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 2025-03-12.

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	4 3 1 4 3 3 4 4 6% 7% 60%	112694
	Night	4 3 1 4 3 3 3 3 5% 7% 64%	115171
Transparency	Day	20% 7% 10% 19% 26% 18%	112448
	Night	19% 6% 9% 19% 28% 19%	115007
Seeing	Day	6% 16% 28% 28% 17% 5%	15586
	Night	5% 10% 31% 35% 17% 2	25826

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 3 3 3 3 5% 7% 63%	3803
	11th to 20th	Day	1 2 1 3 3 2 3 2 3 6% 74%	4100
	21st to end	Day	1 5% 2 5% 3 2 3 3 5% 7% 62%	4510
February	1st to 10th	Day	1 4 2 4 3 3 3 3 5% 8% 65%	1888
	11th to 20th	Day	1 4 1 4 1 3 3 4 6% 7% 66%	1949
	21st to end	Day	1 2 2 3 3 3 4 4 5% 6% 67%	1650
March	1st to 10th	Day	1 4 1 3 2 2 2 3 5% 7% 69%	3280
	11th to 20th	Day	9% 7% 2 4 3 2 3 3 4 7% 55%	3502
	21st to end	Day	2 5% 1 3 3 3 4 3 6% 8% 63%	4027
April	1st to 10th	Day	2 3 1 3 2 3 3 3 6% 7% 67%	2280
	11th to 20th	Day	4 4 1 4 3 3 3 3 4 8% 62%	2251
	21st to end	Day	4 3 1 3 3 2 3 3 6% 8% 65%	2280
May	1st to 10th	Day	6% 3 1 2 3 2 3 3 4 5% 68%	3800
	11th to 20th	Day	10% 4 1 4 3 3 4 4 7% 7% 53%	3981
	21st to end	Day	3 2 1 3 2 3 4 3 5% 6% 69%	4819
June	1st to 10th	Day	3 2 1 3 3 4 5% 5% 9% 9% 57%	2660
	11th to 20th	Day	3 2 1 3 3 3 4 4 6% 7% 66%	2660
	21st to end	Day	5% 3 2 5% 5% 5% 5% 5% 8% 9% 49%	2660
July	1st to 10th	Day	6% 3 1 5% 4 5% 7% 6% 9% 9% 45%	4430
	11th to 20th	Day	3 2 2 5% 5% 6% 9% 8% 9% 10% 40%	4248
	21st to end	Day	6% 5% 2 7% 7% 7% 8% 6% 9% 10% 34%	4454
August	1st to 10th	Day	4 3 1 6% 6% 7% 7% 7% 8% 9% 42%	3890
	11th to 20th	Day	4 3 1 5% 5% 6% 6% 5% 8% 10% 47%	3726
	21st to end	Day	3 2 1 6% 5% 6% 7% 6% 9% 11% 44%	4180
September	1st to 10th	Day	7% 4 2 5% 4 4 5% 4 6% 8% 51%	2280
	11th to 20th	Day	5% 3 2 5% 4 4 5% 4 6% 7% 55%	2260
	21st to end	Day	4 2 1 4 2 2 3 3 4 6% 69%	2090
October	1st to 10th	Day	5% 3 1 4 3 2 2 2 4 6% 67%	3214
	11th to 20th	Day	8% 3 1 4 3 3 3 3 4 7% 61%	3150
	21st to end	Day	2 2 1 2 1 1 2 2 2 4 81%	3438
November	1st to 10th	Day	3 3 1 2 1 1 2 2 4 6% 75%	1819
	11th to 20th	Day	2 2 2 3 1 2 3 3 5% 6% 73%	1800
	21st to end	Day	3 3 1 3 2 2 3 2 5% 6% 70%	1800
December	1st to 10th	Day	1 2 1 2 1 1 2 2 3 7% 79%	2785
	11th to 20th	Day	1 2 1 2 3 2 3 3 4 7% 72%	3026
	21st to end	Day	1 3 1 3 2 2 2 2 4 7% 73%	4004
January	1st to 10th	Night	1 5% 3 5% 3 4 4 3 4 6% 63%	6192
	11th to 20th	Night	1 2 1 4 3 3 3 2 3 5% 73%	5880
	21st to end	Night	1 3 1 5% 3 3 3 3 5% 7% 66%	6468
February	1st to 10th	Night	1 4 1 5% 3 3 3 2 4 6% 68%	2510
	11th to 20th	Night	2 5% 2 4 2 2 3 3 5% 7% 65%	2338
	21st to end	Night	1 3 1 3 2 2 2 3 4 7% 72%	1980
March	1st to 10th	Night	1 4 1 3 2 2 2 2 4 6% 72%	3803
	11th to 20th	Night	10% 8% 2 4 2 2 3 2 4 6% 57%	3506
	21st to end	Night	1 4 2 3 2 3 3 2 5% 6% 68%	3617
