Coaticook
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coaticook clear sky chart from 2005-11-06 to 2025-01-07.

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% 13% 4 10% 5% 5% 5% 4 5% 6% 26%	105078
	Night	18% 15% 5% 11% 6% 4 4 3 4 5% 25%	103983
Transparency	Day	58% 6% 11% 17% 8% 1	108564
	Night	62% 6% 9% 15% 7% 1	108586
Seeing	Day	28% 19% 28% 17% 7% 2	14873
	Night	27% 17% 26% 22% 8% 1	23822

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% 19% 9% 17% 9% 6% 4 3 3 4 12%	2565
	11th to 20th	Day	9% 15% 8% 22% 13% 5% 4 3 4 4 13%	2520
	21st to end	Day	12% 20% 10% 15% 5% 7% 5% 3 4 4 16%	2772
February	1st to 10th	Day	14% 18% 8% 15% 9% 7% 4 3 3 3 17%	1600
	11th to 20th	Day	11% 19% 9% 17% 9% 5% 4 3 4 4 15%	1848
	21st to end	Day	11% 19% 6% 12% 8% 7% 4 4 4 4 20%	1570
March	1st to 10th	Day	20% 17% 4 11% 7% 5% 4 3 3 4 22%	3116
	11th to 20th	Day	14% 23% 8% 13% 5% 3 3 2 3 4 22%	3288
	21st to end	Day	17% 16% 6% 11% 4 4 3 2 3 4 29%	4095
April	1st to 10th	Day	20% 19% 5% 9% 4 3 4 3 3 5% 25%	2280
	11th to 20th	Day	19% 15% 4 6% 5% 4 4 3 4 5% 32%	2296
	21st to end	Day	23% 15% 4 7% 4 4 4 3 4 5% 26%	2470
May	1st to 10th	Day	26% 11% 3 7% 4 5% 4 3 4 5% 26%	4134
	11th to 20th	Day	20% 9% 3 8% 6% 5% 6% 4 6% 7% 27%	4398
	21st to end	Day	16% 7% 2 7% 5% 6% 5% 5% 7% 9% 31%	4837
June	1st to 10th	Day	27% 10% 3 6% 4 5% 5% 4 5% 6% 25%	2660
	11th to 20th	Day	18% 7% 3 6% 4 4 5% 4 6% 8% 33%	2660
	21st to end	Day	23% 9% 2 7% 5% 4 5% 4 7% 7% 27%	2660
July	1st to 10th	Day	15% 7% 2 7% 5% 5% 5% 5% 8% 10% 31%	4440
	11th to 20th	Day	14% 7% 3 7% 5% 6% 6% 5% 8% 10% 29%	4440
	21st to end	Day	16% 7% 3 7% 4 5% 5% 4 6% 7% 36%	4814
August	1st to 10th	Day	19% 9% 3 7% 6% 6% 5% 4 6% 8% 27%	4361
	11th to 20th	Day	19% 7% 3 8% 5% 6% 5% 5% 7% 9% 26%	4045
	21st to end	Day	21% 6% 2 5% 3 4 5% 4 5% 8% 37%	4212
September	1st to 10th	Day	17% 7% 2 6% 4 4 5% 4 4 7% 40%	2280
	11th to 20th	Day	19% 7% 2 6% 3 3 4 3 4 8% 42%	2123
	21st to end	Day	20% 9% 2 6% 3 4 5% 4 5% 9% 33%	2090
October	1st to 10th	Day	23% 11% 4 7% 4 4 4 4 6% 6% 29%	2081
	11th to 20th	Day	20% 14% 3 8% 4 3 4 4 6% 6% 28%	1781
	21st to end	Day	23% 21% 4 6% 4 4 4 3 3 4 24%	1881
November	1st to 10th	Day	19% 17% 4 8% 6% 4 4 3 4 5% 27%	1761
	11th to 20th	Day	17% 18% 5% 11% 6% 4 3 3 4 5% 23%	1800
	21st to end	Day	17% 19% 6% 12% 6% 5% 4 3 5% 5% 18%	1654
December	1st to 10th	Day	13% 21% 8% 22% 11% 4 3 2 3 3 11%	2600
	11th to 20th	Day	15% 18% 7% 15% 5% 4 5% 3 4 4 20%	2986
	21st to end	Day	17% 18% 5% 14% 6% 4 5% 3 4 5% 18%	3960
January	1st to 10th	Night	12% 21% 8% 21% 9% 6% 4 2 3 3 12%	4514
	11th to 20th	Night	11% 17% 9% 20% 13% 6% 5% 3 3 3 11%	4440
	21st to end	Night	13% 20% 8% 16% 8% 7% 4 3 3 3 16%	4884
February	1st to 10th	Night	12% 17% 6% 16% 10% 7% 5% 3 4 4 16%	2580
	11th to 20th	Night	10% 19% 7% 17% 9% 7% 4 2 3 3 18%	2218
