Ranchito de las Estrellas Observator
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ranchito de las Estrellas Observator clear sky chart from 2005-11-06 to 2025-02-06.

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	11% 5% 2 5% 4 3 4 3 5% 7% 51%	109043
	Night	12% 5% 2 4 3 3 3 3 4 6% 55%	109460
Transparency	Day	31% 6% 10% 21% 22% 10%	112851
	Night	29% 5% 10% 21% 22% 13%	113779
Seeing	Day	12% 6% 22% 30% 23% 7%	15239
	Night	13% 6% 27% 37% 16% 1	25289

By Month

Percentage Cloud Cover SE (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	13% 7% 3 5% 3 3 3 3 4 5% 52%	4077
	11th to 20th	Day	12% 5% 1 3 2 2 3 2 5% 5% 59%	4080
	21st to end	Day	22% 7% 2 6% 2 2 2 2 3 4 47%	4691
February	1st to 10th	Day	16% 7% 2 6% 3 2 3 2 3 5% 52%	1950
	11th to 20th	Day	15% 8% 2 5% 3 3 4 3 4 5% 49%	1849
	21st to end	Day	18% 6% 1 4 3 3 2 2 4 5% 52%	1570
March	1st to 10th	Day	15% 7% 2 6% 4 4 3 2 5% 5% 46%	3393
	11th to 20th	Day	20% 6% 2 6% 4 4 4 4 5% 7% 37%	3480
	21st to end	Day	11% 7% 2 6% 5% 4 4 4 6% 7% 46%	3814
April	1st to 10th	Day	13% 7% 2 4 4 4 3 4 5% 6% 47%	2090
	11th to 20th	Day	15% 7% 2 6% 3 3 4 3 5% 6% 46%	2089
	21st to end	Day	13% 5% 2 5% 4 3 4 3 5% 5% 51%	2456
May	1st to 10th	Day	20% 7% 3 6% 4 4 4 4 6% 7% 37%	4082
	11th to 20th	Day	15% 5% 2 6% 4 3 4 3 4 6% 47%	4082
	21st to end	Day	13% 6% 2 6% 4 5% 6% 5% 8% 8% 37%	4477
June	1st to 10th	Day	5% 3 1 4 4 5% 4 4 6% 8% 54%	2470
	11th to 20th	Day	5% 3 1 4 4 4 4 4 7% 8% 54%	2470
	21st to end	Day	7% 4 1 4 5% 4 5% 5% 8% 8% 49%	2470
July	1st to 10th	Day	5% 3 2 5% 5% 5% 5% 4 7% 8% 52%	4120
	11th to 20th	Day	3 2 1 3 3 3 4 3 6% 9% 61%	4120
	21st to end	Day	6% 5% 2 6% 5% 5% 5% 5% 7% 11% 43%	4465
August	1st to 10th	Day	1 1 2 3 3 3 3 4 7% 72%	4104
	11th to 20th	Day	4 2 1 4 2 3 3 3 5% 9% 64%	3819
	21st to end	Day	4 3 1 4 3 4 5% 5% 7% 10% 55%	4025
September	1st to 10th	Day	10% 5% 2 4 5% 4 5% 4 5% 5% 50%	2090
	11th to 20th	Day	10% 6% 2 6% 4 4 4 3 5% 7% 49%	2090
	21st to end	Day	8% 3 1 5% 3 4 5% 3 5% 6% 57%	2090
October	1st to 10th	Day	6% 3 2 4 3 3 3 3 6% 6% 61%	2090
	11th to 20th	Day	11% 4 2 4 3 3 3 2 4 5% 60%	1943
	21st to end	Day	12% 4 1 4 2 2 3 2 3 5% 62%	2090
November	1st to 10th	Day	14% 6% 2 4 3 3 3 3 3 5% 52%	1958
