Strohbehn Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Strohbehn 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
37%
15923
18%
46534
10%
15876
44%
15876
26%
30081

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
28%
900
14%
2458
6%
895
36%
895
23%
1717
January16th to endNight
23%
960
16%
2496
5%
960
31%
960
20%
1820
February1st to 15thNight
23%
880
12%
2288
3%
876
28%
876
20%
1695
February16th to endNight
28%
744
19%
2006
6%
744
37%
744
26%
1342
March1st to 15thNight
34%
540
19%
1980
13%
540
44%
540
23%
1185
March16th to endNight
25%
576
13%
2112
8%
576
34%
576
16%
1444
April1st to 15thNight
29%
539
17%
1807
12%
539
38%
539
22%
1160
April16th to endNight
28%
540
18%
1689
10%
540
41%
540
22%
1142
May1st to 15thNight
39%
540
17%
1578
11%
540
45%
540
26%
1035
May16th to endNight
42%
563
17%
1497
7%
561
48%
561
29%
994
June1st to 15thNight
51%
540
14%
1440
6%
540
54%
540
32%
927
June16th to endNight
56%
540
19%
1440
9%
540
60%
540
43%
839
July1st to 15thNight
64%
510
17%
1360
8%
510
67%
510
46%
762
July16th to endNight
75%
564
23%
1534
19%
531
76%
531
49%
804
August1st to 15thNight
66%
527
21%
1575
22%
524
69%
524
37%
902
August16th to endNight
59%
525
21%
1652
21%
525
64%
525
34%
953
September1st to 15thNight
60%
495
26%
1650
24%
495
67%
495
36%
887
September16th to endNight
48%
517
24%
1827
17%
517
60%
517
33%
1009
October1st to 15thNight
37%
660
25%
1980
14%
660
45%
660
32%
1178
October16th to endNight
34%
704
20%
2112
11%
704
42%
704
27%
1318
November1st to 15thNight
35%
799
25%
2325
13%
799
45%
799
31%
1399
November16th to endNight
28%
900
16%
2520
8%
900
35%
900
24%
1666
December1st to 15thNight
22%
900
12%
2520
4%
900
29%
900
17%
1863
December16th to endNight
23%
960
14%
2688
5%
960
31%
960
16%
2040

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%7%36%5%3445%7%38%
47431
Night
12%7%35%5%24447%43%
46714
Cloud CoverDay
11%6%17%5%423346%33%
47442
Night
9%6%17%4423335%38%
46718
Cloud CoverDay
13%7%36%5%3445%7%38%
47440
Night
12%7%35%424446%43%
46718
TransparencyDay
44%6%14%22%11%1
47129
Night
40%5%13%24%13%1
46535
SeeingDay
14%7%29%30%14%3
5893
Night
15%8%33%31%11%
15923

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
8%9%5%7%8%5%6%5%5%8%29%
1477
16th to endDay
12%11%7%9%6%345%6%7%25%
1728
February1st to 15thDay
12%11%5%9%5%3445%6%30%
1575
16th to endDay
13%7%5%8%5%24448%33%
1476
March1st to 15thDay
13%9%48%5%3445%6%33%
1969
16th to endDay
18%12%46%5%24446%30%
2112
April1st to 15thDay
18%9%36%5%2435%6%35%
2140
16th to endDay
23%9%36%6%2335%430%
2268
May1st to 15thDay
21%6%25%5%35%45%7%32%
2373
16th to endDay
18%6%25%434447%37%
2617
June1st to 15thDay
13%6%26%42446%8%39%
2520
16th to endDay
8%4246%35%5%6%8%43%
2520
July1st to 15thDay
6%4245%35%5%5%9%48%
2520
16th to endDay
7%2135%35%6%6%9%47%
2526
August1st to 15thDay
9%425%5%35%6%5%7%43%
2289
16th to endDay
11%5%25%5%2446%7%45%
2198
September1st to 15thDay
11%5%24424447%47%
1980
16th to endDay
11%5%25%32345%6%49%
1790
October1st to 15thDay
15%4245%33335%47%
1650
16th to endDay
16%6%24424437%42%
1760
November1st to 15thDay
10%6%25%323447%48%
1527
16th to endDay
15%8%445%33346%40%
