Airdrie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Airdrie 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
40%
15148
13%
46715
8%
15117
45%
15117
22%
31294

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
29%
898
12%
2685
7%
895
34%
895
16%
1953
January16th to endNight
30%
825
18%
2745
10%
825
41%
825
20%
1801
February1st to 15thNight
37%
699
13%
2418
11%
696
43%
696
19%
1598
February16th to endNight
37%
632
14%
1980
12%
632
43%
632
20%
1370
March1st to 15thNight
34%
720
13%
2118
8%
720
40%
720
21%
1494
March16th to endNight
33%
768
12%
2085
5%
767
38%
767
20%
1556
April1st to 15thNight
34%
626
11%
1706
5%
626
38%
626
18%
1280
April16th to endNight
35%
540
12%
1620
8%
540
40%
540
20%
1135
May1st to 15thNight
40%
416
11%
1407
9%
416
46%
416
22%
914
May16th to endNight
42%
374
4%
1309
3%
374
44%
374
17%
913
June1st to 15thNight
35%
360
0%
1260
0%
360
35%
360
15%
900
June16th to endNight
54%
360
0%
1260
0%
360
54%
360
22%
813
July1st to 15thNight
60%
340
1%
1190
0%
340
61%
340
27%
699
July16th to endNight
61%
376
9%
1272
9%
354
64%
354
29%
699
August1st to 15thNight
64%
396
10%
1468
13%
394
67%
394
27%
843
August16th to endNight
61%
573
20%
1719
17%
573
64%
573
40%
946
September1st to 15thNight
56%
640
18%
1752
13%
640
58%
640
35%
1063
September16th to endNight
52%
656
19%
1815
13%
656
58%
656
39%
1095
October1st to 15thNight
41%
660
17%
1947
9%
660
48%
660
23%
1314
October16th to endNight
44%
704
18%
2288
12%
704
53%
704
24%
1455
November1st to 15thNight
32%
825
18%
2400
9%
825
42%
825
25%
1575
November16th to endNight
28%
900
14%
2691
6%
900
36%
900
21%
1837
December1st to 15thNight
33%
900
13%
2700
8%
900
38%
900
17%
1987
December16th to endNight
32%
960
16%
2880
8%
960
39%
960
18%
2054

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
10%9%47%6%35%5%6%8%33%
47948
Night
7%9%47%6%35%5%6%8%34%
46868
TransparencyDay
47%5%16%21%7%1
47602
Night
45%5%15%22%8%1
46718
SeeingDay
16%8%25%29%15%4
5998
Night
12%6%29%34%14%1
15157

