ZEC des Nymphes
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the ZEC des Nymphes clear sky chart from 2005-11-06 to 2024-01-10.

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%
22434
14%
74654
7%
22393
35%
22393
15%
52170

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
11%
760
12%
2647
1%
757
24%
757
9%
2024
January11th to 20thNight
15%
720
11%
2520
2%
720
26%
720
9%
1889
January21st to endNight
17%
792
16%
2772
6%
792
30%
792
13%
1921
February1st to 10thNight
17%
720
14%
2412
5%
720
29%
720
11%
1777
February11th to 20thNight
15%
703
14%
2190
2%
700
29%
700
12%
1597
February21st to endNight
19%
592
17%
1776
6%
592
33%
592
14%
1273
March1st to 10thNight
18%
720
15%
2160
8%
720
27%
720
13%
1600
March11th to 20thNight
18%
720
15%
2101
5%
720
28%
720
12%
1552
March21st to endNight
24%
792
21%
1980
6%
792
33%
792
19%
1423
April1st to 10thNight
21%
720
14%
1800
4%
720
26%
720
16%
1377
April11th to 20thNight
25%
711
18%
1775
5%
711
33%
711
23%
1243
April21st to endNight
22%
550
17%
1630
6%
550
32%
550
17%
1134
May1st to 10thNight
24%
392
16%
1472
10%
392
35%
392
16%
978
May11th to 20thNight
30%
354
20%
1416
14%
354
48%
354
17%
895
May21st to endNight
24%
389
12%
1551
6%
388
39%
388
17%
976
June1st to 10thNight
28%
360
9%
1440
6%
360
39%
360
16%
953
June11th to 20thNight
35%
360
9%
1440
9%
360
42%
360
16%
929
June21st to endNight
38%
360
9%
1440
11%
360
44%
360
16%
960
July1st to 10thNight
41%
350
10%
1400
12%
350
50%
350
22%
830
July11th to 20thNight
44%
348
12%
1392
17%
348
50%
348
21%
848
July21st to endNight
45%
394
13%
1486
14%
372
51%
372
22%
889
August1st to 10thNight
53%
358
14%
1422
14%
356
60%
356
22%
848
August11th to 20thNight
46%
479
16%
1543
11%
479
51%
479
26%
962
August21st to endNight
41%
792
19%
1980
9%
792
46%
792
31%
1303
September1st to 10thNight
42%
720
16%
1800
6%
720
46%
720
33%
1181
September11th to 20thNight
39%
720
19%
1879
9%
720
45%
720
34%
1182
September21st to endNight
35%
720
22%
1980
12%
720
43%
720
27%
1299
October1st to 10thNight
31%
720
21%
2096
11%
720
42%
720
20%
1415
October11th to 20thNight
24%
720
15%
2218
7%
720
35%
720
17%
1561
October21st to endNight
20%
792
12%
2574
5%
792
30%
792
14%
1853
November1st to 10thNight
23%
740
17%
2407
8%
740
35%
740
15%
1653
November11th to 20thNight
21%
760
17%
2569
9%
760
32%
760
13%
1812
November21st to endNight
18%
760
13%
2660
5%
760
29%
760
10%
1960
December1st to 10thNight
16%
760
11%
2660
5%
760
24%
760
9%
2042
December11th to 20thNight
14%
760
14%
3245
5%
759
27%
759
7%
2417
December21st to endNight
11%
826
9%
4821
2%
817
22%
817
4%
3614

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
17%10%47%6%45%5%5%7%30%
74741
Night
16%10%47%6%35%45%6%33%
74932
TransparencyDay
52%6%11%19%11%1
74446
Night
51%5%11%20%11%1
74761
SeeingDay
24%19%32%17%7%2
13394
Night
22%15%31%24%8%1
22444

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%15%6%10%8%45%45%5%24%
1509
11th to 20thDay
15%16%7%9%6%4445%5%26%
