Circle City Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Circle City Observatory clear sky chart from 2005-11-06 to 2024-02-25.

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
44%
24659
22%
79720
14%
24563
53%
24563
25%
48910

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
26%
753
27%
3995
10%
737
43%
737
14%
2154
January11th to 20thNight
29%
756
28%
3952
12%
740
45%
740
15%
2151
January21st to endNight
26%
828
19%
4441
13%
814
46%
814
15%
2610
February1st to 10thNight
30%
760
22%
2470
12%
760
45%
760
25%
1511
February11th to 20thNight
19%
740
20%
2384
7%
739
35%
739
19%
1524
February21st to endNight
26%
611
28%
1684
11%
611
42%
611
26%
1070
March1st to 10thNight
29%
720
27%
1980
13%
720
42%
720
31%
1200
March11th to 20thNight
28%
720
20%
1980
10%
720
38%
720
24%
1315
March21st to endNight
28%
792
21%
2178
9%
792
38%
792
25%
1426
April1st to 10thNight
31%
720
24%
1886
10%
720
41%
720
30%
1179
April11th to 20thNight
36%
711
26%
1775
10%
711
45%
711
35%
1108
April21st to endNight
39%
720
23%
1800
9%
720
46%
720
33%
1158
May1st to 10thNight
40%
558
18%
1638
8%
558
47%
558
29%
1016
May11th to 20thNight
49%
531
17%
1592
10%
531
53%
531
25%
1046
May21st to endNight
64%
582
16%
1744
12%
582
65%
582
29%
1089
June1st to 10thNight
59%
540
16%
1620
15%
540
61%
540
26%
1046
June11th to 20thNight
58%
540
15%
1620
10%
540
61%
540
27%
1046
June21st to endNight
66%
540
17%
1620
13%
540
69%
540
28%
1046
July1st to 10thNight
67%
525
13%
1575
11%
525
68%
525
26%
1053
July11th to 20thNight
71%
522
13%
1566
12%
522
71%
522
28%
1018
July21st to endNight
66%
591
16%
1672
12%
558
68%
558
28%
1071
August1st to 10thNight
67%
537
12%
1600
11%
534
67%
534
24%
1093
August11th to 20thNight
63%
570
16%
1634
12%
570
64%
570
25%
1115
August21st to endNight
61%
792
15%
1980
10%
792
63%
792
31%
1340
September1st to 10thNight
66%
720
23%
1800
17%
720
66%
720
35%
1177
September11th to 20thNight
59%
720
25%
1949
20%
720
61%
720
31%
1259
September21st to endNight
48%
720
18%
2002
14%
720
53%
720
24%
1393
October1st to 10thNight
52%
720
26%
2160
23%
720
59%
720
32%
1311
October11th to 20thNight
45%
720
30%
2160
22%
720
57%
720
32%
1271
October21st to endNight
48%
792
32%
2376
21%
792
62%
792
34%
1347
November1st to 10thNight
47%
740
28%
2221
20%
740
58%
740
32%
1305
November11th to 20thNight
41%
760
28%
2301
18%
760
54%
760
29%
1367
November21st to endNight
42%
760
28%
2470
18%
760
56%
760
30%
1406
December1st to 10thNight
32%
760
22%
2557
12%
760
46%
760
20%
1634
December11th to 20thNight
38%
760
27%
2949
18%
758
51%
758
24%
1710
December21st to endNight
32%
828
17%
4389
14%
817
45%
817
15%
2345

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
14%5%25%5%35%5%5%7%44%
78720
Night
14%5%25%5%3445%7%45%
80538
TransparencyDay
39%5%11%21%19%5%
78442
Night
39%5%10%20%20%6%
80335
SeeingDay
17%11%25%25%17%6%
14425
Night
16%9%24%31%18%2
24691

