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 2017-09-22.

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%
14610
13%
46893
7%
14578
33%
14578
15%
33460

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
8%
2506
2%
716
20%
716
8%
1974
January16th to endNight
19%
768
11%
2688
5%
768
27%
768
10%
1985
February1st to 15thNight
15%
704
11%
2308
3%
701
25%
701
11%
1747
February16th to endNight
18%
631
12%
1913
5%
631
28%
631
12%
1419
March1st to 15thNight
17%
720
12%
2157
6%
720
25%
720
13%
1630
March16th to endNight
26%
768
20%
1995
7%
768
35%
768
22%
1370
April1st to 15thNight
23%
718
16%
1796
5%
718
29%
718
19%
1323
April16th to endNight
25%
629
16%
1709
6%
629
33%
629
20%
1167
May1st to 15thNight
28%
360
15%
1440
11%
360
39%
360
15%
981
May16th to endNight
28%
375
13%
1497
10%
374
40%
374
16%
991
June1st to 15thNight
31%
360
7%
1440
6%
360
38%
360
13%
990
June16th to endNight
44%
360
7%
1440
10%
360
47%
360
17%
950
July1st to 15thNight
46%
340
10%
1360
14%
340
51%
340
25%
775
July16th to endNight
48%
376
12%
1418
14%
354
53%
354
23%
856
August1st to 15thNight
52%
362
13%
1433
13%
360
57%
360
21%
884
August16th to endNight
47%
742
17%
1888
8%
742
51%
742
33%
1204
September1st to 15thNight
40%
720
13%
1800
6%
720
42%
720
29%
1236
September16th to endNight
41%
685
20%
1867
12%
685
46%
685
30%
1198
October1st to 15thNight
26%
660
17%
1963
9%
660
37%
660
18%
1381
October16th to endNight
20%
704
11%
2249
5%
704
28%
704
12%
1696
November1st to 15thNight
23%
700
17%
2298
9%
700
34%
700
13%
1654
November16th to endNight
20%
720
12%
2520
7%
720
26%
720
9%
1892
December1st to 15thNight
14%
720
7%
2520
2%
720
20%
720
8%
1997
December16th to endNight
11%
768
10%
2688
3%
768
19%
768
6%
2160

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
19%11%47%6%34446%28%
47996
Night
17%11%47%6%3445%6%29%
47062
Cloud CoverDay
18%10%47%6%34446%28%
48005
Night
16%10%47%5%3445%6%31%
47068
TransparencyDay
56%411%18%8%1
47683
Night
53%412%19%8%
46893
SeeingDay
26%14%29%19%8%2
5542
Night
23%15%28%22%9%1
14610

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
19%15%8%10%7%4433418%
1432
16th to endDay
11%15%7%10%7%345%5%5%23%
1536
February1st to 15thDay
9%17%6%10%9%44446%22%
1552
16th to endDay
13%18%6%10%7%25%43423%
1559
March1st to 15thDay
15%13%5%11%7%44435%25%
1791
16th to endDay
15%10%37%5%24346%35%
2229
April1st to 15thDay
21%13%45%5%23335%30%
2152
16th to endDay
20%10%46%434445%33%
2262
May1st to 15thDay
22%10%46%6%3335%6%27%
2511
16th to endDay
22%9%36%6%34446%28%
2618
June1st to 15thDay
24%8%26%5%36%5%5%6%24%
2520
16th to endDay
22%7%35%7%35%6%5%6%25%
2520
July1st to 15thDay
17%6%36%5%35%5%6%7%31%
2520
16th to endDay
15%7%36%7%36%5%6%8%29%
2654
August1st to 15thDay
18%7%36%7%36%6%7%6%26%
2515
16th to endDay
12%6%26%5%35%5%6%8%37%
2300
September1st to 15thDay
20%6%36%6%2435%7%34%
2160
16th to endDay
19%7%34323346%42%
1905
October1st to 15thDay
25%10%35%5%33446%28%
1664
16th to endDay
27%14%49%6%2333420%
1623
November1st to 15thDay
17%13%46%6%34446%27%
1557
16th to endDay
22%15%48%433335%24%
1440
December1st to 15thDay
22%20%6%8%5%2233419%
1440
16th to endDay
20%17%9%8%5%3333417%
1536
January1st to 15thNight
16%16%8%10%8%35%45%5%15%
2506
16th to endNight
10%14%7%9%7%5%5%45%7%22%
2688
February1st to 15thNight
9%14%7%10%8%45%44424%
2306
16th to endNight
14%13%5%11%6%345%5%6%23%
1913
March1st to 15thNight
17%12%49%6%45%445%26%
2144
16th to endNight
13%9%46%5%24446%38%
1995
April1st to 15thNight
23%9%36%423435%32%
1796
16th to endNight
19%8%35%42445%6%35%
1709
May1st to 15thNight
20%10%45%5%34336%33%
1440
16th to endNight
20%6%36%42445%7%34%
1495
June1st to 15thNight
21%9%36%5%245%5%7%29%
1440
16th to endNight
19%6%25%435%5%5%7%34%
1440
July1st to 15thNight
13%5%136%2445%9%43%
1440
16th to endNight
10%5%24445%6%6%8%41%
1514
August1st to 15thNight
11%7%26%435%6%7%7%38%
1443
16th to endNight
11%5%245%245%5%7%45%
1888
September1st to 15thNight
16%6%2432445%6%40%
1800
16th to endNight
17%5%14423345%46%
1867
October1st to 15thNight
18%9%36%5%34345%35%
1963
16th to endNight
25%12%46%5%34346%24%
2249
November1st to 15thNight
18%10%37%7%35%35%6%27%
2298
16th to endNight
20%15%5%7%6%34346%22%
2520
December1st to 15thNight
20%15%7%10%7%34335%18%
2520
16th to endNight
20%17%7%9%7%34245%17%
2688

