Observatoire de St-Felicien
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de St-Felicien clear sky chart from 2005-11-06 to 2025-09-04.

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	15% 11% 4 10% 6% 6% 5% 4 6% 7% 27%	126218
	Night	14% 12% 4 11% 7% 5% 5% 4 5% 6% 26%	122540
Transparency	Day	56% 5% 12% 18% 8% 1	129623
	Night	59% 5% 12% 17% 7% 1	127224
Seeing	Day	21% 12% 31% 24% 10% 2	16215
	Night	22% 10% 31% 27% 9% 1	24572

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% 24% 8% 14% 6% 5% 5% 4 4 4 13%	3580
	11th to 20th	Day	8% 15% 7% 19% 8% 7% 7% 5% 6% 4 14%	3570
	21st to end	Day	5% 9% 4 14% 9% 7% 8% 5% 5% 6% 28%	3960
February	1st to 10th	Day	6% 13% 5% 13% 10% 9% 7% 6% 6% 6% 20%	1600
	11th to 20th	Day	11% 14% 6% 12% 10% 7% 6% 3 4 6% 19%	1842
	21st to end	Day	10% 14% 4 12% 7% 6% 5% 4 8% 5% 25%	1650
March	1st to 10th	Day	12% 19% 5% 10% 6% 4 4 3 4 4 27%	4476
	11th to 20th	Day	13% 16% 5% 11% 7% 6% 5% 4 6% 6% 22%	4647
	21st to end	Day	12% 13% 3 10% 5% 5% 5% 5% 5% 7% 32%	5967
April	1st to 10th	Day	15% 16% 4 13% 8% 4 4 3 4 5% 24%	2400
	11th to 20th	Day	17% 10% 4 8% 5% 5% 4 4 4 6% 33%	2452
	21st to end	Day	21% 10% 4 8% 6% 4 5% 4 5% 5% 29%	2600
May	1st to 10th	Day	18% 11% 3 8% 5% 5% 5% 4 5% 6% 29%	6346
	11th to 20th	Day	23% 9% 3 8% 5% 5% 5% 3 5% 6% 29%	6318
	21st to end	Day	15% 9% 3 8% 6% 5% 5% 4 6% 6% 33%	7169
June	1st to 10th	Day	18% 8% 3 8% 5% 5% 6% 4 6% 7% 29%	3000
	11th to 20th	Day	15% 7% 3 8% 5% 5% 5% 4 7% 8% 33%	3000
	21st to end	Day	21% 8% 3 7% 6% 5% 6% 5% 6% 6% 27%	3000
July	1st to 10th	Day	16% 9% 3 7% 5% 5% 6% 5% 7% 9% 28%	6636
	11th to 20th	Day	13% 7% 3 9% 6% 6% 6% 5% 8% 9% 29%	6360
	21st to end	Day	11% 6% 3 7% 5% 5% 6% 4 7% 9% 37%	6926
August	1st to 10th	Day	13% 7% 3 8% 7% 7% 7% 6% 8% 9% 25%	4563
	11th to 20th	Day	14% 8% 3 7% 5% 6% 7% 5% 8% 9% 29%	4317
	21st to end	Day	12% 7% 3 9% 6% 6% 5% 4 6% 8% 33%	4427
September	1st to 10th	Day	15% 7% 3 9% 6% 5% 6% 4 6% 8% 32%	2316
	11th to 20th	Day	15% 7% 3 8% 5% 5% 4 4 6% 8% 35%	2164
	21st to end	Day	21% 9% 3 8% 5% 5% 5% 3 4 7% 31%	2090
October	1st to 10th	Day	17% 10% 3 9% 6% 5% 5% 4 6% 6% 30%	2004
	11th to 20th	Day	23% 14% 5% 11% 6% 5% 5% 3 4 6% 18%	1762
	21st to end	Day	24% 13% 3 9% 5% 5% 4 4 5% 5% 23%	1881
November	1st to 10th	Day	18% 13% 4 12% 7% 6% 4 3 4 4 24%	1761
	11th to 20th	Day	17% 15% 5% 11% 7% 4 4 4 5% 5% 22%	1660
	21st to end	Day	19% 18% 5% 11% 7% 6% 5% 4 6% 6% 16%	1400
December	1st to 10th	Day	15% 18% 5% 13% 7% 3 4 3 5% 5% 22%	2280
	11th to 20th	Day	17% 13% 4 11% 8% 7% 5% 3 4 5% 22%	2618
	21st to end	Day	15% 14% 5% 11% 10% 7% 6% 4 4 4 19%	3476
January	1st to 10th	Night	14% 25% 7% 15% 8% 5% 4 2 3 4 12%	6349
	11th to 20th	Night	9% 16% 8% 20% 11% 6% 5% 3 4 4 15%	6315
	21st to end	Night	5% 9% 5% 15% 9% 7% 8% 5% 7% 7% 23%	6996
February	1st to 10th	Night	8% 13% 5% 12% 7% 8% 6% 5% 5% 7% 24%	2800
