Lac de la Montagne noire
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac de la Montagne noire clear sky chart from 2005-11-05 to 2019-06-19.

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%
16805
13%
53965
7%
16773
33%
16773
15%
38366

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%
840
9%
2926
2%
836
21%
836
8%
2283
January16th to endNight
17%
896
10%
3136
4%
896
25%
896
10%
2313
February1st to 15thNight
13%
824
11%
2702
3%
821
24%
821
10%
2037
February16th to endNight
18%
735
12%
2229
5%
735
27%
735
13%
1619
March1st to 15thNight
16%
840
12%
2517
6%
840
23%
840
12%
1923
March16th to endNight
26%
896
21%
2327
7%
896
36%
896
22%
1586
April1st to 15thNight
22%
838
16%
2096
5%
838
28%
838
19%
1546
April16th to endNight
25%
726
15%
1972
6%
726
32%
726
19%
1372
May1st to 15thNight
28%
420
16%
1680
12%
420
40%
420
16%
1123
May16th to endNight
27%
439
13%
1753
9%
438
40%
438
16%
1145
June1st to 15thNight
30%
420
9%
1680
8%
420
39%
420
14%
1131
June16th to endNight
43%
398
7%
1592
10%
398
46%
398
18%
1031
July1st to 15thNight
47%
370
11%
1480
15%
370
53%
370
26%
826
July16th to endNight
49%
408
12%
1546
15%
386
54%
386
23%
931
August1st to 15thNight
53%
386
13%
1527
13%
384
58%
384
20%
953
August16th to endNight
47%
804
17%
2046
9%
804
51%
804
33%
1300
September1st to 15thNight
41%
780
16%
1950
7%
780
44%
780
29%
1328
September16th to endNight
41%
777
19%
2119
12%
777
46%
777
30%
1353
October1st to 15thNight
27%
780
16%
2321
8%
780
37%
780
18%
1630
October16th to endNight
19%
832
11%
2658
5%
832
27%
832
12%
1999
November1st to 15thNight
22%
820
16%
2692
9%
820
32%
820
12%
1956
November16th to endNight
19%
840
11%
2940
6%
840
25%
840
9%
2216
December1st to 15thNight
15%
840
9%
2940
3%
840
22%
840
8%
2294
December16th to endNight
12%
896
11%
3136
4%
896
20%
896
7%
2471

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
18%11%47%6%34446%28%
54764
Night
16%11%47%6%3445%6%29%
54134
Cloud CoverDay
18%10%47%6%34446%28%
54773
Night
16%10%47%5%3445%6%31%
54140
TransparencyDay
56%410%18%9%1
54451
Night
53%312%19%9%1
53965
SeeingDay
27%15%29%18%7%2
7652
Night
23%15%28%22%9%1
16805

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
17%16%8%10%8%4433418%
1672
16th to endDay
10%15%7%11%7%35%5%5%422%
1792
February1st to 15thDay
10%18%6%10%9%44446%21%
1818
16th to endDay
13%17%6%10%7%25%43424%
1815
March1st to 15thDay
15%15%6%10%7%44335%23%
2091
16th to endDay
14%10%37%5%25%346%35%
2600
April1st to 15thDay
20%13%47%5%23345%28%
2512
16th to endDay
21%10%46%434345%31%
2606
May1st to 15thDay
22%10%46%6%33446%28%
2931
16th to endDay
22%9%36%5%34445%29%
3066
June1st to 15thDay
23%8%26%5%35%5%5%6%27%
2940
16th to endDay
21%7%36%6%35%5%5%6%26%
2776
July1st to 15thDay
16%6%36%5%35%46%7%34%
2730
16th to endDay
15%7%36%6%36%5%6%8%30%
2878
August1st to 15thDay
17%8%37%7%36%6%7%6%25%
2674
16th to endDay
13%6%26%5%35%5%5%8%37%
2493
September1st to 15thDay
19%6%36%6%2435%6%35%
2340
16th to endDay
18%7%34324346%41%
2171
October1st to 15thDay
25%10%35%42335%5%28%
1966
16th to endDay
25%13%49%6%2433421%
1918
November1st to 15thDay
19%14%46%6%34446%25%
1823
16th to endDay
22%15%48%5%34335%22%
1680
December1st to 15thDay
20%19%6%9%5%3333420%
1680
16th to endDay
19%16%9%8%6%34445%17%
1792
January1st to 15thNight
16%16%7%10%7%34446%17%
2926
16th to endNight
10%15%7%9%7%5%5%45%6%22%
3136
February1st to 15thNight
10%14%6%10%9%46%44423%
2700
16th to endNight
13%12%410%6%345%5%6%25%
2229
March1st to 15thNight
16%14%49%6%45%445%24%
2504
16th to endNight
13%10%35%424446%39%
2327
April1st to 15thNight
22%10%36%5%33445%31%
2096
16th to endNight
20%8%35%42445%6%34%
1972
May1st to 15thNight
19%9%45%434336%34%
1680
16th to endNight
19%6%26%5%2445%7%35%
1751
June1st to 15thNight
20%8%35%5%3445%7%30%
1680
16th to endNight
18%6%25%435%45%7%35%
1592
July1st to 15thNight
12%5%235%2445%8%45%
1560
16th to endNight
10%5%244446%6%8%41%
1642
August1st to 15thNight
11%8%16%435%6%7%7%37%
1537
16th to endNight
11%5%245%2445%7%45%
2046
September1st to 15thNight
16%6%2433445%6%41%
1950
16th to endNight
17%5%14423346%46%
2119
October1st to 15thNight
17%9%36%6%34345%35%
2321
16th to endNight
23%12%37%6%34346%23%
2658
November1st to 15thNight
20%11%36%6%35%35%6%26%
2692
16th to endNight
19%16%5%8%6%34446%21%
2940
December1st to 15thNight
19%15%7%11%7%33345%18%
2940
16th to endNight
18%16%7%10%7%44345%17%
3136

