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 2005-11-05 to 2017-08-12.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
23%
14556
10%
46639
6%
14524
28%
14524
11%
36555

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
10%
720
6%
2506
3%
716
13%
716
4%
2169
January16th to endNight
11%
768
5%
2688
2%
768
15%
768
5%
2327
February1st to 15thNight
10%
704
6%
2311
2%
701
14%
701
5%
2001
February16th to endNight
13%
631
8%
1893
3%
631
19%
631
7%
1585
March1st to 15thNight
17%
720
11%
2159
7%
720
23%
720
10%
1727
March16th to endNight
22%
768
15%
2025
6%
768
29%
768
15%
1566
April1st to 15thNight
21%
718
12%
1796
4%
718
25%
718
14%
1438
April16th to endNight
23%
555
15%
1635
5%
555
32%
555
16%
1172
May1st to 15thNight
24%
494
12%
1574
7%
494
32%
494
15%
1158
May16th to endNight
28%
375
9%
1497
9%
374
36%
374
11%
1096
June1st to 15thNight
27%
360
7%
1404
7%
360
33%
360
10%
1057
June16th to endNight
40%
360
7%
1410
9%
360
44%
360
15%
976
July1st to 15thNight
44%
340
9%
1360
13%
340
47%
340
16%
911
July16th to endNight
45%
376
10%
1418
12%
354
46%
354
15%
960
August1st to 15thNight
46%
431
10%
1480
10%
429
49%
429
18%
1024
August16th to endNight
44%
607
15%
1657
8%
607
47%
607
27%
1118
September1st to 15thNight
41%
660
10%
1697
5%
660
42%
660
23%
1237
September16th to endNight
40%
657
18%
1815
12%
657
43%
657
26%
1214
October1st to 15thNight
29%
660
14%
1889
8%
660
35%
660
16%
1409
October16th to endNight
18%
704
7%
2288
3%
704
22%
704
8%
1870
November1st to 15thNight
19%
700
13%
2277
9%
700
24%
700
10%
1795
November16th to endNight
20%
721
11%
2421
10%
721
23%
721
9%
1939
December1st to 15thNight
10%
750
3%
2700
1%
750
13%
750
4%
2350
December16th to endNight
8%
777
5%
2739
2%
777
12%
777
3%
2456

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 ForecastData
Points
Cloud CoverDay
22%13%47%6%34445%23%
47277
Night
20%13%5%8%6%34335%24%
46809
TransparencyDay
62%5%9%15%6%
46965
Night
63%5%9%15%6%
46639
SeeingDay
30%16%25%17%7%2
5588
Night
27%16%26%20%7%
14556

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
17%16%9%13%10%45%43212%
1432
16th to endDay
11%16%8%11%11%46%5%3314%
1536
February1st to 15thDay
13%19%9%13%12%46%32211%
1549
16th to endDay
12%20%7%13%9%35%33415%
1580
March1st to 15thDay
16%17%8%10%6%4343322%
1790
16th to endDay
19%15%5%10%6%3322326%
2196
April1st to 15thDay
21%17%46%5%2333426%
2152
16th to endDay
21%14%35%42434431%
2325
May1st to 15thDay
25%10%35%5%3444426%
2388
16th to endDay
26%9%36%5%35%45%7%23%
2618
June1st to 15thDay
35%6%245%3445%6%22%
2525
16th to endDay
25%8%35%5%35%447%25%
2522
July1st to 15thDay
20%7%36%5%36%46%8%26%
2520
16th to endDay
23%8%25%6%45%6%6%7%22%
2654
August1st to 15thDay
25%7%25%6%45%6%5%8%23%
2372
16th to endDay
22%6%2442445%6%34%
2190
September1st to 15thDay
25%7%24424446%34%
1932
16th to endDay
22%8%25%323346%37%
1815
October1st to 15thDay
23%13%36%324445%26%
1740
16th to endDay
25%23%36%42333417%
1584
November1st to 15thDay
22%18%7%4423435%24%
1581
16th to endDay
18%18%6%10%432335%22%
1534
December1st to 15thDay
21%23%8%11%5%3322212%
1260
16th to endDay
21%21%10%13%7%2432210%
1482
January1st to 15thNight
15%18%8%13%9%36%34312%
2506
16th to endNight
11%18%8%12%10%5%7%5%2312%
2688
February1st to 15thNight
10%18%8%15%12%5%6%23313%
2310
16th to endNight
13%19%8%12%7%36%32319%
1893
March1st to 15thNight
18%16%7%7%6%35%32425%
2146
16th to endNight
16%15%6%8%5%2334430%
2025
April1st to 15thNight
22%16%46%43444424%
1796
16th to endNight
22%10%25%423435%34%
1635
May1st to 15thNight
24%10%36%43345%6%29%
1574
16th to endNight
25%7%26%5%35%45%6%26%
1495
June1st to 15thNight
31%7%45%5%24345%24%
1404
16th to endNight
20%6%36%5%25%45%7%32%
1410
July1st to 15thNight
18%6%35%435%5%5%9%31%
1440
16th to endNight
17%6%245%36%46%8%32%
1514
August1st to 15thNight
19%5%36%6%35%45%6%33%
1490
16th to endNight
17%7%25%423448%39%
1657
September1st to 15thNight
23%6%35%414445%36%
1697
16th to endNight
22%5%13324246%42%
1815
October1st to 15thNight
22%10%36%5%24336%30%
1889
16th to endNight
30%16%36%5%2333320%
2288
November1st to 15thNight
22%17%5%7%5%33235%23%
2277
16th to endNight
20%17%7%9%5%2333423%
2421
December1st to 15thNight
21%21%8%11%7%3432213%
2700
16th to endNight
21%21%9%12%8%45%2239%
2739

