Ferme Véronneau
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ferme Véronneau clear sky chart from 2005-11-06 to 2025-02-21.

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% 5% 5% 4 5% 6% 26%	108524
	Night	17% 15% 5% 12% 6% 5% 4 3 4 5% 24%	110060
Transparency	Day	58% 6% 11% 17% 7% 1	112040
	Night	62% 6% 10% 14% 7% 1	114708
Seeing	Day	28% 19% 28% 17% 7% 2	14981
	Night	27% 17% 27% 21% 8% 1	24001

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% 21% 10% 20% 9% 8% 4 2 2 3 10%	3597
	11th to 20th	Day	7% 17% 8% 26% 13% 4 5% 2 3 4 10%	3570
	21st to end	Day	9% 18% 9% 14% 7% 10% 6% 3 3 4 16%	3960
February	1st to 10th	Day	14% 17% 7% 16% 9% 7% 5% 3 3 3 15%	1682
	11th to 20th	Day	11% 18% 10% 17% 9% 5% 5% 3 4 5% 14%	1948
	21st to end	Day	10% 20% 7% 11% 8% 6% 6% 4 4 5% 20%	1570
March	1st to 10th	Day	20% 17% 4 12% 6% 5% 4 2 4 4 22%	3116
	11th to 20th	Day	13% 24% 7% 13% 5% 4 3 2 3 4 22%	3283
	21st to end	Day	17% 16% 6% 11% 4 4 3 3 3 5% 29%	4099
April	1st to 10th	Day	21% 18% 4 10% 4 4 4 3 4 4 26%	2280
	11th to 20th	Day	19% 14% 3 7% 5% 4 3 3 3 5% 32%	2292
	21st to end	Day	23% 14% 4 7% 5% 4 4 3 5% 5% 27%	2470
May	1st to 10th	Day	25% 11% 3 7% 5% 5% 5% 3 5% 5% 26%	4153
	11th to 20th	Day	19% 9% 3 8% 6% 6% 5% 4 6% 7% 26%	4398
	21st to end	Day	15% 7% 3 7% 5% 6% 5% 5% 7% 9% 31%	4837
June	1st to 10th	Day	27% 10% 2 6% 4 5% 5% 4 5% 7% 25%	2660
	11th to 20th	Day	17% 7% 2 7% 5% 4 5% 5% 6% 8% 34%	2660
	21st to end	Day	22% 9% 3 7% 5% 5% 5% 4 6% 7% 27%	2660
July	1st to 10th	Day	15% 7% 2 7% 5% 5% 5% 5% 8% 10% 31%	4440
	11th to 20th	Day	13% 7% 3 7% 5% 6% 6% 5% 8% 10% 30%	4440
	21st to end	Day	16% 7% 3 7% 5% 4 5% 4 7% 7% 37%	4814
August	1st to 10th	Day	18% 9% 3 8% 6% 5% 5% 4 6% 8% 27%	4366
	11th to 20th	Day	18% 7% 3 8% 5% 6% 6% 5% 8% 9% 26%	4045
	21st to end	Day	19% 7% 3 5% 4 4 5% 4 5% 9% 37%	4194
September	1st to 10th	Day	16% 7% 2 6% 4 4 5% 3 5% 6% 40%	2280
	11th to 20th	Day	18% 7% 3 5% 3 3 4 3 4 7% 42%	2124
	21st to end	Day	19% 8% 3 6% 4 4 5% 4 5% 10% 33%	2090
October	1st to 10th	Day	23% 11% 3 6% 4 4 4 4 6% 6% 28%	2076
	11th to 20th	Day	20% 13% 3 7% 4 5% 4 4 6% 6% 28%	1782
	21st to end	Day	24% 21% 3 6% 4 4 4 3 3 4 24%	1881
November	1st to 10th	Day	19% 17% 4 8% 5% 4 4 3 4 5% 27%	1761
	11th to 20th	Day	18% 18% 6% 11% 5% 4 3 4 4 5% 23%	1800
	21st to end	Day	18% 18% 7% 11% 6% 5% 5% 3 5% 6% 17%	1650
December	1st to 10th	Day	13% 21% 8% 22% 10% 5% 3 2 2 4 11%	2600
	11th to 20th	Day	15% 19% 7% 14% 5% 4 4 3 4 4 20%	2986
	21st to end	Day	17% 19% 5% 14% 6% 4 5% 3 4 5% 18%	3960
January	1st to 10th	Night	11% 21% 10% 23% 10% 6% 3 2 2 2 10%	6349
	11th to 20th	Night	9% 19% 10% 23% 12% 5% 4 3 3 3 9%	6315
	21st to end	Night	9% 16% 8% 15% 10% 8% 5% 4 4 4 17%	6996
February	1st to 10th	Night	12% 17% 6% 16% 9% 7% 4 3 4 4 16%	2714
	11th to 20th	Night	10% 19% 6% 18% 9% 7% 4 2 3 4 17%	2338
