Parc de la Frayère
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Parc de la Frayère clear sky chart from 2005-11-06 to 2025-04-26.

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% 3 8% 5% 5% 5% 4 6% 7% 32%	113575
	Night	17% 12% 4 9% 5% 5% 4 3 5% 6% 30%	115037
Transparency	Day	50% 7% 13% 21% 10% 1	117081
	Night	54% 6% 11% 18% 10% 1	119695
Seeing	Day	21% 11% 28% 25% 12% 3	15087
	Night	23% 9% 29% 29% 10% 1	24190

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	16% 20% 7% 12% 5% 5% 4 3 3 3 22%	3597
	11th to 20th	Day	13% 15% 7% 12% 6% 6% 4 3 4 6% 24%	3570
	21st to end	Day	12% 14% 5% 10% 5% 6% 5% 4 6% 6% 27%	3960
February	1st to 10th	Day	15% 16% 4 10% 5% 5% 5% 3 4 6% 27%	1736
	11th to 20th	Day	13% 12% 5% 11% 7% 4 5% 4 6% 5% 27%	1867
	21st to end	Day	17% 16% 4 8% 6% 4 4 3 5% 6% 27%	1650
March	1st to 10th	Day	18% 13% 4 11% 7% 5% 5% 3 4 5% 26%	4476
	11th to 20th	Day	12% 13% 4 9% 5% 5% 4 3 6% 7% 32%	4688
	21st to end	Day	17% 11% 4 10% 5% 4 4 3 5% 5% 33%	5970
April	1st to 10th	Day	21% 11% 3 8% 4 4 5% 3 4 6% 31%	2400
	11th to 20th	Day	20% 9% 3 7% 4 4 3 3 4 5% 37%	2374
	21st to end	Day	21% 9% 3 8% 5% 4 4 4 5% 5% 32%	2512
May	1st to 10th	Day	19% 9% 3 8% 5% 4 5% 4 6% 7% 30%	4348
	11th to 20th	Day	17% 8% 3 8% 5% 5% 5% 4 6% 8% 31%	4398
	21st to end	Day	14% 7% 2 6% 5% 4 5% 4 7% 9% 36%	4837
June	1st to 10th	Day	20% 8% 3 7% 5% 5% 5% 3 6% 8% 30%	2660
	11th to 20th	Day	14% 6% 3 6% 5% 4 4 4 6% 9% 38%	2660
	21st to end	Day	19% 8% 3 8% 6% 5% 5% 4 5% 7% 31%	2660
July	1st to 10th	Day	11% 6% 2 7% 6% 5% 6% 4 7% 9% 37%	4440
	11th to 20th	Day	12% 5% 2 6% 5% 5% 6% 5% 7% 9% 37%	4440
	21st to end	Day	11% 6% 2 5% 4 4 4 4 7% 8% 45%	4814
August	1st to 10th	Day	13% 6% 2 8% 6% 5% 6% 5% 7% 10% 32%	4423
	11th to 20th	Day	13% 6% 3 8% 5% 4 4 4 6% 9% 38%	4018
	21st to end	Day	15% 6% 2 6% 4 4 4 4 6% 8% 40%	4180
September	1st to 10th	Day	11% 5% 2 7% 5% 4 5% 5% 6% 8% 42%	2280
	11th to 20th	Day	14% 5% 2 5% 3 3 4 3 6% 7% 49%	2190
	21st to end	Day	15% 6% 2 7% 4 4 5% 4 5% 7% 41%	2090
October	1st to 10th	Day	18% 6% 3 7% 6% 5% 4 3 5% 8% 35%	1976
	11th to 20th	Day	17% 9% 3 8% 5% 7% 5% 5% 6% 7% 29%	1843
	21st to end	Day	24% 9% 3 7% 4 4 4 3 5% 5% 31%	1881
November	1st to 10th	Day	17% 10% 3 7% 5% 4 5% 4 7% 6% 32%	1761
	11th to 20th	Day	17% 10% 3 9% 5% 5% 5% 5% 6% 5% 31%	1730
	21st to end	Day	22% 12% 3 9% 5% 4 6% 4 4 6% 25%	1600
December	1st to 10th	Day	20% 19% 5% 12% 5% 4 4 3 4 5% 18%	2600
	11th to 20th	Day	19% 13% 4 10% 4 4 4 4 5% 6% 26%	2986
	21st to end	Day	23% 13% 3 10% 6% 5% 6% 5% 6% 5% 19%	3960
January	1st to 10th	Night	14% 20% 7% 15% 5% 4 4 3 3 4 20%	6349
	11th to 20th	Night	10% 15% 7% 16% 8% 6% 5% 3 5% 6% 19%	6315
	21st to end	Night	13% 15% 5% 12% 7% 5% 5% 3 4 6% 24%	6996
February	1st to 10th	Night	14% 15% 6% 12% 7% 5% 4 3 5% 5% 23%	2660
	11th to 20th	Night	14% 13% 5% 10% 5% 6% 4 3 5% 5% 29%	2418
