Bangor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bangor clear sky chart from 2005-11-06 to 2024-11-03.

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% 8% 3 7% 5% 4 4 4 5% 7% 36%	101219
	Night	19% 9% 3 7% 4 4 4 4 5% 6% 35%	97779
Transparency	Day	47% 7% 12% 20% 12% 2	100977
	Night	47% 7% 13% 20% 12% 1	97642
Seeing	Day	25% 17% 31% 19% 7% 2	15756
	Night	23% 14% 32% 24% 6%	24038

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	16% 9% 3 7% 4 4 4 3 5% 5% 39%	2517
	11th to 20th	Day	17% 8% 3 7% 5% 5% 4 2 3 5% 42%	2520
	21st to end	Day	15% 11% 4 8% 4 4 4 4 5% 6% 35%	2806
February	1st to 10th	Day	17% 11% 4 7% 5% 4 4 4 5% 7% 34%	1710
	11th to 20th	Day	13% 11% 3 8% 6% 5% 4 3 5% 5% 35%	1761
	21st to end	Day	14% 12% 2 9% 6% 5% 4 4 4 6% 35%	1570
March	1st to 10th	Day	26% 12% 3 8% 4 4 4 2 4 4 29%	3139
	11th to 20th	Day	19% 12% 3 8% 5% 4 5% 3 4 6% 31%	3480
	21st to end	Day	26% 11% 3 7% 4 3 4 3 5% 6% 29%	3816
April	1st to 10th	Day	23% 11% 3 9% 5% 4 3 3 4 6% 31%	2261
	11th to 20th	Day	20% 9% 2 5% 4 4 5% 3 5% 6% 38%	2422
	21st to end	Day	24% 10% 3 6% 4 4 3 3 4 5% 35%	2470
May	1st to 10th	Day	21% 8% 2 7% 5% 4 4 4 5% 7% 32%	4106
	11th to 20th	Day	19% 9% 3 7% 5% 5% 6% 4 6% 7% 30%	4081
	21st to end	Day	16% 7% 3 6% 5% 5% 5% 4 6% 8% 35%	5000
June	1st to 10th	Day	24% 8% 3 7% 5% 4 4 4 4 7% 30%	2850
	11th to 20th	Day	19% 7% 3 6% 5% 4 4 4 5% 8% 35%	2850
	21st to end	Day	24% 8% 2 6% 4 4 4 5% 6% 6% 29%	2850
July	1st to 10th	Day	14% 6% 2 6% 5% 5% 6% 5% 7% 9% 36%	4605
	11th to 20th	Day	13% 7% 2 6% 5% 5% 5% 5% 7% 9% 37%	4440
	21st to end	Day	17% 7% 2 6% 5% 5% 5% 4 5% 7% 36%	4757
August	1st to 10th	Day	17% 8% 3 7% 5% 5% 5% 4 6% 7% 33%	4105
	11th to 20th	Day	16% 8% 3 8% 4 5% 5% 4 6% 8% 32%	4045
	21st to end	Day	11% 6% 2 7% 4 4 4 3 7% 9% 43%	4515
September	1st to 10th	Day	12% 5% 2 5% 5% 4 4 3 5% 8% 49%	2187
	11th to 20th	Day	14% 5% 2 5% 4 4 3 2 4 5% 52%	2090
	21st to end	Day	16% 7% 3 5% 4 3 4 3 5% 7% 43%	2090
October	1st to 10th	Day	18% 6% 2 6% 5% 4 4 2 6% 6% 40%	2035
	11th to 20th	Day	19% 7% 2 6% 4 4 4 3 4 6% 41%	1882
	21st to end	Day	22% 9% 3 7% 4 4 3 3 5% 6% 35%	1881
November	1st to 10th	Day	18% 7% 2 6% 5% 4 5% 3 5% 6% 40%	1689
	11th to 20th	Day	20% 6% 2 5% 3 4 5% 4 4 8% 39%	1663
	21st to end	Day	22% 8% 3 5% 4 3 3 3 4 5% 40%	1520
December	1st to 10th	Day	22% 12% 2 7% 5% 4 3 3 4 6% 31%	1402
	11th to 20th	Day	23% 11% 2 6% 4 4 3 2 4 4 37%	1668
	21st to end	Day	25% 10% 3 6% 4 3 4 3 4 5% 32%	2436
January	1st to 10th	Night	14% 11% 4 8% 5% 4 4 3 4 6% 38%	4429
	11th to 20th	Night	14% 9% 4 8% 6% 5% 4 4 5% 6% 35%	4440
	21st to end	Night	16% 12% 4 10% 4 4 5% 4 5% 6% 32%	4848
February	1st to 10th	Night	15% 11% 4 8% 5% 5% 5% 4 6% 6% 31%	2470
	11th to 20th	Night	13% 11% 3 8% 5% 5% 5% 3 5% 5% 38%	2303
	21st to end	Night	15% 12% 3 7% 6% 4 4 3 5% 5% 36%	1884
