Camp Tres Ritos
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Camp Tres Ritos clear sky chart from 2005-11-06 to 2026-04-02.

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	3 4 2 5% 4 4 5% 4 6% 8% 56%	139773
	Night	2 3 1 4 3 3 4 3 6% 9% 62%	139556
Transparency	Day	23% 5% 10% 19% 26% 17%	134793
	Night	18% 4 12% 22% 28% 16%	135543
Seeing	Day	16% 23% 28% 22% 10% 2	17050
	Night	9% 19% 31% 27% 12% 2	27266

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 3 7% 2 3 4 3 4 8% 62%	4937
	11th to 20th	Day	1 1 6% 4 2 2 2 3 5% 74%	5340
	21st to end	Day	5% 3 4 3 3 3 3 6% 8% 61%	5844
February	1st to 10th	Day	4 2 6% 3 3 4 3 5% 9% 60%	1949
	11th to 20th	Day	4 2 5% 4 4 4 3 5% 7% 62%	2049
	21st to end	Day	4 2 5% 3 4 3 3 6% 7% 62%	1730
March	1st to 10th	Day	5% 3 5% 2 2 3 2 4 9% 64%	4691
	11th to 20th	Day	1 9% 6% 6% 3 3 4 4 6% 8% 49%	5110
	21st to end	Day	1 4 2 5% 3 4 4 4 7% 9% 59%	5872
April	1st to 10th	Day	1 5% 1 4 4 3 3 4 6% 8% 60%	2413
	11th to 20th	Day	3 6% 2 5% 3 3 3 4 5% 7% 60%	2371
	21st to end	Day	3 6% 2 4 4 4 4 3 5% 9% 58%	2400
May	1st to 10th	Day	5% 11% 2 5% 4 4 4 4 5% 6% 50%	5440
	11th to 20th	Day	5% 4 1 3 3 4 4 3 5% 7% 61%	5803
	21st to end	Day	2 3 1 3 3 4 3 4 5% 8% 66%	6925
June	1st to 10th	Day	2 4 2 5% 4 4 5% 5% 6% 9% 56%	2800
	11th to 20th	Day	2 2 1 3 3 3 4 4 5% 8% 64%	2800
	21st to end	Day	6% 4 2 5% 5% 5% 6% 5% 8% 7% 47%	2800
July	1st to 10th	Day	3 3 1 4 5% 5% 5% 5% 7% 8% 54%	6339
	11th to 20th	Day	3 3 1 5% 5% 7% 10% 8% 11% 10% 37%	6078
	21st to end	Day	7% 6% 3 9% 8% 7% 8% 6% 9% 9% 28%	6401
August	1st to 10th	Day	4 3 2 5% 5% 6% 7% 6% 8% 10% 43%	5570
	11th to 20th	Day	5% 4 2 7% 5% 7% 7% 5% 8% 8% 43%	5366
	21st to end	Day	5% 4 2 7% 6% 7% 7% 6% 9% 10% 37%	5984
September	1st to 10th	Day	8% 6% 2 7% 6% 4 6% 3 6% 7% 45%	2400
	11th to 20th	Day	7% 5% 2 5% 4 4 4 3 6% 7% 54%	2390
	21st to end	Day	5% 4 2 5% 3 3 4 3 5% 6% 61%	2200
October	1st to 10th	Day	5% 4 2 4 3 3 3 3 4 6% 62%	3280
	11th to 20th	Day	5% 6% 2 6% 3 3 4 3 5% 7% 58%	3250
	21st to end	Day	2 3 1 2 1 1 2 2 3 5% 77%	3548
November	1st to 10th	Day	1 3 1 2 2 3 3 3 5% 7% 70%	1916
	11th to 20th	Day	1 4 1 3 2 2 3 3 5% 8% 68%	1890
	21st to end	Day	1 5% 2 4 4 3 3 2 5% 8% 64%	1890
December	1st to 10th	Day	2 1 2 1 2 2 2 4 8% 76%	2799
	11th to 20th	Day	3 1 3 3 3 3 4 6% 9% 66%	3106
	21st to end	Day	3 2 4 2 3 3 3 5% 7% 69%	4092
January	1st to 10th	Night	3 2 6% 3 4 4 3 5% 9% 61%	8039
	11th to 20th	Night	1 1 3 2 2 3 3 4 6% 76%	7650
	21st to end	Night	2 1 4 3 4 3 4 6% 9% 63%	8370
February	1st to 10th	Night	3 2 5% 3 3 4 3 5% 8% 64%	2668
	11th to 20th	Night	1 3 3 5% 3 2 4 4 5% 9% 62%	2458
	21st to end	Night	1 3 1 5% 2 3 3 3 5% 7% 67%	2076
March	1st to 10th	Night	4 2 3 2 2 3 3 5% 9% 68%	5391
	11th to 20th	Night	1 7% 4 5% 3 2 3 3 4 7% 61%	5110