1440
21st to endDay
10%11%7%10%8%46%5%47%28%
1584
February1st to 10thDay
10%18%6%10%9%5%6%345%23%
1544
11th to 20thDay
12%15%6%11%6%45%445%27%
1658
21st to endDay
15%15%7%10%6%45%445%25%
1480
March1st to 10thDay
13%13%5%8%9%5%5%45%6%27%
1797
11th to 20thDay
15%12%5%9%6%45%445%30%
1857
21st to endDay
17%12%47%6%3445%6%32%
2376
April1st to 10thDay
19%13%48%6%34446%28%
2160
11th to 20thDay
21%9%36%6%34446%34%
2134
21st to endDay
20%11%47%6%345%45%30%
2330
May1st to 10thDay
21%9%47%6%34446%32%
2504
11th to 20thDay
19%8%37%6%35%5%5%7%33%
2478
21st to endDay
19%8%46%7%35%5%5%6%33%
2725
June1st to 10thDay
21%9%37%6%45%5%5%7%27%
2520
11th to 20thDay
16%7%36%6%46%5%6%9%32%
2520
21st to endDay
23%9%37%7%46%5%5%7%25%
2520
July1st to 10thDay
14%7%36%7%45%6%7%8%32%
2520
11th to 20thDay
15%7%36%7%5%6%6%8%9%30%
2520
21st to endDay
13%6%38%6%47%6%8%9%30%
2744
August1st to 10thDay
15%6%37%6%5%8%7%8%9%27%
2506
11th to 20thDay
13%6%36%6%46%6%7%9%32%
2337
21st to endDay
13%7%35%6%345%7%9%36%
2376
September1st to 10thDay
15%5%26%5%45%5%5%9%39%
2160
11th to 20thDay
15%6%25%5%35%5%5%6%43%
2080
21st to endDay
20%8%34434447%38%
1980
October1st to 10thDay
23%8%35%5%3445%7%31%
1862
11th to 20thDay
22%11%5%9%7%35%45%5%24%
1741
21st to endDay
25%12%46%5%45%45%5%25%
1782
November1st to 10thDay
16%12%46%7%445%5%6%31%
1671
11th to 20thDay
19%13%5%8%6%35%5%5%6%25%
1608
21st to endDay
19%16%5%6%6%46%446%24%
1520
December1st to 10thDay
24%16%5%9%5%345%45%21%
1520
11th to 20thDay
20%13%5%9%7%35%446%25%
1906
21st to endDay
19%18%5%10%6%34445%22%
2772
January1st to 10thNight
15%17%6%10%6%35%45%6%21%
2647
11th to 20thNight
13%15%7%9%7%44446%26%
2520
21st to endNight
9%11%6%10%9%45%5%5%6%31%
2772
February1st to 10thNight
11%12%6%10%7%5%6%5%5%6%27%
2412
11th to 20thNight
10%13%6%10%7%5%45%5%7%29%
2188
21st to endNight
13%11%5%8%7%35%5%5%6%32%
1776
March1st to 10thNight
14%13%49%6%45%5%5%7%27%
2150
11th to 20thNight
14%15%5%7%6%45%5%45%30%
2101
21st to endNight
13%10%47%6%35%45%6%36%
1980
April1st to 10thNight
20%12%47%6%45%45%5%30%
1800
11th to 20thNight
17%6%37%5%345%5%7%38%
1775
21st to endNight
20%10%45%5%25%5%5%5%34%
1630
May1st to 10thNight
20%9%26%6%44346%37%
1472
11th to 20thNight
18%8%25%5%3445%7%39%
1415
21st to endNight
18%5%36%5%35%5%5%7%38%
1550
June1st to 10thNight
19%7%35%5%35%6%5%8%33%
1440
11th to 20thNight
17%7%35%5%45%5%6%7%36%
1440
21st to endNight
18%7%35%5%35%5%6%8%34%
1440
July1st to 10thNight
12%5%36%445%5%5%9%41%
1440
11th to 20thNight
12%5%26%6%35%5%6%9%42%
1440
21st to endNight
12%6%36%4245%7%7%43%
1574
August1st to 10thNight
11%6%35%6%346%6%9%41%
1432
11th to 20thNight
13%6%35%6%3446%8%42%
1543
21st to endNight
15%6%344335%5%8%44%
1980
September1st to 10thNight
12%5%35%445%46%8%45%
1800
11th to 20thNight
16%4244235%6%6%48%
1879
21st to endNight
17%7%25%42335%7%45%
1980
October1st to 10thNight
17%9%26%6%3445%5%40%
2096
11th to 20thNight
21%9%37%6%3445%7%31%
2218
21st to endNight
23%9%47%6%4445%7%27%
2574
