Fanny Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fanny Bay clear sky chart from 2005-11-05 to 2024-10-14.

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	18% 10% 3 7% 5% 5% 5% 4 5% 6% 31%	101593
	Night	22% 11% 3 8% 5% 4 4 4 5% 6% 29%	97047
Transparency	Day	50% 11% 13% 17% 8% 1	101335
	Night	55% 10% 12% 16% 6% 1	96951
Seeing	Day	23% 10% 22% 24% 16% 5%	15634
	Night	25% 6% 19% 26% 19% 4	23562

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% 19% 5% 8% 5% 5% 4 2 4 5% 12%	2219
	11th to 20th	Day	25% 13% 3 9% 9% 5% 6% 4 5% 7% 15%	2199
	21st to end	Day	46% 16% 4 7% 4 3 3 3 4 3 7%	2698
February	1st to 10th	Day	25% 17% 5% 10% 5% 5% 5% 4 5% 5% 14%	1710
	11th to 20th	Day	21% 16% 5% 10% 5% 4 4 3 4 5% 23%	1665
	21st to end	Day	22% 13% 4 9% 7% 7% 5% 5% 5% 6% 16%	1413
March	1st to 10th	Day	19% 16% 5% 9% 7% 6% 6% 4 6% 6% 17%	3287
	11th to 20th	Day	17% 11% 3 9% 6% 6% 5% 4 5% 5% 30%	3490
	21st to end	Day	23% 15% 4 9% 6% 5% 5% 4 5% 5% 20%	3825
April	1st to 10th	Day	22% 15% 3 10% 7% 5% 6% 4 4 5% 18%	2279
	11th to 20th	Day	20% 13% 4 9% 7% 5% 5% 4 5% 5% 22%	2438
	21st to end	Day	22% 13% 4 8% 6% 5% 5% 4 5% 6% 22%	2470
May	1st to 10th	Day	14% 9% 3 7% 5% 5% 5% 4 6% 6% 35%	4403
	11th to 20th	Day	13% 8% 3 7% 6% 5% 6% 4 6% 9% 32%	4377
	21st to end	Day	21% 12% 4 9% 6% 6% 5% 4 5% 6% 21%	5144
June	1st to 10th	Day	20% 10% 3 9% 7% 5% 6% 4 6% 6% 23%	2850
	11th to 20th	Day	15% 11% 4 10% 8% 6% 7% 5% 6% 8% 20%	2850
	21st to end	Day	17% 8% 3 8% 5% 5% 5% 5% 6% 6% 32%	2850
July	1st to 10th	Day	7% 4 2 4 3 3 3 3 5% 7% 59%	4740
	11th to 20th	Day	4 3 1 3 3 2 3 3 4 5% 69%	4740
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 5% 8% 8% 46%	5083
August	1st to 10th	Day	6% 2 1 3 2 2 3 3 5% 7% 66%	4221
	11th to 20th	Day	11% 7% 2 7% 4 5% 6% 5% 8% 9% 36%	4026
	21st to end	Day	13% 7% 2 6% 4 4 4 4 6% 7% 42%	4521
September	1st to 10th	Day	10% 6% 2 6% 4 4 5% 4 5% 7% 48%	2293
	11th to 20th	Day	17% 8% 3 7% 4 4 4 3 4 7% 38%	2182
	21st to end	Day	21% 7% 3 6% 5% 4 4 4 5% 5% 35%	2063
October	1st to 10th	Day	23% 8% 3 7% 4 4 5% 4 4 6% 31%	1900
	11th to 20th	Day	27% 10% 3 9% 5% 5% 4 4 6% 5% 23%	1831
	21st to end	Day	28% 12% 3 7% 6% 5% 5% 3 4 5% 24%	1812
November	1st to 10th	Day	30% 14% 4 8% 6% 6% 4 3 4 5% 16%	1488
	11th to 20th	Day	26% 14% 4 9% 6% 4 5% 4 3 5% 19%	1520
	21st to end	Day	30% 12% 4 8% 5% 5% 5% 4 4 4 19%	1520
December	1st to 10th	Day	22% 16% 4 9% 6% 4 5% 4 4 6% 19%	1359
	11th to 20th	Day	33% 17% 5% 10% 5% 5% 4 3 3 3 12%	1685
	21st to end	Day	37% 15% 5% 10% 6% 4 3 3 4 3 10%	2442
January	1st to 10th	Night	30% 17% 4 10% 5% 5% 4 3 4 4 14%	4726