	11th to 20th	Night	8% 17% 6% 13% 10% 6% 6% 4 4 5% 21%	2439
	21st to end	Night	9% 14% 6% 11% 7% 5% 6% 4 5% 6% 26%	1980
March	1st to 10th	Night	15% 14% 5% 12% 6% 5% 6% 5% 5% 6% 20%	5364
	11th to 20th	Night	12% 15% 6% 13% 7% 6% 7% 4 5% 6% 21%	5311
	21st to end	Night	13% 14% 4 9% 5% 5% 5% 4 5% 6% 29%	4962
April	1st to 10th	Night	18% 15% 4 9% 6% 5% 5% 3 5% 5% 25%	2000
	11th to 20th	Night	18% 10% 2 8% 5% 4 5% 4 5% 6% 33%	1897
	21st to end	Night	18% 12% 3 8% 5% 5% 3 3 5% 5% 32%	1800
May	1st to 10th	Night	15% 9% 3 8% 5% 6% 5% 4 5% 6% 35%	3624
	11th to 20th	Night	22% 10% 3 8% 5% 5% 5% 4 5% 5% 29%	3575
	21st to end	Night	20% 9% 3 7% 4 5% 4 3 5% 7% 33%	3714
June	1st to 10th	Night	19% 8% 3 7% 5% 4 6% 5% 6% 8% 30%	1400
	11th to 20th	Night	14% 9% 3 7% 5% 6% 5% 5% 6% 7% 35%	1400
	21st to end	Night	17% 7% 3 8% 5% 4 5% 4 7% 8% 31%	1400
July	1st to 10th	Night	10% 6% 3 9% 6% 5% 7% 5% 9% 9% 29%	3331
	11th to 20th	Night	12% 7% 3 7% 6% 5% 6% 5% 8% 9% 33%	3600
	21st to end	Night	10% 6% 2 7% 5% 5% 5% 4 6% 8% 43%	3926
August	1st to 10th	Night	13% 6% 3 7% 5% 6% 5% 5% 8% 9% 34%	2586
	11th to 20th	Night	16% 8% 2 7% 5% 4 4 4 7% 9% 36%	2699
	21st to end	Night	13% 7% 2 6% 5% 5% 5% 5% 6% 7% 38%	3454
September	1st to 10th	Night	14% 7% 3 6% 4 4 4 4 5% 7% 40%	1931
	11th to 20th	Night	18% 7% 3 7% 4 4 3 4 5% 5% 40%	2015
	21st to end	Night	18% 7% 3 7% 5% 5% 4 5% 5% 6% 35%	2090
October	1st to 10th	Night	17% 10% 2 6% 5% 5% 5% 3 6% 8% 34%	2175
	11th to 20th	Night	25% 12% 3 7% 5% 5% 5% 3 5% 5% 24%	2418
	21st to end	Night	24% 13% 3 8% 5% 5% 5% 4 5% 6% 22%	2717
November	1st to 10th	Night	20% 13% 4 9% 5% 5% 5% 4 5% 7% 24%	2537
	11th to 20th	Night	18% 14% 5% 11% 6% 5% 5% 4 5% 6% 22%	2735
	21st to end	Night	18% 18% 5% 12% 7% 6% 5% 4 5% 5% 16%	2997
December	1st to 10th	Night	12% 16% 7% 19% 8% 5% 4 3 4 4 16%	4910
	11th to 20th	Night	19% 14% 5% 10% 8% 6% 5% 4 4 5% 20%	5591
	21st to end	Night	14% 16% 7% 12% 7% 7% 5% 3 4 4 21%	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	75% 5% 9% 9% 2	3581
	11th to 20th	Day	71% 5% 11% 9% 5%	3600
	21st to end	Day	57% 4 9% 19% 10%	3960
February	1st to 10th	Day	63% 4 9% 14% 8% 1	1600
	11th to 20th	Day	65% 6% 10% 12% 7%	1851
	21st to end	Day	56% 7% 9% 16% 9% 2	1650
March	1st to 10th	Day	59% 6% 8% 12% 12% 2	4479
	11th to 20th	Day	62% 4 11% 14% 8%	4647
	21st to end	Day	50% 5% 9% 17% 18% 2	5967
April	1st to 10th	Day	63% 4 9% 14% 9% 2	2400
	11th to 20th	Day	51% 5% 9% 21% 12% 2	2452
	21st to end	Day	56% 5% 8% 17% 12% 1	2600
May	1st to 10th	Day	53% 6% 11% 16% 13% 1	6357
	11th to 20th	Day	54% 7% 9% 19% 10% 1	6322
	21st to end	Day	49% 6% 10% 18% 15% 1	7169
June	1st to 10th	Day	52% 7% 9% 20% 11% 1	3000
	11th to 20th	Day	47% 7% 11% 21% 12% 2	3000
	21st to end	Day	54% 7% 10% 18% 10% 1	3000
July	1st to 10th	Day	52% 4 13% 29% 3	6565
	11th to 20th	Day	51% 4 17% 24% 4	6285
