El Dorado
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the El Dorado clear sky chart from 2005-11-06 to 2026-04-17.

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	13% 6% 2 6% 4 4 4 3 5% 7% 45%	131327
	Night	13% 6% 2 5% 4 4 4 3 5% 6% 48%	130897
Transparency	Day	38% 5% 10% 22% 20% 6%	134934
	Night	35% 4 10% 20% 22% 9%	135368
Seeing	Day	15% 8% 23% 26% 20% 7%	17060
	Night	15% 7% 24% 32% 19% 3	26958

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	17% 10% 3 6% 3 3 3 2 4 5% 45%	5289
	11th to 20th	Day	14% 5% 1 3 2 2 2 2 4 6% 58%	5310
	21st to end	Day	24% 8% 3 5% 2 2 2 2 2 4 45%	5812
February	1st to 10th	Day	21% 8% 2 6% 4 3 3 3 4 4 41%	1890
	11th to 20th	Day	20% 9% 3 6% 4 3 3 3 5% 4 40%	2012
	21st to end	Day	22% 8% 3 7% 3 4 4 3 4 4 39%	1840
March	1st to 10th	Day	21% 10% 2 7% 4 4 3 3 4 5% 37%	5046
	11th to 20th	Day	12% 5% 2 6% 4 4 3 3 5% 7% 50%	5090
	21st to end	Day	14% 8% 3 8% 4 4 4 3 4 5% 43%	5583
April	1st to 10th	Day	13% 7% 2 6% 5% 4 5% 4 6% 6% 43%	2492
	11th to 20th	Day	15% 7% 2 6% 4 4 4 4 5% 6% 42%	2446
	21st to end	Day	11% 6% 2 8% 5% 4 4 4 6% 7% 44%	2400
May	1st to 10th	Day	18% 8% 3 7% 5% 4 5% 4 5% 6% 37%	5405
	11th to 20th	Day	12% 6% 3 8% 5% 6% 5% 4 7% 7% 37%	5647
	21st to end	Day	11% 6% 2 7% 5% 5% 6% 4 6% 9% 38%	6434
June	1st to 10th	Day	7% 4 3 6% 6% 5% 6% 5% 8% 9% 41%	2600
	11th to 20th	Day	6% 5% 2 6% 6% 5% 6% 5% 7% 10% 44%	2600
	21st to end	Day	5% 4 2 4 5% 6% 6% 5% 9% 10% 46%	2600
July	1st to 10th	Day	8% 6% 2 8% 6% 6% 7% 6% 9% 11% 31%	5900
	11th to 20th	Day	8% 4 2 6% 4 4 5% 4 7% 10% 47%	5900
	21st to end	Day	11% 6% 2 6% 5% 5% 5% 4 7% 9% 40%	6422
August	1st to 10th	Day	2 2 1 3 3 4 4 3 6% 7% 65%	4185
	11th to 20th	Day	5% 3 2 6% 5% 5% 6% 4 6% 9% 50%	3849
	21st to end	Day	8% 4 2 5% 5% 5% 5% 5% 6% 8% 47%	4312
September	1st to 10th	Day	9% 5% 2 5% 5% 5% 5% 5% 6% 7% 47%	2400
	11th to 20th	Day	12% 6% 2 5% 4 4 4 4 6% 8% 43%	2380
	21st to end	Day	9% 4 2 5% 4 4 4 4 5% 7% 54%	2093
October	1st to 10th	Day	7% 4 2 4 4 3 4 2 5% 6% 59%	2000
	11th to 20th	Day	12% 5% 1 3 3 3 2 2 3 6% 59%	2000
	21st to end	Day	17% 5% 2 4 3 3 3 2 4 4 53%	2200
November	1st to 10th	Day	14% 5% 2 5% 4 4 3 3 4 5% 53%	2058
	11th to 20th	Day	11% 5% 2 6% 4 4 3 2 4 6% 53%	2100
	21st to end	Day	17% 7% 3 6% 4 4 3 3 4 5% 44%	2100
December	1st to 10th	Day	19% 8% 2 5% 3 3 3 2 4 4 46%	2864
	11th to 20th	Day	21% 8% 3 6% 3 3 3 2 4 5% 42%	3481
	21st to end	Day	16% 9% 2 6% 3 3 3 2 4 6% 45%	4587
January	1st to 10th	Night	17% 7% 2 5% 3 3 3 2 3 5% 49%	7634
	11th to 20th	Night	12% 5% 2 4 3 3 3 2 4 5% 59%	7680
	21st to end	Night	26% 8% 3 6% 3 3 3 2 3 4 38%	8402
February	1st to 10th	Night	17% 7% 2 6% 4 3 3 3 4 5% 46%	2730
	11th to 20th	Night	21% 7% 3 6% 3 3 3 3 4 5% 42%	2491
	21st to end	Night	21% 8% 2 5% 3 3 2 2 4 5% 46%	1982
March	1st to 10th	Night	18% 7% 2 7% 4 4 3 3 4 5% 43%	5029
