Site d'observation de Charles Desjardins
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Site d'observation de Charles Desjardins clear sky chart from 2005-11-06 to 2024-09-14.

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% 12% 4 9% 5% 5% 5% 4 5% 6% 27%	100958
	Night	17% 14% 5% 10% 6% 5% 4 3 4 5% 26%	96953
Transparency	Day	56% 7% 11% 18% 8% 1	100716
	Night	58% 7% 10% 16% 8% 1	96815
Seeing	Day	26% 17% 29% 18% 8% 2	14490
	Night	25% 15% 27% 24% 9% 1	23348

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% 20% 8% 18% 8% 6% 4 2 3 3 14%	2517
	11th to 20th	Day	11% 17% 8% 20% 12% 5% 5% 3 4 4 13%	2520
	21st to end	Day	12% 20% 9% 15% 5% 9% 4 3 4 4 14%	2772
February	1st to 10th	Day	13% 19% 6% 16% 8% 6% 4 3 4 4 16%	1609
	11th to 20th	Day	12% 19% 8% 16% 8% 5% 5% 4 4 4 16%	1831
	21st to end	Day	12% 18% 6% 13% 7% 7% 3 4 4 5% 20%	1570
March	1st to 10th	Day	21% 16% 5% 10% 6% 5% 4 3 4 5% 21%	3116
	11th to 20th	Day	13% 21% 8% 13% 6% 4 4 2 4 3 22%	3249
	21st to end	Day	16% 14% 6% 12% 5% 4 3 2 3 4 32%	4156
April	1st to 10th	Day	20% 18% 4 10% 5% 4 3 3 3 4 25%	2280
	11th to 20th	Day	19% 15% 4 8% 5% 4 4 3 4 4 32%	2271
	21st to end	Day	23% 14% 3 8% 4 4 4 3 4 6% 26%	2470
May	1st to 10th	Day	24% 12% 3 7% 4 4 5% 3 5% 7% 26%	4216
	11th to 20th	Day	19% 9% 3 8% 6% 5% 6% 4 6% 6% 28%	4398
	21st to end	Day	14% 8% 3 7% 5% 5% 5% 5% 7% 8% 33%	4837
June	1st to 10th	Day	26% 9% 3 6% 4 4 5% 5% 5% 6% 27%	2660
	11th to 20th	Day	18% 7% 2 7% 5% 4 4 4 6% 8% 34%	2660
	21st to end	Day	24% 9% 3 7% 5% 4 4 4 6% 6% 27%	2660
July	1st to 10th	Day	14% 8% 3 7% 5% 5% 6% 4 8% 9% 32%	4440
	11th to 20th	Day	14% 7% 3 7% 5% 5% 6% 5% 7% 9% 31%	4440
	21st to end	Day	15% 8% 3 6% 5% 4 5% 4 6% 7% 38%	4814
August	1st to 10th	Day	19% 8% 3 8% 5% 5% 6% 5% 7% 8% 27%	4407
	11th to 20th	Day	18% 8% 3 8% 5% 4 6% 5% 7% 9% 28%	4016
	21st to end	Day	19% 6% 2 6% 4 4 4 4 6% 8% 36%	4180
September	1st to 10th	Day	16% 8% 2 6% 4 4 5% 4 6% 6% 40%	2280
	11th to 20th	Day	19% 7% 2 5% 3 3 3 3 4 7% 43%	2072
	21st to end	Day	18% 9% 2 5% 4 4 5% 3 5% 8% 36%	1980
October	1st to 10th	Day	24% 10% 3 8% 4 4 5% 2 6% 6% 27%	1936
	11th to 20th	Day	21% 12% 3 8% 5% 4 5% 3 5% 5% 27%	1710
	21st to end	Day	26% 21% 4 8% 4 3 3 2 3 4 23%	1782
November	1st to 10th	Day	18% 18% 3 7% 5% 4 3 4 5% 5% 27%	1671
	11th to 20th	Day	16% 20% 6% 11% 5% 5% 4 3 4 4 22%	1710
	21st to end	Day	18% 19% 7% 12% 5% 4 4 4 5% 5% 17%	1530
December	1st to 10th	Day	19% 24% 7% 14% 6% 4 3 2 3 4 14%	1520
	11th to 20th	Day	18% 20% 8% 13% 4 4 5% 2 4 4 19%	1906
	21st to end	Day	22% 18% 6% 15% 6% 4 4 3 3 4 15%	2772
January	1st to 10th	Night	14% 20% 8% 18% 9% 5% 4 3 5% 3 13%	4429
	11th to 20th	Night	10% 17% 7% 19% 11% 6% 5% 3 4 4 13%	4440
	21st to end	Night	13% 20% 8% 14% 7% 6% 4 3 3 3 18%	4884
February	1st to 10th	Night	13% 18% 6% 16% 9% 6% 4 3 4 4 18%	2570
