Becancour
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Becancour clear sky chart from 2005-11-06 to 2024-01-16.

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	19% 9% 3 7% 6% 3 5% 5% 5% 7% 32%	74510
	Night	20% 10% 4 7% 6% 3 4 4 5% 6% 31%	75275
Transparency	Day	52% 5% 12% 21% 10% 1	74216
	Night	54% 5% 10% 19% 10% 1	75104
Seeing	Day	24% 8% 27% 25% 12% 4	13474
	Night	25% 7% 27% 31% 10% 1	22598

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	22% 16% 5% 8% 7% 3 4 3 3 4 23%	1517
	11th to 20th	Day	18% 16% 7% 7% 8% 3 5% 4 3 5% 24%	1480
	21st to end	Day	11% 13% 6% 9% 7% 3 6% 5% 5% 7% 28%	1584
February	1st to 10th	Day	15% 17% 5% 9% 6% 4 5% 5% 4 5% 26%	1494
	11th to 20th	Day	15% 14% 5% 9% 6% 4 6% 4 6% 5% 25%	1704
	21st to end	Day	16% 12% 6% 9% 7% 4 5% 3 5% 5% 28%	1480
March	1st to 10th	Day	15% 11% 4 8% 6% 4 5% 5% 5% 6% 31%	1797
	11th to 20th	Day	18% 12% 4 6% 5% 3 4 3 5% 6% 33%	1844
	21st to end	Day	17% 10% 3 7% 6% 4 4 5% 5% 6% 32%	2370
April	1st to 10th	Day	24% 9% 4 6% 5% 3 5% 5% 4 5% 31%	2160
	11th to 20th	Day	21% 6% 2 5% 5% 4 4 5% 5% 5% 37%	2168
	21st to end	Day	23% 10% 3 6% 5% 3 4 4 5% 5% 31%	2340
May	1st to 10th	Day	22% 7% 3 7% 5% 3 4 4 4 6% 35%	2438
	11th to 20th	Day	18% 6% 3 6% 5% 3 5% 5% 6% 7% 37%	2478
	21st to end	Day	19% 7% 3 7% 6% 4 5% 5% 5% 6% 33%	2725
June	1st to 10th	Day	21% 7% 3 6% 6% 4 5% 5% 7% 7% 30%	2520
	11th to 20th	Day	16% 6% 3 6% 5% 3 5% 5% 7% 8% 36%	2520
	21st to end	Day	20% 8% 3 8% 6% 4 5% 5% 6% 6% 30%	2520
July	1st to 10th	Day	13% 6% 3 5% 6% 3 6% 5% 8% 10% 35%	2520
	11th to 20th	Day	13% 6% 3 5% 6% 3 6% 7% 8% 9% 35%	2520
	21st to end	Day	14% 6% 3 6% 5% 4 6% 7% 7% 8% 34%	2744
August	1st to 10th	Day	16% 6% 2 6% 5% 4 6% 5% 7% 12% 30%	2506
	11th to 20th	Day	12% 6% 3 4 6% 4 6% 6% 7% 8% 38%	2331
	21st to end	Day	15% 5% 2 5% 5% 3 5% 6% 7% 8% 41%	2390
September	1st to 10th	Day	15% 5% 3 6% 5% 3 5% 5% 6% 8% 40%	2160
	11th to 20th	Day	17% 5% 2 4 4 3 4 4 6% 7% 46%	2040
	21st to end	Day	20% 6% 1 4 5% 3 4 4 5% 6% 41%	1980
October	1st to 10th	Day	21% 7% 3 6% 5% 3 4 4 5% 8% 33%	1922
	11th to 20th	Day	21% 8% 3 8% 7% 5% 4 5% 5% 7% 26%	1697
	21st to end	Day	28% 9% 3 7% 5% 2 4 4 4 7% 27%	1782
November	1st to 10th	Day	19% 10% 3 7% 6% 4 4 4 3 6% 33%	1671
	11th to 20th	Day	21% 12% 4 8% 5% 3 4 3 6% 6% 27%	1672
	21st to end	Day	24% 13% 4 6% 6% 4 4 5% 5% 6% 25%	1520
December	1st to 10th	Day	28% 14% 4 8% 6% 3 4 3 4 3 23%	1380
	11th to 20th	Day	22% 14% 5% 9% 6% 4 4 4 3 5% 25%	1764
	21st to end	Day	24% 16% 4 10% 5% 2 3 4 3 5% 22%	2772
January	1st to 10th	Night	20% 18% 6% 9% 7% 3 4 4 4 4 20%	2649
	11th to 20th	Night	18% 16% 6% 9% 7% 3 4 4 4 4 23%	2602
	21st to end	Night	12% 13% 5% 9% 7% 4 5% 5% 5% 6% 29%	2772
February	1st to 10th	Night	14% 13% 6% 10% 7% 4 6% 5% 5% 5% 25%	2462
	11th to 20th	Night	15% 14% 6% 10% 8% 4 5% 4 5% 5% 25%	2141
