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 2025-01-22.

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	16% 11% 4 9% 5% 5% 5% 4 5% 7% 30%	104821
	Night	16% 12% 4 9% 5% 4 4 3 5% 6% 31%	104474
Transparency	Day	51% 7% 11% 19% 11% 1	108510
	Night	51% 7% 11% 19% 11% 1	108924
Seeing	Day	20% 15% 28% 20% 12% 4	14824
	Night	20% 11% 28% 27% 12% 1	24773

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	18% 21% 8% 16% 6% 4 3 2 4 5% 14%	2926
	11th to 20th	Day	13% 23% 8% 13% 6% 6% 5% 2 3 4 14%	2930
	21st to end	Day	26% 19% 10% 12% 8% 4 4 3 3 3 8%	3133
February	1st to 10th	Day	17% 17% 5% 13% 7% 5% 4 3 4 5% 20%	1710
	11th to 20th	Day	15% 14% 6% 14% 7% 5% 5% 4 5% 4 21%	1715
	21st to end	Day	18% 15% 3 11% 7% 4 5% 3 6% 5% 24%	1570
March	1st to 10th	Day	22% 13% 6% 9% 5% 4 3 3 5% 6% 24%	3365
	11th to 20th	Day	12% 13% 5% 11% 6% 5% 4 3 4 5% 33%	3480
	21st to end	Day	21% 10% 5% 9% 5% 4 4 3 5% 6% 28%	3815
April	1st to 10th	Day	14% 13% 4 7% 5% 6% 6% 3 5% 7% 30%	2128
	11th to 20th	Day	18% 11% 4 8% 5% 5% 4 4 5% 6% 32%	2404
	21st to end	Day	19% 10% 3 9% 4 5% 4 3 4 6% 32%	2470
May	1st to 10th	Day	20% 10% 4 8% 4 5% 5% 4 5% 7% 29%	4082
	11th to 20th	Day	19% 8% 3 7% 5% 4 4 4 6% 8% 32%	4081
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 4 7% 9% 39%	4507
June	1st to 10th	Day	13% 7% 3 7% 5% 5% 5% 5% 6% 8% 36%	2660
	11th to 20th	Day	12% 7% 3 8% 5% 4 5% 4 6% 9% 37%	2660
	21st to end	Day	12% 5% 1 6% 5% 5% 5% 5% 7% 10% 38%	2632
July	1st to 10th	Day	9% 6% 3 7% 5% 5% 6% 5% 7% 10% 37%	4120
	11th to 20th	Day	9% 5% 2 6% 5% 6% 6% 4 7% 11% 41%	4120
	21st to end	Day	10% 7% 3 7% 5% 6% 6% 5% 7% 8% 37%	4466
August	1st to 10th	Day	12% 9% 3 8% 5% 5% 5% 5% 6% 10% 33%	4104
	11th to 20th	Day	11% 7% 3 6% 5% 5% 6% 5% 7% 10% 34%	4044
	21st to end	Day	8% 6% 2 7% 5% 5% 6% 5% 8% 10% 38%	4446
September	1st to 10th	Day	13% 6% 2 5% 5% 5% 4 3 5% 7% 44%	2180
	11th to 20th	Day	10% 6% 2 7% 5% 5% 4 4 6% 9% 43%	2090
	21st to end	Day	19% 9% 3 6% 4 4 4 3 5% 7% 37%	2090
October	1st to 10th	Day	14% 7% 3 6% 4 4 5% 3 6% 8% 39%	1962
	11th to 20th	Day	19% 10% 3 7% 4 4 4 3 5% 5% 35%	1900
	21st to end	Day	21% 11% 3 8% 5% 4 4 3 4 7% 29%	2090
November	1st to 10th	Day	13% 9% 3 8% 5% 5% 5% 4 5% 7% 39%	1767
	11th to 20th	Day	18% 14% 4 9% 4 3 5% 4 5% 5% 29%	1780
	21st to end	Day	18% 17% 7% 10% 5% 4 5% 4 5% 6% 20%	1600
December	1st to 10th	Day	18% 14% 7% 16% 6% 5% 4 4 4 4 19%	2600
	11th to 20th	Day	22% 19% 8% 12% 5% 5% 3 2 3 5% 17%	2990
	21st to end	Day	25% 22% 7% 13% 6% 4 4 2 3 4 10%	4204
January	1st to 10th	Night	16% 21% 8% 16% 6% 4 3 3 4 4 15%	4239
	11th to 20th	Night	14% 20% 9% 17% 6% 5% 5% 4 4 4 12%	4250
	21st to end	Night	27% 19% 7% 14% 6% 3 3 2 2 3 14%	4546
February	1st to 10th	Night	21% 15% 5% 11% 6% 5% 4 3 4 5% 21%	2470
	11th to 20th	Night	16% 15% 4 12% 7% 5% 5% 4 4 5% 22%	2346
