Observatoire de Labelle Etoile
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de Labelle Etoile clear sky chart from 2005-11-06 to 2024-06-17.

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	18% 13% 4 9% 6% 4 4 3 5% 6% 28%	89338
	Night	18% 14% 5% 10% 5% 4 4 3 4 5% 27%	89527
Transparency	Day	58% 4 11% 17% 9% 1	89057
	Night	59% 4 12% 17% 8% 1	89362
Seeing	Day	26% 17% 28% 18% 8% 2	13911
	Night	25% 13% 26% 25% 10% 1	22994

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	17% 20% 7% 19% 9% 5% 3 2 2 3 13%	2517
	11th to 20th	Day	13% 16% 7% 23% 8% 3 2 2 3 4 18%	2520
	21st to end	Day	12% 17% 8% 14% 7% 6% 6% 3 5% 4 18%	2772
February	1st to 10th	Day	10% 20% 7% 14% 9% 5% 4 3 4 4 20%	1695
	11th to 20th	Day	12% 20% 6% 12% 7% 5% 4 3 4 5% 23%	1698
	21st to end	Day	16% 19% 5% 10% 8% 5% 5% 4 4 4 22%	1570
March	1st to 10th	Day	16% 17% 5% 11% 6% 4 4 3 4 4 24%	3116
	11th to 20th	Day	13% 20% 7% 12% 6% 4 4 3 4 4 23%	3374
	21st to end	Day	13% 10% 4 10% 7% 4 4 3 5% 6% 35%	4097
April	1st to 10th	Day	21% 17% 4 8% 5% 3 3 2 4 4 29%	2280
	11th to 20th	Day	21% 14% 4 7% 4 4 3 3 4 4 32%	2254
	21st to end	Day	20% 13% 4 8% 5% 4 4 3 4 4 30%	2451
May	1st to 10th	Day	21% 11% 3 8% 5% 5% 4 4 5% 6% 28%	4426
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 4 6% 7% 32%	4398
	21st to end	Day	19% 8% 3 8% 5% 5% 5% 4 5% 6% 34%	4837
June	1st to 10th	Day	24% 10% 3 6% 5% 5% 4 4 6% 6% 27%	2660
	11th to 20th	Day	17% 6% 3 7% 5% 6% 6% 5% 5% 7% 33%	2607
	21st to end	Day	22% 8% 3 7% 5% 5% 5% 4 7% 6% 28%	2520
July	1st to 10th	Day	16% 7% 3 6% 6% 4 5% 4 6% 9% 34%	2520
	11th to 20th	Day	15% 7% 2 7% 5% 5% 5% 5% 7% 9% 32%	2520
	21st to end	Day	15% 8% 2 7% 5% 5% 6% 5% 6% 8% 33%	2744
August	1st to 10th	Day	17% 9% 3 8% 5% 5% 6% 5% 6% 8% 28%	2506
	11th to 20th	Day	16% 7% 2 7% 5% 6% 5% 4 6% 7% 35%	2307
	21st to end	Day	16% 7% 3 7% 4 5% 5% 5% 6% 8% 35%	2376
September	1st to 10th	Day	19% 6% 2 6% 5% 4 5% 4 4 7% 39%	2160
	11th to 20th	Day	18% 8% 3 6% 4 4 4 4 6% 7% 38%	2124
	21st to end	Day	23% 7% 2 6% 4 3 3 4 4 7% 37%	1976
October	1st to 10th	Day	24% 9% 3 6% 5% 4 5% 3 4 7% 30%	1800
	11th to 20th	Day	27% 16% 4 7% 4 4 4 2 4 5% 24%	1793
	21st to end	Day	28% 17% 3 7% 4 4 4 3 4 5% 22%	1782
November	1st to 10th	Day	17% 17% 3 8% 3 3 4 3 4 7% 29%	1671
	11th to 20th	Day	21% 18% 7% 11% 6% 3 4 3 4 4 19%	1549
	21st to end	Day	22% 18% 6% 12% 6% 5% 3 3 3 4 18%	1520
December	1st to 10th	Day	22% 22% 5% 11% 6% 5% 4 2 3 5% 15%	1520
	11th to 20th	Day	20% 18% 7% 14% 5% 4 4 3 5% 4 16%	1906
	21st to end	Day	22% 20% 6% 12% 5% 4 4 3 4 4 16%	2772
January	1st to 10th	Night	15% 22% 8% 13% 6% 4 3 3 3 5% 18%	4429
	11th to 20th	Night	13% 16% 6% 17% 11% 5% 5% 3 4 5% 15%	4440
	21st to end	Night	12% 18% 8% 14% 7% 7% 5% 4 5% 4 16%	4884
February	1st to 10th	Night	13% 17% 6% 13% 7% 6% 5% 4 4 4 22%	2480