	11th to 20th	Night	12% 15% 7% 16% 8% 7% 5% 4 4 4 19%	2233
	21st to end	Night	12% 18% 6% 11% 7% 7% 4 2 4 4 25%	1884
March	1st to 10th	Night	21% 15% 4 8% 5% 4 4 3 4 5% 27%	3724
	11th to 20th	Night	15% 19% 6% 13% 6% 4 4 3 3 3 24%	3709
	21st to end	Night	13% 18% 6% 12% 6% 4 3 3 3 3 29%	3472
April	1st to 10th	Night	21% 14% 4 9% 5% 4 4 3 5% 5% 26%	1900
	11th to 20th	Night	21% 13% 4 6% 5% 4 5% 3 4 6% 31%	1856
	21st to end	Night	21% 11% 3 8% 5% 4 3 3 5% 5% 32%	1710
May	1st to 10th	Night	23% 12% 3 8% 5% 4 4 4 5% 6% 26%	2752
	11th to 20th	Night	21% 9% 3 8% 5% 4 5% 4 5% 5% 32%	2495
	21st to end	Night	17% 7% 2 6% 4 5% 5% 4 6% 8% 37%	2738
June	1st to 10th	Night	26% 8% 2 6% 4 4 4 4 6% 7% 30%	1520
	11th to 20th	Night	19% 7% 2 6% 4 4 4 4 6% 8% 36%	1520
	21st to end	Night	19% 9% 2 7% 5% 4 4 5% 8% 6% 30%	1520
July	1st to 10th	Night	14% 9% 3 9% 6% 5% 5% 4 6% 7% 32%	2520
	11th to 20th	Night	17% 7% 3 6% 4 4 5% 5% 6% 7% 36%	2520
	21st to end	Night	14% 7% 3 7% 5% 4 5% 4 6% 6% 37%	2739
August	1st to 10th	Night	23% 8% 3 8% 4 4 4 4 5% 6% 32%	2506
	11th to 20th	Night	15% 8% 3 9% 5% 6% 6% 4 6% 8% 31%	2792
	21st to end	Night	16% 6% 2 7% 4 4 4 4 5% 6% 41%	3476
September	1st to 10th	Night	16% 7% 2 6% 5% 4 4 3 5% 6% 41%	1900
	11th to 20th	Night	16% 7% 2 5% 3 3 4 3 5% 7% 46%	1966
	21st to end	Night	20% 7% 2 4 3 3 4 3 5% 7% 41%	1980
October	1st to 10th	Night	21% 9% 3 6% 5% 4 4 3 5% 6% 34%	2020
	11th to 20th	Night	21% 12% 4 8% 5% 4 5% 3 4 5% 28%	2250
	21st to end	Night	25% 15% 4 8% 5% 3 4 3 4 5% 24%	2574
November	1st to 10th	Night	19% 14% 4 8% 5% 5% 5% 3 4 6% 26%	2407
	11th to 20th	Night	17% 16% 5% 11% 5% 4 3 3 4 5% 26%	2470
	21st to end	Night	17% 19% 6% 13% 6% 4 3 3 4 5% 21%	2645
December	1st to 10th	Night	20% 24% 7% 11% 7% 4 4 3 3 4 13%	2660
	11th to 20th	Night	18% 21% 7% 16% 7% 4 3 2 3 3 15%	3288
	21st to end	Night	22% 19% 6% 14% 5% 5% 4 2 3 4 16%	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	76% 5% 9% 9% 1	2518
	11th to 20th	Day	74% 6% 8% 9% 3	2520
	21st to end	Day	73% 5% 9% 9% 4 1	2772
February	1st to 10th	Day	73% 4 6% 12% 4 1	1609
	11th to 20th	Day	72% 4 9% 10% 4 1	1840
	21st to end	Day	65% 5% 9% 13% 6% 2	1570
March	1st to 10th	Day	64% 8% 8% 11% 8% 1	3119
	11th to 20th	Day	66% 5% 9% 9% 9% 1	3249
	21st to end	Day	57% 3 7% 16% 15% 1	4156
April	1st to 10th	Day	63% 4 8% 16% 8% 1	2280
	11th to 20th	Day	55% 5% 7% 19% 12% 1	2271
	21st to end	Day	59% 5% 8% 16% 9% 2	2470
May	1st to 10th	Day	56% 7% 11% 18% 8% 1	4230
	11th to 20th	Day	51% 11% 15% 15% 7% 1	4402
	21st to end	Day	44% 9% 12% 23% 10% 1	4837
June	1st to 10th	Day	54% 8% 11% 18% 9% 1	2660
	11th to 20th	Day	46% 7% 12% 22% 11% 2	2660
	21st to end	Day	55% 8% 11% 18% 8% 1	2660
July	1st to 10th	Day	44% 9% 15% 24% 8%	4370
	11th to 20th	Day	44% 10% 13% 29% 4	4365
	21st to end	Day	43% 8% 12% 30% 7%	4661
August	1st to 10th	Day	52% 9% 15% 19% 6%	4393
