Ballauer Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ballauer Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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
51%
15888
30%
47833
20%
15843
60%
15843
41%
25672

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
40%
897
31%
2327
13%
895
50%
895
42%
1334
January16th to endNight
40%
960
35%
2496
14%
960
53%
960
43%
1407
February1st to 15thNight
36%
725
29%
2129
13%
719
48%
719
35%
1200
February16th to endNight
27%
632
31%
1894
10%
632
44%
632
36%
1041
March1st to 15thNight
34%
552
28%
1992
16%
552
48%
552
28%
1115
March16th to endNight
36%
576
25%
2112
16%
576
49%
576
31%
1110
April1st to 15thNight
31%
539
24%
1977
12%
539
50%
539
32%
1024
April16th to endNight
35%
540
29%
1689
16%
540
52%
540
38%
921
May1st to 15thNight
39%
540
24%
1620
14%
540
53%
540
34%
941
May16th to endNight
51%
562
26%
1684
21%
561
64%
561
40%
928
June1st to 15thNight
72%
540
24%
1620
23%
540
78%
540
53%
790
June16th to endNight
75%
540
26%
1620
30%
540
78%
540
47%
830
July1st to 15thNight
79%
510
24%
1530
27%
510
81%
510
47%
794
July16th to endNight
87%
564
32%
1594
38%
531
88%
531
57%
743
August1st to 15thNight
90%
539
36%
1610
43%
536
91%
536
60%
734
August16th to endNight
79%
573
30%
1909
36%
573
80%
573
40%
999
September1st to 15thNight
73%
540
24%
1980
29%
540
75%
540
34%
1038
September16th to endNight
72%
537
33%
1980
34%
537
77%
537
38%
989
October1st to 15thNight
61%
592
35%
2032
28%
592
68%
592
44%
981
October16th to endNight
51%
768
38%
2304
22%
768
62%
768
50%
1118
November1st to 15thNight
50%
817
29%
2337
15%
817
59%
817
43%
1271
November16th to endNight
40%
975
36%
2535
16%
975
52%
975
43%
1444
December1st to 15thNight
40%
910
31%
2366
14%
910
51%
910
39%
1401
December16th to endNight
38%
960
29%
2496
13%
960
47%
960
36%
1519

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
8%3133233419%47%
48604
Night
7%3122122320%51%
48033
Cloud CoverDay
9%41332345%7%54%
48602
Night
8%313323347%59%
48033
TransparencyDay
29%5%11%22%22%8%
48302
Night
25%49%22%25%11%
47838
SeeingDay
10%420%30%26%7%
5803
Night
10%6%28%36%17%1
15892

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
9%4122112220%49%
1611
16th to endDay
7%3123123221%50%
1728
February1st to 15thDay
9%3132122321%46%
1738
16th to endDay
11%3113112220%49%
1580
March1st to 15thDay
15%4133222321%40%
1967
16th to endDay
8%4123123321%46%
2112
April1st to 15thDay
8%3134222421%46%
1971
16th to endDay
9%3133122421%45%
2265
May1st to 15thDay
10%4143233421%41%
2331
16th to endDay
8%41432345%23%36%
2430
June1st to 15thDay
32342345%24%45%
2340
16th to endDay
3123234423%49%
2340
July1st to 15thDay
42332445%17%51%
2340
16th to endDay
311242346%25%44%
2466
August1st to 15thDay
2123245%5%16%53%
2340
16th to endDay
5%4233345%6%16%44%
2288
September1st to 15thDay
10%31342345%16%46%
1980
16th to endDay
9%3123334415%49%
1980
October1st to 15thDay
8%2133133312%54%
1914
16th to endDay
7%222112212%64%
1920
November1st to 15thDay
9%2232222418%49%
1849
16th to endDay
9%322111219%53%
1755
December1st to 15thDay
13%5%242122320%41%
1631
16th to endDay
12%4123123321%42%
1728
January1st to 15thNight
8%3132121221%49%
2327
16th to endNight
7%2121112221%55%
2496
February1st to 15thNight
10%4132122320%48%
2123
16th to endNight
9%322121320%51%
1894
March1st to 15thNight
12%4133123320%43%
1992
16th to endNight
6%2123211321%52%
2112
April1st to 15thNight
6%3122232422%48%
1977
16th to endNight
10%222112321%49%
1689
May1st to 15thNight
7%4123223322%46%
1619
16th to endNight
421222325%25%47%
1683
June1st to 15thNight
2111123325%54%
1620
16th to endNight
11111223424%55%
1620
July1st to 15thNight
3222123418%57%
1620
16th to endNight
212112425%55%
1702
August1st to 15thNight
112133418%63%
1620
16th to endNight
431342346%17%48%
1909
September1st to 15thNight
8%3123243415%50%
1980
16th to endNight
7%3133235%415%51%
1980
October1st to 15thNight
7%3123123314%56%
2032
16th to endNight
6%1122122312%64%
2304
November1st to 15thNight
5%332133317%53%
2337
16th to endNight
9%3132122319%51%
2535
December1st to 15thNight
11%4122212321%44%
2366
16th to endNight
10%4133222322%43%
2496

