Fairborn Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fairborn Observatory clear sky chart from 2005-11-05 to 2017-04-02.

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
61%
15045
35%
45316
25%
15004
71%
15004
42%
22190

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
59%
719
33%
2327
28%
716
69%
716
41%
1096
January16th to endNight
52%
768
34%
2496
24%
768
68%
768
32%
1293
February1st to 15thNight
56%
700
36%
2194
28%
698
70%
698
42%
1021
February16th to endNight
51%
632
39%
1814
26%
632
66%
632
40%
939
March1st to 15thNight
53%
720
41%
1980
25%
720
68%
720
46%
982
March16th to endNight
59%
768
38%
2112
23%
768
72%
768
47%
1038
April1st to 15thNight
52%
633
37%
1800
22%
633
66%
633
44%
875
April16th to endNight
53%
495
41%
1650
25%
495
74%
495
52%
634
May1st to 15thNight
53%
494
41%
1507
25%
494
70%
494
55%
601
May16th to endNight
59%
513
42%
1540
24%
513
74%
513
60%
599
June1st to 15thNight
66%
495
37%
1485
27%
495
73%
495
57%
621
June16th to endNight
68%
495
27%
1485
18%
495
75%
495
46%
702
July1st to 15thNight
71%
465
16%
1395
14%
465
72%
465
31%
822
July16th to endNight
63%
522
12%
1467
8%
489
70%
489
24%
949
August1st to 15thNight
75%
494
21%
1476
19%
491
76%
491
31%
879
August16th to endNight
73%
544
23%
1736
22%
544
76%
544
30%
1011
September1st to 15thNight
69%
660
26%
1815
21%
660
70%
660
35%
1096
September16th to endNight
75%
656
39%
1815
25%
656
83%
656
56%
867
October1st to 15thNight
69%
660
39%
1921
31%
660
75%
660
55%
892
October16th to endNight
75%
704
41%
2112
31%
704
84%
704
62%
901
November1st to 15thNight
63%
700
42%
2100
31%
700
73%
700
53%
901
November16th to endNight
54%
720
39%
2253
26%
720
68%
720
41%
1071
December1st to 15thNight
56%
720
36%
2340
31%
720
67%
720
38%
1111
December16th to endNight
49%
768
35%
2496
25%
768
63%
768
32%
1289

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
4313323446%61%
45795
Night
3212313346%65%
45517
TransparencyDay
24%46%11%26%27%
45490
Night
19%47%14%28%26%
45323
SeeingDay
7%20%23%28%16%4
4745
Night
418%11%29%30%6%
15053

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 15thDay
5%313313345%62%
1611
16th to endDay
6%32332345%459%
1728
February1st to 15thDay
5%314212245%67%
1661
16th to endDay
5%5%23212345%62%
1658
March1st to 15thDay
3313223445%65%
1980
16th to endDay
2312212335%70%
2112
April1st to 15thDay
2212223346%69%
1850
16th to endDay
121221112478%
1980
May1st to 15thDay
111121222478%
2110
16th to endDay
11111212382%
2221
June1st to 15thDay
1112323478%
2145
16th to endDay
321332343465%
2145
July1st to 15thDay
7%426%7%5%8%8%8%8%31%
2145
16th to endDay
11%7%38%8%5%9%8%7%8%21%
2285
August1st to 15thDay
9%6%36%7%47%7%6%8%31%
2145
16th to endDay
5%5%26%7%47%7%7%9%36%
2110
September1st to 15thDay
9%5%35%6%35%5%6%6%40%
1815
16th to endDay
5%313423346%61%
1815
October1st to 15thDay
2312123345%70%
1708
16th to endDay
111212235%75%
1760
November1st to 15thDay
221112245%75%
1759
16th to endDay
4313211335%68%
1704
December1st to 15thDay
6%412223248%60%
1620
16th to endDay
5%6%1331235%7%59%
1728
January1st to 15thNight
4312313345%66%
2327
16th to endNight
7%313324445%58%
2496
February1st to 15thNight
3313213345%67%
2188
16th to endNight
2413323345%64%
1814
March1st to 15thNight
331221334468%
1980
16th to endNight
231231233471%
2112
April1st to 15thNight
232231333468%
1800
16th to endNight
11111222380%
1650
May1st to 15thNight
1212335%78%
1507
16th to endNight
111122385%
1540
June1st to 15thNight
22111123479%
1485
16th to endNight
211223445%69%
1485
July1st to 15thNight
32135%36%7%9%12%43%
1485
16th to endNight
6%325%6%46%7%10%16%30%
1575
August1st to 15thNight
4214436%6%9%11%46%
1485
16th to endNight
6%3134346%9%10%45%
1736
September1st to 15thNight
6%42443346%8%50%
1815
16th to endNight
321122346%72%
1815
October1st to 15thNight
11231323475%
1921
16th to endNight
111121223478%
2112
November1st to 15thNight
111121223476%
2100
16th to endNight
4313312235%66%
2253
December1st to 15thNight
5%312213436%64%
2340
16th to endNight
7%414313335%60%
2496

