Eagle Eye Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eagle Eye Observatory clear sky chart from 2005-11-06 to 2024-11-30.

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% 7% 2 6% 4 4 4 4 6% 7% 40%	101535
	Night	16% 7% 2 6% 4 4 4 3 5% 7% 42%	98048
Transparency	Day	41% 6% 11% 23% 15% 2	105096
	Night	41% 6% 11% 23% 16% 3	102563
Seeing	Day	22% 16% 29% 21% 10% 3	15033
	Night	20% 15% 30% 25% 9% 1	24359

By Month

Percentage Cloud Cover NE (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	14% 8% 3 6% 4 4 4 3 4 5% 45%	2517
	11th to 20th	Day	14% 11% 3 10% 6% 4 4 3 5% 5% 35%	2630
	21st to end	Day	19% 9% 3 7% 5% 4 5% 3 4 5% 35%	3124
February	1st to 10th	Day	15% 9% 2 6% 5% 4 4 4 6% 6% 39%	1710
	11th to 20th	Day	15% 8% 3 8% 4 5% 4 4 5% 5% 40%	1776
	21st to end	Day	18% 11% 4 6% 4 4 3 3 4 5% 37%	1570
March	1st to 10th	Day	26% 6% 2 7% 4 4 4 3 4 5% 37%	3175
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 4 6% 8% 44%	3480
	21st to end	Day	22% 7% 2 5% 4 3 2 2 3 5% 43%	4002
April	1st to 10th	Day	14% 9% 2 6% 4 5% 4 3 5% 7% 40%	2280
	11th to 20th	Day	15% 7% 2 5% 4 4 4 4 5% 7% 42%	2254
	21st to end	Day	16% 6% 2 6% 4 4 4 4 6% 7% 39%	2280
May	1st to 10th	Day	27% 8% 2 6% 4 4 5% 3 5% 7% 29%	4066
	11th to 20th	Day	24% 9% 3 7% 5% 4 4 4 5% 6% 28%	4398
	21st to end	Day	12% 5% 2 6% 4 4 5% 4 6% 9% 44%	4837
June	1st to 10th	Day	13% 6% 2 6% 4 4 5% 5% 7% 9% 39%	2660
	11th to 20th	Day	12% 6% 3 6% 5% 4 5% 5% 7% 10% 37%	2660
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 6% 10% 42%	2660
July	1st to 10th	Day	6% 5% 2 6% 5% 6% 7% 6% 8% 11% 37%	4440
	11th to 20th	Day	9% 6% 2 6% 4 5% 5% 4 8% 10% 40%	4440
	21st to end	Day	11% 8% 3 8% 6% 6% 6% 4 6% 8% 33%	4670
August	1st to 10th	Day	19% 5% 2 7% 4 5% 5% 4 6% 8% 34%	4104
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 7% 9% 41%	3773
	21st to end	Day	12% 5% 2 5% 4 4 4 3 5% 7% 49%	4180
September	1st to 10th	Day	15% 5% 2 6% 4 4 5% 4 4 6% 44%	2280
	11th to 20th	Day	13% 5% 2 3 3 3 4 3 5% 7% 50%	2271
	21st to end	Day	20% 7% 3 7% 4 5% 4 2 5% 6% 38%	2056
October	1st to 10th	Day	18% 6% 2 6% 4 4 4 3 5% 7% 43%	1900
	11th to 20th	Day	15% 6% 2 5% 4 3 4 3 4 7% 48%	1900
	21st to end	Day	18% 7% 2 5% 3 3 4 3 5% 5% 45%	2050
November	1st to 10th	Day	12% 7% 3 5% 3 2 3 3 5% 6% 52%	1761
	11th to 20th	Day	16% 5% 2 5% 4 3 3 4 5% 6% 47%	1800