	11th to 20th	Night	13% 16% 6% 14% 7% 5% 4 3 4 4 22%	2366
	21st to end	Night	15% 16% 6% 9% 7% 4 5% 3 4 6% 24%	1884
March	1st to 10th	Night	19% 14% 5% 10% 6% 4 4 2 4 5% 28%	3724
	11th to 20th	Night	17% 20% 6% 10% 4 4 3 3 4 5% 25%	3581
	21st to end	Night	13% 10% 4 11% 6% 5% 4 4 4 5% 34%	3535
April	1st to 10th	Night	23% 13% 4 6% 4 4 3 3 5% 4 30%	1900
	11th to 20th	Night	20% 10% 4 6% 4 3 3 3 6% 5% 34%	1875
	21st to end	Night	20% 13% 3 8% 4 4 3 3 4 5% 33%	1744
May	1st to 10th	Night	21% 11% 2 7% 4 5% 4 3 5% 6% 31%	2514
	11th to 20th	Night	19% 9% 2 6% 5% 4 4 3 5% 7% 37%	2495
	21st to end	Night	20% 7% 2 7% 5% 5% 5% 4 5% 7% 32%	2738
June	1st to 10th	Night	20% 8% 4 7% 4 5% 4 4 6% 7% 31%	1520
	11th to 20th	Night	17% 8% 2 5% 5% 4 4 4 6% 6% 38%	1496
	21st to end	Night	19% 7% 2 5% 6% 4 5% 4 6% 6% 35%	1440
July	1st to 10th	Night	12% 7% 2 7% 4 5% 4 4 7% 7% 41%	1440
	11th to 20th	Night	14% 6% 3 6% 4 4 5% 3 7% 8% 40%	1440
	21st to end	Night	11% 7% 2 6% 4 5% 5% 5% 7% 8% 39%	1574
August	1st to 10th	Night	13% 6% 3 7% 5% 6% 5% 5% 6% 7% 38%	1432
	11th to 20th	Night	13% 7% 2 7% 4 4 5% 3 6% 7% 41%	1571
	21st to end	Night	17% 6% 3 6% 4 4 5% 3 5% 7% 40%	1980
September	1st to 10th	Night	18% 7% 2 6% 3 3 3 3 5% 6% 43%	1800
	11th to 20th	Night	19% 6% 3 4 3 4 3 3 5% 6% 45%	1836
	21st to end	Night	19% 8% 2 6% 3 3 3 3 5% 7% 41%	1983
October	1st to 10th	Night	21% 9% 3 6% 3 4 5% 3 4 6% 36%	2160
	11th to 20th	Night	25% 14% 3 7% 5% 3 4 3 4 5% 27%	2166
	21st to end	Night	26% 15% 4 8% 5% 4 4 3 4 5% 24%	2574
November	1st to 10th	Night	21% 14% 4 8% 5% 4 4 3 4 6% 27%	2407
	11th to 20th	Night	19% 17% 6% 11% 5% 5% 4 3 4 5% 22%	2627
	21st to end	Night	23% 20% 6% 11% 5% 5% 3 3 4 3 17%	2660
December	1st to 10th	Night	21% 22% 8% 12% 6% 5% 3 3 4 3 14%	2660
	11th to 20th	Night	20% 19% 7% 12% 6% 4 4 2 3 3 20%	3288
	21st to end	Night	22% 23% 6% 12% 6% 4 3 2 3 3 16%	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	78% 2 7% 10% 4	2518
	11th to 20th	Day	73% 2 5% 14% 6% 1	2520
	21st to end	Day	69% 4 10% 11% 5% 1	2772
February	1st to 10th	Day	69% 2 6% 15% 6% 2	1695
	11th to 20th	Day	65% 3 10% 11% 10% 1	1707
	21st to end	Day	65% 2 8% 13% 10% 1	1570
March	1st to 10th	Day	64% 3 8% 15% 10% 1	3119
	11th to 20th	Day	65% 3 9% 12% 9% 2	3374
	21st to end	Day	50% 3 8% 22% 16% 2	4097
April	1st to 10th	Day	60% 2 8% 17% 10% 3	2280
	11th to 20th	Day	56% 3 8% 19% 11% 2	2254
	21st to end	Day	58% 4 8% 16% 12% 3	2451
May	1st to 10th	Day	56% 5% 9% 20% 9% 1	4440
	11th to 20th	Day	50% 7% 15% 18% 9% 1	4402
	21st to end	Day	51% 4 11% 19% 14% 1	4837
June	1st to 10th	Day	56% 6% 10% 17% 10% 1	2660
	11th to 20th	Day	49% 6% 13% 20% 11% 2	2607
	21st to end	Day	56% 6% 12% 17% 9%	2520
July	1st to 10th	Day	45% 6% 14% 24% 10%	2450
	11th to 20th	Day	46% 7% 15% 23% 9%	2445
	21st to end	Day	48% 7% 14% 22% 8%	2591
August	1st to 10th	Day	51% 8% 16% 21% 5%	2492
