Lac Gagnon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac Gagnon clear sky chart from 2005-11-05 to 2017-09-20.

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
28%
14610
12%
46879
7%
14578
34%
14578
15%
34271

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
2%
716
20%
716
7%
2058
January16th to endNight
19%
768
9%
2679
4%
768
26%
768
10%
2049
February1st to 15thNight
17%
704
10%
2287
4%
701
25%
701
10%
1778
February16th to endNight
21%
631
11%
1937
5%
631
30%
631
12%
1469
March1st to 15thNight
20%
720
12%
2127
6%
720
27%
720
13%
1656
March16th to endNight
28%
768
18%
2016
7%
768
37%
768
20%
1427
April1st to 15thNight
25%
718
15%
1796
5%
718
30%
718
20%
1315
April16th to endNight
27%
624
16%
1704
7%
624
33%
624
19%
1210
May1st to 15thNight
30%
360
15%
1440
14%
360
40%
360
14%
987
May16th to endNight
32%
375
13%
1497
11%
374
44%
374
16%
1007
June1st to 15thNight
34%
360
7%
1440
6%
360
42%
360
13%
998
June16th to endNight
45%
360
7%
1440
11%
360
48%
360
17%
939
July1st to 15thNight
52%
340
11%
1360
14%
340
58%
340
25%
777
July16th to endNight
53%
376
12%
1418
14%
354
57%
354
22%
848
August1st to 15thNight
52%
397
12%
1468
12%
395
55%
395
21%
956
August16th to endNight
47%
720
18%
1866
9%
720
51%
720
34%
1184
September1st to 15thNight
42%
720
13%
1800
6%
720
45%
720
27%
1255
September16th to endNight
44%
677
20%
1838
12%
677
49%
677
31%
1193
October1st to 15thNight
27%
660
16%
1980
9%
660
36%
660
17%
1421
October16th to endNight
23%
704
9%
2227
5%
704
29%
704
12%
1730
November1st to 15thNight
26%
700
15%
2325
10%
700
34%
700
14%
1696
November16th to endNight
19%
720
9%
2520
7%
720
23%
720
8%
2014
December1st to 15thNight
15%
720
6%
2520
2%
720
20%
720
6%
2085
December16th to endNight
12%
768
9%
2688
3%
768
19%
768
7%
2219

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%46%6%34446%29%
47973
Night
18%10%47%5%34445%30%
47048
Cloud CoverDay
20%10%36%5%34445%30%
47982
Night
19%10%46%5%34445%31%
47054
TransparencyDay
55%6%11%17%8%1
47660
Night
54%5%11%18%8%
46879
SeeingDay
24%13%28%20%9%3
5492
Night
24%12%28%24%9%
14610

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
21%17%7%9%8%3332317%
1432
16th to endDay
14%15%7%8%8%336%5%5%21%
1542
February1st to 15thDay
12%15%7%11%9%35%335%21%
1575
16th to endDay
15%18%5%8%6%35%335%24%
1535
March1st to 15thDay
17%13%48%6%35%345%26%
1821
16th to endDay
14%9%46%43445%6%36%
2208
April1st to 15thDay
24%12%35%423336%31%
2152
16th to endDay
20%9%36%43434434%
2267
May1st to 15thDay
23%9%26%6%24346%30%
2511
16th to endDay
20%7%36%5%3445%6%31%
2618
June1st to 15thDay
23%7%36%6%45%45%7%27%
2520
16th to endDay
20%5%25%6%45%6%6%7%29%
2520
July1st to 15thDay
16%5%35%5%36%5%5%9%33%
2520
16th to endDay
14%7%35%6%35%5%6%8%32%
2654
August1st to 15thDay
16%7%36%6%36%46%7%31%
2481
16th to endDay
14%5%25%5%3446%7%38%
2324
September1st to 15thDay
19%6%25%5%2435%6%37%
2160
16th to endDay
18%6%34323346%42%
1891
October1st to 15thDay
24%9%345%13446%31%
1650
16th to endDay
28%14%36%6%3434321%
1645
November1st to 15thDay
19%10%445%35%35%6%31%
1531
16th to endDay
24%14%6%7%5%2333323%
1440
December1st to 15thDay
23%18%7%8%5%34435%14%
1440
16th to endDay
21%18%7%9%6%3433317%
1536
January1st to 15thNight
19%16%6%9%8%35%436%17%
2506
16th to endNight
12%15%6%8%7%45%45%6%22%
2679
February1st to 15thNight
10%13%7%11%9%35%44423%
2285
16th to endNight
15%12%5%9%6%35%45%5%26%
1937
March1st to 15thNight
19%13%47%6%45%44425%
2114
16th to endNight
14%8%26%6%3443439%
2016
April1st to 15thNight
23%9%44323346%33%
1796
16th to endNight
20%8%25%5%24445%37%
1704
May1st to 15thNight
21%8%26%5%33435%34%
1440
16th to endNight
17%6%35%6%345%5%6%36%
1495
June1st to 15thNight
20%7%35%5%35%5%6%8%30%
1440
16th to endNight
17%425%5%25%5%6%8%36%
1440
July1st to 15thNight
12%42433445%9%45%
1440
16th to endNight
10%425%5%345%6%7%44%
1514
August1st to 15thNight
12%5%25%5%345%6%8%39%
1478
16th to endNight
11%425%43345%7%48%
1866
September1st to 15thNight
16%6%26%433435%42%
1800
16th to endNight
16%5%35%323246%47%
1838
October1st to 15thNight
22%9%245%24445%34%
1980
16th to endNight
25%10%46%5%34335%26%
2227
November1st to 15thNight
19%10%46%5%35%5%45%29%
2325
16th to endNight
22%14%49%5%2444421%
2520
December1st to 15thNight
22%16%6%8%6%3444417%
2520
16th to endNight
21%17%6%9%6%2443418%
2688

