Observatoire de la Découverte de Val-Bélair
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de la Découverte de Val-Bélair clear sky chart from 2005-11-05 to 2017-12-20.

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
25%
15018
13%
48086
7%
14987
33%
14987
14%
34605

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
12%
720
11%
2506
3%
716
22%
716
8%
1941
January16th to endNight
19%
768
12%
2688
4%
768
29%
768
9%
1995
February1st to 15thNight
18%
703
11%
2358
5%
701
27%
701
11%
1738
February16th to endNight
17%
631
12%
1893
5%
631
26%
631
11%
1454
March1st to 15thNight
20%
720
14%
2160
7%
720
29%
720
14%
1576
March16th to endNight
27%
768
18%
2022
8%
768
34%
768
18%
1444
April1st to 15thNight
23%
718
17%
1796
5%
718
30%
718
17%
1373
April16th to endNight
21%
546
16%
1626
4%
546
32%
546
17%
1112
May1st to 15thNight
25%
448
14%
1528
9%
448
34%
448
13%
1069
May16th to endNight
26%
375
10%
1488
9%
374
35%
374
13%
1014
June1st to 15thNight
27%
360
7%
1260
5%
360
32%
360
13%
896
June16th to endNight
34%
360
7%
1260
7%
360
38%
360
15%
867
July1st to 15thNight
39%
340
8%
1345
11%
340
42%
340
18%
855
July16th to endNight
41%
376
10%
1418
12%
354
48%
354
17%
907
August1st to 15thNight
47%
408
11%
1479
11%
406
51%
406
18%
970
August16th to endNight
40%
649
16%
1795
8%
649
44%
649
24%
1173
September1st to 15thNight
36%
720
12%
1842
5%
720
40%
720
25%
1286
September16th to endNight
41%
717
18%
1980
11%
717
46%
717
28%
1295
October1st to 15thNight
30%
720
17%
2084
8%
720
39%
720
21%
1444
October16th to endNight
23%
768
11%
2496
5%
768
30%
768
14%
1821
November1st to 15thNight
26%
760
16%
2472
10%
760
34%
760
14%
1757
November16th to endNight
22%
802
13%
2762
6%
802
32%
802
12%
2026
December1st to 15thNight
13%
825
7%
2925
2%
825
19%
825
6%
2332
December16th to endNight
12%
816
12%
2903
4%
816
22%
816
7%
2260

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%29%
48749
Night
20%10%46%5%34445%30%
48256
TransparencyDay
54%413%19%8%1
48437
Night
55%311%19%9%1
48086
SeeingDay
26%17%24%19%10%2
6295
Night
22%21%22%24%8%
15019

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
20%13%5%8%6%3444422%
1432
16th to endDay
11%14%6%9%6%345%6%5%24%
1536
February1st to 15thDay
10%13%8%10%8%345%45%25%
1500
16th to endDay
14%13%5%9%8%35%445%23%
1580
March1st to 15thDay
18%11%5%7%5%24446%30%
1790
16th to endDay
14%9%45%6%25%5%46%33%
2201
April1st to 15thDay
23%10%35%5%2433432%
2152
16th to endDay
24%7%25%423435%36%
2334
May1st to 15thDay
24%7%35%5%24346%31%
2433
16th to endDay
22%7%36%6%46%5%5%5%26%
2624
June1st to 15thDay
21%6%36%6%36%5%6%8%27%
2700
16th to endDay
22%7%36%6%46%5%5%7%24%
2700
July1st to 15thDay
15%5%36%6%46%6%6%8%30%
2531
16th to endDay
17%6%36%5%36%5%7%9%27%
2654
August1st to 15thDay
18%5%27%6%35%6%6%9%25%
2457
16th to endDay
14%6%26%5%245%5%9%37%
2405
September1st to 15thDay
20%7%25%32435%6%37%
2118
16th to endDay
20%414323348%41%
1980
October1st to 15thDay
24%6%36%5%245%36%30%
1872
16th to endDay
27%10%35%6%3435%5%23%
1728
November1st to 15thDay
21%8%46%6%45%35%428%
1716
16th to endDay
25%13%5%6%423335%25%
1524
December1st to 15thDay
27%16%45%6%2223423%
1365
16th to endDay
24%16%5%8%5%2434421%
1417
January1st to 15thNight
19%16%5%8%6%3433422%
2506
16th to endNight
12%14%6%9%7%45%5%5%424%
2688
February1st to 15thNight
9%12%5%10%10%45%446%25%
2357
16th to endNight
16%13%6%10%7%34335%25%
1893
March1st to 15thNight
19%10%35%6%35%445%31%
2147
16th to endNight
14%9%36%5%33446%36%
2022
April1st to 15thNight
24%10%46%43345%429%
1796
16th to endNight
22%7%35%423336%37%
1626
May1st to 15thNight
24%6%35%5%345%4433%
1528
16th to endNight
26%5%36%424346%31%
1486
June1st to 15thNight
24%7%36%6%3445%7%27%
1260
16th to endNight
22%5%36%5%2446%6%31%
1260
July1st to 15thNight
18%5%35%5%25%45%8%35%
1425
16th to endNight
16%5%26%5%36%37%7%35%
1514
August1st to 15thNight
16%5%25%5%446%7%7%34%
1489
16th to endNight
15%5%25%6%345%48%39%
1795
September1st to 15thNight
22%6%15%5%2335%7%38%
1842
16th to endNight
22%423323336%44%
1980
October1st to 15thNight
20%7%25%43345%5%36%
2084
16th to endNight
28%9%35%42334429%
2496
November1st to 15thNight
21%8%35%5%34346%32%
2472
16th to endNight
24%11%36%5%2433429%
2762
December1st to 15thNight
24%15%5%8%7%3433320%
2925
16th to endNight
21%16%5%9%6%2334322%
2903

