BGSU Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the BGSU Observatory clear sky chart from 2005-11-05 to 2017-09-23.

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
38%
15803
16%
46818
11%
15760
44%
15760
22%
32162

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 15thNight
16%
900
12%
2506
4%
895
23%
895
13%
1952
January16th to endNight
18%
804
11%
2532
4%
804
26%
804
12%
1975
February1st to 15thNight
19%
702
10%
2238
4%
701
26%
701
12%
1682
February16th to endNight
22%
631
14%
1893
6%
631
30%
631
15%
1390
March1st to 15thNight
30%
720
14%
2076
10%
720
33%
720
17%
1524
March16th to endNight
32%
768
18%
2112
11%
768
38%
768
22%
1485
April1st to 15thNight
29%
593
15%
1830
7%
593
36%
593
19%
1258
April16th to endNight
36%
540
20%
1620
9%
540
46%
540
25%
1068
May1st to 15thNight
39%
540
13%
1620
8%
540
45%
540
18%
1176
May16th to endNight
48%
562
17%
1684
13%
561
53%
561
29%
1052
June1st to 15thNight
55%
540
16%
1489
12%
540
60%
540
32%
947
June16th to endNight
56%
540
17%
1440
12%
540
61%
540
34%
903
July1st to 15thNight
62%
510
17%
1360
14%
510
64%
510
38%
821
July16th to endNight
70%
564
20%
1539
17%
531
73%
531
42%
868
August1st to 15thNight
70%
539
21%
1609
18%
536
71%
536
37%
933
August16th to endNight
65%
573
22%
1760
18%
573
69%
573
35%
1016
September1st to 15thNight
62%
672
26%
1932
20%
672
65%
672
35%
1149
September16th to endNight
60%
689
26%
1903
20%
689
63%
689
35%
1164
October1st to 15thNight
49%
660
22%
1887
18%
660
54%
660
30%
1184
October16th to endNight
29%
704
18%
2192
12%
704
38%
704
20%
1488
November1st to 15thNight
38%
700
23%
2276
18%
700
46%
700
25%
1432
November16th to endNight
26%
720
15%
2340
11%
720
32%
720
14%
1711
December1st to 15thNight
19%
720
9%
2340
4%
720
24%
720
11%
1801
December16th to endNight
16%
912
8%
2640
2%
912
21%
912
9%
2183

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%8%36%6%35%45%7%33%
48075
Night
15%8%36%5%3445%6%36%
47000
Cloud CoverDay
14%8%36%6%35%45%7%33%
48085
Night
15%8%36%5%3445%6%36%
47004
TransparencyDay
49%412%20%11%1
47775
Night
48%411%21%12%1
46818
SeeingDay
17%7%24%24%17%8%
5823
Night
19%7%26%29%14%1
15806

By Month

Percentage Cloud Cover NE (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 15thDay
19%16%5%7%8%45%346%18%
1432
16th to endDay
16%16%8%8%9%45%345%16%
1689
February1st to 15thDay
16%14%6%8%8%46%435%21%
1621
16th to endDay
14%12%5%8%7%36%446%24%
1580
March1st to 15thDay
20%11%5%9%6%24445%24%
1873
16th to endDay
20%10%47%6%24446%27%
2112
April1st to 15thDay
17%10%36%6%245%5%6%29%
2127
16th to endDay
17%6%26%434346%39%
2340
May1st to 15thDay
19%8%35%7%35%5%5%7%29%
2331
16th to endDay
11%425%5%36%5%6%8%38%
2431
June1st to 15thDay
11%5%25%5%345%5%8%40%
2467
16th to endDay
10%5%26%7%36%5%6%9%35%
2520
July1st to 15thDay
8%425%435%6%6%10%40%
2520
16th to endDay
8%426%5%35%5%7%10%39%
2519
August1st to 15thDay
6%5%245%46%7%7%9%40%
2340
16th to endDay
9%5%245%36%5%7%10%39%
2441
September1st to 15thDay
12%6%25%425%5%5%7%42%
2016
16th to endDay
14%6%25%32345%7%43%
1894
October1st to 15thDay
13%6%27%6%34345%41%
1741
16th to endDay
20%8%35%5%2445%6%32%
1678
November1st to 15thDay
14%8%344235%46%41%
1582
16th to endDay
19%12%47%6%2435%7%26%
1620
December1st to 15thDay
19%14%6%9%6%33445%20%
1620
16th to endDay
20%16%7%9%6%34435%16%
1581
January1st to 15thNight
22%12%5%8%5%3434426%
2506
16th to endNight
15%14%7%8%6%35%445%22%
2532
February1st to 15thNight
16%14%6%7%5%3445%5%27%
2236
16th to endNight
17%11%5%6%7%35%45%6%27%
1893
March1st to 15thNight
18%11%36%5%24446%31%
2064
16th to endNight
15%9%36%6%34346%36%
2112
April1st to 15thNight
18%8%35%5%35%45%7%32%
1830
16th to endNight
15%6%35%5%24447%39%
1620
May1st to 15thNight
17%6%36%6%46%6%5%6%31%
1620
16th to endNight
12%435%425%5%5%9%42%
1682
June1st to 15thNight
10%425%425%5%5%7%44%
1489
16th to endNight
8%3245%26%5%6%10%42%
1440
July1st to 15thNight
7%4145%2447%7%50%
1440
16th to endNight
5%2145%2447%9%51%
1646
August1st to 15thNight
5%315%6%345%7%8%49%
1620
16th to endNight
9%314435%45%8%48%
1760
September1st to 15thNight
10%5%25%423347%51%
1932
16th to endNight
11%42442445%6%49%
1903
October1st to 15thNight
12%5%36%5%2335%6%45%
1887
16th to endNight
20%7%35%5%34445%36%
2192
November1st to 15thNight
13%8%25%3245%5%7%41%
2276
16th to endNight
21%11%47%5%34446%26%
2340
December1st to 15thNight
20%13%5%8%7%24336%22%
2340
16th to endNight
23%16%6%8%5%345%45%17%
2640

