Site d'observation de St-Félix d'Otis
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Site d'observation de St-Félix d'Otis clear sky chart from 2005-11-06 to 2026-04-02.

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% 13% 4 10% 6% 6% 5% 4 5% 6% 24%	131171
	Night	16% 15% 5% 12% 7% 6% 5% 4 5% 5% 21%	130754
Transparency	Day	59% 7% 13% 15% 6%	134591
	Night	63% 7% 11% 14% 5%	135422
Seeing	Day	27% 18% 28% 18% 7% 1	17219
	Night	26% 16% 27% 23% 7% 1	25619

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	11% 20% 8% 19% 8% 6% 7% 4 4 4 9%	4338
	11th to 20th	Day	7% 15% 7% 21% 15% 6% 9% 4 4 4 8%	4650
	21st to end	Day	3 8% 6% 17% 11% 11% 10% 6% 7% 4 16%	5124
February	1st to 10th	Day	6% 11% 7% 13% 9% 12% 8% 6% 5% 6% 17%	1680
	11th to 20th	Day	10% 16% 6% 16% 8% 8% 6% 5% 5% 5% 14%	1952
	21st to end	Day	7% 15% 5% 11% 9% 7% 7% 6% 6% 6% 20%	1730
March	1st to 10th	Day	13% 16% 6% 11% 6% 5% 5% 4 5% 5% 24%	4576
	11th to 20th	Day	14% 19% 6% 12% 7% 5% 5% 4 4 6% 18%	4902
	21st to end	Day	13% 18% 5% 12% 6% 6% 4 3 4 5% 24%	5864
April	1st to 10th	Day	18% 19% 5% 9% 6% 4 3 3 4 6% 23%	2412
	11th to 20th	Day	18% 15% 4 8% 5% 4 4 3 4 5% 30%	2522
	21st to end	Day	19% 14% 4 8% 4 4 4 4 6% 5% 28%	2600
May	1st to 10th	Day	23% 13% 3 7% 4 4 3 3 4 5% 29%	6085
	11th to 20th	Day	22% 10% 3 7% 5% 5% 4 4 5% 6% 29%	6318
	21st to end	Day	19% 9% 2 7% 5% 5% 5% 4 6% 8% 29%	7447
June	1st to 10th	Day	22% 9% 3 7% 6% 4 4 4 6% 8% 28%	3000
	11th to 20th	Day	19% 8% 3 8% 5% 5% 5% 4 6% 7% 30%	3000
	21st to end	Day	22% 9% 3 8% 6% 5% 5% 4 5% 6% 28%	3000
July	1st to 10th	Day	21% 10% 3 8% 5% 5% 6% 4 6% 8% 25%	6820
	11th to 20th	Day	16% 8% 3 9% 6% 6% 6% 5% 7% 8% 27%	6464
	21st to end	Day	13% 7% 2 7% 5% 5% 5% 5% 7% 8% 36%	6926
August	1st to 10th	Day	16% 8% 3 7% 5% 5% 6% 5% 7% 9% 29%	4563
	11th to 20th	Day	20% 7% 3 7% 5% 5% 6% 5% 6% 8% 26%	4175
	21st to end	Day	20% 9% 3 8% 4 4 4 3 5% 6% 32%	4591
September	1st to 10th	Day	20% 8% 3 7% 4 6% 5% 4 5% 8% 31%	2400
	11th to 20th	Day	20% 7% 3 7% 3 4 4 3 5% 7% 37%	2205
	21st to end	Day	22% 10% 2 7% 4 5% 4 3 5% 6% 32%	2200
October	1st to 10th	Day	19% 13% 3 8% 6% 5% 4 4 5% 6% 28%	2185
	11th to 20th	Day	25% 17% 4 9% 5% 5% 4 3 5% 5% 18%	1811
	21st to end	Day	24% 22% 5% 9% 4 4 3 2 3 4 20%	1980
November	1st to 10th	Day	20% 21% 6% 11% 5% 4 3 3 4 5% 18%	1851
	11th to 20th	Day	18% 22% 6% 13% 7% 3 4 3 4 5% 16%	1739
	21st to end	Day	17% 23% 8% 15% 7% 6% 3 3 4 4 11%	1470
December	1st to 10th	Day	13% 20% 7% 16% 12% 7% 5% 3 4 5% 8%	2350
	11th to 20th	Day	14% 16% 7% 16% 9% 9% 5% 3 5% 4 13%	2688
	21st to end	Day	15% 17% 5% 12% 9% 7% 8% 4 5% 5% 14%	3553
January	1st to 10th	Night	10% 21% 9% 15% 9% 9% 9% 5% 4 3 6%	8554
	11th to 20th	Night	7% 18% 9% 24% 11% 6% 6% 3 4 3 9%	8235
	21st to end	Night	3 9% 5% 14% 10% 10% 10% 8% 9% 6% 16%	9057
February	1st to 10th	Night	7% 12% 6% 13% 10% 10% 8% 5% 5% 5% 18%	2940
