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 2026-02-16.

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%	130959
	Night	15% 7% 2 6% 4 4 4 3 5% 7% 43%	129857
Transparency	Day	41% 6% 11% 23% 16% 3	134504
	Night	40% 5% 11% 23% 17% 3	134387
Seeing	Day	23% 16% 28% 20% 10% 3	16516
	Night	20% 15% 30% 25% 9% 1	25947

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	13% 6% 3 7% 5% 4 5% 4 5% 5% 44%	4661
	11th to 20th	Day	15% 8% 2 8% 4 4 3 3 4 5% 42%	4871
	21st to end	Day	14% 6% 3 7% 5% 5% 6% 4 5% 6% 39%	5780
February	1st to 10th	Day	14% 8% 2 7% 5% 4 4 4 6% 6% 39%	1890
	11th to 20th	Day	15% 8% 3 8% 4 5% 4 4 5% 5% 39%	1919
	21st to end	Day	18% 10% 3 6% 4 4 3 3 4 6% 39%	1650
March	1st to 10th	Day	21% 5% 2 5% 3 4 4 3 4 6% 45%	4563
	11th to 20th	Day	12% 6% 2 6% 5% 4 4 3 5% 8% 43%	4980
	21st to end	Day	18% 6% 2 6% 4 4 4 3 5% 6% 43%	5736
April	1st to 10th	Day	16% 9% 2 6% 4 5% 4 3 5% 7% 40%	2400
	11th to 20th	Day	15% 7% 2 5% 4 5% 4 4 5% 7% 41%	2374
	21st to end	Day	16% 6% 2 6% 4 4 4 4 6% 7% 40%	2400
May	1st to 10th	Day	25% 7% 2 6% 4 4 5% 4 6% 8% 29%	5832
	11th to 20th	Day	25% 8% 3 7% 4 3 3 3 5% 7% 32%	6318
	21st to end	Day	19% 6% 2 6% 4 4 5% 4 6% 8% 37%	6949
June	1st to 10th	Day	13% 6% 2 6% 4 5% 6% 5% 7% 8% 39%	2800
	11th to 20th	Day	13% 6% 3 6% 5% 4 5% 5% 6% 9% 37%	2800
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 6% 10% 42%	2800
July	1st to 10th	Day	8% 5% 2 7% 5% 5% 6% 5% 7% 11% 39%	6360
	11th to 20th	Day	10% 8% 3 7% 5% 5% 5% 5% 9% 11% 32%	6360
	21st to end	Day	10% 7% 3 7% 5% 5% 5% 4 6% 10% 39%	6712
August	1st to 10th	Day	19% 5% 2 7% 4 5% 5% 4 6% 7% 34%	4234
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 7% 9% 41%	3894
	21st to end	Day	12% 5% 2 5% 4 4 4 3 5% 7% 50%	4312
September	1st to 10th	Day	15% 5% 2 6% 4 4 5% 4 4 7% 45%	2400
	11th to 20th	Day	13% 5% 2 3 3 3 4 3 5% 7% 50%	2390
	21st to end	Day	19% 7% 3 7% 4 5% 5% 3 5% 6% 37%	2164
October	1st to 10th	Day	17% 5% 2 6% 4 4 4 3 5% 7% 44%	2000
	11th to 20th	Day	15% 6% 2 5% 4 3 4 3 4 7% 47%	2000
	21st to end	Day	18% 6% 1 4 3 4 4 3 5% 6% 45%	2158
November	1st to 10th	Day	12% 6% 2 5% 3 2 3 3 5% 7% 52%	1851
	11th to 20th	Day	15% 5% 2 5% 5% 3 4 4 5% 7% 46%	1890
	21st to end	Day	16% 7% 2 5% 3 4 3 4 6% 7% 43%	1717
December	1st to 10th	Day	13% 9% 3 6% 4 5% 4 3 5% 6% 43%	2680
	11th to 20th	Day	21% 9% 2 5% 3 3 3 2 5% 6% 43%	3066
	21st to end	Day	16% 6% 2 6% 5% 5% 5% 4 6% 6% 39%	4048
January	1st to 10th	Night	11% 7% 3 7% 4 4 4 3 5% 7% 45%	8234
	11th to 20th	Night	15% 8% 2 5% 4 3 3 3 5% 6% 47%	7996
	21st to end	Night	15% 8% 2 6% 3 3 3 3 4 6% 46%	8401
February	1st to 10th	Night	16% 9% 3 6% 4 4 3 4 5% 6% 41%	2730
	11th to 20th	Night	17% 7% 3 7% 5% 4 4 3 5% 6% 40%	2476
	21st to end	Night	17% 8% 3 5% 4 3 4 3 6% 6% 40%	1980
March	1st to 10th	Night	17% 8% 2 6% 4 3 4 3 4 6% 44%	5275
