Lander
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lander clear sky chart from 2005-11-06 to 2024-11-10.

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	3 4 1 4 3 3 4 4 6% 9% 59%	105424
	Night	3 5% 2 4 3 3 3 3 5% 8% 59%	102489
Transparency	Day	22% 5% 12% 28% 23% 10%	105177
	Night	23% 4 13% 28% 22% 10%	102326
Seeing	Day	7% 9% 30% 33% 17% 4	15720
	Night	6% 6% 28% 41% 16% 3	25812

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	3 2 6% 3 5% 4 4 7% 12% 53%	2538
	11th to 20th	Day	3 1 7% 6% 6% 4 4 10% 10% 50%	2773
	21st to end	Day	3 2 4 3 3 3 3 5% 10% 64%	3146
February	1st to 10th	Day	1 5% 2 7% 5% 4 5% 4 8% 10% 50%	1710
	11th to 20th	Day	1 5% 2 7% 4 3 4 4 6% 10% 54%	1665
	21st to end	Day	3 3 6% 3 4 4 4 6% 10% 57%	1479
March	1st to 10th	Day	1 3 1 4 3 3 3 4 6% 10% 63%	3434
	11th to 20th	Day	3 8% 2 5% 2 3 2 3 5% 9% 58%	3490
	21st to end	Day	5% 9% 2 5% 4 3 4 4 9% 12% 44%	3825
April	1st to 10th	Day	4 9% 2 5% 3 2 4 3 6% 10% 52%	2270
	11th to 20th	Day	4 10% 4 6% 4 3 4 4 8% 8% 46%	2251
	21st to end	Day	9% 9% 2 5% 4 4 5% 4 6% 10% 42%	2456
May	1st to 10th	Day	10% 11% 3 6% 4 4 5% 4 5% 8% 41%	4110
	11th to 20th	Day	8% 5% 2 4 2 3 3 3 6% 9% 55%	4380
	21st to end	Day	6% 5% 1 4 4 4 5% 4 7% 8% 52%	4825
June	1st to 10th	Day	4 3 1 3 4 3 4 3 8% 12% 55%	2660
	11th to 20th	Day	4 3 1 3 2 3 4 4 7% 8% 61%	2660
	21st to end	Day	2 2 1 2 2 4 4 3 6% 7% 66%	2660
July	1st to 10th	Day	2 2 1 2 2 3 3 3 6% 7% 70%	4430
	11th to 20th	Day	1 1 1 2 3 3 5% 5% 8% 9% 61%	4430
	21st to end	Day	2 2 1 3 3 4 5% 4 6% 8% 61%	4496
August	1st to 10th	Day	4 2 1 3 3 4 4 4 6% 9% 60%	4092
	11th to 20th	Day	2 2 1 3 3 3 5% 4 6% 8% 63%	4028
	21st to end	Day	1 1 2 2 2 3 3 5% 7% 73%	4304
September	1st to 10th	Day	4 3 1 3 3 3 3 3 4 7% 65%	2280
	11th to 20th	Day	5% 3 1 2 3 3 3 3 4 6% 68%	2212
	21st to end	Day	5% 3 1 3 2 2 3 3 4 5% 68%	2040
October	1st to 10th	Day	5% 4 1 3 2 2 2 2 3 5% 72%	3170
	11th to 20th	Day	6% 5% 1 3 2 2 3 2 4 6% 65%	3150
	21st to end	Day	5% 6% 2 4 3 2 3 3 5% 6% 63%	3438
November	1st to 10th	Day	1 4 2 3 2 3 3 4 6% 9% 63%	1742
	11th to 20th	Day	1 3 2 4 3 3 3 2 6% 9% 62%	1520
	21st to end	Day	1 5% 2 5% 3 2 4 4 6% 7% 60%	1520
December	1st to 10th	Day	1 3 2 7% 4 3 3 4 6% 9% 58%	1520
	11th to 20th	Day	1 5% 1 3 3 3 4 3 6% 10% 61%	1926
	21st to end	Day	2 5% 2 5% 3 3 3 3 6% 10% 57%	2794
January	1st to 10th	Night	5% 3 6% 4 4 4 4 8% 9% 53%	4417
	11th to 20th	Night	3 2 7% 4 4 3 4 7% 12% 54%	4224
	21st to end	Night	1 6% 2 6% 3 3 4 3 6% 12% 55%	4521
February	1st to 10th	Night	1 7% 2 6% 5% 4 4 4 6% 9% 53%	2470
	11th to 20th	Night	1 5% 2 6% 4 3 3 3 6% 10% 55%	2402
	21st to end	Night	1 6% 3 6% 5% 4 4 4 5% 6% 57%	1975
March	1st to 10th	Night	1 7% 2 4 3 3 3 3 5% 8% 61%	3437
	11th to 20th	Night	3 11% 2 5% 4 2 3 3 4 9% 55%	3490
