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 2018-02-14.

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%
15864
23%
48744
18%
15821
55%
15821
28%
30082

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%
780
22%
2522
11%
776
39%
776
19%
1626
January16th to endNight
30%
832
24%
2554
13%
832
41%
832
21%
1662
February1st to 15thNight
28%
760
21%
2280
10%
757
38%
757
23%
1471
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%
539
19%
1766
22%
536
77%
536
32%
1042
August16th to endNight
70%
573
21%
1910
25%
573
71%
573
26%
1203
September1st to 15thNight
63%
621
20%
1881
19%
621
65%
621
30%
1169
September16th to endNight
62%
717
30%
1980
24%
717
65%
717
36%
1175
October1st to 15thNight
57%
720
34%
1980
26%
720
63%
720
38%
1170
October16th to endNight
52%
768
34%
2350
29%
768
60%
768
34%
1331
November1st to 15thNight
49%
760
27%
2471
24%
760
57%
760
31%
1405
November16th to endNight
42%
780
29%
2535
21%
780
54%
780
28%
1487
December1st to 15thNight
34%
780
23%
2535
14%
780
45%
780
21%
1627
December16th to endNight
30%
832
19%
2704
14%
832
38%
832
18%
1845

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%40%
49253
Night
12%5%2442445%7%45%
48942
TransparencyDay
42%5%10%20%16%3
48954
Night
38%410%21%19%5%
48745
SeeingDay
16%8%19%21%20%12%
5655
Night
15%8%20%27%22%4
15866

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
20%8%15%413345%39%
1746
16th to endDay
19%5%24313345%44%
2018
February1st to 15thDay
20%9%35%324335%38%
1883
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%7%6%8%7%8%9%33%
2180
16th to endDay
10%6%35%7%47%7%6%8%30%
2292
September1st to 15thDay
13%5%246%46%5%6%8%36%
2067
16th to endDay
10%5%245%3445%7%47%
1980
October1st to 15thDay
10%414434345%52%
1980
16th to endDay
11%5%13323335%55%
1872
November1st to 15thDay
13%5%14323335%52%
1717
16th to endDay
14%5%24423346%47%
1755
December1st to 15thDay
19%7%36%5%23445%37%
1755
16th to endDay
24%8%25%5%13246%34%
1872
January1st to 15thNight
18%6%35%423336%41%
2522
16th to endNight
16%8%25%42434442%
2554
February1st to 15thNight
19%8%2431335%6%42%
2271
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%9%10%45%
1777
16th to endNight
8%5%25%5%45%5%6%8%41%
1910
September1st to 15thNight
8%426%5%25%45%8%45%
1881
16th to endNight
8%425%42345%8%50%
1980
October1st to 15thNight
10%42432344455%
1980
16th to endNight
13%5%13312335%56%
2350
November1st to 15thNight
11%5%23323436%52%
2471
16th to endNight
14%6%2441334450%
2535
December1st to 15thNight
16%6%245%33447%41%
2535
16th to endNight
21%8%34423446%35%
2704

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
47%26%18%20%3
1747
16th to endDay
42%37%22%19%4
2018
February1st to 15thDay
48%36%21%17%2
1885
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
2167
16th to endDay
47%8%12%19%10%2
2292
September1st to 15thDay
43%7%14%17%12%4
2067
16th to endDay
36%5%10%20%21%4
1980
October1st to 15thDay
34%5%6%19%26%7%
1980
16th to endDay
32%3418%30%10%
1872
November1st to 15thDay
35%25%18%29%7%
1717
16th to endDay
38%35%20%26%6%
1755
December1st to 15thDay
49%36%20%16%3
1755
16th to endDay
52%210%18%13%2
1872
January1st to 15thNight
45%37%20%19%3
2522
16th to endNight
45%37%19%19%5%
2554
February1st to 15thNight
43%29%20%18%4
2280
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%10%18%21%16%3
1766
16th to endNight
38%8%14%24%12%2
1910
September1st to 15thNight
35%7%17%17%16%4
1881
16th to endNight
32%49%23%22%7%
1980
October1st to 15thNight
31%46%23%24%9%
1980
16th to endNight
32%2317%30%12%
2350
November1st to 15thNight
34%27%18%24%12%
2471
16th to endNight
37%25%18%27%8%
2535
December1st to 15thNight
44%48%19%19%4
2535
16th to endNight
50%39%18%15%3
2704

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
20%28%31%13%41
135
16th to endDay
20%31%29%11%5%1
144
February1st to 15thDay
30%27%26%14%
130
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%22%29%22%
313
16th to endDay
16%7%25%33%15%
332
September1st to 15thDay
16%310%18%30%20%
315
16th to endDay
14%211%27%34%9%
314
October1st to 15thDay
12%5%27%23%23%7%
315
16th to endDay
15%11%18%29%20%5%
213
November1st to 15thDay
21%9%34%25%8%
135
16th to endDay
11%18%34%22%11%1
135
December1st to 15thDay
25%18%37%10%8%
135
16th to endDay
31%22%32%9%2
144
January1st to 15thNight
22%18%29%22%6%
780
16th to endNight
20%15%30%28%5%
832
February1st to 15thNight
24%15%27%28%4
760
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%
539
16th to endNight
10%7%27%45%9%
573
September1st to 15thNight
11%114%23%39%9%
621
16th to endNight
10%213%29%39%4
717
October1st to 15thNight
13%420%27%30%5%
720
16th to endNight
15%10%18%29%23%2
768
November1st to 15thNight
14%9%21%31%19%3
760
16th to endNight
17%12%23%27%17%1
780
December1st to 15thNight
21%14%23%29%9%
780
16th to endNight
27%13%25%27%6%
832
Page generated at 2018-02-15 09:58:42. Version ac04

Copyright 2018 A. Danko


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