Long Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Long Lake clear sky chart from 2005-11-06 to 2024-09-14.

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	18% 13% 4 9% 6% 4 4 4 5% 6% 27%	100961
	Night	17% 14% 5% 11% 6% 4 4 3 4 5% 26%	96927
Transparency	Day	57% 6% 11% 17% 8% 1	100719
	Night	60% 6% 10% 15% 8% 1	96789
Seeing	Day	27% 18% 28% 17% 8% 3	14480
	Night	26% 18% 25% 21% 8% 1	23501

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	11% 21% 9% 22% 7% 4 4 2 3 2 15%	2517
	11th to 20th	Day	12% 19% 8% 19% 16% 4 3 2 2 3 13%	2520
	21st to end	Day	14% 21% 10% 13% 7% 5% 6% 3 4 4 12%	2846
February	1st to 10th	Day	13% 17% 9% 14% 9% 7% 5% 3 4 4 16%	1710
	11th to 20th	Day	10% 16% 8% 17% 10% 5% 4 3 3 4 18%	1760
	21st to end	Day	14% 18% 5% 15% 7% 6% 3 2 4 5% 20%	1570
March	1st to 10th	Day	22% 15% 7% 12% 6% 3 4 3 4 4 20%	3116
	11th to 20th	Day	11% 25% 8% 11% 5% 4 4 3 4 4 22%	3352
	21st to end	Day	15% 14% 6% 11% 6% 3 3 2 3 4 32%	4120
April	1st to 10th	Day	20% 18% 5% 7% 4 3 3 3 4 5% 29%	2280
	11th to 20th	Day	17% 16% 4 7% 4 4 4 3 4 4 32%	2254
	21st to end	Day	22% 15% 3 7% 4 4 3 3 4 6% 28%	2362
May	1st to 10th	Day	24% 12% 3 7% 4 5% 4 3 4 6% 27%	4349
	11th to 20th	Day	18% 10% 3 9% 6% 5% 5% 4 5% 8% 28%	4398
	21st to end	Day	16% 8% 3 7% 4 4 5% 4 6% 8% 34%	4837
June	1st to 10th	Day	23% 9% 3 7% 6% 5% 5% 4 6% 7% 27%	2660
	11th to 20th	Day	21% 8% 2 7% 5% 4 5% 5% 6% 7% 30%	2660
	21st to end	Day	22% 9% 3 7% 5% 5% 5% 4 6% 7% 27%	2660
July	1st to 10th	Day	15% 7% 2 6% 5% 5% 5% 5% 7% 9% 34%	4440
	11th to 20th	Day	15% 7% 2 7% 5% 5% 5% 6% 7% 10% 31%	4440
	21st to end	Day	16% 7% 2 7% 5% 5% 6% 4 7% 8% 33%	4814
August	1st to 10th	Day	19% 8% 2 6% 4 5% 5% 4 6% 8% 31%	4407
	11th to 20th	Day	18% 9% 2 8% 5% 5% 5% 5% 6% 7% 29%	3831
	21st to end	Day	19% 6% 2 6% 4 5% 5% 4 7% 9% 34%	4180
September	1st to 10th	Day	18% 7% 2 6% 4 4 5% 4 4 9% 37%	2280
	11th to 20th	Day	18% 7% 2 6% 3 3 3 3 6% 6% 43%	2144
	21st to end	Day	19% 10% 2 6% 4 3 5% 4 5% 7% 35%	1980
October	1st to 10th	Day	26% 11% 3 7% 4 4 4 3 4 5% 29%	1828
	11th to 20th	Day	20% 15% 3 7% 4 5% 4 3 6% 7% 27%	1800
	21st to end	Day	25% 18% 4 7% 5% 4 4 3 4 4 22%	1800
November	1st to 10th	Day	14% 17% 5% 9% 6% 4 4 3 4 5% 27%	1671
	11th to 20th	Day	15% 19% 6% 10% 5% 4 4 2 4 5% 25%	1657
	21st to end	Day	16% 21% 6% 12% 5% 5% 4 3 4 5% 19%	1520
December	1st to 10th	Day	17% 25% 9% 14% 7% 3 3 3 3 4 12%	1520
	11th to 20th	Day	17% 17% 9% 18% 7% 3 3 3 4 4 15%	1906
	21st to end	Day	20% 20% 9% 13% 6% 4 4 3 4 4 15%	2772
January	1st to 10th	Night	13% 21% 9% 21% 7% 4 3 3 3 3 14%	4429
	11th to 20th	Night	10% 18% 10% 22% 14% 5% 4 2 3 3 10%	4440
	21st to end	Night	16% 18% 9% 18% 7% 6% 5% 3 3 3 13%	4806
February	1st to 10th	Night	13% 17% 7% 17% 10% 7% 4 3 4 4 15%	2470
	11th to 20th	Night	11% 15% 8% 17% 9% 7% 5% 3 4 5% 17%	2305