	21st to end	Night	4 9% 3 7% 4 4 4 4 6% 11% 44%	3828
April	1st to 10th	Night	5% 8% 2 4 3 3 3 3 6% 8% 56%	1910
	11th to 20th	Night	6% 9% 3 6% 4 3 4 4 6% 8% 46%	1877
	21st to end	Night	9% 8% 2 5% 3 3 4 3 5% 8% 49%	1722
May	1st to 10th	Night	14% 8% 2 5% 3 4 4 3 4 7% 46%	2860
	11th to 20th	Night	10% 5% 2 4 3 3 3 3 6% 7% 54%	2522
	21st to end	Night	9% 4 1 4 3 4 3 3 6% 7% 55%	2762
June	1st to 10th	Night	5% 3 2 3 3 3 3 3 6% 10% 59%	1520
	11th to 20th	Night	7% 3 1 3 2 3 3 3 6% 7% 61%	1520
	21st to end	Night	3 3 1 2 2 3 3 3 5% 6% 69%	1520
July	1st to 10th	Night	2 1 1 2 2 2 3 4 5% 8% 71%	2540
	11th to 20th	Night	1 1 1 1 1 2 3 3 5% 8% 73%	2540
	21st to end	Night	2 1 1 1 2 2 3 3 6% 10% 69%	3065
August	1st to 10th	Night	6% 2 1 3 2 2 3 3 4 7% 66%	2847
	11th to 20th	Night	2 2 1 3 3 3 4 4 6% 7% 65%	2811
	21st to end	Night	2 1 1 2 2 2 2 3 5% 8% 74%	3363
September	1st to 10th	Night	4 3 1 2 2 3 2 3 4 7% 69%	1900
	11th to 20th	Night	5% 3 1 2 2 2 4 3 5% 7% 66%	1966
	21st to end	Night	7% 4 1 2 1 1 2 2 3 6% 71%	2139
October	1st to 10th	Night	5% 5% 1 3 2 2 2 2 2 3 74%	3800
	11th to 20th	Night	7% 5% 2 4 3 3 4 3 4 5% 62%	3778
	21st to end	Night	5% 8% 2 5% 2 3 3 3 4 7% 59%	4120
November	1st to 10th	Night	1 4 1 4 3 3 4 4 7% 10% 60%	2519
	11th to 20th	Night	1 5% 2 4 3 3 3 4 6% 9% 59%	2660
	21st to end	Night	2 6% 3 5% 3 3 4 3 6% 9% 57%	2660
December	1st to 10th	Night	1 4 2 6% 4 3 3 4 6% 9% 58%	2660
	11th to 20th	Night	1 4 2 4 3 4 4 3 7% 12% 57%	3271
	21st to end	Night	1 7% 3 5% 3 3 4 4 7% 10% 55%	4873

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	24% 6% 18% 30% 18% 3	2539
	11th to 20th	Day	26% 6% 20% 26% 18% 3	2773
	21st to end	Day	18% 5% 24% 36% 13% 4	3146
February	1st to 10th	Day	28% 5% 18% 32% 14% 3	1710
	11th to 20th	Day	25% 5% 19% 31% 15% 5%	1674
	21st to end	Day	23% 5% 18% 28% 22% 4	1479
March	1st to 10th	Day	16% 5% 11% 37% 24% 6%	3434
	11th to 20th	Day	23% 5% 19% 36% 15% 1	3490
	21st to end	Day	30% 8% 19% 35% 8% 1	3825
April	1st to 10th	Day	27% 7% 19% 30% 14% 4	2270
	11th to 20th	Day	32% 7% 16% 27% 17% 1	2254
	21st to end	Day	36% 7% 13% 29% 14% 1	2456
May	1st to 10th	Day	39% 7% 10% 23% 15% 7%	4110
	11th to 20th	Day	25% 7% 13% 31% 19% 6%	4384
	21st to end	Day	25% 8% 12% 34% 18% 2	4825
June	1st to 10th	Day	21% 7% 20% 26% 21% 6%	2660
	11th to 20th	Day	19% 6% 13% 22% 26% 15%	2660
	21st to end	Day	15% 6% 7% 25% 31% 17%	2660
July	1st to 10th	Day	12% 5% 7% 18% 36% 23%	4361
	11th to 20th	Day	15% 4 7% 19% 28% 27%	4355
	21st to end	Day	18% 4 6% 16% 32% 23%	4354
August	1st to 10th	Day	18% 6% 8% 26% 22% 19%	4078
	11th to 20th	Day	18% 4 6% 22% 34% 15%	4067
	21st to end	Day	12% 3 6% 19% 38% 23%	4303
September	1st to 10th	Day	20% 5% 7% 18% 32% 19%	2280
	11th to 20th	Day	18% 4 7% 28% 28% 16%	2212
