Otter Lake
Clear Sky Chart
History

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

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% 10% 4 9% 5% 4 4 4 5% 6% 32%	101666
	Night	16% 12% 4 9% 5% 4 4 3 5% 6% 31%	97524
Transparency	Day	51% 6% 12% 20% 9% 1	105162
	Night	53% 6% 12% 19% 9% 1	102117
Seeing	Day	23% 17% 31% 19% 8% 2	14433
	Night	22% 14% 30% 24% 9% 1	23524

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% 18% 6% 14% 8% 5% 4 3 3 4 20%	2517
	11th to 20th	Day	14% 13% 6% 18% 8% 5% 4 3 5% 4 20%	2520
	21st to end	Day	12% 18% 8% 16% 7% 5% 4 3 4 4 18%	2909
February	1st to 10th	Day	12% 17% 6% 13% 7% 5% 5% 3 5% 5% 22%	1710
	11th to 20th	Day	10% 18% 6% 12% 6% 5% 3 3 4 6% 26%	1663
	21st to end	Day	16% 15% 5% 9% 6% 5% 4 3 6% 4 25%	1541
March	1st to 10th	Day	17% 18% 5% 9% 5% 4 3 3 4 5% 26%	3169
	11th to 20th	Day	11% 18% 7% 11% 6% 5% 4 3 4 5% 26%	3480
	21st to end	Day	12% 9% 2 8% 5% 5% 4 3 5% 7% 41%	3994
April	1st to 10th	Day	22% 13% 3 7% 5% 5% 4 3 4 5% 30%	2280
	11th to 20th	Day	23% 9% 3 7% 4 4 3 3 4 5% 34%	2254
	21st to end	Day	23% 11% 4 8% 5% 4 4 2 4 5% 31%	2442
May	1st to 10th	Day	20% 10% 3 8% 5% 4 4 4 6% 6% 30%	4426
	11th to 20th	Day	16% 9% 3 8% 5% 4 4 4 5% 7% 35%	4398
	21st to end	Day	17% 7% 3 8% 4 5% 5% 4 6% 7% 36%	4837
June	1st to 10th	Day	22% 8% 3 8% 6% 4 5% 4 5% 6% 29%	2660
	11th to 20th	Day	16% 6% 2 6% 5% 5% 4 4 6% 8% 38%	2660
	21st to end	Day	19% 7% 3 7% 5% 5% 4 4 6% 7% 32%	2660
July	1st to 10th	Day	13% 7% 3 7% 5% 6% 5% 5% 7% 9% 34%	4440
	11th to 20th	Day	13% 6% 2 6% 5% 4 5% 5% 7% 8% 39%	4440
	21st to end	Day	12% 6% 2 6% 4 4 4 3 6% 8% 46%	4814
August	1st to 10th	Day	13% 6% 3 8% 5% 5% 6% 5% 6% 8% 34%	4328
	11th to 20th	Day	18% 7% 2 6% 4 5% 6% 4 6% 7% 35%	4044
	21st to end	Day	13% 5% 2 6% 4 4 6% 5% 8% 9% 38%	4187
September	1st to 10th	Day	15% 6% 3 6% 3 4 4 4 5% 8% 42%	2280
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 5% 7% 44%	2280
	21st to end	Day	20% 7% 2 6% 4 4 4 3 6% 7% 37%	2014
October	1st to 10th	Day	21% 8% 2 7% 4 4 5% 4 5% 6% 34%	1900
	11th to 20th	Day	24% 12% 3 8% 5% 4 4 3 5% 5% 27%	1900
	21st to end	Day	27% 11% 2 9% 5% 3 4 3 5% 5% 27%	1953
November	1st to 10th	Day	15% 12% 3 8% 5% 5% 5% 4 5% 6% 33%	1720
	11th to 20th	Day	19% 14% 5% 10% 6% 4 5% 3 5% 5% 23%	1528
	21st to end	Day	21% 18% 5% 12% 6% 4 5% 3 3 5% 18%	1520
December	1st to 10th	Day	21% 21% 5% 11% 6% 4 4 3 4 5% 16%	1520
	11th to 20th	Day	19% 15% 5% 11% 6% 4 4 4 4 6% 22%	1906
	21st to end	Day	24% 22% 6% 13% 4 3 3 2 2 3 18%	2772
January	1st to 10th	Night	16% 19% 7% 14% 6% 4 5% 3 4 4 19%	4429
	11th to 20th	Night	12% 12% 5% 14% 8% 6% 5% 4 4 6% 22%	4440
	21st to end	Night	13% 19% 7% 14% 7% 6% 5% 3 3 4 20%	4744
February	1st to 10th	Night	12% 14% 6% 13% 8% 5% 4 3 5% 6% 22%	2470
	11th to 20th	Night	12% 16% 5% 11% 7% 5% 6% 3 4 5% 27%	2403
