Athabasca
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Athabasca 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
43%
15175
9%
46466
7%
15149
46%
15149
19%
33178

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
35%
904
6%
2740
3%
904
37%
904
12%
2131
January16th to endNight
31%
939
13%
2859
8%
939
37%
939
17%
2070
February1st to 15thNight
38%
699
8%
2449
8%
697
41%
697
15%
1762
February16th to endNight
45%
632
11%
2037
11%
632
48%
632
18%
1445
March1st to 15thNight
40%
720
14%
2112
11%
720
44%
720
19%
1525
March16th to endNight
42%
767
12%
2091
7%
767
44%
767
19%
1571
April1st to 15thNight
48%
587
13%
1667
8%
587
51%
587
22%
1174
April16th to endNight
43%
537
11%
1611
10%
537
45%
537
18%
1176
May1st to 15thNight
52%
359
5%
1260
5%
359
53%
359
24%
785
May16th to endNight
48%
374
0%
1309
0%
374
48%
374
17%
907
June1st to 15thNight
51%
360
0%
1164
0%
360
51%
360
17%
833
June16th to endNight
57%
360
0%
1080
0%
360
57%
360
22%
745
July1st to 15thNight
60%
340
0%
1059
0%
340
60%
340
27%
671
July16th to endNight
61%
376
1%
1239
0%
354
63%
354
25%
760
August1st to 15thNight
68%
360
5%
1346
7%
358
69%
358
23%
813
August16th to endNight
57%
567
11%
1713
10%
567
59%
567
26%
1117
September1st to 15thNight
60%
591
14%
1702
11%
591
61%
591
32%
1052
September16th to endNight
51%
656
17%
1815
10%
656
56%
656
33%
1146
October1st to 15thNight
43%
660
14%
1985
9%
660
47%
660
21%
1384
October16th to endNight
38%
731
14%
2315
9%
731
45%
731
18%
1613
November1st to 15thNight
33%
875
13%
2510
8%
875
38%
875
17%
1868
November16th to endNight
32%
900
8%
2700
4%
900
36%
900
14%
2097
December1st to 15thNight
32%
900
8%
2700
5%
900
34%
900
11%
2177
December16th to endNight
36%
981
9%
3003
5%
981
40%
981
13%
2356

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
11%8%47%7%45%5%6%8%30%
48204
Night
10%9%48%7%45%5%6%7%31%
46609
TransparencyDay
50%8%18%17%4
47847
Night
50%7%16%19%5%
46471
SeeingDay
15%5%21%29%20%6%
6518
Night
14%424%36%18%2
15188

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
8%12%6%9%9%5%5%6%6%7%21%
1197
16th to endDay
8%13%5%9%7%45%447%29%
1376
February1st to 15thDay
7%12%49%8%46%5%6%7%26%
1411
16th to endDay
7%12%8%10%8%45%6%5%7%23%
1436
March1st to 15thDay
7%12%6%9%9%37%6%5%7%22%
1847
16th to endDay
12%12%6%7%7%45%6%5%7%23%
2131
April1st to 15thDay
10%11%37%7%46%5%6%7%29%
2281
16th to endDay
14%12%48%7%35%5%7%7%24%
2349
May1st to 15thDay
12%6%36%6%45%6%7%7%33%
2691
16th to endDay
17%7%36%6%35%5%5%6%32%
2802
June1st to 15thDay
17%7%37%7%5%6%6%5%7%26%
2794
16th to endDay
15%6%26%7%36%6%6%7%29%
2880
July1st to 15thDay
11%4246%35%5%7%9%37%
2837
16th to endDay
12%5%25%5%35%7%8%10%34%
2846
August1st to 15thDay
11%5%25%6%35%5%7%9%36%
2604
16th to endDay
9%426%7%35%6%7%10%35%
2489
September1st to 15thDay
12%7%26%5%3445%8%38%
2144
16th to endDay
11%5%145%2447%8%41%
1815
October1st to 15thDay
14%9%46%6%345%47%34%
1642
16th to endDay
11%11%45%6%36%5%47%32%
1546
November1st to 15thDay
11%10%6%8%5%45%5%46%31%
1348
16th to endDay
5%12%7%10%8%35%5%5%6%27%
1260
December1st to 15thDay
8%13%5%10%8%5%8%5%6%6%18%
1260
16th to endDay
5%10%6%13%10%5%7%6%6%7%20%
1218
January1st to 15thNight
7%12%6%8%10%46%6%6%5%23%
2740
16th to endNight
7%11%49%8%45%45%8%30%
2859
February1st to 15thNight
8%11%5%9%8%36%5%5%7%28%
2442
16th to endNight
6%9%49%7%36%6%7%8%28%
2037
March1st to 15thNight
8%9%5%7%8%46%5%6%7%30%
2112
16th to endNight
10%13%48%6%35%5%6%8%27%
2088
April1st to 15thNight
11%8%45%5%47%5%5%9%32%
1667
16th to endNight
12%12%47%6%35%5%46%31%
1611
May1st to 15thNight
10%5%35%7%4447%6%39%
1259
16th to endNight
19%8%35%6%3445%6%32%
1309
June1st to 15thNight
12%7%37%7%46%46%8%29%
1164
16th to endNight
14%6%36%5%35%6%8%8%33%
1080
July1st to 15thNight
9%415%4346%6%11%41%
1122
16th to endNight
10%334435%6%7%9%40%
1323
August1st to 15thNight
8%325%5%36%5%7%10%40%
1353
16th to endNight
12%415%6%36%5%5%8%39%
1713
September1st to 15thNight
11%6%2442345%7%46%
1702
16th to endNight
11%5%2442446%9%44%
1815
October1st to 15thNight
13%9%47%5%3446%8%32%
1985
16th to endNight
11%11%47%5%345%6%6%33%
2315
November1st to 15thNight
12%10%5%9%6%36%35%6%29%
2510
16th to endNight
6%11%7%12%9%45%5%5%7%25%
2700
December1st to 15thNight
10%14%5%9%9%5%6%5%5%7%20%
2700
16th to endNight
5%11%6%11%9%5%7%6%6%7%20%
3003

