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 2026-07-16.

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% 3 8% 5% 5% 5% 4 5% 6% 31%	142045
	Night	20% 11% 3 8% 5% 5% 5% 4 5% 6% 29%	139354
Transparency	Day	49% 10% 15% 18% 7% 1	141743
	Night	54% 10% 14% 16% 6% 1	139238
Seeing	Day	23% 11% 23% 23% 15% 5%	17879
	Night	25% 7% 19% 26% 19% 3	25825

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	27% 20% 5% 10% 6% 6% 5% 3 5% 4 10%	4125
	11th to 20th	Day	17% 9% 3 7% 7% 5% 5% 4 6% 7% 30%	4119
	21st to end	Day	34% 12% 3 8% 5% 4 4 3 3 3 21%	5021
February	1st to 10th	Day	24% 16% 5% 10% 6% 5% 5% 4 5% 5% 13%	1890
	11th to 20th	Day	21% 16% 4 10% 5% 4 4 3 4 5% 23%	1845
	21st to end	Day	22% 13% 4 9% 7% 8% 6% 5% 6% 5% 16%	1557
March	1st to 10th	Day	20% 17% 5% 10% 7% 6% 5% 4 5% 5% 16%	4834
	11th to 20th	Day	16% 16% 4 10% 7% 6% 6% 4 5% 5% 22%	5110
	21st to end	Day	23% 15% 4 11% 7% 6% 7% 4 5% 4 14%	5607
April	1st to 10th	Day	21% 15% 3 9% 7% 5% 6% 4 5% 6% 19%	2519
	11th to 20th	Day	18% 13% 4 9% 7% 6% 5% 4 5% 5% 23%	2698
	21st to end	Day	20% 12% 4 8% 5% 5% 5% 3 5% 6% 26%	2730
May	1st to 10th	Day	10% 8% 3 8% 6% 6% 5% 4 6% 7% 38%	8152
	11th to 20th	Day	13% 10% 4 8% 6% 6% 7% 6% 7% 9% 26%	8160
	21st to end	Day	16% 9% 4 9% 6% 5% 6% 5% 7% 7% 26%	9604
June	1st to 10th	Day	19% 10% 3 8% 7% 5% 6% 5% 6% 6% 26%	3150
	11th to 20th	Day	14% 10% 4 9% 7% 6% 7% 5% 6% 8% 23%	3150
	21st to end	Day	16% 8% 3 8% 6% 5% 6% 5% 6% 6% 32%	3150
July	1st to 10th	Day	8% 5% 2 5% 3 3 4 4 6% 8% 52%	6930
	11th to 20th	Day	3 3 1 3 3 3 3 3 4 6% 69%	6856
	21st to end	Day	5% 4 2 5% 4 4 4 4 7% 8% 55%	7292
August	1st to 10th	Day	6% 2 1 4 2 3 3 3 5% 7% 65%	4355
	11th to 20th	Day	11% 7% 2 7% 4 5% 6% 5% 8% 9% 36%	4156
	21st to end	Day	13% 6% 2 6% 4 4 4 4 6% 7% 43%	4664
September	1st to 10th	Day	10% 6% 2 6% 4 4 5% 4 5% 8% 49%	2413
	11th to 20th	Day	16% 8% 3 7% 4 4 4 3 5% 7% 38%	2297
	21st to end	Day	21% 8% 3 7% 5% 5% 4 4 5% 5% 34%	2171
October	1st to 10th	Day	19% 10% 5% 10% 5% 4 6% 5% 5% 7% 24%	3280
	11th to 20th	Day	25% 8% 3 9% 6% 5% 5% 4 5% 4 25%	3261
	21st to end	Day	23% 12% 3 10% 7% 6% 8% 5% 5% 5% 17%	3247
November	1st to 10th	Day	29% 14% 4 8% 6% 6% 5% 3 4 5% 15%	1648
	11th to 20th	Day	26% 15% 4 9% 7% 4 5% 5% 3 5% 18%	1680
	21st to end	Day	29% 13% 4 8% 6% 5% 5% 4 4 5% 17%	1680
December	1st to 10th	Day	18% 16% 6% 10% 8% 6% 5% 4 5% 5% 17%	2404
	11th to 20th	Day	34% 18% 5% 9% 5% 5% 5% 3 3 3 10%	2715
	21st to end	Day	34% 17% 5% 10% 6% 5% 4 4 5% 3 8%	3575
January	1st to 10th	Night	26% 19% 5% 12% 6% 5% 4 3 4 4 12%	8770
	11th to 20th	Night	19% 7% 2 7% 5% 4 4 4 5% 7% 35%	8779
	21st to end	Night	30% 11% 3 7% 4 4 4 3 4 4 26%	9157
February	1st to 10th	Night	23% 15% 4 9% 5% 4 5% 4 5% 5% 20%	2730
	11th to 20th	Night	19% 14% 4 8% 4 5% 4 4 4 7% 26%	2662
	21st to end	Night	20% 14% 4 10% 6% 6% 5% 3 4 6% 22%	2249
