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 2005-11-06 to 2024-02-25.

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%
22877
13%
80766
7%
22778
35%
22778
14%
57661

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 10thNight
13%
756
10%
4381
2%
737
23%
737
4%
3332
January11th to 20thNight
18%
758
12%
4373
4%
740
28%
740
6%
3168
January21st to endNight
22%
831
10%
4836
6%
814
33%
814
7%
3283
February1st to 10thNight
21%
760
14%
2660
7%
760
32%
760
12%
1930
February11th to 20thNight
14%
742
11%
2231
2%
740
25%
740
13%
1688
February21st to endNight
23%
611
16%
1831
8%
611
33%
611
16%
1339
March1st to 10thNight
23%
720
14%
2160
8%
720
33%
720
16%
1592
March11th to 20thNight
21%
720
15%
2080
5%
720
30%
720
15%
1529
March21st to endNight
30%
792
18%
2034
7%
792
38%
792
21%
1497
April1st to 10thNight
24%
720
14%
1800
5%
720
29%
720
17%
1392
April11th to 20thNight
26%
632
18%
1696
6%
632
33%
632
23%
1190
April21st to endNight
24%
540
16%
1620
7%
540
31%
540
17%
1156
May1st to 10thNight
27%
493
14%
1573
8%
493
36%
493
17%
1109
May11th to 20thNight
34%
354
17%
1416
18%
354
43%
354
16%
930
May21st to endNight
30%
389
12%
1541
9%
388
42%
388
17%
999
June1st to 10thNight
33%
360
8%
1260
7%
360
40%
360
16%
872
June11th to 20thNight
41%
360
11%
1260
11%
360
46%
360
20%
824
June21st to endNight
37%
360
8%
1260
8%
360
41%
360
17%
885
July1st to 10thNight
41%
350
8%
1378
11%
350
46%
350
20%
866
July11th to 20thNight
46%
348
11%
1392
16%
348
50%
348
20%
880
July21st to endNight
50%
394
10%
1486
14%
372
53%
372
18%
973
August1st to 10thNight
56%
358
13%
1422
15%
356
60%
356
22%
865
August11th to 20thNight
44%
516
11%
1580
8%
516
47%
516
21%
1072
August21st to endNight
42%
707
18%
1895
10%
707
45%
707
27%
1256
September1st to 10thNight
42%
720
13%
1800
5%
720
46%
720
29%
1242
September11th to 20thNight
43%
720
15%
1952
8%
720
48%
720
29%
1292
September21st to endNight
39%
720
19%
1980
11%
720
45%
720
27%
1349
October1st to 10thNight
34%
720
21%
1988
12%
720
43%
720
24%
1380
October11th to 20thNight
31%
720
12%
2306
6%
720
39%
720
16%
1683
October21st to endNight
22%
792
11%
2574
5%
792
29%
792
15%
1865
November1st to 10thNight
27%
740
14%
2407
8%
740
36%
740
15%
1706
November11th to 20thNight
26%
760
17%
2474
10%
760
35%
760
14%
1782
November21st to endNight
20%
825
11%
2797
5%
825
28%
825
11%
2138
December1st to 10thNight
18%
850
9%
2850
5%
850
24%
850
9%
2283
December11th to 20thNight
18%
850
12%
3441
5%
848
26%
848
8%
2602
December21st to endNight
12%
889
8%
5032
2%
873
21%
873
5%
3712

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
19%10%47%6%35%5%5%7%30%
78009
Night
19%11%47%6%3445%6%30%
81266
TransparencyDay
54%413%20%9%1
77714
Night
56%311%19%9%1
81096
SeeingDay
26%12%29%22%9%2
14161
Night
25%10%27%28%9%1
22899

