Edson
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Edson clear sky chart from 2005-11-05 to 2017-03-14.

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
34%
14610
10%
45149
6%
14583
39%
14583
16%
33130

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
24%
924
8%
2844
5%
922
28%
922
11%
2221
January16th to endNight
27%
831
16%
2751
8%
831
37%
831
14%
1965
February1st to 15thNight
28%
697
8%
2464
6%
697
32%
697
12%
1827
February16th to endNight
37%
632
11%
1990
9%
632
41%
632
18%
1431
March1st to 15thNight
30%
716
13%
2148
8%
716
36%
716
17%
1589
March16th to endNight
33%
704
9%
1853
3%
703
36%
703
15%
1462
April1st to 15thNight
30%
601
10%
1591
4%
601
34%
601
15%
1253
April16th to endNight
28%
437
9%
1427
7%
437
32%
437
15%
1047
May1st to 15thNight
37%
329
5%
1244
5%
329
40%
329
15%
865
May16th to endNight
36%
342
0%
1197
0%
342
37%
342
15%
869
June1st to 15thNight
40%
330
0%
1007
0%
330
40%
330
14%
779
June16th to endNight
42%
330
0%
990
0%
330
42%
330
15%
745
July1st to 15thNight
50%
310
0%
930
0%
310
50%
310
19%
664
July16th to endNight
50%
348
1%
1147
0%
326
51%
326
17%
789
August1st to 15thNight
56%
330
5%
1312
7%
328
58%
328
16%
875
August16th to endNight
48%
474
9%
1524
10%
474
49%
474
20%
1034
September1st to 15thNight
56%
647
15%
1645
9%
647
57%
647
32%
1104
September16th to endNight
47%
656
18%
1815
9%
656
52%
656
30%
1164
October1st to 15thNight
37%
660
14%
1990
10%
660
42%
660
19%
1417
October16th to endNight
32%
704
12%
2288
7%
704
40%
704
15%
1649
November1st to 15thNight
28%
812
13%
2498
7%
812
35%
812
15%
1847
November16th to endNight
23%
900
9%
2700
3%
900
29%
900
13%
2089
December1st to 15thNight
29%
904
11%
2722
7%
904
32%
904
13%
2110
December16th to endNight
33%
992
11%
3072
6%
992
38%
992
13%
2335

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
12%9%47%7%46%5%6%7%28%
45592
Night
10%11%5%8%7%45%5%6%7%28%
45290
TransparencyDay
52%7%16%17%5%
45235
Night
53%6%14%17%5%
45152
SeeingDay
17%11%26%26%14%3
5713
Night
15%9%27%31%14%1
14622

