Lac Echo
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac Echo clear sky chart from 2005-11-06 to 2024-12-02.

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	17% 11% 4 9% 5% 5% 4 4 5% 6% 30%	101803
	Night	16% 13% 4 9% 5% 4 4 3 5% 6% 30%	97828
Transparency	Day	53% 5% 12% 20% 9% 1	105273
	Night	55% 4 12% 19% 9% 1	102447
Seeing	Day	25% 17% 30% 18% 7% 2	14510
	Night	24% 14% 28% 24% 9% 1	23588

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	15% 19% 7% 16% 8% 4 4 3 3 3 17%	2517
	11th to 20th	Day	14% 15% 7% 17% 8% 5% 4 3 4 5% 19%	2520
	21st to end	Day	12% 16% 7% 16% 8% 6% 5% 4 4 4 17%	2818
February	1st to 10th	Day	11% 19% 6% 13% 8% 5% 4 4 5% 6% 20%	1710
	11th to 20th	Day	12% 19% 6% 13% 6% 4 4 3 3 5% 26%	1672
	21st to end	Day	17% 16% 6% 8% 7% 5% 4 3 4 4 25%	1570
March	1st to 10th	Day	17% 18% 5% 11% 5% 4 4 3 4 5% 24%	3116
	11th to 20th	Day	11% 19% 7% 12% 7% 5% 4 3 4 5% 24%	3441
	21st to end	Day	12% 10% 2 7% 6% 5% 5% 4 6% 7% 37%	4056
April	1st to 10th	Day	21% 15% 4 8% 4 4 3 3 4 5% 29%	2280
	11th to 20th	Day	22% 11% 4 8% 5% 3 3 3 4 6% 33%	2254
	21st to end	Day	21% 12% 4 8% 5% 4 4 3 4 5% 29%	2441
May	1st to 10th	Day	20% 11% 4 8% 5% 5% 4 4 5% 6% 28%	4426
	11th to 20th	Day	18% 9% 3 8% 5% 5% 4 4 5% 7% 31%	4398
	21st to end	Day	18% 7% 3 8% 5% 4 5% 4 6% 7% 34%	4837
June	1st to 10th	Day	22% 9% 3 8% 5% 5% 4 4 5% 7% 28%	2660
	11th to 20th	Day	16% 6% 2 6% 5% 4 5% 4 7% 9% 35%	2660
	21st to end	Day	21% 7% 3 7% 6% 4 5% 4 7% 7% 28%	2660
July	1st to 10th	Day	13% 7% 3 8% 6% 5% 6% 4 7% 9% 31%	4440
	11th to 20th	Day	14% 8% 3 7% 5% 5% 5% 5% 6% 8% 35%	4440
	21st to end	Day	12% 7% 2 6% 4 4 4 4 5% 7% 45%	4814
August	1st to 10th	Day	15% 7% 3 8% 6% 5% 5% 5% 7% 9% 31%	4423
	11th to 20th	Day	17% 8% 3 6% 4 5% 4 4 6% 8% 36%	3993
	21st to end	Day	14% 7% 3 6% 4 5% 4 4 6% 9% 38%	4180
September	1st to 10th	Day	15% 7% 3 6% 4 4 4 3 4 7% 41%	2280
	11th to 20th	Day	15% 6% 2 6% 4 4 5% 3 6% 8% 43%	2269
	21st to end	Day	20% 8% 2 5% 4 3 3 3 5% 8% 38%	2046
October	1st to 10th	Day	20% 10% 3 7% 4 4 5% 4 5% 5% 33%	1900
	11th to 20th	Day	24% 13% 4 8% 5% 4 4 3 5% 5% 24%	1900
	21st to end	Day	25% 14% 3 8% 4 4 5% 3 4 5% 24%	1910
November	1st to 10th	Day	17% 13% 4 8% 5% 3 3 3 5% 7% 32%	1761
	11th to 20th	Day	19% 16% 5% 10% 7% 4 5% 4 4 5% 21%	1605
	21st to end	Day	22% 17% 6% 12% 6% 4 4 4 4 4 17%	1600
December	1st to 10th	Day	21% 22% 6% 12% 5% 6% 4 3 3 5% 13%	1528
	11th to 20th	Day	19% 15% 8% 14% 6% 3 4 3 4 5% 19%	1906
	21st to end	Day	22% 22% 7% 12% 5% 3 3 2 3 3 18%	2772
January	1st to 10th	Night	14% 20% 8% 11% 6% 4 4 3 4 5% 20%	4429
	11th to 20th	Night	11% 15% 6% 14% 8% 6% 5% 4 4 5% 21%	4440
	21st to end	Night	12% 18% 9% 14% 7% 7% 5% 3 4 4 18%	4821
February	1st to 10th	Night	12% 16% 5% 12% 9% 6% 5% 4 4 5% 22%	2470
	11th to 20th	Night	12% 15% 7% 12% 6% 6% 4 3 4 5% 26%	2392