	21st to end	Night	13% 16% 6% 15% 10% 6% 4 3 4 5% 20%	1884
March	1st to 10th	Night	19% 15% 5% 10% 8% 5% 4 3 4 5% 23%	3724
	11th to 20th	Night	13% 20% 9% 11% 4 3 3 2 3 4 26%	3589
	21st to end	Night	16% 16% 6% 11% 5% 3 3 2 3 4 31%	3512
April	1st to 10th	Night	19% 16% 6% 8% 4 4 3 3 4 5% 27%	1900
	11th to 20th	Night	20% 16% 3 6% 5% 4 3 2 4 5% 30%	1875
	21st to end	Night	21% 12% 4 8% 4 3 4 4 4 5% 31%	1816
May	1st to 10th	Night	25% 12% 3 7% 5% 4 4 3 5% 5% 26%	2620
	11th to 20th	Night	20% 14% 3 8% 4 3 4 3 4 6% 31%	2495
	21st to end	Night	16% 8% 2 6% 4 4 5% 4 7% 8% 36%	2738
June	1st to 10th	Night	21% 7% 2 6% 4 5% 4 5% 5% 7% 33%	1520
	11th to 20th	Night	20% 6% 2 6% 4 4 4 4 5% 8% 37%	1520
	21st to end	Night	20% 7% 3 7% 5% 4 5% 3 6% 8% 33%	1520
July	1st to 10th	Night	15% 6% 2 8% 5% 5% 6% 4 5% 7% 36%	2520
	11th to 20th	Night	17% 7% 2 5% 4 4 4 4 5% 8% 39%	2520
	21st to end	Night	14% 7% 3 7% 4 5% 4 3 5% 8% 40%	2739
August	1st to 10th	Night	23% 8% 2 6% 3 3 3 2 4 7% 37%	2506
	11th to 20th	Night	20% 10% 3 7% 4 4 4 3 5% 6% 34%	2966
	21st to end	Night	15% 9% 2 5% 3 4 5% 4 5% 8% 40%	3476
September	1st to 10th	Night	15% 8% 2 5% 4 4 4 3 5% 7% 42%	1900
	11th to 20th	Night	14% 8% 2 5% 3 3 3 3 5% 6% 47%	1893
	21st to end	Night	19% 9% 2 6% 3 3 3 3 6% 7% 39%	1980
October	1st to 10th	Night	24% 11% 3 6% 5% 3 5% 3 5% 6% 29%	2128
	11th to 20th	Night	18% 14% 4 8% 4 4 4 4 6% 6% 28%	2160
	21st to end	Night	24% 20% 4 7% 4 4 4 3 4 5% 21%	2556
November	1st to 10th	Night	16% 16% 7% 9% 4 4 4 3 5% 5% 27%	2407
	11th to 20th	Night	17% 17% 6% 9% 6% 4 3 4 4 6% 24%	2521
	21st to end	Night	16% 19% 7% 13% 5% 4 4 3 5% 5% 18%	2660
December	1st to 10th	Night	17% 23% 10% 16% 6% 3 3 2 4 4 11%	2660
	11th to 20th	Night	17% 20% 7% 14% 7% 4 4 3 3 4 17%	3288
	21st to end	Night	21% 20% 6% 18% 5% 4 3 3 3 4 12%	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	77% 3 6% 10% 3	2518
	11th to 20th	Day	79% 3 5% 7% 4 2	2520
	21st to end	Day	75% 4 8% 7% 4 1	2846
February	1st to 10th	Day	72% 5% 7% 11% 4 2	1710
	11th to 20th	Day	69% 4 8% 9% 8% 1	1769
	21st to end	Day	68% 4 8% 10% 9% 1	1570
March	1st to 10th	Day	67% 6% 7% 10% 9% 1	3119
	11th to 20th	Day	67% 5% 10% 10% 7% 1	3352
	21st to end	Day	56% 3 8% 15% 16% 2	4120
April	1st to 10th	Day	59% 4 9% 16% 10% 2	2280
	11th to 20th	Day	55% 5% 8% 17% 13% 1	2254
	21st to end	Day	59% 5% 9% 14% 10% 3	2362
May	1st to 10th	Day	58% 6% 9% 18% 7% 1	4363
	11th to 20th	Day	54% 8% 11% 20% 7% 1	4402
	21st to end	Day	46% 8% 11% 25% 10% 1	4837
June	1st to 10th	Day	56% 7% 12% 15% 10% 1	2660
	11th to 20th	Day	51% 8% 10% 21% 9% 1	2660
	21st to end	Day	55% 7% 11% 18% 8% 1	2660
July	1st to 10th	Day	43% 8% 15% 24% 10%	4370
	11th to 20th	Day	43% 10% 16% 26% 5%	4365
	21st to end	Day	46% 9% 12% 26% 7%	4661
August	1st to 10th	Day	49% 8% 15% 19% 9%	4393
	11th to 20th	Day	50% 8% 16% 21% 5%	3870
