Etna
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Etna clear sky chart from 2005-11-05 to 2017-12-01.

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
56%
15294
20%
47826
18%
15257
59%
15257
29%
29242

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
47%
717
13%
2476
13%
716
51%
716
18%
1704
January16th to endNight
49%
768
20%
2496
21%
768
51%
768
22%
1650
February1st to 15thNight
45%
698
13%
2288
14%
697
47%
697
17%
1613
February16th to endNight
43%
632
15%
1972
14%
632
46%
632
19%
1394
March1st to 15thNight
39%
720
10%
2004
8%
720
41%
720
17%
1494
March16th to endNight
35%
768
11%
2100
7%
768
38%
768
17%
1578
April1st to 15thNight
34%
719
10%
1799
4%
719
36%
719
19%
1365
April16th to endNight
50%
669
16%
1749
9%
669
53%
669
33%
1126
May1st to 15thNight
54%
482
17%
1562
13%
482
58%
482
33%
892
May16th to endNight
56%
374
15%
1496
16%
374
61%
374
22%
883
June1st to 15thNight
60%
360
18%
1440
23%
360
66%
360
27%
801
June16th to endNight
75%
360
28%
1440
38%
360
80%
360
52%
567
July1st to 15thNight
89%
340
28%
1360
41%
340
91%
340
59%
491
July16th to endNight
90%
494
35%
1524
37%
462
92%
462
69%
595
August1st to 15thNight
91%
538
35%
1611
31%
535
92%
535
71%
655
August16th to endNight
82%
699
42%
1845
29%
699
84%
699
75%
820
September1st to 15thNight
85%
720
41%
1800
26%
720
87%
720
81%
802
September16th to endNight
72%
716
32%
1980
28%
716
75%
716
52%
1013
October1st to 15thNight
65%
720
25%
2160
23%
720
71%
720
45%
1123
October16th to endNight
62%
768
23%
2304
24%
768
64%
768
32%
1380
November1st to 15thNight
47%
760
14%
2468
13%
760
50%
760
19%
1689
November16th to endNight
42%
780
12%
2730
12%
780
45%
780
18%
1868
December1st to 15thNight
41%
724
13%
2534
11%
724
46%
724
18%
1744
December16th to endNight
35%
768
14%
2688
14%
768
38%
768
13%
1995

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
45%2443445%7%52%
48604
Night
3414435%5%6%8%52%
48009
TransparencyDay
32%8%11%19%19%8%
48286
Night
32%9%13%20%17%6%
47827
SeeingDay
12%18%29%25%11%2
6093
Night
6%11%22%30%24%4
15305

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
36%35%5%36%7%9%10%37%
1459
16th to endDay
36%25%6%45%6%7%8%41%
1728
February1st to 15thDay
35%26%45%8%8%9%10%34%
1576
16th to endDay
311%46%6%46%6%6%6%36%
1502
March1st to 15thDay
39%37%8%48%6%7%10%30%
1953
16th to endDay
5%9%37%7%46%7%6%9%31%
2124
April1st to 15thDay
6%9%37%8%5%6%6%6%7%31%
2149
16th to endDay
6%7%36%5%3435%7%45%
2210
May1st to 15thDay
5%6%25%42445%7%50%
2386
16th to endDay
10%7%25%5%245%48%42%
2615
June1st to 15thDay
7%5%23324346%55%
2520
16th to endDay
322212245%70%
2520
July1st to 15thDay
111113335%74%
2520
16th to endDay
111121223477%
2536
August1st to 15thDay
11212345%74%
2340
16th to endDay
111122481%
2357
September1st to 15thDay
11212235%78%
2160
16th to endDay
221231335%7%66%
1977
October1st to 15thDay
5%21341445%6%59%
1800
16th to endDay
5%5%245%335%6%7%49%
1920
November1st to 15thDay
6%7%36%6%46%6%7%9%36%
1716
16th to endDay
37%25%6%46%7%8%11%35%
1560
December1st to 15thDay
45%26%6%46%7%8%10%37%
1440
16th to endDay
38%26%8%5%8%7%8%11%28%
1536
January1st to 15thNight
3435%6%36%7%7%9%40%
2476
16th to endNight
36%25%6%37%7%6%7%42%
2496
February1st to 15thNight
46%247%47%7%7%10%36%
2276
16th to endNight
36%36%6%46%6%7%10%38%
1972
March1st to 15thNight
36%26%6%49%8%7%9%35%
2004
16th to endNight
36%35%6%48%7%8%10%35%
2100
April1st to 15thNight
48%37%7%46%6%6%9%34%
1799
16th to endNight
47%24424447%52%
1749
May1st to 15thNight
33134345%47%57%
1562
16th to endNight
6%6%14325%5%5%7%51%
1496
June1st to 15thNight
44245%2435%7%55%
1440
16th to endNight
312112126%76%
1440
July1st to 15thNight
11113246%76%
1440
16th to endNight
1121112384%
1630
August1st to 15thNight
1111222481%
1620
16th to endNight
1123483%
1845
September1st to 15thNight
11225%84%
1800
16th to endNight
212312345%70%
1980
October1st to 15thNight
323323346%65%
2160
16th to endNight
3413425%5%5%9%53%
2304
November1st to 15thNight
4415%5%37%6%9%10%38%
2468
16th to endNight
36%25%5%47%6%7%9%39%
2730
December1st to 15thNight
45%25%7%46%7%8%10%38%
2534
16th to endNight
39%36%6%37%8%8%9%33%
2688

