South Hill
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Hill clear sky chart from 2005-11-06 to 2024-02-15.

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	13% 5% 2 5% 5% 3 5% 5% 5% 8% 44%	78409
	Night	14% 6% 2 5% 5% 3 4 4 5% 7% 45%	80643
Transparency	Day	38% 5% 12% 23% 18% 4	78130
	Night	39% 5% 10% 21% 20% 5%	80441
Seeing	Day	18% 11% 25% 25% 15% 5%	14161
	Night	17% 9% 26% 31% 15% 2	24147

By Month

Percentage Cloud Cover SE (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	18% 5% 2 3 3 2 3 3 4 6% 51%	2836
	11th to 20th	Day	14% 7% 3 4 4 3 3 4 4 6% 50%	2840
	21st to end	Day	22% 7% 3 6% 4 2 3 3 4 5% 40%	3124
February	1st to 10th	Day	13% 7% 2 6% 4 3 4 5% 6% 8% 41%	1710
	11th to 20th	Day	22% 6% 2 4 4 2 3 4 3 5% 46%	1648
	21st to end	Day	19% 6% 2 5% 5% 3 4 5% 5% 6% 39%	1542
March	1st to 10th	Day	14% 6% 2 4 3 2 4 4 4 6% 50%	1980
	11th to 20th	Day	16% 6% 2 6% 5% 3 4 5% 5% 7% 41%	1980
	21st to end	Day	18% 7% 3 6% 4 3 4 5% 5% 7% 39%	2178
April	1st to 10th	Day	12% 4 2 3 3 2 4 5% 5% 7% 54%	2135
	11th to 20th	Day	11% 5% 2 4 5% 3 5% 5% 5% 6% 50%	2134
	21st to end	Day	15% 5% 2 6% 4 3 4 5% 5% 7% 44%	2160
May	1st to 10th	Day	12% 5% 2 5% 5% 3 6% 4 7% 9% 41%	2286
	11th to 20th	Day	16% 5% 2 6% 5% 3 4 6% 6% 9% 38%	2301
	21st to end	Day	13% 7% 2 4 5% 4 5% 6% 6% 10% 39%	2593
June	1st to 10th	Day	10% 4 2 5% 5% 3 5% 6% 8% 10% 42%	2520
	11th to 20th	Day	9% 5% 2 5% 5% 3 5% 6% 6% 10% 43%	2520
	21st to end	Day	8% 4 3 5% 5% 4 7% 6% 8% 12% 39%	2498
July	1st to 10th	Day	8% 5% 3 5% 6% 4 7% 6% 7% 11% 37%	2340
	11th to 20th	Day	6% 4 3 6% 6% 4 6% 7% 9% 13% 38%	2340
	21st to end	Day	7% 5% 2 5% 7% 5% 7% 7% 8% 10% 36%	2547
August	1st to 10th	Day	10% 6% 2 6% 6% 5% 7% 6% 6% 10% 35%	2327
	11th to 20th	Day	11% 7% 3 7% 7% 4 6% 6% 7% 9% 34%	2210
	21st to end	Day	9% 5% 3 6% 6% 4 6% 5% 6% 11% 38%	2376
September	1st to 10th	Day	10% 5% 2 5% 6% 3 5% 5% 6% 7% 44%	2160
	11th to 20th	Day	13% 5% 3 5% 6% 4 5% 4 5% 8% 42%	2113
	21st to end	Day	19% 7% 3 6% 4 3 4 4 5% 6% 39%	1903
October	1st to 10th	Day	16% 5% 2 5% 5% 3 4 3 3 6% 48%	1800
	11th to 20th	Day	14% 6% 2 4 4 2 3 3 4 6% 53%	1800
	21st to end	Day	11% 5% 2 4 4 3 3 4 4 5% 54%	1980
November	1st to 10th	Day	13% 4 2 4 4 2 3 4 4 5% 55%	1857
	11th to 20th	Day	15% 5% 2 5% 3 2 3 4 5% 6% 51%	1797
