Oberlin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oberlin clear sky chart from 2005-11-06 to 2024-01-31.

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
34%
23631
14%
74718
10%
23580
39%
23580
18%
53394

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
13%
758
10%
2459
4%
757
20%
757
9%
1946
January11th to 20thNight
12%
760
5%
2470
3%
760
16%
760
7%
2083
January21st to endNight
15%
835
9%
2711
4%
835
21%
835
9%
2188
February1st to 10thNight
14%
720
7%
2340
3%
720
20%
720
9%
1864
February11th to 20thNight
18%
701
10%
2185
5%
700
23%
700
10%
1725
February21st to endNight
15%
592
11%
1776
2%
592
24%
592
11%
1396
March1st to 10thNight
23%
720
14%
2060
8%
720
30%
720
17%
1525
March11th to 20thNight
27%
720
18%
1980
8%
720
35%
720
20%
1409
March21st to endNight
29%
792
15%
2178
10%
792
34%
792
18%
1616
April1st to 10thNight
27%
719
12%
1974
5%
719
33%
719
20%
1429
April11th to 20thNight
30%
533
18%
1597
8%
533
38%
533
21%
1109
April21st to endNight
33%
540
16%
1620
7%
540
40%
540
22%
1108
May1st to 10thNight
35%
540
10%
1620
7%
540
38%
540
17%
1202
May11th to 20thNight
42%
531
15%
1592
11%
531
45%
531
23%
1080
May21st to endNight
56%
582
15%
1745
11%
582
60%
582
30%
1067
June1st to 10thNight
51%
446
14%
1526
12%
446
56%
446
25%
931
June11th to 20thNight
51%
360
18%
1353
18%
360
58%
360
24%
802
June21st to endNight
56%
488
18%
1388
16%
488
60%
488
32%
866
July1st to 10thNight
64%
525
15%
1408
14%
525
66%
525
35%
885
July11th to 20thNight
63%
522
16%
1566
15%
522
65%
522
35%
921
July21st to endNight
63%
591
18%
1672
15%
558
65%
558
34%
1012
August1st to 10thNight
68%
537
20%
1600
17%
534
69%
534
35%
951
August11th to 20thNight
64%
534
21%
1598
17%
534
66%
534
30%
988
August21st to endNight
60%
594
21%
1782
17%
594
63%
594
32%
1074
September1st to 10thNight
59%
710
19%
1929
14%
710
61%
710
31%
1243
September11th to 20thNight
61%
720
27%
1980
20%
720
65%
720
37%
1196
September21st to endNight
47%
720
21%
1980
16%
720
51%
720
27%
1329
October1st to 10thNight
47%
720
18%
2070
15%
720
50%
720
26%
1345
October11th to 20thNight
30%
720
16%
2160
11%
720
37%
720
20%
1497
October21st to endNight
23%
792
16%
2418
10%
792
31%
792
15%
1774
November1st to 10thNight
32%
740
18%
2406
14%
740
39%
740
20%
1586
November11th to 20thNight
21%
760
15%
2470
8%
760
29%
760
14%
1789
November21st to endNight
22%
760
11%
2603
8%
760
27%
760
11%
1983
December1st to 10thNight
16%
760
7%
2660
4%
760
20%
760
8%
2136
December11th to 20thNight
14%
759
8%
3262
3%
759
21%
759
8%
2476
December21st to endNight
14%
830
4%
4580
3%
817
20%
817
4%
3863

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
15%10%47%6%45%5%5%7%32%
75141
Night
16%10%47%6%35%45%7%33%
74958
TransparencyDay
51%7%12%18%11%1
74858
Night
51%7%12%18%11%2
74761
SeeingDay
20%13%28%22%12%5%
13949
Night
21%11%27%27%12%1
23644

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
17%17%7%11%8%46%445%17%
1706
11th to 20thDay
19%19%8%12%9%4444414%
