Star Hill Inn
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Star Hill Inn clear sky chart from 2005-11-06 to 2026-07-16.

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	3 3 1 4 3 4 4 4 6% 8% 59%	146159
	Night	4 3 1 4 3 3 3 3 5% 7% 64%	144039
Transparency	Day	20% 7% 10% 18% 26% 20%	141201
	Night	19% 6% 9% 19% 28% 20%	140017
Seeing	Day	7% 16% 28% 28% 17% 5%	17504
	Night	5% 10% 31% 35% 16% 2	27548

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	1 6% 3 4 2 3 3 3 5% 7% 63%	4941
	11th to 20th	Day	1 1 3 2 2 2 2 3 5% 79%	5340
	21st to end	Day	1 4 2 5% 3 3 4 3 5% 7% 63%	5844
February	1st to 10th	Day	1 4 2 4 3 3 3 2 5% 8% 66%	1983
	11th to 20th	Day	1 4 2 4 2 3 3 4 6% 7% 65%	2049
	21st to end	Day	1 2 1 3 3 2 4 4 5% 7% 68%	1730
March	1st to 10th	Day	1 4 1 3 2 2 3 3 5% 6% 70%	4664
	11th to 20th	Day	6% 6% 2 4 3 2 3 2 4 7% 60%	5110
	21st to end	Day	2 4 1 3 3 3 4 3 6% 9% 62%	5906
April	1st to 10th	Day	2 4 1 3 2 3 3 3 6% 7% 67%	2520
	11th to 20th	Day	4 4 1 4 3 3 3 3 4 8% 63%	2491
	21st to end	Day	4 3 1 3 3 2 3 3 5% 7% 66%	2520
May	1st to 10th	Day	8% 5% 2 4 4 3 4 3 5% 6% 56%	7057
	11th to 20th	Day	6% 2 1 3 2 3 4 3 5% 7% 64%	7444
	21st to end	Day	3 3 1 3 3 4 5% 5% 7% 7% 59%	9020
June	1st to 10th	Day	3 2 1 4 3 4 5% 5% 9% 9% 56%	2940
	11th to 20th	Day	3 2 1 3 3 3 4 4 7% 7% 65%	2940
	21st to end	Day	5% 3 2 4 4 4 6% 5% 8% 9% 50%	2940
July	1st to 10th	Day	5% 3 1 4 4 5% 6% 5% 8% 9% 48%	6479
	11th to 20th	Day	3 2 2 5% 5% 7% 9% 8% 10% 10% 40%	6145
	21st to end	Day	5% 5% 2 8% 7% 7% 8% 6% 9% 9% 34%	6401
August	1st to 10th	Day	3 2 1 5% 5% 6% 7% 7% 9% 9% 46%	5493
	11th to 20th	Day	3 3 2 6% 6% 6% 7% 6% 8% 10% 44%	5366
	21st to end	Day	3 2 1 6% 5% 6% 7% 6% 9% 12% 43%	5984
September	1st to 10th	Day	6% 4 2 5% 4 4 5% 4 7% 8% 50%	2400
	11th to 20th	Day	5% 3 2 5% 4 4 5% 4 6% 7% 55%	2379
	21st to end	Day	4 2 1 4 2 2 4 3 5% 6% 68%	2200
October	1st to 10th	Day	5% 2 1 4 3 2 2 2 4 6% 67%	3315
	11th to 20th	Day	8% 3 1 4 3 3 3 3 4 7% 60%	3250
	21st to end	Day	2 2 1 2 1 1 2 2 3 4 80%	3548
November	1st to 10th	Day	3 3 1 2 1 1 2 2 4 6% 76%	1912
	11th to 20th	Day	2 2 2 3 1 2 3 3 5% 6% 72%	1890
	21st to end	Day	3 3 1 3 2 2 3 2 5% 6% 70%	1890
December	1st to 10th	Day	1 2 1 2 1 1 2 2 3 7% 79%	2870
	11th to 20th	Day	1 2 1 2 3 2 3 3 4 7% 72%	3106
	21st to end	Day	1 3 1 3 2 2 2 2 4 8% 73%	4092
January	1st to 10th	Night	1 5% 3 5% 3 4 4 3 5% 6% 62%	8024
	11th to 20th	Night	1 2 1 3 3 2 2 2 3 5% 78%	7650
	21st to end	Night	1 3 1 5% 4 3 3 3 5% 7% 65%	8370
February	1st to 10th	Night	1 4 1 5% 3 3 3 2 4 7% 68%	2635
	11th to 20th	Night	2 5% 2 4 2 2 3 3 5% 7% 64%	2458
	21st to end	Night	1 3 1 3 2 2 2 2 4 7% 73%	2076
March	1st to 10th	Night	1 5% 1 3 2 2 2 2 4 6% 72%	5418
	11th to 20th	Night	7% 6% 1 3 2 2 3 2 4 5% 64%	5110