	21st to end	Night	15% 15% 3 9% 5% 5% 4 3 4 6% 31%	1980
March	1st to 10th	Night	22% 12% 4 8% 5% 4 4 3 4 5% 30%	5364
	11th to 20th	Night	14% 14% 3 8% 5% 5% 5% 4 5% 7% 30%	5269
	21st to end	Night	15% 12% 4 9% 6% 5% 4 3 4 5% 32%	4962
April	1st to 10th	Night	23% 10% 3 7% 5% 4 4 3 4 6% 31%	2000
	11th to 20th	Night	22% 9% 3 7% 5% 4 4 4 4 6% 34%	1975
	21st to end	Night	22% 10% 3 6% 4 4 4 3 5% 5% 35%	1783
May	1st to 10th	Night	21% 9% 3 7% 5% 5% 5% 4 5% 6% 31%	2620
	11th to 20th	Night	22% 8% 3 7% 4 4 4 3 6% 7% 33%	2495
	21st to end	Night	14% 8% 3 7% 5% 5% 4 4 6% 8% 36%	2738
June	1st to 10th	Night	22% 7% 2 8% 4 4 5% 4 6% 7% 32%	1520
	11th to 20th	Night	15% 6% 3 7% 4 4 5% 3 8% 7% 38%	1520
	21st to end	Night	18% 7% 2 7% 5% 6% 5% 4 5% 8% 32%	1520
July	1st to 10th	Night	13% 7% 3 8% 5% 5% 6% 4 7% 9% 34%	2520
	11th to 20th	Night	14% 6% 2 6% 4 4 5% 4 7% 8% 40%	2520
	21st to end	Night	10% 6% 2 6% 5% 5% 4 4 7% 8% 43%	2739
August	1st to 10th	Night	14% 9% 4 8% 5% 5% 5% 3 6% 6% 36%	2506
	11th to 20th	Night	15% 7% 3 8% 5% 5% 5% 3 6% 7% 37%	2775
	21st to end	Night	16% 6% 3 7% 5% 5% 4 4 6% 7% 38%	3476
September	1st to 10th	Night	12% 5% 2 7% 5% 4 4 4 6% 7% 44%	1900
	11th to 20th	Night	15% 6% 2 5% 3 2 3 3 5% 7% 49%	1990
	21st to end	Night	16% 7% 2 5% 5% 4 3 3 5% 7% 43%	2090
October	1st to 10th	Night	17% 7% 2 7% 4 4 5% 3 5% 7% 39%	2199
	11th to 20th	Night	21% 9% 3 7% 5% 4 4 3 4 6% 34%	2335
	21st to end	Night	23% 9% 3 9% 5% 4 4 3 4 5% 31%	2717
November	1st to 10th	Night	19% 9% 3 8% 5% 5% 4 3 5% 5% 33%	2537
	11th to 20th	Night	19% 11% 3 8% 5% 5% 4 3 5% 6% 33%	2665
	21st to end	Night	22% 13% 3 8% 6% 4 4 3 4 6% 26%	2800
December	1st to 10th	Night	18% 17% 6% 13% 6% 5% 5% 3 4 5% 18%	4580
	11th to 20th	Night	23% 13% 4 9% 5% 4 4 3 6% 5% 24%	5208
	21st to end	Night	24% 15% 5% 9% 4 3 4 4 6% 5% 21%	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	65% 7% 9% 16% 3	3598
	11th to 20th	Day	61% 6% 10% 15% 7% 1	3600
	21st to end	Day	57% 6% 11% 15% 11% 1	3960
February	1st to 10th	Day	60% 5% 9% 18% 7% 2	1736
	11th to 20th	Day	58% 7% 11% 14% 9% 1	1876
	21st to end	Day	58% 4 10% 16% 9% 2	1650
March	1st to 10th	Day	59% 5% 8% 14% 10% 3	4479
	11th to 20th	Day	50% 7% 16% 14% 11% 2	4688
	21st to end	Day	53% 5% 8% 16% 16% 2	5970
April	1st to 10th	Day	55% 5% 8% 19% 12% 2	2400
	11th to 20th	Day	49% 4 9% 22% 14% 2	2374
	21st to end	Day	54% 5% 9% 18% 11% 3	2512
May	1st to 10th	Day	49% 8% 11% 22% 9% 1	4362
	11th to 20th	Day	47% 10% 16% 17% 9% 1	4402
	21st to end	Day	42% 8% 13% 23% 13% 1	4837
June	1st to 10th	Day	50% 7% 11% 19% 11% 2	2660
	11th to 20th	Day	41% 7% 13% 24% 12% 3	2660
	21st to end	Day	52% 7% 13% 19% 10% 1	2660
July	1st to 10th	Day	42% 7% 15% 27% 9% 1	4370
	11th to 20th	Day	40% 8% 17% 28% 7%	4365
	21st to end	Day	36% 7% 15% 33% 9%	4661
August	1st to 10th	Day	46% 7% 18% 22% 7%	4409