	11th to 20th	Night	26% 12% 3 9% 7% 4 4 4 4 6% 21%	4699
	21st to end	Night	43% 15% 4 8% 4 4 4 3 4 3 10%	4959
February	1st to 10th	Night	24% 15% 4 9% 6% 4 5% 5% 5% 4 19%	2470
	11th to 20th	Night	20% 14% 4 8% 4 5% 4 3 4 6% 26%	2402
	21st to end	Night	20% 14% 4 9% 6% 5% 4 3 4 6% 23%	2041
March	1st to 10th	Night	22% 14% 3 9% 5% 5% 5% 4 6% 6% 22%	3583
	11th to 20th	Night	12% 7% 3 6% 5% 6% 7% 5% 8% 8% 33%	3489
	21st to end	Night	22% 15% 4 8% 6% 5% 4 4 5% 5% 23%	3828
April	1st to 10th	Night	18% 12% 3 8% 5% 6% 6% 5% 6% 7% 24%	1898
	11th to 20th	Night	18% 11% 5% 7% 5% 5% 4 5% 6% 6% 29%	1691
	21st to end	Night	21% 9% 3 8% 6% 5% 4 4 6% 8% 26%	1710
May	1st to 10th	Night	14% 6% 3 7% 5% 5% 4 3 5% 6% 41%	2555
	11th to 20th	Night	14% 6% 2 5% 5% 5% 5% 5% 7% 8% 39%	2516
	21st to end	Night	20% 13% 4 8% 5% 5% 5% 4 5% 7% 25%	2427
June	1st to 10th	Night	15% 10% 3 8% 6% 6% 6% 4 5% 7% 30%	1330
	11th to 20th	Night	15% 8% 5% 8% 7% 6% 7% 4 7% 7% 27%	1330
	21st to end	Night	13% 8% 4 6% 5% 4 4 4 7% 9% 37%	1330
July	1st to 10th	Night	7% 4 2 4 3 3 3 2 5% 6% 62%	2220
	11th to 20th	Night	4 2 1 2 3 2 3 3 4 6% 70%	2220
	21st to end	Night	8% 4 1 5% 4 4 4 5% 7% 7% 50%	2467
August	1st to 10th	Night	5% 3 1 3 2 2 2 2 4 5% 70%	2712
	11th to 20th	Night	13% 6% 2 6% 4 5% 5% 4 6% 9% 41%	2812
	21st to end	Night	15% 6% 2 7% 4 4 4 4 4 4 45%	3146
September	1st to 10th	Night	9% 5% 2 5% 3 3 4 4 5% 8% 53%	1886
	11th to 20th	Night	17% 8% 3 6% 4 4 5% 4 6% 6% 38%	1995
	21st to end	Night	20% 6% 3 8% 4 3 4 3 4 6% 38%	2116
October	1st to 10th	Night	19% 7% 2 8% 4 4 4 3 4 6% 39%	2280
	11th to 20th	Night	24% 9% 3 8% 4 4 5% 4 5% 6% 28%	2207
	21st to end	Night	27% 9% 3 8% 5% 4 4 3 4 5% 28%	2541
November	1st to 10th	Night	29% 12% 4 8% 5% 4 5% 4 5% 5% 18%	2590
	11th to 20th	Night	26% 12% 3 8% 7% 5% 5% 5% 4 5% 20%	2660
	21st to end	Night	28% 11% 3 9% 5% 5% 4 4 4 4 22%	2660
December	1st to 10th	Night	23% 17% 4 9% 6% 4 4 3 4 5% 21%	2817
	11th to 20th	Night	32% 16% 5% 11% 6% 5% 4 3 4 4 12%	3520
	21st to end	Night	39% 13% 3 8% 5% 4 4 3 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	76% 8% 6% 8% 2	2219
	11th to 20th	Day	66% 15% 9% 8% 2	2220
	21st to end	Day	83% 7% 5% 4 1	2698
February	1st to 10th	Day	71% 10% 7% 7% 4 1	1710
	11th to 20th	Day	66% 10% 9% 11% 4	1674
	21st to end	Day	65% 9% 12% 8% 5% 1	1413
March	1st to 10th	Day	64% 12% 10% 9% 6%	3287
	11th to 20th	Day	55% 10% 10% 20% 5%	3490
	21st to end	Day	62% 13% 12% 11% 2	3825
April	1st to 10th	Day	66% 12% 9% 10% 4	2279
	11th to 20th	Day	60% 11% 8% 12% 7% 2	2438
	21st to end	Day	60% 10% 10% 14% 6% 1	2470
May	1st to 10th	Day	45% 14% 15% 19% 8%	4403
	11th to 20th	Day	40% 15% 19% 21% 4	4380