March	1st to 10th	Night	29% 13% 2 5% 4 3 3 3 3 4 30%	3700
	11th to 20th	Night	16% 12% 4 8% 6% 5% 6% 5% 6% 6% 28%	3479
	21st to end	Night	27% 10% 3 7% 4 4 4 4 6% 6% 25%	3816
April	1st to 10th	Night	23% 11% 3 7% 3 3 3 2 4 5% 35%	1917
	11th to 20th	Night	20% 8% 2 7% 5% 4 4 5% 5% 7% 33%	1706
	21st to end	Night	25% 8% 3 5% 4 3 4 3 6% 5% 33%	1710
May	1st to 10th	Night	24% 8% 3 5% 3 3 4 3 7% 8% 33%	2834
	11th to 20th	Night	18% 7% 3 8% 6% 5% 6% 4 7% 8% 28%	2813
	21st to end	Night	14% 6% 2 6% 5% 5% 5% 4 6% 8% 40%	2606
June	1st to 10th	Night	23% 9% 3 7% 4 4 5% 4 6% 8% 29%	1330
	11th to 20th	Night	17% 7% 2 6% 4 4 4 5% 6% 10% 36%	1330
	21st to end	Night	24% 9% 3 7% 5% 4 4 4 6% 7% 29%	1330
July	1st to 10th	Night	12% 6% 2 6% 5% 6% 7% 5% 8% 9% 34%	2355
	11th to 20th	Night	14% 7% 3 8% 5% 5% 5% 4 7% 8% 35%	2520
	21st to end	Night	14% 6% 2 5% 5% 4 5% 4 7% 8% 40%	2762
August	1st to 10th	Night	19% 8% 2 8% 6% 5% 4 4 6% 7% 31%	2825
	11th to 20th	Night	15% 8% 3 8% 5% 5% 6% 5% 6% 7% 31%	2782
	21st to end	Night	11% 6% 2 7% 4 4 5% 4 5% 8% 44%	3124
September	1st to 10th	Night	13% 5% 2 5% 3 3 4 4 5% 7% 50%	1992
	11th to 20th	Night	15% 5% 2 4 3 3 3 3 5% 6% 51%	2090
	21st to end	Night	17% 6% 2 5% 4 3 4 3 6% 7% 43%	2090
October	1st to 10th	Night	19% 6% 2 5% 4 5% 4 4 5% 5% 40%	2144
	11th to 20th	Night	18% 6% 1 7% 4 4 4 3 5% 6% 41%	2294
	21st to end	Night	25% 8% 3 6% 4 4 3 3 4 6% 35%	2717
November	1st to 10th	Night	18% 7% 2 6% 4 5% 3 3 5% 5% 41%	2434
	11th to 20th	Night	18% 7% 2 5% 4 5% 4 4 5% 7% 39%	2513
	21st to end	Night	18% 8% 3 5% 4 3 4 4 6% 6% 38%	2660
December	1st to 10th	Night	23% 9% 3 7% 4 4 4 3 5% 5% 32%	2774
	11th to 20th	Night	23% 9% 2 6% 3 3 4 3 4 5% 37%	3531
	21st to end	Night	25% 10% 3 6% 3 3 3 3 4 5% 35%	5227

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	46% 6% 16% 23% 9% 1	2518
	11th to 20th	Day	43% 6% 12% 25% 11% 2	2520
	21st to end	Day	48% 6% 15% 17% 13% 1	2806
February	1st to 10th	Day	48% 6% 12% 18% 12% 3	1710
	11th to 20th	Day	50% 5% 10% 20% 13% 1	1769
	21st to end	Day	49% 6% 11% 19% 9% 5%	1570
March	1st to 10th	Day	58% 5% 8% 13% 13% 3	3142
	11th to 20th	Day	50% 7% 13% 16% 12% 2	3480
	21st to end	Day	55% 5% 7% 14% 15% 4	3816
April	1st to 10th	Day	54% 5% 9% 15% 13% 4	2261
	11th to 20th	Day	46% 6% 10% 22% 14% 2	2422
	21st to end	Day	51% 5% 8% 18% 15% 4	2470
May	1st to 10th	Day	48% 10% 13% 18% 9% 2	4120
	11th to 20th	Day	47% 11% 15% 17% 8% 1	4085
	21st to end	Day	42% 12% 16% 17% 13% 1	5000
June	1st to 10th	Day	53% 7% 12% 18% 9% 1	2850
	11th to 20th	Day	45% 8% 12% 18% 15% 2	2850
	21st to end	Day	53% 8% 11% 17% 9% 2	2850
July	1st to 10th	Day	44% 7% 13% 25% 11% 1	4534
	11th to 20th	Day	41% 8% 15% 25% 11% 1	4365
	21st to end	Day	46% 7% 12% 22% 12% 1	4605
August	1st to 10th	Day	49% 7% 14% 24% 5%	4092
	11th to 20th	Day	48% 8% 16% 20% 8%	4084
