Eagle's Nest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eagle's Nest clear sky chart from 2005-11-06 to 2026-05-17.

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	15% 11% 4 10% 5% 5% 5% 4 5% 7% 29%	131611
	Night	15% 12% 5% 10% 5% 4 4 3 5% 6% 30%	131197
Transparency	Day	52% 6% 11% 19% 10% 1	135256
	Night	53% 6% 11% 18% 11% 1	135622
Seeing	Day	21% 15% 28% 20% 11% 4	16544
	Night	20% 11% 28% 27% 12% 1	26491

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	15% 20% 7% 22% 7% 4 4 2 4 4 11%	5258
	11th to 20th	Day	10% 20% 8% 19% 9% 6% 6% 2 3 4 13%	5280
	21st to end	Day	18% 17% 7% 13% 10% 7% 5% 3 4 4 13%	5780
February	1st to 10th	Day	16% 17% 5% 13% 7% 5% 4 3 5% 5% 21%	1890
	11th to 20th	Day	15% 14% 6% 15% 7% 5% 5% 4 5% 4 21%	1901
	21st to end	Day	17% 14% 4 12% 7% 4 5% 3 6% 5% 24%	1730
March	1st to 10th	Day	17% 12% 6% 13% 5% 4 4 3 5% 5% 26%	4944
	11th to 20th	Day	11% 10% 4 11% 5% 5% 4 3 4 5% 36%	5090
	21st to end	Day	20% 12% 5% 9% 5% 4 4 3 5% 6% 27%	5586
April	1st to 10th	Day	15% 13% 4 7% 5% 5% 5% 4 5% 6% 29%	2352
	11th to 20th	Day	17% 11% 4 8% 5% 5% 4 4 5% 7% 31%	2660
	21st to end	Day	18% 10% 3 8% 4 5% 4 3 5% 7% 33%	2730
May	1st to 10th	Day	21% 10% 3 8% 5% 5% 5% 3 5% 6% 28%	5992
	11th to 20th	Day	17% 9% 3 8% 5% 4 5% 4 6% 8% 31%	5939
	21st to end	Day	18% 7% 2 7% 4 5% 5% 4 6% 8% 34%	6478
June	1st to 10th	Day	14% 7% 3 7% 5% 5% 5% 5% 6% 8% 36%	2800
	11th to 20th	Day	12% 7% 3 8% 5% 4 5% 4 6% 9% 36%	2800
	21st to end	Day	12% 5% 1 6% 5% 5% 5% 5% 7% 10% 39%	2770
July	1st to 10th	Day	8% 6% 3 7% 4 5% 5% 5% 7% 10% 41%	5900
	11th to 20th	Day	10% 6% 2 7% 5% 6% 6% 5% 8% 10% 36%	5900
	21st to end	Day	11% 6% 3 7% 5% 5% 5% 5% 6% 8% 39%	6424
August	1st to 10th	Day	12% 9% 3 8% 5% 5% 5% 5% 6% 10% 33%	4234
	11th to 20th	Day	11% 7% 2 6% 5% 5% 6% 5% 7% 10% 35%	4174
	21st to end	Day	8% 6% 2 7% 5% 5% 6% 5% 8% 10% 39%	4586
September	1st to 10th	Day	13% 6% 2 5% 5% 4 5% 3 5% 7% 45%	2295
	11th to 20th	Day	10% 5% 2 6% 5% 5% 4 4 6% 9% 44%	2200
	21st to end	Day	19% 9% 3 6% 4 4 4 3 5% 7% 37%	2200
October	1st to 10th	Day	14% 7% 3 6% 4 4 5% 3 6% 8% 40%	2065
	11th to 20th	Day	19% 10% 3 7% 4 4 4 3 5% 6% 36%	2000
	21st to end	Day	21% 10% 3 8% 5% 4 4 3 5% 7% 29%	2200
November	1st to 10th	Day	13% 9% 3 8% 5% 5% 5% 4 5% 7% 38%	1857
	11th to 20th	Day	17% 14% 4 9% 4 4 5% 4 5% 5% 29%	1869
	21st to end	Day	18% 17% 7% 10% 5% 4 5% 4 5% 6% 19%	1680
December	1st to 10th	Day	18% 14% 7% 16% 6% 5% 4 4 4 4 18%	2680
	11th to 20th	Day	22% 19% 8% 12% 5% 5% 3 2 3 5% 17%	3070
	21st to end	Day	25% 22% 7% 13% 6% 4 4 2 3 4 10%	4297
January	1st to 10th	Night	14% 19% 8% 23% 7% 4 4 3 4 4 11%	7635
	11th to 20th	Night	10% 19% 10% 19% 9% 6% 5% 3 3 4 12%	7680
	21st to end	Night	17% 18% 6% 12% 6% 6% 5% 3 4 5% 18%	8401
February	1st to 10th	Night	19% 15% 5% 12% 6% 5% 4 3 4 5% 21%	2730
	11th to 20th	Night	17% 15% 4 13% 7% 5% 5% 4 4 5% 21%	2600
