LEO Scope
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the LEO Scope clear sky chart from 2005-11-06 to 2026-02-16.

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	4 5% 2 5% 4 4 4 4 6% 8% 55%	139513
	Night	4 5% 2 5% 4 4 4 4 5% 7% 56%	138806
Transparency	Day	24% 5% 10% 24% 25% 12%	134518
	Night	26% 5% 11% 24% 25% 10%	134820
Seeing	Day	7% 7% 27% 30% 21% 7%	17227
	Night	7% 6% 29% 39% 17% 2	27362

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 5% 3 6% 3 4 4 3 5% 7% 59%	4720
	11th to 20th	Day	1 2 1 5% 4 3 3 3 5% 7% 65%	4832
	21st to end	Day	1 5% 3 7% 3 3 3 2 4 7% 62%	5844
February	1st to 10th	Day	2 7% 2 6% 3 3 4 3 5% 8% 57%	1957
	11th to 20th	Day	1 5% 2 6% 4 4 4 4 5% 7% 58%	1999
	21st to end	Day	2 5% 2 7% 4 4 4 2 4 7% 59%	1650
March	1st to 10th	Day	1 3 1 4 3 3 4 4 6% 6% 63%	4500
	11th to 20th	Day	3 8% 3 6% 4 4 4 4 4 7% 53%	4803
	21st to end	Day	2 5% 2 6% 4 4 5% 4 6% 9% 53%	5915
April	1st to 10th	Day	4 7% 2 4 3 4 4 4 6% 6% 56%	2400
	11th to 20th	Day	7% 8% 2 5% 4 4 5% 4 7% 8% 48%	2371
	21st to end	Day	7% 6% 3 6% 4 3 4 4 6% 8% 49%	2400
May	1st to 10th	Day	11% 7% 2 5% 3 4 4 4 5% 6% 49%	5803
	11th to 20th	Day	6% 5% 1 5% 3 4 4 4 7% 9% 51%	6026
	21st to end	Day	8% 5% 2 4 4 4 4 4 7% 10% 48%	6925
June	1st to 10th	Day	6% 4 2 4 3 4 5% 5% 8% 11% 50%	2800
	11th to 20th	Day	4 4 1 4 4 3 4 5% 7% 9% 55%	2800
	21st to end	Day	3 3 2 5% 5% 5% 5% 6% 8% 10% 50%	2800
July	1st to 10th	Day	3 3 1 4 4 4 5% 5% 8% 11% 52%	6339
	11th to 20th	Day	3 3 1 4 5% 5% 6% 6% 8% 10% 48%	6340
	21st to end	Day	4 4 2 6% 5% 5% 6% 5% 7% 9% 47%	6860
August	1st to 10th	Day	7% 4 2 4 4 5% 5% 5% 8% 11% 44%	5577
	11th to 20th	Day	4 3 1 4 4 5% 6% 4 8% 11% 51%	5366
	21st to end	Day	6% 5% 2 6% 4 5% 6% 4 7% 9% 45%	5984
September	1st to 10th	Day	3 4 2 4 3 4 4 4 6% 10% 56%	2400
	11th to 20th	Day	5% 3 1 3 3 3 4 3 5% 7% 62%	2331
	21st to end	Day	4 4 1 4 3 2 3 2 4 7% 65%	2200
October	1st to 10th	Day	4 3 1 2 1 2 2 2 4 5% 74%	3416
	11th to 20th	Day	4 5% 2 4 3 3 3 3 4 7% 61%	3250
	21st to end	Day	3 4 1 3 2 2 2 2 3 5% 72%	3364
November	1st to 10th	Day	2 4 1 4 2 3 3 3 6% 8% 64%	1853
	11th to 20th	Day	1 5% 1 4 2 3 3 3 4 6% 66%	1890
	21st to end	Day	2 5% 2 5% 3 2 3 2 4 6% 65%	1890
December	1st to 10th	Day	2 6% 2 3 2 2 3 2 3 6% 70%	2710
	11th to 20th	Day	1 4 1 4 3 2 3 3 5% 7% 66%	3106
	21st to end	Day	2 5% 2 5% 4 3 3 3 4 8% 60%	4092
January	1st to 10th	Night	1 7% 3 7% 4 3 4 3 5% 8% 55%	8201
	11th to 20th	Night	1 4 2 6% 4 3 3 3 5% 7% 63%	8213
	21st to end	Night	1 4 3 7% 4 3 3 3 4 6% 63%	8370
February	1st to 10th	Night	2 6% 2 6% 4 3 4 3 4 7% 59%	2662
	11th to 20th	Night	3 7% 3 7% 4 3 4 4 6% 7% 52%	2398
	21st to end	Night	2 5% 3 5% 4 3 3 3 4 7% 62%	1980
March	1st to 10th	Night	1 5% 2 5% 3 4 4 3 4 7% 61%	5374
	11th to 20th	Night	4 7% 2 7% 4 4 3 3 4 6% 54%	5186
