Lajitas
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lajitas clear sky chart from 2005-11-06 to 2024-01-14.

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 3 1 3 3 2 4 4 5% 8% 63%	74688
	Night	4 3 1 3 3 2 4 5% 6% 8% 61%	75093
Transparency	Day	12% 37% 6% 12% 17% 17%	74438
	Night	13% 37% 6% 12% 16% 17%	74865
Seeing	Day	5% 5% 17% 33% 30% 10%	13226
	Night	5% 3 18% 47% 26% 2	23553

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	6% 3 1 3 4 2 3 3 5% 6% 63%	1897
	11th to 20th	Day	8% 3 2 4 3 1 2 3 4 6% 65%	1830
	21st to end	Day	3 5% 2 3 4 3 4 3 3 5% 65%	1980
February	1st to 10th	Day	3 4 2 4 4 2 4 4 5% 5% 64%	1800
	11th to 20th	Day	4 4 2 5% 3 2 3 3 5% 6% 63%	1749
	21st to end	Day	3 3 1 2 2 2 3 4 4 6% 70%	1480
March	1st to 10th	Day	2 4 1 4 4 2 4 5% 5% 8% 62%	1800
	11th to 20th	Day	5% 4 2 3 4 2 4 4 5% 6% 60%	1903
	21st to end	Day	3 2 1 3 2 2 2 3 4 7% 71%	2362
April	1st to 10th	Day	2 2 1 3 3 2 4 4 6% 7% 67%	2160
	11th to 20th	Day	2 2 1 2 2 2 3 3 4 5% 73%	2131
	21st to end	Day	3 2 1 3 3 1 3 3 4 5% 72%	2160
May	1st to 10th	Day	2 2 1 2 3 2 3 3 4 7% 71%	2160
	11th to 20th	Day	3 2 1 3 3 2 4 4 4 7% 68%	2125
	21st to end	Day	3 2 1 2 2 2 4 5% 6% 8% 66%	2395
June	1st to 10th	Day	1 1 1 1 2 2 3 5% 6% 7% 72%	2340
	11th to 20th	Day	2 2 1 2 3 3 4 4 6% 8% 66%	2340
	21st to end	Day	2 3 1 3 4 2 4 5% 7% 9% 61%	2215
July	1st to 10th	Day	4 2 1 5% 4 4 6% 7% 7% 10% 49%	2160
	11th to 20th	Day	3 2 1 3 3 2 4 5% 7% 11% 59%	2160
	21st to end	Day	3 2 2 3 4 3 6% 7% 7% 12% 53%	2349
August	1st to 10th	Day	3 1 1 2 3 2 4 5% 6% 11% 61%	2149
	11th to 20th	Day	5% 3 2 5% 5% 4 5% 5% 8% 11% 47%	2123
	21st to end	Day	4 2 2 3 5% 3 5% 6% 8% 11% 51%	2376
September	1st to 10th	Day	6% 4 2 5% 5% 3 5% 5% 8% 10% 47%	2160
	11th to 20th	Day	8% 6% 2 4 4 2 4 5% 7% 9% 50%	2039
	21st to end	Day	5% 3 2 3 4 2 4 4 5% 7% 61%	1980
October	1st to 10th	Day	3 2 1 2 3 2 3 4 5% 8% 67%	1980
	11th to 20th	Day	6% 3 1 3 3 2 3 4 6% 7% 63%	1904
	21st to end	Day	5% 4 1 2 2 1 2 2 3 5% 74%	1980
November	1st to 10th	Day	6% 2 1 2 2 1 2 3 4 6% 71%	1843
	11th to 20th	Day	4 3 1 2 3 1 3 2 5% 5% 70%	1710
	21st to end	Day	6% 3 1 3 3 3 3 3 5% 6% 65%	1710
December	1st to 10th	Day	5% 5% 2 3 3 2 3 3 4 7% 63%	1710
	11th to 20th	Day	3 4 2 4 4 3 4 3 6% 8% 57%	2161
	21st to end	Day	3 3 1 2 3 2 4 4 6% 8% 65%	3367
January	1st to 10th	Night	4 3 1 3 2 2 4 4 5% 5% 67%	2268
	11th to 20th	Night	7% 2 1 3 2 2 2 4 5% 7% 64%	2202
	21st to end	Night	5% 4 2 4 3 2 4 3 6% 6% 60%	2376
February	1st to 10th	Night	4 4 2 3 3 2 4 4 4 6% 65%	2160
	11th to 20th	Night	5% 3 2 4 4 2 4 4 5% 7% 60%	2098
	21st to end	Night	4 2 1 3 3 2 4 3 4 6% 67%	1776
March	1st to 10th	Night	4 4 2 4 3 2 4 4 5% 7% 61%	2160
	11th to 20th	Night	6% 5% 1 3 3 2 3 4 5% 6% 61%	2052