1440
December1st to 15thDay
16%12%47%7%345%46%27%
1440
16th to endDay
16%13%5%10%7%34337%23%
1536
January1st to 15thNight
9%8%46%6%445%5%7%36%
2458
16th to endNight
12%11%47%6%24447%34%
2496
February1st to 15thNight
11%11%5%9%6%2435%6%32%
2285
16th to endNight
11%7%45%5%24445%42%
2006
March1st to 15thNight
14%6%25%422348%45%
1968
16th to endNight
16%9%47%424436%35%
2112
April1st to 15thNight
14%7%15%5%25%35%7%40%
1807
16th to endNight
20%8%24423435%38%
1689
May1st to 15thNight
16%41442445%7%43%
1578
16th to endNight
11%425%435%45%8%44%
1496
June1st to 15thNight
9%4245%35%5%6%9%43%
1440
16th to endNight
6%31342446%8%53%
1440
July1st to 15thNight
42125%244410%58%
1440
16th to endNight
421232445%10%57%
1640
August1st to 15thNight
6%3244235%5%6%54%
1585
16th to endNight
9%5%24423335%54%
1652
September1st to 15thNight
10%314413346%56%
1650
16th to endNight
10%41332335%7%52%
1827
October1st to 15thNight
13%424423435%51%
1980
16th to endNight
15%6%24423246%47%
2112
November1st to 15thNight
10%6%34323346%50%
2325
16th to endNight
13%9%35%323445%43%
2520
December1st to 15thNight
15%12%47%6%34446%31%
2520
16th to endNight
18%11%5%7%7%24345%29%
2688

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
5%7%19%7%6%5%5%45%7%24%
1477
16th to endDay
10%10%22%8%5%33446%21%
1728
February1st to 15thDay
10%10%19%8%5%24245%26%
1575
16th to endDay
10%7%19%7%5%23346%28%
1476
March1st to 15thDay
10%8%20%7%423345%29%
1980
16th to endDay
12%10%20%5%413346%27%
2112
April1st to 15thDay
14%8%19%4422345%29%
2140
16th to endDay
19%8%19%5%42323424%
2268
May1st to 15thDay
16%5%18%4334345%28%
2373
16th to endDay
16%5%19%4323335%30%
2617
June1st to 15thDay
12%6%18%5%42345%6%31%
2520
16th to endDay
6%318%443445%6%37%
2520
July1st to 15thDay
5%318%45%2345%7%39%
2520
16th to endDay
5%218%342445%7%39%
2526
August1st to 15thDay
7%410%5%5%345%47%40%
2289
16th to endDay
8%5%11%442345%7%42%
2198
September1st to 15thDay
9%410%4324447%44%
1980
16th to endDay
10%411%4323345%46%
1790
October1st to 15thDay
14%410%442333444%
1650
16th to endDay
14%6%11%4423336%39%
1760
November1st to 15thDay
7%5%16%5%212446%43%
1527
16th to endDay
12%7%19%4322235%36%
1440
December1st to 15thDay
13%10%20%7%6%32435%22%
1440
16th to endDay
12%11%21%10%5%22336%20%
1536
January1st to 15thNight
6%7%19%5%5%435%46%31%
2458
16th to endNight
10%9%20%6%6%23345%28%
2496
February1st to 15thNight
8%10%19%8%5%23335%29%
2278
16th to endNight
8%7%18%5%5%2343435%
2006
March1st to 15thNight
11%5%19%5%322336%37%
1980
16th to endNight
11%8%19%7%323335%31%
2112
April1st to 15thNight
12%7%18%4423245%35%
1807
16th to endNight
16%8%18%442333430%
1689
May1st to 15thNight
13%318%3323345%37%
1577
16th to endNight
10%318%4434347%35%
1496
June1st to 15thNight
8%418%34235%5%7%35%
1440
16th to endNight
5%217%242345%6%45%
1440
July1st to 15thNight
2217%2323448%47%
1440
16th to endNight
3217%222345%7%48%
1640
August1st to 15thNight
5%310%331345%5%51%
1585
16th to endNight
7%411%4422335%50%
1652
September1st to 15thNight
7%310%4312345%52%
1650
16th to endNight
8%310%3322346%49%
1827
October1st to 15thNight
12%411%332332447%
1980
16th to endNight