	21st to end	Night	5% 7% 3 6% 4 4 4 4 6% 8% 51%	5039
April	1st to 10th	Night	5% 7% 2 5% 3 3 4 4 5% 8% 55%	2000
	11th to 20th	Night	8% 7% 2 6% 4 4 4 4 6% 8% 48%	1977
	21st to end	Night	9% 8% 2 6% 4 3 3 5% 5% 8% 46%	2000
May	1st to 10th	Night	11% 7% 2 5% 3 3 4 3 6% 7% 49%	4175
	11th to 20th	Night	7% 7% 2 6% 3 4 5% 4 6% 9% 48%	3884
	21st to end	Night	10% 7% 2 6% 4 4 5% 4 6% 8% 46%	3972
June	1st to 10th	Night	5% 4 1 4 4 4 5% 4 8% 10% 51%	1600
	11th to 20th	Night	4 3 1 3 4 3 5% 4 6% 8% 59%	1600
	21st to end	Night	5% 6% 2 5% 5% 4 4 5% 7% 10% 48%	1600
July	1st to 10th	Night	5% 4 2 6% 5% 5% 5% 5% 8% 9% 47%	3640
	11th to 20th	Night	4 3 2 6% 5% 5% 6% 6% 9% 11% 43%	3640
	21st to end	Night	4 5% 2 6% 5% 6% 6% 5% 7% 8% 45%	4008
August	1st to 10th	Night	8% 6% 3 7% 4 5% 6% 5% 7% 9% 41%	4221
	11th to 20th	Night	5% 4 2 6% 5% 5% 6% 4 7% 9% 45%	4483
	21st to end	Night	10% 5% 2 5% 4 5% 5% 5% 8% 10% 40%	4993
September	1st to 10th	Night	5% 4 2 5% 4 4 5% 3 6% 8% 53%	2000
	11th to 20th	Night	5% 4 1 4 3 3 4 4 5% 8% 58%	2068
	21st to end	Night	5% 4 1 4 3 3 3 3 5% 6% 62%	2200
October	1st to 10th	Night	5% 3 1 3 2 2 3 2 4 5% 69%	3754
	11th to 20th	Night	5% 5% 1 4 3 3 3 4 6% 7% 58%	3898
	21st to end	Night	3 4 1 4 2 2 3 2 4 6% 69%	4402
November	1st to 10th	Night	2 5% 2 3 3 2 3 2 5% 6% 68%	2665
	11th to 20th	Night	1 4 1 4 2 3 4 3 4 5% 69%	2730
	21st to end	Night	3 6% 2 4 3 3 3 3 5% 6% 61%	2730
December	1st to 10th	Night	1 3 1 4 2 2 3 2 4 6% 71%	4694
	11th to 20th	Night	1 4 2 5% 3 3 3 3 5% 8% 63%	5321
	21st to end	Night	2 6% 2 6% 4 4 5% 4 5% 7% 56%	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	25% 3 6% 31% 26% 9%	4723
	11th to 20th	Day	18% 4 10% 24% 31% 12%	4832
	21st to end	Day	25% 3 6% 24% 29% 13%	5844
February	1st to 10th	Day	24% 5% 11% 25% 24% 11%	1957
	11th to 20th	Day	26% 4 8% 27% 27% 8%	2009
	21st to end	Day	26% 4 7% 20% 24% 19%	1650
March	1st to 10th	Day	17% 5% 7% 17% 33% 22%	4500
	11th to 20th	Day	27% 5% 9% 21% 29% 9%	4803
	21st to end	Day	23% 7% 10% 38% 19% 3	5915
April	1st to 10th	Day	25% 6% 11% 24% 23% 11%	2400
	11th to 20th	Day	29% 6% 11% 23% 19% 11%	2374
	21st to end	Day	28% 7% 14% 26% 21% 5%	2400
May	1st to 10th	Day	31% 6% 11% 24% 20% 9%	5803
	11th to 20th	Day	24% 9% 11% 19% 24% 13%	6030
	21st to end	Day	25% 8% 15% 23% 21% 8%	6926
June	1st to 10th	Day	23% 8% 15% 27% 17% 10%	2800
	11th to 20th	Day	21% 7% 11% 20% 25% 18%	2800
	21st to end	Day	23% 8% 11% 21% 23% 13%	2800
July	1st to 10th	Day	21% 6% 10% 20% 28% 14%	6271
	11th to 20th	Day	26% 6% 16% 26% 18% 8%	6265
	21st to end	Day	29% 5% 14% 18% 17% 16%	6662
August	1st to 10th	Day	31% 8% 18% 26% 12% 5%	4061
	11th to 20th	Day	25% 6% 14% 20% 23% 11%	3882
	21st to end	Day	24% 6% 13% 23% 25% 9%	4311
September	1st to 10th	Day	22% 5% 11% 23% 25% 15%	2400
	11th to 20th	Day	19% 5% 9% 19% 30% 18%	2331
