Rutenbeck Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rutenbeck Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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%
24631
17%
74675
11%
24576
44%
24576
23%
49808

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 10thNight
23%
950
13%
2648
4%
946
31%
946
20%
1905
January11th to 20thNight
23%
915
11%
2561
4%
915
28%
915
17%
1925
January21st to endNight
22%
990
12%
2606
4%
990
28%
990
16%
1989
February1st to 10thNight
22%
900
12%
2340
2%
900
28%
900
20%
1739
February11th to 20thNight
27%
774
18%
2173
8%
774
34%
774
22%
1486
February21st to endNight
23%
592
18%
1776
5%
592
36%
592
20%
1233
March1st to 10thNight
25%
720
15%
2160
7%
720
32%
720
21%
1459
March11th to 20thNight
34%
572
19%
2012
12%
572
43%
572
21%
1281
March21st to endNight
23%
594
14%
2044
8%
594
31%
594
13%
1486
April1st to 10thNight
26%
540
16%
1800
9%
540
37%
540
20%
1187
April11th to 20thNight
33%
533
20%
1775
15%
533
44%
533
21%
1176
April21st to endNight
32%
540
15%
1800
10%
540
41%
540
19%
1236
May1st to 10thNight
35%
540
15%
1545
9%
540
41%
540
23%
1080
May11th to 20thNight
37%
531
18%
1417
9%
531
43%
531
25%
996
May21st to endNight
49%
584
16%
1551
9%
582
54%
582
30%
1049
June1st to 10thNight
59%
540
17%
1440
11%
540
61%
540
37%
881
June11th to 20thNight
52%
540
20%
1440
11%
540
56%
540
35%
912
June21st to endNight
52%
540
18%
1440
9%
540
56%
540
31%
951
July1st to 10thNight
70%
525
18%
1400
13%
525
71%
525
42%
818
July11th to 20thNight
66%
522
23%
1392
15%
522
69%
522
45%
791
July21st to endNight
68%
591
23%
1487
18%
558
70%
558
42%
872
August1st to 10thNight
70%
537
21%
1553
20%
534
72%
534
38%
907
August11th to 20thNight
71%
534
24%
1715
26%
534
74%
534
37%
950
August21st to endNight
69%
594
24%
1980
26%
594
74%
594
38%
1049
September1st to 10thNight
62%
540
24%
1800
24%
540
66%
540
35%
991
September11th to 20thNight
59%
550
32%
1810
31%
550
64%
550
35%
995
September21st to endNight
50%
720
25%
1980
15%
720
57%
720
34%
1187
October1st to 10thNight
47%
720
23%
2160
17%
720
52%
720
33%
1260
October11th to 20thNight
34%
720
22%
2160
12%
720
44%
720
26%
1341
October21st to endNight
29%
792
17%
2483
10%
792
38%
792
20%
1668
November1st to 10thNight
34%
740
26%
2406
16%
740
47%
740
29%
1400
November11th to 20thNight
26%
764
19%
2474
9%
764
37%
764
20%
1635
November21st to endNight
28%
950
18%
2660
8%
950
36%
950
22%
1832
December1st to 10thNight
22%
950
12%
2660
4%
950
28%
950
18%
1933
December11th to 20thNight
26%
949
14%
3179
5%
948
32%
948
15%
2235
December21st to endNight
18%
1038
7%
4848
4%
1026
25%
1026
7%
3973

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%8%36%6%35%5%5%7%38%
74769
Night
14%8%46%5%3445%7%40%
74994
TransparencyDay
44%7%13%22%12%1
74469
Night
44%6%12%22%14%2
74814
SeeingDay
16%9%28%27%16%5%
14661
Night
17%8%31%31%12%1
24642

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 10thDay
12%10%7%9%8%46%5%5%7%27%
1517
11th to 20thDay
