Lake Hall
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Hall clear sky chart from 2005-11-06 to 2024-01-17.

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	7% 4 2 4 4 2 4 4 5% 7% 59%	74919
	Night	7% 4 2 3 3 2 3 4 5% 7% 60%	74943
Transparency	Day	26% 5% 9% 24% 26% 11%	74647
	Night	24% 5% 9% 22% 27% 13%	74738
Seeing	Day	9% 6% 24% 32% 23% 6%	14162
	Night	8% 6% 31% 38% 15% 1	24223

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	5% 4 2 3 3 2 3 3 4 6% 64%	1707
	11th to 20th	Day	8% 4 2 3 3 2 4 3 4 5% 62%	1674
	21st to end	Day	6% 4 1 4 3 2 3 4 4 7% 61%	1871
February	1st to 10th	Day	7% 7% 3 5% 3 2 3 3 3 5% 60%	1800
	11th to 20th	Day	7% 6% 2 4 4 2 3 3 3 6% 59%	1749
	21st to end	Day	7% 6% 3 4 3 3 2 3 4 5% 60%	1480
March	1st to 10th	Day	10% 5% 2 4 4 2 3 4 4 8% 53%	1812
	11th to 20th	Day	13% 4 2 4 3 2 3 3 3 6% 57%	1980
	21st to end	Day	8% 5% 3 5% 4 2 4 4 4 6% 56%	2178
April	1st to 10th	Day	7% 4 2 3 4 2 3 3 5% 6% 62%	2088
	11th to 20th	Day	12% 6% 2 4 3 2 4 3 4 6% 55%	2131
	21st to end	Day	10% 3 2 3 3 2 4 4 4 7% 59%	2281
May	1st to 10th	Day	9% 5% 2 5% 3 2 3 4 4 6% 56%	2340
	11th to 20th	Day	10% 4 2 4 4 2 4 4 5% 6% 56%	2302
	21st to end	Day	9% 4 2 4 4 3 5% 4 6% 7% 52%	2531
June	1st to 10th	Day	5% 3 1 3 4 3 5% 6% 6% 9% 54%	2340
	11th to 20th	Day	4 2 2 4 4 3 5% 4 6% 9% 58%	2340
	21st to end	Day	4 3 2 3 3 3 5% 4 5% 7% 62%	2340
July	1st to 10th	Day	6% 3 2 3 5% 3 5% 5% 7% 8% 52%	2340
	11th to 20th	Day	4 2 1 3 3 3 4 4 5% 7% 63%	2340
	21st to end	Day	3 2 1 3 4 3 5% 5% 6% 10% 59%	2546
August	1st to 10th	Day	3 2 1 3 3 2 4 5% 7% 10% 60%	2328
	11th to 20th	Day	5% 4 1 4 6% 2 4 6% 6% 9% 52%	2130
	21st to end	Day	4 2 2 4 5% 3 5% 5% 6% 8% 57%	2376
September	1st to 10th	Day	7% 4 2 4 4 3 3 4 5% 6% 59%	2048
	11th to 20th	Day	9% 4 2 3 4 3 5% 5% 6% 7% 52%	1980
	21st to end	Day	8% 2 1 4 3 2 3 4 5% 6% 63%	1980
October	1st to 10th	Day	9% 3 1 3 4 2 3 3 4 6% 60%	1980
	11th to 20th	Day	9% 2 1 2 3 2 3 2 3 4 68%	1907
	21st to end	Day	10% 4 2 3 3 2 3 2 3 4 65%	1921
November	1st to 10th	Day	6% 4 2 3 3 2 2 3 4 6% 66%	1673
	11th to 20th	Day	6% 4 2 1 2 2 2 3 3 5% 71%	1710
	21st to end	Day	10% 5% 2 3 2 2 2 2 3 5% 64%	1710
December	1st to 10th	Day	7% 4 2 4 4 2 3 4 5% 6% 61%	1710
	11th to 20th	Day	8% 6% 2 4 3 3 4 3 4 5% 58%	2161
	21st to end	Day	8% 6% 3 6% 5% 3 4 4 5% 6% 51%	3135
January	1st to 10th	Night	5% 4 1 4 3 2 3 3 5% 8% 61%	2458
	11th to 20th	Night	7% 4 2 3 3 2 3 4 4 5% 63%	2431
	21st to end	Night	6% 3 1 3 3 2 2 4 4 5% 66%	2501
February	1st to 10th	Night	10% 5% 2 4 2 2 3 4 4 6% 58%	2160
	11th to 20th	Night	9% 5% 2 4 3 2 3 4 4 6% 59%	2098
	21st to end	Night	8% 5% 2 4 3 2 3 4 4 6% 59%	1776
March	1st to 10th	Night	6% 5% 2 4 5% 3 4 4 6% 7% 55%	2147
	11th to 20th	Night	11% 5% 2 3 3 2 3 3 3 7% 59%	1980