	11th to 20th	Night	13% 6% 1 4 4 4 3 3 5% 7% 49%	5090
	21st to end	Night	15% 7% 3 7% 4 4 3 3 5% 6% 43%	5588
April	1st to 10th	Night	12% 5% 2 5% 4 4 4 4 5% 6% 48%	2126
	11th to 20th	Night	12% 6% 2 6% 5% 3 4 3 4 6% 49%	2035
	21st to end	Night	10% 6% 2 5% 5% 4 4 3 4 7% 50%	2000
May	1st to 10th	Night	17% 7% 2 7% 4 4 4 4 6% 7% 38%	4490
	11th to 20th	Night	17% 8% 3 7% 4 4 5% 4 5% 8% 36%	4242
	21st to end	Night	12% 7% 2 6% 5% 4 5% 4 6% 8% 42%	4443
June	1st to 10th	Night	5% 4 1 4 4 4 4 4 7% 12% 49%	1800
	11th to 20th	Night	5% 3 2 4 4 3 4 4 6% 10% 56%	1800
	21st to end	Night	5% 3 1 4 4 4 4 4 6% 9% 56%	1800
July	1st to 10th	Night	6% 5% 3 7% 5% 6% 6% 5% 8% 11% 38%	4078
	11th to 20th	Night	6% 3 1 5% 3 4 4 4 7% 12% 50%	4077
	21st to end	Night	10% 6% 2 6% 4 4 4 4 7% 9% 44%	4449
August	1st to 10th	Night	2 1 1 2 2 2 3 3 4 9% 72%	2957
	11th to 20th	Night	4 2 1 4 4 4 5% 5% 7% 11% 52%	3200
	21st to end	Night	5% 4 2 5% 4 4 5% 4 7% 9% 51%	3586
September	1st to 10th	Night	7% 4 2 6% 3 5% 5% 3 5% 8% 52%	2000
	11th to 20th	Night	9% 5% 2 6% 3 4 4 4 5% 7% 50%	2015
	21st to end	Night	8% 3 1 4 3 3 4 3 5% 6% 59%	2285
October	1st to 10th	Night	7% 3 1 4 3 3 3 3 4 6% 63%	2400
	11th to 20th	Night	10% 5% 2 3 3 3 3 3 3 5% 61%	2400
	21st to end	Night	13% 5% 1 4 3 3 3 2 4 4 56%	2640
November	1st to 10th	Night	12% 4 2 5% 4 4 3 3 4 5% 54%	2460
	11th to 20th	Night	10% 6% 2 5% 3 3 4 3 4 5% 55%	2520
	21st to end	Night	14% 6% 2 6% 4 3 3 3 3 5% 51%	2520
December	1st to 10th	Night	19% 7% 2 4 3 3 3 2 4 5% 48%	4369
	11th to 20th	Night	16% 7% 3 6% 4 4 4 3 4 4 44%	4946
	21st to end	Night	16% 9% 3 6% 4 3 3 2 4 4 46%	6633

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	44% 2 7% 28% 17% 2	5290
	11th to 20th	Day	29% 1 7% 26% 30% 6%	5310
	21st to end	Day	47% 2 4 12% 25% 11%	5812
February	1st to 10th	Day	47% 3 6% 18% 18% 8%	1890
	11th to 20th	Day	48% 3 6% 19% 17% 6%	2022
	21st to end	Day	49% 4 6% 11% 21% 10%	1840
March	1st to 10th	Day	51% 3 6% 14% 17% 9%	5046
	11th to 20th	Day	35% 4 6% 17% 23% 15%	5090
	21st to end	Day	44% 3 8% 21% 20% 4	5585
April	1st to 10th	Day	41% 5% 8% 21% 17% 7%	2492
	11th to 20th	Day	42% 5% 9% 17% 21% 6%	2446
	21st to end	Day	39% 5% 10% 21% 22% 3	2400
May	1st to 10th	Day	47% 6% 9% 25% 11% 2	5440
	11th to 20th	Day	43% 6% 12% 19% 18% 2	5651
	21st to end	Day	40% 8% 13% 24% 13% 2	6447
June	1st to 10th	Day	36% 9% 13% 24% 17% 1	2600
	11th to 20th	Day	34% 6% 15% 26% 17% 2	2600
	21st to end	Day	31% 7% 15% 26% 19% 3	2600
July	1st to 10th	Day	41% 10% 19% 22% 8%	5836
	11th to 20th	Day	30% 7% 20% 31% 11% 1	5831
	21st to end	Day	39% 7% 15% 28% 11%	6240
August	1st to 10th	Day	18% 5% 15% 29% 28% 5%	4171
	11th to 20th	Day	29% 7% 19% 33% 11% 1	3885
	21st to end	Day	34% 7% 12% 24% 21% 2	4311
September	1st to 10th	Day	36% 7% 12% 19% 19% 8%	2400
