Fanny Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fanny Bay clear sky chart from 2005-11-06 to 2024-02-10.

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	21% 10% 4 7% 6% 4 5% 5% 5% 6% 27%	77762
	Night	23% 10% 4 7% 6% 3 5% 5% 5% 6% 27%	81158
Transparency	Day	37% 40% 10% 9% 4	77465
	Night	40% 39% 9% 8% 3	81035
Seeing	Day	23% 9% 22% 24% 17% 5%	14599
	Night	26% 6% 19% 26% 19% 4	22814

By Month

Percentage Cloud Cover NW (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	32% 18% 5% 7% 6% 4 4 3 4 5% 12%	2219
	11th to 20th	Day	25% 12% 4 7% 10% 4 5% 5% 5% 7% 16%	2199
	21st to end	Day	46% 15% 4 7% 5% 2 4 3 4 3 7%	2698
February	1st to 10th	Day	26% 16% 6% 9% 6% 3 4 6% 5% 6% 14%	1702
	11th to 20th	Day	22% 15% 5% 9% 6% 3 5% 4 4 5% 22%	1575
	21st to end	Day	23% 12% 5% 8% 7% 5% 6% 6% 5% 6% 17%	1332
March	1st to 10th	Day	21% 13% 5% 8% 7% 5% 7% 5% 5% 5% 18%	1885
	11th to 20th	Day	22% 13% 4 9% 8% 4 6% 5% 5% 6% 18%	1980
	21st to end	Day	23% 13% 5% 9% 8% 4 5% 5% 4 4 19%	2178
April	1st to 10th	Day	23% 15% 4 9% 7% 3 6% 5% 4 6% 18%	2158
	11th to 20th	Day	21% 12% 5% 9% 7% 5% 5% 5% 5% 6% 21%	2308
	21st to end	Day	22% 12% 4 7% 7% 5% 5% 4 5% 6% 22%	2340
May	1st to 10th	Day	15% 9% 4 7% 6% 5% 7% 6% 7% 6% 28%	2503
	11th to 20th	Day	17% 9% 4 7% 6% 4 5% 6% 6% 7% 26%	2477
	21st to end	Day	18% 9% 3 6% 7% 5% 6% 6% 6% 7% 27%	2900
June	1st to 10th	Day	20% 10% 4 8% 8% 4 7% 5% 5% 6% 24%	2700
	11th to 20th	Day	16% 10% 4 9% 8% 5% 7% 6% 6% 8% 20%	2700
	21st to end	Day	17% 7% 4 7% 6% 4 6% 6% 5% 6% 33%	2700
July	1st to 10th	Day	13% 7% 3 6% 5% 3 5% 4 5% 8% 41%	2700
	11th to 20th	Day	8% 5% 3 4 6% 3 5% 6% 6% 7% 48%	2700
	21st to end	Day	7% 4 2 4 3 3 4 4 6% 7% 55%	2909
August	1st to 10th	Day	11% 4 2 5% 4 3 4 4 6% 7% 50%	2405
	11th to 20th	Day	7% 4 2 4 4 3 4 5% 6% 9% 52%	2298
	21st to end	Day	12% 6% 3 5% 6% 3 5% 5% 7% 9% 41%	2574
September	1st to 10th	Day	10% 6% 2 5% 5% 3 4 5% 4 8% 47%	2173
	11th to 20th	Day	17% 8% 3 6% 5% 3 5% 3 4 7% 39%	2068
	21st to end	Day	21% 7% 3 5% 6% 4 4 4 5% 6% 36%	1955
October	1st to 10th	Day	24% 8% 3 6% 5% 3 6% 5% 4 6% 32%	1800
	11th to 20th	Day	28% 9% 3 7% 6% 3 5% 5% 6% 6% 23%	1800
	21st to end	Day	28% 11% 3 6% 7% 3 5% 5% 4 5% 24%	1812
November	1st to 10th	Day	30% 13% 4 7% 7% 5% 5% 4 4 5% 16%	1488
	11th to 20th	Day	26% 13% 5% 8% 7% 3 5% 5% 4 6% 19%	1520
