Lac des Piles
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac des Piles clear sky chart from 2005-11-06 to 2024-11-01.

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% 10% 3 8% 5% 5% 5% 4 5% 7% 31%	101292
	Night	17% 11% 4 8% 5% 4 5% 3 5% 6% 32%	97653
Transparency	Day	52% 5% 14% 20% 9% 1	101053
	Night	53% 4 12% 20% 9% 1	97513
Seeing	Day	24% 13% 31% 21% 9% 2	14517
	Night	24% 9% 29% 28% 9% 1	23482

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% 15% 5% 10% 6% 5% 4 4 5% 6% 25%	2517
	11th to 20th	Day	12% 14% 6% 13% 7% 5% 5% 3 4 4 27%	2520
	21st to end	Day	12% 13% 5% 12% 6% 5% 5% 4 6% 8% 25%	2772
February	1st to 10th	Day	13% 17% 6% 12% 7% 5% 4 2 3 5% 26%	1586
	11th to 20th	Day	12% 16% 5% 11% 6% 5% 5% 3 5% 6% 27%	1778
	21st to end	Day	16% 16% 5% 10% 7% 4 5% 3 3 5% 27%	1570
March	1st to 10th	Day	20% 13% 4 9% 6% 4 5% 3 4 4 28%	3116
	11th to 20th	Day	12% 18% 4 11% 6% 5% 4 3 5% 5% 27%	3246
	21st to end	Day	13% 13% 4 8% 6% 5% 4 3 4 5% 36%	4166
April	1st to 10th	Day	22% 13% 4 8% 4 4 4 3 4 5% 30%	2280
	11th to 20th	Day	21% 7% 2 7% 5% 4 4 4 4 6% 36%	2281
	21st to end	Day	21% 12% 3 7% 4 5% 4 3 5% 6% 30%	2470
May	1st to 10th	Day	22% 8% 2 7% 5% 4 4 3 5% 6% 34%	4348
	11th to 20th	Day	17% 6% 2 7% 5% 5% 5% 4 6% 9% 33%	4398
	21st to end	Day	17% 7% 3 8% 5% 5% 6% 4 6% 7% 31%	4837
June	1st to 10th	Day	20% 8% 3 8% 6% 5% 5% 4 6% 7% 27%	2660
	11th to 20th	Day	17% 7% 2 7% 5% 5% 5% 4 6% 7% 33%	2660
	21st to end	Day	23% 10% 3 8% 6% 5% 4 4 5% 6% 27%	2660
July	1st to 10th	Day	14% 7% 2 8% 6% 6% 6% 5% 7% 9% 31%	4440
	11th to 20th	Day	15% 6% 2 7% 5% 6% 6% 5% 8% 9% 31%	4440
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 5% 6% 7% 41%	4814
August	1st to 10th	Day	14% 6% 2 7% 6% 6% 7% 5% 8% 10% 29%	4423
	11th to 20th	Day	19% 7% 2 6% 5% 4 5% 5% 7% 8% 31%	4121
	21st to end	Day	18% 6% 3 6% 4 5% 5% 4 5% 8% 37%	4181
September	1st to 10th	Day	16% 5% 2 6% 4 4 5% 4 7% 7% 41%	2280
	11th to 20th	Day	15% 6% 2 5% 4 4 4 3 5% 7% 45%	2167
	21st to end	Day	21% 7% 3 6% 3 3 3 3 4 7% 39%	2090
October	1st to 10th	Day	21% 8% 2 7% 4 4 5% 3 4 7% 34%	2005
	11th to 20th	Day	22% 10% 2 8% 6% 6% 4 5% 5% 6% 26%	1801
	21st to end	Day	26% 11% 3 8% 3 4 4 3 5% 6% 27%	1881
November	1st to 10th	Day	17% 12% 4 8% 5% 5% 5% 3 4 5% 33%	1671
	11th to 20th	Day	21% 13% 4 8% 6% 4 4 3 4 6% 27%	1639
	21st to end	Day	21% 15% 4 7% 6% 4 4 3 5% 5% 26%	1520
December	1st to 10th	Day	23% 16% 4 9% 5% 4 5% 3 3 5% 23%	1398
	11th to 20th	Day	22% 15% 5% 9% 4 4 4 3 5% 5% 26%	1784
	21st to end	Day	21% 18% 6% 10% 5% 4 4 3 4 5% 23%	2772
January	1st to 10th	Night	15% 17% 5% 10% 6% 4 4 4 4 5% 24%	4429
	11th to 20th	Night	11% 16% 6% 10% 7% 5% 5% 3 4 6% 28%	4440
	21st to end	Night	12% 13% 5% 13% 7% 6% 6% 3 5% 5% 25%	4884
February	1st to 10th	Night	12% 15% 4 10% 6% 5% 5% 4 5% 5% 29%	2591
