Observatoire Les Trois Étangs - La Patrie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire Les Trois Étangs - La Patrie clear sky chart from 2005-11-06 to 2025-01-22.

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	19% 14% 5% 10% 6% 5% 4 3 5% 6% 24%	104517
	Night	18% 16% 5% 11% 6% 5% 4 3 4 5% 23%	104769
Transparency	Day	60% 6% 11% 16% 7% 1	108003
	Night	63% 5% 9% 14% 7% 1	109360
Seeing	Day	29% 20% 28% 16% 6% 1	14915
	Night	27% 17% 27% 21% 7% 1	24052

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% 20% 10% 16% 11% 7% 6% 3 3 3 9%	2597
	11th to 20th	Day	10% 15% 7% 25% 14% 7% 3 2 2 2 13%	2600
	21st to end	Day	10% 19% 10% 17% 7% 7% 5% 3 3 3 16%	2780
February	1st to 10th	Day	14% 20% 6% 16% 10% 6% 4 3 3 3 15%	1581
	11th to 20th	Day	13% 20% 9% 16% 8% 5% 4 3 3 4 14%	1848
	21st to end	Day	11% 21% 4 13% 8% 6% 5% 4 4 5% 18%	1570
March	1st to 10th	Day	20% 18% 6% 11% 6% 5% 3 3 3 5% 21%	3116
	11th to 20th	Day	15% 24% 8% 13% 5% 5% 3 2 3 3 19%	3334
	21st to end	Day	18% 17% 5% 13% 4 3 3 2 3 4 27%	4038
April	1st to 10th	Day	21% 20% 4 9% 5% 3 3 3 4 4 24%	2280
	11th to 20th	Day	18% 16% 5% 7% 4 4 3 2 4 5% 32%	2323
	21st to end	Day	23% 17% 4 8% 4 4 4 3 4 4 26%	2470
May	1st to 10th	Day	24% 12% 3 8% 5% 5% 5% 4 4 5% 25%	4106
	11th to 20th	Day	22% 9% 3 8% 6% 6% 5% 4 5% 6% 26%	4392
	21st to end	Day	18% 8% 3 7% 5% 5% 5% 4 7% 8% 29%	4837
June	1st to 10th	Day	30% 8% 2 7% 4 4 4 4 6% 7% 23%	2660
	11th to 20th	Day	21% 8% 2 6% 5% 5% 5% 4 6% 8% 31%	2667
	21st to end	Day	26% 9% 3 7% 5% 5% 5% 4 6% 6% 24%	2660
July	1st to 10th	Day	17% 7% 3 8% 6% 5% 6% 5% 7% 9% 28%	4440
	11th to 20th	Day	17% 9% 3 8% 6% 5% 5% 4 7% 8% 28%	4440
	21st to end	Day	18% 8% 2 6% 5% 5% 5% 4 5% 7% 35%	4814
August	1st to 10th	Day	22% 8% 3 8% 5% 6% 5% 4 6% 7% 25%	4329
	11th to 20th	Day	22% 10% 3 7% 6% 5% 5% 5% 6% 8% 22%	4045
	21st to end	Day	22% 8% 2 6% 4 4 5% 4 5% 7% 33%	4281
September	1st to 10th	Day	20% 7% 2 6% 5% 4 4 3 5% 7% 36%	2280
	11th to 20th	Day	22% 7% 1 5% 3 3 4 3 5% 7% 40%	2102
	21st to end	Day	21% 10% 2 6% 4 4 4 3 5% 8% 32%	2090
October	1st to 10th	Day	22% 12% 3 6% 4 4 4 4 5% 7% 28%	2090
	11th to 20th	Day	21% 16% 4 8% 4 5% 5% 3 5% 6% 24%	1771
	21st to end	Day	24% 24% 3 8% 3 4 3 3 4 4 21%	1881
November	1st to 10th	Day	20% 20% 5% 7% 4 3 3 3 4 4 26%	1761
	11th to 20th	Day	17% 20% 7% 12% 5% 4 3 3 3 5% 21%	1800
	21st to end	Day	18% 22% 7% 12% 5% 5% 3 2 4 6% 16%	1654
December	1st to 10th	Day	14% 24% 9% 19% 11% 5% 2 2 2 2 9%	2280
	11th to 20th	Day	16% 19% 9% 15% 6% 4 4 2 3 3 19%	2640
	21st to end	Day	17% 20% 6% 14% 6% 3 6% 3 3 4 18%	3960
January	1st to 10th	Night	13% 21% 9% 20% 11% 6% 5% 2 3 2 9%	4569
	11th to 20th	Night	11% 18% 8% 20% 14% 7% 5% 3 2 2 9%	4580
	21st to end	Night	11% 20% 10% 16% 8% 8% 5% 3 3 3 13%	4899
February	1st to 10th	Night	12% 19% 7% 16% 10% 6% 5% 2 4 5% 16%	2595
