Zomerlust
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Zomerlust clear sky chart from 2005-11-05 to 2017-09-19.

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
27%
14634
12%
46874
7%
14602
34%
14602
16%
33346

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
16%
720
6%
2506
2%
716
21%
716
7%
2022
January16th to endNight
18%
768
10%
2646
5%
768
25%
768
11%
1983
February1st to 15thNight
17%
704
11%
2287
3%
701
26%
701
10%
1746
February16th to endNight
20%
631
13%
1956
6%
631
30%
631
12%
1459
March1st to 15thNight
16%
720
12%
2097
6%
720
24%
720
14%
1584
March16th to endNight
21%
768
16%
2036
7%
768
29%
768
20%
1410
April1st to 15thNight
20%
718
15%
1796
5%
718
27%
718
19%
1334
April16th to endNight
27%
630
17%
1710
7%
630
34%
630
21%
1196
May1st to 15thNight
28%
360
15%
1440
14%
360
36%
360
15%
940
May16th to endNight
27%
375
12%
1497
8%
374
39%
374
18%
960
June1st to 15thNight
32%
360
9%
1440
7%
360
41%
360
14%
957
June16th to endNight
42%
360
8%
1440
10%
360
47%
360
17%
913
July1st to 15thNight
52%
340
13%
1360
18%
340
59%
340
26%
755
July16th to endNight
54%
376
14%
1418
16%
354
59%
354
27%
795
August1st to 15thNight
49%
437
13%
1508
12%
435
54%
435
24%
921
August16th to endNight
45%
702
18%
1848
9%
702
50%
702
35%
1150
September1st to 15thNight
42%
720
14%
1800
6%
720
45%
720
28%
1249
September16th to endNight
42%
673
21%
1836
13%
673
47%
673
31%
1178
October1st to 15thNight
28%
660
18%
1980
10%
660
38%
660
19%
1378
October16th to endNight
23%
704
10%
2202
6%
704
30%
704
13%
1661
November1st to 15thNight
24%
700
16%
2343
10%
700
34%
700
15%
1669
November16th to endNight
18%
720
8%
2520
6%
720
23%
720
9%
1945
December1st to 15thNight
16%
720
7%
2520
3%
720
21%
720
8%
1997
December16th to endNight
12%
768
9%
2688
3%
768
20%
768
8%
2144

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
18%9%36%5%34446%31%
47949
Night
17%10%46%5%34445%32%
47043
Cloud CoverDay
27%8%35%423345%30%
47958
Night
25%9%35%42333431%
47049
TransparencyDay
53%412%19%9%1
47636
Night
53%411%20%9%
46874
SeeingDay
24%12%28%21%9%3
5462
Night
24%12%27%24%9%
14634

By Month

Percentage Cloud Cover NE (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
22%16%6%9%6%3433320%
1432
16th to endDay
15%15%6%9%6%3445%423%
1577
February1st to 15thDay
12%15%412%6%45%345%23%
1575
16th to endDay
17%15%6%8%6%35%345%25%
1516
March1st to 15thDay
17%11%5%8%6%35%445%27%
1850
16th to endDay
15%8%36%5%3435%5%38%
2187
April1st to 15thDay
24%10%46%422335%32%
2152
16th to endDay
21%9%36%424335%35%
2258
May1st to 15thDay
22%8%36%6%24346%32%
2511
16th to endDay
20%6%26%5%3445%6%32%
2618
June1st to 15thDay
22%6%36%5%25%5%5%8%28%
2520
16th to endDay
19%6%25%5%35%6%5%7%32%
2520
July1st to 15thDay
14%6%25%5%35%5%6%8%35%
2520
16th to endDay
13%5%26%5%36%5%6%8%35%
2654
August1st to 15thDay
13%6%26%7%45%5%5%8%34%
2440
16th to endDay
13%4245%35%5%6%8%40%
2342
September1st to 15thDay
17%5%245%24446%39%
2160
16th to endDay
17%5%24323346%44%
1868
October1st to 15thDay
23%8%25%5%23346%32%
1650
16th to endDay
29%10%47%6%2333423%
1669
November1st to 15thDay
16%9%46%5%35%46%6%31%
1514
16th to endDay
24%14%38%6%33245%22%
1440
December1st to 15thDay
20%17%7%9%7%34345%15%
1440
16th to endDay
22%17%7%8%6%3333419%
1536
January1st to 15thNight
19%16%6%9%8%36%44317%
2506
16th to endNight
12%16%6%9%7%34445%25%
2646
February1st to 15thNight
11%15%6%11%8%45%44423%
2285
16th to endNight
15%13%5%8%7%35%445%26%
1956
March1st to 15thNight
19%11%5%8%5%34335%28%
2084
16th to endNight
14%9%36%5%3423441%
2036
April1st to 15thNight
22%9%45%423345%33%
1796
16th to endNight
18%9%36%433246%36%
1710
May1st to 15thNight
22%7%46%423335%36%
1440
16th to endNight
16%7%25%4345%6%6%36%
1495
June1st to 15thNight
19%6%246%3446%8%32%
1440
16th to endNight
16%6%25%5%35%5%5%8%36%
1440
July1st to 15thNight
11%5%1442445%8%47%
1440
16th to endNight
9%5%234345%7%9%45%
1514
August1st to 15thNight
10%5%25%5%345%6%9%40%
1518
16th to endNight
10%325%4245%47%49%
1848
September1st to 15thNight
15%5%25%7%2445%6%40%
1800
16th to endNight
17%5%24322225%49%
1836
October1st to 15thNight
21%8%25%5%33336%35%
1980
16th to endNight
26%10%36%5%33345%26%
2202
November1st to 15thNight
19%9%46%5%3445%6%30%
2343
16th to endNight
23%13%5%8%6%3444423%
2520
December1st to 15thNight
21%16%6%8%6%2345%419%
2520
16th to endNight
22%18%6%8%5%2434420%
2688