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
23%25%12%28%27%
1612
16th to endDay
25%3316%27%23%
1728
February1st to 15thDay
20%1212%30%31%
1661
16th to endDay
24%2312%30%27%
1658
March1st to 15thDay
19%337%35%30%
1980
16th to endDay
17%129%36%31%
2112
April1st to 15thDay
16%139%39%30%
1850
16th to endDay
12%127%28%46%
1980
May1st to 15thDay
11%128%27%49%
2110
16th to endDay
9%126%33%46%
2224
June1st to 15thDay
11%125%26%52%
2145
16th to endDay
21%348%24%37%
2145
July1st to 15thDay
42%12%13%12%12%6%
2006
16th to endDay
53%13%18%9%4
2130
August1st to 15thDay
46%11%12%13%11%3
2130
16th to endDay
39%11%15%15%10%7%
2110
September1st to 15thDay
41%7%10%15%17%8%
1815
16th to endDay
24%35%14%31%20%
1815
October1st to 15thDay
16%35%13%31%29%
1708
16th to endDay
12%2312%30%39%
1760
November1st to 15thDay
12%2411%36%32%
1759
16th to endDay
19%2412%28%32%
1704
December1st to 15thDay
23%25%15%31%21%
1620
16th to endDay
24%27%16%30%18%
1728
January1st to 15thNight
20%3412%31%27%
2327
16th to endNight
27%3415%29%19%
2496
February1st to 15thNight
18%25%13%27%31%
2199
16th to endNight
22%3313%31%24%
1814
March1st to 15thNight
17%2211%30%34%
1980
16th to endNight
17%249%35%31%
2112
April1st to 15thNight
18%2311%40%24%
1800
16th to endNight
10%139%30%45%
1650
May1st to 15thNight
9%148%34%42%
1508
16th to endNight
7%128%38%41%
1541
June1st to 15thNight
11%12427%52%
1485
16th to endNight
15%4410%23%40%
1485
July1st to 15thNight
25%12%23%18%11%8%
1395
16th to endNight
34%12%31%15%31
1467
August1st to 15thNight
27%12%17%20%16%5%
1476
16th to endNight
29%10%18%19%15%7%
1736
September1st to 15thNight
30%6%14%19%20%7%
1815
16th to endNight
14%36%17%39%19%
1815
October1st to 15thNight
14%36%17%29%27%
1921
16th to endNight
10%25%12%28%39%
2112
November1st to 15thNight
12%2417%32%31%
2100
16th to endNight
21%1312%28%32%
2253
December1st to 15thNight
21%2416%33%21%
2340
16th to endNight
26%35%17%27%18%
2496

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
13%12%28%38%6%
90
16th to endDay
10%11%27%34%12%4
96
February1st to 15thDay
6%23%21%28%18%2
176
16th to endDay
8%37%25%19%8%
238
March1st to 15thDay
6%31%27%20%11%3
270
16th to endDay
335%27%18%10%4
288
April1st to 15thDay
5%36%33%17%5%1
214
16th to endDay
437%34%16%5%1
210
May1st to 15thDay
434%35%18%6%1
228
16th to endDay
325%35%27%6%1
266
June1st to 15thDay
5%18%35%30%8%1
255
16th to endDay
5%13%21%39%14%4
255
July1st to 15thDay
9%9%13%38%24%4
245
16th to endDay
9%11%11%30%29%6%
271
August1st to 15thDay
10%6%10%34%30%7%
255
16th to endDay
7%6%8%33%35%8%
268
September1st to 15thDay
14%7%14%37%21%4
255
16th to endDay
7%11%24%26%23%5%
255
October1st to 15thDay
5%14%25%27%19%6%
148
16th to endDay
4320%31%25%15%
96
November1st to 15thDay
5%14%27%33%13%5%
90
16th to endDay
8%20%25%30%15%
90
December1st to 15thDay
5%12%16%30%31%4
90
16th to endDay
12%21%21%31%12%
96
January1st to 15thNight
419%12%34%23%5%
720
16th to endNight
7%20%13%32%21%3
768
February1st to 15thNight
421%12%33%23%4
704
16th to endNight
421%17%36%16%2
632
March1st to 15thNight
323%15%30%22%4
720
16th to endNight
222%12%33%25%3
768
April1st to 15thNight
323%17%38%16%
633
16th to endNight
123%20%34%18%2
495
May1st to 15thNight
24%19%32%21%1
495
16th to endNight
122%13%34%25%1
515
June1st to 15thNight
320%8%34%29%3
495
16th to endNight
118%7%28%39%4
495
July1st to 15thNight
313%215%54%10%
465
16th to endNight
5%17%211%48%14%
522
August1st to 15thNight
5%10%111%53%18%
494
16th to endNight
5%9%314%49%17%
544
September1st to 15thNight
7%9%416%47%14%
660
16th to endNight
49%6%29%40%9%
656
October1st to 15thNight
212%11%32%32%8%
660
16th to endNight
210%9%30%38%9%
704
November1st to 15thNight
219%12%30%30%5%
700
16th to endNight
5%19%15%27%24%6%
720
December1st to 15thNight
6%21%11%30%24%4
720
16th to endNight
8%21%15%31%18%4
768
Page generated at 2017-04-02 22:35:07. Version ac04

Copyright 2017 A. Danko


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