Beaver Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Beaver Island clear sky chart from 2005-11-06 to 2024-12-09.

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	23% 11% 3 7% 5% 4 4 4 5% 6% 28%	101887
	Night	24% 11% 3 7% 4 4 4 3 5% 6% 29%	98020
Transparency	Day	55% 7% 11% 17% 9% 1	105438
	Night	56% 6% 12% 17% 8% 1	102562
Seeing	Day	28% 10% 28% 24% 9% 1	17589
	Night	29% 11% 28% 23% 9% 1	25242

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% 10% 3 9% 6% 5% 6% 5% 6% 7% 29%	2526
	11th to 20th	Day	16% 13% 3 9% 6% 4 4 3 6% 7% 29%	2530
	21st to end	Day	17% 9% 4 8% 5% 5% 5% 4 7% 7% 29%	3066
February	1st to 10th	Day	22% 11% 4 6% 5% 5% 5% 4 5% 6% 25%	1710
	11th to 20th	Day	18% 11% 4 9% 6% 4 5% 5% 5% 5% 28%	1663
	21st to end	Day	14% 13% 4 6% 5% 4 5% 4 6% 6% 33%	1513
March	1st to 10th	Day	23% 13% 3 7% 5% 4 3 3 4 5% 29%	3269
	11th to 20th	Day	16% 13% 4 7% 5% 5% 4 4 7% 7% 27%	3480
	21st to end	Day	32% 9% 3 9% 5% 5% 4 3 4 4 23%	3925
April	1st to 10th	Day	26% 9% 3 6% 4 5% 5% 4 4 6% 29%	2280
	11th to 20th	Day	24% 9% 3 7% 4 3 4 3 5% 6% 31%	2254
	21st to end	Day	25% 9% 3 6% 5% 4 4 3 5% 6% 31%	2437
May	1st to 10th	Day	29% 12% 3 7% 5% 4 4 3 5% 5% 22%	4356
	11th to 20th	Day	26% 11% 3 7% 4 4 4 3 4 5% 28%	4398
	21st to end	Day	22% 13% 4 8% 6% 5% 5% 4 5% 7% 22%	4836
June	1st to 10th	Day	30% 10% 3 7% 4 4 4 4 5% 7% 21%	2660
	11th to 20th	Day	24% 10% 2 7% 5% 4 4 4 5% 6% 29%	2660
	21st to end	Day	35% 14% 4 7% 4 3 3 3 4 4 19%	2660
July	1st to 10th	Day	28% 13% 3 8% 5% 5% 4 4 4 6% 21%	4440
	11th to 20th	Day	27% 17% 4 7% 5% 3 3 3 4 6% 21%	4440
	21st to end	Day	22% 12% 4 8% 5% 4 4 4 5% 6% 28%	4815
August	1st to 10th	Day	25% 12% 4 9% 4 4 4 4 5% 6% 22%	4147
	11th to 20th	Day	20% 9% 3 7% 4 4 4 4 7% 9% 29%	4045
	21st to end	Day	12% 7% 2 6% 4 4 4 4 4 7% 46%	4225
September	1st to 10th	Day	19% 8% 2 6% 4 4 4 3 5% 7% 39%	2280
	11th to 20th	Day	20% 7% 2 5% 3 3 4 4 6% 7% 38%	2280
	21st to end	Day	20% 8% 3 5% 4 5% 4 4 5% 7% 36%	1995
October	1st to 10th	Day	18% 7% 2 6% 5% 6% 4 4 7% 7% 34%	1900
	11th to 20th	Day	21% 7% 3 6% 4 4 4 4 6% 7% 35%	1900
	21st to end	Day	22% 8% 3 6% 5% 4 4 4 5% 8% 30%	2024
November	1st to 10th	Day	23% 8% 3 8% 4 4 4 3 6% 7% 31%	1700
	11th to 20th	Day	23% 10% 2 7% 4 5% 5% 4 6% 6% 28%	1600
	21st to end	Day	19% 10% 3 8% 6% 5% 4 4 7% 8% 27%	1600
December	1st to 10th	Day	23% 12% 4 7% 6% 4 4 4 5% 6% 24%	1584
	11th to 20th	Day	29% 11% 3 6% 5% 5% 5% 3 5% 5% 21%	1906
	21st to end	Day	22% 10% 5% 9% 5% 5% 4 3 4 6% 27%	2783
January	1st to 10th	Night	16% 11% 3 7% 5% 4 4 3 6% 7% 33%	4429
	11th to 20th	Night	21% 11% 4 9% 5% 5% 5% 4 6% 7% 23%	4440
	21st to end	Night	17% 11% 6% 9% 5% 4 4 4 6% 6% 27%	4589
February	1st to 10th	Night	22% 11% 4 9% 5% 5% 4 4 6% 7% 24%	2470
	11th to 20th	Night	18% 11% 4 9% 6% 5% 5% 4 6% 5% 25%	2403