	21st to end	Day	15% 6% 2 5% 3 4 3 4 6% 7% 44%	1633
December	1st to 10th	Day	17% 9% 3 7% 4 4 3 3 6% 6% 38%	1520
	11th to 20th	Day	19% 8% 2 5% 4 3 4 3 6% 6% 41%	1906
	21st to end	Day	16% 7% 3 7% 6% 5% 5% 5% 6% 6% 35%	2772
January	1st to 10th	Night	15% 7% 2 6% 4 4 4 3 4 6% 43%	4429
	11th to 20th	Night	18% 8% 2 5% 4 4 4 3 5% 5% 42%	4312
	21st to end	Night	22% 10% 3 8% 4 3 3 3 4 5% 37%	4532
February	1st to 10th	Night	16% 9% 3 6% 4 4 3 3 5% 6% 41%	2470
	11th to 20th	Night	17% 8% 3 6% 5% 4 4 3 5% 6% 40%	2288
	21st to end	Night	18% 8% 3 5% 4 3 4 3 6% 6% 40%	1884
March	1st to 10th	Night	21% 9% 2 6% 4 4 3 2 4 6% 37%	3663
	11th to 20th	Night	11% 6% 2 5% 4 4 4 3 5% 6% 49%	3479
	21st to end	Night	16% 9% 3 6% 4 3 3 2 4 5% 46%	3628
April	1st to 10th	Night	16% 6% 3 7% 5% 4 4 4 5% 6% 40%	1900
	11th to 20th	Night	14% 7% 3 6% 5% 3 5% 3 5% 7% 42%	1875
	21st to end	Night	17% 7% 2 4 3 4 4 3 5% 7% 43%	1900
May	1st to 10th	Night	24% 8% 3 7% 4 5% 4 4 5% 7% 30%	2887
	11th to 20th	Night	25% 10% 3 7% 4 3 4 4 5% 6% 28%	2495
	21st to end	Night	12% 6% 2 6% 4 4 4 4 6% 10% 42%	2738
June	1st to 10th	Night	14% 6% 3 6% 5% 3 4 3 6% 8% 42%	1520
	11th to 20th	Night	10% 6% 2 6% 4 5% 5% 4 7% 10% 40%	1520
	21st to end	Night	10% 5% 2 6% 4 3 4 5% 7% 10% 43%	1520
July	1st to 10th	Night	7% 5% 2 8% 5% 6% 6% 5% 7% 10% 39%	2520
	11th to 20th	Night	10% 6% 2 7% 5% 5% 5% 5% 8% 9% 38%	2520
	21st to end	Night	14% 8% 2 6% 4 4 5% 4 7% 8% 38%	2880
August	1st to 10th	Night	20% 6% 2 5% 5% 5% 5% 4 6% 8% 35%	2825
	11th to 20th	Night	13% 6% 3 7% 4 4 4 4 6% 7% 41%	3024
	21st to end	Night	11% 5% 2 5% 4 3 4 5% 5% 7% 48%	3476
September	1st to 10th	Night	14% 6% 2 6% 3 3 3 3 5% 6% 47%	1900
	11th to 20th	Night	13% 6% 1 4 3 3 3 3 5% 6% 53%	1909
	21st to end	Night	20% 6% 2 5% 5% 3 3 4 5% 6% 41%	2120
October	1st to 10th	Night	20% 7% 2 5% 4 4 3 2 4 6% 43%	2280
	11th to 20th	Night	15% 6% 2 5% 2 3 3 3 5% 6% 50%	2280
	21st to end	Night	17% 7% 2 4 2 3 3 3 5% 6% 49%	2546
November	1st to 10th	Night	10% 6% 2 5% 3 3 4 3 5% 6% 53%	2537
	11th to 20th	Night	16% 8% 2 5% 4 3 3 3 5% 5% 47%	2600
	21st to end	Night	13% 5% 2 5% 5% 5% 4 4 5% 7% 45%	2759
December	1st to 10th	Night	18% 7% 3 6% 5% 4 5% 3 5% 7% 38%	2660
	11th to 20th	Night	18% 6% 2 6% 4 4 4 3 5% 6% 41%	3288
	21st to end	Night	17% 7% 3 7% 4 4 5% 4 6% 7% 37%	4884

