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 2024-01-15.

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% 6% 3 5% 5% 3 5% 5% 6% 7% 40%	74740
	Night	15% 6% 3 5% 5% 3 4 4 5% 7% 43%	75021
Transparency	Day	42% 7% 12% 23% 15% 2	74450
	Night	41% 6% 12% 23% 16% 3	74845
Seeing	Day	23% 16% 28% 20% 10% 3	13825
	Night	20% 15% 30% 25% 9% 1	23256

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	12% 7% 4 5% 5% 4 5% 5% 6% 6% 41%	1517
	11th to 20th	Day	15% 7% 2 6% 7% 3 5% 4 6% 6% 38%	1540
	21st to end	Day	14% 8% 4 6% 6% 4 5% 5% 5% 6% 39%	1782
February	1st to 10th	Day	16% 8% 3 5% 6% 3 4 5% 6% 6% 38%	1620
	11th to 20th	Day	16% 7% 3 7% 5% 4 4 4 5% 5% 39%	1680
	21st to end	Day	19% 10% 4 6% 4 3 3 4 4 5% 37%	1480
March	1st to 10th	Day	13% 5% 2 7% 5% 3 4 4 4 6% 46%	1828
	11th to 20th	Day	16% 7% 3 6% 6% 3 5% 4 5% 7% 38%	1980
	21st to end	Day	21% 7% 2 5% 5% 3 4 4 4 7% 38%	2282
April	1st to 10th	Day	14% 8% 3 5% 4 3 4 4 5% 8% 41%	2160
	11th to 20th	Day	15% 6% 3 4 4 3 5% 5% 4 8% 42%	2134
	21st to end	Day	17% 5% 3 6% 5% 3 5% 5% 6% 8% 38%	2160
May	1st to 10th	Day	18% 7% 2 6% 5% 3 5% 5% 5% 7% 36%	2312
	11th to 20th	Day	20% 6% 2 5% 5% 3 5% 5% 6% 7% 36%	2478
	21st to end	Day	14% 6% 2 6% 5% 4 4 5% 6% 8% 40%	2725
June	1st to 10th	Day	14% 5% 2 5% 5% 3 6% 6% 7% 9% 39%	2520
	11th to 20th	Day	13% 6% 3 6% 6% 3 5% 5% 6% 9% 37%	2520
	21st to end	Day	11% 5% 2 5% 6% 3 6% 5% 6% 10% 42%	2520
July	1st to 10th	Day	10% 5% 2 5% 6% 4 6% 7% 6% 10% 38%	2520
	11th to 20th	Day	7% 4 2 5% 5% 4 5% 6% 9% 10% 43%	2520
	21st to end	Day	9% 7% 3 6% 6% 5% 7% 6% 6% 9% 36%	2667
August	1st to 10th	Day	10% 5% 3 6% 6% 4 6% 6% 7% 9% 39%	2327
	11th to 20th	Day	11% 5% 3 5% 6% 4 4 6% 6% 10% 39%	2156
	21st to end	Day	14% 5% 2 4 6% 3 5% 5% 6% 8% 42%	2376
September	1st to 10th	Day	16% 5% 2 5% 5% 3 5% 5% 4 7% 43%	2160
	11th to 20th	Day	14% 5% 2 3 4 2 4 4 5% 7% 50%	2152
	21st to end	Day	18% 7% 3 5% 5% 3 5% 4 5% 6% 39%	1948
October	1st to 10th	Day	18% 5% 2 4 4 3 4 4 5% 8% 42%	1800
	11th to 20th	Day	16% 6% 2 5% 4 2 4 4 4 7% 46%	1800
	21st to end	Day	19% 7% 2 4 4 2 4 4 5% 6% 43%	1943
November	1st to 10th	Day	13% 6% 3 4 3 2 3 4 4 6% 52%	1671
	11th to 20th	Day	16% 4 2 4 5% 3 4 4 5% 6% 47%	1710
	21st to end	Day	16% 5% 3 5% 4 3 4 5% 6% 7% 44%	1554
December	1st to 10th	Day	17% 9% 3 6% 5% 3 4 4 5% 7% 38%	1520
	11th to 20th	Day	20% 7% 3 5% 4 2 4 3 5% 7% 41%	1906
	21st to end	Day	16% 6% 3 6% 7% 4 5% 6% 6% 6% 35%	2772
January	1st to 10th	Night	14% 7% 3 5% 5% 2 5% 4 4 7% 45%	2649
	11th to 20th	Night	18% 7% 2 5% 5% 4 4 5% 5% 6% 38%	2505
	21st to end	Night	13% 7% 3 6% 5% 3 4 5% 5% 6% 44%	2574
February	1st to 10th	Night	17% 9% 3 5% 5% 3 4 4 5% 6% 39%	2340
