10th	Night	4 3 1 3 2 2 2 1 2 4 77%	3920
	11th to 20th	Night	6% 4 2 8% 4 4 3 3 5% 6% 56%	3897
	21st to end	Night	9% 5% 2 6% 4 4 4 3 5% 6% 51%	4253
November	1st to 10th	Night	14% 7% 2 6% 5% 4 4 3 5% 7% 43%	2469
	11th to 20th	Night	16% 8% 2 7% 4 5% 5% 4 6% 7% 36%	2877
	21st to end	Night	13% 7% 2 6% 4 3 4 3 5% 7% 46%	2940
December	1st to 10th	Night	14% 4 2 5% 3 3 4 3 6% 8% 49%	4700
	11th to 20th	Night	30% 10% 2 7% 4 4 4 4 6% 6% 21%	5316
	21st to end	Night	32% 10% 3 7% 4 4 4 3 4 5% 24%	7106

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	54% 5% 9% 14% 12% 5%	5019
	11th to 20th	Day	35% 2 6% 8% 18% 31%	5340
	21st to end	Day	44% 3 7% 14% 15% 17%	5843
February	1st to 10th	Day	47% 2 8% 16% 17% 9%	1890
	11th to 20th	Day	48% 4 8% 18% 18% 4	1854
	21st to end	Day	48% 5% 11% 18% 13% 6%	1724
March	1st to 10th	Day	55% 4 5% 17% 16% 2	5062
	11th to 20th	Day	45% 4 13% 18% 13% 7%	5110
	21st to end	Day	56% 6% 11% 20% 7% 1	5607
April	1st to 10th	Day	45% 5% 11% 22% 14% 2	2499
	11th to 20th	Day	39% 5% 13% 23% 15% 5%	2492
	21st to end	Day	31% 5% 15% 27% 19% 4	2590
May	1st to 10th	Day	19% 6% 10% 23% 25% 16%	5894
	11th to 20th	Day	15% 2 9% 30% 35% 8%	5960
	21st to end	Day	13% 3 9% 46% 28% 1	6904
June	1st to 10th	Day	25% 5% 12% 28% 24% 5%	2800
	11th to 20th	Day	11% 3 11% 26% 34% 14%	2800
	21st to end	Day	11% 2 4 23% 38% 22%	2800
July	1st to 10th	Day	5% 1 2 14% 27% 51%	6251
	11th to 20th	Day	5% 1 3 7% 23% 60%	5859
	21st to end	Day	6% 2 6% 21% 34% 33%	6217
August	1st to 10th	Day	9% 2 3 16% 27% 44%	4206
	11th to 20th	Day	7% 2 3 23% 41% 24%	4195
	21st to end	Day	10% 2 5% 24% 29% 30%	4314
September	1st to 10th	Day	8% 2 4 17% 31% 39%	2400
	11th to 20th	Day	17% 3 8% 28% 32% 11%	2329
	21st to end	Day	13% 3 6% 22% 31% 24%	2142
October	1st to 10th	Day	17% 2 3 16% 21% 41%	3280
	11th to 20th	Day	24% 3 7% 24% 30% 11%	3261
	21st to end	Day	33% 4 7% 21% 25% 10%	3558
November	1st to 10th	Day	37% 4 9% 22% 18% 9%	2048
	11th to 20th	Day	44% 5% 11% 16% 16% 8%	1739
	21st to end	Day	36% 4 10% 17% 19% 14%	1680
December	1st to 10th	Day	33% 3 6% 19% 25% 14%	2700
	11th to 20th	Day	63% 4 8% 12% 9% 4	3108
	21st to end	Day	60% 5% 7% 17% 8% 3	4092
January	1st to 10th	Night	58% 5% 11% 13% 11% 3	7887
	11th to 20th	Night	36% 3 5% 12% 20% 24%	7650
	21st to end	Night	48% 3 5% 10% 15% 18%	8371
February	1st to 10th	Night	45% 4 8% 17% 17% 10%	2730
	11th to 20th	Night	50% 4 8% 17% 15% 5%	2664
	21st to end	Night	43% 5% 12% 19% 16% 4	2076