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	41% 4 13% 27% 13% 3	2518
	11th to 20th	Day	50% 4 11% 19% 13% 3	2630
	21st to end	Day	50% 6% 11% 22% 9% 1	3124
February	1st to 10th	Day	44% 5% 14% 24% 11% 2	1710
	11th to 20th	Day	45% 5% 9% 25% 14% 2	1785
	21st to end	Day	48% 4 9% 22% 13% 4	1570
March	1st to 10th	Day	49% 4 8% 27% 10% 2	3178
	11th to 20th	Day	36% 5% 10% 29% 16% 3	3480
	21st to end	Day	45% 4 8% 19% 20% 3	4002
April	1st to 10th	Day	43% 5% 11% 21% 16% 5%	2280
	11th to 20th	Day	40% 6% 11% 22% 16% 4	2254
	21st to end	Day	42% 6% 12% 18% 18% 4	2280
May	1st to 10th	Day	54% 7% 9% 19% 10% 2	4078
	11th to 20th	Day	55% 7% 11% 18% 8% 1	4402
	21st to end	Day	35% 8% 12% 26% 17% 2	4837
June	1st to 10th	Day	39% 8% 13% 24% 15% 1	2660
	11th to 20th	Day	41% 9% 13% 24% 11% 3	2660
	21st to end	Day	36% 9% 13% 26% 15% 1	2660
July	1st to 10th	Day	37% 12% 14% 21% 12% 3	4370
	11th to 20th	Day	37% 8% 17% 24% 12% 1	4365
	21st to end	Day	46% 8% 10% 18% 16% 1	4521
August	1st to 10th	Day	47% 8% 13% 22% 10%	4091
	11th to 20th	Day	37% 7% 11% 30% 13% 1	3810
	21st to end	Day	33% 7% 11% 28% 20% 2	4180
September	1st to 10th	Day	40% 6% 10% 20% 20% 3	2280
	11th to 20th	Day	32% 6% 9% 26% 23% 4	2271
	21st to end	Day	49% 4 8% 17% 20% 2	2056
October	1st to 10th	Day	37% 5% 9% 17% 28% 5%	3160
	11th to 20th	Day	25% 4 12% 26% 25% 7%	3140
	21st to end	Day	24% 3 12% 27% 28% 4	3352
November	1st to 10th	Day	34% 4 12% 25% 20% 5%	1761
	11th to 20th	Day	37% 5% 10% 25% 21% 2	1800
	21st to end	Day	39% 5% 13% 30% 11% 2	1633
December	1st to 10th	Day	46% 6% 15% 20% 12% 1	1520
	11th to 20th	Day	44% 4 13% 29% 10% 1	1906
	21st to end	Day	48% 5% 14% 22% 11% 1	2772
January	1st to 10th	Night	42% 4 11% 28% 13% 3	4429
	11th to 20th	Night	44% 4 11% 25% 13% 3	4312
	21st to end	Night	51% 4 7% 26% 10% 2	4532
February	1st to 10th	Night	45% 5% 13% 24% 12% 2	2470
	11th to 20th	Night	46% 4 9% 20% 18% 3	2290
	21st to end	Night	43% 5% 9% 22% 15% 5%	1884
March	1st to 10th	Night	49% 4 9% 24% 13% 2	3673
	11th to 20th	Night	35% 6% 11% 30% 16% 2	3480
	21st to end	Night	42% 4 7% 18% 24% 5%	3628
April	1st to 10th	Night	43% 5% 10% 21% 17% 4	1900
	11th to 20th	Night	40% 6% 10% 20% 20% 4	1875
	21st to end	Night	41% 5% 10% 21% 18% 5%	1900
May	1st to 10th	Night	53% 7% 9% 18% 11% 2	2894
	11th to 20th	Night	55% 8% 12% 13% 10% 1	2496
	21st to end	Night	36% 9% 14% 21% 16% 3	2739
June	1st to 10th	Night	39% 7% 10% 23% 19% 1	1520
	11th to 20th	Night	37% 9% 14% 24% 15% 1	1520
	21st to end	Night	34% 9% 14% 27% 14% 2	1520
July	1st to 10th	Night	38% 11% 17% 17% 13% 3	2480
	11th to 20th	Night	40% 9% 15% 22% 12% 1	2472
	21st to end	Night	42% 8% 12% 19% 17% 1	2788
August	1st to 10th	Night	46% 8% 18% 18% 9% 1	2814
	11th to 20th	Night	40% 6% 12% 25% 15% 1	3053
	21st to end	Night	33% 6% 12% 29% 19% 1	3476
September	1st to 10th	Night	38% 7% 10% 20% 22% 3	1900
	11th to 20th	Night	32% 5% 9% 23% 26% 4	1909
	21st to end	Night	44% 6% 8% 19% 21% 2	2120
October	1st to 10th	Night	42% 5% 9% 20% 21% 2	3800
	11th to 20th	Night	24% 4 10% 29% 28% 5%	3779
	21st to end	Night	26% 3 11% 32% 23% 5%	4182
November	1st to 10th	Night	32% 5% 12% 26% 20% 5%	2537
	11th to 20th	Night	40% 5% 9% 23% 20% 5%	2600
	21st to end	Night	37% 5% 12% 28% 16% 2	2759
December	1st to 10th	Night	46% 5% 12% 22% 14% 1	2660
	11th to 20th	Night	42% 5% 12% 22% 16% 3	3288
	21st to end	Night	45% 6% 14% 24% 11% 1	4884

