Observatoire astronomique du bois de Belle-Rivière
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire astronomique du bois de Belle-Rivière clear sky chart from 2005-11-05 to 2017-10-16.

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
32%
14745
13%
47169
8%
14713
38%
14713
17%
33687

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%
720
8%
2506
5%
716
22%
716
9%
1967
January16th to endNight
22%
768
10%
2688
5%
768
29%
768
11%
2015
February1st to 15thNight
21%
704
9%
2302
4%
701
27%
701
11%
1785
February16th to endNight
24%
631
13%
1901
6%
631
33%
631
15%
1431
March1st to 15thNight
21%
720
13%
2160
8%
720
28%
720
14%
1636
March16th to endNight
33%
768
19%
1992
10%
768
40%
768
24%
1402
April1st to 15thNight
29%
718
16%
1796
5%
718
35%
718
21%
1340
April16th to endNight
29%
632
16%
1712
6%
632
36%
632
21%
1224
May1st to 15thNight
31%
378
15%
1458
12%
378
41%
378
16%
987
May16th to endNight
34%
375
12%
1497
11%
374
44%
374
17%
989
June1st to 15thNight
33%
360
8%
1440
8%
360
41%
360
14%
1017
June16th to endNight
44%
360
8%
1440
11%
360
48%
360
17%
929
July1st to 15thNight
51%
340
13%
1360
18%
340
56%
340
24%
783
July16th to endNight
54%
376
12%
1418
16%
354
57%
354
23%
834
August1st to 15thNight
53%
367
14%
1438
16%
365
57%
365
22%
876
August16th to endNight
53%
755
19%
1901
10%
755
57%
755
35%
1229
September1st to 15thNight
50%
720
14%
1800
7%
720
51%
720
29%
1265
September16th to endNight
51%
717
22%
1962
15%
717
55%
717
32%
1251
October1st to 15thNight
36%
720
18%
2133
10%
720
45%
720
22%
1451
October16th to endNight
27%
708
10%
2260
7%
708
32%
708
14%
1681
November1st to 15thNight
27%
700
16%
2277
10%
700
36%
700
16%
1625
November16th to endNight
23%
720
12%
2520
8%
720
29%
720
11%
1871
December1st to 15thNight
20%
720
8%
2520
4%
720
25%
720
9%
1974
December16th to endNight
14%
768
10%
2688
3%
768
22%
768
8%
2125

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
17%7%36%5%3445%6%33%
48259
Night
17%9%36%5%34446%33%
47338
Cloud CoverDay
17%7%36%5%35%45%6%33%
48268
Night
18%9%36%5%34446%33%
47344
TransparencyDay
49%7%12%19%9%1
47946
Night
51%6%11%18%9%1
47169
SeeingDay
21%8%27%25%13%3
5676
Night
22%8%30%28%10%
14745

