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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 2018-03-11.

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%
15419
10%
49246
6%
15387
28%
15387
11%
38535

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%
780
6%
2716
3%
776
14%
776
5%
2316
January16th to endNight
12%
832
5%
2912
2%
832
15%
832
5%
2514
February1st to 15thNight
9%
764
6%
2507
2%
761
14%
761
5%
2154
February16th to endNight
12%
683
9%
2049
3%
683
19%
683
8%
1693
March1st to 15thNight
15%
764
11%
2287
6%
764
22%
764
9%
1841
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%
446
10%
1517
9%
444
47%
444
17%
1054
August16th to endNight
45%
660
16%
1806
9%
660
48%
660
28%
1217
September1st to 15thNight
39%
720
10%
1854
5%
720
40%
720
22%
1348
September16th to endNight
42%
717
20%
1980
14%
717
46%
717
28%
1290
October1st to 15thNight
30%
720
13%
2059
8%
720
35%
720
17%
1539
October16th to endNight
18%
768
8%
2496
4%
768
23%
768
8%
2026
November1st to 15thNight
20%
760
13%
2472
9%
760
26%
760
10%
1940
November16th to endNight
18%
785
11%
2635
8%
785
23%
785
9%
2101
December1st to 15thNight
10%
825
4%
2925
1%
825
13%
825
4%
2542
December16th to endNight
8%
848
5%
2980
2%
848
11%
848
3%
2677

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%13%5%7%6%34445%23%
49372
Night
18%14%5%8%6%35%43424%
49416
TransparencyDay
62%5%10%14%6%
49060
Night
62%5%9%14%6%
49246
SeeingDay
30%16%26%17%7%1
6361
Night
26%17%27%20%7%1
15419

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
15%16%9%13%11%4444212%
1552
16th to endDay
10%16%7%12%11%46%6%3414%
1664
February1st to 15thDay
12%19%9%14%12%45%42212%
1682
16th to endDay
12%21%7%12%9%45%33316%
1710
March1st to 15thDay
14%19%8%10%6%2443321%
1899
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%
2421
16th to endDay
21%7%25%5%3445%7%34%
2394
September1st to 15thDay
24%7%25%423346%34%
2105
16th to endDay
19%9%2441435%7%37%
1980
October1st to 15thDay
21%13%36%424446%27%
1899
16th to endDay
23%23%46%42334418%
1728
November1st to 15thDay
21%18%6%6%5%23335%23%
1716
16th to endDay
17%17%8%10%6%2333421%
1652
December1st to 15thDay
19%23%9%12%6%3322213%
1365
16th to endDay
18%22%9%14%8%35%32210%
1591
January1st to 15thNight
13%18%7%14%10%46%44312%
2716
16th to endNight
10%16%8%13%10%6%8%5%3312%
2912
February1st to 15thNight
9%18%7%14%13%5%7%33313%
2506
16th to endNight
13%18%7%12%8%35%32419%
2049
March1st to 15thNight
17%17%7%8%5%35%32323%
2274
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%
1527
16th to endNight
16%7%2432345%7%41%
1806
September1st to 15thNight
22%7%35%424335%36%
1854
16th to endNight
19%5%13423346%44%
1980
October1st to 15thNight
19%11%37%5%24435%31%
2059
16th to endNight
27%16%37%42433420%
2496
November1st to 15thNight
20%17%6%6%5%24335%23%
2472
16th to endNight
16%17%8%9%7%2333423%
2635
December1st to 15thNight
19%21%9%12%7%3432312%
2925
16th to endNight
19%19%9%13%9%45%3239%
2980

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
75%48%7%3
1553
16th to endDay
70%5%7%11%3
1664
February1st to 15thDay
79%35%8%3
1685
16th to endDay
72%37%9%5%1
1710
March1st to 15thDay
67%48%11%5%1
1909
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
2407
16th to endDay
48%6%15%20%8%
2394
September1st to 15thDay
50%5%12%20%9%
2105
16th to endDay
45%5%11%25%11%
1980
October1st to 15thDay
57%5%11%18%6%
1899
16th to endDay
69%48%13%4
1728
November1st to 15thDay
63%5%9%13%6%1
1716
16th to endDay
66%5%8%13%4
1652
December1st to 15thDay
78%45%9%2
1365
16th to endDay
81%4445%
1591
January1st to 15thNight
75%47%8%3
2716
16th to endNight
75%5%6%9%3
2912
February1st to 15thNight
75%46%10%3
2507
16th to endNight
69%46%11%7%
2049
March1st to 15thNight
65%46%14%6%1
2287
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%3
1517
16th to endNight
40%7%17%25%9%
1806
September1st to 15thNight
49%5%12%24%7%
1854
16th to endNight
41%413%27%12%1
1980
October1st to 15thNight
55%5%10%20%8%
2059
16th to endNight
66%5%9%13%4
2496
November1st to 15thNight
63%410%13%6%1
2472
16th to endNight
66%49%12%6%
2635
December1st to 15thNight
78%36%8%2
2925
16th to endNight
80%445%4
2980

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
25%27%33%13%
90
16th to endDay
27%28%33%8%21
96
February1st to 15thDay
32%24%28%10%3
198
16th to endDay
30%26%26%14%3
291
March1st to 15thDay
31%23%28%13%4
312
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%26%23%12%
313
16th to endDay
26%10%21%21%12%7%
332
September1st to 15thDay
23%10%27%16%16%4
315
16th to endDay
20%11%21%23%16%7%
314
October1st to 15thDay
27%18%19%19%11%3
306
16th to endDay
39%20%20%15%4
288
November1st to 15thDay
31%18%26%15%7%1
280
16th to endDay
30%20%25%13%6%3
207
December1st to 15thDay
32%32%25%7%2
90
16th to endDay
40%34%18%5%1
96
January1st to 15thNight
23%28%32%12%2
780
16th to endNight
20%26%33%15%3
832
February1st to 15thNight
19%26%36%15%2
764
16th to endNight
23%24%33%15%2
683
March1st to 15thNight
30%19%30%17%2
764
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%422%34%19%
446
16th to endNight
20%5%23%30%18%2
660
September1st to 15thNight
25%6%22%29%13%1
720
16th to endNight
22%8%23%25%17%2
717
October1st to 15thNight
27%10%26%21%11%2
720
16th to endNight
37%17%22%16%5%
768
November1st to 15thNight
29%19%25%16%8%
760
16th to endNight
28%21%26%14%6%2
785
December1st to 15thNight
32%25%25%13%2
825
16th to endNight
32%24%26%13%2
848
Page generated at 2018-03-12 13:28:08. Version ac04

Copyright 2018 A. Danko


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