	21st to end	Night	1 2 1 4 2 3 3 3 4 8% 70%	5332
April	1st to 10th	Night	1 4 2 3 3 3 3 3 5% 7% 67%	2010
	11th to 20th	Night	1 6% 2 4 3 3 3 3 5% 7% 63%	1977
	21st to end	Night	3 4 1 3 3 3 3 3 5% 8% 65%	2000
May	1st to 10th	Night	4 9% 2 3 3 3 3 3 5% 7% 58%	4540
	11th to 20th	Night	3 7% 1 3 2 2 3 3 5% 8% 63%	4091
	21st to end	Night	2 2 1 3 3 3 4 3 5% 8% 66%	3972
June	1st to 10th	Night	2 4 1 4 4 5% 5% 5% 7% 10% 54%	1600
	11th to 20th	Night	1 2 1 2 2 3 4 4 7% 6% 68%	1600
	21st to end	Night	6% 5% 1 4 3 5% 5% 5% 8% 9% 50%	1600
July	1st to 10th	Night	3 5% 2 7% 6% 5% 5% 4 7% 8% 48%	3640
	11th to 20th	Night	2 2 1 5% 5% 4 6% 6% 11% 14% 44%	3884
	21st to end	Night	6% 5% 2 5% 4 5% 5% 6% 9% 13% 40%	4472
August	1st to 10th	Night	4 4 1 4 4 5% 7% 6% 10% 13% 42%	4240
	11th to 20th	Night	3 3 1 5% 4 5% 6% 5% 9% 14% 45%	4483
	21st to end	Night	4 5% 2 6% 4 5% 6% 6% 11% 13% 37%	4993
September	1st to 10th	Night	5% 4 2 4 4 4 6% 4 6% 9% 54%	2000
	11th to 20th	Night	4 4 1 4 2 3 3 3 7% 8% 61%	2009
	21st to end	Night	4 3 1 3 3 2 4 3 5% 7% 65%	2200
October	1st to 10th	Night	3 2 1 2 2 2 2 2 3 4 75%	3906
	11th to 20th	Night	4 6% 2 3 2 2 2 2 4 6% 67%	3898
	21st to end	Night	2 3 1 2 2 2 2 2 4 6% 76%	4252
November	1st to 10th	Night	1 2 1 2 2 2 2 2 4 6% 75%	2580
	11th to 20th	Night	2 1 3 1 2 2 3 5% 8% 73%	2730
	21st to end	Night	1 4 2 4 3 3 3 3 6% 8% 64%	2730
December	1st to 10th	Night	2 1 3 2 2 2 2 3 6% 77%	4606
	11th to 20th	Night	2 1 3 2 3 3 2 4 9% 69%	5321
	21st to end	Night	1 2 1 3 3 3 3 3 5% 10% 66%	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	18% 2 7% 23% 37% 13%	4940
	11th to 20th	Day	12% 1 7% 25% 30% 25%	5340
	21st to end	Day	18% 2 8% 18% 30% 24%	5844
February	1st to 10th	Day	20% 3 12% 22% 26% 17%	1949
	11th to 20th	Day	19% 3 9% 27% 26% 16%	2059
	21st to end	Day	18% 2 8% 17% 32% 23%	1730
March	1st to 10th	Day	18% 3 4 14% 32% 30%	4691
	11th to 20th	Day	28% 3 5% 17% 29% 17%	5110
	21st to end	Day	18% 4 7% 32% 32% 7%	5872
April	1st to 10th	Day	19% 4 10% 25% 27% 16%	2413
	11th to 20th	Day	23% 3 7% 22% 29% 17%	2374
	21st to end	Day	22% 4 9% 23% 31% 11%	2400
May	1st to 10th	Day	30% 4 10% 18% 22% 16%	5440
	11th to 20th	Day	22% 5% 7% 12% 30% 24%	5807
	21st to end	Day	15% 5% 10% 16% 24% 30%	6926
June	1st to 10th	Day	23% 7% 13% 20% 23% 15%	2800
	11th to 20th	Day	17% 6% 7% 16% 24% 30%	2800
	21st to end	Day	31% 7% 11% 17% 18% 17%	2800
July	1st to 10th	Day	24% 9% 12% 12% 19% 23%	6271
	11th to 20th	Day	31% 14% 20% 25% 7% 4	6004
	21st to end	Day	43% 11% 18% 16% 9% 3	6217
August	1st to 10th	Day	40% 11% 18% 17% 9% 5%	4054
	11th to 20th	Day	31% 8% 15% 21% 16% 10%	3882
	21st to end	Day	37% 8% 18% 22% 13% 2	4311
September	1st to 10th	Day	34% 8% 12% 19% 19% 8%	2400
	11th to 20th	Day	28% 6% 10% 18% 24% 15%	2390
