L'acceuil du Petit Lac
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the L'acceuil du Petit Lac clear sky chart from 2005-11-05 to 2017-09-17.

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
29%
14575
11%
46846
8%
14545
34%
14545
15%
34388

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
16%
720
6%
2506
3%
716
20%
716
7%
2081
January16th to endNight
22%
768
8%
2688
5%
768
28%
768
10%
2075
February1st to 15thNight
19%
703
10%
2287
5%
701
26%
701
11%
1778
February16th to endNight
21%
631
11%
1937
6%
631
28%
631
12%
1489
March1st to 15thNight
22%
720
11%
2131
7%
720
28%
720
12%
1656
March16th to endNight
29%
768
18%
2013
8%
768
36%
768
21%
1413
April1st to 15thNight
27%
718
15%
1796
6%
718
30%
718
20%
1343
April16th to endNight
28%
615
16%
1695
6%
615
35%
615
21%
1189
May1st to 15thNight
31%
360
15%
1440
15%
360
40%
360
15%
984
May16th to endNight
33%
374
12%
1497
12%
374
43%
374
17%
996
June1st to 15thNight
33%
360
7%
1440
6%
360
40%
360
14%
997
June16th to endNight
46%
360
7%
1440
10%
360
49%
360
18%
939
July1st to 15thNight
52%
340
10%
1360
14%
340
56%
340
23%
789
July16th to endNight
53%
376
11%
1418
15%
354
56%
354
22%
860
August1st to 15thNight
53%
386
12%
1457
13%
384
56%
384
20%
950
August16th to endNight
48%
719
17%
1865
9%
719
52%
719
32%
1192
September1st to 15thNight
42%
720
12%
1800
6%
720
44%
720
27%
1260
September16th to endNight
44%
665
19%
1807
13%
665
48%
665
31%
1179
October1st to 15thNight
28%
660
16%
1980
10%
660
36%
660
17%
1423
October16th to endNight
24%
704
9%
2233
5%
704
29%
704
11%
1763
November1st to 15thNight
26%
700
15%
2328
11%
700
34%
700
14%
1700
November16th to endNight
19%
720
9%
2520
7%
720
23%
720
8%
2009
December1st to 15thNight
16%
720
6%
2520
3%
720
20%
720
7%
2090
December16th to endNight
13%
768
8%
2688
4%
768
19%
768
6%
2233

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%10%47%6%34446%28%
47939
Night
18%10%47%5%34445%29%
47015
Cloud CoverDay
24%9%46%5%24345%29%
47948
Night
21%10%46%5%24445%30%
47021
TransparencyDay
56%410%17%8%
47626
Night
56%411%18%8%
46846
SeeingDay
26%11%27%20%10%3
5477
Night
25%10%26%25%10%1
14577

