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 2025-01-07.

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	11% 6% 2 4 3 3 3 3 4 6% 58%	108847
	Night	13% 7% 2 5% 3 3 3 3 4 5% 52%	108935
Transparency	Day	29% 4 8% 20% 22% 18%	108606
	Night	34% 4 8% 18% 20% 16%	108766
Seeing	Day	15% 10% 24% 28% 17% 6%	15438
	Night	16% 5% 14% 29% 28% 7%	24686

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% 12% 4 7% 4 4 4 3 5% 6% 28%	2745
	11th to 20th	Day	31% 10% 3 7% 4 4 3 2 4 5% 28%	2860
	21st to end	Day	28% 11% 3 6% 4 3 3 3 5% 6% 27%	3146
February	1st to 10th	Day	21% 9% 2 5% 4 3 3 3 4 6% 40%	1710
	11th to 20th	Day	18% 10% 2 6% 5% 3 3 3 5% 7% 38%	1665
	21st to end	Day	20% 11% 3 5% 3 3 4 3 5% 6% 37%	1564
March	1st to 10th	Day	29% 20% 3 6% 3 3 2 2 3 4 26%	3442
	11th to 20th	Day	14% 7% 2 5% 3 3 3 2 4 6% 51%	3490
	21st to end	Day	24% 11% 3 7% 4 5% 5% 4 5% 6% 27%	3825
April	1st to 10th	Day	17% 10% 2 6% 5% 3 4 5% 6% 8% 33%	2261
	11th to 20th	Day	16% 7% 2 5% 3 4 3 3 5% 7% 44%	2249
	21st to end	Day	8% 7% 2 5% 3 3 3 3 6% 8% 51%	2343
May	1st to 10th	Day	6% 5% 1 4 3 3 3 3 4 6% 62%	4110
	11th to 20th	Day	4 3 1 2 2 2 2 2 3 5% 73%	4148
	21st to end	Day	5% 3 1 3 2 2 2 2 4 6% 70%	4813
June	1st to 10th	Day	8% 4 2 4 3 3 3 4 6% 6% 57%	2660
	11th to 20th	Day	3 2 2 2 2 2 2 4 5% 76%	2660
	21st to end	Day	3 2 1 2 1 2 2 2 2 4 80%	2660
July	1st to 10th	Day	1 1 1 1 1 1 1 2 90%	4420
	11th to 20th	Day	2 1 1 1 1 1 2 2 5% 84%	4147
	21st to end	Day	1 1 1 1 1 1 2 4 88%	4455
August	1st to 10th	Day	1 1 2 1 2 2 3 4 6% 79%	4091
	11th to 20th	Day	1 1 2 1 1 2 2 3 5% 82%	4026
	21st to end	Day	1 2 1 2 2 1 2 2 3 5% 80%	4183
September	1st to 10th	Day	1 1 1 1 1 2 2 2 4 84%	2280
	11th to 20th	Day	3 3 1 3 2 3 3 3 4 6% 69%	2213
	21st to end	Day	4 2 1 3 1 2 2 1 3 6% 75%	2035
October	1st to 10th	Day	4 2 1 2 2 2 3 2 3 4 75%	3180
	11th to 20th	Day	7% 3 1 3 2 3 4 4 5% 7% 60%	3161
	21st to end	Day	9% 6% 2 7% 4 4 3 3 5% 7% 49%	3448
November	1st to 10th	Day	14% 7% 2 5% 4 4 4 3 6% 7% 45%	1949
	11th to 20th	Day	17% 6% 2 7% 4 3 4 3 5% 8% 39%	1656
	21st to end	Day	16% 6% 2 5% 4 4 4 3 5% 7% 45%	1600
December	1st to 10th	Day	12% 5% 2 5% 4 3 4 3 6% 7% 49%	2620
	11th to 20th	Day	28% 10% 4 8% 4 5% 5% 4 6% 7% 18%	3028
	21st to end	Day	26% 11% 3 8% 5% 4 5% 3 6% 6% 23%	4004
January	1st to 10th	Night	20% 12% 3 6% 5% 5% 5% 4 6% 7% 28%	4334
	11th to 20th	Night	25% 12% 4 10% 5% 5% 4 3 4 4 25%	4110
	21st to end	Night	31% 12% 4 8% 4 3 2 2 4 5% 25%	4521
February	1st to 10th	Night	19% 9% 3 6% 4 3 4 3 4 6% 41%	2470
	11th to 20th	Night	17% 10% 3 7% 4 4 4 3 5% 5% 37%	2402
	21st to end	Night	18% 8% 2 6% 3 3 4 3 5% 7% 42%	1885
March	1st to 10th	Night	26% 21% 3 5% 3 3 3 2 3 4 26%	3432
	11th to 20th	Night	16% 6% 2 4 4 3 3 2 4 5% 51%	3490
