Lunar Crater
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lunar Crater clear sky chart from 2005-11-06 to 2026-01-02.

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	2 4 1 4 3 3 3 3 4 6% 67%	135696
	Night	3 4 1 4 3 3 4 3 4 6% 64%	133096
Transparency	Day	17% 4 8% 17% 26% 27%	130633
	Night	19% 5% 10% 19% 26% 22%	129143
Seeing	Day	5% 8% 20% 30% 25% 12%	16473
	Night	5% 4 20% 43% 26% 3	26159

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	2 4 2 6% 4 3 4 4 6% 9% 57%	3647
	11th to 20th	Day	4 4 2 4 4 3 4 2 5% 6% 63%	3640
	21st to end	Day	4 7% 3 6% 4 4 4 3 6% 9% 50%	4504
February	1st to 10th	Day	4 4 2 6% 3 3 5% 4 6% 10% 54%	2000
	11th to 20th	Day	5% 6% 2 5% 6% 5% 5% 3 4 8% 52%	1950
	21st to end	Day	3 8% 2 4 4 4 3 4 5% 8% 55%	1650
March	1st to 10th	Day	3 8% 2 7% 4 5% 4 3 5% 9% 49%	4518
	11th to 20th	Day	2 7% 2 6% 4 4 4 4 6% 7% 53%	4862
	21st to end	Day	3 7% 2 6% 5% 5% 4 4 6% 9% 49%	5648
April	1st to 10th	Day	3 4 2 5% 4 4 4 4 6% 7% 59%	2400
	11th to 20th	Day	3 5% 2 4 3 3 3 4 4 6% 63%	2369
	21st to end	Day	4 4 1 4 3 3 3 3 5% 6% 64%	2545
May	1st to 10th	Day	3 4 2 4 3 3 3 3 3 4 69%	5880
	11th to 20th	Day	3 5% 2 5% 3 3 3 3 4 5% 63%	5841
	21st to end	Day	2 3 2 4 3 3 3 3 4 5% 68%	6423
June	1st to 10th	Day	2 3 1 3 3 3 3 3 6% 8% 65%	2734
	11th to 20th	Day	2 2 1 3 2 3 3 2 3 5% 75%	2800
	21st to end	Day	2 2 1 2 2 2 3 2 3 5% 78%	2800
July	1st to 10th	Day	2 2 1 2 2 2 2 2 2 3 82%	6319
	11th to 20th	Day	2 2 1 3 3 4 4 3 6% 6% 67%	6320
	21st to end	Day	2 1 1 2 3 3 3 3 5% 5% 72%	6458
August	1st to 10th	Day	2 2 1 2 2 2 2 2 3 4 80%	5779
	11th to 20th	Day	1 1 1 1 1 2 1 2 3 86%	5452
	21st to end	Day	2 2 1 3 3 3 4 3 4 5% 71%	5984
September	1st to 10th	Day	2 2 1 2 3 3 3 3 4 4 74%	2370
	11th to 20th	Day	2 2 1 2 2 2 3 3 3 6% 76%	2200
	21st to end	Day	2 2 1 3 2 1 2 2 3 5% 80%	2200
October	1st to 10th	Day	2 1 1 3 2 2 2 2 4 5% 77%	3600
	11th to 20th	Day	1 2 1 2 2 3 2 2 3 5% 78%	3431
	21st to end	Day	2 2 1 3 2 2 2 2 3 6% 76%	3200
November	1st to 10th	Day	2 4 1 3 2 3 3 3 5% 8% 66%	1854
	11th to 20th	Day	2 3 1 3 1 2 3 3 4 9% 68%	1890
	21st to end	Day	3 5% 1 4 4 4 3 3 4 7% 64%	1890
December	1st to 10th	Day	2 3 1 3 2 2 3 3 5% 6% 70%	3040
	11th to 20th	Day	5% 8% 2 6% 4 3 3 4 6% 9% 50%	3406
	21st to end	Day	3 4 2 5% 5% 4 5% 4 6% 9% 55%	4092
January	1st to 10th	Night	2 4 2 5% 4 3 4 3 5% 8% 62%	6320
	11th to 20th	Night	2 3 1 4 3 4 4 3 4 7% 63%	6320
	21st to end	Night	5% 9% 2 5% 3 4 3 2 4 7% 55%	6466
February	1st to 10th	Night	4 5% 2 4 4 3 4 4 5% 7% 57%	2400
	11th to 20th	Night	4 7% 1 4 3 4 4 4 5% 7% 56%	2338
	21st to end	Night	3 7% 2 5% 4 3 4 3 5% 6% 58%	1980
March	1st to 10th	Night	2 6% 2 6% 4 4 4 3 4 5% 60%	5376
	11th to 20th	Night	4 6% 2 6% 5% 5% 5% 3 5% 7% 51%	5137