March	1st to 10th	Night	57% 5% 5% 18% 12% 3	5052
	11th to 20th	Night	45% 4 11% 20% 12% 8%	5110
	21st to end	Night	57% 6% 12% 17% 7% 1	5610
April	1st to 10th	Night	44% 6% 13% 21% 13% 3	2121
	11th to 20th	Night	37% 5% 14% 23% 16% 5%	2079
	21st to end	Night	27% 5% 15% 31% 18% 3	2027
May	1st to 10th	Night	17% 4 9% 22% 32% 16%	4106
	11th to 20th	Night	19% 2 7% 29% 34% 9%	3947
	21st to end	Night	12% 3 10% 42% 33% 1	3972
June	1st to 10th	Night	24% 6% 13% 28% 24% 5%	1600
	11th to 20th	Night	11% 2 9% 25% 36% 17%	1600
	21st to end	Night	12% 1 6% 17% 38% 25%	1600
July	1st to 10th	Night	4 1 2 13% 28% 52%	3600
	11th to 20th	Night	5% 1 2 6% 25% 61%	3992
	21st to end	Night	6% 2 8% 18% 32% 35%	4345
August	1st to 10th	Night	9% 2 3 14% 28% 43%	2929
	11th to 20th	Night	7% 1 3 21% 37% 31%	2929
	21st to end	Night	10% 1 4 26% 27% 33%	3603
September	1st to 10th	Night	7% 1 3 18% 32% 39%	2000
	11th to 20th	Night	16% 3 7% 27% 37% 9%	2068
	21st to end	Night	16% 2 8% 20% 29% 25%	2256
October	1st to 10th	Night	15% 2 4 14% 21% 44%	3920
	11th to 20th	Night	29% 3 7% 21% 31% 8%	3897
	21st to end	Night	33% 4 7% 24% 19% 14%	4253
November	1st to 10th	Night	40% 5% 11% 17% 17% 10%	2469
	11th to 20th	Night	44% 6% 12% 16% 16% 6%	2877
	21st to end	Night	37% 4 9% 17% 20% 12%	2940
December	1st to 10th	Night	32% 3 7% 20% 25% 13%	4700
	11th to 20th	Night	63% 4 6% 13% 11% 4	5316
	21st to end	Night	61% 4 8% 15% 8% 3	7106

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	36% 14% 22% 17% 9% 2	321
	11th to 20th	Day	28% 8% 21% 20% 19% 4	430
	21st to end	Day	24% 10% 21% 25% 15% 5%	473
February	1st to 10th	Day	27% 12% 22% 21% 15% 3	430
	11th to 20th	Day	33% 16% 21% 21% 9% 1	425
	21st to end	Day	27% 13% 27% 23% 9% 1	430
March	1st to 10th	Day	35% 17% 28% 13% 6% 1	540
	11th to 20th	Day	28% 12% 28% 21% 9% 2	540
	21st to end	Day	28% 17% 27% 18% 8% 1	594
April	1st to 10th	Day	24% 17% 28% 20% 8% 3	540
	11th to 20th	Day	24% 14% 27% 22% 10% 2	532
	21st to end	Day	13% 20% 30% 21% 11% 4	540
May	1st to 10th	Day	14% 18% 29% 25% 11% 3	508
	11th to 20th	Day	19% 14% 24% 27% 9% 7%	528
	21st to end	Day	12% 12% 30% 27% 13% 6%	573
June	1st to 10th	Day	11% 10% 27% 31% 16% 5%	530
	11th to 20th	Day	8% 14% 32% 29% 13% 4	530
	21st to end	Day	2 7% 27% 37% 19% 9%	530
July	1st to 10th	Day	2 4 27% 40% 18% 8%	526
	11th to 20th	Day	1 2 19% 44% 22% 12%	524
	21st to end	Day	1 1 15% 46% 24% 13%	575
August	1st to 10th	Day	2 2 22% 42% 22% 10%	527