	21st to end	Night	13% 13% 5% 9% 6% 4 4 4 5% 6% 30%	1941
March	1st to 10th	Night	22% 12% 4 8% 5% 5% 5% 3 5% 5% 25%	3569
	11th to 20th	Night	23% 12% 4 7% 5% 4 5% 3 5% 7% 24%	3479
	21st to end	Night	31% 10% 5% 8% 4 4 3 2 4 4 26%	3706
April	1st to 10th	Night	27% 11% 3 6% 4 4 3 3 5% 6% 28%	1900
	11th to 20th	Night	25% 8% 2 5% 4 5% 4 4 4 6% 33%	1876
	21st to end	Night	27% 9% 3 5% 4 3 3 4 5% 6% 31%	1739
May	1st to 10th	Night	28% 14% 5% 8% 5% 4 4 2 4 5% 20%	2592
	11th to 20th	Night	29% 11% 3 5% 4 4 4 3 4 5% 29%	2506
	21st to end	Night	28% 15% 3 6% 4 3 4 4 5% 6% 23%	2749
June	1st to 10th	Night	33% 13% 3 5% 3 4 3 3 5% 7% 23%	1520
	11th to 20th	Night	26% 9% 3 6% 4 4 4 3 5% 6% 30%	1520
	21st to end	Night	35% 15% 4 7% 3 4 3 2 3 4 20%	1520
July	1st to 10th	Night	31% 16% 4 6% 4 3 3 2 4 5% 21%	2530
	11th to 20th	Night	30% 22% 3 6% 3 2 3 2 3 5% 20%	2530
	21st to end	Night	26% 12% 2 5% 4 3 4 3 5% 5% 31%	2750
August	1st to 10th	Night	30% 12% 3 6% 3 3 3 3 4 6% 27%	2782
	11th to 20th	Night	19% 12% 3 8% 4 4 4 4 6% 8% 29%	2782
	21st to end	Night	16% 6% 1 4 3 3 3 3 5% 7% 49%	3430
September	1st to 10th	Night	19% 8% 2 5% 4 3 4 4 4 8% 40%	1900
	11th to 20th	Night	21% 6% 2 5% 3 3 3 4 5% 7% 40%	1900
	21st to end	Night	22% 8% 4 6% 4 4 4 3 5% 7% 35%	2182
October	1st to 10th	Night	18% 5% 2 6% 4 4 5% 3 6% 7% 39%	2280
	11th to 20th	Night	22% 6% 2 4 4 4 4 4 5% 8% 38%	2280
	21st to end	Night	25% 8% 2 6% 4 4 4 3 5% 6% 33%	2574
November	1st to 10th	Night	21% 9% 3 7% 4 4 4 3 5% 6% 33%	2596
	11th to 20th	Night	22% 10% 3 7% 5% 5% 4 3 5% 6% 29%	2800
	21st to end	Night	22% 11% 3 7% 5% 5% 4 3 5% 7% 28%	2800
December	1st to 10th	Night	25% 12% 4 7% 5% 4 4 3 5% 6% 25%	2779
	11th to 20th	Night	32% 12% 3 7% 4 4 4 3 4 5% 23%	3293
	21st to end	Night	27% 10% 3 8% 4 5% 4 4 5% 6% 23%	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	53% 10% 15% 16% 5% 1	2527
	11th to 20th	Day	52% 8% 11% 20% 8% 1	2530
	21st to end	Day	53% 7% 13% 15% 12% 1	3066
February	1st to 10th	Day	59% 7% 11% 12% 10% 1	1710
	11th to 20th	Day	57% 8% 11% 14% 8% 2	1671
	21st to end	Day	49% 7% 12% 18% 11% 3	1513
March	1st to 10th	Day	57% 5% 10% 16% 10% 1	3273
	11th to 20th	Day	49% 11% 13% 17% 8% 1	3480
	21st to end	Day	63% 6% 9% 12% 8% 2	3925
April	1st to 10th	Day	53% 8% 10% 15% 12% 2	2280
	11th to 20th	Day	52% 6% 8% 19% 13% 1	2254
	21st to end	Day	54% 5% 11% 17% 11% 2	2437
May	1st to 10th	Day	61% 8% 12% 13% 5% 1	4371
	11th to 20th	Day	56% 9% 10% 18% 7%	4402
	21st to end	Day	57% 11% 13% 13% 5%	4836
June	1st to 10th	Day	62% 8% 10% 15% 5%	2660
	11th to 20th	Day	55% 7% 10% 17% 10% 1	2660
	21st to end	Day	70% 5% 6% 11% 7% 1	2660
July	1st to 10th	Day	66% 5% 8% 10% 9% 1	4370
	11th to 20th	Day	66% 6% 7% 13% 7%	4364
	21st to end	Day	54% 8% 11% 17% 9%	4662
August	1st to 10th	Day	62% 7% 9% 16% 5%	4133
	11th to 20th	Day	49% 9% 14% 22% 5%	4084
