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Winer Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Winer Observatory 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
70%
15523
34%
46824
28%
15484
77%
15484
50%
22833

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%
718
32%
2327
31%
716
75%
716
49%
1100
January16th to endNight
62%
768
34%
2496
30%
768
72%
768
39%
1295
February1st to 15thNight
66%
697
36%
2205
32%
696
76%
696
50%
1016
February16th to endNight
58%
632
39%
1814
31%
632
69%
632
48%
914
March1st to 15thNight
59%
720
40%
1980
28%
720
71%
720
55%
968
March16th to endNight
65%
768
38%
2112
24%
768
76%
768
55%
1038
April1st to 15thNight
60%
677
35%
1936
22%
677
71%
677
52%
938
April16th to endNight
61%
540
44%
1800
32%
540
78%
540
63%
685
May1st to 15thNight
64%
539
38%
1643
26%
539
76%
539
67%
655
May16th to endNight
70%
561
43%
1684
32%
561
79%
561
71%
674
June1st to 15thNight
78%
540
35%
1620
29%
540
80%
540
66%
685
June16th to endNight
81%
540
28%
1620
25%
540
82%
540
55%
761
July1st to 15thNight
79%
510
15%
1530
13%
510
79%
510
36%
880
July16th to endNight
79%
564
12%
1593
11%
531
78%
531
25%
1059
August1st to 15thNight
85%
539
21%
1611
21%
536
85%
536
34%
943
August16th to endNight
80%
582
26%
1884
27%
582
80%
582
34%
1073
September1st to 15thNight
73%
700
25%
1925
21%
700
74%
700
37%
1178
September16th to endNight
82%
656
39%
1815
30%
656
87%
656
63%
866
October1st to 15thNight
76%
660
39%
1925
30%
660
83%
660
63%
866
October16th to endNight
81%
704
42%
2112
35%
704
86%
704
67%
907
November1st to 15thNight
74%
700
43%
2100
33%
700
83%
700
64%
888
November16th to endNight
66%
720
39%
2256
34%
720
73%
720
49%
1073
December1st to 15thNight
68%
720
36%
2340
35%
720
74%
720
47%
1111
December16th to endNight
62%
768
34%
2496
33%
768
68%
768
41%
1260

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
3313424446%61%
47797
Night
2212323446%65%
47026
TransparencyDay
22%46%11%26%26%
47492
Night
18%47%14%28%26%
46832
SeeingDay
7%12%25%32%17%5%
5368
Night
35%15%33%34%7%
15535

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
212442345%5%61%
1611
16th to endDay
342331335%7%60%
1728
February1st to 15thDay
4312212235%68%
1651
16th to endDay
3323314346%63%
1660
March1st to 15thDay
22133135%46%66%
1980
16th to endDay
2212212245%71%
2112
April1st to 15thDay
1112213346%70%
2012
16th to endDay
111111112480%
2160
May1st to 15thDay
111211123477%
2304
16th to endDay
11111222481%
2429
June1st to 15thDay
11121222477%
2340
16th to endDay
321232445%6%64%
2340
July1st to 15thDay
4425%6%48%8%9%10%34%
2340
16th to endDay
9%7%38%9%5%8%8%7%9%23%
2467
August1st to 15thDay
7%6%36%8%47%7%7%7%32%
2340
16th to endDay
5%425%6%48%7%7%9%40%
2315
September1st to 15thDay
7%425%6%47%6%5%6%42%
1922
16th to endDay
42133245%46%62%
1815
October1st to 15thDay
2112212346%71%
1703
16th to endDay
112212235%75%
1760
November1st to 15thDay
111212235%75%
1759
16th to endDay
3312223235%70%
1701
December1st to 15thDay
431241335%7%62%
1620
16th to endDay
331332235%8%60%
1728
January1st to 15thNight
2213313445%66%
2327
16th to endNight
5%31343445%6%57%
2496
February1st to 15thNight
2212323346%67%
2200
16th to endNight
121332435%5%64%
1814
March1st to 15thNight
1213321246%69%
1980
16th to endNight
121222333471%
2112
April1st to 15thNight
121232333470%
1936
16th to endNight
1111122381%
1800
May1st to 15thNight
111346%78%
1643
16th to endNight
111122383%
1684
June1st to 15thNight
21111112479%
1620
16th to endNight
211132245%6%67%
1620
July1st to 15thNight
23245%35%7%9%12%44%
1620
16th to endNight
3325%5%47%8%10%14%32%
1701
August1st to 15thNight
3223336%7%7%10%49%
1620
16th to endNight
5%3235%25%5%6%9%48%
1884
September1st to 15thNight
5%4244245%5%10%49%
1925
16th to endNight
2211212346%72%
1815
October1st to 15thNight
111221234475%
1925
16th to endNight
1121122478%
2112
November1st to 15thNight
112211235%76%
2100
16th to endNight
3313322335%68%
2256
December1st to 15thNight
4212223446%65%
2340
16th to endNight
332432345%6%60%
2496