	21st to end	Night	13% 15% 6% 10% 6% 6% 5% 4 4 4 28%	1913
March	1st to 10th	Night	17% 14% 5% 8% 5% 4 4 3 3 5% 32%	3670
	11th to 20th	Night	15% 19% 4 11% 5% 4 4 4 5% 5% 24%	3479
	21st to end	Night	13% 10% 4 10% 5% 4 4 3 5% 6% 38%	3637
April	1st to 10th	Night	21% 12% 3 8% 5% 4 4 2 5% 6% 30%	1900
	11th to 20th	Night	19% 9% 3 7% 5% 5% 4 4 5% 6% 35%	1875
	21st to end	Night	21% 10% 4 8% 5% 4 3 3 4 5% 32%	1751
May	1st to 10th	Night	21% 10% 3 7% 4 4 4 4 5% 7% 30%	2514
	11th to 20th	Night	18% 9% 4 6% 5% 4 4 3 6% 7% 34%	2495
	21st to end	Night	14% 7% 3 7% 5% 5% 4 4 5% 7% 37%	2738
June	1st to 10th	Night	18% 6% 2 6% 6% 4 5% 4 7% 9% 33%	1520
	11th to 20th	Night	15% 6% 2 5% 5% 4 4 3 7% 7% 42%	1520
	21st to end	Night	18% 8% 2 5% 5% 4 5% 4 6% 7% 36%	1520
July	1st to 10th	Night	13% 7% 3 8% 5% 5% 5% 4 6% 7% 36%	2520
	11th to 20th	Night	13% 7% 2 8% 4 4 5% 4 6% 7% 40%	2520
	21st to end	Night	9% 5% 3 6% 4 4 5% 4 7% 8% 46%	2739
August	1st to 10th	Night	12% 6% 3 7% 5% 5% 5% 5% 6% 7% 39%	2598
	11th to 20th	Night	16% 8% 2 7% 4 3 4 4 5% 7% 40%	2785
	21st to end	Night	15% 5% 2 7% 4 4 4 3 6% 7% 42%	3435
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 4 7% 46%	1900
	11th to 20th	Night	15% 5% 2 5% 4 2 3 3 4 8% 49%	1900
	21st to end	Night	18% 7% 3 7% 4 3 3 2 4 5% 43%	2162
October	1st to 10th	Night	19% 8% 2 6% 4 4 4 3 4 6% 41%	2280
	11th to 20th	Night	21% 11% 3 7% 5% 5% 4 4 4 6% 30%	2280
	21st to end	Night	23% 12% 3 8% 5% 5% 5% 3 4 5% 27%	2643
November	1st to 10th	Night	17% 12% 3 8% 5% 4 5% 4 5% 7% 31%	2577
	11th to 20th	Night	19% 12% 5% 9% 6% 6% 5% 3 5% 5% 27%	2675
	21st to end	Night	21% 15% 5% 10% 6% 4 4 4 4 5% 22%	2660
December	1st to 10th	Night	19% 21% 6% 11% 6% 6% 4 3 4 4 17%	2660
	11th to 20th	Night	20% 17% 6% 9% 5% 4 3 3 4 4 25%	3288
	21st to end	Night	25% 21% 6% 12% 5% 3 3 2 3 4 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	68% 7% 10% 9% 6%	2518
	11th to 20th	Day	66% 6% 9% 12% 6%	2520
	21st to end	Day	70% 5% 8% 10% 6% 1	2909
February	1st to 10th	Day	63% 5% 10% 16% 5% 1	1710
	11th to 20th	Day	60% 4 12% 13% 10% 1	1672
	21st to end	Day	60% 5% 10% 13% 10% 1	1541
March	1st to 10th	Day	61% 4 9% 15% 10% 1	3172
	11th to 20th	Day	59% 6% 11% 14% 8% 2	3480
	21st to end	Day	42% 6% 9% 24% 16% 3	3994
April	1st to 10th	Day	57% 4 7% 17% 12% 3	2280
	11th to 20th	Day	52% 4 7% 20% 15% 2	2254
	21st to end	Day	56% 5% 7% 15% 13% 4	2442
May	1st to 10th	Day	51% 7% 10% 20% 9% 2	4440
	11th to 20th	Day	46% 8% 13% 22% 10% 1	4402
	21st to end	Day	46% 7% 12% 18% 15% 2	4837
June	1st to 10th	Day	53% 6% 11% 18% 11% 1	2660
	11th to 20th	Day	43% 8% 11% 24% 12% 2	2660
	21st to end	Day	49% 8% 13% 19% 10% 1	2660
July	1st to 10th	Day	43% 7% 15% 25% 9%	4370
	11th to 20th	Day	39% 7% 17% 28% 8%	4365
	21st to end	Day	36% 7% 14% 32% 10%	4661
August	1st to 10th	Day	46% 7% 16% 23% 8%	4314
