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 2017-03-13.

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%
14033
11%
45203
8%
14003
34%
14003
14%
33818

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%
712
11%
2102
7%
712
28%
712
12%
1655
March16th to endNight
31%
704
18%
1851
8%
704
38%
704
20%
1326
April1st to 15thNight
27%
658
15%
1646
6%
658
31%
658
19%
1236
April16th to endNight
30%
553
17%
1543
8%
553
36%
553
22%
1072
May1st to 15thNight
31%
330
17%
1320
17%
330
39%
330
16%
884
May16th to endNight
33%
342
12%
1369
12%
342
42%
342
16%
914
June1st to 15thNight
31%
330
7%
1320
7%
330
36%
330
13%
941
June16th to endNight
47%
330
6%
1320
9%
330
48%
330
19%
836
July1st to 15thNight
51%
310
10%
1240
14%
310
55%
310
22%
752
July16th to endNight
54%
348
10%
1306
14%
326
56%
326
22%
796
August1st to 15thNight
50%
356
13%
1337
14%
354
53%
354
20%
869
August16th to endNight
50%
649
16%
1699
8%
649
54%
649
31%
1108
September1st to 15thNight
40%
660
11%
1650
5%
660
41%
660
26%
1171
September16th to endNight
42%
657
17%
1790
11%
657
46%
657
28%
1210
October1st to 15thNight
28%
660
15%
1980
10%
660
35%
660
16%
1451
October16th to endNight
24%
704
8%
2229
6%
704
28%
704
10%
1788
November1st to 15thNight
23%
700
15%
2343
11%
700
30%
700
12%
1766
November16th to endNight
19%
720
9%
2520
7%
720
23%
720
7%
2056
December1st to 15thNight
16%
720
6%
2520
3%
720
20%
720
6%
2113
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%11%47%5%34446%27%
45490
Night
19%12%47%6%34445%28%
45372
TransparencyDay
58%410%17%8%
45177
Night
58%410%17%7%
45203
SeeingDay
27%10%26%21%10%3
4709
Night
27%10%24%25%10%1
14035

