Observatoire de La Sérénité
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de La Sérénité clear sky chart from 2005-11-05 to 2018-01-12.

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
25%
15117
13%
48407
6%
15086
33%
15086
14%
34833

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
12%
765
11%
2662
3%
761
22%
761
8%
2057
January16th to endNight
19%
768
12%
2688
4%
768
29%
768
9%
1995
February1st to 15thNight
18%
703
11%
2360
5%
701
27%
701
11%
1740
February16th to endNight
17%
631
12%
1893
5%
631
26%
631
11%
1454
March1st to 15thNight
20%
720
14%
2160
7%
720
29%
720
14%
1576
March16th to endNight
27%
768
19%
2021
8%
768
34%
768
18%
1444
April1st to 15thNight
23%
718
17%
1796
5%
718
30%
718
17%
1373
April16th to endNight
21%
543
16%
1623
4%
543
32%
543
17%
1109
May1st to 15thNight
25%
450
14%
1530
9%
450
34%
450
14%
1071
May16th to endNight
26%
375
10%
1485
9%
374
35%
374
13%
1012
June1st to 15thNight
27%
360
7%
1260
5%
360
32%
360
13%
896
June16th to endNight
34%
360
7%
1260
7%
360
38%
360
15%
867
July1st to 15thNight
39%
340
8%
1342
11%
340
42%
340
18%
853
July16th to endNight
41%
376
10%
1418
12%
354
48%
354
17%
907
August1st to 15thNight
47%
410
11%
1481
11%
408
51%
408
18%
972
August16th to endNight
39%
648
16%
1794
8%
648
44%
648
24%
1172
September1st to 15thNight
36%
720
12%
1842
5%
720
40%
720
25%
1286
September16th to endNight
41%
717
18%
1980
11%
717
46%
717
28%
1295
October1st to 15thNight
30%
720
17%
2085
8%
720
39%
720
21%
1445
October16th to endNight
23%
768
11%
2496
5%
768
30%
768
14%
1821
November1st to 15thNight
26%
760
16%
2472
10%
760
34%
760
14%
1757
November16th to endNight
22%
803
13%
2763
6%
803
32%
803
12%
2027
December1st to 15thNight
13%
825
7%
2925
2%
825
19%
825
6%
2332
December16th to endNight
12%
869
12%
3071
4%
869
23%
869
7%
2372

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
20%8%36%5%35%45%6%29%
48930
Night
20%10%46%5%34445%30%
48577
TransparencyDay
54%413%19%8%
48618
Night
55%311%19%9%1
48407
SeeingDay
26%17%24%19%10%2
6351
Night
22%21%22%24%8%
15118

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
20%14%5%8%7%34445%22%
1520
16th to endDay
11%14%6%9%6%345%6%5%24%
1536
February1st to 15thDay
10%13%8%10%8%345%45%25%
1500
16th to endDay
14%13%5%9%8%35%445%23%
1580
March1st to 15thDay
18%11%5%7%5%24446%30%
1790
16th to endDay
15%9%45%6%25%5%46%33%
2199
April1st to 15thDay
23%10%35%5%2433432%
2152
16th to endDay
24%7%25%423435%36%
2336
May1st to 15thDay
24%7%35%5%24346%31%
2432
16th to endDay
22%7%36%6%46%5%5%5%26%
2627
June1st to 15thDay
21%6%36%6%36%5%6%8%27%
2700
16th to endDay
22%7%36%6%46%5%5%7%24%
2700
July1st to 15thDay
15%5%36%6%46%6%6%8%30%
2535
16th to endDay
17%6%36%5%36%5%7%9%27%
2654
August1st to 15thDay
18%5%27%6%35%6%6%9%25%
2457
16th to endDay
14%6%26%5%245%5%9%37%
2406
September1st to 15thDay
20%7%25%32435%6%37%
2117
16th to endDay
20%414323348%41%
1980
October1st to 15thDay
24%6%36%5%245%36%30%
1875
16th to endDay
27%10%35%6%3435%5%23%
1728
November1st to 15thDay
21%8%46%6%45%35%428%
1716
16th to endDay
26%13%5%6%423335%25%
1523
December1st to 15thDay
27%16%45%6%2223423%
1365
16th to endDay
23%15%5%7%6%2434421%
1502
January1st to 15thNight
19%17%5%8%6%3333423%
2662
16th to endNight
12%14%6%9%7%45%5%5%424%
2688
February1st to 15thNight
9%12%5%10%10%45%446%25%
2359
16th to endNight
16%13%6%10%7%34335%25%
1893
March1st to 15thNight
19%10%35%6%35%445%31%
2147
16th to endNight
14%9%36%5%33446%36%
2021
April1st to 15thNight
24%10%46%43345%429%
1796
16th to endNight
22%6%35%423336%37%
1623
May1st to 15thNight
24%6%35%5%345%4433%
1530
16th to endNight
26%6%36%424346%31%
1483
June1st to 15thNight
24%7%36%6%3445%7%27%
1260
16th to endNight
22%5%36%5%2446%6%31%
1260
July1st to 15thNight
18%5%35%5%2445%8%35%
1422
16th to endNight
16%5%26%5%36%37%7%35%
1514
August1st to 15thNight
16%5%25%5%446%7%7%34%
1491
16th to endNight
15%5%25%6%345%48%39%
1794
September1st to 15thNight
22%6%15%5%2335%7%38%
1842
16th to endNight
22%423323336%44%
1980
October1st to 15thNight
20%7%25%43345%5%36%
2085
16th to endNight
28%9%35%42334429%
2496
November1st to 15thNight
21%8%35%5%34346%32%
2472
16th to endNight
24%11%36%5%2433429%
2763
December1st to 15thNight
24%15%5%8%7%3433320%
2925
16th to endNight
20%16%5%10%6%2334422%
3071

