Perrysburg Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Perrysburg Observatory clear sky chart from 2005-11-06 to 2024-01-27.

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
35%
24381
15%
74751
10%
24326
41%
24326
20%
52502

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
16%
949
12%
2648
4%
946
24%
946
13%
2066
January11th to 20thNight
15%
924
7%
2634
3%
924
19%
924
10%
2139
January21st to endNight
17%
820
9%
2664
4%
820
23%
820
10%
2096
February1st to 10thNight
17%
720
7%
2340
3%
720
23%
720
10%
1832
February11th to 20thNight
22%
700
14%
2113
7%
700
29%
700
13%
1582
February21st to endNight
16%
592
14%
1776
3%
592
26%
592
14%
1333
March1st to 10thNight
27%
720
15%
2124
8%
720
33%
720
17%
1541
March11th to 20thNight
26%
720
19%
1980
10%
720
35%
720
22%
1371
March21st to endNight
29%
792
17%
2178
10%
792
36%
792
20%
1565
April1st to 10thNight
26%
622
14%
1882
6%
622
33%
622
19%
1275
April11th to 20thNight
30%
533
19%
1651
8%
533
40%
533
20%
1126
April21st to endNight
32%
540
17%
1620
6%
540
41%
540
23%
1104
May1st to 10thNight
35%
540
12%
1620
6%
540
40%
540
18%
1199
May11th to 20thNight
40%
531
17%
1592
10%
531
46%
531
23%
1078
May21st to endNight
54%
583
15%
1745
11%
582
57%
582
30%
1096
June1st to 10thNight
51%
540
15%
1504
11%
540
56%
540
31%
965
June11th to 20thNight
53%
540
18%
1440
14%
540
58%
540
31%
928
June21st to endNight
55%
540
19%
1440
13%
540
61%
540
33%
915
July1st to 10thNight
65%
525
17%
1400
15%
525
66%
525
36%
861
July11th to 20thNight
62%
522
20%
1392
15%
522
66%
522
39%
841
July21st to endNight
67%
591
18%
1668
15%
558
70%
558
37%
973
August1st to 10thNight
67%
537
20%
1600
16%
534
69%
534
37%
928
August11th to 20thNight
65%
534
23%
1598
18%
534
70%
534
33%
972
August21st to endNight
61%
594
22%
1837
17%
594
65%
594
33%
1098
September1st to 10thNight
57%
648
20%
1908
16%
648
60%
648
30%
1182
September11th to 20thNight
60%
720
28%
1980
21%
720
63%
720
38%
1178
September21st to endNight
50%
720
23%
1980
17%
720
54%
720
29%
1282
October1st to 10thNight
48%
720
21%
2011
16%
720
53%
720
30%
1279
October11th to 20thNight
32%
720
17%
2160
11%
720
40%
720
20%
1488
October21st to endNight
27%
792
17%
2510
12%
792
36%
792
17%
1749
November1st to 10thNight
35%
740
20%
2406
16%
740
43%
740
23%
1515
November11th to 20thNight
24%
760
17%
2470
10%
760
34%
760
17%
1714
November21st to endNight
24%
760
14%
2470
10%
760
29%
760
14%
1842
December1st to 10thNight
19%
760
9%
2470
5%
760
24%
760
11%
1917
December11th to 20thNight
19%
792
10%
3064
4%
791
27%
791
10%
2310
December21st to endNight
15%
1040
4%
4876
2%
1026
20%
1026
5%
4162

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%9%47%6%45%5%6%7%34%
75070
Night
16%9%47%5%35%45%7%35%
74978
TransparencyDay
48%8%12%19%11%1
74783
Night
48%7%12%19%12%1
74786
SeeingDay
17%12%29%24%13%5%
14451
Night
19%10%29%28%12%1
24392

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
18%14%6%11%8%46%5%36%19%
1517
11th to 20thDay
