Fairborn Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fairborn Observatory clear sky chart from 2005-11-06 to 2024-02-20.

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
65%
24094
34%
79286
26%
24000
74%
24000
45%
38005

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
61%
755
40%
3974
28%
736
71%
736
35%
1468
January11th to 20thNight
64%
750
47%
3879
31%
740
77%
740
45%
1227
January21st to endNight
51%
828
23%
4296
26%
814
66%
814
23%
2279
February1st to 10thNight
57%
760
35%
2418
29%
760
70%
760
45%
1175
February11th to 20thNight
50%
738
33%
2212
22%
738
64%
738
42%
1142
February21st to endNight
49%
592
39%
1655
26%
592
63%
592
46%
870
March1st to 10thNight
49%
720
37%
1980
23%
720
63%
720
44%
1041
March11th to 20thNight
60%
720
37%
1980
24%
720
71%
720
52%
1009
March21st to endNight
55%
792
37%
2178
21%
792
68%
792
50%
1105
April1st to 10thNight
60%
720
38%
1980
22%
720
72%
720
61%
920
April11th to 20thNight
56%
569
41%
1813
28%
569
72%
569
54%
773
April21st to endNight
60%
540
44%
1800
33%
540
76%
540
64%
678
May1st to 10thNight
65%
540
41%
1658
29%
540
78%
540
61%
689
May11th to 20thNight
68%
531
42%
1594
31%
531
77%
531
68%
639
May21st to endNight
70%
583
45%
1746
34%
582
79%
582
76%
669
June1st to 10thNight
76%
540
37%
1620
32%
540
78%
540
65%
693
June11th to 20thNight
77%
540
38%
1620
30%
540
81%
540
70%
664
June21st to endNight
77%
540
28%
1620
24%
540
79%
540
53%
782
July1st to 10thNight
76%
525
19%
1575
17%
525
77%
525
38%
890
July11th to 20thNight
77%
522
12%
1566
11%
522
77%
522
25%
1037
July21st to endNight
73%
591
9%
1674
8%
558
72%
558
23%
1146
August1st to 10thNight
81%
537
17%
1602
16%
534
81%
534
32%
960
August11th to 20thNight
78%
534
21%
1636
20%
534
78%
534
32%
966
August21st to endNight
76%
625
23%
2011
23%
625
76%
625
30%
1196
September1st to 10thNight
69%
720
24%
1980
20%
720
70%
720
35%
1224
September11th to 20thNight
82%
720
39%
1980
32%
720
83%
720
56%
1004
September21st to endNight
77%
720
37%
1980
26%
720
83%
720
58%
984
October1st to 10thNight
74%
720
39%
2063
29%
720
80%
720
61%
951
October11th to 20thNight
71%
720
40%
2160
29%
720
80%
720
60%
973
October21st to endNight
74%
792
44%
2376
34%
792
83%
792
69%
971
November1st to 10thNight
71%
740
44%
2220
34%
740
80%
740
62%
955
November11th to 20thNight
69%
760
41%
2280
31%
760
79%
760
57%
1037
November21st to endNight
54%
760
37%
2427
28%
760
65%
760
42%
1209
December1st to 10thNight
62%
760
36%
2470
33%
760
70%
760
44%
1206
December11th to 20thNight
55%
759
31%
2940
28%
759
66%
759
32%
1572
December21st to endNight
52%
831
23%
4323
29%
817
64%
817
28%
1901

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
5%42442445%6%61%
78883
Night
441332345%6%64%
80370
TransparencyDay
23%5%6%11%27%28%
78610
Night
20%47%13%28%27%
80165
SeeingDay
8%14%27%29%17%5%
13897
Night
5%6%18%36%29%6%
24128

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