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 10thDay
16%16%7%10%8%4445%6%21%
2517
11th to 20thDay
10%15%8%14%9%3444426%
2520
21st to endDay
10%13%5%9%6%345%5%6%33%
2772
February1st to 10thDay
11%14%7%10%9%45%5%46%25%
1520
11th to 20thDay
14%15%6%10%6%35%5%45%26%
1832
21st to endDay
13%14%6%10%8%35%347%27%
1520
March1st to 10thDay
15%12%5%8%6%3445%6%30%
1797
11th to 20thDay
17%12%6%6%6%25%5%46%30%
1880
21st to endDay
15%11%47%7%36%6%45%32%
2320
April1st to 10thDay
22%12%47%7%34445%28%
2160
11th to 20thDay
21%7%36%5%3335%6%37%
2212
21st to endDay
25%8%46%6%33446%31%
2340
May1st to 10thDay
23%8%36%6%35%45%6%33%
2402
11th to 20thDay
19%7%36%7%45%5%5%7%33%
2478
21st to endDay
22%7%36%6%36%5%5%6%32%
2733
June1st to 10thDay
20%6%36%7%37%6%7%8%26%
2700
11th to 20thDay
20%6%36%5%45%6%6%7%34%
2700
21st to endDay
23%8%37%6%45%5%5%7%26%
2700
July1st to 10thDay
15%6%37%6%46%6%7%9%31%
2537
11th to 20thDay
16%6%37%6%45%6%7%10%31%
2520
21st to endDay
16%7%46%6%37%5%8%8%31%
2744
August1st to 10thDay
18%6%37%6%46%6%7%10%28%
2503
11th to 20thDay
17%6%26%6%35%5%7%8%35%
2304
21st to endDay
17%7%26%5%346%5%8%36%
2458
September1st to 10thDay
18%7%35%5%345%6%8%36%
2160
11th to 20thDay
19%5%2443335%7%44%
2008
21st to endDay
23%7%25%424447%38%
1980
October1st to 10thDay
22%6%36%5%35%6%46%33%
1967
11th to 20thDay
26%8%38%7%4446%6%23%
1653
21st to endDay
29%11%36%6%35%35%425%
1782
November1st to 10thDay
21%10%46%7%35%35%5%31%
1671
11th to 20thDay
23%13%5%8%5%35%45%5%25%
1703
21st to endDay
23%15%5%8%6%345%4423%
1380
December1st to 10thDay
25%17%47%7%3434422%
1330
11th to 20thDay
22%12%5%9%7%3333427%
1668
21st to endDay
22%18%5%7%6%2334426%
2538
January1st to 10thNight
16%19%6%11%8%3433422%
4429
11th to 20thNight
13%16%6%11%7%45%445%25%
4440
21st to endNight
11%14%5%9%8%45%5%6%6%26%
4884
February1st to 10thNight
12%13%6%10%8%35%5%46%28%
2660
11th to 20thNight
13%16%6%9%8%35%445%27%
2229
21st to endNight
15%13%6%9%6%34446%29%
1831
March1st to 10thNight
15%12%47%8%46%446%30%
2150
11th to 20thNight
18%13%47%6%45%5%46%29%
2079
21st to endNight
17%11%37%5%34446%36%
2034
April1st to 10thNight
23%13%5%7%5%3445%428%
1800
11th to 20thNight
20%8%36%5%445%5%6%35%
1696
21st to endNight
24%9%47%5%33336%34%
1620
May1st to 10thNight
24%7%36%5%35%5%5%433%
1573
11th to 20thNight
22%7%36%5%35%445%36%
1415
21st to endNight
23%5%35%5%3445%7%36%
1540
June1st to 10thNight
22%7%36%7%35%5%6%8%28%
1260
11th to 20thNight
21%5%35%4345%6%7%37%
1260
21st to endNight
23%7%47%6%3445%8%30%
1260
July1st to 10thNight
17%6%36%5%35%5%5%8%37%
1418
11th to 20thNight
18%6%26%5%26%5%6%8%36%
1440
21st to endNight
17%6%37%5%36%5%6%8%35%
1574
August1st to 10thNight
16%425%5%45%5%8%8%39%
1432
11th to 20thNight
16%6%47%6%36%5%6%7%34%
1580
21st to endNight
17%6%25%5%345%47%40%
1895
September1st to 10thNight
19%6%25%6%3445%8%40%
1800
11th to 20thNight
20%5%25%43345%5%43%
1952
21st to endNight
21%5%26%424446%42%
1980
October1st to 10thNight
20%6%36%5%35%46%5%38%
1988
11th to 20thNight
25%9%36%6%345%5%5%30%
2306
21st to endNight
27%10%35%5%3445%5%29%
2574
November1st to 10thNight
21%10%36%5%44447%31%
2407
11th to 20thNight
21%10%47%6%34446%31%
2474
21st to endNight
23%14%5%8%6%35%345%25%
2797
December1st to 10thNight
24%16%5%9%7%35%44420%
2850
11th to 20thNight
22%13%5%9%7%34445%25%
3531
21st to endNight
24%19%5%8%5%2334325%
5108

