Observatoire de Lac Creux
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de Lac Creux clear sky chart from 2005-11-05 to 2017-12-02.

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
29%
14859
11%
47814
8%
14829
34%
14829
14%
35701

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
16%
720
6%
2506
4%
716
19%
716
6%
2113
January16th to endNight
23%
768
8%
2688
5%
768
27%
768
9%
2121
February1st to 15thNight
21%
703
10%
2287
5%
701
28%
701
10%
1811
February16th to endNight
23%
631
10%
1949
6%
631
28%
631
10%
1555
March1st to 15thNight
23%
720
11%
2124
7%
720
28%
720
12%
1677
March16th to endNight
32%
768
19%
2019
9%
768
38%
768
20%
1445
April1st to 15thNight
27%
718
15%
1796
6%
718
31%
718
19%
1357
April16th to endNight
29%
603
17%
1683
8%
603
35%
603
21%
1177
May1st to 15thNight
31%
360
15%
1440
16%
360
37%
360
15%
986
May16th to endNight
32%
374
11%
1497
11%
374
41%
374
15%
1008
June1st to 15thNight
32%
360
6%
1440
6%
360
37%
360
13%
1015
June16th to endNight
46%
360
7%
1440
9%
360
47%
360
19%
921
July1st to 15thNight
51%
340
9%
1360
13%
340
54%
340
21%
832
July16th to endNight
54%
376
12%
1418
17%
354
56%
354
22%
858
August1st to 15thNight
50%
389
12%
1460
13%
387
52%
387
19%
960
August16th to endNight
50%
708
17%
1854
9%
708
55%
708
30%
1216
September1st to 15thNight
41%
720
12%
1800
6%
720
42%
720
27%
1267
September16th to endNight
44%
717
18%
1953
12%
717
47%
717
28%
1307
October1st to 15thNight
30%
720
15%
2160
10%
720
37%
720
18%
1558
October16th to endNight
23%
768
9%
2432
6%
768
29%
768
11%
1941
November1st to 15thNight
23%
760
14%
2544
10%
760
30%
760
12%
1930
November16th to endNight
20%
780
9%
2730
7%
780
23%
780
7%
2235
December1st to 15thNight
16%
728
6%
2546
2%
728
20%
728
6%
2137
December16th to endNight
15%
768
9%
2688
5%
768
20%
768
5%
2274

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%47%5%34446%27%
48645
Night
19%11%47%6%34445%28%
47983
TransparencyDay
57%410%17%8%
48332
Night
58%410%18%7%
47814
SeeingDay
28%10%26%21%10%3
5693
Night
27%10%24%25%11%1
14861

