El Cariso
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the El Cariso clear sky chart from 2005-11-06 to 2025-06-10.

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 3 1 3 2 3 3 3 4 6% 67%	124232
	Night	4 4 2 5% 3 3 3 3 4 6% 63%	123002
Transparency	Day	17% 4 5% 16% 27% 29%	124002
	Night	19% 6% 6% 15% 24% 29%	122821
Seeing	Day	5% 7% 19% 33% 25% 10%	16567
	Night	5% 3 9% 34% 39% 9%	26653

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	5% 3 1 3 2 2 2 2 3 5% 71%	4098
	11th to 20th	Day	5% 2 1 4 3 2 3 3 4 7% 67%	4358
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 49%	5016
February	1st to 10th	Day	8% 6% 2 5% 3 3 4 3 4 4 58%	2000
	11th to 20th	Day	7% 6% 2 5% 3 3 3 3 5% 7% 57%	1950
	21st to end	Day	8% 7% 2 7% 4 4 3 2 5% 5% 52%	1650
March	1st to 10th	Day	5% 6% 3 6% 5% 4 5% 4 7% 7% 46%	4518
	11th to 20th	Day	5% 6% 2 6% 4 3 4 3 5% 8% 53%	4726
	21st to end	Day	7% 5% 1 4 3 4 4 3 5% 7% 57%	5871
April	1st to 10th	Day	6% 5% 2 4 3 3 3 4 5% 7% 58%	2400
	11th to 20th	Day	2 4 2 5% 3 3 4 3 5% 6% 63%	2369
	21st to end	Day	3 4 2 3 2 3 3 3 5% 7% 65%	2400
May	1st to 10th	Day	3 5% 2 3 2 2 2 2 4 5% 69%	5694
	11th to 20th	Day	1 3 1 4 3 3 4 3 5% 7% 65%	5841
	21st to end	Day	1 3 1 4 3 3 3 3 5% 8% 66%	6423
June	1st to 10th	Day	3 4 1 3 2 3 3 3 5% 7% 66%	2589
	11th to 20th	Day	1 3 1 3 2 2 3 2 3 5% 75%	2470
	21st to end	Day	1 2 1 2 2 2 2 2 3 3 81%	2619
July	1st to 10th	Day	1 1 1 1 1 1 1 1 2 3 87%	4310
	11th to 20th	Day	1 1 1 2 1 2 2 2 3 5% 79%	4110
	21st to end	Day	1 1 1 1 2 2 2 3 5% 82%	4248
August	1st to 10th	Day	1 1 1 2 1 2 2 1 3 5% 82%	3783
	11th to 20th	Day	1 1 1 1 1 1 2 4 87%	3724
	21st to end	Day	1 1 1 1 1 1 1 2 3 87%	4180
September	1st to 10th	Day	2 1 1 2 2 2 2 2 2 5% 79%	2280
	11th to 20th	Day	1 2 1 2 1 1 2 2 3 5% 80%	2097
	21st to end	Day	1 2 1 3 2 2 2 2 3 5% 79%	2090
October	1st to 10th	Day	2 2 2 2 1 2 2 3 5% 80%	3490
	11th to 20th	Day	3 2 1 3 2 2 2 2 4 6% 75%	3392
	21st to end	Day	2 2 1 3 2 3 4 3 6% 6% 69%	3303
November	1st to 10th	Day	3 3 1 2 2 2 3 3 4 5% 71%	1764
	11th to 20th	Day	3 2 1 3 3 3 3 3 4 5% 69%	1800
	21st to end	Day	5% 4 2 5% 3 4 3 3 5% 7% 58%	1800
December	1st to 10th	Day	4 3 1 3 2 2 3 3 6% 7% 65%	2950
	11th to 20th	Day	7% 5% 2 5% 3 4 5% 5% 7% 7% 50%	3409
	21st to end	Day	6% 6% 3 6% 5% 6% 5% 5% 6% 9% 44%	4510
January	1st to 10th	Night	4 3 1 3 3 3 2 2 3 6% 68%	5867
	11th to 20th	Night	3 4 2 5% 4 4 3 3 5% 7% 62%	5617
	21st to end	Night	9% 8% 2 7% 5% 4 4 4 5% 6% 46%	5984
February	1st to 10th	Night	7% 6% 2 4 3 3 4 3 5% 5% 58%	2400
	11th to 20th	Night	7% 6% 2 4 3 4 3 3 4 6% 58%	2338
	21st to end	Night	8% 8% 2 6% 3 4 3 3 5% 4 53%	1980
March	1st to 10th	Night	6% 9% 4 10% 4 5% 5% 3 5% 7% 40%	5376
	11th to 20th	Night	4 7% 3 9% 5% 4 5% 4 5% 7% 49%	5272