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
12%5%2232223458%
1611
16th to endDay
11%412223335%57%
1728
February1st to 15thDay
12%5%13212336%55%
1738
16th to endDay
15%5%1231233457%
1580
March1st to 15thDay
15%424423346%49%
1967
16th to endDay
12%5%23423346%52%
2110
April1st to 15thDay
9%32442325%6%53%
1971
16th to endDay
11%42332336%6%52%
2265
May1st to 15thDay
12%425%42445%6%47%
2331
16th to endDay
11%5%24425%5%6%8%43%
2430
June1st to 15thDay
4314425%46%8%54%
2340
16th to endDay
6%21443445%8%54%
2340
July1st to 15thDay
6%314425%5%6%10%49%
2340
16th to endDay
4113435%5%7%10%52%
2466
August1st to 15thDay
31124345%6%8%58%
2340
16th to endDay
6%423425%5%6%8%49%
2288
September1st to 15thDay
10%324425%45%7%49%
1980
16th to endDay
9%31232435%7%54%
1980
October1st to 15thDay
8%314323435%58%
1914
16th to endDay
7%21321122370%
1920
November1st to 15thDay
10%313322345%58%
1849
16th to endDay
10%41221223464%
1755
December1st to 15thDay
13%5%23312245%52%
1631
16th to endDay
15%5%23213345%51%
1728
January1st to 15thNight
10%413312225%61%
2327
16th to endNight
10%312212245%61%
2496
February1st to 15thNight
11%5%2331223458%
2123
16th to endNight
12%412222236%58%
1894
March1st to 15thNight
13%413423445%51%
1992
16th to endNight
9%414322246%57%
2112
April1st to 15thNight
7%31342445%6%55%
1977
16th to endNight
11%312312346%57%
1689
May1st to 15thNight
10%423323448%52%
1619
16th to endNight
6%21332445%8%56%
1683
June1st to 15thNight
211222345%10%64%
1620
16th to endNight
311222435%9%61%
1620
July1st to 15thNight
5%21232445%11%57%
1620
16th to endNight
211231335%12%63%
1702
August1st to 15thNight
2121345%8%68%
1620
16th to endNight
431431446%11%53%
1909
September1st to 15thNight
9%41333336%6%54%
1980
16th to endNight
7%31432345%6%57%
1980
October1st to 15thNight
8%313212336%62%
2032
16th to endNight
8%21221223469%
2304
November1st to 15thNight
6%413314345%62%
2337
16th to endNight
10%413312235%61%
2535
December1st to 15thNight
11%423322346%55%
2366
16th to endNight
12%424323336%53%
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
31%36%20%28%10%
1612
16th to endDay
29%36%19%29%11%
1728
February1st to 15thDay
30%47%21%25%11%
1739
16th to endDay
31%26%19%24%14%
1580
March1st to 15thDay
37%48%17%21%10%
1967
16th to endDay
34%410%20%21%8%
2112
April1st to 15thDay
31%411%22%17%12%
1971
16th to endDay
31%410%21%23%8%
2265
May1st to 15thDay
36%6%9%18%20%8%
2331
16th to endDay
36%7%13%20%18%2
2434
June1st to 15thDay
25%6%15%26%22%3
2340
16th to endDay
27%6%12%27%20%5%
2340
July1st to 15thDay
28%6%16%28%16%2
2201
16th to endDay
22%8%17%29%19%1
2311
August1st to 15thDay
20%7%14%28%24%3
2326
16th to endDay
28%8%15%29%14%2
2288
September1st to 15thDay
31%6%12%21%20%7%
1980
16th to endDay
27%5%8%24%23%9%
1980
October1st to 15thDay
27%411%21%20%14%
1914
16th to endDay
20%37%19%30%19%
1920
November1st to 15thDay
28%410%21%24%11%
1849
16th to endDay
25%37%19%30%14%
1755
December1st to 15thDay
34%38%21%26%6%
1631
16th to endDay