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
59%8%17%9%4
1197
16th to endDay
55%6%11%18%6%1
1376
February1st to 15thDay
55%7%17%14%5%
1411
16th to endDay
57%7%15%14%4
1436
March1st to 15thDay
58%8%14%14%4
1847
16th to endDay
58%8%13%15%4
2132
April1st to 15thDay
51%7%17%16%6%
2281
16th to endDay
56%7%14%14%7%
2349
May1st to 15thDay
46%6%14%21%10%
2691
16th to endDay
50%6%12%20%8%
2807
June1st to 15thDay
55%6%16%18%2
2794
16th to endDay
50%8%17%18%4
2880
July1st to 15thDay
39%11%23%21%4
2671
16th to endDay
42%12%25%18%2
2667
August1st to 15thDay
42%11%29%15%1
2586
16th to endDay
40%10%27%17%3
2489
September1st to 15thDay
42%8%22%19%5%
2144
16th to endDay
37%8%22%23%7%1
1815
October1st to 15thDay
49%6%20%19%3
1642
16th to endDay
50%7%16%23%2
1546
November1st to 15thDay
52%7%18%17%4
1348
16th to endDay
55%8%16%15%3
1260
December1st to 15thDay
62%8%13%12%2
1260
16th to endDay
60%8%14%12%3
1218
January1st to 15thNight
58%8%16%11%4
2740
16th to endNight
51%6%16%16%6%1
2859
February1st to 15thNight
53%6%16%16%6%
2454
16th to endNight
50%7%17%18%6%
2037
March1st to 15thNight
50%7%14%20%6%
2112
16th to endNight
53%6%14%18%7%
2091
April1st to 15thNight
47%6%12%22%9%1
1667
16th to endNight
53%5%9%17%11%1
1611
May1st to 15thNight
41%5%14%23%13%1
1260
16th to endNight
51%5%11%20%8%1
1309
June1st to 15thNight
52%6%16%18%5%
1164
16th to endNight
44%8%18%22%5%
1080
July1st to 15thNight
33%12%21%27%4
1059
16th to endNight
36%9%22%27%3
1239
August1st to 15thNight
35%10%29%22%1
1346
16th to endNight
40%7%22%23%6%
1713
September1st to 15thNight
35%6%22%27%6%1
1702
16th to endNight
34%7%19%26%9%1
1815
October1st to 15thNight
48%6%15%23%5%
1985
16th to endNight
48%7%16%23%3
2315
November1st to 15thNight
55%5%13%20%4
2510
16th to endNight
57%8%16%13%3
2700
December1st to 15thNight
62%8%12%13%2
2700
16th to endNight
58%9%14%14%3
3003

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
11%5%21%28%26%6%
60
16th to endDay
17%332%28%12%6%
64
February1st to 15thDay
19%335%25%14%1
62
16th to endDay
15%422%36%15%5%
95
March1st to 15thDay
12%7%36%27%13%2
270
16th to endDay
17%5%29%25%16%4
288
April1st to 15thDay
13%8%30%30%13%2
269
16th to endDay
24%8%24%26%13%2
276
May1st to 15thDay
14%7%18%32%21%6%
468
16th to endDay
19%416%30%22%7%
517
June1st to 15thDay
19%5%20%28%20%6%
589
16th to endDay
15%417%28%26%8%
675
July1st to 15thDay
11%216%35%28%5%
605
16th to endDay
14%219%30%25%7%
515
August1st to 15thDay
12%213%26%25%18%
398
16th to endDay
9%5%30%32%19%2
332
September1st to 15thDay
21%8%20%28%17%5%
294
16th to endDay
15%10%27%27%14%4
255
October1st to 15thDay
23%7%26%21%14%6%
126
16th to endDay
23%218%25%22%7%
96
November1st to 15thDay
30%128%31%8%
80
16th to endDay
10%131%25%13%18%
60
December1st to 15thDay
13%125%36%15%8%
60
16th to endDay
46%25%39%18%6%
64
January1st to 15thNight
13%5%26%38%13%1
909
16th to endNight
12%6%33%34%10%2
939
February1st to 15thNight
13%5%26%33%19%2
704
16th to endNight
9%224%39%21%3
632
March1st to 15thNight
12%428%38%14%2
720
16th to endNight
15%425%33%19%2
768
April1st to 15thNight
14%323%39%17%2
587
16th to endNight
17%5%21%35%18%1
537
May1st to 15thNight
10%6%18%38%21%3
360
16th to endNight
24%215%32%23%2
375
June1st to 15thNight
15%5%16%38%20%4
360
16th to endNight
14%314%38%26%3
360
July1st to 15thNight
10%117%42%27%
340
16th to endNight
12%114%39%29%3
376
August1st to 15thNight
10%111%37%33%5%
360
16th to endNight
12%218%40%24%1
567
September1st to 15thNight
15%214%39%26%2
591
16th to endNight
12%227%39%16%1
656
October1st to 15thNight
18%125%35%16%2
660
16th to endNight
17%426%35%13%2
731
November1st to 15thNight
17%5%30%33%11%2
875
16th to endNight
11%5%30%33%15%2
900
December1st to 15thNight
16%6%26%33%13%3
900
16th to endNight
9%428%35%18%4
981
Page generated at 2017-09-11 17:35:20. Version ac04

Copyright 2017 A. Danko


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