La Butte à Mounette
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the La Butte à Mounette clear sky chart from 2005-11-06 to 2024-01-27.

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%
23637
8%
74509
5%
23578
30%
23578
11%
59404

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
6%
850
2%
2649
0%
847
7%
847
1%
2515
January11th to 20thNight
8%
850
2%
2660
0%
850
11%
850
2%
2471
January21st to endNight
10%
892
6%
2817
2%
892
15%
892
4%
2504
February1st to 10thNight
13%
720
4%
2340
1%
720
17%
720
6%
2000
February11th to 20thNight
14%
703
7%
2276
3%
700
20%
700
8%
1860
February21st to endNight
23%
592
12%
1845
4%
592
32%
592
13%
1411
March1st to 10thNight
25%
717
14%
2124
6%
717
32%
717
17%
1570
March11th to 20thNight
27%
720
12%
1980
5%
720
32%
720
16%
1520
March21st to endNight
27%
707
12%
2093
6%
707
33%
707
14%
1602
April1st to 10thNight
26%
540
10%
1800
6%
540
32%
540
12%
1369
April11th to 20thNight
36%
534
16%
1767
12%
534
42%
534
19%
1214
April21st to endNight
36%
540
13%
1566
9%
540
40%
540
18%
1173
May1st to 10thNight
36%
540
13%
1440
8%
540
40%
540
19%
1077
May11th to 20thNight
46%
532
14%
1417
8%
532
49%
532
23%
1018
May21st to endNight
38%
582
10%
1551
4%
582
41%
582
21%
1129
June1st to 10thNight
37%
540
5%
1440
4%
540
37%
540
15%
1152
June11th to 20thNight
45%
398
10%
1298
8%
398
48%
398
20%
885
June21st to endNight
45%
360
6%
1260
5%
360
46%
360
14%
935
July1st to 10thNight
48%
354
9%
1229
8%
354
50%
354
18%
845
July11th to 20thNight
55%
522
9%
1392
7%
522
56%
522
25%
971
July21st to endNight
48%
590
9%
1486
7%
558
50%
558
19%
1114
August1st to 10thNight
56%
538
9%
1438
7%
534
56%
534
25%
1023
August11th to 20thNight
50%
532
11%
1596
9%
532
52%
532
21%
1122
August21st to endNight
54%
594
15%
1926
13%
594
56%
594
24%
1276
September1st to 10thNight
43%
540
12%
1800
9%
540
48%
540
22%
1182
September11th to 20thNight
40%
540
18%
1800
16%
540
45%
540
19%
1221
September21st to endNight
34%
656
14%
2055
10%
656
38%
656
18%
1438
October1st to 10thNight
34%
720
13%
2160
7%
720
40%
720
17%
1570
October11th to 20thNight
30%
720
10%
2160
6%
720
33%
720
14%
1640
October21st to endNight
19%
861
10%
2515
5%
861
23%
861
10%
2096
November1st to 10thNight
20%
830
9%
2519
5%
830
24%
830
9%
2057
November11th to 20thNight
13%
850
5%
2660
3%
850
16%
850
6%
2319
November21st to endNight
13%
850
2%
2660
1%
850
14%
850
3%
2425
December1st to 10thNight
8%
850
3%
2660
0%
850
11%
850
3%
2458
December11th to 20thNight
4%
850
2%
3273
0%
849
6%
849
1%
3065
December21st to endNight
5%
923
1%
4857
0%
907
8%
907
1%
4177

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%12%5%9%7%34446%27%
75332
Night
21%13%6%10%7%34345%22%
74722
TransparencyDay
59%6%12%16%7%
75031
Night
64%5%10%14%6%1
74558
SeeingDay
25%8%23%27%14%2
16542
Night
27%10%25%26%11%2
23653

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
20%21%10%19%12%432125%
1516
11th to 20thDay
19%18%10%19%11%5%43324