April	1st to 10th	Night	2 4 1 3 2 2 2 3 4 6% 73%	1900
	11th to 20th	Night	4 4 2 4 2 2 3 2 4 7% 67%	1877
	21st to end	Night	3 3 1 2 2 2 3 3 5% 5% 70%	1900
May	1st to 10th	Night	8% 3 1 2 2 2 2 3 4 5% 68%	3170
	11th to 20th	Night	10% 5% 1 4 2 3 4 4 6% 9% 52%	2919
	21st to end	Night	4 2 1 2 2 2 2 2 4 6% 74%	2763
June	1st to 10th	Night	3 3 2 3 3 3 5% 4 8% 9% 56%	1520
	11th to 20th	Night	2 2 2 1 3 4 2 5% 7% 71%	1520
	21st to end	Night	7% 4 2 4 3 4 4 5% 8% 8% 52%	1520
July	1st to 10th	Night	9% 4 1 5% 4 5% 5% 6% 7% 9% 45%	2540
	11th to 20th	Night	4 3 1 4 4 5% 6% 7% 9% 14% 41%	2717
	21st to end	Night	7% 4 2 5% 4 4 6% 5% 8% 11% 44%	3109
August	1st to 10th	Night	5% 3 2 7% 5% 6% 7% 6% 10% 12% 36%	3049
	11th to 20th	Night	4 2 1 5% 4 4 5% 5% 7% 12% 50%	3113
	21st to end	Night	3 4 2 7% 5% 6% 6% 6% 11% 13% 37%	3487
September	1st to 10th	Night	6% 3 2 4 3 3 4 4 7% 7% 57%	1900
	11th to 20th	Night	7% 3 1 4 3 3 3 4 5% 6% 61%	1919
	21st to end	Night	6% 2 1 2 2 2 3 3 4 7% 67%	2090
October	1st to 10th	Night	5% 2 1 3 2 2 2 2 3 4 72%	3751
	11th to 20th	Night	9% 3 1 3 2 2 2 2 3 5% 69%	3778
	21st to end	Night	3 2 1 2 2 2 2 2 3 3 79%	4120
November	1st to 10th	Night	2 3 1 2 1 1 2 3 3 5% 76%	2458
	11th to 20th	Night	1 2 1 3 2 2 3 2 4 6% 76%	2600
	21st to end	Night	4 3 1 2 2 3 3 3 4 6% 70%	2600
December	1st to 10th	Night	1 3 2 3 2 2 2 2 4 6% 74%	4402
	11th to 20th	Night	1 2 1 3 2 2 3 3 5% 7% 71%	5181
	21st to end	Night	1 3 2 4 3 3 3 3 4 7% 68%	6974

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% 5% 7% 17% 36% 15%	3804
	11th to 20th	Day	12% 4 6% 18% 34% 26%	4100
	21st to end	Day	18% 6% 8% 16% 31% 21%	4510
February	1st to 10th	Day	19% 3 9% 20% 30% 19%	1888
	11th to 20th	Day	18% 4 10% 23% 27% 20%	1959
	21st to end	Day	16% 3 6% 14% 32% 28%	1650
March	1st to 10th	Day	14% 3 6% 15% 33% 29%	3280
	11th to 20th	Day	27% 5% 10% 20% 29% 9%	3502
	21st to end	Day	17% 5% 10% 19% 37% 11%	4027
April	1st to 10th	Day	16% 5% 8% 21% 31% 19%	2280
	11th to 20th	Day	21% 5% 8% 18% 26% 22%	2254
	21st to end	Day	18% 5% 11% 21% 32% 14%	2280
May	1st to 10th	Day	17% 6% 9% 15% 23% 29%	3800
	11th to 20th	Day	24% 8% 10% 17% 24% 17%	3985
	21st to end	Day	12% 6% 8% 15% 21% 38%	4819
June	1st to 10th	Day	19% 9% 13% 19% 22% 19%	2660
	11th to 20th	Day	16% 6% 9% 14% 22% 33%	2660
	21st to end	Day	28% 8% 13% 16% 19% 16%	2660
July	1st to 10th	Day	28% 11% 17% 14% 12% 18%	4361
	11th to 20th	Day	29% 14% 18% 25% 10% 4	4174
	21st to end	Day	37% 12% 16% 24% 8% 4	4314
August	1st to 10th	Day	30% 14% 20% 18% 12% 5%	3876
	11th to 20th	Day	25% 10% 13% 24% 17% 10%	3762
	21st to end	Day	28% 12% 17% 24% 17% 3	4179
September	1st to 10th	Day	30% 8% 11% 19% 22% 10%	2280
	11th to 20th	Day	26% 7% 10% 18% 21% 19%	2260
	21st to end	Day	16% 5% 9% 22% 33% 16%	2090
