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 2017-12-02.

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
35%
15424
10%
47632
6%
15397
39%
15397
16%
34820

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%
720
13%
2160
8%
720
36%
720
17%
1593
March16th to endNight
34%
768
10%
2022
4%
767
37%
767
16%
1574
April1st to 15thNight
28%
656
9%
1736
4%
656
32%
656
14%
1375
April16th to endNight
28%
477
9%
1557
7%
477
32%
477
14%
1155
May1st to 15thNight
38%
359
5%
1357
4%
359
40%
359
14%
951
May16th to endNight
38%
374
0%
1309
0%
374
38%
374
16%
933
June1st to 15thNight
40%
360
0%
1098
0%
360
40%
360
14%
847
June16th to endNight
40%
360
0%
1080
0%
360
40%
360
15%
813
July1st to 15thNight
52%
340
0%
1020
0%
340
52%
340
21%
713
July16th to endNight
51%
376
1%
1246
0%
354
52%
354
18%
847
August1st to 15thNight
58%
360
5%
1432
7%
358
60%
358
17%
929
August16th to endNight
50%
517
12%
1663
11%
517
52%
517
22%
1100
September1st to 15thNight
56%
706
14%
1795
9%
706
57%
706
32%
1196
September16th to endNight
47%
716
18%
1980
10%
716
52%
716
30%
1276
October1st to 15thNight
37%
720
13%
2171
10%
720
42%
720
19%
1552
October16th to endNight
32%
768
14%
2496
8%
768
41%
768
16%
1779
November1st to 15thNight
28%
882
12%
2712
6%
882
35%
882
14%
2024
November16th to endNight
22%
975
9%
2925
2%
975
29%
975
13%
2256
December1st to 15thNight
29%
914
11%
2752
7%
914
32%
914
13%
2128
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%6%45%5%6%7%29%
48850
Night
10%11%5%8%7%45%5%6%7%28%
47773
TransparencyDay
52%6%16%17%5%
48493
Night
53%6%14%18%6%
47635
SeeingDay
17%11%27%26%14%3
6802
Night
15%9%27%31%14%1
15436