	21st to end	Night	7% 4 2 3 3 2 3 4 5% 7% 60%	2178
April	1st to 10th	Night	6% 3 2 3 4 2 4 5% 5% 6% 61%	1868
	11th to 20th	Night	10% 5% 2 4 4 2 3 4 6% 7% 54%	1777
	21st to end	Night	10% 3 2 2 3 2 5% 3 4 7% 59%	1678
May	1st to 10th	Night	11% 4 1 3 3 2 4 4 5% 5% 57%	1620
	11th to 20th	Night	8% 4 2 4 4 2 4 4 6% 8% 53%	1593
	21st to end	Night	7% 4 2 4 4 3 4 5% 6% 9% 54%	1745
June	1st to 10th	Night	4 3 1 2 3 3 5% 4 6% 12% 56%	1620
	11th to 20th	Night	4 2 1 3 3 2 4 5% 6% 11% 58%	1620
	21st to end	Night	4 3 1 3 3 2 4 4 5% 9% 62%	1620
July	1st to 10th	Night	5% 4 1 4 4 3 5% 6% 6% 11% 52%	1620
	11th to 20th	Night	4 2 1 3 3 2 3 4 5% 10% 64%	1620
	21st to end	Night	2 2 1 2 4 3 4 4 6% 10% 63%	1772
August	1st to 10th	Night	2 2 1 3 3 2 4 4 6% 11% 61%	1611
	11th to 20th	Night	6% 4 2 4 5% 3 4 5% 7% 10% 50%	1768
	21st to end	Night	3 2 1 3 3 2 4 5% 7% 11% 58%	1980
September	1st to 10th	Night	7% 3 2 3 3 3 4 4 5% 7% 59%	1912
	11th to 20th	Night	10% 4 3 5% 4 2 4 4 6% 7% 50%	1980
	21st to end	Night	6% 3 1 3 3 2 2 3 5% 6% 65%	1980
October	1st to 10th	Night	8% 3 2 3 3 2 3 4 4 6% 61%	1980
	11th to 20th	Night	9% 3 1 3 3 1 1 2 3 4 70%	2034
	21st to end	Night	7% 3 1 2 3 2 2 3 3 5% 68%	2433
November	1st to 10th	Night	6% 3 1 2 2 1 3 3 5% 5% 69%	2405
	11th to 20th	Night	4 3 1 2 2 1 3 3 4 5% 70%	2470
	21st to end	Night	7% 3 2 3 3 3 3 3 4 6% 62%	2470
December	1st to 10th	Night	7% 3 1 3 3 1 2 4 5% 6% 64%	2470
	11th to 20th	Night	7% 4 2 4 4 3 4 3 5% 6% 57%	3036
	21st to end	Night	8% 6% 2 5% 4 3 3 4 4 6% 55%	4532

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	22% 3 8% 25% 29% 12%	1708
	11th to 20th	Day	26% 3 6% 20% 35% 11%	1674
	21st to end	Day	24% 3 7% 24% 32% 10%	1871
February	1st to 10th	Day	29% 2 7% 24% 28% 9%	1800
	11th to 20th	Day	28% 3 7% 26% 24% 12%	1759
	21st to end	Day	29% 3 6% 18% 28% 17%	1480
March	1st to 10th	Day	31% 3 7% 19% 24% 15%	1812
	11th to 20th	Day	30% 4 7% 23% 24% 12%	1980
	21st to end	Day	30% 4 10% 23% 23% 12%	2178
April	1st to 10th	Day	23% 4 9% 22% 25% 17%	2088
	11th to 20th	Day	33% 4 7% 19% 23% 14%	2134
	21st to end	Day	27% 4 9% 23% 28% 9%	2281
May	1st to 10th	Day	31% 4 10% 17% 23% 15%	2340
	11th to 20th	Day	29% 5% 12% 27% 19% 8%	2306
	21st to end	Day	30% 8% 12% 23% 18% 8%	2531
June	1st to 10th	Day	24% 7% 16% 27% 17% 9%	2340
	11th to 20th	Day	23% 5% 11% 27% 24% 11%	2340
	21st to end	Day	21% 6% 12% 24% 25% 11%	2340
July	1st to 10th	Day	26% 7% 12% 29% 20% 5%	2276
	11th to 20th	Day	18% 6% 10% 25% 32% 9%	2271
	21st to end	Day	19% 7% 14% 33% 24% 4	2405
August	1st to 10th	Day	18% 6% 13% 30% 25% 8%	2314
	11th to 20th	Day	27% 7% 14% 25% 21% 6%	2130
	21st to end	Day	22% 8% 12% 26% 22% 9%	2376
September	1st to 10th	Day	27% 5% 8% 23% 23% 14%	2048
	11th to 20th	Day	31% 6% 11% 20% 26% 7%	1980