	11th to 20th	Night	12% 14% 5% 12% 6% 5% 5% 3 4 6% 28%	2287
	21st to end	Night	15% 12% 4 9% 6% 5% 5% 3 4 5% 31%	1884
March	1st to 10th	Night	22% 13% 4 9% 5% 4 4 3 4 5% 27%	3724
	11th to 20th	Night	16% 19% 5% 9% 5% 4 4 3 4 4 26%	3709
	21st to end	Night	13% 10% 4 9% 6% 6% 5% 4 5% 5% 34%	3466
April	1st to 10th	Night	22% 11% 3 7% 4 4 3 4 5% 6% 31%	1900
	11th to 20th	Night	20% 9% 3 7% 4 4 4 3 5% 6% 37%	1847
	21st to end	Night	23% 9% 3 7% 4 3 4 3 4 5% 35%	1710
May	1st to 10th	Night	21% 9% 3 7% 5% 4 5% 4 5% 6% 32%	2622
	11th to 20th	Night	21% 6% 2 5% 3 4 6% 4 5% 8% 36%	2495
	21st to end	Night	18% 6% 2 7% 6% 6% 5% 3 6% 9% 32%	2738
June	1st to 10th	Night	20% 6% 2 7% 4 4 5% 3 6% 8% 34%	1520
	11th to 20th	Night	19% 7% 2 6% 5% 4 4 4 6% 8% 35%	1520
	21st to end	Night	20% 8% 3 7% 5% 4 5% 4 6% 7% 32%	1520
July	1st to 10th	Night	14% 6% 2 8% 6% 6% 6% 4 7% 8% 33%	2520
	11th to 20th	Night	16% 5% 2 6% 5% 4 5% 4 6% 7% 39%	2520
	21st to end	Night	12% 4 1 5% 4 4 5% 4 6% 8% 46%	2739
August	1st to 10th	Night	14% 5% 3 7% 5% 5% 5% 4 7% 8% 37%	2506
	11th to 20th	Night	17% 7% 3 7% 4 4 4 3 6% 7% 38%	2674
	21st to end	Night	17% 7% 3 8% 4 4 4 3 4 6% 39%	3471
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 5% 7% 45%	1900
	11th to 20th	Night	15% 5% 2 4 4 3 3 3 5% 7% 49%	2012
	21st to end	Night	18% 6% 2 5% 4 3 4 3 4 5% 45%	2090
October	1st to 10th	Night	18% 8% 3 7% 5% 3 4 3 5% 5% 40%	2172
	11th to 20th	Night	22% 8% 3 7% 5% 4 4 3 5% 6% 34%	2378
	21st to end	Night	24% 9% 3 7% 4 4 4 3 4 7% 31%	2717
November	1st to 10th	Night	18% 10% 3 8% 5% 4 4 4 5% 5% 33%	2414
	11th to 20th	Night	20% 10% 3 8% 6% 5% 5% 3 5% 6% 30%	2537
	21st to end	Night	22% 15% 4 7% 5% 4 4 3 5% 5% 28%	2660
December	1st to 10th	Night	21% 14% 5% 9% 6% 4 5% 3 4 6% 22%	2774
	11th to 20th	Night	22% 14% 5% 10% 6% 4 4 3 4 4 25%	3399
	21st to end	Night	22% 19% 6% 9% 4 3 3 3 3 4 24%	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	58% 3 15% 18% 5%	2518
	11th to 20th	Day	61% 3 10% 19% 6%	2520
	21st to end	Day	58% 3 12% 20% 6% 1	2772
February	1st to 10th	Day	62% 2 9% 17% 8% 2	1586
	11th to 20th	Day	58% 3 13% 14% 11% 1	1787
	21st to end	Day	61% 3 9% 16% 9% 3	1570
March	1st to 10th	Day	60% 2 11% 15% 10% 2	3119
	11th to 20th	Day	58% 4 11% 15% 10% 2	3246
	21st to end	Day	49% 5% 8% 20% 15% 4	4166
April	1st to 10th	Day	57% 3 10% 15% 12% 3	2280
	11th to 20th	Day	50% 3 10% 22% 12% 3	2281
	21st to end	Day	55% 4 9% 17% 13% 3	2470
May	1st to 10th	Day	51% 3 12% 19% 14% 2	4362
	11th to 20th	Day	46% 5% 20% 20% 9% 1	4402
	21st to end	Day	49% 5% 12% 17% 16% 2	4837
June	1st to 10th	Day	54% 5% 11% 19% 9% 2	2660
	11th to 20th	Day	46% 5% 14% 22% 11% 2	2660
	21st to end	Day	57% 5% 11% 16% 10% 1	2660
July	1st to 10th	Day	46% 7% 15% 23% 8%	4370
	11th to 20th	Day	45% 9% 19% 21% 6%	4365
	21st to end	Day	40% 6% 17% 27% 9%	4661
August	1st to 10th	Day	45% 8% 19% 20% 6%	4409