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
23%36%12%29%25%
1612
16th to endDay
24%35%16%27%23%
1728
February1st to 15thDay
20%2313%30%29%
1651
16th to endDay
23%2413%30%26%
1660
March1st to 15thDay
19%337%36%28%
1980
16th to endDay
16%239%37%29%
2112
April1st to 15thDay
15%238%40%29%
2012
16th to endDay
10%128%30%46%
2160
May1st to 15thDay
11%138%29%44%
2304
16th to endDay
9%227%32%45%
2432
June1st to 15thDay
11%225%25%52%
2340
16th to endDay
20%35%8%21%39%
2340
July1st to 15thDay
36%13%14%13%12%8%
2201
16th to endDay
51%15%16%10%4
2312
August1st to 15thDay
45%10%11%14%14%3
2325
16th to endDay
36%10%14%15%14%8%
2315
September1st to 15thDay
38%7%11%15%17%9%
1922
16th to endDay
22%38%13%30%21%
1815
October1st to 15thDay
14%46%13%30%30%
1703
16th to endDay
12%2411%31%37%
1760
November1st to 15thDay
11%2411%38%30%
1759
16th to endDay
18%2312%29%32%
1701
December1st to 15thDay
22%35%15%33%19%
1620
16th to endDay
22%28%18%31%15%
1728
January1st to 15thNight
19%35%12%31%26%
2327
16th to endNight
26%45%16%28%18%
2496
February1st to 15thNight
17%35%15%26%31%
2211
16th to endNight
20%35%14%32%23%
1814
March1st to 15thNight
17%2411%31%33%
1980
16th to endNight
17%2410%36%28%
2112
April1st to 15thNight
17%3310%40%24%
1936
16th to endNight
9%129%30%45%
1800
May1st to 15thNight
8%2410%33%41%
1644
16th to endNight
7%238%35%42%
1685
June1st to 15thNight
11%12427%51%
1620
16th to endNight
15%45%9%22%41%
1620
July1st to 15thNight
25%10%23%17%13%10%
1530
16th to endNight
35%14%28%15%41
1593
August1st to 15thNight
25%12%15%21%20%4
1611
16th to endNight
28%8%17%17%18%9%
1884
September1st to 15thNight
30%8%13%19%20%8%
1925
16th to endNight
13%37%16%37%21%
1815
October1st to 15thNight
12%37%18%29%28%
1925
16th to endNight
11%2413%28%39%
2112
November1st to 15thNight
11%2418%33%30%
2100
16th to endNight
20%2312%28%32%
2256
December1st to 15thNight
19%35%15%34%20%
2340
16th to endNight
24%48%18%27%17%
2496

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
8%21%22%37%10%
90
16th to endDay
5%14%23%38%12%5%
96
February1st to 15thDay
9%15%24%31%16%3
166
16th to endDay
10%33%25%22%7%
238
March1st to 15thDay
8%22%32%19%12%4
270
16th to endDay
5%29%29%20%9%5%
288
April1st to 15thDay
7%21%36%23%8%2
269
16th to endDay
7%23%39%18%9%1
270
May1st to 15thDay
7%19%36%22%10%2
288
16th to endDay
5%15%38%31%7%2
330
June1st to 15thDay
46%41%33%11%3
315
16th to endDay
4125%42%20%4
315
July1st to 15thDay
6%15%48%24%4
305
16th to endDay
12%11%37%26%10%
327
August1st to 15thDay
10%9%33%32%13%
315
16th to endDay
6%18%38%34%11%
332
September1st to 15thDay
9%116%41%24%5%
294
16th to endDay
8%7%20%34%22%6%
255
October1st to 15thDay
39%27%31%20%8%
143
16th to endDay
4222%35%31%4
96
November1st to 15thDay
5%17%22%37%12%4
90
16th to endDay
5%25%22%32%14%
90
December1st to 15thDay
7%8%22%30%30%1
90
16th to endDay
12%17%27%32%9%1
96
January1st to 15thNight
3318%40%28%5%
720
16th to endNight
7%6%18%38%25%3
768
February1st to 15thNight
36%19%36%28%4
704
16th to endNight
210%24%40%18%2
632
March1st to 15thNight
39%23%33%25%3
720
16th to endNight
27%19%35%29%4
768
April1st to 15thNight
29%23%41%20%2
677
16th to endNight
210%24%39%19%3
540
May1st to 15thNight
16%26%35%27%2
540
16th to endNight
420%39%31%2
563
June1st to 15thNight
3212%47%31%2
540
16th to endNight
28%34%47%5%
540
July1st to 15thNight
3425%56%10%
510
16th to endNight
5%218%54%18%
564
August1st to 15thNight
3214%57%22%
539
16th to endNight
7%315%52%19%
582
September1st to 15thNight
6%17%21%48%14%
700
16th to endNight
219%32%43%10%
656
October1st to 15thNight
1315%35%36%7%
660
16th to endNight
1211%33%40%9%
704
November1st to 15thNight
26%14%33%36%8%
700
16th to endNight
5%7%15%34%29%7%
720
December1st to 15thNight
6%7%14%38%27%6%
720
16th to endNight
5%7%17%40%22%6%
768
Page generated at 2017-09-11 16:35:31. Version ac04

Copyright 2017 A. Danko


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