	21st to end	Night	17% 12% 5% 8% 6% 4 5% 4 4 5% 32%	1776
March	1st to 10th	Night	16% 13% 5% 9% 7% 3 4 5% 5% 5% 28%	2150
	11th to 20th	Night	19% 12% 5% 7% 6% 4 5% 4 4 5% 30%	2114
	21st to end	Night	18% 11% 4 6% 5% 2 5% 4 3 6% 35%	1984
April	1st to 10th	Night	24% 11% 4 6% 6% 3 3 5% 5% 6% 28%	1800
	11th to 20th	Night	22% 7% 3 6% 5% 3 4 4 4 7% 36%	1740
	21st to end	Night	23% 10% 3 6% 5% 2 4 3 4 7% 34%	1620
May	1st to 10th	Night	23% 8% 3 7% 6% 3 4 4 4 4 33%	1536
	11th to 20th	Night	20% 8% 3 6% 6% 3 4 4 5% 6% 35%	1415
	21st to end	Night	21% 7% 2 4 4 3 4 5% 5% 8% 37%	1550
June	1st to 10th	Night	22% 6% 3 5% 5% 3 5% 5% 7% 9% 31%	1440
	11th to 20th	Night	19% 6% 3 5% 5% 3 6% 5% 6% 9% 35%	1440
	21st to end	Night	18% 7% 3 6% 5% 3 5% 5% 8% 8% 31%	1440
July	1st to 10th	Night	13% 5% 3 5% 6% 4 6% 6% 7% 10% 35%	1440
	11th to 20th	Night	14% 5% 2 6% 5% 3 6% 5% 6% 10% 37%	1440
	21st to end	Night	13% 6% 2 6% 7% 3 5% 4 7% 8% 38%	1574
August	1st to 10th	Night	13% 5% 2 5% 5% 4 5% 6% 8% 9% 39%	1432
	11th to 20th	Night	15% 6% 2 7% 6% 3 5% 5% 5% 7% 37%	1551
	21st to end	Night	14% 6% 2 5% 5% 4 5% 5% 4 8% 42%	1963
September	1st to 10th	Night	16% 5% 2 5% 4 3 4 5% 5% 7% 43%	1800
	11th to 20th	Night	17% 5% 2 4 3 2 3 3 5% 7% 48%	1919
	21st to end	Night	19% 6% 2 5% 5% 3 4 3 4 7% 42%	1980
October	1st to 10th	Night	18% 7% 3 5% 6% 3 5% 5% 4 5% 39%	2035
	11th to 20th	Night	23% 8% 3 6% 5% 3 4 3 5% 5% 32%	2262
	21st to end	Night	27% 8% 3 7% 6% 3 4 5% 4 6% 27%	2574
November	1st to 10th	Night	21% 10% 4 7% 6% 3 4 5% 4 6% 31%	2407
	11th to 20th	Night	21% 10% 5% 8% 5% 3 4 4 4 5% 29%	2508
	21st to end	Night	25% 13% 3 7% 6% 3 4 3 4 5% 26%	2660
December	1st to 10th	Night	24% 14% 5% 9% 7% 3 4 4 5% 4 21%	2793
	11th to 20th	Night	22% 14% 6% 9% 6% 3 4 4 4 5% 24%	3422
	21st to end	Night	26% 19% 5% 7% 5% 2 3 3 3 4 23%	4884

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	66% 4 9% 15% 6%	1518
	11th to 20th	Day	64% 3 10% 14% 8% 1	1480
	21st to end	Day	55% 4 8% 20% 10% 1	1584
February	1st to 10th	Day	62% 3 8% 18% 8% 2	1494
	11th to 20th	Day	59% 5% 12% 13% 9% 1	1713
	21st to end	Day	59% 3 9% 18% 9% 2	1480
March	1st to 10th	Day	53% 4 11% 18% 11% 2	1800
	11th to 20th	Day	53% 3 12% 14% 15% 2	1844
	21st to end	Day	52% 5% 9% 20% 11% 3	2370
April	1st to 10th	Day	55% 4 10% 17% 11% 2	2160
	11th to 20th	Day	48% 4 9% 23% 13% 2	2168
	21st to end	Day	56% 4 9% 16% 13% 3	2340
May	1st to 10th	Day	50% 4 9% 20% 14% 3	2438
	11th to 20th	Day	46% 5% 10% 21% 15% 2	2482
	21st to end	Day	51% 5% 10% 18% 14% 2	2725
June	1st to 10th	Day	51% 6% 11% 21% 9% 2	2520
	11th to 20th	Day	46% 5% 12% 24% 12% 2	2520
	21st to end	Day	54% 6% 11% 18% 10% 1	2520
July	1st to 10th	Day	41% 8% 15% 27% 9%	2450
	11th to 20th	Day	42% 6% 17% 26% 9%	2445
	21st to end	Day	45% 8% 16% 23% 7%	2591