	11th to 20th	Day	8% 5% 1 5% 3 3 3 4 4 7% 58%	1830
	21st to end	Day	15% 6% 2 5% 3 3 3 2 4 5% 52%	1800
December	1st to 10th	Day	17% 6% 2 6% 4 3 4 3 4 5% 47%	2940
	11th to 20th	Day	14% 7% 2 7% 4 3 4 3 5% 5% 46%	3391
	21st to end	Day	13% 5% 2 4 2 2 2 2 3 5% 59%	4488
January	1st to 10th	Night	16% 5% 2 4 2 3 2 2 3 4 58%	5888
	11th to 20th	Night	10% 4 1 2 2 2 2 1 3 5% 69%	5900
	21st to end	Night	25% 7% 3 5% 3 3 3 2 3 4 43%	6329
February	1st to 10th	Night	13% 8% 2 5% 3 3 3 2 3 5% 53%	2340
	11th to 20th	Night	17% 5% 2 5% 3 2 2 2 4 6% 53%	2218
	21st to end	Night	18% 5% 1 4 3 2 2 2 5% 6% 52%	1884
March	1st to 10th	Night	13% 6% 1 5% 4 4 4 3 5% 6% 49%	3463
	11th to 20th	Night	18% 6% 2 6% 4 4 4 4 6% 7% 40%	3480
	21st to end	Night	11% 6% 2 6% 4 4 4 3 5% 6% 49%	3817
April	1st to 10th	Night	9% 5% 2 5% 4 3 4 3 5% 6% 53%	2090
	11th to 20th	Night	14% 5% 2 6% 4 3 3 3 5% 5% 49%	2036
	21st to end	Night	13% 6% 2 3 4 3 3 3 4 7% 52%	1722
May	1st to 10th	Night	24% 7% 2 4 3 3 3 3 4 6% 43%	2823
	11th to 20th	Night	11% 6% 2 5% 3 3 4 3 5% 7% 50%	2823
	21st to end	Night	13% 5% 1 5% 4 3 5% 4 6% 8% 46%	3090
June	1st to 10th	Night	3 3 1 3 3 3 3 3 7% 10% 61%	1710
	11th to 20th	Night	4 3 1 3 2 3 3 3 6% 9% 62%	1710
	21st to end	Night	6% 3 1 4 3 3 4 4 6% 9% 57%	1710
July	1st to 10th	Night	4 2 1 4 3 3 3 3 6% 9% 63%	2850
	11th to 20th	Night	2 2 1 2 2 3 3 3 6% 10% 66%	2850
	21st to end	Night	4 6% 2 5% 4 3 4 4 6% 10% 51%	3098
August	1st to 10th	Night	1 1 1 1 1 2 2 4 6% 79%	2836
	11th to 20th	Night	4 2 1 3 2 2 3 3 6% 10% 64%	3014
	21st to end	Night	3 2 1 3 3 3 4 3 7% 11% 60%	3634
September	1st to 10th	Night	9% 4 1 4 3 4 4 4 6% 7% 54%	2090
	11th to 20th	Night	10% 6% 2 6% 4 3 3 3 5% 9% 49%	2090
	21st to end	Night	8% 2 1 4 3 3 4 3 5% 7% 61%	2090
October	1st to 10th	Night	6% 3 1 3 2 2 3 3 5% 5% 68%	2090
	11th to 20th	Night	11% 3 1 3 3 3 3 3 4 5% 61%	2216
	21st to end	Night	13% 4 1 4 2 2 2 1 3 4 62%	2508
November	1st to 10th	Night	12% 5% 2 5% 2 3 3 2 3 5% 58%	2340
	11th to 20th	Night	7% 5% 2 5% 3 4 3 3 3 6% 61%	2565
	21st to end	Night	16% 5% 2 4 3 3 3 2 4 6% 51%	2600
December	1st to 10th	Night	18% 5% 2 5% 3 3 3 2 5% 6% 48%	4250
	11th to 20th	Night	17% 9% 2 5% 3 2 3 2 3 5% 48%	4816
	21st to end	Night	15% 6% 1 4 2 2 2 2 3 4 59%	6490

