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 2024-03-28.

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	16% 10% 4 8% 7% 4 6% 5% 6% 7% 27%	78316
	Night	15% 12% 5% 9% 8% 4 5% 5% 5% 6% 26%	81665
Transparency	Day	56% 7% 12% 17% 8% 1	78020
	Night	58% 7% 12% 16% 6% 1	81497
Seeing	Day	20% 11% 31% 25% 11% 3	14248
	Night	22% 10% 31% 27% 9% 1	22905

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% 15% 8% 13% 9% 5% 6% 6% 4 5% 16%	2500
	11th to 20th	Day	11% 13% 7% 13% 11% 6% 7% 7% 6% 5% 15%	2520
	21st to end	Day	8% 12% 5% 13% 10% 5% 6% 5% 5% 6% 26%	2772
February	1st to 10th	Day	6% 12% 6% 10% 12% 7% 9% 7% 6% 6% 21%	1520
	11th to 20th	Day	11% 12% 6% 11% 12% 5% 8% 4 4 6% 20%	1747
	21st to end	Day	10% 13% 5% 10% 7% 5% 6% 5% 8% 5% 25%	1570
March	1st to 10th	Day	13% 15% 5% 9% 7% 3 5% 5% 6% 5% 27%	1897
	11th to 20th	Day	14% 12% 5% 8% 8% 4 7% 5% 5% 6% 26%	1946
	21st to end	Day	14% 12% 4 10% 6% 3 5% 5% 5% 7% 29%	2457
April	1st to 10th	Day	17% 15% 5% 11% 9% 3 5% 3 4 4 23%	2160
	11th to 20th	Day	17% 9% 4 7% 6% 3 4 4 5% 6% 34%	2204
	21st to end	Day	21% 8% 4 7% 6% 3 4 5% 5% 5% 30%	2340
May	1st to 10th	Day	19% 9% 4 5% 5% 3 5% 5% 5% 6% 33%	2520
	11th to 20th	Day	18% 8% 3 6% 5% 3 5% 5% 5% 7% 36%	2478
	21st to end	Day	16% 8% 4 8% 6% 3 6% 5% 5% 6% 34%	2805
June	1st to 10th	Day	18% 8% 3 7% 6% 4 6% 6% 5% 7% 30%	2700
	11th to 20th	Day	16% 7% 3 7% 6% 4 5% 5% 6% 9% 33%	2700
	21st to end	Day	21% 7% 3 6% 7% 3 6% 6% 6% 6% 28%	2700
July	1st to 10th	Day	14% 7% 3 7% 6% 5% 6% 7% 7% 9% 28%	2628
	11th to 20th	Day	13% 6% 4 7% 7% 4 6% 7% 7% 9% 29%	2520
	21st to end	Day	13% 6% 3 7% 8% 4 7% 6% 7% 8% 29%	2744
August	1st to 10th	Day	15% 8% 4 8% 7% 5% 6% 7% 8% 8% 25%	2506
	11th to 20th	Day	15% 7% 3 6% 6% 4 6% 6% 7% 8% 31%	2388
	21st to end	Day	14% 7% 4 7% 7% 4 7% 5% 6% 9% 30%	2445
September	1st to 10th	Day	16% 7% 3 7% 7% 4 6% 5% 6% 8% 33%	2160
	11th to 20th	Day	16% 7% 3 7% 7% 4 5% 5% 6% 8% 34%	2051
	21st to end	Day	21% 8% 3 7% 6% 4 5% 4 4 7% 32%	1980
October	1st to 10th	Day	17% 9% 4 7% 7% 4 5% 4 6% 6% 30%	1899
	11th to 20th	Day	24% 13% 5% 9% 8% 4 5% 4 5% 6% 18%	1670
	21st to end	Day	25% 13% 3 8% 6% 3 4 5% 5% 5% 23%	1782
November	1st to 10th	Day	18% 12% 5% 11% 8% 5% 5% 4 4 5% 24%	1671
	11th to 20th	Day	17% 14% 6% 10% 9% 3 5% 5% 5% 6% 21%	1577
	21st to end	Day	19% 16% 5% 10% 8% 4 5% 5% 6% 6% 16%	1330
December	1st to 10th	Day	16% 18% 5% 9% 11% 3 5% 4 5% 5% 18%	1330
	11th to 20th	Day	20% 16% 6% 8% 6% 3 3 3 4 5% 26%	1668
	21st to end	Day	16% 15% 7% 10% 11% 5% 7% 6% 5% 4 16%	2431
January	1st to 10th	Night	13% 18% 6% 12% 13% 5% 5% 4 4 4 15%	4429
	11th to 20th	Night	11% 13% 6% 13% 14% 6% 5% 5% 4 5% 19%	4440
	21st to end	Night	7% 12% 7% 14% 11% 5% 6% 6% 5% 6% 21%	4884
February	1st to 10th	Night	9% 11% 6% 10% 8% 6% 6% 7% 5% 7% 24%	2660
	11th to 20th	Night	8% 15% 6% 13% 10% 5% 6% 4 4 5% 21%	2314
