Le Domaine
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Le Domaine clear sky chart from 2005-11-06 to 2025-04-11.

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% 13% 5% 10% 6% 5% 5% 4 5% 6% 26%	113853
	Night	16% 15% 5% 11% 6% 5% 5% 3 4 5% 24%	114395
Transparency	Day	60% 3 9% 19% 9% 1	117366
	Night	62% 2 9% 17% 8% 1	119033
Seeing	Day	27% 14% 32% 18% 7% 2	15024
	Night	26% 12% 30% 23% 8% 1	23989

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% 18% 7% 20% 12% 7% 5% 2 3 4 9%	3597
	11th to 20th	Day	9% 17% 8% 20% 10% 6% 3 3 5% 5% 14%	3570
	21st to end	Day	8% 16% 9% 17% 7% 5% 5% 5% 5% 5% 18%	4076
February	1st to 10th	Day	8% 20% 7% 15% 10% 7% 4 4 5% 6% 16%	1800
	11th to 20th	Day	11% 18% 7% 16% 7% 5% 4 4 5% 5% 19%	1753
	21st to end	Day	16% 18% 5% 11% 6% 6% 5% 4 3 5% 21%	1592
March	1st to 10th	Day	18% 19% 4 12% 5% 4 4 3 4 4 22%	4555
	11th to 20th	Day	13% 15% 5% 13% 7% 5% 5% 3 4 5% 25%	4980
	21st to end	Day	14% 14% 5% 10% 5% 5% 4 3 4 4 31%	5712
April	1st to 10th	Day	21% 16% 4 9% 4 4 3 2 3 4 29%	2400
	11th to 20th	Day	21% 13% 4 8% 4 3 3 3 5% 6% 30%	2254
	21st to end	Day	19% 13% 4 9% 5% 4 4 3 4 5% 31%	2513
May	1st to 10th	Day	21% 13% 4 8% 5% 4 5% 4 5% 5% 27%	4426
	11th to 20th	Day	19% 9% 3 8% 5% 5% 4 4 6% 7% 31%	4398
	21st to end	Day	18% 8% 3 7% 5% 5% 5% 3 6% 6% 33%	4837
June	1st to 10th	Day	22% 10% 3 8% 6% 5% 5% 4 6% 6% 25%	2660
	11th to 20th	Day	14% 7% 2 7% 6% 5% 5% 4 7% 7% 34%	2683
	21st to end	Day	19% 7% 3 9% 6% 6% 5% 4 6% 7% 27%	2850
July	1st to 10th	Day	15% 8% 3 7% 6% 6% 5% 5% 7% 8% 29%	4542
	11th to 20th	Day	15% 8% 3 7% 6% 5% 5% 5% 6% 8% 32%	4440
	21st to end	Day	13% 8% 2 7% 5% 5% 5% 4 6% 7% 38%	4814
August	1st to 10th	Day	15% 7% 3 9% 6% 7% 6% 5% 6% 7% 29%	4392
	11th to 20th	Day	17% 8% 3 7% 5% 5% 6% 4 7% 7% 32%	4044
	21st to end	Day	13% 7% 3 7% 5% 5% 6% 4 6% 9% 35%	4244
September	1st to 10th	Day	19% 7% 2 7% 5% 3 4 3 4 7% 38%	2280
	11th to 20th	Day	17% 8% 3 6% 4 4 4 3 5% 7% 39%	2280
	21st to end	Day	21% 11% 3 6% 4 3 4 3 5% 6% 33%	2010
October	1st to 10th	Day	20% 14% 4 8% 4 4 3 3 5% 7% 30%	1900
	11th to 20th	Day	26% 18% 5% 10% 4 4 4 3 4 4 20%	1900
	21st to end	Day	27% 19% 4 8% 4 5% 4 3 3 5% 18%	1937
November	1st to 10th	Day	17% 19% 5% 11% 3 4 3 3 3 5% 26%	1668
	11th to 20th	Day	17% 18% 7% 14% 8% 4 4 3 3 4 17%	1600
	21st to end	Day	23% 21% 9% 14% 6% 4 3 3 4 4 9%	1600
December	1st to 10th	Day	17% 25% 9% 16% 6% 6% 3 3 3 4 8%	2600
	11th to 20th	Day	15% 20% 6% 14% 11% 6% 5% 3 2 3 15%	2986
	21st to end	Day	16% 20% 9% 13% 8% 4 4 3 4 4 14%	3960
January	1st to 10th	Night	11% 22% 11% 17% 9% 6% 4 3 3 3 12%	6349
	11th to 20th	Night	10% 17% 7% 17% 10% 7% 6% 4 5% 4 12%	6315
	21st to end	Night	7% 16% 10% 17% 7% 7% 7% 4 5% 5% 16%	6876
February	1st to 10th	Night	10% 14% 5% 12% 10% 8% 5% 4 5% 5% 20%	2600