13%14%6%10%8%5%4447%24%
1456
21st to endDay
14%13%7%10%7%45%5%5%6%25%
1746
February1st to 10thDay
13%13%5%8%8%46%6%45%28%
1620
11th to 20thDay
15%9%36%6%5%5%45%7%35%
1675
21st to endDay
14%13%5%9%6%2445%8%30%
1480
March1st to 10thDay
16%10%5%7%5%335%5%8%34%
1800
11th to 20thDay
13%8%36%6%45%47%7%37%
1962
21st to endDay
21%10%5%8%6%35%5%5%7%27%
2312
April1st to 10thDay
16%9%5%8%6%35%447%33%
2160
11th to 20thDay
16%8%37%6%45%45%7%35%
2134
21st to endDay
21%9%35%5%3445%6%33%
2160
May1st to 10thDay
15%8%38%6%35%5%6%8%32%
2411
11th to 20thDay
20%7%36%6%345%5%7%34%
2479
21st to endDay
14%7%36%6%35%5%6%8%35%
2725
June1st to 10thDay
9%425%5%36%6%7%9%45%
2520
11th to 20thDay
10%5%345%35%5%5%9%46%
2520
21st to endDay
11%6%36%7%35%5%6%8%40%
2520
July1st to 10thDay
8%4235%35%5%6%10%47%
2520
11th to 20thDay
8%5%245%345%7%9%48%
2520
21st to endDay
6%425%6%36%6%7%10%46%
2743
August1st to 10thDay
5%5%26%6%36%7%9%11%42%
2374
11th to 20thDay
9%5%35%435%5%5%8%48%
2186
21st to endDay
9%425%435%45%8%51%
2376
September1st to 10thDay
13%4245%245%6%8%46%
2160
11th to 20thDay
11%42333445%6%55%
2131
21st to endDay
10%5%26%5%3446%7%48%
1976
October1st to 10thDay
13%6%35%4345%5%7%46%
1800
11th to 20thDay
17%8%46%5%34447%39%
1800
21st to endDay
20%8%35%423446%40%
1872
November1st to 10thDay
12%8%345%345%5%8%45%
1672
11th to 20thDay
14%11%5%8%6%445%5%7%33%
1701
21st to endDay
17%11%47%5%24445%37%
1520
December1st to 10thDay
15%12%310%6%3445%7%31%
1520
11th to 20thDay
14%12%5%9%6%45%45%6%29%
1918
21st to endDay
22%18%8%11%8%34335%15%
2783
January1st to 10thNight
13%11%5%9%7%4445%5%35%
2648
11th to 20thNight
13%13%6%9%7%45%5%5%6%28%
2561
21st to endNight
15%12%7%9%6%35%5%5%6%28%
2606
February1st to 10thNight
15%13%5%7%7%35%445%33%
2340
11th to 20thNight
13%9%47%5%34446%40%
2172
21st to endNight
16%11%46%5%34236%38%
1776
March1st to 10thNight
17%10%45%5%34446%38%
2160
11th to 20thNight
12%8%36%6%3445%7%41%
2012
21st to endNight
21%10%47%5%35%446%30%
2044
April1st to 10thNight
17%9%35%5%3445%6%40%
1800
11th to 20thNight
19%8%35%5%33445%40%
1775
21st to endNight
17%9%37%5%45%5%5%7%34%
1800
May1st to 10thNight
15%7%27%6%345%6%7%37%
1545
11th to 20thNight
18%6%35%6%445%5%6%38%
1416
21st to endNight
11%425%5%36%5%7%9%41%
1551
June1st to 10thNight
7%5%25%5%346%7%8%49%
1440
11th to 20thNight
9%6%35%5%345%7%9%46%
1440
21st to endNight
10%435%6%46%5%5%8%44%
1440
July1st to 10thNight
6%42442447%10%53%
1440
11th to 20thNight
6%32442345%9%57%
1440
21st to endNight
5%4344346%6%10%50%
1575
August1st to 10thNight
44246%346%7%9%51%
1562
11th to 20thNight
6%4245%3445%8%55%
1715
21st to endNight
8%32442445%8%56%
1980
September1st to 10thNight
10%5%34424347%56%
1800
11th to 20thNight
10%41443446%7%52%
1810
21st to endNight
8%426%43445%7%52%
1980
October1st to 10thNight
12%5%245%23346%53%
2160
11th to 20thNight
15%7%35%423447%45%
2160
21st to endNight
19%8%36%5%24346%38%
2483
November1st to 10thNight
11%7%25%424346%52%
2406
11th to 20thNight
