La Sarre
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the La Sarre clear sky chart from 2005-11-06 to 2024-04-10.

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% 13% 5% 9% 7% 4 5% 5% 5% 6% 25%	82667
	Night	16% 14% 6% 10% 8% 4 5% 5% 5% 6% 22%	86139
Transparency	Day	59% 7% 10% 16% 7% 1	82357
	Night	63% 7% 10% 14% 6% 1	85984
Seeing	Day	22% 10% 29% 25% 11% 3	14344
	Night	23% 8% 29% 28% 10% 1	23527

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	14% 23% 9% 11% 6% 5% 8% 6% 5% 5% 8%	2208
	11th to 20th	Day	9% 14% 6% 15% 13% 5% 7% 7% 6% 6% 12%	2210
	21st to end	Day	11% 22% 10% 13% 9% 4 4 4 5% 5% 12%	2834
February	1st to 10th	Day	8% 13% 7% 10% 10% 6% 10% 6% 7% 6% 16%	1710
	11th to 20th	Day	10% 16% 8% 10% 10% 4 7% 6% 5% 7% 17%	1663
	21st to end	Day	10% 13% 6% 13% 7% 4 6% 6% 4 7% 23%	1413
March	1st to 10th	Day	18% 15% 5% 8% 6% 3 5% 5% 4 6% 25%	3321
	11th to 20th	Day	11% 17% 6% 14% 7% 3 4 3 3 4 26%	3480
	21st to end	Day	10% 14% 5% 12% 8% 5% 6% 5% 4 5% 25%	3836
April	1st to 10th	Day	18% 15% 6% 8% 6% 3 4 5% 5% 5% 24%	2270
	11th to 20th	Day	18% 10% 4 8% 6% 3 4 4 6% 5% 32%	2289
	21st to end	Day	19% 12% 4 8% 6% 3 4 4 4 5% 32%	2340
May	1st to 10th	Day	15% 11% 4 7% 7% 4 5% 6% 5% 7% 29%	2508
	11th to 20th	Day	22% 9% 4 6% 6% 2 5% 4 4 6% 31%	2478
	21st to end	Day	18% 9% 3 6% 6% 3 4 4 6% 7% 34%	2822
June	1st to 10th	Day	21% 8% 3 6% 7% 3 4 6% 6% 8% 29%	2700
	11th to 20th	Day	15% 8% 3 6% 6% 4 5% 5% 6% 8% 35%	2700
	21st to end	Day	19% 6% 3 6% 5% 3 5% 4 6% 8% 33%	2700
July	1st to 10th	Day	17% 7% 3 6% 6% 4 5% 5% 5% 8% 33%	2700
	11th to 20th	Day	14% 7% 4 6% 6% 4 7% 7% 6% 8% 32%	2700
	21st to end	Day	16% 8% 3 6% 7% 4 6% 6% 7% 8% 29%	2846
August	1st to 10th	Day	18% 9% 3 7% 7% 4 5% 6% 6% 8% 28%	2411
	11th to 20th	Day	17% 8% 3 7% 6% 3 5% 4 6% 7% 33%	2303
	21st to end	Day	15% 7% 3 7% 7% 4 5% 6% 6% 9% 31%	2538
September	1st to 10th	Day	20% 8% 3 6% 5% 3 5% 5% 5% 7% 33%	2160
	11th to 20th	Day	22% 9% 3 7% 6% 3 5% 5% 5% 7% 28%	2098
	21st to end	Day	21% 11% 5% 7% 6% 3 4 3 3 6% 30%	1920
October	1st to 10th	Day	24% 11% 2 7% 5% 3 4 5% 4 5% 30%	1800
	11th to 20th	Day	30% 18% 5% 7% 5% 3 3 4 4 5% 17%	1800
	21st to end	Day	27% 18% 6% 9% 6% 3 5% 4 4 5% 14%	1832
November	1st to 10th	Day	22% 17% 7% 9% 7% 3 5% 4 4 5% 16%	1486
	11th to 20th	Day	22% 17% 8% 13% 7% 4 4 5% 3 4 12%	1520
	21st to end	Day	22% 24% 9% 10% 8% 3 5% 3 3 3 10%	1520
December	1st to 10th	Day	17% 20% 8% 14% 9% 2 4 3 5% 5% 11%	1449
	11th to 20th	Day	15% 20% 6% 10% 8% 4 6% 6% 4 6% 16%	1671
	21st to end	Day	16% 22% 9% 17% 11% 3 4 3 3 3 9%	2431
January	1st to 10th	Night	13% 17% 8% 14% 11% 5% 6% 5% 5% 5% 12%	4748
	11th to 20th	Night	11% 16% 7% 14% 11% 6% 7% 7% 5% 5% 13%	4760
	21st to end	Night	10% 19% 11% 12% 9% 5% 6% 5% 5% 5% 13%	4821
February	1st to 10th	Night	9% 14% 6% 9% 10% 6% 9% 6% 7% 8% 17%	2470
