Observatoire de Daniel Brousseau de Sherbrooke
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de Daniel Brousseau de Sherbrooke clear sky chart from 2005-11-05 to 2017-10-31.

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%
14824
11%
47352
7%
14793
32%
14793
13%
35855

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
14%
720
7%
2506
4%
716
17%
716
6%
2098
January16th to endNight
17%
768
6%
2688
4%
768
21%
768
7%
2227
February1st to 15thNight
16%
703
6%
2310
3%
701
20%
701
7%
1940
February16th to endNight
19%
631
8%
1893
5%
631
23%
631
9%
1538
March1st to 15thNight
21%
720
12%
2160
8%
720
27%
720
12%
1689
March16th to endNight
26%
768
17%
2018
7%
768
33%
768
17%
1514
April1st to 15thNight
24%
718
14%
1796
5%
718
29%
718
16%
1410
April16th to endNight
26%
572
16%
1652
5%
572
34%
572
18%
1174
May1st to 15thNight
28%
468
14%
1548
10%
468
36%
468
16%
1089
May16th to endNight
32%
375
11%
1497
11%
374
40%
374
13%
1054
June1st to 15thNight
33%
360
8%
1440
9%
360
39%
360
12%
1016
June16th to endNight
40%
360
7%
1440
10%
360
44%
360
16%
972
July1st to 15thNight
48%
340
10%
1360
15%
340
50%
340
18%
878
July16th to endNight
52%
376
11%
1418
13%
354
54%
354
18%
904
August1st to 15thNight
50%
422
12%
1493
12%
420
51%
420
19%
999
August16th to endNight
50%
690
18%
1836
10%
690
53%
690
31%
1199
September1st to 15thNight
43%
720
11%
1836
6%
720
44%
720
25%
1301
September16th to endNight
47%
717
21%
1980
15%
717
50%
717
31%
1269
October1st to 15thNight
33%
720
15%
2065
9%
720
39%
720
19%
1505
October16th to endNight
24%
768
9%
2494
6%
768
29%
768
11%
1934
November1st to 15thNight
22%
700
14%
2277
10%
700
29%
700
12%
1746
November16th to endNight
23%
720
12%
2437
10%
720
28%
720
10%
1904
December1st to 15thNight
13%
720
5%
2520
1%
720
17%
720
5%
2164
December16th to endNight
12%
768
6%
2688
4%
768
16%
768
4%
2331

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%11%47%6%34446%26%
48408
Night
19%12%47%5%34445%27%
47522
TransparencyDay
58%5%11%17%6%
48096
Night
59%410%17%7%
47352
SeeingDay
28%13%26%18%9%2
5849
Night
28%11%25%24%9%
14825