	21st to end	Night	10% 14% 6% 10% 7% 4 6% 6% 5% 7% 27%	1884
March	1st to 10th	Night	14% 13% 6% 9% 7% 4 7% 6% 5% 6% 24%	2270
	11th to 20th	Night	13% 13% 5% 10% 8% 4 6% 5% 5% 6% 25%	2232
	21st to end	Night	15% 14% 5% 8% 7% 3 5% 4 4 6% 29%	2051
April	1st to 10th	Night	19% 14% 6% 8% 7% 4 5% 4 5% 5% 23%	1800
	11th to 20th	Night	18% 9% 3 6% 6% 3 5% 5% 6% 6% 33%	1705
	21st to end	Night	18% 10% 3 7% 6% 4 3 4 6% 5% 33%	1620
May	1st to 10th	Night	20% 10% 4 7% 6% 3 5% 4 3 5% 33%	1456
	11th to 20th	Night	19% 9% 3 5% 5% 3 4 5% 4 6% 35%	1415
	21st to end	Night	19% 8% 3 6% 5% 4 4 4 5% 7% 35%	1468
June	1st to 10th	Night	19% 8% 2 7% 6% 3 5% 7% 5% 9% 29%	1260
	11th to 20th	Night	15% 8% 4 5% 4 4 5% 5% 6% 7% 37%	1260
	21st to end	Night	16% 6% 3 7% 7% 3 6% 5% 7% 8% 31%	1260
July	1st to 10th	Night	16% 7% 3 6% 6% 3 7% 6% 7% 8% 31%	1327
	11th to 20th	Night	10% 6% 3 7% 7% 3 6% 6% 7% 8% 37%	1440
	21st to end	Night	12% 7% 3 7% 8% 4 6% 6% 6% 7% 33%	1574
August	1st to 10th	Night	13% 5% 3 7% 6% 5% 5% 6% 8% 9% 32%	1432
	11th to 20th	Night	16% 8% 3 6% 5% 3 3 5% 7% 8% 34%	1495
	21st to end	Night	15% 6% 3 5% 6% 4 5% 7% 7% 8% 34%	1908
September	1st to 10th	Night	14% 7% 3 6% 5% 3 4 5% 5% 7% 40%	1800
	11th to 20th	Night	19% 7% 3 6% 5% 3 4 5% 5% 5% 38%	1908
	21st to end	Night	18% 6% 3 6% 6% 3 5% 6% 5% 6% 36%	1980
October	1st to 10th	Night	17% 9% 3 5% 5% 3 5% 4 6% 8% 35%	2060
	11th to 20th	Night	25% 12% 4 7% 6% 4 5% 5% 5% 5% 23%	2290
	21st to end	Night	25% 12% 3 7% 6% 4 6% 5% 5% 6% 21%	2574
November	1st to 10th	Night	20% 12% 4 8% 6% 4 4 5% 5% 7% 24%	2407
	11th to 20th	Night	19% 12% 5% 9% 8% 4 5% 5% 5% 6% 22%	2598
	21st to end	Night	18% 16% 5% 11% 8% 4 6% 5% 5% 5% 16%	2847
December	1st to 10th	Night	16% 17% 7% 11% 9% 4 5% 4 4 4 20%	2850
	11th to 20th	Night	19% 15% 6% 8% 7% 3 5% 5% 5% 6% 22%	3531
	21st to end	Night	14% 18% 7% 12% 9% 4 5% 4 4 4 20%	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	69% 7% 13% 9% 3	2501
	11th to 20th	Day	68% 7% 12% 10% 4	2520
	21st to end	Day	57% 6% 11% 17% 9%	2772
February	1st to 10th	Day	63% 5% 9% 14% 8% 1	1520
	11th to 20th	Day	65% 6% 9% 13% 7%	1756
	21st to end	Day	57% 7% 9% 16% 8% 2	1570
March	1st to 10th	Day	58% 5% 9% 16% 11% 1	1900
	11th to 20th	Day	58% 5% 9% 17% 9% 1	1946
	21st to end	Day	54% 5% 10% 18% 10% 2	2457
April	1st to 10th	Day	65% 3 10% 12% 8% 2	2160
	11th to 20th	Day	50% 5% 9% 22% 12% 2	2204
	21st to end	Day	55% 5% 8% 17% 13% 1	2340
May	1st to 10th	Day	50% 5% 11% 18% 14% 2	2520
	11th to 20th	Day	47% 6% 9% 22% 14% 1	2482
	21st to end	Day	51% 7% 7% 19% 15% 1	2805
June	1st to 10th	Day	53% 7% 9% 19% 11% 1	2700
	11th to 20th	Day	47% 7% 11% 21% 12% 2	2700
	21st to end	Day	54% 8% 11% 18% 9%	2700
July	1st to 10th	Day	48% 9% 16% 22% 5%	2557
	11th to 20th	Day	47% 10% 16% 20% 6%	2445
	21st to end	Day	51% 10% 15% 19% 5%	2591