March	1st to 10th	Night	19% 12% 3 10% 6% 5% 5% 4 6% 5% 23%	5273
	11th to 20th	Night	11% 10% 4 9% 6% 7% 7% 5% 7% 8% 26%	5109
	21st to end	Night	22% 17% 5% 10% 6% 5% 5% 4 4 5% 19%	5610
April	1st to 10th	Night	18% 12% 4 8% 5% 5% 6% 5% 6% 7% 24%	2097
	11th to 20th	Night	17% 11% 4 7% 5% 5% 4 5% 6% 6% 30%	1871
	21st to end	Night	19% 9% 3 8% 6% 5% 4 4 6% 8% 28%	1890
May	1st to 10th	Night	11% 6% 3 7% 4 5% 3 3 5% 7% 45%	4767
	11th to 20th	Night	12% 7% 3 10% 6% 5% 5% 5% 7% 7% 31%	4700
	21st to end	Night	15% 10% 4 10% 5% 5% 4 4 5% 7% 30%	4563
June	1st to 10th	Night	15% 10% 3 8% 6% 6% 6% 4 5% 7% 32%	1470
	11th to 20th	Night	14% 7% 4 8% 7% 6% 6% 4 6% 7% 30%	1470
	21st to end	Night	13% 7% 3 6% 4 4 5% 4 7% 9% 37%	1470
July	1st to 10th	Night	8% 4 2 4 3 3 4 3 6% 7% 55%	3250
	11th to 20th	Night	3 2 1 2 2 2 4 3 5% 7% 71%	3215
	21st to end	Night	6% 3 1 4 3 3 4 4 6% 7% 58%	3549
August	1st to 10th	Night	6% 4 1 3 2 2 2 2 5% 6% 68%	2798
	11th to 20th	Night	13% 6% 2 6% 4 5% 5% 4 5% 9% 41%	2902
	21st to end	Night	14% 6% 2 7% 4 4 4 4 4 5% 46%	3245
September	1st to 10th	Night	10% 5% 2 5% 3 3 4 4 5% 8% 53%	1986
	11th to 20th	Night	16% 8% 3 6% 4 4 5% 4 6% 6% 38%	2100
	21st to end	Night	20% 6% 3 9% 4 3 4 3 5% 6% 37%	2228
October	1st to 10th	Night	17% 9% 4 11% 6% 5% 5% 3 4 6% 30%	3920
	11th to 20th	Night	23% 8% 4 10% 6% 5% 5% 4 4 6% 25%	3897
	21st to end	Night	22% 10% 3 11% 6% 5% 5% 4 5% 6% 24%	4552
November	1st to 10th	Night	28% 12% 4 9% 6% 5% 5% 4 5% 5% 17%	2870
	11th to 20th	Night	26% 13% 3 8% 6% 5% 5% 4 4 5% 19%	2940
	21st to end	Night	27% 11% 4 9% 6% 5% 5% 4 4 4 21%	2940
December	1st to 10th	Night	21% 14% 5% 11% 6% 7% 5% 3 4 5% 18%	4992
	11th to 20th	Night	32% 18% 5% 11% 6% 5% 4 3 4 4 9%	5710
	21st to end	Night	35% 14% 4 8% 5% 5% 6% 5% 5% 4 11%	7623

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	76% 8% 7% 8% 2	4125
	11th to 20th	Day	51% 14% 12% 18% 4	4140
	21st to end	Day	68% 7% 8% 13% 4	5022
February	1st to 10th	Day	72% 10% 7% 7% 4 1	1890
	11th to 20th	Day	65% 9% 10% 11% 4	1854
	21st to end	Day	65% 9% 12% 8% 5% 1	1557
March	1st to 10th	Day	64% 10% 11% 10% 5%	4834
	11th to 20th	Day	60% 8% 10% 16% 5%	5110
	21st to end	Day	68% 11% 11% 9% 2	5607
April	1st to 10th	Day	64% 12% 10% 11% 3	2519
	11th to 20th	Day	59% 11% 9% 13% 7% 2	2698
	21st to end	Day	56% 10% 12% 16% 6% 1	2730
May	1st to 10th	Day	40% 11% 16% 25% 8%	8152
	11th to 20th	Day	43% 13% 23% 17% 4	8163
	21st to end	Day	47% 12% 18% 15% 8%	9605
June	1st to 10th	Day	53% 11% 13% 14% 6% 2	3150
	11th to 20th	Day	51% 14% 15% 15% 5%	3150
	21st to end	Day	45% 11% 16% 20% 8%	3150
July	1st to 10th	Day	25% 7% 20% 26% 17% 5%	6856
	11th to 20th	Day	14% 6% 21% 39% 17% 1	6775
	21st to end	Day	20% 8% 32% 27% 12% 1	7086
August	1st to 10th	Day	18% 6% 13% 43% 18% 1	4338
	11th to 20th	Day	37% 13% 24% 17% 8% 1	4195
	21st to end	Day	36% 12% 22% 23% 8% 1	4663