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%7%10%7%35%6%46%25%
1092
16th to endDay
8%14%6%9%7%45%46%6%28%
1485
February1st to 15thDay
9%10%5%9%8%47%5%6%6%26%
1400
16th to endDay
6%12%7%10%9%36%5%6%5%26%
1483
March1st to 15thDay
6%13%6%9%6%46%5%6%8%27%
1783
16th to endDay
8%13%6%9%7%46%5%7%8%22%
2012
April1st to 15thDay
8%12%5%8%7%46%5%6%8%24%
2026
16th to endDay
13%14%47%7%35%5%5%7%24%
2201
May1st to 15thDay
12%9%47%7%46%6%5%5%30%
2376
16th to endDay
23%7%36%7%35%5%45%26%
2562
June1st to 15thDay
21%7%37%6%36%6%5%7%24%
2621
16th to endDay
16%6%37%7%46%6%6%8%26%
2640
July1st to 15thDay
15%5%35%6%46%6%6%8%29%
2640
16th to endDay
10%425%6%5%6%8%7%8%32%
2622
August1st to 15thDay
14%5%26%6%36%7%7%7%31%
2310
16th to endDay
10%6%27%6%46%7%7%8%32%
2326
September1st to 15thDay
14%7%25%5%25%45%7%37%
1983
16th to endDay
10%7%35%5%345%5%9%39%
1815
October1st to 15thDay
12%12%48%6%2346%7%31%
1636
16th to endDay
13%11%5%7%5%35%35%5%33%
1584
November1st to 15thDay
10%12%6%7%6%35%5%6%7%27%
1347
16th to endDay
7%13%7%9%7%36%5%5%5%27%
1260
December1st to 15thDay
10%13%6%12%8%46%445%23%
1236
16th to endDay
6%13%410%7%5%6%46%7%26%
1152
January1st to 15thNight
7%14%7%10%9%46%5%5%6%22%
2844
16th to endNight
6%13%5%9%6%45%5%5%6%29%
2751
February1st to 15thNight
7%15%5%10%8%45%46%6%24%
2452
16th to endNight
5%12%5%10%8%46%46%6%29%
1990
March1st to 15thNight
7%12%5%8%7%46%6%47%27%
2148
16th to endNight
8%14%7%7%7%46%7%6%7%21%
1853
April1st to 15thNight
8%13%5%9%8%5%5%6%7%6%23%
1591
16th to endNight
14%12%5%8%5%25%45%8%27%
1427
May1st to 15thNight
15%9%47%6%35%5%6%6%28%
1243
16th to endNight
23%8%26%6%245%5%7%27%
1197
June1st to 15thNight
19%8%38%7%36%5%46%25%
1007
16th to endNight
18%6%27%7%45%6%7%8%24%
990
July1st to 15thNight
12%6%26%7%37%6%8%8%31%
990
16th to endNight
11%5%28%6%46%6%7%9%31%
1233
August1st to 15thNight
11%5%35%6%36%6%8%9%32%
1320
16th to endNight
11%6%27%5%5%5%5%8%8%33%
1524
September1st to 15thNight
13%6%35%43345%8%42%
1645
16th to endNight
11%6%25%42446%8%42%
1815
October1st to 15thNight
14%9%47%6%35%45%6%32%
1990
16th to endNight
12%11%47%6%45%46%8%28%
2288
November1st to 15thNight
12%13%6%7%7%245%5%6%28%
2498
16th to endNight
9%14%6%10%7%46%5%5%5%24%
2700
December1st to 15thNight
7%15%5%9%7%45%6%45%26%
2722
16th to endNight
5%13%6%10%8%5%7%6%5%6%24%
3072

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
58%5%14%14%5%1
1092
16th to endDay
56%5%11%14%9%1
1485
February1st to 15thDay
54%6%15%14%8%1
1400
16th to endDay
57%5%12%15%8%
1483
March1st to 15thDay
52%7%14%19%5%
1783
16th to endDay
58%6%15%14%3
2013
April1st to 15thDay
56%6%14%16%4
2026
16th to endDay
57%6%12%14%6%1
2201
May1st to 15thDay
54%413%17%10%
2376
16th to endDay
58%5%12%13%8%
2567
June1st to 15thDay
57%7%16%14%3
2621
16th to endDay
53%8%17%17%3
2640
July1st to 15thDay
49%7%19%19%4
2471
16th to endDay
43%10%26%17%2
2445
August1st to 15thDay
47%9%25%14%2
2293
16th to endDay
45%8%23%18%4
2326
September1st to 15thDay
45%5%19%23%6%
1983
16th to endDay
42%6%15%24%8%2
1815
October1st to 15thDay
50%6%15%22%4
1636
16th to endDay
52%5%11%25%3
1584
November1st to 15thDay
53%6%16%17%5%
1347
16th to endDay
56%7%14%13%5%2
1260
December1st to 15thDay
63%6%12%14%3
1236
16th to endDay
54%6%14%15%8%1
1152
January1st to 15thNight
61%6%12%15%21
2844
16th to endNight
54%411%18%8%2
2751
February1st to 15thNight
58%6%13%15%5%1
2464
16th to endNight
53%5%13%18%8%1
1990
March1st to 15thNight
54%6%13%17%6%
2148
16th to endNight
59%6%12%15%6%
1856
April1st to 15thNight
57%7%13%13%6%
1591
16th to endNight
54%7%14%17%6%1
1427
May1st to 15thNight
52%5%13%17%10%
1244
16th to endNight
55%5%14%16%7%
1197
June1st to 15thNight
58%7%14%16%2
1007
16th to endNight
54%9%16%16%3
990
July1st to 15thNight
47%9%17%18%5%
930
16th to endNight
46%10%25%14%2
1147
August1st to 15thNight
43%12%25%17%1
1312
16th to endNight
43%9%21%18%6%
1524
September1st to 15thNight
40%5%20%24%8%
1645
16th to endNight
36%6%17%27%9%1
1815
October1st to 15thNight
50%6%16%19%6%
1990
16th to endNight
53%6%15%21%3
2288
November1st to 15thNight
55%6%11%20%5%
2498
16th to endNight
61%412%13%5%1
2700
December1st to 15thNight
60%5%12%16%4
2722
16th to endNight
58%6%11%16%6%
3072