45%2432333467%
2858
11th to 20thDay
441342344466%
2860
21st to endDay
10%6%2332346%7%54%
3146
February1st to 10thDay
6%5%14323345%65%
1757
11th to 20thDay
6%6%24323345%61%
1841
21st to endDay
6%5%23322236%66%
1599
March1st to 10thDay
5%4144345%5%6%60%
1980
11th to 20thDay
45%23323345%67%
1980
21st to endDay
2213323446%69%
2178
April1st to 10thDay
221332345%7%70%
1980
11th to 20thDay
321221223479%
2094
21st to endDay
1212222235%79%
2160
May1st to 10thDay
2212213335%77%
2296
11th to 20thDay
211221333478%
2301
21st to endDay
11221222285%
2530
June1st to 10thDay
2212314346%71%
2340
11th to 20thDay
121131233479%
2340
21st to endDay
43244345%5%6%60%
2340
July1st to 10thDay
7%425%7%5%7%7%8%8%40%
2340
11th to 20thDay
6%6%38%8%6%10%9%9%10%25%
2340
21st to endDay
11%7%38%8%6%8%9%7%9%23%
2545
August1st to 10thDay
8%5%36%6%5%8%8%7%9%35%
2328
11th to 20thDay
6%5%36%7%47%9%8%10%36%
2263
21st to endDay
6%5%36%8%47%7%7%8%39%
2340
September1st to 10thDay
9%6%36%6%36%5%6%7%42%
1980
11th to 20thDay
5%4244345%5%7%58%
1980
21st to endDay
4214424447%64%
1980
October1st to 10thDay
2212224346%70%
1895
11th to 20thDay
221222223477%
1800
21st to endDay
2212223345%75%
1980
November1st to 10thDay
221232335%6%72%
1859
11th to 20thDay
331322234471%
1900
21st to endDay
6%414323446%62%
1748
December1st to 10thDay
6%31343445%7%60%
1710
11th to 20thDay
6%8%35%5%2335%8%52%
2169
21st to endDay
5%6%2332345%6%61%
3146
January1st to 10thNight
5%422323445%66%
4097
11th to 20thNight
3212213345%74%
4110
21st to endNight
13%9%2432345%7%49%
4521
February1st to 10thNight
5%5%23323346%65%
2418
11th to 20thNight
46%24423345%62%
2211
21st to endNight
46%13324335%65%
1655
March1st to 10thNight
35%233245%6%6%62%
1980
11th to 20thNight
442231334469%
1980
21st to endNight
3313423345%67%
2178
April1st to 10thNight
1222323446%73%
1980
11th to 20thNight
231222333476%
1813
21st to endNight
211221224480%
1800
May1st to 10thNight
211121343478%
1658
11th to 20thNight
1112212346%78%
1594
21st to endNight
11111222387%
1746
June1st to 10thNight
3211212345%75%
1620
11th to 20thNight
221111223479%
1620
21st to endNight
221233445%7%66%
1620
July1st to 10thNight
33246%35%7%8%11%48%
1620
11th to 20thNight
4426%7%48%9%10%13%32%
1620
21st to endNight
5%337%8%5%8%9%10%15%27%
1773
August1st to 10thNight
4325%5%46%7%8%11%45%
1611
11th to 20thNight
5%4245%45%6%11%12%43%
1636
21st to endNight
6%4246%46%6%8%10%44%
2011
September1st to 10thNight
8%5%25%6%345%7%9%47%
1980
11th to 20thNight
432232335%6%67%
1980
21st to endNight
4312213346%70%
1980
October1st to 10thNight
111232345%5%73%
2063
11th to 20thNight
321232333476%
2160
21st to endNight
1112212235%80%
2376
November1st to 10thNight
2112313345%75%
2220
11th to 20thNight
3312313346%70%
2280
21st to endNight
5%5%2442335%6%62%
2427
December1st to 10thNight
6%413423446%62%
2470
11th to 20thNight
5%6%35%5%25%446%56%