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
63%310%14%8%
1521
16th to endDay
57%310%19%8%
1536
February1st to 15thDay
59%213%15%7%1
1503
16th to endDay
60%38%17%8%2
1580
March1st to 15thDay
54%411%16%12%1
1800
16th to endDay
50%49%19%12%3
2199
April1st to 15thDay
54%110%17%9%4
2152
16th to endDay
50%310%19%13%2
2336
May1st to 15thDay
53%212%19%11%1
2432
16th to endDay
57%411%17%8%
2631
June1st to 15thDay
53%5%13%17%8%1
2700
16th to endDay
56%412%16%8%
2700
July1st to 15thDay
47%6%18%20%6%
2386
16th to endDay
52%418%18%5%
2487
August1st to 15thDay
51%6%21%17%3
2443
16th to endDay
43%418%26%6%
2406
September1st to 15thDay
47%216%24%9%
2117
16th to endDay
42%216%28%9%
1980
October1st to 15thDay
52%214%21%7%
1875
16th to endDay
61%312%18%3
1728
November1st to 15thDay
57%411%19%6%
1716
16th to endDay
61%310%17%6%
1523
December1st to 15thDay
65%210%15%6%
1365
16th to endDay
64%47%14%8%
1502
January1st to 15thNight
64%38%16%5%
2662
16th to endNight
60%38%17%8%
2688
February1st to 15thNight
58%310%17%8%
2360
16th to endNight
63%28%14%10%1
1893
March1st to 15thNight
55%310%15%12%2
2160
16th to endNight
48%5%9%20%13%3
2021
April1st to 15thNight
57%2418%13%3
1796
16th to endNight
48%49%19%15%3
1623
May1st to 15thNight
53%38%18%12%2
1530
16th to endNight
52%412%17%11%
1485
June1st to 15thNight
55%313%18%6%1
1260
16th to endNight
51%412%19%11%
1260
July1st to 15thNight
44%5%19%21%7%
1342
16th to endNight
45%5%18%20%9%
1418
August1st to 15thNight
45%5%21%22%4
1481
16th to endNight
42%417%28%6%
1794
September1st to 15thNight
46%314%24%9%
1842
16th to endNight
42%316%26%10%
1980
October1st to 15thNight
48%412%24%9%
2085
16th to endNight
57%313%19%6%
2496
November1st to 15thNight
52%5%12%18%10%
2472
16th to endNight
58%310%19%7%
2763
December1st to 15thNight
69%210%11%5%
2925
16th to endNight
64%37%14%9%
3071

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
31%12%31%23%1
82
16th to endDay
29%21%25%17%6%
64
February1st to 15thDay
24%22%30%15%42
119
16th to endDay
23%20%27%20%7%
239
March1st to 15thDay
25%24%26%17%5%
270
16th to endDay
22%21%19%21%11%3
288
April1st to 15thDay
28%19%25%15%10%1
270
16th to endDay
29%21%21%18%8%1
270
May1st to 15thDay
32%17%25%14%7%1
288
16th to endDay
26%22%26%15%8%
340
June1st to 15thDay
23%19%22%24%9%
495
16th to endDay
28%18%22%20%9%1
495
July1st to 15thDay
21%14%25%22%13%2
320
16th to endDay
20%15%24%26%11%1
326
August1st to 15thDay
21%9%26%22%16%3
313
16th to endDay
20%11%23%21%15%7%
332
September1st to 15thDay
25%13%23%17%16%3
315
16th to endDay
20%14%22%21%16%5%
314
October1st to 15thDay
26%13%25%20%10%2
305
16th to endDay
36%16%20%17%8%
288
November1st to 15thDay
27%20%21%20%10%
280
16th to endDay
35%17%24%15%6%1
152
December1st to 15thDay
40%11%28%14%32
90
16th to endDay
33%23%27%12%3
96
January1st to 15thNight
21%27%26%19%4
765
16th to endNight
17%27%23%23%6%
768
February1st to 15thNight
13%27%27%24%6%
704
16th to endNight
26%22%24%21%4
631
March1st to 15thNight
22%25%25%21%4
720
16th to endNight
17%25%23%25%8%1
768
April1st to 15thNight
25%22%22%22%6%
718
16th to endNight
23%23%26%20%6%
543
May1st to 15thNight
22%23%23%24%5%
450
16th to endNight
23%20%23%24%7%
375
June1st to 15thNight
23%20%20%28%6%
360
16th to endNight
21%17%17%30%12%
360
July1st to 15thNight
20%14%19%28%15%1
340
16th to endNight
17%17%15%35%13%1
376
August1st to 15thNight
20%10%13%34%20%1
410
16th to endNight
17%11%22%32%14%2
648
September1st to 15thNight
22%11%22%28%14%1
720
16th to endNight
23%11%19%28%16%1
717
October1st to 15thNight
23%14%24%27%8%1
720
16th to endNight
31%16%24%21%6%
768
November1st to 15thNight
22%22%20%24%9%1
760
16th to endNight
26%25%19%19%7%
803
December1st to 15thNight
29%25%21%17%6%
825
16th to endNight
26%26%22%17%5%1
869
Page generated at 2018-01-12 22:01:25. Version ac04

Copyright 2018 A. Danko


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