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
19%14%8%8%7%3443419%
1432
16th to endDay
10%15%7%11%6%35%446%25%
1536
February1st to 15thDay
9%16%7%10%8%35%5%45%23%
1552
16th to endDay
13%19%5%8%7%3444424%
1559
March1st to 15thDay
14%13%5%9%8%45%33425%
1801
16th to endDay
15%10%46%434337%35%
2228
April1st to 15thDay
21%12%35%5%24345%30%
2152
16th to endDay
20%11%36%424445%33%
2262
May1st to 15thDay
22%9%37%6%34346%28%
2511
16th to endDay
22%8%45%6%25%45%6%28%
2618
June1st to 15thDay
23%7%36%5%35%5%6%6%25%
2520
16th to endDay
22%7%36%7%35%5%5%5%26%
2520
July1st to 15thDay
16%6%36%6%35%6%6%7%31%
2520
16th to endDay
14%6%37%6%46%6%6%9%29%
2654
August1st to 15thDay
17%7%36%7%36%6%6%7%26%
2515
16th to endDay
11%6%25%6%35%45%9%38%
2300
September1st to 15thDay
19%6%27%5%3445%6%35%
2160
16th to endDay
18%6%35%423336%42%
1905
October1st to 15thDay
24%9%35%43435%6%29%
1664
16th to endDay
26%12%47%6%3444421%
1623
November1st to 15thDay
16%12%46%5%35%446%28%
1557
16th to endDay
21%15%47%5%23445%25%
1440
December1st to 15thDay
21%18%7%8%5%2343420%
1440
16th to endDay
19%17%7%9%6%34345%18%
1536
January1st to 15thNight
15%15%7%9%7%35%45%7%18%
2506
16th to endNight
9%14%7%9%7%35%45%7%24%
2688
February1st to 15thNight
9%14%6%10%8%5%6%445%25%
2299
16th to endNight
13%13%49%6%2446%7%25%
1913
March1st to 15thNight
16%12%5%7%6%45%445%26%
2157
16th to endNight
12%9%45%5%3445%5%39%
1995
April1st to 15thNight
23%8%46%423446%32%
1796
16th to endNight
18%8%245%235%5%6%36%
1709
May1st to 15thNight
19%9%36%5%34336%33%
1440
16th to endNight
20%7%26%42345%7%35%
1495
June1st to 15thNight
21%7%46%5%245%5%7%29%
1440
16th to endNight
19%5%24436%5%5%7%34%
1440
July1st to 15thNight
12%5%235%3346%8%43%
1440
16th to endNight
9%425%5%35%6%6%8%42%
1514
August1st to 15thNight
11%6%25%6%25%5%7%8%39%
1443
16th to endNight
11%4235%34448%47%
1888
September1st to 15thNight
15%6%244235%5%8%40%
1800
16th to endNight
17%5%13323346%47%
1867
October1st to 15thNight
18%8%36%5%25%346%35%
1963
16th to endNight
24%9%37%5%34347%26%
2249
November1st to 15thNight
18%9%37%5%35%5%5%7%29%
2298
16th to endNight
19%14%5%7%5%2445%5%25%
2520
December1st to 15thNight
19%14%6%9%7%3445%5%20%
2520
16th to endNight
20%15%6%9%7%34445%18%
2688