1520
21st to endDay
13%12%10%21%16%4433312%
1678
February1st to 10thDay
18%13%7%17%13%6%6%32313%
1620
11th to 20thDay
18%14%5%12%11%6%5%33418%
1573
21st to endDay
11%12%5%9%10%6%5%45%6%26%
1410
March1st to 10thDay
13%13%7%11%8%34336%27%
1832
11th to 20thDay
15%11%7%12%8%4444426%
1980
21st to endDay
17%13%6%9%8%3433430%
2263
April1st to 10thDay
22%11%48%6%34446%29%
2160
11th to 20thDay
19%10%5%6%424447%34%
2141
21st to endDay
21%12%46%433447%32%
2393
May1st to 10thDay
25%10%46%5%3335%5%31%
2520
11th to 20thDay
23%9%35%5%2345%6%36%
2478
21st to endDay
20%8%35%5%3445%7%36%
2724
June1st to 10thDay
26%11%47%5%3345%6%27%
2520
11th to 20thDay
17%8%46%5%345%47%36%
2674
21st to endDay
23%10%47%5%33346%31%
2700
July1st to 10thDay
16%7%36%5%35%46%9%36%
2674
11th to 20thDay
15%8%36%6%35%6%6%7%36%
2520
21st to endDay
21%9%36%5%35%5%5%6%31%
2745
August1st to 10thDay
17%5%25%5%35%6%6%9%37%
2488
11th to 20thDay
18%8%36%6%35%46%8%34%
2304
21st to endDay
18%7%25%5%35%45%9%37%
2430
September1st to 10thDay
18%6%35%5%345%6%8%36%
2160
11th to 20thDay
20%9%46%6%34447%34%
2160
21st to endDay
19%9%46%6%34346%35%
1902
October1st to 10thDay
20%8%36%5%35%5%6%7%32%
1800
11th to 20thDay
23%13%38%7%35%5%5%6%23%
1800
21st to endDay
24%18%39%444345%21%
1841
November1st to 10thDay
24%20%5%8%6%3445%5%18%
1557
11th to 20thDay
25%23%7%10%7%35%33410%
1520
21st to endDay
20%23%14%10%6%34345%10%
1520
December1st to 10thDay
25%21%12%15%7%333236%
1520
11th to 20thDay
25%21%12%19%8%332223
1906
21st to endDay
22%18%11%14%7%3433312%
2783
January1st to 10thNight
22%18%13%19%9%432235%
2649
11th to 20thNight
20%17%9%21%10%443237%
2660
21st to endNight
16%14%10%20%14%4422312%
2817
February1st to 10thNight
17%12%5%15%15%45%44415%
2340
11th to 20thNight
17%15%6%12%11%44346%18%
2273
21st to endNight
12%12%6%12%9%45%45%6%25%
1845
March1st to 10thNight
16%12%5%10%7%34446%30%
2115
11th to 20thNight
19%12%6%9%7%44446%26%
1979
21st to endNight
18%15%5%9%7%34435%28%
2093
April1st to 10thNight
23%12%5%8%7%33345%25%
1800
11th to 20thNight
20%10%46%5%3446%7%33%
1767
21st to endNight
22%11%38%5%35%445%30%
1566
May1st to 10thNight
27%9%35%433346%32%
1440
11th to 20thNight
24%7%25%435%35%6%36%
1416
21st to endNight
20%8%36%6%345%6%6%34%
1550
June1st to 10thNight
26%11%47%5%35%45%6%23%
1440
11th to 20thNight
22%6%35%5%35%447%37%
1298
21st to endNight
22%11%46%6%35%46%7%27%
1260
July1st to 10thNight
20%7%36%5%35%6%6%8%31%
1264
11th to 20thNight
14%7%36%5%36%5%8%8%34%
1440
21st to endNight
19%9%38%6%35%5%5%6%30%
1573
August1st to 10thNight
17%5%25%5%36%6%8%8%34%
1449
11th to 20thNight
17%9%37%5%2446%6%35%
1596
21st to endNight
16%7%35%435%5%6%9%38%
1926
September1st to 10thNight
17%6%36%6%3435%8%38%
1800
11th to 20thNight
25%8%35%433336%38%
1800
21st to endNight
21%7%36%5%34446%36%
2055
October1st to 10thNight
22%8%36%6%35%5%46%32%
2160
11th to 20thNight
25%12%46%6%34446%26%
2160
21st to endNight
27%15%5%8%6%34345%19%
2515
