Observatoire St Marc des Carrières
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire St Marc des Carrières 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
27%
22663
12%
74898
7%
22618
34%
22618
14%
55017

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
2%
757
20%
757
7%
2163
January11th to 20thNight
14%
737
9%
2577
3%
737
22%
737
8%
2045
January21st to endNight
23%
792
13%
2772
6%
792
33%
792
13%
2037
February1st to 10thNight
18%
720
11%
2489
4%
720
28%
720
11%
1906
February11th to 20thNight
15%
703
10%
2132
3%
700
24%
700
11%
1663
February21st to endNight
21%
592
15%
1776
8%
592
32%
592
15%
1321
March1st to 10thNight
22%
720
14%
2160
7%
720
31%
720
14%
1629
March11th to 20thNight
20%
720
13%
2100
5%
720
29%
720
14%
1605
March21st to endNight
29%
792
18%
2004
6%
792
37%
792
21%
1474
April1st to 10thNight
22%
720
12%
1800
4%
720
26%
720
16%
1405
April11th to 20thNight
25%
656
16%
1720
5%
656
32%
656
21%
1249
April21st to endNight
24%
540
15%
1620
6%
540
32%
540
16%
1168
May1st to 10thNight
25%
468
15%
1548
8%
468
34%
468
15%
1092
May11th to 20thNight
29%
354
16%
1416
14%
354
41%
354
16%
931
May21st to endNight
29%
389
11%
1551
8%
388
42%
388
16%
1022
June1st to 10thNight
34%
360
8%
1355
8%
360
40%
360
16%
930
June11th to 20thNight
39%
360
10%
1260
10%
360
45%
360
19%
845
June21st to endNight
40%
360
8%
1348
9%
360
44%
360
15%
954
July1st to 10thNight
42%
350
8%
1400
11%
350
47%
350
18%
915
July11th to 20thNight
45%
348
10%
1392
15%
348
49%
348
18%
896
July21st to endNight
48%
394
10%
1486
13%
372
52%
372
17%
995
August1st to 10thNight
55%
358
13%
1422
14%
356
59%
356
19%
894
August11th to 20thNight
46%
498
11%
1562
8%
498
50%
498
20%
1084
August21st to endNight
43%
744
17%
1932
9%
744
47%
744
26%
1340
September1st to 10thNight
42%
720
13%
1800
5%
720
45%
720
28%
1246
September11th to 20thNight
45%
720
16%
1933
9%
720
49%
720
28%
1286
September21st to endNight
38%
720
18%
1980
11%
720
44%
720
25%
1362
October1st to 10thNight
35%
720
20%
2017
11%
720
43%
720
22%
1423
October11th to 20thNight
27%
720
12%
2281
6%
720
35%
720
14%
1702
October21st to endNight
22%
792
10%
2574
5%
792
28%
792
13%
1952
November1st to 10thNight
25%
740
13%
2407
7%
740
33%
740
14%
1754
November11th to 20thNight
23%
760
15%
2498
9%
760
31%
760
13%
1858
November21st to endNight
21%
787
10%
2717
5%
787
28%
787
10%
2109
December1st to 10thNight
18%
850
7%
2850
3%
850
22%
850
8%
2310
December11th to 20thNight
17%
849
9%
3462
3%
848
22%
848
7%
2698
December21st to endNight
13%
850
7%
4908
2%
837
20%
837
5%
3754

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%9%47%6%35%5%5%6%31%
74552
Night
20%11%47%6%34446%30%
75203
TransparencyDay
52%8%12%18%8%1
74257
Night
55%6%11%18%9%1
75033
SeeingDay
24%15%29%21%9%2
13816
Night
25%11%29%26%8%
22673

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
22%15%5%9%7%3445%5%21%
1517
11th to 20thDay
19%16%6%10%7%45%43423%
1472
21st to endDay
