Acadia University
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Acadia University clear sky chart from 2005-11-05 to 2017-09-10.

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
22%
15009
10%
46453
4%
14964
28%
14964
12%
35282

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
10%
750
6%
2506
2%
746
16%
746
5%
2080
January16th to endNight
11%
771
7%
2511
1%
771
18%
771
6%
2091
February1st to 15thNight
10%
704
4%
2286
2%
701
14%
701
5%
1959
February16th to endNight
16%
631
7%
2040
2%
631
22%
631
8%
1625
March1st to 15thNight
16%
720
13%
1980
4%
720
24%
720
13%
1538
March16th to endNight
16%
768
13%
2112
3%
768
25%
768
14%
1601
April1st to 15thNight
16%
554
12%
1808
5%
554
24%
554
11%
1355
April16th to endNight
21%
540
13%
1620
5%
540
27%
540
15%
1184
May1st to 15thNight
25%
540
9%
1533
4%
540
29%
540
15%
1189
May16th to endNight
24%
561
10%
1496
2%
560
30%
560
19%
1110
June1st to 15thNight
25%
489
7%
1389
3%
489
29%
489
14%
1073
June16th to endNight
34%
360
9%
1260
5%
360
39%
360
15%
906
July1st to 15thNight
44%
373
10%
1223
6%
373
49%
373
25%
764
July16th to endNight
39%
565
9%
1473
6%
532
40%
532
20%
1074
August1st to 15thNight
43%
539
12%
1608
9%
535
45%
535
21%
1121
August16th to endNight
42%
573
16%
1773
9%
573
48%
573
23%
1159
September1st to 15thNight
38%
525
17%
1749
12%
525
47%
525
23%
1104
September16th to endNight
34%
655
20%
1840
10%
655
41%
655
25%
1200
October1st to 15thNight
26%
660
17%
1980
7%
660
34%
660
20%
1347
October16th to endNight
17%
704
13%
2112
4%
704
26%
704
13%
1559
November1st to 15thNight
22%
727
12%
2426
7%
727
27%
727
12%
1819
November16th to endNight
17%
750
8%
2520
4%
750
23%
750
8%
1994
December1st to 15thNight
10%
750
7%
2520
0%
750
16%
750
6%
2089
December16th to endNight
8%
800
5%
2688
0%
800
13%
800
3%
2341

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
18%10%47%6%34446%28%
48153
Night
18%10%47%6%35%446%26%
46624
TransparencyDay
56%5%11%17%8%
47842
Night
57%6%11%16%7%
46453
SeeingDay
27%15%29%18%7%1
7449
Night
27%15%29%21%5%
15009