	21st to end	Day	19% 4 5% 28% 34% 9%	2040
October	1st to 10th	Day	18% 3 6% 22% 27% 23%	3170
	11th to 20th	Day	22% 3 9% 34% 25% 7%	3150
	21st to end	Day	24% 2 11% 37% 21% 4	3438
November	1st to 10th	Day	18% 6% 15% 31% 22% 7%	1742
	11th to 20th	Day	20% 4 19% 30% 22% 5%	1520
	21st to end	Day	23% 5% 16% 30% 21% 5%	1520
December	1st to 10th	Day	24% 5% 20% 30% 16% 5%	1520
	11th to 20th	Day	19% 6% 23% 35% 17% 1	1924
	21st to end	Day	23% 5% 11% 32% 22% 6%	2794
January	1st to 10th	Night	27% 3 20% 29% 17% 3	4417
	11th to 20th	Night	23% 6% 23% 26% 16% 6%	4224
	21st to end	Night	23% 5% 17% 39% 13% 3	4521
February	1st to 10th	Night	30% 5% 15% 33% 14% 3	2470
	11th to 20th	Night	26% 4 16% 30% 19% 4	2403
	21st to end	Night	28% 3 14% 26% 24% 5%	1975
March	1st to 10th	Night	22% 4 10% 32% 23% 9%	3437
	11th to 20th	Night	27% 5% 15% 36% 15% 2	3490
	21st to end	Night	34% 6% 20% 29% 9% 1	3828
April	1st to 10th	Night	26% 6% 17% 27% 18% 6%	1910
	11th to 20th	Night	34% 5% 17% 24% 17% 2	1877
	21st to end	Night	34% 4 13% 31% 17% 1	1722
May	1st to 10th	Night	39% 4 9% 25% 17% 6%	2860
	11th to 20th	Night	27% 6% 13% 29% 16% 9%	2523
	21st to end	Night	26% 5% 12% 34% 19% 3	2762
June	1st to 10th	Night	21% 6% 21% 27% 20% 5%	1520
	11th to 20th	Night	22% 3 11% 21% 25% 18%	1520
	21st to end	Night	14% 6% 8% 19% 31% 21%	1520
July	1st to 10th	Night	12% 4 10% 18% 37% 19%	2500
	11th to 20th	Night	10% 3 6% 20% 34% 28%	2492
	21st to end	Night	10% 3 7% 20% 36% 24%	2969
August	1st to 10th	Night	18% 4 7% 29% 21% 21%	2838
	11th to 20th	Night	18% 5% 8% 25% 28% 16%	2838
	21st to end	Night	12% 3 6% 23% 26% 30%	3363
September	1st to 10th	Night	17% 4 8% 18% 30% 23%	1900
	11th to 20th	Night	17% 5% 9% 23% 30% 16%	1966
	21st to end	Night	17% 4 7% 26% 35% 12%	2139
October	1st to 10th	Night	19% 2 6% 19% 34% 20%	3800
	11th to 20th	Night	26% 3 8% 29% 26% 7%	3778
	21st to end	Night	27% 3 9% 31% 21% 8%	4120
November	1st to 10th	Night	21% 6% 15% 29% 22% 6%	2519
	11th to 20th	Night	22% 4 16% 32% 21% 4	2660
	21st to end	Night	24% 4 15% 30% 21% 5%	2660
December	1st to 10th	Night	24% 5% 18% 31% 18% 4	2660
	11th to 20th	Night	21% 6% 21% 35% 16% 2	3272
	21st to end	Night	26% 5% 10% 32% 21% 6%	4873

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	3 5% 34% 39% 15% 4	270
	11th to 20th	Day	4 5% 33% 39% 19% 1	270
	21st to end	Day	4 5% 33% 37% 17% 4	297
February	1st to 10th	Day	3 13% 51% 29% 4 1	270
	11th to 20th	Day	1 9% 49% 31% 10%	270
	21st to end	Day	4 13% 44% 29% 9%	225
March	1st to 10th	Day	6% 18% 42% 25% 8% 1	450
	11th to 20th	Day	8% 17% 40% 25% 9% 2	460
	21st to end	Day	14% 15% 33% 26% 10% 2	506
April	1st to 10th	Day	13% 19% 30% 27% 9% 2	460
	11th to 20th	Day	11% 26% 32% 22% 8% 1	452
	21st to end	Day	17% 17% 28% 25% 12% 2	460
May	1st to 10th	Day	17% 14% 33% 23% 10% 2	463