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
77%5%7%6%3
1433
16th to endDay
71%5%6%11%4
1536
February1st to 15thDay
79%348%3
1552
16th to endDay
73%36%9%5%1
1580
March1st to 15thDay
67%48%12%6%1
1800
16th to endDay
65%36%13%9%1
2196
April1st to 15thDay
62%37%15%9%2
2152
16th to endDay
56%48%16%10%2
2325
May1st to 15thDay
59%48%17%8%
2388
16th to endDay
60%7%11%14%7%
2622
June1st to 15thDay
63%5%10%15%4
2525
16th to endDay
58%6%11%18%5%
2522
July1st to 15thDay
52%7%15%18%5%
2371
16th to endDay
60%7%11%15%4
2487
August1st to 15thDay
58%8%15%16%2
2358
16th to endDay
48%5%15%20%8%
2190
September1st to 15thDay
50%5%12%21%9%
1932
16th to endDay
48%411%24%11%
1815
October1st to 15thDay
58%412%17%7%
1740
16th to endDay
70%48%11%4
1584
November1st to 15thDay
63%5%9%12%7%1
1581
16th to endDay
65%49%14%5%1
1534
December1st to 15thDay
79%45%8%2
1260
16th to endDay
81%3445%
1482
January1st to 15thNight
77%37%7%3
2506
16th to endNight
75%5%5%9%3
2688
February1st to 15thNight
76%35%10%3
2311
16th to endNight
71%46%10%7%
1893
March1st to 15thNight
65%46%15%6%1
2159
16th to endNight
59%47%15%10%2
2025
April1st to 15thNight
61%46%15%10%
1796
16th to endNight
51%5%10%17%12%2
1635
May1st to 15thNight
55%5%10%17%9%1
1574
16th to endNight
57%6%12%16%6%
1497
June1st to 15thNight
61%5%9%17%5%
1404
16th to endNight
49%8%11%22%7%
1410
July1st to 15thNight
47%8%16%20%7%
1360
16th to endNight
48%9%14%20%7%
1418
August1st to 15thNight
49%7%17%21%4
1480
16th to endNight
42%6%17%23%10%
1657
September1st to 15thNight
49%5%13%24%6%
1697
16th to endNight
43%412%26%11%
1815
October1st to 15thNight
55%410%18%9%
1889
16th to endNight
68%5%8%13%4
2288
November1st to 15thNight
64%49%13%6%1
2277
16th to endNight
67%38%13%6%
2421
December1st to 15thNight
79%36%8%2
2700
16th to endNight
82%345%4
2739

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
26%25%35%13%
60
16th to endDay
31%25%31%9%11
64
February1st to 15thDay
32%22%26%13%4
153
16th to endDay
25%25%29%15%3
239
March1st to 15thDay
30%24%27%14%3
270
16th to endDay
28%21%20%17%10%1
288
April1st to 15thDay
34%19%26%12%5%1
270
16th to endDay
32%17%25%12%7%3
270
May1st to 15thDay
40%12%27%11%6%2
288
16th to endDay
26%20%29%18%4
331
June1st to 15thDay
38%12%24%17%6%
320
16th to endDay
25%15%34%18%5%
317
July1st to 15thDay
24%11%34%20%8%1
305
16th to endDay
28%7%28%26%7%1
326
August1st to 15thDay
30%5%25%23%13%
297
16th to endDay
27%7%22%23%11%7%
268
September1st to 15thDay
21%10%27%18%16%5%
255
16th to endDay
25%9%21%22%12%7%
254
October1st to 15thDay
28%18%17%18%12%4
250
16th to endDay
39%21%18%14%5%
240
November1st to 15thDay
33%19%23%16%6%
235
16th to endDay
33%20%20%14%6%3
164
December1st to 15thDay
41%26%25%5%1
60
16th to endDay
46%32%15%31
64
January1st to 15thNight
25%26%31%13%2
720
16th to endNight
20%26%34%14%4
768
February1st to 15thNight
19%25%36%16%2
704
16th to endNight
24%22%33%16%3
631
March1st to 15thNight
29%19%29%18%2
720
16th to endNight
24%20%26%20%7%1
768
April1st to 15thNight
32%18%24%18%5%
718
16th to endNight
28%18%26%18%7%
555
May1st to 15thNight
28%13%29%18%8%1
494
16th to endNight
29%9%27%25%7%
375
June1st to 15thNight
35%5%21%27%9%
360
16th to endNight
19%7%25%35%11%
360
July1st to 15thNight
19%5%25%34%12%2
340
16th to endNight
18%423%36%15%
376
August1st to 15thNight
19%320%34%19%
431
16th to endNight
21%420%32%17%1
607
September1st to 15thNight
27%5%20%31%13%1
660
16th to endNight
25%7%23%26%15%2
657
October1st to 15thNight
30%10%24%20%10%2
660
16th to endNight
39%17%20%17%4
704
November1st to 15thNight
31%17%26%16%7%1
700
16th to endNight
31%20%23%14%7%2
721
December1st to 15thNight
34%25%24%12%2
750
16th to endNight
33%22%26%13%3
777
Page generated at 2017-08-13 14:16:55. Version ac04

Copyright 2017 A. Danko


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