	21st to end	Day	23% 5% 7% 21% 31% 13%	2200
October	1st to 10th	Day	20% 5% 5% 16% 32% 22%	3280
	11th to 20th	Day	26% 3 7% 16% 30% 17%	3250
	21st to end	Day	12% 1 4 15% 40% 28%	3548
November	1st to 10th	Day	12% 2 9% 20% 37% 19%	1916
	11th to 20th	Day	13% 3 8% 26% 35% 15%	1890
	21st to end	Day	18% 2 7% 22% 30% 22%	1890
December	1st to 10th	Day	9% 2 9% 24% 35% 22%	2799
	11th to 20th	Day	14% 2 9% 19% 39% 17%	3104
	21st to end	Day	14% 2 8% 23% 37% 16%	4092
January	1st to 10th	Night	19% 2 8% 25% 33% 12%	8040
	11th to 20th	Night	9% 1 11% 23% 35% 21%	7650
	21st to end	Night	16% 2 11% 18% 33% 21%	8370
February	1st to 10th	Night	17% 2 13% 23% 27% 18%	2668
	11th to 20th	Night	17% 3 11% 29% 25% 14%	2458
	21st to end	Night	15% 1 9% 20% 34% 21%	2076
March	1st to 10th	Night	13% 2 5% 17% 36% 28%	5391
	11th to 20th	Night	22% 3 6% 22% 30% 16%	5110
	21st to end	Night	13% 2 9% 35% 34% 7%	5332
April	1st to 10th	Night	15% 3 12% 27% 29% 15%	2010
	11th to 20th	Night	19% 3 9% 23% 29% 16%	1977
	21st to end	Night	18% 4 12% 28% 29% 9%	2000
May	1st to 10th	Night	25% 4 8% 23% 26% 14%	4537
	11th to 20th	Night	19% 3 10% 20% 28% 20%	4092
	21st to end	Night	15% 4 12% 13% 23% 33%	3972
June	1st to 10th	Night	21% 7% 16% 20% 20% 16%	1600
	11th to 20th	Night	14% 4 9% 18% 26% 29%	1600
	21st to end	Night	28% 7% 13% 17% 20% 16%	1600
July	1st to 10th	Night	30% 12% 12% 13% 16% 18%	3600
	11th to 20th	Night	24% 11% 30% 24% 6% 6%	3835
	21st to end	Night	31% 8% 26% 21% 12% 1	4344
August	1st to 10th	Night	32% 13% 23% 17% 9% 5%	3080
	11th to 20th	Night	25% 8% 22% 23% 16% 7%	3243
	21st to end	Night	28% 10% 28% 22% 10% 2	3597
September	1st to 10th	Night	24% 7% 17% 26% 18% 8%	2000
	11th to 20th	Night	20% 5% 14% 19% 30% 13%	2009
	21st to end	Night	19% 4 10% 25% 32% 11%	2200
October	1st to 10th	Night	13% 3 7% 19% 39% 19%	3906
	11th to 20th	Night	19% 3 7% 21% 30% 19%	3898
	21st to end	Night	12% 2 4 17% 40% 25%	4252
November	1st to 10th	Night	11% 2 7% 26% 38% 17%	2580
	11th to 20th	Night	9% 3 9% 27% 34% 17%	2730
	21st to end	Night	16% 2 10% 24% 27% 20%	2730
December	1st to 10th	Night	10% 3 8% 25% 38% 17%	4606
	11th to 20th	Night	12% 2 8% 21% 34% 23%	5322
	21st to end	Night	14% 3 11% 24% 34% 15%	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	24% 33% 23% 14% 6%	330
	11th to 20th	Day	25% 34% 22% 14% 4 1	330
	21st to end	Day	18% 33% 30% 13% 5% 1	363
February	1st to 10th	Day	25% 33% 25% 13% 3	330
	11th to 20th	Day	26% 40% 20% 12% 2	330
	21st to end	Day	37% 31% 25% 6% 1	273
March	1st to 10th	Day	29% 31% 24% 13% 2	369
	11th to 20th	Day	30% 27% 29% 11% 3 1	540
	21st to end	Day	30% 37% 24% 8% 1	594
April	1st to 10th	Day	20% 39% 29% 8% 3	505
	11th to 20th	Day	27% 38% 26% 8% 1	492
	21st to end	Day	21% 39% 30% 9% 1	500
May	1st to 10th	Day	17% 35% 37% 9% 3 1	503