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	36% 4 4 24% 22% 10%	4078
	11th to 20th	Day	28% 2 5% 19% 27% 18%	4080
	21st to end	Day	44% 3 4 11% 23% 15%	4691
February	1st to 10th	Day	38% 3 7% 14% 22% 17%	1950
	11th to 20th	Day	38% 4 6% 18% 20% 14%	1859
	21st to end	Day	36% 3 5% 15% 23% 17%	1570
March	1st to 10th	Day	40% 5% 6% 13% 22% 13%	3393
	11th to 20th	Day	45% 8% 12% 10% 16% 8%	3480
	21st to end	Day	35% 8% 11% 15% 23% 9%	3814
April	1st to 10th	Day	39% 5% 8% 17% 17% 15%	2090
	11th to 20th	Day	39% 6% 9% 16% 19% 11%	2089
	21st to end	Day	35% 5% 8% 20% 23% 9%	2456
May	1st to 10th	Day	45% 7% 12% 16% 15% 5%	4120
	11th to 20th	Day	38% 6% 8% 17% 26% 4	4086
	21st to end	Day	38% 11% 14% 21% 11% 4	4489
June	1st to 10th	Day	25% 8% 13% 29% 21% 4	2470
	11th to 20th	Day	25% 7% 14% 28% 19% 7%	2470
	21st to end	Day	29% 8% 14% 22% 22% 5%	2470
July	1st to 10th	Day	28% 7% 18% 36% 10% 1	4056
	11th to 20th	Day	19% 6% 15% 37% 19% 5%	4051
	21st to end	Day	31% 8% 15% 31% 14% 1	4325
August	1st to 10th	Day	12% 4 12% 33% 38% 1	4090
	11th to 20th	Day	18% 6% 18% 39% 18% 3	3858
	21st to end	Day	22% 10% 19% 27% 20% 3	4024
September	1st to 10th	Day	33% 7% 11% 20% 18% 11%	2090
	11th to 20th	Day	35% 7% 11% 20% 21% 6%	2090
	21st to end	Day	27% 7% 9% 21% 22% 15%	2090
October	1st to 10th	Day	14% 3 6% 13% 26% 37%	3480
	11th to 20th	Day	18% 3 7% 17% 33% 22%	3209
	21st to end	Day	22% 3 3 19% 39% 13%	3428
November	1st to 10th	Day	35% 4 8% 18% 23% 11%	1958
	11th to 20th	Day	28% 5% 9% 17% 24% 18%	1830
	21st to end	Day	37% 3 6% 18% 21% 14%	1800
December	1st to 10th	Day	41% 4 6% 17% 22% 10%	2940
	11th to 20th	Day	41% 5% 6% 11% 24% 13%	3389
	21st to end	Day	31% 2 4 17% 29% 16%	4488
January	1st to 10th	Night	33% 2 5% 22% 27% 12%	5888
	11th to 20th	Night	22% 2 4 18% 32% 23%	5900
	21st to end	Night	46% 3 3 11% 20% 17%	6329
February	1st to 10th	Night	36% 4 6% 13% 22% 19%	2340
	11th to 20th	Night	35% 3 7% 17% 22% 15%	2218
	21st to end	Night	35% 4 6% 15% 20% 20%	1884
March	1st to 10th	Night	34% 7% 9% 13% 24% 12%	3463
	11th to 20th	Night	41% 8% 11% 15% 16% 9%	3480
	21st to end	Night	35% 7% 10% 18% 22% 8%	3817
April	1st to 10th	Night	31% 6% 10% 19% 18% 16%	2090
	11th to 20th	Night	36% 5% 11% 14% 19% 15%	2036
	21st to end	Night	33% 5% 10% 20% 23% 9%	1722
May	1st to 10th	Night	42% 7% 11% 19% 15% 7%	2850
	11th to 20th	Night	31% 8% 13% 21% 20% 7%	2824
	21st to end	Night	33% 9% 14% 29% 10% 5%	3099
June	1st to 10th	Night	17% 8% 17% 32% 22% 4	1710
	11th to 20th	Night	19% 6% 16% 32% 21% 7%	1710
	21st to end	Night	23% 8% 12% 29% 23% 5%	1710
July	1st to 10th	Night	19% 7% 21% 43% 9% 1	2805
	11th to 20th	Night	14% 5% 18% 41% 19% 2	2796
	21st to end	Night	28% 6% 20% 34% 11% 1	2999
August	1st to 10th	Night	7% 4 13% 38% 36% 2	2826
	11th to 20th	Night	17% 5% 23% 36% 17% 3	3041
	21st to end	Night	19% 10% 21% 30% 17% 3	3634
September	1st to 10th	Night	28% 7% 13% 23% 18% 11%	2090
	11th to 20th	Night	33% 7% 14% 22% 19% 7%	2090
	21st to end	Night	23% 5% 12% 24% 21% 15%	2090
October	1st to 10th	Night	11% 3 7% 15% 22% 42%	3480
	11th to 20th	Night	17% 3 9% 17% 31% 23%	3676
	21st to end	Night	22% 3 4 20% 35% 16%	4120
November	1st to 10th	Night	30% 4 8% 20% 24% 14%	2340
	11th to 20th	Night	26% 5% 8% 19% 24% 18%	2565
	21st to end	Night	35% 4 8% 16% 22% 15%	2600
December	1st to 10th	Night	39% 4 6% 19% 22% 11%	4250
	11th to 20th	Night	40% 3 6% 10% 25% 16%	4817
	21st to end	Night	32% 2 4 17% 26% 19%	6490