	21st to end	Night	12% 17% 5% 10% 5% 5% 4 4 5% 6% 26%	1884
March	1st to 10th	Night	19% 14% 4 9% 5% 4 4 3 4 5% 30%	3724
	11th to 20th	Night	15% 19% 6% 10% 4 4 3 3 4 5% 26%	3516
	21st to end	Night	13% 11% 4 9% 5% 4 4 3 5% 5% 36%	3576
April	1st to 10th	Night	21% 13% 2 7% 4 5% 4 3 4 6% 30%	1900
	11th to 20th	Night	19% 10% 3 7% 4 4 4 3 5% 5% 36%	1875
	21st to end	Night	20% 11% 4 8% 3 4 4 3 4 6% 33%	1755
May	1st to 10th	Night	19% 12% 4 8% 5% 4 5% 3 6% 6% 28%	2514
	11th to 20th	Night	18% 8% 3 7% 4 5% 4 3 5% 6% 36%	2495
	21st to end	Night	18% 7% 3 7% 4 5% 5% 4 6% 7% 35%	2738
June	1st to 10th	Night	18% 8% 2 6% 5% 4 5% 4 6% 10% 31%	1520
	11th to 20th	Night	15% 7% 2 7% 5% 4 4 4 4 8% 40%	1520
	21st to end	Night	18% 7% 3 6% 5% 3 6% 4 5% 8% 34%	1520
July	1st to 10th	Night	15% 9% 3 7% 5% 5% 5% 4 5% 6% 36%	2520
	11th to 20th	Night	15% 8% 3 6% 4 3 4 4 6% 8% 40%	2520
	21st to end	Night	9% 7% 2 5% 4 4 5% 4 6% 8% 47%	2739
August	1st to 10th	Night	13% 8% 3 8% 5% 5% 5% 4 6% 7% 38%	2506
	11th to 20th	Night	16% 8% 3 6% 3 3 5% 4 5% 6% 41%	2800
	21st to end	Night	16% 7% 2 6% 4 4 4 3 5% 8% 40%	3476
September	1st to 10th	Night	14% 7% 3 7% 3 4 4 3 5% 6% 45%	1900
	11th to 20th	Night	14% 6% 2 5% 3 4 3 2 5% 6% 48%	1910
	21st to end	Night	17% 8% 3 5% 4 3 3 3 5% 6% 43%	2133
October	1st to 10th	Night	20% 9% 2 6% 4 4 4 3 5% 5% 37%	2280
	11th to 20th	Night	21% 12% 3 8% 6% 4 4 3 4 5% 30%	2280
	21st to end	Night	23% 13% 4 9% 5% 4 3 3 5% 6% 25%	2688
November	1st to 10th	Night	18% 13% 4 8% 5% 4 4 3 4 6% 29%	2537
	11th to 20th	Night	18% 13% 6% 10% 6% 5% 5% 3 4 5% 25%	2792
	21st to end	Night	20% 17% 6% 12% 6% 5% 4 3 4 5% 19%	2800
December	1st to 10th	Night	19% 20% 7% 11% 6% 4 4 3 4 4 16%	2686
	11th to 20th	Night	21% 17% 6% 11% 5% 3 4 3 3 4 23%	3288
	21st to end	Night	23% 23% 6% 11% 5% 3 3 2 3 3 17%	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	73% 3 9% 11% 4	2518
	11th to 20th	Day	68% 3 9% 13% 6%	2520
	21st to end	Day	70% 4 9% 11% 6% 1	2818
February	1st to 10th	Day	65% 4 7% 16% 7% 1	1710
	11th to 20th	Day	63% 3 10% 13% 10% 1	1681
	21st to end	Day	63% 3 9% 14% 10% 1	1570
March	1st to 10th	Day	63% 3 8% 14% 10% 1	3119
	11th to 20th	Day	63% 3 10% 14% 8% 2	3441
	21st to end	Day	46% 4 7% 24% 16% 2	4056
April	1st to 10th	Day	58% 3 7% 18% 11% 3	2280
	11th to 20th	Day	54% 3 6% 21% 13% 2	2254
	21st to end	Day	58% 4 7% 15% 13% 3	2441
May	1st to 10th	Day	55% 5% 8% 21% 9% 2	4440
	11th to 20th	Day	50% 6% 14% 20% 9% 1	4402
	21st to end	Day	48% 5% 12% 19% 14% 1	4837
June	1st to 10th	Day	55% 5% 10% 18% 11% 1	2660
	11th to 20th	Day	43% 6% 13% 25% 11% 2	2660
	21st to end	Day	52% 6% 14% 19% 10%	2660
July	1st to 10th	Day	45% 7% 14% 25% 8%	4370
	11th to 20th	Day	43% 7% 16% 27% 7%	4365
	21st to end	Day	37% 5% 15% 33% 10%	4661
August	1st to 10th	Day	48% 7% 16% 22% 7%	4409