	21st to end	Day	37% 7% 13% 27% 16%	4225
September	1st to 10th	Day	45% 6% 12% 22% 13% 2	2280
	11th to 20th	Day	43% 6% 13% 24% 12% 1	2280
	21st to end	Day	46% 8% 9% 22% 14%	1995
October	1st to 10th	Day	46% 8% 11% 24% 10% 1	3160
	11th to 20th	Day	37% 6% 13% 28% 16%	3140
	21st to end	Day	47% 5% 15% 20% 11% 2	3318
November	1st to 10th	Day	53% 7% 12% 19% 8% 1	1700
	11th to 20th	Day	56% 6% 12% 16% 8% 1	1600
	21st to end	Day	56% 6% 16% 14% 7% 1	1600
December	1st to 10th	Day	61% 6% 12% 16% 5%	1584
	11th to 20th	Day	66% 5% 12% 11% 6%	1905
	21st to end	Day	61% 4 19% 10% 5% 1	2783
January	1st to 10th	Night	52% 7% 20% 18% 4	4429
	11th to 20th	Night	59% 7% 13% 13% 6% 1	4440
	21st to end	Night	57% 6% 13% 17% 7%	4589
February	1st to 10th	Night	61% 7% 12% 11% 8% 1	2470
	11th to 20th	Night	59% 6% 14% 12% 8% 2	2406
	21st to end	Night	54% 4 14% 18% 9% 2	1941
March	1st to 10th	Night	60% 5% 8% 17% 8% 2	3578
	11th to 20th	Night	58% 7% 12% 15% 8% 1	3480
	21st to end	Night	63% 4 8% 16% 8% 1	3706
April	1st to 10th	Night	57% 6% 9% 15% 11% 2	1900
	11th to 20th	Night	50% 7% 9% 19% 13% 2	1876
	21st to end	Night	54% 5% 9% 18% 12% 2	1739
May	1st to 10th	Night	64% 8% 9% 14% 5% 1	2597
	11th to 20th	Night	56% 8% 11% 19% 6%	2507
	21st to end	Night	61% 7% 12% 15% 5% 1	2750
June	1st to 10th	Night	62% 6% 9% 18% 6%	1520
	11th to 20th	Night	55% 5% 10% 16% 13%	1520
	21st to end	Night	70% 4 7% 13% 5% 1	1520
July	1st to 10th	Night	68% 4 8% 11% 7% 1	2491
	11th to 20th	Night	69% 5% 7% 12% 7%	2482
	21st to end	Night	54% 6% 11% 19% 10% 1	2663
August	1st to 10th	Night	60% 5% 12% 19% 4	2771
	11th to 20th	Night	52% 8% 15% 21% 4	2809
	21st to end	Night	34% 7% 15% 29% 15%	3429
September	1st to 10th	Night	44% 6% 12% 24% 13% 1	1900
	11th to 20th	Night	43% 5% 12% 24% 14% 1	1900
	21st to end	Night	49% 6% 9% 24% 11% 1	2182
October	1st to 10th	Night	48% 7% 14% 21% 10%	3800
	11th to 20th	Night	36% 6% 12% 30% 17%	3779
	21st to end	Night	45% 5% 14% 22% 13%	4234
November	1st to 10th	Night	52% 8% 12% 18% 9%	2596
	11th to 20th	Night	56% 6% 14% 14% 10% 1	2800
	21st to end	Night	58% 7% 15% 14% 6%	2800
December	1st to 10th	Night	61% 6% 13% 14% 5%	2779
	11th to 20th	Night	66% 4 11% 13% 6%	3295
	21st to end	Night	63% 5% 14% 14% 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	24% 19% 34% 19% 4	370
	11th to 20th	Day	26% 19% 34% 16% 5%	370
	21st to end	Day	22% 14% 36% 23% 5%	407
February	1st to 10th	Day	29% 18% 31% 18% 4 1	370
	11th to 20th	Day	25% 19% 36% 18% 2	366
	21st to end	Day	21% 14% 39% 21% 5%	307
March	1st to 10th	Day	23% 15% 40% 19% 3	413
	11th to 20th	Day	21% 17% 33% 23% 5%	460
	21st to end	Day	26% 15% 35% 17% 6% 1	506
April	1st to 10th	Day	30% 14% 33% 19% 3	460
	11th to 20th	Day	31% 11% 35% 17% 6% 1	452
	21st to end	Day	25% 10% 29% 27% 7% 2	460