	21st to end	Day	15% 4 1 4 5% 1 3 4 5% 6% 52%	1530
December	1st to 10th	Day	16% 7% 2 6% 4 3 4 6% 6% 6% 40%	1520
	11th to 20th	Day	16% 5% 1 3 3 2 3 3 4 5% 54%	1910
	21st to end	Day	15% 6% 2 5% 4 3 4 5% 5% 7% 44%	2914
January	1st to 10th	Night	14% 7% 3 5% 4 3 4 4 4 6% 46%	4109
	11th to 20th	Night	16% 8% 3 4 4 2 3 4 4 5% 46%	4120
	21st to end	Night	21% 7% 2 5% 4 2 4 3 3 4 44%	4532
February	1st to 10th	Night	16% 6% 2 5% 4 2 3 4 4 7% 46%	2470
	11th to 20th	Night	21% 7% 2 5% 4 3 4 4 4 5% 42%	2292
	21st to end	Night	16% 7% 2 5% 4 2 3 4 4 6% 47%	1709
March	1st to 10th	Night	13% 4 2 4 4 3 5% 3 4 6% 51%	1980
	11th to 20th	Night	17% 5% 2 5% 4 4 4 4 6% 7% 41%	1980
	21st to end	Night	16% 6% 3 6% 5% 3 4 5% 4 6% 42%	2178
April	1st to 10th	Night	14% 5% 3 4 4 2 4 4 5% 7% 46%	1823
	11th to 20th	Night	12% 5% 2 4 3 2 4 5% 5% 8% 49%	1775
	21st to end	Night	14% 5% 2 4 5% 3 4 4 5% 7% 46%	1800
May	1st to 10th	Night	12% 6% 3 4 4 2 5% 5% 6% 9% 43%	1688
	11th to 20th	Night	17% 5% 3 5% 4 3 4 5% 5% 8% 40%	1592
	21st to end	Night	13% 5% 3 6% 5% 3 4 4 5% 10% 43%	1677
June	1st to 10th	Night	10% 5% 3 5% 6% 3 4 5% 7% 10% 44%	1440
	11th to 20th	Night	10% 5% 2 6% 5% 3 5% 5% 6% 10% 41%	1440
	21st to end	Night	8% 4 3 5% 6% 4 6% 5% 7% 10% 41%	1455
July	1st to 10th	Night	8% 5% 2 5% 6% 3 5% 5% 8% 10% 41%	1620
	11th to 20th	Night	5% 5% 2 5% 5% 5% 7% 7% 8% 10% 42%	1620
	21st to end	Night	6% 5% 3 6% 7% 4 8% 6% 7% 12% 38%	1771
August	1st to 10th	Night	9% 7% 3 6% 8% 3 6% 6% 6% 10% 36%	1611
	11th to 20th	Night	10% 6% 4 6% 6% 5% 6% 6% 7% 9% 36%	1672
	21st to end	Night	10% 4 2 5% 7% 4 6% 6% 7% 10% 38%	1980
September	1st to 10th	Night	11% 6% 2 5% 4 3 4 4 5% 8% 47%	1800
	11th to 20th	Night	12% 6% 2 6% 5% 3 4 5% 5% 7% 45%	1843
	21st to end	Night	19% 8% 3 5% 5% 3 5% 4 5% 6% 37%	2056
October	1st to 10th	Night	14% 6% 3 5% 5% 2 4 4 5% 5% 48%	2160
	11th to 20th	Night	13% 6% 2 4 4 2 4 3 4 5% 51%	2160
	21st to end	Night	13% 5% 2 5% 4 3 4 4 5% 6% 51%	2376
November	1st to 10th	Night	14% 5% 2 4 5% 2 3 4 5% 5% 52%	2221
	11th to 20th	Night	13% 5% 2 4 3 2 5% 4 4 7% 51%	2379
	21st to end	Night	13% 4 2 4 4 3 4 4 4 6% 52%	2645
December	1st to 10th	Night	18% 7% 3 5% 6% 3 4 4 4 5% 42%	2660
	11th to 20th	Night	17% 6% 2 4 4 2 4 4 4 5% 48%	3285
	21st to end	Night	16% 7% 3 4 4 3 4 4 5% 7% 43%	4724