	11th to 20th	Night	11% 17% 7% 15% 8% 7% 6% 5% 4 4 16%	2551
	21st to end	Night	9% 18% 6% 13% 8% 6% 5% 3 5% 4 23%	2076
March	1st to 10th	Night	16% 18% 6% 12% 6% 5% 6% 5% 4 5% 17%	5484
	11th to 20th	Night	14% 19% 5% 12% 7% 6% 5% 4 4 6% 17%	5277
	21st to end	Night	15% 18% 5% 11% 4 3 3 3 5% 5% 28%	5307
April	1st to 10th	Night	21% 18% 4 10% 5% 4 4 3 4 4 24%	2011
	11th to 20th	Night	21% 13% 4 7% 4 4 3 3 4 6% 30%	1827
	21st to end	Night	22% 13% 3 6% 4 4 4 3 5% 5% 32%	1800
May	1st to 10th	Night	21% 12% 3 6% 4 4 4 3 5% 6% 31%	3898
	11th to 20th	Night	24% 10% 3 7% 4 4 4 3 5% 6% 31%	3575
	21st to end	Night	21% 8% 3 7% 4 5% 4 3 6% 8% 31%	3450
June	1st to 10th	Night	19% 9% 3 8% 6% 4 5% 4 6% 6% 28%	1400
	11th to 20th	Night	19% 8% 3 6% 5% 5% 6% 4 4 7% 34%	1400
	21st to end	Night	21% 8% 3 8% 7% 4 6% 3 6% 8% 27%	1400
July	1st to 10th	Night	19% 9% 3 9% 5% 5% 5% 4 6% 6% 27%	3160
	11th to 20th	Night	17% 9% 3 8% 5% 6% 5% 6% 8% 8% 26%	3484
	21st to end	Night	18% 7% 3 7% 5% 4 5% 4 5% 7% 35%	3926
August	1st to 10th	Night	16% 7% 3 8% 6% 5% 5% 5% 7% 9% 30%	2586
	11th to 20th	Night	19% 9% 3 8% 6% 5% 6% 4 6% 7% 26%	2840
	21st to end	Night	18% 9% 3 7% 4 5% 5% 3 5% 7% 33%	3304
September	1st to 10th	Night	21% 8% 3 7% 5% 4 4 4 6% 6% 34%	2000
	11th to 20th	Night	21% 8% 3 7% 5% 5% 5% 4 5% 5% 34%	2194
	21st to end	Night	22% 9% 3 6% 4 4 4 3 5% 6% 36%	2200
October	1st to 10th	Night	20% 11% 2 7% 5% 4 3 3 6% 7% 32%	2214
	11th to 20th	Night	28% 16% 4 7% 5% 4 4 3 4 5% 22%	2585
	21st to end	Night	26% 19% 5% 7% 5% 4 4 3 4 5% 19%	2860
November	1st to 10th	Night	25% 20% 6% 9% 4 3 4 2 4 5% 19%	2667
	11th to 20th	Night	18% 22% 7% 11% 6% 4 3 3 4 4 17%	2874
	21st to end	Night	17% 23% 7% 15% 9% 4 3 3 3 3 11%	3150
December	1st to 10th	Night	12% 17% 10% 21% 12% 6% 4 3 3 3 8%	5060
	11th to 20th	Night	17% 17% 6% 17% 9% 7% 5% 3 3 4 12%	5741
	21st to end	Night	14% 19% 6% 14% 8% 6% 5% 4 3 3 19%	7667

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	78% 6% 9% 7% 1	4339
	11th to 20th	Day	79% 5% 7% 6% 3	4680
	21st to end	Day	64% 6% 9% 15% 7%	5124
February	1st to 10th	Day	63% 7% 12% 11% 6% 1	1680
	11th to 20th	Day	69% 6% 12% 8% 5%	1960
	21st to end	Day	61% 6% 11% 15% 6% 1	1730
March	1st to 10th	Day	60% 7% 12% 12% 9% 2	4579
	11th to 20th	Day	66% 7% 11% 10% 6%	4902
	21st to end	Day	62% 5% 9% 14% 8% 2	5864
April	1st to 10th	Day	64% 5% 9% 14% 6% 2	2412
	11th to 20th	Day	56% 5% 12% 18% 8% 1	2522
	21st to end	Day	56% 7% 11% 15% 10% 1	2600
May	1st to 10th	Day	56% 7% 12% 16% 10% 1	6096
	11th to 20th	Day	53% 8% 12% 19% 7% 1	6322
	21st to end	Day	50% 8% 13% 18% 10%	7447
June	1st to 10th	Day	54% 8% 10% 18% 10% 1	3000
	11th to 20th	Day	51% 7% 14% 18% 10% 1	3000
	21st to end	Day	56% 8% 11% 16% 8% 1	3000
July	1st to 10th	Day	55% 7% 12% 23% 3	6745
	11th to 20th	Day	51% 9% 19% 17% 3	6386
