Observatoire astronomique de Charlevoix
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire astronomique de Charlevoix 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
28%
14469
12%
46457
7%
14439
34%
14439
15%
33197

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
17%
729
11%
2562
5%
725
25%
725
10%
1910
January16th to endNight
26%
768
13%
2688
6%
768
35%
768
12%
1917
February1st to 15thNight
22%
702
12%
2380
6%
701
32%
701
14%
1680
February16th to endNight
21%
631
13%
1893
6%
631
30%
631
12%
1423
March1st to 15thNight
22%
720
14%
2136
10%
720
28%
720
15%
1543
March16th to endNight
28%
768
18%
2058
8%
768
35%
768
20%
1431
April1st to 15thNight
22%
682
15%
1760
6%
682
27%
682
16%
1343
April16th to endNight
27%
540
16%
1620
8%
540
34%
540
16%
1121
May1st to 15thNight
29%
474
12%
1554
9%
474
35%
474
14%
1111
May16th to endNight
27%
375
10%
1375
5%
374
37%
374
11%
997
June1st to 15thNight
31%
360
7%
1260
4%
360
35%
360
14%
895
June16th to endNight
33%
360
5%
1260
3%
360
37%
360
14%
877
July1st to 15thNight
39%
340
7%
1223
8%
340
42%
340
17%
821
July16th to endNight
44%
376
8%
1418
10%
354
51%
354
16%
946
August1st to 15thNight
50%
421
10%
1470
9%
419
53%
419
16%
983
August16th to endNight
44%
541
13%
1591
8%
541
47%
541
23%
1036
September1st to 15thNight
38%
660
10%
1713
4%
660
41%
660
23%
1192
September16th to endNight
40%
657
17%
1815
12%
657
44%
657
27%
1190
October1st to 15thNight
31%
660
17%
1911
8%
660
39%
660
20%
1311
October16th to endNight
23%
704
10%
2288
5%
704
29%
704
14%
1693
November1st to 15thNight
25%
701
15%
2280
9%
701
32%
701
15%
1616
November16th to endNight
26%
750
11%
2622
6%
750
32%
750
11%
1909
December1st to 15thNight
16%
750
9%
2700
2%
750
23%
750
8%
2084
December16th to endNight
17%
800
12%
2880
4%
800
27%
800
9%
2168

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
16%7%36%5%35%45%7%32%
47527
Night
16%9%36%5%3445%6%33%
46620
TransparencyDay
50%7%13%18%8%
47208
Night
51%6%12%19%8%
46457
SeeingDay
22%17%23%23%11%2
6146
Night
20%20%24%25%8%
14471

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
13%12%37%8%4446%7%28%
1373
16th to endDay
8%9%6%8%8%36%6%5%8%28%
1536
February1st to 15thDay
6%11%6%7%8%6%7%6%5%6%26%
1479
16th to endDay
14%11%48%7%45%45%5%27%
1580
March1st to 15thDay
14%10%47%5%35%5%5%6%30%
1814
16th to endDay
11%11%5%7%5%34446%35%
2166
April1st to 15thDay
20%9%45%5%2445%6%32%
2188
16th to endDay
21%7%345%24445%35%
2340
May1st to 15thDay
20%7%25%5%3345%6%34%
2406
16th to endDay
21%6%35%5%35%5%5%6%31%
2740
June1st to 15thDay
21%6%25%5%35%46%7%30%
2700
16th to endDay
18%6%25%6%45%5%6%7%29%
2700
July1st to 15thDay
14%5%25%5%36%5%8%9%33%
2661
16th to endDay
14%5%25%5%35%6%7%9%34%
2654
August1st to 15thDay
12%5%25%7%46%6%8%10%31%
2381
16th to endDay
12%425%4245%6%9%41%
2258
September1st to 15thDay
16%5%25%5%2445%7%40%
1917
16th to endDay
14%42432335%9%45%
1815
October1st to 15thDay
19%5%26%42435%6%36%
1717
16th to endDay
23%9%35%435%45%6%28%
1584
November1st to 15thDay
16%8%37%7%45%45%6%29%
1576
16th to endDay
18%11%5%7%6%35%445%28%
1338
December1st to 15thDay
20%14%5%6%6%33235%28%
1260
16th to endDay
17%14%5%10%5%2434328%
1344
January1st to 15thNight
13%12%5%9%7%45%5%46%26%
2562
16th to endNight
9%10%5%8%7%46%5%6%7%27%
2688
February1st to 15thNight
6%11%49%8%45%5%6%7%30%
2379
16th to endNight
14%12%6%10%5%34446%27%
1893
March1st to 15thNight
14%11%46%6%34446%33%
2123
16th to endNight
13%11%45%4345%4438%
2058
April1st to 15thNight
21%9%5%6%5%2444431%
1760
16th to endNight
23%7%25%32344438%
1620
May1st to 15thNight
24%7%45%424345%33%
1554
16th to endNight
24%7%35%425%45%5%31%
1373
June1st to 15thNight
19%6%35%6%345%5%5%31%
1260
16th to endNight
19%6%26%5%35%5%48%33%
1260
July1st to 15thNight
16%6%25%445%46%8%35%
1296
16th to endNight
13%426%5%36%5%6%9%35%
1514
August1st to 15thNight
14%5%25%5%45%5%6%7%36%
1480
16th to endNight
14%415%335%5%5%9%41%
1591
September1st to 15thNight
17%6%244245%5%6%40%
1713
16th to endNight
18%424323335%46%
1815
October1st to 15thNight
18%7%244235%46%39%
1911
16th to endNight
23%8%36%434446%31%
2288
November1st to 15thNight
19%8%35%4245%5%7%32%
2280
16th to endNight
17%10%37%6%35%446%30%
2622
December1st to 15thNight
19%13%5%7%6%2444427%
2700
16th to endNight
17%12%5%7%5%34445%26%
2880