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	32% 22% 29% 13% 1 2	180
	11th to 20th	Day	35% 29% 28% 7% 1	213
	21st to end	Day	30% 30% 25% 13% 2	297
February	1st to 10th	Day	30% 27% 31% 9% 2	270
	11th to 20th	Day	34% 26% 32% 7% 1	384
	21st to end	Day	35% 22% 27% 13% 3	382
March	1st to 10th	Day	32% 20% 31% 13% 4	460
	11th to 20th	Day	32% 24% 29% 12% 3 1	460
	21st to end	Day	30% 26% 29% 10% 4 1	506
April	1st to 10th	Day	28% 26% 30% 11% 3 1	460
	11th to 20th	Day	25% 22% 30% 15% 6% 2	452
	21st to end	Day	28% 18% 35% 14% 3 1	460
May	1st to 10th	Day	32% 19% 28% 14% 5% 1	463
	11th to 20th	Day	23% 16% 34% 18% 7% 1	487
	21st to end	Day	19% 10% 27% 25% 16% 2	529
June	1st to 10th	Day	18% 12% 32% 25% 12% 2	490
	11th to 20th	Day	17% 10% 31% 27% 13% 1	490
	21st to end	Day	14% 13% 30% 28% 12% 4	490
July	1st to 10th	Day	13% 5% 24% 31% 20% 6%	485
	11th to 20th	Day	8% 5% 25% 38% 21% 4	484
	21st to end	Day	12% 7% 31% 31% 17% 3	532
August	1st to 10th	Day	13% 7% 28% 29% 17% 7%	486
	11th to 20th	Day	13% 5% 23% 35% 18% 6%	479
	21st to end	Day	12% 9% 24% 29% 17% 9%	539
September	1st to 10th	Day	19% 11% 20% 27% 15% 7%	490
	11th to 20th	Day	17% 6% 26% 27% 16% 9%	490
	21st to end	Day	25% 14% 23% 24% 11% 3	490
October	1st to 10th	Day	22% 9% 28% 22% 13% 5%	490
	11th to 20th	Day	20% 17% 27% 23% 10% 2	490
	21st to end	Day	21% 17% 33% 16% 10% 2	517
November	1st to 10th	Day	21% 15% 32% 20% 9% 3	395
	11th to 20th	Day	22% 22% 33% 19% 5%	400
	21st to end	Day	25% 26% 29% 17% 3	235
December	1st to 10th	Day	32% 26% 28% 10% 5%	180
	11th to 20th	Day	37% 22% 29% 9% 3	180
	21st to end	Day	29% 23% 29% 13% 6% 1	198
January	1st to 10th	Night	22% 25% 36% 15% 2	760
	11th to 20th	Night	28% 20% 30% 20% 2	760
	21st to end	Night	21% 23% 38% 17% 2	836
February	1st to 10th	Night	24% 21% 35% 18% 1	760
	11th to 20th	Night	28% 27% 33% 11% 1	743
	21st to end	Night	28% 21% 35% 14% 2	628
March	1st to 10th	Night	24% 24% 31% 18% 3	760
	11th to 20th	Night	24% 24% 31% 16% 5% 1	760
	21st to end	Night	22% 17% 40% 16% 4	836
April	1st to 10th	Night	22% 23% 35% 16% 3	760
	11th to 20th	Night	20% 15% 36% 23% 5%	751
	21st to end	Night	21% 18% 32% 23% 6%	760
May	1st to 10th	Night	24% 12% 33% 24% 6%	611
	11th to 20th	Night	20% 11% 35% 28% 6%	374
	21st to end	Night	16% 8% 25% 38% 12% 1	411
June	1st to 10th	Night	14% 7% 30% 38% 11%	380
	11th to 20th	Night	10% 6% 32% 42% 10%	380
	21st to end	Night	11% 4 28% 44% 13%	380
July	1st to 10th	Night	11% 5% 25% 40% 18% 1	370
	11th to 20th	Night	7% 3 20% 45% 24% 1	368
	21st to end	Night	9% 5% 23% 42% 18% 2	495
August	1st to 10th	Night	12% 2 21% 40% 22% 3	567
	11th to 20th	Night	15% 5% 18% 38% 24% 2	701
	21st to end	Night	13% 4 19% 41% 22% 2	836
September	1st to 10th	Night	16% 6% 28% 30% 18% 3	760
	11th to 20th	Night	14% 5% 21% 33% 23% 3	760
	21st to end	Night	22% 7% 24% 28% 18% 1	760
October	1st to 10th	Night	22% 9% 26% 24% 15% 3	760
	11th to 20th	Night	18% 13% 28% 29% 11%	760
	21st to end	Night	23% 15% 30% 24% 8%	836
November	1st to 10th	Night	16% 13% 34% 26% 10% 1	780
	11th to 20th	Night	22% 18% 29% 23% 7% 1	800
	21st to end	Night	21% 18% 34% 21% 6%	800
December	1st to 10th	Night	27% 19% 31% 17% 6% 1	760
	11th to 20th	Night	21% 19% 35% 20% 4	760
	21st to end	Night	23% 20% 33% 22% 2	836

Page generated at 2024-11-27 17:30:48. Version ac07

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