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Observatoires du Mont Megantic
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoires du Mont Megantic clear sky chart from 2005-11-05 to 2017-08-12.

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
23%
14563
9%
46593
6%
14531
27%
14531
11%
36479

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
10%
720
6%
2506
3%
716
14%
716
4%
2155
January16th to endNight
12%
768
5%
2688
2%
768
16%
768
5%
2318
February1st to 15thNight
9%
704
6%
2311
2%
701
14%
701
5%
1980
February16th to endNight
12%
631
8%
1893
3%
631
18%
631
7%
1582
March1st to 15thNight
16%
720
11%
2156
6%
720
22%
720
10%
1717
March16th to endNight
22%
768
15%
2031
6%
768
28%
768
15%
1566
April1st to 15thNight
20%
718
12%
1796
4%
718
25%
718
14%
1441
April16th to endNight
23%
552
15%
1632
5%
552
32%
552
16%
1171
May1st to 15thNight
22%
498
12%
1578
7%
498
30%
498
15%
1161
May16th to endNight
30%
375
9%
1497
9%
374
37%
374
11%
1097
June1st to 15thNight
27%
360
7%
1367
7%
360
32%
360
10%
1033
June16th to endNight
39%
360
7%
1372
8%
360
43%
360
16%
951
July1st to 15thNight
42%
340
8%
1360
12%
340
46%
340
16%
905
July16th to endNight
45%
376
10%
1418
11%
354
47%
354
15%
958
August1st to 15thNight
45%
435
10%
1484
9%
433
48%
433
17%
1027
August16th to endNight
44%
605
15%
1655
8%
605
47%
605
26%
1126
September1st to 15thNight
39%
660
10%
1699
5%
660
41%
660
23%
1234
September16th to endNight
39%
657
18%
1815
12%
657
43%
657
26%
1208
October1st to 15thNight
28%
660
14%
1887
8%
660
34%
660
16%
1415
October16th to endNight
17%
704
7%
2288
3%
704
22%
704
8%
1877
November1st to 15thNight
19%
700
13%
2277
9%
700
25%
700
10%
1792
November16th to endNight
19%
723
11%
2432
9%
723
23%
723
9%
1948
December1st to 15thNight
10%
750
3%
2700
1%
750
13%
750
4%
2349
December16th to endNight
7%
779
5%
2751
2%
779
11%
779
3%
2468

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
21%13%5%7%6%34445%23%
47371
Night
18%14%5%8%6%34435%24%
46763
TransparencyDay
62%5%10%14%6%
47059
Night
62%5%9%14%6%
46593
SeeingDay
30%15%26%17%7%1
5711
Night
26%17%27%20%7%
14563

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
14%16%9%14%11%45%34212%
1432
16th to endDay
11%16%8%11%11%46%6%3414%
1536
February1st to 15thDay
12%19%9%14%12%4442212%
1549
16th to endDay
11%20%7%13%9%5%5%33315%
1580
March1st to 15thDay
15%17%8%11%6%2443322%
1793
16th to endDay
18%14%7%9%6%4322326%
2193
April1st to 15thDay
20%17%5%6%5%2333426%
2152
16th to endDay
21%14%46%423345%30%
2328
May1st to 15thDay
25%11%35%6%3434426%
2384
16th to endDay
25%9%36%6%3445%7%22%
2618
June1st to 15thDay
33%7%35%5%24446%22%
2586
16th to endDay
23%8%46%6%35%35%8%24%
2579
July1st to 15thDay
20%7%36%6%35%5%6%8%26%
2520
16th to endDay
23%8%36%6%45%5%6%7%21%
2654
August1st to 15thDay
23%8%26%6%36%6%5%8%22%
2369
16th to endDay
22%7%2442335%7%34%
2194
September1st to 15thDay
23%7%26%424446%34%
1930
16th to endDay
20%9%25%314346%36%
1815
October1st to 15thDay
22%14%36%424445%26%
1741
16th to endDay
24%23%46%5%2334417%
1584
November1st to 15thDay
20%19%6%5%423335%24%
1581
16th to endDay
17%17%7%9%6%2333422%
1525
December1st to 15thDay
20%23%8%11%6%4332213%
1260
16th to endDay
18%22%10%14%7%25%22210%
1468
January1st to 15thNight
13%18%7%14%10%46%34312%
2506
16th to endNight
10%16%9%13%10%6%8%5%3312%
2688
February1st to 15thNight
9%17%7%14%13%5%6%33313%
2310
16th to endNight
12%18%8%13%8%35%32318%
1893
March1st to 15thNight
17%15%7%8%6%45%32324%
2143
16th to endNight
15%14%7%8%6%3433430%
2031
April1st to 15thNight
21%16%47%43444425%
1796
16th to endNight
21%11%35%423346%34%
1632
May1st to 15thNight
23%10%45%43345%5%28%
1578
16th to endNight
23%9%46%5%3445%6%27%
1495
June1st to 15thNight
30%8%46%423345%24%
1367
16th to endNight
20%7%25%5%245%5%7%32%
1372
July1st to 15thNight
17%6%35%6%35%5%5%9%31%
1440
16th to endNight
15%7%25%5%36%5%5%8%32%
1514
August1st to 15thNight
17%6%37%5%25%5%6%7%32%
1494
16th to endNight
16%7%2442345%7%40%
1655
September1st to 15thNight
22%7%35%424435%36%
1699
16th to endNight
21%6%13423345%42%
1815
October1st to 15thNight
20%12%36%5%23435%31%
1887
16th to endNight
28%17%37%42433419%
2288
November1st to 15thNight
20%17%6%6%5%33335%23%
2277
16th to endNight
17%17%8%9%7%2333422%
2432
December1st to 15thNight
19%20%9%12%7%3432312%
2700
16th to endNight
19%20%9%13%8%45%2239%
2751