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%
1793
16th to endDay
16%10%46%5%44445%34%
2021
April1st to 15thDay
24%12%46%42343428%
1972
16th to endDay
21%9%36%5%3334434%
2095
May1st to 15thDay
23%7%36%5%33347%30%
2301
16th to endDay
23%8%35%5%34336%31%
2394
June1st to 15thDay
26%7%35%6%35%46%6%25%
2310
16th to endDay
20%5%25%5%45%5%6%7%30%
2310
July1st to 15thDay
19%6%36%5%25%46%8%31%
2310
16th to endDay
17%6%36%5%36%5%6%7%31%
2458
August1st to 15thDay
20%7%36%5%45%6%5%6%26%
2280
16th to endDay
15%7%26%6%345%5%8%35%
2140
September1st to 15thDay
22%7%35%5%23345%34%
1980
16th to endDay
23%5%24422347%38%
1837
October1st to 15thDay
26%11%25%42345%6%27%
1650
16th to endDay
33%16%36%5%2333418%
1642
November1st to 15thDay
19%14%5%6%43345%5%27%
1515
16th to endDay
27%15%6%8%42232421%
1440
December1st to 15thDay
23%20%7%8%5%24445%13%
1440
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
19%13%47%6%45%5%4423%
2089
16th to endNight
14%10%46%5%23445%37%
1851
April1st to 15thNight
24%10%345%24335%32%
1646
16th to endNight
20%8%35%413446%37%
1543
May1st to 15thNight
20%9%25%5%2435%6%34%
1320
16th to endNight
21%6%35%5%33446%35%
1367
June1st to 15thNight
22%8%35%6%3446%6%29%
1320
16th to endNight
15%6%35%435%5%5%8%37%
1320
July1st to 15thNight
14%424435%5%6%6%40%
1320
16th to endNight
12%6%35%4335%6%9%40%
1402
August1st to 15thNight
14%6%26%4245%7%7%36%
1347
16th to endNight
13%5%245%22447%44%
1699
September1st to 15thNight
21%6%26%5%23446%37%
1650
16th to endNight
21%6%24323335%43%
1790
October1st to 15thNight
23%9%35%423345%32%
1980
16th to endNight
31%13%35%424445%21%
2229
November1st to 15thNight
22%11%5%7%5%33245%27%
2343
16th to endNight
26%16%5%8%6%2333419%
2520
December1st to 15thNight
22%20%8%9%5%3333316%
2520
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%16%8%1
1803
16th to endDay
52%39%18%12%3
2021
April1st to 15thDay
58%37%16%10%2
1972
16th to endDay
54%37%18%12%3
2095
May1st to 15thDay
53%36%21%12%1
2301
16th to endDay
54%39%19%11%1
2398
June1st to 15thDay
58%410%16%8%
2310
16th to endDay
50%5%13%21%8%
2310
July1st to 15thDay
47%5%15%21%8%
2161
16th to endDay
51%6%15%19%6%
2291
August1st to 15thDay
56%6%14%17%5%
2266
16th to endDay
46%5%17%21%8%
2140
September1st to 15thDay
51%314%20%9%
1980
16th to endDay
46%414%27%6%
1837
October1st to 15thDay
57%5%11%18%7%
1650
16th to endDay
71%38%12%3
1642
November1st to 15thDay
58%412%15%7%
1515
16th to endDay
69%38%13%5%
1440
December1st to 15thDay
74%38%11%1
1440
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
63%37%15%7%
2102
16th to endNight
50%48%21%13%1
1851
April1st to 15thNight
55%26%19%12%2
1646
16th to endNight
48%38%20%15%3
1543
May1st to 15thNight
50%48%18%14%3
1320
16th to endNight
51%49%23%10%1
1369
June1st to 15thNight
54%6%11%18%7%
1320
16th to endNight
45%5%14%22%11%
1320
July1st to 15thNight
40%6%16%23%11%
1240
16th to endNight
41%5%19%25%8%
1306
August1st to 15thNight
45%6%18%24%5%
1337
16th to endNight
39%5%19%28%7%
1699
September1st to 15thNight
47%416%22%9%
1650
16th to endNight
44%314%30%6%
1790
October1st to 15thNight
55%410%19%9%
1980
16th to endNight
65%49%15%4
2229
November1st to 15thNight
60%311%16%7%
2343
16th to endNight
70%37%13%4
2520
December1st to 15thNight
73%38%11%2
2520
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
28%13%30%21%5%1
259
16th to endDay
20%16%25%21%10%5%
224
April1st to 15thDay
29%13%20%25%9%1
210
16th to endDay
24%11%28%18%12%4
210
May1st to 15thDay
27%10%24%25%6%5%
228
16th to endDay
29%11%26%20%10%1
267
June1st to 15thDay
34%9%26%18%9%1
255
16th to endDay
18%6%32%26%12%3
255
July1st to 15thDay
20%6%30%28%10%2
245
16th to endDay
20%324%34%13%4
270
August1st to 15thDay
26%6%17%25%16%6%
253
16th to endDay
21%5%29%18%15%9%
268
September1st to 15thDay
29%7%19%18%13%12%
255
16th to endDay
25%8%24%20%12%8%
254
October1st to 15thDay
34%10%21%20%10%2
255
16th to endDay
41%11%20%17%9%
251
November1st to 15thDay
27%8%31%21%7%2
169
16th to endDay
36%13%33%10%6%
60
December1st to 15thDay
36%13%33%11%31
60
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%
712
16th to endNight
20%14%26%25%11%1
704
April1st to 15thNight
31%12%22%26%6%
658
16th to endNight
25%13%25%24%11%
553
May1st to 15thNight
26%5%28%25%11%1
330
16th to endNight
22%9%27%30%9%
343
June1st to 15thNight
26%6%26%30%9%
330
16th to endNight
17%5%22%38%14%1
330
July1st to 15thNight
14%5%22%35%22%
310
16th to endNight
14%320%43%15%1
348
August1st to 15thNight
21%315%32%24%2
356
16th to endNight
17%5%20%33%22%1
649
September1st to 15thNight
26%421%28%17%1
660
16th to endNight
26%5%23%24%18%1
657
October1st to 15thNight
29%10%24%23%10%2
660
16th to endNight
40%10%19%22%6%
704
November1st to 15thNight
29%11%26%20%10%1
700
16th to endNight
37%14%19%19%7%1
720
December1st to 15thNight
33%16%23%20%5%
720
16th to endNight
34%14%24%19%5%1
768
Page generated at 2017-03-14 04:34:42. Version ac04

Copyright 2017 A. Danko


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