Roadrunner Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Roadrunner 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
74%
24014
36%
74355
32%
23964
79%
23964
52%
35551

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
65%
759
32%
2457
29%
756
73%
756
44%
1234
January11th to 20thNight
63%
732
36%
2379
31%
732
73%
732
46%
1154
January21st to endNight
61%
792
36%
2574
32%
792
71%
792
40%
1345
February1st to 10thNight
68%
720
36%
2290
33%
720
77%
720
51%
1073
February11th to 20thNight
60%
700
33%
2099
29%
700
68%
700
43%
1114
February21st to endNight
61%
592
35%
1736
32%
592
68%
592
45%
908
March1st to 10thNight
62%
720
37%
1980
29%
720
71%
720
53%
1001
March11th to 20thNight
69%
720
37%
1980
30%
720
75%
720
55%
1001
March21st to endNight
68%
792
37%
2178
27%
792
76%
792
56%
1079
April1st to 10thNight
74%
720
35%
1980
26%
720
80%
720
60%
946
April11th to 20thNight
69%
587
39%
1831
32%
587
77%
587
62%
769
April21st to endNight
76%
540
46%
1686
39%
540
85%
540
69%
674
May1st to 10thNight
77%
540
42%
1620
35%
540
83%
540
68%
676
May11th to 20thNight
80%
531
41%
1594
35%
531
83%
531
68%
670
May21st to endNight
83%
582
41%
1746
35%
582
86%
582
76%
684
June1st to 10thNight
86%
540
36%
1620
32%
540
87%
540
68%
677
June11th to 20thNight
92%
540
40%
1620
34%
540
93%
540
83%
604
June21st to endNight
87%
540
32%
1620
28%
540
87%
540
65%
706
July1st to 10thNight
84%
525
25%
1575
22%
525
84%
525
48%
811
July11th to 20thNight
85%
522
25%
1566
21%
522
85%
522
44%
826
July21st to endNight
79%
591
23%
1674
20%
558
79%
558
34%
998
August1st to 10thNight
87%
537
27%
1602
24%
534
87%
534
48%
817
August11th to 20thNight
81%
534
33%
1602
31%
534
81%
534
41%
887
August21st to endNight
84%
660
30%
1992
29%
660
84%
660
45%
1056
September1st to 10thNight
80%
720
33%
1980
30%
720
81%
720
51%
1043
September11th to 20thNight
84%
720
41%
1980
35%
720
86%
720
62%
951
September21st to endNight
82%
720
39%
1980
30%
720
86%
720
60%
955
October1st to 10thNight
77%
720
39%
2034
31%
720
82%
720
61%
956
October11th to 20thNight
83%
720
44%
2160
39%
720
86%
720
72%
885
October21st to endNight
79%
792
46%
2376
38%
792
86%
792
71%
979
November1st to 10thNight
78%
740
43%
2220
37%
740
83%
740
62%
984
November11th to 20thNight
75%
760
41%
2389
37%
760
82%
760
59%
1045
November21st to endNight
67%
760
39%
2470
36%
760
75%
760
49%
1163
December1st to 10thNight
65%
760
38%
2470
36%
760
72%
760
46%
1196
December11th to 20thNight
63%
759
33%
2943
34%
758
70%
758
32%
1608
December21st to endNight
61%
827
23%
4352
32%
817
69%
817
26%
2076

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
4213323346%68%
74958
Night
5%313323446%66%
74828
TransparencyDay
18%35%12%24%38%
74685
Night
19%3411%23%38%
74623
SeeingDay
5%5%17%35%28%9%
13806
Night
5%213%43%33%4
24031