September	1st to 10th	Day	32% 11% 18% 27% 11% 2	2413
	11th to 20th	Day	44% 10% 14% 19% 12% 1	2297
	21st to end	Day	49% 11% 14% 16% 9% 1	2171
October	1st to 10th	Day	54% 8% 16% 16% 5%	3280
	11th to 20th	Day	60% 9% 11% 16% 4	3261
	21st to end	Day	60% 11% 12% 12% 4	3247
November	1st to 10th	Day	71% 10% 7% 7% 4	1648
	11th to 20th	Day	67% 10% 8% 9% 5% 1	1680
	21st to end	Day	70% 11% 7% 7% 5%	1680
December	1st to 10th	Day	67% 9% 10% 11% 3	2404
	11th to 20th	Day	77% 9% 7% 5% 1	2718
	21st to end	Day	76% 8% 9% 6% 2	3575
January	1st to 10th	Night	77% 8% 6% 7% 2	8770
	11th to 20th	Night	48% 12% 13% 18% 9% 1	8820
	21st to end	Night	63% 8% 10% 16% 4	9157
February	1st to 10th	Night	66% 9% 8% 10% 6% 1	2730
	11th to 20th	Night	59% 10% 11% 13% 6% 1	2664
	21st to end	Night	62% 8% 10% 14% 5% 1	2249
March	1st to 10th	Night	58% 9% 12% 15% 6%	5273
	11th to 20th	Night	52% 14% 11% 19% 4	5110
	21st to end	Night	67% 10% 10% 10% 3	5610
April	1st to 10th	Night	55% 12% 13% 15% 5%	2097
	11th to 20th	Night	51% 11% 11% 17% 8% 1	1871
	21st to end	Night	51% 13% 12% 16% 7% 1	1890
May	1st to 10th	Night	37% 8% 16% 31% 8%	4764
	11th to 20th	Night	42% 14% 22% 16% 5%	4700
	21st to end	Night	50% 9% 16% 22% 3	4567
June	1st to 10th	Night	49% 8% 18% 15% 7% 2	1470
	11th to 20th	Night	46% 10% 20% 17% 6%	1470
	21st to end	Night	40% 10% 21% 20% 6% 2	1470
July	1st to 10th	Night	25% 7% 23% 24% 15% 6%	3215
	11th to 20th	Night	11% 6% 26% 38% 18% 1	3173
	21st to end	Night	18% 9% 34% 27% 11% 1	3450
August	1st to 10th	Night	17% 5% 13% 41% 24% 1	2790
	11th to 20th	Night	36% 12% 27% 16% 8% 1	2929
	21st to end	Night	36% 10% 23% 24% 6% 1	3245
September	1st to 10th	Night	27% 10% 18% 30% 13% 2	1986
	11th to 20th	Night	43% 9% 13% 18% 14% 3	2100
	21st to end	Night	45% 9% 17% 18% 9% 2	2228
October	1st to 10th	Night	53% 10% 15% 15% 7%	3920
	11th to 20th	Night	58% 9% 12% 18% 4	3897
	21st to end	Night	58% 10% 15% 13% 4	4552
November	1st to 10th	Night	67% 11% 9% 8% 4 1	2870
	11th to 20th	Night	67% 11% 9% 7% 4 1	2940
	21st to end	Night	67% 9% 10% 9% 4 1	2940
December	1st to 10th	Night	69% 10% 10% 9% 2	4992
	11th to 20th	Night	78% 8% 6% 5% 2	5706
	21st to end	Night	71% 10% 10% 7% 2	7623

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	40% 11% 24% 16% 4 5%	220
	11th to 20th	Day	35% 8% 24% 16% 12% 5%	220
	21st to end	Day	36% 11% 20% 19% 11% 4	348
February	1st to 10th	Day	33% 14% 28% 15% 8% 2	430
	11th to 20th	Day	29% 14% 25% 20% 10% 1	425
	21st to end	Day	30% 20% 24% 15% 8% 3	355
March	1st to 10th	Day	25% 18% 23% 20% 12% 2	507
	11th to 20th	Day	32% 15% 19% 19% 11% 3	540
	21st to end	Day	30% 15% 26% 18% 9% 3	594
April	1st to 10th	Day	29% 16% 24% 19% 9% 3	540
	11th to 20th	Day	24% 14% 27% 20% 11% 3	532
	21st to end	Day	26% 16% 25% 19% 11% 4	540
May	1st to 10th	Day	15% 13% 25% 27% 16% 3	543