	11th to 20th	Night	11% 18% 6% 13% 8% 7% 5% 4 4 5% 19%	2533
	21st to end	Night	11% 17% 5% 11% 8% 6% 6% 3 5% 5% 22%	2037
March	1st to 10th	Night	17% 20% 5% 10% 6% 4 4 3 4 4 23%	5282
	11th to 20th	Night	12% 16% 5% 13% 7% 6% 5% 4 5% 6% 22%	4979
	21st to end	Night	15% 12% 4 11% 6% 6% 5% 4 5% 5% 27%	5206
April	1st to 10th	Night	19% 14% 5% 10% 6% 4 4 2 4 5% 28%	2000
	11th to 20th	Night	17% 11% 4 7% 4 4 4 3 5% 5% 35%	1882
	21st to end	Night	22% 10% 4 8% 5% 4 4 3 4 5% 31%	1681
May	1st to 10th	Night	21% 11% 3 8% 5% 4 5% 3 4 6% 30%	2514
	11th to 20th	Night	18% 10% 3 8% 5% 4 4 3 5% 5% 34%	2495
	21st to end	Night	17% 9% 3 7% 4 5% 4 4 5% 7% 34%	2738
June	1st to 10th	Night	18% 9% 3 7% 6% 6% 5% 5% 6% 6% 30%	1520
	11th to 20th	Night	16% 8% 3 7% 6% 4 5% 4 5% 7% 37%	1489
	21st to end	Night	18% 9% 2 7% 5% 4 4 5% 5% 7% 35%	1330
July	1st to 10th	Night	16% 9% 3 9% 6% 5% 6% 5% 6% 7% 29%	2413
	11th to 20th	Night	16% 9% 3 6% 4 5% 5% 4 6% 7% 35%	2520
	21st to end	Night	11% 6% 2 6% 5% 4 5% 3 6% 7% 44%	2739
August	1st to 10th	Night	10% 9% 2 7% 4 4 5% 4 6% 8% 40%	2534
	11th to 20th	Night	19% 8% 3 7% 4 4 4 4 5% 6% 36%	2785
	21st to end	Night	16% 6% 3 7% 4 5% 5% 4 7% 8% 35%	3380
September	1st to 10th	Night	15% 8% 3 5% 4 4 4 3 5% 7% 42%	1900
	11th to 20th	Night	17% 8% 2 5% 3 4 4 4 5% 5% 42%	1900
	21st to end	Night	20% 9% 3 6% 4 4 3 3 5% 6% 37%	2167
October	1st to 10th	Night	21% 10% 3 8% 4 4 3 3 4 6% 34%	2280
	11th to 20th	Night	24% 17% 4 8% 4 4 3 3 4 5% 24%	2280
	21st to end	Night	24% 18% 4 9% 4 4 4 3 4 5% 20%	2660
November	1st to 10th	Night	18% 18% 5% 9% 6% 4 4 3 4 5% 25%	2627
	11th to 20th	Night	18% 17% 6% 12% 7% 6% 3 3 5% 5% 19%	2800
	21st to end	Night	22% 21% 8% 13% 7% 4 3 2 4 4 13%	2800
December	1st to 10th	Night	16% 20% 8% 18% 10% 7% 4 3 3 3 8%	4580
	11th to 20th	Night	20% 19% 5% 13% 7% 4 4 3 4 4 17%	5208
	21st to end	Night	18% 22% 7% 14% 8% 4 4 3 2 4 14%	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	81% 1 6% 7% 4	3598
	11th to 20th	Day	74% 2 4 13% 8%	3600
	21st to end	Day	66% 2 5% 15% 11%	4076
February	1st to 10th	Day	69% 2 5% 13% 9% 1	1800
	11th to 20th	Day	68% 1 8% 11% 10% 1	1762
	21st to end	Day	67% 2 5% 15% 10% 1	1592
March	1st to 10th	Day	67% 1 5% 13% 12% 2	4558
	11th to 20th	Day	64% 2 10% 14% 10% 1	4980
	21st to end	Day	58% 1 4 18% 16% 2	5712
April	1st to 10th	Day	61% 1 7% 16% 12% 2	2400
	11th to 20th	Day	57% 2 6% 22% 12% 2	2254
	21st to end	Day	57% 2 7% 17% 15% 3	2513
May	1st to 10th	Day	60% 1 6% 20% 11% 2	4440
	11th to 20th	Day	54% 1 9% 26% 9% 1	4402
	21st to end	Day	52% 1 9% 19% 17% 1	4837
June	1st to 10th	Day	59% 3 7% 20% 11% 1	2660
	11th to 20th	Day	46% 3 11% 25% 12% 2	2683
	21st to end	Day	56% 3 11% 21% 9%	2850
July	1st to 10th	Day	50% 5% 13% 26% 6%	4472
	11th to 20th	Day	48% 5% 14% 27% 7%	4365
	21st to end	Day	44% 4 15% 27% 9%	4661