By Month

Percentage Cloud Cover NW (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
6%11%5%7%6%346%6%7%33%
1253
16th to endDay
5%10%5%10%6%35%5%6%8%31%
1488
February1st to 15thDay
6%9%6%7%7%36%5%7%6%32%
1443
16th to endDay
5%9%7%10%7%5%5%6%6%8%26%
1494
March1st to 15thDay
312%5%10%8%36%5%6%7%30%
1842
16th to endDay
8%15%6%8%6%36%5%7%7%23%
2134
April1st to 15thDay
11%16%6%8%6%35%5%5%7%22%
2242
16th to endDay
14%12%47%6%345%5%7%27%
2340
May1st to 15thDay
11%9%37%6%35%5%6%7%32%
2544
16th to endDay
20%8%36%6%45%6%5%7%24%
2802
June1st to 15thDay
20%8%38%6%36%5%6%7%24%
2700
16th to endDay
12%6%37%6%37%5%7%8%31%
2700
July1st to 15thDay
11%425%5%36%5%6%9%38%
2700
16th to endDay
7%324436%6%7%10%44%
2807
August1st to 15thDay
12%5%14435%5%6%9%40%
2484
16th to endDay
9%424435%46%8%47%
2483
September1st to 15thDay
12%6%35%5%23345%47%
2091
16th to endDay
11%6%25%4345%5%7%43%
1815
October1st to 15thDay
14%8%37%6%35%46%7%31%
1683
16th to endDay
7%9%36%6%35%6%5%8%36%
1584
November1st to 15thDay
6%12%5%7%7%35%5%6%8%32%
1446
16th to endDay
5%13%5%8%5%3346%8%35%
1269
December1st to 15thDay
412%5%11%7%5%7%6%6%5%26%
1260
16th to endDay
311%48%7%46%7%6%9%29%
1344
January1st to 15thNight
411%49%8%5%7%5%7%8%25%
2685
16th to endNight
412%38%5%36%6%7%8%33%
2745
February1st to 15thNight
5%9%5%8%7%46%5%5%8%33%
2407
16th to endNight
311%6%9%8%45%6%6%7%30%
1980
March1st to 15thNight
410%5%8%8%47%6%7%9%28%
2118
16th to endNight
7%12%6%8%7%35%6%6%8%26%
2085
April1st to 15thNight
12%11%5%8%6%46%6%7%6%25%
1706
16th to endNight
13%10%5%8%5%345%5%8%30%
1620
May1st to 15thNight
10%9%37%5%35%46%6%37%
1406
16th to endNight
18%6%25%7%37%5%5%9%27%
1309
June1st to 15thNight
19%7%47%6%35%6%5%6%27%
1260
16th to endNight
13%5%345%46%5%7%8%35%
1260
July1st to 15thNight
8%4245%36%5%8%10%41%
1260
16th to endNight
6%325%4245%6%8%50%
1359
August1st to 15thNight
11%325%43447%10%42%
1476
16th to endNight
7%315%3135%6%8%53%
1719
September1st to 15thNight
11%6%14423348%48%
1752
16th to endNight
10%4133245%5%9%48%
1815
October1st to 15thNight
11%9%36%5%346%6%7%35%
1947
16th to endNight
7%9%36%435%5%6%9%37%
2288
November1st to 15thNight
5%10%46%5%35%5%6%8%38%
2400
16th to endNight
5%11%6%7%6%35%5%5%8%34%
2691
December1st to 15thNight
410%5%10%7%47%6%6%7%28%
2700
16th to endNight
310%5%10%10%46%6%6%7%29%
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
47%5%14%24%6%2
1253
16th to endDay
49%5%14%15%11%3
1488
February1st to 15thDay
48%5%15%21%6%2
1443
16th to endDay
53%414%18%7%
1494
March1st to 15thDay
50%5%18%17%6%
1842
16th to endDay
56%6%14%17%5%
2135
April1st to 15thDay
59%5%12%14%6%1
2242
16th to endDay
54%413%18%7%1
2340
May1st to 15thDay
48%315%21%9%
2544
16th to endDay
56%416%16%4
2807
June1st to 15thDay
56%5%15%16%5%1
2700
16th to endDay
48%6%17%22%5%
2700
July1st to 15thDay
41%6%21%23%6%1
2541
16th to endDay
32%6%22%28%9%
2631
August1st to 15thDay
38%6%24%23%5%
2467
16th to endDay
32%421%30%9%1
2483
September1st to 15thDay
38%314%24%15%3
2091
16th to endDay
38%5%12%29%10%2
1815
October1st to 15thDay
50%5%14%21%7%
1683
16th to endDay
43%5%15%26%9%
1584
November1st to 15thDay
48%5%14%21%8%1
1446
16th to endDay
45%417%21%9%2
1269
December1st to 15thDay
54%5%15%15%7%
1260
16th to endDay
47%5%15%19%10%1
1344
January1st to 15thNight
53%5%14%17%6%2
2685
16th to endNight
44%6%14%20%10%3
2745
February1st to 15thNight
47%414%22%9%1
2418
16th to endNight
50%412%20%12%
1980
March1st to 15thNight
48%6%18%19%6%
2118
16th to endNight
52%6%13%19%7%1
2088
April1st to 15thNight
54%5%12%17%8%
1706
16th to endNight
51%313%22%6%1
1620
May1st to 15thNight
44%415%23%10%
1407
16th to endNight
51%6%17%18%5%1
1309
June1st to 15thNight
54%5%15%16%6%
1260
16th to endNight
42%7%20%22%5%1
1260
July1st to 15thNight
34%7%24%25%7%
1190
16th to endNight
30%7%18%31%10%1
1272
August1st to 15thNight
35%5%22%28%7%
1468
16th to endNight
27%5%19%32%13%2
1719
September1st to 15thNight
35%315%24%16%4
1752
16th to endNight
31%419%26%13%4
1815
October1st to 15thNight
45%6%13%23%9%1
1947
16th to endNight
40%6%18%24%9%
2288
November1st to 15thNight
41%5%15%24%12%1
2400
16th to endNight
47%417%18%8%3
2691
December1st to 15thNight
53%6%13%20%5%
2700
16th to endNight
52%412%22%7%
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
16%5%21%23%15%18%
60
16th to endDay
4429%31%18%10%
64
February1st to 15thDay
13%11%26%27%16%4
68
16th to endDay
11%7%24%40%14%1
153
March1st to 15thDay
9%16%41%27%5%
270
16th to endDay
14%17%36%19%9%2
288
April1st to 15thDay
23%15%27%24%7%1
269
16th to endDay
23%13%22%28%10%2
270
May1st to 15thDay
17%8%24%27%16%5%
378
16th to endDay
23%6%16%30%18%3
517
June1st to 15thDay
21%8%24%29%13%2
495
16th to endDay
17%5%27%27%18%3
495
July1st to 15thDay
16%418%33%24%3
475
16th to endDay
6%6%30%34%18%3
476
August1st to 15thDay
16%319%33%21%6%
315
16th to endDay
10%8%23%35%15%6%
332
September1st to 15thDay
18%8%24%26%15%7%
294
16th to endDay
12%12%30%30%10%3
255
October1st to 15thDay
20%7%24%28%16%1
153
16th to endDay
16%122%32%23%3
96
November1st to 15thDay
16%6%31%36%5%3
90
16th to endDay
6%11%27%22%16%14%
61
December1st to 15thDay
6%343%25%18%3
60
16th to endDay
6%9%29%23%25%6%
64
January1st to 15thNight
11%10%36%30%10%
900
16th to endNight
10%12%36%29%9%1
825
February1st to 15thNight
10%9%29%32%14%3
704
16th to endNight
8%6%31%32%17%3
632
March1st to 15thNight
8%5%38%33%11%1
720
16th to endNight
13%6%29%38%11%1
768
April1st to 15thNight
16%7%27%33%13%1
626
16th to endNight
19%5%26%35%12%
540
May1st to 15thNight
13%9%28%31%16%
417
16th to endNight
22%5%19%33%17%1
375
June1st to 15thNight
23%326%29%15%1
360
16th to endNight
16%319%42%16%1
360
July1st to 15thNight
10%217%38%28%2
340
16th to endNight
7%319%46%21%2
376
August1st to 15thNight
13%111%39%31%3
396
16th to endNight
8%219%42%25%1
573
September1st to 15thNight
15%218%36%24%2
640
16th to endNight
12%226%37%17%3
656
October1st to 15thNight
15%5%28%31%16%2
660
16th to endNight
12%5%27%40%10%2
704
November1st to 15thNight
10%9%39%30%7%1
825
16th to endNight
10%8%42%27%9%1
900
December1st to 15thNight
9%10%33%32%11%2
900
16th to endNight
7%9%34%34%11%2
960
Page generated at 2017-09-11 17:35:31. Version ac04

Copyright 2017 A. Danko


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