Observatoire du Cégep de Trois-Rivières à Champlain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire du Cégep de Trois-Rivières à Champlain clear sky chart from 2005-11-05 to 2018-02-14.

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%
15226
12%
48996
7%
15194
34%
15194
14%
35739

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
18%
780
9%
2716
5%
776
24%
776
9%
2142
January16th to endNight
23%
832
11%
2912
6%
832
30%
832
10%
2223
February1st to 15thNight
18%
760
9%
2531
5%
757
25%
757
10%
1979
February16th to endNight
22%
631
12%
1893
7%
631
29%
631
11%
1474
March1st to 15thNight
23%
720
14%
2160
8%
720
31%
720
13%
1624
March16th to endNight
29%
768
19%
2013
8%
768
37%
768
19%
1436
April1st to 15thNight
23%
718
15%
1796
5%
718
29%
718
17%
1377
April16th to endNight
25%
572
16%
1652
3%
572
34%
572
17%
1138
May1st to 15thNight
27%
425
14%
1505
11%
425
36%
425
14%
1041
May16th to endNight
24%
375
11%
1497
7%
374
37%
374
13%
1030
June1st to 15thNight
30%
360
7%
1412
5%
360
38%
360
12%
987
June16th to endNight
35%
360
7%
1411
7%
360
39%
360
14%
959
July1st to 15thNight
42%
340
9%
1360
12%
340
47%
340
18%
874
July16th to endNight
42%
376
11%
1418
12%
354
50%
354
18%
900
August1st to 15thNight
50%
389
11%
1460
12%
387
54%
387
16%
969
August16th to endNight
45%
687
17%
1833
9%
687
49%
687
26%
1233
September1st to 15thNight
41%
720
14%
1822
7%
720
44%
720
26%
1256
September16th to endNight
42%
717
20%
1980
13%
717
47%
717
28%
1282
October1st to 15thNight
31%
720
18%
2086
9%
720
40%
720
20%
1466
October16th to endNight
23%
768
11%
2496
6%
768
29%
768
14%
1867
November1st to 15thNight
26%
760
15%
2472
10%
760
34%
760
14%
1776
November16th to endNight
23%
780
13%
2689
7%
780
31%
780
11%
2026
December1st to 15thNight
16%
824
7%
2918
2%
824
22%
824
8%
2308
December16th to endNight
16%
844
10%
2964
4%
844
24%
844
7%
2372

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%8%36%5%35%45%6%31%
49024
Night
20%9%36%5%24445%31%
49166
TransparencyDay
53%5%11%19%9%1
48712
Night
55%5%10%18%9%
48996
SeeingDay
22%14%23%23%12%3
6011
Night
22%19%23%25%9%
15226

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
22%14%5%7%7%25%33322%
1552
16th to endDay
12%14%6%8%7%46%345%24%
1664
February1st to 15thDay
12%14%5%10%7%36%44425%
1627
16th to endDay
17%13%48%7%35%5%45%24%
1580
March1st to 15thDay
18%10%46%5%35%335%31%
1790
16th to endDay
16%9%36%5%2445%6%34%
2210
April1st to 15thDay
25%8%35%42343433%
2152
16th to endDay
22%6%25%5%33335%36%
2307
May1st to 15thDay
23%6%36%5%25%445%32%
2457
16th to endDay
22%6%36%5%45%5%5%6%29%
2618
June1st to 15thDay
23%6%35%5%25%5%5%7%29%
2520
16th to endDay
19%6%35%7%36%6%5%7%27%
2520
July1st to 15thDay
14%5%36%5%36%6%6%9%32%
2520
16th to endDay
15%5%26%5%47%5%6%7%32%
2654
August1st to 15thDay
16%6%25%5%36%6%7%8%29%
2478
16th to endDay
12%414425%5%6%8%43%
2366
September1st to 15thDay
19%425%434346%40%
2137
16th to endDay
17%424323347%45%
1980
October1st to 15thDay
24%7%25%433445%31%
1872
16th to endDay
26%9%25%6%34346%25%
1728
November1st to 15thDay
21%8%46%6%34345%30%
1716
16th to endDay
24%11%45%5%2335%5%27%
1599
December1st to 15thDay
29%11%5%6%5%2333424%
1368
16th to endDay
26%13%47%5%34325%23%
1609
January1st to 15thNight
22%16%5%8%6%2344422%
2716
16th to endNight
15%14%5%9%6%36%44425%
2912
February1st to 15thNight
11%12%7%11%9%45%44423%
2530
16th to endNight
18%13%5%9%6%35%43426%
1893
March1st to 15thNight
19%11%47%6%3444429%
2147
16th to endNight
15%11%35%5%24445%37%
2013
April1st to 15thNight
26%10%35%5%23345%30%
1796
16th to endNight
23%6%24423347%36%
1652
May1st to 15thNight
23%8%24415%345%34%
1505
16th to endNight
24%7%343345%46%32%
1495
June1st to 15thNight
24%6%35%5%2445%7%30%
1412
16th to endNight
19%6%35%5%35%46%8%31%
1411
July1st to 15thNight
15%5%25%5%35%6%5%7%37%
1440
16th to endNight
14%5%25%5%35%5%5%8%37%
1514
August1st to 15thNight
14%5%25%7%35%6%7%8%34%
1470
16th to endNight
13%416%5%35%45%7%42%
1833
September1st to 15thNight
19%5%25%42335%7%40%
1822
16th to endNight
20%5%14322336%47%
1980
October1st to 15thNight
18%6%35%5%25%446%37%
2086
16th to endNight
27%8%35%5%23335%29%
2496
November1st to 15thNight
21%9%36%6%34445%31%
2472
16th to endNight
26%11%46%42333428%
2689
December1st to 15thNight
25%12%5%8%7%2433422%
2918
16th to endNight
23%17%5%7%6%2434321%
2964