	11th to 20th	Day	47% 7% 20% 21% 6%	4162
	21st to end	Day	44% 6% 16% 20% 14% 1	4181
September	1st to 10th	Day	40% 4 18% 26% 11% 1	2280
	11th to 20th	Day	38% 4 17% 29% 10% 1	2167
	21st to end	Day	46% 4 13% 27% 10%	2090
October	1st to 10th	Day	51% 3 12% 24% 9%	2005
	11th to 20th	Day	57% 6% 13% 20% 3	1801
	21st to end	Day	58% 4 13% 17% 8% 1	1881
November	1st to 10th	Day	53% 4 14% 19% 9% 1	1671
	11th to 20th	Day	58% 3 11% 18% 9%	1639
	21st to end	Day	61% 5% 12% 16% 6%	1520
December	1st to 10th	Day	65% 3 9% 18% 5%	1398
	11th to 20th	Day	61% 3 9% 19% 8%	1785
	21st to end	Day	66% 3 9% 13% 8% 1	2772
January	1st to 10th	Night	62% 4 14% 14% 6%	4429
	11th to 20th	Night	59% 4 12% 19% 5% 1	4440
	21st to end	Night	61% 3 12% 14% 8% 1	4884
February	1st to 10th	Night	58% 3 10% 18% 10% 1	2591
	11th to 20th	Night	58% 4 9% 18% 10% 1	2289
	21st to end	Night	55% 4 8% 18% 14% 2	1884
March	1st to 10th	Night	61% 3 11% 14% 8% 3	3734
	11th to 20th	Night	61% 4 8% 16% 10% 2	3710
	21st to end	Night	51% 5% 8% 21% 12% 3	3466
April	1st to 10th	Night	54% 3 9% 16% 15% 2	1900
	11th to 20th	Night	48% 4 9% 23% 14% 2	1847
	21st to end	Night	51% 4 8% 19% 15% 3	1710
May	1st to 10th	Night	53% 4 13% 19% 9% 2	2628
	11th to 20th	Night	46% 4 16% 20% 12% 2	2496
	21st to end	Night	49% 4 13% 17% 15% 1	2739
June	1st to 10th	Night	47% 5% 14% 22% 12% 1	1520
	11th to 20th	Night	46% 5% 13% 20% 13% 4	1520
	21st to end	Night	50% 5% 13% 18% 13%	1520
July	1st to 10th	Night	45% 7% 19% 19% 9%	2480
	11th to 20th	Night	42% 6% 20% 25% 6%	2472
	21st to end	Night	36% 5% 20% 27% 11%	2651
August	1st to 10th	Night	44% 7% 17% 24% 8%	2496
	11th to 20th	Night	45% 6% 19% 22% 7%	2699
	21st to end	Night	45% 6% 13% 24% 12%	3471
September	1st to 10th	Night	38% 5% 17% 27% 12% 1	1900
	11th to 20th	Night	36% 3 18% 32% 10% 1	2012
	21st to end	Night	42% 4 11% 31% 12%	2090
October	1st to 10th	Night	47% 4 10% 26% 13%	2172
	11th to 20th	Night	51% 4 14% 24% 7%	2378
	21st to end	Night	53% 5% 13% 19% 9% 1	2717
November	1st to 10th	Night	52% 5% 13% 21% 8% 1	2414
	11th to 20th	Night	55% 4 12% 18% 9% 1	2537
	21st to end	Night	59% 4 11% 17% 8%	2660
December	1st to 10th	Night	65% 3 11% 16% 5%	2774
	11th to 20th	Night	62% 4 8% 18% 8%	3399
	21st to end	Night	66% 3 8% 17% 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	26% 13% 37% 17% 6% 1	180
	11th to 20th	Day	29% 11% 38% 16% 6% 1	180
	21st to end	Day	18% 13% 39% 21% 9% 1	198
February	1st to 10th	Day	28% 22% 36% 11% 2	211
	11th to 20th	Day	24% 19% 37% 18% 2	386
	21st to end	Day	27% 16% 36% 17% 4	382
March	1st to 10th	Day	23% 16% 34% 21% 6%	460
	11th to 20th	Day	24% 19% 33% 17% 5% 1	460
	21st to end	Day	26% 20% 28% 17% 7% 2	506
April	1st to 10th	Day	31% 13% 28% 21% 7% 1	460
	11th to 20th	Day	27% 17% 30% 18% 5% 3	452
	21st to end	Day	31% 13% 38% 13% 4 2	460