	21st to end	Day	31% 11% 5% 7% 6% 4 6% 4 4 4 19%	1520
December	1st to 10th	Day	23% 14% 5% 8% 7% 3 4 5% 4 6% 20%	1359
	11th to 20th	Day	33% 16% 5% 9% 7% 4 4 4 3 3 12%	1685
	21st to end	Day	37% 14% 5% 9% 7% 3 4 4 4 3 10%	2442
January	1st to 10th	Night	30% 16% 4 9% 6% 3 5% 4 4 4 14%	4726
	11th to 20th	Night	27% 11% 4 7% 8% 3 4 4 4 6% 21%	4699
	21st to end	Night	43% 14% 4 7% 5% 3 4 3 4 3 10%	4959
February	1st to 10th	Night	24% 14% 5% 8% 7% 3 5% 6% 5% 4 19%	2462
	11th to 20th	Night	20% 14% 4 7% 6% 4 5% 4 4 7% 26%	2272
	21st to end	Night	20% 13% 5% 8% 7% 4 5% 5% 4 6% 24%	1924
March	1st to 10th	Night	20% 11% 3 8% 6% 4 7% 5% 6% 6% 23%	2074
	11th to 20th	Night	21% 10% 4 7% 6% 4 5% 5% 6% 8% 24%	1979
	21st to end	Night	21% 12% 6% 7% 8% 4 5% 6% 5% 6% 21%	2178
April	1st to 10th	Night	19% 11% 4 7% 6% 4 6% 6% 6% 7% 24%	1799
	11th to 20th	Night	19% 10% 5% 6% 6% 4 5% 5% 6% 6% 27%	1601
	21st to end	Night	21% 9% 3 7% 6% 4 4 5% 6% 8% 27%	1620
May	1st to 10th	Night	16% 7% 4 6% 7% 4 5% 4 5% 6% 36%	1455
	11th to 20th	Night	14% 8% 3 7% 7% 5% 7% 7% 8% 7% 28%	1416
	21st to end	Night	14% 8% 4 7% 6% 4 6% 6% 5% 7% 33%	1371
June	1st to 10th	Night	16% 8% 4 7% 7% 5% 6% 5% 5% 7% 30%	1260
	11th to 20th	Night	15% 7% 6% 7% 7% 4 8% 5% 7% 8% 26%	1260
	21st to end	Night	13% 6% 4 6% 5% 3 4 6% 6% 9% 39%	1260
July	1st to 10th	Night	11% 5% 3 4 6% 3 4 5% 6% 7% 47%	1260
	11th to 20th	Night	7% 3 2 4 5% 2 4 5% 6% 8% 53%	1260
	21st to end	Night	6% 4 2 3 3 2 4 5% 5% 5% 62%	1406
August	1st to 10th	Night	10% 6% 2 4 4 3 3 2 5% 6% 55%	1531
	11th to 20th	Night	5% 3 2 4 4 3 4 4 4 9% 58%	1602
	21st to end	Night	11% 5% 2 5% 4 4 4 6% 6% 7% 46%	1782
September	1st to 10th	Night	10% 5% 2 4 4 2 4 4 5% 8% 53%	1786
	11th to 20th	Night	17% 7% 3 6% 5% 3 5% 4 5% 6% 39%	1890
	21st to end	Night	20% 6% 3 7% 5% 2 4 3 4 6% 39%	2004
October	1st to 10th	Night	19% 7% 2 6% 5% 3 4 4 4 6% 40%	2160
	11th to 20th	Night	25% 9% 4 7% 5% 3 5% 5% 5% 6% 28%	2160
	21st to end	Night	27% 9% 3 7% 6% 3 4 4 4 5% 28%	2541
November	1st to 10th	Night	29% 12% 4 7% 6% 3 5% 5% 5% 5% 18%	2590
	11th to 20th	Night	26% 11% 4 7% 7% 3 6% 5% 4 5% 20%	2660
	21st to end	Night	28% 10% 4 8% 6% 3 5% 4 4 5% 22%	2660
December	1st to 10th	Night	23% 15% 5% 8% 7% 3 5% 4 4 5% 21%	2817
	11th to 20th	Night	32% 15% 5% 10% 7% 4 4 3 4 4 12%	3520
	21st to end	Night	39% 13% 4 7% 5% 3 4 4 3 4 14%	5214