1710
21st to endDay
18%18%9%14%9%43445%13%
1872
February1st to 10thDay
18%17%6%11%8%35%44421%
1620
11th to 20thDay
15%13%7%13%10%5%45%45%19%
1662
21st to endDay
19%13%5%11%6%445%5%6%23%
1480
March1st to 10thDay
20%12%6%8%6%3445%6%27%
1898
11th to 20thDay
16%12%6%9%7%35%445%30%
1980
21st to endDay
21%11%5%9%6%34446%26%
2178
April1st to 10thDay
14%13%47%7%345%5%6%32%
2001
11th to 20thDay
17%10%46%6%35%446%34%
2312
21st to endDay
21%9%36%5%24447%34%
2340
May1st to 10thDay
17%9%37%6%45%45%6%33%
2340
11th to 20thDay
18%8%36%6%35%46%7%34%
2301
21st to endDay
10%5%35%6%45%6%6%9%40%
2531
June1st to 10thDay
13%6%35%5%45%6%6%8%39%
2430
11th to 20thDay
12%6%26%6%45%6%5%8%40%
2599
21st to endDay
11%5%246%46%5%7%10%41%
2563
July1st to 10thDay
10%5%25%6%45%5%5%8%44%
2506
11th to 20thDay
11%4345%25%5%7%11%42%
2340
21st to endDay
9%5%35%5%46%6%6%10%41%
2547
August1st to 10thDay
8%5%26%6%46%5%7%8%44%
2327
11th to 20thDay
10%6%36%6%46%6%6%9%37%
2303
21st to endDay
10%6%26%5%45%5%6%10%42%
2566
September1st to 10thDay
14%5%25%5%45%5%6%7%42%
2016
11th to 20thDay
11%6%35%6%3445%9%43%
1980
21st to endDay
17%7%25%5%445%5%7%40%
1980
October1st to 10thDay
13%8%26%5%45%5%6%7%39%
1890
11th to 20thDay
18%8%46%5%445%5%6%36%
1800
21st to endDay
21%12%36%6%445%5%6%28%
1936
November1st to 10thDay
12%11%47%435%5%5%7%38%
1672
11th to 20thDay
17%15%46%6%34446%31%
1710
21st to endDay
16%17%6%7%7%45%5%5%6%22%
1573
December1st to 10thDay
17%18%7%9%7%35%5%5%418%
1520
11th to 20thDay
17%17%7%13%6%3445%6%18%
1910
21st to endDay
23%23%7%9%7%4444411%
3042
January1st to 10thNight
19%14%7%10%7%4445%422%
2459
11th to 20thNight
19%18%7%12%8%34445%16%
2470
21st to endNight
19%17%6%11%8%44435%20%
2711
February1st to 10thNight
21%13%6%10%7%3445%5%22%
2340
11th to 20thNight
17%14%6%10%7%46%445%23%
2183
21st to endNight
20%13%5%10%6%44445%25%
1776
March1st to 10thNight
17%12%6%8%6%34446%32%
2060
11th to 20thNight
15%9%5%6%5%346%5%6%35%
1980
21st to endNight
19%11%5%6%6%2445%6%32%
2178
April1st to 10thNight
14%11%5%6%6%25%46%7%34%
1974
11th to 20thNight
16%9%46%6%35%5%6%7%34%
1597
21st to endNight
17%8%36%5%35%46%7%36%
1620
May1st to 10thNight
17%9%47%7%45%5%6%7%29%
1620
11th to 20thNight
16%8%45%43447%8%36%
1592
21st to endNight
9%5%246%35%6%7%10%44%
1744
June1st to 10thNight
11%5%35%5%35%46%7%45%
1526
11th to 20thNight
9%6%26%5%46%5%7%10%41%
1353
21st to endNight
10%5%35%445%6%5%9%45%
1388
July1st to 10thNight
8%425%5%35%5%6%9%48%
1448
11th to 20thNight
8%3245%246%7%11%47%
1620
21st to endNight
8%425%5%35%5%7%9%47%
1771
August1st to 10thNight
7%426%435%5%7%9%49%
1611
11th to 20thNight
8%6%35%5%35%5%7%8%46%
1598
21st to endNight
8%5%25%436%5%7%8%46%
1782
September1st to 10thNight
11%5%246%45%5%5%7%47%
1929
11th to 20thNight
11%425%42445%7%52%
1980
21st to endNight
13%6%36%6%35%5%5%6%43%
1980
October1st to 10thNight
14%6%26%5%35%5%46%43%
2070
11th to 20thNight
20%8%26%6%35%45%7%36%
2160
21st to endNight
24%10%36%5%4445%6%29%
2418
