Club d'Astronomie Sirius du Saguenay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Club d'Astronomie Sirius du Saguenay clear sky chart from 2005-11-06 to 2024-01-13.

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% 11% 4 8% 7% 4 5% 5% 5% 6% 25%	74557
	Night	19% 14% 5% 9% 7% 4 5% 5% 5% 6% 23%	75188
Transparency	Day	58% 9% 12% 14% 6% 1	74254
	Night	62% 8% 10% 14% 6% 1	75025
Seeing	Day	26% 16% 28% 20% 8% 1	14275
	Night	26% 14% 27% 25% 8% 1	22701

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	13% 18% 9% 15% 9% 5% 6% 5% 5% 4 11%	1423
	11th to 20th	Day	15% 16% 7% 13% 8% 4 6% 6% 7% 5% 14%	1456
	21st to end	Day	10% 11% 7% 10% 9% 5% 8% 9% 7% 6% 18%	1584
February	1st to 10th	Day	6% 13% 7% 11% 10% 7% 10% 6% 7% 6% 17%	1440
	11th to 20th	Day	12% 15% 6% 13% 10% 6% 7% 5% 6% 5% 16%	1652
	21st to end	Day	9% 13% 6% 10% 8% 5% 7% 7% 6% 6% 21%	1480
March	1st to 10th	Day	14% 14% 6% 11% 7% 4 6% 6% 7% 6% 21%	1797
	11th to 20th	Day	16% 13% 7% 9% 8% 5% 5% 5% 3 5% 23%	1888
	21st to end	Day	17% 12% 5% 9% 5% 4 5% 5% 4 6% 27%	2310
April	1st to 10th	Day	19% 13% 6% 10% 6% 4 5% 5% 4 5% 22%	2160
	11th to 20th	Day	18% 9% 4 6% 7% 4 5% 4 5% 6% 31%	2251
	21st to end	Day	19% 9% 4 7% 6% 3 5% 5% 5% 6% 30%	2340
May	1st to 10th	Day	22% 11% 3 5% 5% 3 4 5% 5% 6% 32%	2452
	11th to 20th	Day	17% 7% 4 6% 7% 4 5% 5% 5% 7% 34%	2478
	21st to end	Day	21% 6% 3 6% 6% 3 5% 4 5% 8% 32%	2898
June	1st to 10th	Day	21% 8% 3 6% 6% 4 4 6% 6% 6% 30%	2700
	11th to 20th	Day	19% 6% 3 6% 6% 4 5% 6% 5% 8% 32%	2700
	21st to end	Day	23% 7% 4 6% 6% 4 6% 4 5% 7% 28%	2700
July	1st to 10th	Day	21% 8% 3 6% 6% 3 5% 6% 6% 9% 27%	2700
	11th to 20th	Day	18% 7% 3 7% 7% 4 6% 6% 7% 9% 27%	2550
	21st to end	Day	18% 8% 3 7% 7% 4 6% 6% 6% 8% 27%	2744
August	1st to 10th	Day	20% 8% 3 8% 6% 5% 6% 7% 7% 7% 23%	2506
	11th to 20th	Day	18% 7% 3 8% 6% 4 5% 5% 7% 8% 29%	2334
	21st to end	Day	20% 9% 3 6% 6% 4 4 5% 5% 8% 29%	2512
September	1st to 10th	Day	21% 8% 3 6% 6% 3 5% 6% 5% 7% 29%	2160
	11th to 20th	Day	21% 8% 3 5% 6% 3 5% 4 5% 8% 33%	2007
	21st to end	Day	24% 9% 3 6% 5% 3 4 4 4 6% 31%	1980
October	1st to 10th	Day	21% 10% 3 7% 7% 2 5% 4 5% 7% 29%	1962
	11th to 20th	Day	28% 13% 5% 9% 8% 3 5% 5% 4 6% 15%	1625
	21st to end	Day	29% 17% 4 8% 6% 3 4 3 4 4 20%	1782
November	1st to 10th	Day	22% 16% 5% 10% 7% 3 4 4 4 5% 19%	1671
	11th to 20th	Day	21% 19% 5% 10% 8% 3 4 5% 5% 4 14%	1556
	21st to end	Day	20% 21% 7% 11% 8% 3 5% 4 4 4 11%	1330
December	1st to 10th	Day	20% 20% 6% 13% 11% 5% 5% 3 4 3 10%	1330
	11th to 20th	Day	18% 16% 6% 12% 9% 6% 7% 5% 3 3 15%	1668
	21st to end	Day	18% 19% 6% 11% 10% 5% 5% 5% 4 5% 13%	2431
January	1st to 10th	Night	14% 21% 7% 12% 11% 5% 6% 5% 5% 4 10%	2739
	11th to 20th	Night	15% 17% 5% 13% 9% 4 5% 6% 5% 6% 14%	2560
	21st to end	Night	9% 13% 6% 10% 10% 6% 8% 6% 8% 6% 17%	2772
