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 2025-12-18.

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	17% 12% 4 10% 6% 5% 5% 4 6% 7% 25%	127286
	Night	17% 14% 5% 11% 6% 5% 5% 4 5% 6% 22%	123831
Transparency	Day	57% 9% 13% 15% 6%	130708
	Night	62% 8% 11% 14% 5%	128496
Seeing	Day	25% 16% 29% 20% 8% 2	16820
	Night	25% 14% 27% 26% 8% 1	25127

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	12% 24% 10% 20% 7% 5% 5% 2 3 3 8%	3391
	11th to 20th	Day	9% 15% 7% 20% 12% 8% 8% 4 5% 4 9%	3570
	21st to end	Day	5% 10% 7% 14% 7% 8% 8% 5% 7% 6% 23%	3960
February	1st to 10th	Day	6% 14% 5% 13% 8% 10% 8% 5% 7% 6% 17%	1600
	11th to 20th	Day	11% 17% 5% 15% 9% 8% 6% 3 6% 4 16%	1841
	21st to end	Day	9% 15% 5% 10% 9% 7% 7% 6% 6% 6% 21%	1650
March	1st to 10th	Day	14% 17% 5% 11% 4 4 5% 4 6% 5% 25%	4476
	11th to 20th	Day	15% 17% 6% 13% 7% 5% 5% 4 5% 6% 18%	4748
	21st to end	Day	13% 15% 5% 11% 7% 6% 6% 4 5% 6% 23%	5820
April	1st to 10th	Day	17% 15% 4 11% 5% 5% 4 3 4 5% 24%	2400
	11th to 20th	Day	17% 10% 4 8% 6% 5% 5% 3 5% 7% 30%	2505
	21st to end	Day	19% 11% 4 7% 5% 5% 4 4 5% 6% 29%	2600
May	1st to 10th	Day	22% 11% 3 7% 5% 4 4 4 4 6% 30%	6180
	11th to 20th	Day	23% 8% 3 7% 5% 5% 4 3 5% 6% 30%	6318
	21st to end	Day	18% 9% 3 7% 4 5% 5% 4 6% 8% 31%	7402
June	1st to 10th	Day	20% 9% 3 7% 6% 5% 4 5% 6% 7% 30%	3000
	11th to 20th	Day	18% 6% 2 8% 6% 5% 6% 5% 6% 7% 31%	3000
	21st to end	Day	23% 8% 3 7% 5% 6% 4 4 5% 7% 27%	3000
July	1st to 10th	Day	20% 8% 3 8% 6% 5% 5% 5% 7% 8% 25%	6820
	11th to 20th	Day	17% 8% 3 8% 6% 5% 6% 4 7% 9% 27%	6418
	21st to end	Day	14% 7% 2 7% 5% 5% 5% 5% 7% 10% 34%	6926
August	1st to 10th	Day	16% 8% 3 8% 5% 6% 6% 5% 8% 9% 26%	4563
	11th to 20th	Day	18% 7% 3 9% 5% 6% 5% 5% 8% 8% 26%	4219
	21st to end	Day	19% 8% 3 9% 5% 5% 4 4 5% 7% 32%	4553
September	1st to 10th	Day	20% 8% 3 7% 5% 5% 5% 5% 6% 8% 29%	2400
	11th to 20th	Day	19% 8% 3 6% 4 4 4 3 6% 8% 34%	2229
	21st to end	Day	23% 10% 3 6% 4 4 4 3 5% 7% 31%	2200
October	1st to 10th	Day	20% 10% 3 8% 6% 4 5% 3 5% 8% 29%	2180
	11th to 20th	Day	26% 13% 5% 10% 6% 5% 5% 4 4 6% 17%	1805
	21st to end	Day	27% 17% 4 9% 5% 4 4 2 4 5% 20%	1980
November	1st to 10th	Day	21% 17% 5% 12% 6% 4 4 3 4 5% 18%	1851
	11th to 20th	Day	21% 20% 5% 12% 7% 5% 4 3 5% 4 15%	1718
	21st to end	Day	19% 25% 7% 13% 6% 5% 5% 3 4 4 10%	1470
December	1st to 10th	Day	14% 19% 7% 16% 13% 7% 4 3 4 3 11%	2350
	11th to 20th	Day	17% 16% 7% 14% 8% 8% 7% 4 4 5% 11%	2667
	21st to end	Day	17% 18% 5% 12% 8% 6% 6% 4 5% 6% 13%	3476
January	1st to 10th	Night	12% 26% 10% 14% 8% 6% 5% 3 4 3 8%	6560
	11th to 20th	Night	9% 18% 7% 23% 11% 6% 5% 4 4 4 9%	6315
	21st to end	Night	5% 12% 5% 13% 9% 8% 7% 6% 8% 7% 20%	6996
February	1st to 10th	Night	8% 14% 6% 12% 9% 6% 6% 5% 6% 7% 21%	2800
	11th to 20th	Night	10% 19% 6% 14% 9% 7% 4 3 5% 4 17%	2443
