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 2024-01-12.

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	14% 10% 4 8% 6% 3 4 4 5% 7% 34%	74565
	Night	16% 12% 5% 9% 7% 3 4 4 4 6% 28%	75145
Transparency	Day	34% 37% 8% 14% 6% 1	74271
	Night	39% 37% 7% 11% 5% 1	74974
Seeing	Day	17% 5% 19% 31% 23% 6%	14515
	Night	21% 7% 24% 30% 16% 3	24301

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	14% 15% 12% 18% 10% 5% 6% 3 3 5% 10%	1517
	11th to 20th	Day	17% 16% 10% 15% 12% 5% 5% 4 4 4 9%	1448
	21st to end	Day	14% 16% 8% 15% 10% 5% 7% 4 3 6% 12%	1584
February	1st to 10th	Day	9% 12% 7% 12% 10% 5% 5% 5% 7% 6% 21%	1508
	11th to 20th	Day	13% 13% 6% 10% 9% 5% 5% 6% 5% 6% 21%	1730
	21st to end	Day	13% 13% 6% 9% 8% 4 7% 6% 5% 5% 25%	1480
March	1st to 10th	Day	12% 10% 5% 8% 9% 3 5% 3 5% 7% 33%	1798
	11th to 20th	Day	10% 9% 4 11% 6% 4 4 5% 4 7% 36%	1918
	21st to end	Day	15% 9% 3 7% 7% 3 6% 4 5% 6% 33%	2265
April	1st to 10th	Day	18% 10% 5% 7% 5% 3 5% 5% 5% 7% 30%	2160
	11th to 20th	Day	18% 9% 4 6% 5% 2 4 4 5% 7% 35%	2234
	21st to end	Day	15% 8% 3 9% 5% 4 5% 5% 4 7% 35%	2340
May	1st to 10th	Day	15% 7% 3 6% 5% 3 4 5% 5% 6% 41%	2340
	11th to 20th	Day	15% 6% 3 5% 6% 3 4 5% 5% 6% 41%	2422
	21st to end	Day	11% 6% 2 4 5% 3 5% 5% 6% 8% 46%	2725
June	1st to 10th	Day	11% 6% 2 5% 5% 3 5% 5% 5% 10% 44%	2689
	11th to 20th	Day	11% 6% 3 5% 5% 3 5% 4 6% 10% 43%	2700
	21st to end	Day	14% 6% 2 5% 4 4 4 5% 5% 8% 42%	2686
July	1st to 10th	Day	7% 3 2 4 4 2 3 4 5% 9% 56%	2520
	11th to 20th	Day	9% 5% 2 4 4 2 4 4 5% 9% 52%	2520
	21st to end	Day	8% 5% 2 5% 4 3 3 5% 6% 8% 52%	2743
August	1st to 10th	Day	9% 4 2 4 5% 3 5% 5% 6% 8% 49%	2443
	11th to 20th	Day	9% 6% 2 4 5% 2 4 5% 5% 8% 50%	2303
	21st to end	Day	13% 6% 2 4 5% 3 4 4 5% 7% 48%	2484
September	1st to 10th	Day	17% 6% 2 4 4 2 4 4 6% 8% 43%	2145
	11th to 20th	Day	13% 6% 3 5% 5% 3 4 5% 5% 7% 43%	1980
	21st to end	Day	17% 7% 3 6% 5% 3 5% 5% 5% 8% 36%	1980
October	1st to 10th	Day	20% 9% 3 7% 6% 3 4 4 4 6% 34%	1980
	11th to 20th	Day	23% 15% 5% 8% 6% 4 5% 4 4 5% 21%	1684
	21st to end	Day	25% 16% 4 9% 6% 4 5% 4 5% 5% 18%	1782
November	1st to 10th	Day	19% 16% 6% 8% 5% 3 4 4 5% 6% 24%	1672
	11th to 20th	Day	17% 19% 9% 12% 7% 3 5% 4 5% 4 15%	1710
	21st to end	Day	22% 21% 9% 10% 8% 4 3 4 4 4 12%	1483
December	1st to 10th	Day	18% 20% 13% 16% 6% 4 4 3 3 3 9%	1330
	11th to 20th	Day	19% 21% 7% 15% 10% 4 3 3 4 4 9%	1671
	21st to end	Day	26% 22% 9% 13% 7% 3 3 2 2 3 8%	2591
January	1st to 10th	Night	14% 17% 10% 16% 10% 5% 4 4 5% 4 12%	2648
	11th to 20th	Night	16% 18% 9% 14% 11% 4 4 4 4 4 13%	2541
	21st to end	Night	15% 15% 7% 14% 12% 4 5% 4 4 5% 15%	2772
February	1st to 10th	Night	10% 15% 6% 11% 11% 6% 7% 5% 5% 5% 20%	2450
	11th to 20th	Night	11% 13% 5% 11% 9% 4 6% 4 5% 7% 23%	2116
