Edja Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Edja Lake clear sky chart from 2005-11-06 to 2025-05-11.

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% 12% 4 9% 6% 5% 5% 4 5% 6% 30%	113870
	Night	16% 13% 4 10% 6% 5% 4 3 5% 6% 28%	115024
Transparency	Day	55% 5% 11% 19% 9% 1	117383
	Night	57% 5% 11% 18% 9% 1	119675
Seeing	Day	24% 16% 30% 19% 8% 2	14961
	Night	24% 12% 28% 26% 10% 1	24171

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% 20% 7% 19% 8% 5% 4 2 2 3 15%	3597
	11th to 20th	Day	11% 17% 6% 18% 9% 5% 4 3 3 4 20%	3570
	21st to end	Day	10% 18% 9% 13% 6% 5% 5% 4 5% 6% 20%	4080
February	1st to 10th	Day	12% 16% 6% 15% 8% 5% 3 4 5% 5% 21%	1800
	11th to 20th	Day	12% 17% 6% 13% 6% 4 4 2 4 5% 25%	1753
	21st to end	Day	17% 17% 4 9% 7% 5% 4 2 4 4 26%	1630
March	1st to 10th	Day	17% 17% 4 11% 6% 5% 4 3 4 5% 23%	4493
	11th to 20th	Day	12% 15% 6% 10% 6% 5% 5% 4 5% 6% 27%	4980
	21st to end	Day	16% 12% 3 8% 6% 4 4 3 4 5% 35%	5758
April	1st to 10th	Day	22% 14% 3 8% 5% 4 3 3 4 4 31%	2400
	11th to 20th	Day	22% 11% 3 7% 5% 3 3 3 4 5% 34%	2374
	21st to end	Day	22% 11% 4 8% 4 4 4 3 4 5% 31%	2590
May	1st to 10th	Day	19% 10% 3 8% 5% 5% 5% 4 5% 7% 30%	4566
	11th to 20th	Day	17% 8% 3 7% 5% 4 4 3 6% 8% 34%	4398
	21st to end	Day	16% 8% 3 7% 5% 5% 5% 4 6% 7% 36%	4837
June	1st to 10th	Day	21% 8% 3 9% 5% 5% 6% 4 6% 6% 27%	2660
	11th to 20th	Day	15% 6% 2 6% 5% 4 5% 4 7% 7% 37%	2660
	21st to end	Day	18% 7% 2 7% 7% 5% 5% 4 7% 7% 29%	2660
July	1st to 10th	Day	13% 8% 2 7% 6% 6% 5% 5% 7% 9% 31%	4440
	11th to 20th	Day	13% 7% 3 7% 5% 5% 5% 4 6% 8% 37%	4440
	21st to end	Day	11% 6% 2 6% 4 4 4 4 6% 8% 43%	4814
August	1st to 10th	Day	12% 7% 3 9% 6% 6% 7% 5% 8% 8% 31%	4378
	11th to 20th	Day	16% 7% 2 7% 5% 5% 5% 4 6% 7% 36%	4030
	21st to end	Day	12% 6% 2 8% 4 5% 5% 5% 7% 9% 37%	4180
September	1st to 10th	Day	15% 6% 2 6% 5% 4 4 4 5% 7% 42%	2280
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 5% 7% 43%	2280
	21st to end	Day	20% 7% 2 6% 5% 4 4 3 5% 8% 35%	2021
October	1st to 10th	Day	20% 9% 2 8% 4 4 4 4 4 6% 34%	1900
	11th to 20th	Day	24% 12% 3 8% 5% 4 4 3 5% 5% 26%	1900
	21st to end	Day	25% 12% 2 9% 4 4 4 4 6% 6% 25%	1929
November	1st to 10th	Day	16% 13% 4 8% 5% 4 4 4 5% 6% 32%	1726
	11th to 20th	Day	18% 14% 5% 11% 7% 4 5% 4 5% 5% 22%	1600
	21st to end	Day	24% 18% 5% 13% 5% 4 5% 3 3 4 17%	1600
December	1st to 10th	Day	20% 24% 7% 10% 6% 5% 4 3 4 4 11%	2600
	11th to 20th	Day	17% 17% 7% 12% 6% 5% 5% 3 4 4 20%	2986
	21st to end	Day	21% 19% 4 12% 5% 4 5% 3 3 4 18%	3960
January	1st to 10th	Night	13% 22% 7% 16% 7% 4 3 2 3 4 18%	6349
	11th to 20th	Night	12% 15% 6% 17% 8% 5% 5% 3 4 5% 20%	6315
	21st to end	Night	9% 18% 8% 13% 7% 7% 6% 4 4 5% 19%	6858
February	1st to 10th	Night	12% 16% 6% 13% 8% 6% 5% 3 4 5% 23%	2600
	11th to 20th	Night	13% 15% 5% 12% 6% 5% 5% 4 4 4 25%	2533