	21st to end	Night	3 3 2 3 2 2 3 4 5% 6% 69%	1993
April	1st to 10th	Night	3 3 1 3 3 3 4 4 4 6% 65%	1800
	11th to 20th	Night	3 2 1 2 3 2 3 4 5% 6% 69%	1777
	21st to end	Night	3 2 1 2 3 1 4 4 4 5% 71%	1800
May	1st to 10th	Night	4 3 1 3 3 2 3 3 5% 7% 66%	1800
	11th to 20th	Night	5% 2 1 4 4 3 4 4 6% 8% 59%	1770
	21st to end	Night	3 2 2 4 4 3 5% 5% 6% 8% 59%	1877
June	1st to 10th	Night	2 1 1 3 3 3 5% 6% 8% 11% 57%	1620
	11th to 20th	Night	2 1 1 4 5% 3 6% 6% 9% 10% 53%	1620
	21st to end	Night	3 2 1 3 4 2 4 5% 7% 11% 56%	1734
July	1st to 10th	Night	4 4 1 5% 5% 3 8% 7% 9% 12% 42%	1800
	11th to 20th	Night	3 1 2 3 3 3 4 5% 7% 12% 58%	1800
	21st to end	Night	3 2 2 3 4 3 6% 7% 8% 10% 51%	1969
August	1st to 10th	Night	2 1 1 3 3 3 5% 6% 10% 14% 52%	1790
	11th to 20th	Night	4 3 2 4 5% 4 5% 7% 8% 14% 46%	1778
	21st to end	Night	3 4 1 4 6% 3 6% 7% 9% 13% 43%	1980
September	1st to 10th	Night	4 3 2 5% 6% 4 6% 5% 7% 10% 48%	1800
	11th to 20th	Night	6% 4 2 6% 5% 3 6% 7% 8% 10% 43%	1921
	21st to end	Night	4 4 2 4 5% 3 5% 5% 6% 10% 52%	1980
October	1st to 10th	Night	3 2 1 3 4 3 4 5% 6% 9% 61%	1980
	11th to 20th	Night	7% 2 1 3 4 2 3 4 5% 6% 63%	2052
	21st to end	Night	5% 3 1 3 2 1 2 2 3 5% 74%	2376
November	1st to 10th	Night	6% 3 1 2 2 1 2 2 4 4 75%	2220
	11th to 20th	Night	4 2 1 2 3 2 3 3 5% 5% 71%	2462
	21st to end	Night	5% 3 1 2 2 2 4 3 4 6% 66%	2470
December	1st to 10th	Night	6% 3 1 2 2 2 4 5% 5% 6% 63%	2470
	11th to 20th	Night	3 3 1 3 3 2 4 4 5% 8% 63%	3036
	21st to end	Night	3 3 1 3 3 2 3 4 6% 8% 64%	4326

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	10% 39% 4 11% 22% 14%	1898
	11th to 20th	Day	12% 40% 2 13% 18% 13%	1830
	21st to end	Day	14% 36% 4 11% 21% 13%	1980
February	1st to 10th	Day	12% 36% 4 8% 17% 23%	1800
	11th to 20th	Day	14% 37% 4 8% 19% 18%	1759
	21st to end	Day	9% 34% 4 9% 19% 25%	1480
March	1st to 10th	Day	10% 35% 4 10% 19% 23%	1800
	11th to 20th	Day	13% 37% 4 6% 14% 25%	1903
	21st to end	Day	9% 35% 3 7% 18% 28%	2362
April	1st to 10th	Day	10% 36% 5% 8% 15% 27%	2160
	11th to 20th	Day	7% 34% 3 8% 16% 32%	2134
	21st to end	Day	10% 35% 4 6% 15% 31%	2160
May	1st to 10th	Day	11% 36% 3 9% 15% 26%	2160
	11th to 20th	Day	12% 38% 5% 11% 16% 18%	2128
	21st to end	Day	8% 38% 6% 13% 15% 19%	2395
June	1st to 10th	Day	5% 36% 5% 15% 20% 18%	2340
	11th to 20th	Day	8% 36% 7% 10% 20% 19%	2340
	21st to end	Day	14% 38% 9% 13% 16% 11%	2215
July	1st to 10th	Day	19% 40% 10% 12% 12% 6%	2101
	11th to 20th	Day	11% 38% 7% 20% 16% 9%	2097
	21st to end	Day	15% 41% 12% 20% 10% 2	2219
August	1st to 10th	Day	10% 38% 9% 21% 15% 7%	2136
	11th to 20th	Day	18% 38% 9% 18% 13% 4	2123
	21st to end	Day	18% 40% 11% 15% 11% 6%	2376
September	1st to 10th	Day	20% 39% 11% 12% 10% 8%	2160
	11th to 20th	Day	20% 38% 7% 12% 15% 7%	2039