	11th to 20th	Day	42% 7% 20% 25% 6%	4060
	21st to end	Day	42% 7% 15% 21% 14%	4180
September	1st to 10th	Day	37% 8% 15% 29% 11% 1	2280
	11th to 20th	Day	35% 6% 14% 32% 13% 1	2190
	21st to end	Day	42% 8% 14% 25% 11%	2090
October	1st to 10th	Day	44% 6% 15% 27% 7%	3288
	11th to 20th	Day	44% 6% 18% 25% 7%	3046
	21st to end	Day	43% 6% 19% 23% 9% 1	3081
November	1st to 10th	Day	49% 7% 13% 22% 9% 1	1761
	11th to 20th	Day	51% 7% 11% 19% 12%	1730
	21st to end	Day	58% 8% 14% 14% 6%	1600
December	1st to 10th	Day	69% 4 8% 16% 3	2600
	11th to 20th	Day	59% 5% 9% 17% 11%	2986
	21st to end	Day	65% 6% 11% 11% 6%	3960
January	1st to 10th	Night	67% 6% 11% 12% 4	6349
	11th to 20th	Night	64% 8% 10% 13% 4	6360
	21st to end	Night	60% 5% 10% 11% 13%	6996
February	1st to 10th	Night	62% 5% 9% 15% 8% 1	2660
	11th to 20th	Night	59% 5% 9% 17% 10%	2420
	21st to end	Night	55% 6% 8% 17% 12% 2	1980
March	1st to 10th	Night	58% 4 8% 14% 11% 5%	5374
	11th to 20th	Night	52% 6% 13% 15% 13% 1	5270
	21st to end	Night	55% 5% 6% 21% 11% 2	4962
April	1st to 10th	Night	55% 4 7% 18% 14% 2	2000
	11th to 20th	Night	52% 4 7% 20% 14% 2	1975
	21st to end	Night	51% 4 8% 20% 14% 3	1783
May	1st to 10th	Night	51% 9% 10% 19% 8% 3	2626
	11th to 20th	Night	48% 9% 12% 19% 10% 2	2496
	21st to end	Night	45% 6% 11% 20% 17% 2	2739
June	1st to 10th	Night	49% 7% 10% 21% 12% 1	1520
	11th to 20th	Night	44% 7% 11% 21% 14% 3	1520
	21st to end	Night	49% 7% 10% 18% 14% 1	1520
July	1st to 10th	Night	45% 7% 15% 20% 12% 1	2480
	11th to 20th	Night	40% 7% 18% 26% 9%	2472
	21st to end	Night	38% 7% 19% 24% 12%	2651
August	1st to 10th	Night	48% 7% 12% 25% 9%	2496
	11th to 20th	Night	46% 7% 17% 22% 7%	2799
	21st to end	Night	45% 6% 13% 21% 14% 1	3476
September	1st to 10th	Night	38% 8% 12% 26% 15% 1	1900
	11th to 20th	Night	36% 5% 14% 31% 13% 1	1990
	21st to end	Night	40% 8% 10% 27% 15%	2090
October	1st to 10th	Night	44% 6% 13% 26% 10%	3667
	11th to 20th	Night	45% 5% 11% 30% 8%	3871
	21st to end	Night	48% 4 15% 18% 12% 2	4467
November	1st to 10th	Night	53% 5% 12% 21% 8% 1	2537
	11th to 20th	Night	52% 6% 11% 19% 11% 2	2665
	21st to end	Night	60% 5% 11% 17% 7%	2800
December	1st to 10th	Night	69% 5% 11% 11% 4	4580
	11th to 20th	Night	61% 5% 8% 14% 11%	5208
	21st to end	Night	64% 4 9% 14% 9%	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% 14% 31% 17% 11%	200
	11th to 20th	Day	25% 15% 35% 20% 6% 1	200
	21st to end	Day	19% 11% 37% 22% 10% 1	220
February	1st to 10th	Day	28% 16% 35% 18% 3	268
	11th to 20th	Day	22% 16% 33% 25% 4	415
	21st to end	Day	26% 13% 33% 24% 4	414
March	1st to 10th	Day	23% 13% 30% 25% 9%	500
	11th to 20th	Day	21% 15% 36% 22% 6% 1	500
	21st to end	Day	27% 12% 32% 21% 7% 1	550
April	1st to 10th	Day	28% 15% 27% 20% 8% 1	500
	11th to 20th	Day	28% 18% 24% 20% 7% 3	492
	21st to end	Day	28% 13% 31% 18% 9% 1	480