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
19%17%6%12%7%45%44412%
1432
16th to endDay
13%15%6%11%8%46%5%4417%
1536
February1st to 15thDay
13%18%8%14%10%46%34313%
1549
16th to endDay
14%17%8%11%8%45%33419%
1580
March1st to 15thDay
18%14%6%8%6%3434423%
1790
16th to endDay
18%12%6%8%5%3333430%
2205
April1st to 15thDay
23%13%46%5%2434428%
2152
16th to endDay
22%9%25%433345%33%
2307
May1st to 15thDay
24%8%35%6%34346%28%
2412
16th to endDay
22%8%36%6%25%5%5%7%27%
2618
June1st to 15thDay
29%7%35%5%2445%6%25%
2520
16th to endDay
21%7%35%6%35%5%5%7%28%
2520
July1st to 15thDay
18%5%25%6%36%6%5%9%30%
2520
16th to endDay
18%5%36%5%45%6%6%9%28%
2654
August1st to 15thDay
20%7%26%7%35%5%6%8%25%
2445
16th to endDay
16%6%244345%47%38%
2365
September1st to 15thDay
21%7%24423346%38%
2124
16th to endDay
19%6%24323348%40%
1980
October1st to 15thDay
23%10%36%5%34345%30%
1893
16th to endDay
26%15%35%5%3434422%
1728
November1st to 15thDay
22%14%45%5%33345%26%
1581
16th to endDay
19%17%6%7%423445%24%
1521
December1st to 15thDay
23%19%7%9%7%3432414%
1440
16th to endDay
24%20%8%10%6%25%22213%
1536
January1st to 15thNight
17%18%7%11%7%35%34416%
2506
16th to endNight
12%17%7%11%8%46%43417%
2688
February1st to 15thNight
12%15%7%14%9%45%43416%
2309
16th to endNight
15%18%6%9%6%35%42422%
1893
March1st to 15thNight
19%14%5%7%6%2433426%
2147
16th to endNight
17%12%5%7%5%2334333%
2018
April1st to 15thNight
24%11%37%5%3334427%
1796
16th to endNight
22%9%25%423336%35%
1652
May1st to 15thNight
22%8%35%424346%32%
1548
16th to endNight
21%7%36%5%3445%7%30%
1495
June1st to 15thNight
30%6%25%41346%7%27%
1440
16th to endNight
19%6%344346%5%8%33%
1440
July1st to 15thNight
14%6%246%45%5%5%9%33%
1440
16th to endNight
13%6%245%35%5%6%7%38%
1514
August1st to 15thNight
16%5%36%5%245%6%8%34%
1503
16th to endNight
14%5%25%5%2345%7%44%
1836
September1st to 15thNight
20%6%25%423447%38%
1836
16th to endNight
19%5%13222337%47%
1980
October1st to 15thNight
21%8%36%5%24445%33%
2065
16th to endNight
28%10%36%5%2444425%
2494
November1st to 15thNight
20%13%47%5%34446%25%
2277
16th to endNight
22%14%5%9%5%2333326%
2437
December1st to 15thNight
24%18%6%10%7%2422315%
2520
16th to endNight
22%21%6%11%6%3433313%
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
76%5%7%8%2
1433
16th to endDay
70%39%13%2
1536
February1st to 15thDay
78%26%10%2
1552
16th to endDay
70%38%10%6%1
1580
March1st to 15thDay
65%39%13%6%1
1800
16th to endDay
60%38%16%9%1
2205
April1st to 15thDay
60%37%17%9%2
2152
16th to endDay
53%48%18%11%3
2307
May1st to 15thDay
56%49%17%10%
2412
16th to endDay
55%7%11%16%8%
2622
June1st to 15thDay
58%6%11%16%6%
2520
16th to endDay
53%6%11%20%6%
2520
July1st to 15thDay
48%7%15%22%6%
2371
16th to endDay
52%8%15%19%4
2487
August1st to 15thDay
54%9%16%17%3
2431
16th to endDay
43%6%15%23%9%
2365
September1st to 15thDay
47%5%12%24%9%
2124
16th to endDay
42%5%12%27%11%
1980
October1st to 15thDay
55%412%20%6%
1893
16th to endDay
64%412%14%4
1728
November1st to 15thDay
61%410%14%7%1
1581
16th to endDay
62%5%10%14%5%
1521
December1st to 15thDay
75%48%9%1
1440
16th to endDay
79%35%5%5%
1536
January1st to 15thNight
72%49%10%2
2506
16th to endNight
72%48%11%3
2688
February1st to 15thNight
73%37%11%3
2310
16th to endNight
67%48%11%8%
1893
March1st to 15thNight
63%37%16%7%1
2160
16th to endNight
56%38%16%12%2
2018
April1st to 15thNight
59%46%17%11%1
1796
16th to endNight
50%5%8%20%12%2
1652
May1st to 15thNight
52%5%7%17%14%1
1548
16th to endNight
54%6%10%18%8%1
1497
June1st to 15thNight
55%5%11%19%6%
1440
16th to endNight
47%8%12%21%9%
1440
July1st to 15thNight
44%7%15%22%9%
1360
16th to endNight
43%8%17%21%9%
1418
August1st to 15thNight
46%7%17%22%5%
1493
16th to endNight
39%5%17%27%10%
1836
September1st to 15thNight
47%413%24%8%
1836
16th to endNight
38%413%29%13%
1980
October1st to 15thNight
52%410%22%8%
2065
16th to endNight
62%411%16%4
2494
November1st to 15thNight
61%411%14%6%1
2277
16th to endNight
64%49%15%6%
2437
December1st to 15thNight
76%47%10%2
2520
16th to endNight
78%37%7%3
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
21%20%38%16%3
60
16th to endDay
39%17%31%9%11
64
February1st to 15thDay
31%22%25%14%5%
135
16th to endDay
28%18%27%20%41
239
March1st to 15thDay
32%19%21%22%4
270
16th to endDay
29%16%21%17%10%3
288
April1st to 15thDay
36%14%23%17%6%1
270
16th to endDay
30%17%27%12%9%2
270
May1st to 15thDay
38%9%29%10%10%1
288
16th to endDay
25%17%26%23%6%
331
June1st to 15thDay
33%14%24%18%8%
315
16th to endDay
25%14%35%17%6%
315
July1st to 15thDay
25%6%33%21%10%2
305
16th to endDay
20%7%31%30%8%1
326
August1st to 15thDay
26%6%28%21%15%1
313
16th to endDay
21%9%23%18%16%8%
332
September1st to 15thDay
23%5%26%19%15%9%
315
16th to endDay
17%11%20%23%15%11%
314
October1st to 15thDay
24%18%24%14%14%3
311
16th to endDay
41%13%19%17%7%
288
November1st to 15thDay
31%15%22%22%7%
235
16th to endDay
36%18%16%17%8%3
141
December1st to 15thDay
41%13%33%10%1
60
16th to endDay
50%18%25%41
64
January1st to 15thNight
30%17%29%18%3
720
16th to endNight
25%18%28%22%5%
768
February1st to 15thNight
22%17%31%24%4
704
16th to endNight
27%14%31%20%5%
631
March1st to 15thNight
32%14%26%21%4
720
16th to endNight
26%15%26%21%8%1
768
April1st to 15thNight
33%12%25%23%5%
718
16th to endNight
27%16%26%22%8%
572
May1st to 15thNight
28%8%30%22%9%
468
16th to endNight
25%8%27%30%7%
375
June1st to 15thNight
34%420%30%9%
360
16th to endNight
20%6%27%33%11%
360
July1st to 15thNight
16%325%35%17%
340
16th to endNight
17%220%40%18%
376
August1st to 15thNight
19%418%37%19%
422
16th to endNight
18%320%33%21%2
690
September1st to 15thNight
25%5%19%32%15%1
720
16th to endNight
23%6%21%25%20%2
717
October1st to 15thNight
29%8%23%21%14%1
720
16th to endNight
37%11%23%21%5%
768
November1st to 15thNight
29%13%28%19%9%
700
16th to endNight
32%15%23%17%8%2
720
December1st to 15thNight
37%16%26%14%4
720
16th to endNight
37%16%24%16%4
768
Page generated at 2017-11-01 17:23:33. Version ac04

Copyright 2017 A. Danko


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