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 15thDay
19%16%5%7%8%45%346%18%
1432
16th to endDay
16%16%7%9%9%45%345%16%
1689
February1st to 15thDay
15%14%6%8%8%45%435%21%
1621
16th to endDay
14%12%5%8%7%36%446%24%
1580
March1st to 15thDay
21%11%5%9%6%24445%24%
1884
16th to endDay
20%9%48%6%24345%28%
2111
April1st to 15thDay
17%10%46%6%245%5%6%29%
2127
16th to endDay
17%7%35%5%33447%39%
2340
May1st to 15thDay
19%8%36%6%45%5%5%7%29%
2331
16th to endDay
12%425%5%36%5%7%8%39%
2431
June1st to 15thDay
11%5%25%5%35%5%5%7%40%
2467
16th to endDay
10%5%26%6%36%6%6%8%35%
2520
July1st to 15thDay
8%425%5%35%6%5%10%40%
2520
16th to endDay
8%425%5%35%5%7%9%39%
2519
August1st to 15thDay
6%415%5%47%7%7%9%40%
2340
16th to endDay
9%5%245%36%5%7%10%39%
2441
September1st to 15thDay
12%6%25%425%5%47%42%
2016
16th to endDay
14%6%26%32345%7%43%
1894
October1st to 15thDay
13%6%36%6%34345%41%
1741
16th to endDay
20%8%35%5%3435%6%32%
1678
November1st to 15thDay
14%8%344235%47%41%
1582
16th to endDay
19%12%47%6%2425%7%26%
1620
December1st to 15thDay
19%15%6%9%6%24445%20%
1620
16th to endDay
20%16%7%9%6%34335%17%
1581
January1st to 15thNight
22%12%5%8%5%3434426%
2506
16th to endNight
16%14%7%8%6%35%45%5%22%
2532
February1st to 15thNight
16%14%6%8%5%3445%5%27%
2229
16th to endNight
17%11%5%6%7%35%45%6%27%
1893
March1st to 15thNight
18%11%36%5%24445%31%
2076
16th to endNight
15%8%36%6%34346%36%
2112
April1st to 15thNight
18%8%35%5%35%46%6%32%
1830
16th to endNight
15%7%35%5%3445%6%39%
1620
May1st to 15thNight
17%6%36%6%35%6%5%6%31%
1619
16th to endNight
12%434425%5%5%8%42%
1682
June1st to 15thNight
10%425%435%5%5%7%44%
1489
16th to endNight
8%4245%26%5%6%10%42%
1440
July1st to 15thNight
7%4145%235%7%8%50%
1440
16th to endNight
5%3145%2447%8%51%
1646
August1st to 15thNight
5%3146%345%6%9%49%
1620
16th to endNight
9%324435%45%8%48%
1760
September1st to 15thNight
10%425%423346%51%
1932
16th to endNight
11%424423447%49%
1903
October1st to 15thNight
12%5%26%5%2335%6%45%
1887
16th to endNight
20%6%35%5%24445%36%
2192
November1st to 15thNight
13%8%25%3245%5%6%42%
2276
16th to endNight
21%11%46%5%24446%26%
2340
December1st to 15thNight
20%13%5%8%7%34336%22%
2340
16th to endNight
23%16%6%7%5%335%45%17%
2640