	11th to 20th	Day	15% 24% 32% 20% 7% 1	660
	21st to end	Day	10% 23% 34% 25% 8%	789
June	1st to 10th	Day	4 15% 34% 32% 14% 1	730
	11th to 20th	Day	7% 17% 34% 27% 14% 1	730
	21st to end	Day	7% 14% 29% 29% 17% 3	730
July	1st to 10th	Day	7% 7% 25% 36% 23% 3	721
	11th to 20th	Day	6% 2 20% 38% 25% 7%	613
	21st to end	Day	9% 4 17% 37% 27% 5%	575
August	1st to 10th	Day	9% 8% 25% 38% 16% 4	527
	11th to 20th	Day	6% 6% 30% 37% 18% 2	517
	21st to end	Day	9% 7% 29% 34% 19% 2	583
September	1st to 10th	Day	8% 9% 28% 38% 15% 2	530
	11th to 20th	Day	10% 11% 37% 29% 12% 1	520
	21st to end	Day	8% 19% 32% 28% 10% 3	330
October	1st to 10th	Day	9% 25% 30% 22% 11% 2	330
	11th to 20th	Day	15% 26% 31% 18% 7% 2	330
	21st to end	Day	20% 25% 29% 19% 7% 1	363
November	1st to 10th	Day	18% 31% 27% 21% 4	330
	11th to 20th	Day	15% 29% 31% 18% 7%	330
	21st to end	Day	18% 33% 28% 13% 8% 1	330
December	1st to 10th	Day	23% 28% 28% 14% 7% 1	330
	11th to 20th	Day	21% 33% 28% 14% 4	330
	21st to end	Day	30% 34% 24% 9% 3	363
January	1st to 10th	Night	13% 26% 30% 21% 9% 1	992
	11th to 20th	Night	11% 26% 33% 23% 6% 2	840
	21st to end	Night	8% 27% 36% 19% 8% 2	924
February	1st to 10th	Night	11% 27% 40% 16% 5%	840
	11th to 20th	Night	13% 31% 36% 16% 4	824
	21st to end	Night	15% 33% 40% 11% 1	692
March	1st to 10th	Night	12% 31% 34% 18% 5% 1	840
	11th to 20th	Night	15% 22% 31% 23% 8%	840
	21st to end	Night	15% 27% 39% 17% 3	801
April	1st to 10th	Night	13% 27% 41% 17% 2	603
	11th to 20th	Night	12% 30% 32% 22% 4	593
	21st to end	Night	10% 27% 38% 22% 3	600
May	1st to 10th	Night	10% 19% 39% 23% 8% 1	600
	11th to 20th	Night	11% 18% 29% 28% 12% 1	591
	21st to end	Night	7% 16% 38% 31% 8%	650
June	1st to 10th	Night	4 7% 30% 42% 17%	600
	11th to 20th	Night	2 10% 38% 40% 10% 1	600
	21st to end	Night	4 7% 29% 36% 23% 2	600
July	1st to 10th	Night	3 4 17% 43% 30% 3	585
	11th to 20th	Night	3 1 10% 41% 39% 5%	582
	21st to end	Night	5% 2 12% 34% 39% 9%	657
August	1st to 10th	Night	5% 2 11% 40% 34% 8%	597
	11th to 20th	Night	6% 3 15% 46% 28% 3	594
	21st to end	Night	4 2 15% 43% 32% 4	660
September	1st to 10th	Night	6% 3 21% 43% 25% 3	600
	11th to 20th	Night	5% 5% 24% 44% 21% 2	600
	21st to end	Night	6% 10% 26% 42% 15% 1	600
October	1st to 10th	Night	5% 13% 34% 35% 12% 1	786
	11th to 20th	Night	8% 19% 31% 29% 10% 3	800
	21st to end	Night	11% 21% 28% 24% 12% 4	880
November	1st to 10th	Night	9% 20% 33% 27% 10% 1	940
	11th to 20th	Night	7% 23% 33% 26% 9% 2	1050
	21st to end	Night	11% 24% 31% 21% 10% 1	1050
December	1st to 10th	Night	14% 24% 35% 19% 7% 1	1050
	11th to 20th	Night	12% 29% 31% 22% 6% 1	1050
	21st to end	Night	16% 27% 35% 18% 3 1	1155

Page generated at 2026-03-30 00:18:45. Version ac07

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