	21st to end	Day	57% 14% 11% 12% 6%	5145
June	1st to 10th	Day	56% 12% 12% 13% 6% 2	2850
	11th to 20th	Day	53% 14% 15% 13% 4	2850
	21st to end	Day	45% 12% 16% 19% 8% 1	2850
July	1st to 10th	Day	23% 6% 11% 28% 24% 8%	4666
	11th to 20th	Day	16% 7% 15% 41% 20% 1	4659
	21st to end	Day	26% 10% 22% 26% 15% 2	4922
August	1st to 10th	Day	18% 6% 13% 44% 18% 1	4204
	11th to 20th	Day	36% 14% 25% 17% 8% 1	4065
	21st to end	Day	37% 12% 21% 22% 7%	4520
September	1st to 10th	Day	32% 11% 17% 26% 12% 2	2293
	11th to 20th	Day	45% 9% 14% 18% 13% 1	2182
	21st to end	Day	49% 11% 14% 17% 9% 1	2063
October	1st to 10th	Day	51% 11% 15% 14% 7%	1900
	11th to 20th	Day	60% 13% 13% 12% 2	1831
	21st to end	Day	62% 9% 10% 11% 7%	1812
November	1st to 10th	Day	72% 10% 6% 7% 5%	1488
	11th to 20th	Day	67% 10% 8% 9% 5% 1	1520
	21st to end	Day	70% 10% 7% 7% 5%	1520
December	1st to 10th	Day	69% 10% 8% 8% 4	1359
	11th to 20th	Day	80% 10% 4 4 2	1688
	21st to end	Day	77% 8% 7% 6% 2	2442
January	1st to 10th	Night	76% 9% 6% 6% 2	4726
	11th to 20th	Night	63% 13% 11% 9% 4 1	4740
	21st to end	Night	82% 6% 4 6% 2	4959
February	1st to 10th	Night	67% 10% 8% 9% 5% 1	2470
	11th to 20th	Night	59% 10% 11% 13% 6% 1	2404
	21st to end	Night	62% 7% 10% 15% 5% 1	2041
March	1st to 10th	Night	59% 10% 11% 14% 5%	3583
	11th to 20th	Night	45% 17% 10% 23% 5%	3490
	21st to end	Night	63% 13% 10% 12% 2	3828
April	1st to 10th	Night	56% 13% 12% 14% 5%	1898
	11th to 20th	Night	53% 11% 10% 16% 8% 2	1691
	21st to end	Night	54% 13% 10% 15% 7% 1	1710
May	1st to 10th	Night	39% 9% 19% 26% 8%	2555
	11th to 20th	Night	35% 16% 24% 19% 5% 1	2516
	21st to end	Night	56% 10% 15% 17% 3	2427
June	1st to 10th	Night	51% 9% 18% 15% 6% 2	1330
	11th to 20th	Night	48% 11% 21% 15% 5%	1330
	21st to end	Night	40% 10% 21% 20% 7% 2	1330
July	1st to 10th	Night	22% 6% 13% 28% 22% 8%	2185
	11th to 20th	Night	14% 5% 17% 43% 19% 2	2178
	21st to end	Night	23% 11% 22% 29% 13% 2	2389
August	1st to 10th	Night	16% 5% 12% 41% 24% 1	2704
	11th to 20th	Night	35% 12% 27% 15% 8% 1	2839
	21st to end	Night	37% 10% 23% 24% 5%	3146
September	1st to 10th	Night	26% 10% 18% 30% 13% 2	1886
	11th to 20th	Night	44% 10% 13% 17% 14% 3	1995
	21st to end	Night	46% 10% 16% 18% 9% 2	2116
October	1st to 10th	Night	46% 10% 16% 18% 10% 1	2280
	11th to 20th	Night	55% 10% 12% 17% 5%	2207
	21st to end	Night	58% 10% 11% 15% 6%	2541
November	1st to 10th	Night	68% 11% 8% 8% 4 1	2590
	11th to 20th	Night	67% 12% 9% 7% 4 1	2660
	21st to end	Night	67% 9% 9% 10% 4 1	2660
December	1st to 10th	Night	68% 10% 9% 9% 4	2817
	11th to 20th	Night	78% 9% 5% 6% 1	3516