November1st to 10thNight
17%9%5%6%6%35%5%5%7%33%
2407
11th to 20thNight
18%10%5%7%6%35%45%6%30%
2569
21st to endNight
19%14%5%8%6%335%45%28%
2660
December1st to 10thNight
19%15%6%10%6%4445%6%20%
2660
11th to 20thNight
20%13%5%9%6%35%445%25%
3288
21st to endNight
20%16%7%10%6%34445%22%
4884

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
61%6%9%15%8%
1510
11th to 20thDay
60%48%15%12%1
1440
21st to endDay
55%47%19%12%2
1584
February1st to 10thDay
62%36%17%10%2
1544
11th to 20thDay
59%411%14%11%1
1667
21st to endDay
61%46%17%9%3
1480
March1st to 10thDay
57%5%8%17%12%2
1800
11th to 20thDay
55%410%14%14%3
1857
21st to endDay
53%48%17%14%4
2376
April1st to 10thDay
57%5%8%15%12%3
2160
11th to 20thDay
51%49%21%13%3
2134
21st to endDay
55%6%7%16%13%3
2330
May1st to 10thDay
51%49%20%14%2
2504
11th to 20thDay
50%5%9%17%15%3
2482
21st to endDay
51%6%11%18%13%1
2725
June1st to 10thDay
54%8%9%18%9%2
2520
11th to 20thDay
47%7%11%21%11%2
2520
21st to endDay
57%7%10%16%9%
2520
July1st to 10thDay
44%9%13%24%10%
2450
11th to 20thDay
45%8%14%24%9%
2445
21st to endDay
47%10%14%21%8%
2591
August1st to 10thDay
49%9%16%21%5%
2492
11th to 20thDay
43%11%14%23%9%
2337
21st to endDay
41%8%14%25%13%1
2376
September1st to 10thDay
40%6%16%26%12%1
2160
11th to 20thDay
40%7%13%28%11%1
2080
21st to endDay
45%5%12%27%11%
1980
October1st to 10thDay
50%412%23%10%1
1862
11th to 20thDay
59%7%11%18%5%
1741
21st to endDay
59%5%11%15%9%1
1782
November1st to 10thDay
51%6%14%19%9%1
1671
11th to 20thDay
57%5%10%16%11%1
1608
21st to endDay
60%6%11%16%7%1
1520
December1st to 10thDay
65%49%15%7%
1520
11th to 20thDay
60%48%18%9%
1906
21st to endDay
64%5%7%14%10%
2772
January1st to 10thNight
62%5%8%17%8%1
2647
11th to 20thNight
60%5%10%14%9%2
2520
21st to endNight
52%5%9%17%15%2
2772
February1st to 10thNight
58%5%8%19%10%2
2412
11th to 20thNight
55%5%9%18%12%1
2190
21st to endNight
52%5%8%18%14%2
1776
March1st to 10thNight
56%5%9%16%12%2
2160
11th to 20thNight
56%47%16%13%3
2102
21st to endNight
47%6%7%21%15%4
1980
April1st to 10thNight
55%6%8%15%15%2
1800
11th to 20thNight
44%6%10%23%14%3
1775
21st to endNight
50%48%21%15%2
1630
May1st to 10thNight
50%39%18%15%4
1472
11th to 20thNight
46%5%10%21%15%4
1416
21st to endNight
45%6%13%20%15%2
1551
June1st to 10thNight
47%7%12%22%11%1
1440
11th to 20thNight
45%7%11%20%12%3
1440
21st to endNight
47%8%13%19%13%
1440
July1st to 10thNight
38%8%17%25%11%1
1400
11th to 20thNight
39%8%15%27%10%1
1392
21st to endNight
37%9%17%27%10%
1486
August1st to 10thNight
37%9%19%27%8%
1422
11th to 20thNight
38%7%18%26%11%
1543
21st to endNight
38%5%16%30%11%
1980
September1st to 10thNight
36%6%16%27%14%1
1800
11th to 20thNight
36%417%31%11%1
1879
21st to endNight
39%6%11%30%13%
1980
October1st to 10thNight
46%5%10%26%13%1
2096
11th to 20thNight
50%6%13%23%8%
2218
21st to endNight
55%412%18%10%1
2574
November1st to 10thNight
50%5%13%22%9%1
2407
11th to 20thNight
52%6%12%19%10%1
2569
21st to endNight
58%5%10%17%9%1
