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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 2020-06-03.

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
69%
19160
35%
57807
28%
19121
76%
19121
49%
28431

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
67%
898
31%
2912
30%
896
73%
896
47%
1404
January16th to endNight
64%
960
36%
3120
32%
960
74%
960
42%
1565
February1st to 15thNight
62%
877
35%
2769
30%
876
74%
876
47%
1323
February16th to endNight
54%
792
38%
2273
29%
792
66%
792
45%
1185
March1st to 15thNight
57%
900
38%
2475
25%
900
69%
900
50%
1261
March16th to endNight
62%
960
37%
2640
23%
960
74%
960
51%
1344
April1st to 15thNight
58%
847
37%
2421
23%
847
71%
847
54%
1150
April16th to endNight
60%
669
44%
2229
33%
669
77%
669
62%
862
May1st to 15thNight
65%
674
38%
2054
27%
674
76%
674
64%
853
May16th to endNight
68%
705
44%
2116
32%
705
78%
705
72%
837
June1st to 15thNight
77%
637
36%
1911
30%
637
79%
637
65%
816
June16th to endNight
81%
630
28%
1890
25%
630
82%
630
56%
880
July1st to 15thNight
77%
600
17%
1800
15%
600
78%
600
35%
1042
July16th to endNight
78%
660
11%
1881
10%
627
78%
627
24%
1271
August1st to 15thNight
85%
620
19%
1854
19%
617
84%
617
33%
1099
August16th to endNight
80%
679
25%
2199
26%
679
80%
679
34%
1251
September1st to 15thNight
75%
840
27%
2310
23%
840
76%
840
39%
1382
September16th to endNight
80%
836
40%
2310
29%
836
86%
836
63%
1094
October1st to 15thNight
75%
840
39%
2450
30%
840
82%
840
63%
1099
October16th to endNight
77%
896
43%
2688
34%
896
85%
896
66%
1154
November1st to 15thNight
74%
880
43%
2640
34%
880
83%
880
61%
1154
November16th to endNight
66%
900
38%
2820
33%
900
73%
900
47%
1372
December1st to 15thNight
65%
900
35%
2925
34%
900
71%
900
43%
1446
December16th to endNight
60%
960
35%
3120
31%
960
68%
960
40%
1587

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%
58598
Night
2213323446%65%
58009
TransparencyDay
23%46%11%27%26%
58293
Night
19%47%14%28%25%
57815
SeeingDay
7%12%25%31%18%5%
8947
Night
45%16%35%32%6%
19172

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
222442345%5%60%
2016
16th to endDay
342331335%6%62%
2160
February1st to 15thDay
4423222345%65%
2076
16th to endDay
3423313346%62%
2080
March1st to 15thDay
3214423446%61%
2475
16th to endDay
2212213346%68%
2640
April1st to 15thDay
1112323346%70%
2517
16th to endDay
111111122479%
2666
May1st to 15thDay
111221223475%
2882
16th to endDay
11111212381%
3053
June1st to 15thDay
21121222475%
2758
16th to endDay
3111323346%66%
2730
July1st to 15thDay
4425%6%48%7%8%9%35%
2730
16th to endDay
8%6%37%9%5%8%9%8%10%23%
2883
August1st to 15thDay
6%6%36%8%47%8%7%8%32%
2680
16th to endDay
4425%6%48%7%6%10%40%
2703
September1st to 15thDay
6%425%6%47%6%6%7%44%
2310
16th to endDay
4213323446%64%
2310
October1st to 15thDay
2112212346%71%
2168
16th to endDay
112212235%75%
2240
November1st to 15thDay
112212346%71%
2209
16th to endDay
3312223335%67%
2127
December1st to 15thDay
5%31242335%7%59%
2025
16th to endDay
342432336%7%59%
2160
January1st to 15thNight
231331345%5%63%
2912
16th to endNight
4313323446%60%
3120
February1st to 15thNight
2212323347%65%
2764
16th to endNight
231342435%5%63%
2273
March1st to 15thNight
221332235%6%65%
2475
16th to endNight
2213333345%66%
2640
April1st to 15thNight
1212223335%71%
2421
16th to endNight
1211122480%
2229
May1st to 15thNight
12112346%76%
2054
16th to endNight
111212383%
2116
June1st to 15thNight
211111113477%
1911
16th to endNight
2112322446%68%
1890
July1st to 15thNight
23246%35%6%8%11%44%
1890
16th to endNight
3326%6%5%7%8%10%15%30%
1989
August1st to 15thNight
3223436%6%7%10%47%
1863
16th to endNight
5%3235%35%5%6%10%48%
2199
September1st to 15thNight
5%3244245%5%10%50%
2310
16th to endNight
2211212346%73%
2310
October1st to 15thNight
11221224376%
2450
16th to endNight
11121123478%
2688
November1st to 15thNight
112212346%72%
2640
16th to endNight
3313323445%65%
2820
December1st to 15thNight
3313324446%62%
2925
16th to endNight
3424323446%60%
3120