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
7%324323346%62%
1708
11th to 20thDay
8%323214335%66%
1642
21st to endDay
8%413323346%63%
1782
February1st to 10thDay
5%413313346%67%
1667
11th to 20thDay
10%314423346%59%
1750
21st to endDay
8%42332335%6%62%
1520
March1st to 10thDay
6%42432345%6%60%
1980
11th to 20thDay
6%31242245%7%64%
1980
21st to endDay
5%32332334469%
2178
April1st to 10thDay
3212223348%71%
1980
11th to 20thDay
221221323477%
2074
21st to endDay
221213235%79%
2270
May1st to 10thDay
1212212235%78%
2340
11th to 20thDay
1111223335%78%
2301
21st to endDay
211111121386%
2530
June1st to 10thDay
2112213235%79%
2340
11th to 20thDay
11111122388%
2340
21st to endDay
2112222335%77%
2340
July1st to 10thDay
321332446%7%64%
2340
11th to 20thDay
32145%35%6%7%11%52%
2340
21st to endDay
6%325%5%46%6%7%12%45%
2545
August1st to 10thDay
4313425%5%6%9%58%
2328
11th to 20thDay
3314425%6%7%10%54%
2299
21st to endDay
3223435%5%6%8%59%
2358
September1st to 10thDay
432332345%6%65%
1980
11th to 20thDay
321212245%78%
1980
21st to endDay
3112223335%75%
1980
October1st to 10thDay
321222335%5%72%
1926
11th to 20thDay
21111223383%
1800
21st to endDay
211221223479%
1980
November1st to 10thDay
3112213247%74%
1859
11th to 20thDay
2312322345%73%
1786
21st to endDay
7%314323336%65%
1710
December1st to 10thDay
8%313424446%61%
1710
11th to 20thDay
7%5%25%5%3446%7%52%
2169
21st to endDay
12%5%24423445%54%
3146
January1st to 10thNight
8%313425%45%6%60%
2457
11th to 20thNight
8%31332333466%
2379
21st to endNight
10%424323335%60%
2574
February1st to 10thNight
6%313213446%67%
2290
11th to 20thNight
9%424323445%60%
2098
21st to endNight
10%324323435%61%
1736
March1st to 10thNight
6%31332345%7%63%
1980
11th to 20thNight
8%31332234468%
1980
21st to endNight
5%213323347%66%
2178
April1st to 10thNight
3222225%337%69%
1980
11th to 20thNight
3112213335%75%
1831
21st to endNight
3211212235%79%
1686
May1st to 10thNight
2212122347%75%
1620
11th to 20thNight
2112212345%78%
1594
21st to endNight
21111122386%
1746
June1st to 10thNight
2111212336%76%
1620
11th to 20thNight
1112235%86%
1620
21st to endNight
2112222345%75%
1620
July1st to 10thNight
21246%3446%9%59%
1620
11th to 20thNight
12145%36%6%9%12%51%
1620
21st to endNight
4325%6%47%7%10%14%39%
1773
August1st to 10thNight
22135%345%8%10%55%
1611
11th to 20thNight
3425%5%45%6%7%8%52%
1602
21st to endNight
42245%35%6%7%9%55%
1992
September1st to 10thNight
43234335%6%8%59%
1980
11th to 20thNight
2213322345%74%
1980
21st to endNight
3113223345%72%
1980
October1st to 10thNight
421331235%5%71%
2034
11th to 20thNight
321111123481%
2160
21st to endNight
221211222481%
2376
November1st to 10thNight
421221235%5%73%
2220
11th to 20thNight
2313323325%75%
2389
21st to endNight
7%313323345%66%
2470
December1st to 10thNight
8%313323446%63%
2470
11th to 20thNight
11%5%25%42345%6%52%
3041
21st to endNight
12%41343444457%
4521

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
24%35%16%29%23%
1709
11th to 20thDay
22%3412%27%31%
1642
21st to endDay
24%2416%27%27%
1782
February1st to 10thDay
20%25%15%23%36%
1667
11th to 20thDay
27%35%12%25%28%
1760
21st to endDay
24%4313%27%29%
1520
March1st to 10thDay
24%2310%27%33%
1980
11th to 20thDay
20%3411%25%37%
1980
21st to endDay
20%3310%34%31%
2178
April1st to 10thDay
14%2210%35%37%
1980
11th to 20thDay
13%228%26%49%
2077
21st to endDay
10%2210%25%52%
2270
May1st to 10thDay
11%237%25%53%
2340
11th to 20thDay
11%238%24%53%
2304
21st to endDay
7%125%22%63%
2530
June1st to 10thDay
9%12420%63%
2340
11th to 20thDay
6%11210%80%
2340
21st to endDay
10%337%15%62%
2340
July1st to 10thDay
18%5%6%11%19%42%
2276
11th to 20thDay
23%8%13%24%19%12%
2271
21st to endDay
28%8%16%22%17%10%
2404
August1st to 10thDay
22%5%10%17%16%29%
2313
11th to 20thDay
22%7%11%20%21%20%
2299
21st to endDay
20%6%8%17%27%22%
2358
September1st to 10thDay
19%48%14%24%30%
1980
11th to 20thDay
10%239%30%45%
1980
21st to endDay
13%338%23%50%
1980
October1st to 10thDay
14%3413%24%41%
1926
11th to 20thDay
8%137%25%56%
1800
21st to endDay
11%2310%26%48%
1980
November1st to 10thDay
12%2312%34%37%
1859
11th to 20thDay
16%2211%25%44%
1786
21st to endDay
22%3312%23%36%
1710
December1st to 10thDay
26%3415%23%30%
1710
11th to 20thDay
30%46%18%23%19%
2168
21st to endDay
31%45%18%26%16%
3146
January1st to 10thNight
25%35%13%31%24%
2457
11th to 20thNight
23%3411%29%31%
2379
21st to endNight
28%3412%27%27%
2574
February1st to 10thNight
19%3412%23%38%
2290
11th to 20thNight
26%4314%24%29%
2099
21st to endNight
26%2410%26%33%
1736
March1st to 10thNight
20%3312%25%36%
1980
11th to 20thNight
20%2210%25%40%
1980
21st to endNight
19%2311%34%31%
2178
April1st to 10thNight
17%229%29%42%
1980
11th to 20thNight
13%237%26%50%
1831
21st to endNight
10%227%23%56%
1686
May1st to 10thNight
11%239%25%51%
1620
11th to 20thNight
11%238%21%56%
1595
21st to endNight
8%115%18%67%
1746
June1st to 10thNight
11%21417%65%
1620
11th to 20thNight
421411%77%
1620
21st to endNight
12%35%412%64%
1620
July1st to 10thNight
21%6%6%12%14%41%
1575
11th to 20thNight
20%9%13%20%22%14%
1566
21st to endNight
30%9%15%19%15%11%
1674
August1st to 10thNight
21%6%10%18%15%30%
1602
11th to 20thNight
26%7%10%18%18%21%
1602
21st to endNight
23%6%9%16%24%22%
1992
September1st to 10thNight
21%49%18%19%28%
1980
11th to 20thNight
14%4310%24%46%
1980
21st to endNight
14%437%22%49%
1980
October1st to 10thNight
15%3412%22%44%
2034
11th to 20thNight
10%227%21%58%
2160
21st to endNight
9%2310%23%53%
2376
November1st to 10thNight
14%329%30%42%
2220
11th to 20thNight
15%2311%24%45%
2389
21st to endNight
21%2310%28%36%
2470
December1st to 10thNight
22%3416%22%32%
2470
11th to 20thNight
32%35%14%24%21%
3041
21st to endNight
30%46%16%25%20%
4521

