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 2017-12-04.

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
62%
15885
35%
47831
25%
15844
72%
15844
43%
23396

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
55%
683
36%
1942
21%
683
68%
683
47%
933
April16th to endNight
55%
540
43%
1800
28%
540
75%
540
54%
685
May1st to 15thNight
55%
539
39%
1644
24%
539
71%
539
56%
653
May16th to endNight
60%
561
44%
1684
27%
561
75%
561
61%
654
June1st to 15thNight
67%
540
35%
1620
25%
540
73%
540
58%
677
June16th to endNight
69%
540
29%
1620
20%
540
75%
540
46%
771
July1st to 15thNight
70%
510
16%
1530
14%
510
71%
510
30%
913
July16th to endNight
63%
564
11%
1593
8%
531
70%
531
22%
1053
August1st to 15thNight
76%
539
20%
1611
18%
536
77%
536
32%
949
August16th to endNight
74%
594
26%
1895
24%
594
76%
594
31%
1089
September1st to 15thNight
69%
720
25%
1980
20%
720
71%
720
35%
1196
September16th to endNight
75%
716
43%
1980
28%
716
84%
716
59%
927
October1st to 15thNight
70%
720
38%
2096
30%
720
76%
720
57%
954
October16th to endNight
76%
768
43%
2304
33%
768
84%
768
62%
982
November1st to 15thNight
64%
760
41%
2280
30%
760
74%
760
52%
1004
November16th to endNight
56%
780
41%
2441
29%
780
69%
780
42%
1150
December1st to 15thNight
56%
736
36%
2392
30%
736
66%
736
38%
1148
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
4313323445%61%
48653
Night
3212313346%65%
48032
TransparencyDay
23%46%11%26%27%
48348
Night
19%47%14%28%26%
47838
SeeingDay
6%18%23%28%18%5%
5662
Night
417%11%29%30%6%
15893

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%
2006
16th to endDay
111221112479%
2160
May1st to 15thDay
111221222478%
2303
16th to endDay
11111222382%
2429
June1st to 15thDay
21123225%77%
2340
16th to endDay
221332444465%
2340
July1st to 15thDay
7%426%7%5%8%8%8%8%31%
2340
16th to endDay
11%7%38%8%6%9%8%7%8%20%
2467
August1st to 15thDay
9%6%36%7%47%7%6%8%32%
2340
16th to endDay
5%425%6%46%7%7%8%38%
2303
September1st to 15thDay
9%5%35%6%35%5%6%6%41%
1980
16th to endDay
5%213423346%63%
1980
October1st to 15thDay
2212123345%71%
1863
16th to endDay
121222235%75%
1920
November1st to 15thDay
221112345%72%
1909
16th to endDay
4313211335%69%
1846
December1st to 15thDay
6%413223248%60%
1649
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
232231333470%
1942
16th to endNight
11111122381%
1800
May1st to 15thNight
1212335%78%
1644
16th to endNight
111122385%
1684
June1st to 15thNight
2211223478%
1620
16th to endNight
21122445%5%68%
1620
July1st to 15thNight
32246%36%7%8%12%42%
1620
16th to endNight
5%326%6%46%7%10%16%29%
1701
August1st to 15thNight
3214436%5%9%11%47%
1620
16th to endNight
6%3134345%9%10%46%
1895
September1st to 15thNight
6%425%43446%8%50%
1980
16th to endNight
31122235%74%
1980
October1st to 15thNight
11221323376%
2096
16th to endNight
111121223478%
2304
November1st to 15thNight
1111212335%73%
2280
16th to endNight
4313312245%66%
2441
December1st to 15thNight
5%313213436%63%
2392
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%128%39%31%
2006
16th to endDay
11%128%28%47%
2160
May1st to 15thDay
11%127%28%48%
2303
16th to endDay
9%126%32%47%
2432
June1st to 15thDay
12%126%26%51%
2340
16th to endDay
21%348%23%38%
2340
July1st to 15thDay
41%12%13%12%11%7%
2201
16th to endDay
54%13%17%8%4
2312
August1st to 15thDay
45%11%12%14%12%3
2325
16th to endDay
39%10%14%15%12%8%
2303
September1st to 15thDay
40%7%10%15%17%8%
1980
16th to endDay
22%35%13%32%21%
1980
October1st to 15thDay
15%35%13%32%30%
1863
16th to endDay
12%2311%30%39%
1920
November1st to 15thDay
12%2413%35%30%
1909
16th to endDay
18%2411%29%33%
1846
December1st to 15thDay
24%25%15%31%21%
1649
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
17%2310%39%26%
1942
16th to endNight
9%139%29%46%
1800
May1st to 15thNight
8%148%34%42%
1645
16th to endNight
6%128%37%42%
1685
June1st to 15thNight
11%135%28%50%
1620
16th to endNight
16%4411%22%40%
1620
July1st to 15thNight
27%11%21%18%11%8%
1530
16th to endNight
36%13%31%14%31
1593
August1st to 15thNight
26%11%17%21%17%5%
1611
16th to endNight
28%9%17%19%17%8%
1895
September1st to 15thNight
30%6%13%19%21%8%
1980
16th to endNight
13%36%16%41%20%
1980
October1st to 15thNight
13%26%17%31%28%
2096
16th to endNight
10%2413%29%39%
2304
November1st to 15thNight
13%2418%32%29%
2280
16th to endNight
20%1311%29%32%
2441
December1st to 15thNight
22%2416%32%20%
2392
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
431%32%20%8%2
269
16th to endDay
334%33%18%8%2
270
May1st to 15thDay
5%31%32%18%10%2
288
16th to endDay
225%34%27%7%2
330
June1st to 15thDay
6%15%36%28%11%2
315
16th to endDay
411%22%38%18%5%
315
July1st to 15thDay
8%8%11%41%25%5%
305
16th to endDay
11%9%10%29%29%9%
327
August1st to 15thDay
10%5%10%32%29%13%
315
16th to endDay
7%5%7%33%34%10%
332
September1st to 15thDay
13%6%14%37%22%5%
315
16th to endDay
6%12%26%28%21%5%
315
October1st to 15thDay
412%26%27%22%7%
198
16th to endDay
2419%29%29%14%
144
November1st to 15thDay
5%11%25%31%21%3
135
16th to endDay
7%13%21%31%22%3
135
December1st to 15thDay
7%12%16%29%32%4
100
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
222%16%38%18%
683
16th to endNight
121%20%34%19%2
540
May1st to 15thNight
122%19%32%22%1
540
16th to endNight
121%14%35%25%1
563
June1st to 15thNight
318%9%35%30%3
540
16th to endNight
117%7%29%40%4
540
July1st to 15thNight
411%216%54%10%
510
16th to endNight
5%16%111%48%16%
564
August1st to 15thNight
49%111%53%19%
539
16th to endNight
6%8%315%49%17%
594
September1st to 15thNight
7%8%5%17%47%13%
720
16th to endNight
48%7%32%38%8%
716
October1st to 15thNight
111%11%32%34%7%
720
16th to endNight
29%9%29%39%9%
768
November1st to 15thNight
218%11%31%31%5%
760
16th to endNight
5%17%15%27%27%6%
780
December1st to 15thNight
6%20%11%31%24%4
736
16th to endNight
8%21%15%31%18%4
768
Page generated at 2017-12-05 08:19:03. Version ac04

Copyright 2017 A. Danko


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