	11th to 20th	Day	47% 6% 18% 22% 7%	2307
	21st to end	Day	47% 6% 13% 22% 11% 1	2376
September	1st to 10th	Day	46% 4 14% 24% 12%	2160
	11th to 20th	Day	44% 5% 14% 28% 9% 1	2124
	21st to end	Day	47% 5% 14% 24% 9%	1976
October	1st to 10th	Day	56% 4 12% 20% 8% 1	1800
	11th to 20th	Day	65% 5% 11% 14% 4 1	1793
	21st to end	Day	66% 4 11% 14% 5% 1	1782
November	1st to 10th	Day	55% 5% 13% 20% 6% 1	1671
	11th to 20th	Day	69% 4 10% 11% 6% 1	1549
	21st to end	Day	71% 5% 9% 10% 4 1	1520
December	1st to 10th	Day	74% 3 8% 10% 4	1520
	11th to 20th	Day	71% 4 9% 11% 5%	1906
	21st to end	Day	73% 2 7% 13% 5%	2772
January	1st to 10th	Night	70% 3 14% 10% 3	4429
	11th to 20th	Night	70% 3 13% 9% 4 1	4440
	21st to end	Night	71% 5% 9% 8% 7% 1	4884
February	1st to 10th	Night	66% 3 9% 15% 6% 1	2480
	11th to 20th	Night	65% 3 9% 15% 7% 1	2368
	21st to end	Night	61% 3 11% 15% 9% 1	1884
March	1st to 10th	Night	60% 2 12% 13% 10% 2	3734
	11th to 20th	Night	63% 4 9% 15% 9% 1	3582
	21st to end	Night	53% 3 7% 22% 12% 3	3535
April	1st to 10th	Night	57% 3 10% 16% 11% 3	1900
	11th to 20th	Night	49% 4 10% 21% 13% 2	1875
	21st to end	Night	54% 3 10% 18% 13% 3	1744
May	1st to 10th	Night	52% 6% 12% 19% 8% 2	2520
	11th to 20th	Night	48% 6% 15% 18% 12% 2	2496
	21st to end	Night	51% 4 11% 19% 13% 2	2739
June	1st to 10th	Night	50% 7% 12% 20% 10%	1520
	11th to 20th	Night	45% 6% 13% 22% 12% 3	1496
	21st to end	Night	48% 7% 12% 21% 11% 1	1440
July	1st to 10th	Night	40% 6% 17% 24% 12% 1	1400
	11th to 20th	Night	41% 7% 15% 27% 9% 1	1392
	21st to end	Night	39% 9% 18% 25% 9%	1486
August	1st to 10th	Night	41% 9% 17% 26% 6%	1422
	11th to 20th	Night	40% 7% 18% 24% 10%	1571
	21st to end	Night	44% 5% 17% 25% 9% 1	1980
September	1st to 10th	Night	42% 5% 15% 25% 13% 1	1800
	11th to 20th	Night	41% 4 15% 31% 8% 1	1836
	21st to end	Night	43% 5% 14% 29% 9%	1983
October	1st to 10th	Night	51% 5% 10% 23% 11% 1	2160
	11th to 20th	Night	59% 4 14% 16% 6% 1	2166
	21st to end	Night	64% 4 10% 15% 6% 1	2574
November	1st to 10th	Night	58% 4 15% 16% 5%	2407
	11th to 20th	Night	64% 3 12% 13% 6% 1	2627
	21st to end	Night	72% 3 9% 12% 3	2660
December	1st to 10th	Night	75% 3 9% 9% 3	2660
	11th to 20th	Night	70% 3 8% 13% 5% 1	3288
	21st to end	Night	75% 3 6% 12% 4	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	20% 21% 40% 17% 3	180
	11th to 20th	Day	29% 17% 33% 13% 7% 1	180
	21st to end	Day	23% 19% 34% 19% 4 1	198
February	1st to 10th	Day	32% 29% 29% 7% 3	263
	11th to 20th	Day	29% 28% 31% 11%	305
	21st to end	Day	31% 24% 29% 13% 2	382
March	1st to 10th	Day	26% 20% 33% 16% 4 1	460
	11th to 20th	Day	28% 22% 28% 17% 3 1	460
	21st to end	Day	31% 23% 25% 15% 6% 2	506
April	1st to 10th	Day	31% 19% 26% 15% 7% 1	460
	11th to 20th	Day	35% 16% 25% 11% 10% 2	452
	21st to end	Day	30% 22% 28% 15% 5% 1	460