	21st to end	Night	14% 15% 5% 10% 9% 4 6% 5% 4 5% 23%	1776
March	1st to 10th	Night	12% 11% 4 7% 7% 3 4 4 4 7% 38%	2149
	11th to 20th	Night	12% 9% 4 8% 7% 3 5% 4 4 6% 36%	2039
	21st to end	Night	15% 9% 4 7% 5% 3 4 5% 5% 7% 36%	2106
April	1st to 10th	Night	19% 11% 3 7% 7% 3 6% 4 5% 6% 29%	1800
	11th to 20th	Night	18% 9% 4 6% 5% 3 4 4 5% 5% 35%	1674
	21st to end	Night	16% 7% 4 8% 7% 3 5% 4 5% 6% 36%	1620
May	1st to 10th	Night	16% 8% 3 6% 5% 4 5% 5% 5% 7% 35%	1620
	11th to 20th	Night	15% 8% 4 7% 8% 4 3 5% 5% 6% 35%	1470
	21st to end	Night	12% 6% 2 5% 5% 3 4 5% 7% 8% 43%	1551
June	1st to 10th	Night	14% 5% 2 6% 5% 3 4 5% 6% 10% 41%	1269
	11th to 20th	Night	12% 7% 3 5% 7% 3 4 5% 6% 7% 40%	1260
	21st to end	Night	13% 7% 3 5% 4 2 4 4 5% 8% 45%	1268
July	1st to 10th	Night	10% 3 2 5% 4 3 4 4 6% 9% 52%	1440
	11th to 20th	Night	9% 6% 3 5% 5% 3 4 4 5% 7% 49%	1440
	21st to end	Night	8% 5% 3 5% 5% 3 6% 4 5% 8% 49%	1575
August	1st to 10th	Night	6% 6% 2 4 5% 3 5% 6% 5% 10% 48%	1493
	11th to 20th	Night	8% 5% 1 5% 4 3 4 5% 4 9% 52%	1598
	21st to end	Night	13% 7% 2 5% 5% 3 3 4 5% 6% 47%	1870
September	1st to 10th	Night	13% 6% 3 5% 6% 3 3 3 5% 7% 46%	1800
	11th to 20th	Night	17% 7% 3 5% 4 3 4 4 5% 6% 43%	1976
	21st to end	Night	19% 7% 4 5% 5% 3 3 4 5% 8% 38%	1980
October	1st to 10th	Night	18% 9% 3 6% 5% 3 4 4 4 7% 36%	1980
	11th to 20th	Night	24% 12% 4 7% 6% 3 5% 5% 4 6% 24%	2275
	21st to end	Night	28% 14% 5% 8% 6% 3 4 4 4 5% 20%	2574
November	1st to 10th	Night	18% 13% 5% 8% 6% 3 4 4 5% 6% 28%	2406
	11th to 20th	Night	19% 18% 7% 12% 7% 4 4 4 4 4 18%	2470
	21st to end	Night	19% 21% 10% 11% 7% 3 4 4 4 4 12%	2691
December	1st to 10th	Night	16% 23% 11% 15% 7% 3 4 3 4 4 10%	2850
	11th to 20th	Night	18% 18% 7% 16% 10% 3 4 4 4 4 12%	3526
	21st to end	Night	24% 22% 11% 14% 7% 3 3 3 2 3 8%	5072

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% 40% 3 4 1	1518
	11th to 20th	Day	52% 43% 3 2	1448
	21st to end	Day	51% 40% 5% 3 1	1584
February	1st to 10th	Day	44% 38% 6% 11% 1	1508
	11th to 20th	Day	42% 40% 8% 7% 3	1740
	21st to end	Day	41% 36% 7% 12% 2	1480
March	1st to 10th	Day	35% 37% 8% 15% 4 1	1800
	11th to 20th	Day	31% 37% 11% 15% 5% 1	1918
	21st to end	Day	37% 37% 8% 13% 5%	2265
April	1st to 10th	Day	35% 37% 7% 14% 7%	2160
	11th to 20th	Day	33% 35% 7% 16% 9%	2234
	21st to end	Day	34% 36% 7% 12% 9% 3	2340
May	1st to 10th	Day	30% 37% 8% 15% 9% 1	2340
	11th to 20th	Day	27% 38% 6% 16% 11% 1	2426
	21st to end	Day	23% 38% 10% 18% 10% 2	2725
June	1st to 10th	Day	25% 37% 9% 19% 8% 1	2689
	11th to 20th	Day	22% 37% 10% 18% 13%	2700
	21st to end	Day	29% 37% 11% 14% 8% 1	2686
July	1st to 10th	Day	19% 38% 10% 20% 12% 1	2451
	11th to 20th	Day	19% 39% 9% 22% 11% 1	2445
	21st to end	Day	21% 39% 12% 19% 8%	2591
August	1st to 10th	Day	23% 38% 11% 19% 7% 1	2428
	11th to 20th	Day	19% 37% 10% 24% 10% 1	2303