	11th to 20th	Night	17% 7% 3 6% 6% 3 4 4 5% 6% 39%	2164
	21st to end	Night	18% 8% 3 4 4 2 5% 5% 5% 6% 40%	1776
March	1st to 10th	Night	14% 5% 2 5% 5% 3 4 4 5% 7% 46%	2117
	11th to 20th	Night	18% 7% 3 5% 4 3 4 4 4 5% 43%	1979
	21st to end	Night	17% 7% 3 5% 5% 3 4 3 4 6% 43%	2072
April	1st to 10th	Night	16% 5% 3 6% 5% 3 4 5% 5% 6% 41%	1800
	11th to 20th	Night	14% 7% 3 5% 6% 2 5% 4 5% 8% 42%	1775
	21st to end	Night	18% 7% 2 4 4 3 5% 4 5% 7% 42%	1800
May	1st to 10th	Night	18% 8% 3 6% 5% 3 6% 5% 5% 6% 36%	1660
	11th to 20th	Night	17% 7% 3 6% 5% 2 5% 6% 5% 7% 37%	1415
	21st to end	Night	14% 6% 3 5% 4 3 4 4 5% 10% 41%	1550
June	1st to 10th	Night	15% 5% 3 5% 6% 2 4 4 6% 8% 42%	1440
	11th to 20th	Night	11% 6% 3 6% 4 4 6% 5% 6% 10% 39%	1440
	21st to end	Night	10% 4 2 4 5% 2 4 6% 7% 11% 44%	1440
July	1st to 10th	Night	10% 5% 2 7% 6% 4 6% 5% 6% 10% 39%	1440
	11th to 20th	Night	7% 4 1 5% 6% 4 5% 5% 8% 10% 45%	1440
	21st to end	Night	9% 6% 2 6% 5% 2 5% 6% 8% 10% 42%	1648
August	1st to 10th	Night	9% 6% 2 4 5% 4 5% 6% 8% 9% 43%	1611
	11th to 20th	Night	12% 5% 3 7% 6% 4 5% 6% 6% 8% 39%	1727
	21st to end	Night	13% 5% 2 5% 5% 3 5% 7% 6% 7% 43%	1980
September	1st to 10th	Night	15% 6% 2 6% 4 3 3 4 5% 7% 46%	1800
	11th to 20th	Night	13% 6% 2 3 3 2 3 4 5% 6% 53%	1808
	21st to end	Night	17% 5% 2 4 6% 3 4 5% 6% 6% 43%	2008
October	1st to 10th	Night	20% 6% 2 5% 4 3 4 3 4 6% 43%	2160
	11th to 20th	Night	16% 6% 2 4 3 3 3 4 5% 6% 49%	2160
	21st to end	Night	18% 7% 2 3 3 2 3 4 4 6% 47%	2412
November	1st to 10th	Night	11% 5% 2 4 4 2 4 3 5% 6% 52%	2407
	11th to 20th	Night	16% 7% 2 4 4 2 4 4 5% 5% 47%	2470
	21st to end	Night	13% 5% 2 4 5% 4 5% 5% 5% 7% 46%	2622
December	1st to 10th	Night	18% 6% 3 5% 5% 3 5% 4 5% 7% 38%	2660
	11th to 20th	Night	18% 6% 2 5% 5% 3 5% 4 5% 6% 42%	3288
	21st to end	Night	17% 7% 3 6% 5% 3 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	42% 5% 13% 23% 14% 4	1518
	11th to 20th	Day	46% 6% 14% 20% 12% 3	1540
	21st to end	Day	45% 6% 10% 24% 14% 3	1782
February	1st to 10th	Day	45% 6% 14% 23% 10% 2	1620
	11th to 20th	Day	46% 6% 9% 25% 13% 2	1689
	21st to end	Day	48% 4 9% 21% 13% 4	1480
March	1st to 10th	Day	40% 4 12% 26% 15% 3	1831
	11th to 20th	Day	45% 5% 10% 21% 15% 4	1980
	21st to end	Day	48% 4 7% 20% 17% 3	2282
April	1st to 10th	Day	42% 5% 11% 21% 16% 5%	2160
	11th to 20th	Day	40% 6% 11% 22% 17% 4	2134
	21st to end	Day	43% 6% 12% 18% 17% 4	2160
May	1st to 10th	Day	47% 7% 9% 19% 15% 3	2312
	11th to 20th	Day	47% 7% 10% 20% 14% 2	2482
	21st to end	Day	41% 8% 14% 21% 13% 2	2725
June	1st to 10th	Day	40% 8% 13% 24% 14% 1	2520
	11th to 20th	Day	42% 9% 13% 23% 11% 3	2520
	21st to end	Day	36% 9% 13% 25% 15% 1	2520