	21st to end	Night	1 3 1 2 2 2 2 2 4 6% 74%	5295
April	1st to 10th	Night	2 4 1 3 2 2 2 2 4 6% 73%	2100
	11th to 20th	Night	4 4 2 3 2 2 3 2 4 7% 68%	2077
	21st to end	Night	3 3 1 2 2 3 3 3 5% 5% 70%	2100
May	1st to 10th	Night	12% 5% 1 3 2 2 3 3 4 5% 58%	5890
	11th to 20th	Night	6% 3 1 3 2 2 3 3 5% 7% 66%	5443
	21st to end	Night	5% 4 2 5% 3 3 3 3 4 6% 62%	5182
June	1st to 10th	Night	4 3 2 3 4 3 5% 4 8% 9% 56%	1680
	11th to 20th	Night	2 2 1 3 1 3 3 3 5% 7% 70%	1680
	21st to end	Night	7% 4 2 4 3 4 4 4 7% 8% 53%	1680
July	1st to 10th	Night	8% 4 2 6% 4 4 4 5% 7% 8% 50%	3720
	11th to 20th	Night	3 3 1 4 4 5% 7% 7% 10% 14% 41%	3927
	21st to end	Night	6% 4 2 6% 5% 5% 7% 6% 10% 12% 39%	4472
August	1st to 10th	Night	4 3 2 6% 5% 6% 7% 6% 8% 11% 44%	4307
	11th to 20th	Night	4 3 2 5% 4 5% 6% 5% 8% 13% 47%	4483
	21st to end	Night	6% 5% 2 8% 5% 6% 6% 5% 9% 12% 35%	4993
September	1st to 10th	Night	6% 3 2 4 4 3 4 4 7% 7% 57%	2000
	11th to 20th	Night	7% 3 1 4 3 3 4 4 5% 6% 61%	2020
	21st to end	Night	6% 2 1 2 2 2 3 3 4 7% 67%	2200
October	1st to 10th	Night	5% 2 1 3 2 2 2 2 3 5% 72%	3869
	11th to 20th	Night	9% 3 1 3 2 2 2 2 3 5% 68%	3898
	21st to end	Night	3 2 1 2 2 2 2 2 3 3 79%	4252
November	1st to 10th	Night	2 2 1 2 1 1 2 3 3 5% 77%	2584
	11th to 20th	Night	1 2 1 3 2 2 3 2 4 6% 75%	2730
	21st to end	Night	4 3 1 2 2 3 3 3 5% 6% 70%	2730
December	1st to 10th	Night	1 3 2 3 2 2 2 2 4 6% 74%	4537
	11th to 20th	Night	1 2 1 3 2 2 3 3 5% 7% 72%	5321
	21st to end	Night	1 3 2 4 3 3 3 3 4 7% 68%	7128

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	20% 4 7% 17% 37% 15%	4944
	11th to 20th	Day	10% 4 6% 17% 36% 27%	5340
	21st to end	Day	19% 6% 6% 15% 32% 22%	5844
February	1st to 10th	Day	19% 3 9% 20% 30% 20%	1983
	11th to 20th	Day	18% 3 10% 22% 28% 19%	2059
	21st to end	Day	16% 3 6% 14% 34% 27%	1730
March	1st to 10th	Day	13% 3 5% 12% 30% 37%	4664
	11th to 20th	Day	22% 4 8% 15% 29% 22%	5110
	21st to end	Day	16% 5% 8% 22% 40% 9%	5906
April	1st to 10th	Day	16% 5% 8% 21% 32% 19%	2520
	11th to 20th	Day	20% 5% 8% 18% 26% 23%	2494
	21st to end	Day	17% 5% 10% 20% 32% 16%	2520
May	1st to 10th	Day	25% 8% 9% 17% 23% 18%	7057
	11th to 20th	Day	16% 6% 7% 15% 22% 34%	7448
	21st to end	Day	17% 10% 11% 15% 17% 31%	9021
June	1st to 10th	Day	19% 9% 12% 19% 21% 19%	2940
	11th to 20th	Day	15% 6% 9% 15% 22% 33%	2940
	21st to end	Day	27% 8% 12% 16% 19% 18%	2940
July	1st to 10th	Day	25% 11% 16% 16% 15% 17%	6411
	11th to 20th	Day	27% 15% 20% 25% 9% 4	6071
	21st to end	Day	37% 13% 17% 20% 9% 4	6217
August	1st to 10th	Day	29% 14% 20% 19% 12% 6%	3999
	11th to 20th	Day	26% 10% 13% 24% 17% 10%	3882
	21st to end	Day	28% 12% 17% 24% 17% 2	4311
September	1st to 10th	Day	29% 9% 12% 20% 21% 10%	2400
	11th to 20th	Day	25% 7% 10% 18% 21% 18%	2379
	21st to end	Day	16% 5% 9% 21% 33% 16%	2200