May	1st to 10th	Day	28% 13% 34% 17% 6% 1	463
	11th to 20th	Day	22% 14% 30% 25% 8% 2	487
	21st to end	Day	23% 15% 36% 17% 8% 1	529
June	1st to 10th	Day	22% 12% 36% 20% 7% 2	490
	11th to 20th	Day	20% 13% 32% 21% 11% 1	490
	21st to end	Day	27% 12% 29% 22% 10% 2	490
July	1st to 10th	Day	16% 9% 33% 28% 12% 2	485
	11th to 20th	Day	17% 9% 31% 32% 9% 2	484
	21st to end	Day	15% 8% 30% 28% 16% 3	532
August	1st to 10th	Day	16% 7% 27% 31% 16% 3	486
	11th to 20th	Day	17% 5% 24% 33% 16% 5%	479
	21st to end	Day	17% 11% 28% 22% 16% 6%	539
September	1st to 10th	Day	18% 10% 33% 22% 12% 5%	490
	11th to 20th	Day	18% 9% 24% 26% 16% 7%	490
	21st to end	Day	24% 11% 26% 21% 12% 6%	490
October	1st to 10th	Day	25% 12% 29% 20% 12% 2	490
	11th to 20th	Day	27% 12% 32% 18% 10% 1	437
	21st to end	Day	33% 11% 30% 20% 7%	429
November	1st to 10th	Day	28% 12% 32% 20% 7% 1	365
	11th to 20th	Day	29% 12% 30% 22% 6%	299
	21st to end	Day	28% 18% 32% 18% 3 2	180
December	1st to 10th	Day	35% 11% 31% 15% 7% 1	180
	11th to 20th	Day	29% 16% 35% 17% 2 1	180
	21st to end	Day	34% 17% 27% 17% 5% 1	198
January	1st to 10th	Night	29% 9% 33% 24% 4	760
	11th to 20th	Night	28% 12% 32% 22% 6%	760
	21st to end	Night	18% 9% 34% 33% 6% 1	836
February	1st to 10th	Night	20% 10% 37% 28% 5% 1	760
	11th to 20th	Night	21% 14% 38% 23% 5%	743
	21st to end	Night	23% 11% 32% 27% 6%	628
March	1st to 10th	Night	24% 11% 32% 29% 4	760
	11th to 20th	Night	24% 13% 34% 23% 5% 1	760
	21st to end	Night	23% 13% 32% 24% 7% 1	836
April	1st to 10th	Night	30% 11% 28% 24% 7%	760
	11th to 20th	Night	27% 12% 29% 26% 5%	723
	21st to end	Night	28% 14% 31% 23% 5%	570
May	1st to 10th	Night	27% 12% 28% 27% 6% 1	449
	11th to 20th	Night	24% 8% 29% 30% 8%	374
	21st to end	Night	22% 6% 36% 26% 9%	411
June	1st to 10th	Night	24% 4 27% 36% 8%	380
	11th to 20th	Night	22% 5% 23% 38% 10% 1	380
	21st to end	Night	23% 4 24% 35% 13%	380
July	1st to 10th	Night	15% 5% 28% 36% 16%	370
	11th to 20th	Night	15% 3 24% 40% 17% 1	368
	21st to end	Night	16% 5% 23% 40% 16% 1	416
August	1st to 10th	Night	13% 4 17% 47% 18% 1	378
	11th to 20th	Night	17% 4 21% 36% 20% 2	490
	21st to end	Night	19% 6% 25% 31% 19% 1	831
September	1st to 10th	Night	17% 4 28% 36% 13% 1	760
	11th to 20th	Night	17% 7% 24% 31% 20% 2	760
	21st to end	Night	22% 6% 27% 27% 15% 2	760
October	1st to 10th	Night	22% 9% 28% 30% 10%	760
	11th to 20th	Night	26% 9% 28% 26% 10% 1	760
	21st to end	Night	31% 8% 32% 22% 6%	836
November	1st to 10th	Night	26% 10% 31% 26% 7% 1	743
	11th to 20th	Night	27% 10% 30% 23% 10% 1	760
	21st to end	Night	31% 13% 24% 26% 5% 1	760
December	1st to 10th	Night	30% 8% 29% 24% 8%	814
	11th to 20th	Night	28% 12% 32% 22% 6% 1	810
	21st to end	Night	34% 10% 29% 22% 5%	836

Page generated at 2024-10-29 11:20:50. Version ac07

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