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 2024-10-24.

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% 12% 4 10% 6% 5% 5% 4 5% 6% 27%	101842
	Night	16% 14% 5% 10% 6% 5% 4 3 5% 5% 26%	96917
Transparency	Day	58% 3 9% 20% 9% 1	101600
	Night	60% 2 10% 18% 8% 1	96779
Seeing	Day	26% 14% 32% 19% 7% 2	14554
	Night	26% 12% 30% 23% 8% 1	23311

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	15% 20% 7% 17% 9% 5% 5% 3 4 5% 12%	2517
	11th to 20th	Day	13% 15% 7% 20% 9% 5% 4 3 4 5% 16%	2520
	21st to end	Day	12% 19% 10% 15% 7% 5% 5% 4 4 5% 14%	2846
February	1st to 10th	Day	8% 20% 7% 14% 10% 7% 4 4 5% 6% 16%	1710
	11th to 20th	Day	11% 18% 6% 15% 7% 5% 4 4 5% 5% 20%	1663
	21st to end	Day	17% 18% 5% 10% 6% 5% 5% 4 3 5% 21%	1514
March	1st to 10th	Day	18% 20% 4 9% 5% 4 4 3 4 5% 25%	3167
	11th to 20th	Day	11% 17% 7% 15% 6% 5% 4 3 3 4 25%	3480
	21st to end	Day	11% 9% 4 10% 6% 6% 5% 4 5% 5% 33%	3992
April	1st to 10th	Day	22% 17% 4 9% 4 4 3 2 3 4 29%	2280
	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 4 4 2 3 5% 19%	1865
November	1st to 10th	Day	17% 19% 6% 10% 3 4 3 3 3 5% 27%	1583
	11th to 20th	Day	18% 18% 7% 14% 8% 4 4 3 3 4 17%	1520
	21st to end	Day	22% 21% 8% 14% 7% 4 3 3 4 4 10%	1520
December	1st to 10th	Day	20% 23% 7% 13% 7% 6% 3 3 3 5% 11%	1520
	11th to 20th	Day	19% 17% 6% 14% 9% 5% 6% 4 3 4 13%	1906
	21st to end	Day	20% 20% 9% 14% 7% 3 3 2 3 4 14%	2772
January	1st to 10th	Night	14% 19% 8% 15% 9% 6% 4 3 3 4 15%	4429
	11th to 20th	Night	12% 16% 6% 16% 9% 6% 5% 5% 5% 5% 15%	4440
	21st to end	Night	10% 18% 10% 17% 7% 7% 6% 3 5% 5% 13%	4806
February	1st to 10th	Night	11% 14% 6% 12% 10% 8% 5% 4 5% 5% 20%	2470
	11th to 20th	Night	12% 17% 6% 13% 8% 7% 5% 4 5% 5% 20%	2403
	21st to end	Night	11% 17% 5% 11% 8% 6% 6% 3 5% 5% 21%	1939
March	1st to 10th	Night	17% 17% 4 8% 5% 4 5% 3 4 5% 27%	3670
	11th to 20th	Night	14% 19% 5% 13% 5% 5% 4 3 4 4 22%	3479
	21st to end	Night	12% 10% 4 11% 6% 5% 5% 4 5% 5% 32%	3640
April	1st to 10th	Night	19% 13% 5% 9% 5% 4 4 2 4 6% 29%	1900
	11th to 20th	Night	17% 11% 4 7% 4 4 4 3 5% 5% 36%	1875
	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% 5% 4 3 3 4 5% 20%	2557
November	1st to 10th	Night	18% 17% 5% 9% 6% 4 4 3 4 5% 25%	2492
	11th to 20th	Night	19% 16% 6% 12% 7% 6% 3 3 4 5% 19%	2660
	21st to end	Night	23% 20% 6% 13% 7% 4 4 2 4 4 13%	2660
December	1st to 10th	Night	19% 21% 7% 13% 8% 6% 4 4 3 4 13%	2660
	11th to 20th	Night	20% 19% 5% 12% 5% 5% 5% 3 4 5% 16%	3288
	21st to end	Night	19% 21% 7% 16% 7% 4 3 2 2 3 14%	4884

