Lac de la Montagne noire
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac de la Montagne noire clear sky chart from 2005-11-06 to 2024-11-12.

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 9% 6% 5% 5% 4 5% 6% 29%	101637
	Night	16% 12% 4 10% 6% 5% 4 3 5% 6% 29%	97554
Transparency	Day	54% 5% 12% 19% 9% 1	105087
	Night	54% 4 13% 19% 9% 1	102193
Seeing	Day	26% 17% 31% 18% 6% 2	14513
	Night	23% 15% 29% 23% 9% 1	23475

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	13% 17% 8% 17% 7% 5% 5% 4 4 4 17%	2517
	11th to 20th	Day	12% 15% 7% 18% 11% 7% 3 2 3 3 20%	2520
	21st to end	Day	10% 14% 9% 16% 6% 5% 6% 4 6% 5% 20%	2772
February	1st to 10th	Day	9% 20% 6% 11% 10% 6% 3 4 4 6% 22%	1674
	11th to 20th	Day	11% 17% 6% 13% 7% 5% 4 3 4 6% 24%	1723
	21st to end	Day	13% 19% 7% 11% 6% 4 5% 3 4 4 24%	1570
March	1st to 10th	Day	16% 18% 5% 11% 6% 6% 4 3 4 4 23%	3116
	11th to 20th	Day	10% 20% 7% 13% 7% 4 4 3 4 5% 24%	3334
	21st to end	Day	13% 12% 3 9% 5% 5% 4 3 5% 6% 35%	4129
April	1st to 10th	Day	18% 17% 4 9% 4 3 3 3 4 6% 28%	2280
	11th to 20th	Day	22% 10% 4 8% 5% 4 4 3 4 4 32%	2254
	21st to end	Day	20% 12% 4 9% 5% 5% 4 4 4 5% 29%	2440
May	1st to 10th	Day	20% 11% 3 8% 5% 5% 4 4 5% 6% 28%	4426
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 4 7% 8% 29%	4398
	21st to end	Day	18% 8% 3 8% 5% 5% 5% 4 5% 7% 33%	4837
June	1st to 10th	Day	23% 9% 3 8% 4 5% 6% 4 6% 6% 26%	2660
	11th to 20th	Day	17% 7% 3 8% 6% 5% 5% 4 6% 7% 31%	2660
	21st to end	Day	24% 9% 3 7% 7% 5% 5% 4 5% 6% 25%	2660
July	1st to 10th	Day	14% 8% 3 9% 7% 5% 6% 5% 7% 8% 29%	4440
	11th to 20th	Day	14% 7% 2 7% 6% 6% 5% 5% 7% 8% 33%	4440
	21st to end	Day	13% 7% 3 6% 5% 4 4 4 6% 7% 42%	4814
August	1st to 10th	Day	15% 7% 3 8% 7% 6% 6% 5% 7% 8% 28%	4423
	11th to 20th	Day	17% 8% 3 7% 5% 4 5% 5% 6% 7% 33%	4035
	21st to end	Day	15% 7% 3 7% 5% 5% 5% 4 7% 8% 35%	4180
September	1st to 10th	Day	17% 6% 3 7% 5% 4 5% 3 5% 7% 38%	2280
	11th to 20th	Day	15% 6% 3 6% 4 4 5% 3 5% 7% 42%	2223
	21st to end	Day	19% 9% 2 6% 4 4 4 3 5% 6% 37%	2090
October	1st to 10th	Day	23% 10% 3 7% 5% 4 4 4 6% 5% 31%	1924
	11th to 20th	Day	23% 13% 4 9% 5% 4 4 3 5% 5% 24%	1872
	21st to end	Day	24% 14% 4 9% 5% 3 5% 3 4 6% 24%	1881
November	1st to 10th	Day	17% 15% 4 9% 4 4 4 3 4 6% 30%	1761
	11th to 20th	Day	20% 16% 6% 10% 6% 4 3 4 5% 5% 21%	1586
	21st to end	Day	18% 19% 6% 12% 6% 5% 5% 3 3 4 20%	1520
December	1st to 10th	Day	20% 21% 6% 12% 6% 4 3 3 4 4 18%	1520
	11th to 20th	Day	18% 18% 6% 12% 6% 4 4 3 4 5% 19%	1906
	21st to end	Day	20% 20% 7% 11% 5% 4 3 3 4 5% 19%	2772
January	1st to 10th	Night	13% 18% 7% 14% 6% 5% 5% 4 5% 5% 19%	4429
	11th to 20th	Night	10% 13% 6% 16% 11% 8% 4 3 4 6% 18%	4440
	21st to end	Night	9% 14% 9% 18% 8% 6% 5% 3 5% 6% 17%	4884
February	1st to 10th	Night	11% 16% 5% 13% 8% 6% 5% 4 4 5% 23%	2504