3041
21st to endNight
7%5%13334445%60%
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
21%449%32%31%
2859
11th to 20thDay
21%4412%38%21%
2860
21st to endDay
28%45%14%34%16%
3146
February1st to 10thDay
23%2311%24%36%
1757
11th to 20thDay
26%3312%26%30%
1851
21st to endDay
22%229%27%38%
1599
March1st to 10thDay
24%339%31%29%
1980
11th to 20thDay
22%338%32%34%
1980
21st to endDay
17%3311%37%29%
2178
April1st to 10thDay
15%238%38%33%
1980
11th to 20thDay
13%227%30%47%
2097
21st to endDay
11%238%32%44%
2160
May1st to 10thDay
13%227%25%51%
2296
11th to 20thDay
12%339%29%45%
2304
21st to endDay
8%125%31%54%
2530
June1st to 10thDay
15%336%29%44%
2340
11th to 20thDay
10%337%22%57%
2340
21st to endDay
23%5%6%11%24%31%
2340
July1st to 10thDay
37%9%10%14%16%14%
2276
11th to 20thDay
45%15%18%15%5%2
2271
21st to endDay
52%14%17%10%6%1
2404
August1st to 10thDay
40%12%14%16%13%4
2313
11th to 20thDay
38%13%15%15%13%5%
2263
21st to endDay
39%10%13%16%14%8%
2340
September1st to 10thDay
39%8%10%14%16%13%
1980
11th to 20thDay
24%6%7%14%28%21%
1980
21st to endDay
22%46%16%31%20%
1980
October1st to 10thDay
15%47%15%30%29%
1895
11th to 20thDay
12%2410%33%38%
1800
21st to endDay
13%2311%29%42%
1980
November1st to 10thDay
13%3412%36%32%
1859
11th to 20thDay
17%3411%32%33%
1900
21st to endDay
23%3414%26%30%
1748
December1st to 10thDay
24%35%14%28%26%
1710
11th to 20thDay
31%36%12%28%21%
2168
21st to endDay
23%3410%39%19%
3146
January1st to 10thNight
19%45%11%35%27%
4097
11th to 20thNight
13%2319%39%24%
4110
21st to endNight
33%5%5%15%28%13%
4521
February1st to 10thNight
22%3411%23%37%
2418
11th to 20thNight
24%35%12%25%29%
2212
21st to endNight
23%339%25%36%
1655
March1st to 10thNight
22%4412%28%30%
1980
11th to 20thNight
19%3310%28%37%
1980
21st to endNight
19%45%10%36%27%
2178
April1st to 10thNight
14%2311%39%31%
1980
11th to 20thNight
14%228%30%43%
1813
21st to endNight
10%249%33%42%
1800
May1st to 10thNight
11%247%30%45%
1658
11th to 20thNight
9%25%9%31%44%
1595
21st to endNight
6%217%36%49%
1746
June1st to 10thNight
12%237%32%44%
1620
11th to 20thNight
10%23425%56%
1620
21st to endNight
17%5%7%12%22%37%
1620
July1st to 10thNight
26%9%17%17%15%17%
1575
11th to 20thNight
36%14%24%18%7%2
1566
21st to endNight
39%13%29%13%41
1674
August1st to 10thNight
28%12%17%22%14%6%
1602
11th to 20thNight
30%10%20%17%17%6%
1636
21st to endNight
32%10%16%19%17%7%
2011
September1st to 10thNight
32%8%13%18%19%11%
1980
11th to 20thNight
18%47%19%30%22%
1980
21st to endNight
16%5%7%18%35%20%
1980
October1st to 10thNight
13%5%7%18%30%28%
2063
11th to 20thNight
14%2413%28%38%
2160
21st to endNight
9%25%14%30%40%
2376
November1st to 10thNight
12%2415%35%31%
2220
11th to 20thNight
16%2315%32%32%
2280
21st to endNight
24%3414%29%27%
2427
December1st to 10thNight
23%35%16%28%25%
2470
11th to 20thNight
29%5%5%13%27%21%
3041
21st to endNight
25%45%12%28%25%