Percentage Cloud Cover SE (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
17%15%8%9%8%4443419%
1672
16th to endDay
10%15%7%11%7%35%5%46%23%
1792
February1st to 15thDay
9%16%6%10%8%45%5%45%22%
1818
16th to endDay
13%17%5%8%7%34445%24%
1815
March1st to 15thDay
14%15%5%9%8%35%33424%
2101
16th to endDay
14%10%36%5%35%437%35%
2599
April1st to 15thDay
20%12%36%6%24345%29%
2512
16th to endDay
22%11%36%424345%31%
2606
May1st to 15thDay
22%9%36%6%33346%29%
2931
16th to endDay
21%8%45%6%25%45%6%29%
3066
June1st to 15thDay
22%8%36%5%35%5%5%6%27%
2940
16th to endDay
21%7%36%7%35%5%5%5%27%
2776
July1st to 15thDay
15%5%35%6%35%5%6%7%34%
2730
16th to endDay
14%6%36%6%46%5%6%8%30%
2878
August1st to 15thDay
16%8%37%7%36%7%6%7%25%
2674
16th to endDay
12%6%26%6%35%45%8%38%
2493
September1st to 15thDay
18%6%26%5%3445%6%36%
2340
16th to endDay
17%6%35%423446%41%
2171
October1st to 15thDay
24%9%46%43335%6%28%
1966
16th to endDay
25%12%47%6%3435%422%
1918
November1st to 15thDay
18%13%46%6%35%446%27%
1823
16th to endDay
21%15%47%6%23445%24%
1680
December1st to 15thDay
19%18%7%8%5%2443421%
1680
16th to endDay
18%16%7%9%6%44445%18%
1792
January1st to 15thNight
15%15%7%10%7%25%446%19%
2926
16th to endNight
10%14%7%9%7%35%45%7%24%
3136
February1st to 15thNight
9%13%6%10%8%5%6%445%25%
2693
16th to endNight
13%12%49%6%3446%7%27%
2229
March1st to 15thNight
15%14%5%7%6%45%446%25%
2517
16th to endNight
12%9%35%5%3445%6%40%
2327
April1st to 15thNight
22%8%46%5%23346%31%
2096
16th to endNight
19%9%245%2345%6%35%
1972
May1st to 15thNight
18%9%36%5%34336%35%
1680
16th to endNight
19%7%26%42345%7%35%
1751
June1st to 15thNight
21%7%45%42445%7%31%
1680
16th to endNight
18%5%24435%5%5%7%36%
1592
July1st to 15thNight
11%4235%3345%8%45%
1560
16th to endNight
9%425%5%35%5%6%8%42%
1642
August1st to 15thNight
11%7%25%6%25%5%7%8%38%
1537
16th to endNight
11%4235%34448%47%
2046
September1st to 15thNight
14%6%244235%5%8%41%
1950
16th to endNight
17%5%13323347%46%
2119
October1st to 15thNight
17%8%36%5%25%346%35%
2321
16th to endNight
23%9%37%6%34447%25%
2658
November1st to 15thNight
19%9%37%5%3445%7%28%
2692
16th to endNight
18%15%5%7%5%2445%6%24%
2940
December1st to 15thNight
17%14%6%9%7%3445%5%21%
2940
16th to endNight
18%14%6%9%7%44446%19%
3136