	21st to end	Day	44% 8% 17% 25% 6%	6728
August	1st to 10th	Day	48% 10% 19% 20% 3	4549
	11th to 20th	Day	53% 9% 20% 14% 3	4214
	21st to end	Day	52% 7% 16% 17% 8%	4591
September	1st to 10th	Day	50% 8% 16% 20% 6%	2400
	11th to 20th	Day	46% 7% 18% 22% 6%	2205
	21st to end	Day	52% 9% 13% 19% 6%	2200
October	1st to 10th	Day	60% 7% 11% 18% 4	3562
	11th to 20th	Day	67% 7% 11% 14% 1	2923
	21st to end	Day	64% 5% 14% 14% 2	3180
November	1st to 10th	Day	69% 6% 12% 10% 2	1851
	11th to 20th	Day	71% 8% 9% 9% 3	1739
	21st to end	Day	77% 9% 10% 5% 1	1470
December	1st to 10th	Day	77% 6% 10% 6% 1	2350
	11th to 20th	Day	73% 5% 12% 8% 3	2688
	21st to end	Day	69% 7% 9% 11% 4	3553
January	1st to 10th	Night	80% 6% 8% 5% 1	8554
	11th to 20th	Night	78% 5% 8% 7% 2	8280
	21st to end	Night	59% 7% 11% 16% 7%	9057
February	1st to 10th	Night	62% 7% 12% 13% 6%	2940
	11th to 20th	Night	68% 6% 11% 10% 4	2554
	21st to end	Night	63% 5% 9% 17% 7%	2076
March	1st to 10th	Night	68% 6% 8% 12% 6%	5494
	11th to 20th	Night	67% 7% 11% 9% 5%	5278
	21st to end	Night	58% 6% 7% 18% 10% 1	5307
April	1st to 10th	Night	65% 4 8% 13% 8% 2	2011
	11th to 20th	Night	55% 6% 8% 19% 12% 1	1827
	21st to end	Night	53% 5% 11% 20% 9% 2	1800
May	1st to 10th	Night	52% 8% 11% 17% 12% 1	3904
	11th to 20th	Night	52% 7% 11% 21% 8% 1	3576
	21st to end	Night	49% 6% 13% 18% 12% 1	3451
June	1st to 10th	Night	54% 8% 11% 19% 7% 2	1400
	11th to 20th	Night	49% 7% 12% 18% 12% 3	1400
	21st to end	Night	53% 9% 13% 18% 7%	1400
July	1st to 10th	Night	55% 7% 12% 21% 5%	3125
	11th to 20th	Night	51% 10% 18% 17% 2	3439
	21st to end	Night	47% 8% 18% 21% 7%	3809
August	1st to 10th	Night	48% 10% 20% 18% 5%	2576
	11th to 20th	Night	54% 11% 18% 13% 3	2867
	21st to end	Night	49% 8% 12% 25% 5% 1	3304
September	1st to 10th	Night	48% 8% 15% 21% 8%	2000
	11th to 20th	Night	51% 8% 16% 19% 6%	2194
	21st to end	Night	50% 7% 12% 23% 7% 1	2200
October	1st to 10th	Night	53% 7% 11% 23% 5% 1	3617
	11th to 20th	Night	64% 5% 11% 17% 4	4212
	21st to end	Night	65% 5% 13% 13% 2	4610
November	1st to 10th	Night	68% 7% 10% 11% 3	2667
	11th to 20th	Night	70% 7% 10% 10% 3	2874
	21st to end	Night	78% 7% 8% 5% 2	3150
December	1st to 10th	Night	80% 6% 7% 6% 1	5060
	11th to 20th	Night	76% 6% 6% 10% 3	5742
	21st to end	Night	68% 6% 8% 13% 4	7667

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	24% 26% 31% 16% 2	220
	11th to 20th	Day	21% 27% 30% 17% 4 1	220
	21st to end	Day	17% 26% 34% 18% 5%	242
February	1st to 10th	Day	17% 25% 40% 13% 4 1	220
	11th to 20th	Day	24% 27% 32% 14% 3	479
	21st to end	Day	24% 23% 30% 17% 4	446
March	1st to 10th	Day	28% 22% 32% 14% 4	540
	11th to 20th	Day	32% 23% 26% 13% 5% 1	540
	21st to end	Day	33% 20% 26% 14% 6% 1	594
April	1st to 10th	Day	35% 22% 28% 12% 3 1	504
	11th to 20th	Day	30% 18% 32% 14% 5% 1	492
	21st to end	Day	26% 22% 30% 17% 3 1	500