13%6%10%4422235%43%
2112
November1st to 15thNight
8%416%3313246%44%
2325
16th to endNight
10%7%19%432223438%
2520
December1st to 15thNight
12%11%20%7%5%23335%24%
2520
16th to endNight
14%10%20%7%6%2322325%
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
7%10%5%8%7%5%6%46%8%29%
1477
16th to endDay
12%11%6%10%7%35%5%5%7%24%
1728
February1st to 15thDay
12%11%5%10%6%34447%29%
1575
16th to endDay
13%7%48%6%345%47%33%
1476
March1st to 15thDay
13%9%48%5%35%45%7%33%
1980
16th to endDay
18%12%47%42435%7%29%
2110
April1st to 15thDay
17%9%46%6%24347%34%
2140
16th to endDay
24%9%36%5%34345%30%
2268
May1st to 15thDay
20%6%44435%45%6%32%
2373
16th to endDay
18%6%35%5%25%45%7%37%
2617
June1st to 15thDay
13%6%35%4245%6%8%39%
2520
16th to endDay
8%425%5%35%6%5%8%44%
2520
July1st to 15thDay
6%3245%25%46%9%48%
2520
16th to endDay
6%3145%35%5%6%10%47%
2526
August1st to 15thDay
7%5%25%6%35%6%6%7%43%
2289
16th to endDay
10%5%25%5%2445%8%45%
2198
September1st to 15thDay
11%42442445%6%47%
1980
16th to endDay
11%5%2442335%5%50%
1790
October1st to 15thDay
15%5%25%5%33245%47%
1650
16th to endDay
16%7%24423446%42%
1760
November1st to 15thDay
9%6%35%314447%48%
1527
16th to endDay
14%8%45%5%24347%39%
1440
December1st to 15thDay
16%12%48%7%335%47%26%
1440
16th to endDay
15%15%5%11%6%33447%22%
1536
January1st to 15thNight
9%9%37%6%45%5%5%8%35%
2458
16th to endNight
12%11%5%7%6%2445%6%33%
2496
February1st to 15thNight
11%12%5%9%6%24445%33%
2278
16th to endNight
10%8%36%5%34446%42%
2006
March1st to 15thNight
13%7%35%422347%45%
1980
16th to endNight
15%9%5%8%424436%34%
2112
April1st to 15thNight
14%7%25%5%35%346%41%
1807
16th to endNight
20%8%245%23336%38%
1689
May1st to 15thNight
16%415%42435%7%43%
1577
16th to endNight
12%4144345%6%8%43%
1496
June1st to 15thNight
9%425%425%47%9%42%
1440
16th to endNight
6%22343437%9%52%
1440
July1st to 15thNight
421242445%9%58%
1440
16th to endNight
33133245%7%9%57%
1640
August1st to 15thNight
6%4244245%5%6%54%
1585
16th to endNight
9%6%24432336%53%
1652
September1st to 15thNight
9%323323445%56%
1650
16th to endNight
10%42332335%7%53%
1827
October1st to 15thNight
12%423433335%51%
1980
16th to endNight
15%7%245%23336%46%
2112
November1st to 15thNight
10%6%24323346%50%
2325
16th to endNight
14%8%36%323346%42%
2520
December1st to 15thNight
15%12%48%5%34445%30%
2520
16th to endNight
18%11%5%8%7%23345%29%
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
50%6%14%17%9%
1478
16th to endDay
56%6%15%16%6%
1728
February1st to 15thDay
54%5%12%20%5%
1576
16th to endDay
49%5%14%19%9%1
1476
March1st to 15thDay
50%6%15%19%7%
1980
16th to endDay
54%6%14%18%5%
2112
April1st to 15thDay
49%5%13%22%9%
2140
16th to endDay
56%5%9%19%8%
2268
May1st to 15thDay
50%6%12%22%7%
2373
16th to endDay
46%6%13%19%11%2
2621
June1st to 15thDay
40%6%15%21%14%
2520
16th to endDay
35%8%14%25%14%1
2520
July1st to 15thDay
32%7%15%27%12%3
2371
16th to endDay
29%9%17%26%15%2
2370
August1st to 15thDay
37%7%15%25%12%1
2275
16th to endDay
36%6%12%25%15%3
2198
September1st to 15thDay
35%5%13%26%18%1
1980
16th to endDay
35%5%13%29%15%
1790
October1st to 15thDay
39%411%23%19%1
1650
16th to endDay
