Rolling Roof Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rolling Roof Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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
72%
24317
34%
74553
28%
24261
78%
24261
49%
36818

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
54%
760
28%
2632
23%
756
64%
756
36%
1345
January11th to 20thNight
54%
736
36%
2392
25%
736
70%
736
45%
1156
January21st to endNight
49%
792
38%
2466
24%
792
67%
792
40%
1266
February1st to 10thNight
59%
720
37%
2160
28%
720
71%
720
43%
1115
February11th to 20thNight
61%
700
34%
2098
29%
700
71%
700
46%
1073
February21st to endNight
55%
592
29%
1776
25%
592
64%
592
39%
963
March1st to 10thNight
57%
720
25%
2160
23%
720
65%
720
39%
1193
March11th to 20thNight
67%
720
27%
2066
24%
720
72%
720
42%
1131
March21st to endNight
65%
792
31%
1994
21%
792
70%
792
48%
1128
April1st to 10thNight
69%
720
31%
1800
21%
720
72%
720
48%
1025
April11th to 20thNight
69%
711
34%
1779
19%
711
74%
711
53%
963
April21st to endNight
75%
720
33%
1800
19%
720
79%
720
58%
949
May1st to 10thNight
75%
718
27%
1798
17%
718
76%
718
50%
1014
May11th to 20thNight
77%
531
30%
1595
24%
531
79%
531
49%
808
May21st to endNight
77%
582
30%
1746
23%
582
80%
582
58%
828
June1st to 10thNight
84%
413
29%
1493
31%
413
85%
413
45%
695
June11th to 20thNight
91%
360
36%
1440
44%
360
91%
360
58%
529
June21st to endNight
91%
360
37%
1440
46%
360
91%
360
62%
511
July1st to 10thNight
93%
350
37%
1400
44%
350
93%
350
67%
467
July11th to 20thNight
91%
387
37%
1431
40%
387
91%
387
61%
543
July21st to endNight
90%
717
34%
1793
26%
677
91%
677
67%
842
August1st to 10thNight
91%
716
34%
1780
22%
712
91%
712
71%
849
August11th to 20thNight
92%
712
38%
1780
24%
712
92%
712
76%
831
August21st to endNight
92%
792
43%
1980
29%
792
92%
792
76%
909
September1st to 10thNight
88%
720
41%
1800
32%
720
88%
720
70%
875
September11th to 20thNight
88%
720
42%
1894
37%
720
89%
720
72%
857
September21st to endNight
90%
720
42%
1980
40%
720
92%
720
74%
853
October1st to 10thNight
82%
720
37%
1980
35%
720
86%
720
61%
949
October11th to 20thNight
78%
720
40%
2160
42%
720
81%
720
56%
1005
October21st to endNight
72%
792
42%
2376
39%
792
80%
792
59%
1072
November1st to 10thNight
73%
740
37%
2391
36%
740
81%
740
56%
1052
November11th to 20thNight
67%
760
37%
2470
33%
760
78%
760
54%
1094
November21st to endNight
60%
760
36%
2470
31%
760
69%
760
46%
1187
December1st to 10thNight
55%
760
34%
2470
26%
760
66%
760
39%
1255
December11th to 20thNight
51%
760
29%
3006
25%
759
66%
759
26%
1790
December21st to endNight
54%
824
19%
4757
26%
817
66%
817
19%
2696

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
5%313323347%66%
74859
Night
5%423323346%65%
74924
TransparencyDay
19%47%17%27%26%
74582
Night
20%48%16%25%27%
74722
SeeingDay
6%8%26%35%19%6%
14454
Night
6%313%34%35%9%
24335