	21st to end	Night	12% 18% 7% 10% 9% 6% 4 3 3 4 24%	1885
March	1st to 10th	Night	21% 18% 4 8% 5% 4 3 2 4 4 26%	3724
	11th to 20th	Night	16% 24% 5% 11% 6% 4 3 3 3 4 21%	3675
	21st to end	Night	16% 19% 6% 13% 6% 4 3 2 3 3 26%	3530
April	1st to 10th	Night	20% 17% 4 8% 5% 4 3 3 5% 4 26%	1900
	11th to 20th	Night	20% 14% 3 7% 5% 4 3 3 5% 5% 31%	1836
	21st to end	Night	22% 14% 3 7% 5% 4 3 3 4 6% 29%	1710
May	1st to 10th	Night	25% 11% 3 8% 4 4 4 3 5% 6% 27%	2816
	11th to 20th	Night	20% 10% 3 8% 6% 4 4 4 5% 6% 29%	2495
	21st to end	Night	17% 7% 2 6% 5% 4 5% 4 5% 8% 35%	2738
June	1st to 10th	Night	27% 9% 3 5% 3 3 4 4 6% 6% 29%	1520
	11th to 20th	Night	19% 6% 2 5% 4 4 5% 5% 6% 7% 35%	1520
	21st to end	Night	21% 7% 3 7% 5% 4 5% 5% 6% 8% 30%	1520
July	1st to 10th	Night	15% 7% 2 7% 6% 6% 6% 4 7% 8% 32%	2520
	11th to 20th	Night	18% 8% 2 8% 4 4 4 3 6% 7% 35%	2520
	21st to end	Night	15% 8% 2 7% 5% 5% 5% 4 6% 7% 36%	2739
August	1st to 10th	Night	24% 8% 3 6% 5% 4 4 4 6% 6% 31%	2532
	11th to 20th	Night	17% 7% 3 8% 5% 5% 5% 5% 7% 9% 29%	2782
	21st to end	Night	19% 8% 2 6% 4 4 4 3 5% 6% 40%	3458
September	1st to 10th	Night	17% 8% 3 5% 4 4 4 4 5% 6% 40%	1900
	11th to 20th	Night	17% 6% 2 5% 3 4 4 3 4 7% 46%	2055
	21st to end	Night	21% 6% 2 5% 3 3 4 3 5% 8% 40%	2090
October	1st to 10th	Night	21% 10% 3 7% 5% 4 3 4 6% 6% 33%	2100
	11th to 20th	Night	22% 13% 3 8% 5% 4 4 3 4 5% 28%	2396
	21st to end	Night	25% 16% 3 7% 4 4 4 3 5% 5% 24%	2717
November	1st to 10th	Night	20% 17% 4 9% 5% 4 4 3 4 6% 25%	2537
	11th to 20th	Night	17% 16% 6% 10% 6% 3 3 3 4 5% 26%	2600
	21st to end	Night	18% 20% 6% 13% 5% 4 4 3 3 4 21%	2749
December	1st to 10th	Night	13% 23% 13% 21% 7% 4 4 2 3 3 8%	4580
	11th to 20th	Night	16% 22% 6% 18% 6% 4 4 2 3 3 15%	5208
	21st to end	Night	18% 18% 6% 13% 7% 5% 5% 3 4 4 20%	6996

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	82% 4 7% 6% 1	3598
	11th to 20th	Day	79% 5% 6% 7% 3 1	3600
	21st to end	Day	72% 4 7% 9% 7% 1	3960
February	1st to 10th	Day	74% 4 5% 10% 5% 1	1682
	11th to 20th	Day	74% 4 8% 8% 4 1	1957
	21st to end	Day	67% 5% 8% 12% 6% 2	1570
March	1st to 10th	Day	67% 7% 7% 10% 8% 1	3119
	11th to 20th	Day	67% 5% 8% 10% 9% 1	3283
	21st to end	Day	59% 4 7% 15% 14% 1	4099
April	1st to 10th	Day	63% 4 8% 15% 8% 2	2280
	11th to 20th	Day	55% 4 9% 19% 11% 1	2292
	21st to end	Day	60% 6% 9% 15% 8% 3	2470
May	1st to 10th	Day	59% 7% 9% 17% 7% 1	4167
	11th to 20th	Day	53% 10% 16% 14% 6% 1	4402
	21st to end	Day	44% 10% 14% 22% 9%	4837
June	1st to 10th	Day	58% 7% 12% 16% 6% 1	2660
	11th to 20th	Day	47% 7% 12% 22% 10% 1	2660
	21st to end	Day	55% 8% 12% 18% 7%	2660
July	1st to 10th	Day	45% 8% 16% 24% 7%	4370
	11th to 20th	Day	45% 9% 16% 27% 4	4365
	21st to end	Day	46% 8% 12% 28% 7%	4661
August	1st to 10th	Day	54% 7% 15% 18% 5%	4352