	21st to end	Night	3 6% 2 6% 3 3 4 3 5% 7% 56%	5324
April	1st to 10th	Night	5% 4 2 4 3 3 4 3 5% 7% 61%	2000
	11th to 20th	Night	3 5% 2 4 3 3 4 3 3 5% 64%	1979
	21st to end	Night	4 5% 2 5% 3 2 4 3 5% 6% 63%	1853
May	1st to 10th	Night	4 4 1 5% 3 3 3 3 4 7% 63%	4100
	11th to 20th	Night	4 4 2 4 3 3 3 3 4 6% 64%	4074
	21st to end	Night	3 3 1 6% 4 4 4 4 5% 7% 59%	4474
June	1st to 10th	Night	3 2 1 3 3 3 4 3 6% 8% 63%	1660
	11th to 20th	Night	3 3 1 3 2 3 2 2 3 5% 73%	1600
	21st to end	Night	3 2 1 3 2 3 2 3 4 5% 74%	1600
July	1st to 10th	Night	2 2 1 2 2 2 3 2 3 3 79%	3640
	11th to 20th	Night	3 3 2 4 4 4 5% 3 5% 7% 60%	3640
	21st to end	Night	2 2 1 4 5% 4 4 3 4 4 66%	4398
August	1st to 10th	Night	3 3 1 2 2 3 3 3 4 5% 71%	4033
	11th to 20th	Night	2 1 1 2 1 2 2 2 2 3 83%	4409
	21st to end	Night	2 2 1 4 3 3 4 3 5% 6% 68%	5015
September	1st to 10th	Night	3 2 1 2 2 2 3 2 5% 5% 73%	2030
	11th to 20th	Night	2 2 1 3 2 2 3 3 4 5% 74%	2200
	21st to end	Night	2 2 1 2 2 2 2 1 2 4 79%	2200
October	1st to 10th	Night	3 2 1 3 2 2 2 2 3 4 74%	3600
	11th to 20th	Night	3 3 1 2 2 2 3 2 3 5% 74%	3720
	21st to end	Night	1 3 1 3 3 2 3 2 3 4 74%	4600
November	1st to 10th	Night	3 3 1 3 2 2 2 2 4 7% 70%	2665
	11th to 20th	Night	2 3 1 4 3 3 3 3 5% 7% 67%	2730
	21st to end	Night	2 3 1 4 3 3 3 3 5% 6% 65%	2730
December	1st to 10th	Night	2 3 1 3 2 3 4 3 5% 6% 68%	4370
	11th to 20th	Night	4 5% 2 4 3 3 4 3 5% 10% 56%	5009
	21st to end	Night	3 5% 2 7% 5% 5% 6% 4 7% 10% 45%	7106

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	21% 8% 21% 29% 18% 3	3647
	11th to 20th	Day	20% 5% 13% 22% 27% 12%	3640
	21st to end	Day	29% 8% 14% 17% 24% 8%	4504
February	1st to 10th	Day	24% 6% 14% 27% 21% 8%	2000
	11th to 20th	Day	29% 5% 11% 26% 25% 5%	1960
	21st to end	Day	24% 6% 13% 28% 23% 7%	1650
March	1st to 10th	Day	28% 5% 8% 23% 27% 8%	4518
	11th to 20th	Day	26% 8% 10% 27% 23% 5%	4862
	21st to end	Day	26% 8% 14% 24% 21% 7%	5648
April	1st to 10th	Day	24% 5% 10% 23% 24% 14%	2400
	11th to 20th	Day	20% 5% 9% 21% 29% 16%	2372
	21st to end	Day	19% 5% 8% 23% 35% 10%	2545
May	1st to 10th	Day	18% 5% 5% 22% 38% 13%	5880
	11th to 20th	Day	19% 4 5% 14% 38% 20%	5844
	21st to end	Day	16% 4 5% 13% 39% 22%	6424
June	1st to 10th	Day	16% 3 7% 17% 28% 28%	2734
	11th to 20th	Day	13% 3 4 9% 26% 47%	2800
	21st to end	Day	10% 2 3 6% 22% 57%	2800
July	1st to 10th	Day	10% 2 2 3 10% 73%	6251
	11th to 20th	Day	13% 4 5% 7% 16% 54%	6245
	21st to end	Day	12% 4 5% 9% 17% 53%	6272
August	1st to 10th	Day	13% 2 3 10% 27% 45%	4208
	11th to 20th	Day	7% 2 3 6% 17% 65%	3946
	21st to end	Day	10% 2 4 7% 19% 58%	4311
September	1st to 10th	Day	13% 4 5% 9% 23% 47%	2370
	11th to 20th	Day	11% 3 5% 14% 27% 41%	2200
	21st to end	Day	10% 2 4 11% 35% 38%	2200