	11th to 20th	Night	11% 20% 8% 17% 7% 7% 5% 2 3 4 15%	2218
	21st to end	Night	12% 18% 7% 12% 7% 7% 5% 3 3 4 22%	1884
March	1st to 10th	Night	21% 19% 5% 8% 5% 4 5% 2 3 4 25%	3724
	11th to 20th	Night	13% 26% 7% 12% 5% 4 3 2 3 3 20%	3624
	21st to end	Night	19% 20% 5% 11% 6% 3 3 2 3 3 25%	3577
April	1st to 10th	Night	22% 18% 4 8% 4 4 4 3 3 4 26%	1900
	11th to 20th	Night	21% 16% 3 6% 4 3 4 3 4 5% 31%	1806
	21st to end	Night	23% 15% 3 5% 4 4 4 4 4 5% 29%	1710
May	1st to 10th	Night	27% 10% 3 7% 4 4 5% 4 5% 6% 25%	2834
	11th to 20th	Night	21% 9% 3 8% 5% 5% 4 3 5% 6% 31%	2530
	21st to end	Night	20% 7% 2 6% 4 4 5% 4 6% 8% 34%	2738
June	1st to 10th	Night	29% 10% 3 6% 5% 3 3 3 6% 7% 26%	1520
	11th to 20th	Night	21% 7% 2 6% 5% 3 4 4 6% 7% 34%	1419
	21st to end	Night	22% 9% 3 7% 6% 5% 5% 3 5% 6% 29%	1520
July	1st to 10th	Night	17% 9% 3 9% 6% 6% 5% 4 5% 7% 30%	2520
	11th to 20th	Night	23% 9% 3 6% 4 4 5% 4 6% 7% 30%	2520
	21st to end	Night	17% 8% 3 6% 5% 4 5% 4 6% 6% 36%	2739
August	1st to 10th	Night	27% 8% 3 7% 4 4 5% 3 5% 6% 28%	2568
	11th to 20th	Night	20% 8% 3 8% 5% 5% 6% 5% 5% 7% 27%	2782
	21st to end	Night	20% 8% 2 6% 4 4 4 3 4 6% 38%	3371
September	1st to 10th	Night	21% 7% 3 6% 4 3 4 3 5% 5% 39%	1900
	11th to 20th	Night	20% 6% 2 5% 3 4 4 4 5% 6% 43%	2077
	21st to end	Night	22% 7% 2 4 4 3 4 2 5% 7% 39%	2090
October	1st to 10th	Night	22% 10% 2 6% 5% 4 3 3 4 6% 33%	2090
	11th to 20th	Night	23% 15% 3 8% 5% 4 3 3 4 5% 26%	2406
	21st to end	Night	27% 18% 3 7% 4 3 4 3 4 5% 24%	2717
November	1st to 10th	Night	22% 19% 5% 9% 5% 4 2 2 4 5% 23%	2537
	11th to 20th	Night	19% 18% 6% 12% 4 3 3 2 4 4 25%	2600
	21st to end	Night	18% 21% 7% 13% 6% 4 3 2 4 4 18%	2736
December	1st to 10th	Night	15% 22% 11% 23% 9% 4 3 1 2 2 8%	4910
	11th to 20th	Night	17% 22% 7% 17% 8% 5% 4 2 3 3 14%	5563
	21st to end	Night	17% 21% 7% 12% 6% 4 5% 2 3 4 20%	6996

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% 7% 7% 2	2598
	11th to 20th	Day	77% 4 5% 10% 3 1	2600
	21st to end	Day	71% 6% 8% 8% 5% 1	2780
February	1st to 10th	Day	76% 4 5% 9% 6% 1	1581
	11th to 20th	Day	76% 3 7% 9% 4 1	1857
	21st to end	Day	68% 5% 8% 12% 6% 2	1570
March	1st to 10th	Day	67% 4 7% 11% 9% 2	3119
	11th to 20th	Day	71% 4 6% 10% 7% 1	3334
	21st to end	Day	63% 3 5% 14% 14% 1	4038
April	1st to 10th	Day	65% 3 9% 13% 8% 2	2280
	11th to 20th	Day	56% 4 8% 20% 11% 1	2323
	21st to end	Day	62% 4 7% 15% 9% 3	2470
May	1st to 10th	Day	61% 5% 10% 16% 7% 1	4120
	11th to 20th	Day	57% 8% 15% 13% 6% 1	4396
	21st to end	Day	49% 9% 13% 20% 9%	4837
June	1st to 10th	Day	61% 6% 10% 18% 5% 1	2660
	11th to 20th	Day	51% 7% 12% 21% 8% 1	2667
	21st to end	Day	59% 7% 11% 17% 6%	2660
July	1st to 10th	Day	49% 8% 16% 22% 7%	4370
	11th to 20th	Day	50% 9% 15% 23% 3	4365
	21st to end	Day	48% 8% 12% 26% 6%	4661