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 10thDay
9%41443345%7%56%
1530
11th to 20thDay
7%424333246%62%
1657
21st to endDay
10%5%23313245%60%
1886
February1st to 10thDay
9%423323445%63%
1800
11th to 20thDay
7%31332335%8%62%
1750
21st to endDay
7%414434447%59%
1480
March1st to 10thDay
7%5%25%5%245%5%6%54%
1800
11th to 20thDay
7%4235%235%5%8%56%
1890
21st to endDay
5%323335%448%60%
2362
April1st to 10thDay
6%42442345%8%59%
2160
11th to 20thDay
4324323347%66%
2129
21st to endDay
5%312312337%68%
2160
May1st to 10thDay
5%5%24213348%62%
2160
11th to 20thDay
342332345%8%64%
2301
21st to endDay
3423322349%65%
2530
June1st to 10thDay
45%2432345%8%61%
2461
11th to 20thDay
3323223348%67%
2520
21st to endDay
1312213336%76%
2520
July1st to 10thDay
1212324346%72%
2520
11th to 20thDay
2212212336%76%
2476
21st to endDay
2112313347%73%
2416
August1st to 10thDay
2212213336%76%
2149
11th to 20thDay
1111111245%81%
2122
21st to endDay
111212345%79%
2376
September1st to 10thDay
1211123336%78%
2160
11th to 20thDay
2212212225%80%
2066
21st to endDay
2212212235%79%
1980
October1st to 10thDay
421232235%5%73%
1976
11th to 20thDay
431332222475%
1800
21st to endDay
2213323345%73%
1980
November1st to 10thDay
3213323346%71%
1685
11th to 20thDay
4312323345%69%
1710
21st to endDay
432342435%7%63%
1710
December1st to 10thDay
7%42432445%7%58%
1710
11th to 20thDay
14%6%35%5%2445%7%45%
2133
21st to endDay
11%6%25%6%445%5%7%45%
2794
January1st to 10thNight
9%42343345%7%55%
2632
11th to 20thNight
6%423323347%63%
2392
21st to endNight
10%5%23212336%63%
2466
February1st to 10thNight
6%434323345%64%
2160
11th to 20thNight
8%313323346%63%
2098
21st to endNight
10%5%23323345%59%
1776
March1st to 10thNight
8%5%244245%6%7%54%
2160
11th to 20thNight
6%5%2442445%6%57%
2066
21st to endNight
6%42432345%7%61%
1994
April1st to 10thNight
6%42432435%7%60%
1800
11th to 20thNight
4313223446%68%
1779
21st to endNight
4312223248%68%
1800
May1st to 10thNight
432432345%7%63%
1798
11th to 20thNight
25%1332345%7%65%
1594
21st to endNight
2313323236%72%
1746
June1st to 10thNight
2323324448%65%
1493
11th to 20thNight
1212212337%75%
1440
21st to endNight
1312212235%78%
1440
July1st to 10thNight
1212212346%78%
1440
11th to 20thNight
1112323346%75%
1479
21st to endNight
2112323347%73%
1899
August1st to 10thNight
221222235%7%74%
1790
11th to 20thNight
1112212346%78%
1780
21st to endNight
112213246%78%
1980
September1st to 10thNight
2313212335%75%
1800
11th to 20thNight
211221223479%
1894
21st to endNight
2111212245%80%
1980
October1st to 10thNight
3113323445%71%
1980
11th to 20thNight
4313223235%72%
2160
21st to endNight
341222223474%
2376
November1st to 10thNight
331322335%6%69%
2391
11th to 20thNight
4323222335%70%
2470
21st to endNight
5%323434446%63%
2470
December1st to 10thNight
7%424423446%59%
2470
11th to 20thNight
18%6%3442345%7%46%
3069
21st to endNight
12%7%35%6%45%446%45%
4862