	11th to 20th	Day	49% 9% 17% 20% 5%	4055
	21st to end	Day	44% 7% 15% 19% 13% 1	4180
September	1st to 10th	Day	41% 8% 12% 27% 11% 1	2280
	11th to 20th	Day	41% 6% 11% 30% 13%	2072
	21st to end	Day	45% 8% 13% 23% 10% 1	1980
October	1st to 10th	Day	57% 6% 11% 17% 8%	1936
	11th to 20th	Day	56% 6% 15% 17% 6%	1710
	21st to end	Day	68% 4 9% 13% 6% 1	1782
November	1st to 10th	Day	58% 6% 11% 17% 8%	1671
	11th to 20th	Day	66% 5% 9% 11% 7% 2	1710
	21st to end	Day	66% 6% 14% 11% 3	1530
December	1st to 10th	Day	76% 4 9% 8% 3	1520
	11th to 20th	Day	68% 5% 8% 13% 5%	1906
	21st to end	Day	74% 6% 8% 9% 4	2772
January	1st to 10th	Night	73% 8% 10% 6% 2	4429
	11th to 20th	Night	73% 6% 9% 8% 3	4440
	21st to end	Night	70% 6% 9% 9% 5% 1	4884
February	1st to 10th	Night	70% 5% 8% 11% 5%	2570
	11th to 20th	Night	68% 6% 8% 13% 6%	2235
	21st to end	Night	63% 4 10% 13% 9% 1	1884
March	1st to 10th	Night	58% 7% 10% 15% 8% 2	3734
	11th to 20th	Night	64% 7% 8% 12% 10% 1	3710
	21st to end	Night	61% 4 6% 16% 11% 1	3472
April	1st to 10th	Night	59% 4 9% 15% 11% 1	1900
	11th to 20th	Night	54% 4 9% 20% 12% 1	1856
	21st to end	Night	54% 6% 9% 17% 12% 2	1710
May	1st to 10th	Night	56% 7% 10% 17% 8% 1	2758
	11th to 20th	Night	50% 10% 14% 16% 9% 1	2496
	21st to end	Night	44% 9% 12% 19% 15% 1	2739
June	1st to 10th	Night	51% 6% 11% 22% 9% 1	1520
	11th to 20th	Night	44% 7% 13% 23% 11% 3	1520
	21st to end	Night	50% 8% 14% 18% 9% 1	1520
July	1st to 10th	Night	48% 8% 13% 20% 11%	2480
	11th to 20th	Night	42% 9% 14% 28% 7%	2472
	21st to end	Night	44% 9% 13% 24% 9%	2651
August	1st to 10th	Night	50% 8% 14% 23% 5%	2496
	11th to 20th	Night	46% 11% 17% 19% 7%	2819
	21st to end	Night	41% 8% 13% 23% 14% 1	3476
September	1st to 10th	Night	41% 9% 12% 26% 12% 1	1900
	11th to 20th	Night	37% 8% 16% 28% 11% 1	1966
	21st to end	Night	42% 7% 13% 25% 11% 1	1980
October	1st to 10th	Night	51% 7% 11% 21% 11%	2020
	11th to 20th	Night	56% 7% 11% 19% 6%	2250
	21st to end	Night	61% 6% 10% 13% 8% 1	2574
November	1st to 10th	Night	58% 6% 11% 17% 7% 1	2407
	11th to 20th	Night	60% 6% 10% 14% 8% 2	2470
	21st to end	Night	66% 6% 11% 14% 4	2645
December	1st to 10th	Night	76% 5% 8% 8% 2	2660
	11th to 20th	Night	75% 4 7% 8% 5%	3288
	21st to end	Night	73% 5% 7% 12% 3	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	27% 19% 34% 16% 4	180
	11th to 20th	Day	28% 25% 32% 10% 4 1	180
	21st to end	Day	25% 20% 36% 12% 7% 1	198
February	1st to 10th	Day	37% 30% 22% 9% 2	222
	11th to 20th	Day	29% 28% 31% 10% 2	439
	21st to end	Day	30% 22% 31% 16% 1	382
March	1st to 10th	Day	31% 18% 31% 17% 3	460
	11th to 20th	Day	29% 24% 27% 15% 4 1	460
	21st to end	Day	31% 24% 24% 14% 7% 1	506
April	1st to 10th	Day	35% 18% 27% 14% 5% 1	460
	11th to 20th	Day	36% 18% 25% 13% 5% 3	452
	21st to end	Day	34% 17% 29% 12% 6% 2	460