	21st to end	Day	24% 37% 10% 19% 9% 1	2484
September	1st to 10th	Day	26% 36% 8% 21% 9% 1	2145
	11th to 20th	Day	27% 38% 13% 19% 3	1980
	21st to end	Day	32% 37% 11% 15% 5%	1980
October	1st to 10th	Day	32% 37% 9% 17% 5%	1980
	11th to 20th	Day	46% 38% 7% 7% 2	1684
	21st to end	Day	44% 39% 8% 8% 1	1782
November	1st to 10th	Day	37% 41% 8% 11% 4	1672
	11th to 20th	Day	45% 41% 7% 5% 2	1710
	21st to end	Day	48% 40% 8% 4	1483
December	1st to 10th	Day	53% 40% 3 3 1	1330
	11th to 20th	Day	57% 34% 5% 3 1	1671
	21st to end	Day	66% 25% 4 3 2	2591
January	1st to 10th	Night	49% 41% 6% 5%	2648
	11th to 20th	Night	49% 43% 4 4	2541
	21st to end	Night	51% 39% 5% 4 1	2772
February	1st to 10th	Night	47% 38% 5% 8% 2	2450
	11th to 20th	Night	43% 39% 7% 8% 2	2117
	21st to end	Night	45% 37% 7% 8% 2	1776
March	1st to 10th	Night	33% 36% 9% 16% 5%	2160
	11th to 20th	Night	33% 37% 9% 13% 7% 1	2040
	21st to end	Night	34% 37% 9% 14% 6%	2106
April	1st to 10th	Night	35% 37% 8% 12% 8%	1800
	11th to 20th	Night	33% 36% 7% 14% 9% 1	1674
	21st to end	Night	31% 37% 8% 13% 9% 2	1620
May	1st to 10th	Night	33% 36% 7% 14% 8% 2	1620
	11th to 20th	Night	33% 37% 5% 14% 10% 2	1471
	21st to end	Night	25% 38% 9% 15% 10% 3	1552
June	1st to 10th	Night	27% 37% 8% 17% 10% 1	1269
	11th to 20th	Night	26% 37% 10% 15% 10% 2	1260
	21st to end	Night	27% 37% 11% 16% 9% 1	1268
July	1st to 10th	Night	20% 38% 9% 20% 11% 1	1400
	11th to 20th	Night	21% 39% 9% 17% 12% 2	1392
	21st to end	Night	24% 39% 9% 18% 10% 1	1487
August	1st to 10th	Night	23% 38% 12% 19% 7% 1	1484
	11th to 20th	Night	18% 37% 13% 20% 11% 1	1598
	21st to end	Night	25% 38% 9% 17% 10% 1	1870
September	1st to 10th	Night	26% 37% 8% 18% 12% 1	1800
	11th to 20th	Night	28% 37% 13% 18% 4	1976
	21st to end	Night	30% 38% 11% 15% 5%	1980
October	1st to 10th	Night	31% 36% 9% 16% 6% 1	1980
	11th to 20th	Night	41% 39% 7% 9% 3	2275
	21st to end	Night	45% 39% 7% 9% 2	2574
November	1st to 10th	Night	34% 42% 7% 12% 4	2406
	11th to 20th	Night	45% 40% 6% 5% 4	2470
	21st to end	Night	48% 40% 7% 4	2691
December	1st to 10th	Night	53% 40% 4 3	2850
	11th to 20th	Night	54% 34% 8% 3 1	3525
	21st to end	Night	67% 26% 4 2	5072

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	19% 9% 32% 29% 10% 1	270
	11th to 20th	Day	25% 9% 25% 30% 9% 2	243
	21st to end	Day	25% 3 28% 30% 15%	264
February	1st to 10th	Day	14% 7% 37% 34% 7% 1	240
	11th to 20th	Day	17% 5% 36% 28% 13% 1	240
	21st to end	Day	21% 8% 32% 33% 5%	198
March	1st to 10th	Day	16% 6% 25% 38% 14% 1	240
	11th to 20th	Day	14% 6% 27% 34% 16% 4	358
	21st to end	Day	22% 6% 21% 34% 15% 3	462
April	1st to 10th	Day	20% 6% 20% 37% 13% 2	420
	11th to 20th	Day	20% 8% 22% 27% 18% 5%	412
	21st to end	Day	15% 4 22% 35% 19% 4	420
May	1st to 10th	Day	20% 4 15% 36% 20% 5%	423