	21st to end	Day	45% 4 17% 26% 9%	6728
August	1st to 10th	Day	53% 6% 16% 22% 3	4549
	11th to 20th	Day	49% 6% 21% 20% 4	4359
	21st to end	Day	49% 5% 14% 21% 10%	4427
September	1st to 10th	Day	47% 8% 17% 20% 7%	2316
	11th to 20th	Day	47% 7% 18% 22% 6%	2164
	21st to end	Day	53% 7% 14% 19% 6%	2090
October	1st to 10th	Day	56% 4 13% 22% 4 1	3329
	11th to 20th	Day	66% 4 15% 14% 2	2900
	21st to end	Day	60% 5% 17% 14% 3	3081
November	1st to 10th	Day	64% 5% 12% 13% 5% 1	1761
	11th to 20th	Day	64% 4 14% 13% 4	1660
	21st to end	Day	69% 5% 14% 9% 2	1400
December	1st to 10th	Day	66% 4 15% 13% 2	2280
	11th to 20th	Day	66% 3 9% 14% 7%	2618
	21st to end	Day	67% 5% 9% 14% 5%	3476
January	1st to 10th	Night	78% 3 8% 8% 3	6349
	11th to 20th	Night	74% 3 9% 9% 4	6360
	21st to end	Night	58% 5% 11% 18% 8%	6996
February	1st to 10th	Night	59% 5% 10% 16% 9%	2800
	11th to 20th	Night	66% 4 11% 13% 6%	2441
	21st to end	Night	58% 6% 11% 18% 8%	1980
March	1st to 10th	Night	65% 4 8% 14% 9% 1	5374
	11th to 20th	Night	63% 5% 10% 13% 7% 1	5312
	21st to end	Night	55% 4 9% 22% 9% 1	4962
April	1st to 10th	Night	61% 4 10% 16% 7% 2	2000
	11th to 20th	Night	51% 4 10% 22% 12% 1	1897
	21st to end	Night	54% 4 9% 20% 12% 1	1800
May	1st to 10th	Night	49% 7% 9% 20% 14% 1	3630
	11th to 20th	Night	53% 8% 10% 18% 9% 1	3576
	21st to end	Night	51% 4 12% 16% 13% 3	3715
June	1st to 10th	Night	49% 8% 11% 22% 9% 1	1400
	11th to 20th	Night	46% 7% 12% 20% 12% 3	1400
	21st to end	Night	48% 9% 12% 19% 11% 1	1400
July	1st to 10th	Night	49% 5% 13% 25% 8%	3293
	11th to 20th	Night	47% 4 20% 25% 4	3552
	21st to end	Night	40% 5% 17% 29% 8%	3809
August	1st to 10th	Night	45% 7% 18% 23% 7%	2576
	11th to 20th	Night	45% 6% 22% 22% 4	2723
	21st to end	Night	43% 6% 18% 25% 8%	3454
September	1st to 10th	Night	43% 7% 17% 24% 9%	1931
	11th to 20th	Night	46% 7% 18% 23% 6%	2015
	21st to end	Night	49% 8% 13% 24% 7%	2090
October	1st to 10th	Night	50% 4 17% 24% 5%	3630
	11th to 20th	Night	61% 4 14% 17% 4	4019
	21st to end	Night	61% 5% 14% 14% 7%	4467
November	1st to 10th	Night	60% 6% 14% 14% 5%	2537
	11th to 20th	Night	64% 5% 13% 14% 4	2735
	21st to end	Night	69% 7% 13% 8% 2	2997
December	1st to 10th	Night	73% 3 11% 10% 2	4910
	11th to 20th	Night	66% 4 10% 16% 4	5592
	21st to end	Night	67% 4 9% 15% 4	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	26% 12% 27% 28% 8% 1	200
	11th to 20th	Day	16% 11% 31% 31% 12% 1	200
	21st to end	Day	15% 5% 32% 33% 13% 2	220
February	1st to 10th	Day	12% 12% 44% 23% 9% 1	200
	11th to 20th	Day	19% 13% 38% 26% 4	391
	21st to end	Day	18% 13% 42% 20% 6% 1	414
March	1st to 10th	Day	22% 15% 31% 22% 9% 1	500
	11th to 20th	Day	22% 14% 32% 22% 9% 1	500
	21st to end	Day	22% 14% 32% 23% 7% 1	550
April	1st to 10th	Day	23% 15% 31% 23% 7% 1	500
	11th to 20th	Day	25% 13% 26% 23% 10% 2	492