August	1st to 10th	Day	53% 10% 17% 18% 1	2492
	11th to 20th	Day	48% 10% 17% 19% 6%	2388
	21st to end	Day	50% 8% 15% 22% 5%	2445
September	1st to 10th	Day	47% 8% 16% 20% 8%	2160
	11th to 20th	Day	48% 7% 17% 21% 6%	2051
	21st to end	Day	53% 7% 15% 19% 6%	1980
October	1st to 10th	Day	53% 7% 16% 17% 6% 1	1899
	11th to 20th	Day	68% 6% 12% 11% 2	1670
	21st to end	Day	63% 7% 13% 13% 4	1782
November	1st to 10th	Day	63% 6% 12% 13% 5% 1	1671
	11th to 20th	Day	65% 5% 15% 12% 4	1577
	21st to end	Day	68% 5% 15% 9% 2	1330
December	1st to 10th	Day	68% 6% 12% 10% 3	1330
	11th to 20th	Day	62% 4 11% 19% 5%	1668
	21st to end	Day	69% 7% 10% 8% 6%	2431
January	1st to 10th	Night	73% 4 11% 8% 3	4429
	11th to 20th	Night	68% 5% 11% 12% 4	4440
	21st to end	Night	62% 7% 11% 15% 5%	4884
February	1st to 10th	Night	59% 5% 11% 17% 8%	2660
	11th to 20th	Night	66% 5% 10% 13% 6%	2316
	21st to end	Night	57% 6% 11% 18% 8%	1884
March	1st to 10th	Night	61% 5% 9% 17% 8% 1	2280
	11th to 20th	Night	60% 6% 8% 15% 10% 1	2233
	21st to end	Night	57% 4 9% 19% 10% 1	2051
April	1st to 10th	Night	64% 4 10% 14% 6% 2	1800
	11th to 20th	Night	50% 4 11% 23% 11% 1	1705
	21st to end	Night	53% 4 9% 20% 12% 2	1620
May	1st to 10th	Night	54% 5% 10% 14% 15% 2	1456
	11th to 20th	Night	48% 7% 10% 19% 14% 2	1416
	21st to end	Night	51% 5% 9% 20% 14% 1	1469
June	1st to 10th	Night	50% 9% 12% 21% 9% 1	1260
	11th to 20th	Night	45% 8% 11% 21% 13% 3	1260
	21st to end	Night	48% 10% 12% 18% 11%	1260
July	1st to 10th	Night	46% 10% 13% 23% 7% 1	1289
	11th to 20th	Night	42% 9% 16% 26% 7% 1	1392
	21st to end	Night	48% 12% 12% 22% 6%	1486
August	1st to 10th	Night	45% 12% 20% 22% 2	1422
	11th to 20th	Night	45% 11% 18% 20% 6%	1495
	21st to end	Night	44% 11% 18% 23% 4	1908
September	1st to 10th	Night	43% 8% 17% 24% 9% 1	1800
	11th to 20th	Night	47% 7% 18% 21% 6%	1908
	21st to end	Night	48% 8% 13% 24% 7%	1980
October	1st to 10th	Night	48% 7% 16% 21% 8% 1	2060
	11th to 20th	Night	63% 7% 13% 14% 4	2290
	21st to end	Night	62% 7% 12% 13% 6%	2574
November	1st to 10th	Night	60% 7% 14% 14% 5%	2407
	11th to 20th	Night	64% 6% 14% 13% 4	2598
	21st to end	Night	68% 8% 13% 9% 2	2847
December	1st to 10th	Night	69% 6% 13% 10% 2	2850
	11th to 20th	Night	63% 7% 13% 13% 5%	3532
	21st to end	Night	68% 5% 12% 10% 4 1	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	22% 12% 28% 29% 8% 1	180
	11th to 20th	Day	16% 11% 29% 31% 13%	180
	21st to end	Day	15% 5% 29% 35% 14% 3	198
February	1st to 10th	Day	11% 12% 42% 24% 9% 1	180
	11th to 20th	Day	17% 13% 37% 28% 4	356
	21st to end	Day	19% 12% 41% 21% 6% 1	382
March	1st to 10th	Day	21% 16% 30% 22% 9% 1	460
	11th to 20th	Day	20% 13% 34% 22% 9% 1	460
	21st to end	Day	22% 14% 31% 24% 7% 1	490
April	1st to 10th	Day	20% 16% 31% 23% 7% 2	420
	11th to 20th	Day	23% 13% 26% 26% 10% 2	412
	21st to end	Day	23% 13% 31% 23% 9%	420