	11th to 20th	Day	37% 7% 12% 19% 20% 6%	2380
	21st to end	Day	30% 5% 10% 21% 25% 9%	2093
October	1st to 10th	Day	16% 3 6% 13% 23% 39%	3260
	11th to 20th	Day	18% 2 3 16% 33% 27%	3240
	21st to end	Day	30% 3 4 17% 34% 12%	3538
November	1st to 10th	Day	35% 4 7% 19% 26% 9%	2058
	11th to 20th	Day	34% 3 5% 19% 27% 12%	2100
	21st to end	Day	43% 3 6% 17% 24% 7%	2100
December	1st to 10th	Day	44% 3 5% 21% 23% 5%	2864
	11th to 20th	Day	47% 3 4 19% 19% 8%	3479
	21st to end	Day	41% 3 7% 20% 26% 4	4587
January	1st to 10th	Night	39% 2 8% 25% 22% 3	7635
	11th to 20th	Night	31% 2 6% 18% 33% 11%	7680
	21st to end	Night	52% 2 5% 13% 19% 8%	8402
February	1st to 10th	Night	41% 4 6% 18% 22% 8%	2730
	11th to 20th	Night	46% 3 6% 18% 19% 7%	2492
	21st to end	Night	43% 3 7% 15% 19% 13%	1982
March	1st to 10th	Night	44% 3 7% 13% 20% 13%	5029
	11th to 20th	Night	34% 4 8% 17% 19% 18%	5090
	21st to end	Night	42% 4 7% 20% 22% 5%	5588
April	1st to 10th	Night	35% 5% 10% 21% 19% 10%	2126
	11th to 20th	Night	37% 4 9% 17% 23% 10%	2035
	21st to end	Night	34% 5% 8% 25% 23% 5%	2000
May	1st to 10th	Night	44% 7% 11% 21% 14% 3	4520
	11th to 20th	Night	45% 7% 12% 21% 14% 1	4243
	21st to end	Night	38% 8% 14% 21% 13% 5%	4452
June	1st to 10th	Night	26% 10% 17% 26% 20% 2	1800
	11th to 20th	Night	24% 6% 16% 29% 22% 4	1800
	21st to end	Night	24% 7% 16% 27% 23% 4	1800
July	1st to 10th	Night	37% 10% 20% 25% 8% 1	4035
	11th to 20th	Night	25% 8% 23% 31% 11% 1	4026
	21st to end	Night	36% 6% 17% 27% 13% 1	4320
August	1st to 10th	Night	11% 4 15% 33% 32% 5%	2947
	11th to 20th	Night	24% 6% 19% 32% 16% 3	3230
	21st to end	Night	29% 7% 13% 22% 26% 3	3586
September	1st to 10th	Night	29% 7% 15% 20% 19% 10%	2000
	11th to 20th	Night	32% 6% 12% 20% 23% 7%	2015
	21st to end	Night	25% 5% 10% 22% 25% 13%	2285
October	1st to 10th	Night	16% 3 6% 16% 21% 39%	3920
	11th to 20th	Night	17% 2 4 14% 33% 30%	3899
	21st to end	Night	24% 3 6% 15% 36% 16%	4252
November	1st to 10th	Night	32% 3 8% 18% 26% 12%	2460
	11th to 20th	Night	30% 4 7% 18% 28% 13%	2520
	21st to end	Night	38% 3 6% 19% 25% 9%	2520
December	1st to 10th	Night	41% 3 6% 23% 23% 4	4369
	11th to 20th	Night	44% 3 8% 15% 21% 8%	4947
	21st to end	Night	42% 3 6% 20% 26% 3	6633

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	26% 14% 41% 14% 3 1	330
	11th to 20th	Day	25% 19% 40% 12% 4 1	330
	21st to end	Day	27% 23% 32% 16% 3	363
February	1st to 10th	Day	26% 19% 38% 13% 5%	330
	11th to 20th	Day	35% 23% 32% 8% 2	330
	21st to end	Day	33% 23% 30% 9% 5%	273
March	1st to 10th	Day	25% 18% 34% 19% 3	330
	11th to 20th	Day	23% 23% 39% 14% 1	330
	21st to end	Day	21% 18% 43% 16% 2	363
April	1st to 10th	Day	22% 17% 35% 20% 5% 1	512
	11th to 20th	Day	23% 14% 33% 20% 8% 2	516
	21st to end	Day	16% 13% 34% 25% 10% 3	500