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
53%7%12%18%8%
1374
16th to endDay
51%7%13%17%9%
1536
February1st to 15thDay
55%6%14%14%8%1
1482
16th to endDay
56%6%8%18%8%
1580
March1st to 15thDay
54%5%11%14%13%2
1824
16th to endDay
51%410%20%11%2
2166
April1st to 15thDay
54%49%18%9%3
2188
16th to endDay
50%411%17%13%2
2340
May1st to 15thDay
50%6%13%17%10%
2406
16th to endDay
52%9%12%18%6%
2744
June1st to 15thDay
50%9%13%18%7%
2700
16th to endDay
52%8%14%17%7%
2700
July1st to 15thDay
44%9%18%21%5%
2505
16th to endDay
45%11%16%19%6%
2487
August1st to 15thDay
45%11%22%16%4
2367
16th to endDay
37%12%21%23%5%
2258
September1st to 15thDay
43%7%17%20%9%
1917
16th to endDay
39%8%16%25%9%
1815
October1st to 15thDay
48%6%15%20%9%
1717
16th to endDay
57%8%12%15%4
1584
November1st to 15thDay
55%7%10%19%5%
1576
16th to endDay
58%7%11%16%4
1338
December1st to 15thDay
61%6%10%15%6%
1260
16th to endDay
61%49%16%7%
1344
January1st to 15thNight
58%6%10%16%7%
2562
16th to endNight
52%6%11%19%8%
2688
February1st to 15thNight
52%5%12%20%8%
2380
16th to endNight
58%410%17%8%
1893
March1st to 15thNight
52%5%11%17%10%1
2136
16th to endNight
47%411%23%12%1
2058
April1st to 15thNight
57%46%17%11%2
1760
16th to endNight
47%6%9%20%14%2
1620
May1st to 15thNight
54%5%9%19%10%1
1554
16th to endNight
54%7%11%16%8%1
1375
June1st to 15thNight
52%6%12%18%8%1
1260
16th to endNight
50%7%14%18%8%
1260
July1st to 15thNight
42%10%17%23%5%
1223
16th to endNight
44%10%15%21%8%
1418
August1st to 15thNight
44%10%20%20%4
1470
16th to endNight
37%9%22%23%6%
1591
September1st to 15thNight
43%7%17%21%9%
1713
16th to endNight
40%6%15%27%9%
1815
October1st to 15thNight
45%6%13%25%8%
1911
16th to endNight
55%6%13%18%5%
2288
November1st to 15thNight
50%7%14%18%8%
2280
16th to endNight
54%7%12%17%6%
2622
December1st to 15thNight
61%6%11%14%4
2700
16th to endNight
59%5%11%15%6%
2880

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%43%16%
60
16th to endDay
20%15%28%23%12%
64
February1st to 15thDay
19%13%31%26%8%
136
16th to endDay
26%17%26%20%7%1
239
March1st to 15thDay
20%22%25%18%11%1
270
16th to endDay
18%20%23%20%14%2
288
April1st to 15thDay
27%22%21%18%7%1
270
16th to endDay
24%20%22%23%5%2
270
May1st to 15thDay
28%18%18%23%8%3
288
16th to endDay
23%19%26%20%8%1
453
June1st to 15thDay
23%18%24%20%11%1
495
16th to endDay
21%16%23%24%12%1
495
July1st to 15thDay
18%15%24%26%12%2
439
16th to endDay
16%13%21%28%16%3
326
August1st to 15thDay
15%10%21%26%18%7%
297
16th to endDay
16%14%22%23%17%5%
268
September1st to 15thDay
22%12%19%26%15%4
255
16th to endDay
16%15%25%24%12%5%
254
October1st to 15thDay
20%16%23%24%11%2
242
16th to endDay
32%17%20%21%6%1
240
November1st to 15thDay
22%18%26%22%8%1
235
16th to endDay
28%22%18%20%10%
138
December1st to 15thDay
31%341%15%6%1
60
16th to endDay
35%20%28%15%
64
January1st to 15thNight
18%23%31%22%3
729
16th to endNight
14%22%25%28%7%
768
February1st to 15thNight
13%22%29%26%7%
704
16th to endNight
23%22%22%24%41
631
March1st to 15thNight
19%23%28%21%6%
720
16th to endNight
18%23%24%25%7%
768
April1st to 15thNight
22%25%24%20%6%
682
16th to endNight
22%23%21%24%6%
540
May1st to 15thNight
24%22%18%23%9%
474
16th to endNight
23%22%21%23%8%
375
June1st to 15thNight
21%19%19%28%9%
360
16th to endNight
17%18%21%30%11%
360
July1st to 15thNight
18%14%21%30%13%1
340
16th to endNight
13%19%14%39%11%
376
August1st to 15thNight
15%12%12%34%22%2
421
16th to endNight
15%12%21%34%14%
541
September1st to 15thNight
19%13%23%31%11%1
660
16th to endNight
19%13%23%29%12%1
657
October1st to 15thNight
22%15%26%25%8%1
660
16th to endNight
26%17%27%19%8%
704
November1st to 15thNight
22%22%25%21%6%1
701
16th to endNight
22%25%19%23%8%1
750
December1st to 15thNight
26%22%27%18%5%
750
16th to endNight
24%24%24%18%7%1
800
Page generated at 2017-08-13 14:16:34. Version ac04

Copyright 2017 A. Danko


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