February	1st to 10th	Night	8% 13% 7% 11% 10% 4 7% 6% 6% 7% 21%	2520
	11th to 20th	Night	11% 18% 7% 14% 9% 5% 5% 4 5% 5% 18%	2192
	21st to end	Night	9% 17% 6% 11% 10% 3 6% 5% 5% 5% 23%	1776
March	1st to 10th	Night	14% 15% 6% 10% 7% 4 5% 4 4 5% 25%	2150
	11th to 20th	Night	15% 14% 6% 10% 9% 4 6% 5% 4 6% 22%	2070
	21st to end	Night	15% 15% 5% 8% 6% 4 4 4 4 6% 29%	2044
April	1st to 10th	Night	22% 14% 5% 9% 7% 3 5% 3 4 5% 24%	1800
	11th to 20th	Night	21% 11% 3 6% 5% 3 4 4 4 6% 31%	1657
	21st to end	Night	20% 10% 4 5% 5% 3 4 4 5% 7% 33%	1620
May	1st to 10th	Night	24% 10% 3 7% 6% 3 4 4 4 5% 31%	1525
	11th to 20th	Night	19% 9% 3 6% 6% 3 4 5% 5% 6% 34%	1415
	21st to end	Night	23% 8% 4 6% 5% 3 6% 4 4 6% 30%	1377
June	1st to 10th	Night	21% 7% 4 6% 6% 3 6% 4 6% 7% 30%	1260
	11th to 20th	Night	17% 8% 4 5% 6% 3 5% 4 5% 8% 35%	1260
	21st to end	Night	21% 8% 3 6% 5% 4 5% 5% 5% 7% 29%	1260
July	1st to 10th	Night	21% 8% 2 7% 6% 4 5% 5% 5% 8% 28%	1260
	11th to 20th	Night	17% 6% 4 6% 7% 5% 6% 7% 6% 8% 28%	1407
	21st to end	Night	17% 8% 4 8% 6% 4 6% 5% 6% 6% 30%	1574
August	1st to 10th	Night	19% 9% 3 7% 7% 4 5% 6% 7% 9% 26%	1432
	11th to 20th	Night	20% 8% 3 6% 7% 4 6% 5% 6% 7% 29%	1549
	21st to end	Night	21% 7% 2 6% 6% 3 5% 5% 6% 8% 30%	1841
September	1st to 10th	Night	21% 7% 3 5% 6% 4 4 4 5% 8% 34%	1800
	11th to 20th	Night	20% 7% 3 7% 6% 4 5% 4 5% 5% 32%	1952
	21st to end	Night	21% 7% 4 7% 5% 4 5% 3 4 7% 33%	1980
October	1st to 10th	Night	22% 8% 2 6% 7% 3 4 4 5% 7% 33%	1996
	11th to 20th	Night	30% 12% 4 7% 5% 3 4 4 4 6% 20%	2335
	21st to end	Night	28% 15% 4 7% 5% 4 4 4 5% 6% 19%	2574
November	1st to 10th	Night	25% 18% 4 9% 6% 3 4 4 4 4 20%	2407
	11th to 20th	Night	21% 17% 6% 9% 7% 3 5% 5% 4 6% 18%	2617
	21st to end	Night	20% 21% 6% 12% 8% 4 5% 4 4 4 14%	2850
December	1st to 10th	Night	20% 20% 7% 13% 8% 4 5% 5% 4 4 10%	2850
	11th to 20th	Night	20% 16% 7% 12% 9% 3 5% 5% 5% 5% 13%	3531
	21st to end	Night	16% 24% 7% 10% 8% 3 4 4 3 3 17%	5236

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% 7% 8% 7% 2	1424
	11th to 20th	Day	69% 7% 9% 10% 4	1456
	21st to end	Day	60% 8% 8% 16% 7%	1584
February	1st to 10th	Day	64% 9% 10% 11% 5% 1	1440
	11th to 20th	Day	69% 7% 10% 9% 5%	1660
	21st to end	Day	61% 9% 9% 14% 5% 1	1480
March	1st to 10th	Day	62% 9% 9% 12% 8% 1	1800
	11th to 20th	Day	63% 7% 9% 13% 8%	1888
	21st to end	Day	59% 8% 10% 15% 7% 1	2310
April	1st to 10th	Day	64% 8% 10% 10% 6% 2	2160
	11th to 20th	Day	53% 8% 11% 18% 8% 1	2251
	21st to end	Day	54% 9% 11% 16% 11% 1	2340
May	1st to 10th	Day	52% 8% 11% 16% 12% 1	2452
	11th to 20th	Day	49% 8% 11% 20% 11% 1	2482
	21st to end	Day	50% 8% 11% 19% 11% 1	2898
June	1st to 10th	Day	53% 9% 11% 16% 11% 1	2700
	11th to 20th	Day	49% 9% 12% 19% 10% 1	2700
	21st to end	Day	54% 9% 13% 16% 7% 1	2700
July	1st to 10th	Day	52% 10% 17% 18% 4	2625
	11th to 20th	Day	51% 11% 16% 17% 5%	2473