	21st to end	Night	5% 7% 3 7% 4 4 4 4 5% 7% 49%	5099
April	1st to 10th	Night	7% 6% 2 5% 4 4 4 3 5% 8% 53%	2000
	11th to 20th	Night	4 4 2 5% 4 4 4 3 5% 6% 60%	1979
	21st to end	Night	3 5% 2 5% 4 4 4 4 5% 5% 60%	2000
May	1st to 10th	Night	3 6% 2 6% 4 3 3 3 4 5% 61%	4293
	11th to 20th	Night	1 4 2 6% 5% 4 5% 3 5% 6% 60%	4074
	21st to end	Night	1 4 2 6% 4 4 3 3 5% 5% 63%	4474
June	1st to 10th	Night	1 5% 2 4 4 3 3 3 5% 7% 64%	1795
	11th to 20th	Night	1 2 1 2 2 2 2 3 5% 6% 74%	1710
	21st to end	Night	1 2 1 1 1 1 2 1 3 5% 81%	1547
July	1st to 10th	Night	1 1 1 1 1 2 3 4 87%	2626
	11th to 20th	Night	1 1 1 1 1 2 2 2 4 5% 82%	2860
	21st to end	Night	1 1 1 2 2 2 2 3 4 82%	3318
August	1st to 10th	Night	1 1 1 1 1 1 2 3 5% 82%	3166
	11th to 20th	Night	1 1 1 1 1 1 1 3 7% 84%	3126
	21st to end	Night	1 1 1 1 1 1 1 2 2 89%	3498
September	1st to 10th	Night	2 2 1 2 1 2 3 2 4 5% 75%	1900
	11th to 20th	Night	2 3 1 2 2 2 2 1 2 4 78%	2081
	21st to end	Night	2 3 1 2 2 1 1 1 2 4 80%	2090
October	1st to 10th	Night	2 1 1 2 2 2 2 2 4 4 79%	3490
	11th to 20th	Night	3 4 2 4 2 3 3 2 4 7% 66%	3529
	21st to end	Night	1 2 1 3 2 3 3 3 4 5% 72%	4259
November	1st to 10th	Night	2 4 1 3 3 2 3 2 4 6% 69%	2535
	11th to 20th	Night	3 3 2 4 3 3 3 2 4 6% 66%	2600
	21st to end	Night	5% 5% 2 6% 4 3 4 3 7% 8% 53%	2600
December	1st to 10th	Night	4 3 1 3 3 3 4 3 4 6% 67%	4240
	11th to 20th	Night	7% 6% 2 6% 4 4 5% 4 6% 7% 49%	4811
	21st to end	Night	6% 6% 3 7% 5% 5% 5% 4 7% 11% 43%	6468

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	17% 3 3 19% 32% 27%	4099
	11th to 20th	Day	19% 4 8% 18% 18% 33%	4358
	21st to end	Day	29% 5% 6% 13% 25% 22%	5016
February	1st to 10th	Day	28% 4 4 13% 25% 27%	2000
	11th to 20th	Day	25% 5% 4 17% 27% 21%	1960
	21st to end	Day	33% 4 6% 14% 23% 20%	1650
March	1st to 10th	Day	28% 7% 7% 20% 19% 18%	4518
	11th to 20th	Day	26% 7% 9% 24% 21% 12%	4726
	21st to end	Day	23% 7% 10% 32% 17% 11%	5871
April	1st to 10th	Day	25% 4 9% 24% 24% 14%	2400
	11th to 20th	Day	21% 5% 5% 20% 30% 19%	2372
	21st to end	Day	18% 5% 7% 24% 33% 12%	2400
May	1st to 10th	Day	18% 5% 6% 20% 36% 16%	5694
	11th to 20th	Day	16% 7% 6% 19% 38% 13%	5844
	21st to end	Day	15% 7% 5% 22% 39% 13%	6424
June	1st to 10th	Day	19% 4 7% 21% 32% 17%	2589
	11th to 20th	Day	14% 3 4 12% 31% 36%	2470
	21st to end	Day	12% 2 3 9% 25% 50%	2619
July	1st to 10th	Day	7% 2 2 5% 14% 71%	4244
	11th to 20th	Day	9% 2 4 12% 33% 40%	4041
	21st to end	Day	8% 2 4 21% 27% 38%	4114
August	1st to 10th	Day	8% 2 2 14% 40% 34%	3770
	11th to 20th	Day	5% 2 2 13% 24% 54%	3760
	21st to end	Day	6% 2 2 6% 25% 60%	4179
September	1st to 10th	Day	10% 2 5% 7% 33% 43%	2280
	11th to 20th	Day	9% 2 2 9% 37% 40%	2097
	21st to end	Day	11% 2 2 12% 34% 39%	2090