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	59% 28% 6% 6% 1	2219
	11th to 20th	Day	49% 33% 9% 6% 2	2220
	21st to end	Day	69% 24% 4 3 1	2698
February	1st to 10th	Day	49% 40% 5% 5% 1	1702
	11th to 20th	Day	43% 40% 7% 8% 2	1584
	21st to end	Day	41% 41% 9% 4 3 1	1332
March	1st to 10th	Day	42% 42% 6% 6% 2	1885
	11th to 20th	Day	42% 42% 8% 6% 2 1	1980
	21st to end	Day	42% 41% 8% 8% 1	2178
April	1st to 10th	Day	41% 44% 8% 6% 2	2158
	11th to 20th	Day	38% 41% 6% 9% 6% 1	2308
	21st to end	Day	39% 41% 8% 8% 4	2340
May	1st to 10th	Day	36% 42% 10% 11% 2	2503
	11th to 20th	Day	32% 41% 11% 12% 3	2480
	21st to end	Day	36% 44% 10% 8% 2	2901
June	1st to 10th	Day	38% 42% 8% 7% 4 2	2700
	11th to 20th	Day	37% 45% 11% 6% 1	2700
	21st to end	Day	30% 42% 13% 10% 6% 1	2700
July	1st to 10th	Day	23% 42% 13% 15% 6% 1	2626
	11th to 20th	Day	19% 41% 17% 19% 4	2619
	21st to end	Day	15% 41% 12% 20% 10% 2	2747
August	1st to 10th	Day	20% 42% 15% 17% 5%	2388
	11th to 20th	Day	17% 41% 16% 15% 9% 2	2298
	21st to end	Day	24% 43% 16% 13% 3 1	2574
September	1st to 10th	Day	17% 41% 14% 18% 8% 1	2173
	11th to 20th	Day	27% 41% 11% 12% 9% 1	2068
	21st to end	Day	31% 41% 11% 11% 5%	1955
October	1st to 10th	Day	31% 42% 12% 10% 5%	1800
	11th to 20th	Day	39% 44% 9% 7% 1	1800
	21st to end	Day	40% 41% 8% 7% 4	1812
November	1st to 10th	Day	43% 45% 5% 4 3	1488
	11th to 20th	Day	44% 43% 6% 5% 1	1520
	21st to end	Day	43% 44% 5% 5% 2	1520
December	1st to 10th	Day	42% 44% 6% 4 3	1359
	11th to 20th	Day	55% 37% 4 2 1	1688
	21st to end	Day	60% 29% 6% 4 1	2442
January	1st to 10th	Night	58% 32% 5% 4 1	4726
	11th to 20th	Night	44% 35% 11% 6% 3 1	4740
	21st to end	Night	67% 25% 3 4 1	4959
February	1st to 10th	Night	47% 39% 7% 6% 2	2462
	11th to 20th	Night	36% 41% 8% 10% 4 1	2274
	21st to end	Night	42% 39% 7% 8% 3	1924
March	1st to 10th	Night	38% 43% 9% 7% 3	2074
	11th to 20th	Night	37% 44% 9% 5% 4	1980
	21st to end	Night	40% 43% 7% 8% 2	2178
April	1st to 10th	Night	36% 43% 10% 9% 2	1799
	11th to 20th	Night	33% 41% 9% 11% 6% 1	1601
	21st to end	Night	35% 42% 9% 10% 4	1620
May	1st to 10th	Night	32% 41% 11% 13% 3	1455
	11th to 20th	Night	32% 43% 10% 12% 3 1	1416
	21st to end	Night	35% 42% 12% 9% 2	1371
June	1st to 10th	Night	34% 41% 12% 7% 3 2	1260
	11th to 20th	Night	36% 42% 14% 6% 2	1260
	21st to end	Night	27% 41% 14% 11% 5% 2	1260
July	1st to 10th	Night	21% 42% 16% 14% 7%	1225
	11th to 20th	Night	17% 41% 17% 20% 4	1218
	21st to end	Night	12% 41% 13% 22% 10% 3	1328
August	1st to 10th	Night	21% 39% 14% 20% 5%	1523
	11th to 20th	Night	14% 41% 19% 13% 11% 2	1602
	21st to end	Night	22% 42% 16% 17% 2	1782
September	1st to 10th	Night	15% 40% 13% 21% 10% 2	1786
	11th to 20th	Night	26% 41% 9% 11% 11% 2	1890
	21st to end	Night	31% 40% 13% 9% 6% 2	2004
October	1st to 10th	Night	28% 40% 12% 14% 6%	2160
	11th to 20th	Night	35% 41% 10% 12% 3	2160
	21st to end	Night	36% 41% 9% 9% 4	2541
November	1st to 10th	Night	41% 46% 6% 4 2 1	2590
	11th to 20th	Night	41% 45% 8% 4 1	2660
	21st to end	Night	42% 44% 8% 5% 1	2660
December	1st to 10th	Night	43% 43% 7% 4 2	2817
	11th to 20th	Night	55% 37% 4 3 1	3516
	21st to end	Night	58% 30% 6% 5% 1	5214