August	1st to 10th	Day	46% 7% 18% 23% 5%	2492
	11th to 20th	Day	42% 7% 17% 25% 9%	2331
	21st to end	Day	40% 6% 15% 27% 12%	2390
September	1st to 10th	Day	41% 5% 16% 25% 12% 1	2160
	11th to 20th	Day	37% 5% 15% 31% 12% 1	2040
	21st to end	Day	44% 5% 13% 27% 11%	1980
October	1st to 10th	Day	49% 4 10% 26% 10%	1922
	11th to 20th	Day	57% 5% 13% 21% 4	1697
	21st to end	Day	58% 5% 11% 18% 7% 1	1782
November	1st to 10th	Day	54% 4 12% 21% 9% 1	1671
	11th to 20th	Day	58% 4 11% 17% 10%	1672
	21st to end	Day	60% 6% 13% 17% 4 1	1520
December	1st to 10th	Day	66% 4 9% 16% 5%	1380
	11th to 20th	Day	63% 4 7% 20% 6%	1765
	21st to end	Day	66% 4 10% 11% 8%	2772
January	1st to 10th	Night	68% 4 8% 14% 5%	2649
	11th to 20th	Night	65% 4 9% 14% 7% 1	2602
	21st to end	Night	57% 4 9% 17% 11% 1	2772
February	1st to 10th	Night	62% 3 8% 16% 9% 1	2462
	11th to 20th	Night	61% 4 8% 15% 10% 1	2143
	21st to end	Night	56% 3 8% 17% 14% 2	1776
March	1st to 10th	Night	58% 4 9% 17% 10% 2	2160
	11th to 20th	Night	57% 4 8% 14% 14% 3	2115
	21st to end	Night	52% 4 7% 20% 13% 4	1984
April	1st to 10th	Night	57% 4 8% 16% 13% 2	1800
	11th to 20th	Night	49% 5% 8% 22% 15% 2	1740
	21st to end	Night	52% 4 8% 18% 15% 3	1620
May	1st to 10th	Night	55% 3 7% 16% 15% 4	1536
	11th to 20th	Night	50% 4 9% 17% 16% 4	1416
	21st to end	Night	46% 5% 11% 19% 16% 3	1551
June	1st to 10th	Night	49% 5% 12% 21% 12% 1	1440
	11th to 20th	Night	45% 6% 9% 22% 14% 4	1440
	21st to end	Night	49% 6% 12% 20% 12% 1	1440
July	1st to 10th	Night	41% 8% 15% 23% 12% 1	1400
	11th to 20th	Night	41% 7% 14% 26% 11% 1	1392
	21st to end	Night	41% 7% 16% 24% 10%	1486
August	1st to 10th	Night	38% 8% 18% 28% 7%	1422
	11th to 20th	Night	44% 6% 17% 24% 9%	1551
	21st to end	Night	41% 6% 14% 28% 12%	1963
September	1st to 10th	Night	40% 5% 15% 27% 12% 2	1800
	11th to 20th	Night	37% 4 15% 31% 11% 1	1919
	21st to end	Night	44% 5% 10% 27% 14%	1980
October	1st to 10th	Night	47% 5% 8% 26% 13%	2035
	11th to 20th	Night	53% 6% 12% 22% 7%	2262
	21st to end	Night	58% 5% 11% 17% 9%	2574
November	1st to 10th	Night	55% 5% 11% 20% 8% 1	2407
	11th to 20th	Night	57% 5% 11% 17% 9% 1	2508
	21st to end	Night	61% 5% 12% 16% 7%	2660
December	1st to 10th	Night	66% 4 11% 14% 5%	2793
	11th to 20th	Night	63% 4 8% 18% 7%	3422
	21st to end	Night	67% 3 8% 17% 5% 1	4884

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	33% 4 34% 24% 5% 1	180
	11th to 20th	Day	28% 9% 29% 24% 7% 2	170
	21st to end	Day	22% 7% 34% 25% 10% 2	176
February	1st to 10th	Day	30% 13% 37% 16% 4	184
	11th to 20th	Day	24% 8% 37% 26% 3 1	372
	21st to end	Day	24% 11% 32% 26% 6%	346
March	1st to 10th	Day	25% 10% 26% 30% 9%	420
	11th to 20th	Day	25% 14% 30% 21% 8% 2	420
	21st to end	Day	27% 8% 28% 24% 11% 3	462
April	1st to 10th	Day	29% 8% 25% 28% 8% 1	420
	11th to 20th	Day	27% 13% 26% 22% 9% 3	412