18%19%6%10%8%36%445%17%
1542
21st to endDay
18%17%9%10%7%45%445%18%
1836
February1st to 10thDay
16%15%6%10%8%5%5%45%420%
1620
11th to 20thDay
16%11%410%9%5%6%5%5%5%23%
1730
21st to endDay
19%12%5%10%6%335%5%7%26%
1480
March1st to 10thDay
18%11%49%8%35%5%5%6%26%
1836
11th to 20thDay
16%12%47%6%34447%33%
1980
21st to endDay
23%13%5%7%5%35%446%25%
2178
April1st to 10thDay
14%10%47%7%46%5%6%5%31%
2092
11th to 20thDay
18%7%36%5%45%5%6%8%33%
2258
21st to endDay
20%8%36%5%3445%7%35%
2340
May1st to 10thDay
17%8%37%6%45%5%7%7%31%
2340
11th to 20thDay
18%8%36%6%45%5%5%7%34%
2301
21st to endDay
11%5%26%7%36%7%6%8%39%
2531
June1st to 10thDay
13%6%25%5%46%7%6%7%39%
2452
11th to 20thDay
10%5%35%6%35%5%6%9%43%
2520
21st to endDay
11%5%26%5%46%6%7%9%39%
2520
July1st to 10thDay
9%435%5%35%6%6%9%45%
2520
11th to 20thDay
9%325%446%6%8%10%43%
2520
21st to endDay
9%5%25%6%45%6%7%8%42%
2547
August1st to 10thDay
8%425%6%45%6%6%9%45%
2327
11th to 20thDay
9%435%5%46%6%8%10%40%
2303
21st to endDay
10%4245%45%5%6%10%44%
2516
September1st to 10thDay
13%6%35%5%345%6%7%43%
2034
11th to 20thDay
9%5%35%5%35%47%8%46%
1980
21st to endDay
15%7%25%4245%5%8%43%
1980
October1st to 10thDay
12%6%26%6%445%5%7%43%
1949
11th to 20thDay
18%9%26%6%3445%6%37%
1800
21st to endDay
19%10%36%6%35%6%6%6%30%
1845
November1st to 10thDay
12%8%36%5%35%46%7%42%
1672
11th to 20thDay
17%12%46%6%345%46%33%
1710
21st to endDay
19%12%5%6%6%45%45%6%27%
1710
December1st to 10thDay
16%17%7%11%8%44445%21%
1710
11th to 20thDay
15%14%6%11%6%46%5%5%6%23%
2091
21st to endDay
24%20%8%10%7%3444412%
2783
January1st to 10thNight
18%13%6%9%7%45%45%5%26%
2648
11th to 20thNight
20%15%6%10%6%36%45%5%20%
2634
21st to endNight
18%14%8%9%7%44446%23%
2664
February1st to 10thNight
18%14%6%9%7%34446%23%
2340
11th to 20thNight
16%13%5%10%5%45%446%27%
2112
21st to endNight
22%11%48%5%345%46%28%
1776
March1st to 10thNight
16%9%5%8%7%45%445%33%
2124
11th to 20thNight
14%9%35%5%35%45%7%39%
1980
21st to endNight
20%9%46%6%3435%6%35%
2178
April1st to 10thNight
16%8%5%6%5%25%5%5%6%36%
1882
11th to 20thNight
18%8%26%6%35%46%6%37%
1651
21st to endNight
17%7%45%5%3445%8%37%
1620
May1st to 10thNight
18%7%47%6%36%45%7%31%
1620
11th to 20thNight
20%7%35%43445%8%39%
1592
21st to endNight
10%5%26%6%36%5%6%9%42%
1744
June1st to 10thNight
11%5%25%5%36%6%5%7%45%
1504
11th to 20thNight
10%5%35%5%345%6%9%44%
1440
21st to endNight
11%424435%6%6%10%45%
1440
July1st to 10thNight
8%5%2443446%8%52%
1440
11th to 20thNight
8%424435%46%10%50%
1440
21st to endNight
6%424435%6%6%10%50%
1766
August1st to 10thNight
6%425%5%35%5%6%9%51%
1611
11th to 20thNight
9%424435%6%6%8%49%
1598
21st to endNight
9%425%5%35%5%5%8%50%
1837
September1st to 10thNight
11%6%35%5%3345%7%48%
1908
11th to 20thNight
10%425%5%3236%7%52%
1980
21st to endNight
12%6%35%6%35%45%6%47%
1980
October1st to 10thNight
13%6%345%3445%7%46%
2011
11th to 20thNight
17%9%36%5%35%5%46%38%
2160
21st to endNight
22%8%36%5%35%45%6%35%
2510
November1st to 10thNight
