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 2005-11-05 to 2017-09-24.

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
28%
14634
11%
46921
6%
14602
34%
14602
14%
34653

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
13%
720
9%
2506
3%
716
21%
716
8%
1977
January16th to endNight
20%
768
11%
2688
4%
768
29%
768
10%
1992
February1st to 15thNight
20%
704
11%
2366
3%
701
30%
701
12%
1766
February16th to endNight
18%
631
11%
1893
5%
631
26%
631
11%
1482
March1st to 15thNight
21%
720
14%
2160
7%
720
30%
720
14%
1593
March16th to endNight
28%
768
17%
2022
6%
768
35%
768
19%
1455
April1st to 15thNight
24%
717
15%
1795
4%
717
30%
717
17%
1388
April16th to endNight
25%
540
15%
1620
6%
540
32%
540
17%
1145
May1st to 15thNight
28%
447
12%
1527
10%
447
34%
447
14%
1098
May16th to endNight
29%
375
10%
1464
9%
374
37%
374
13%
1036
June1st to 15thNight
32%
360
6%
1260
3%
360
36%
360
12%
932
June16th to endNight
39%
360
7%
1260
7%
360
41%
360
15%
912
July1st to 15thNight
47%
340
6%
1318
9%
340
49%
340
18%
876
July16th to endNight
46%
376
9%
1418
12%
354
48%
354
16%
957
August1st to 15thNight
51%
408
10%
1479
10%
406
54%
406
17%
1019
August16th to endNight
43%
640
14%
1786
8%
640
45%
640
23%
1228
September1st to 15thNight
41%
720
10%
1845
5%
720
42%
720
24%
1329
September16th to endNight
41%
693
17%
1913
11%
693
44%
693
26%
1292
October1st to 15thNight
29%
660
15%
1911
8%
660
37%
660
19%
1386
October16th to endNight
22%
704
9%
2288
4%
704
28%
704
12%
1752
November1st to 15thNight
28%
700
15%
2277
9%
700
35%
700
14%
1658
November16th to endNight
27%
738
11%
2570
7%
738
33%
738
10%
1940
December1st to 15thNight
15%
750
6%
2700
2%
750
21%
750
7%
2199
December16th to endNight
16%
795
10%
2855
4%
795
24%
795
8%
2241

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%11%47%5%34445%26%
48003
Night
19%11%46%5%34446%29%
47091
TransparencyDay
57%6%11%15%7%1
47691
Night
55%6%12%16%8%1
46921
SeeingDay
28%12%26%20%9%1
6097
Night
25%11%27%25%8%
14634

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
16%16%6%8%6%34445%23%
1432
16th to endDay
9%15%8%10%6%345%6%5%24%
1536
February1st to 15thDay
7%14%7%14%8%45%43424%
1492
16th to endDay
14%15%6%10%7%35%446%21%
1580
March1st to 15thDay
18%13%5%9%5%2434428%
1790
16th to endDay
14%13%47%6%25%435%32%
2199
April1st to 15thDay
24%13%35%42333428%
2152
16th to endDay
25%11%3442334433%
2340
May1st to 15thDay
27%8%34424346%28%
2433
16th to endDay
25%8%36%6%45%44425%
2648
June1st to 15thDay
24%8%36%5%35%45%7%25%
2700
16th to endDay
28%8%37%6%24446%22%
2700
July1st to 15thDay
20%7%36%6%5%6%45%8%24%
2560
16th to endDay
23%7%36%6%45%5%5%6%23%
2654
August1st to 15thDay
23%8%37%5%45%46%7%21%
2457
16th to endDay
18%7%27%6%45%45%8%28%
2414
September1st to 15thDay
25%7%24424345%33%
2115
16th to endDay
24%5%24422346%37%
1906
October1st to 15thDay
27%10%26%5%23335%27%
1716
16th to endDay
29%15%36%424335%20%
1584
November1st to 15thDay
23%14%48%43333425%
1581
16th to endDay
23%18%5%6%42233325%
1386
December1st to 15thDay
25%18%5%8%43231322%
1260
16th to endDay
18%19%7%7%5%2443321%
1368
January1st to 15thNight
16%16%7%9%8%33235%22%
2506
16th to endNight
9%14%6%9%8%36%45%6%24%
2688
February1st to 15thNight
7%12%6%11%10%46%446%25%
2365
16th to endNight
13%17%6%10%7%3444424%
1893
March1st to 15thNight
17%12%37%6%25%336%30%
2147
16th to endNight
12%12%46%5%34445%35%
2022
April1st to 15thNight
23%13%45%423445%28%
1795
16th to endNight
22%8%35%323345%35%
1620
May1st to 15thNight
26%6%345%33436%32%
1527
16th to endNight
28%6%26%333336%32%
1462
June1st to 15thNight
21%9%26%5%3445%7%28%
1260
16th to endNight
25%5%36%5%34345%31%
1260
July1st to 15thNight
21%6%244245%6%9%33%
1398
16th to endNight
18%6%36%4245%5%7%36%
1514
August1st to 15thNight
20%5%15%336%5%6%8%33%
1489
16th to endNight
16%5%245%3445%7%38%
1786
September1st to 15thNight
23%6%24333345%38%
1845
16th to endNight
24%5%13213336%43%
1913
October1st to 15thNight
24%9%25%424346%33%
1911
16th to endNight
27%12%35%424445%26%
2288
November1st to 15thNight
21%10%46%5%24446%30%
2277
16th to endNight
23%13%46%433345%26%
2570
December1st to 15thNight
21%18%5%8%7%3433420%
2700
16th to endNight
19%17%6%8%6%33245%21%
2855