	11th to 20th	Night	10% 14% 6% 14% 6% 6% 5% 4 5% 4 25%	2342
	21st to end	Night	12% 15% 5% 11% 6% 5% 5% 4 6% 6% 25%	1884
March	1st to 10th	Night	18% 15% 4 10% 5% 4 5% 3 4 5% 28%	3724
	11th to 20th	Night	12% 20% 7% 11% 5% 4 3 3 4 4 26%	3621
	21st to end	Night	12% 12% 4 10% 6% 5% 4 4 4 5% 34%	3503
April	1st to 10th	Night	21% 12% 4 8% 5% 4 4 3 5% 6% 29%	1900
	11th to 20th	Night	18% 9% 3 7% 4 3 5% 4 5% 6% 35%	1875
	21st to end	Night	19% 10% 3 8% 5% 4 4 3 5% 5% 33%	1756
May	1st to 10th	Night	18% 11% 4 8% 5% 5% 5% 4 4 6% 30%	2514
	11th to 20th	Night	20% 8% 3 7% 4 4 4 3 4 7% 37%	2495
	21st to end	Night	18% 7% 3 8% 6% 4 5% 4 6% 7% 32%	2738
June	1st to 10th	Night	18% 10% 3 7% 4 5% 5% 4 6% 8% 31%	1520
	11th to 20th	Night	18% 8% 2 6% 4 4 4 4 5% 7% 37%	1520
	21st to end	Night	21% 8% 2 6% 5% 4 5% 4 6% 6% 35%	1520
July	1st to 10th	Night	14% 8% 3 8% 7% 5% 6% 4 5% 7% 34%	2520
	11th to 20th	Night	15% 6% 3 7% 4 4 5% 4 6% 7% 38%	2520
	21st to end	Night	11% 5% 2 5% 4 4 4 4 7% 8% 46%	2739
August	1st to 10th	Night	12% 8% 3 8% 4 5% 4 4 6% 7% 38%	2506
	11th to 20th	Night	17% 8% 3 8% 3 4 5% 4 5% 6% 38%	2759
	21st to end	Night	18% 6% 3 6% 4 5% 5% 3 6% 6% 39%	3476
September	1st to 10th	Night	14% 7% 3 6% 3 4 4 3 5% 6% 45%	1900
	11th to 20th	Night	17% 6% 1 4 3 4 3 3 5% 7% 47%	1957
	21st to end	Night	18% 7% 2 5% 4 4 3 3 5% 7% 42%	2090
October	1st to 10th	Night	17% 10% 3 7% 5% 5% 4 3 5% 5% 37%	2252
	11th to 20th	Night	21% 12% 3 8% 4 5% 4 3 4 6% 30%	2308
	21st to end	Night	22% 13% 4 9% 6% 4 4 2 5% 7% 25%	2717
November	1st to 10th	Night	17% 13% 4 9% 5% 4 5% 3 6% 5% 27%	2537
	11th to 20th	Night	16% 14% 5% 11% 6% 5% 5% 4 6% 7% 22%	2612
	21st to end	Night	18% 19% 5% 10% 6% 4 4 3 5% 5% 20%	2660
December	1st to 10th	Night	17% 17% 7% 16% 7% 5% 3 3 4 5% 15%	2660
	11th to 20th	Night	19% 17% 5% 12% 7% 5% 4 3 4 5% 21%	3288
	21st to end	Night	20% 21% 6% 11% 6% 4 4 2 4 4 18%	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	69% 2 11% 14% 4	2518
	11th to 20th	Day	70% 2 5% 14% 7% 1	2520
	21st to end	Day	65% 4 11% 13% 6% 2	2772
February	1st to 10th	Day	64% 3 8% 17% 7% 2	1674
	11th to 20th	Day	62% 3 10% 14% 10% 1	1732
	21st to end	Day	64% 2 8% 14% 9% 3	1570
March	1st to 10th	Day	64% 4 6% 13% 11% 2	3119
	11th to 20th	Day	64% 3 9% 12% 9% 3	3334
	21st to end	Day	48% 5% 8% 20% 17% 2	4129
April	1st to 10th	Day	58% 3 8% 17% 11% 3	2280
	11th to 20th	Day	55% 4 8% 20% 11% 2	2254
	21st to end	Day	57% 3 8% 16% 11% 3	2440
May	1st to 10th	Day	55% 5% 8% 22% 9% 1	4440
	11th to 20th	Day	50% 6% 17% 17% 8% 1	4402
	21st to end	Day	51% 4 10% 20% 14% 1	4837
June	1st to 10th	Day	57% 6% 9% 18% 10% 1	2660
	11th to 20th	Day	50% 5% 12% 20% 10% 3	2660
	21st to end	Day	58% 6% 10% 17% 9%	2660
July	1st to 10th	Day	49% 8% 14% 22% 7%	4370
	11th to 20th	Day	44% 7% 19% 24% 6%	4365
	21st to end	Day	40% 6% 15% 30% 9%	4661