October	1st to 10th	Day	18% 5% 7% 16% 30% 25%	3315
	11th to 20th	Day	23% 5% 7% 16% 26% 23%	3250
	21st to end	Day	11% 2 5% 13% 39% 30%	3548
November	1st to 10th	Day	12% 2 6% 17% 39% 23%	1912
	11th to 20th	Day	13% 3 7% 22% 37% 18%	1890
	21st to end	Day	16% 3 7% 17% 31% 25%	1890
December	1st to 10th	Day	10% 2 6% 21% 39% 22%	2870
	11th to 20th	Day	14% 3 6% 19% 38% 19%	3104
	21st to end	Day	12% 4 6% 22% 35% 22%	4092
January	1st to 10th	Night	21% 4 6% 17% 37% 14%	8025
	11th to 20th	Night	11% 4 5% 20% 35% 25%	7650
	21st to end	Night	17% 5% 7% 16% 32% 22%	8370
February	1st to 10th	Night	18% 4 7% 21% 28% 22%	2635
	11th to 20th	Night	19% 5% 9% 22% 29% 16%	2458
	21st to end	Night	13% 3 5% 16% 35% 27%	2076
March	1st to 10th	Night	14% 3 4 12% 32% 35%	5418
	11th to 20th	Night	22% 4 6% 16% 30% 22%	5110
	21st to end	Night	11% 4 7% 24% 41% 13%	5295
April	1st to 10th	Night	14% 5% 7% 21% 33% 21%	2100
	11th to 20th	Night	19% 4 8% 18% 26% 24%	2077
	21st to end	Night	16% 5% 10% 22% 30% 17%	2100
May	1st to 10th	Night	25% 6% 8% 23% 22% 17%	5888
	11th to 20th	Night	17% 6% 8% 15% 23% 30%	5444
	21st to end	Night	22% 8% 10% 12% 14% 34%	5183
June	1st to 10th	Night	22% 9% 16% 19% 17% 17%	1680
	11th to 20th	Night	14% 5% 10% 18% 21% 32%	1680
	21st to end	Night	27% 9% 14% 16% 18% 17%	1680
July	1st to 10th	Night	30% 10% 12% 21% 14% 14%	3680
	11th to 20th	Night	25% 14% 25% 24% 7% 5%	3878
	21st to end	Night	32% 12% 22% 21% 12% 1	4344
August	1st to 10th	Night	34% 12% 19% 17% 13% 5%	3136
	11th to 20th	Night	24% 9% 18% 24% 19% 7%	3243
	21st to end	Night	32% 13% 20% 24% 8% 3	3597
September	1st to 10th	Night	25% 8% 15% 24% 20% 8%	2000
	11th to 20th	Night	24% 6% 11% 18% 24% 16%	2020
	21st to end	Night	17% 7% 12% 18% 32% 14%	2200
October	1st to 10th	Night	16% 5% 6% 15% 32% 25%	3869
	11th to 20th	Night	20% 4 7% 15% 28% 26%	3898
	21st to end	Night	12% 2 4 14% 38% 29%	4252
November	1st to 10th	Night	12% 3 6% 20% 36% 23%	2584
	11th to 20th	Night	11% 4 6% 20% 39% 20%	2730
	21st to end	Night	17% 3 7% 19% 28% 25%	2730
December	1st to 10th	Night	14% 3 6% 25% 35% 17%	4537
	11th to 20th	Night	13% 3 6% 17% 37% 23%	5322
	21st to end	Night	15% 4 8% 21% 33% 19%	7128

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% 25% 35% 24% 9% 1	330
	11th to 20th	Day	6% 24% 30% 27% 11% 2	330
	21st to end	Day	3 20% 31% 31% 11% 4	363
February	1st to 10th	Day	5% 22% 34% 27% 9% 2	330
	11th to 20th	Day	8% 28% 36% 21% 6% 1	330
	21st to end	Day	5% 39% 30% 23% 3 1	273
March	1st to 10th	Day	6% 31% 35% 19% 8% 1	355
	11th to 20th	Day	13% 27% 34% 21% 4 1	540
	21st to end	Day	8% 37% 30% 19% 5% 1	594
April	1st to 10th	Day	7% 29% 39% 17% 7% 1	540
	11th to 20th	Day	12% 34% 35% 15% 3 1	532
	21st to end	Day	13% 30% 34% 18% 6% 1	540
May	1st to 10th	Day	10% 22% 39% 21% 6% 1	543