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	77% 1 9% 9% 4	2518
	11th to 20th	Day	72% 2 4 16% 6%	2520
	21st to end	Day	73% 2 5% 12% 7% 1	2846
February	1st to 10th	Day	69% 3 6% 14% 8% 1	1710
	11th to 20th	Day	67% 1 9% 11% 11% 1	1672
	21st to end	Day	66% 2 6% 16% 10% 1	1514
March	1st to 10th	Day	64% 2 6% 16% 12% 1	3170
	11th to 20th	Day	66% 1 7% 14% 10% 2	3480
	21st to end	Day	53% 1 6% 20% 17% 3	3992
April	1st to 10th	Day	61% 1 7% 15% 12% 2	2280
	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	56% 2 11% 21% 9% 1	1900
	11th to 20th	Day	70% 2 10% 14% 4 1	1900
	21st to end	Day	70% 2 9% 13% 5% 1	1865
November	1st to 10th	Day	62% 3 10% 18% 7%	1583
	11th to 20th	Day	72% 2 9% 12% 6%	1520
	21st to end	Day	79% 3 7% 8% 4	1520
December	1st to 10th	Day	78% 2 6% 10% 4	1520
	11th to 20th	Day	75% 3 3 12% 6%	1906
	21st to end	Day	76% 1 6% 13% 3	2772
January	1st to 10th	Night	75% 1 11% 10% 3	4429
	11th to 20th	Night	72% 1 8% 14% 4 1	4440
	21st to end	Night	74% 2 6% 11% 7%	4806
February	1st to 10th	Night	66% 2 7% 17% 8% 1	2470
	11th to 20th	Night	66% 2 7% 15% 9% 1	2405
	21st to end	Night	64% 2 7% 16% 10% 1	1939
March	1st to 10th	Night	62% 1 9% 14% 12% 3	3680
	11th to 20th	Night	66% 2 8% 15% 7% 1	3480
	21st to end	Night	55% 2 6% 20% 15% 3	3640
April	1st to 10th	Night	60% 1 6% 17% 14% 2	1900
	11th to 20th	Night	51% 2 6% 24% 14% 2	1875
	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% 21% 12% 1	2280
	11th to 20th	Night	64% 2 10% 19% 4 1	2280
	21st to end	Night	67% 2 10% 15% 5% 1	2557
November	1st to 10th	Night	62% 2 12% 18% 6%	2492
	11th to 20th	Night	68% 2 9% 14% 6%	2660
	21st to end	Night	76% 2 7% 11% 3	2660
December	1st to 10th	Night	76% 2 7% 10% 4	2660
	11th to 20th	Night	71% 2 6% 14% 7%	3288
	21st to end	Night	77% 1 4 12% 5%	4884

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	23% 21% 42% 12% 2 1	180
	11th to 20th	Day	25% 16% 39% 14% 4 2	180
	21st to end	Day	22% 18% 35% 19% 5%	221
February	1st to 10th	Day	29% 24% 37% 6% 4	270
	11th to 20th	Day	28% 27% 34% 11% 1	270
	21st to end	Day	34% 21% 35% 9% 1	326
March	1st to 10th	Day	28% 17% 35% 16% 4	460
	11th to 20th	Day	29% 18% 33% 15% 4	460
	21st to end	Day	30% 17% 36% 13% 4 1	506
April	1st to 10th	Day	35% 18% 25% 16% 5% 1	460
	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% 28% 18% 3 1	434
November	1st to 10th	Day	33% 15% 34% 13% 4 1	277
	11th to 20th	Day	28% 21% 34% 13% 3 1	180
	21st to end	Day	32% 23% 33% 8% 3 1	180
December	1st to 10th	Day	34% 14% 33% 15% 3 1	180
	11th to 20th	Day	33% 21% 34% 8% 3 1	180
	21st to end	Day	32% 15% 39% 10% 3 2	198
January	1st to 10th	Night	31% 14% 33% 19% 3	760
	11th to 20th	Night	31% 14% 30% 21% 5% 1	760
	21st to end	Night	18% 12% 36% 26% 7% 1	836
February	1st to 10th	Night	21% 16% 36% 21% 6% 1	760
	11th to 20th	Night	24% 16% 36% 20% 3 1	743
	21st to end	Night	25% 18% 30% 22% 4	628
March	1st to 10th	Night	24% 18% 32% 22% 4	760
	11th to 20th	Night	27% 17% 30% 19% 6% 1	760
	21st to end	Night	24% 14% 33% 21% 6%	836
April	1st to 10th	Night	29% 13% 30% 23% 5%	760
	11th to 20th	Night	27% 15% 28% 21% 9%	751
	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% 12% 29% 20% 4 1	805
November	1st to 10th	Night	30% 14% 30% 19% 5% 1	740
	11th to 20th	Night	31% 16% 31% 15% 7% 1	760
	21st to end	Night	36% 16% 24% 18% 5% 1	760
December	1st to 10th	Night	34% 15% 29% 17% 5% 1	760
	11th to 20th	Night	31% 14% 31% 18% 5% 1	760
	21st to end	Night	35% 15% 27% 19% 4 1	836

Page generated at 2024-10-21 02:20:04. Version ac07

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