	11th to 20th	Night	11% 16% 7% 12% 8% 4 7% 5% 5% 6% 19%	2403
	21st to end	Night	9% 16% 6% 12% 8% 5% 7% 6% 5% 6% 20%	2041
March	1st to 10th	Night	17% 13% 4 8% 7% 4 7% 4 5% 5% 27%	3517
	11th to 20th	Night	12% 17% 7% 12% 12% 5% 5% 4 4 5% 19%	3479
	21st to end	Night	13% 12% 6% 10% 7% 5% 5% 4 5% 6% 28%	3796
April	1st to 10th	Night	19% 13% 5% 10% 7% 2 4 3 4 5% 28%	1900
	11th to 20th	Night	17% 10% 4 9% 6% 4 6% 5% 5% 5% 31%	1635
	21st to end	Night	20% 10% 4 7% 5% 3 3 4 4 6% 33%	1620
May	1st to 10th	Night	14% 10% 3 6% 6% 4 5% 6% 4 6% 36%	1451
	11th to 20th	Night	18% 9% 2 5% 4 3 6% 5% 7% 7% 34%	1415
	21st to end	Night	17% 7% 3 6% 6% 3 5% 5% 6% 8% 34%	1450
June	1st to 10th	Night	21% 8% 3 7% 4 3 4 5% 5% 6% 33%	1260
	11th to 20th	Night	16% 7% 3 6% 6% 2 4 4 5% 8% 40%	1260
	21st to end	Night	17% 5% 3 6% 5% 3 6% 4 6% 8% 38%	1260
July	1st to 10th	Night	15% 6% 2 4 6% 3 5% 5% 6% 8% 37%	1260
	11th to 20th	Night	14% 6% 2 5% 5% 3 4 7% 7% 7% 38%	1260
	21st to end	Night	13% 6% 3 7% 6% 4 6% 5% 7% 8% 35%	1472
August	1st to 10th	Night	12% 9% 4 6% 6% 3 5% 5% 7% 8% 34%	1525
	11th to 20th	Night	12% 6% 3 6% 6% 3 5% 5% 6% 9% 40%	1598
	21st to end	Night	16% 8% 3 7% 6% 3 5% 5% 4 7% 35%	1799
September	1st to 10th	Night	19% 6% 4 7% 6% 3 4 5% 5% 6% 35%	1800
	11th to 20th	Night	20% 8% 3 6% 5% 3 4 4 5% 7% 36%	1858
	21st to end	Night	21% 9% 3 6% 6% 2 4 4 4 5% 36%	2039
October	1st to 10th	Night	21% 10% 3 7% 6% 3 5% 5% 5% 7% 30%	2160
	11th to 20th	Night	27% 17% 5% 9% 6% 4 4 3 3 4 18%	2160
	21st to end	Night	21% 20% 5% 9% 6% 4 5% 3 5% 5% 18%	2521
November	1st to 10th	Night	20% 17% 7% 10% 6% 3 5% 5% 4 5% 19%	2592
	11th to 20th	Night	20% 18% 7% 11% 8% 3 5% 5% 4 4 15%	2660
	21st to end	Night	21% 20% 8% 11% 9% 3 5% 4 4 4 13%	2660
December	1st to 10th	Night	15% 20% 7% 14% 11% 4 6% 5% 4 4 10%	2727
	11th to 20th	Night	17% 18% 8% 11% 10% 5% 6% 5% 4 5% 11%	3526
	21st to end	Night	19% 20% 10% 14% 10% 4 4 3 4 4 9%	5236

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% 7% 8% 7% 1	2209
	11th to 20th	Day	70% 7% 7% 12% 4	2210
	21st to end	Day	74% 5% 6% 11% 4	2834
February	1st to 10th	Day	65% 7% 8% 12% 7%	1710
	11th to 20th	Day	64% 7% 9% 14% 6%	1672
	21st to end	Day	62% 5% 9% 17% 6% 1	1413
March	1st to 10th	Day	60% 6% 8% 18% 7%	3324
	11th to 20th	Day	63% 4 8% 16% 8% 1	3480
	21st to end	Day	58% 6% 8% 17% 9% 2	3836
April	1st to 10th	Day	61% 5% 9% 15% 9% 1	2270
	11th to 20th	Day	53% 5% 11% 19% 11% 1	2289
	21st to end	Day	55% 6% 9% 14% 14% 2	2340
May	1st to 10th	Day	51% 8% 11% 18% 10% 2	2508
	11th to 20th	Day	53% 7% 8% 19% 12% 1	2482
	21st to end	Day	49% 8% 10% 20% 12% 1	2822
June	1st to 10th	Day	51% 6% 12% 20% 10% 1	2700
	11th to 20th	Day	46% 8% 10% 22% 13% 1	2700
	21st to end	Day	48% 8% 12% 22% 10% 1	2700
July	1st to 10th	Day	46% 8% 14% 23% 7%	2626
	11th to 20th	Day	45% 10% 17% 21% 8%	2619
	21st to end	Day	51% 11% 14% 20% 4	2688
