Observatoire de l'Aigle
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de l'Aigle clear sky chart from 2005-11-06 to 2024-01-15.

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
26%
22731
12%
74917
6%
22679
33%
22679
14%
55025

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 10thNight
12%
760
8%
2649
1%
757
20%
757
7%
2131
January11th to 20thNight
16%
737
11%
2577
4%
737
25%
737
9%
1963
January21st to endNight
20%
792
13%
2772
5%
792
31%
792
13%
1975
February1st to 10thNight
17%
720
13%
2520
4%
720
29%
720
11%
1856
February11th to 20thNight
13%
703
9%
2123
1%
700
22%
700
11%
1648
February21st to endNight
19%
592
15%
1776
7%
592
30%
592
14%
1330
March1st to 10thNight
21%
720
14%
2160
7%
720
30%
720
14%
1603
March11th to 20thNight
20%
720
12%
2075
5%
720
27%
720
14%
1550
March21st to endNight
25%
792
17%
2040
5%
792
33%
792
19%
1504
April1st to 10thNight
20%
720
12%
1800
3%
720
25%
720
15%
1425
April11th to 20thNight
25%
622
16%
1686
5%
622
32%
622
20%
1200
April21st to endNight
21%
540
14%
1620
6%
540
28%
540
15%
1184
May1st to 10thNight
26%
491
12%
1571
7%
491
34%
491
14%
1144
May11th to 20thNight
30%
354
16%
1416
14%
354
42%
354
15%
962
May21st to endNight
28%
389
11%
1502
7%
388
40%
388
15%
1005
June1st to 10thNight
33%
360
6%
1260
5%
360
37%
360
13%
908
June11th to 20thNight
38%
360
11%
1260
9%
360
44%
360
19%
835
June21st to endNight
37%
360
7%
1260
7%
360
40%
360
14%
923
July1st to 10thNight
43%
350
7%
1335
8%
350
48%
350
19%
881
July11th to 20thNight
44%
348
9%
1392
12%
348
48%
348
17%
926
July21st to endNight
45%
394
9%
1486
13%
372
47%
372
16%
1008
August1st to 10thNight
55%
358
12%
1422
13%
356
60%
356
20%
903
August11th to 20thNight
42%
516
10%
1580
8%
516
44%
516
19%
1118
August21st to endNight
41%
694
16%
1882
9%
694
44%
694
23%
1299
September1st to 10thNight
39%
720
11%
1800
5%
720
42%
720
25%
1275
September11th to 20thNight
40%
720
14%
1957
7%
720
44%
720
24%
1372
September21st to endNight
36%
720
17%
1980
10%
720
41%
720
24%
1371
October1st to 10thNight
33%
720
18%
1984
11%
720
39%
720
20%
1417
October11th to 20thNight
26%
720
10%
2312
4%
720
33%
720
14%
1746
October21st to endNight
20%
792
9%
2574
4%
792
26%
792
12%
1954
November1st to 10thNight
25%
740
12%
2407
7%
740
31%
740
12%
1750
November11th to 20thNight
25%
760
15%
2476
9%
760
33%
760
13%
1843
November21st to endNight
18%
841
9%
2830
4%
841
24%
841
9%
2226
December1st to 10thNight
18%
850
8%
2850
5%
850
23%
850
8%
2338
December11th to 20thNight
17%
850
11%
3477
5%
848
25%
848
8%
2647
December21st to endNight
14%
906
7%
5106
3%
887
21%
887
5%
3805

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
21%11%47%6%35%45%6%27%
74558
Night
19%12%5%8%6%34446%30%
75206
TransparencyDay
55%8%12%16%8%1
74263
Night
54%7%12%17%9%1
75036
SeeingDay
26%18%30%18%7%1
14122
Night
24%13%29%25%8%1
22740

