Observatoire de Ste-Christine
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de Ste-Christine clear sky chart from 2005-11-05 to 2017-09-17.

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%
14631
11%
46834
7%
14600
31%
14600
13%
35002

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
7%
2506
3%
716
17%
716
6%
2070
January16th to endNight
13%
768
7%
2688
3%
768
19%
768
7%
2190
February1st to 15thNight
13%
703
6%
2318
2%
701
19%
701
7%
1907
February16th to endNight
16%
631
9%
1893
4%
631
22%
631
9%
1522
March1st to 15thNight
17%
720
13%
2160
8%
720
25%
720
13%
1665
March16th to endNight
26%
768
18%
2011
7%
768
33%
768
18%
1483
April1st to 15thNight
20%
718
13%
1796
4%
718
26%
718
15%
1441
April16th to endNight
24%
585
16%
1665
5%
585
33%
585
18%
1168
May1st to 15thNight
26%
441
15%
1521
11%
441
35%
441
16%
1054
May16th to endNight
28%
375
10%
1497
9%
374
36%
374
14%
1017
June1st to 15thNight
30%
360
8%
1440
7%
360
38%
360
12%
1024
June16th to endNight
38%
360
8%
1440
9%
360
44%
360
17%
947
July1st to 15thNight
45%
340
11%
1360
15%
340
49%
340
19%
846
July16th to endNight
47%
376
11%
1418
14%
354
50%
354
20%
866
August1st to 15thNight
45%
401
13%
1472
12%
399
48%
399
20%
948
August16th to endNight
48%
708
18%
1854
10%
708
51%
708
31%
1212
September1st to 15thNight
41%
720
12%
1821
6%
720
43%
720
27%
1281
September16th to endNight
41%
665
19%
1836
12%
665
46%
665
29%
1193
October1st to 15thNight
27%
660
17%
1902
8%
660
35%
660
18%
1376
October16th to endNight
21%
704
9%
2288
5%
704
26%
704
11%
1773
November1st to 15thNight
21%
700
14%
2277
9%
700
29%
700
12%
1734
November16th to endNight
20%
720
12%
2463
8%
720
26%
720
10%
1893
December1st to 15thNight
11%
720
5%
2520
1%
720
15%
720
5%
2133
December16th to endNight
9%
768
7%
2688
2%
768
15%
768
5%
2259

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
21%10%36%5%34446%29%
47951
Night
20%11%47%5%34345%29%
47004
TransparencyDay
57%5%11%17%7%
47639
Night
58%5%10%17%8%
46834
SeeingDay
27%14%28%18%8%2
5644
Night
26%13%28%21%8%
14632