	21st to end	Day	19% 3 7% 21% 34% 16%	2200
October	1st to 10th	Day	14% 3 6% 16% 36% 25%	3416
	11th to 20th	Day	23% 3 8% 23% 32% 10%	3250
	21st to end	Day	16% 2 4 20% 41% 16%	3364
November	1st to 10th	Day	17% 5% 8% 25% 27% 17%	1853
	11th to 20th	Day	18% 4 7% 27% 34% 11%	1890
	21st to end	Day	21% 2 8% 22% 29% 17%	1890
December	1st to 10th	Day	18% 3 7% 28% 33% 10%	2710
	11th to 20th	Day	17% 3 7% 29% 34% 10%	3104
	21st to end	Day	22% 5% 8% 27% 27% 10%	4092
January	1st to 10th	Night	28% 4 6% 30% 26% 6%	8202
	11th to 20th	Night	20% 4 10% 25% 27% 13%	8213
	21st to end	Night	24% 4 8% 22% 30% 12%	8370
February	1st to 10th	Night	25% 4 9% 26% 25% 10%	2662
	11th to 20th	Night	30% 5% 12% 26% 20% 7%	2398
	21st to end	Night	21% 5% 7% 24% 27% 16%	1980
March	1st to 10th	Night	20% 5% 7% 15% 37% 16%	5374
	11th to 20th	Night	29% 5% 10% 15% 27% 13%	5186
	21st to end	Night	28% 7% 13% 31% 19% 3	5039
April	1st to 10th	Night	26% 6% 10% 25% 23% 11%	2000
	11th to 20th	Night	31% 6% 11% 24% 19% 8%	1977
	21st to end	Night	34% 7% 12% 24% 17% 5%	2000
May	1st to 10th	Night	31% 8% 14% 28% 13% 6%	4173
	11th to 20th	Night	30% 8% 11% 23% 17% 10%	3885
	21st to end	Night	33% 8% 16% 22% 16% 4	3972
June	1st to 10th	Night	25% 9% 20% 23% 15% 8%	1600
	11th to 20th	Night	20% 7% 17% 21% 20% 15%	1600
	21st to end	Night	29% 7% 12% 21% 20% 12%	1600
July	1st to 10th	Night	30% 7% 12% 22% 24% 5%	3600
	11th to 20th	Night	31% 6% 21% 23% 16% 3	3592
	21st to end	Night	34% 6% 16% 16% 18% 10%	3894
August	1st to 10th	Night	45% 7% 16% 18% 8% 6%	3072
	11th to 20th	Night	36% 6% 16% 20% 18% 4	3243
	21st to end	Night	29% 7% 17% 26% 17% 5%	3597
September	1st to 10th	Night	27% 6% 12% 22% 23% 11%	2000
	11th to 20th	Night	21% 6% 12% 23% 24% 15%	2068
	21st to end	Night	22% 4 8% 22% 30% 13%	2200
October	1st to 10th	Night	18% 4 6% 20% 34% 18%	3754
	11th to 20th	Night	23% 4 8% 28% 28% 10%	3898
	21st to end	Night	19% 3 7% 25% 30% 16%	4402
November	1st to 10th	Night	17% 3 9% 26% 28% 16%	2665
	11th to 20th	Night	17% 4 7% 26% 33% 13%	2730
	21st to end	Night	24% 3 9% 22% 29% 13%	2730
December	1st to 10th	Night	17% 3 7% 30% 33% 10%	4694
	11th to 20th	Night	21% 3 6% 25% 35% 9%	5322
	21st to end	Night	25% 5% 10% 23% 26% 11%	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	5% 8% 30% 36% 18% 3	330
	11th to 20th	Day	6% 9% 33% 33% 16% 2	330
	21st to end	Day	4 11% 31% 36% 15% 4	363
February	1st to 10th	Day	4 9% 43% 31% 10% 3	330
	11th to 20th	Day	2 10% 44% 32% 12% 1	315
	21st to end	Day	4 10% 49% 26% 8% 3	249
March	1st to 10th	Day	3 10% 33% 34% 17% 3	300
	11th to 20th	Day	9% 13% 34% 29% 12% 4	407
	21st to end	Day	8% 20% 39% 21% 9% 2	550
April	1st to 10th	Day	10% 15% 36% 26% 10% 3	500
	11th to 20th	Day	11% 18% 42% 18% 8% 3	492
	21st to end	Day	13% 13% 34% 27% 11% 2	500
May	1st to 10th	Day	14% 11% 33% 26% 12% 3	658