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 10thDay
14%18%6%11%8%45%45%6%21%
1517
11th to 20thDay
13%18%8%11%7%345%4424%
1472
21st to endDay
9%11%8%10%7%45%6%6%5%29%
1584
February1st to 10thDay
8%14%7%15%8%6%6%43424%
1440
11th to 20thDay
12%15%8%13%8%34445%23%
1721
21st to endDay
12%15%6%12%8%3445%6%25%
1480
March1st to 10thDay
15%13%7%11%7%3435%5%28%
1797
11th to 20thDay
17%15%5%8%5%35%5%45%28%
1885
21st to endDay
15%15%5%8%6%25%5%46%30%
2312
April1st to 10thDay
23%16%5%8%5%33345%25%
2160
11th to 20thDay
22%12%36%5%24445%34%
2222
21st to endDay
25%12%36%6%3445%5%28%
2340
May1st to 10thDay
24%10%45%43445%5%31%
2403
11th to 20thDay
22%9%36%6%45%45%6%30%
2478
21st to endDay
24%7%35%6%45%5%5%6%31%
2769
June1st to 10thDay
24%8%36%6%36%5%6%8%24%
2700
11th to 20thDay
25%8%35%5%3445%6%31%
2700
21st to endDay
28%8%48%6%25%45%6%24%
2700
July1st to 10thDay
19%8%37%7%46%5%6%9%27%
2580
11th to 20thDay
21%7%36%6%5%6%6%7%8%26%
2520
21st to endDay
20%7%36%7%5%6%6%6%7%25%
2744
August1st to 10thDay
22%8%47%6%46%5%7%8%23%
2503
11th to 20thDay
21%7%47%6%45%5%6%7%28%
2304
21st to endDay
22%7%37%6%45%5%6%7%30%
2471
September1st to 10thDay
24%7%35%5%35%5%5%6%32%
2160
11th to 20thDay
22%6%245%33446%40%
2003
21st to endDay
27%7%245%33446%34%
1980
October1st to 10thDay
25%10%36%5%345%45%30%
1972
11th to 20thDay
28%14%47%434446%22%
1647
21st to endDay
29%14%36%5%34345%23%
1782
November1st to 10thDay
21%15%5%7%5%33446%27%
1671
11th to 20thDay
22%17%6%9%5%3424423%
1701
21st to endDay
19%19%5%8%7%35%5%4421%
1349
December1st to 10thDay
22%18%7%8%7%3432421%
1330
11th to 20thDay
20%15%49%6%4433426%
1668
21st to endDay
17%18%9%8%5%24345%26%
2493
January1st to 10thNight
14%18%9%12%9%34345%20%
2649
11th to 20thNight
14%16%7%11%7%34445%25%
2577
21st to endNight
8%11%7%10%9%46%5%6%7%27%
2772
February1st to 10thNight
10%13%6%11%9%45%5%46%26%
2520
11th to 20thNight
10%18%7%11%7%46%446%24%
2121
21st to endNight
12%14%6%11%7%445%5%5%27%
1776
March1st to 10thNight
13%13%6%9%7%36%45%7%28%
2150
11th to 20thNight
16%15%47%6%36%45%6%28%
2074
21st to endNight
14%13%5%7%5%35%445%35%
2040
April1st to 10thNight
22%15%6%6%5%25%445%26%
1800
11th to 20thNight
19%10%46%4445%5%7%33%
1686
21st to endNight
23%11%47%433346%32%
1620
May1st to 10thNight
25%8%36%5%44345%32%
1571
11th to 20thNight
22%8%46%5%34436%35%
1415
21st to endNight
26%6%25%433446%37%
1501
June1st to 10thNight
20%9%36%7%35%6%6%7%29%
1260
11th to 20thNight
21%5%36%5%3445%7%37%
1260
21st to endNight
26%7%37%5%34447%31%
1260
July1st to 10thNight
20%6%25%5%345%6%9%35%
1375
11th to 20thNight
19%6%36%5%35%5%7%8%33%
1440
21st to endNight
19%8%36%5%25%5%6%7%35%
1574
August1st to 10thNight
19%425%435%5%6%9%39%
1432
11th to 20thNight
20%7%35%5%36%47%7%33%
1580
21st to endNight
19%6%25%5%345%47%40%
1882
September1st to 10thNight
21%7%35%434346%40%
1800
11th to 20thNight
23%6%2443445%5%41%
1957
21st to endNight
23%7%34324436%41%
1980
October1st to 10thNight
23%9%25%424446%36%
1984
11th to 20thNight
29%9%36%5%34446%29%
2312
21st to endNight
27%14%35%4245%5%6%25%
2574
November1st to 10thNight
20%12%5%7%5%34447%28%
2407
11th to 20thNight
21%12%5%8%5%3345%6%27%
2476
21st to endNight
21%16%6%9%6%33445%23%
2830
December1st to 10thNight
19%18%7%10%8%4434419%
2850
11th to 20thNight
21%14%6%9%7%35%345%23%
3531
21st to endNight
20%19%7%9%5%3333425%
5170