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	36% 3 6% 27% 24% 4	2837
	11th to 20th	Day	37% 3 6% 20% 27% 6%	2840
	21st to end	Day	47% 4 7% 20% 17% 4	3124
February	1st to 10th	Day	40% 5% 11% 23% 18% 4	1710
	11th to 20th	Day	43% 3 6% 21% 22% 6%	1657
	21st to end	Day	46% 3 12% 16% 17% 6%	1542
March	1st to 10th	Day	35% 4 9% 25% 21% 6%	1980
	11th to 20th	Day	41% 5% 10% 20% 17% 7%	1980
	21st to end	Day	46% 5% 10% 20% 16% 4	2178
April	1st to 10th	Day	30% 5% 11% 24% 22% 8%	2135
	11th to 20th	Day	35% 4 12% 22% 21% 7%	2134
	21st to end	Day	40% 4 12% 22% 16% 5%	2160
May	1st to 10th	Day	38% 7% 16% 21% 16% 3	2286
	11th to 20th	Day	43% 6% 14% 25% 10% 2	2305
	21st to end	Day	40% 6% 15% 27% 11%	2593
June	1st to 10th	Day	35% 8% 14% 26% 16% 1	2520
	11th to 20th	Day	34% 7% 18% 24% 16% 2	2520
	21st to end	Day	35% 9% 18% 22% 15% 2	2498
July	1st to 10th	Day	38% 9% 16% 21% 14% 3	2275
	11th to 20th	Day	32% 10% 22% 23% 11% 2	2271
	21st to end	Day	38% 9% 17% 23% 13%	2405
August	1st to 10th	Day	42% 7% 17% 24% 9% 1	2314
	11th to 20th	Day	44% 8% 16% 19% 11% 2	2210
	21st to end	Day	39% 7% 18% 21% 13% 2	2376
September	1st to 10th	Day	38% 7% 15% 16% 19% 5%	2160
	11th to 20th	Day	39% 6% 9% 23% 19% 3	2113
	21st to end	Day	45% 6% 9% 21% 17% 3	1903
October	1st to 10th	Day	41% 4 7% 23% 21% 4	1800
	11th to 20th	Day	34% 3 7% 29% 21% 6%	1800
	21st to end	Day	32% 4 6% 25% 24% 8%	1980
November	1st to 10th	Day	32% 3 8% 24% 27% 6%	1857
	11th to 20th	Day	35% 2 10% 22% 23% 8%	1797
	21st to end	Day	34% 3 7% 24% 26% 5%	1530
December	1st to 10th	Day	44% 4 11% 21% 18% 4	1520
	11th to 20th	Day	34% 2 8% 27% 20% 8%	1906
	21st to end	Day	40% 4 10% 27% 18% 2	2914
January	1st to 10th	Night	39% 4 7% 21% 24% 6%	4109
	11th to 20th	Night	42% 4 6% 19% 24% 4	4120
	21st to end	Night	46% 3 5% 20% 20% 6%	4532
February	1st to 10th	Night	40% 3 10% 22% 20% 5%	2470
	11th to 20th	Night	45% 3 7% 18% 20% 6%	2294
	21st to end	Night	40% 3 8% 23% 19% 8%	1709
March	1st to 10th	Night	36% 4 9% 23% 22% 6%	1980
	11th to 20th	Night	42% 5% 8% 21% 19% 5%	1980
	21st to end	Night	42% 4 9% 22% 19% 4	2178
April	1st to 10th	Night	37% 5% 10% 19% 24% 6%	1823
	11th to 20th	Night	33% 6% 9% 23% 23% 6%	1775
	21st to end	Night	38% 5% 9% 25% 18% 5%	1800
May	1st to 10th	Night	37% 6% 13% 23% 17% 3	1688
	11th to 20th	Night	42% 6% 13% 21% 14% 3	1593
	21st to end	Night	38% 6% 15% 26% 14% 1	1678
June	1st to 10th	Night	35% 7% 16% 25% 15% 1	1440
	11th to 20th	Night	38% 8% 17% 20% 14% 2	1440
	21st to end	Night	37% 8% 14% 21% 17% 3	1455
July	1st to 10th	Night	36% 9% 18% 22% 12% 4	1575
	11th to 20th	Night	32% 12% 19% 24% 10% 3	1566
	21st to end	Night	36% 8% 20% 25% 11%	1672
August	1st to 10th	Night	42% 8% 19% 19% 11% 1	1600
	11th to 20th	Night	42% 7% 18% 20% 11% 2	1672
	21st to end	Night	39% 8% 19% 21% 10% 3	1980
September	1st to 10th	Night	35% 8% 14% 21% 18% 4	1800
	11th to 20th	Night	39% 6% 11% 20% 21% 3	1843
	21st to end	Night	48% 6% 10% 16% 16% 4	2056
October	1st to 10th	Night	38% 5% 9% 22% 22% 4	2160
	11th to 20th	Night	36% 4 7% 24% 24% 6%	2160
	21st to end	Night	34% 4 6% 23% 25% 8%	2376
November	1st to 10th	Night	35% 4 8% 20% 26% 6%	2221
	11th to 20th	Night	35% 4 9% 19% 23% 11%	2379
	21st to end	Night	35% 3 7% 22% 27% 6%	2645
December	1st to 10th	Night	46% 4 9% 20% 18% 4	2660
	11th to 20th	Night	39% 4 8% 21% 22% 7%	3288
	21st to end	Night	41% 4 8% 25% 21% 2	4724