	21st to end	Night	13% 17% 6% 11% 9% 7% 5% 3 3 4 23%	1884
March	1st to 10th	Night	21% 18% 5% 8% 5% 4 3 2 4 4 25%	3724
	11th to 20th	Night	15% 24% 7% 11% 6% 4 3 2 3 4 21%	3671
	21st to end	Night	16% 19% 6% 12% 6% 4 3 1 3 3 26%	3535
April	1st to 10th	Night	20% 17% 4 9% 5% 3 3 3 4 5% 25%	1900
	11th to 20th	Night	21% 14% 3 7% 5% 3 3 3 4 6% 31%	1833
	21st to end	Night	23% 14% 3 6% 5% 4 4 3 4 6% 29%	1710
May	1st to 10th	Night	25% 12% 3 7% 4 4 3 4 4 6% 27%	2834
	11th to 20th	Night	22% 8% 3 7% 6% 5% 4 4 5% 6% 30%	2495
	21st to end	Night	18% 6% 2 7% 4 4 5% 4 6% 8% 36%	2738
June	1st to 10th	Night	27% 9% 3 6% 3 3 4 4 6% 6% 29%	1520
	11th to 20th	Night	20% 6% 3 5% 4 4 5% 5% 6% 7% 35%	1520
	21st to end	Night	21% 8% 3 7% 6% 4 5% 4 6% 7% 30%	1520
July	1st to 10th	Night	15% 7% 3 8% 6% 5% 5% 4 6% 8% 32%	2520
	11th to 20th	Night	18% 8% 3 7% 4 4 5% 4 5% 8% 35%	2520
	21st to end	Night	16% 6% 3 7% 5% 5% 5% 4 6% 7% 37%	2739
August	1st to 10th	Night	24% 8% 3 6% 4 4 3 4 5% 6% 31%	2536
	11th to 20th	Night	18% 7% 3 8% 5% 5% 6% 5% 7% 8% 29%	2782
	21st to end	Night	19% 7% 2 6% 4 4 4 4 5% 6% 40%	3440
September	1st to 10th	Night	16% 9% 2 7% 3 4 4 4 5% 6% 40%	1900
	11th to 20th	Night	18% 6% 2 5% 3 3 4 3 4 6% 46%	2057
	21st to end	Night	21% 7% 2 4 3 3 4 3 5% 7% 41%	2090
October	1st to 10th	Night	22% 9% 3 7% 4 4 4 3 5% 6% 33%	2097
	11th to 20th	Night	23% 14% 3 8% 5% 4 4 3 4 5% 28%	2399
	21st to end	Night	26% 15% 3 6% 4 3 4 4 4 6% 24%	2717
November	1st to 10th	Night	20% 18% 4 8% 5% 4 4 3 5% 5% 25%	2537
	11th to 20th	Night	17% 17% 6% 11% 5% 3 3 3 4 5% 26%	2600
	21st to end	Night	18% 20% 6% 13% 5% 4 3 3 3 4 20%	2745
December	1st to 10th	Night	13% 22% 12% 23% 7% 4 4 2 3 3 8%	4580
	11th to 20th	Night	16% 22% 6% 18% 7% 4 3 2 3 3 15%	5208
	21st to end	Night	17% 17% 6% 13% 7% 4 5% 3 3 4 20%	6996

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	78% 4 8% 9% 1	2566
	11th to 20th	Day	75% 6% 6% 9% 3 1	2520
	21st to end	Day	73% 4 8% 9% 5% 1	2772
February	1st to 10th	Day	75% 3 5% 11% 5% 1	1600
	11th to 20th	Day	75% 3 7% 8% 5% 1	1857
	21st to end	Day	68% 4 7% 12% 7% 2	1570
March	1st to 10th	Day	67% 6% 7% 10% 8% 2	3119
	11th to 20th	Day	68% 3 8% 9% 9% 2	3288
	21st to end	Day	61% 2 7% 14% 14% 1	4095
April	1st to 10th	Day	64% 4 7% 16% 8% 2	2280
	11th to 20th	Day	55% 4 8% 20% 11% 1	2296
	21st to end	Day	61% 5% 8% 15% 9% 3	2470
May	1st to 10th	Day	60% 6% 9% 18% 7% 1	4148
	11th to 20th	Day	55% 8% 15% 15% 6% 1	4402
	21st to end	Day	46% 9% 13% 22% 9%	4837
June	1st to 10th	Day	59% 6% 11% 18% 6% 1	2660
	11th to 20th	Day	48% 7% 12% 22% 10% 1	2660
	21st to end	Day	56% 8% 10% 18% 7%	2660
July	1st to 10th	Day	45% 9% 15% 23% 8%	4370
	11th to 20th	Day	46% 10% 14% 27% 3	4365
	21st to end	Day	47% 8% 10% 28% 6%	4661
August	1st to 10th	Day	54% 8% 14% 18% 5%	4347