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 10thDay
62%7%10%12%7%1
1518
11th to 20thDay
61%6%10%13%8%2
1472
21st to endDay
52%6%9%17%14%1
1584
February1st to 10thDay
62%5%9%13%8%2
1440
11th to 20thDay
62%6%10%12%9%2
1730
21st to endDay
59%5%8%16%9%3
1480
March1st to 10thDay
56%6%9%15%11%3
1800
11th to 20thDay
57%7%9%14%12%2
1885
21st to endDay
54%7%10%16%10%4
2312
April1st to 10thDay
60%6%11%11%8%4
2160
11th to 20thDay
51%5%10%20%11%2
2222
21st to endDay
56%6%11%14%10%3
2340
May1st to 10thDay
51%7%12%14%13%2
2403
11th to 20thDay
52%9%10%18%10%1
2482
21st to endDay
53%9%10%18%10%1
2769
June1st to 10thDay
54%11%11%16%6%1
2700
11th to 20thDay
51%8%15%16%9%1
2700
21st to endDay
59%8%11%14%8%
2700
July1st to 10thDay
51%10%17%18%5%
2510
11th to 20thDay
51%11%15%17%6%
2445
21st to endDay
52%12%15%16%5%
2591
August1st to 10thDay
54%12%18%14%3
2489
11th to 20thDay
49%10%19%15%6%
2304
21st to endDay
50%9%14%20%8%
2471
September1st to 10thDay
47%8%16%20%9%
2160
11th to 20thDay
42%6%18%24%9%1
2003
21st to endDay
49%8%12%21%9%
1980
October1st to 10thDay
53%6%13%20%8%1
1972
11th to 20thDay
62%9%13%14%2
1647
21st to endDay
64%6%11%14%5%1
1782
November1st to 10thDay
57%8%13%16%6%
1671
11th to 20thDay
62%6%10%15%5%1
1701
21st to endDay
64%9%11%12%41
1349
December1st to 10thDay
67%6%9%11%6%
1330
11th to 20thDay
60%7%9%15%9%
1668
21st to endDay
58%9%10%14%7%2
2493
January1st to 10thNight
67%6%8%12%6%1
2649
11th to 20thNight
61%5%10%14%8%2
2577
21st to endNight
54%6%10%15%13%2
2772
February1st to 10thNight
57%5%9%17%10%1
2520
11th to 20thNight
60%6%10%12%10%1
2123
21st to endNight
56%6%9%15%12%2
1776
March1st to 10thNight
54%7%10%16%10%2
2160
11th to 20thNight
55%7%11%15%10%3
2075
21st to endNight
51%6%11%18%10%4
2040
April1st to 10thNight
58%6%10%11%11%3
1800
11th to 20thNight
47%8%11%21%12%2
1686
21st to endNight
53%7%9%16%13%2
1620
May1st to 10thNight
54%7%10%15%13%2
1571
11th to 20thNight
49%7%11%18%13%1
1416
21st to endNight
48%7%12%18%13%2
1502
June1st to 10thNight
52%9%13%17%8%1
1260
11th to 20thNight
45%8%13%21%10%3
1260
21st to endNight
54%8%11%17%10%
1260
July1st to 10thNight
43%10%21%19%7%
1335
11th to 20thNight
45%10%18%20%6%1
1392
21st to endNight
46%10%16%20%7%
1486
August1st to 10thNight
41%9%21%25%4
1422
11th to 20thNight
46%11%21%16%7%
1580
21st to endNight
43%9%14%28%7%
1882
September1st to 10thNight
43%9%15%22%11%1
1800
11th to 20thNight
44%8%17%24%7%
1957
21st to endNight
44%7%14%23%11%1
1980
October1st to 10thNight
49%6%11%23%10%1
1984
11th to 20thNight
55%9%14%17%5%
2312
21st to endNight
57%8%13%15%7%1
2574
November1st to 10thNight
54%7%15%17%6%1
2407
11th to 20thNight
54%9%13%14%10%
2476
21st to endNight
63%7%11%13%6%1
2830
December1st to 10thNight
68%7%9%11%5%1
2850
11th to 20thNight
60%7%11%13%9%1
3532
21st to endNight
62%7%9%13%7%2
5170