	11th to 20th	Day	52% 9% 17% 18% 5%	4084
	21st to end	Day	44% 7% 15% 19% 12% 3	4194
September	1st to 10th	Day	43% 6% 14% 27% 10%	2280
	11th to 20th	Day	43% 5% 11% 28% 13% 1	2124
	21st to end	Day	46% 8% 13% 21% 10% 1	2090
October	1st to 10th	Day	50% 6% 14% 22% 8%	3453
	11th to 20th	Day	54% 5% 13% 21% 8%	2933
	21st to end	Day	54% 3 14% 20% 8% 1	3081
November	1st to 10th	Day	60% 6% 11% 16% 7% 1	1761
	11th to 20th	Day	64% 6% 10% 10% 8% 2	1800
	21st to end	Day	69% 6% 12% 11% 2	1650
December	1st to 10th	Day	81% 4 7% 6% 2	2600
	11th to 20th	Day	68% 4 7% 14% 6%	2986
	21st to end	Day	70% 5% 6% 9% 8% 2	3960
January	1st to 10th	Night	83% 4 7% 5% 1	6349
	11th to 20th	Night	82% 5% 6% 6% 2	6360
	21st to end	Night	72% 4 8% 7% 8% 1	6996
February	1st to 10th	Night	73% 5% 7% 11% 5%	2714
	11th to 20th	Night	73% 5% 7% 11% 5%	2340
	21st to end	Night	66% 5% 7% 13% 9% 1	1885
March	1st to 10th	Night	62% 5% 10% 14% 6% 2	3734
	11th to 20th	Night	67% 6% 7% 11% 8% 1	3676
	21st to end	Night	65% 4 4 14% 12% 1	3530
April	1st to 10th	Night	61% 5% 9% 14% 10% 1	1900
	11th to 20th	Night	54% 6% 9% 19% 11% 1	1836
	21st to end	Night	57% 5% 10% 15% 11% 2	1710
May	1st to 10th	Night	57% 8% 12% 15% 8% 1	2822
	11th to 20th	Night	51% 9% 14% 17% 7% 1	2496
	21st to end	Night	45% 9% 14% 18% 14% 1	2739
June	1st to 10th	Night	54% 7% 10% 21% 8% 1	1520
	11th to 20th	Night	46% 8% 12% 22% 9% 3	1520
	21st to end	Night	53% 8% 14% 18% 7% 1	1520
July	1st to 10th	Night	47% 8% 14% 22% 9%	2480
	11th to 20th	Night	46% 8% 14% 26% 6%	2472
	21st to end	Night	46% 8% 13% 23% 9%	2651
August	1st to 10th	Night	53% 6% 14% 22% 4	2522
	11th to 20th	Night	49% 10% 18% 15% 7%	2809
	21st to end	Night	44% 6% 13% 23% 13% 1	3458
September	1st to 10th	Night	44% 7% 14% 25% 11%	1900
	11th to 20th	Night	39% 6% 15% 28% 11% 1	2055
	21st to end	Night	43% 7% 14% 24% 11% 2	2090
October	1st to 10th	Night	52% 5% 11% 23% 8%	3503
	11th to 20th	Night	55% 5% 10% 20% 10%	3984
	21st to end	Night	54% 5% 14% 18% 9% 1	4467
November	1st to 10th	Night	61% 6% 11% 15% 7% 1	2537
	11th to 20th	Night	62% 5% 8% 15% 8% 2	2600
	21st to end	Night	69% 6% 10% 11% 3	2749
December	1st to 10th	Night	84% 5% 5% 5% 1	4580
	11th to 20th	Night	76% 3 6% 8% 7%	5208
	21st to end	Night	69% 6% 6% 11% 7% 1	6996

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	28% 25% 34% 12% 2	200
	11th to 20th	Day	31% 28% 30% 8% 3 1	200
	21st to end	Day	28% 26% 32% 10% 4	220
February	1st to 10th	Day	38% 30% 23% 8% 1	250
	11th to 20th	Day	32% 29% 27% 9% 2	496
	21st to end	Day	30% 28% 27% 13% 1	382
March	1st to 10th	Day	32% 22% 29% 14% 3	460
	11th to 20th	Day	31% 28% 25% 13% 3	460
	21st to end	Day	35% 22% 23% 14% 5% 1	506
April	1st to 10th	Day	38% 20% 23% 13% 5% 1	460
	11th to 20th	Day	35% 23% 25% 10% 6% 2	452
	21st to end	Day	34% 23% 25% 13% 4 1	460