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
76%5%8%7%3
1433
16th to endDay
70%5%7%11%4
1536
February1st to 15thDay
78%35%8%3
1552
16th to endDay
73%36%9%5%1
1580
March1st to 15thDay
66%49%12%5%1
1803
16th to endDay
64%37%13%9%1
2193
April1st to 15thDay
62%47%14%8%2
2152
16th to endDay
56%48%16%11%2
2328
May1st to 15thDay
59%48%17%8%
2384
16th to endDay
59%7%11%13%6%
2622
June1st to 15thDay
62%6%10%15%4
2586
16th to endDay
58%6%11%17%5%
2579
July1st to 15thDay
52%7%15%18%5%
2371
16th to endDay
60%7%11%15%4
2487
August1st to 15thDay
57%8%15%15%2
2355
16th to endDay
48%6%15%20%8%
2194
September1st to 15thDay
50%5%12%21%9%
1930
16th to endDay
48%5%10%24%10%
1815
October1st to 15thDay
58%5%12%17%7%
1741
16th to endDay
70%48%11%4
1584
November1st to 15thDay
63%5%9%13%6%1
1581
16th to endDay
65%5%8%14%41
1525
December1st to 15thDay
78%45%8%2
1260
16th to endDay
81%3445%
1468
January1st to 15thNight
76%37%8%3
2506
16th to endNight
74%6%6%9%3
2688
February1st to 15thNight
75%46%10%3
2311
16th to endNight
71%46%9%7%
1893
March1st to 15thNight
64%46%15%6%1
2156
16th to endNight
58%48%15%10%2
2031
April1st to 15thNight
61%46%15%10%1
1796
16th to endNight
51%5%10%17%11%2
1632
May1st to 15thNight
54%6%10%17%9%1
1578
16th to endNight
57%6%12%16%6%
1497
June1st to 15thNight
61%5%9%17%5%
1367
16th to endNight
49%7%12%21%7%
1372
July1st to 15thNight
47%8%17%18%8%
1360
16th to endNight
48%7%14%20%7%
1418
August1st to 15thNight
48%8%18%20%4
1484
16th to endNight
41%7%17%23%9%
1655
September1st to 15thNight
49%5%13%24%6%
1699
16th to endNight
43%413%26%11%
1815
October1st to 15thNight
55%5%10%19%9%
1887
16th to endNight
67%5%8%12%4
2288
November1st to 15thNight
64%410%13%6%1
2277
16th to endNight
66%48%12%6%
2432
December1st to 15thNight
78%36%8%2
2700
16th to endNight
81%445%4
2751

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%23%38%11%
60
16th to endDay
31%25%29%9%31
64
February1st to 15thDay
32%21%29%12%4
155
16th to endDay
25%26%28%15%3
239
March1st to 15thDay
30%23%27%13%4
270
16th to endDay
28%21%21%17%10%1
288
April1st to 15thDay
35%17%28%13%41
270
16th to endDay
34%17%25%12%7%2
270
May1st to 15thDay
41%12%25%11%6%2
288
16th to endDay
28%17%31%18%3
331
June1st to 15thDay
36%11%25%18%7%
381
16th to endDay
27%12%30%22%7%
374
July1st to 15thDay
24%11%34%20%8%1
305
16th to endDay
26%9%27%27%7%
326
August1st to 15thDay
28%8%24%24%13%
297
16th to endDay
27%7%22%22%12%7%
268
September1st to 15thDay
20%10%27%18%18%3
255
16th to endDay
24%11%22%22%12%7%
254
October1st to 15thDay
29%17%18%19%11%4
249
16th to endDay
38%21%19%15%5%
240
November1st to 15thDay
30%20%26%15%6%1
235
16th to endDay
30%20%22%14%7%4
168
December1st to 15thDay
41%25%25%6%1
60
16th to endDay
46%32%15%31
64
January1st to 15thNight
24%28%32%12%2
720
16th to endNight
19%26%33%15%4
768
February1st to 15thNight
18%25%36%16%2
704
16th to endNight
22%23%34%16%3
631
March1st to 15thNight
29%20%30%17%2
720
16th to endNight
23%20%27%20%6%1
768
April1st to 15thNight
31%19%25%19%4
718
16th to endNight
27%19%27%18%6%1
552
May1st to 15thNight
27%14%31%17%8%1
498
16th to endNight
26%11%27%25%8%
375
June1st to 15thNight
33%6%23%26%9%
360
16th to endNight
21%5%26%34%11%
360
July1st to 15thNight
17%6%27%32%12%2
340
16th to endNight
18%423%38%14%
376
August1st to 15thNight
18%322%34%19%
435
16th to endNight
20%5%22%31%17%1
605
September1st to 15thNight
25%6%22%30%13%1
660
16th to endNight
23%8%24%26%14%2
657
October1st to 15thNight
29%11%26%21%10%2
660
16th to endNight
37%17%22%16%4
704
November1st to 15thNight
29%19%26%16%7%
700
16th to endNight
29%20%25%14%6%2
723
December1st to 15thNight
32%26%26%12%2
750
16th to endNight
32%24%26%12%21
779
Page generated at 2017-08-13 14:16:59. Version ac04

Copyright 2017 A. Danko


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