	11th to 20th	Day	23% 8% 22% 26% 15% 5%	568
	21st to end	Day	18% 9% 25% 29% 15% 4	826
June	1st to 10th	Day	25% 11% 25% 22% 14% 3	780
	11th to 20th	Day	17% 14% 30% 23% 14% 3	780
	21st to end	Day	16% 10% 25% 28% 18% 3	780
July	1st to 10th	Day	14% 8% 23% 29% 22% 4	771
	11th to 20th	Day	7% 8% 26% 35% 20% 5%	744
	21st to end	Day	6% 8% 20% 31% 28% 8%	761
August	1st to 10th	Day	11% 5% 17% 30% 26% 12%	527
	11th to 20th	Day	10% 8% 17% 29% 28% 8%	517
	21st to end	Day	12% 7% 23% 31% 20% 8%	583
September	1st to 10th	Day	14% 6% 23% 33% 18% 7%	530
	11th to 20th	Day	23% 7% 21% 25% 18% 5%	530
	21st to end	Day	26% 12% 23% 18% 15% 5%	530
October	1st to 10th	Day	28% 12% 18% 18% 17% 7%	530
	11th to 20th	Day	31% 12% 22% 15% 14% 6%	530
	21st to end	Day	34% 14% 22% 16% 9% 5%	456
November	1st to 10th	Day	35% 19% 20% 13% 11% 2	220
	11th to 20th	Day	34% 15% 15% 14% 15% 8%	220
	21st to end	Day	40% 7% 20% 15% 10% 8%	220
December	1st to 10th	Day	31% 12% 21% 17% 9% 10%	220
	11th to 20th	Day	38% 10% 19% 17% 13% 3	220
	21st to end	Day	40% 10% 19% 19% 10% 1	242
January	1st to 10th	Night	39% 12% 20% 18% 8% 3	950
	11th to 20th	Night	33% 7% 19% 23% 16% 1	950
	21st to end	Night	34% 5% 21% 22% 14% 4	1011
February	1st to 10th	Night	31% 9% 21% 26% 12% 1	840
	11th to 20th	Night	28% 7% 21% 28% 16% 1	824
	21st to end	Night	28% 11% 21% 25% 12% 3	692
March	1st to 10th	Night	24% 10% 25% 23% 15% 3	840
	11th to 20th	Night	25% 12% 24% 24% 14% 2	840
	21st to end	Night	28% 9% 22% 23% 16% 3	924
April	1st to 10th	Night	23% 10% 18% 28% 18% 3	832
	11th to 20th	Night	21% 5% 26% 32% 14% 2	623
	21st to end	Night	20% 7% 23% 31% 17% 3	630
May	1st to 10th	Night	16% 4 20% 35% 23% 2	437
	11th to 20th	Night	18% 5% 17% 34% 22% 4	414
	21st to end	Night	17% 4 19% 33% 25% 2	455
June	1st to 10th	Night	17% 8% 20% 33% 22% 1	420
	11th to 20th	Night	15% 7% 27% 29% 22% 1	420
	21st to end	Night	14% 5% 20% 36% 21% 4	420
July	1st to 10th	Night	9% 2 17% 33% 35% 3	410
	11th to 20th	Night	6% 6% 12% 40% 34% 3	398
	21st to end	Night	7% 3 8% 37% 40% 6%	438
August	1st to 10th	Night	10% 3 9% 28% 42% 9%	509
	11th to 20th	Night	8% 3 10% 30% 42% 8%	594
	21st to end	Night	12% 3 14% 31% 36% 5%	660
September	1st to 10th	Night	12% 2 13% 34% 32% 7%	786
	11th to 20th	Night	19% 5% 14% 23% 28% 12%	800
	21st to end	Night	23% 6% 19% 26% 20% 6%	800
October	1st to 10th	Night	23% 6% 16% 27% 24% 5%	800
	11th to 20th	Night	29% 6% 18% 23% 19% 6%	800
	21st to end	Night	29% 8% 23% 24% 14% 3	880
November	1st to 10th	Night	36% 9% 20% 25% 9%	820
	11th to 20th	Night	33% 8% 23% 22% 11% 3	840
	21st to end	Night	32% 9% 19% 23% 13% 4	840
December	1st to 10th	Night	30% 8% 19% 23% 16% 4	933
	11th to 20th	Night	40% 9% 21% 20% 9% 2	950
	21st to end	Night	37% 10% 24% 21% 7%	1045

Page generated at 2026-07-13 00:14:49. Version ac07

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