	11th to 20th	Day	12% 7% 28% 29% 18% 5%	725
	21st to end	Day	10% 8% 30% 27% 19% 6%	789
June	1st to 10th	Day	7% 5% 22% 30% 26% 9%	730
	11th to 20th	Day	5% 5% 28% 31% 24% 7%	730
	21st to end	Day	4 5% 24% 34% 26% 8%	730
July	1st to 10th	Day	5% 3 16% 29% 37% 10%	721
	11th to 20th	Day	4 2 10% 33% 38% 13%	718
	21st to end	Day	6% 1 12% 28% 36% 18%	776
August	1st to 10th	Day	5% 2 19% 36% 26% 12%	527
	11th to 20th	Day	4 2 19% 34% 28% 12%	517
	21st to end	Day	6% 2 18% 37% 27% 11%	583
September	1st to 10th	Day	5% 2 21% 33% 28% 11%	530
	11th to 20th	Day	5% 2 26% 33% 22% 11%	461
	21st to end	Day	8% 4 19% 27% 26% 16%	330
October	1st to 10th	Day	7% 7% 23% 24% 25% 15%	330
	11th to 20th	Day	5% 6% 31% 30% 19% 9%	330
	21st to end	Day	9% 8% 28% 28% 21% 7%	363
November	1st to 10th	Day	5% 8% 30% 33% 17% 8%	330
	11th to 20th	Day	3 7% 31% 33% 21% 4	330
	21st to end	Day	5% 12% 27% 34% 16% 6%	330
December	1st to 10th	Day	5% 8% 35% 31% 17% 3	330
	11th to 20th	Day	5% 8% 33% 33% 18% 3	330
	21st to end	Day	5% 12% 33% 39% 10% 1	363
January	1st to 10th	Night	5% 6% 33% 39% 13% 3	1050
	11th to 20th	Night	5% 6% 39% 36% 12% 3	1039
	21st to end	Night	4 5% 32% 45% 12% 2	924
February	1st to 10th	Night	5% 5% 43% 39% 8% 1	840
	11th to 20th	Night	5% 7% 42% 37% 8% 1	804
	21st to end	Night	5% 8% 44% 35% 8% 1	660
March	1st to 10th	Night	5% 7% 37% 38% 12% 1	800
	11th to 20th	Night	8% 8% 33% 38% 13% 2	800
	21st to end	Night	7% 9% 41% 34% 9% 1	689
April	1st to 10th	Night	7% 11% 43% 32% 8%	600
	11th to 20th	Night	13% 12% 32% 34% 8% 1	593
	21st to end	Night	16% 12% 25% 36% 11% 1	600
May	1st to 10th	Night	12% 9% 32% 34% 12% 1	600
	11th to 20th	Night	12% 6% 26% 38% 17% 1	591
	21st to end	Night	12% 6% 34% 33% 14% 1	650
June	1st to 10th	Night	6% 4 24% 45% 20% 1	600
	11th to 20th	Night	5% 3 29% 46% 16% 1	600
	21st to end	Night	8% 3 20% 46% 22% 1	600
July	1st to 10th	Night	7% 3 15% 43% 29% 3	585
	11th to 20th	Night	5% 1 10% 43% 38% 2	582
	21st to end	Night	7% 2 10% 38% 40% 4	657
August	1st to 10th	Night	8% 2 12% 43% 33% 3	597
	11th to 20th	Night	7% 2 14% 46% 28% 3	594
	21st to end	Night	7% 2 12% 42% 35% 3	660
September	1st to 10th	Night	9% 2 13% 46% 28% 3	600
	11th to 20th	Night	7% 2 18% 45% 25% 4	600
	21st to end	Night	7% 3 21% 42% 24% 3	600
October	1st to 10th	Night	10% 7% 24% 35% 21% 3	699
	11th to 20th	Night	5% 6% 29% 38% 20% 4	800
	21st to end	Night	5% 8% 28% 36% 19% 4	968
November	1st to 10th	Night	5% 4 28% 43% 19% 2	1025
	11th to 20th	Night	4 6% 32% 42% 14% 2	1050
	21st to end	Night	6% 7% 30% 38% 15% 3	1050
December	1st to 10th	Night	3 5% 36% 40% 14% 2	1050
	11th to 20th	Night	5% 6% 34% 41% 13% 2	1050
	21st to end	Night	6% 8% 35% 39% 10% 1	1155

Page generated at 2026-02-12 23:42:18. Version ac07

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