	21st to end	Night	21% 13% 5% 11% 7% 5% 3 3 4 5% 24%	1884
March	1st to 10th	Night	23% 14% 3 7% 3 3 3 2 3 5% 33%	3488
	11th to 20th	Night	17% 10% 3 8% 4 5% 4 4 5% 6% 34%	3480
	21st to end	Night	17% 12% 4 7% 5% 3 4 3 5% 5% 35%	3817
April	1st to 10th	Night	16% 12% 4 7% 5% 4 4 4 5% 6% 32%	2052
	11th to 20th	Night	16% 11% 3 7% 4 5% 4 4 5% 6% 34%	1740
	21st to end	Night	15% 9% 3 7% 5% 5% 4 3 7% 6% 36%	1710
May	1st to 10th	Night	24% 10% 4 7% 5% 5% 4 3 5% 6% 28%	2813
	11th to 20th	Night	16% 10% 3 6% 4 4 4 4 5% 8% 38%	2812
	21st to end	Night	10% 5% 2 5% 3 4 4 4 7% 11% 44%	3030
June	1st to 10th	Night	9% 6% 3 7% 6% 5% 5% 4 6% 7% 43%	1520
	11th to 20th	Night	10% 6% 2 5% 5% 5% 5% 4 8% 8% 42%	1520
	21st to end	Night	11% 5% 3 5% 4 5% 4 5% 7% 10% 40%	1542
July	1st to 10th	Night	10% 6% 3 7% 4 4 4 4 5% 8% 45%	2840
	11th to 20th	Night	10% 5% 1 5% 4 4 5% 4 5% 9% 48%	2840
	21st to end	Night	8% 6% 2 7% 5% 4 4 4 7% 8% 44%	3087
August	1st to 10th	Night	10% 9% 3 8% 5% 5% 4 3 6% 7% 39%	2825
	11th to 20th	Night	13% 9% 3 6% 4 4 4 4 4 7% 43%	2785
	21st to end	Night	7% 5% 2 7% 5% 6% 5% 5% 6% 7% 44%	3178
September	1st to 10th	Night	12% 6% 2 5% 4 4 4 4 5% 7% 47%	1995
	11th to 20th	Night	9% 4 2 4 4 4 4 3 6% 7% 52%	2090
	21st to end	Night	15% 8% 3 6% 5% 4 4 3 5% 7% 41%	2090
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 6% 7% 44%	2218
	11th to 20th	Night	17% 8% 4 8% 4 4 4 4 4 6% 35%	2280
	21st to end	Night	22% 10% 2 7% 4 4 4 4 6% 6% 31%	2508
November	1st to 10th	Night	15% 9% 3 6% 4 4 4 4 5% 6% 41%	2529
	11th to 20th	Night	17% 13% 5% 8% 4 4 4 3 5% 6% 29%	2617
	21st to end	Night	20% 15% 5% 8% 5% 4 4 4 5% 6% 24%	2800
December	1st to 10th	Night	16% 17% 7% 11% 6% 5% 4 3 5% 6% 21%	4580
	11th to 20th	Night	19% 20% 8% 12% 5% 3 3 3 4 5% 18%	5205
	21st to end	Night	24% 20% 6% 12% 5% 4 4 3 4 5% 13%	6748

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	73% 6% 9% 10% 3	2927
	11th to 20th	Day	73% 5% 9% 9% 3	2930
	21st to end	Day	81% 5% 6% 5% 2	3133
February	1st to 10th	Day	67% 4 9% 13% 6% 1	1710
	11th to 20th	Day	65% 6% 8% 13% 7%	1724
	21st to end	Day	61% 6% 11% 14% 7% 1	1570
March	1st to 10th	Day	60% 6% 9% 20% 5%	3365
	11th to 20th	Day	52% 6% 13% 21% 7% 1	3480
	21st to end	Day	54% 7% 11% 16% 12% 1	3815
April	1st to 10th	Day	53% 7% 11% 17% 12% 1	2128
	11th to 20th	Day	51% 6% 12% 16% 12% 2	2404
	21st to end	Day	51% 7% 11% 19% 10% 2	2470
May	1st to 10th	Day	53% 7% 11% 20% 8% 1	4120
	11th to 20th	Day	47% 9% 13% 21% 9% 1	4085
	21st to end	Day	38% 10% 14% 20% 14% 4	4521
June	1st to 10th	Day	43% 8% 12% 23% 13% 1	2660
	11th to 20th	Day	42% 9% 13% 21% 14% 1	2660
	21st to end	Day	38% 9% 13% 23% 15% 2	2632
July	1st to 10th	Day	40% 7% 12% 23% 16% 2	4055
	11th to 20th	Day	35% 7% 13% 25% 19% 1	4051
	21st to end	Day	41% 8% 14% 17% 19% 2	4324
August	1st to 10th	Day	45% 8% 13% 22% 11%	4091
	11th to 20th	Day	40% 8% 12% 28% 11% 1	4083