	21st to end	Night	20% 13% 5% 11% 6% 5% 3 3 4 5% 24%	2076
March	1st to 10th	Night	22% 13% 4 9% 4 3 3 2 3 5% 31%	5129
	11th to 20th	Night	14% 9% 3 8% 4 4 4 4 6% 7% 38%	5090
	21st to end	Night	17% 12% 4 8% 5% 4 4 4 5% 5% 33%	5588
April	1st to 10th	Night	18% 13% 4 7% 5% 4 4 4 5% 6% 31%	2268
	11th to 20th	Night	15% 11% 3 8% 4 5% 5% 4 5% 6% 33%	1926
	21st to end	Night	15% 9% 3 7% 5% 5% 4 3 7% 6% 37%	1890
May	1st to 10th	Night	24% 10% 4 8% 4 5% 4 3 5% 6% 26%	4123
	11th to 20th	Night	16% 10% 3 6% 4 4 4 3 5% 8% 38%	4086
	21st to end	Night	16% 7% 2 6% 4 5% 4 4 6% 9% 37%	4358
June	1st to 10th	Night	9% 6% 3 7% 5% 5% 5% 4 6% 7% 43%	1600
	11th to 20th	Night	10% 6% 2 6% 5% 5% 5% 4 7% 7% 41%	1600
	21st to end	Night	11% 5% 3 5% 4 5% 4 5% 7% 10% 40%	1623
July	1st to 10th	Night	9% 6% 2 6% 4 4 4 4 6% 9% 44%	4058
	11th to 20th	Night	10% 6% 2 6% 5% 5% 5% 4 6% 10% 41%	4057
	21st to end	Night	8% 6% 3 7% 4 4 4 4 6% 8% 46%	4427
August	1st to 10th	Night	10% 8% 3 8% 5% 5% 4 3 6% 7% 40%	2915
	11th to 20th	Night	12% 8% 3 6% 4 4 4 4 4 7% 44%	2875
	21st to end	Night	7% 5% 2 7% 5% 5% 5% 5% 6% 8% 43%	3279
September	1st to 10th	Night	11% 5% 2 5% 4 4 4 4 5% 7% 48%	2100
	11th to 20th	Night	9% 4 2 4 4 4 4 3 6% 7% 53%	2200
	21st to end	Night	16% 8% 3 6% 5% 4 4 3 5% 7% 40%	2200
October	1st to 10th	Night	13% 6% 2 5% 4 4 4 4 6% 7% 45%	2335
	11th to 20th	Night	17% 8% 4 8% 4 4 4 4 5% 7% 37%	2400
	21st to end	Night	22% 10% 2 7% 4 4 4 4 5% 6% 32%	2640
November	1st to 10th	Night	14% 9% 3 6% 4 4 4 4 5% 7% 41%	2659
	11th to 20th	Night	17% 13% 5% 8% 4 4 4 3 5% 6% 29%	2748
	21st to end	Night	20% 15% 5% 8% 5% 4 4 4 5% 6% 24%	2940
December	1st to 10th	Night	16% 17% 7% 11% 6% 5% 4 3 5% 6% 21%	4720
	11th to 20th	Night	19% 19% 7% 13% 5% 3 3 3 4 5% 18%	5345
	21st to end	Night	23% 20% 7% 12% 5% 4 4 3 4 5% 13%	6896

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	76% 5% 9% 7% 2	5259
	11th to 20th	Day	76% 4 7% 7% 6%	5280
	21st to end	Day	76% 4 6% 11% 2	5780
February	1st to 10th	Day	66% 4 9% 14% 7%	1890
	11th to 20th	Day	66% 6% 8% 13% 6%	1910
	21st to end	Day	61% 5% 11% 15% 6% 1	1730
March	1st to 10th	Day	59% 5% 10% 20% 6%	4944
	11th to 20th	Day	49% 5% 13% 24% 7% 1	5090
	21st to end	Day	57% 6% 9% 17% 12% 1	5586
April	1st to 10th	Day	54% 7% 11% 16% 11% 1	2352
	11th to 20th	Day	51% 7% 13% 16% 12% 2	2660
	21st to end	Day	50% 7% 11% 20% 10% 2	2730
May	1st to 10th	Day	54% 7% 9% 17% 9% 3	6027
	11th to 20th	Day	49% 8% 11% 20% 11% 1	5943
	21st to end	Day	45% 8% 12% 19% 12% 3	6493
June	1st to 10th	Day	43% 8% 12% 23% 13% 1	2800
	11th to 20th	Day	43% 9% 13% 20% 13% 1	2800
	21st to end	Day	37% 9% 14% 23% 15% 1	2770
July	1st to 10th	Day	37% 6% 12% 28% 15% 2	5835
	11th to 20th	Day	39% 8% 14% 23% 15% 1	5831
	21st to end	Day	39% 7% 12% 21% 19% 2	6240
August	1st to 10th	Day	44% 8% 13% 22% 12%	4221