November1st to 10thNight
15%9%36%5%3445%7%38%
2406
11th to 20thNight
16%13%48%6%44446%30%
2470
21st to endNight
21%14%5%8%6%35%446%24%
2603
December1st to 10thNight
19%18%8%8%5%35%445%21%
2660
11th to 20thNight
17%16%7%10%6%345%5%6%23%
3285
21st to endNight
25%19%6%8%6%34445%13%
4596

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
69%6%10%11%3
1707
11th to 20thDay
74%6%11%7%2
1710
21st to endDay
75%5%8%9%3
1872
February1st to 10thDay
67%411%12%5%
1620
11th to 20thDay
68%5%9%12%5%1
1671
21st to endDay
60%7%14%11%7%1
1480
March1st to 10thDay
58%5%11%19%6%
1898
11th to 20thDay
58%6%9%16%9%1
1980
21st to endDay
59%6%8%18%7%1
2178
April1st to 10thDay
52%7%11%18%11%1
2001
11th to 20thDay
51%6%12%16%13%2
2312
21st to endDay
50%6%11%20%10%2
2340
May1st to 10thDay
52%7%11%19%10%2
2340
11th to 20thDay
48%8%11%17%13%2
2305
21st to endDay
39%9%14%24%13%2
2531
June1st to 10thDay
42%8%11%24%14%1
2430
11th to 20thDay
41%8%14%21%14%2
2599
21st to endDay
36%9%14%21%17%3
2563
July1st to 10thDay
38%7%11%23%18%3
2437
11th to 20thDay
34%7%15%26%15%2
2271
21st to endDay
35%9%16%23%15%2
2405
August1st to 10thDay
37%8%15%25%14%
2314
11th to 20thDay
40%8%16%23%10%2
2303
21st to endDay
37%8%14%22%16%3
2566
September1st to 10thDay
39%9%15%19%15%3
2016
11th to 20thDay
39%6%14%24%15%2
1980
21st to endDay
43%7%11%21%18%
1980
October1st to 10thDay
42%8%12%22%15%1
1890
11th to 20thDay
47%7%13%20%12%1
1800
21st to endDay
56%7%13%15%9%1
1936
November1st to 10thDay
46%5%12%21%14%1
1672
11th to 20thDay
55%5%11%19%9%1
1710
21st to endDay
61%7%13%13%6%
1573
December1st to 10thDay
69%6%10%11%3
1520
11th to 20thDay
67%7%10%13%3
1906
21st to endDay
78%5%8%6%2
3042
January1st to 10thNight
66%5%10%13%6%
2459
11th to 20thNight
71%6%11%10%3
2470
21st to endNight
67%5%11%12%41
2711
February1st to 10thNight
65%5%11%13%4
2340
11th to 20thNight
63%6%10%14%7%
2185
21st to endNight
62%6%9%13%7%2
1776
March1st to 10thNight
54%5%11%20%9%1
2060
11th to 20thNight
48%7%11%19%12%2
1980
21st to endNight
53%6%8%21%10%2
2178
April1st to 10thNight
50%6%12%17%13%2
1974
11th to 20thNight
47%7%12%16%16%3
1597
21st to endNight
46%6%13%19%14%3
1620
May1st to 10thNight
53%8%11%15%11%2
1620
11th to 20thNight
44%8%13%16%17%3
1593
21st to endNight
33%9%16%24%15%2
1745
June1st to 10thNight
38%7%12%25%14%3
1526
11th to 20thNight
36%8%16%20%18%2
1353
21st to endNight
34%8%14%25%16%3
1388
July1st to 10thNight
33%8%13%23%19%4
1408
11th to 20thNight
28%10%16%24%19%3
1566
21st to endNight
31%8%17%23%17%4
1672
August1st to 10thNight
29%9%15%27%18%1
1600
11th to 20thNight
34%9%16%27%13%2
1598
21st to endNight
32%8%16%23%18%3
1782
September1st to 10thNight
37%7%14%23%16%4
1929
11th to 20thNight
30%8%12%27%21%1
1980
21st to endNight
41%7%12%21%18%2
1980
October1st to 10thNight
40%7%13%20%19%1
2070
11th to 20thNight
48%6%11%21%13%1
2160
21st to endNight
54%6%11%18%9%1
2418
November1st to 10thNight
44%7%13%20%14%2
2406
11th to 20thNight
54%6%12%17%9%2
2470
21st to endNight
