Von Braun Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Von Braun Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
49%
15144
23%
46511
17%
15101
55%
15101
28%
28728

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
26%
720
23%
2327
11%
716
39%
716
19%
1509
January16th to endNight
29%
768
23%
2358
12%
768
39%
768
20%
1565
February1st to 15thNight
29%
704
22%
2112
10%
701
39%
701
24%
1344
February16th to endNight
28%
631
22%
1893
11%
631
36%
631
21%
1265
March1st to 15thNight
31%
720
18%
2148
12%
720
35%
720
21%
1431
March16th to endNight
37%
717
21%
2061
13%
717
43%
717
27%
1314
April1st to 15thNight
41%
539
24%
1797
15%
539
53%
539
31%
1013
April16th to endNight
48%
540
26%
1788
20%
540
58%
540
32%
994
May1st to 15thNight
54%
540
21%
1620
15%
540
60%
540
29%
1015
May16th to endNight
67%
561
21%
1683
17%
561
69%
561
34%
1009
June1st to 15thNight
68%
540
19%
1620
16%
540
71%
540
35%
971
June16th to endNight
79%
540
20%
1571
17%
540
80%
540
39%
907
July1st to 15thNight
72%
510
15%
1500
14%
510
73%
510
29%
968
July16th to endNight
77%
564
19%
1595
18%
531
78%
531
32%
982
August1st to 15thNight
77%
527
19%
1728
22%
524
77%
524
32%
1014
August16th to endNight
70%
525
21%
1750
24%
525
71%
525
26%
1094
September1st to 15thNight
64%
569
21%
1724
20%
569
66%
569
30%
1070
September16th to endNight
60%
657
28%
1815
22%
657
63%
657
34%
1100
October1st to 15thNight
56%
660
35%
1815
27%
660
62%
660
38%
1077
October16th to endNight
52%
704
33%
2154
28%
704
59%
704
33%
1229
November1st to 15thNight
49%
700
29%
2276
25%
700
58%
700
33%
1263
November16th to endNight
39%
720
27%
2340
19%
720
52%
720
26%
1397
December1st to 15thNight
34%
720
22%
2340
15%
720
44%
720
21%
1504
December16th to endNight
30%
768
20%
2496
15%
768
38%
768
18%
1693

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
13%5%25%5%35%5%5%7%39%
47383
Night
12%5%2442445%7%45%
46709
TransparencyDay
42%5%10%20%16%3
47084
Night
38%410%20%19%5%
46512
SeeingDay
16%8%18%21%20%13%
5025
Night
15%8%20%27%22%4
15146