	21st to end	Day	37% 8% 13% 29% 10% 2	4446
September	1st to 10th	Day	38% 7% 14% 21% 16% 3	2180
	11th to 20th	Day	36% 8% 14% 24% 16% 2	2090
	21st to end	Day	46% 7% 10% 22% 15% 1	2090
October	1st to 10th	Day	32% 6% 14% 29% 19% 1	3261
	11th to 20th	Day	46% 6% 11% 20% 15% 4	3140
	21st to end	Day	42% 5% 12% 25% 16% 1	3428
November	1st to 10th	Day	45% 6% 11% 23% 14% 1	1767
	11th to 20th	Day	56% 6% 10% 18% 8% 2	1780
	21st to end	Day	64% 8% 9% 13% 6%	1600
December	1st to 10th	Day	69% 5% 11% 12% 2	2600
	11th to 20th	Day	72% 5% 8% 12% 3	2986
	21st to end	Day	79% 5% 7% 8% 2	4204
January	1st to 10th	Night	71% 7% 8% 10% 4	4239
	11th to 20th	Night	75% 7% 8% 8% 2	4250
	21st to end	Night	77% 4 7% 10% 2	4546
February	1st to 10th	Night	65% 5% 9% 14% 6%	2470
	11th to 20th	Night	62% 6% 10% 15% 6%	2348
	21st to end	Night	63% 6% 8% 13% 8% 1	1884
March	1st to 10th	Night	54% 5% 10% 21% 9%	3488
	11th to 20th	Night	46% 9% 17% 19% 8% 1	3480
	21st to end	Night	48% 8% 10% 23% 11% 1	3817
April	1st to 10th	Night	51% 7% 10% 17% 13% 1	2052
	11th to 20th	Night	49% 7% 12% 16% 15% 3	1740
	21st to end	Night	45% 7% 13% 18% 15% 2	1710
May	1st to 10th	Night	54% 8% 9% 18% 9% 2	2840
	11th to 20th	Night	43% 8% 12% 23% 12% 2	2813
	21st to end	Night	31% 9% 15% 26% 16% 3	3037
June	1st to 10th	Night	39% 7% 11% 25% 15% 2	1520
	11th to 20th	Night	37% 8% 14% 21% 17% 3	1520
	21st to end	Night	35% 11% 13% 23% 16% 2	1542
July	1st to 10th	Night	36% 6% 12% 23% 17% 5%	2795
	11th to 20th	Night	32% 7% 13% 29% 18% 1	2786
	21st to end	Night	35% 8% 14% 18% 24% 2	2988
August	1st to 10th	Night	42% 7% 13% 23% 14% 1	2814
	11th to 20th	Night	40% 7% 11% 27% 14% 1	2812
	21st to end	Night	35% 8% 13% 28% 14% 2	3178
September	1st to 10th	Night	35% 8% 11% 25% 18% 4	1995
	11th to 20th	Night	30% 7% 13% 25% 23% 2	2090
	21st to end	Night	42% 7% 11% 21% 18% 1	2090
October	1st to 10th	Night	30% 6% 10% 29% 24% 1	3699
	11th to 20th	Night	43% 7% 10% 20% 17% 3	3779
	21st to end	Night	38% 5% 11% 28% 16% 2	4120
November	1st to 10th	Night	42% 6% 12% 22% 15% 3	2529
	11th to 20th	Night	55% 5% 9% 17% 11% 3	2617
	21st to end	Night	60% 6% 12% 16% 5%	2800
December	1st to 10th	Night	63% 6% 12% 15% 4	4580
	11th to 20th	Night	69% 5% 11% 13% 2	5208
	21st to end	Night	73% 6% 10% 9% 1	6748

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% 26% 32% 10% 4 1	300
	11th to 20th	Day	28% 26% 35% 8% 2 1	300
	21st to end	Day	27% 31% 28% 11% 2	300
February	1st to 10th	Day	30% 24% 36% 9% 1	270
	11th to 20th	Day	27% 31% 32% 8% 1	270
	21st to end	Day	30% 31% 31% 8%	225
March	1st to 10th	Day	26% 21% 31% 17% 5%	412
	11th to 20th	Day	29% 17% 33% 15% 5% 1	460
	21st to end	Day	31% 20% 28% 17% 4 1	506
April	1st to 10th	Day	22% 23% 31% 17% 7% 1	460
	11th to 20th	Day	27% 20% 26% 14% 9% 4	452
	21st to end	Day	25% 17% 34% 15% 7% 2	460