	11th to 20th	Day	40% 8% 12% 29% 11% 1	4213
	21st to end	Day	37% 8% 13% 29% 10% 2	4586
September	1st to 10th	Day	38% 7% 14% 22% 17% 3	2295
	11th to 20th	Day	35% 8% 15% 25% 16% 2	2200
	21st to end	Day	46% 7% 10% 21% 15% 1	2200
October	1st to 10th	Day	31% 6% 13% 30% 19% 1	3364
	11th to 20th	Day	45% 5% 11% 20% 15% 4	3240
	21st to end	Day	42% 5% 12% 24% 16% 1	3538
November	1st to 10th	Day	46% 6% 11% 22% 14% 1	1857
	11th to 20th	Day	56% 6% 10% 18% 8% 3	1869
	21st to end	Day	64% 7% 9% 13% 5%	1680
December	1st to 10th	Day	69% 5% 11% 12% 3	2680
	11th to 20th	Day	71% 5% 9% 13% 3	3066
	21st to end	Day	79% 5% 7% 8% 2	4297
January	1st to 10th	Night	77% 5% 6% 9% 3	7636
	11th to 20th	Night	76% 5% 7% 8% 4	7680
	21st to end	Night	69% 3 9% 12% 6%	8401
February	1st to 10th	Night	65% 5% 9% 15% 6%	2730
	11th to 20th	Night	63% 6% 10% 14% 6%	2602
	21st to end	Night	63% 5% 8% 14% 8% 1	2076
March	1st to 10th	Night	56% 4 11% 19% 9%	5129
	11th to 20th	Night	42% 7% 15% 24% 10% 2	5090
	21st to end	Night	51% 6% 9% 19% 14% 1	5588
April	1st to 10th	Night	53% 7% 9% 17% 12% 1	2268
	11th to 20th	Night	49% 7% 12% 16% 14% 2	1926
	21st to end	Night	45% 7% 12% 18% 15% 2	1890
May	1st to 10th	Night	57% 7% 9% 14% 8% 5%	4150
	11th to 20th	Night	44% 7% 11% 22% 14% 2	4087
	21st to end	Night	41% 8% 13% 24% 13% 2	4365
June	1st to 10th	Night	39% 7% 11% 25% 16% 3	1600
	11th to 20th	Night	39% 7% 14% 21% 17% 2	1600
	21st to end	Night	35% 11% 13% 23% 17% 2	1623
July	1st to 10th	Night	35% 6% 14% 24% 18% 3	4015
	11th to 20th	Night	36% 8% 15% 27% 13% 1	4006
	21st to end	Night	34% 7% 13% 20% 26% 1	4297
August	1st to 10th	Night	41% 7% 13% 23% 14% 2	2904
	11th to 20th	Night	40% 6% 10% 28% 14% 1	2902
	21st to end	Night	35% 8% 13% 28% 13% 2	3279
September	1st to 10th	Night	34% 7% 11% 26% 18% 4	2100
	11th to 20th	Night	29% 7% 13% 27% 23% 2	2200
	21st to end	Night	43% 8% 11% 20% 18% 1	2200
October	1st to 10th	Night	30% 6% 10% 29% 25% 1	3816
	11th to 20th	Night	42% 7% 10% 20% 18% 3	3899
	21st to end	Night	38% 5% 11% 27% 16% 1	4252
November	1st to 10th	Night	42% 6% 12% 22% 15% 3	2659
	11th to 20th	Night	55% 5% 9% 17% 10% 2	2748
	21st to end	Night	60% 6% 12% 16% 5%	2940
December	1st to 10th	Night	64% 6% 12% 15% 4	4720
	11th to 20th	Night	68% 5% 11% 14% 2	5348
	21st to end	Night	73% 6% 10% 9% 2	6896

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	28% 25% 34% 9% 3 1	330
	11th to 20th	Day	31% 25% 34% 7% 2 1	330
	21st to end	Day	28% 31% 29% 10% 2	363
February	1st to 10th	Day	27% 26% 34% 12% 1 1	330
	11th to 20th	Day	28% 29% 31% 9% 2	330
	21st to end	Day	29% 29% 35% 7%	273
March	1st to 10th	Day	26% 21% 34% 16% 4	487
	11th to 20th	Day	30% 19% 32% 14% 5% 1	540
	21st to end	Day	31% 22% 28% 16% 3 1	594
April	1st to 10th	Day	24% 23% 30% 16% 6% 1	540
	11th to 20th	Day	27% 22% 25% 15% 8% 3	532
	21st to end	Day	25% 17% 33% 16% 7% 1	540