	21st to end	Day	35% 6% 13% 26% 18% 1	4515
September	1st to 10th	Day	32% 6% 16% 27% 17% 1	2187
	11th to 20th	Day	35% 4 11% 27% 20% 3	2090
	21st to end	Day	40% 5% 12% 26% 16% 1	2090
October	1st to 10th	Day	44% 6% 11% 23% 14% 1	2035
	11th to 20th	Day	44% 6% 13% 26% 10% 1	1882
	21st to end	Day	49% 6% 11% 21% 13% 1	1881
November	1st to 10th	Day	43% 6% 14% 21% 13% 2	1689
	11th to 20th	Day	43% 6% 12% 21% 15% 3	1663
	21st to end	Day	45% 5% 17% 23% 9% 1	1520
December	1st to 10th	Day	53% 6% 12% 19% 9% 1	1402
	11th to 20th	Day	51% 5% 10% 19% 13% 2	1668
	21st to end	Day	54% 6% 11% 19% 8% 3	2436
January	1st to 10th	Night	45% 7% 15% 23% 9% 1	4429
	11th to 20th	Night	47% 7% 15% 18% 10% 2	4440
	21st to end	Night	51% 7% 11% 20% 10% 1	4848
February	1st to 10th	Night	50% 7% 12% 17% 12% 2	2470
	11th to 20th	Night	48% 5% 10% 20% 14% 2	2306
	21st to end	Night	48% 6% 9% 19% 13% 4	1884
March	1st to 10th	Night	58% 5% 8% 16% 10% 3	3710
	11th to 20th	Night	50% 11% 14% 14% 9% 2	3480
	21st to end	Night	56% 6% 8% 15% 14% 2	3816
April	1st to 10th	Night	53% 4 9% 15% 16% 3	1917
	11th to 20th	Night	47% 6% 11% 21% 13% 2	1706
	21st to end	Night	50% 7% 10% 16% 14% 3	1710
May	1st to 10th	Night	46% 8% 20% 17% 8% 1	2840
	11th to 20th	Night	47% 12% 18% 15% 7% 1	2814
	21st to end	Night	39% 11% 19% 19% 11% 1	2607
June	1st to 10th	Night	52% 9% 13% 19% 8%	1330
	11th to 20th	Night	42% 8% 18% 19% 11% 2	1330
	21st to end	Night	53% 10% 11% 16% 8% 2	1330
July	1st to 10th	Night	44% 8% 15% 21% 11%	2316
	11th to 20th	Night	44% 8% 15% 25% 8%	2472
	21st to end	Night	42% 7% 15% 24% 11% 1	2674
August	1st to 10th	Night	52% 9% 13% 19% 6%	2813
	11th to 20th	Night	49% 8% 15% 18% 10%	2809
	21st to end	Night	35% 8% 15% 23% 17% 1	3124
September	1st to 10th	Night	33% 8% 14% 30% 14% 1	1992
	11th to 20th	Night	33% 6% 12% 28% 18% 2	2090
	21st to end	Night	39% 7% 10% 28% 14% 1	2090
October	1st to 10th	Night	43% 7% 13% 24% 13% 1	2144
	11th to 20th	Night	43% 6% 14% 26% 11% 1	2294
	21st to end	Night	50% 6% 12% 20% 12% 1	2717
November	1st to 10th	Night	44% 6% 13% 22% 14% 1	2434
	11th to 20th	Night	44% 6% 10% 22% 16% 2	2513
	21st to end	Night	44% 7% 16% 19% 13% 1	2660
December	1st to 10th	Night	53% 5% 11% 20% 11%	2774
	11th to 20th	Night	48% 6% 10% 21% 15% 1	3532
	21st to end	Night	50% 6% 13% 18% 11% 2	5227

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	31% 16% 33% 18% 3	180
	11th to 20th	Day	32% 19% 35% 11% 2 1	180
	21st to end	Day	20% 23% 37% 17% 3	219
February	1st to 10th	Day	29% 20% 28% 20% 3	370
	11th to 20th	Day	26% 26% 35% 10% 2	413
	21st to end	Day	27% 21% 32% 18% 2	382
March	1st to 10th	Day	30% 22% 32% 14% 2	460
	11th to 20th	Day	25% 24% 32% 14% 4 1	460
	21st to end	Day	33% 22% 26% 12% 4 3	506
April	1st to 10th	Day	36% 23% 25% 10% 4 2	460
	11th to 20th	Day	33% 24% 25% 12% 5% 1	452
	21st to end	Day	28% 23% 29% 15% 3 1	460