	11th to 20th	Day	2 3 25% 38% 22% 10%	517
	21st to end	Day	2 3 21% 40% 24% 10%	583
September	1st to 10th	Day	2 6% 23% 35% 25% 8%	530
	11th to 20th	Day	6% 6% 24% 35% 23% 7%	530
	21st to end	Day	7% 8% 21% 32% 25% 7%	530
October	1st to 10th	Day	9% 9% 22% 26% 26% 8%	530
	11th to 20th	Day	12% 8% 21% 23% 28% 8%	530
	21st to end	Day	14% 9% 21% 28% 21% 7%	583
November	1st to 10th	Day	17% 11% 22% 24% 19% 8%	524
	11th to 20th	Day	20% 9% 17% 26% 21% 8%	250
	21st to end	Day	19% 5% 20% 27% 23% 6%	220
December	1st to 10th	Day	22% 9% 22% 22% 15% 10%	220
	11th to 20th	Day	33% 11% 14% 21% 14% 7%	220
	21st to end	Day	29% 12% 21% 20% 15% 3	242
January	1st to 10th	Night	31% 7% 15% 26% 17% 4	840
	11th to 20th	Night	24% 5% 16% 30% 18% 6%	840
	21st to end	Night	23% 5% 16% 30% 20% 5%	924
February	1st to 10th	Night	24% 8% 17% 31% 19% 2	840
	11th to 20th	Night	25% 7% 20% 25% 19% 4	824
	21st to end	Night	25% 8% 21% 33% 12% 2	692
March	1st to 10th	Night	30% 11% 17% 28% 11% 3	840
	11th to 20th	Night	27% 5% 15% 31% 19% 3	840
	21st to end	Night	25% 10% 19% 29% 14% 3	924
April	1st to 10th	Night	20% 8% 22% 29% 18% 3	840
	11th to 20th	Night	16% 10% 21% 28% 20% 5%	831
	21st to end	Night	12% 6% 22% 31% 24% 5%	767
May	1st to 10th	Night	8% 8% 23% 26% 29% 6%	603
	11th to 20th	Night	9% 3 16% 30% 35% 7%	542
	21st to end	Night	8% 7% 18% 30% 30% 6%	433
June	1st to 10th	Night	7% 4 17% 39% 27% 5%	400
	11th to 20th	Night	3 7% 18% 39% 31% 3	400
	21st to end	Night	4 2 6% 41% 41% 7%	400
July	1st to 10th	Night	2 9% 30% 51% 8%	390
	11th to 20th	Night	2 1 4 27% 51% 16%	554
	21st to end	Night	1 2 19% 57% 21%	657
August	1st to 10th	Night	2 3 28% 51% 16%	597
	11th to 20th	Night	1 1 5% 30% 48% 16%	594
	21st to end	Night	2 1 4 27% 53% 12%	875
September	1st to 10th	Night	2 2 8% 32% 45% 12%	800
	11th to 20th	Night	6% 2 10% 33% 36% 12%	800
	21st to end	Night	5% 4 12% 29% 37% 13%	800
October	1st to 10th	Night	7% 4 14% 33% 35% 8%	800
	11th to 20th	Night	10% 2 12% 31% 34% 10%	800
	21st to end	Night	14% 4 12% 31% 29% 10%	880
November	1st to 10th	Night	17% 6% 16% 26% 27% 8%	820
	11th to 20th	Night	21% 6% 15% 34% 20% 5%	840
	21st to end	Night	16% 7% 16% 35% 20% 6%	840
December	1st to 10th	Night	23% 4 18% 30% 20% 5%	840
	11th to 20th	Night	31% 6% 13% 31% 15% 4	840
	21st to end	Night	32% 9% 17% 24% 14% 3	924

Page generated at 2026-04-28 23:21:47. Version ac07

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