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%12%47%7%3445%322%
1432
16th to endDay
12%16%47%7%25%446%27%
1536
February1st to 15thDay
13%13%5%8%7%45%5%5%5%24%
1557
16th to endDay
17%13%5%8%5%34445%27%
1572
March1st to 15thDay
17%10%49%7%35%44428%
1790
16th to endDay
17%7%35%5%23345%39%
2230
April1st to 15thDay
22%8%45%5%33435%33%
2152
16th to endDay
20%7%345%34345%37%
2247
May1st to 15thDay
21%7%26%6%35%445%32%
2502
16th to endDay
20%6%25%5%35%46%7%33%
2618
June1st to 15thDay
22%6%26%4345%5%6%31%
2520
16th to endDay
17%6%26%5%36%6%6%9%28%
2520
July1st to 15thDay
12%425%5%46%5%6%8%38%
2520
16th to endDay
12%425%5%35%6%7%9%35%
2654
August1st to 15thDay
12%6%26%6%36%6%6%8%35%
2508
16th to endDay
9%415%425%5%5%9%45%
2292
September1st to 15thDay
15%5%25%5%3445%8%39%
2160
16th to endDay
13%425%323336%50%
1998
October1st to 15thDay
21%6%245%2445%6%35%
1824
16th to endDay
23%8%37%7%34445%26%
1633
November1st to 15thDay
16%7%45%6%35%5%47%33%
1578
16th to endDay
23%8%35%445%446%29%
1440
December1st to 15thDay
23%12%5%8%4245%5%5%21%
1440
16th to endDay
25%12%5%7%6%3443422%
1536
January1st to 15thNight
18%14%6%8%6%3445%5%22%
2506
16th to endNight
12%12%5%10%8%35%445%27%
2688
February1st to 15thNight
12%12%5%10%7%46%5%5%6%24%
2300
16th to endNight
16%11%5%7%5%25%45%429%
1901
March1st to 15thNight
18%11%5%7%6%24445%28%
2147
16th to endNight
15%9%35%43334441%
1992
April1st to 15thNight
25%7%44424335%34%
1796
16th to endNight
20%6%45%423347%36%
1712
May1st to 15thNight
22%7%27%43444435%
1458
16th to endNight
20%5%35%5%24347%38%
1495
June1st to 15thNight
23%7%25%43446%6%30%
1440
16th to endNight
16%5%245%26%5%5%8%37%
1440
July1st to 15thNight
10%314435%5%7%10%43%
1440
16th to endNight
10%4245%345%7%10%40%
1514
August1st to 15thNight
11%5%27%43446%9%40%
1448
16th to endNight
12%4144235%5%6%50%
1901
September1st to 15thNight
14%5%25%5%34448%41%
1800
16th to endNight
15%413323447%48%
1962
October1st to 15thNight
18%6%24424446%40%
2133
16th to endNight
24%8%37%434435%30%
2260
November1st to 15thNight
19%7%36%5%35%45%6%34%
2277
16th to endNight
21%11%37%5%34435%29%
2520
December1st to 15thNight
22%13%46%6%25%44425%
2520
16th to endNight
23%15%5%7%5%3433424%
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%13%47%7%45%44322%
1432
16th to endDay
12%15%48%6%35%446%28%
1536
February1st to 15thDay
13%12%5%11%7%35%446%24%
1557
16th to endDay
17%13%5%8%6%3444428%
1572
March1st to 15thDay
18%10%5%8%7%35%44327%
1800
16th to endDay
18%8%26%5%24345%38%
2229
April1st to 15thDay
22%8%36%5%23345%32%
2152
16th to endDay
20%7%35%5%24345%37%
2247
May1st to 15thDay
20%6%25%6%45%446%32%
2502
16th to endDay
19%6%35%5%2445%7%33%
2618
June1st to 15thDay
22%6%26%5%3445%7%31%
2520
16th to endDay
17%6%25%6%36%6%5%8%30%
2520
July1st to 15thDay
11%425%5%36%5%6%9%39%
2520
16th to endDay
11%435%446%6%7%10%35%
2654
August1st to 15thDay
11%6%26%7%35%5%6%8%35%
2508
16th to endDay
9%3144345%6%8%46%
2292
September1st to 15thDay
14%5%25%5%25%46%7%40%
2160
16th to endDay
13%424413347%49%
1998
October1st to 15thDay
21%6%25%5%34445%35%
1824
16th to endDay
23%8%37%6%3345%426%
1633
November1st to 15thDay
16%9%36%5%35%5%5%6%32%
1578
16th to endDay
23%8%26%5%34445%29%
1440
December1st to 15thDay
25%11%49%5%25%5%5%5%20%
1440
16th to endDay
25%13%48%5%25%44422%
1536
January1st to 15thNight
18%14%6%8%6%3445%5%21%
2506
16th to endNight
13%13%5%9%7%45%445%27%
2688
February1st to 15thNight
13%12%5%10%7%46%5%5%6%23%
2293
16th to endNight
16%12%48%5%345%4429%
1901
March1st to 15thNight
20%11%47%6%35%44428%
2160
16th to endNight
16%9%36%42333440%
1992
April1st to 15thNight
25%8%35%423336%32%
1796
16th to endNight
21%7%25%5%33346%36%
1712
May1st to 15thNight
21%8%26%5%3344435%
1458
16th to endNight
20%5%25%5%24437%37%
1495
June1st to 15thNight
24%6%25%5%245%5%8%29%
1440
16th to endNight
16%5%16%5%35%5%6%8%36%
1440
July1st to 15thNight
10%414435%5%6%9%42%
1440
16th to endNight
10%4345%2448%9%42%
1514
August1st to 15thNight
11%5%26%4245%6%10%40%
1448
16th to endNight
11%414423448%48%
1901
September1st to 15thNight
14%5%26%5%34447%40%
1800
16th to endNight
16%413413346%48%
1962
October1st to 15thNight