	11th to 20th	Day	18% 9% 19% 31% 18% 5%	667
	21st to end	Day	12% 9% 23% 29% 21% 6%	734
June	1st to 10th	Day	4 9% 27% 33% 21% 5%	680
	11th to 20th	Day	7% 11% 27% 36% 16% 2	680
	21st to end	Day	3 7% 26% 38% 22% 4	680
July	1st to 10th	Day	4 4 20% 38% 28% 6%	671
	11th to 20th	Day	1 4 26% 39% 26% 3	668
	21st to end	Day	3 3 27% 38% 23% 6%	560
August	1st to 10th	Day	3 4 26% 40% 22% 4	487
	11th to 20th	Day	3 4 26% 38% 22% 7%	477
	21st to end	Day	2 7% 29% 33% 22% 7%	539
September	1st to 10th	Day	4 6% 28% 35% 20% 9%	490
	11th to 20th	Day	6% 9% 28% 29% 21% 7%	490
	21st to end	Day	8% 7% 25% 33% 20% 7%	440
October	1st to 10th	Day	10% 5% 23% 31% 23% 9%	300
	11th to 20th	Day	7% 12% 23% 31% 18% 10%	300
	21st to end	Day	8% 7% 33% 37% 15% 1	330
November	1st to 10th	Day	6% 8% 36% 33% 11% 5%	297
	11th to 20th	Day	6% 7% 36% 33% 15% 3	270
	21st to end	Day	4 6% 29% 44% 15% 2	270
December	1st to 10th	Day	3 5% 33% 41% 15% 3	270
	11th to 20th	Day	7% 5% 39% 38% 10% 1	270
	21st to end	Day	8% 9% 35% 31% 12% 5%	297
January	1st to 10th	Night	2 7% 31% 41% 16% 2	950
	11th to 20th	Night	2 9% 30% 41% 14% 3	822
	21st to end	Night	4 6% 29% 46% 11% 3	836
February	1st to 10th	Night	4 7% 39% 39% 9% 1	760
	11th to 20th	Night	3 7% 36% 39% 12% 2	744
	21st to end	Night	4 9% 40% 36% 10% 1	628
March	1st to 10th	Night	5% 7% 37% 39% 10% 2	760
	11th to 20th	Night	6% 8% 32% 40% 13% 2	760
	21st to end	Night	9% 9% 31% 40% 11% 1	836
April	1st to 10th	Night	10% 10% 35% 35% 9% 1	580
	11th to 20th	Night	10% 9% 35% 35% 10%	563
	21st to end	Night	13% 8% 29% 35% 13% 2	570
May	1st to 10th	Night	17% 6% 24% 34% 16% 3	570
	11th to 20th	Night	16% 3 19% 38% 20% 3	561
	21st to end	Night	13% 5% 20% 38% 21% 3	617
June	1st to 10th	Night	5% 5% 25% 38% 22% 5%	570
	11th to 20th	Night	8% 5% 32% 42% 14% 1	570
	21st to end	Night	4 2 20% 46% 25% 2	570
July	1st to 10th	Night	3 1 17% 43% 32% 4	555
	11th to 20th	Night	2 1 19% 51% 24% 2	552
	21st to end	Night	4 2 11% 49% 32% 3	624
August	1st to 10th	Night	2 2 12% 49% 32% 3	567
	11th to 20th	Night	3 1 16% 49% 28% 3	564
	21st to end	Night	3 2 19% 44% 27% 5%	627
September	1st to 10th	Night	6% 3 19% 44% 21% 6%	570
	11th to 20th	Night	6% 2 21% 45% 20% 5%	636
	21st to end	Night	9% 3 21% 39% 21% 8%	760
October	1st to 10th	Night	11% 4 23% 38% 19% 4	760
	11th to 20th	Night	8% 4 24% 41% 19% 4	760
	21st to end	Night	8% 4 29% 43% 12% 4	836
November	1st to 10th	Night	4 6% 35% 41% 11% 3	889
	11th to 20th	Night	4 11% 31% 41% 10% 3	950
	21st to end	Night	4 8% 28% 44% 14% 2	950
December	1st to 10th	Night	3 7% 33% 44% 12% 1	950
	11th to 20th	Night	4 5% 34% 45% 11% 1	950
	21st to end	Night	5% 9% 33% 40% 12% 2	1045

Page generated at 2024-11-07 04:55:46. Version ac07

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