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
69%17%13%6%
1673
16th to endDay
60%48%16%8%1
1792
February1st to 15thDay
63%29%16%7%
1820
16th to endDay
62%28%14%9%2
1815
March1st to 15thDay
64%38%14%8%1
2101
16th to endDay
50%49%17%15%4
2600
April1st to 15thDay
57%27%18%10%2
2512
16th to endDay
55%37%17%12%3
2606
May1st to 15thDay
57%37%18%12%1
2931
16th to endDay
56%310%18%9%1
3070
June1st to 15thDay
56%5%10%17%10%1
2940
16th to endDay
56%5%10%18%8%1
2776
July1st to 15thDay
44%5%15%23%9%
2581
16th to endDay
51%5%15%19%8%
2711
August1st to 15thDay
54%7%16%17%3
2660
16th to endDay
43%416%24%9%
2493
September1st to 15thDay
48%413%22%11%
2340
16th to endDay
43%413%28%9%
2171
October1st to 15thDay
56%310%20%7%
1966
16th to endDay
66%311%13%4
1918
November1st to 15thDay
58%413%15%7%
1823
16th to endDay
63%39%15%6%
1680
December1st to 15thDay
68%210%13%4
1680
16th to endDay
68%37%11%8%
1792
January1st to 15thNight
66%210%14%4
2926
16th to endNight
60%39%15%9%1
3136
February1st to 15thNight
61%310%18%6%
2702
16th to endNight
55%311%18%9%1
2229
March1st to 15thNight
61%310%15%7%1
2517
16th to endNight
45%210%20%18%2
2327
April1st to 15thNight
53%28%21%11%2
2096
16th to endNight
48%411%19%14%2
1972
May1st to 15thNight
51%39%19%13%2
1680
16th to endNight
48%411%22%11%1
1753
June1st to 15thNight
51%412%19%10%1
1680
16th to endNight
46%5%12%22%12%
1592
July1st to 15thNight
34%5%19%26%12%1
1480
16th to endNight
38%7%18%25%9%
1546
August1st to 15thNight
41%6%20%24%5%
1527
16th to endNight
35%419%28%10%
2046
September1st to 15thNight
41%5%14%25%12%
1950
16th to endNight
38%317%31%8%
2119
October1st to 15thNight
51%312%21%10%
2321
16th to endNight
59%311%18%5%
2658
November1st to 15thNight
56%412%18%6%1
2692
16th to endNight
62%310%16%5%
2940
December1st to 15thNight
66%312%14%4
2940
16th to endNight
67%38%13%7%
3136

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
23%15%36%19%5%
120
16th to endDay
24%21%38%10%31
128
February1st to 15thDay
36%22%34%41
173
16th to endDay
32%20%31%14%1
318
March1st to 15thDay
27%21%28%17%3
390
16th to endDay
26%19%27%16%7%2
416
April1st to 15thDay
33%18%26%13%7%1
390
16th to endDay
34%15%27%14%6%1
379
May1st to 15thDay
32%20%26%14%42
408
16th to endDay
29%18%29%15%5%
459
June1st to 15thDay
30%13%31%18%5%
435
16th to endDay
23%15%36%18%6%1
388
July1st to 15thDay
16%8%39%27%6%1
365
16th to endDay
17%7%32%30%9%2
390
August1st to 15thDay
18%9%29%26%12%2
358
16th to endDay
18%8%29%21%12%8%
396
September1st to 15thDay
20%12%25%21%13%7%
375
16th to endDay
20%13%23%22%13%6%
374
October1st to 15thDay
29%16%25%17%8%2
375
16th to endDay
38%16%23%15%6%
350
November1st to 15thDay
30%18%22%19%7%
297
16th to endDay
41%20%24%10%3
120
December1st to 15thDay
30%14%35%14%5%
120
16th to endDay
32%21%28%12%21
128
January1st to 15thNight
25%21%29%17%6%
840
16th to endNight
20%18%33%19%6%1
896
February1st to 15thNight
19%22%34%18%4
824
16th to endNight
23%17%33%20%3
735
March1st to 15thNight
27%18%32%18%3
840
16th to endNight
19%17%32%20%8%1
896
April1st to 15thNight
28%17%26%22%4
838
16th to endNight
28%14%28%19%7%1
726
May1st to 15thNight
23%11%29%24%8%2
420
16th to endNight
21%13%33%23%8%
439
June1st to 15thNight
25%9%27%28%8%
420
16th to endNight
18%6%23%33%15%1
398
July1st to 15thNight
12%5%28%34%17%1
370
16th to endNight
12%428%36%17%
408
August1st to 15thNight
15%418%39%20%1
386
16th to endNight
13%7%26%30%18%2
804
September1st to 15thNight
19%7%26%29%15%1
780
16th to endNight
20%11%23%25%17%2
777
October1st to 15thNight
22%15%26%22%12%1
780
16th to endNight
30%17%25%18%6%
832
November1st to 15thNight
27%17%26%18%9%1
820
16th to endNight
29%19%25%17%5%2
840
December1st to 15thNight
29%19%26%18%6%
840
16th to endNight
29%18%28%16%41
896
Page generated at 2019-06-20 08:02:29. Version ac04

Copyright 2019 A. Danko


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