11%14%5%9%8%45%6%5%6%27%
1584
February1st to 10thDay
13%16%6%10%8%46%445%24%
1467
11th to 20thDay
16%16%6%9%6%46%445%25%
1716
21st to endDay
15%13%5%10%7%35%45%6%27%
1480
March1st to 10thDay
17%11%5%8%7%3445%5%31%
1797
11th to 20thDay
19%11%5%7%5%44446%31%
1859
21st to endDay
17%9%48%6%36%5%5%5%31%
2348
April1st to 10thDay
23%11%5%6%7%35%33429%
2160
11th to 20thDay
21%8%36%5%3335%5%38%
2188
21st to endDay
24%9%36%5%35%45%7%30%
2340
May1st to 10thDay
22%7%36%5%345%5%6%35%
2428
11th to 20thDay
18%7%36%6%45%5%6%8%34%
2478
21st to endDay
21%7%36%6%45%45%7%32%
2725
June1st to 10thDay
21%6%37%6%45%5%7%8%28%
2600
11th to 20thDay
18%7%35%6%346%6%8%34%
2700
21st to endDay
22%7%46%6%36%5%5%6%29%
2605
July1st to 10thDay
14%6%36%6%46%6%7%8%33%
2520
11th to 20thDay
15%6%26%6%47%6%7%9%32%
2520
21st to endDay
15%6%36%6%46%7%7%8%32%
2744
August1st to 10thDay
18%6%25%6%46%6%7%10%29%
2506
11th to 20thDay
15%6%35%5%46%5%5%8%37%
2321
21st to endDay
17%7%25%5%25%5%6%8%39%
2422
September1st to 10thDay
18%6%25%5%35%5%6%7%39%
2160
11th to 20thDay
18%5%25%5%2445%7%44%
2026
21st to endDay
24%6%145%2345%6%39%
1980
October1st to 10thDay
24%7%36%5%345%5%6%32%
1940
11th to 20thDay
24%8%37%7%45%5%46%26%
1678
21st to endDay
29%11%36%6%335%46%24%
1782
November1st to 10thDay
20%9%46%6%345%46%32%
1671
11th to 20thDay
23%12%5%8%6%44445%25%
1681
21st to endDay
24%14%5%6%5%345%45%23%
1459
December1st to 10thDay
28%13%5%9%5%3433423%
1330
11th to 20thDay
23%13%49%7%3443426%
1668
21st to endDay
23%19%48%5%3444422%
2680
January1st to 10thNight
20%18%7%10%6%34445%19%
2649
11th to 20thNight
19%16%6%9%7%35%44422%
2577
21st to endNight
12%13%5%10%8%45%5%46%29%
2772
February1st to 10thNight
13%13%6%11%8%35%445%26%
2489
11th to 20thNight
14%15%6%10%8%46%35%5%25%
2130
21st to endNight
17%13%49%6%45%346%30%
1776
March1st to 10thNight
17%12%49%8%35%445%29%
2150
11th to 20thNight
19%11%6%8%5%45%5%5%6%28%
2099
21st to endNight
18%11%36%5%345%45%36%
2004
April1st to 10thNight
24%12%46%5%3445%5%28%
1800
11th to 20thNight
23%7%35%5%34346%36%
1720
21st to endNight
24%9%36%433346%34%
1620
May1st to 10thNight
23%7%37%5%35%445%34%
1548
11th to 20thNight
22%7%36%5%2445%6%37%
1415
21st to endNight
23%6%25%5%3445%7%36%
1550
June1st to 10thNight
22%7%36%5%45%5%6%8%31%
1355
11th to 20thNight
21%6%26%4345%6%7%36%
1260
21st to endNight
21%7%46%5%36%5%6%7%30%
1348
July1st to 10thNight
15%6%37%5%346%7%9%35%
1440
11th to 20thNight
16%6%36%7%35%5%6%8%38%
1440
21st to endNight
15%6%36%5%46%6%6%9%35%
1574
August1st to 10thNight
14%5%26%5%45%6%6%11%36%
1432
11th to 20thNight
14%6%37%6%45%5%5%8%35%
1562
21st to endNight
16%6%26%6%35%35%7%40%
1932
September1st to 10thNight
18%6%35%5%2446%6%41%
1800
11th to 20thNight
18%5%24435%447%45%
1933
21st to endNight
22%6%15%433347%41%
1980
October1st to 10thNight
20%6%36%6%35%45%6%37%
2017
11th to 20thNight
24%9%37%6%3443431%
2281
21st to endNight
29%8%45%5%33446%28%
2574
November1st to 10thNight