July	1st to 10th	Day	39% 11% 12% 22% 14% 3	2450
	11th to 20th	Day	31% 10% 16% 25% 15% 3	2445
	21st to end	Day	41% 9% 11% 21% 16% 2	2518
August	1st to 10th	Day	39% 10% 13% 22% 15% 1	2314
	11th to 20th	Day	39% 9% 14% 22% 15% 2	2156
	21st to end	Day	38% 9% 12% 22% 17% 3	2376
September	1st to 10th	Day	41% 7% 11% 20% 18% 3	2160
	11th to 20th	Day	33% 6% 10% 26% 22% 4	2152
	21st to end	Day	47% 4 8% 18% 21% 3	1948
October	1st to 10th	Day	41% 6% 11% 23% 17% 2	1800
	11th to 20th	Day	38% 5% 11% 24% 20% 2	1800
	21st to end	Day	41% 5% 10% 26% 17% 2	1943
November	1st to 10th	Day	34% 4 12% 26% 19% 4	1671
	11th to 20th	Day	38% 5% 10% 24% 20% 2	1710
	21st to end	Day	39% 5% 12% 31% 11% 2	1554
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	41% 5% 10% 25% 16% 3	2649
	11th to 20th	Night	46% 5% 13% 23% 11% 2	2505
	21st to end	Night	40% 5% 10% 26% 16% 3	2574
February	1st to 10th	Night	46% 5% 13% 24% 11% 2	2340
	11th to 20th	Night	46% 4 10% 20% 17% 4	2166
	21st to end	Night	44% 5% 8% 22% 16% 5%	1776
March	1st to 10th	Night	38% 4 12% 26% 18% 3	2127
	11th to 20th	Night	43% 5% 9% 22% 16% 4	1980
	21st to end	Night	43% 4 9% 20% 18% 5%	2072
April	1st to 10th	Night	43% 5% 11% 20% 17% 4	1800
	11th to 20th	Night	39% 6% 10% 20% 20% 4	1775
	21st to end	Night	42% 5% 10% 20% 18% 5%	1800
May	1st to 10th	Night	48% 6% 10% 16% 16% 3	1660
	11th to 20th	Night	45% 7% 12% 15% 18% 2	1416
	21st to end	Night	40% 9% 15% 18% 15% 3	1551
June	1st to 10th	Night	40% 8% 10% 22% 19% 1	1440
	11th to 20th	Night	39% 9% 15% 22% 15% 1	1440
	21st to end	Night	34% 9% 14% 27% 14% 2	1440
July	1st to 10th	Night	40% 12% 14% 18% 14% 3	1400
	11th to 20th	Night	32% 10% 16% 24% 15% 2	1392
	21st to end	Night	34% 10% 15% 23% 16% 2	1556
August	1st to 10th	Night	35% 11% 15% 23% 15% 1	1600
	11th to 20th	Night	41% 9% 14% 19% 16% 2	1727
	21st to end	Night	37% 7% 15% 20% 18% 2	1980
September	1st to 10th	Night	39% 7% 10% 21% 20% 3	1800
	11th to 20th	Night	32% 5% 9% 23% 26% 4	1808
	21st to end	Night	41% 7% 8% 20% 22% 2	2008
October	1st to 10th	Night	44% 6% 11% 22% 16% 2	2160
	11th to 20th	Night	36% 6% 12% 28% 17% 3	2160
	21st to end	Night	39% 4 9% 27% 18% 2	2412
November	1st to 10th	Night	33% 5% 12% 26% 19% 5%	2407
	11th to 20th	Night	40% 5% 9% 23% 20% 4	2470
	21st to end	Night	37% 5% 12% 28% 16% 2	2622
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% 28% 28% 8% 1	198
	21st to end	Day	29% 33% 23% 11% 3	264
February	1st to 10th	Day	34% 28% 28% 8% 1	240
	11th to 20th	Day	34% 26% 33% 6% 1	348
	21st to end	Day	34% 24% 28% 12% 2	346
March	1st to 10th	Day	31% 20% 32% 14% 3	420
	11th to 20th	Day	31% 24% 30% 11% 3 1	420
	21st to end	Day	31% 27% 28% 10% 4 1	462
April	1st to 10th	Day	27% 27% 30% 11% 4 1	420
