Port-Aux-Quilles Astronomical Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port-Aux-Quilles Astronomical Observatory clear sky chart from 2005-11-05 to 2017-09-21.

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%
14598
13%
46853
6%
14566
36%
14566
14%
33135

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
18%
733
12%
2586
4%
729
27%
729
8%
1924
January16th to endNight
18%
768
14%
2688
3%
768
31%
768
11%
1918
February1st to 15thNight
20%
704
13%
2387
4%
701
32%
701
11%
1698
February16th to endNight
20%
631
12%
1898
4%
631
30%
631
11%
1423
March1st to 15thNight
22%
720
16%
2132
7%
720
32%
720
14%
1524
March16th to endNight
24%
768
18%
2062
6%
768
33%
768
18%
1428
April1st to 15thNight
22%
673
16%
1751
5%
673
29%
673
15%
1314
April16th to endNight
27%
540
16%
1620
8%
540
35%
540
18%
1111
May1st to 15thNight
29%
471
11%
1551
7%
471
36%
471
14%
1108
May16th to endNight
29%
375
10%
1353
7%
374
38%
374
12%
985
June1st to 15thNight
38%
360
6%
1260
5%
360
41%
360
15%
871
June16th to endNight
37%
360
5%
1260
3%
360
39%
360
15%
885
July1st to 15thNight
43%
340
8%
1199
8%
340
47%
340
19%
792
July16th to endNight
46%
376
8%
1418
10%
354
49%
354
16%
934
August1st to 15thNight
48%
431
10%
1502
9%
429
51%
429
17%
1015
August16th to endNight
43%
579
14%
1725
8%
579
47%
579
24%
1114
September1st to 15thNight
39%
720
11%
1872
5%
720
42%
720
25%
1299
September16th to endNight
39%
681
17%
1880
10%
681
45%
681
27%
1225
October1st to 15thNight
32%
660
18%
1915
8%
660
42%
660
20%
1282
October16th to endNight
24%
704
11%
2288
6%
704
32%
704
14%
1622
November1st to 15thNight
26%
704
16%
2301
9%
704
36%
704
14%
1618
November16th to endNight
25%
750
12%
2625
5%
750
34%
750
11%
1884
December1st to 15thNight
15%
750
9%
2700
3%
750
24%
750
9%
2018
December16th to endNight
18%
800
11%
2880
3%
800
28%
800
8%
2143

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
17%9%47%6%35%45%6%29%
48020
Night
16%9%47%5%35%45%6%31%
47013
TransparencyDay
52%413%19%8%
47698
Night
52%412%20%8%
46853
SeeingDay
25%14%25%20%10%2
6345
Night
23%15%23%26%10%1
14598

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
12%11%7%8%8%36%45%6%26%
1349
16th to endDay
9%8%49%8%5%6%5%5%6%29%
1536
February1st to 15thDay
6%12%6%9%9%5%6%6%6%5%25%
1473
16th to endDay
11%14%410%7%45%445%26%
1575
March1st to 15thDay
15%12%5%7%5%35%35%5%29%
1817
16th to endDay
12%12%5%7%5%35%445%32%
2160
April1st to 15thDay
18%11%45%5%3445%5%29%
2196
16th to endDay
21%10%34423345%34%
2340
May1st to 15thDay
20%8%36%5%34345%33%
2409
16th to endDay
21%7%36%5%36%5%5%6%28%
2762
June1st to 15thDay
20%8%26%5%35%5%6%7%27%
2700
16th to endDay
22%7%36%6%45%46%7%25%
2700
July1st to 15thDay
15%6%36%7%46%6%6%9%26%
2689
16th to endDay
16%6%27%6%46%46%8%30%
2654
August1st to 15thDay
17%6%37%7%46%5%7%8%25%
2436
16th to endDay
11%5%25%6%45%7%7%8%33%
2475
September1st to 15thDay
18%6%36%6%34446%35%
2087
16th to endDay
15%5%25%435%45%7%38%
1873
October1st to 15thDay
20%7%37%435%45%6%30%
1712
16th to endDay
21%11%37%6%34446%24%
1584
November1st to 15thDay
17%11%49%6%345%5%5%26%
1557
16th to endDay
17%12%5%7%7%2435%6%26%
1332
December1st to 15thDay
20%14%46%5%3443426%
1260
16th to endDay
17%16%5%7%7%3434425%
1344
January1st to 15thNight
13%10%5%8%6%46%5%6%6%25%
2586
16th to endNight
10%10%6%9%6%46%6%5%7%25%
2688
February1st to 15thNight
6%11%5%8%8%37%47%8%27%
2386
16th to endNight
12%14%5%10%5%35%436%27%
1898
March1st to 15thNight
14%11%48%42445%6%31%
2119
16th to endNight
11%11%46%5%35%45%6%36%
2062
April1st to 15thNight
20%10%37%5%23445%31%
1751
16th to endNight
22%9%34323345%37%
1620
May1st to 15thNight
23%8%36%5%3435%5%29%
1551
16th to endNight
20%9%38%435%45%5%28%
1351
June1st to 15thNight
18%7%47%6%34447%31%
1260
16th to endNight
21%6%37%5%35%46%7%29%
1260
July1st to 15thNight
17%5%25%5%345%5%7%34%
1269
16th to endNight
13%6%25%5%46%6%5%8%35%
1514
August1st to 15thNight
16%5%26%6%446%7%7%32%
1512
16th to endNight
12%415%6%35%5%5%9%39%
1725
September1st to 15thNight
15%6%26%6%245%46%39%
1872
16th to endNight
17%5%25%323336%45%
1880
October1st to 15thNight
17%7%26%43435%7%37%
1915
16th to endNight
23%7%36%5%2445%7%28%
2288
November1st to 15thNight
20%8%36%43436%6%31%
2301
16th to endNight
16%9%47%6%36%5%5%5%27%
2625
December1st to 15thNight
16%15%6%7%5%3444426%
2700
16th to endNight
15%12%5%8%5%35%5%5%5%24%
2880