	11th to 20th	Day	46% 7% 15% 26% 6% 1	4083
	21st to end	Day	38% 8% 17% 24% 12% 1	4187
September	1st to 10th	Day	40% 7% 14% 28% 11%	2280
	11th to 20th	Day	39% 7% 12% 30% 12% 1	2280
	21st to end	Day	45% 7% 14% 24% 10%	2014
October	1st to 10th	Day	50% 6% 11% 27% 6%	3160
	11th to 20th	Day	51% 7% 12% 22% 8%	3140
	21st to end	Day	53% 5% 19% 17% 5%	3191
November	1st to 10th	Day	50% 7% 13% 23% 6% 1	1720
	11th to 20th	Day	61% 7% 12% 12% 7% 1	1528
	21st to end	Day	69% 6% 10% 8% 6% 1	1520
December	1st to 10th	Day	72% 5% 10% 8% 4	1520
	11th to 20th	Day	63% 8% 10% 12% 7%	1906
	21st to end	Day	74% 3 6% 13% 3	2772
January	1st to 10th	Night	68% 6% 15% 9% 3	4429
	11th to 20th	Night	62% 7% 14% 12% 4	4440
	21st to end	Night	69% 6% 9% 10% 7%	4744
February	1st to 10th	Night	63% 5% 10% 15% 6% 1	2470
	11th to 20th	Night	60% 4 10% 18% 7% 1	2405
	21st to end	Night	57% 5% 10% 18% 9% 1	1913
March	1st to 10th	Night	56% 4 12% 17% 9% 2	3680
	11th to 20th	Night	59% 6% 11% 15% 7% 1	3480
	21st to end	Night	44% 6% 10% 21% 15% 4	3637
April	1st to 10th	Night	55% 4 9% 17% 12% 2	1900
	11th to 20th	Night	49% 5% 9% 21% 14% 2	1875
	21st to end	Night	54% 5% 7% 16% 15% 3	1751
May	1st to 10th	Night	50% 9% 11% 19% 10% 3	2520
	11th to 20th	Night	45% 9% 12% 21% 10% 2	2496
	21st to end	Night	45% 6% 11% 21% 15% 2	2739
June	1st to 10th	Night	46% 7% 15% 23% 8% 1	1520
	11th to 20th	Night	40% 7% 12% 26% 14% 2	1520
	21st to end	Night	46% 8% 13% 21% 12% 1	1520
July	1st to 10th	Night	44% 6% 17% 19% 13% 1	2480
	11th to 20th	Night	40% 6% 15% 29% 9%	2472
	21st to end	Night	34% 8% 15% 31% 12%	2651
August	1st to 10th	Night	41% 8% 15% 25% 11%	2588
	11th to 20th	Night	42% 6% 16% 28% 8%	2812
	21st to end	Night	40% 6% 17% 25% 11% 2	3435
September	1st to 10th	Night	37% 7% 12% 29% 14%	1900
	11th to 20th	Night	35% 5% 15% 34% 10% 1	1900
	21st to end	Night	43% 5% 14% 28% 10%	2162
October	1st to 10th	Night	41% 5% 13% 28% 13%	3800
	11th to 20th	Night	47% 6% 16% 22% 8%	3779
	21st to end	Night	52% 5% 19% 16% 8%	4355
November	1st to 10th	Night	51% 7% 14% 19% 8%	2577
	11th to 20th	Night	59% 6% 12% 15% 7% 1	2675
	21st to end	Night	64% 6% 12% 14% 3	2660
December	1st to 10th	Night	70% 6% 9% 11% 3	2660
	11th to 20th	Night	64% 5% 9% 14% 8%	3288
	21st to end	Night	74% 4 7% 12% 4	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	22% 23% 34% 18% 2 1	180
	11th to 20th	Day	24% 18% 38% 16% 4	180
	21st to end	Day	17% 25% 35% 17% 5%	238
February	1st to 10th	Day	30% 26% 31% 10% 3	270
	11th to 20th	Day	27% 31% 34% 8% 1	270
	21st to end	Day	32% 24% 32% 11% 1	353
March	1st to 10th	Day	26% 21% 35% 13% 5%	460
	11th to 20th	Day	25% 24% 32% 15% 3 1	460
	21st to end	Day	29% 23% 29% 14% 4 1	506
April	1st to 10th	Day	32% 21% 27% 15% 4 1	460
	11th to 20th	Day	35% 20% 22% 14% 8% 1	452
	21st to end	Day	30% 22% 30% 12% 5% 1	460