May	1st to 10th	Day	27% 19% 29% 15% 7% 2	543
	11th to 20th	Day	20% 13% 34% 21% 9% 4	551
	21st to end	Day	18% 9% 26% 24% 17% 5%	573
June	1st to 10th	Day	15% 11% 31% 28% 13% 2	530
	11th to 20th	Day	18% 8% 24% 32% 13% 4	530
	21st to end	Day	14% 9% 29% 28% 15% 5%	530
July	1st to 10th	Day	11% 6% 21% 31% 21% 11%	525
	11th to 20th	Day	14% 6% 23% 28% 21% 7%	524
	21st to end	Day	12% 6% 24% 26% 22% 10%	576
August	1st to 10th	Day	13% 6% 23% 25% 24% 9%	526
	11th to 20th	Day	15% 7% 20% 28% 20% 10%	519
	21st to end	Day	10% 5% 22% 28% 22% 11%	583
September	1st to 10th	Day	15% 9% 20% 25% 20% 11%	530
	11th to 20th	Day	8% 4 18% 28% 28% 14%	530
	21st to end	Day	24% 10% 23% 23% 14% 6%	530
October	1st to 10th	Day	11% 11% 28% 25% 21% 4	530
	11th to 20th	Day	21% 16% 35% 17% 8% 2	530
	21st to end	Day	28% 18% 31% 19% 4	583
November	1st to 10th	Day	19% 24% 33% 13% 10% 1	335
	11th to 20th	Day	29% 25% 28% 13% 4 1	319
	21st to end	Day	26% 25% 37% 11% 1	220
December	1st to 10th	Day	25% 22% 36% 12% 3 2	220
	11th to 20th	Day	25% 27% 33% 13% 3	220
	21st to end	Day	34% 21% 33% 12% 1	298
January	1st to 10th	Night	26% 19% 36% 15% 4	840
	11th to 20th	Night	31% 20% 31% 15% 3	840
	21st to end	Night	26% 19% 31% 21% 3	924
February	1st to 10th	Night	27% 17% 34% 20% 3	840
	11th to 20th	Night	25% 19% 35% 19% 2	823
	21st to end	Night	28% 18% 36% 16% 2	692
March	1st to 10th	Night	23% 16% 36% 21% 5%	840
	11th to 20th	Night	23% 16% 33% 23% 5% 1	840
	21st to end	Night	24% 11% 35% 22% 6% 1	924
April	1st to 10th	Night	23% 15% 33% 23% 5% 1	840
	11th to 20th	Night	22% 13% 35% 20% 9% 1	682
	21st to end	Night	19% 11% 34% 30% 7%	630
May	1st to 10th	Night	21% 9% 27% 32% 9% 1	630
	11th to 20th	Night	19% 8% 24% 38% 10% 1	609
	21st to end	Night	13% 3 22% 39% 20% 3	625
June	1st to 10th	Night	9% 5% 32% 38% 16% 1	400
	11th to 20th	Night	12% 4 25% 44% 14% 1	400
	21st to end	Night	12% 4 24% 39% 19% 1	423
July	1st to 10th	Night	9% 3 14% 43% 27% 4	585
	11th to 20th	Night	10% 3 18% 40% 26% 3	582
	21st to end	Night	9% 3 15% 43% 28% 2	657
August	1st to 10th	Night	10% 2 16% 43% 27% 3	597
	11th to 20th	Night	11% 2 15% 39% 29% 4	594
	21st to end	Night	9% 3 21% 34% 30% 3	690
September	1st to 10th	Night	13% 5% 18% 34% 26% 5%	800
	11th to 20th	Night	9% 3 15% 38% 31% 4	800
	21st to end	Night	18% 7% 21% 31% 19% 4	800
October	1st to 10th	Night	15% 7% 24% 31% 21% 3	800
	11th to 20th	Night	22% 10% 31% 27% 9% 1	800
	21st to end	Night	25% 14% 28% 27% 6%	880
November	1st to 10th	Night	19% 12% 30% 28% 10%	820
	11th to 20th	Night	24% 18% 31% 20% 6% 1	840
	21st to end	Night	30% 16% 31% 17% 6%	840
December	1st to 10th	Night	30% 16% 32% 18% 4	840
	11th to 20th	Night	26% 19% 33% 19% 3	840
	21st to end	Night	28% 16% 34% 19% 2	924

Page generated at 2026-05-14 01:58:54. Version ac07

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