	11th to 20th	Day	52% 10% 16% 17% 5%	4084
	21st to end	Day	44% 7% 16% 19% 12% 2	4212
September	1st to 10th	Day	44% 6% 12% 27% 10%	2280
	11th to 20th	Day	43% 5% 11% 27% 14% 1	2123
	21st to end	Day	47% 8% 12% 22% 10% 1	2090
October	1st to 10th	Day	50% 6% 14% 21% 9%	3458
	11th to 20th	Day	53% 6% 12% 21% 8%	2932
	21st to end	Day	54% 4 14% 20% 8% 1	3081
November	1st to 10th	Day	61% 4 10% 16% 8% 1	1761
	11th to 20th	Day	65% 5% 9% 10% 9% 2	1800
	21st to end	Day	69% 6% 11% 11% 3	1654
December	1st to 10th	Day	81% 4 7% 6% 2	2600
	11th to 20th	Day	68% 4 7% 13% 7%	2986
	21st to end	Day	70% 5% 5% 10% 8% 2	3960
January	1st to 10th	Night	80% 4 8% 6% 2	4514
	11th to 20th	Night	81% 5% 6% 7% 2	4440
	21st to end	Night	76% 4 7% 8% 4 1	4884
February	1st to 10th	Night	73% 4 7% 10% 6%	2580
	11th to 20th	Night	74% 4 6% 11% 5% 1	2220
	21st to end	Night	67% 4 7% 13% 8% 1	1884
March	1st to 10th	Night	64% 4 8% 14% 7% 2	3734
	11th to 20th	Night	69% 4 8% 11% 8% 1	3672
	21st to end	Night	66% 3 4 13% 12% 1	3535
April	1st to 10th	Night	62% 5% 8% 15% 10% 1	1900
	11th to 20th	Night	56% 5% 9% 19% 11%	1833
	21st to end	Night	58% 5% 9% 15% 11% 2	1710
May	1st to 10th	Night	57% 8% 12% 14% 7% 1	2840
	11th to 20th	Night	52% 8% 14% 18% 7% 1	2496
	21st to end	Night	45% 8% 14% 19% 13%	2739
June	1st to 10th	Night	55% 7% 9% 20% 8%	1520
	11th to 20th	Night	47% 7% 12% 22% 9% 2	1520
	21st to end	Night	54% 8% 13% 19% 7% 1	1520
July	1st to 10th	Night	47% 9% 13% 22% 9%	2480
	11th to 20th	Night	47% 8% 13% 26% 6%	2472
	21st to end	Night	46% 9% 13% 23% 9%	2651
August	1st to 10th	Night	53% 7% 13% 22% 5%	2526
	11th to 20th	Night	50% 11% 17% 16% 6%	2809
	21st to end	Night	45% 6% 13% 22% 13% 1	3440
September	1st to 10th	Night	44% 6% 14% 25% 11%	1900
	11th to 20th	Night	40% 5% 14% 29% 11% 1	2057
	21st to end	Night	43% 7% 13% 25% 11% 2	2090
October	1st to 10th	Night	51% 6% 11% 23% 8%	3500
	11th to 20th	Night	56% 5% 9% 20% 10%	3987
	21st to end	Night	54% 5% 14% 17% 8% 1	4467
November	1st to 10th	Night	62% 5% 11% 15% 7% 1	2537
	11th to 20th	Night	63% 4 8% 15% 8% 2	2600
	21st to end	Night	70% 5% 9% 11% 4	2745
December	1st to 10th	Night	84% 4 5% 5% 1	4580
	11th to 20th	Night	77% 3 5% 8% 7%	5208
	21st to end	Night	70% 5% 6% 10% 7% 2	6996

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	27% 23% 35% 13% 2	192
	11th to 20th	Day	32% 29% 27% 9% 3 1	180
	21st to end	Day	26% 25% 34% 11% 4 1	198
February	1st to 10th	Day	39% 29% 22% 9% 1	228
	11th to 20th	Day	31% 31% 27% 8% 2	456
	21st to end	Day	30% 28% 27% 13% 1	382
March	1st to 10th	Day	32% 22% 29% 14% 3	460
	11th to 20th	Day	31% 28% 25% 13% 3	460
	21st to end	Day	35% 22% 23% 14% 5% 1	506
April	1st to 10th	Day	38% 20% 23% 13% 5% 1	460
	11th to 20th	Day	35% 23% 25% 10% 6% 2	452
	21st to end	Day	34% 23% 25% 13% 4 1	460