	21st to end	Night	18% 18% 4 7% 5% 4 4 3 5% 5% 27%	3828
April	1st to 10th	Night	16% 10% 2 6% 5% 3 4 4 4 6% 39%	1919
	11th to 20th	Night	10% 9% 3 6% 4 3 3 3 5% 8% 46%	1879
	21st to end	Night	8% 5% 1 4 3 3 4 3 6% 8% 56%	1834
May	1st to 10th	Night	6% 5% 1 4 2 2 2 2 3 6% 67%	2860
	11th to 20th	Night	3 3 1 3 2 2 2 1 3 5% 75%	2748
	21st to end	Night	4 2 1 2 2 2 2 2 3 5% 75%	2762
June	1st to 10th	Night	5% 5% 2 4 4 3 3 3 5% 7% 59%	1520
	11th to 20th	Night	3 2 1 2 2 1 1 2 3 4 79%	1520
	21st to end	Night	3 2 1 2 2 2 2 3 4 80%	1520
July	1st to 10th	Night	1 1 1 1 1 1 1 2 92%	2540
	11th to 20th	Night	1 1 1 2 1 1 1 1 2 2 87%	2818
	21st to end	Night	1 1 1 1 2 3 91%	3109
August	1st to 10th	Night	1 1 2 2 2 2 1 3 4 81%	2848
	11th to 20th	Night	1 1 2 1 1 1 1 2 3 87%	2812
	21st to end	Night	3 2 1 2 1 1 1 1 2 3 84%	3493
September	1st to 10th	Night	1 1 1 1 1 1 1 3 4 86%	1900
	11th to 20th	Night	4 3 1 3 2 2 2 2 4 6% 71%	1964
	21st to end	Night	4 3 1 3 2 2 2 2 4 5% 74%	2143
October	1st to 10th	Night	3 2 1 3 2 2 2 1 2 4 78%	3800
	11th to 20th	Night	6% 4 2 8% 4 4 3 3 4 5% 56%	3777
	21st to end	Night	9% 5% 2 6% 4 4 4 3 5% 7% 51%	4121
November	1st to 10th	Night	14% 7% 2 6% 5% 4 4 3 5% 7% 44%	2348
	11th to 20th	Night	16% 7% 2 7% 4 5% 5% 4 6% 7% 37%	2740
	21st to end	Night	14% 7% 2 6% 4 3 4 3 4 7% 46%	2800
December	1st to 10th	Night	14% 4 2 5% 3 3 4 3 6% 8% 49%	4560
	11th to 20th	Night	30% 10% 3 7% 5% 4 4 4 6% 6% 20%	5176
	21st to end	Night	32% 10% 3 7% 4 4 4 3 4 5% 24%	6952

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% 6% 12% 16% 9% 3	2745
	11th to 20th	Day	60% 3 10% 9% 9% 8%	2860
	21st to end	Day	57% 3 8% 14% 11% 6%	3146
February	1st to 10th	Day	47% 3 9% 17% 16% 8%	1710
	11th to 20th	Day	45% 5% 8% 19% 20% 4	1674
	21st to end	Day	46% 5% 12% 19% 13% 5%	1564
March	1st to 10th	Day	63% 4 6% 12% 12% 2	3442
	11th to 20th	Day	35% 4 13% 22% 17% 9%	3490
	21st to end	Day	56% 6% 10% 18% 8% 1	3825
April	1st to 10th	Day	47% 5% 12% 21% 13% 2	2261
	11th to 20th	Day	39% 6% 14% 22% 15% 4	2252
	21st to end	Day	31% 5% 16% 27% 18% 4	2343
May	1st to 10th	Day	21% 8% 13% 25% 19% 13%	4110
	11th to 20th	Day	16% 3 7% 20% 42% 12%	4151
	21st to end	Day	17% 4 12% 46% 21% 1	4814
June	1st to 10th	Day	27% 6% 13% 27% 23% 5%	2660
	11th to 20th	Day	11% 3 12% 26% 34% 14%	2660
	21st to end	Day	12% 2 4 22% 38% 22%	2660
July	1st to 10th	Day	5% 1 2 10% 19% 62%	4351
	11th to 20th	Day	7% 2 4 10% 22% 55%	4076
	21st to end	Day	4 1 2 13% 33% 47%	4315
August	1st to 10th	Day	9% 2 4 15% 26% 45%	4076
	11th to 20th	Day	7% 2 3 23% 42% 24%	4065
	21st to end	Day	10% 2 6% 25% 28% 30%	4182
September	1st to 10th	Day	7% 1 4 15% 31% 41%	2280
	11th to 20th	Day	17% 3 8% 27% 33% 11%	2213
	21st to end	Day	13% 3 6% 23% 31% 25%	2035
October	1st to 10th	Day	16% 3 3 16% 20% 42%	3180