2660
December1st to 10thNight
63%5%11%16%6%
2660
11th to 20thNight
61%47%17%10%1
3288
21st to endNight
64%5%6%17%7%1
4884

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
23%19%40%15%4
178
11th to 20thDay
26%16%39%13%6%1
160
21st to endDay
16%23%43%13%31
176
February1st to 10thDay
34%28%30%6%2
206
11th to 20thDay
24%30%35%10%1
325
21st to endDay
27%26%30%13%3
346
March1st to 10thDay
23%24%33%16%3
420
11th to 20thDay
27%26%31%13%3
420
21st to endDay
30%24%25%13%7%1
462
April1st to 10thDay
30%20%30%14%6%
420
11th to 20thDay
33%19%25%13%8%1
412
21st to endDay
32%20%33%10%5%1
420
May1st to 10thDay
30%19%33%13%32
423
11th to 20thDay
25%21%32%15%5%1
447
21st to endDay
24%23%34%14%41
485
June1st to 10thDay
24%16%42%11%6%
450
11th to 20thDay
22%19%32%17%10%1
450
21st to endDay
26%13%33%19%7%1
450
July1st to 10thDay
14%11%41%25%7%2
445
11th to 20thDay
15%14%37%28%5%1
444
21st to endDay
15%10%34%29%10%2
488
August1st to 10thDay
16%11%34%25%11%2
446
11th to 20thDay
15%9%33%25%12%5%
439
21st to endDay
18%18%27%20%14%4
495
September1st to 10thDay
19%12%34%21%10%4
450
11th to 20thDay
17%12%32%21%11%6%
450
21st to endDay
22%17%28%17%11%4
450
October1st to 10thDay
27%17%25%20%9%2
450
11th to 20thDay
27%22%26%15%8%1
420
21st to endDay
33%19%28%16%4
396
November1st to 10thDay
28%20%28%18%5%1
365
11th to 20thDay
28%19%34%15%3
268
21st to endDay
28%29%30%11%21
180
December1st to 10thDay
31%18%31%13%7%1
180
11th to 20thDay
30%28%29%10%3
180
21st to endDay
33%23%28%11%5%1
198
January1st to 10thNight
25%17%37%18%4
760
11th to 20thNight
21%20%33%20%5%
720
21st to endNight
15%18%38%23%5%
792
February1st to 10thNight
18%20%36%21%5%
720
11th to 20thNight
20%22%35%19%41
703
21st to endNight
21%20%33%22%3
592
March1st to 10thNight
25%17%33%20%4
720
11th to 20thNight
25%24%28%17%5%1
720
21st to endNight
22%18%30%24%6%1
792
April1st to 10thNight
29%16%27%22%5%
720
11th to 20thNight
23%17%32%22%6%
711
21st to endNight
27%19%28%20%5%1
550
May1st to 10thNight
26%15%30%20%7%1
392
11th to 20thNight
24%13%31%26%7%
354
21st to endNight
21%12%40%20%7%
389
June1st to 10thNight
23%10%34%26%7%
360
11th to 20thNight
19%11%27%31%11%1
360
21st to endNight
21%6%30%32%11%1
360
July1st to 10thNight
14%6%35%33%11%1
350
11th to 20thNight
14%5%28%39%13%1
348
21st to endNight
14%6%29%38%13%1
394
August1st to 10thNight
11%5%22%44%17%1
358
11th to 20thNight
14%5%25%35%19%2
479
21st to endNight
15%9%29%29%16%2
792
September1st to 10thNight
15%9%30%34%12%1
720
11th to 20thNight
19%9%29%27%16%1
720
21st to endNight
22%10%30%23%13%2
720
October1st to 10thNight
21%15%28%25%10%1
720
11th to 20thNight
28%13%29%22%8%
720
21st to endNight
28%16%29%21%5%1
792
November1st to 10thNight
23%19%27%24%6%1
740
11th to 20thNight
25%17%30%19%8%1
760
21st to endNight
28%21%25%20%5%1
760
December1st to 10thNight
27%17%29%21%4
760
11th to 20thNight
28%18%33%16%5%1
760
21st to endNight
31%19%28%18%3
836
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