	11th to 20th	Day	44% 7% 15% 28% 6%	4032
	21st to end	Day	40% 6% 17% 24% 12% 1	4180
September	1st to 10th	Day	42% 5% 13% 28% 12%	2280
	11th to 20th	Day	39% 5% 14% 30% 11% 1	2269
	21st to end	Day	45% 5% 15% 25% 10%	2046
October	1st to 10th	Day	51% 5% 11% 27% 6%	3160
	11th to 20th	Day	54% 6% 13% 20% 8%	3140
	21st to end	Day	54% 5% 19% 16% 5%	3122
November	1st to 10th	Day	52% 4 14% 23% 6% 1	1761
	11th to 20th	Day	65% 4 10% 13% 8%	1605
	21st to end	Day	70% 5% 11% 9% 5% 1	1600
December	1st to 10th	Day	73% 5% 9% 9% 3	1528
	11th to 20th	Day	67% 4 10% 12% 5%	1906
	21st to end	Day	73% 3 5% 14% 4	2772
January	1st to 10th	Night	68% 3 16% 11% 3	4429
	11th to 20th	Night	66% 4 13% 12% 5%	4440
	21st to end	Night	70% 4 9% 10% 7%	4821
February	1st to 10th	Night	64% 4 9% 16% 7% 1	2470
	11th to 20th	Night	61% 3 9% 19% 8% 1	2394
	21st to end	Night	58% 4 10% 17% 10% 1	1884
March	1st to 10th	Night	58% 3 10% 16% 10% 2	3734
	11th to 20th	Night	61% 3 11% 16% 8% 1	3517
	21st to end	Night	49% 4 8% 21% 15% 3	3576
April	1st to 10th	Night	55% 4 9% 17% 13% 2	1900
	11th to 20th	Night	50% 4 7% 23% 15% 1	1875
	21st to end	Night	53% 4 9% 17% 14% 3	1755
May	1st to 10th	Night	55% 6% 10% 19% 9% 2	2520
	11th to 20th	Night	48% 6% 12% 22% 11% 2	2496
	21st to end	Night	48% 5% 11% 20% 15% 2	2739
June	1st to 10th	Night	46% 6% 14% 23% 10% 1	1520
	11th to 20th	Night	43% 5% 12% 25% 13% 2	1520
	21st to end	Night	46% 8% 13% 21% 12% 1	1520
July	1st to 10th	Night	46% 6% 17% 20% 11% 1	2480
	11th to 20th	Night	42% 6% 16% 28% 8%	2472
	21st to end	Night	34% 7% 16% 30% 12%	2651
August	1st to 10th	Night	43% 7% 15% 26% 9%	2496
	11th to 20th	Night	42% 6% 17% 28% 7%	2827
	21st to end	Night	42% 5% 15% 24% 12% 2	3476
September	1st to 10th	Night	40% 5% 12% 30% 14% 1	1900
	11th to 20th	Night	37% 4 14% 34% 10% 1	1910
	21st to end	Night	42% 4 13% 29% 11%	2133
October	1st to 10th	Night	43% 5% 14% 27% 11%	3800
	11th to 20th	Night	50% 6% 14% 22% 8%	3779
	21st to end	Night	53% 4 18% 15% 9%	4426
November	1st to 10th	Night	55% 5% 13% 19% 7%	2537
	11th to 20th	Night	62% 4 10% 14% 9% 1	2792
	21st to end	Night	67% 5% 11% 13% 3	2800
December	1st to 10th	Night	71% 4 10% 11% 4	2686
	11th to 20th	Night	66% 3 9% 15% 7% 1	3288
	21st to end	Night	73% 3 6% 13% 5%	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	21% 23% 32% 20% 3	180
	11th to 20th	Day	29% 18% 33% 15% 4 1	180
	21st to end	Day	24% 21% 34% 17% 4	213
February	1st to 10th	Day	30% 31% 28% 8% 3	270
	11th to 20th	Day	29% 30% 33% 8%	279
	21st to end	Day	34% 22% 30% 13% 2	382
March	1st to 10th	Day	28% 18% 35% 13% 5% 1	460
	11th to 20th	Day	27% 23% 33% 13% 4 1	460
	21st to end	Day	31% 23% 25% 15% 6% 1	506
April	1st to 10th	Day	32% 19% 28% 14% 5% 1	460
	11th to 20th	Day	35% 20% 22% 12% 9% 1	452
	21st to end	Day	32% 21% 29% 13% 5% 1	460
May	1st to 10th	Day	30% 17% 32% 15% 5% 2	463