	21st to end	Night	13% 16% 5% 11% 7% 4 3 3 6% 5% 26%	1999
March	1st to 10th	Night	21% 18% 4 9% 5% 4 4 2 4 4 26%	5345
	11th to 20th	Night	12% 14% 5% 11% 6% 5% 5% 4 6% 7% 26%	4979
	21st to end	Night	15% 11% 4 10% 5% 4 3 3 5% 6% 33%	5174
April	1st to 10th	Night	21% 11% 3 8% 5% 4 3 3 5% 6% 30%	2000
	11th to 20th	Night	18% 11% 3 5% 5% 4 3 4 5% 5% 37%	1975
	21st to end	Night	23% 10% 2 7% 5% 4 3 3 4 5% 34%	1825
May	1st to 10th	Night	21% 11% 4 7% 5% 4 5% 4 5% 6% 28%	2594
	11th to 20th	Night	17% 8% 3 8% 4 4 5% 4 6% 6% 35%	2501
	21st to end	Night	15% 9% 3 7% 5% 4 5% 4 6% 7% 35%	2738
June	1st to 10th	Night	18% 8% 2 6% 5% 4 4 4 7% 8% 33%	1520
	11th to 20th	Night	15% 7% 2 7% 5% 4 4 4 5% 7% 40%	1520
	21st to end	Night	17% 7% 2 7% 6% 5% 4 3 5% 7% 36%	1520
July	1st to 10th	Night	12% 8% 3 8% 5% 6% 6% 4 7% 7% 34%	2520
	11th to 20th	Night	13% 8% 3 7% 4 4 5% 4 7% 8% 38%	2520
	21st to end	Night	9% 6% 2 6% 4 4 4 4 6% 8% 46%	2739
August	1st to 10th	Night	12% 6% 3 7% 5% 5% 5% 4 7% 8% 38%	2535
	11th to 20th	Night	16% 7% 2 5% 4 4 5% 4 6% 9% 38%	2785
	21st to end	Night	16% 6% 3 7% 4 4 4 4 7% 7% 38%	3444
September	1st to 10th	Night	13% 6% 3 7% 4 4 4 3 6% 6% 45%	1900
	11th to 20th	Night	15% 6% 2 5% 3 3 3 3 5% 8% 47%	1900
	21st to end	Night	19% 7% 2 7% 4 4 3 3 4 7% 40%	2156
October	1st to 10th	Night	20% 9% 2 6% 4 4 3 3 5% 6% 39%	2280
	11th to 20th	Night	22% 10% 4 8% 6% 5% 4 3 4 6% 29%	2280
	21st to end	Night	23% 10% 4 7% 5% 5% 4 3 5% 6% 27%	2667
November	1st to 10th	Night	18% 12% 4 10% 5% 5% 4 3 4 6% 29%	2569
	11th to 20th	Night	19% 13% 4 11% 6% 5% 5% 4 4 5% 26%	2800
	21st to end	Night	22% 17% 4 10% 6% 4 4 4 5% 5% 19%	2800
December	1st to 10th	Night	19% 19% 6% 14% 7% 6% 5% 3 5% 4 12%	4580
	11th to 20th	Night	22% 15% 5% 11% 5% 4 4 3 4 6% 23%	5208
	21st to end	Night	23% 20% 5% 12% 5% 4 3 2 4 4 19%	6996

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	74% 4 7% 11% 4	3598
	11th to 20th	Day	70% 4 7% 12% 8%	3600
	21st to end	Day	65% 4 8% 13% 9% 1	4080
February	1st to 10th	Day	65% 5% 8% 14% 6% 1	1800
	11th to 20th	Day	63% 3 11% 13% 9% 1	1762
	21st to end	Day	63% 4 8% 14% 10% 1	1630
March	1st to 10th	Day	64% 4 7% 11% 12% 2	4496
	11th to 20th	Day	57% 4 15% 14% 9% 1	4980
	21st to end	Day	52% 4 6% 20% 15% 2	5758
April	1st to 10th	Day	58% 4 7% 17% 12% 3	2400
	11th to 20th	Day	53% 4 7% 21% 12% 2	2374
	21st to end	Day	56% 5% 7% 17% 13% 3	2590
May	1st to 10th	Day	51% 7% 10% 20% 10% 2	4580
	11th to 20th	Day	46% 8% 13% 22% 10% 1	4402
	21st to end	Day	47% 7% 11% 18% 15% 2	4837
June	1st to 10th	Day	55% 6% 11% 17% 10% 1	2660
	11th to 20th	Day	43% 7% 12% 25% 11% 2	2660
	21st to end	Day	51% 8% 12% 19% 9%	2660
July	1st to 10th	Day	47% 5% 15% 26% 8%	4370
	11th to 20th	Day	45% 4 16% 27% 7%	4365
	21st to end	Day	39% 5% 15% 31% 9%	4661
August	1st to 10th	Day	50% 6% 15% 23% 7%	4364