	11th to 20th	Day	24% 4 7% 23% 30% 11%	3161
	21st to end	Day	33% 4 7% 21% 24% 10%	3448
November	1st to 10th	Day	37% 4 9% 22% 17% 9%	1949
	11th to 20th	Day	42% 5% 12% 16% 16% 9%	1656
	21st to end	Day	38% 4 10% 16% 18% 14%	1600
December	1st to 10th	Day	34% 3 6% 19% 25% 14%	2620
	11th to 20th	Day	64% 4 8% 12% 10% 3	3028
	21st to end	Day	60% 5% 7% 17% 8% 3	4004
January	1st to 10th	Night	52% 6% 16% 14% 8% 4	4334
	11th to 20th	Night	60% 6% 8% 11% 8% 8%	4110
	21st to end	Night	63% 4 6% 10% 11% 6%	4521
February	1st to 10th	Night	44% 4 8% 18% 17% 9%	2470
	11th to 20th	Night	48% 4 8% 18% 16% 6%	2404
	21st to end	Night	41% 5% 13% 20% 16% 4	1885
March	1st to 10th	Night	62% 6% 6% 13% 11% 1	3432
	11th to 20th	Night	35% 5% 12% 24% 14% 10%	3490
	21st to end	Night	55% 7% 13% 16% 7% 2	3828
April	1st to 10th	Night	44% 6% 13% 22% 11% 3	1919
	11th to 20th	Night	36% 5% 14% 24% 16% 4	1879
	21st to end	Night	26% 6% 16% 31% 18% 3	1834
May	1st to 10th	Night	20% 5% 13% 26% 23% 13%	2860
	11th to 20th	Night	14% 2 9% 21% 40% 13%	2749
	21st to end	Night	15% 3 12% 46% 23% 1	2762
June	1st to 10th	Night	26% 6% 13% 27% 22% 5%	1520
	11th to 20th	Night	12% 2 9% 25% 35% 16%	1520
	21st to end	Night	12% 1 6% 17% 37% 26%	1520
July	1st to 10th	Night	4 1 2 9% 21% 63%	2500
	11th to 20th	Night	7% 2 3 8% 23% 58%	2766
	21st to end	Night	3 1 4 10% 32% 50%	3011
August	1st to 10th	Night	9% 2 4 14% 27% 44%	2839
	11th to 20th	Night	7% 1 3 21% 37% 30%	2839
	21st to end	Night	10% 1 4 26% 26% 33%	3493
September	1st to 10th	Night	6% 1 3 17% 32% 41%	1900
	11th to 20th	Night	16% 3 8% 27% 38% 9%	1964
	21st to end	Night	15% 2 8% 21% 29% 26%	2143
October	1st to 10th	Night	15% 2 4 14% 21% 45%	3800
	11th to 20th	Night	29% 3 7% 20% 32% 9%	3777
	21st to end	Night	33% 4 7% 24% 19% 14%	4121
November	1st to 10th	Night	40% 5% 11% 17% 17% 10%	2348
	11th to 20th	Night	43% 6% 13% 16% 16% 6%	2740
	21st to end	Night	38% 4 9% 16% 19% 12%	2800
December	1st to 10th	Night	33% 3 7% 19% 25% 13%	4560
	11th to 20th	Night	63% 4 6% 13% 11% 3	5176
	21st to end	Night	61% 4 9% 15% 8% 3	6952

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	38% 14% 21% 17% 9% 1	285
	11th to 20th	Day	32% 9% 23% 18% 15% 3	370
	21st to end	Day	27% 11% 21% 23% 14% 4	407
February	1st to 10th	Day	26% 13% 21% 21% 15% 3	370
	11th to 20th	Day	32% 15% 21% 22% 9% 1	365
	21st to end	Day	26% 13% 28% 22% 9% 2	368
March	1st to 10th	Day	39% 16% 25% 13% 6% 1	460
	11th to 20th	Day	28% 13% 28% 19% 9% 2	460
	21st to end	Day	29% 18% 27% 17% 8% 1	506
April	1st to 10th	Day	25% 18% 28% 19% 7% 2	460
	11th to 20th	Day	26% 14% 27% 22% 10% 2	452
	21st to end	Day	14% 22% 29% 21% 10% 4	460
May	1st to 10th	Day	14% 18% 29% 25% 10% 3	463
	11th to 20th	Day	18% 13% 24% 28% 10% 8%	488