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
19%424423335%51%
2836
11th to 20thDay
14%6%25%423335%53%
2840
21st to endDay
19%10%35%42344442%
3124
February1st to 10thDay
15%6%345%345%5%7%44%
1710
11th to 20thDay
21%7%34323435%46%
1677
21st to endDay
20%7%26%433446%41%
1666
March1st to 10thDay
15%5%24333346%52%
1980
11th to 20thDay
16%5%35%43445%8%43%
1980
21st to endDay
17%6%36%5%34446%41%
2178
April1st to 10thDay
11%31442445%8%54%
2074
11th to 20thDay
11%5%2443445%8%49%
2134
21st to endDay
14%5%245%36%446%46%
2160
May1st to 10thDay
11%6%35%5%35%5%6%8%43%
2336
11th to 20thDay
14%6%26%5%45%6%6%7%40%
2301
21st to endDay
12%5%26%7%45%6%7%8%39%
2531
June1st to 10thDay
9%5%25%6%37%7%8%9%39%
2340
11th to 20thDay
9%325%6%36%6%7%10%43%
2340
21st to endDay
7%425%6%46%8%7%10%39%
2340
July1st to 10thDay
9%435%8%5%7%6%8%11%34%
2340
11th to 20thDay
8%5%36%6%48%8%9%12%32%
2340
21st to endDay
6%5%26%7%47%8%7%11%35%
2547
August1st to 10thDay
11%6%36%6%46%7%8%10%33%
2327
11th to 20thDay
10%6%37%7%6%7%7%8%9%31%
2249
21st to endDay
11%7%25%6%46%6%7%10%37%
2376
September1st to 10thDay
9%4145%46%5%6%9%47%
2160
11th to 20thDay
14%6%26%5%345%5%7%43%
2007
21st to endDay
20%6%25%43446%6%39%
1958
October1st to 10thDay
17%5%34422347%49%
1800
11th to 20thDay
14%313434345%55%
1800
21st to endDay
12%5%25%423235%57%
1980
November1st to 10thDay
15%5%23322345%56%
1857
11th to 20thDay
14%5%2432345%6%53%
1877
21st to endDay
14%5%14424446%50%
1710
December1st to 10thDay
19%7%25%42435%7%42%
1568
11th to 20thDay
16%423312346%56%
2153
21st to endDay
18%6%245%345%5%7%42%
3124
January1st to 10thNight
16%6%245%34345%48%
4109
11th to 20thNight
14%6%25%5%24445%47%
4120
21st to endNight
20%6%25%423445%44%
4532
February1st to 10thNight
17%5%25%42445%6%45%
2470
11th to 20thNight
21%7%24434446%43%
2384
21st to endNight
16%6%2442445%6%46%
1684
March1st to 10thNight
13%434423446%51%
1980
11th to 20thNight
17%5%25%6%3445%6%42%
1980
21st to endNight
16%6%26%435%45%6%44%
2178
April1st to 10thNight
15%42442435%7%50%
1886
11th to 20thNight
13%5%245%23447%51%
1775
21st to endNight
12%425%5%35%5%6%7%46%
1800
May1st to 10thNight
11%5%26%5%26%46%8%45%
1638
11th to 20thNight
14%6%25%6%45%5%6%8%40%
1592
21st to endNight
11%425%6%345%7%9%42%
1744
June1st to 10thNight
10%5%35%6%45%6%7%10%39%
1620
11th to 20thNight
10%5%26%6%45%5%8%10%38%
1620
21st to endNight
7%6%35%5%45%6%8%11%40%
1620
July1st to 10thNight
7%5%37%6%46%7%8%11%36%
1620
11th to 20thNight
7%5%25%6%46%8%9%12%38%
1620
21st to endNight
7%436%6%46%7%8%11%38%
1771
August1st to 10thNight
12%435%6%5%6%7%7%11%33%
1611
11th to 20thNight
12%5%35%6%46%6%8%10%35%
1634
21st to endNight
10%6%36%6%45%6%7%11%37%
1980
September1st to 10thNight
10%5%26%5%345%5%8%47%
1800
11th to 20thNight
14%5%25%5%2445%7%45%
1949
21st to endNight
19%7%35%6%3445%7%37%
2002
October1st to 10thNight
14%5%35%5%32336%51%
2160
11th to 20thNight
14%6%25%41335%5%52%
2160
21st to endNight
12%5%24433345%56%
2376
November1st to 10thNight
14%6%2442334454%
2221
11th to 20thNight
13%5%25%424446%51%
2301
21st to endNight
14%42443445%7%51%
2470
December1st to 10thNight
18%6%26%5%34446%42%
2557
11th to 20thNight
17%6%24423445%49%
3042
21st to endNight
18%5%24433446%47%
4532