	11th to 20th	Day	17% 2 14% 36% 26% 5%	568
	21st to end	Day	14% 2 11% 34% 31% 8%	679
June	1st to 10th	Day	11% 1 13% 38% 31% 6%	630
	11th to 20th	Day	13% 1 13% 37% 29% 7%	630
	21st to end	Day	15% 2 10% 35% 30% 7%	630
July	1st to 10th	Day	8% 1 8% 35% 38% 10%	621
	11th to 20th	Day	10% 1 14% 30% 35% 11%	618
	21st to end	Day	9% 1 9% 34% 37% 10%	684
August	1st to 10th	Day	10% 3 8% 32% 35% 12%	562
	11th to 20th	Day	10% 4 9% 26% 38% 12%	439
	21st to end	Day	16% 4 12% 30% 29% 9%	495
September	1st to 10th	Day	20% 2 16% 29% 24% 9%	450
	11th to 20th	Day	13% 3 15% 31% 29% 8%	450
	21st to end	Day	18% 5% 21% 25% 25% 6%	450
October	1st to 10th	Day	20% 7% 24% 25% 18% 5%	450
	11th to 20th	Day	26% 11% 25% 25% 12% 1	324
	21st to end	Day	33% 8% 25% 23% 8% 2	297
November	1st to 10th	Day	19% 12% 29% 27% 13%	270
	11th to 20th	Day	21% 13% 36% 23% 6% 1	270
	21st to end	Day	25% 14% 39% 18% 4	205
December	1st to 10th	Day	28% 12% 30% 21% 7% 2	180
	11th to 20th	Day	26% 15% 33% 21% 4 1	180
	21st to end	Day	33% 16% 32% 13% 4 1	243
January	1st to 10th	Night	21% 9% 33% 27% 8% 1	950
	11th to 20th	Night	23% 9% 32% 26% 10% 1	908
	21st to end	Night	21% 6% 30% 31% 9% 1	990
February	1st to 10th	Night	17% 5% 35% 33% 9% 1	830
	11th to 20th	Night	18% 6% 34% 32% 10% 1	703
	21st to end	Night	20% 7% 28% 35% 8% 1	592
March	1st to 10th	Night	16% 4 28% 36% 15% 2	720
	11th to 20th	Night	17% 5% 28% 36% 12% 2	720
	21st to end	Night	18% 4 23% 38% 15% 2	720
April	1st to 10th	Night	22% 4 29% 34% 9% 3	540
	11th to 20th	Night	22% 5% 20% 35% 17% 2	533
	21st to end	Night	18% 5% 21% 39% 16% 1	540
May	1st to 10th	Night	18% 3 18% 38% 21% 2	540
	11th to 20th	Night	18% 2 16% 42% 19% 3	531
	21st to end	Night	13% 2 13% 35% 32% 4	584
June	1st to 10th	Night	15% 1 12% 40% 28% 4	369
	11th to 20th	Night	13% 2 16% 38% 27% 5%	360
	21st to end	Night	15% 2 14% 29% 36% 4	368
July	1st to 10th	Night	12% 1 10% 36% 34% 7%	525
	11th to 20th	Night	10% 3 12% 34% 31% 10%	522
	21st to end	Night	9% 1 12% 40% 32% 5%	591
August	1st to 10th	Night	9% 2 10% 40% 32% 6%	537
	11th to 20th	Night	9% 2 13% 31% 37% 9%	534
	21st to end	Night	15% 3 13% 39% 27% 3	594
September	1st to 10th	Night	16% 3 18% 30% 26% 8%	540
	11th to 20th	Night	21% 4 17% 27% 24% 7%	716
	21st to end	Night	22% 6% 18% 26% 22% 7%	720
October	1st to 10th	Night	23% 6% 23% 26% 18% 4	720
	11th to 20th	Night	29% 10% 24% 25% 10% 1	720
	21st to end	Night	38% 8% 23% 23% 7% 1	792
November	1st to 10th	Night	26% 10% 29% 25% 10%	740
	11th to 20th	Night	28% 14% 31% 19% 7% 1	760
	21st to end	Night	29% 13% 34% 20% 5%	847
December	1st to 10th	Night	27% 14% 32% 20% 5% 1	950
	11th to 20th	Night	27% 13% 36% 16% 5% 2	950
	21st to end	Night	30% 12% 34% 20% 4	1045

Page generated at 2024-01-09 07:14:44. Version ac07

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