	21st to end	Day	22% 4 7% 24% 33% 10%	1980
October	1st to 10th	Day	26% 5% 10% 22% 25% 11%	1980
	11th to 20th	Day	22% 3 6% 17% 31% 21%	1907
	21st to end	Day	25% 3 7% 24% 27% 15%	1921
November	1st to 10th	Day	21% 3 6% 23% 30% 17%	1673
	11th to 20th	Day	18% 2 6% 25% 35% 13%	1710
	21st to end	Day	26% 2 4 20% 34% 14%	1710
December	1st to 10th	Day	25% 4 8% 26% 28% 9%	1710
	11th to 20th	Day	29% 4 8% 18% 29% 11%	2159
	21st to end	Day	33% 4 8% 19% 27% 9%	3135
January	1st to 10th	Night	22% 3 9% 25% 30% 11%	2458
	11th to 20th	Night	24% 4 7% 19% 33% 14%	2431
	21st to end	Night	22% 3 6% 22% 32% 15%	2501
February	1st to 10th	Night	28% 4 8% 21% 27% 12%	2160
	11th to 20th	Night	28% 3 7% 23% 24% 15%	2098
	21st to end	Night	27% 4 5% 19% 26% 20%	1776
March	1st to 10th	Night	28% 4 7% 19% 23% 18%	2147
	11th to 20th	Night	28% 3 7% 24% 23% 15%	1980
	21st to end	Night	25% 4 12% 26% 24% 10%	2178
April	1st to 10th	Night	22% 5% 10% 19% 26% 18%	1868
	11th to 20th	Night	29% 5% 9% 20% 23% 13%	1777
	21st to end	Night	25% 5% 11% 24% 24% 11%	1678
May	1st to 10th	Night	29% 6% 9% 17% 23% 16%	1620
	11th to 20th	Night	28% 7% 14% 21% 21% 10%	1594
	21st to end	Night	27% 7% 13% 24% 20% 9%	1746
June	1st to 10th	Night	20% 8% 16% 31% 18% 7%	1620
	11th to 20th	Night	20% 6% 15% 26% 24% 10%	1620
	21st to end	Night	20% 5% 12% 25% 24% 14%	1620
July	1st to 10th	Night	25% 7% 17% 28% 18% 5%	1575
	11th to 20th	Night	16% 5% 10% 23% 34% 13%	1566
	21st to end	Night	16% 5% 13% 29% 31% 6%	1673
August	1st to 10th	Night	17% 6% 11% 28% 27% 11%	1601
	11th to 20th	Night	29% 6% 14% 24% 21% 6%	1768
	21st to end	Night	18% 7% 13% 26% 25% 10%	1980
September	1st to 10th	Night	24% 6% 9% 22% 25% 14%	1912
	11th to 20th	Night	33% 6% 10% 17% 27% 8%	1980
	21st to end	Night	20% 4 8% 23% 31% 14%	1980
October	1st to 10th	Night	24% 6% 9% 20% 28% 14%	1980
	11th to 20th	Night	21% 2 5% 17% 31% 24%	2034
	21st to end	Night	20% 4 6% 23% 29% 19%	2433
November	1st to 10th	Night	18% 3 8% 24% 30% 18%	2405
	11th to 20th	Night	17% 3 5% 26% 34% 15%	2470
	21st to end	Night	25% 3 5% 19% 32% 16%	2470
December	1st to 10th	Night	22% 3 8% 25% 29% 13%	2470
	11th to 20th	Night	29% 3 6% 20% 31% 13%	3037
	21st to end	Night	30% 5% 7% 20% 26% 12%	4532

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	9% 10% 36% 31% 12% 1	270
	11th to 20th	Day	14% 10% 31% 31% 14% 1	258
	21st to end	Day	5% 12% 39% 33% 11%	264
February	1st to 10th	Day	15% 9% 35% 33% 8% 1	240
	11th to 20th	Day	10% 9% 46% 24% 10% 1	240
	21st to end	Day	12% 16% 41% 23% 8%	198
March	1st to 10th	Day	12% 14% 38% 29% 7%	240
	11th to 20th	Day	17% 13% 33% 25% 11% 2	240
	21st to end	Day	13% 14% 39% 24% 9% 1	264
April	1st to 10th	Day	10% 18% 40% 21% 11%	348
	11th to 20th	Day	14% 18% 43% 21% 4	412
	21st to end	Day	12% 14% 37% 27% 8% 2	541