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
38%2425%24%6%
2837
11th to 20thDay
36%35%17%33%6%
2840
21st to endDay
46%4417%22%7%
3124
February1st to 10thDay
40%310%21%20%5%
1710
11th to 20thDay
43%36%19%22%7%
1686
21st to endDay
45%47%17%19%6%
1666
March1st to 10thDay
36%38%22%24%7%
1980
11th to 20thDay
41%410%20%18%7%
1980
21st to endDay
45%410%18%18%4
2178
April1st to 10thDay
29%410%24%24%8%
2074
11th to 20thDay
34%411%23%20%9%
2134
21st to endDay
39%410%23%19%5%
2160
May1st to 10thDay
38%5%16%21%17%4
2336
11th to 20thDay
43%5%14%22%13%2
2305
21st to endDay
41%6%15%23%14%1
2531
June1st to 10thDay
39%8%15%23%14%1
2340
11th to 20thDay
35%6%17%24%15%2
2340
21st to endDay
36%9%17%22%15%2
2340
July1st to 10thDay
41%9%16%20%12%3
2275
11th to 20thDay
39%9%20%21%8%2
2271
21st to endDay
39%9%20%22%9%
2405
August1st to 10thDay
43%9%19%20%9%1
2314
11th to 20thDay
46%9%16%18%9%1
2249
21st to endDay
41%7%17%21%10%3
2376
September1st to 10thDay
33%7%16%20%18%5%
2160
11th to 20thDay
40%5%12%17%22%4
2007
21st to endDay
45%49%21%16%5%
1958
October1st to 10thDay
37%39%23%24%4
1800
11th to 20thDay
32%48%27%22%8%
1800
21st to endDay
33%36%23%25%9%
1980
November1st to 10thDay
33%38%21%28%9%
1857
11th to 20thDay
33%38%21%27%8%
1877
21st to endDay
35%48%23%24%7%
1710
December1st to 10thDay
43%310%21%19%4
1568
11th to 20thDay
33%27%25%25%9%
2150
21st to endDay
42%39%22%21%3
3124
January1st to 10thNight
39%36%21%25%6%
4109
11th to 20thNight
39%38%17%27%6%
4120
21st to endNight
44%35%18%23%7%
4532
February1st to 10thNight
40%38%22%21%6%
2470
11th to 20thNight
44%38%15%22%8%
2386
21st to endNight
38%48%19%22%8%
1684
March1st to 10thNight
35%38%21%23%10%
1980
11th to 20thNight
43%49%18%19%6%
1980
21st to endNight
42%410%20%20%4
2178
April1st to 10thNight
35%49%18%26%8%
1886
11th to 20thNight
34%410%23%22%8%
1775
21st to endNight
36%5%11%24%19%5%
1800
May1st to 10thNight
36%6%15%22%18%4
1638
11th to 20thNight
42%6%13%22%16%1
1593
21st to endNight
37%7%17%24%14%1
1745
June1st to 10thNight
39%8%15%22%14%2
1620
11th to 20thNight
39%8%17%19%16%2
1620
21st to endNight
36%10%16%22%14%3
1620
July1st to 10thNight
39%10%17%18%13%3
1575
11th to 20thNight
35%11%22%20%9%2
1566
21st to endNight
37%8%22%21%11%
1672
August1st to 10thNight
43%9%20%19%9%1
1600
11th to 20thNight
41%10%20%19%9%1
1634
21st to endNight
39%7%20%21%9%3
1980
September1st to 10thNight
35%7%15%21%16%6%
1800
11th to 20thNight
38%6%11%19%22%3
1949
21st to endNight
46%5%12%16%16%4
2002
October1st to 10thNight
37%47%24%24%4
2160
11th to 20thNight
35%37%23%24%8%
2160
21st to endNight
32%37%21%26%11%
2376
November1st to 10thNight
35%37%19%26%10%
2221
11th to 20thNight
36%37%16%25%12%
2301
21st to endNight
34%37%23%26%7%
2470
December1st to 10thNight
45%48%20%19%5%
2557
11th to 20thNight
39%28%20%23%9%
3044
21st to endNight
40%37%24%24%3
4532