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
43%11%12%16%10%4
1459
16th to endDay
41%9%9%18%11%8%
1728
February1st to 15thDay
44%13%14%15%10%1
1576
16th to endDay
50%10%12%17%7%1
1502
March1st to 15thDay
53%11%11%12%11%
1953
16th to endDay
51%11%16%11%6%1
2124
April1st to 15thDay
52%11%13%15%7%
2149
16th to endDay
39%7%18%21%12%
2210
May1st to 15thDay
33%7%13%26%16%2
2386
16th to endDay
41%7%14%24%10%1
2619
June1st to 15thDay
32%7%12%22%21%4
2520
16th to endDay
18%5%8%30%30%7%
2520
July1st to 15thDay
12%39%26%27%20%
2371
16th to endDay
11%35%16%32%29%
2379
August1st to 15thDay
10%411%21%34%16%
2324
16th to endDay
8%37%19%41%19%
2357
September1st to 15thDay
10%35%18%36%26%
2160
16th to endDay
19%6%11%23%26%11%
1977
October1st to 15thDay
26%6%12%24%22%7%
1800
16th to endDay
34%8%12%18%18%7%
1920
November1st to 15thDay
44%9%14%17%10%3
1716
16th to endDay
44%13%12%12%12%4
1560
December1st to 15thDay
45%11%13%14%13%
1440
16th to endDay
54%12%10%12%7%3
1536
January1st to 15thNight
42%13%13%15%11%4
2476
16th to endNight
41%10%9%18%12%8%
2496
February1st to 15thNight
46%11%13%15%10%2
2288
16th to endNight
43%12%13%18%9%1
1972
March1st to 15thNight
48%12%13%12%13%
2004
16th to endNight
44%16%16%14%6%1
2100
April1st to 15thNight
47%13%17%14%6%
1799
16th to endNight
33%8%22%24%7%1
1749
May1st to 15thNight
27%9%16%31%12%2
1563
16th to endNight
36%8%19%25%8%1
1496
June1st to 15thNight
31%8%13%29%14%2
1440
16th to endNight
12%5%12%39%25%3
1440
July1st to 15thNight
9%5%11%29%29%15%
1360
16th to endNight
9%25%20%41%20%
1524
August1st to 15thNight
7%310%30%34%13%
1611
16th to endNight
7%38%24%40%15%
1845
September1st to 15thNight
5%27%21%40%22%
1800
16th to endNight
17%6%13%25%22%15%
1980
October1st to 15thNight
21%5%12%25%25%8%
2160
16th to endNight
29%10%15%18%18%8%
2304
November1st to 15thNight
41%13%16%15%9%3
2468
16th to endNight
43%12%12%14%12%4
2730
December1st to 15thNight
44%12%11%16%14%1
2534
16th to endNight
50%12%9%13%11%1
2688

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%21%32%20%8%1
87
16th to endDay
14%23%26%17%16%1
256
February1st to 15thDay
22%21%27%21%7%
236
16th to endDay
19%28%26%18%5%1
225
March1st to 15thDay
25%28%24%14%6%
270
16th to endDay
23%34%23%14%3
288
April1st to 15thDay
24%24%28%17%4
269
16th to endDay
19%31%27%15%31
270
May1st to 15thDay
17%25%28%18%8%1
288
16th to endDay
19%16%26%21%13%2
330
June1st to 15thDay
14%20%29%23%8%2
315
16th to endDay
5%16%35%27%13%2
315
July1st to 15thDay
37%30%37%16%4
305
16th to endDay
17%28%43%14%3
327
August1st to 15thDay
16%33%35%16%6%
315
16th to endDay
211%28%31%18%7%
332
September1st to 15thDay
47%25%39%17%5%
315
16th to endDay
416%32%29%16%
315
October1st to 15thDay
12%19%27%24%13%2
315
16th to endDay
12%19%27%24%12%3
336
November1st to 15thDay
12%17%26%30%11%1
170
16th to endDay
10%22%47%11%7%1
90
December1st to 15thDay
13%35%43%6%1
60
16th to endDay
15%12%29%29%12%
64
January1st to 15thNight
6%14%27%30%17%3
720
16th to endNight
7%16%23%26%18%6%
768
February1st to 15thNight
10%15%24%29%18%1
704
16th to endNight
9%17%26%30%14%1
632
March1st to 15thNight
10%22%24%23%15%4
720
16th to endNight
8%23%28%24%12%1
768
April1st to 15thNight
11%16%31%23%14%1
719
16th to endNight
8%13%26%28%19%3
669
May1st to 15thNight
6%7%29%33%22%1
483
16th to endNight
8%6%24%30%28%1
375
June1st to 15thNight
7%5%22%39%24%
360
16th to endNight
2318%43%31%
360
July1st to 15thNight
6%44%46%1
340
16th to endNight
1442%48%3
494
August1st to 15thNight
2435%50%6%
538
16th to endNight
1112%37%41%5%
699
September1st to 15thNight
1210%32%46%7%
720
16th to endNight
4317%34%32%8%
716
October1st to 15thNight
47%21%35%25%5%
720
16th to endNight
8%10%17%27%27%8%
768
November1st to 15thNight
7%11%29%31%14%4
760
16th to endNight
9%16%29%24%17%3
780
December1st to 15thNight
9%16%27%27%14%4
724
16th to endNight
10%24%26%25%9%3
768
Page generated at 2017-12-02 06:14:16. Version ac04

Copyright 2017 A. Danko


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