May	1st to 10th	Day	32% 17% 27% 16% 6% 2	463
	11th to 20th	Day	22% 18% 30% 20% 8% 3	487
	21st to end	Day	19% 20% 32% 22% 6% 2	529
June	1st to 10th	Day	30% 15% 30% 17% 8% 1	490
	11th to 20th	Day	21% 15% 31% 21% 11% 1	490
	21st to end	Day	28% 13% 32% 18% 8% 2	490
July	1st to 10th	Day	18% 12% 32% 25% 12% 2	485
	11th to 20th	Day	15% 12% 37% 25% 8% 2	484
	21st to end	Day	20% 9% 35% 26% 9% 1	532
August	1st to 10th	Day	18% 12% 27% 28% 13% 2	486
	11th to 20th	Day	19% 9% 28% 25% 15% 4	479
	21st to end	Day	18% 15% 25% 24% 12% 6%	539
September	1st to 10th	Day	20% 11% 29% 22% 13% 5%	490
	11th to 20th	Day	19% 12% 24% 21% 18% 8%	463
	21st to end	Day	18% 14% 26% 24% 14% 5%	450
October	1st to 10th	Day	26% 16% 25% 16% 12% 5%	450
	11th to 20th	Day	29% 20% 22% 18% 10% 1	405
	21st to end	Day	37% 19% 22% 17% 5%	396
November	1st to 10th	Day	31% 18% 29% 16% 5% 1	365
	11th to 20th	Day	29% 23% 29% 12% 6% 2	370
	21st to end	Day	32% 18% 35% 13% 3	190
December	1st to 10th	Day	32% 23% 24% 14% 6% 2	180
	11th to 20th	Day	32% 26% 29% 12% 1 1	180
	21st to end	Day	35% 24% 27% 11% 4	198
January	1st to 10th	Night	28% 21% 29% 19% 3 1	760
	11th to 20th	Night	26% 22% 30% 17% 4	760
	21st to end	Night	19% 20% 33% 22% 5% 1	836
February	1st to 10th	Night	23% 20% 32% 20% 4	760
	11th to 20th	Night	21% 23% 34% 19% 3	743
	21st to end	Night	26% 18% 31% 23% 3	628
March	1st to 10th	Night	29% 16% 30% 21% 4	760
	11th to 20th	Night	27% 19% 27% 21% 6%	760
	21st to end	Night	27% 18% 26% 21% 8% 1	836
April	1st to 10th	Night	30% 15% 29% 21% 6%	760
	11th to 20th	Night	28% 17% 27% 21% 7%	732
	21st to end	Night	29% 15% 29% 20% 7%	570
May	1st to 10th	Night	26% 12% 29% 25% 8% 1	527
	11th to 20th	Night	23% 10% 31% 26% 9% 1	374
	21st to end	Night	19% 12% 27% 32% 9%	411
June	1st to 10th	Night	27% 8% 26% 27% 10% 1	380
	11th to 20th	Night	20% 7% 26% 32% 14%	380
	21st to end	Night	19% 9% 25% 35% 11% 1	380
July	1st to 10th	Night	15% 5% 28% 37% 14%	370
	11th to 20th	Night	13% 4 25% 38% 19% 1	368
	21st to end	Night	13% 6% 23% 42% 16%	416
August	1st to 10th	Night	19% 5% 17% 38% 20%	378
	11th to 20th	Night	14% 6% 23% 35% 20% 2	559
	21st to end	Night	16% 7% 23% 33% 19% 2	836
September	1st to 10th	Night	18% 8% 24% 34% 14% 1	760
	11th to 20th	Night	19% 8% 21% 30% 20% 2	736
	21st to end	Night	23% 8% 28% 24% 16% 2	720
October	1st to 10th	Night	26% 13% 22% 25% 13% 1	720
	11th to 20th	Night	28% 13% 26% 21% 10% 1	720
	21st to end	Night	30% 17% 28% 21% 4	792
November	1st to 10th	Night	27% 17% 30% 20% 5% 1	740
	11th to 20th	Night	25% 20% 28% 16% 9% 1	760
	21st to end	Night	28% 23% 26% 17% 5% 1	760
December	1st to 10th	Night	31% 24% 26% 15% 4	760
	11th to 20th	Night	28% 22% 28% 17% 5% 1	760
	21st to end	Night	33% 21% 25% 18% 3	836

Page generated at 2024-09-11 10:00:01. Version ac07

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