August	1st to 10th	Day	52% 10% 16% 19% 3	2397
	11th to 20th	Day	50% 8% 16% 18% 7% 1	2303
	21st to end	Day	47% 9% 16% 21% 6%	2538
September	1st to 10th	Day	49% 8% 15% 20% 8%	2160
	11th to 20th	Day	54% 9% 14% 17% 4	2098
	21st to end	Day	58% 6% 10% 20% 6%	1920
October	1st to 10th	Day	56% 6% 13% 17% 8%	1800
	11th to 20th	Day	71% 6% 9% 10% 3	1800
	21st to end	Day	74% 7% 7% 9% 2	1832
November	1st to 10th	Day	72% 7% 10% 7% 4	1486
	11th to 20th	Day	77% 6% 8% 8% 2	1520
	21st to end	Day	82% 5% 7% 5% 1	1520
December	1st to 10th	Day	76% 5% 7% 9% 2	1449
	11th to 20th	Day	69% 7% 6% 14% 3	1671
	21st to end	Day	82% 4 6% 6% 1	2431
January	1st to 10th	Night	75% 7% 10% 7% 1	4748
	11th to 20th	Night	70% 7% 8% 12% 3	4760
	21st to end	Night	73% 5% 6% 11% 5%	4821
February	1st to 10th	Night	64% 6% 10% 11% 8%	2470
	11th to 20th	Night	65% 6% 9% 14% 6%	2405
	21st to end	Night	65% 5% 8% 15% 7% 1	2041
March	1st to 10th	Night	59% 6% 9% 14% 11% 2	3527
	11th to 20th	Night	67% 6% 8% 12% 5% 1	3480
	21st to end	Night	56% 7% 8% 14% 13% 2	3796
April	1st to 10th	Night	60% 4 7% 16% 13% 1	1900
	11th to 20th	Night	54% 6% 8% 18% 12% 1	1635
	21st to end	Night	52% 5% 8% 16% 16% 3	1620
May	1st to 10th	Night	48% 7% 10% 19% 13% 3	1451
	11th to 20th	Night	48% 7% 8% 20% 16% 1	1416
	21st to end	Night	47% 8% 10% 19% 15% 1	1451
June	1st to 10th	Night	51% 7% 9% 20% 12% 1	1260
	11th to 20th	Night	43% 6% 9% 22% 17% 2	1260
	21st to end	Night	44% 7% 12% 25% 10% 1	1260
July	1st to 10th	Night	41% 9% 13% 25% 11%	1225
	11th to 20th	Night	40% 9% 17% 23% 10%	1218
	21st to end	Night	46% 11% 15% 24% 4	1390
August	1st to 10th	Night	47% 9% 17% 24% 4	1515
	11th to 20th	Night	39% 9% 19% 25% 7% 1	1598
	21st to end	Night	48% 9% 15% 21% 7%	1799
September	1st to 10th	Night	48% 9% 14% 21% 8%	1800
	11th to 20th	Night	50% 7% 18% 20% 6%	1858
	21st to end	Night	50% 6% 14% 23% 6%	2039
October	1st to 10th	Night	55% 8% 13% 17% 7% 1	2160
	11th to 20th	Night	72% 5% 9% 11% 2	2160
	21st to end	Night	70% 6% 11% 8% 5%	2521
November	1st to 10th	Night	68% 7% 11% 11% 2	2592
	11th to 20th	Night	73% 7% 9% 8% 3	2660
	21st to end	Night	77% 7% 8% 7% 1	2660
December	1st to 10th	Night	79% 5% 7% 7% 2	2727
	11th to 20th	Night	75% 5% 7% 10% 3	3525
	21st to end	Night	80% 5% 6% 6% 3	5236

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	24% 13% 36% 19% 7% 1	180
	11th to 20th	Day	16% 11% 34% 26% 10% 3	180
	21st to end	Day	18% 5% 29% 35% 12% 1	251
February	1st to 10th	Day	13% 16% 40% 23% 6% 1	270
	11th to 20th	Day	14% 11% 39% 29% 5% 2	270
	21st to end	Day	20% 16% 40% 20% 4	225
March	1st to 10th	Day	17% 11% 36% 26% 10%	431
	11th to 20th	Day	19% 12% 35% 25% 8% 2	460
	21st to end	Day	21% 12% 32% 25% 9% 1	506
April	1st to 10th	Day	22% 10% 32% 23% 10% 4	457
	11th to 20th	Day	20% 11% 30% 27% 11% 2	412
	21st to end	Day	24% 9% 27% 26% 12% 2	420