	11th to 20th	Night	11% 7% 3 6% 4 3 4 3 4 6% 50%	4979
	21st to end	Night	14% 8% 3 6% 4 4 4 3 5% 6% 44%	5194
April	1st to 10th	Night	17% 6% 3 7% 5% 4 4 4 5% 6% 40%	2000
	11th to 20th	Night	15% 7% 3 6% 5% 3 5% 3 5% 8% 41%	1975
	21st to end	Night	17% 7% 2 4 3 4 5% 3 5% 7% 44%	2000
May	1st to 10th	Night	24% 8% 3 7% 4 5% 5% 4 5% 8% 28%	4135
	11th to 20th	Night	24% 9% 3 6% 4 3 4 4 5% 7% 31%	3575
	21st to end	Night	21% 6% 3 6% 3 3 4 3 5% 8% 38%	3926
June	1st to 10th	Night	14% 6% 3 6% 6% 3 4 4 6% 8% 42%	1600
	11th to 20th	Night	12% 6% 2 6% 4 5% 5% 4 6% 10% 39%	1600
	21st to end	Night	11% 5% 2 6% 4 3 4 5% 7% 10% 43%	1600
July	1st to 10th	Night	8% 6% 2 8% 5% 5% 6% 5% 6% 10% 39%	3600
	11th to 20th	Night	13% 8% 3 8% 5% 6% 5% 5% 8% 9% 30%	3600
	21st to end	Night	11% 6% 2 5% 4 4 5% 4 7% 8% 44%	4123
August	1st to 10th	Night	20% 6% 2 5% 4 5% 5% 4 6% 8% 35%	2915
	11th to 20th	Night	13% 7% 3 7% 4 4 4 4 6% 7% 41%	3121
	21st to end	Night	11% 5% 2 5% 4 3 4 5% 6% 7% 48%	3586
September	1st to 10th	Night	14% 6% 2 7% 3 4 3 3 5% 6% 47%	2000
	11th to 20th	Night	12% 6% 2 5% 3 3 4 3 5% 6% 52%	2010
	21st to end	Night	20% 6% 2 5% 5% 3 3 4 5% 6% 40%	2232
October	1st to 10th	Night	19% 6% 2 5% 4 4 3 2 4 6% 44%	2400
	11th to 20th	Night	16% 6% 2 5% 2 3 3 3 5% 6% 50%	2400
	21st to end	Night	17% 7% 2 4 3 3 3 3 5% 6% 49%	2680
November	1st to 10th	Night	11% 6% 2 5% 3 3 4 3 5% 6% 52%	2667
	11th to 20th	Night	16% 8% 2 5% 3 3 3 3 5% 5% 47%	2730
	21st to end	Night	13% 6% 2 5% 5% 5% 4 4 4 7% 45%	2899
December	1st to 10th	Night	12% 6% 3 6% 5% 3 4 3 5% 7% 45%	4720
	11th to 20th	Night	22% 7% 2 5% 3 3 3 3 4 6% 41%	5348
	21st to end	Night	18% 7% 3 7% 4 4 4 3 5% 6% 39%	7150

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 10% 26% 17% 2	4662
	11th to 20th	Day	44% 3 8% 21% 17% 6%	4902
	21st to end	Day	44% 5% 12% 24% 14% 1	5780
February	1st to 10th	Day	43% 5% 13% 24% 12% 2	1890
	11th to 20th	Day	46% 5% 9% 24% 14% 2	1928
	21st to end	Day	47% 4 10% 23% 13% 4	1650
March	1st to 10th	Day	41% 3 8% 24% 17% 6%	4566
	11th to 20th	Day	39% 4 10% 28% 14% 5%	4980
	21st to end	Day	43% 4 9% 17% 22% 5%	5736
April	1st to 10th	Day	44% 5% 11% 20% 15% 5%	2400
	11th to 20th	Day	41% 6% 11% 21% 16% 4	2374
	21st to end	Day	42% 6% 11% 19% 18% 4	2400
May	1st to 10th	Day	52% 6% 12% 19% 10% 2	5841
	11th to 20th	Day	51% 6% 9% 23% 11% 1	6322
	21st to end	Day	44% 7% 11% 23% 15% 1	6949
June	1st to 10th	Day	39% 8% 13% 23% 15% 2	2800
	11th to 20th	Day	42% 8% 12% 24% 11% 3	2800
	21st to end	Day	36% 9% 13% 25% 16% 1	2800
July	1st to 10th	Day	38% 11% 14% 21% 15% 2	6290
	11th to 20th	Day	43% 9% 18% 21% 9% 1	6285
	21st to end	Day	39% 7% 10% 21% 22% 1	6519
August	1st to 10th	Day	47% 8% 12% 22% 10%	4221
	11th to 20th	Day	38% 7% 11% 30% 13% 1	3931
	21st to end	Day	33% 7% 10% 28% 20% 2	4312