15%8%47%6%3445%5%38%
2474
21st to endNight
17%8%46%5%34446%39%
2660
December1st to 10thNight
16%11%48%6%35%45%6%33%
2660
11th to 20thNight
15%10%5%8%5%345%47%33%
3279
21st to endNight
21%16%6%10%6%45%5%5%5%18%
4884

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 10thDay
54%7%14%15%10%
1518
11th to 20thDay
61%5%14%16%5%
1456
21st to endDay
59%6%13%13%8%1
1746
February1st to 10thDay
57%5%14%17%7%1
1620
11th to 20thDay
49%6%12%22%10%1
1684
21st to endDay
53%7%11%20%8%1
1480
March1st to 10thDay
49%6%16%21%8%1
1800
11th to 20thDay
45%7%14%22%11%1
1962
21st to endDay
56%7%12%19%5%1
2312
April1st to 10thDay
50%7%12%21%9%
2160
11th to 20thDay
49%6%11%22%12%1
2134
21st to endDay
49%8%12%18%12%2
2160
May1st to 10thDay
49%7%14%21%8%1
2411
11th to 20thDay
49%7%12%21%11%
2483
21st to endDay
45%8%12%19%13%2
2725
June1st to 10thDay
33%9%15%26%16%2
2520
11th to 20thDay
35%6%13%22%22%3
2520
21st to endDay
39%9%13%24%13%1
2520
July1st to 10thDay
31%8%16%28%14%3
2451
11th to 20thDay
31%7%16%28%15%3
2445
21st to endDay
31%8%18%25%15%2
2591
August1st to 10thDay
32%11%17%28%12%1
2359
11th to 20thDay
34%7%14%27%16%2
2186
21st to endDay
30%8%12%28%20%3
2376
September1st to 10thDay
35%7%12%25%18%3
2160
11th to 20thDay
29%6%12%30%19%3
2131
21st to endDay
34%6%11%28%18%2
1976
October1st to 10thDay
37%6%11%28%17%1
1800
11th to 20thDay
45%6%12%22%14%2
1800
21st to endDay
46%413%23%11%2
1872
November1st to 10thDay
38%6%15%26%13%2
1672
11th to 20thDay
51%5%14%20%9%1
1701
21st to endDay
51%6%14%21%8%
1520
December1st to 10thDay
53%6%14%18%8%1
1520
11th to 20thDay
54%7%14%17%8%1
1915
21st to endDay
74%5%8%8%4
2783
January1st to 10thNight
50%5%13%19%12%
2648
11th to 20thNight
56%5%17%14%8%
2561
21st to endNight
55%7%12%16%9%1
2606
February1st to 10thNight
54%5%11%18%11%1
2340
11th to 20thNight
46%5%12%23%12%1
2173
21st to endNight
49%5%12%20%11%3
1776
March1st to 10thNight
47%5%14%23%11%1
2160
11th to 20thNight
43%6%13%20%16%3
2012
21st to endNight
56%6%10%18%9%1
2044
April1st to 10thNight
45%6%11%23%14%2
1800
11th to 20thNight
46%5%8%21%16%4
1775
21st to endNight
48%7%11%21%11%2
1800
May1st to 10thNight
44%8%13%21%13%1
1545
11th to 20thNight
45%7%11%20%16%1
1417
21st to endNight
38%9%14%21%16%3
1552
June1st to 10thNight
30%8%15%24%20%3
1440
11th to 20thNight
33%7%10%23%23%4
1440
21st to endNight
35%10%12%22%16%4
1440
July1st to 10thNight
27%7%15%29%18%4
1400
11th to 20thNight
25%6%14%32%19%3
1392
21st to endNight
27%7%18%26%17%5%
1487
August1st to 10thNight
26%10%16%31%14%3
1553
11th to 20thNight
27%7%13%31%19%2
1715
21st to endNight
26%7%11%29%22%5%
1980
September1st to 10thNight
29%7%11%25%25%3
1800
11th to 20thNight
29%6%10%30%20%4
1810
21st to endNight
32%6%11%28%20%3
1980
October1st to 10thNight
32%5%11%27%21%3
2160
11th to 20thNight
39%411%23%19%2
2160
21st to endNight
48%410%23%13%2
2483
November1st to 10thNight
34%6%12%27%19%3
2406
11th to 20thNight
47%412%23%13%1
2474
21st to endNight
47%5%12%25%10%1