By Month

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
21%8%25%413345%38%
1611
16th to endDay
20%5%24313446%43%
1863
February1st to 15thDay
18%9%35%324335%39%
1750
16th to endDay
19%6%46%424346%37%
1580
March1st to 15thDay
18%8%45%433445%37%
1812
16th to endDay
15%6%345%35%5%5%7%38%
2171
April1st to 15thDay
14%5%235%3435%7%43%
2151
16th to endDay
11%6%35%6%335%5%8%42%
2171
May1st to 15thDay
13%5%24435%5%5%7%40%
2331
16th to endDay
10%6%35%5%35%45%8%40%
2431
June1st to 15thDay
7%4245%47%7%8%10%35%
2340
16th to endDay
5%425%5%36%6%7%11%41%
2344
July1st to 15thDay
9%5%35%7%46%7%8%10%30%
2340
16th to endDay
7%425%6%5%8%8%8%10%31%
2465
August1st to 15thDay
5%416%6%6%8%7%9%9%34%
2132
16th to endDay
10%6%35%7%47%8%6%8%30%
2100
September1st to 15thDay
11%5%25%6%46%6%7%9%35%
1895
16th to endDay
11%5%245%3445%7%46%
1815
October1st to 15thDay
10%414434345%52%
1815
16th to endDay
11%5%14323335%54%
1716
November1st to 15thDay
12%414323335%54%
1582
16th to endDay
15%5%24423346%46%
1620
December1st to 15thDay
20%6%36%5%2345%5%36%
1620
16th to endDay
23%8%25%5%13346%35%
1728
January1st to 15thNight
18%6%25%423336%41%
2327
16th to endNight
17%8%25%425%34440%
2358
February1st to 15thNight
17%7%2431335%6%43%
2103
16th to endNight
18%6%25%5%2434441%
1893
March1st to 15thNight
17%6%25%43445%6%38%
2148
16th to endNight
13%6%35%334446%45%
2061
April1st to 15thNight
13%32342335%10%48%
1797
16th to endNight
10%424323347%52%
1788
May1st to 15thNight
11%424425%5%5%8%46%
1619
16th to endNight
6%3235%26%6%6%9%47%
1682
June1st to 15thNight
5%325%5%25%5%6%11%45%
1620
16th to endNight
4214445%5%6%11%49%
1571
July1st to 15thNight
8%435%5%46%6%6%9%40%
1590
16th to endNight
5%3135%27%6%9%13%40%
1703
August1st to 15thNight
5%324435%6%8%10%45%
1739
16th to endNight
8%425%5%445%6%8%42%
1750
September1st to 15thNight
7%436%5%25%45%8%45%
1724
16th to endNight
8%426%42445%8%48%
1815
October1st to 15thNight
10%5%2432344455%
1815
16th to endNight
13%5%13312325%56%
2154
November1st to 15thNight
11%5%22323436%54%
2276
16th to endNight
14%6%2441324449%
2340
December1st to 15thNight
17%6%245%23447%41%
2340
16th to endNight
22%8%34423345%36%
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
48%26%17%20%3
1612
16th to endDay
43%37%23%18%3
1863
February1st to 15thDay
47%36%21%17%2
1752
16th to endDay
48%37%18%17%3
1580
March1st to 15thDay
49%38%16%17%5%
1812
16th to endDay
44%5%13%21%13%1
2172
April1st to 15thDay
40%5%9%22%17%5%
2151
16th to endDay
39%49%24%18%3
2171
May1st to 15thDay
42%5%11%22%14%3
2331
16th to endDay
41%6%12%24%13%1
2435
June1st to 15thDay
39%8%15%22%13%1
2340
16th to endDay
34%6%15%21%17%3
2344
July1st to 15thDay
42%9%16%19%8%3
2201
16th to endDay
42%9%17%21%8%
2310
August1st to 15thDay
40%10%14%17%14%1
2119
16th to endDay
47%8%12%19%10%2
2100
September1st to 15thDay
43%7%14%16%12%5%
1895
16th to endDay
37%5%10%18%22%4
1815
October1st to 15thDay
34%5%6%18%26%8%
1815
16th to endDay
33%3418%30%9%
1716
November1st to 15thDay
34%2419%30%8%
1582
16th to endDay
39%35%20%25%5%
1620
December1st to 15thDay
49%46%19%16%4
1620
16th to endDay
51%210%18%14%2
1728
January1st to 15thNight
45%37%19%20%3
2327
16th to endNight
47%37%18%18%5%
2358
February1st to 15thNight
42%29%20%19%5%
2112
16th to endNight
46%36%22%17%4
1893
March1st to 15thNight
45%48%18%16%6%
2148
16th to endNight
40%312%23%17%1
2061
April1st to 15thNight
33%412%22%20%7%
1797
16th to endNight
32%310%25%22%5%
1788
May1st to 15thNight
37%5%12%19%22%2
1620
16th to endNight
31%7%16%26%15%3
1684
June1st to 15thNight
30%8%16%26%16%1
1620
16th to endNight
28%6%16%24%20%3
1571
July1st to 15thNight
36%8%18%20%11%4
1500
16th to endNight
30%10%18%24%14%1
1595
August1st to 15thNight
29%9%18%21%17%3
1728
16th to endNight
37%8%14%24%12%3
1750
September1st to 15thNight
35%7%18%16%16%5%
1724
16th to endNight
34%48%20%23%8%
1815
October1st to 15thNight
31%46%21%25%10%
1815
16th to endNight
33%2316%30%12%
2154
November1st to 15thNight
32%26%19%25%13%
2276
16th to endNight
39%25%18%26%7%
2340
December1st to 15thNight
44%48%18%19%5%
2340
16th to endNight
50%38%18%15%3
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
24%26%27%13%5%2
90
16th to endDay
20%31%36%7%4
96
February1st to 15thDay
25%35%25%12%1
90
16th to endDay
24%20%39%12%2
81
March1st to 15thDay
26%29%29%11%2
102
16th to endDay
20%12%29%23%12%1
288
April1st to 15thDay
17%13%24%26%15%2
270
16th to endDay
18%7%25%28%15%4
270
May1st to 15thDay
17%9%26%20%15%10%
288
16th to endDay
16%418%28%14%17%
331
June1st to 15thDay
11%210%21%30%24%
315
16th to endDay
10%312%24%23%25%
319
July1st to 15thDay
13%212%20%24%26%
305
16th to endDay
10%418%32%34%
326
August1st to 15thDay
12%12%21%28%23%
297
16th to endDay
17%5%22%36%16%
268
September1st to 15thDay
13%210%17%32%23%
255
16th to endDay
17%312%28%32%6%
254
October1st to 15thDay
12%5%27%23%23%8%
255
16th to endDay
17%7%16%30%22%5%
159
November1st to 15thDay
20%13%30%27%8%
90
16th to endDay
15%22%33%20%7%1
90
December1st to 15thDay
26%20%37%7%6%1
90
16th to endDay
26%26%33%10%4
96
January1st to 15thNight
24%17%29%20%7%
720
16th to endNight
21%15%30%28%4
768
February1st to 15thNight
23%14%28%28%4
704
16th to endNight
23%16%27%27%3
631
March1st to 15thNight
21%14%27%30%5%
720
16th to endNight
17%13%26%27%14%
717
April1st to 15thNight
15%8%31%27%15%1
539
16th to endNight
12%8%26%34%17%1
540
May1st to 15thNight
14%421%30%26%2
540
16th to endNight
7%213%37%33%5%
563
June1st to 15thNight
7%12%28%40%10%
540
16th to endNight
5%7%28%46%11%
540
July1st to 15thNight
10%8%27%38%14%
510
16th to endNight
7%6%19%47%18%
564
August1st to 15thNight
7%5%22%52%11%
527
16th to endNight
10%8%27%45%8%
525
September1st to 15thNight
10%114%23%40%10%
569
16th to endNight
11%214%31%37%2
657
October1st to 15thNight
13%420%26%28%5%
660
16th to endNight
15%9%18%28%24%2
704
November1st to 15thNight
14%10%20%30%20%4
700
16th to endNight
18%13%24%26%15%1
720
December1st to 15thNight
22%14%23%29%9%
720
16th to endNight
27%13%25%26%6%
768
Page generated at 2017-08-13 13:16:22. Version ac04

Copyright 2017 A. Danko


Von Braun Observatory Clear Sky Chart | Charts Home