	11th to 20th	Day	47% 5% 15% 27% 6%	4069
	21st to end	Day	42% 5% 16% 24% 12% 1	4180
September	1st to 10th	Day	41% 6% 14% 26% 12%	2280
	11th to 20th	Day	40% 7% 13% 29% 11% 1	2280
	21st to end	Day	46% 7% 14% 24% 9%	2021
October	1st to 10th	Day	53% 4 9% 28% 6%	3160
	11th to 20th	Day	55% 6% 12% 21% 6%	3140
	21st to end	Day	57% 4 18% 15% 5%	3154
November	1st to 10th	Day	51% 6% 13% 23% 6% 1	1726
	11th to 20th	Day	63% 7% 11% 13% 6%	1600
	21st to end	Day	72% 5% 10% 8% 5%	1600
December	1st to 10th	Day	77% 4 8% 10% 2	2600
	11th to 20th	Day	67% 5% 7% 14% 7%	2986
	21st to end	Day	72% 3 6% 16% 3	3960
January	1st to 10th	Night	73% 5% 11% 10% 2	6349
	11th to 20th	Night	67% 5% 10% 12% 5%	6360
	21st to end	Night	68% 4 7% 9% 11%	6858
February	1st to 10th	Night	64% 5% 9% 15% 7% 1	2600
	11th to 20th	Night	62% 5% 9% 17% 6% 1	2535
	21st to end	Night	59% 5% 9% 18% 8% 1	1999
March	1st to 10th	Night	62% 3 8% 12% 11% 3	5355
	11th to 20th	Night	57% 5% 13% 16% 7% 2	4980
	21st to end	Night	52% 4 8% 22% 11% 2	5174
April	1st to 10th	Night	54% 5% 10% 16% 13% 2	2000
	11th to 20th	Night	48% 5% 9% 23% 14% 2	1975
	21st to end	Night	53% 4 8% 17% 15% 2	1825
May	1st to 10th	Night	52% 9% 10% 18% 9% 2	2600
	11th to 20th	Night	45% 9% 14% 20% 10% 2	2502
	21st to end	Night	46% 8% 10% 20% 14% 2	2739
June	1st to 10th	Night	47% 8% 15% 21% 9% 1	1520
	11th to 20th	Night	42% 6% 13% 25% 12% 2	1520
	21st to end	Night	47% 8% 11% 21% 12%	1520
July	1st to 10th	Night	48% 4 17% 20% 11%	2480
	11th to 20th	Night	44% 5% 15% 29% 8%	2472
	21st to end	Night	35% 7% 15% 33% 11%	2651
August	1st to 10th	Night	44% 7% 13% 27% 9%	2525
	11th to 20th	Night	44% 5% 17% 27% 7%	2812
	21st to end	Night	44% 5% 14% 23% 11% 2	3444
September	1st to 10th	Night	38% 7% 13% 29% 12%	1900
	11th to 20th	Night	37% 6% 15% 33% 9%	1900
	21st to end	Night	44% 6% 13% 27% 9%	2156
October	1st to 10th	Night	45% 4 12% 28% 10%	3800
	11th to 20th	Night	51% 4 14% 23% 7%	3779
	21st to end	Night	55% 5% 16% 15% 9%	4392
November	1st to 10th	Night	55% 7% 13% 18% 7%	2569
	11th to 20th	Night	60% 6% 11% 15% 7% 1	2800
	21st to end	Night	67% 6% 11% 13% 2	2800
December	1st to 10th	Night	76% 3 10% 9% 2	4580
	11th to 20th	Night	64% 4 7% 14% 11%	5208
	21st to end	Night	71% 3 5% 12% 9%	6996

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	22% 20% 38% 17% 4 1	200
	11th to 20th	Day	30% 12% 38% 15% 6% 1	200
	21st to end	Day	21% 19% 35% 19% 6%	247
February	1st to 10th	Day	27% 27% 33% 10% 3	300
	11th to 20th	Day	26% 29% 36% 8% 1	300
	21st to end	Day	30% 19% 35% 14% 2	394
March	1st to 10th	Day	24% 20% 34% 17% 4	500
	11th to 20th	Day	26% 20% 32% 18% 4 1	500
	21st to end	Day	31% 17% 31% 15% 5% 1	550
April	1st to 10th	Day	33% 19% 25% 16% 6% 1	500
	11th to 20th	Day	35% 18% 21% 14% 9% 3	492
	21st to end	Day	32% 20% 29% 13% 6% 1	500