	21st to end	Night	9% 19% 6% 12% 8% 5% 6% 3 6% 5% 22%	1980
March	1st to 10th	Night	19% 16% 5% 12% 6% 5% 6% 4 4 5% 18%	5364
	11th to 20th	Night	14% 16% 5% 12% 7% 6% 6% 5% 6% 7% 18%	5210
	21st to end	Night	14% 16% 5% 11% 5% 5% 3 3 5% 6% 28%	5110
April	1st to 10th	Night	21% 15% 4 10% 6% 4 4 3 4 5% 25%	2000
	11th to 20th	Night	21% 12% 3 7% 4 4 4 3 4 6% 31%	1843
	21st to end	Night	21% 11% 3 5% 5% 4 4 3 6% 6% 32%	1800
May	1st to 10th	Night	23% 10% 3 7% 4 4 4 3 5% 5% 33%	3791
	11th to 20th	Night	24% 10% 4 8% 5% 4 4 3 5% 6% 28%	3575
	21st to end	Night	20% 9% 3 8% 4 4 5% 3 4 7% 32%	3493
June	1st to 10th	Night	21% 8% 3 6% 5% 4 5% 4 6% 7% 31%	1400
	11th to 20th	Night	17% 9% 4 6% 5% 5% 5% 3 5% 8% 34%	1400
	21st to end	Night	21% 9% 3 7% 5% 5% 4 4 5% 7% 29%	1400
July	1st to 10th	Night	18% 8% 3 9% 6% 5% 5% 5% 6% 8% 27%	3160
	11th to 20th	Night	18% 8% 3 8% 6% 6% 6% 5% 6% 8% 24%	3528
	21st to end	Night	15% 7% 3 7% 4 5% 4 4 6% 7% 37%	3926
August	1st to 10th	Night	17% 8% 3 8% 6% 5% 6% 5% 7% 8% 28%	2586
	11th to 20th	Night	19% 7% 3 7% 6% 6% 6% 4 6% 8% 27%	2796
	21st to end	Night	17% 7% 3 9% 5% 5% 5% 4 7% 7% 31%	3342
September	1st to 10th	Night	21% 7% 2 6% 5% 4 4 4 5% 8% 34%	2000
	11th to 20th	Night	19% 7% 3 8% 5% 5% 5% 4 6% 5% 33%	2170
	21st to end	Night	21% 8% 3 7% 5% 5% 5% 2 4 7% 34%	2200
October	1st to 10th	Night	22% 8% 2 7% 5% 4 4 3 5% 7% 32%	2218
	11th to 20th	Night	29% 12% 3 8% 4 5% 5% 3 4 6% 21%	2595
	21st to end	Night	27% 16% 4 8% 4 5% 4 3 5% 6% 19%	2860
November	1st to 10th	Night	25% 19% 4 10% 5% 4 4 3 4 4 19%	2667
	11th to 20th	Night	20% 19% 5% 10% 5% 5% 4 4 4 6% 17%	2894
	21st to end	Night	20% 24% 6% 13% 6% 4 4 3 4 3 12%	3150
December	1st to 10th	Night	13% 17% 8% 20% 11% 7% 5% 4 4 3 9%	5060
	11th to 20th	Night	19% 17% 7% 16% 7% 5% 4 4 5% 5% 12%	5697
	21st to end	Night	15% 21% 6% 13% 6% 5% 5% 3 3 5% 18%	7502

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	81% 7% 6% 6% 1	3392
	11th to 20th	Day	77% 7% 7% 6% 2	3600
	21st to end	Day	59% 8% 9% 17% 7%	3960
February	1st to 10th	Day	64% 9% 10% 11% 6% 1	1600
	11th to 20th	Day	69% 6% 10% 9% 5%	1849
	21st to end	Day	60% 10% 10% 14% 5% 1	1650
March	1st to 10th	Day	57% 9% 12% 11% 10% 1	4479
	11th to 20th	Day	65% 8% 11% 9% 7%	4748
	21st to end	Day	59% 8% 9% 14% 9% 1	5820
April	1st to 10th	Day	62% 8% 10% 12% 6% 2	2400
	11th to 20th	Day	53% 9% 11% 18% 8% 1	2505
	21st to end	Day	54% 9% 11% 16% 10% 1	2600
May	1st to 10th	Day	52% 8% 13% 16% 10%	6191
	11th to 20th	Day	53% 9% 11% 18% 7% 1	6322
	21st to end	Day	49% 9% 13% 19% 10% 1	7402
June	1st to 10th	Day	52% 9% 11% 17% 10% 1	3000
	11th to 20th	Day	49% 9% 13% 18% 10% 1	3000
	21st to end	Day	55% 9% 12% 16% 8% 1	3000
July	1st to 10th	Day	53% 8% 14% 23% 2	6745
	11th to 20th	Day	51% 9% 18% 19% 3	6341
	21st to end	Day	43% 10% 18% 23% 6%	6728