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
21%19%8%10%6%2322416%
1432
16th to endDay
13%15%7%10%7%45%5%5%420%
1536
February1st to 15thDay
10%16%7%11%10%4435%5%19%
1572
16th to endDay
16%17%6%10%7%3423323%
1535
March1st to 15thDay
17%12%6%8%6%3434426%
1817
16th to endDay
15%9%47%5%3445%7%33%
2211
April1st to 15thDay
24%13%35%5%2333430%
2152
16th to endDay
20%10%36%42444434%
2274
May1st to 15thDay
25%9%35%5%33346%29%
2511
16th to endDay
21%8%35%6%34446%30%
2618
June1st to 15thDay
24%7%36%6%3445%6%26%
2520
16th to endDay
20%5%26%6%36%46%8%29%
2520
July1st to 15thDay
17%5%35%5%35%5%6%8%32%
2520
16th to endDay
15%6%37%5%35%5%6%8%32%
2654
August1st to 15thDay
17%8%36%6%45%5%6%7%28%
2490
16th to endDay
14%6%26%5%345%5%8%36%
2324
September1st to 15thDay
19%7%35%5%24346%36%
2160
16th to endDay
21%6%24423346%41%
1858
October1st to 15thDay
24%10%26%434346%29%
1650
16th to endDay
29%15%38%6%2333419%
1639
November1st to 15thDay
18%11%46%5%35%446%28%
1530
16th to endDay
26%15%6%7%6%2323422%
1440
December1st to 15thDay
22%20%7%8%6%33345%13%
1440
16th to endDay
23%17%6%9%6%3432416%
1536
January1st to 15thNight
20%15%6%11%8%34445%14%
2506
16th to endNight
14%15%6%9%7%45%5%5%6%20%
2688
February1st to 15thNight
10%15%6%11%10%35%44422%
2285
16th to endNight
15%13%6%10%7%3445%423%
1937
March1st to 15thNight
19%13%48%5%44445%24%
2118
16th to endNight
14%9%46%6%24445%37%
2013
April1st to 15thNight
24%10%34423345%32%
1796
16th to endNight
20%8%35%423345%37%
1695
May1st to 15thNight
21%10%35%424346%33%
1440
16th to endNight
19%6%35%5%3445%6%35%
1495
June1st to 15thNight
19%7%36%5%45%5%5%7%28%
1440
16th to endNight
15%5%15%5%35%46%8%36%
1440
July1st to 15thNight
12%424425%5%6%9%41%
1440
16th to endNight
10%6%25%4345%8%8%41%
1514
August1st to 15thNight
13%5%25%6%45%5%6%7%36%
1467
16th to endNight
12%42442446%8%45%
1865
September1st to 15thNight
19%6%25%424346%40%
1800
16th to endNight
17%6%14322446%45%
1807
October1st to 15thNight
22%8%346%23445%33%
1980
16th to endNight
28%10%37%5%3443423%
2233
November1st to 15thNight
21%10%46%5%34445%29%
2328
16th to endNight
24%14%5%9%5%25%33420%
2520
December1st to 15thNight
23%17%7%7%6%3443417%
2520
16th to endNight
22%17%7%9%6%3434316%
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
21%19%7%11%6%2322416%
1432
16th to endDay
13%17%7%8%7%35%45%420%
1536
February1st to 15thDay
11%16%7%12%10%4434420%
1572
16th to endDay
16%18%6%9%7%3423424%
1535
March1st to 15thDay
24%10%5%6%5%2333431%
1827
16th to endDay
25%7%36%423336%34%
2210
April1st to 15thDay
28%12%345%1323429%
2152
16th to endDay
24%9%35%42334433%
2274
May1st to 15thDay
33%8%25%42233428%
2511
16th to endDay
30%6%35%424335%29%
2618
June1st to 15thDay
28%6%25%5%24446%27%
2520
16th to endDay
25%4245%35%5%5%6%30%
2520
July1st to 15thDay
17%6%37%5%35%5%6%8%32%
2520
16th to endDay
16%6%36%6%35%5%6%8%32%
2654
August1st to 15thDay
29%5%245%34446%30%
2490
16th to endDay
25%413423346%38%
2324
September1st to 15thDay
20%6%25%5%33445%36%
2160
16th to endDay
21%6%24323336%42%
1858
October1st to 15thDay
24%10%35%5%23435%31%
1650
16th to endDay
29%15%37%5%3233420%
1639
November1st to 15thDay
22%10%46%5%24346%28%
1530
16th to endDay
27%15%6%6%5%1323424%
1440
December1st to 15thDay
24%19%7%8%434345%15%
1440
16th to endDay
24%17%6%7%6%3433318%
1536
January1st to 15thNight
20%16%7%10%7%44445%15%
2506
16th to endNight
14%16%6%9%7%35%45%6%20%
2688
February1st to 15thNight
12%14%6%11%9%3444323%
2278
16th to endNight
18%12%5%10%7%24445%24%
1937
March1st to 15thNight
29%10%35%43433427%
2131
16th to endNight
23%7%35%32233340%
2013
April1st to 15thNight
27%9%3432334432%
1796
16th to endNight
23%8%25%42334437%
1695
May1st to 15thNight
26%8%25%413335%33%
1440
16th to endNight
24%5%25%434336%35%
1495
June1st to 15thNight
22%7%36%44445%7%29%
1440
16th to endNight
18%4245%35%5%5%7%37%
1440
July1st to 15thNight
13%3244335%7%7%42%
1440
16th to endNight
10%4345%245%7%8%41%
1514
August1st to 15thNight
18%4145%3445%6%41%
1467
16th to endNight
19%323323347%45%
1865
September1st to 15thNight
19%5%25%423346%40%
1800
16th to endNight
18%6%24313345%46%
1807