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
14%16%8%11%11%5%6%44413%
1402
16th to endDay
14%12%7%10%11%6%9%43414%
1713
February1st to 15thDay
16%12%7%13%11%7%5%34312%
1575
16th to endDay
11%15%7%12%7%35%436%21%
1431
March1st to 15thDay
14%14%5%10%8%45%33425%
1969
16th to endDay
14%14%7%8%6%2433330%
2112
April1st to 15thDay
17%13%48%6%34446%26%
2140
16th to endDay
22%10%26%42335%6%31%
2340
May1st to 15thDay
24%10%36%5%35%445%27%
2419
16th to endDay
21%10%36%5%3445%7%28%
2618
June1st to 15thDay
27%9%36%5%34446%24%
2580
16th to endDay
22%7%37%5%25%46%7%27%
2700
July1st to 15thDay
14%7%25%42445%9%37%
2649
16th to endDay
17%7%47%5%35%5%5%7%29%
2591
August1st to 15thDay
17%6%26%5%35%46%6%34%
2340
16th to endDay
13%6%2442346%8%44%
2429
September1st to 15thDay
19%7%24423446%40%
2099
16th to endDay
16%6%24323336%46%
1788
October1st to 15thDay
21%7%24424347%37%
1650
16th to endDay
22%11%37%5%335%5%5%26%
1760
November1st to 15thDay
22%14%46%444235%25%
1432
16th to endDay
18%15%5%10%7%45%345%18%
1440
December1st to 15thDay
21%15%7%12%8%35%43314%
1440
16th to endDay
22%17%8%12%9%2423213%
1536
January1st to 15thNight
14%13%6%13%9%5%5%45%416%
2506
16th to endNight
15%12%5%9%11%6%7%5%45%14%
2511
February1st to 15thNight
17%13%6%12%12%5%6%44412%
2285
16th to endNight
13%16%6%11%7%46%34421%
2040
March1st to 15thNight
17%12%5%7%7%44435%26%
1968
16th to endNight
17%12%6%7%5%34336%28%
2112
April1st to 15thNight
20%12%5%5%6%3433427%
1808
16th to endNight
22%9%35%5%24445%31%
1620
May1st to 15thNight
23%9%36%6%35%45%6%25%
1533
16th to endNight
18%8%46%5%2446%8%30%
1494
June1st to 15thNight
26%8%35%6%24447%25%
1389
16th to endNight
20%7%35%5%45%46%7%30%
1260
July1st to 15thNight
13%5%243246%7%11%38%
1296
16th to endNight
14%7%35%6%37%5%6%8%30%
1574
August1st to 15thNight
17%6%25%5%345%6%7%36%
1620
16th to endNight
14%5%245%35%35%8%41%
1773
September1st to 15thNight
15%5%2432446%8%41%
1749
16th to endNight
15%5%25%424447%43%
1840
October1st to 15thNight
19%6%15%43345%7%36%
1980
16th to endNight
22%10%36%5%24446%28%
2112
November1st to 15thNight
20%12%37%6%35%445%26%
2426
16th to endNight
18%14%5%8%8%45%445%22%
2520
December1st to 15thNight
20%13%5%12%8%35%445%16%
2520
16th to endNight
23%17%7%10%8%3433312%
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
73%5%10%8%1
1403
16th to endDay
71%7%7%10%4
1713
February1st to 15thDay
74%5%7%7%3
1578
16th to endDay
64%5%9%14%4
1431
March1st to 15thDay
63%39%14%8%
1980
16th to endDay
58%38%18%8%1
2112
April1st to 15thDay
58%5%8%14%11%1
2140
16th to endDay
54%39%18%12%1
2340
May1st to 15thDay
57%5%8%18%8%
2419
16th to endDay
55%7%10%18%6%
2622
June1st to 15thDay
60%5%10%15%6%
2580
16th to endDay
54%7%12%16%8%
2700
July1st to 15thDay
42%7%17%21%11%
2494
16th to endDay
53%6%12%20%6%
2429
August1st to 15thDay
47%7%13%20%10%
2327
16th to endDay
37%6%17%27%11%
2429
September1st to 15thDay
45%412%23%12%1
2099
16th to endDay
39%310%28%15%1
1788
October1st to 15thDay
46%5%11%25%10%
1650
16th to endDay
58%5%12%17%6%
1760
November1st to 15thDay
61%411%13%7%1
1432
16th to endDay
67%7%10%10%4
1440
December1st to 15thDay
73%5%8%10%2
1440
16th to endDay
77%47%6%3
1536
January1st to 15thNight
67%7%10%10%2
2506
16th to endNight
69%6%9%11%2
2511
February1st to 15thNight
73%5%9%7%3
2286
16th to endNight
64%5%11%11%5%
2040
March1st to 15thNight
59%5%9%16%8%
1980
16th to endNight
57%49%18%9%
2112
April1st to 15thNight
59%47%15%10%2
1808
16th to endNight
55%5%9%15%13%1
1620
May1st to 15thNight
59%5%10%17%6%1
1533
16th to endNight
51%7%13%20%6%1
1496
June1st to 15thNight
57%7%11%17%5%
1389
16th to endNight
52%8%11%19%7%
1260
July1st to 15thNight
37%8%21%21%10%
1223
16th to endNight
48%9%15%19%6%
1473
August1st to 15thNight
46%7%13%23%8%
1608
16th to endNight
40%8%15%25%10%
1773
September1st to 15thNight
40%7%11%29%10%
1749
16th to endNight
40%5%11%28%13%
1840
October1st to 15thNight
46%5%13%23%10%
1980
16th to endNight
55%5%10%19%8%
2112
November1st to 15thNight
57%5%11%17%6%
2426
16th to endNight
63%7%11%13%4
2520
December1st to 15thNight
69%6%9%12%2
2520
16th to endNight
75%5%6%8%3
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
22%24%36%14%1
210
16th to endDay
23%26%33%12%2
256
February1st to 15thDay
26%22%34%14%2
236
16th to endDay
26%19%30%18%4
214
March1st to 15thDay
24%27%32%10%4
270
16th to endDay
29%24%25%14%5%1
288
April1st to 15thDay
31%20%31%14%1
270
16th to endDay
24%20%31%16%6%
270
May1st to 15thDay
33%14%26%17%42
375
16th to endDay
31%14%28%19%5%1
519
June1st to 15thDay
34%12%26%18%7%
495
16th to endDay
26%8%31%23%7%2
495
July1st to 15thDay
21%5%32%28%10%1
475
16th to endDay
25%5%31%23%12%1
452
August1st to 15thDay
21%430%29%10%2
313
16th to endDay
18%9%29%23%16%3
332
September1st to 15thDay
23%9%35%21%9%
294
16th to endDay
22%10%30%22%10%3
249
October1st to 15thDay
28%8%29%20%8%4
225
16th to endDay
30%24%25%12%6%
240
November1st to 15thDay
32%14%25%16%6%2
235
16th to endDay
31%20%26%14%7%
240
December1st to 15thDay
35%21%29%10%2
240
16th to endDay
37%24%25%8%2
256
January1st to 15thNight
28%22%32%15%1
750
16th to endNight
30%22%30%12%2
771
February1st to 15thNight
29%23%31%14%1
704
16th to endNight
29%19%29%16%4
631
March1st to 15thNight
27%19%32%17%4
720
16th to endNight
28%19%29%16%5%
768
April1st to 15thNight
29%16%32%16%5%
554
16th to endNight
27%15%32%18%4
540
May1st to 15thNight
31%10%28%21%7%
540
16th to endNight
23%10%36%23%6%
561
June1st to 15thNight
30%9%27%25%6%
489
16th to endNight
22%6%27%34%7%1
360
July1st to 15thNight
15%230%40%10%
373
16th to endNight
19%5%29%34%10%
565
August1st to 15thNight
19%424%36%13%
539
16th to endNight
17%5%28%33%13%1
573
September1st to 15thNight
18%7%30%32%10%
525
16th to endNight
19%10%31%27%9%1
655
October1st to 15thNight
25%12%33%18%8%1
660
16th to endNight
30%20%28%17%3
704
November1st to 15thNight
27%16%28%19%6%
727
16th to endNight
31%19%25%18%4
750
December1st to 15thNight
32%22%29%11%2
750
16th to endNight
36%21%26%12%2
800
Page generated at 2017-09-11 20:35:20. Version ac04

Copyright 2017 A. Danko


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