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 10thDay
64%212%16%5%1
2518
11th to 20thDay
63%210%19%6%1
2520
21st to endDay
51%212%25%9%1
2772
February1st to 10thDay
59%410%16%9%2
1520
11th to 20thDay
60%312%15%10%1
1841
21st to endDay
58%28%20%9%3
1520
March1st to 10thDay
54%411%17%12%2
1800
11th to 20thDay
54%5%9%19%12%2
1880
21st to endDay
52%311%19%12%3
2320
April1st to 10thDay
59%212%14%9%4
2160
11th to 20thDay
48%211%25%11%3
2212
21st to endDay
55%311%17%12%2
2340
May1st to 10thDay
51%312%19%14%2
2402
11th to 20thDay
51%311%21%11%1
2482
21st to endDay
52%5%11%19%12%1
2733
June1st to 10thDay
53%5%13%19%8%2
2700
11th to 20thDay
48%5%14%20%11%2
2700
21st to endDay
57%413%17%9%
2700
July1st to 10thDay
47%6%18%23%6%
2467
11th to 20thDay
47%419%23%7%
2445
21st to endDay
50%418%20%7%
2591
August1st to 10thDay
50%6%21%20%3
2489
11th to 20thDay
45%419%23%7%
2304
21st to endDay
46%415%26%9%
2458
September1st to 10thDay
46%316%25%10%
2160
11th to 20thDay
40%218%29%10%
2008
21st to endDay
48%315%25%9%
1980
October1st to 10thDay
51%313%24%9%
1967
11th to 20thDay
59%416%17%3
1653
21st to endDay
62%410%18%5%1
1782
November1st to 10thDay
56%412%20%8%
1671
11th to 20thDay
61%310%19%6%1
1703
21st to endDay
64%411%14%6%1
1380
December1st to 10thDay
66%310%15%6%
1330
11th to 20thDay
62%36%20%9%
1668
21st to endDay
63%312%14%7%2
2538
January1st to 10thNight
68%39%13%6%1
4429
11th to 20thNight
64%29%20%5%1
4440
21st to endNight
58%311%18%9%1
4884
February1st to 10thNight
58%38%20%10%1
2660
11th to 20thNight
61%310%16%10%1
2231
21st to endNight
58%27%18%13%2
1831
March1st to 10thNight
57%310%17%11%2
2160
11th to 20thNight
56%48%16%12%3
2080
21st to endNight
51%5%9%20%11%4
2034
April1st to 10thNight
60%28%15%13%3
1800
11th to 20thNight
49%48%24%14%2
1696
21st to endNight
54%48%18%14%2
1620
May1st to 10thNight
54%410%17%14%2
1573
11th to 20thNight
51%39%20%15%2
1416
21st to endNight
48%5%11%20%15%1
1541
June1st to 10thNight
53%413%20%9%1
1260
11th to 20thNight
47%5%11%23%11%3
1260
21st to endNight
54%413%17%12%
1260
July1st to 10thNight
45%420%22%8%
1378
11th to 20thNight
45%5%18%24%7%1
1392
21st to endNight
47%6%17%21%8%
1486
August1st to 10thNight
41%6%20%27%5%
1422
11th to 20thNight
47%5%21%19%7%
1580
21st to endNight
42%5%13%31%9%
1895
September1st to 10thNight
45%414%25%12%1
1800
11th to 20thNight
44%318%27%8%1
1952
21st to endNight
45%312%27%12%
1980
October1st to 10thNight
47%410%26%12%1
1988
11th to 20thNight
57%414%20%6%
2306
21st to endNight
57%313%18%8%
2574
November1st to 10thNight
54%413%21%7%1
2407
11th to 20thNight
55%412%18%10%
2474
21st to endNight
63%310%17%7%1
2797
December1st to 10thNight
69%310%14%5%
2850
11th to 20thNight
63%37%18%9%
3532
21st to endNight
66%28%16%7%2
5108