May	1st to 10th	Day	28% 14% 33% 16% 6% 3	503
	11th to 20th	Day	23% 16% 32% 19% 8% 2	487
	21st to end	Day	23% 17% 30% 21% 8% 2	529
June	1st to 10th	Day	25% 13% 33% 21% 7% 1	490
	11th to 20th	Day	18% 16% 30% 22% 12% 2	490
	21st to end	Day	20% 14% 32% 22% 10% 1	490
July	1st to 10th	Day	14% 8% 32% 34% 10% 2	485
	11th to 20th	Day	14% 10% 36% 26% 12% 2	484
	21st to end	Day	13% 8% 32% 29% 15% 2	532
August	1st to 10th	Day	17% 7% 28% 30% 15% 3	486
	11th to 20th	Day	19% 7% 26% 25% 16% 8%	479
	21st to end	Day	15% 13% 31% 21% 13% 6%	539
September	1st to 10th	Day	18% 13% 28% 22% 13% 6%	490
	11th to 20th	Day	15% 12% 24% 21% 17% 10%	490
	21st to end	Day	21% 12% 27% 19% 14% 7%	490
October	1st to 10th	Day	27% 14% 23% 21% 11% 3	490
	11th to 20th	Day	30% 21% 27% 14% 6% 1	490
	21st to end	Day	31% 14% 29% 19% 6%	454
November	1st to 10th	Day	27% 17% 29% 21% 5% 1	360
	11th to 20th	Day	27% 21% 33% 12% 7% 1	200
	21st to end	Day	33% 22% 30% 13% 2 1	200
December	1st to 10th	Day	29% 16% 35% 18% 3 1	200
	11th to 20th	Day	30% 25% 32% 10% 4 1	200
	21st to end	Day	29% 18% 32% 15% 5%	220
January	1st to 10th	Night	28% 13% 34% 19% 5%	800
	11th to 20th	Night	30% 15% 25% 24% 6%	800
	21st to end	Night	18% 12% 34% 28% 8% 1	880
February	1st to 10th	Night	20% 16% 35% 24% 4	800
	11th to 20th	Night	23% 16% 36% 20% 4	783
	21st to end	Night	23% 17% 30% 26% 5%	660
March	1st to 10th	Night	25% 18% 29% 24% 4	800
	11th to 20th	Night	24% 16% 30% 23% 6%	800
	21st to end	Night	23% 15% 30% 25% 8%	880
April	1st to 10th	Night	27% 16% 25% 26% 5%	800
	11th to 20th	Night	25% 16% 26% 23% 9% 1	791
	21st to end	Night	28% 13% 26% 24% 8%	625
May	1st to 10th	Night	26% 10% 31% 23% 10% 1	400
	11th to 20th	Night	22% 11% 28% 31% 9%	376
	21st to end	Night	16% 9% 36% 29% 9%	411
June	1st to 10th	Night	17% 9% 34% 34% 6% 1	380
	11th to 20th	Night	18% 9% 24% 33% 13% 1	380
	21st to end	Night	19% 6% 25% 36% 14%	380
July	1st to 10th	Night	12% 5% 25% 42% 16%	370
	11th to 20th	Night	13% 5% 21% 43% 18%	368
	21st to end	Night	11% 5% 25% 41% 17% 2	416
August	1st to 10th	Night	10% 6% 23% 39% 22% 1	394
	11th to 20th	Night	14% 3 17% 37% 26% 2	564
	21st to end	Night	16% 7% 25% 31% 19% 2	817
September	1st to 10th	Night	17% 5% 28% 31% 18% 1	760
	11th to 20th	Night	18% 6% 22% 30% 20% 4	760
	21st to end	Night	21% 9% 23% 27% 19% 1	760
October	1st to 10th	Night	25% 9% 27% 23% 14% 2	760
	11th to 20th	Night	29% 12% 28% 21% 8% 1	760
	21st to end	Night	30% 12% 28% 23% 6%	836
November	1st to 10th	Night	28% 16% 24% 24% 6% 1	780
	11th to 20th	Night	27% 16% 28% 20% 9% 1	800
	21st to end	Night	34% 13% 26% 21% 5%	800
December	1st to 10th	Night	31% 15% 29% 20% 5%	800
	11th to 20th	Night	27% 16% 30% 21% 5% 1	800
	21st to end	Night	34% 15% 26% 21% 4 1	880

Page generated at 2025-05-08 09:34:01. Version ac07

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