May	1st to 10th	Day	11% 9% 37% 32% 10% 1	603
	11th to 20th	Day	12% 7% 27% 33% 18% 4	625
	21st to end	Day	11% 7% 25% 36% 18% 4	679
June	1st to 10th	Day	6% 3 19% 41% 25% 5%	630
	11th to 20th	Day	5% 3 23% 44% 23% 3	630
	21st to end	Day	4 2 15% 45% 26% 8%	630
July	1st to 10th	Day	6% 1 7% 33% 40% 13%	621
	11th to 20th	Day	3 1 8% 32% 44% 13%	618
	21st to end	Day	2 1 4 31% 46% 16%	684
August	1st to 10th	Day	5% 1 8% 35% 44% 7%	626
	11th to 20th	Day	6% 2 9% 37% 35% 11%	444
	21st to end	Day	5% 1 8% 32% 39% 15%	495
September	1st to 10th	Day	6% 1 8% 29% 41% 15%	338
	11th to 20th	Day	8% 1 11% 35% 33% 12%	270
	21st to end	Day	10% 3 11% 30% 33% 13%	270
October	1st to 10th	Day	8% 1 21% 41% 22% 6%	270
	11th to 20th	Day	7% 8% 28% 33% 21% 3	270
	21st to end	Day	18% 5% 28% 29% 17% 3	297
November	1st to 10th	Day	10% 6% 28% 33% 19% 4	270
	11th to 20th	Day	11% 10% 26% 29% 19% 4	270
	21st to end	Day	19% 9% 29% 24% 15% 4	270
December	1st to 10th	Day	7% 7% 39% 31% 14% 1	270
	11th to 20th	Day	10% 9% 32% 36% 12% 1	270
	21st to end	Day	16% 12% 39% 25% 8% 1	297
January	1st to 10th	Night	8% 8% 35% 38% 10%	950
	11th to 20th	Night	8% 9% 32% 40% 9% 1	935
	21st to end	Night	8% 7% 35% 40% 9%	917
February	1st to 10th	Night	13% 8% 40% 33% 6% 1	720
	11th to 20th	Night	12% 9% 42% 31% 6%	704
	21st to end	Night	10% 14% 41% 31% 3	592
March	1st to 10th	Night	9% 10% 43% 33% 5%	707
	11th to 20th	Night	13% 12% 37% 32% 6%	540
	21st to end	Night	9% 14% 44% 29% 4	594
April	1st to 10th	Night	7% 12% 48% 29% 4	540
	11th to 20th	Night	14% 12% 49% 23% 2	533
	21st to end	Night	11% 10% 43% 30% 7% 1	540
May	1st to 10th	Night	12% 8% 43% 32% 4	540
	11th to 20th	Night	10% 8% 36% 32% 13% 1	531
	21st to end	Night	8% 5% 36% 38% 13% 1	584
June	1st to 10th	Night	5% 3 27% 48% 16% 1	540
	11th to 20th	Night	4 3 40% 43% 10%	540
	21st to end	Night	5% 2 27% 44% 21%	540
July	1st to 10th	Night	5% 2 12% 46% 32% 3	525
	11th to 20th	Night	4 1 8% 50% 34% 2	522
	21st to end	Night	2 6% 52% 37% 3	591
August	1st to 10th	Night	2 1 8% 48% 39% 1	537
	11th to 20th	Night	7% 2 13% 46% 31% 1	534
	21st to end	Night	4 9% 41% 43% 2	594
September	1st to 10th	Night	8% 1 14% 46% 32% 1	540
	11th to 20th	Night	12% 2 19% 39% 27% 1	540
	21st to end	Night	7% 2 21% 45% 24% 1	540
October	1st to 10th	Night	9% 4 25% 42% 20% 1	540
	11th to 20th	Night	10% 6% 30% 41% 13% 1	594
	21st to end	Night	9% 7% 32% 35% 17%	849
November	1st to 10th	Night	7% 5% 31% 42% 13% 1	925
	11th to 20th	Night	6% 6% 36% 40% 11% 1	950
	21st to end	Night	9% 8% 33% 36% 13% 1	950
December	1st to 10th	Night	9% 7% 35% 38% 11%	950
	11th to 20th	Night	11% 7% 37% 37% 8% 1	950
	21st to end	Night	11% 7% 38% 36% 8%	1045

Page generated at 2024-01-14 08:55:00. Version ac07

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