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 10thDay
27%14%32%22%42
180
11th to 20thDay
27%22%32%14%4
180
21st to endDay
20%20%32%22%5%1
198
February1st to 10thDay
28%21%35%15%11
180
11th to 20thDay
23%21%37%16%31
442
21st to endDay
24%20%29%21%6%
362
March1st to 10thDay
25%18%32%18%7%1
420
11th to 20thDay
26%16%32%17%7%1
420
21st to endDay
24%16%23%24%11%2
462
April1st to 10thDay
30%12%30%19%9%
420
11th to 20thDay
27%13%28%22%9%1
412
21st to endDay
33%10%31%19%5%1
420
May1st to 10thDay
27%17%33%16%6%1
423
11th to 20thDay
22%12%34%22%8%2
447
21st to endDay
27%18%31%17%6%1
493
June1st to 10thDay
25%12%30%24%9%
630
11th to 20thDay
24%11%27%25%12%1
630
21st to endDay
29%7%27%23%12%2
630
July1st to 10thDay
20%10%31%25%12%2
462
11th to 20thDay
19%8%32%28%10%2
444
21st to endDay
20%8%32%28%11%2
488
August1st to 10thDay
22%432%24%14%4
446
11th to 20thDay
19%5%26%30%17%3
439
21st to endDay
24%9%24%21%13%8%
495
September1st to 10thDay
22%10%26%25%14%3
450
11th to 20thDay
22%10%28%20%15%4
450
21st to endDay
24%11%23%23%13%6%
450
October1st to 10thDay
24%11%27%24%11%3
450
11th to 20thDay
35%9%24%20%11%1
376
21st to endDay
38%12%27%17%5%
396
November1st to 10thDay
32%12%24%23%8%1
365
11th to 20thDay
31%13%27%20%9%1
363
21st to endDay
33%16%29%17%6%
180
December1st to 10thDay
34%8%27%22%7%3
180
11th to 20thDay
32%18%29%16%32
180
21st to endDay
32%18%30%15%5%
198
January1st to 10thNight
26%16%30%24%5%
760
11th to 20thNight
27%14%29%24%6%1
760
21st to endNight
17%13%32%30%7%1
836
February1st to 10thNight
20%13%33%28%6%
760
11th to 20thNight
23%15%36%21%5%1
743
21st to endNight
26%12%30%27%5%
611
March1st to 10thNight
22%10%35%27%6%
720
11th to 20thNight
26%14%30%22%6%1
720
21st to endNight
24%10%27%30%8%1
792
April1st to 10thNight
30%11%26%26%6%1
720
11th to 20thNight
27%7%33%26%7%
632
21st to endNight
30%10%30%23%7%
540
May1st to 10thNight
26%9%30%28%6%
493
11th to 20thNight
24%9%28%32%7%
354
21st to endNight
26%432%28%9%
389
June1st to 10thNight
26%5%27%34%7%
360
11th to 20thNight
21%425%38%13%
360
21st to endNight
25%422%37%10%1
360
July1st to 10thNight
20%327%38%11%1
350
11th to 20thNight
19%420%41%16%
348
21st to endNight
19%316%45%16%1
394
August1st to 10thNight
20%413%46%18%
358
11th to 20thNight
19%321%39%16%2
516
21st to endNight
21%423%33%18%2
707
September1st to 10thNight
22%325%33%15%1
720
11th to 20thNight
22%5%22%31%17%2
720
21st to endNight
25%5%25%29%14%2
720
October1st to 10thNight
24%7%26%33%9%1
720
11th to 20thNight
30%7%24%27%11%1
720
21st to endNight
33%10%28%24%5%
792
November1st to 10thNight
29%11%24%28%9%1
740
11th to 20thNight
27%13%24%26%8%1
760
21st to endNight
31%12%29%21%6%1
825
December1st to 10thNight
32%11%26%22%8%1
850
11th to 20thNight
27%17%27%23%6%1
850
21st to endNight
33%14%28%19%5%1
899
Page generated at 2024-02-22 06:05:43. Version ac07

Copyright 2024 Attilla Danko


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