May	1st to 10th	Day	31% 18% 30% 12% 6% 2	463
	11th to 20th	Day	24% 17% 29% 18% 9% 2	487
	21st to end	Day	25% 18% 30% 18% 7% 1	529
June	1st to 10th	Day	30% 14% 32% 18% 6% 1	490
	11th to 20th	Day	22% 17% 31% 20% 10% 1	475
	21st to end	Day	25% 15% 29% 19% 9% 2	450
July	1st to 10th	Day	17% 11% 36% 26% 9% 3	445
	11th to 20th	Day	16% 14% 32% 27% 9% 2	444
	21st to end	Day	15% 11% 34% 26% 11% 2	488
August	1st to 10th	Day	20% 11% 25% 30% 13% 2	446
	11th to 20th	Day	18% 7% 28% 25% 14% 8%	439
	21st to end	Day	21% 15% 27% 17% 14% 7%	495
September	1st to 10th	Day	21% 13% 26% 19% 14% 7%	450
	11th to 20th	Day	19% 12% 27% 20% 16% 7%	450
	21st to end	Day	24% 15% 23% 19% 12% 7%	450
October	1st to 10th	Day	29% 16% 21% 18% 13% 3	450
	11th to 20th	Day	36% 20% 22% 14% 7% 2	446
	21st to end	Day	40% 14% 22% 17% 6%	396
November	1st to 10th	Day	32% 15% 26% 20% 5% 1	365
	11th to 20th	Day	29% 26% 28% 9% 8% 1	209
	21st to end	Day	33% 24% 26% 13% 3 1	180
December	1st to 10th	Day	35% 16% 29% 14% 6%	180
	11th to 20th	Day	31% 27% 26% 14% 2 1	180
	21st to end	Day	35% 20% 27% 12% 5% 2	198
January	1st to 10th	Night	29% 18% 31% 16% 5%	760
	11th to 20th	Night	31% 17% 26% 21% 6%	760
	21st to end	Night	19% 15% 33% 25% 7% 1	836
February	1st to 10th	Night	21% 17% 34% 21% 5% 1	760
	11th to 20th	Night	22% 22% 33% 20% 3	743
	21st to end	Night	25% 19% 27% 25% 4	628
March	1st to 10th	Night	25% 17% 30% 23% 5%	760
	11th to 20th	Night	28% 19% 26% 21% 6% 1	760
	21st to end	Night	24% 14% 28% 24% 8% 1	836
April	1st to 10th	Night	31% 15% 23% 24% 6%	760
	11th to 20th	Night	28% 15% 27% 22% 8% 1	751
	21st to end	Night	26% 17% 26% 22% 8% 1	604
May	1st to 10th	Night	26% 11% 24% 27% 10% 2	380
	11th to 20th	Night	23% 9% 27% 30% 11%	374
	21st to end	Night	20% 8% 34% 28% 9%	411
June	1st to 10th	Night	22% 7% 31% 31% 9% 1	380
	11th to 20th	Night	21% 7% 24% 31% 16% 1	374
	21st to end	Night	21% 5% 18% 38% 18% 1	360
July	1st to 10th	Night	15% 5% 23% 43% 14%	350
	11th to 20th	Night	16% 4 20% 40% 20% 1	348
	21st to end	Night	13% 5% 23% 38% 19% 2	394
August	1st to 10th	Night	15% 4 17% 39% 24% 1	358
	11th to 20th	Night	15% 4 18% 35% 26% 2	507
	21st to end	Night	19% 8% 22% 30% 18% 3	792
September	1st to 10th	Night	22% 6% 22% 32% 17% 1	720
	11th to 20th	Night	22% 7% 18% 32% 21% 1	720
	21st to end	Night	22% 10% 21% 28% 18% 2	720
October	1st to 10th	Night	26% 11% 23% 24% 15% 1	720
	11th to 20th	Night	33% 11% 23% 22% 9% 1	720
	21st to end	Night	33% 13% 24% 24% 6%	792
November	1st to 10th	Night	29% 13% 25% 23% 8% 1	740
	11th to 20th	Night	28% 17% 27% 18% 9% 1	760
	21st to end	Night	35% 16% 23% 19% 6% 1	760
December	1st to 10th	Night	31% 17% 27% 18% 6% 1	760
	11th to 20th	Night	30% 18% 27% 18% 6% 1	760
	21st to end	Night	35% 16% 26% 17% 6%	836

Page generated at 2024-06-14 13:06:08. Version ac07

Copyright © 2024 Attilla Danko.