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
13%422%41%18%1
270
11th to 20thDay
14%419%39%21%4
248
21st to endDay
8%6%22%40%20%4
264
February1st to 10thDay
7%6%22%41%20%4
287
11th to 20thDay
13%10%26%34%17%1
415
21st to endDay
10%11%30%37%12%
346
March1st to 10thDay
7%11%30%38%12%2
420
11th to 20thDay
8%9%26%31%23%3
420
21st to endDay
7%13%29%35%14%2
462
April1st to 10thDay
5%7%26%37%19%5%
420
11th to 20thDay
312%29%38%15%3
412
21st to endDay
311%28%34%18%7%
420
May1st to 10thDay
39%23%36%23%5%
423
11th to 20thDay
2423%39%26%5%
448
21st to endDay
17%24%38%27%3
485
June1st to 10thDay
3217%35%34%8%
450
11th to 20thDay
2120%38%30%9%
450
21st to endDay
229%44%35%8%
450
July1st to 10thDay
27%35%41%15%
446
11th to 20thDay
5%5%28%40%23%
444
21st to endDay
41322%45%25%
487
August1st to 10thDay
4227%43%24%
447
11th to 20thDay
32326%43%22%
437
21st to endDay
21422%46%26%
495
September1st to 10thDay
4110%29%44%12%
450
11th to 20thDay
418%35%42%9%
450
21st to endDay
4313%38%32%10%
450
October1st to 10thDay
4318%37%33%5%
396
11th to 20thDay
3417%34%33%9%
270
21st to endDay
35%13%41%28%10%
297
November1st to 10thDay
7%414%45%25%6%
270
11th to 20thDay
5%315%44%29%5%
270
21st to endDay
9%422%39%22%4
270
December1st to 10thDay
10%219%41%25%3
270
11th to 20thDay
5%5%23%46%19%2
270
21st to endDay
18%6%26%33%15%3
297
January1st to 10thNight
9%218%49%20%1
760
11th to 20thNight
9%220%45%22%2
732
21st to endNight
12%418%45%18%3
792
February1st to 10thNight
7%318%49%22%2
720
11th to 20thNight
11%220%49%17%1
704
21st to endNight
11%319%49%17%2
592
March1st to 10thNight
7%323%51%15%2
720
11th to 20thNight
8%315%41%28%5%
720
21st to endNight
5%318%45%27%2
792
April1st to 10thNight
4314%53%24%2
720
11th to 20thNight
3321%49%22%1
587
21st to endNight
4216%50%24%4
540
May1st to 10thNight
3315%49%28%3
540
11th to 20thNight
2213%51%29%3
531
21st to endNight
3111%50%32%3
584
June1st to 10thNight
216%48%41%2
540
11th to 20thNight
16%52%38%2
540
21st to endNight
215%36%51%4
540
July1st to 10thNight
216%33%54%5%
525
11th to 20thNight
2319%68%7%
522
21st to endNight
41317%64%10%
591
August1st to 10thNight
2119%67%10%
537
11th to 20thNight
31323%62%7%
534
21st to endNight
3322%64%8%
660
September1st to 10thNight
5%15%31%51%7%
720
11th to 20thNight
217%40%44%4
720
21st to endNight
318%45%38%5%
720
October1st to 10thNight
4112%49%32%2
720
11th to 20thNight
4111%48%33%3
720
21st to endNight
2114%44%32%6%
792
November1st to 10thNight
5%211%50%28%4
740
11th to 20thNight
4115%49%28%3
760
21st to endNight
7%118%47%24%2
760
December1st to 10thNight
9%217%45%26%1
760
11th to 20thNight
12%315%47%22%2
760
21st to endNight
11%319%45%19%3
836
Page generated at 2024-01-10 17:35:19. Version ac07

Copyright 2024 Attilla Danko


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