	21st to end	Day	12% 37% 6% 13% 19% 14%	1980
October	1st to 10th	Day	10% 37% 7% 15% 17% 14%	1980
	11th to 20th	Day	11% 36% 6% 15% 15% 17%	1904
	21st to end	Day	9% 35% 3 9% 23% 21%	1980
November	1st to 10th	Day	4 39% 3 11% 23% 21%	1843
	11th to 20th	Day	6% 39% 6% 12% 22% 16%	1710
	21st to end	Day	11% 40% 5% 14% 13% 16%	1710
December	1st to 10th	Day	11% 39% 5% 8% 23% 14%	1710
	11th to 20th	Day	18% 32% 5% 16% 20% 10%	2159
	21st to end	Day	11% 24% 4 10% 28% 22%	3367
January	1st to 10th	Night	9% 39% 3 11% 22% 17%	2268
	11th to 20th	Night	12% 41% 4 10% 19% 15%	2202
	21st to end	Night	16% 37% 4 11% 18% 14%	2376
February	1st to 10th	Night	13% 35% 4 8% 17% 24%	2160
	11th to 20th	Night	16% 37% 5% 7% 14% 21%	2098
	21st to end	Night	11% 35% 3 7% 18% 26%	1776
March	1st to 10th	Night	13% 35% 3 8% 18% 23%	2160
	11th to 20th	Night	15% 36% 4 7% 12% 26%	2052
	21st to end	Night	10% 36% 5% 9% 12% 29%	1993
April	1st to 10th	Night	13% 36% 4 9% 14% 24%	1800
	11th to 20th	Night	9% 34% 5% 8% 13% 30%	1777
	21st to end	Night	11% 35% 4 9% 14% 27%	1800
May	1st to 10th	Night	13% 36% 5% 10% 12% 23%	1800
	11th to 20th	Night	16% 39% 5% 12% 13% 14%	1771
	21st to end	Night	14% 39% 7% 13% 11% 15%	1878
June	1st to 10th	Night	10% 39% 9% 17% 14% 12%	1620
	11th to 20th	Night	14% 38% 8% 11% 15% 14%	1620
	21st to end	Night	15% 39% 8% 13% 15% 10%	1734
July	1st to 10th	Night	20% 41% 11% 15% 10% 3	1750
	11th to 20th	Night	11% 39% 7% 18% 17% 8%	1740
	21st to end	Night	18% 42% 10% 20% 9% 1	1859
August	1st to 10th	Night	12% 40% 9% 18% 16% 5%	1779
	11th to 20th	Night	16% 38% 11% 20% 13% 2	1778
	21st to end	Night	19% 40% 11% 13% 12% 5%	1980
September	1st to 10th	Night	19% 40% 12% 14% 8% 7%	1800
	11th to 20th	Night	23% 39% 9% 11% 12% 5%	1921
	21st to end	Night	15% 38% 8% 13% 14% 13%	1980
October	1st to 10th	Night	11% 37% 9% 14% 14% 15%	1980
	11th to 20th	Night	15% 36% 5% 14% 14% 17%	2052
	21st to end	Night	9% 35% 2 10% 19% 24%	2376
November	1st to 10th	Night	5% 39% 2 9% 24% 22%	2220
	11th to 20th	Night	7% 39% 5% 10% 18% 21%	2462
	21st to end	Night	11% 39% 6% 12% 14% 19%	2470
December	1st to 10th	Night	11% 40% 6% 10% 19% 15%	2470
	11th to 20th	Night	13% 32% 5% 16% 22% 13%	3037
	21st to end	Night	12% 24% 5% 11% 25% 23%	4326

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% 4 24% 38% 19% 3	270
	11th to 20th	Day	7% 5% 20% 40% 27% 1	249
	21st to end	Day	4 12% 27% 34% 20% 3	264
February	1st to 10th	Day	8% 7% 23% 31% 28% 4	240
	11th to 20th	Day	10% 12% 23% 35% 18% 2	240
	21st to end	Day	7% 12% 29% 40% 11% 2	198
March	1st to 10th	Day	6% 4 30% 37% 22% 2	240
	11th to 20th	Day	6% 12% 33% 31% 12% 5%	343
	21st to end	Day	8% 13% 31% 33% 13% 2	462
April	1st to 10th	Day	3 13% 35% 35% 12% 1	420
	11th to 20th	Day	3 15% 39% 30% 10% 3	412