August	1st to 10th	Day	52% 5% 12% 25% 6%	4378
	11th to 20th	Day	49% 4 14% 25% 7%	4083
	21st to end	Day	45% 4 11% 28% 11% 1	4244
September	1st to 10th	Day	47% 3 12% 25% 13% 1	2280
	11th to 20th	Day	46% 3 15% 26% 10% 1	2280
	21st to end	Day	53% 3 12% 24% 8%	2010
October	1st to 10th	Day	57% 3 9% 25% 6%	3160
	11th to 20th	Day	60% 2 13% 18% 6% 1	3140
	21st to end	Day	67% 3 13% 12% 4 1	3162
November	1st to 10th	Day	62% 3 10% 18% 7%	1668
	11th to 20th	Day	72% 2 9% 12% 6%	1600
	21st to end	Day	80% 3 6% 8% 4	1600
December	1st to 10th	Day	81% 2 5% 10% 2	2600
	11th to 20th	Day	76% 2 3 14% 5%	2986
	21st to end	Day	75% 2 5% 15% 4	3960
January	1st to 10th	Night	80% 1 8% 8% 3	6349
	11th to 20th	Night	76% 1 7% 11% 5% 1	6360
	21st to end	Night	70% 2 5% 12% 10%	6876
February	1st to 10th	Night	65% 2 7% 17% 8% 1	2600
	11th to 20th	Night	67% 2 6% 15% 8% 1	2535
	21st to end	Night	64% 2 7% 16% 9% 1	2037
March	1st to 10th	Night	67% 1 6% 11% 12% 3	5292
	11th to 20th	Night	64% 3 11% 14% 7% 1	4980
	21st to end	Night	60% 2 5% 19% 12% 2	5206
April	1st to 10th	Night	60% 1 6% 17% 14% 2	2000
	11th to 20th	Night	51% 2 6% 24% 14% 2	1882
	21st to end	Night	56% 2 7% 19% 15% 2	1681
May	1st to 10th	Night	56% 2 12% 18% 11% 2	2520
	11th to 20th	Night	53% 1 11% 21% 12% 1	2496
	21st to end	Night	50% 1 11% 22% 14% 2	2739
June	1st to 10th	Night	53% 3 10% 24% 10% 1	1520
	11th to 20th	Night	47% 3 11% 23% 14% 2	1489
	21st to end	Night	48% 4 12% 25% 10% 1	1330
July	1st to 10th	Night	52% 6% 13% 21% 8% 1	2373
	11th to 20th	Night	47% 4 19% 23% 6%	2472
	21st to end	Night	40% 3 16% 29% 13%	2651
August	1st to 10th	Night	41% 5% 19% 28% 7%	2524
	11th to 20th	Night	47% 4 16% 26% 7%	2812
	21st to end	Night	46% 4 14% 25% 9% 2	3380
September	1st to 10th	Night	43% 3 17% 27% 10%	1900
	11th to 20th	Night	43% 3 17% 29% 8%	1900
	21st to end	Night	49% 3 13% 27% 8%	2167
October	1st to 10th	Night	52% 3 11% 22% 13%	3800
	11th to 20th	Night	60% 3 11% 21% 6%	3779
	21st to end	Night	61% 2 15% 12% 9% 1	4372
November	1st to 10th	Night	63% 2 11% 18% 6%	2627
	11th to 20th	Night	68% 2 9% 14% 7%	2800
	21st to end	Night	78% 2 7% 10% 3	2800
December	1st to 10th	Night	82% 3 5% 7% 3	4580
	11th to 20th	Night	72% 2 4 14% 7%	5208
	21st to end	Night	76% 1 3 12% 7%	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	22% 21% 44% 12% 2 1	200
	11th to 20th	Day	25% 15% 39% 15% 5% 2	200
	21st to end	Day	20% 21% 35% 18% 5%	246
February	1st to 10th	Day	30% 25% 36% 6% 3	300
	11th to 20th	Day	28% 27% 34% 10% 1	300
	21st to end	Day	33% 19% 36% 10% 1	356
March	1st to 10th	Day	28% 18% 34% 15% 4	500
	11th to 20th	Day	30% 19% 32% 15% 4	500
	21st to end	Day	31% 17% 35% 13% 4 1	550
April	1st to 10th	Day	36% 19% 24% 16% 4 1	500
	11th to 20th	Day	36% 15% 26% 14% 8% 2	452
	21st to end	Day	29% 19% 32% 14% 5% 1	460
May	1st to 10th	Day	31% 14% 32% 15% 6% 2	463