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
24%35%11%29%24%
2017
16th to endDay
22%35%16%29%23%
2160
February1st to 15thDay
22%3312%29%28%
2076
16th to endDay
24%2412%27%28%
2080
March1st to 15thDay
23%438%34%25%
2475
16th to endDay
18%2310%37%27%
2640
April1st to 15thDay
16%238%39%29%
2517
16th to endDay
10%138%31%44%
2666
May1st to 15thDay
13%139%28%42%
2882
16th to endDay
10%126%31%47%
3056
June1st to 15thDay
13%126%26%49%
2758
16th to endDay
18%35%8%21%42%
2730
July1st to 15thDay
36%12%13%13%13%9%
2591
16th to endDay
48%16%18%11%4
2728
August1st to 15thDay
44%10%12%14%13%2
2665
16th to endDay
35%10%14%17%13%8%
2703
September1st to 15thDay
35%8%11%16%18%9%
2310
16th to endDay
20%37%14%32%20%
2310
October1st to 15thDay
15%46%12%31%29%
2168
16th to endDay
12%2411%30%38%
2240
November1st to 15thDay
13%2414%36%27%
2209
16th to endDay
20%2413%29%29%
2127
December1st to 15thDay
25%36%15%33%16%
2025
16th to endDay
24%28%17%30%17%
2160
January1st to 15thNight
21%46%12%29%26%
2912
16th to endNight
24%3415%30%20%
3120
February1st to 15thNight
19%35%14%25%31%
2775
16th to endNight
23%35%13%29%25%
2273
March1st to 15thNight
20%25%12%29%29%
2475
16th to endNight
20%2411%35%25%
2640
April1st to 15thNight
16%2311%39%25%
2421
16th to endNight
10%129%31%43%
2229
May1st to 15thNight
10%249%32%40%
2055
16th to endNight
7%139%33%45%
2117
June1st to 15thNight
12%125%27%50%
1911
16th to endNight
15%45%8%22%43%
1890
July1st to 15thNight
27%10%20%16%14%11%
1800
16th to endNight
36%15%27%15%41
1881
August1st to 15thNight
27%12%17%19%19%4
1854
16th to endNight
28%9%18%18%17%8%
2199
September1st to 15thNight
28%7%13%19%22%8%
2310
16th to endNight
13%37%16%37%20%
2310
October1st to 15thNight
12%26%17%31%28%
2450
16th to endNight
11%2413%30%37%
2688
November1st to 15thNight
13%2420%33%25%
2640
16th to endNight
21%2413%29%28%
2820
December1st to 15thNight
22%46%15%33%18%
2925
16th to endNight
25%37%16%27%19%
3120

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
9%16%20%39%14%
225
16th to endDay
5%9%27%39%15%3
240
February1st to 15thDay
9%18%24%27%15%3
321
16th to endDay
11%31%28%22%6%
398
March1st to 15thDay
10%24%33%20%10%2
450
16th to endDay
5%29%32%18%10%3
480
April1st to 15thDay
7%22%35%21%9%3
449
16th to endDay
5%21%36%23%10%3
438
May1st to 15thDay
6%17%33%26%13%3
468
16th to endDay
415%37%28%10%2
522
June1st to 15thDay
46%40%32%13%3
444
16th to endDay
4125%42%21%5%
435
July1st to 15thDay
6%114%46%25%6%
425
16th to endDay
9%9%38%31%10%
455
August1st to 15thDay
9%8%31%33%16%
419
16th to endDay
5%16%38%35%13%
460
September1st to 15thDay
7%214%39%28%7%
435
16th to endDay
6%7%23%34%20%6%
435
October1st to 15thDay
48%29%33%18%6%
293
16th to endDay
27%26%30%26%5%
240
November1st to 15thDay
6%12%23%38%18%1
225
16th to endDay
10%16%16%36%17%2
225
December1st to 15thDay
12%11%26%31%18%
225
16th to endDay
9%19%25%26%15%3
240
January1st to 15thNight
4418%41%26%4
900
16th to endNight
6%5%18%40%25%3
960
February1st to 15thNight
48%20%35%26%4
884
16th to endNight
5%10%25%40%16%2
792
March1st to 15thNight
411%23%36%21%2
900
16th to endNight
38%21%36%26%3
960
April1st to 15thNight
29%25%39%20%2
847
16th to endNight
29%25%39%19%3
669
May1st to 15thNight
25%24%38%26%2
675
16th to endNight
5%22%41%28%1
707
June1st to 15thNight
3214%46%31%2
637
16th to endNight
29%35%46%4
630
July1st to 15thNight
35%26%55%9%
600
16th to endNight
4221%53%16%
660
August1st to 15thNight
3215%58%19%
620
16th to endNight
6%317%53%19%
679
September1st to 15thNight
5%18%21%50%13%
840
16th to endNight
2111%33%41%9%
836
October1st to 15thNight
2315%37%35%6%
840
16th to endNight
2313%33%38%9%
896
November1st to 15thNight
35%13%38%33%6%
880
16th to endNight
6%7%14%36%29%6%
900
December1st to 15thNight
6%6%16%40%25%5%
900
16th to endNight
6%7%19%38%22%5%
960
Page generated at 2020-06-04 00:18:57. Version ac04

Copyright 2020 A. Danko


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