May	1st to 10th	Day	26% 18% 29% 17% 8% 3	463
	11th to 20th	Day	20% 13% 32% 22% 9% 4	487
	21st to end	Day	16% 9% 26% 26% 19% 5%	529
June	1st to 10th	Day	14% 11% 30% 30% 13% 3	490
	11th to 20th	Day	18% 8% 24% 31% 14% 5%	490
	21st to end	Day	14% 10% 30% 27% 13% 5%	490
July	1st to 10th	Day	11% 6% 20% 31% 20% 12%	485
	11th to 20th	Day	13% 7% 23% 28% 21% 8%	484
	21st to end	Day	12% 6% 24% 27% 22% 10%	532
August	1st to 10th	Day	14% 7% 23% 23% 24% 9%	486
	11th to 20th	Day	15% 8% 21% 27% 19% 10%	479
	21st to end	Day	10% 6% 20% 29% 23% 12%	539
September	1st to 10th	Day	15% 8% 21% 26% 20% 11%	490
	11th to 20th	Day	9% 4 18% 29% 28% 12%	490
	21st to end	Day	24% 10% 22% 22% 15% 6%	490
October	1st to 10th	Day	11% 12% 29% 24% 20% 4	490
	11th to 20th	Day	22% 16% 34% 18% 8% 2	490
	21st to end	Day	28% 17% 30% 20% 5%	539
November	1st to 10th	Day	18% 25% 32% 13% 10% 2	305
	11th to 20th	Day	28% 24% 29% 14% 4 1	290
	21st to end	Day	23% 26% 40% 11% 1	200
December	1st to 10th	Day	26% 22% 34% 13% 4 2	200
	11th to 20th	Day	25% 26% 34% 13% 3	200
	21st to end	Day	32% 21% 34% 12% 1	271
January	1st to 10th	Night	26% 19% 36% 15% 4	800
	11th to 20th	Night	32% 19% 31% 16% 3	800
	21st to end	Night	26% 18% 31% 22% 3	841
February	1st to 10th	Night	28% 16% 33% 20% 3	760
	11th to 20th	Night	25% 18% 35% 20% 2	743
	21st to end	Night	28% 17% 36% 17% 2	628
March	1st to 10th	Night	22% 16% 36% 22% 5%	760
	11th to 20th	Night	22% 16% 32% 24% 6% 1	760
	21st to end	Night	24% 10% 34% 24% 7% 1	836
April	1st to 10th	Night	21% 14% 35% 24% 5% 1	760
	11th to 20th	Night	22% 12% 34% 21% 10% 1	616
	21st to end	Night	18% 10% 35% 30% 6% 1	570
May	1st to 10th	Night	21% 9% 28% 32% 10% 1	570
	11th to 20th	Night	19% 7% 24% 38% 11% 2	561
	21st to end	Night	12% 3 22% 39% 21% 3	593
June	1st to 10th	Night	9% 4 31% 38% 17% 1	380
	11th to 20th	Night	12% 4 25% 44% 15% 1	380
	21st to end	Night	12% 4 25% 40% 19%	402
July	1st to 10th	Night	9% 3 14% 43% 27% 4	555
	11th to 20th	Night	10% 3 18% 41% 25% 3	552
	21st to end	Night	9% 3 14% 44% 27% 2	624
August	1st to 10th	Night	10% 2 16% 41% 28% 3	567
	11th to 20th	Night	12% 2 16% 39% 28% 4	564
	21st to end	Night	9% 3 20% 34% 31% 4	655
September	1st to 10th	Night	14% 5% 18% 34% 25% 5%	760
	11th to 20th	Night	9% 3 16% 38% 31% 4	760
	21st to end	Night	18% 7% 22% 30% 18% 4	760
October	1st to 10th	Night	16% 7% 25% 31% 20% 3	760
	11th to 20th	Night	22% 11% 30% 26% 10% 1	760
	21st to end	Night	25% 14% 28% 27% 6%	836
November	1st to 10th	Night	20% 11% 30% 28% 11% 1	780
	11th to 20th	Night	24% 17% 32% 20% 7% 1	800
	21st to end	Night	29% 16% 31% 18% 6%	800
December	1st to 10th	Night	31% 16% 31% 18% 4	800
	11th to 20th	Night	26% 19% 32% 20% 3	800
	21st to end	Night	28% 16% 34% 20% 2	880

Page generated at 2025-01-19 03:06:48. Version ac07

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