August	1st to 10th	Day	56% 8% 14% 18% 4	4315
	11th to 20th	Day	56% 9% 16% 15% 4	4084
	21st to end	Day	48% 7% 14% 17% 11% 2	4281
September	1st to 10th	Day	47% 6% 14% 24% 9% 1	2280
	11th to 20th	Day	46% 4 12% 26% 12% 1	2102
	21st to end	Day	50% 6% 11% 21% 10% 1	2090
October	1st to 10th	Day	53% 6% 14% 19% 8%	3480
	11th to 20th	Day	58% 4 11% 21% 6%	2909
	21st to end	Day	57% 4 14% 17% 7%	3081
November	1st to 10th	Day	62% 6% 9% 15% 7% 1	1761
	11th to 20th	Day	67% 5% 8% 11% 7% 2	1800
	21st to end	Day	70% 6% 10% 12% 2	1654
December	1st to 10th	Day	83% 3 6% 5% 3	2280
	11th to 20th	Day	71% 4 6% 12% 7%	2640
	21st to end	Day	71% 4 6% 9% 8% 2	3960
January	1st to 10th	Night	80% 6% 7% 5% 2	4569
	11th to 20th	Night	83% 4 5% 6% 2	4580
	21st to end	Night	76% 5% 6% 7% 4 1	4899
February	1st to 10th	Night	73% 4 6% 11% 5% 1	2595
	11th to 20th	Night	75% 5% 6% 9% 5% 1	2220
	21st to end	Night	68% 4 6% 13% 8% 1	1884
March	1st to 10th	Night	65% 3 10% 14% 6% 2	3734
	11th to 20th	Night	71% 5% 6% 11% 6% 1	3625
	21st to end	Night	66% 3 5% 14% 11% 2	3577
April	1st to 10th	Night	63% 4 7% 15% 10% 1	1900
	11th to 20th	Night	55% 6% 8% 19% 11% 1	1806
	21st to end	Night	58% 6% 9% 15% 10% 2	1710
May	1st to 10th	Night	57% 7% 14% 15% 7% 1	2840
	11th to 20th	Night	52% 11% 12% 18% 6% 1	2531
	21st to end	Night	46% 9% 14% 17% 14%	2739
June	1st to 10th	Night	57% 5% 12% 20% 6%	1520
	11th to 20th	Night	47% 8% 11% 22% 10% 2	1419
	21st to end	Night	55% 7% 11% 19% 7%	1520
July	1st to 10th	Night	52% 7% 14% 19% 7%	2480
	11th to 20th	Night	52% 8% 14% 22% 5%	2472
	21st to end	Night	47% 9% 13% 25% 6%	2651
August	1st to 10th	Night	57% 7% 12% 21% 3	2558
	11th to 20th	Night	53% 10% 16% 15% 5%	2809
	21st to end	Night	45% 6% 14% 21% 13%	3371
September	1st to 10th	Night	46% 6% 13% 24% 10%	1900
	11th to 20th	Night	42% 6% 14% 27% 10% 1	2077
	21st to end	Night	45% 6% 13% 24% 11% 2	2090
October	1st to 10th	Night	51% 6% 12% 20% 11%	3480
	11th to 20th	Night	58% 5% 10% 20% 8%	3994
	21st to end	Night	57% 5% 13% 16% 8% 2	4467
November	1st to 10th	Night	64% 5% 10% 14% 6% 1	2537
	11th to 20th	Night	65% 4 9% 13% 8% 2	2600
	21st to end	Night	72% 4 10% 10% 3	2736
December	1st to 10th	Night	86% 3 4 5% 1	4910
	11th to 20th	Night	77% 4 5% 9% 6%	5564
	21st to end	Night	69% 5% 7% 11% 7% 1	6996

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	31% 27% 33% 10%	200
	11th to 20th	Day	30% 30% 25% 14% 2 1	200
	21st to end	Day	24% 26% 37% 11% 2 1	200
February	1st to 10th	Day	39% 30% 21% 8% 2	229
	11th to 20th	Day	32% 29% 31% 6% 2	456
	21st to end	Day	32% 26% 27% 13% 2	382
March	1st to 10th	Day	31% 25% 30% 12% 3	460
	11th to 20th	Day	31% 29% 25% 11% 4	460
	21st to end	Day	35% 23% 21% 14% 6% 1	506
April	1st to 10th	Day	40% 20% 23% 12% 5%	460
	11th to 20th	Day	34% 24% 24% 12% 5% 2	452
	21st to end	Day	36% 21% 28% 10% 4 1	460