May	1st to 10th	Day	23% 11% 33% 20% 11% 2	463
	11th to 20th	Day	17% 11% 28% 26% 14% 4	487
	21st to end	Day	19% 13% 30% 26% 10% 2	529
June	1st to 10th	Day	22% 11% 25% 29% 10% 2	490
	11th to 20th	Day	16% 10% 26% 32% 14% 2	490
	21st to end	Day	23% 11% 23% 26% 14% 3	490
July	1st to 10th	Day	13% 8% 24% 31% 19% 5%	485
	11th to 20th	Day	14% 8% 26% 33% 16% 4	484
	21st to end	Day	14% 7% 24% 33% 18% 3	532
August	1st to 10th	Day	15% 5% 23% 30% 21% 6%	486
	11th to 20th	Day	12% 6% 20% 30% 22% 9%	479
	21st to end	Day	16% 8% 22% 26% 18% 10%	539
September	1st to 10th	Day	12% 9% 27% 29% 16% 7%	490
	11th to 20th	Day	14% 8% 20% 27% 19% 13%	490
	21st to end	Day	18% 8% 26% 24% 18% 6%	490
October	1st to 10th	Day	20% 13% 26% 23% 14% 4	490
	11th to 20th	Day	23% 12% 29% 23% 11% 2	460
	21st to end	Day	30% 11% 27% 24% 8%	429
November	1st to 10th	Day	26% 13% 30% 21% 9%	395
	11th to 20th	Day	23% 15% 31% 21% 8% 2	330
	21st to end	Day	33% 13% 30% 16% 9% 1	200
December	1st to 10th	Day	30% 10% 25% 21% 12% 3	200
	11th to 20th	Day	26% 22% 32% 16% 4 1	200
	21st to end	Day	33% 16% 26% 18% 4 2	220
January	1st to 10th	Night	28% 10% 31% 26% 5%	800
	11th to 20th	Night	25% 11% 33% 25% 7%	800
	21st to end	Night	19% 9% 34% 31% 6% 1	880
February	1st to 10th	Night	22% 10% 36% 27% 5% 1	800
	11th to 20th	Night	20% 11% 38% 24% 4 1	783
	21st to end	Night	22% 11% 33% 30% 4	660
March	1st to 10th	Night	26% 9% 31% 29% 6%	800
	11th to 20th	Night	25% 11% 31% 26% 7% 1	800
	21st to end	Night	23% 9% 31% 28% 8%	880
April	1st to 10th	Night	28% 12% 26% 28% 6%	800
	11th to 20th	Night	25% 13% 30% 26% 6% 1	791
	21st to end	Night	28% 11% 30% 24% 7%	609
May	1st to 10th	Night	26% 7% 32% 27% 8% 1	447
	11th to 20th	Night	23% 9% 28% 30% 9% 1	374
	21st to end	Night	18% 9% 36% 29% 9%	411
June	1st to 10th	Night	23% 6% 26% 35% 9% 1	380
	11th to 20th	Night	19% 3 29% 36% 13%	380
	21st to end	Night	18% 7% 27% 33% 14% 1	380
July	1st to 10th	Night	12% 5% 29% 38% 15% 1	370
	11th to 20th	Night	12% 2 24% 46% 14% 1	368
	21st to end	Night	13% 4 21% 45% 16%	416
August	1st to 10th	Night	14% 5% 17% 44% 19% 2	378
	11th to 20th	Night	14% 3 20% 38% 24% 2	551
	21st to end	Night	16% 4 21% 36% 20% 2	836
September	1st to 10th	Night	15% 5% 23% 41% 15% 1	760
	11th to 20th	Night	17% 5% 21% 34% 21% 2	760
	21st to end	Night	18% 6% 26% 31% 15% 3	760
October	1st to 10th	Night	21% 7% 27% 31% 13% 1	760
	11th to 20th	Night	26% 8% 27% 29% 9% 1	760
	21st to end	Night	27% 10% 31% 25% 7%	836
November	1st to 10th	Night	24% 12% 31% 25% 8%	780
	11th to 20th	Night	25% 10% 33% 23% 9% 1	800
	21st to end	Night	30% 12% 30% 21% 7%	800
December	1st to 10th	Night	29% 11% 29% 25% 7%	800
	11th to 20th	Night	28% 12% 31% 21% 6% 1	800
	21st to end	Night	31% 11% 30% 21% 7%	880

Page generated at 2025-04-23 09:25:03. Version ac07

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