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%18%29%31%9%1
270
11th to 20thDay
13%10%37%24%14%1
270
21st to endDay
8%17%31%31%10%2
297
February1st to 10thDay
11%19%27%26%14%3
317
11th to 20thDay
16%30%27%20%7%
452
21st to endDay
16%32%29%17%6%
346
March1st to 10thDay
14%27%34%18%6%2
420
11th to 20thDay
15%20%27%22%12%3
420
21st to endDay
12%29%33%18%6%2
462
April1st to 10thDay
423%38%23%9%3
420
11th to 20thDay
8%27%35%20%8%1
412
21st to endDay
7%22%35%21%11%4
420
May1st to 10thDay
8%20%37%21%11%3
423
11th to 20thDay
416%39%27%12%2
448
21st to endDay
319%41%25%10%2
485
June1st to 10thDay
6%9%40%29%14%2
450
11th to 20thDay
28%37%34%15%3
450
21st to endDay
46%28%39%18%5%
450
July1st to 10thDay
7%115%43%27%7%
446
11th to 20thDay
6%37%41%34%9%
444
21st to endDay
12%210%31%34%11%
487
August1st to 10thDay
9%19%31%33%17%
447
11th to 20thDay
7%111%37%33%12%
437
21st to endDay
7%28%33%34%16%
495
September1st to 10thDay
12%417%35%26%7%
450
11th to 20thDay
6%321%40%24%6%
450
21st to endDay
49%28%32%21%7%
450
October1st to 10thDay
411%27%32%20%6%
365
11th to 20thDay
49%24%36%20%7%
270
21st to endDay
5%8%29%31%22%6%
297
November1st to 10thDay
5%16%29%33%14%3
270
11th to 20thDay
7%10%28%31%24%
270
21st to endDay
13%21%25%28%12%2
270
December1st to 10thDay
11%15%28%27%17%2
270
11th to 20thDay
8%13%38%28%12%1
270
21st to endDay
15%22%23%28%9%2
297
January1st to 10thNight
7%5%22%39%22%5%
760
11th to 20thNight
6%6%21%40%23%3
760
21st to endNight
11%9%24%37%18%3
836
February1st to 10thNight
7%9%23%35%23%4
760
11th to 20thNight
8%10%26%39%15%2
742
21st to endNight
8%10%30%35%15%2
592
March1st to 10thNight
6%13%26%38%14%2
720
11th to 20thNight
8%9%20%33%25%5%
720
21st to endNight
5%8%25%38%21%2
792
April1st to 10thNight
36%28%41%20%2
720
11th to 20thNight
412%26%40%17%1
569
21st to endNight
29%27%41%18%2
540
May1st to 10thNight
210%21%43%22%2
540
11th to 20thNight
15%22%45%24%3
531
21st to endNight
15%22%45%26%1
584
June1st to 10thNight
3214%47%31%3
540
11th to 20thNight
3215%48%31%2
540
21st to endNight
3111%38%42%5%
540
July1st to 10thNight
416%29%52%7%
525
11th to 20thNight
5%1422%59%10%
522
21st to endNight
6%1421%52%17%
591
August1st to 10thNight
5%1219%55%18%
537
11th to 20thNight
6%2421%51%15%
534
21st to endNight
7%1321%53%15%
625
September1st to 10thNight
9%29%24%44%13%
720
11th to 20thNight
6%15%35%45%8%
720
21st to endNight
4212%40%35%8%
720
October1st to 10thNight
2415%40%34%5%
720
11th to 20thNight
4317%39%32%6%
720
21st to endNight
3416%39%30%8%
792
November1st to 10thNight
36%17%39%29%6%
740
11th to 20thNight
45%18%39%30%4
760
21st to endNight
7%8%24%35%20%5%
760
December1st to 10thNight
8%6%18%42%22%5%
760
11th to 20thNight
8%9%23%40%19%2
760
21st to endNight
9%9%23%35%20%5%
836
Page generated at 2024-02-17 04:28:36. Version ac07

Copyright 2024 Attilla Danko


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