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
26%23%35%14%2
270
11th to 20thDay
26%23%34%13%3
270
21st to endDay
21%25%39%13%3
297
February1st to 10thDay
20%20%40%15%4
270
11th to 20thDay
36%22%32%8%1
270
21st to endDay
25%21%34%16%4
356
March1st to 10thDay
20%20%34%20%6%
420
11th to 20thDay
21%21%38%14%5%1
420
21st to endDay
23%21%34%17%5%1
462
April1st to 10thDay
20%18%30%21%8%2
420
11th to 20thDay
14%19%30%22%10%4
412
21st to endDay
19%13%28%28%11%1
420
May1st to 10thDay
13%17%34%23%9%4
423
11th to 20thDay
14%9%23%27%21%6%
447
21st to endDay
18%5%20%26%25%8%
485
June1st to 10thDay
12%7%23%31%22%6%
450
11th to 20thDay
11%6%20%29%25%9%
450
21st to endDay
9%321%37%22%8%
450
July1st to 10thDay
11%111%31%32%14%
445
11th to 20thDay
7%211%27%39%13%
444
21st to endDay
6%214%36%29%12%
488
August1st to 10thDay
13%415%30%25%14%
446
11th to 20thDay
10%312%27%31%16%
439
21st to endDay
14%311%29%25%19%
495
September1st to 10thDay
12%214%27%28%17%
450
11th to 20thDay
17%412%29%26%12%
450
21st to endDay
23%5%21%30%17%4
450
October1st to 10thDay
20%6%21%25%21%8%
450
11th to 20thDay
14%10%24%30%18%6%
450
21st to endDay
15%11%28%29%15%3
495
November1st to 10thDay
20%9%27%27%13%4
455
11th to 20thDay
19%17%25%28%10%1
437
21st to endDay
13%20%32%21%12%1
270
December1st to 10thDay
25%17%37%15%6%
202
11th to 20thDay
21%17%33%21%8%1
270
21st to endDay
24%15%34%16%9%1
297
January1st to 10thNight
20%18%30%26%6%1
760
11th to 20thNight
20%13%33%28%6%
760
21st to endNight
20%13%35%28%3
836
February1st to 10thNight
20%13%35%29%4
760
11th to 20thNight
25%18%35%21%1
743
21st to endNight
18%15%37%26%4
611
March1st to 10thNight
17%14%36%28%4
720
11th to 20thNight
21%14%33%23%9%1
720
21st to endNight
18%15%35%26%6%
792
April1st to 10thNight
19%16%30%27%7%
720
11th to 20thNight
16%13%31%27%12%1
711
21st to endNight
14%8%34%34%10%
720
May1st to 10thNight
12%12%31%35%9%
558
11th to 20thNight
17%421%39%17%2
531
21st to endNight
13%211%42%29%3
584
June1st to 10thNight
13%314%42%26%2
540
11th to 20thNight
12%5%14%32%31%6%
540
21st to endNight
10%214%36%36%3
540
July1st to 10thNight
8%311%34%39%6%
525
11th to 20thNight
9%27%36%39%7%
522
21st to endNight
7%211%37%38%4
591
August1st to 10thNight
13%27%38%36%4
537
11th to 20thNight
14%39%31%38%6%
570
21st to endNight
11%411%28%39%7%
792
September1st to 10thNight
11%210%33%39%5%
720
11th to 20thNight
16%413%29%35%5%
720
21st to endNight
23%415%32%24%2
720
October1st to 10thNight
16%417%30%28%5%
720
11th to 20thNight
17%8%25%28%21%2
720
21st to endNight
15%10%23%33%19%1
792
November1st to 10thNight
16%8%24%34%16%3
740
11th to 20thNight
16%12%26%34%12%
760
21st to endNight
15%10%27%33%14%1
760
December1st to 10thNight
22%12%28%31%7%
760
11th to 20thNight
20%9%29%35%8%
760
21st to endNight
23%12%25%31%8%
836
Page generated at 2024-02-22 06:05:44. Version ac07

Copyright 2024 Attilla Danko


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