October1st to 15thNight
23%8%25%5%24335%34%
1980
16th to endNight
28%11%36%5%24435%23%
2233
November1st to 15thNight
26%8%35%423335%30%
2328
16th to endNight
27%14%5%6%42333423%
2520
December1st to 15thNight
24%17%6%8%5%2443419%
2520
16th to endNight
23%18%6%7%6%3433318%
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
74%26%11%5%
1433
16th to endDay
65%47%14%7%
1536
February1st to 15thDay
67%29%14%6%
1574
16th to endDay
66%17%14%9%
1535
March1st to 15thDay
61%39%16%8%1
1827
16th to endDay
50%38%19%14%3
2211
April1st to 15thDay
58%27%18%10%2
2152
16th to endDay
53%37%18%12%3
2274
May1st to 15thDay
56%36%19%12%1
2511
16th to endDay
54%410%17%10%1
2622
June1st to 15thDay
56%6%10%17%9%
2520
16th to endDay
51%5%13%19%9%
2520
July1st to 15thDay
46%5%14%22%9%
2371
16th to endDay
50%7%14%19%8%
2487
August1st to 15thDay
52%7%15%18%4
2476
16th to endDay
43%6%16%22%9%
2324
September1st to 15thDay
49%413%21%11%
2160
16th to endDay
43%414%28%8%
1858
October1st to 15thDay
56%411%19%8%
1650
16th to endDay
69%49%12%4
1639
November1st to 15thDay
57%413%15%7%
1530
16th to endDay
67%310%13%5%
1440
December1st to 15thDay
72%49%11%1
1440
16th to endDay
72%37%9%6%
1536
January1st to 15thNight
71%49%10%3
2506
16th to endNight
64%39%14%7%
2688
February1st to 15thNight
65%210%16%5%
2287
16th to endNight
63%210%14%8%
1937
March1st to 15thNight
62%38%16%7%
2131
16th to endNight
47%49%20%15%1
2013
April1st to 15thNight
54%37%20%11%2
1796
16th to endNight
49%39%18%15%2
1695
May1st to 15thNight
52%47%18%13%3
1440
16th to endNight
49%411%21%11%1
1497
June1st to 15thNight
52%5%12%20%7%
1440
16th to endNight
44%8%13%21%11%
1440
July1st to 15thNight
36%6%19%23%12%1
1360
16th to endNight
38%7%18%25%9%
1418
August1st to 15thNight
44%7%17%24%5%
1457
16th to endNight
36%5%18%30%8%
1865
September1st to 15thNight
45%414%24%10%
1800
16th to endNight
39%414%33%7%
1807
October1st to 15thNight
52%410%21%10%
1980
16th to endNight
63%5%10%15%5%
2233
November1st to 15thNight
56%412%17%7%
2328
16th to endNight
68%310%13%4
2520
December1st to 15thNight
71%49%11%2
2520
16th to endNight
73%38%9%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
30%21%30%10%8%
60
16th to endDay
35%12%31%12%7%
64
February1st to 15thDay
29%16%38%12%12
89
16th to endDay
28%21%27%17%4
194
March1st to 15thDay
26%17%29%20%5%
270
16th to endDay
23%15%27%19%9%3
288
April1st to 15thDay
30%15%23%20%8%1
270
16th to endDay
28%13%28%16%10%2
270
May1st to 15thDay
36%10%26%17%6%3
288
16th to endDay
27%13%30%17%9%1
331
June1st to 15thDay
30%10%31%19%6%
315
16th to endDay
20%10%33%21%10%2
315
July1st to 15thDay
18%6%35%24%12%2
305
16th to endDay
17%6%26%31%14%3
326
August1st to 15thDay
23%6%19%30%13%6%
313
16th to endDay
20%6%25%21%15%9%
332
September1st to 15thDay
23%8%22%19%14%11%
315
16th to endDay
25%8%23%19%12%10%
259
October1st to 15thDay
32%11%21%18%12%3
255
16th to endDay
40%12%23%15%8%
250
November1st to 15thDay
25%10%30%23%8%1
184
16th to endDay
38%13%28%13%5%1
60
December1st to 15thDay
40%16%26%13%3
60
16th to endDay
42%23%26%6%1
64
January1st to 15thNight
30%11%31%19%6%
720
16th to endNight
22%12%32%23%8%1
768
February1st to 15thNight
18%15%34%23%7%
704
16th to endNight
25%14%30%24%4
631
March1st to 15thNight
28%15%27%24%4
720
16th to endNight
20%14%29%24%10%1
768
April1st to 15thNight
29%12%25%26%5%
718
16th to endNight
26%13%25%23%9%
615
May1st to 15thNight
26%7%28%25%10%
360
16th to endNight
22%7%30%28%9%
375
June1st to 15thNight
23%7%26%33%8%
360
16th to endNight
17%423%35%16%1
360
July1st to 15thNight
12%424%40%17%
340
16th to endNight
12%323%41%16%2
376
August1st to 15thNight
16%220%34%24%1
386
16th to endNight
15%5%21%33%21%2
719
September1st to 15thNight
23%421%30%17%1
720
16th to endNight
22%7%24%26%17%2
665
October1st to 15thNight
26%10%26%22%10%2
660
16th to endNight
35%11%23%21%6%
704
November1st to 15thNight
27%12%28%21%9%1
700
16th to endNight
34%16%21%18%7%1
720
December1st to 15thNight
33%15%26%20%4
720
16th to endNight
35%11%29%16%41
768
Page generated at 2017-09-18 08:38:25. Version ac04

Copyright 2017 A. Danko


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