	21st to end	Day	30% 8% 30% 20% 10% 1	420
May	1st to 10th	Day	27% 9% 32% 19% 10% 3	423
	11th to 20th	Day	20% 6% 33% 24% 13% 4	447
	21st to end	Day	22% 9% 35% 19% 13% 2	485
June	1st to 10th	Day	23% 7% 30% 25% 11% 4	450
	11th to 20th	Day	20% 8% 26% 25% 17% 4	450
	21st to end	Day	23% 3 25% 26% 19% 4	450
July	1st to 10th	Day	16% 5% 22% 34% 19% 4	445
	11th to 20th	Day	17% 5% 27% 31% 16% 4	444
	21st to end	Day	18% 5% 23% 31% 19% 5%	488
August	1st to 10th	Day	18% 4 20% 31% 22% 5%	446
	11th to 20th	Day	17% 4 18% 33% 20% 9%	439
	21st to end	Day	17% 6% 28% 20% 17% 12%	495
September	1st to 10th	Day	18% 4 27% 28% 16% 7%	450
	11th to 20th	Day	18% 6% 23% 27% 18% 8%	450
	21st to end	Day	22% 5% 24% 25% 17% 7%	450
October	1st to 10th	Day	22% 10% 22% 28% 13% 5%	450
	11th to 20th	Day	27% 6% 29% 23% 12% 3	399
	21st to end	Day	35% 7% 26% 24% 9%	396
November	1st to 10th	Day	28% 12% 26% 25% 8% 1	365
	11th to 20th	Day	30% 10% 27% 23% 9% 1	332
	21st to end	Day	35% 12% 23% 21% 7% 2	180
December	1st to 10th	Day	35% 9% 23% 24% 5% 4	180
	11th to 20th	Day	26% 16% 35% 16% 6% 1	180
	21st to end	Day	34% 13% 25% 18% 8% 3	198
January	1st to 10th	Night	31% 7% 29% 26% 6%	760
	11th to 20th	Night	29% 6% 31% 27% 7%	744
	21st to end	Night	20% 6% 28% 37% 9%	792
February	1st to 10th	Night	20% 8% 35% 30% 6% 1	720
	11th to 20th	Night	23% 10% 32% 28% 6% 1	703
	21st to end	Night	24% 8% 31% 30% 6%	592
March	1st to 10th	Night	25% 7% 30% 33% 5%	720
	11th to 20th	Night	27% 8% 32% 27% 5% 1	720
	21st to end	Night	25% 7% 29% 29% 8% 1	792
April	1st to 10th	Night	30% 8% 27% 28% 7%	720
	11th to 20th	Night	27% 10% 29% 29% 6%	676
	21st to end	Night	30% 7% 29% 27% 8%	540
May	1st to 10th	Night	30% 6% 27% 29% 8%	456
	11th to 20th	Night	26% 4 32% 29% 6% 2	354
	21st to end	Night	24% 5% 33% 30% 8%	389
June	1st to 10th	Night	25% 5% 25% 36% 9%	360
	11th to 20th	Night	22% 2 24% 39% 13% 1	360
	21st to end	Night	21% 3 25% 37% 13%	360
July	1st to 10th	Night	15% 3 27% 40% 15% 1	350
	11th to 20th	Night	15% 2 21% 46% 14% 2	348
	21st to end	Night	14% 3 24% 42% 16% 1	394
August	1st to 10th	Night	15% 3 15% 44% 22% 2	358
	11th to 20th	Night	17% 2 20% 41% 18% 2	487
	21st to end	Night	18% 3 22% 34% 20% 2	775
September	1st to 10th	Night	19% 4 24% 39% 13% 2	720
	11th to 20th	Night	21% 3 22% 32% 20% 2	720
	21st to end	Night	21% 6% 24% 33% 14% 2	720
October	1st to 10th	Night	22% 7% 28% 31% 12%	720
	11th to 20th	Night	28% 7% 25% 30% 10% 1	720
	21st to end	Night	31% 7% 30% 25% 7%	792
November	1st to 10th	Night	27% 10% 26% 27% 9%	740
	11th to 20th	Night	27% 9% 30% 23% 11% 1	760
	21st to end	Night	33% 9% 25% 25% 7% 1	760
December	1st to 10th	Night	33% 8% 26% 25% 7% 1	823
	11th to 20th	Night	29% 10% 28% 25% 7% 1	817
	21st to end	Night	36% 9% 25% 24% 6% 1	836

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