May	1st to 10th	Day	22% 5% 31% 25% 16% 2	423
	11th to 20th	Day	24% 9% 29% 23% 12% 4	447
	21st to end	Day	21% 10% 28% 27% 12% 1	582
June	1st to 10th	Day	23% 9% 27% 27% 12% 2	630
	11th to 20th	Day	19% 11% 31% 24% 13% 2	630
	21st to end	Day	19% 8% 23% 30% 17% 3	630
July	1st to 10th	Day	18% 8% 29% 29% 12% 3	621
	11th to 20th	Day	17% 9% 28% 29% 16% 2	618
	21st to end	Day	17% 6% 25% 33% 15% 5%	590
August	1st to 10th	Day	22% 8% 21% 28% 15% 7%	446
	11th to 20th	Day	18% 5% 22% 29% 18% 9%	439
	21st to end	Day	22% 9% 23% 23% 15% 8%	495
September	1st to 10th	Day	22% 10% 26% 25% 11% 7%	450
	11th to 20th	Day	25% 9% 24% 28% 12% 2	450
	21st to end	Day	25% 12% 25% 23% 11% 4	450
October	1st to 10th	Day	28% 12% 24% 24% 9% 3	450
	11th to 20th	Day	36% 14% 29% 16% 4 1	450
	21st to end	Day	32% 13% 29% 19% 5% 1	383
November	1st to 10th	Day	33% 19% 29% 16% 3	180
	11th to 20th	Day	26% 19% 29% 19% 6% 1	180
	21st to end	Day	38% 13% 34% 10% 3 2	180
December	1st to 10th	Day	24% 13% 28% 21% 11% 3	180
	11th to 20th	Day	17% 17% 38% 18% 9% 1	180
	21st to end	Day	28% 10% 34% 16% 8% 4	198
January	1st to 10th	Night	23% 7% 32% 27% 9% 1	950
	11th to 20th	Night	24% 6% 31% 30% 7% 1	950
	21st to end	Night	16% 7% 26% 33% 16% 2	913
February	1st to 10th	Night	15% 9% 32% 33% 10% 1	760
	11th to 20th	Night	19% 9% 31% 31% 10% 1	743
	21st to end	Night	18% 10% 37% 26% 8% 1	628
March	1st to 10th	Night	17% 9% 33% 31% 9% 1	760
	11th to 20th	Night	22% 11% 30% 30% 7% 1	760
	21st to end	Night	18% 8% 33% 31% 9% 1	836
April	1st to 10th	Night	25% 11% 29% 26% 8% 1	760
	11th to 20th	Night	21% 9% 28% 30% 11% 1	571
	21st to end	Night	24% 8% 28% 29% 10% 1	540
May	1st to 10th	Night	20% 5% 29% 34% 11% 1	371
	11th to 20th	Night	23% 7% 29% 32% 8% 1	354
	21st to end	Night	20% 5% 33% 34% 8%	389
June	1st to 10th	Night	23% 6% 29% 30% 11% 1	360
	11th to 20th	Night	17% 9% 30% 33% 10% 1	360
	21st to end	Night	18% 4 25% 36% 15% 1	360
July	1st to 10th	Night	18% 6% 25% 37% 13% 1	350
	11th to 20th	Night	17% 3 22% 43% 15%	348
	21st to end	Night	16% 3 21% 38% 20% 2	394
August	1st to 10th	Night	17% 5% 25% 31% 21% 2	451
	11th to 20th	Night	16% 4 23% 36% 20% 2	534
	21st to end	Night	21% 6% 25% 29% 17% 2	611
September	1st to 10th	Night	22% 6% 25% 31% 15% 1	720
	11th to 20th	Night	26% 7% 26% 28% 12% 2	720
	21st to end	Night	26% 7% 23% 30% 12% 2	720
October	1st to 10th	Night	25% 9% 27% 29% 9% 1	720
	11th to 20th	Night	36% 10% 28% 18% 7% 1	720
	21st to end	Night	32% 13% 26% 22% 6% 1	792
November	1st to 10th	Night	29% 10% 34% 21% 5% 1	740
	11th to 20th	Night	29% 13% 30% 20% 8%	760
	21st to end	Night	32% 10% 34% 20% 4 1	760
December	1st to 10th	Night	27% 10% 29% 25% 8% 1	827
	11th to 20th	Night	25% 9% 30% 25% 9% 1	950
	21st to end	Night	28% 10% 26% 24% 9% 3	1045

Page generated at 2024-04-07 09:28:14. Version ac07

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