13%8%35%5%3445%7%43%
2406
11th to 20thNight
16%10%47%5%35%5%6%7%33%
2470
21st to endNight
21%12%47%6%3445%6%27%
2470
December1st to 10thNight
18%12%7%9%6%45%447%24%
2470
11th to 20thNight
17%15%6%8%5%45%6%46%25%
3088
21st to endNight
28%18%7%9%6%34445%13%
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
66%7%11%13%3
1518
11th to 20thDay
70%6%13%8%3
1542
21st to endDay
69%6%9%11%5%1
1836
February1st to 10thDay
66%6%11%12%5%
1620
11th to 20thDay
61%7%10%14%7%
1740
21st to endDay
56%7%14%15%6%2
1480
March1st to 10thDay
58%7%12%17%6%
1836
11th to 20thDay
52%5%12%19%10%2
1980
21st to endDay
60%5%10%19%5%1
2178
April1st to 10thDay
52%8%11%17%12%
2092
11th to 20thDay
47%8%12%19%12%2
2258
21st to endDay
49%6%13%20%10%2
2340
May1st to 10thDay
49%8%12%18%11%1
2340
11th to 20thDay
49%8%11%17%13%2
2305
21st to endDay
39%10%14%23%12%2
2531
June1st to 10thDay
39%9%12%24%13%3
2452
11th to 20thDay
37%8%15%21%16%3
2520
21st to endDay
39%10%13%19%15%4
2520
July1st to 10thDay
35%8%12%23%18%3
2451
11th to 20thDay
32%9%16%24%17%3
2445
21st to endDay
35%8%15%22%17%2
2405
August1st to 10thDay
32%10%17%26%15%1
2314
11th to 20thDay
36%11%15%23%13%2
2303
21st to endDay
34%9%14%23%17%3
2516
September1st to 10thDay
39%9%14%20%16%3
2034
11th to 20thDay
34%7%13%28%17%1
1980
21st to endDay
38%8%14%24%16%1
1980
October1st to 10thDay
40%7%12%24%15%2
1949
11th to 20thDay
47%6%12%21%13%1
1800
21st to endDay
51%7%14%18%10%1
1845
November1st to 10thDay
41%7%12%23%16%1
1672
11th to 20thDay
53%6%11%18%11%1
1710
21st to endDay
56%6%14%16%7%
1710
December1st to 10thDay
66%7%10%13%4
1710
11th to 20thDay
60%9%12%15%4
2088
21st to endDay
75%7%8%6%3
2783
January1st to 10thNight
60%6%11%16%7%
2648
11th to 20thNight
65%6%13%11%4
2634
21st to endNight
64%6%12%13%5%1
2664
February1st to 10thNight
62%7%12%14%41
2340
11th to 20thNight
57%6%10%18%8%1
2113
21st to endNight
57%6%11%16%8%2
1776
March1st to 10thNight
52%6%11%20%10%1
2124
11th to 20thNight
44%8%13%18%15%2
1980
21st to endNight
51%5%10%23%9%2
2178
April1st to 10thNight
46%7%13%17%14%2
1882
11th to 20thNight
46%7%11%17%17%2
1651
21st to endNight
45%6%12%20%14%2
1620
May1st to 10thNight
52%8%10%16%12%2
1620
11th to 20thNight
44%8%9%20%17%2
1593
21st to endNight
35%9%13%27%14%2
1745
June1st to 10thNight
35%8%12%25%17%3
1504
11th to 20thNight
34%9%13%24%16%3
1440
21st to endNight
32%10%14%24%19%1
1440
July1st to 10thNight
31%9%12%25%21%3
1400
11th to 20thNight
29%8%16%26%19%2
1392
21st to endNight
26%10%17%24%18%4
1668
August1st to 10thNight
28%9%16%30%16%2
1600
11th to 20thNight
30%10%14%27%16%2
1598
21st to endNight
32%8%12%24%21%3
1837
September1st to 10thNight
35%7%14%23%17%4
1908
11th to 20thNight
31%6%12%27%24%1
1980
21st to endNight
38%7%13%23%18%2
1980
October1st to 10thNight
37%6%13%23%20%1
2011
11th to 20thNight
46%7%11%20%15%1
2160
21st to endNight
50%6%11%22%10%1
2510
November1st to 10thNight
41%6%12%24%16%1
2406
11th to 20thNight
48%8%13%20%10%1
2470
21st to endNight