	21st to end	Day	43% 9% 16% 23% 9%	4180
September	1st to 10th	Day	45% 6% 10% 27% 11% 1	2280
	11th to 20th	Day	41% 6% 10% 26% 16% 1	2144
	21st to end	Day	47% 6% 13% 21% 12% 1	1980
October	1st to 10th	Day	59% 5% 10% 16% 10%	1828
	11th to 20th	Day	57% 6% 13% 17% 6% 1	1800
	21st to end	Day	67% 6% 8% 11% 8% 1	1800
November	1st to 10th	Day	58% 6% 12% 15% 8%	1671
	11th to 20th	Day	61% 6% 10% 12% 8% 3	1657
	21st to end	Day	67% 7% 11% 10% 5%	1520
December	1st to 10th	Day	77% 5% 8% 8% 2 1	1520
	11th to 20th	Day	74% 5% 8% 8% 5%	1906
	21st to end	Day	73% 6% 5% 6% 9%	2772
January	1st to 10th	Night	77% 5% 6% 7% 4	4429
	11th to 20th	Night	82% 4 5% 5% 3 1	4440
	21st to end	Night	78% 4 5% 8% 4 1	4806
February	1st to 10th	Night	74% 5% 7% 8% 5% 1	2470
	11th to 20th	Night	69% 6% 8% 9% 7%	2307
	21st to end	Night	66% 6% 8% 12% 7% 1	1884
March	1st to 10th	Night	63% 5% 8% 13% 9% 1	3734
	11th to 20th	Night	63% 4 10% 14% 7% 1	3590
	21st to end	Night	59% 4 6% 16% 13% 2	3512
April	1st to 10th	Night	60% 5% 9% 16% 9% 1	1900
	11th to 20th	Night	56% 6% 10% 17% 11%	1875
	21st to end	Night	55% 6% 10% 16% 12% 2	1816
May	1st to 10th	Night	58% 7% 10% 15% 9% 1	2626
	11th to 20th	Night	54% 7% 10% 19% 8% 1	2496
	21st to end	Night	44% 8% 13% 21% 13% 1	2739
June	1st to 10th	Night	50% 8% 13% 20% 8% 1	1520
	11th to 20th	Night	45% 7% 14% 21% 11% 1	1520
	21st to end	Night	49% 9% 13% 20% 9%	1520
July	1st to 10th	Night	45% 8% 15% 19% 13% 1	2480
	11th to 20th	Night	42% 8% 16% 27% 7%	2472
	21st to end	Night	43% 8% 14% 28% 7% 1	2651
August	1st to 10th	Night	48% 6% 16% 23% 7%	2496
	11th to 20th	Night	49% 8% 16% 21% 6%	2993
	21st to end	Night	41% 8% 15% 28% 8% 1	3476
September	1st to 10th	Night	42% 7% 13% 28% 10% 1	1900
	11th to 20th	Night	37% 6% 14% 31% 11%	1893
	21st to end	Night	44% 7% 12% 24% 11% 2	1980
October	1st to 10th	Night	55% 6% 12% 16% 10% 1	2128
	11th to 20th	Night	55% 8% 14% 16% 6% 1	2160
	21st to end	Night	67% 5% 10% 10% 6% 1	2556
November	1st to 10th	Night	59% 6% 10% 13% 9% 2	2407
	11th to 20th	Night	62% 6% 10% 13% 7% 3	2521
	21st to end	Night	68% 7% 9% 11% 5% 1	2660
December	1st to 10th	Night	78% 6% 7% 7% 3	2660
	11th to 20th	Night	72% 6% 8% 9% 6% 1	3288
	21st to end	Night	77% 5% 6% 6% 6%	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	26% 22% 34% 9% 7% 1	180
	11th to 20th	Day	32% 25% 33% 7% 1 1	180
	21st to end	Day	23% 24% 39% 11% 3	221
February	1st to 10th	Day	37% 32% 26% 4	270
	11th to 20th	Day	34% 26% 32% 7% 1	367
	21st to end	Day	35% 25% 28% 10% 3	382
March	1st to 10th	Day	32% 22% 29% 14% 3	460
	11th to 20th	Day	31% 23% 30% 11% 4 1	460
	21st to end	Day	34% 26% 22% 12% 6% 1	506
April	1st to 10th	Day	36% 22% 23% 13% 5% 1	460
	11th to 20th	Day	35% 21% 20% 16% 5% 2	452
	21st to end	Day	35% 18% 28% 11% 6% 2	460
May	1st to 10th	Day	32% 20% 25% 11% 6% 4	463