20%11%37%6%3445%6%31%
2407
11th to 20thNight
23%10%5%7%5%3445%5%29%
2498
21st to endNight
25%13%47%6%34345%26%
2717
December1st to 10thNight
25%15%6%9%7%3444421%
2850
11th to 20thNight
24%14%5%9%7%33445%23%
3531
21st to endNight
26%19%5%7%5%2333423%
4973

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
67%7%8%14%6%
1518
11th to 20thDay
65%6%9%13%6%1
1472
21st to endDay
56%6%9%18%10%1
1584
February1st to 10thDay
63%5%11%13%7%2
1467
11th to 20thDay
62%6%11%12%8%1
1725
21st to endDay
57%6%11%17%8%2
1480
March1st to 10thDay
54%7%10%17%11%2
1800
11th to 20thDay
54%6%12%16%11%1
1859
21st to endDay
53%7%10%17%11%3
2348
April1st to 10thDay
59%5%11%13%9%3
2160
11th to 20thDay
49%5%10%22%11%3
2188
21st to endDay
55%6%9%15%12%2
2340
May1st to 10thDay
50%6%11%18%13%3
2428
11th to 20thDay
46%8%12%19%13%2
2482
21st to endDay
51%8%10%16%13%1
2725
June1st to 10thDay
51%10%11%18%8%2
2600
11th to 20thDay
45%8%13%20%12%1
2700
21st to endDay
54%9%11%16%9%
2605
July1st to 10thDay
44%10%16%23%6%
2450
11th to 20thDay
44%9%18%21%7%
2445
21st to endDay
47%12%16%19%6%
2591
August1st to 10thDay
47%12%20%18%3
2492
11th to 20thDay
43%11%16%22%8%
2321
21st to endDay
42%9%15%24%9%
2422
September1st to 10thDay
42%10%15%22%11%1
2160
11th to 20thDay
39%7%17%27%10%1
2026
21st to endDay
46%7%15%24%8%
1980
October1st to 10thDay
50%7%12%23%7%
1940
11th to 20thDay
58%9%14%16%2
1678
21st to endDay
62%7%9%16%5%1
1782
November1st to 10thDay
53%7%13%19%8%
1671
11th to 20thDay
62%6%10%16%6%
1681
21st to endDay
63%9%11%13%4
1459
December1st to 10thDay
66%6%10%14%4
1330
11th to 20thDay
62%6%8%18%7%
1668
21st to endDay
65%7%10%11%7%1
2680
January1st to 10thNight
68%6%8%12%4
2649
11th to 20thNight
65%6%9%13%6%1
2577
21st to endNight
57%6%10%17%10%1
2772
February1st to 10thNight
61%6%8%16%8%1
2489
11th to 20thNight
62%6%10%13%8%1
2132
21st to endNight
57%5%8%16%13%1
1776
March1st to 10thNight
58%5%9%16%10%2
2160
11th to 20thNight
57%6%8%14%13%2
2100
21st to endNight
50%6%10%19%11%4
2004
April1st to 10thNight
58%6%10%14%10%2
1800
11th to 20thNight
49%6%10%20%13%2
1720
21st to endNight
52%7%9%18%13%2
1620
May1st to 10thNight
53%5%9%16%14%3
1548
11th to 20thNight
48%6%13%17%14%3
1416
21st to endNight
47%7%10%18%16%1
1551
June1st to 10thNight
49%8%14%19%9%1
1355
11th to 20thNight
47%7%12%20%12%3
1260
21st to endNight
52%7%13%17%10%1
1348
July1st to 10thNight
42%12%17%20%9%
1400
11th to 20thNight
44%8%16%22%9%1
1392
21st to endNight
43%12%16%21%8%
1486
August1st to 10thNight
41%9%19%25%5%
1422
11th to 20thNight
45%10%18%20%7%
1562
21st to endNight
43%8%15%27%8%
1932
September1st to 10thNight
42%7%15%23%12%1
1800
11th to 20thNight
40%7%18%26%8%1
1933
21st to endNight
44%6%12%25%12%
1980
October1st to 10thNight
47%7%10%24%11%
2017
11th to 20thNight
56%7%13%19%5%
2281
21st to endNight
58%7%11%16%8%
2574
November1st to 10thNight
54%7%13%20%6%1
2407
11th to 20thNight
56%6%13%16%8%
2498
21st to endNight
63%6%11%15%6%
2717