	21st to end	Day	7% 13% 32% 37% 11%	420
May	1st to 10th	Day	3 9% 32% 38% 15% 3	423
	11th to 20th	Day	2 8% 31% 38% 19% 2	448
	21st to end	Day	3 5% 24% 42% 23% 2	543
June	1st to 10th	Day	2 3 13% 36% 39% 6%	630
	11th to 20th	Day	2 9% 40% 42% 7%	630
	21st to end	Day	3 1 11% 33% 43% 10%	505
July	1st to 10th	Day	4 1 7% 25% 40% 22%	446
	11th to 20th	Day	2 5% 34% 42% 17%	444
	21st to end	Day	2 1 4 34% 42% 16%	487
August	1st to 10th	Day	2 1 4 20% 52% 21%	447
	11th to 20th	Day	5% 1 7% 24% 38% 26%	437
	21st to end	Day	3 1 6% 25% 40% 25%	495
September	1st to 10th	Day	8% 1 6% 29% 39% 18%	450
	11th to 20th	Day	5% 6% 19% 47% 22%	329
	21st to end	Day	7% 2 7% 22% 41% 21%	270
October	1st to 10th	Day	4 3 9% 26% 42% 16%	270
	11th to 20th	Day	10% 2 9% 29% 33% 17%	270
	21st to end	Day	9% 3 13% 27% 34% 14%	297
November	1st to 10th	Day	7% 4 11% 29% 36% 12%	270
	11th to 20th	Day	9% 7% 16% 26% 31% 11%	270
	21st to end	Day	8% 9% 18% 36% 25% 4	270
December	1st to 10th	Day	8% 6% 13% 32% 36% 6%	270
	11th to 20th	Day	4 9% 22% 39% 25% 1	270
	21st to end	Day	6% 6% 19% 44% 24% 1	297
January	1st to 10th	Night	6% 3 20% 53% 18% 1	760
	11th to 20th	Night	8% 3 17% 51% 20% 1	734
	21st to end	Night	7% 5% 23% 48% 16% 1	792
February	1st to 10th	Night	5% 4 24% 47% 20% 1	720
	11th to 20th	Night	7% 4 21% 55% 12% 1	704
	21st to end	Night	6% 5% 28% 53% 8%	592
March	1st to 10th	Night	6% 5% 29% 48% 10% 1	720
	11th to 20th	Night	8% 6% 23% 47% 15% 1	720
	21st to end	Night	5% 6% 32% 46% 11%	607
April	1st to 10th	Night	3 7% 31% 49% 10%	540
	11th to 20th	Night	3 8% 37% 44% 7%	533
	21st to end	Night	3 7% 33% 49% 7%	540
May	1st to 10th	Night	4 5% 27% 54% 10%	540
	11th to 20th	Night	5% 5% 25% 54% 10%	531
	21st to end	Night	3 3 24% 57% 13%	584
June	1st to 10th	Night	2 1 19% 55% 22% 1	540
	11th to 20th	Night	2 1 17% 54% 25%	540
	21st to end	Night	4 1 14% 45% 37%	540
July	1st to 10th	Night	4 1 11% 40% 42% 2	525
	11th to 20th	Night	3 5% 43% 47% 2	522
	21st to end	Night	3 1 6% 40% 47% 3	591
August	1st to 10th	Night	2 1 3 31% 59% 4	537
	11th to 20th	Night	3 1 4 28% 57% 6%	534
	21st to end	Night	4 1 6% 31% 55% 4	594
September	1st to 10th	Night	5% 1 6% 33% 52% 3	540
	11th to 20th	Night	7% 1 7% 36% 47% 2	540
	21st to end	Night	6% 1 9% 41% 41% 2	540
October	1st to 10th	Night	3 1 11% 46% 37% 1	540
	11th to 20th	Night	9% 1 10% 51% 26% 2	612
	21st to end	Night	6% 3 12% 42% 32% 4	792
November	1st to 10th	Night	7% 1 9% 45% 34% 4	740
	11th to 20th	Night	4 3 12% 49% 30% 1	942
	21st to end	Night	7% 3 22% 45% 21% 3	950
December	1st to 10th	Night	7% 2 13% 52% 25% 1	950
	11th to 20th	Night	5% 3 19% 53% 19% 1	950
	21st to end	Night	5% 4 20% 53% 15% 2	917

Page generated at 2024-01-11 03:22:38. Version ac07

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