August	1st to 10th	Day	49% 11% 18% 20% 2	4549
	11th to 20th	Day	51% 11% 21% 14% 3	4259
	21st to end	Day	51% 8% 16% 17% 8%	4553
September	1st to 10th	Day	51% 10% 15% 18% 6%	2400
	11th to 20th	Day	47% 11% 17% 20% 6%	2229
	21st to end	Day	52% 10% 14% 19% 5%	2200
October	1st to 10th	Day	54% 10% 11% 20% 4 1	3557
	11th to 20th	Day	66% 9% 13% 11% 1	2917
	21st to end	Day	62% 9% 15% 12% 2	3180
November	1st to 10th	Day	68% 9% 12% 9% 2	1851
	11th to 20th	Day	73% 8% 8% 9% 2	1718
	21st to end	Day	78% 9% 8% 4	1470
December	1st to 10th	Day	77% 7% 10% 6% 1	2350
	11th to 20th	Day	74% 8% 9% 7% 2	2667
	21st to end	Day	69% 8% 8% 11% 4	3476
January	1st to 10th	Night	81% 6% 6% 5% 1	6560
	11th to 20th	Night	76% 8% 7% 6% 2	6360
	21st to end	Night	58% 7% 11% 16% 7%	6996
February	1st to 10th	Night	60% 8% 10% 15% 6%	2800
	11th to 20th	Night	69% 5% 10% 10% 5%	2445
	21st to end	Night	61% 7% 9% 16% 6%	1980
March	1st to 10th	Night	65% 7% 8% 12% 7%	5374
	11th to 20th	Night	62% 9% 12% 11% 5%	5211
	21st to end	Night	57% 6% 6% 20% 10% 1	5110
April	1st to 10th	Night	62% 5% 9% 15% 8% 2	2000
	11th to 20th	Night	54% 6% 9% 18% 12% 1	1843
	21st to end	Night	52% 7% 11% 19% 10% 2	1800
May	1st to 10th	Night	51% 7% 10% 19% 13% 1	3797
	11th to 20th	Night	53% 8% 9% 21% 9%	3576
	21st to end	Night	49% 9% 12% 17% 13%	3494
June	1st to 10th	Night	50% 9% 13% 18% 9% 1	1400
	11th to 20th	Night	48% 8% 12% 18% 12% 3	1400
	21st to end	Night	53% 10% 11% 18% 9%	1400
July	1st to 10th	Night	53% 7% 12% 21% 7%	3125
	11th to 20th	Night	53% 10% 18% 16% 2	3482
	21st to end	Night	44% 9% 18% 23% 6%	3809
August	1st to 10th	Night	49% 11% 18% 18% 4	2576
	11th to 20th	Night	51% 12% 19% 14% 3	2822
	21st to end	Night	49% 9% 13% 24% 5%	3342
September	1st to 10th	Night	47% 10% 15% 20% 7%	2000
	11th to 20th	Night	51% 9% 16% 18% 6%	2170
	21st to end	Night	50% 9% 11% 22% 8%	2200
October	1st to 10th	Night	54% 9% 12% 20% 5% 1	3621
	11th to 20th	Night	62% 8% 10% 16% 3	4222
	21st to end	Night	65% 7% 14% 11% 3	4610
November	1st to 10th	Night	68% 8% 11% 10% 3	2667
	11th to 20th	Night	70% 8% 10% 10% 3	2894
	21st to end	Night	77% 7% 9% 5% 1	3150
December	1st to 10th	Night	78% 8% 8% 4 1	5060
	11th to 20th	Night	74% 6% 7% 11% 1	5698
	21st to end	Night	69% 6% 8% 14% 3	7502

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	22% 21% 40% 13% 5%	200
	11th to 20th	Day	22% 16% 37% 18% 8% 1	200
	21st to end	Day	14% 18% 35% 24% 8% 2	220
February	1st to 10th	Day	18% 24% 42% 12% 4 2	200
	11th to 20th	Day	22% 24% 33% 18% 4	420
	21st to end	Day	22% 22% 32% 18% 6%	414
March	1st to 10th	Day	26% 15% 33% 18% 7%	500
	11th to 20th	Day	26% 20% 28% 17% 7% 1	500
	21st to end	Day	29% 20% 25% 18% 7%	550
April	1st to 10th	Day	30% 19% 28% 18% 5% 1	500
	11th to 20th	Day	27% 15% 32% 19% 6% 1	492
	21st to end	Day	26% 21% 31% 16% 5% 1	500