May	1st to 10th	Day	18% 10% 33% 27% 10% 2	503
	11th to 20th	Day	16% 5% 29% 30% 16% 3	627
	21st to end	Day	10% 4 25% 37% 18% 6%	789
June	1st to 10th	Day	11% 2 15% 35% 28% 9%	730
	11th to 20th	Day	6% 3 17% 37% 30% 8%	730
	21st to end	Day	7% 2 13% 33% 32% 13%	730
July	1st to 10th	Day	10% 2 9% 31% 35% 13%	721
	11th to 20th	Day	8% 2 7% 30% 39% 15%	718
	21st to end	Day	7% 2 6% 30% 39% 16%	794
August	1st to 10th	Day	5% 1 8% 31% 39% 16%	703
	11th to 20th	Day	8% 1 5% 28% 43% 14%	519
	21st to end	Day	13% 2 5% 24% 35% 21%	583
September	1st to 10th	Day	10% 2 9% 30% 35% 14%	530
	11th to 20th	Day	13% 2 8% 25% 37% 15%	510
	21st to end	Day	11% 4 15% 37% 25% 8%	330
October	1st to 10th	Day	7% 1 28% 35% 25% 4	330
	11th to 20th	Day	12% 5% 33% 32% 15% 3	330
	21st to end	Day	25% 7% 31% 22% 13% 2	363
November	1st to 10th	Day	20% 10% 29% 25% 14% 2	330
	11th to 20th	Day	12% 10% 41% 30% 6% 1	330
	21st to end	Day	21% 15% 35% 18% 8% 2	330
December	1st to 10th	Day	24% 12% 41% 18% 3 2	330
	11th to 20th	Day	25% 15% 33% 18% 9%	330
	21st to end	Day	25% 18% 36% 15% 4 1	363
January	1st to 10th	Night	23% 13% 31% 28% 6%	1050
	11th to 20th	Night	22% 14% 33% 25% 6%	1050
	21st to end	Night	23% 13% 34% 27% 3	1155
February	1st to 10th	Night	22% 13% 34% 26% 5%	1050
	11th to 20th	Night	25% 13% 36% 22% 3	856
	21st to end	Night	27% 16% 32% 23% 3	598
March	1st to 10th	Night	21% 10% 35% 29% 6%	630
	11th to 20th	Night	22% 10% 35% 28% 5%	630
	21st to end	Night	17% 10% 37% 29% 6%	693
April	1st to 10th	Night	15% 12% 37% 28% 8%	630
	11th to 20th	Night	18% 9% 34% 28% 11%	611
	21st to end	Night	14% 9% 35% 31% 11% 1	600
May	1st to 10th	Night	11% 6% 32% 38% 13% 1	600
	11th to 20th	Night	14% 6% 28% 35% 16% 2	591
	21st to end	Night	9% 3 22% 38% 24% 4	650
June	1st to 10th	Night	8% 1 12% 43% 33% 4	600
	11th to 20th	Night	6% 1 11% 40% 40% 3	600
	21st to end	Night	5% 1 11% 37% 37% 8%	600
July	1st to 10th	Night	5% 2 7% 35% 41% 10%	585
	11th to 20th	Night	6% 2 4 34% 43% 11%	582
	21st to end	Night	5% 1 6% 37% 38% 12%	657
August	1st to 10th	Night	3 1 6% 36% 43% 13%	597
	11th to 20th	Night	7% 1 4 34% 44% 9%	594
	21st to end	Night	9% 2 7% 29% 43% 10%	660
September	1st to 10th	Night	8% 2 7% 39% 38% 6%	600
	11th to 20th	Night	11% 2 8% 31% 39% 9%	600
	21st to end	Night	9% 2 11% 36% 38% 5%	685
October	1st to 10th	Night	9% 1 13% 40% 32% 5%	800
	11th to 20th	Night	13% 5% 19% 38% 25% 1	800
	21st to end	Night	16% 5% 27% 32% 17% 3	880
November	1st to 10th	Night	14% 5% 26% 33% 20% 2	820
	11th to 20th	Night	13% 8% 28% 34% 16% 1	840
	21st to end	Night	17% 9% 30% 33% 11% 1	840
December	1st to 10th	Night	22% 8% 30% 31% 8%	1019
	11th to 20th	Night	22% 10% 30% 30% 7%	1050
	21st to end	Night	23% 12% 30% 28% 7%	1155

Page generated at 2026-04-14 01:44:27. Version ac07

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