Copernicus Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Copernicus Observatory clear sky chart from 2005-11-05 to 2019-06-24.

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
72%
18298
38%
54057
30%
18261
80%
18261
61%
23935

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
69%
837
35%
2717
30%
836
79%
836
50%
1242
January16th to endNight
66%
896
37%
2870
31%
896
78%
896
50%
1337
February1st to 15thNight
67%
816
38%
2472
30%
816
79%
816
53%
1155
February16th to endNight
58%
736
37%
2207
32%
736
69%
736
49%
1070
March1st to 15thNight
60%
840
36%
2461
28%
840
73%
840
56%
1127
March16th to endNight
63%
896
37%
2464
24%
896
75%
896
59%
1145
April1st to 15thNight
52%
839
37%
2110
16%
839
65%
839
57%
1057
April16th to endNight
60%
733
40%
1981
20%
733
71%
733
63%
891
May1st to 15thNight
67%
629
38%
1889
26%
629
74%
629
64%
789
May16th to endNight
64%
657
35%
1973
24%
657
71%
657
61%
845
June1st to 15thNight
73%
630
36%
1890
29%
630
79%
630
75%
733
June16th to endNight
78%
609
35%
1827
29%
609
83%
609
82%
675
July1st to 15thNight
88%
555
30%
1665
28%
555
89%
555
64%
726
July16th to endNight
89%
612
34%
1737
30%
579
89%
579
60%
783
August1st to 15thNight
86%
621
40%
1765
29%
618
87%
618
68%
776
August16th to endNight
89%
828
42%
2070
28%
828
91%
828
73%
983
September1st to 15thNight
87%
780
40%
2073
31%
780
89%
780
67%
976
September16th to endNight
85%
776
47%
2145
38%
776
91%
776
82%
856
October1st to 15thNight
72%
780
43%
2145
32%
780
81%
780
64%
982
October16th to endNight
75%
832
43%
2559
37%
832
84%
832
65%
1061
November1st to 15thNight
77%
820
42%
2665
38%
820
87%
820
68%
1035
November16th to endNight
76%
840
43%
2730
41%
840
84%
840
63%
1095
December1st to 15thNight
71%
840
38%
2730
34%
840
81%
840
53%
1222
December16th to endNight
64%
896
36%
2912
29%
896
74%
896
44%
1374

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
111212346%74%
54764
Night
111212336%74%
54252
TransparencyDay
12%35%15%28%34%
54459
Night
12%35%15%28%34%
54058
SeeingDay
39%24%36%20%6%
8008
Night
25%16%33%32%9%
18312

By Month

Percentage Cloud Cover SW (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
312212237%73%
1881
16th to endDay
3111223346%69%
2056
February1st to 15thDay
21121245%8%68%
2051
16th to endDay
311221235%7%67%
1839
March1st to 15thDay
112212347%71%
2158
16th to endDay
111221345%7%69%
2464
April1st to 15thDay
1211213347%70%
2495
16th to endDay
111112225%79%
2583
May1st to 15thDay
1112346%76%
2721
16th to endDay
111212345%74%
2845
June1st to 15thDay
1212484%
2730
16th to endDay
112288%
2641
July1st to 15thDay
11122145%5%6%66%
2535
16th to endDay
21133236%6%8%60%
2675
August1st to 15thDay
21121324474%
2436
16th to endDay
111213345%73%
2484
September1st to 15thDay
11121224475%
2217
16th to endDay
11112484%
2145
October1st to 15thDay
21131223476%
2145
16th to endDay
111223481%
2013
November1st to 15thDay
111111245%78%
1854
16th to endDay
11112246%76%
1890
December1st to 15thDay
212313337%69%
1890
16th to endDay
211122345%7%67%
2016
January1st to 15thNight
122213447%68%
2717
16th to endNight
422213447%67%
2870
February1st to 15thNight
1112213346%71%
2461
16th to endNight
322212347%66%
2207
March1st to 15thNight
112212348%70%
2461
16th to endNight
111212347%72%
2464
April1st to 15thNight
112112346%73%
2110
16th to endNight
1121223479%
1981
May1st to 15thNight
11112237%76%
1889
16th to endNight
111112236%76%
1972
June1st to 15thNight
1112484%
1890
16th to endNight
111388%
1827
July1st to 15thNight
111222236%6%70%
1755
16th to endNight
22222335%8%67%
1845
August1st to 15thNight
1111212245%75%
1774
16th to endNight
11112235%78%
2070
September1st to 15thNight
11112345%76%
2073
16th to endNight
1111388%
2145
October1st to 15thNight
1112112225%77%
2145
16th to endNight
111212225%79%
2559
November1st to 15thNight
1112235%80%
2665
16th to endNight
11112235%79%
2730
December1st to 15thNight
311112347%70%
2730
16th to endNight
3212213347%67%
2912