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
66%5%7%13%6%
1553
16th to endDay
60%49%17%6%
1664
February1st to 15thDay
60%412%15%6%
1630
16th to endDay
61%48%15%8%1
1580
March1st to 15thDay
55%412%15%11%1
1800
16th to endDay
49%410%18%13%3
2210
April1st to 15thDay
54%38%18%10%3
2152
16th to endDay
50%39%18%14%3
2307
May1st to 15thDay
52%5%8%18%13%1
2457
16th to endDay
54%6%9%16%11%1
2622
June1st to 15thDay
52%5%11%17%9%1
2520
16th to endDay
54%7%10%18%8%
2520
July1st to 15thDay
43%8%15%22%8%
2371
16th to endDay
50%7%14%20%6%
2487
August1st to 15thDay
49%8%17%19%4
2464
16th to endDay
37%7%16%28%9%
2366
September1st to 15thDay
44%5%14%24%11%
2137
16th to endDay
39%414%30%10%
1980
October1st to 15thDay
53%411%22%7%
1872
16th to endDay
59%5%11%19%4
1728
November1st to 15thDay
56%5%11%18%8%
1716
16th to endDay
59%311%18%6%
1599
December1st to 15thDay
64%412%13%5%
1368
16th to endDay
65%48%13%7%
1609
January1st to 15thNight
66%49%14%5%
2716
16th to endNight
62%49%15%7%
2912
February1st to 15thNight
63%5%9%14%6%
2531
16th to endNight
62%46%14%10%
1893
March1st to 15thNight
58%48%15%10%1
2160
16th to endNight
48%5%9%18%15%3
2013
April1st to 15thNight
56%46%17%12%2
1796
16th to endNight
47%5%10%17%15%3
1652
May1st to 15thNight
52%410%14%15%3
1505
16th to endNight
52%6%9%17%11%2
1497
June1st to 15thNight
53%5%11%18%9%1
1412
16th to endNight
49%7%10%19%12%1
1411
July1st to 15thNight
43%8%14%21%11%1
1360
16th to endNight
43%7%15%22%11%
1418
August1st to 15thNight
44%10%16%23%5%
1460
16th to endNight
40%6%15%27%9%
1833
September1st to 15thNight
43%5%13%25%11%
1822
16th to endNight
41%313%28%12%
1980
October1st to 15thNight
48%5%10%23%11%
2086
16th to endNight
59%412%18%6%
2496
November1st to 15thNight
54%412%17%9%
2472
16th to endNight
61%39%17%6%
2689
December1st to 15thNight
67%311%12%4
2918
16th to endNight
67%48%11%6%
2964

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
31%10%23%28%6%
90
16th to endDay
26%8%31%23%8%2
96
February1st to 15thDay
25%12%33%23%5%
139
16th to endDay
25%16%22%28%6%
239
March1st to 15thDay
25%18%24%22%8%
270
16th to endDay
21%15%27%17%13%3
288
April1st to 15thDay
26%18%21%23%7%1
270
16th to endDay
20%21%27%18%11%1
270
May1st to 15thDay
27%19%19%20%10%3
288
16th to endDay
20%19%25%19%12%1
331
June1st to 15thDay
22%16%26%20%10%3
315
16th to endDay
19%13%23%28%11%3
315
July1st to 15thDay
17%10%24%27%16%4
305
16th to endDay
16%13%16%29%20%2
326
August1st to 15thDay
17%9%15%31%19%7%
313
16th to endDay
12%10%23%21%18%13%
332
September1st to 15thDay
20%9%20%22%17%8%
315
16th to endDay
14%11%23%21%18%9%
314
October1st to 15thDay
26%9%23%23%13%3
312
16th to endDay
30%12%23%21%11%
288
November1st to 15thDay
24%16%24%22%9%1
280
16th to endDay
31%17%19%18%11%2
129
December1st to 15thDay
38%6%24%24%32
90
16th to endDay
34%11%32%16%5%
96
January1st to 15thNight
25%20%26%22%5%
780
16th to endNight
21%20%24%25%6%
832
February1st to 15thNight
16%22%28%25%6%
760
16th to endNight
24%20%23%26%5%
631
March1st to 15thNight
22%21%25%25%4
720
16th to endNight
18%23%23%25%8%
768
April1st to 15thNight
24%21%24%22%5%
718
16th to endNight
22%24%24%21%6%
572
May1st to 15thNight
23%22%20%25%7%
425
16th to endNight
23%21%26%22%6%
375
June1st to 15thNight
23%19%19%30%6%
360
16th to endNight
18%19%20%30%10%
360
July1st to 15thNight
14%14%22%30%16%1
340
16th to endNight
13%18%16%36%13%
376
August1st to 15thNight
14%11%13%35%23%1
389
16th to endNight
14%11%21%33%18%1
687
September1st to 15thNight
20%11%20%32%12%1
720
16th to endNight
20%12%21%24%19%
717
October1st to 15thNight
20%13%28%27%8%
720
16th to endNight
28%15%27%22%5%
768
November1st to 15thNight
23%19%23%22%10%
760
16th to endNight
27%22%20%21%7%
780
December1st to 15thNight
28%21%24%20%4
824
16th to endNight
30%21%20%19%6%
844
Page generated at 2018-02-15 10:58:45. Version ac04

Copyright 2018 A. Danko


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