	21st to end	Day	25% 14% 32% 21% 9%	500
May	1st to 10th	Day	23% 14% 31% 22% 7% 2	503
	11th to 20th	Day	20% 11% 30% 25% 12% 2	527
	21st to end	Day	20% 15% 31% 24% 9% 1	663
June	1st to 10th	Day	22% 8% 32% 24% 11% 2	730
	11th to 20th	Day	19% 11% 32% 26% 10% 2	730
	21st to end	Day	23% 8% 28% 26% 11% 3	730
July	1st to 10th	Day	16% 9% 31% 30% 11% 2	644
	11th to 20th	Day	17% 7% 32% 27% 13% 4	524
	21st to end	Day	16% 7% 28% 28% 17% 3	576
August	1st to 10th	Day	14% 8% 26% 30% 17% 5%	526
	11th to 20th	Day	16% 6% 24% 31% 15% 7%	519
	21st to end	Day	17% 10% 30% 22% 14% 7%	583
September	1st to 10th	Day	19% 10% 33% 19% 16% 4	502
	11th to 20th	Day	16% 11% 27% 28% 15% 2	490
	21st to end	Day	21% 11% 29% 19% 14% 5%	490
October	1st to 10th	Day	18% 15% 31% 20% 12% 4	490
	11th to 20th	Day	28% 13% 33% 16% 7% 3	417
	21st to end	Day	30% 13% 30% 20% 6% 1	429
November	1st to 10th	Day	30% 17% 31% 17% 4 1	395
	11th to 20th	Day	27% 15% 29% 22% 6% 1	260
	21st to end	Day	31% 12% 33% 19% 5% 2	200
December	1st to 10th	Day	21% 11% 23% 28% 16% 2	200
	11th to 20th	Day	27% 12% 31% 24% 5% 3	200
	21st to end	Day	24% 13% 30% 23% 8% 2	220
January	1st to 10th	Night	25% 10% 33% 25% 7% 1	800
	11th to 20th	Night	22% 11% 28% 30% 10% 1	800
	21st to end	Night	13% 9% 29% 36% 12% 1	880
February	1st to 10th	Night	14% 8% 38% 29% 10% 1	800
	11th to 20th	Night	19% 9% 37% 28% 7% 1	783
	21st to end	Night	18% 12% 33% 29% 7% 1	660
March	1st to 10th	Night	20% 11% 32% 30% 7%	800
	11th to 20th	Night	20% 15% 29% 26% 9% 1	800
	21st to end	Night	21% 13% 32% 28% 6%	880
April	1st to 10th	Night	26% 11% 27% 29% 6% 1	800
	11th to 20th	Night	24% 12% 28% 28% 8%	713
	21st to end	Night	26% 13% 33% 24% 5%	600
May	1st to 10th	Night	25% 8% 33% 28% 6%	417
	11th to 20th	Night	22% 8% 33% 25% 10% 1	394
	21st to end	Night	22% 9% 39% 23% 7% 1	433
June	1st to 10th	Night	22% 8% 29% 32% 8% 1	400
	11th to 20th	Night	19% 6% 36% 28% 11% 1	400
	21st to end	Night	19% 7% 27% 36% 10% 2	400
July	1st to 10th	Night	18% 7% 34% 29% 12%	390
	11th to 20th	Night	12% 6% 31% 37% 14%	388
	21st to end	Night	13% 6% 29% 40% 11% 1	438
August	1st to 10th	Night	13% 4 28% 39% 15% 2	398
	11th to 20th	Night	19% 5% 26% 33% 16% 1	480
	21st to end	Night	18% 10% 27% 28% 15% 3	800
September	1st to 10th	Night	18% 8% 29% 31% 11% 1	773
	11th to 20th	Night	20% 9% 31% 27% 12% 2	760
	21st to end	Night	21% 8% 35% 25% 10% 1	760
October	1st to 10th	Night	22% 10% 31% 26% 10% 1	760
	11th to 20th	Night	32% 10% 28% 20% 9% 1	760
	21st to end	Night	32% 12% 28% 21% 7%	836
November	1st to 10th	Night	28% 16% 29% 20% 6% 1	780
	11th to 20th	Night	26% 15% 31% 21% 8%	800
	21st to end	Night	29% 12% 30% 23% 5% 1	899
December	1st to 10th	Night	25% 12% 29% 25% 9% 1	900
	11th to 20th	Night	23% 12% 32% 25% 7% 1	900
	21st to end	Night	25% 12% 28% 28% 7% 1	990

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