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	29% 23% 32% 11% 4	270
	11th to 20th	Day	28% 29% 33% 9% 2	270
	21st to end	Day	25% 22% 38% 14% 1	297
February	1st to 10th	Day	23% 24% 37% 14% 2	270
	11th to 20th	Day	42% 23% 27% 6% 1	291
	21st to end	Day	28% 20% 34% 16% 3	346
March	1st to 10th	Day	24% 21% 33% 17% 5%	420
	11th to 20th	Day	24% 22% 35% 14% 5% 1	420
	21st to end	Day	23% 18% 36% 17% 5% 1	462
April	1st to 10th	Day	23% 18% 32% 20% 7% 1	420
	11th to 20th	Day	19% 16% 32% 19% 10% 4	412
	21st to end	Day	23% 13% 30% 23% 10% 1	420
May	1st to 10th	Day	17% 15% 38% 20% 9% 2	423
	11th to 20th	Day	20% 6% 26% 30% 16% 3	447
	21st to end	Day	22% 4 20% 26% 22% 6%	485
June	1st to 10th	Day	12% 5% 26% 29% 21% 6%	450
	11th to 20th	Day	11% 7% 23% 30% 23% 6%	450
	21st to end	Day	11% 4 20% 37% 22% 6%	450
July	1st to 10th	Day	10% 3 13% 33% 29% 11%	445
	11th to 20th	Day	5% 1 15% 38% 33% 9%	444
	21st to end	Day	11% 2 18% 36% 26% 8%	488
August	1st to 10th	Day	13% 5% 16% 30% 26% 10%	446
	11th to 20th	Day	13% 3 12% 31% 30% 12%	439
	21st to end	Day	10% 2 15% 29% 27% 17%	495
September	1st to 10th	Day	13% 4 14% 28% 24% 16%	450
	11th to 20th	Day	16% 4 14% 31% 22% 13%	450
	21st to end	Day	25% 6% 21% 28% 15% 4	450
October	1st to 10th	Day	21% 5% 22% 25% 22% 6%	450
	11th to 20th	Day	16% 9% 27% 28% 17% 3	450
	21st to end	Day	15% 14% 26% 27% 15% 3	495
November	1st to 10th	Day	17% 11% 30% 24% 15% 3	455
	11th to 20th	Day	20% 15% 30% 23% 11% 1	411
	21st to end	Day	25% 13% 25% 25% 8% 4	190
December	1st to 10th	Day	24% 19% 39% 9% 7% 1	180
	11th to 20th	Day	23% 16% 36% 20% 3 2	180
	21st to end	Day	25% 18% 29% 20% 5% 3	240
January	1st to 10th	Night	20% 18% 34% 24% 4	760
	11th to 20th	Night	23% 16% 31% 27% 4	760
	21st to end	Night	20% 16% 38% 24% 3	836
February	1st to 10th	Night	21% 16% 35% 24% 4	760
	11th to 20th	Night	28% 18% 38% 16% 1	722
	21st to end	Night	21% 15% 38% 24% 3	592
March	1st to 10th	Night	19% 15% 36% 25% 5%	720
	11th to 20th	Night	21% 15% 35% 23% 6%	720
	21st to end	Night	19% 14% 38% 23% 6%	792
April	1st to 10th	Night	20% 13% 37% 25% 6%	720
	11th to 20th	Night	16% 11% 34% 28% 10%	711
	21st to end	Night	17% 7% 36% 33% 8%	720
May	1st to 10th	Night	16% 10% 32% 31% 10%	608
	11th to 20th	Night	20% 5% 25% 37% 13% 1	531
	21st to end	Night	15% 1 19% 39% 25% 2	517
June	1st to 10th	Night	12% 2 19% 45% 22% 1	360
	11th to 20th	Night	11% 3 18% 41% 24% 4	360
	21st to end	Night	8% 3 16% 47% 23% 3	375
July	1st to 10th	Night	11% 2 11% 40% 32% 4	525
	11th to 20th	Night	6% 2 10% 39% 39% 4	522
	21st to end	Night	7% 3 15% 39% 32% 4	591
August	1st to 10th	Night	12% 2 10% 43% 29% 4	537
	11th to 20th	Night	12% 3 9% 38% 34% 4	608
	21st to end	Night	12% 3 10% 34% 35% 7%	792
September	1st to 10th	Night	13% 2 10% 36% 33% 6%	720
	11th to 20th	Night	15% 4 14% 32% 31% 5%	720
	21st to end	Night	23% 4 20% 33% 19% 1	720
October	1st to 10th	Night	17% 6% 19% 30% 24% 5%	720
	11th to 20th	Night	16% 9% 25% 30% 18% 2	720
	21st to end	Night	16% 10% 27% 30% 16% 2	792
November	1st to 10th	Night	17% 7% 29% 29% 16% 2	740
	11th to 20th	Night	16% 12% 29% 33% 10% 1	760
	21st to end	Night	15% 11% 29% 31% 12% 1	760
December	1st to 10th	Night	23% 13% 30% 24% 8%	760
	11th to 20th	Night	19% 11% 32% 32% 6%	760
	21st to end	Night	22% 15% 27% 30% 5%	836

Page generated at 2024-02-12 06:35:33. Version ac07

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