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%18%6%11%6%35%33316%
1432
16th to endDay
14%16%6%10%6%45%446%20%
1536
February1st to 15thDay
16%16%7%12%8%46%43417%
1543
16th to endDay
15%19%6%9%7%4443421%
1580
March1st to 15thDay
19%13%5%8%7%35%43424%
1790
16th to endDay
19%11%47%5%3323433%
2211
April1st to 15thDay
24%13%35%5%2433429%
2152
16th to endDay
23%8%24433335%35%
2295
May1st to 15thDay
24%7%35%6%34446%29%
2440
16th to endDay
22%6%36%5%3445%7%29%
2618
June1st to 15thDay
28%6%24424447%28%
2520
16th to endDay
22%5%36%5%35%46%8%29%
2520
July1st to 15thDay
16%6%25%5%36%5%5%9%32%
2520
16th to endDay
17%6%25%5%35%5%6%9%30%
2654
August1st to 15thDay
18%7%26%5%35%6%6%7%28%
2466
16th to endDay
15%5%2442445%8%42%
2345
September1st to 15thDay
20%6%2442345%6%40%
2139
16th to endDay
19%6%23314347%42%
1830
October1st to 15thDay
25%9%34424346%30%
1725
16th to endDay
27%13%36%5%23445%22%
1584
November1st to 15thDay
20%12%36%434436%29%
1581
16th to endDay
22%16%5%7%422345%26%
1494
December1st to 15thDay
27%17%5%7%5%34335%15%
1440
16th to endDay
26%19%6%9%5%2433315%
1536
January1st to 15thNight
20%16%7%10%6%3433419%
2506
16th to endNight
14%17%6%9%9%45%43419%
2688
February1st to 15thNight
13%16%6%13%8%45%43418%
2317
16th to endNight
16%15%6%10%6%3433424%
1893
March1st to 15thNight
20%14%5%7%5%3333328%
2147
16th to endNight
18%12%45%42333436%
2011
April1st to 15thNight
26%10%46%5%24436%26%
1796
16th to endNight
23%7%25%423446%36%
1665
May1st to 15thNight
23%7%36%424346%33%
1521
16th to endNight
23%5%25%5%335%5%7%31%
1495
June1st to 15thNight
29%6%25%424448%27%
1440
16th to endNight
18%5%345%245%6%7%35%
1440
July1st to 15thNight
15%5%25%5%45%5%6%8%36%
1440
16th to endNight
13%5%245%345%7%8%40%
1514
August1st to 15thNight
16%6%245%3446%8%37%
1482
16th to endNight
14%5%25%42435%8%43%
1854
September1st to 15thNight
20%6%16%33335%5%40%
1821
16th to endNight
19%413424236%46%
1836
October1st to 15thNight
20%9%35%5%33346%34%
1902
16th to endNight
30%11%35%424335%25%
2288
November1st to 15thNight
21%10%37%43445%5%27%
2277
16th to endNight
24%15%5%7%42323426%
2463
December1st to 15thNight
25%17%6%9%6%3422317%
2520
16th to endNight
25%19%6%8%5%2323318%
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
75%47%9%3
1433
16th to endDay
66%6%10%12%3
1536
February1st to 15thDay
72%48%11%1
1546
16th to endDay
68%48%11%6%1
1580
March1st to 15thDay
64%310%13%7%1
1800
16th to endDay
56%48%17%11%1
2211
April1st to 15thDay
60%36%16%10%1
2152
16th to endDay
53%49%17%12%3
2295
May1st to 15thDay
55%410%17%11%
2440
16th to endDay
54%6%10%18%8%
2622
June1st to 15thDay
56%6%11%16%8%
2520
16th to endDay
53%6%12%20%7%
2520
July1st to 15thDay
45%8%16%23%6%
2371
16th to endDay
49%9%15%19%5%
2487
August1st to 15thDay
52%7%16%18%4
2452
16th to endDay
42%5%16%25%10%
2345
September1st to 15thDay
46%5%13%23%10%
2139
16th to endDay
42%413%29%9%
1830
October1st to 15thDay
55%6%12%19%6%
1725
16th to endDay
65%5%10%14%4
1584
November1st to 15thDay
57%5%12%16%7%
1581
16th to endDay
62%410%15%6%
1494
December1st to 15thDay
73%5%8%10%1
1440
16th to endDay
77%45%6%5%
1536
January1st to 15thNight
70%49%10%3
2506
16th to endNight
69%48%12%4
2688
February1st to 15thNight
70%48%12%3
2318
16th to endNight
66%38%11%8%
1893
March1st to 15thNight
61%38%17%7%1
2160
16th to endNight
53%38%16%14%3
2011
April1st to 15thNight
62%3416%11%1
1796
16th to endNight
49%5%8%19%14%2
1665
May1st to 15thNight
53%38%16%15%2
1521
16th to endNight
50%6%11%19%9%1
1497
June1st to 15thNight
55%5%10%19%7%
1440
16th to endNight
47%7%11%22%11%
1440
July1st to 15thNight
42%7%14%24%10%
1360
16th to endNight
39%8%17%22%11%
1418
August1st to 15thNight
43%7%17%23%7%
1472
16th to endNight
38%5%16%28%10%
1854
September1st to 15thNight
45%5%12%25%10%
1821
16th to endNight
39%5%13%29%12%
1836
October1st to 15thNight
51%5%10%21%9%
1902
16th to endNight
62%410%16%5%
2288
November1st to 15thNight
58%6%11%15%5%2
2277
16th to endNight
63%39%15%6%
2463
December1st to 15thNight
74%48%10%2
2520
16th to endNight
73%48%9%4
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
26%15%38%16%3
60
16th to endDay
32%21%32%9%11
64
February1st to 15thDay
32%24%28%12%1
117
16th to endDay
24%23%34%13%3
239
March1st to 15thDay
30%22%27%15%3
270
16th to endDay
26%18%28%14%10%2
288
April1st to 15thDay
33%18%24%17%41
270
16th to endDay
28%18%27%11%8%4
270
May1st to 15thDay
35%13%27%12%7%2
288
16th to endDay
22%19%31%19%6%1
331
June1st to 15thDay
34%12%26%18%6%
315
16th to endDay
27%11%35%18%6%1
315
July1st to 15thDay
22%6%36%22%8%2
305
16th to endDay
20%435%27%10%1
326
August1st to 15thDay
24%9%25%24%13%2
313
16th to endDay
20%8%28%19%16%6%
332
September1st to 15thDay
22%9%26%19%15%6%
315
16th to endDay
21%12%27%18%12%7%
259
October1st to 15thDay
28%13%25%19%9%3
254
16th to endDay
40%14%19%20%5%
240
November1st to 15thDay
29%16%28%18%5%2
235
16th to endDay
33%19%21%14%8%2
114
December1st to 15thDay
41%18%28%8%3
60
16th to endDay
43%25%26%31
64
January1st to 15thNight
28%19%33%14%3
720
16th to endNight
23%21%32%16%5%
768
February1st to 15thNight
22%19%33%20%3
704
16th to endNight
25%16%35%18%3
631
March1st to 15thNight
31%15%31%19%2
720
16th to endNight
25%16%27%22%7%
768
April1st to 15thNight
32%15%27%20%4
718
16th to endNight
28%17%26%19%8%
585
May1st to 15thNight
26%12%31%20%8%1
441
16th to endNight
26%9%30%25%8%
375
June1st to 15thNight
33%7%22%25%10%
360
16th to endNight
19%6%30%31%11%
360
July1st to 15thNight
15%6%27%34%15%1
340
16th to endNight
15%229%36%15%
376
August1st to 15thNight
19%423%32%19%
401
16th to endNight
16%5%22%36%16%2
708
September1st to 15thNight
23%5%25%30%12%1
720
16th to endNight
22%6%27%25%15%1
665
October1st to 15thNight
26%12%28%21%9%1
660
16th to endNight
37%12%24%19%4
704
November1st to 15thNight
26%16%30%17%8%
700
16th to endNight
32%18%23%15%9%1
720
December1st to 15thNight
34%20%29%11%3
720
16th to endNight
35%19%27%14%3
768
Page generated at 2017-09-18 08:38:19. Version ac04

Copyright 2017 A. Danko


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