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
23%16%8%12%6%3423415%
1432
16th to endDay
15%15%7%10%7%35%45%6%19%
1536
February1st to 15thDay
9%17%7%13%10%45%44418%
1574
16th to endDay
16%18%6%9%7%2442422%
1524
March1st to 15thDay
16%14%5%10%7%2433426%
1824
16th to endDay
16%9%46%5%34345%34%
2205
April1st to 15thDay
25%12%45%42343429%
2152
16th to endDay
22%9%36%5%33345%33%
2286
May1st to 15thDay
24%8%36%5%33346%29%
2511
16th to endDay
23%8%25%5%34346%31%
2618
June1st to 15thDay
25%7%35%6%35%45%6%26%
2520
16th to endDay
20%5%25%6%45%5%6%7%29%
2520
July1st to 15thDay
18%6%36%5%35%46%7%31%
2520
16th to endDay
17%6%36%5%36%5%6%7%31%
2654
August1st to 15thDay
19%7%36%5%45%6%6%6%27%
2487
16th to endDay
15%7%26%5%345%5%8%34%
2336
September1st to 15thDay
22%7%25%5%23345%36%
2160
16th to endDay
21%5%24422347%40%
2004
October1st to 15thDay
25%11%25%42345%6%28%
1800
16th to endDay
31%16%26%5%2333419%
1791
November1st to 15thDay
19%14%5%6%43345%5%26%
1644
16th to endDay
27%15%6%8%5%3232420%
1560
December1st to 15thDay
23%20%7%8%5%24345%13%
1451
16th to endDay
22%18%7%8%7%3432416%
1536
January1st to 15thNight
22%17%7%10%9%3343413%
2506
16th to endNight
15%16%7%8%7%45%5%45%19%
2688
February1st to 15thNight
11%14%7%11%10%45%45%420%
2285
16th to endNight
15%14%7%9%7%35%6%3421%
1949
March1st to 15thNight
20%13%47%6%45%5%4423%
2111
16th to endNight
15%10%46%5%23445%38%
2019
April1st to 15thNight
24%11%45%5%23335%31%
1796
16th to endNight
20%8%35%413446%37%
1683
May1st to 15thNight
22%10%25%42435%6%32%
1440
16th to endNight
21%6%36%5%34446%34%
1495
June1st to 15thNight
22%7%25%6%3446%6%29%
1440
16th to endNight
16%6%35%5%35%45%8%36%
1440
July1st to 15thNight
14%424435%6%6%6%40%
1440
16th to endNight
12%6%35%4335%6%8%40%
1514
August1st to 15thNight
14%6%36%4345%7%7%35%
1470
16th to endNight
14%5%245%235%47%44%
1854
September1st to 15thNight
20%6%25%423436%38%
1800
16th to endNight
19%6%24323346%43%
1953
October1st to 15thNight
23%8%35%433345%33%
2160
16th to endNight
30%13%35%424445%21%
2432
November1st to 15thNight
21%12%5%7%6%33245%27%
2544
16th to endNight
26%16%5%8%6%2333418%
2730
December1st to 15thNight
22%20%8%9%5%3333316%
2546
16th to endNight
22%20%7%9%7%3433315%
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%35%9%5%
1433
16th to endDay
64%5%7%14%7%
1536
February1st to 15thDay
68%38%13%6%
1576
16th to endDay
66%36%15%8%
1524
March1st to 15thDay
61%38%15%8%1
1834
16th to endDay
51%38%18%13%3
2205
April1st to 15thDay
59%36%17%10%2
2152
16th to endDay
54%38%18%12%3
2286
May1st to 15thDay
56%36%20%11%1
2511
16th to endDay
55%310%18%11%1
2622
June1st to 15thDay
58%410%17%9%
2520
16th to endDay
51%5%13%20%8%
2520
July1st to 15thDay
48%5%14%22%8%
2371
16th to endDay
51%6%15%19%7%
2487
August1st to 15thDay
55%6%15%18%4
2473
16th to endDay
46%5%17%22%8%
2336
September1st to 15thDay
50%314%20%10%
2160
16th to endDay
44%414%28%7%
2004
October1st to 15thDay
56%411%19%6%
1800
16th to endDay
70%39%12%3
1791
November1st to 15thDay
59%412%15%7%
1644
16th to endDay
70%38%12%5%
1560
December1st to 15thDay
74%38%11%1
1451
16th to endDay
73%36%10%6%
1536
January1st to 15thNight
74%37%10%3
2506
16th to endNight
66%46%15%6%
2688
February1st to 15thNight
65%38%15%5%
2287
16th to endNight
65%47%13%7%
1949
March1st to 15thNight
64%37%15%7%
2124
16th to endNight
49%48%21%14%1
2019
April1st to 15thNight
56%26%19%12%2
1796
16th to endNight
48%38%20%14%3
1683
May1st to 15thNight
52%47%17%14%3
1440
16th to endNight
51%410%21%10%1
1497
June1st to 15thNight
53%6%11%19%7%
1440
16th to endNight
46%414%22%11%
1440
July1st to 15thNight
40%6%16%22%12%
1360
16th to endNight
41%5%18%26%8%
1418
August1st to 15thNight
46%6%17%23%5%
1460
16th to endNight
39%5%18%29%6%
1854
September1st to 15thNight
46%416%22%10%
1800
16th to endNight
43%415%30%7%
1953
October1st to 15thNight
53%410%21%10%
2160
16th to endNight
65%410%15%4
2432
November1st to 15thNight
61%311%16%6%
2544
16th to endNight
70%37%13%3
2730
December1st to 15thNight
73%38%11%2
2546
16th to endNight
74%36%9%5%
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
30%20%30%16%3
60
16th to endDay
31%6%37%17%7%
64
February1st to 15thDay
20%23%35%18%2
90
16th to endDay
35%15%24%16%7%
183
March1st to 15thDay
29%13%31%20%41
270
16th to endDay
22%17%26%19%10%4
288
April1st to 15thDay
31%15%21%22%7%1
270
16th to endDay
28%12%27%18%10%3
270
May1st to 15thDay
33%11%23%21%5%4
288
16th to endDay
31%12%26%18%9%1
331
June1st to 15thDay
33%9%28%18%8%
315
16th to endDay
21%8%30%25%10%3
315
July1st to 15thDay
20%7%31%28%9%2
305
16th to endDay
19%423%35%13%3
326
August1st to 15thDay
24%6%19%28%15%5%
313
16th to endDay
21%6%27%19%15%9%
332
September1st to 15thDay
28%7%20%18%14%10%
315
16th to endDay
21%7%23%23%15%8%
314
October1st to 15thDay
32%9%22%20%11%2
315
16th to endDay
39%13%22%16%8%
304
November1st to 15thDay
29%9%30%20%7%2
208
16th to endDay
37%24%26%6%4
90
December1st to 15thDay
34%12%34%12%31
63
16th to endDay
35%25%29%7%1
64
January1st to 15thNight
30%11%28%22%5%
720
16th to endNight
24%11%27%25%9%1
768
February1st to 15thNight
18%12%33%25%8%
704
16th to endNight
24%14%29%24%6%
631
March1st to 15thNight
29%13%25%25%5%
720
16th to endNight
20%14%26%25%11%1
768
April1st to 15thNight
32%11%22%26%6%
718
16th to endNight
26%13%25%23%10%
603
May1st to 15thNight
28%5%26%25%11%1
360
16th to endNight
22%9%27%30%8%
375
June1st to 15thNight
26%6%25%32%8%
360
16th to endNight
18%5%22%37%14%1
360
July1st to 15thNight
13%5%23%35%22%
340
16th to endNight
15%319%44%15%1
376
August1st to 15thNight
21%215%33%24%2
389
16th to endNight
18%5%19%32%22%2
708
September1st to 15thNight
26%420%29%17%1
720
16th to endNight
24%5%21%24%21%1
717
October1st to 15thNight
28%9%24%24%10%2
720
16th to endNight
39%9%21%21%7%
768
November1st to 15thNight
29%11%26%20%10%1
760
16th to endNight
37%14%19%19%7%1
780
December1st to 15thNight
34%16%23%20%4
728
16th to endNight
34%14%24%19%5%1
768
Page generated at 2017-12-03 11:16:47. Version ac04

Copyright 2017 A. Danko


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