September	1st to 10th	Day	40% 6% 11% 21% 20% 3	2400
	11th to 20th	Day	32% 6% 9% 27% 22% 4	2390
	21st to end	Day	49% 4 9% 17% 19% 2	2164
October	1st to 10th	Day	36% 5% 9% 17% 28% 5%	3260
	11th to 20th	Day	26% 4 12% 26% 25% 7%	3240
	21st to end	Day	24% 3 12% 27% 28% 4	3460
November	1st to 10th	Day	33% 4 13% 25% 20% 4	1851
	11th to 20th	Day	38% 5% 11% 24% 20% 2	1890
	21st to end	Day	39% 5% 12% 30% 12% 2	1717
December	1st to 10th	Day	42% 4 16% 25% 12% 2	2680
	11th to 20th	Day	44% 3 12% 30% 10% 1	3066
	21st to end	Day	44% 5% 13% 22% 15% 2	4048
January	1st to 10th	Night	40% 4 13% 25% 16% 4	8234
	11th to 20th	Night	39% 3 11% 22% 19% 7%	8040
	21st to end	Night	41% 3 8% 26% 19% 2	8401
February	1st to 10th	Night	44% 5% 12% 25% 12% 2	2730
	11th to 20th	Night	45% 4 9% 21% 18% 3	2478
	21st to end	Night	43% 5% 9% 22% 16% 5%	1980
March	1st to 10th	Night	42% 4 9% 24% 12% 9%	5285
	11th to 20th	Night	35% 5% 13% 27% 14% 5%	4980
	21st to end	Night	42% 4 7% 17% 25% 4	5194
April	1st to 10th	Night	44% 5% 10% 20% 17% 4	2000
	11th to 20th	Night	41% 6% 10% 20% 20% 4	1975
	21st to end	Night	40% 5% 10% 21% 19% 5%	2000
May	1st to 10th	Night	54% 6% 11% 15% 11% 2	4142
	11th to 20th	Night	52% 7% 11% 18% 11% 1	3576
	21st to end	Night	44% 7% 11% 21% 14% 2	3927
June	1st to 10th	Night	39% 7% 10% 22% 20% 1	1600
	11th to 20th	Night	39% 8% 14% 24% 14% 1	1600
	21st to end	Night	34% 9% 15% 26% 15% 2	1600
July	1st to 10th	Night	40% 10% 15% 19% 14% 2	3560
	11th to 20th	Night	48% 9% 16% 18% 9% 1	3552
	21st to end	Night	35% 7% 12% 23% 21% 1	4002
August	1st to 10th	Night	46% 8% 18% 19% 9% 1	2904
	11th to 20th	Night	41% 6% 12% 25% 15% 1	3150
	21st to end	Night	33% 6% 12% 29% 20% 1	3586
September	1st to 10th	Night	38% 7% 10% 21% 22% 3	2000
	11th to 20th	Night	33% 5% 9% 24% 26% 4	2010
	21st to end	Night	44% 6% 8% 19% 21% 2	2232
October	1st to 10th	Night	42% 5% 9% 21% 22% 2	3920
	11th to 20th	Night	24% 4 11% 28% 27% 5%	3899
	21st to end	Night	26% 3 11% 32% 24% 4	4316
November	1st to 10th	Night	32% 5% 12% 26% 20% 5%	2667
	11th to 20th	Night	39% 5% 9% 22% 20% 5%	2730
	21st to end	Night	38% 5% 12% 27% 17% 1	2899
December	1st to 10th	Night	39% 4 13% 30% 13% 2	4720
	11th to 20th	Night	45% 3 11% 25% 13% 3	5348
	21st to end	Night	45% 5% 11% 20% 18% 1	7150

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	34% 23% 29% 12% 1 1	220
	11th to 20th	Day	39% 28% 26% 6% 1	261
	21st to end	Day	32% 31% 23% 12% 2	363
February	1st to 10th	Day	29% 28% 32% 9% 2	330
	11th to 20th	Day	37% 25% 31% 6% 1	437
	21st to end	Day	33% 25% 28% 12% 2	414
March	1st to 10th	Day	33% 20% 31% 13% 3	500
	11th to 20th	Day	31% 23% 30% 12% 2 1	500
	21st to end	Day	30% 26% 30% 10% 4 1	550
April	1st to 10th	Day	30% 26% 29% 10% 3 1	500
	11th to 20th	Day	27% 22% 29% 14% 5% 1	492
	21st to end	Day	27% 18% 36% 14% 4 1	500