17%6%26%425%446%39%
2133
16th to endNight
24%8%36%434435%30%
2260
November1st to 15thNight
19%7%26%5%3445%6%33%
2277
16th to endNight
21%11%38%5%3344428%
2520
December1st to 15thNight
22%14%48%5%23435%24%
2520
16th to endNight
23%16%47%5%2433423%
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
64%6%9%13%5%
1433
16th to endDay
56%7%12%14%8%
1536
February1st to 15thDay
61%5%11%17%3
1559
16th to endDay
59%5%10%14%8%1
1572
March1st to 15thDay
59%5%11%14%8%1
1800
16th to endDay
48%410%17%14%4
2230
April1st to 15thDay
53%48%19%11%2
2152
16th to endDay
49%48%19%14%4
2247
May1st to 15thDay
52%5%9%16%13%2
2502
16th to endDay
48%7%11%19%11%1
2622
June1st to 15thDay
51%7%11%18%10%
2520
16th to endDay
48%9%12%18%8%1
2520
July1st to 15thDay
38%9%15%24%11%
2371
16th to endDay
41%10%18%21%8%
2487
August1st to 15thDay
43%10%17%20%7%
2494
16th to endDay
32%8%18%27%11%
2292
September1st to 15thDay
41%6%15%24%12%
2160
16th to endDay
36%5%13%33%11%
1998
October1st to 15thDay
49%5%11%22%9%
1824
16th to endDay
58%6%13%14%6%
1633
November1st to 15thDay
49%7%15%18%8%
1578
16th to endDay
55%7%11%17%6%
1440
December1st to 15thDay
64%7%12%11%2
1440
16th to endDay
65%6%10%10%6%
1536
January1st to 15thNight
62%6%11%14%4
2506
16th to endNight
59%6%11%14%7%1
2688
February1st to 15thNight
59%8%11%15%4
2302
16th to endNight
56%6%10%16%10%
1901
March1st to 15thNight
58%5%10%16%8%1
2160
16th to endNight
47%5%9%19%15%3
1992
April1st to 15thNight
53%37%18%14%1
1796
16th to endNight
49%5%7%17%15%3
1712
May1st to 15thNight
51%5%8%16%14%4
1458
16th to endNight
47%7%10%19%13%1
1497
June1st to 15thNight
52%7%11%18%9%
1440
16th to endNight
43%9%12%18%14%
1440
July1st to 15thNight
33%9%14%26%15%
1360
16th to endNight
36%8%18%23%12%
1418
August1st to 15thNight
38%8%19%22%10%
1438
16th to endNight
34%7%16%28%12%
1901
September1st to 15thNight
42%7%12%23%13%
1800
16th to endNight
36%6%11%31%13%
1962
October1st to 15thNight
45%6%10%25%11%
2133
16th to endNight
56%6%13%17%7%
2260
November1st to 15thNight
51%6%13%17%8%2
2277
16th to endNight
57%6%12%17%5%
2520
December1st to 15thNight
62%7%12%14%3
2520
16th to endNight
65%5%10%12%6%
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
15%25%23%30%5%1
60
16th to endDay
28%14%31%18%6%1
64
February1st to 15thDay
32%20%31%14%1
87
16th to endDay
27%7%33%26%4
231
March1st to 15thDay
21%14%31%27%5%
270
16th to endDay
24%7%31%22%10%2
288
April1st to 15thDay
30%12%27%18%7%2
270
16th to endDay
21%11%28%22%12%2
270
May1st to 15thDay
28%7%28%19%12%3
288
16th to endDay
21%10%32%20%12%2
331
June1st to 15thDay
25%8%27%26%10%1
315
16th to endDay
21%5%24%33%14%1
315
July1st to 15thDay
14%428%30%16%5%
305
16th to endDay
14%219%38%20%4
326
August1st to 15thDay
14%419%36%20%5%
313
16th to endDay
9%325%28%19%12%
332
September1st to 15thDay
14%7%21%26%19%10%
315
16th to endDay
14%7%23%20%24%9%
314
October1st to 15thDay
20%8%26%24%18%1
315
16th to endDay
28%11%29%20%9%
251
November1st to 15thDay
22%9%33%22%10%1
232
16th to endDay
35%8%25%25%6%
60
December1st to 15thDay
28%8%30%26%6%
60
16th to endDay
37%15%35%10%
64
January1st to 15thNight
24%14%32%24%4
720
16th to endNight
18%13%37%22%7%
768
February1st to 15thNight
19%10%37%25%6%
704
16th to endNight
22%8%36%26%5%
631
March1st to 15thNight
25%11%34%25%3
720
16th to endNight
20%7%31%30%8%
768
April1st to 15thNight
26%9%27%31%4
718
16th to endNight
25%10%30%24%9%
632
May1st to 15thNight
24%333%27%8%1
378
16th to endNight
21%5%33%30%8%
375
June1st to 15thNight
28%426%31%8%
360
16th to endNight
18%229%34%13%
360
July1st to 15thNight
9%329%35%20%
340
16th to endNight
11%125%43%16%1
376
August1st to 15thNight
14%219%40%20%2
367
16th to endNight
13%323%33%24%1
755
September1st to 15thNight
17%321%40%15%1
720
16th to endNight
17%424%26%23%2
717
October1st to 15thNight
21%6%29%29%12%
720
16th to endNight
28%8%30%25%5%
708
November1st to 15thNight
24%10%30%24%9%
700
16th to endNight
26%13%29%18%10%
720
December1st to 15thNight
31%12%29%22%4
720
16th to endNight
32%11%33%18%3
768
Page generated at 2017-10-17 16:35:29. Version ac04

Copyright 2017 A. Danko


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