October	1st to 10th	Day	10% 2 5% 9% 33% 40%	3600
	11th to 20th	Day	12% 2 3 15% 37% 31%	3431
	21st to end	Day	11% 2 3 23% 47% 13%	3200
November	1st to 10th	Day	17% 3 10% 29% 29% 12%	1854
	11th to 20th	Day	15% 4 10% 31% 33% 7%	1890
	21st to end	Day	20% 3 11% 28% 30% 8%	1890
December	1st to 10th	Day	15% 4 9% 27% 32% 13%	3040
	11th to 20th	Day	27% 6% 14% 26% 23% 3	3405
	21st to end	Day	25% 7% 19% 28% 19% 3	4092
January	1st to 10th	Night	21% 5% 22% 28% 22% 3	6320
	11th to 20th	Night	19% 6% 14% 22% 27% 12%	6320
	21st to end	Night	27% 8% 14% 16% 25% 9%	6466
February	1st to 10th	Night	24% 5% 15% 29% 21% 6%	2400
	11th to 20th	Night	25% 5% 14% 22% 27% 7%	2339
	21st to end	Night	24% 4 14% 26% 24% 8%	1980
March	1st to 10th	Night	24% 6% 8% 24% 28% 11%	5376
	11th to 20th	Night	28% 8% 10% 29% 20% 4	5137
	21st to end	Night	23% 6% 15% 25% 26% 6%	5324
April	1st to 10th	Night	22% 5% 10% 27% 25% 11%	2000
	11th to 20th	Night	21% 4 8% 25% 27% 15%	1979
	21st to end	Night	22% 3 8% 23% 34% 9%	1853
May	1st to 10th	Night	18% 5% 6% 18% 41% 12%	4097
	11th to 20th	Night	16% 7% 7% 14% 39% 17%	4075
	21st to end	Night	20% 7% 7% 12% 35% 20%	4474
June	1st to 10th	Night	13% 5% 9% 16% 30% 28%	1660
	11th to 20th	Night	14% 3 5% 9% 24% 45%	1600
	21st to end	Night	12% 3 4 7% 22% 53%	1600
July	1st to 10th	Night	11% 2 3 4 7% 72%	3600
	11th to 20th	Night	18% 5% 5% 8% 17% 48%	3592
	21st to end	Night	18% 5% 6% 8% 9% 53%	4272
August	1st to 10th	Night	19% 3 4 8% 25% 40%	2928
	11th to 20th	Night	7% 3 4 6% 14% 66%	3183
	21st to end	Night	9% 2 4 8% 19% 58%	3608
September	1st to 10th	Night	12% 3 6% 8% 22% 48%	2030
	11th to 20th	Night	12% 3 5% 11% 27% 42%	2200
	21st to end	Night	11% 2 4 12% 28% 43%	2200
October	1st to 10th	Night	14% 3 5% 10% 26% 43%	3600
	11th to 20th	Night	14% 3 3 13% 35% 33%	3720
	21st to end	Night	15% 2 3 16% 45% 18%	4600
November	1st to 10th	Night	15% 3 10% 26% 33% 15%	2665
	11th to 20th	Night	16% 4 8% 28% 35% 9%	2730
	21st to end	Night	18% 4 9% 28% 33% 9%	2730
December	1st to 10th	Night	17% 4 8% 26% 30% 15%	4370
	11th to 20th	Night	21% 7% 15% 26% 28% 4	5009
	21st to end	Night	30% 8% 17% 25% 18% 3	7106

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	12% 3 20% 36% 22% 6%	202
	11th to 20th	Day	9% 8% 14% 33% 27% 12%	200
	21st to end	Day	6% 5% 15% 33% 31% 10%	341
February	1st to 10th	Day	8% 9% 26% 31% 19% 8%	500
	11th to 20th	Day	9% 9% 22% 37% 17% 7%	495
	21st to end	Day	4 10% 27% 36% 19% 4	414
March	1st to 10th	Day	11% 12% 24% 29% 20% 4	500
	11th to 20th	Day	8% 13% 26% 32% 15% 5%	500
	21st to end	Day	10% 14% 31% 28% 12% 4	550
April	1st to 10th	Day	6% 16% 26% 28% 18% 7%	500
	11th to 20th	Day	8% 16% 28% 26% 17% 4	492
	21st to end	Day	7% 14% 26% 28% 16% 9%	500
May	1st to 10th	Day	5% 13% 27% 27% 20% 7%	503