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 15thDay
68%311%12%3
1433
16th to endDay
70%310%9%4
1689
February1st to 15thDay
65%410%13%5%
1623
16th to endDay
60%413%16%5%
1580
March1st to 15thDay
61%412%15%5%
1884
16th to endDay
58%39%21%6%
2112
April1st to 15thDay
53%411%18%11%
2127
16th to endDay
46%311%22%12%3
2340
May1st to 15thDay
53%5%11%18%9%1
2331
16th to endDay
40%6%13%25%12%2
2435
June1st to 15thDay
39%5%13%25%14%1
2467
16th to endDay
42%7%13%18%15%2
2520
July1st to 15thDay
37%5%10%24%18%2
2371
16th to endDay
36%6%13%26%14%1
2363
August1st to 15thDay
35%6%14%25%15%1
2327
16th to endDay
37%6%14%23%15%3
2441
September1st to 15thDay
39%5%10%24%17%2
2016
16th to endDay
39%49%27%17%
1894
October1st to 15thDay
44%49%24%14%1
1741
16th to endDay
51%314%21%8%
1678
November1st to 15thDay
42%5%9%22%17%1
1582
16th to endDay
57%213%18%7%
1620
December1st to 15thDay
65%311%14%4
1620
16th to endDay
70%411%10%3
1581
January1st to 15thNight
62%39%16%8%
2506
16th to endNight
63%412%15%5%
2532
February1st to 15thNight
59%411%17%5%1
2238
16th to endNight
57%311%20%6%
1893
March1st to 15thNight
54%411%18%9%1
2076
16th to endNight
48%411%23%9%1
2112
April1st to 15thNight
50%310%19%15%
1830
16th to endNight
44%310%20%15%4
1620
May1st to 15thNight
51%6%10%18%11%1
1620
16th to endNight
38%5%10%27%15%3
1684
June1st to 15thNight
36%6%11%26%17%1
1489
16th to endNight
34%6%15%24%15%2
1440
July1st to 15thNight
31%5%12%27%20%3
1360
16th to endNight
26%5%16%28%18%4
1539
August1st to 15thNight
29%6%13%30%18%1
1609
16th to endNight
32%412%24%22%3
1760
September1st to 15thNight
33%410%26%20%4
1932
16th to endNight
34%410%25%22%1
1903
October1st to 15thNight
38%312%24%19%1
1887
16th to endNight
49%310%26%9%1
2192
November1st to 15thNight
41%410%24%16%2
2276
16th to endNight
58%311%19%7%
2340
December1st to 15thNight
63%311%14%6%
2340
16th to endNight
69%410%11%4
2640

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 15thDay
24%14%34%15%8%2
90
16th to endDay
28%14%41%12%12
96
February1st to 15thDay
27%22%38%10%1
90
16th to endDay
18%13%40%22%4
81
March1st to 15thDay
35%10%24%20%8%
174
16th to endDay
25%10%33%18%10%1
288
April1st to 15thDay
21%12%29%24%11%
270
16th to endDay
20%7%31%21%12%6%
270
May1st to 15thDay
25%5%26%23%14%4
288
16th to endDay
15%6%24%25%16%10%
331
June1st to 15thDay
10%428%30%19%6%
442
16th to endDay
14%6%27%28%17%6%
495
July1st to 15thDay
11%223%31%21%9%
475
16th to endDay
7%317%27%24%18%
379
August1st to 15thDay
11%212%27%27%19%
313
16th to endDay
10%312%24%27%21%
332
September1st to 15thDay
16%310%26%25%18%
315
16th to endDay
16%5%9%19%30%18%
283
October1st to 15thDay
14%6%21%25%25%5%
255
16th to endDay
22%8%32%29%7%
190
November1st to 15thDay
13%11%26%23%18%6%
90
16th to endDay
28%15%33%15%5%1
90
December1st to 15thDay
20%22%41%10%5%1
90
16th to endDay
25%25%38%10%1
96
January1st to 15thNight
29%12%32%18%5%
900
16th to endNight
22%14%34%23%4
804
February1st to 15thNight
23%13%34%24%3
704
16th to endNight
22%11%33%27%4
631
March1st to 15thNight
24%9%27%30%8%
720
16th to endNight
19%10%31%26%11%
768
April1st to 15thNight
22%11%33%26%5%
593
16th to endNight
19%7%32%28%10%1
540
May1st to 15thNight
20%5%26%33%12%1
540
16th to endNight
14%225%33%21%3
563
June1st to 15thNight
10%320%45%18%
540
16th to endNight
10%123%41%20%2
540
July1st to 15thNight
8%118%41%27%1
510
16th to endNight
7%110%45%30%4
564
August1st to 15thNight
7%11%41%33%5%
539
16th to endNight
9%111%31%38%6%
573
September1st to 15thNight
12%314%34%29%5%
672
16th to endNight
13%214%31%32%5%
689
October1st to 15thNight
15%6%23%30%21%3
660
16th to endNight
23%10%30%25%9%
704
November1st to 15thNight
17%10%30%27%13%2
700
16th to endNight
27%12%27%23%8%
720
December1st to 15thNight
28%11%33%21%4
720
16th to endNight
30%10%33%21%3
912
Page generated at 2017-09-24 09:15:45. Version ac04

Copyright 2017 A. Danko


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