May	1st to 10th	Day	33% 8% 30% 21% 5% 2	610
	11th to 20th	Day	28% 5% 28% 31% 6% 2	674
	21st to end	Day	33% 8% 25% 27% 6% 1	735
June	1st to 10th	Day	35% 5% 22% 28% 9% 1	680
	11th to 20th	Day	28% 5% 23% 34% 10% 1	680
	21st to end	Day	41% 5% 17% 26% 10% 1	680
July	1st to 10th	Day	34% 4 17% 31% 13% 1	670
	11th to 20th	Day	36% 4 15% 29% 14% 1	668
	21st to end	Day	33% 3 18% 31% 13% 2	740
August	1st to 10th	Day	23% 4 23% 32% 16% 3	515
	11th to 20th	Day	27% 4 23% 27% 15% 4	479
	21st to end	Day	22% 6% 22% 31% 16% 4	539
September	1st to 10th	Day	23% 6% 25% 29% 16% 2	490
	11th to 20th	Day	23% 8% 24% 28% 14% 3	490
	21st to end	Day	24% 5% 28% 25% 17% 2	423
October	1st to 10th	Day	21% 8% 28% 25% 15% 3	390
	11th to 20th	Day	21% 10% 31% 24% 14% 1	390
	21st to end	Day	25% 13% 33% 19% 8% 1	429
November	1st to 10th	Day	21% 14% 33% 24% 6% 2	395
	11th to 20th	Day	30% 18% 31% 16% 6% 1	400
	21st to end	Day	24% 19% 36% 16% 5% 1	400
December	1st to 10th	Day	27% 15% 32% 21% 4	394
	11th to 20th	Day	32% 22% 29% 15% 1	370
	21st to end	Day	25% 18% 33% 19% 5%	407
January	1st to 10th	Night	29% 17% 33% 18% 3	850
	11th to 20th	Night	29% 18% 34% 16% 3	850
	21st to end	Night	22% 18% 37% 18% 5%	850
February	1st to 10th	Night	29% 17% 31% 20% 3	760
	11th to 20th	Night	25% 20% 38% 15% 2	743
	21st to end	Night	19% 14% 38% 21% 7%	628
March	1st to 10th	Night	23% 16% 39% 19% 3	760
	11th to 20th	Night	25% 13% 29% 24% 9% 1	760
	21st to end	Night	27% 14% 30% 23% 7%	777
April	1st to 10th	Night	32% 11% 28% 23% 5%	570
	11th to 20th	Night	28% 8% 30% 26% 7% 1	564
	21st to end	Night	32% 7% 24% 28% 8% 1	570
May	1st to 10th	Night	35% 5% 27% 21% 9% 2	570
	11th to 20th	Night	32% 4 22% 27% 12% 3	562
	21st to end	Night	31% 5% 26% 28% 8% 1	616
June	1st to 10th	Night	39% 4 20% 28% 8% 1	570
	11th to 20th	Night	32% 4 18% 34% 12% 1	570
	21st to end	Night	40% 3 18% 24% 14% 1	570
July	1st to 10th	Night	33% 3 15% 33% 15% 1	556
	11th to 20th	Night	36% 4 15% 28% 17% 1	552
	21st to end	Night	37% 4 14% 26% 19% 1	623
August	1st to 10th	Night	28% 4 14% 33% 19% 2	568
	11th to 20th	Night	26% 3 18% 32% 19% 2	562
	21st to end	Night	24% 3 17% 30% 22% 3	627
September	1st to 10th	Night	22% 4 24% 31% 18% 2	570
	11th to 20th	Night	24% 5% 23% 29% 17% 2	570
	21st to end	Night	25% 7% 26% 28% 12% 2	725
October	1st to 10th	Night	21% 7% 28% 31% 11% 2	760
	11th to 20th	Night	25% 10% 29% 24% 9% 2	760
	21st to end	Night	30% 12% 33% 20% 6%	871
November	1st to 10th	Night	26% 13% 30% 24% 5% 1	880
	11th to 20th	Night	28% 17% 29% 18% 7%	900
	21st to end	Night	30% 16% 32% 18% 4	900
December	1st to 10th	Night	31% 15% 32% 16% 5%	893
	11th to 20th	Night	31% 20% 33% 14% 2	850
	21st to end	Night	29% 16% 34% 16% 4 1	935

Page generated at 2024-12-06 04:54:48. Version ac07

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