May	1st to 10th	Day	31% 20% 27% 16% 5% 1	503
	11th to 20th	Day	22% 16% 34% 19% 8% 2	527
	21st to end	Day	29% 15% 26% 21% 9% 1	785
June	1st to 10th	Day	27% 14% 28% 24% 6% 1	730
	11th to 20th	Day	24% 15% 26% 23% 10% 1	730
	21st to end	Day	26% 15% 27% 22% 8% 1	730
July	1st to 10th	Day	24% 14% 28% 26% 8% 1	720
	11th to 20th	Day	23% 12% 30% 25% 9% 1	573
	21st to end	Day	20% 14% 32% 22% 10% 1	576
August	1st to 10th	Day	22% 12% 27% 24% 11% 3	526
	11th to 20th	Day	21% 10% 29% 26% 11% 3	519
	21st to end	Day	26% 12% 26% 21% 11% 3	583
September	1st to 10th	Day	25% 18% 25% 18% 10% 5%	530
	11th to 20th	Day	24% 16% 29% 18% 11% 3	530
	21st to end	Day	27% 16% 24% 19% 11% 2	530
October	1st to 10th	Day	25% 18% 28% 18% 8% 3	522
	11th to 20th	Day	36% 19% 23% 14% 8% 1	420
	21st to end	Day	39% 18% 24% 15% 3	462
November	1st to 10th	Day	39% 20% 22% 15% 3	425
	11th to 20th	Day	30% 23% 26% 14% 6% 1	399
	21st to end	Day	41% 22% 25% 9% 2	220
December	1st to 10th	Day	23% 25% 35% 13% 3 1	220
	11th to 20th	Day	32% 25% 30% 9% 4	220
	21st to end	Day	30% 23% 29% 11% 6% 1	242
January	1st to 10th	Night	25% 21% 31% 18% 4	900
	11th to 20th	Night	21% 22% 30% 20% 6% 1	840
	21st to end	Night	16% 18% 37% 23% 6% 1	924
February	1st to 10th	Night	15% 23% 33% 22% 6% 1	840
	11th to 20th	Night	23% 23% 31% 17% 5%	823
	21st to end	Night	22% 18% 34% 20% 5% 1	692
March	1st to 10th	Night	24% 17% 34% 22% 3	840
	11th to 20th	Night	26% 21% 28% 16% 7% 1	840
	21st to end	Night	25% 19% 28% 22% 5% 1	924
April	1st to 10th	Night	33% 16% 27% 19% 4	805
	11th to 20th	Night	28% 14% 28% 23% 5%	643
	21st to end	Night	30% 14% 28% 23% 5%	600
May	1st to 10th	Night	29% 9% 31% 26% 4	535
	11th to 20th	Night	22% 9% 27% 32% 10%	394
	21st to end	Night	28% 12% 27% 26% 8%	433
June	1st to 10th	Night	21% 9% 31% 32% 8% 1	400
	11th to 20th	Night	21% 8% 24% 34% 13% 1	400
	21st to end	Night	21% 10% 27% 34% 10% 1	400
July	1st to 10th	Night	23% 8% 27% 33% 9% 1	390
	11th to 20th	Night	14% 10% 24% 42% 10% 1	388
	21st to end	Night	24% 8% 22% 35% 11% 1	438
August	1st to 10th	Night	15% 8% 20% 40% 17% 1	398
	11th to 20th	Night	22% 9% 21% 30% 16% 1	572
	21st to end	Night	23% 10% 24% 29% 12% 1	702
September	1st to 10th	Night	23% 13% 24% 28% 11% 1	800
	11th to 20th	Night	26% 9% 25% 25% 13% 3	800
	21st to end	Night	25% 13% 24% 26% 11% 1	800
October	1st to 10th	Night	27% 13% 26% 26% 8% 1	800
	11th to 20th	Night	37% 14% 23% 18% 8% 1	800
	21st to end	Night	37% 17% 22% 18% 5%	880
November	1st to 10th	Night	35% 18% 23% 18% 5% 1	820
	11th to 20th	Night	29% 23% 23% 17% 6% 1	903
	21st to end	Night	31% 21% 28% 15% 5% 1	950
December	1st to 10th	Night	28% 20% 29% 18% 5% 1	950
	11th to 20th	Night	30% 20% 28% 16% 6%	950
	21st to end	Night	28% 19% 28% 18% 6% 1	1045

Page generated at 2026-03-30 02:18:42. Version ac07

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