December1st to 10thNight
68%5%11%12%3
2850
11th to 20thNight
65%5%9%15%6%
3532
21st to endNight
66%5%8%15%5%1
4973

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
30%19%30%19%2
180
11th to 20thDay
32%17%29%17%5%
168
21st to endDay
19%20%36%16%7%1
176
February1st to 10thDay
26%30%30%11%21
172
11th to 20thDay
23%23%36%16%3
384
21st to endDay
24%24%32%17%4
346
March1st to 10thDay
26%20%31%19%5%
420
11th to 20thDay
26%22%28%18%42
420
21st to endDay
24%20%28%18%8%2
462
April1st to 10thDay
27%17%30%21%5%
420
11th to 20thDay
29%17%26%21%5%2
412
21st to endDay
30%18%29%16%5%1
420
May1st to 10thDay
26%18%34%16%5%1
423
11th to 20thDay
19%16%32%24%8%2
447
21st to endDay
22%20%33%15%10%
485
June1st to 10thDay
23%13%34%21%8%1
530
11th to 20thDay
22%12%27%25%12%1
630
21st to endDay
22%11%29%25%11%1
535
July1st to 10thDay
17%11%30%27%14%1
445
11th to 20thDay
16%10%33%29%10%2
444
21st to endDay
17%10%28%31%12%2
488
August1st to 10thDay
18%8%27%30%15%3
446
11th to 20thDay
18%7%22%32%17%3
439
21st to endDay
21%14%26%16%17%6%
495
September1st to 10thDay
19%11%28%24%13%4
450
11th to 20thDay
20%12%25%24%15%4
450
21st to endDay
22%13%26%20%13%6%
450
October1st to 10thDay
26%10%28%23%11%2
450
11th to 20thDay
27%14%30%19%8%2
389
21st to endDay
35%13%30%17%6%
396
November1st to 10thDay
32%13%26%23%5%1
365
11th to 20thDay
30%17%28%18%7%
341
21st to endDay
29%24%28%14%41
180
December1st to 10thDay
35%11%30%20%32
180
11th to 20thDay
29%21%29%16%41
180
21st to endDay
38%18%27%11%5%1
198
January1st to 10thNight
28%13%35%20%4
760
11th to 20thNight
28%15%31%21%5%
737
21st to endNight
18%11%34%30%6%1
792
February1st to 10thNight
19%12%39%25%5%
720
11th to 20thNight
22%17%38%18%6%
703
21st to endNight
25%14%32%25%4
592
March1st to 10thNight
23%12%35%26%4
720
11th to 20thNight
25%13%35%20%6%1
720
21st to endNight
22%13%31%26%7%1
792
April1st to 10thNight
30%12%29%23%5%
720
11th to 20thNight
27%11%31%25%5%
656
21st to endNight
28%15%29%23%5%
540
May1st to 10thNight
26%11%31%26%5%1
468
11th to 20thNight
25%9%31%28%6%
354
21st to endNight
24%9%33%26%8%
389
June1st to 10thNight
25%6%29%33%7%
360
11th to 20thNight
22%8%26%31%13%
360
21st to endNight
23%6%23%34%13%1
360
July1st to 10thNight
15%5%31%37%12%1
350
11th to 20thNight
17%5%24%39%14%1
348
21st to endNight
14%5%24%42%13%
394
August1st to 10thNight
15%318%43%20%1
358
11th to 20thNight
17%5%22%38%17%1
498
21st to endNight
17%8%25%32%16%1
744
September1st to 10thNight
20%5%28%34%12%2
720
11th to 20thNight
20%6%23%32%17%2
720
21st to endNight
21%10%25%28%14%1
720
October1st to 10thNight
23%9%27%32%9%
720
11th to 20thNight
29%10%25%26%9%1
720
21st to endNight
32%11%31%22%4
792
November1st to 10thNight
27%11%29%25%7%1
740
11th to 20thNight
29%14%29%19%9%1
760
21st to endNight
32%14%25%22%6%
787
December1st to 10thNight
34%12%25%22%7%
850
11th to 20thNight
27%17%29%20%6%
850
21st to endNight
35%14%29%19%3
859
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