May	1st to 10th	Day	22% 14% 32% 22% 7% 2	423
	11th to 20th	Day	19% 12% 31% 24% 13% 2	447
	21st to end	Day	19% 16% 31% 25% 8% 1	565
June	1st to 10th	Day	22% 9% 32% 24% 10% 3	630
	11th to 20th	Day	18% 10% 31% 27% 12% 2	630
	21st to end	Day	23% 7% 27% 28% 12% 3	630
July	1st to 10th	Day	14% 8% 32% 31% 12% 3	552
	11th to 20th	Day	17% 7% 29% 29% 14% 5%	444
	21st to end	Day	15% 6% 27% 29% 20% 3	488
August	1st to 10th	Day	15% 8% 25% 30% 17% 5%	446
	11th to 20th	Day	17% 5% 23% 32% 15% 8%	439
	21st to end	Day	17% 11% 32% 20% 14% 7%	495
September	1st to 10th	Day	19% 10% 32% 20% 16% 4	450
	11th to 20th	Day	17% 12% 28% 26% 14% 2	450
	21st to end	Day	21% 12% 29% 20% 14% 5%	450
October	1st to 10th	Day	16% 15% 32% 19% 13% 4	450
	11th to 20th	Day	29% 12% 32% 17% 7% 3	385
	21st to end	Day	30% 12% 30% 20% 6% 1	396
November	1st to 10th	Day	28% 17% 33% 17% 4 1	365
	11th to 20th	Day	25% 15% 30% 22% 5% 1	237
	21st to end	Day	31% 11% 32% 19% 6% 2	180
December	1st to 10th	Day	20% 11% 22% 28% 17% 2	180
	11th to 20th	Day	26% 13% 29% 24% 5% 3	180
	21st to end	Day	25% 14% 28% 23% 8% 2	198
January	1st to 10th	Night	24% 10% 33% 25% 7% 1	760
	11th to 20th	Night	22% 11% 29% 30% 9%	760
	21st to end	Night	14% 9% 28% 37% 12% 1	836
February	1st to 10th	Night	14% 8% 36% 30% 10% 1	760
	11th to 20th	Night	18% 8% 36% 29% 7% 1	743
	21st to end	Night	18% 12% 33% 29% 7% 1	628
March	1st to 10th	Night	19% 11% 32% 30% 7%	760
	11th to 20th	Night	20% 15% 29% 26% 9% 1	760
	21st to end	Night	21% 13% 32% 28% 6%	821
April	1st to 10th	Night	27% 10% 27% 29% 6% 1	720
	11th to 20th	Night	23% 12% 29% 28% 7%	641
	21st to end	Night	24% 12% 33% 25% 6%	540
May	1st to 10th	Night	26% 8% 32% 28% 6%	376
	11th to 20th	Night	22% 9% 33% 25% 10% 1	354
	21st to end	Night	22% 9% 39% 22% 7% 1	389
June	1st to 10th	Night	22% 8% 31% 31% 8% 1	360
	11th to 20th	Night	17% 6% 36% 29% 11% 1	360
	21st to end	Night	18% 7% 26% 38% 11% 2	360
July	1st to 10th	Night	19% 7% 33% 28% 14%	350
	11th to 20th	Night	11% 5% 31% 38% 14%	348
	21st to end	Night	13% 6% 27% 41% 11% 1	394
August	1st to 10th	Night	14% 4 27% 38% 16% 2	358
	11th to 20th	Night	19% 5% 25% 33% 16% 1	431
	21st to end	Night	17% 10% 28% 27% 15% 3	720
September	1st to 10th	Night	18% 8% 29% 32% 12% 1	720
	11th to 20th	Night	21% 10% 31% 25% 11% 2	720
	21st to end	Night	21% 8% 36% 24% 9% 1	720
October	1st to 10th	Night	21% 10% 31% 27% 10% 1	720
	11th to 20th	Night	32% 10% 28% 21% 9% 1	720
	21st to end	Night	33% 11% 27% 21% 8%	792
November	1st to 10th	Night	28% 16% 29% 20% 6% 1	740
	11th to 20th	Night	26% 16% 30% 20% 7%	760
	21st to end	Night	28% 13% 31% 23% 5% 1	849
December	1st to 10th	Night	26% 12% 28% 25% 9% 1	850
	11th to 20th	Night	22% 12% 32% 24% 8% 1	850
	21st to end	Night	25% 12% 27% 27% 7% 1	935

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