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	19% 14% 36% 26% 5% 1	300
	11th to 20th	Day	21% 11% 35% 24% 8% 2	300
	21st to end	Day	19% 12% 37% 23% 8%	330
February	1st to 10th	Day	22% 15% 36% 20% 6%	285
	11th to 20th	Day	23% 15% 39% 20% 3	270
	21st to end	Day	24% 18% 37% 20% 2	225
March	1st to 10th	Day	20% 16% 34% 26% 4	270
	11th to 20th	Day	18% 17% 37% 20% 7%	270
	21st to end	Day	15% 15% 42% 22% 7%	297
April	1st to 10th	Day	17% 17% 43% 17% 5% 1	270
	11th to 20th	Day	19% 10% 42% 21% 7% 1	287
	21st to end	Day	17% 14% 39% 23% 7% 1	636
May	1st to 10th	Day	14% 9% 37% 31% 9%	653
	11th to 20th	Day	17% 7% 27% 34% 13% 3	675
	21st to end	Day	15% 6% 24% 35% 15% 4	734
June	1st to 10th	Day	6% 1 15% 43% 29% 6%	680
	11th to 20th	Day	6% 2 15% 48% 24% 5%	680
	21st to end	Day	6% 1 11% 36% 34% 11%	680
July	1st to 10th	Day	7% 1 7% 35% 36% 14%	671
	11th to 20th	Day	2 5% 33% 47% 13%	668
	21st to end	Day	4 1 3 32% 44% 14%	739
August	1st to 10th	Day	2 4 31% 45% 17%	676
	11th to 20th	Day	6% 1 3 32% 41% 16%	534
	21st to end	Day	5% 6% 24% 39% 26%	449
September	1st to 10th	Day	11% 1 4 19% 41% 24%	300
	11th to 20th	Day	6% 1 4 22% 44% 23%	300
	21st to end	Day	12% 2 4 30% 35% 16%	300
October	1st to 10th	Day	5% 1 11% 34% 38% 11%	300
	11th to 20th	Day	11% 4 24% 33% 24% 4	300
	21st to end	Day	20% 8% 22% 23% 22% 4	330
November	1st to 10th	Day	19% 8% 28% 28% 13% 4	300
	11th to 20th	Day	13% 12% 23% 31% 16% 4	300
	21st to end	Day	20% 12% 33% 20% 12% 2	300
December	1st to 10th	Day	18% 7% 32% 26% 13% 4	300
	11th to 20th	Day	18% 11% 38% 21% 10% 1	300
	21st to end	Day	18% 10% 37% 24% 10% 2	330
January	1st to 10th	Night	18% 8% 36% 30% 7% 1	1000
	11th to 20th	Night	17% 11% 33% 33% 6% 1	1000
	21st to end	Night	19% 9% 35% 30% 6%	1030
February	1st to 10th	Night	19% 11% 34% 31% 5%	780
	11th to 20th	Night	21% 10% 40% 25% 3	744
	21st to end	Night	22% 10% 44% 21% 3	628
March	1st to 10th	Night	17% 12% 38% 29% 3	603
	11th to 20th	Night	16% 11% 38% 29% 5%	570
	21st to end	Night	11% 11% 46% 29% 4	627
April	1st to 10th	Night	11% 10% 48% 28% 4	570
	11th to 20th	Night	15% 10% 43% 28% 4	563
	21st to end	Night	15% 7% 43% 26% 8%	570
May	1st to 10th	Night	15% 8% 43% 29% 5%	570
	11th to 20th	Night	12% 5% 34% 37% 12% 1	561
	21st to end	Night	10% 5% 32% 38% 15%	617
June	1st to 10th	Night	3 2 21% 50% 22% 3	570
	11th to 20th	Night	5% 1 26% 52% 16%	570
	21st to end	Night	5% 1 16% 48% 28% 2	570
July	1st to 10th	Night	5% 10% 52% 29% 4	555
	11th to 20th	Night	4 1 7% 52% 34% 2	552
	21st to end	Night	3 6% 50% 37% 4	624
August	1st to 10th	Night	1 4 52% 39% 3	567
	11th to 20th	Night	7% 1 4 46% 38% 4	564
	21st to end	Night	4 3 43% 42% 7%	627
September	1st to 10th	Night	10% 2 9% 40% 34% 6%	570
	11th to 20th	Night	12% 1 4 41% 38% 4	570
	21st to end	Night	9% 1 10% 40% 36% 3	570
October	1st to 10th	Night	7% 14% 47% 29% 3	570
	11th to 20th	Night	12% 3 25% 41% 18% 1	696
	21st to end	Night	14% 8% 28% 34% 16% 1	836
November	1st to 10th	Night	14% 4 24% 43% 14% 1	780
	11th to 20th	Night	10% 7% 29% 38% 15% 1	965
	21st to end	Night	17% 9% 31% 32% 11%	1000
December	1st to 10th	Night	14% 9% 29% 37% 10% 1	1000
	11th to 20th	Night	20% 9% 30% 34% 7%	1000
	21st to end	Night	17% 8% 33% 34% 8%	1100

Page generated at 2025-02-03 02:05:51. Version ac07

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