May	1st to 10th	Day	39% 17% 23% 14% 6% 1	463
	11th to 20th	Day	25% 19% 31% 18% 5% 2	487
	21st to end	Day	22% 20% 33% 18% 6% 1	529
June	1st to 10th	Day	32% 15% 30% 15% 7%	490
	11th to 20th	Day	23% 18% 29% 21% 8% 1	490
	21st to end	Day	27% 17% 32% 15% 8% 2	490
July	1st to 10th	Day	20% 13% 33% 24% 8% 1	485
	11th to 20th	Day	18% 12% 37% 23% 7% 2	484
	21st to end	Day	20% 10% 37% 25% 7% 2	532
August	1st to 10th	Day	19% 12% 30% 26% 11% 1	486
	11th to 20th	Day	19% 10% 30% 22% 15% 4	479
	21st to end	Day	24% 14% 24% 22% 12% 4	539
September	1st to 10th	Day	21% 14% 28% 20% 13% 4	490
	11th to 20th	Day	21% 13% 20% 22% 17% 8%	490
	21st to end	Day	19% 16% 23% 24% 12% 5%	490
October	1st to 10th	Day	27% 17% 25% 17% 11% 3	490
	11th to 20th	Day	30% 20% 25% 15% 8% 1	427
	21st to end	Day	35% 23% 23% 13% 5%	429
November	1st to 10th	Day	35% 20% 27% 14% 4 1	395
	11th to 20th	Day	32% 23% 26% 13% 6% 1	400
	21st to end	Day	33% 21% 30% 13% 2	254
December	1st to 10th	Day	31% 23% 29% 12% 6%	200
	11th to 20th	Day	37% 28% 26% 9% 1	200
	21st to end	Day	40% 20% 29% 9% 2	220
January	1st to 10th	Night	27% 26% 29% 15% 2	785
	11th to 20th	Night	25% 27% 29% 15% 3	760
	21st to end	Night	21% 25% 30% 19% 5%	836
February	1st to 10th	Night	24% 26% 29% 18% 3	760
	11th to 20th	Night	24% 26% 33% 15% 3	743
	21st to end	Night	26% 20% 33% 18% 2	628
March	1st to 10th	Night	28% 21% 29% 19% 3	760
	11th to 20th	Night	30% 20% 27% 17% 6%	760
	21st to end	Night	32% 19% 24% 18% 6% 1	836
April	1st to 10th	Night	34% 20% 24% 18% 4	760
	11th to 20th	Night	31% 19% 25% 19% 7%	709
	21st to end	Night	32% 16% 27% 19% 5%	570
May	1st to 10th	Night	30% 13% 29% 21% 6% 1	570
	11th to 20th	Night	23% 12% 33% 25% 7% 1	374
	21st to end	Night	22% 11% 27% 32% 7% 1	411
June	1st to 10th	Night	31% 8% 25% 27% 9% 1	380
	11th to 20th	Night	21% 8% 25% 34% 12%	380
	21st to end	Night	20% 8% 29% 34% 9%	380
July	1st to 10th	Night	17% 6% 29% 35% 13% 1	370
	11th to 20th	Night	15% 6% 27% 35% 15% 1	368
	21st to end	Night	16% 6% 24% 39% 15%	416
August	1st to 10th	Night	21% 4 16% 40% 18% 1	395
	11th to 20th	Night	18% 6% 23% 32% 19% 1	562
	21st to end	Night	20% 6% 23% 32% 16% 2	813
September	1st to 10th	Night	20% 8% 26% 31% 14% 1	760
	11th to 20th	Night	21% 8% 19% 29% 20% 2	760
	21st to end	Night	23% 11% 25% 25% 14% 2	760
October	1st to 10th	Night	28% 12% 22% 24% 13% 1	760
	11th to 20th	Night	31% 15% 23% 21% 8% 1	760
	21st to end	Night	34% 17% 26% 18% 4	836
November	1st to 10th	Night	33% 16% 28% 17% 5%	780
	11th to 20th	Night	27% 21% 28% 16% 7% 1	800
	21st to end	Night	30% 24% 26% 15% 5% 1	800
December	1st to 10th	Night	32% 25% 27% 13% 3	800
	11th to 20th	Night	32% 24% 27% 14% 4	800
	21st to end	Night	33% 23% 26% 16% 2	880

Page generated at 2025-01-04 03:24:00. Version ac07

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