61%5%13%15%5%
2603
December1st to 10thNight
66%6%11%11%6%
2660
11th to 20thNight
61%7%13%15%3
3288
21st to endNight
73%7%11%8%2
4596

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
27%21%34%11%6%1
270
11th to 20thDay
30%27%31%7%4
270
21st to endDay
29%26%28%15%11
294
February1st to 10thDay
35%21%34%10%
240
11th to 20thDay
32%23%33%11%1
240
21st to endDay
28%31%33%8%1
198
March1st to 10thDay
27%19%34%14%5%
338
11th to 20thDay
25%16%34%19%5%
420
21st to endDay
31%15%31%18%5%1
462
April1st to 10thDay
24%17%32%19%8%1
420
11th to 20thDay
25%17%27%17%9%4
412
21st to endDay
27%15%31%17%8%2
420
May1st to 10thDay
27%13%30%22%7%3
423
11th to 20thDay
22%9%32%22%10%4
447
21st to endDay
14%7%27%28%19%5%
485
June1st to 10thDay
12%8%29%33%15%3
450
11th to 20thDay
13%9%28%30%17%3
529
21st to endDay
11%10%30%30%16%3
630
July1st to 10thDay
10%5%21%30%23%11%
607
11th to 20thDay
13%5%23%29%22%9%
444
21st to endDay
10%5%25%31%22%8%
488
August1st to 10thDay
9%421%30%24%11%
446
11th to 20thDay
14%5%21%28%22%10%
439
21st to endDay
11%6%21%27%23%12%
495
September1st to 10thDay
15%7%22%22%22%11%
450
11th to 20thDay
11%6%18%27%25%13%
450
21st to endDay
18%12%26%21%14%9%
450
October1st to 10thDay
13%10%28%24%18%7%
450
11th to 20thDay
19%18%32%23%7%1
450
21st to endDay
30%20%28%17%4
451
November1st to 10thDay
18%21%32%17%10%2
270
11th to 20thDay
28%23%27%16%6%
270
21st to endDay
29%22%36%12%1
205
December1st to 10thDay
23%26%32%14%32
180
11th to 20thDay
23%26%40%10%1
180
21st to endDay
27%25%34%11%3
276
January1st to 10thNight
27%20%32%16%4
760
11th to 20thNight
31%19%31%16%4
760
21st to endNight
26%15%34%21%3
835
February1st to 10thNight
28%16%32%21%2
720
11th to 20thNight
26%17%32%22%3
703
21st to endNight
28%16%35%18%3
592
March1st to 10thNight
23%14%33%23%6%
720
11th to 20thNight
21%14%33%25%6%1
720
21st to endNight
25%11%29%26%9%
792
April1st to 10thNight
20%15%32%28%4
719
11th to 20thNight
21%12%32%25%9%1
533
21st to endNight
21%7%34%30%7%1
540
May1st to 10thNight
20%9%27%33%9%1
540
11th to 20thNight
20%7%26%31%14%2
531
21st to endNight
11%5%21%36%24%3
584
June1st to 10thNight
12%426%43%15%1
446
11th to 20thNight
10%327%43%16%1
360
21st to endNight
11%324%41%19%1
488
July1st to 10thNight
10%215%40%30%2
525
11th to 20thNight
9%418%43%23%4
522
21st to endNight
9%217%42%28%2
591
August1st to 10thNight
9%214%43%28%4
537
11th to 20thNight
10%315%40%28%4
534
21st to endNight
10%319%33%31%4
594
September1st to 10thNight
13%5%17%36%25%5%
710
11th to 20thNight
12%414%35%30%5%
720
21st to endNight
15%9%22%30%20%3
720
October1st to 10thNight
17%8%23%31%18%2
720
11th to 20thNight
23%13%30%25%8%1
720
21st to endNight
28%16%28%22%5%
792
November1st to 10thNight
20%12%31%25%10%1
740
11th to 20thNight
26%14%34%19%6%1
760
21st to endNight
30%16%29%20%6%
760
December1st to 10thNight
28%18%31%17%5%
760
11th to 20thNight
26%16%36%18%3
760
21st to endNight
29%17%32%19%2
836
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