	21st to end	Day	54% 13% 14% 16% 3	2591
August	1st to 10th	Day	56% 14% 16% 13% 2	2492
	11th to 20th	Day	50% 12% 18% 15% 5%	2334
	21st to end	Day	52% 10% 15% 19% 4	2512
September	1st to 10th	Day	52% 10% 13% 18% 6%	2160
	11th to 20th	Day	50% 11% 15% 18% 6%	2007
	21st to end	Day	53% 10% 14% 17% 6%	1980
October	1st to 10th	Day	54% 10% 12% 16% 6% 1	1962
	11th to 20th	Day	71% 9% 9% 9% 1	1625
	21st to end	Day	69% 7% 11% 10% 3 1	1782
November	1st to 10th	Day	67% 10% 11% 10% 2	1671
	11th to 20th	Day	73% 8% 9% 8% 2	1556
	21st to end	Day	76% 10% 9% 5% 1	1330
December	1st to 10th	Day	80% 6% 7% 6% 1	1330
	11th to 20th	Day	71% 8% 7% 10% 3	1668
	21st to end	Day	70% 9% 8% 8% 5% 1	2431
January	1st to 10th	Night	77% 7% 7% 7% 2	2739
	11th to 20th	Night	69% 7% 8% 11% 4	2560
	21st to end	Night	64% 7% 10% 14% 5%	2772
February	1st to 10th	Night	61% 8% 10% 15% 6%	2520
	11th to 20th	Night	69% 5% 10% 11% 5%	2194
	21st to end	Night	61% 7% 9% 17% 5%	1776
March	1st to 10th	Night	62% 5% 9% 16% 7% 1	2160
	11th to 20th	Night	63% 7% 8% 14% 7% 1	2071
	21st to end	Night	57% 6% 9% 19% 8% 1	2044
April	1st to 10th	Night	64% 5% 9% 13% 8% 2	1800
	11th to 20th	Night	53% 6% 10% 18% 12% 1	1657
	21st to end	Night	50% 7% 11% 20% 10% 2	1620
May	1st to 10th	Night	56% 6% 9% 14% 13% 2	1525
	11th to 20th	Night	49% 7% 11% 19% 13% 1	1416
	21st to end	Night	55% 7% 9% 17% 12% 1	1378
June	1st to 10th	Night	51% 9% 13% 17% 9% 2	1260
	11th to 20th	Night	47% 8% 12% 19% 12% 3	1260
	21st to end	Night	53% 10% 11% 17% 9%	1260
July	1st to 10th	Night	53% 9% 14% 19% 5%	1225
	11th to 20th	Night	50% 12% 15% 17% 5% 1	1361
	21st to end	Night	54% 12% 11% 17% 5%	1486
August	1st to 10th	Night	51% 13% 18% 16% 2	1422
	11th to 20th	Night	52% 12% 16% 15% 5%	1549
	21st to end	Night	51% 10% 15% 20% 4	1841
September	1st to 10th	Night	48% 10% 15% 20% 8%	1800
	11th to 20th	Night	53% 9% 16% 16% 6%	1952
	21st to end	Night	51% 9% 12% 21% 8%	1980
October	1st to 10th	Night	51% 8% 13% 18% 8% 2	1996
	11th to 20th	Night	67% 8% 10% 12% 3	2335
	21st to end	Night	66% 8% 10% 12% 4 1	2574
November	1st to 10th	Night	68% 9% 11% 10% 3	2407
	11th to 20th	Night	69% 8% 10% 9% 3	2617
	21st to end	Night	75% 7% 10% 6% 1	2850
December	1st to 10th	Night	77% 8% 8% 6% 2	2850
	11th to 20th	Night	72% 7% 8% 10% 2	3532
	21st to end	Night	71% 6% 8% 10% 3	5236

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	21% 20% 41% 13% 6%	180
	11th to 20th	Day	24% 16% 34% 20% 6% 1	164
	21st to end	Day	15% 18% 32% 25% 7% 2	176
February	1st to 10th	Day	19% 28% 40% 9% 2 2	160
	11th to 20th	Day	23% 25% 32% 17% 3	351
	21st to end	Day	24% 21% 29% 19% 6%	346
March	1st to 10th	Day	25% 15% 34% 19% 7%	420
	11th to 20th	Day	26% 20% 27% 18% 8% 1	420
	21st to end	Day	28% 19% 25% 20% 7%	462
April	1st to 10th	Day	29% 19% 28% 18% 5% 1	420
	11th to 20th	Day	28% 13% 34% 19% 6% 1	412