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
14%38%27%37%8%
1882
16th to endDay
17%48%25%31%11%
2056
February1st to 15thDay
14%5%7%23%32%16%
2051
16th to endDay
17%47%19%33%17%
1839
March1st to 15thDay
13%35%22%37%17%
2158
16th to endDay
15%38%21%33%17%
2464
April1st to 15thDay
14%45%17%31%27%
2495
16th to endDay
10%2315%36%32%
2583
May1st to 15thDay
10%25%13%33%34%
2721
16th to endDay
11%3411%31%37%
2848
June1st to 15thDay
6%127%20%61%
2730
16th to endDay
5%11312%76%
2641
July1st to 15thDay
16%447%15%51%
2396
16th to endDay
17%46%13%21%35%
2520
August1st to 15thDay
12%338%20%51%
2421
16th to endDay
12%339%21%49%
2484
September1st to 15thDay
11%347%18%54%
2217
16th to endDay
7%115%29%54%
2145
October1st to 15thDay
13%2311%28%39%
2145
16th to endDay
8%2312%38%34%
2013
November1st to 15thDay
10%25%17%39%23%
1854
16th to endDay
10%3423%37%20%
1890
December1st to 15thDay
17%49%23%32%13%
1890
16th to endDay
17%412%27%25%12%
2016
January1st to 15thNight
16%5%7%24%33%12%
2717
16th to endNight
18%36%24%29%17%
2870
February1st to 15thNight
15%47%19%32%20%
2472
16th to endNight
18%35%19%34%17%
2207
March1st to 15thNight
13%36%19%36%19%
2461
16th to endNight
12%36%19%37%20%
2464
April1st to 15thNight
13%35%17%33%26%
2110
16th to endNight
10%2214%32%37%
1981
May1st to 15thNight
10%2413%32%36%
1890
16th to endNight
11%2411%29%40%
1973
June1st to 15thNight
6%126%18%64%
1890
16th to endNight
41311%77%
1827
July1st to 15thNight
12%249%15%53%
1665
16th to endNight
14%3415%22%38%
1737
August1st to 15thNight
11%239%17%55%
1765
16th to endNight
9%238%21%53%
2070
September1st to 15thNight
11%349%15%54%
2073
16th to endNight
5%125%26%59%
2145
October1st to 15thNight
12%2311%26%44%
2145
16th to endNight
10%2310%29%42%
2559
November1st to 15thNight
9%2317%39%26%
2665
16th to endNight
11%1418%35%28%
2730
December1st to 15thNight
15%48%23%32%16%
2730
16th to endNight
18%49%26%27%12%
2912

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
12%6%16%40%20%4
180
16th to endDay
39%22%30%27%6%
232
February1st to 15thDay
5%11%28%30%18%5%
386
16th to endDay
418%33%30%12%1
342
March1st to 15thDay
317%34%25%17%1
390
16th to endDay
417%34%30%11%1
416
April1st to 15thDay
5%18%32%28%11%3
389
16th to endDay
5%22%29%27%11%3
378
May1st to 15thDay
211%30%33%15%6%
408
16th to endDay
412%25%35%16%5%
458
June1st to 15thDay
15%27%37%20%7%
435
16th to endDay
5%21%39%23%10%
408
July1st to 15thDay
1113%46%25%10%
365
16th to endDay
218%46%30%10%
391
August1st to 15thDay
319%47%18%8%
359
16th to endDay
3114%41%28%10%
396
September1st to 15thDay
222%45%23%5%
375
16th to endDay
15%21%37%27%5%
375
October1st to 15thDay
38%32%36%16%2
375
16th to endDay
27%14%32%34%8%
218
November1st to 15thDay
15%20%37%28%6%
180
16th to endDay
110%17%33%31%6%
180
December1st to 15thDay
19%18%36%27%6%
180
16th to endDay
47%20%34%26%6%
192
January1st to 15thNight
35%17%35%27%10%
840
16th to endNight
5%419%34%28%7%
896
February1st to 15thNight
26%20%39%23%7%
824
16th to endNight
46%26%35%21%5%
736
March1st to 15thNight
27%25%34%22%7%
840
16th to endNight
110%21%36%23%5%
896
April1st to 15thNight
213%28%26%22%6%
839
16th to endNight
110%25%32%23%7%
733
May1st to 15thNight
26%21%36%27%5%
630
16th to endNight
28%22%31%30%5%
659
June1st to 15thNight
1318%38%31%5%
630
16th to endNight
217%36%35%7%
609
July1st to 15thNight
25%33%48%10%
555
16th to endNight
21231%54%7%
612
August1st to 15thNight
16%35%48%8%
621
16th to endNight
1427%47%18%
828
September1st to 15thNight
25%30%45%14%
780
16th to endNight
111%31%39%16%
776
October1st to 15thNight
1418%35%30%9%
780
16th to endNight
2414%26%35%15%
832
November1st to 15thNight
1216%35%34%10%
820
16th to endNight
1414%34%34%10%
840
December1st to 15thNight
4317%35%32%6%
840
16th to endNight
410%17%33%27%6%
896
Page generated at 2019-06-24 17:41:30. Version ac04

Copyright 2019 A. Danko


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