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
70%27%14%5%
1433
16th to endDay
59%48%16%8%1
1536
February1st to 15thDay
62%39%16%6%
1554
16th to endDay
63%37%14%9%2
1559
March1st to 15thDay
62%38%14%9%1
1801
16th to endDay
49%49%17%15%3
2229
April1st to 15thDay
56%27%18%11%2
2152
16th to endDay
53%38%18%12%3
2262
May1st to 15thDay
58%37%18%11%1
2511
16th to endDay
57%310%17%9%1
2622
June1st to 15thDay
57%5%11%16%8%
2520
16th to endDay
57%5%10%18%7%1
2520
July1st to 15thDay
47%5%16%21%8%
2371
16th to endDay
52%5%16%18%7%
2487
August1st to 15thDay
53%7%16%18%3
2501
16th to endDay
43%418%24%9%
2300
September1st to 15thDay
49%413%21%10%
2160
16th to endDay
43%413%28%9%
1905
October1st to 15thDay
56%310%20%8%
1664
16th to endDay
68%310%13%5%
1623
November1st to 15thDay
56%414%15%8%
1557
16th to endDay
62%310%17%6%
1440
December1st to 15thDay
69%210%13%3
1440
16th to endDay
69%37%11%7%
1536
January1st to 15thNight
67%310%14%4
2506
16th to endNight
59%310%15%8%1
2688
February1st to 15thNight
61%39%18%5%
2308
16th to endNight
57%311%16%9%1
1913
March1st to 15thNight
59%310%16%8%1
2157
16th to endNight
46%210%19%18%1
1995
April1st to 15thNight
53%28%22%11%2
1796
16th to endNight
46%412%19%13%2
1709
May1st to 15thNight
53%39%17%13%3
1440
16th to endNight
49%411%22%10%1
1497
June1st to 15thNight
53%5%13%19%8%
1440
16th to endNight
47%5%12%21%11%
1440
July1st to 15thNight
35%6%20%25%11%
1360
16th to endNight
38%7%18%25%9%
1418
August1st to 15thNight
40%7%20%24%6%
1433
16th to endNight
35%5%20%29%9%
1888
September1st to 15thNight
42%5%15%25%10%
1800
16th to endNight
39%315%31%9%
1867
October1st to 15thNight
51%212%21%10%
1963
16th to endNight
60%311%18%5%
2249
November1st to 15thNight
54%413%17%7%2
2298
16th to endNight
61%311%16%5%1
2520
December1st to 15thNight
67%311%13%3
2520
16th to endNight
69%38%11%5%
2688

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%13%36%20%3
60
16th to endDay
26%17%35%10%6%3
64
February1st to 15thDay
32%22%34%5%31
87
16th to endDay
30%16%33%16%2
218
March1st to 15thDay
25%22%28%19%3
270
16th to endDay
26%17%27%17%7%3
288
April1st to 15thDay
32%18%23%16%7%1
270
16th to endDay
30%15%28%16%7%1
270
May1st to 15thDay
31%18%26%15%43
288
16th to endDay
29%13%31%17%7%1
331
June1st to 15thDay
30%14%31%18%4
315
16th to endDay
23%13%36%18%6%1
315
July1st to 15thDay
19%8%38%23%8%1
305
16th to endDay
16%6%32%31%10%2
326
August1st to 15thDay
18%7%31%26%12%2
313
16th to endDay
18%8%30%19%12%9%
332
September1st to 15thDay
20%11%24%22%13%6%
315
16th to endDay
21%11%23%21%15%7%
278
October1st to 15thDay
30%14%23%19%9%2
255
16th to endDay
38%13%23%14%9%
247
November1st to 15thDay
22%18%25%23%8%
211
16th to endDay
36%21%21%16%3
60
December1st to 15thDay
38%13%33%11%3
60
16th to endDay
42%28%25%4
64
January1st to 15thNight
24%22%30%16%5%
720
16th to endNight
19%16%33%20%7%1
768
February1st to 15thNight
19%21%34%19%5%
704
16th to endNight
23%16%34%20%4
631
March1st to 15thNight
25%18%33%19%2
720
16th to endNight
19%16%32%21%7%2
768
April1st to 15thNight
29%16%25%22%4
718
16th to endNight
26%15%28%19%7%1
629
May1st to 15thNight
25%12%29%21%8%2
360
16th to endNight
21%12%32%23%9%
375
June1st to 15thNight
25%10%26%29%8%
360
16th to endNight
19%6%24%33%15%1
360
July1st to 15thNight
13%5%28%32%17%1
340
16th to endNight
12%428%36%16%1
376
August1st to 15thNight
15%418%40%20%1
362
16th to endNight
13%7%26%30%18%2
742
September1st to 15thNight
20%7%27%29%14%1
720
16th to endNight
20%10%23%24%18%2
685
October1st to 15thNight
23%15%25%21%11%1
660
16th to endNight
31%17%25%18%6%
704
November1st to 15thNight
23%18%28%18%9%1
700
16th to endNight
29%20%23%17%6%2
720
December1st to 15thNight
30%20%26%16%4
720
16th to endNight
32%18%28%14%41
768
Page generated at 2017-09-23 06:43:48. Version ac04

Copyright 2017 A. Danko


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