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
28%37%16%25%20%
1530
11th to 20thDay
26%38%13%25%26%
1657
21st to endDay
28%36%17%20%26%
1886
February1st to 10thDay
24%35%14%24%29%
1800
11th to 20thDay
21%38%16%28%23%
1760
21st to endDay
25%48%19%24%19%
1480
March1st to 10thDay
30%49%18%18%21%
1800
11th to 20thDay
25%411%19%24%18%
1890
21st to endDay
23%6%12%22%23%14%
2362
April1st to 10thDay
23%5%13%24%22%13%
2160
11th to 20thDay
19%5%8%22%30%17%
2132
21st to endDay
18%49%24%32%13%
2160
May1st to 10thDay
21%5%11%21%27%15%
2160
11th to 20thDay
19%5%11%25%29%12%
2304
21st to endDay
19%5%12%28%28%8%
2530
June1st to 10thDay
22%410%20%29%13%
2461
11th to 20thDay
17%39%15%31%26%
2520
21st to endDay
12%25%11%34%36%
2520
July1st to 10thDay
13%35%12%24%43%
2451
11th to 20thDay
12%36%17%33%29%
2401
21st to endDay
13%39%21%32%21%
2282
August1st to 10thDay
13%2413%33%35%
2135
11th to 20thDay
8%1414%36%36%
2122
21st to endDay
9%25%11%35%38%
2376
September1st to 10thDay
10%26%10%30%42%
2160
11th to 20thDay
10%2415%30%39%
2066
21st to endDay
11%16%15%35%32%
1980
October1st to 10thDay
14%47%20%23%33%
1976
11th to 20thDay
17%35%13%27%36%
1800
21st to endDay
14%45%13%23%42%
1980
November1st to 10thDay
16%45%17%25%34%
1685
11th to 20thDay
17%46%13%21%39%
1710
21st to endDay
21%38%13%22%33%
1710
December1st to 10thDay
26%46%16%22%25%
1710
11th to 20thDay
39%47%14%21%15%
2132
21st to endDay
36%6%8%22%16%12%
2794
January1st to 10thNight
28%37%13%28%21%
2632
11th to 20thNight
22%38%15%22%29%
2392
21st to endNight
26%38%14%20%30%
2466
February1st to 10thNight
25%35%13%24%30%
2160
11th to 20thNight
23%35%17%24%27%
2099
21st to endNight
27%47%14%24%23%
1776
March1st to 10thNight
28%5%10%18%21%18%
2160
11th to 20thNight
26%5%9%17%25%19%
2066
21st to endNight
24%410%23%24%15%
1994
April1st to 10thNight
24%5%12%24%20%15%
1800
11th to 20thNight
18%6%8%23%27%18%
1779
21st to endNight
16%5%10%22%32%14%
1800
May1st to 10thNight
21%6%11%21%25%16%
1798
11th to 20thNight
20%5%10%23%29%13%
1595
21st to endNight
15%413%29%29%9%
1746
June1st to 10thNight
17%8%13%22%26%14%
1493
11th to 20thNight
11%410%19%33%23%
1440
21st to endNight
12%29%12%29%37%
1440
July1st to 10thNight
9%27%16%21%45%
1400
11th to 20thNight
12%38%18%26%33%
1431
21st to endNight
12%39%24%31%21%
1793
August1st to 10thNight
11%37%13%30%37%
1780
11th to 20thNight
9%28%12%36%34%
1780
21st to endNight
9%25%12%34%38%
1980
September1st to 10thNight
13%27%10%26%43%
1800
11th to 20thNight
10%26%13%29%40%
1894
21st to endNight
9%28%12%32%37%
1980
October1st to 10thNight
15%37%17%24%35%
1980
11th to 20thNight
16%45%15%22%38%
2160
21st to endNight
15%25%11%20%47%
2376
November1st to 10thNight
16%36%15%25%35%
2391
11th to 20thNight
17%28%11%21%40%
2470
21st to endNight
22%37%16%19%33%
2470
December1st to 10thNight
25%46%15%20%30%
2470
11th to 20thNight
38%48%13%21%17%
3069
21st to endNight
38%6%7%19%18%12%
4862