Percentage Cloud Cover SE (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
25%16%5%9%5%3433319%
1432
16th to endDay
18%15%6%9%6%4444423%
1577
February1st to 15thDay
14%15%411%7%4433426%
1575
16th to endDay
19%14%6%7%5%3433427%
1516
March1st to 15thDay
35%7%25%5%2333427%
1860
16th to endDay
33%5%2332223435%
2186
April1st to 15thDay
30%9%25%32122434%
2152
16th to endDay
26%8%3432323436%
2258
May1st to 15thDay
40%6%25%5%2332325%
2511
16th to endDay
38%5%1442322427%
2618
June1st to 15thDay
31%5%35%5%24346%28%
2520
16th to endDay
28%42443445%6%31%
2520
July1st to 15thDay
15%5%35%435%5%6%8%37%
2520
16th to endDay
14%6%25%5%36%5%6%8%35%
2654
August1st to 15thDay
32%3145%33345%32%
2440
16th to endDay
31%313323336%38%
2342
September1st to 15thDay
22%5%245%23445%38%
2160
16th to endDay
22%5%24413346%42%
1868
October1st to 15thDay
26%7%25%433346%32%
1650
16th to endDay
32%9%37%5%3333323%
1669
November1st to 15thDay
23%9%35%424445%31%
1514
16th to endDay
30%13%36%5%23235%23%
1440
December1st to 15thDay
26%15%6%9%6%2434416%
1440
16th to endDay
26%17%6%7%5%2323319%
1536
January1st to 15thNight
24%16%6%9%7%35%44315%
2506
16th to endNight
18%15%5%8%6%34335%24%
2646
February1st to 15thNight
15%13%5%9%7%3444327%
2278
16th to endNight
20%12%47%6%3433428%
1956
March1st to 15thNight
38%6%3431422328%
2097
16th to endNight
32%6%2331322238%
2036
April1st to 15thNight
27%8%25%323335%35%
1796
16th to endNight
22%8%34323245%39%
1710
May1st to 15thNight
36%6%3431323331%
1440
16th to endNight
29%5%24314345%33%
1495
June1st to 15thNight
23%5%245%2445%6%33%
1440
16th to endNight
21%5%145%35%446%36%
1440
July1st to 15thNight
11%42442435%7%48%
1440
16th to endNight
9%5%134346%7%8%45%
1514
August1st to 15thNight
24%41442335%6%41%
1518
16th to endNight
25%213313335%45%
1848
September1st to 15thNight
18%5%246%23445%39%
1800
16th to endNight
22%41341223448%
1836
October1st to 15thNight
26%7%25%42333435%
1980
16th to endNight
30%9%35%5%3333426%
2202
November1st to 15thNight
32%8%3442323429%
2343
16th to endNight
35%10%46%42332323%
2520
December1st to 15thNight
29%14%5%6%5%3344318%
2520
16th to endNight
30%16%5%6%5%2323318%
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
68%29%13%5%
1433
16th to endDay
62%410%14%8%
1577
February1st to 15thDay
63%211%16%4
1577
16th to endDay
61%210%13%9%1
1516
March1st to 15thDay
59%311%16%7%1
1860
16th to endDay
47%39%19%15%5%
2187
April1st to 15thDay
55%27%18%12%2
2152
16th to endDay
52%36%20%13%3
2258
May1st to 15thDay
53%37%19%13%1
2511
16th to endDay
51%411%19%11%1
2622
June1st to 15thDay
53%5%11%20%8%
2520
16th to endDay
49%5%13%20%9%
2520
July1st to 15thDay
41%6%15%25%11%
2371
16th to endDay
45%6%17%21%8%
2487
August1st to 15thDay
46%5%17%22%8%
2426
16th to endDay
39%417%28%9%
2342
September1st to 15thDay
44%413%26%11%
2160
16th to endDay
40%415%30%8%
1868
October1st to 15thDay
52%314%18%10%
1650
16th to endDay
64%311%14%5%
1669
November1st to 15thDay
50%415%20%8%
1514
16th to endDay
64%312%12%6%
1440
December1st to 15thDay