34%37%20%25%8%
1728
January1st to 15thNight
28%26%17%30%14%
2327
16th to endNight
26%26%19%28%16%
2496
February1st to 15thNight
30%36%17%24%17%
2133
16th to endNight
29%37%20%24%15%
1894
March1st to 15thNight
33%47%17%22%14%
1992
16th to endNight
28%5%12%21%25%6%
2112
April1st to 15thNight
27%5%11%19%19%15%
1977
16th to endNight
28%410%20%25%10%
1689
May1st to 15thNight
31%5%12%18%21%10%
1620
16th to endNight
24%7%16%24%21%4
1685
June1st to 15thNight
15%6%14%32%22%7%
1620
16th to endNight
20%6%12%27%26%6%
1620
July1st to 15thNight
21%5%12%33%22%4
1530
16th to endNight
14%5%18%33%24%3
1594
August1st to 15thNight
12%5%14%30%30%6%
1610
16th to endNight
24%7%12%29%21%4
1909
September1st to 15thNight
28%5%11%23%21%9%
1980
16th to endNight
25%5%8%22%25%12%
1980
October1st to 15thNight
23%312%23%20%17%
2032
16th to endNight
19%35%16%32%22%
2304
November1st to 15thNight
24%47%24%23%15%
2337
16th to endNight
27%25%16%32%15%
2535
December1st to 15thNight
30%38%22%24%10%
2366
16th to endNight
33%37%20%23%11%
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
21%11%27%31%7%1
90
16th to endDay
10%9%50%18%10%1
96
February1st to 15thDay
6%10%42%33%7%
90
16th to endDay
16%13%44%18%7%
81
March1st to 15thDay
24%14%31%20%10%
90
16th to endDay
6%16%37%28%9%2
96
April1st to 15thDay
14%20%22%26%16%
90
16th to endDay
14%11%41%22%10%
375
May1st to 15thDay
14%10%36%28%7%1
468
16th to endDay
17%5%31%29%13%3
517
June1st to 15thDay
6%115%43%26%7%
495
16th to endDay
5%112%36%33%9%
495
July1st to 15thDay
49%39%36%9%
475
16th to endDay
3426%48%17%
515
August1st to 15thDay
45%27%48%12%
493
16th to endDay
10%17%33%34%11%
328
September1st to 15thDay
25%18%49%23%
135
16th to endDay
11%324%42%18%
135
October1st to 15thDay
314%35%37%8%
135
16th to endDay
13%424%32%22%2
144
November1st to 15thDay
22%427%27%13%4
135
16th to endDay
18%9%37%20%11%2
135
December1st to 15thDay
22%5%26%27%15%2
94
16th to endDay
11%15%44%19%8%
96
January1st to 15thNight
12%9%33%34%9%
900
16th to endNight
12%10%35%35%6%
960
February1st to 15thNight
14%10%37%32%5%
725
16th to endNight
13%13%43%26%2
632
March1st to 15thNight
15%9%39%30%5%
552
16th to endNight
9%11%41%31%6%
576
April1st to 15thNight
9%11%45%28%5%
539
16th to endNight
12%7%43%30%6%
540
May1st to 15thNight
11%7%37%33%7%1
540
16th to endNight
6%335%35%17%1
563
June1st to 15thNight
3121%49%23%2
540
16th to endNight
315%49%28%2
540
July1st to 15thNight
410%48%32%3
510
16th to endNight
25%43%44%3
564
August1st to 15thNight
2340%48%3
539
16th to endNight
6%5%43%39%5%
573
September1st to 15thNight
11%7%38%37%4
540
16th to endNight
8%10%40%35%3
537
October1st to 15thNight
9%322%37%24%2
592
16th to endNight
9%6%31%34%17%1
768
November1st to 15thNight
7%432%37%16%1
817
16th to endNight
12%8%36%28%12%1
975
December1st to 15thNight
15%8%33%34%7%
910
16th to endNight
15%8%35%33%7%
960
Page generated at 2017-12-03 10:16:35. Version ac04

Copyright 2017 A. Danko


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