November1st to 10thNight
23%18%5%7%6%3444422%
2519
11th to 20thNight
24%21%7%8%7%3445%5%12%
2660
21st to endNight
25%24%10%11%6%343349%
2660
December1st to 10thNight
27%21%11%13%7%323247%
2660
11th to 20thNight
28%20%9%18%8%332227%
3293
21st to endNight
26%18%10%15%6%2222411%
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
90%3421
1517
11th to 20thDay
88%45%21
1520
21st to endDay
78%46%9%3
1678
February1st to 10thDay
79%36%8%3
1620
11th to 20thDay
71%5%9%10%41
1581
21st to endDay
58%7%11%15%9%1
1410
March1st to 10thDay
59%5%8%19%8%
1836
11th to 20thDay
60%5%9%18%7%1
1980
21st to endDay
59%410%16%10%2
2263
April1st to 10thDay
57%5%10%16%10%1
2160
11th to 20thDay
50%412%21%11%1
2141
21st to endDay
53%5%13%18%11%1
2393
May1st to 10thDay
56%5%8%18%12%1
2520
11th to 20thDay
50%5%11%22%11%1
2482
21st to endDay
48%7%14%21%10%
2724
June1st to 10thDay
59%7%11%16%7%
2520
11th to 20thDay
48%6%13%22%9%1
2674
21st to endDay
56%7%12%16%8%1
2700
July1st to 10thDay
43%9%19%23%6%
2600
11th to 20thDay
46%8%15%22%9%
2444
21st to endDay
53%7%15%18%7%
2592
August1st to 10thDay
41%9%22%24%5%
2474
11th to 20thDay
48%8%18%22%4
2304
21st to endDay
44%7%18%25%6%
2430
September1st to 10thDay
44%9%16%22%9%
2160
11th to 20thDay
51%6%13%20%9%
2160
21st to endDay
50%6%13%23%8%
1902
October1st to 10thDay
50%7%14%21%8%
1800
11th to 20thDay
62%6%15%14%31
1800
21st to endDay
67%6%11%13%4
1841
November1st to 10thDay
68%7%12%11%3
1557
11th to 20thDay
79%6%8%6%1
1520
21st to endDay
79%5%10%42
1520
December1st to 10thDay
87%45%32
1520
11th to 20thDay
92%2321
1905
21st to endDay
78%6%10%5%1
2783
January1st to 10thNight
89%4431
2649
11th to 20thNight
85%45%41
2660
21st to endNight
81%35%7%3
2817
February1st to 10thNight
74%6%9%8%4
2340
11th to 20thNight
69%5%10%13%31
2276
21st to endNight
59%6%11%14%10%1
1845
March1st to 10thNight
56%410%19%8%2
2124
11th to 20thNight
59%49%18%7%2
1980
21st to endNight
60%5%10%15%8%3
2093
April1st to 10thNight
61%410%13%11%1
1800
11th to 20thNight
51%410%21%12%2
1767
21st to endNight
56%5%10%16%12%2
1566
May1st to 10thNight
54%6%10%18%11%1
1440
11th to 20thNight
49%6%9%22%12%2
1417
21st to endNight
50%7%11%22%9%1
1551
June1st to 10thNight
62%6%9%17%6%
1440
11th to 20thNight
48%6%11%24%11%
1298
21st to endNight
56%7%12%16%8%
1260
July1st to 10thNight
48%8%15%22%6%
1229
11th to 20thNight
44%8%16%22%9%
1392
21st to endNight
53%7%14%20%5%
1486
August1st to 10thNight
42%11%18%22%6%
1438
11th to 20thNight
47%8%17%21%6%1
1596
21st to endNight
42%8%17%26%6%
1926
September1st to 10thNight
44%6%14%25%9%
1800
11th to 20thNight
50%412%24%10%1
1800
21st to endNight
49%7%13%23%8%
2055
October1st to 10thNight
52%7%13%19%9%1
2160
11th to 20thNight
60%5%14%18%3
2160
21st to endNight
69%5%9%12%5%
2515
November1st to 10thNight
65%7%10%12%4
2519
11th to 20thNight
75%6%9%8%2
2660
21st to endNight
82%6%8%41
2660
December1st to 10thNight
85%45%5%1
2660
11th to 20thNight
88%3441
3295