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
57%5%9%18%9%
1350
16th to endDay
52%5%12%18%10%
1536
February1st to 15thDay
57%413%15%7%1
1476
16th to endDay
58%36%19%9%1
1575
March1st to 15thDay
54%38%16%13%2
1827
16th to endDay
53%49%19%12%1
2160
April1st to 15thDay
53%39%20%8%4
2196
16th to endDay
51%311%18%13%2
2340
May1st to 15thDay
51%213%20%11%
2409
16th to endDay
53%5%12%20%7%
2766
June1st to 15thDay
53%5%11%19%8%1
2700
16th to endDay
56%5%13%17%7%
2700
July1st to 15thDay
48%6%17%22%5%
2530
16th to endDay
49%5%18%19%7%
2487
August1st to 15thDay
50%6%21%17%4
2422
16th to endDay
41%6%22%26%4
2475
September1st to 15thDay
47%316%23%8%
2087
16th to endDay
42%5%17%25%8%
1873
October1st to 15thDay
52%414%19%9%
1712
16th to endDay
59%314%18%3
1584
November1st to 15thDay
57%6%11%19%5%
1557
16th to endDay
58%412%18%5%
1332
December1st to 15thDay
60%411%17%5%
1260
16th to endDay
63%48%14%9%
1344
January1st to 15thNight
58%6%10%16%7%
2586
16th to endNight
55%49%20%8%
2688
February1st to 15thNight
54%5%10%20%8%1
2387
16th to endNight
60%28%19%9%
1898
March1st to 15thNight
52%310%19%12%1
2132
16th to endNight
48%310%23%13%1
2062
April1st to 15thNight
54%46%17%14%2
1751
16th to endNight
49%39%19%15%2
1620
May1st to 15thNight
55%39%19%11%1
1551
16th to endNight
56%5%10%17%8%1
1353
June1st to 15thNight
52%412%19%9%
1260
16th to endNight
52%5%12%18%9%
1260
July1st to 15thNight
45%6%16%24%6%
1199
16th to endNight
47%7%15%21%8%
1418
August1st to 15thNight
46%8%18%21%4
1502
16th to endNight
40%6%21%24%6%
1725
September1st to 15thNight
45%417%23%8%
1872
16th to endNight
40%417%27%9%
1880
October1st to 15thNight
46%314%25%9%1
1915
16th to endNight
53%415%21%5%
2288
November1st to 15thNight
52%5%13%19%8%
2301
16th to endNight
55%5%13%17%7%
2625
December1st to 15thNight
59%412%17%5%
2700
16th to endNight
59%5%11%16%6%
2880

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
23%26%36%11%1
60
16th to endDay
18%26%34%15%4
64
February1st to 15thDay
20%11%33%23%9%
134
16th to endDay
26%21%27%15%6%1
238
March1st to 15thDay
28%20%25%14%7%2
270
16th to endDay
22%22%23%18%9%3
288
April1st to 15thDay
30%19%27%12%5%3
270
16th to endDay
32%15%26%15%7%1
270
May1st to 15thDay
29%12%29%19%7%1
288
16th to endDay
27%15%29%17%8%1
476
June1st to 15thDay
30%12%19%23%10%2
495
16th to endDay
23%10%26%22%15%2
495
July1st to 15thDay
22%9%25%25%14%2
464
16th to endDay
19%8%30%30%9%
326
August1st to 15thDay
18%6%27%26%17%4
313
16th to endDay
21%13%25%20%15%4
332
September1st to 15thDay
23%8%26%25%9%6%
315
16th to endDay
20%12%27%20%12%7%
275
October1st to 15thDay
24%17%17%24%13%2
241
16th to endDay
32%16%25%14%9%2
240
November1st to 15thDay
28%16%20%25%8%1
235
16th to endDay
35%14%25%12%11%
132
December1st to 15thDay
33%21%23%13%6%1
60
16th to endDay
40%18%21%15%3
64
January1st to 15thNight
18%22%29%24%4
733
16th to endNight
19%18%31%23%6%1
768
February1st to 15thNight
15%21%30%24%7%
704
16th to endNight
24%20%24%21%7%
631
March1st to 15thNight
25%18%24%23%5%1
720
16th to endNight
21%22%24%22%8%
768
April1st to 15thNight
28%15%25%20%9%1
673
16th to endNight
32%11%21%24%8%1
540
May1st to 15thNight
29%9%19%26%12%1
471
16th to endNight
24%14%20%28%11%1
375
June1st to 15thNight
22%8%21%33%13%1
360
16th to endNight
25%6%19%32%14%1
360
July1st to 15thNight
19%7%18%36%16%2
340
16th to endNight
17%7%20%37%17%1
376
August1st to 15thNight
18%5%15%35%24%1
431
16th to endNight
14%8%22%34%16%2
579
September1st to 15thNight
19%8%22%32%14%2
720
16th to endNight
22%9%22%29%13%2
681
October1st to 15thNight
21%15%21%28%11%1
660
16th to endNight
29%15%22%21%9%
704
November1st to 15thNight
27%16%21%23%9%
704
16th to endNight
25%16%24%24%7%1
750
December1st to 15thNight
27%20%27%19%5%
750
16th to endNight
26%19%24%20%7%1
800
Page generated at 2017-09-22 07:35:35. Version ac04

Copyright 2017 A. Danko


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