May	1st to 10th	Day	30% 20% 32% 14% 3 1	463
	11th to 20th	Day	23% 17% 36% 17% 6% 1	487
	21st to end	Day	23% 18% 35% 18% 6%	630
June	1st to 10th	Day	26% 15% 30% 19% 8% 1	680
	11th to 20th	Day	22% 14% 30% 23% 10% 1	680
	21st to end	Day	28% 13% 29% 21% 8% 1	680
July	1st to 10th	Day	20% 12% 36% 21% 10% 1	584
	11th to 20th	Day	17% 10% 42% 21% 9% 2	484
	21st to end	Day	16% 12% 39% 24% 8% 2	532
August	1st to 10th	Day	15% 11% 34% 29% 9% 1	486
	11th to 20th	Day	18% 10% 32% 26% 10% 3	479
	21st to end	Day	16% 13% 32% 24% 11% 3	539
September	1st to 10th	Day	14% 14% 35% 24% 10% 2	490
	11th to 20th	Day	21% 10% 30% 20% 13% 6%	490
	21st to end	Day	18% 15% 33% 19% 10% 6%	490
October	1st to 10th	Day	21% 16% 26% 20% 13% 3	460
	11th to 20th	Day	24% 17% 29% 20% 8% 3	390
	21st to end	Day	30% 17% 29% 18% 5% 1	429
November	1st to 10th	Day	25% 16% 26% 24% 7% 2	371
	11th to 20th	Day	30% 15% 33% 15% 7%	370
	21st to end	Day	30% 19% 26% 20% 5%	370
December	1st to 10th	Day	28% 21% 35% 12% 4	252
	11th to 20th	Day	36% 24% 29% 10% 1 1	180
	21st to end	Day	34% 24% 26% 11% 5% 1	198
January	1st to 10th	Night	23% 21% 34% 20% 3	760
	11th to 20th	Night	25% 20% 32% 19% 3	760
	21st to end	Night	19% 20% 37% 20% 4	836
February	1st to 10th	Night	23% 19% 34% 20% 3	760
	11th to 20th	Night	21% 23% 37% 17% 2	743
	21st to end	Night	24% 17% 36% 20% 3	628
March	1st to 10th	Night	27% 17% 35% 20% 1	760
	11th to 20th	Night	23% 20% 32% 20% 5%	760
	21st to end	Night	26% 18% 31% 20% 5%	836
April	1st to 10th	Night	30% 18% 32% 18% 2	760
	11th to 20th	Night	24% 16% 37% 19% 4	582
	21st to end	Night	30% 13% 32% 20% 5%	570
May	1st to 10th	Night	25% 13% 33% 25% 4	570
	11th to 20th	Night	25% 12% 36% 23% 4	562
	21st to end	Night	19% 11% 35% 29% 6%	442
June	1st to 10th	Night	24% 8% 32% 29% 7%	380
	11th to 20th	Night	20% 6% 32% 33% 9%	380
	21st to end	Night	29% 5% 25% 36% 5%	380
July	1st to 10th	Night	16% 5% 36% 35% 8%	370
	11th to 20th	Night	16% 3 30% 39% 11%	368
	21st to end	Night	19% 4 30% 37% 11% 1	427
August	1st to 10th	Night	16% 5% 31% 38% 9%	568
	11th to 20th	Night	16% 6% 31% 36% 10% 1	562
	21st to end	Night	15% 7% 28% 37% 11% 1	627
September	1st to 10th	Night	16% 6% 33% 33% 11% 1	760
	11th to 20th	Night	18% 9% 27% 27% 16% 3	760
	21st to end	Night	18% 10% 31% 29% 11% 1	760
October	1st to 10th	Night	22% 9% 28% 27% 14% 1	760
	11th to 20th	Night	21% 13% 30% 25% 9% 1	760
	21st to end	Night	28% 16% 31% 20% 5%	836
November	1st to 10th	Night	24% 13% 31% 24% 7% 1	749
	11th to 20th	Night	24% 16% 33% 20% 7% 1	781
	21st to end	Night	26% 19% 29% 21% 4	850
December	1st to 10th	Night	29% 14% 34% 18% 4	850
	11th to 20th	Night	25% 22% 32% 18% 3	850
	21st to end	Night	29% 19% 31% 17% 3	931

Page generated at 2024-10-31 03:39:21. Version ac07

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