	21st to end	Day	26% 21% 31% 17% 5% 1	420
May	1st to 10th	Day	31% 17% 27% 19% 6%	423
	11th to 20th	Day	18% 17% 33% 23% 7% 1	447
	21st to end	Day	27% 16% 30% 20% 7%	658
June	1st to 10th	Day	25% 13% 32% 22% 7%	630
	11th to 20th	Day	21% 14% 29% 23% 11% 1	630
	21st to end	Day	25% 11% 29% 24% 9% 2	630
July	1st to 10th	Day	23% 11% 28% 26% 10% 1	620
	11th to 20th	Day	21% 11% 30% 25% 11% 2	472
	21st to end	Day	21% 14% 30% 22% 12% 2	488
August	1st to 10th	Day	24% 10% 25% 28% 9% 4	446
	11th to 20th	Day	18% 12% 23% 29% 15% 3	439
	21st to end	Day	25% 15% 25% 16% 15% 5%	495
September	1st to 10th	Day	26% 14% 27% 18% 10% 4	450
	11th to 20th	Day	24% 14% 26% 24% 9% 3	450
	21st to end	Day	28% 13% 24% 22% 10% 2	450
October	1st to 10th	Day	24% 17% 27% 18% 11% 4	450
	11th to 20th	Day	39% 16% 22% 13% 8% 2	363
	21st to end	Day	38% 18% 23% 15% 5% 1	396
November	1st to 10th	Day	38% 18% 25% 16% 4	365
	11th to 20th	Day	30% 19% 27% 16% 6% 1	304
	21st to end	Day	32% 21% 29% 14% 3	180
December	1st to 10th	Day	26% 17% 32% 16% 9% 1	180
	11th to 20th	Day	26% 24% 32% 12% 3 2	180
	21st to end	Day	26% 29% 22% 16% 6% 1	198
January	1st to 10th	Night	24% 17% 31% 22% 5%	803
	11th to 20th	Night	25% 15% 26% 25% 8% 1	732
	21st to end	Night	16% 11% 32% 31% 8% 1	792
February	1st to 10th	Night	13% 18% 36% 27% 6% 1	720
	11th to 20th	Night	23% 16% 32% 22% 7%	703
	21st to end	Night	18% 17% 29% 28% 6% 2	592
March	1st to 10th	Night	23% 13% 32% 25% 6%	720
	11th to 20th	Night	24% 17% 30% 20% 9%	720
	21st to end	Night	23% 17% 28% 25% 7% 1	792
April	1st to 10th	Night	29% 14% 29% 22% 5% 1	720
	11th to 20th	Night	26% 13% 32% 23% 6%	593
	21st to end	Night	26% 13% 31% 24% 6%	540
May	1st to 10th	Night	30% 12% 30% 23% 5%	445
	11th to 20th	Night	23% 10% 32% 26% 8% 1	354
	21st to end	Night	28% 12% 30% 24% 7%	389
June	1st to 10th	Night	24% 6% 35% 30% 6%	360
	11th to 20th	Night	18% 10% 24% 36% 12%	360
	21st to end	Night	24% 7% 29% 32% 8% 1	360
July	1st to 10th	Night	25% 7% 28% 30% 9% 1	350
	11th to 20th	Night	19% 7% 20% 40% 13% 1	348
	21st to end	Night	20% 9% 20% 38% 12% 1	394
August	1st to 10th	Night	22% 4 20% 36% 16% 1	358
	11th to 20th	Night	22% 7% 22% 33% 15% 1	485
	21st to end	Night	22% 10% 21% 32% 14% 1	653
September	1st to 10th	Night	24% 11% 21% 30% 12% 1	720
	11th to 20th	Night	24% 10% 24% 28% 11% 2	720
	21st to end	Night	26% 11% 25% 26% 10% 2	720
October	1st to 10th	Night	26% 11% 24% 28% 10% 1	720
	11th to 20th	Night	38% 12% 21% 20% 8% 1	720
	21st to end	Night	39% 15% 19% 20% 7% 1	792
November	1st to 10th	Night	35% 16% 23% 19% 6% 1	740
	11th to 20th	Night	27% 20% 25% 21% 6%	801
	21st to end	Night	31% 19% 27% 17% 5% 1	850
December	1st to 10th	Night	32% 14% 25% 20% 8% 1	850
	11th to 20th	Night	27% 18% 26% 21% 7% 1	850
	21st to end	Night	25% 18% 27% 22% 8% 1	935

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