May	1st to 10th	Day	31% 17% 26% 18% 6% 1	503
	11th to 20th	Day	19% 17% 31% 24% 8% 1	527
	21st to end	Day	27% 16% 29% 20% 7% 1	766
June	1st to 10th	Day	25% 13% 32% 23% 7%	730
	11th to 20th	Day	21% 14% 29% 24% 10% 2	730
	21st to end	Day	25% 13% 29% 23% 8% 1	730
July	1st to 10th	Day	23% 11% 30% 26% 9% 1	720
	11th to 20th	Day	21% 12% 31% 24% 11% 2	554
	21st to end	Day	19% 14% 31% 22% 12% 2	576
August	1st to 10th	Day	21% 10% 26% 27% 12% 4	526
	11th to 20th	Day	18% 12% 22% 29% 16% 3	519
	21st to end	Day	24% 14% 25% 18% 15% 5%	583
September	1st to 10th	Day	25% 14% 28% 19% 10% 5%	530
	11th to 20th	Day	21% 15% 24% 24% 11% 5%	530
	21st to end	Day	28% 13% 23% 22% 11% 2	530
October	1st to 10th	Day	22% 17% 27% 18% 12% 4	530
	11th to 20th	Day	36% 16% 23% 14% 9% 1	423
	21st to end	Day	36% 19% 23% 16% 5%	462
November	1st to 10th	Day	37% 18% 26% 15% 4	425
	11th to 20th	Day	30% 18% 28% 17% 6% 1	356
	21st to end	Day	30% 24% 29% 14% 3	220
December	1st to 10th	Day	23% 17% 34% 18% 8%	220
	11th to 20th	Day	27% 20% 34% 12% 5% 2	214
	21st to end	Day	26% 27% 21% 17% 7% 1	220
January	1st to 10th	Night	24% 18% 31% 22% 5%	847
	11th to 20th	Night	24% 16% 26% 24% 9% 1	800
	21st to end	Night	15% 11% 32% 33% 8% 1	880
February	1st to 10th	Night	13% 17% 36% 28% 6% 1	800
	11th to 20th	Night	22% 16% 33% 22% 6%	783
	21st to end	Night	20% 17% 28% 28% 6% 1	660
March	1st to 10th	Night	23% 14% 33% 25% 6%	800
	11th to 20th	Night	24% 17% 31% 20% 9%	800
	21st to end	Night	23% 17% 28% 25% 6% 1	880
April	1st to 10th	Night	29% 14% 31% 21% 5% 1	800
	11th to 20th	Night	26% 14% 32% 23% 6%	659
	21st to end	Night	28% 13% 30% 23% 6%	600
May	1st to 10th	Night	30% 12% 31% 22% 5%	493
	11th to 20th	Night	23% 11% 32% 26% 7% 1	394
	21st to end	Night	27% 12% 30% 23% 8%	433
June	1st to 10th	Night	24% 6% 34% 30% 6%	400
	11th to 20th	Night	18% 10% 24% 36% 12% 1	400
	21st to end	Night	24% 8% 28% 32% 7% 1	400
July	1st to 10th	Night	25% 7% 27% 32% 9% 1	390
	11th to 20th	Night	20% 6% 20% 41% 12% 1	388
	21st to end	Night	20% 9% 20% 39% 12%	438
August	1st to 10th	Night	21% 4 20% 38% 16% 1	398
	11th to 20th	Night	22% 7% 22% 34% 16% 1	540
	21st to end	Night	22% 10% 20% 32% 14% 1	727
September	1st to 10th	Night	24% 12% 21% 31% 12% 1	800
	11th to 20th	Night	23% 10% 23% 29% 14% 2	800
	21st to end	Night	26% 11% 26% 27% 9% 2	800
October	1st to 10th	Night	25% 11% 24% 28% 10% 1	800
	11th to 20th	Night	36% 12% 22% 22% 8% 1	800
	21st to end	Night	38% 15% 19% 21% 6%	880
November	1st to 10th	Night	35% 17% 22% 20% 6% 1	820
	11th to 20th	Night	28% 19% 24% 21% 7%	891
	21st to end	Night	32% 19% 26% 17% 6% 1	950
December	1st to 10th	Night	30% 15% 26% 21% 8% 1	950
	11th to 20th	Night	27% 17% 26% 22% 7% 1	936
	21st to end	Night	25% 17% 26% 23% 8% 1	990

Page generated at 2025-12-15 01:13:53. Version ac07

Copyright © 2025 Attilla Danko.