	11th to 20th	Day	24% 17% 29% 22% 6% 2	487
	21st to end	Day	23% 19% 29% 16% 11% 2	529
June	1st to 10th	Day	27% 18% 28% 19% 6% 2	490
	11th to 20th	Day	24% 14% 28% 21% 9% 3	490
	21st to end	Day	29% 18% 27% 17% 7% 2	490
July	1st to 10th	Day	17% 11% 32% 25% 13% 4	485
	11th to 20th	Day	16% 12% 33% 26% 11% 2	484
	21st to end	Day	17% 11% 36% 26% 8% 2	532
August	1st to 10th	Day	19% 10% 26% 25% 14% 5%	486
	11th to 20th	Day	19% 11% 28% 22% 13% 7%	479
	21st to end	Day	17% 15% 28% 23% 11% 6%	539
September	1st to 10th	Day	19% 13% 29% 18% 13% 8%	490
	11th to 20th	Day	18% 14% 23% 19% 15% 12%	463
	21st to end	Day	19% 15% 27% 20% 14% 5%	450
October	1st to 10th	Day	33% 14% 23% 12% 13% 6%	450
	11th to 20th	Day	28% 22% 24% 18% 7% 1	450
	21st to end	Day	34% 20% 24% 17% 4	405
November	1st to 10th	Day	32% 17% 25% 19% 7% 1	365
	11th to 20th	Day	33% 24% 24% 14% 5% 1	317
	21st to end	Day	33% 26% 27% 13% 1	180
December	1st to 10th	Day	34% 21% 31% 13% 2	180
	11th to 20th	Day	35% 26% 31% 7% 1 1	180
	21st to end	Day	35% 23% 31% 10% 1 1	198
January	1st to 10th	Night	28% 28% 29% 14% 2	760
	11th to 20th	Night	29% 25% 30% 13% 3	760
	21st to end	Night	20% 25% 33% 18% 4	836
February	1st to 10th	Night	26% 26% 32% 14% 2	760
	11th to 20th	Night	24% 29% 30% 14% 2	743
	21st to end	Night	27% 23% 32% 15% 3	628
March	1st to 10th	Night	28% 21% 30% 18% 3	760
	11th to 20th	Night	30% 24% 24% 16% 4 1	760
	21st to end	Night	28% 19% 28% 18% 6% 1	836
April	1st to 10th	Night	28% 22% 26% 20% 4	760
	11th to 20th	Night	30% 21% 25% 17% 7%	751
	21st to end	Night	30% 19% 23% 21% 7%	676
May	1st to 10th	Night	32% 11% 26% 20% 11%	447
	11th to 20th	Night	20% 13% 26% 33% 7%	374
	21st to end	Night	16% 13% 28% 29% 13% 1	411
June	1st to 10th	Night	23% 10% 24% 30% 11% 1	380
	11th to 20th	Night	23% 6% 20% 36% 14%	380
	21st to end	Night	22% 8% 27% 33% 9% 1	380
July	1st to 10th	Night	14% 5% 25% 37% 18% 1	370
	11th to 20th	Night	13% 6% 25% 38% 16% 2	368
	21st to end	Night	13% 8% 22% 43% 13% 1	416
August	1st to 10th	Night	19% 7% 18% 39% 17% 1	378
	11th to 20th	Night	18% 8% 20% 29% 21% 3	667
	21st to end	Night	18% 8% 22% 33% 19% 1	836
September	1st to 10th	Night	18% 10% 23% 30% 16% 3	760
	11th to 20th	Night	19% 8% 20% 28% 21% 4	736
	21st to end	Night	25% 11% 23% 20% 19% 3	720
October	1st to 10th	Night	30% 15% 21% 18% 14% 2	720
	11th to 20th	Night	26% 17% 23% 25% 8% 1	720
	21st to end	Night	35% 19% 22% 19% 5%	792
November	1st to 10th	Night	29% 18% 26% 19% 7% 1	740
	11th to 20th	Night	30% 20% 26% 16% 8% 1	760
	21st to end	Night	31% 23% 25% 16% 5% 1	760
December	1st to 10th	Night	33% 26% 23% 14% 4	760
	11th to 20th	Night	29% 26% 24% 17% 3 1	760
	21st to end	Night	32% 27% 26% 13% 2	836

Page generated at 2024-09-11 10:00:05. Version ac07

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