May	1st to 10th	Day	39% 17% 23% 14% 6% 1	463
	11th to 20th	Day	25% 19% 31% 18% 5% 2	487
	21st to end	Day	22% 20% 33% 18% 6% 1	529
June	1st to 10th	Day	32% 15% 30% 15% 7%	490
	11th to 20th	Day	23% 18% 29% 21% 8% 1	490
	21st to end	Day	27% 17% 32% 15% 8% 2	490
July	1st to 10th	Day	20% 13% 33% 24% 8% 1	485
	11th to 20th	Day	18% 12% 37% 23% 7% 2	484
	21st to end	Day	20% 10% 37% 25% 7% 2	532
August	1st to 10th	Day	19% 12% 30% 26% 11% 1	486
	11th to 20th	Day	19% 10% 30% 22% 15% 4	479
	21st to end	Day	24% 14% 24% 22% 12% 4	539
September	1st to 10th	Day	21% 14% 28% 20% 13% 4	490
	11th to 20th	Day	21% 13% 20% 22% 17% 8%	490
	21st to end	Day	19% 16% 23% 24% 12% 5%	490
October	1st to 10th	Day	27% 17% 25% 17% 11% 3	490
	11th to 20th	Day	30% 20% 25% 15% 8% 1	427
	21st to end	Day	35% 23% 23% 13% 5%	429
November	1st to 10th	Day	35% 20% 27% 14% 4 1	395
	11th to 20th	Day	32% 23% 26% 13% 6% 1	400
	21st to end	Day	33% 21% 30% 14% 2	250
December	1st to 10th	Day	31% 23% 29% 12% 6%	200
	11th to 20th	Day	37% 28% 26% 9% 1	200
	21st to end	Day	40% 20% 29% 9% 2	220
January	1st to 10th	Night	27% 26% 29% 15% 2	800
	11th to 20th	Night	25% 27% 29% 16% 3	800
	21st to end	Night	21% 25% 31% 19% 4	880
February	1st to 10th	Night	25% 26% 29% 18% 3	800
	11th to 20th	Night	25% 26% 33% 14% 2	783
	21st to end	Night	26% 20% 33% 18% 2	629
March	1st to 10th	Night	28% 21% 29% 19% 3	760
	11th to 20th	Night	30% 20% 27% 17% 6%	760
	21st to end	Night	32% 19% 24% 18% 6% 1	836
April	1st to 10th	Night	34% 20% 24% 18% 4	760
	11th to 20th	Night	31% 19% 24% 19% 7%	712
	21st to end	Night	32% 16% 27% 19% 5%	570
May	1st to 10th	Night	30% 13% 29% 21% 6% 1	565
	11th to 20th	Night	23% 12% 33% 25% 7% 1	374
	21st to end	Night	22% 11% 27% 32% 7% 1	411
June	1st to 10th	Night	31% 8% 25% 27% 9% 1	380
	11th to 20th	Night	21% 8% 25% 34% 12%	380
	21st to end	Night	20% 8% 29% 34% 9%	380
July	1st to 10th	Night	17% 6% 29% 35% 13% 1	370
	11th to 20th	Night	15% 6% 27% 35% 15% 1	368
	21st to end	Night	16% 6% 24% 39% 15%	416
August	1st to 10th	Night	21% 4 17% 39% 18% 1	391
	11th to 20th	Night	18% 6% 23% 32% 19% 1	562
	21st to end	Night	20% 6% 23% 32% 16% 2	818
September	1st to 10th	Night	20% 8% 26% 31% 14% 1	760
	11th to 20th	Night	21% 8% 19% 29% 20% 2	760
	21st to end	Night	23% 11% 25% 25% 14% 2	760
October	1st to 10th	Night	28% 12% 22% 24% 13% 1	760
	11th to 20th	Night	31% 15% 23% 21% 8% 1	760
	21st to end	Night	34% 17% 26% 18% 4	836
November	1st to 10th	Night	33% 16% 28% 17% 5%	780
	11th to 20th	Night	27% 21% 28% 16% 7% 1	800
	21st to end	Night	30% 24% 26% 15% 5% 1	800
December	1st to 10th	Night	32% 25% 27% 13% 3	800
	11th to 20th	Night	32% 24% 27% 14% 4	800
	21st to end	Night	33% 23% 26% 16% 2	880

Page generated at 2025-02-18 03:26:32. Version ac07

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