August	1st to 10th	Day	49% 7% 17% 21% 6%	4409
	11th to 20th	Day	47% 7% 17% 25% 5%	4077
	21st to end	Day	44% 7% 15% 22% 12% 1	4180
September	1st to 10th	Day	44% 5% 14% 25% 12%	2280
	11th to 20th	Day	41% 6% 14% 28% 10% 1	2223
	21st to end	Day	48% 5% 12% 24% 10%	2090
October	1st to 10th	Day	51% 5% 12% 26% 7% 1	3197
	11th to 20th	Day	52% 6% 13% 22% 7%	3088
	21st to end	Day	53% 4 20% 14% 8% 1	3081
November	1st to 10th	Day	56% 4 12% 20% 8% 1	1761
	11th to 20th	Day	65% 3 11% 14% 7% 1	1586
	21st to end	Day	68% 4 10% 13% 5% 1	1520
December	1st to 10th	Day	70% 3 10% 12% 5%	1520
	11th to 20th	Day	67% 3 10% 14% 6% 1	1906
	21st to end	Day	68% 2 8% 15% 7%	2772
January	1st to 10th	Night	66% 3 12% 14% 4	4429
	11th to 20th	Night	66% 3 13% 13% 4 2	4440
	21st to end	Night	67% 4 9% 11% 7% 1	4884
February	1st to 10th	Night	61% 4 9% 19% 6% 1	2504
	11th to 20th	Night	59% 3 11% 18% 8% 1	2344
	21st to end	Night	57% 3 10% 18% 10% 2	1884
March	1st to 10th	Night	59% 4 10% 13% 11% 3	3734
	11th to 20th	Night	61% 3 9% 14% 12% 1	3622
	21st to end	Night	51% 4 8% 21% 11% 4	3503
April	1st to 10th	Night	54% 3 9% 19% 12% 2	1900
	11th to 20th	Night	48% 4 11% 22% 13% 2	1875
	21st to end	Night	52% 5% 9% 20% 13% 2	1756
May	1st to 10th	Night	53% 6% 13% 19% 8% 2	2520
	11th to 20th	Night	46% 6% 16% 18% 12% 2	2496
	21st to end	Night	51% 5% 11% 19% 12% 2	2739
June	1st to 10th	Night	51% 4 13% 22% 9%	1520
	11th to 20th	Night	45% 4 13% 22% 12% 2	1520
	21st to end	Night	49% 6% 13% 20% 12% 1	1520
July	1st to 10th	Night	48% 6% 18% 19% 8%	2480
	11th to 20th	Night	42% 6% 21% 26% 5%	2472
	21st to end	Night	34% 7% 20% 27% 11%	2651
August	1st to 10th	Night	43% 7% 17% 27% 7%	2496
	11th to 20th	Night	45% 5% 22% 22% 6%	2783
	21st to end	Night	43% 6% 16% 22% 10% 2	3476
September	1st to 10th	Night	39% 4 16% 27% 13% 1	1900
	11th to 20th	Night	36% 5% 17% 32% 10% 1	1957
	21st to end	Night	42% 5% 15% 28% 11%	2090
October	1st to 10th	Night	47% 5% 14% 22% 11%	3759
	11th to 20th	Night	50% 5% 13% 24% 8%	3831
	21st to end	Night	51% 5% 18% 16% 9% 2	4467
November	1st to 10th	Night	56% 4 14% 19% 6% 1	2537
	11th to 20th	Night	59% 5% 11% 17% 7% 2	2612
	21st to end	Night	63% 4 12% 15% 5% 1	2660
December	1st to 10th	Night	72% 3 10% 11% 4	2660
	11th to 20th	Night	66% 3 8% 15% 7% 1	3288
	21st to end	Night	70% 3 7% 14% 6% 1	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	19% 21% 38% 18% 3	180
	11th to 20th	Day	29% 16% 36% 13% 5% 1	180
	21st to end	Day	21% 20% 39% 16% 4 1	198
February	1st to 10th	Day	32% 27% 33% 6% 2	254
	11th to 20th	Day	27% 25% 39% 7% 1	330
	21st to end	Day	31% 23% 32% 13% 2	382
March	1st to 10th	Day	27% 20% 32% 18% 3	460
	11th to 20th	Day	29% 20% 34% 13% 3 1	460
	21st to end	Day	33% 21% 27% 13% 5% 2	506
April	1st to 10th	Day	32% 17% 31% 13% 6% 1	460
	11th to 20th	Day	37% 17% 24% 14% 8% 1	452
	21st to end	Day	33% 19% 32% 11% 4 1	460