	11th to 20th	Day	7% 12% 22% 27% 22% 11%	528
	21st to end	Day	6% 9% 21% 28% 25% 12%	573
June	1st to 10th	Day	2 8% 18% 28% 27% 17%	530
	11th to 20th	Day	4 10% 24% 27% 26% 10%	530
	21st to end	Day	3 3 19% 32% 31% 12%	530
July	1st to 10th	Day	3 2 17% 33% 32% 11%	526
	11th to 20th	Day	3 1 11% 31% 37% 16%	524
	21st to end	Day	3 2 10% 34% 33% 17%	575
August	1st to 10th	Day	4 3 19% 34% 25% 15%	527
	11th to 20th	Day	3 4 15% 27% 29% 21%	517
	21st to end	Day	3 3 13% 31% 32% 18%	583
September	1st to 10th	Day	2 5% 15% 28% 28% 22%	530
	11th to 20th	Day	2 10% 17% 29% 28% 14%	530
	21st to end	Day	3 6% 15% 28% 34% 14%	530
October	1st to 10th	Day	2 8% 20% 28% 25% 17%	530
	11th to 20th	Day	5% 7% 19% 24% 30% 16%	480
	21st to end	Day	4 4 15% 33% 32% 12%	363
November	1st to 10th	Day	4 5% 19% 30% 26% 16%	330
	11th to 20th	Day	1 8% 16% 41% 20% 14%	330
	21st to end	Day	4 3 19% 32% 29% 12%	330
December	1st to 10th	Day	6% 4 14% 37% 29% 10%	330
	11th to 20th	Day	6% 4 15% 38% 28% 9%	308
	21st to end	Day	10% 8% 20% 32% 24% 6%	242
January	1st to 10th	Night	6% 4 20% 41% 23% 5%	804
	11th to 20th	Night	4 3 20% 45% 24% 4	800
	21st to end	Night	7% 3 21% 43% 22% 5%	880
February	1st to 10th	Night	7% 5% 26% 41% 20% 3	800
	11th to 20th	Night	6% 4 24% 44% 19% 3	784
	21st to end	Night	5% 5% 27% 45% 16% 2	660
March	1st to 10th	Night	6% 6% 24% 44% 18% 2	800
	11th to 20th	Night	6% 6% 24% 41% 20% 3	800
	21st to end	Night	6% 8% 30% 40% 15% 1	880
April	1st to 10th	Night	5% 8% 26% 42% 19% 1	800
	11th to 20th	Night	5% 8% 30% 38% 17% 2	791
	21st to end	Night	6% 7% 29% 37% 19% 3	653
May	1st to 10th	Night	5% 7% 30% 41% 16% 2	600
	11th to 20th	Night	6% 7% 21% 40% 24% 2	591
	21st to end	Night	6% 7% 22% 38% 24% 3	650
June	1st to 10th	Night	2 4 17% 43% 32% 2	460
	11th to 20th	Night	3 4 23% 47% 24% 1	400
	21st to end	Night	2 2 14% 52% 30% 1	400
July	1st to 10th	Night	4 10% 52% 33% 2	390
	11th to 20th	Night	3 1 6% 48% 38% 3	388
	21st to end	Night	4 1 8% 49% 36% 1	622
August	1st to 10th	Night	5% 2 14% 51% 27% 1	597
	11th to 20th	Night	2 1 9% 43% 41% 4	745
	21st to end	Night	2 1 10% 42% 43% 3	880
September	1st to 10th	Night	2 2 12% 36% 45% 4	800
	11th to 20th	Night	2 2 14% 41% 37% 4	800
	21st to end	Night	3 2 14% 40% 35% 7%	800
October	1st to 10th	Night	4 2 19% 42% 30% 4	800
	11th to 20th	Night	6% 2 15% 40% 33% 5%	800
	21st to end	Night	3 2 20% 38% 33% 5%	880
November	1st to 10th	Night	4 4 16% 37% 33% 6%	820
	11th to 20th	Night	3 2 18% 47% 25% 4	840
	21st to end	Night	3 2 21% 42% 28% 4	840
December	1st to 10th	Night	6% 2 18% 50% 19% 5%	840
	11th to 20th	Night	8% 2 21% 44% 23% 3	840
	21st to end	Night	6% 3 25% 47% 18% 1	924

Page generated at 2025-12-29 22:14:06. Version ac07

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