	11th to 20th	Day	28% 14% 28% 20% 8% 2	487
	21st to end	Day	25% 17% 32% 19% 7% 1	529
June	1st to 10th	Day	27% 10% 36% 20% 6% 1	490
	11th to 20th	Day	21% 16% 32% 19% 10% 2	513
	21st to end	Day	22% 12% 31% 24% 9% 1	680
July	1st to 10th	Day	16% 9% 37% 28% 9% 1	548
	11th to 20th	Day	20% 9% 35% 24% 10% 3	484
	21st to end	Day	18% 9% 29% 31% 11% 2	532
August	1st to 10th	Day	20% 7% 32% 28% 9% 4	486
	11th to 20th	Day	19% 6% 29% 27% 14% 6%	479
	21st to end	Day	19% 10% 32% 22% 11% 5%	539
September	1st to 10th	Day	24% 8% 32% 21% 11% 4	490
	11th to 20th	Day	22% 8% 27% 23% 15% 6%	490
	21st to end	Day	26% 12% 26% 19% 14% 3	490
October	1st to 10th	Day	27% 15% 28% 19% 9% 2	490
	11th to 20th	Day	32% 18% 30% 14% 4 1	490
	21st to end	Day	39% 12% 29% 17% 3 1	458
November	1st to 10th	Day	34% 14% 34% 13% 4 1	302
	11th to 20th	Day	27% 22% 34% 14% 3 1	200
	21st to end	Day	34% 24% 32% 8% 3 1	200
December	1st to 10th	Day	34% 13% 33% 16% 4 1	200
	11th to 20th	Day	31% 22% 34% 9% 4 1	200
	21st to end	Day	30% 16% 39% 10% 4 1	220
January	1st to 10th	Night	31% 15% 33% 18% 3	800
	11th to 20th	Night	30% 14% 30% 21% 5% 1	800
	21st to end	Night	18% 12% 36% 26% 7% 1	880
February	1st to 10th	Night	20% 17% 36% 21% 5% 1	800
	11th to 20th	Night	24% 17% 37% 19% 3 1	783
	21st to end	Night	25% 17% 31% 23% 4	660
March	1st to 10th	Night	24% 18% 32% 22% 4	800
	11th to 20th	Night	27% 18% 31% 18% 6% 1	800
	21st to end	Night	25% 15% 33% 21% 6%	880
April	1st to 10th	Night	29% 14% 29% 23% 5%	800
	11th to 20th	Night	27% 15% 28% 21% 8%	754
	21st to end	Night	28% 10% 30% 23% 8% 1	541
May	1st to 10th	Night	24% 8% 30% 28% 10% 1	380
	11th to 20th	Night	26% 9% 28% 28% 9% 1	374
	21st to end	Night	22% 9% 35% 26% 8%	411
June	1st to 10th	Night	24% 7% 32% 28% 9%	380
	11th to 20th	Night	20% 8% 29% 30% 12% 1	380
	21st to end	Night	21% 6% 29% 32% 12%	380
July	1st to 10th	Night	15% 5% 32% 39% 9%	370
	11th to 20th	Night	17% 6% 25% 38% 14%	368
	21st to end	Night	15% 4 27% 39% 15%	416
August	1st to 10th	Night	15% 5% 24% 36% 20% 1	393
	11th to 20th	Night	18% 3 22% 33% 22% 3	564
	21st to end	Night	20% 5% 30% 26% 17% 3	779
September	1st to 10th	Night	22% 5% 30% 28% 13% 2	760
	11th to 20th	Night	24% 6% 25% 25% 18% 2	760
	21st to end	Night	26% 6% 26% 27% 14% 1	760
October	1st to 10th	Night	26% 9% 31% 23% 10% 1	760
	11th to 20th	Night	34% 11% 28% 20% 6% 2	760
	21st to end	Night	34% 13% 29% 20% 4 1	836
November	1st to 10th	Night	31% 14% 31% 18% 5% 1	780
	11th to 20th	Night	31% 16% 31% 15% 7% 1	800
	21st to end	Night	37% 17% 24% 18% 5% 1	800
December	1st to 10th	Night	34% 15% 29% 17% 5% 1	800
	11th to 20th	Night	31% 14% 31% 18% 5% 1	800
	21st to end	Night	34% 14% 27% 19% 5% 1	880

Page generated at 2025-04-08 09:17:24. Version ac07

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