May	1st to 10th	Day	40% 16% 27% 12% 4 1	463
	11th to 20th	Day	26% 19% 32% 17% 5% 1	487
	21st to end	Day	22% 24% 31% 18% 5% 1	529
June	1st to 10th	Day	33% 19% 29% 15% 4 1	490
	11th to 20th	Day	24% 19% 30% 20% 7% 1	497
	21st to end	Day	28% 17% 32% 15% 7% 1	490
July	1st to 10th	Day	22% 13% 36% 22% 6% 1	485
	11th to 20th	Day	21% 13% 38% 20% 7% 1	484
	21st to end	Day	24% 13% 32% 24% 6% 1	532
August	1st to 10th	Day	23% 12% 31% 23% 10% 1	486
	11th to 20th	Day	21% 12% 30% 24% 10% 3	479
	21st to end	Day	25% 15% 25% 21% 10% 4	539
September	1st to 10th	Day	25% 11% 30% 19% 11% 3	490
	11th to 20th	Day	23% 11% 23% 23% 13% 7%	490
	21st to end	Day	22% 15% 25% 23% 11% 4	490
October	1st to 10th	Day	28% 18% 23% 19% 10% 3	490
	11th to 20th	Day	31% 19% 26% 15% 8% 1	413
	21st to end	Day	38% 25% 20% 14% 3	429
November	1st to 10th	Day	38% 20% 25% 13% 3	395
	11th to 20th	Day	30% 24% 29% 11% 6% 1	400
	21st to end	Day	35% 24% 26% 11% 3 1	272
December	1st to 10th	Day	33% 25% 27% 14% 2	200
	11th to 20th	Day	39% 26% 27% 6% 3 1	200
	21st to end	Day	35% 25% 28% 7% 4	220
January	1st to 10th	Night	26% 28% 34% 11% 2	800
	11th to 20th	Night	25% 27% 29% 16% 3	800
	21st to end	Night	19% 25% 35% 16% 4	841
February	1st to 10th	Night	21% 27% 35% 14% 2	760
	11th to 20th	Night	24% 27% 33% 14% 2	743
	21st to end	Night	25% 23% 32% 17% 2	628
March	1st to 10th	Night	27% 21% 32% 18% 2	760
	11th to 20th	Night	28% 23% 28% 16% 5%	760
	21st to end	Night	28% 20% 25% 19% 6% 1	836
April	1st to 10th	Night	33% 21% 25% 17% 4	760
	11th to 20th	Night	33% 17% 26% 18% 6% 1	682
	21st to end	Night	32% 20% 25% 18% 4 1	570
May	1st to 10th	Night	30% 14% 30% 18% 7% 1	570
	11th to 20th	Night	25% 11% 29% 27% 7% 1	396
	21st to end	Night	24% 11% 31% 26% 7%	411
June	1st to 10th	Night	33% 7% 26% 25% 9%	380
	11th to 20th	Night	24% 7% 22% 32% 14% 1	380
	21st to end	Night	21% 11% 26% 33% 9%	380
July	1st to 10th	Night	21% 6% 28% 35% 9% 1	370
	11th to 20th	Night	18% 7% 27% 34% 13% 1	368
	21st to end	Night	19% 7% 23% 38% 12%	416
August	1st to 10th	Night	21% 4 18% 37% 19% 1	414
	11th to 20th	Night	19% 7% 22% 35% 17% 1	562
	21st to end	Night	23% 7% 23% 30% 16% 2	770
September	1st to 10th	Night	23% 7% 25% 31% 13% 1	760
	11th to 20th	Night	24% 7% 20% 27% 20% 2	760
	21st to end	Night	24% 10% 25% 24% 16% 1	760
October	1st to 10th	Night	28% 11% 25% 24% 13% 1	760
	11th to 20th	Night	33% 15% 22% 21% 8% 2	760
	21st to end	Night	36% 18% 25% 17% 4	836
November	1st to 10th	Night	34% 19% 24% 18% 5% 1	780
	11th to 20th	Night	29% 20% 28% 15% 7% 2	800
	21st to end	Night	32% 24% 24% 15% 4 1	806
December	1st to 10th	Night	33% 24% 25% 14% 4	900
	11th to 20th	Night	31% 26% 24% 15% 4	893
	21st to end	Night	34% 22% 27% 14% 3	880

Page generated at 2025-01-19 03:06:45. Version ac07

Copyright © 2025 Attilla Danko.