October	1st to 10th	Day	18% 5% 6% 16% 29% 25%	3214
	11th to 20th	Day	22% 5% 7% 16% 27% 22%	3150
	21st to end	Day	11% 2 4 14% 39% 31%	3438
November	1st to 10th	Day	13% 2 7% 17% 38% 24%	1819
	11th to 20th	Day	13% 3 7% 23% 36% 19%	1800
	21st to end	Day	16% 3 8% 16% 30% 26%	1800
December	1st to 10th	Day	10% 2 6% 21% 39% 23%	2785
	11th to 20th	Day	14% 3 7% 20% 37% 19%	3024
	21st to end	Day	12% 4 6% 22% 35% 21%	4004
January	1st to 10th	Night	21% 4 6% 19% 35% 14%	6192
	11th to 20th	Night	14% 5% 6% 18% 31% 26%	5880
	21st to end	Night	17% 6% 8% 17% 33% 19%	6468
February	1st to 10th	Night	19% 4 7% 22% 28% 21%	2510
	11th to 20th	Night	19% 5% 8% 23% 28% 17%	2338
	21st to end	Night	14% 3 6% 16% 34% 28%	1980
March	1st to 10th	Night	14% 3 5% 15% 34% 28%	3803
	11th to 20th	Night	29% 5% 7% 21% 28% 10%	3506
	21st to end	Night	15% 5% 8% 22% 38% 11%	3617
April	1st to 10th	Night	13% 5% 7% 21% 32% 21%	1900
	11th to 20th	Night	19% 5% 8% 18% 27% 23%	1877
	21st to end	Night	16% 5% 11% 23% 31% 14%	1900
May	1st to 10th	Night	17% 7% 7% 14% 25% 29%	3170
	11th to 20th	Night	26% 8% 12% 23% 17% 14%	2920
	21st to end	Night	12% 6% 9% 13% 19% 41%	2763
June	1st to 10th	Night	21% 9% 17% 19% 17% 17%	1520
	11th to 20th	Night	13% 5% 9% 17% 22% 33%	1520
	21st to end	Night	27% 9% 15% 15% 18% 15%	1520
July	1st to 10th	Night	32% 11% 14% 16% 13% 15%	2500
	11th to 20th	Night	25% 14% 23% 27% 7% 4	2668
	21st to end	Night	30% 11% 19% 27% 13% 1	3011
August	1st to 10th	Night	35% 12% 19% 17% 12% 5%	3040
	11th to 20th	Night	24% 9% 18% 24% 19% 7%	3143
	21st to end	Night	31% 13% 21% 24% 8% 3	3487
September	1st to 10th	Night	24% 8% 15% 24% 20% 8%	1900
	11th to 20th	Night	25% 6% 11% 17% 25% 16%	1919
	21st to end	Night	17% 7% 12% 18% 32% 15%	2090
October	1st to 10th	Night	16% 5% 6% 15% 32% 26%	3751
	11th to 20th	Night	19% 4 7% 15% 29% 25%	3778
	21st to end	Night	12% 2 4 14% 38% 29%	4120
November	1st to 10th	Night	12% 3 6% 20% 35% 23%	2458
	11th to 20th	Night	11% 4 6% 20% 38% 20%	2600
	21st to end	Night	17% 4 7% 18% 28% 26%	2600
December	1st to 10th	Night	14% 3 6% 25% 35% 17%	4402
	11th to 20th	Night	14% 3 7% 17% 36% 23%	5182
	21st to end	Night	16% 4 8% 21% 33% 19%	6974

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	5% 24% 35% 25% 10% 1	300
	11th to 20th	Day	7% 26% 29% 27% 10% 2	300
	21st to end	Day	3 21% 29% 30% 12% 5%	330
February	1st to 10th	Day	5% 23% 35% 25% 10% 1	300
	11th to 20th	Day	6% 29% 37% 21% 7% 1	300
	21st to end	Day	5% 39% 30% 22% 2	249
March	1st to 10th	Day	5% 30% 37% 18% 9% 1	324
	11th to 20th	Day	11% 27% 35% 21% 5% 1	465
	21st to end	Day	7% 40% 31% 18% 4 1	506
April	1st to 10th	Day	5% 30% 40% 17% 6% 1	460
	11th to 20th	Day	8% 34% 37% 17% 4 1	452
	21st to end	Day	9% 31% 36% 19% 5% 1	460
May	1st to 10th	Day	8% 23% 40% 23% 5% 1	463