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 10thDay
24%21%34%17%4
180
11th to 20thDay
27%20%33%17%2
168
21st to endDay
15%25%40%14%5%1
176
February1st to 10thDay
29%31%32%6%11
160
11th to 20thDay
22%28%35%12%4
399
21st to endDay
24%25%32%15%4
346
March1st to 10thDay
23%23%34%16%5%
420
11th to 20thDay
27%22%30%14%6%1
420
21st to endDay
24%26%26%17%6%1
462
April1st to 10thDay
30%22%27%15%5%
420
11th to 20thDay
30%17%29%17%5%2
412
21st to endDay
31%19%34%11%41
420
May1st to 10thDay
28%20%31%16%41
423
11th to 20thDay
24%19%32%18%5%1
447
21st to endDay
28%22%29%16%6%
529
June1st to 10thDay
25%17%30%21%7%
630
11th to 20thDay
26%17%26%22%9%
630
21st to endDay
28%11%28%23%8%1
630
July1st to 10thDay
21%13%33%22%10%
505
11th to 20thDay
21%11%37%21%8%1
444
21st to endDay
21%13%34%24%8%1
488
August1st to 10thDay
22%10%33%22%10%2
446
11th to 20thDay
22%9%28%28%11%3
439
21st to endDay
23%17%25%19%11%5%
495
September1st to 10thDay
24%15%26%21%10%3
450
11th to 20thDay
24%13%28%21%12%3
450
21st to endDay
25%15%28%18%11%4
450
October1st to 10thDay
25%15%31%19%9%1
450
11th to 20thDay
34%17%25%16%7%2
373
21st to endDay
39%18%24%15%4
396
November1st to 10thDay
33%18%25%18%41
365
11th to 20thDay
28%19%27%18%7%1
361
21st to endDay
32%24%30%12%2
180
December1st to 10thDay
29%17%28%17%7%1
180
11th to 20thDay
31%24%30%11%41
180
21st to endDay
28%25%31%12%5%
198
January1st to 10thNight
21%17%36%21%4
760
11th to 20thNight
23%18%32%21%6%
737
21st to endNight
15%14%38%27%6%1
792
February1st to 10thNight
17%17%37%24%4
720
11th to 20thNight
21%17%39%18%4
703
21st to endNight
20%18%34%23%5%1
592
March1st to 10thNight
21%15%37%25%3
720
11th to 20thNight
22%20%33%19%6%1
720
21st to endNight
21%17%31%24%6%1
792
April1st to 10thNight
29%15%30%21%5%
720
11th to 20thNight
25%13%31%25%6%
622
21st to endNight
30%15%28%20%6%1
540
May1st to 10thNight
27%11%31%25%6%
491
11th to 20thNight
23%10%29%29%9%
354
21st to endNight
29%8%29%25%8%
389
June1st to 10thNight
24%9%27%33%8%
360
11th to 20thNight
22%6%26%36%10%1
360
21st to endNight
28%424%35%9%1
360
July1st to 10thNight
20%6%26%36%11%1
350
11th to 20thNight
20%424%38%14%1
348
21st to endNight
20%5%19%42%14%1
394
August1st to 10thNight
20%317%40%19%
358
11th to 20thNight
19%6%24%34%17%1
516
21st to endNight
20%8%24%31%15%2
694
September1st to 10thNight
21%8%25%32%13%1
720
11th to 20thNight
23%8%24%28%15%2
720
21st to endNight
25%10%24%29%12%1
720
October1st to 10thNight
26%11%24%29%9%1
720
11th to 20thNight
31%9%26%23%10%
720
21st to endNight
34%14%27%20%5%
792
November1st to 10thNight
28%15%25%25%6%1
740
11th to 20thNight
26%18%24%23%8%1
760
21st to endNight
28%19%27%20%5%1
841
December1st to 10thNight
29%14%27%22%7%
850
11th to 20thNight
24%20%28%22%5%1
850
21st to endNight
27%19%31%18%5%
915
Page generated at 2024-01-11 22:33:46. Version ac07

Copyright 2024 Attilla Danko


Observatoire de l'Aigle Clear Sky Chart |Charts Home