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
62%310%15%8%
1433
16th to endDay
57%310%19%8%
1536
February1st to 15thDay
59%213%15%7%1
1503
16th to endDay
60%38%17%8%2
1580
March1st to 15thDay
54%411%16%12%1
1800
16th to endDay
50%49%19%12%3
2201
April1st to 15thDay
54%110%17%9%4
2152
16th to endDay
50%310%19%13%2
2334
May1st to 15thDay
53%212%19%11%1
2433
16th to endDay
57%411%17%8%
2628
June1st to 15thDay
53%5%13%17%8%1
2700
16th to endDay
56%412%16%8%
2700
July1st to 15thDay
47%6%18%20%6%
2382
16th to endDay
52%418%18%5%
2487
August1st to 15thDay
51%6%21%17%3
2443
16th to endDay
43%418%26%6%
2405
September1st to 15thDay
47%216%24%9%
2118
16th to endDay
42%216%28%9%
1980
October1st to 15thDay
52%214%21%7%
1872
16th to endDay
61%312%18%3
1728
November1st to 15thDay
57%411%19%6%
1716
16th to endDay
61%310%17%6%
1524
December1st to 15thDay
65%210%15%6%
1365
16th to endDay
66%47%13%7%
1417
January1st to 15thNight
65%38%16%5%
2506
16th to endNight
60%38%17%8%
2688
February1st to 15thNight
58%310%17%8%
2358
16th to endNight
63%28%14%10%1
1893
March1st to 15thNight
55%310%15%12%2
2160
16th to endNight
48%5%9%20%13%3
2022
April1st to 15thNight
57%2418%13%3
1796
16th to endNight
48%49%19%15%3
1626
May1st to 15thNight
53%38%18%12%2
1528
16th to endNight
52%412%17%11%
1488
June1st to 15thNight
55%313%18%6%1
1260
16th to endNight
51%412%19%11%
1260
July1st to 15thNight
44%5%19%22%7%
1345
16th to endNight
45%5%18%20%9%
1418
August1st to 15thNight
45%5%21%22%4
1479
16th to endNight
42%417%28%6%
1795
September1st to 15thNight
46%314%24%9%
1842
16th to endNight
42%316%26%10%
1980
October1st to 15thNight
48%412%24%9%
2084
16th to endNight
57%313%19%6%
2496
November1st to 15thNight
52%5%12%18%10%
2472
16th to endNight
58%310%19%8%
2762
December1st to 15thNight
69%210%11%5%
2925
16th to endNight
65%38%13%8%
2903

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
30%10%36%23%
60
16th to endDay
29%21%25%17%6%
64
February1st to 15thDay
24%22%30%16%42
118
16th to endDay
23%20%27%20%7%
239
March1st to 15thDay
25%24%26%17%5%
270
16th to endDay
22%21%19%21%11%3
288
April1st to 15thDay
28%19%25%15%10%1
270
16th to endDay
29%21%21%18%8%1
270
May1st to 15thDay
32%17%25%14%7%1
288
16th to endDay
26%21%26%15%8%
337
June1st to 15thDay
23%19%22%24%9%
495
16th to endDay
28%18%22%20%9%1
495
July1st to 15thDay
21%14%26%23%12%2
316
16th to endDay
20%15%24%26%11%1
326
August1st to 15thDay
21%9%26%22%16%3
313
16th to endDay
20%11%23%21%15%7%
332
September1st to 15thDay
25%13%23%17%16%3
315
16th to endDay
20%14%22%21%16%5%
314
October1st to 15thDay
26%13%25%20%10%2
305
16th to endDay
36%16%20%17%8%
288
November1st to 15thDay
27%20%21%20%10%
280
16th to endDay
36%17%23%15%6%1
150
December1st to 15thDay
40%11%28%14%32
90
16th to endDay
38%20%26%11%2
72
January1st to 15thNight
20%28%26%19%4
720
16th to endNight
17%27%23%23%6%
768
February1st to 15thNight
13%27%27%24%6%
704
16th to endNight
26%22%24%21%4
631
March1st to 15thNight
22%25%25%21%4
720
16th to endNight
17%25%23%25%8%1
768
April1st to 15thNight
25%22%22%22%6%
718
16th to endNight
23%23%26%20%6%
546
May1st to 15thNight
22%23%23%24%5%
448
16th to endNight
23%20%23%24%7%
375
June1st to 15thNight
23%20%20%28%6%
360
16th to endNight
21%17%17%30%12%
360
July1st to 15thNight
20%14%19%28%15%1
340
16th to endNight
17%17%15%35%13%1
376
August1st to 15thNight
19%10%13%35%19%1
408
16th to endNight
17%11%22%32%14%2
649
September1st to 15thNight
22%11%22%28%14%1
720
16th to endNight
23%11%19%28%16%1
717
October1st to 15thNight
23%14%24%27%8%1
720
16th to endNight
31%16%24%21%6%
768
November1st to 15thNight
22%22%20%24%9%1
760
16th to endNight
25%25%19%19%7%
802
December1st to 15thNight
29%25%21%17%6%
825
16th to endNight
26%26%22%17%5%1
816
Page generated at 2017-12-21 07:04:42. Version ac04

Copyright 2017 A. Danko


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