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	38% 11% 25% 16% 4 6%	180
	11th to 20th	Day	41% 8% 22% 16% 11% 3	180
	21st to end	Day	38% 10% 19% 19% 12% 2	293
February	1st to 10th	Day	36% 13% 27% 14% 9% 1	368
	11th to 20th	Day	30% 13% 26% 20% 10% 1	335
	21st to end	Day	28% 18% 25% 18% 9% 3	280
March	1st to 10th	Day	25% 17% 22% 20% 13% 2	396
	11th to 20th	Day	29% 14% 23% 21% 10% 4	420
	21st to end	Day	29% 13% 26% 19% 10% 3	462
April	1st to 10th	Day	31% 16% 25% 17% 9% 3	420
	11th to 20th	Day	26% 14% 25% 18% 12% 4	412
	21st to end	Day	29% 15% 22% 19% 11% 5%	420
May	1st to 10th	Day	16% 12% 23% 29% 18% 3	423
	11th to 20th	Day	25% 5% 19% 28% 17% 6%	448
	21st to end	Day	17% 6% 23% 32% 17% 5%	663
June	1st to 10th	Day	25% 10% 23% 22% 17% 3	630
	11th to 20th	Day	18% 12% 30% 23% 15% 3	630
	21st to end	Day	16% 8% 23% 28% 21% 4	630
July	1st to 10th	Day	16% 6% 19% 29% 26% 5%	621
	11th to 20th	Day	7% 6% 25% 34% 23% 5%	618
	21st to end	Day	6% 7% 18% 31% 30% 8%	655
August	1st to 10th	Day	13% 4 13% 29% 28% 13%	447
	11th to 20th	Day	8% 5% 16% 31% 31% 9%	437
	21st to end	Day	12% 7% 23% 30% 21% 7%	495
September	1st to 10th	Day	16% 6% 23% 31% 18% 6%	450
	11th to 20th	Day	24% 6% 21% 24% 19% 6%	450
	21st to end	Day	25% 10% 22% 20% 18% 5%	450
October	1st to 10th	Day	28% 7% 20% 19% 19% 8%	450
	11th to 20th	Day	32% 7% 22% 16% 16% 7%	450
	21st to end	Day	34% 13% 21% 18% 10% 5%	388
November	1st to 10th	Day	34% 14% 20% 15% 13% 3	180
	11th to 20th	Day	33% 11% 14% 16% 17% 9%	180
	21st to end	Day	41% 5% 19% 16% 10% 9%	180
December	1st to 10th	Day	30% 11% 22% 18% 10% 9%	180
	11th to 20th	Day	33% 7% 21% 21% 15% 4	180
	21st to end	Day	40% 7% 19% 20% 12% 1	198
January	1st to 10th	Night	40% 10% 21% 18% 9% 3	850
	11th to 20th	Night	36% 7% 18% 22% 15% 2	850
	21st to end	Night	36% 5% 21% 20% 13% 4	908
February	1st to 10th	Night	33% 8% 21% 26% 12% 1	758
	11th to 20th	Night	28% 7% 21% 27% 16% 1	704
	21st to end	Night	28% 9% 20% 28% 13% 3	592
March	1st to 10th	Night	24% 8% 25% 23% 16% 4	720
	11th to 20th	Night	25% 9% 24% 26% 13% 3	720
	21st to end	Night	27% 7% 21% 24% 17% 3	792
April	1st to 10th	Night	24% 9% 17% 28% 18% 3	714
	11th to 20th	Night	23% 3 24% 32% 15% 2	533
	21st to end	Night	22% 5% 22% 31% 16% 4	540
May	1st to 10th	Night	16% 4 21% 33% 24% 2	375
	11th to 20th	Night	18% 4 14% 35% 25% 5%	354
	21st to end	Night	15% 3 19% 33% 28% 3	389
June	1st to 10th	Night	17% 6% 18% 33% 24% 1	360
	11th to 20th	Night	15% 5% 26% 29% 23% 1	360
	21st to end	Night	14% 4 18% 37% 23% 5%	360
July	1st to 10th	Night	10% 1 14% 33% 37% 4	350
	11th to 20th	Night	6% 5% 11% 40% 35% 3	348
	21st to end	Night	6% 2 8% 36% 42% 6%	394
August	1st to 10th	Night	11% 2 8% 27% 42% 9%	457
	11th to 20th	Night	6% 1 9% 30% 46% 8%	534
	21st to end	Night	12% 2 14% 31% 35% 5%	594
September	1st to 10th	Night	12% 2 14% 35% 30% 8%	706
	11th to 20th	Night	19% 5% 14% 21% 29% 13%	720
	21st to end	Night	23% 6% 17% 27% 22% 7%	720
October	1st to 10th	Night	23% 4 14% 28% 25% 5%	720
	11th to 20th	Night	30% 4 17% 23% 20% 6%	720
	21st to end	Night	29% 6% 23% 24% 15% 3	792
November	1st to 10th	Night	36% 8% 20% 25% 10% 1	740
	11th to 20th	Night	32% 7% 24% 22% 12% 3	760
	21st to end	Night	32% 7% 20% 22% 14% 4	760
December	1st to 10th	Night	31% 7% 20% 23% 16% 4	835
	11th to 20th	Night	38% 7% 21% 22% 9% 2	850
	21st to end	Night	38% 8% 25% 21% 8% 1	935

Page generated at 2024-02-07 03:11:54. Version ac07

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