Percentage Cloud Cover SE (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
21%18%6%11%8%2422318%
1432
16th to endDay
14%15%7%9%7%345%5%5%21%
1542
February1st to 15thDay
12%15%7%11%9%34345%21%
1575
16th to endDay
16%17%5%9%6%3433424%
1535
March1st to 15thDay
21%12%46%5%2434428%
1831
16th to endDay
20%9%35%423346%36%
2207
April1st to 15thDay
23%11%34323235%35%
2152
16th to endDay
19%8%36%5%2434437%
2267
May1st to 15thDay
26%8%26%5%23335%32%
2511
16th to endDay
24%7%25%434445%34%
2618
June1st to 15thDay
21%7%36%5%35%45%6%30%
2520
16th to endDay
19%5%25%5%36%5%5%7%33%
2520
July1st to 15thDay
15%5%35%6%36%5%5%8%33%
2520
16th to endDay
15%6%26%5%36%5%6%7%32%
2654
August1st to 15thDay
25%5%25%5%3445%6%30%
2481
16th to endDay
21%5%245%2445%6%37%
2324
September1st to 15thDay
19%6%25%42345%6%37%
2160
16th to endDay
19%7%24324336%43%
1891
October1st to 15thDay
25%9%345%23435%32%
1650
16th to endDay
28%14%37%6%3334420%
1645
November1st to 15thDay
19%11%34434346%33%
1531
16th to endDay
23%14%5%7%42334326%
1440
December1st to 15thDay
23%19%6%8%5%24435%15%
1440
16th to endDay
22%19%6%10%5%3433318%
1536
January1st to 15thNight
19%16%6%8%7%35%446%16%
2506
16th to endNight
13%15%6%8%6%445%5%6%21%
2679
February1st to 15thNight
11%14%7%11%8%35%44324%
2278
16th to endNight
16%12%5%8%6%3435%6%26%
1937
March1st to 15thNight
25%11%36%43433428%
2127
16th to endNight
19%7%25%5%2433341%
2016
April1st to 15thNight
23%9%34323346%36%
1796
16th to endNight
19%7%3442435%440%
1704
May1st to 15thNight
23%7%35%5%23335%36%
1440
16th to endNight
19%5%36%5%23447%37%
1495
June1st to 15thNight
20%6%35%435%5%5%8%31%
1440
16th to endNight
16%4245%26%6%6%7%38%
1440
July1st to 15thNight
12%5%2342446%8%45%
1440
16th to endNight
11%5%25%5%345%6%7%43%
1514
August1st to 15thNight
16%5%245%2446%7%38%
1478
16th to endNight
16%414423346%47%
1866
September1st to 15thNight
17%6%25%5%24445%42%
1800
16th to endNight
16%5%25%423336%47%
1838
October1st to 15thNight
23%8%34434345%33%
1980
16th to endNight
26%11%46%5%24445%25%
2227
November1st to 15thNight
19%9%45%425%445%33%
2325
16th to endNight
21%13%5%9%5%2433426%
2520
December1st to 15thNight
22%17%6%7%6%3344418%
2520
16th to endNight
22%18%5%9%6%33335%19%
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
72%46%11%4
1433
16th to endDay
62%6%9%13%7%
1542
February1st to 15thDay
65%49%14%5%
1577
16th to endDay
63%37%14%9%1
1535
March1st to 15thDay
60%49%15%7%1
1831
16th to endDay
48%49%19%14%3
2208
April1st to 15thDay
56%38%18%10%2
2152
16th to endDay
53%47%18%11%4
2267
May1st to 15thDay
55%47%17%12%1
2511
16th to endDay
53%6%10%17%10%1
2622
June1st to 15thDay
56%6%10%17%8%
2520
16th to endDay
50%8%13%18%8%
2520
July1st to 15thDay
44%7%14%23%9%
2371
16th to endDay
49%8%15%17%8%
2487
August1st to 15thDay
51%9%15%19%5%
2467
16th to endDay
42%7%16%23%8%
2324
September1st to 15thDay
46%6%13%21%11%
2160
16th to endDay
43%5%13%28%8%
1891
October1st to 15thDay
53%6%12%18%8%
1650
16th to endDay
67%5%10%12%4
1645
November1st to 15thDay
53%6%15%16%7%
1531
16th to endDay