	21st to end	Day	13% 13% 28% 27% 13% 6%	529
June	1st to 10th	Day	12% 11% 27% 30% 16% 5%	490
	11th to 20th	Day	9% 14% 31% 29% 13% 4	490
	21st to end	Day	2 6% 27% 37% 19% 9%	490
July	1st to 10th	Day	2 5% 25% 41% 19% 8%	486
	11th to 20th	Day	1 2 20% 44% 22% 11%	484
	21st to end	Day	1 1 16% 45% 25% 12%	531
August	1st to 10th	Day	2 3 23% 41% 22% 10%	487
	11th to 20th	Day	2 3 25% 38% 22% 10%	477
	21st to end	Day	1 4 21% 40% 24% 9%	539
September	1st to 10th	Day	2 6% 23% 36% 25% 8%	490
	11th to 20th	Day	5% 7% 25% 35% 22% 7%	490
	21st to end	Day	6% 8% 21% 33% 24% 7%	490
October	1st to 10th	Day	8% 9% 22% 26% 27% 8%	490
	11th to 20th	Day	12% 7% 20% 22% 30% 9%	490
	21st to end	Day	14% 9% 21% 28% 20% 7%	539
November	1st to 10th	Day	16% 12% 22% 24% 18% 8%	485
	11th to 20th	Day	19% 8% 16% 26% 22% 9%	227
	21st to end	Day	21% 6% 20% 26% 23% 6%	200
December	1st to 10th	Day	25% 10% 21% 20% 15% 11%	200
	11th to 20th	Day	32% 12% 15% 22% 13% 7%	200
	21st to end	Day	28% 13% 20% 21% 15% 3	220
January	1st to 10th	Night	29% 7% 15% 27% 18% 4	784
	11th to 20th	Night	26% 5% 17% 29% 17% 6%	760
	21st to end	Night	25% 5% 16% 29% 20% 5%	836
February	1st to 10th	Night	23% 8% 15% 31% 20% 3	760
	11th to 20th	Night	24% 7% 19% 25% 21% 4	744
	21st to end	Night	24% 8% 21% 33% 13% 2	628
March	1st to 10th	Night	32% 10% 16% 27% 12% 3	760
	11th to 20th	Night	27% 6% 15% 29% 21% 3	760
	21st to end	Night	26% 11% 20% 27% 14% 3	836
April	1st to 10th	Night	21% 8% 22% 28% 17% 3	760
	11th to 20th	Night	17% 10% 21% 28% 19% 5%	751
	21st to end	Night	11% 7% 23% 31% 24% 5%	694
May	1st to 10th	Night	9% 8% 24% 26% 27% 6%	570
	11th to 20th	Night	9% 2 15% 30% 37% 8%	515
	21st to end	Night	9% 7% 18% 30% 30% 6%	411
June	1st to 10th	Night	8% 4 18% 39% 26% 5%	380
	11th to 20th	Night	3 6% 19% 37% 32% 3	380
	21st to end	Night	4 1 5% 41% 42% 7%	380
July	1st to 10th	Night	2 9% 29% 52% 8%	370
	11th to 20th	Night	2 1 4 28% 49% 16%	525
	21st to end	Night	1 2 20% 57% 20%	624
August	1st to 10th	Night	2 3 27% 51% 17%	567
	11th to 20th	Night	1 1 5% 30% 48% 16%	564
	21st to end	Night	2 1 4 28% 52% 13%	831
September	1st to 10th	Night	1 2 8% 31% 45% 13%	760
	11th to 20th	Night	6% 2 10% 34% 35% 13%	760
	21st to end	Night	5% 4 12% 29% 36% 14%	760
October	1st to 10th	Night	6% 4 13% 33% 36% 8%	760
	11th to 20th	Night	11% 3 11% 30% 35% 11%	760
	21st to end	Night	14% 4 12% 31% 29% 11%	836
November	1st to 10th	Night	17% 6% 16% 26% 28% 8%	780
	11th to 20th	Night	20% 6% 14% 35% 21% 5%	800
	21st to end	Night	17% 7% 16% 33% 20% 7%	800
December	1st to 10th	Night	24% 5% 17% 29% 20% 6%	800
	11th to 20th	Night	31% 7% 14% 31% 14% 4	800
	21st to end	Night	31% 9% 18% 24% 15% 3	880

Page generated at 2025-01-04 00:23:57. Version ac07

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