	21st to end	Night	74% 9% 7% 7% 2	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	35% 13% 26% 15% 9% 2	370
	11th to 20th	Day	30% 13% 26% 20% 10% 1	365
	21st to end	Day	27% 19% 24% 18% 8% 3	307
March	1st to 10th	Day	25% 16% 23% 21% 13% 2	433
	11th to 20th	Day	28% 13% 22% 21% 13% 3	460
	21st to end	Day	28% 13% 26% 20% 10% 3	506
April	1st to 10th	Day	30% 15% 24% 19% 9% 3	460
	11th to 20th	Day	25% 14% 27% 19% 11% 4	452
	21st to end	Day	28% 15% 23% 18% 11% 5%	460
May	1st to 10th	Day	16% 11% 23% 28% 18% 3	463
	11th to 20th	Day	23% 6% 20% 28% 17% 6%	488
	21st to end	Day	18% 7% 23% 31% 16% 4	718
June	1st to 10th	Day	25% 10% 23% 22% 16% 3	680
	11th to 20th	Day	18% 13% 29% 23% 14% 3	680
	21st to end	Day	16% 10% 23% 27% 20% 4	680
July	1st to 10th	Day	15% 6% 21% 29% 24% 5%	671
	11th to 20th	Day	7% 6% 24% 36% 22% 5%	668
	21st to end	Day	6% 8% 19% 31% 28% 8%	708
August	1st to 10th	Day	11% 4 15% 30% 26% 13%	487
	11th to 20th	Day	10% 6% 15% 30% 30% 9%	477
	21st to end	Day	13% 8% 23% 29% 19% 7%	539
September	1st to 10th	Day	14% 6% 23% 32% 18% 7%	490
	11th to 20th	Day	24% 7% 21% 24% 18% 6%	490
	21st to end	Day	26% 11% 22% 19% 17% 5%	490
October	1st to 10th	Day	28% 10% 19% 18% 18% 7%	490
	11th to 20th	Day	32% 8% 22% 16% 16% 7%	463
	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	760
	11th to 20th	Night	28% 7% 21% 28% 16% 1	744
	21st to end	Night	27% 9% 21% 27% 13% 3	628
March	1st to 10th	Night	24% 8% 25% 23% 16% 3	760
	11th to 20th	Night	24% 9% 24% 25% 15% 3	760
	21st to end	Night	27% 7% 21% 24% 17% 3	836
April	1st to 10th	Night	23% 10% 18% 29% 18% 3	753
	11th to 20th	Night	22% 3 26% 33% 14% 2	563
	21st to end	Night	22% 6% 22% 31% 16% 4	570
May	1st to 10th	Night	16% 4 21% 33% 24% 2	395
	11th to 20th	Night	17% 4 15% 35% 24% 5%	374
	21st to end	Night	17% 3 19% 33% 26% 2	411
June	1st to 10th	Night	17% 7% 19% 33% 23% 1	380
	11th to 20th	Night	15% 6% 26% 29% 23% 1	380
	21st to end	Night	14% 5% 18% 36% 22% 4	380
July	1st to 10th	Night	10% 1 15% 34% 36% 4	370
	11th to 20th	Night	6% 5% 11% 40% 35% 3	368
	21st to end	Night	7% 3 8% 36% 40% 6%	416
August	1st to 10th	Night	11% 2 8% 27% 43% 9%	483
	11th to 20th	Night	7% 2 9% 30% 44% 8%	564
	21st to end	Night	13% 3 15% 31% 34% 5%	627
September	1st to 10th	Night	11% 1 13% 34% 32% 8%	746
	11th to 20th	Night	19% 5% 14% 21% 28% 13%	760
	21st to end	Night	23% 6% 17% 27% 21% 6%	760
October	1st to 10th	Night	23% 5% 16% 27% 24% 5%	760
	11th to 20th	Night	30% 4 17% 24% 20% 6%	734
	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 2024-10-11 07:49:57. Version ac07

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