May	1st to 10th	Day	27% 17% 33% 15% 6% 3	463
	11th to 20th	Day	20% 18% 32% 19% 7% 3	487
	21st to end	Day	22% 17% 33% 19% 7% 1	529
June	1st to 10th	Day	25% 13% 34% 20% 6% 1	490
	11th to 20th	Day	17% 15% 32% 24% 10% 3	490
	21st to end	Day	21% 14% 32% 22% 9% 2	490
July	1st to 10th	Day	12% 8% 34% 34% 9% 2	485
	11th to 20th	Day	14% 11% 35% 27% 10% 3	484
	21st to end	Day	13% 9% 33% 31% 11% 2	532
August	1st to 10th	Day	16% 8% 30% 28% 13% 4	486
	11th to 20th	Day	17% 7% 26% 31% 13% 6%	479
	21st to end	Day	16% 12% 31% 23% 13% 5%	539
September	1st to 10th	Day	17% 11% 33% 20% 13% 6%	490
	11th to 20th	Day	15% 10% 26% 22% 19% 9%	490
	21st to end	Day	21% 14% 28% 19% 12% 6%	490
October	1st to 10th	Day	25% 17% 25% 20% 11% 3	490
	11th to 20th	Day	28% 21% 29% 14% 6% 1	490
	21st to end	Day	31% 17% 31% 16% 4	466
November	1st to 10th	Day	26% 19% 32% 18% 3 1	354
	11th to 20th	Day	26% 28% 30% 11% 4 1	182
	21st to end	Day	28% 26% 30% 11% 4 1	180
December	1st to 10th	Day	31% 14% 41% 12% 2	180
	11th to 20th	Day	32% 27% 32% 7% 1 1	180
	21st to end	Day	34% 19% 33% 12% 2 1	198
January	1st to 10th	Night	27% 16% 36% 16% 4	760
	11th to 20th	Night	27% 18% 29% 20% 5%	760
	21st to end	Night	17% 15% 39% 23% 6% 1	836
February	1st to 10th	Night	19% 22% 35% 20% 4	760
	11th to 20th	Night	22% 19% 39% 16% 3	743
	21st to end	Night	22% 22% 32% 21% 4	628
March	1st to 10th	Night	24% 18% 34% 20% 4	760
	11th to 20th	Night	24% 18% 35% 18% 5% 1	760
	21st to end	Night	22% 18% 35% 18% 7%	836
April	1st to 10th	Night	28% 15% 31% 21% 5%	760
	11th to 20th	Night	25% 20% 28% 19% 7% 1	751
	21st to end	Night	27% 16% 28% 23% 5%	611
May	1st to 10th	Night	24% 11% 31% 25% 8% 1	380
	11th to 20th	Night	24% 12% 28% 29% 8%	374
	21st to end	Night	17% 10% 37% 26% 10%	411
June	1st to 10th	Night	19% 9% 32% 33% 7% 1	380
	11th to 20th	Night	17% 9% 28% 31% 14% 1	380
	21st to end	Night	19% 7% 29% 32% 13% 1	380
July	1st to 10th	Night	9% 6% 29% 40% 15% 1	370
	11th to 20th	Night	14% 6% 24% 38% 18%	368
	21st to end	Night	9% 6% 27% 42% 15% 1	416
August	1st to 10th	Night	11% 6% 23% 39% 20%	431
	11th to 20th	Night	13% 3 20% 37% 23% 3	564
	21st to end	Night	14% 8% 27% 31% 18% 2	808
September	1st to 10th	Night	15% 7% 30% 30% 16% 1	760
	11th to 20th	Night	16% 6% 24% 30% 20% 3	760
	21st to end	Night	21% 11% 25% 25% 16% 2	760
October	1st to 10th	Night	23% 13% 26% 22% 14% 1	760
	11th to 20th	Night	25% 14% 30% 22% 7% 1	760
	21st to end	Night	29% 16% 28% 23% 4	836
November	1st to 10th	Night	25% 18% 28% 23% 6% 1	780
	11th to 20th	Night	26% 19% 30% 16% 9%	765
	21st to end	Night	31% 18% 26% 20% 5%	760
December	1st to 10th	Night	30% 20% 29% 18% 3	760
	11th to 20th	Night	27% 19% 31% 18% 5% 1	760
	21st to end	Night	33% 17% 30% 16% 3 1	836

Page generated at 2024-11-08 22:45:40. Version ac07

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