	11th to 20th	Day	8% 13% 32% 28% 14% 4	613
	21st to end	Day	6% 15% 35% 29% 13% 2	734
June	1st to 10th	Day	4 7% 23% 36% 25% 5%	680
	11th to 20th	Day	4 10% 28% 35% 19% 4	680
	21st to end	Day	6% 4 25% 35% 23% 7%	680
July	1st to 10th	Day	6% 3 16% 31% 32% 12%	671
	11th to 20th	Day	4 2 11% 29% 37% 18%	565
	21st to end	Day	5% 1 10% 30% 35% 18%	531
August	1st to 10th	Day	7% 3 14% 29% 34% 13%	487
	11th to 20th	Day	6% 3 16% 34% 32% 10%	477
	21st to end	Day	4 2 19% 37% 26% 12%	539
September	1st to 10th	Day	7% 4 19% 37% 24% 9%	490
	11th to 20th	Day	4 5% 28% 33% 22% 8%	470
	21st to end	Day	6% 9% 21% 34% 25% 6%	300
October	1st to 10th	Day	14% 13% 21% 23% 21% 8%	300
	11th to 20th	Day	10% 13% 28% 26% 16% 6%	300
	21st to end	Day	11% 16% 25% 27% 17% 4	330
November	1st to 10th	Day	7% 20% 31% 28% 13% 2	300
	11th to 20th	Day	7% 11% 32% 30% 17% 3	300
	21st to end	Day	8% 22% 32% 22% 14% 3	300
December	1st to 10th	Day	3 21% 35% 26% 13% 2	300
	11th to 20th	Day	4 20% 32% 32% 10% 1	300
	21st to end	Day	8% 26% 35% 24% 5% 1	330
January	1st to 10th	Night	2 16% 37% 31% 11% 2	943
	11th to 20th	Night	4 14% 39% 31% 10% 2	800
	21st to end	Night	3 13% 39% 32% 11% 2	880
February	1st to 10th	Night	3 15% 47% 27% 7% 1	800
	11th to 20th	Night	4 17% 44% 28% 5% 1	784
	21st to end	Night	2 21% 50% 24% 3	660
March	1st to 10th	Night	4 20% 40% 28% 7% 1	800
	11th to 20th	Night	7% 14% 33% 36% 10% 1	766
	21st to end	Night	4 17% 45% 29% 5%	715
April	1st to 10th	Night	4 16% 47% 27% 5%	570
	11th to 20th	Night	6% 15% 41% 32% 7%	563
	21st to end	Night	5% 14% 39% 36% 6%	570
May	1st to 10th	Night	6% 8% 36% 41% 8%	570
	11th to 20th	Night	10% 4 30% 39% 15% 2	561
	21st to end	Night	6% 8% 31% 42% 12% 1	617
June	1st to 10th	Night	4 5% 22% 44% 23% 2	570
	11th to 20th	Night	2 3 30% 48% 16%	570
	21st to end	Night	8% 2 16% 46% 27% 1	570
July	1st to 10th	Night	6% 2 10% 37% 40% 5%	555
	11th to 20th	Night	2 1 7% 34% 49% 7%	552
	21st to end	Night	7% 1 5% 27% 50% 9%	624
August	1st to 10th	Night	6% 2 5% 31% 47% 9%	567
	11th to 20th	Night	6% 1 7% 39% 43% 4	564
	21st to end	Night	4 1 12% 38% 38% 7%	627
September	1st to 10th	Night	6% 2 12% 44% 33% 3	570
	11th to 20th	Night	8% 2 14% 45% 30% 2	570
	21st to end	Night	6% 6% 19% 44% 24% 1	570
October	1st to 10th	Night	8% 4 28% 38% 19% 2	724
	11th to 20th	Night	6% 6% 29% 39% 18% 3	760
	21st to end	Night	6% 9% 29% 33% 17% 5%	836
November	1st to 10th	Night	3 11% 33% 36% 14% 3	898
	11th to 20th	Night	2 13% 34% 38% 11% 3	1000
	21st to end	Night	6% 14% 34% 30% 14% 3	1000
December	1st to 10th	Night	3 15% 40% 31% 9% 2	1000
	11th to 20th	Night	4 16% 38% 33% 9% 1	1000
	21st to end	Night	5% 18% 42% 29% 6%	1100

Page generated at 2025-03-09 06:08:48. Version ac07

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