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
17%11%34%29%10%
191
11th to 20thDay
13%14%36%27%10%
353
21st to endDay
13%18%38%22%8%1
420
February1st to 10thDay
11%11%38%26%10%3
420
11th to 20thDay
9%16%37%30%6%2
415
21st to endDay
12%15%39%26%7%1
346
March1st to 10thDay
12%19%36%24%9%1
420
11th to 20thDay
13%13%35%27%10%2
420
21st to endDay
11%16%35%30%7%2
462
April1st to 10thDay
9%10%34%31%12%3
420
11th to 20thDay
6%17%34%29%10%3
412
21st to endDay
414%32%31%13%6%
420
May1st to 10thDay
8%10%31%36%12%4
423
11th to 20thDay
5%9%27%36%19%4
448
21st to endDay
7%9%31%32%18%4
485
June1st to 10thDay
6%5%23%34%26%7%
450
11th to 20thDay
4418%39%28%8%
450
21st to endDay
3214%39%31%10%
450
July1st to 10thDay
18%46%35%11%
446
11th to 20thDay
25%37%37%18%
444
21st to endDay
16%42%33%18%
487
August1st to 10thDay
2110%47%28%12%
447
11th to 20thDay
216%45%32%15%
437
21st to endDay
1112%46%28%13%
495
September1st to 10thDay
2218%44%25%9%
450
11th to 20thDay
3323%44%22%6%
450
21st to endDay
25%21%41%24%8%
450
October1st to 10thDay
26%28%39%20%3
450
11th to 20thDay
3430%40%19%2
450
21st to endDay
47%32%33%18%5%
495
November1st to 10thDay
5%5%24%37%21%7%
281
11th to 20thDay
412%29%37%16%3
270
21st to endDay
8%10%34%29%17%3
270
December1st to 10thDay
12%8%31%31%15%2
270
11th to 20thDay
6%12%29%34%18%2
259
21st to endDay
14%14%31%30%10%1
198
January1st to 10thNight
11%423%40%17%5%
760
11th to 20thNight
8%6%27%40%17%2
736
21st to endNight
14%7%24%37%16%3
792
February1st to 10thNight
9%6%20%38%23%5%
720
11th to 20thNight
9%321%41%20%6%
704
21st to endNight
13%6%21%38%19%3
592
March1st to 10thNight
9%422%43%19%2
720
11th to 20thNight
8%415%40%28%6%
720
21st to endNight
8%417%44%24%3
792
April1st to 10thNight
7%213%44%29%5%
720
11th to 20thNight
4417%40%31%4
711
21st to endNight
5%411%41%31%9%
720
May1st to 10thNight
6%211%41%35%5%
718
11th to 20thNight
3211%35%44%5%
531
21st to endNight
2213%35%41%7%
584
June1st to 10thNight
216%34%47%10%
413
11th to 20thNight
11128%59%10%
360
21st to endNight
3125%61%11%
360
July1st to 10thNight
219%71%18%
350
11th to 20thNight
117%65%25%
387
21st to endNight
2119%63%25%
717
August1st to 10thNight
21119%60%18%
716
11th to 20thNight
11112%62%23%
712
21st to endNight
2115%60%22%
792
September1st to 10thNight
21421%54%18%
720
11th to 20thNight
21327%52%15%
720
21st to endNight
2431%49%13%
720
October1st to 10thNight
47%42%41%5%
720
11th to 20thNight
4210%39%38%7%
720
21st to endNight
4216%37%30%11%
792
November1st to 10thNight
4315%42%29%8%
740
11th to 20thNight
5%318%41%28%6%
760
21st to endNight
6%425%37%24%4
760
December1st to 10thNight
9%5%24%37%20%5%
760
11th to 20thNight
13%5%23%38%18%3
760
21st to endNight
11%6%22%39%18%3
836
Page generated at 2024-01-11 19:33:51. Version ac07

Copyright 2024 Attilla Danko


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