May	1st to 10th	Day	30% 19% 31% 15% 3 2	463
	11th to 20th	Day	24% 18% 30% 19% 7% 1	487
	21st to end	Day	27% 18% 31% 18% 5% 1	529
June	1st to 10th	Day	27% 14% 35% 17% 6% 1	490
	11th to 20th	Day	22% 18% 30% 19% 9% 2	490
	21st to end	Day	28% 14% 32% 18% 7% 1	490
July	1st to 10th	Day	17% 10% 39% 25% 7% 2	485
	11th to 20th	Day	18% 10% 39% 26% 6%	484
	21st to end	Day	17% 11% 34% 28% 8% 2	532
August	1st to 10th	Day	16% 13% 30% 28% 12% 1	486
	11th to 20th	Day	18% 9% 30% 26% 10% 6%	479
	21st to end	Day	19% 15% 31% 19% 10% 7%	539
September	1st to 10th	Day	19% 14% 31% 21% 10% 5%	490
	11th to 20th	Day	15% 13% 26% 24% 14% 7%	490
	21st to end	Day	24% 14% 26% 20% 11% 6%	490
October	1st to 10th	Day	29% 16% 25% 18% 9% 3	490
	11th to 20th	Day	34% 18% 25% 15% 6% 1	475
	21st to end	Day	36% 14% 29% 17% 4	429
November	1st to 10th	Day	35% 17% 28% 16% 4 1	395
	11th to 20th	Day	30% 22% 30% 12% 7%	240
	21st to end	Day	31% 26% 30% 11% 3	180
December	1st to 10th	Day	33% 16% 29% 17% 4 1	180
	11th to 20th	Day	28% 29% 31% 10% 2 1	180
	21st to end	Day	37% 22% 24% 11% 3 3	198
January	1st to 10th	Night	25% 22% 33% 15% 5%	760
	11th to 20th	Night	26% 19% 29% 20% 5%	760
	21st to end	Night	16% 16% 38% 22% 7% 1	836
February	1st to 10th	Night	19% 23% 34% 20% 4	760
	11th to 20th	Night	22% 21% 38% 16% 3	743
	21st to end	Night	24% 17% 34% 22% 3	628
March	1st to 10th	Night	27% 18% 32% 19% 4	760
	11th to 20th	Night	25% 20% 32% 17% 5% 1	760
	21st to end	Night	23% 16% 33% 21% 6% 1	836
April	1st to 10th	Night	30% 16% 27% 22% 5%	760
	11th to 20th	Night	26% 17% 29% 21% 6% 1	751
	21st to end	Night	28% 13% 31% 20% 7% 1	616
May	1st to 10th	Night	23% 12% 30% 24% 9% 2	380
	11th to 20th	Night	21% 14% 28% 28% 8% 1	374
	21st to end	Night	18% 13% 36% 24% 8%	411
June	1st to 10th	Night	22% 10% 31% 28% 9%	380
	11th to 20th	Night	21% 9% 26% 29% 13% 1	380
	21st to end	Night	23% 5% 22% 34% 15% 1	380
July	1st to 10th	Night	14% 5% 29% 35% 16%	370
	11th to 20th	Night	13% 5% 26% 38% 15% 1	368
	21st to end	Night	13% 6% 26% 38% 16% 1	416
August	1st to 10th	Night	13% 6% 19% 45% 16% 1	378
	11th to 20th	Night	13% 6% 23% 33% 24% 2	535
	21st to end	Night	18% 8% 27% 28% 16% 3	836
September	1st to 10th	Night	17% 8% 30% 31% 13% 1	760
	11th to 20th	Night	19% 7% 23% 29% 20% 2	760
	21st to end	Night	21% 12% 25% 24% 16% 2	760
October	1st to 10th	Night	23% 14% 24% 24% 14% 1	760
	11th to 20th	Night	28% 15% 28% 19% 9% 1	760
	21st to end	Night	28% 17% 28% 20% 6%	836
November	1st to 10th	Night	27% 18% 29% 19% 6% 1	780
	11th to 20th	Night	25% 19% 29% 17% 9% 1	765
	21st to end	Night	30% 21% 25% 17% 5% 1	760
December	1st to 10th	Night	29% 19% 27% 17% 7% 1	760
	11th to 20th	Night	29% 20% 28% 17% 5% 1	760
	21st to end	Night	33% 18% 27% 17% 5%	836

Page generated at 2024-11-08 22:45:35. Version ac07

Copyright © 2024 Attilla Danko.