May	1st to 10th	Day	32% 20% 28% 15% 5% 1	503
	11th to 20th	Day	24% 16% 34% 18% 7% 1	527
	21st to end	Day	22% 10% 27% 24% 15% 2	573
June	1st to 10th	Day	18% 12% 32% 24% 12% 2	530
	11th to 20th	Day	19% 11% 30% 26% 13% 2	530
	21st to end	Day	14% 12% 30% 28% 13% 4	530
July	1st to 10th	Day	13% 6% 24% 31% 20% 6%	525
	11th to 20th	Day	9% 4 26% 35% 21% 4	524
	21st to end	Day	12% 6% 30% 33% 16% 3	576
August	1st to 10th	Day	13% 6% 28% 29% 17% 7%	526
	11th to 20th	Day	14% 5% 22% 35% 17% 7%	519
	21st to end	Day	11% 9% 25% 29% 17% 8%	583
September	1st to 10th	Day	19% 11% 22% 26% 15% 7%	530
	11th to 20th	Day	17% 6% 25% 28% 16% 8%	530
	21st to end	Day	24% 13% 24% 25% 11% 3	530
October	1st to 10th	Day	21% 9% 28% 21% 14% 6%	530
	11th to 20th	Day	22% 17% 27% 22% 10% 2	530
	21st to end	Day	21% 18% 34% 16% 9% 2	559
November	1st to 10th	Day	22% 16% 31% 20% 9% 3	425
	11th to 20th	Day	23% 21% 32% 18% 5%	430
	21st to end	Day	28% 25% 28% 16% 3	257
December	1st to 10th	Day	32% 26% 27% 10% 4	220
	11th to 20th	Day	36% 24% 29% 8% 3	220
	21st to end	Day	29% 24% 29% 12% 6%	242
January	1st to 10th	Night	22% 25% 36% 15% 2	840
	11th to 20th	Night	29% 21% 29% 19% 2	840
	21st to end	Night	21% 24% 38% 16% 1	924
February	1st to 10th	Night	25% 21% 35% 18% 1	840
	11th to 20th	Night	30% 25% 34% 10% 1	804
	21st to end	Night	27% 21% 35% 14% 2	660
March	1st to 10th	Night	24% 24% 31% 18% 3	800
	11th to 20th	Night	24% 23% 31% 16% 5% 1	800
	21st to end	Night	22% 17% 40% 16% 4	880
April	1st to 10th	Night	23% 22% 35% 16% 3	800
	11th to 20th	Night	21% 15% 36% 23% 5%	791
	21st to end	Night	21% 18% 33% 23% 6%	800
May	1st to 10th	Night	24% 12% 33% 24% 5%	643
	11th to 20th	Night	20% 12% 35% 27% 6%	394
	21st to end	Night	17% 9% 25% 37% 11% 1	433
June	1st to 10th	Night	14% 6% 31% 38% 11%	400
	11th to 20th	Night	12% 6% 31% 41% 10%	400
	21st to end	Night	11% 4 28% 43% 13% 1	400
July	1st to 10th	Night	11% 5% 24% 40% 19% 1	390
	11th to 20th	Night	7% 3 20% 44% 24% 1	388
	21st to end	Night	9% 5% 23% 42% 19% 2	521
August	1st to 10th	Night	12% 3 20% 40% 22% 3	597
	11th to 20th	Night	14% 5% 17% 38% 24% 2	738
	21st to end	Night	13% 4 19% 41% 21% 2	880
September	1st to 10th	Night	16% 6% 28% 30% 19% 3	800
	11th to 20th	Night	13% 5% 21% 34% 23% 3	800
	21st to end	Night	22% 6% 24% 30% 17% 1	800
October	1st to 10th	Night	22% 9% 25% 25% 17% 3	800
	11th to 20th	Night	19% 14% 28% 28% 11%	800
	21st to end	Night	22% 15% 31% 24% 8%	880
November	1st to 10th	Night	17% 13% 34% 26% 10% 1	820
	11th to 20th	Night	23% 19% 28% 23% 6% 1	840
	21st to end	Night	21% 18% 34% 21% 6%	840
December	1st to 10th	Night	27% 19% 32% 17% 5% 1	840
	11th to 20th	Night	22% 20% 34% 20% 4	840
	21st to end	Night	23% 20% 32% 23% 2	924

Page generated at 2026-02-13 01:42:11. Version ac07

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