October	1st to 10th	Day	10% 2 2 11% 17% 58%	3490
	11th to 20th	Day	12% 3 3 12% 32% 39%	3392
	21st to end	Day	13% 4 5% 9% 32% 37%	3303
November	1st to 10th	Day	16% 2 5% 16% 25% 35%	1764
	11th to 20th	Day	17% 3 6% 14% 22% 39%	1800
	21st to end	Day	25% 5% 6% 12% 21% 31%	1800
December	1st to 10th	Day	17% 3 5% 14% 24% 37%	2950
	11th to 20th	Day	28% 5% 8% 13% 24% 21%	3408
	21st to end	Day	33% 6% 8% 22% 21% 10%	4510
January	1st to 10th	Night	18% 3 4 14% 32% 29%	5867
	11th to 20th	Night	21% 5% 7% 18% 16% 32%	5617
	21st to end	Night	32% 6% 7% 11% 19% 23%	5984
February	1st to 10th	Night	27% 4 6% 14% 23% 27%	2400
	11th to 20th	Night	28% 4 6% 15% 22% 24%	2339
	21st to end	Night	32% 6% 3 13% 21% 24%	1980
March	1st to 10th	Night	30% 12% 10% 17% 16% 16%	5376
	11th to 20th	Night	28% 9% 9% 23% 20% 11%	5272
	21st to end	Night	25% 13% 9% 20% 23% 9%	5099
April	1st to 10th	Night	28% 7% 7% 21% 21% 16%	2000
	11th to 20th	Night	23% 7% 6% 20% 24% 20%	1979
	21st to end	Night	22% 9% 7% 22% 26% 14%	2000
May	1st to 10th	Night	22% 12% 7% 17% 29% 13%	4290
	11th to 20th	Night	16% 15% 6% 20% 31% 12%	4075
	21st to end	Night	16% 13% 6% 22% 29% 14%	4474
June	1st to 10th	Night	21% 9% 8% 18% 28% 17%	1795
	11th to 20th	Night	13% 6% 5% 12% 30% 34%	1710
	21st to end	Night	9% 3 5% 7% 30% 45%	1547
July	1st to 10th	Night	4 3 2 6% 14% 71%	2584
	11th to 20th	Night	7% 3 4 9% 29% 48%	2806
	21st to end	Night	9% 3 4 17% 28% 39%	3214
August	1st to 10th	Night	7% 2 3 11% 43% 34%	3156
	11th to 20th	Night	4 3 3 15% 24% 51%	3156
	21st to end	Night	5% 2 2 6% 19% 66%	3498
September	1st to 10th	Night	13% 3 5% 8% 29% 43%	1900
	11th to 20th	Night	12% 4 4 7% 30% 43%	2081
	21st to end	Night	12% 2 2 11% 35% 38%	2090
October	1st to 10th	Night	11% 2 3 10% 15% 58%	3490
	11th to 20th	Night	15% 7% 6% 9% 25% 39%	3529
	21st to end	Night	12% 5% 4 7% 29% 43%	4259
November	1st to 10th	Night	17% 3 4 15% 24% 37%	2535
	11th to 20th	Night	20% 3 4 12% 20% 40%	2600
	21st to end	Night	27% 4 6% 14% 18% 31%	2600
December	1st to 10th	Night	18% 3 4 13% 21% 41%	4240
	11th to 20th	Night	28% 6% 7% 13% 23% 22%	4811
	21st to end	Night	30% 7% 10% 22% 22% 10%	6468

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% 8% 18% 38% 19% 5%	300
	11th to 20th	Day	11% 8% 20% 35% 21% 4	415
	21st to end	Day	9% 12% 27% 30% 19% 3	550
February	1st to 10th	Day	9% 13% 26% 28% 17% 7%	500
	11th to 20th	Day	10% 14% 28% 29% 16% 3	495
	21st to end	Day	8% 17% 29% 29% 14% 3	414
March	1st to 10th	Day	10% 18% 29% 29% 11% 4	500
	11th to 20th	Day	9% 13% 29% 31% 13% 5%	500
	21st to end	Day	8% 14% 34% 29% 11% 4	550
April	1st to 10th	Day	9% 10% 30% 26% 19% 6%	500
	11th to 20th	Day	3 16% 32% 30% 14% 5%	492
	21st to end	Day	4 12% 28% 30% 16% 10%	500
May	1st to 10th	Day	6% 12% 28% 31% 18% 5%	503