2660
December1st to 10thNight
52%5%13%21%8%1
2660
11th to 20thNight
50%6%14%22%8%1
3281
21st to endNight
67%7%9%12%4
4884

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 10thDay
19%11%33%26%10%1
270
11th to 20thDay
24%11%42%17%6%
246
21st to endDay
19%10%40%23%7%1
264
February1st to 10thDay
20%16%38%21%5%
240
11th to 20thDay
24%19%28%22%7%
240
21st to endDay
22%18%40%18%3
198
March1st to 10thDay
15%20%38%20%7%
240
11th to 20thDay
23%15%33%20%7%2
240
21st to endDay
26%15%32%18%7%2
398
April1st to 10thDay
22%13%36%23%5%
420
11th to 20thDay
21%16%30%20%12%2
412
21st to endDay
26%10%30%21%10%1
420
May1st to 10thDay
20%11%32%27%8%2
505
11th to 20thDay
22%10%28%24%13%3
625
21st to endDay
15%10%25%25%17%7%
679
June1st to 10thDay
9%5%24%35%21%7%
630
11th to 20thDay
10%431%32%18%4
630
21st to endDay
13%7%27%30%17%5%
630
July1st to 10thDay
10%315%30%27%15%
621
11th to 20thDay
9%421%34%23%10%
618
21st to endDay
5%221%39%28%5%
684
August1st to 10thDay
6%219%33%29%10%
626
11th to 20thDay
12%416%29%25%14%
500
21st to endDay
8%318%33%27%11%
495
September1st to 10thDay
15%6%20%27%23%9%
450
11th to 20thDay
9%319%37%22%10%
450
21st to endDay
11%9%28%24%22%7%
446
October1st to 10thDay
16%7%28%29%17%4
270
11th to 20thDay
21%22%33%16%7%1
270
21st to endDay
27%16%27%24%41
297
November1st to 10thDay
15%13%35%22%10%4
270
11th to 20thDay
23%17%33%17%7%3
270
21st to endDay
24%13%33%24%5%
270
December1st to 10thDay
16%15%39%21%7%2
270
11th to 20thDay
17%11%39%24%9%
270
21st to endDay
27%10%43%18%2
297
January1st to 10thNight
18%11%38%26%6%
950
11th to 20thNight
18%11%36%28%6%1
915
21st to endNight
20%12%35%29%4
990
February1st to 10thNight
23%9%39%25%4
900
11th to 20thNight
19%10%39%28%5%
777
21st to endNight
22%10%40%23%41
592
March1st to 10thNight
23%10%37%25%6%
720
11th to 20thNight
17%9%35%32%7%
572
21st to endNight
26%9%34%25%5%1
594
April1st to 10thNight
23%11%37%25%4
540
11th to 20thNight
22%11%30%28%8%1
533
21st to endNight
21%10%31%30%8%1
540
May1st to 10thNight
17%7%36%31%8%1
540
11th to 20thNight
18%6%29%33%13%
531
21st to endNight
12%5%29%34%18%2
584
June1st to 10thNight
7%5%22%49%16%1
540
11th to 20thNight
11%327%42%15%1
540
21st to endNight
10%5%26%41%17%1
540
July1st to 10thNight
8%312%41%32%5%
525
11th to 20thNight
7%318%42%27%3
522
21st to endNight
7%215%45%29%2
591
August1st to 10thNight
5%214%42%33%4
537
11th to 20thNight
6%213%41%33%5%
534
21st to endNight
9%115%43%28%3
594
September1st to 10thNight
11%418%37%26%4
540
11th to 20thNight
10%322%34%27%5%
550
21st to endNight
9%9%26%32%22%2
720
October1st to 10thNight
13%7%28%33%19%1
720
11th to 20thNight
20%13%29%27%12%
720
21st to endNight
24%11%32%25%8%
792
November1st to 10thNight
16%8%39%27%10%1
740
11th to 20thNight
19%14%36%24%6%
764
21st to endNight
21%12%33%26%7%
950
December1st to 10thNight
21%12%37%23%6%
950
11th to 20thNight
22%10%33%28%7%
950
21st to endNight
27%11%35%24%3
1045
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