21st to endNight
79%5%9%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
29%16%32%17%5%
370
11th to 20thDay
25%18%28%23%5%1
370
21st to endDay
18%13%34%28%7%1
393
February1st to 10thDay
29%16%34%16%5%1
340
11th to 20thDay
27%14%31%23%31
336
21st to endDay
18%12%30%28%11%2
280
March1st to 10thDay
19%10%32%29%8%2
356
11th to 20thDay
18%12%28%26%12%4
420
21st to endDay
24%10%28%27%9%2
462
April1st to 10thDay
28%13%29%23%7%1
420
11th to 20thDay
21%10%26%26%14%2
412
21st to endDay
27%6%22%27%17%1
473
May1st to 10thDay
30%5%19%29%12%4
603
11th to 20thDay
25%420%27%21%4
624
21st to endDay
25%324%34%12%2
680
June1st to 10thDay
30%5%17%28%18%3
630
11th to 20thDay
21%417%35%22%2
630
21st to endDay
28%214%30%22%3
630
July1st to 10thDay
22%217%38%18%3
620
11th to 20thDay
17%217%34%25%4
618
21st to endDay
25%213%33%23%3
685
August1st to 10thDay
16%313%34%29%5%
607
11th to 20thDay
22%314%30%27%5%
439
21st to endDay
19%5%18%29%27%3
495
September1st to 10thDay
18%426%31%17%3
450
11th to 20thDay
26%9%22%28%14%1
450
21st to endDay
22%7%31%26%12%1
381
October1st to 10thDay
22%8%23%31%15%1
360
11th to 20thDay
27%10%25%23%13%1
360
21st to endDay
30%15%28%19%7%1
396
November1st to 10thDay
30%18%28%19%5%1
365
11th to 20thDay
34%14%24%19%7%2
370
21st to endDay
34%16%27%20%3
370
December1st to 10thDay
34%12%30%19%5%
370
11th to 20thDay
31%22%26%19%2
370
21st to endDay
28%18%29%16%8%1
407
January1st to 10thNight
30%16%28%19%7%
850
11th to 20thNight
31%15%27%22%5%1
850
21st to endNight
23%14%33%21%9%
892
February1st to 10thNight
24%14%33%22%7%
720
11th to 20thNight
26%11%34%22%41
703
21st to endNight
19%10%30%26%12%2
592
March1st to 10thNight
20%8%35%27%9%1
720
11th to 20thNight
24%9%28%28%9%2
720
21st to endNight
24%10%28%28%9%3
707
April1st to 10thNight
26%9%26%30%9%
540
11th to 20thNight
23%8%25%28%13%2
534
21st to endNight
25%5%25%30%13%2
540
May1st to 10thNight
31%421%25%13%5%
540
11th to 20thNight
27%416%31%18%5%
532
21st to endNight
22%5%25%32%14%2
583
June1st to 10thNight
29%418%34%13%2
540
11th to 20thNight
23%317%36%19%2
398
21st to endNight
24%215%37%19%3
360
July1st to 10thNight
23%314%37%20%3
354
11th to 20thNight
16%316%39%24%1
522
21st to endNight
21%5%14%37%21%2
590
August1st to 10thNight
18%115%40%22%4
538
11th to 20thNight
20%414%36%23%3
532
21st to endNight
18%318%35%23%4
594
September1st to 10thNight
19%426%34%15%2
540
11th to 20thNight
28%7%19%28%16%2
540
21st to endNight
23%8%29%27%11%2
656
October1st to 10thNight
27%7%25%29%12%1
720
11th to 20thNight
32%9%22%23%12%2
720
21st to endNight
36%14%24%20%5%1
861
November1st to 10thNight
33%16%23%21%6%1
830
11th to 20thNight
32%16%27%17%6%2
850
21st to endNight
37%15%24%19%4
850
December1st to 10thNight
35%16%28%14%6%
850
11th to 20thNight
34%22%26%15%4
850
21st to endNight
33%15%27%19%5%1
935
Page generated at 2024-01-24 09:37:27. Version ac07

Copyright 2024 Attilla Danko


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