	11th to 20th	Day	25% 21% 29% 16% 7% 2	412
	21st to end	Day	29% 20% 35% 12% 3 1	420
May	1st to 10th	Day	32% 18% 29% 14% 5% 1	423
	11th to 20th	Day	23% 16% 34% 18% 7% 1	447
	21st to end	Day	21% 9% 26% 25% 16% 2	485
June	1st to 10th	Day	18% 12% 32% 25% 12% 2	450
	11th to 20th	Day	19% 11% 32% 25% 11% 2	450
	21st to end	Day	14% 13% 29% 28% 12% 4	450
July	1st to 10th	Day	14% 5% 24% 29% 21% 7%	445
	11th to 20th	Day	9% 4 25% 37% 22% 4	444
	21st to end	Day	12% 7% 30% 31% 17% 3	488
August	1st to 10th	Day	11% 7% 27% 29% 18% 7%	446
	11th to 20th	Day	14% 5% 21% 35% 19% 7%	439
	21st to end	Day	12% 8% 25% 30% 16% 9%	495
September	1st to 10th	Day	20% 10% 20% 26% 15% 8%	450
	11th to 20th	Day	18% 6% 27% 25% 15% 9%	450
	21st to end	Day	22% 15% 23% 25% 12% 4	450
October	1st to 10th	Day	24% 9% 27% 22% 14% 5%	450
	11th to 20th	Day	20% 17% 27% 24% 11% 1	450
	21st to end	Day	23% 18% 34% 15% 9% 2	476
November	1st to 10th	Day	21% 15% 30% 20% 10% 4	365
	11th to 20th	Day	23% 21% 32% 19% 5%	370
	21st to end	Day	22% 25% 31% 18% 4	214
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% 18% 30% 21% 2	737
	21st to end	Night	20% 23% 38% 17% 2	792
February	1st to 10th	Night	25% 22% 34% 17% 1	720
	11th to 20th	Night	28% 26% 33% 11% 1	703
	21st to end	Night	28% 22% 35% 13% 2	592
March	1st to 10th	Night	23% 23% 32% 19% 3	720
	11th to 20th	Night	25% 23% 31% 16% 5% 1	720
	21st to end	Night	22% 16% 41% 16% 5%	792
April	1st to 10th	Night	22% 23% 35% 16% 4	720
	11th to 20th	Night	20% 15% 36% 24% 6%	711
	21st to end	Night	22% 18% 32% 23% 6%	720
May	1st to 10th	Night	24% 13% 33% 25% 6%	580
	11th to 20th	Night	20% 11% 35% 27% 6%	354
	21st to end	Night	16% 8% 23% 39% 12% 1	389
June	1st to 10th	Night	15% 6% 30% 38% 11%	360
	11th to 20th	Night	11% 7% 32% 40% 10%	360
	21st to end	Night	11% 3 28% 45% 13%	360
July	1st to 10th	Night	11% 5% 25% 39% 19% 1	350
	11th to 20th	Night	7% 3 20% 44% 25% 1	348
	21st to end	Night	9% 5% 23% 41% 19% 2	468
August	1st to 10th	Night	10% 2 21% 41% 23% 3	537
	11th to 20th	Night	15% 4 17% 38% 24% 2	663
	21st to end	Night	13% 4 19% 40% 22% 2	792
September	1st to 10th	Night	16% 6% 27% 31% 18% 3	720
	11th to 20th	Night	14% 6% 22% 33% 23% 3	720
	21st to end	Night	19% 7% 25% 29% 18% 1	720
October	1st to 10th	Night	23% 9% 25% 24% 15% 3	720
	11th to 20th	Night	19% 13% 28% 29% 11%	720
	21st to end	Night	24% 15% 30% 22% 8%	792
November	1st to 10th	Night	16% 13% 34% 26% 10% 1	740
	11th to 20th	Night	23% 18% 28% 24% 7% 1	760
	21st to end	Night	19% 18% 34% 22% 6%	760
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 2024-01-11 22:33:45. Version ac07

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