	11th to 20th	Day	23% 18% 30% 19% 7% 2	487
	21st to end	Day	24% 18% 32% 19% 7% 1	529
June	1st to 10th	Day	26% 15% 33% 20% 6% 1	490
	11th to 20th	Day	20% 17% 32% 19% 10% 2	490
	21st to end	Day	25% 14% 31% 21% 8% 2	490
July	1st to 10th	Day	16% 8% 35% 29% 8% 3	485
	11th to 20th	Day	14% 14% 36% 26% 9% 2	484
	21st to end	Day	15% 10% 35% 28% 11% 2	532
August	1st to 10th	Day	18% 10% 26% 33% 11% 2	486
	11th to 20th	Day	18% 8% 26% 28% 13% 7%	479
	21st to end	Day	19% 12% 32% 20% 11% 5%	539
September	1st to 10th	Day	18% 12% 33% 20% 12% 6%	490
	11th to 20th	Day	16% 12% 24% 22% 17% 9%	490
	21st to end	Day	22% 14% 24% 22% 11% 7%	490
October	1st to 10th	Day	26% 18% 23% 20% 11% 3	490
	11th to 20th	Day	33% 21% 25% 13% 6% 2	490
	21st to end	Day	34% 15% 29% 17% 5%	444
November	1st to 10th	Day	33% 15% 28% 19% 4	395
	11th to 20th	Day	28% 23% 32% 11% 4 1	205
	21st to end	Day	35% 23% 27% 14% 1 1	200
December	1st to 10th	Day	35% 13% 35% 14% 3	182
	11th to 20th	Day	31% 25% 34% 8% 1 1	180
	21st to end	Day	32% 22% 30% 12% 2 1	198
January	1st to 10th	Night	27% 16% 35% 17% 4	760
	11th to 20th	Night	29% 15% 28% 22% 6%	760
	21st to end	Night	19% 16% 34% 23% 8% 1	836
February	1st to 10th	Night	20% 19% 33% 22% 5%	760
	11th to 20th	Night	20% 21% 35% 19% 4	743
	21st to end	Night	24% 21% 27% 25% 3	628
March	1st to 10th	Night	25% 17% 32% 21% 6%	760
	11th to 20th	Night	24% 21% 30% 19% 5%	760
	21st to end	Night	25% 16% 29% 23% 7%	836
April	1st to 10th	Night	28% 15% 27% 24% 6%	760
	11th to 20th	Night	26% 17% 29% 21% 7% 1	751
	21st to end	Night	26% 17% 25% 24% 8%	615
May	1st to 10th	Night	26% 12% 26% 25% 9% 2	380
	11th to 20th	Night	22% 8% 32% 29% 9%	374
	21st to end	Night	18% 12% 36% 25% 9% 1	411
June	1st to 10th	Night	20% 7% 32% 32% 8% 1	380
	11th to 20th	Night	19% 9% 27% 31% 13% 1	380
	21st to end	Night	20% 8% 23% 35% 14%	380
July	1st to 10th	Night	12% 4 28% 39% 16% 1	370
	11th to 20th	Night	14% 4 24% 40% 17% 1	368
	21st to end	Night	11% 5% 26% 40% 17% 2	416
August	1st to 10th	Night	11% 7% 22% 39% 21% 1	378
	11th to 20th	Night	15% 3 17% 37% 23% 4	566
	21st to end	Night	18% 6% 24% 32% 17% 3	836
September	1st to 10th	Night	18% 6% 29% 29% 18% 1	760
	11th to 20th	Night	18% 7% 23% 28% 21% 3	760
	21st to end	Night	21% 9% 25% 26% 17% 2	760
October	1st to 10th	Night	24% 12% 27% 23% 13% 1	760
	11th to 20th	Night	28% 14% 27% 22% 8% 1	760
	21st to end	Night	29% 15% 27% 22% 5%	836
November	1st to 10th	Night	29% 13% 28% 22% 7% 1	780
	11th to 20th	Night	26% 19% 30% 15% 10% 1	800
	21st to end	Night	31% 19% 25% 19% 5% 1	800
December	1st to 10th	Night	29% 19% 26% 21% 5%	768
	11th to 20th	Night	28% 19% 29% 18% 5% 1	760
	21st to end	Night	34% 15% 28% 18% 5%	836

Page generated at 2024-11-29 10:43:09. Version ac07

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