65%410%13%5%
1440
December1st to 15thDay
71%5%10%10%2
1440
16th to endDay
72%47%9%6%
1536
January1st to 15thNight
68%6%10%10%3
2506
16th to endNight
61%5%10%14%6%
2679
February1st to 15thNight
63%410%16%5%
2287
16th to endNight
59%410%15%8%
1937
March1st to 15thNight
61%5%7%16%7%1
2127
16th to endNight
48%49%19%15%2
2016
April1st to 15thNight
51%49%19%13%1
1796
16th to endNight
48%5%9%18%15%2
1704
May1st to 15thNight
52%5%7%17%13%3
1440
16th to endNight
48%7%10%20%11%1
1497
June1st to 15thNight
50%7%14%19%7%
1440
16th to endNight
44%8%13%19%12%
1440
July1st to 15thNight
36%6%17%25%14%
1360
16th to endNight
37%8%17%24%10%
1418
August1st to 15thNight
40%10%18%23%7%
1468
16th to endNight
34%6%19%30%9%
1866
September1st to 15thNight
43%5%13%25%10%
1800
16th to endNight
40%314%33%7%
1838
October1st to 15thNight
52%5%10%21%10%
1980
16th to endNight
60%5%11%16%5%
2227
November1st to 15thNight
54%6%13%16%8%
2325
16th to endNight
66%5%9%13%4
2520
December1st to 15thNight
69%6%10%10%2
2520
16th to endNight
69%5%7%10%6%
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
33%18%28%15%5%
60
16th to endDay
30%15%35%10%6%1
65
February1st to 15thDay
30%22%36%7%3
90
16th to endDay
31%18%29%18%2
194
March1st to 15thDay
25%21%27%18%5%1
270
16th to endDay
23%16%29%18%9%2
288
April1st to 15thDay
28%21%24%15%8%
270
16th to endDay
28%15%28%15%8%2
270
May1st to 15thDay
31%13%26%18%7%1
288
16th to endDay
25%15%32%17%9%1
331
June1st to 15thDay
28%13%32%18%6%
315
16th to endDay
19%12%33%22%9%2
315
July1st to 15thDay
15%7%36%26%11%1
305
16th to endDay
17%6%28%31%12%3
326
August1st to 15thDay
17%7%24%33%13%4
313
16th to endDay
19%6%27%21%16%8%
332
September1st to 15thDay
20%7%26%19%14%10%
315
16th to endDay
22%10%23%18%14%10%
270
October1st to 15thDay
30%13%21%21%10%3
255
16th to endDay
36%13%25%16%7%
251
November1st to 15thDay
22%12%29%24%9%1
185
16th to endDay
35%18%31%11%3
60
December1st to 15thDay
33%20%31%11%3
60
16th to endDay
39%28%25%7%
64
January1st to 15thNight
30%12%32%19%5%
720
16th to endNight
21%16%32%21%7%
768
February1st to 15thNight
18%17%36%21%6%
704
16th to endNight
23%18%31%21%4
631
March1st to 15thNight
27%16%29%22%3
720
16th to endNight
20%14%30%23%8%1
768
April1st to 15thNight
29%14%27%24%4
718
16th to endNight
25%16%26%22%8%
624
May1st to 15thNight
26%8%28%25%9%1
360
16th to endNight
20%8%33%27%9%
375
June1st to 15thNight
21%8%30%32%6%
360
16th to endNight
17%6%25%33%15%
360
July1st to 15thNight
12%425%39%18%
340
16th to endNight
13%424%37%18%1
376
August1st to 15thNight
13%320%35%23%2
397
16th to endNight
13%5%24%34%19%2
720
September1st to 15thNight
21%5%26%27%17%1
720
16th to endNight
20%7%24%27%18%2
677
October1st to 15thNight
25%12%28%21%10%1
660
16th to endNight
31%14%26%20%6%
704
November1st to 15thNight
25%13%29%19%11%
700
16th to endNight
30%19%24%17%7%1
720
December1st to 15thNight
33%16%27%18%3
720
16th to endNight
32%15%30%16%41
768
Page generated at 2017-09-21 07:18:13. Version ac04

Copyright 2017 A. Danko


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