57%6%12%18%6%
2470
December1st to 10thNight
60%7%12%14%7%
2470
11th to 20thNight
57%9%14%13%6%1
3090
21st to endNight
73%8%11%7%2
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
21%24%31%19%41
270
11th to 20thDay
23%20%41%11%4
270
21st to endDay
31%15%33%17%5%
282
February1st to 10thDay
31%18%38%12%1
240
11th to 20thDay
28%18%38%15%2
240
21st to endDay
27%23%39%10%2
198
March1st to 10thDay
24%19%35%17%4
276
11th to 20thDay
24%12%38%19%6%1
420
21st to endDay
30%15%31%17%6%
462
April1st to 10thDay
19%17%31%21%10%1
420
11th to 20thDay
20%22%26%20%9%3
412
21st to endDay
26%14%30%19%9%2
420
May1st to 10thDay
22%13%30%19%12%3
423
11th to 20thDay
19%12%31%21%11%7%
447
21st to endDay
12%6%30%24%20%9%
485
June1st to 10thDay
12%7%30%32%15%4
562
11th to 20thDay
12%9%29%30%16%4
630
21st to endDay
13%6%30%31%16%5%
630
July1st to 10thDay
8%422%33%20%12%
621
11th to 20thDay
10%6%23%32%19%11%
618
21st to endDay
8%324%28%25%10%
488
August1st to 10thDay
11%216%31%26%14%
446
11th to 20thDay
10%5%21%29%22%13%
439
21st to endDay
11%221%28%25%13%
495
September1st to 10thDay
14%6%18%30%20%12%
450
11th to 20thDay
10%420%25%28%14%
450
21st to endDay
15%11%23%24%19%8%
450
October1st to 10thDay
13%8%29%24%18%8%
450
11th to 20thDay
18%20%31%21%9%2
450
21st to endDay
26%14%35%18%5%1
360
November1st to 10thDay
14%17%32%23%10%4
270
11th to 20thDay
23%21%27%23%41
270
21st to endDay
25%17%38%17%3
270
December1st to 10thDay
23%24%30%15%7%
270
11th to 20thDay
20%24%35%17%4
270
21st to endDay
27%22%33%16%2
297
January1st to 10thNight
23%16%35%20%5%
950
11th to 20thNight
27%14%36%19%5%1
924
21st to endNight
23%15%37%22%4
820
February1st to 10thNight
27%12%35%23%3
720
11th to 20thNight
23%14%33%27%2
703
21st to endNight
26%16%38%19%2
592
March1st to 10thNight
21%12%33%27%7%
720
11th to 20thNight
18%14%37%24%6%1
720
21st to endNight
23%12%31%26%8%
792
April1st to 10thNight
19%15%35%26%4
622
11th to 20thNight
19%13%34%26%8%1
533
21st to endNight
21%9%34%27%9%1
540
May1st to 10thNight
22%6%31%31%10%1
540
11th to 20thNight
21%5%29%31%13%2
531
21st to endNight
10%326%36%22%3
584
June1st to 10thNight
12%426%42%16%
540
11th to 20thNight
12%425%41%18%1
540
21st to endNight
12%323%38%22%2
540
July1st to 10thNight
9%215%41%29%3
525
11th to 20thNight
9%320%40%23%5%
522
21st to endNight
6%217%45%28%2
591
August1st to 10thNight
7%214%43%30%3
537
11th to 20thNight
11%216%34%33%4
534
21st to endNight
9%217%36%33%4
594
September1st to 10thNight
13%5%17%33%27%5%
648
11th to 20thNight
9%418%33%33%3
720
21st to endNight
14%7%22%33%22%3
720
October1st to 10thNight
14%8%25%32%19%3
720
11th to 20thNight
19%16%28%27%8%2
720
21st to endNight
25%13%30%25%7%
792
November1st to 10thNight
15%14%32%26%11%2
740
11th to 20thNight
22%15%33%22%7%1
760
21st to endNight
25%13%33%23%6%
760
December1st to 10thNight
22%18%35%21%41
760
11th to 20thNight
25%13%35%22%5%
793
21st to endNight
30%13%34%20%2
1045
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