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%8%30%21%16%6%
60
16th to endDay
14%7%21%32%15%7%
64
February1st to 15thDay
16%11%31%28%8%3
60
16th to endDay
13%10%30%23%20%2
176
March1st to 15thDay
13%19%31%27%7%
264
16th to endDay
15%18%36%22%6%
224
April1st to 15thDay
17%22%34%17%7%
209
16th to endDay
23%17%28%19%10%1
210
May1st to 15thDay
10%17%26%25%17%1
303
16th to endDay
26%7%21%22%17%5%
437
June1st to 15thDay
20%13%21%28%12%3
566
16th to endDay
17%7%24%27%18%4
585
July1st to 15thDay
14%7%27%29%18%2
555
16th to endDay
12%7%29%27%18%4
430
August1st to 15thDay
14%7%24%29%16%7%
255
16th to endDay
13%13%32%29%10%1
268
September1st to 15thDay
20%10%25%29%9%3
255
16th to endDay
16%14%29%25%10%2
255
October1st to 15thDay
23%12%23%25%13%1
186
16th to endDay
20%125%32%15%5%
96
November1st to 15thDay
19%7%21%38%11%2
71
16th to endDay
13%6%30%31%6%11%
60
December1st to 15thDay
15%6%30%25%18%5%
60
16th to endDay
15%12%23%26%14%7%
64
January1st to 15thNight
15%10%33%28%9%1
927
16th to endNight
16%14%28%30%9%
831
February1st to 15thNight
15%14%25%28%14%1
704
16th to endNight
10%8%29%33%16%2
632
March1st to 15thNight
11%9%36%29%11%1
716
16th to endNight
12%10%27%35%12%
704
April1st to 15thNight
14%11%30%29%12%
601
16th to endNight
21%9%29%29%9%
437
May1st to 15thNight
18%9%22%33%14%1
330
16th to endNight
23%6%23%28%16%1
343
June1st to 15thNight
23%6%19%31%16%1
330
16th to endNight
17%5%23%27%23%3
330
July1st to 15thNight
15%118%39%23%1
310
16th to endNight
12%420%36%22%2
348
August1st to 15thNight
13%216%31%33%3
330
16th to endNight
13%422%39%18%1
474
September1st to 15thNight
16%316%38%22%2
647
16th to endNight
13%5%26%34%17%1
656
October1st to 15thNight
17%8%25%31%16%
660
16th to endNight
16%9%26%33%11%
704
November1st to 15thNight
18%10%31%29%9%
812
16th to endNight
16%10%33%27%10%2
900
December1st to 15thNight
15%11%30%29%11%
904
16th to endNight
11%11%27%32%14%2
992
Page generated at 2017-03-15 09:32:34. Version ac04

Copyright 2017 A. Danko


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