70%411%11%1
1440
16th to endDay
69%310%11%5%
1536
January1st to 15thNight
69%310%11%4
2506
16th to endNight
61%39%17%7%
2646
February1st to 15thNight
62%39%17%6%
2287
16th to endNight
58%49%18%9%
1956
March1st to 15thNight
59%38%19%7%1
2097
16th to endNight
47%38%20%16%4
2036
April1st to 15thNight
53%36%19%15%1
1796
16th to endNight
49%38%19%16%3
1710
May1st to 15thNight
50%36%20%15%3
1440
16th to endNight
46%5%11%21%12%1
1497
June1st to 15thNight
49%5%11%24%7%1
1440
16th to endNight
44%6%12%21%14%
1440
July1st to 15thNight
34%5%14%29%15%
1360
16th to endNight
33%7%16%28%14%
1418
August1st to 15thNight
38%7%18%25%10%
1508
16th to endNight
33%5%16%33%10%
1848
September1st to 15thNight
43%5%12%25%12%
1800
16th to endNight
40%211%35%8%
1836
October1st to 15thNight
50%310%23%11%
1980
16th to endNight
58%413%17%5%
2202
November1st to 15thNight
53%412%17%9%
2343
16th to endNight
63%411%16%3
2520
December1st to 15thNight
66%411%14%3
2520
16th to endNight
67%39%12%5%
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
33%23%21%16%5%
60
16th to endDay
35%16%35%5%7%
71
February1st to 15thDay
31%24%36%7%
90
16th to endDay
33%21%25%16%4
175
March1st to 15thDay
25%18%33%16%5%
270
16th to endDay
23%18%29%17%8%2
288
April1st to 15thDay
32%23%23%15%5%
270
16th to endDay
26%18%27%17%9%1
270
May1st to 15thDay
31%12%28%16%6%3
288
16th to endDay
25%12%32%17%8%2
331
June1st to 15thDay
27%9%34%20%5%1
315
16th to endDay
19%11%32%23%10%2
315
July1st to 15thDay
16%7%30%28%11%4
305
16th to endDay
15%432%28%15%4
326
August1st to 15thDay
14%6%23%35%12%6%
313
16th to endDay
15%5%27%26%16%8%
332
September1st to 15thDay
20%9%22%23%13%10%
315
16th to endDay
18%10%25%19%18%7%
266
October1st to 15thDay
25%12%24%23%11%1
255
16th to endDay
34%15%25%17%7%
255
November1st to 15thDay
22%10%31%25%8%1
168
16th to endDay
31%18%33%15%1
60
December1st to 15thDay
28%13%45%11%1
60
16th to endDay
37%26%32%3
64
January1st to 15thNight
30%14%30%20%4
720
16th to endNight
22%14%32%23%5%
768
February1st to 15thNight
19%20%33%21%5%
704
16th to endNight
25%18%29%21%5%
631
March1st to 15thNight
28%15%31%21%3
720
16th to endNight
22%17%29%22%8%
768
April1st to 15thNight
30%16%26%21%5%
718
16th to endNight
25%16%26%24%6%
630
May1st to 15thNight
27%10%24%28%8%1
360
16th to endNight
20%10%31%26%10%
375
June1st to 15thNight
20%10%28%30%8%
360
16th to endNight
17%6%25%36%12%1
360
July1st to 15thNight
10%325%40%18%
340
16th to endNight
10%326%40%16%1
376
August1st to 15thNight
13%419%40%19%2
437
16th to endNight
12%5%23%34%21%2
702
September1st to 15thNight
19%5%25%28%18%2
720
16th to endNight
21%5%24%25%20%2
673
October1st to 15thNight
26%13%24%24%10%1
660
16th to endNight
31%12%25%22%6%
704
November1st to 15thNight
26%12%29%20%10%1
700
16th to endNight
33%17%21%18%7%
720
December1st to 15thNight
29%17%28%20%3
720
16th to endNight
33%14%31%14%4
768
Page generated at 2017-09-20 04:49:46. Version ac04

Copyright 2017 A. Danko


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