	11th to 20th	Day	6% 8% 25% 37% 19% 6%	528
	21st to end	Day	5% 8% 24% 38% 19% 7%	573
June	1st to 10th	Day	2 4 16% 35% 31% 12%	527
	11th to 20th	Day	2 3 19% 34% 29% 13%	490
	21st to end	Day	2 1 13% 37% 32% 14%	490
July	1st to 10th	Day	2 6% 35% 37% 20%	486
	11th to 20th	Day	2 6% 30% 38% 24%	484
	21st to end	Day	1 1 6% 30% 40% 22%	531
August	1st to 10th	Day	2 7% 38% 36% 17%	487
	11th to 20th	Day	2 5% 36% 36% 21%	477
	21st to end	Day	1 6% 31% 41% 20%	539
September	1st to 10th	Day	2 9% 44% 29% 15%	490
	11th to 20th	Day	2 3 13% 40% 31% 10%	490
	21st to end	Day	1 3 18% 35% 29% 15%	490
October	1st to 10th	Day	4 4 16% 38% 29% 10%	490
	11th to 20th	Day	4 4 15% 36% 29% 11%	490
	21st to end	Day	4 4 19% 32% 29% 13%	456
November	1st to 10th	Day	4 6% 17% 31% 29% 14%	300
	11th to 20th	Day	3 6% 15% 37% 27% 11%	300
	21st to end	Day	3 10% 18% 37% 23% 9%	300
December	1st to 10th	Day	10% 3 16% 34% 29% 8%	300
	11th to 20th	Day	5% 4 18% 35% 28% 9%	300
	21st to end	Day	13% 10% 21% 34% 18% 5%	330
January	1st to 10th	Night	9% 4 15% 40% 24% 8%	800
	11th to 20th	Night	7% 4 12% 43% 27% 7%	800
	21st to end	Night	11% 4 14% 40% 25% 5%	880
February	1st to 10th	Night	9% 4 16% 40% 25% 7%	800
	11th to 20th	Night	8% 4 14% 42% 24% 7%	784
	21st to end	Night	11% 5% 16% 41% 23% 4	660
March	1st to 10th	Night	7% 5% 14% 47% 22% 4	800
	11th to 20th	Night	8% 6% 11% 40% 28% 8%	800
	21st to end	Night	5% 6% 13% 43% 28% 5%	880
April	1st to 10th	Night	8% 4 12% 42% 30% 4	800
	11th to 20th	Night	5% 4 15% 40% 32% 5%	791
	21st to end	Night	5% 5% 11% 36% 36% 7%	800
May	1st to 10th	Night	3 4 13% 36% 38% 6%	689
	11th to 20th	Night	1 3 14% 32% 42% 7%	591
	21st to end	Night	4 2 12% 40% 38% 3	650
June	1st to 10th	Night	3 2 10% 37% 41% 8%	599
	11th to 20th	Night	1 7% 38% 49% 4	570
	21st to end	Night	2 1 3 28% 57% 9%	407
July	1st to 10th	Night	1 1 16% 67% 14%	415
	11th to 20th	Night	2 1 15% 68% 14%	552
	21st to end	Night	2 1 2 13% 64% 19%	745
August	1st to 10th	Night	3 1 1 18% 61% 17%	756
	11th to 20th	Night	1 1 12% 64% 21%	752
	21st to end	Night	1 1 14% 63% 21%	836
September	1st to 10th	Night	2 1 3 19% 58% 17%	760
	11th to 20th	Night	3 2 5% 23% 56% 13%	760
	21st to end	Night	3 1 5% 29% 49% 13%	760
October	1st to 10th	Night	4 1 4 38% 44% 7%	760
	11th to 20th	Night	5% 2 7% 34% 41% 11%	760
	21st to end	Night	4 2 10% 32% 38% 14%	836
November	1st to 10th	Night	3 3 6% 39% 37% 11%	780
	11th to 20th	Night	3 3 7% 42% 35% 11%	800
	21st to end	Night	6% 4 12% 41% 31% 7%	800
December	1st to 10th	Night	9% 2 11% 42% 29% 7%	800
	11th to 20th	Night	11% 3 13% 42% 26% 5%	800
	21st to end	Night	9% 7% 14% 39% 24% 7%	880

Page generated at 2025-06-07 07:28:16. Version ac07

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