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%
1800
16th to endDay
8%12%6%9%7%46%5%7%8%22%
2195
April1st to 15thDay
10%13%5%8%7%46%5%6%7%23%
2211
16th to endDay
14%15%48%6%35%5%5%6%24%
2401
May1st to 15thDay
12%8%48%7%46%6%6%6%29%
2593
16th to endDay
22%7%36%7%35%5%46%27%
2802
June1st to 15thDay
21%7%37%6%35%6%6%7%24%
2860
16th to endDay
16%6%37%7%46%6%6%8%26%
2880
July1st to 15thDay
14%5%35%6%46%5%6%9%31%
2880
16th to endDay
10%5%25%6%5%6%8%8%8%32%
2831
August1st to 15thDay
14%5%26%6%36%7%7%7%32%
2520
16th to endDay
10%6%26%6%46%6%7%8%34%
2539
September1st to 15thDay
14%7%25%5%2445%7%38%
2163
16th to endDay
11%7%36%5%345%48%38%
1980
October1st to 15thDay
13%12%47%6%2345%6%32%
1785
16th to endDay
13%11%5%7%5%35%35%6%32%
1728
November1st to 15thDay
10%15%6%7%6%35%5%6%6%25%
1462
16th to endDay
7%13%6%9%7%36%5%5%6%28%
1365
December1st to 15thDay
9%13%6%11%8%46%5%45%23%
1243
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%
2160
16th to endNight
8%14%7%7%7%46%7%6%8%22%
2022
April1st to 15thNight
9%13%5%8%8%5%5%6%7%6%22%
1736
16th to endNight
15%13%48%5%25%46%8%25%
1557
May1st to 15thNight
15%9%48%6%35%5%6%7%27%
1356
16th to endNight
22%8%26%6%245%5%7%29%
1309
June1st to 15thNight
19%8%48%7%36%5%46%25%
1098
16th to endNight
18%6%37%7%45%7%7%7%24%
1080
July1st to 15thNight
11%5%26%6%36%6%8%8%34%
1080
16th to endNight
11%5%27%6%46%7%6%9%32%
1332
August1st to 15thNight
11%5%35%6%36%5%7%9%35%
1440
16th to endNight
10%5%27%5%5%5%5%7%8%35%
1663
September1st to 15thNight
13%6%35%43345%8%42%
1795
16th to endNight
12%6%25%4245%6%8%42%
1980
October1st to 15thNight
14%9%47%6%35%45%6%32%
2171
16th to endNight
11%11%47%6%45%46%8%29%
2496
November1st to 15thNight
11%13%6%8%7%345%46%27%
2712
16th to endNight
9%14%6%10%7%46%5%5%5%24%
2925
December1st to 15thNight
7%15%5%10%7%45%6%5%6%26%
2752
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%
1800
16th to endDay
57%6%15%15%4
2196
April1st to 15thDay
58%6%13%15%5%
2211
16th to endDay
58%6%12%15%6%1
2401
May1st to 15thDay
53%5%13%17%9%
2593
16th to endDay
56%5%13%15%7%
2807
June1st to 15thDay
57%7%16%14%3
2860
16th to endDay
53%7%16%17%4
2880
July1st to 15thDay
47%7%20%20%4
2711
16th to endDay
43%10%26%17%2
2654
August1st to 15thDay
46%9%24%17%2
2503
16th to endDay
43%8%24%18%5%
2539
September1st to 15thDay
44%5%18%23%7%
2163
16th to endDay
44%6%15%23%8%2
1980
October1st to 15thDay
50%5%16%21%5%
1785
16th to endDay
52%6%12%24%4
1728
November1st to 15thDay
55%6%15%16%5%
1462
16th to endDay
54%7%15%13%6%2
1365
December1st to 15thDay
62%6%12%14%3
1243
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
53%6%13%18%6%
2160
16th to endNight
57%6%12%16%6%
2025
April1st to 15thNight
58%7%13%13%6%
1736
16th to endNight
55%7%14%16%5%
1557
May1st to 15thNight
53%5%13%17%9%
1357
16th to endNight
53%5%14%18%7%
1309
June1st to 15thNight
58%7%15%16%2
1098
16th to endNight
54%8%15%15%4
1080
July1st to 15thNight
45%9%19%19%6%
1020
16th to endNight
45%9%26%15%3
1246
August1st to 15thNight
41%11%23%20%3
1432
16th to endNight
41%9%22%20%6%
1663
September1st to 15thNight
39%420%24%8%1
1795
16th to endNight
37%6%17%26%9%1
1980
October1st to 15thNight
51%5%15%19%7%
2171
16th to endNight
51%6%15%22%4
2496
November1st to 15thNight
56%6%11%20%5%
2712
16th to endNight
60%5%13%13%5%1
2925
December1st to 15thNight
60%5%12%16%4
2752
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
14%18%30%27%7%
270
16th to endDay
14%18%36%22%6%1
288
April1st to 15thDay
24%19%32%16%6%
269
16th to endDay
26%14%27%21%9%1
270
May1st to 15thDay
11%18%26%25%15%2
370
16th to endDay
24%6%21%24%17%4
517
June1st to 15thDay
21%12%22%27%12%3
655
16th to endDay
18%8%25%26%16%4
675
July1st to 15thDay
13%7%28%29%18%2
645
16th to endDay
11%7%28%28%18%5%
499
August1st to 15thDay
13%6%23%29%18%8%
315
16th to endDay
12%12%31%30%11%1
332
September1st to 15thDay
20%10%26%28%9%4
315
16th to endDay
19%12%25%25%13%3
315
October1st to 15thDay
25%11%24%20%14%4
240
16th to endDay
21%6%29%27%11%3
144
November1st to 15thDay
22%6%17%33%14%4
107
16th to endDay
11%10%30%35%48%
90
December1st to 15thDay
14%6%29%27%17%4
62
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
720
16th to endNight
12%9%27%35%13%1
768
April1st to 15thNight
16%11%30%28%11%
656
16th to endNight
22%8%28%29%9%
477
May1st to 15thNight
19%9%21%33%14%1
360
16th to endNight
22%6%22%30%16%1
375
June1st to 15thNight
23%6%20%31%16%1
360
16th to endNight
17%5%23%28%21%3
360
July1st to 15thNight
15%217%40%24%1
340
16th to endNight
12%420%37%23%2
376
August1st to 15thNight
12%215%31%34%4
360
16th to endNight
13%322%40%18%
517
September1st to 15thNight
16%316%37%22%3
706
16th to endNight
14%5%24%33%18%2
716
October1st to 15thNight
18%8%24%30%16%1
720
16th to endNight
16%10%27%33%10%
768
November1st to 15thNight
18%9%30%29%10%1
882
16th to endNight
16%11%33%26%9%2
975
December1st to 15thNight
15%11%30%30%11%
914
16th to endNight
11%11%27%32%14%2
992
Page generated at 2017-12-03 09:16:38. Version ac04

Copyright 2017 A. Danko


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