42%6%13%24%13%
1760
November1st to 15thDay
34%6%13%26%18%1
1527
16th to endDay
45%5%17%23%8%
1440
December1st to 15thDay
56%6%15%13%6%1
1440
16th to endDay
61%412%13%7%
1536
January1st to 15thNight
45%6%15%19%12%
2458
16th to endNight
49%6%14%19%8%
2496
February1st to 15thNight
52%5%13%20%8%
2288
16th to endNight
42%5%14%24%12%1
2006
March1st to 15thNight
38%5%14%28%11%1
1980
16th to endNight
50%5%14%21%7%
2112
April1st to 15thNight
43%412%26%12%1
1807
16th to endNight
48%312%20%12%2
1689
May1st to 15thNight
39%7%14%24%13%
1578
16th to endNight
37%8%14%23%14%2
1498
June1st to 15thNight
34%8%16%24%13%2
1440
16th to endNight
26%6%15%26%20%4
1440
July1st to 15thNight
22%7%17%31%17%4
1360
16th to endNight
20%5%18%32%20%2
1534
August1st to 15thNight
28%7%13%31%15%3
1575
16th to endNight
33%412%25%20%5%
1652
September1st to 15thNight
29%411%26%25%2
1650
16th to endNight
30%5%11%29%21%1
1827
October1st to 15thNight
35%410%25%20%3
1980
16th to endNight
39%414%24%15%1
2112
November1st to 15thNight
34%412%26%19%2
2325
16th to endNight
43%415%26%10%1
2520
December1st to 15thNight
54%413%18%7%
2520
16th to endNight
57%412%15%8%
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
16%13%36%28%22
90
16th to endDay
20%10%42%21%13
96
February1st to 15thDay
10%24%38%21%5%
90
16th to endDay
22%11%34%20%9%1
81
March1st to 15thDay
14%14%46%21%3
90
16th to endDay
37%11%25%21%4
96
April1st to 15thDay
20%8%33%27%8%
259
16th to endDay
28%12%28%20%7%1
378
May1st to 15thDay
23%12%30%22%9%1
468
16th to endDay
20%9%29%27%11%1
517
June1st to 15thDay
11%6%30%32%16%3
495
16th to endDay
7%6%36%32%15%2
495
July1st to 15thDay
5%227%35%20%9%
475
16th to endDay
6%223%37%25%5%
515
August1st to 15thDay
9%120%38%25%4
474
16th to endDay
13%319%35%22%5%
366
September1st to 15thDay
12%223%35%20%6%
255
16th to endDay
6%10%24%41%12%2
101
October1st to 15thDay
48%32%33%17%3
90
16th to endDay
18%8%36%26%10%
96
November1st to 15thDay
35%38%36%10%5%
90
16th to endDay
36%11%31%17%3
90
December1st to 15thDay
17%24%32%16%8%
90
16th to endDay
28%20%34%14%2
96
January1st to 15thNight
12%12%39%26%8%
900
16th to endNight
17%11%38%27%5%
960
February1st to 15thNight
17%10%38%26%6%
880
16th to endNight
15%10%40%25%7%1
744
March1st to 15thNight
17%9%33%28%10%1
540
16th to endNight
19%12%37%21%7%1
576
April1st to 15thNight
18%12%36%27%5%
539
16th to endNight
23%8%35%22%7%1
540
May1st to 15thNight
17%7%33%32%9%
540
16th to endNight
14%432%35%12%
563
June1st to 15thNight
11%5%28%40%13%
540
16th to endNight
6%228%50%12%
540
July1st to 15thNight
4122%44%24%1
510
16th to endNight
412%52%26%2
564
August1st to 15thNight
7%118%45%25%2
527
16th to endNight
11%320%37%22%4
525
September1st to 15thNight
10%319%39%24%2
495
16th to endNight
11%5%32%30%18%1
517
October1st to 15thNight
15%6%36%28%12%
660
16th to endNight
17%8%34%28%9%
704
November1st to 15thNight
13%10%37%30%8%
799
16th to endNight
17%14%36%22%8%
900
December1st to 15thNight
20%11%38%25%5%
900
16th to endNight
23%8%34%27%6%
960
Page generated at 2017-08-13 13:16:21. Version ac04

Copyright 2017 A. Danko


Strohbehn Observatory Clear Sky Chart | Charts Home