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
60%6%10%13%8%
1433
16th to endDay
57%5%10%16%9%
1536
February1st to 15thDay
61%411%13%7%1
1495
16th to endDay
62%48%13%7%2
1580
March1st to 15thDay
58%49%14%10%2
1800
16th to endDay
54%5%8%15%12%3
2199
April1st to 15thDay
57%49%15%9%4
2152
16th to endDay
53%410%16%12%2
2340
May1st to 15thDay
54%6%11%15%10%1
2433
16th to endDay
60%7%9%14%6%
2652
June1st to 15thDay
56%8%11%14%6%1
2700
16th to endDay
61%6%11%12%6%
2700
July1st to 15thDay
54%8%16%15%4
2411
16th to endDay
58%9%12%15%4
2487
August1st to 15thDay
57%9%17%11%3
2443
16th to endDay
50%8%16%19%5%
2414
September1st to 15thDay
50%5%15%19%8%
2115
16th to endDay
46%5%15%22%8%
1906
October1st to 15thDay
57%5%13%15%7%
1716
16th to endDay
66%5%10%14%3
1584
November1st to 15thDay
61%6%10%16%5%
1581
16th to endDay
62%5%10%15%41
1386
December1st to 15thDay
66%410%12%5%
1260
16th to endDay
65%6%8%10%8%
1368
January1st to 15thNight
64%5%9%13%5%
2506
16th to endNight
58%5%10%16%8%
2688
February1st to 15thNight
58%5%10%16%8%1
2366
16th to endNight
62%5%8%12%10%1
1893
March1st to 15thNight
55%5%10%15%10%2
2160
16th to endNight
49%5%11%18%11%3
2022
April1st to 15thNight
56%47%16%11%2
1795
16th to endNight
49%6%9%17%13%3
1620
May1st to 15thNight
54%6%10%15%11%1
1527
16th to endNight
54%6%12%16%9%
1464
June1st to 15thNight
55%8%12%16%6%
1260
16th to endNight
53%7%10%18%10%
1260
July1st to 15thNight
45%8%19%19%6%
1318
16th to endNight
47%8%16%19%8%
1418
August1st to 15thNight
46%9%19%20%3
1479
16th to endNight
43%8%18%23%5%
1786
September1st to 15thNight
46%7%14%22%8%
1845
16th to endNight
42%6%16%25%8%
1913
October1st to 15thNight
51%5%12%21%8%
1911
16th to endNight
58%7%12%15%5%
2288
November1st to 15thNight
53%7%14%15%8%
2277
16th to endNight
60%5%11%15%7%
2570
December1st to 15thNight
68%6%10%9%5%
2700
16th to endNight
64%5%9%11%7%1
2855

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%18%35%18%1
60
16th to endDay
26%21%31%14%41
64
February1st to 15thDay
21%19%33%17%8%
118
16th to endDay
23%12%38%19%5%
239
March1st to 15thDay
25%19%28%20%6%
270
16th to endDay
23%18%21%23%11%2
288
April1st to 15thDay
33%15%24%17%7%1
270
16th to endDay
33%12%30%12%8%2
270
May1st to 15thDay
34%12%28%15%8%1
288
16th to endDay
31%16%26%18%5%
361
June1st to 15thDay
28%12%24%26%8%
495
16th to endDay
29%10%28%22%8%1
495
July1st to 15thDay
26%8%30%20%13%
345
16th to endDay
27%7%26%28%8%1
326
August1st to 15thDay
26%426%26%12%3
313
16th to endDay
22%12%21%22%13%6%
332
September1st to 15thDay
26%10%22%21%14%4
315
16th to endDay
21%10%26%21%15%4
287
October1st to 15thDay
28%10%28%20%10%2
248
16th to endDay
40%10%21%19%7%
240
November1st to 15thDay
31%16%20%20%9%2
235
16th to endDay
32%20%20%18%7%1
114
December1st to 15thDay
40%13%33%8%5%
60
16th to endDay
39%31%21%7%
64
January1st to 15thNight
23%16%34%20%4
720
16th to endNight
18%15%34%24%7%
768
February1st to 15thNight
13%14%38%26%6%
704
16th to endNight
22%14%34%22%5%
631
March1st to 15thNight
23%16%32%23%3
720
16th to endNight
17%16%31%24%8%1
768
April1st to 15thNight
30%12%27%23%5%
717
16th to endNight
27%13%27%22%7%
540
May1st to 15thNight
26%10%29%24%9%
447
16th to endNight
32%6%25%28%7%
375
June1st to 15thNight
27%6%25%32%8%
360
16th to endNight
26%321%35%12%
360
July1st to 15thNight
23%420%34%16%1
340
16th to endNight
19%321%40%14%1
376
August1st to 15thNight
21%317%34%22%
408
16th to endNight
18%425%34%15%1
640
September1st to 15thNight
24%5%21%32%12%2
720
16th to endNight
25%7%22%27%15%1
693
October1st to 15thNight
27%9%26%25%10%1
660
16th to endNight
35%12%25%18%7%
704
November1st to 15thNight
26%14%23%26%7%1
700
16th to endNight
31%15%19%22%8%1
738
December1st to 15thNight
31%14%27%20%5%
750
16th to endNight
28%17%27%19%41
795
Page generated at 2017-09-25 09:02:22. Version ac04

Copyright 2017 A. Danko


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