	11th to 20th	Day	9% 15% 31% 27% 14% 4	707
	21st to end	Day	6% 16% 34% 29% 13% 2	844
June	1st to 10th	Day	4 9% 24% 35% 23% 5%	780
	11th to 20th	Day	4 11% 28% 34% 18% 4	780
	21st to end	Day	6% 6% 27% 33% 22% 6%	780
July	1st to 10th	Day	6% 3 18% 32% 31% 10%	771
	11th to 20th	Day	3 2 11% 30% 36% 17%	635
	21st to end	Day	5% 2 11% 30% 35% 17%	575
August	1st to 10th	Day	7% 3 15% 30% 33% 12%	527
	11th to 20th	Day	5% 3 16% 34% 32% 9%	517
	21st to end	Day	4 2 19% 38% 26% 11%	583
September	1st to 10th	Day	7% 4 20% 37% 24% 8%	530
	11th to 20th	Day	3 6% 29% 32% 22% 8%	509
	21st to end	Day	6% 9% 22% 33% 25% 5%	330
October	1st to 10th	Day	14% 13% 23% 22% 20% 8%	330
	11th to 20th	Day	12% 15% 28% 25% 15% 5%	330
	21st to end	Day	10% 17% 27% 27% 16% 4	363
November	1st to 10th	Day	7% 20% 30% 28% 13% 2	330
	11th to 20th	Day	7% 13% 31% 31% 16% 3	330
	21st to end	Day	8% 22% 32% 22% 13% 3	330
December	1st to 10th	Day	3 21% 37% 25% 12% 2	330
	11th to 20th	Day	4 21% 32% 32% 10% 2	330
	21st to end	Day	9% 26% 33% 25% 6% 1	363
January	1st to 10th	Night	2 16% 38% 31% 11% 2	990
	11th to 20th	Night	4 13% 39% 32% 10% 2	840
	21st to end	Night	3 13% 40% 32% 10% 2	924
February	1st to 10th	Night	3 14% 47% 28% 8% 1	840
	11th to 20th	Night	5% 17% 45% 27% 5% 1	824
	21st to end	Night	2 21% 50% 24% 3	692
March	1st to 10th	Night	4 20% 40% 28% 7% 1	840
	11th to 20th	Night	7% 15% 34% 34% 9% 1	840
	21st to end	Night	4 16% 44% 31% 6%	790
April	1st to 10th	Night	5% 16% 45% 28% 5%	630
	11th to 20th	Night	6% 15% 42% 31% 6%	623
	21st to end	Night	6% 14% 39% 34% 6%	630
May	1st to 10th	Night	7% 9% 35% 41% 8%	630
	11th to 20th	Night	9% 5% 33% 37% 14% 1	621
	21st to end	Night	6% 8% 31% 43% 12% 1	683
June	1st to 10th	Night	4 5% 23% 44% 22% 2	630
	11th to 20th	Night	2 3 30% 48% 16%	630
	21st to end	Night	8% 2 17% 46% 25% 1	630
July	1st to 10th	Night	6% 2 12% 38% 38% 5%	615
	11th to 20th	Night	3 1 7% 35% 48% 6%	597
	21st to end	Night	7% 1 5% 28% 50% 9%	657
August	1st to 10th	Night	6% 2 5% 32% 47% 9%	597
	11th to 20th	Night	6% 1 7% 40% 43% 4	594
	21st to end	Night	5% 2 12% 38% 37% 6%	660
September	1st to 10th	Night	6% 2 12% 46% 32% 3	600
	11th to 20th	Night	8% 2 14% 46% 29% 2	600
	21st to end	Night	6% 6% 20% 44% 23% 1	600
October	1st to 10th	Night	8% 4 28% 39% 19% 2	762
	11th to 20th	Night	6% 6% 29% 39% 17% 3	800
	21st to end	Night	6% 9% 30% 34% 17% 4	880
November	1st to 10th	Night	3 11% 33% 37% 14% 3	944
	11th to 20th	Night	2 13% 33% 38% 11% 3	1050
	21st to end	Night	6% 14% 35% 30% 13% 3	1050
December	1st to 10th	Night	3 14% 42% 31% 9% 2	1050
	11th to 20th	Night	4 15% 38% 33% 9% 1	1050
	21st to end	Night	5% 18% 42% 28% 6%	1155

Page generated at 2026-07-13 01:14:48. Version ac07

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