Georgia Southern Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Georgia Southern Planetarium clear sky chart from 2005-11-06 to 2024-11-25.

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
49%
25275
19%
97133
15%
25018
57%
25018
22%
59456

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
30%
755
24%
3986
10%
737
47%
737
16%
2228
January11th to 20thNight
35%
757
27%
3942
15%
740
51%
740
17%
2112
January21st to endNight
26%
830
17%
4446
10%
814
42%
814
14%
2602
February1st to 10thNight
35%
760
23%
2343
13%
760
47%
760
27%
1460
February11th to 20thNight
28%
743
22%
2218
8%
739
43%
739
25%
1402
February21st to endNight
29%
628
23%
1848
12%
628
40%
628
27%
1161
March1st to 10thNight
39%
757
20%
3412
17%
745
50%
745
17%
2364
March11th to 20thNight
36%
751
27%
3411
11%
740
47%
740
21%
1726
March21st to endNight
35%
831
16%
3714
10%
814
45%
814
19%
2219
April1st to 10thNight
39%
760
25%
2090
14%
760
47%
760
32%
1278
April11th to 20thNight
43%
751
24%
1969
13%
751
51%
751
36%
1197
April21st to endNight
53%
642
30%
1782
18%
642
61%
642
41%
1009
May1st to 10thNight
57%
563
26%
2789
16%
559
64%
559
24%
1423
May11th to 20thNight
57%
553
18%
2757
12%
541
62%
541
19%
1578
May21st to endNight
62%
599
16%
3027
14%
593
65%
593
22%
1444
June1st to 10thNight
64%
570
14%
1710
11%
570
66%
570
25%
1146
June11th to 20thNight
68%
570
14%
1710
11%
570
69%
570
29%
1098
June21st to endNight
71%
570
10%
1710
7%
570
72%
570
25%
1158
July1st to 10thNight
68%
538
10%
2746
10%
535
70%
535
13%
1945
July11th to 20thNight
69%
534
7%
2761
9%
533
69%
533
14%
1837
July21st to endNight
71%
608
7%
2985
11%
569
73%
569
13%
2275
August1st to 10thNight
68%
556
7%
2800
10%
545
69%
545
12%
2003
August11th to 20thNight
66%
547
10%
2523
11%
543
67%
543
14%
1578
August21st to endNight
60%
758
15%
3227
12%
752
60%
752
16%
1816
September1st to 10thNight
66%
760
15%
2090
15%
760
66%
760
25%
1445
September11th to 20thNight
63%
760
16%
2090
15%
760
64%
760
27%
1422
September21st to endNight
58%
760
19%
2090
16%
760
62%
760
27%
1416
October1st to 10thNight
57%
760
18%
2890
22%
740
63%
740
21%
1981
October11th to 20thNight
56%
760
31%
2199
28%
740
64%
740
38%
1253
October21st to endNight
57%
836
28%
2698
28%
814
65%
814
30%
1637
November1st to 10thNight
53%
780
27%
2341
23%
780
61%
780
33%
1376
November11th to 20thNight
44%
800
26%
2500
20%
800
53%
800
31%
1462
November21st to endNight
44%
779
27%
2529
20%
779
55%
779
30%
1461
December1st to 10thNight
41%
760
24%
2470
16%
760
53%
760
25%
1524
December11th to 20thNight
38%
759
25%
2917
16%
758
49%
758
22%
1705
December21st to endNight
34%
830
15%
4413
16%
817
45%
817
13%
2715

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
11%6%26%5%5%5%47%9%40%
101268
Night
11%6%26%445%46%8%43%
98145
TransparencyDay
38%8%13%18%17%7%
105010
Night
37%8%12%18%18%8%
102542
SeeingDay
12%8%22%25%21%12%
15385
Night
12%7%23%33%22%3
25441

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
12%6%35%5%45%45%7%45%
2836
11th to 20thDay
12%6%25%33335%9%50%
2840
21st to endDay
13%8%37%5%3335%6%44%
3124
February1st to 10thDay
14%7%36%445%36%7%40%
1833
11th to 20thDay
17%6%25%33335%6%47%
1848
21st to endDay
14%6%36%44335%7%45%
1603
March1st to 10thDay
19%9%37%5%4335%6%35%
3435
11th to 20thDay
8%425%44446%7%53%
3480
21st to endDay
16%6%36%44335%7%43%
3815
April1st to 10thDay
8%425%5%5%5%45%7%48%
2090
11th to 20thDay
11%5%26%445%35%7%47%
2159
21st to endDay
6%425%445%46%7%53%
2411
May1st to 10thDay
8%426%6%5%6%46%8%45%
4082
11th to 20thDay
14%7%37%5%5%5%45%7%39%
4081
21st to endDay
5%326%5%45%46%10%49%
4476
June1st to 10thDay
9%6%37%5%6%7%5%9%9%33%
2470
11th to 20thDay
6%5%26%6%5%6%7%8%11%39%
2470
21st to endDay
6%6%27%7%6%8%8%10%11%31%
2470
July1st to 10thDay
11%8%310%7%7%7%6%9%10%23%
4120
11th to 20thDay
4428%7%7%7%7%10%15%30%
4120
21st to endDay
6%6%38%7%7%8%7%10%14%23%
4466
August1st to 10thDay
15%6%39%6%7%7%6%9%10%22%
4104
11th to 20thDay
7%427%5%6%7%6%9%12%36%
4044
21st to endDay
7%5%37%6%6%7%6%8%12%32%
4004
September1st to 10thDay
9%7%39%6%7%6%5%7%8%33%
2090
11th to 20thDay
14%6%37%5%6%5%46%8%38%
2090
21st to endDay
13%7%38%5%45%35%7%39%
2090
October1st to 10thDay
10%6%37%5%4335%6%48%
2042
11th to 20thDay
9%42332325%7%59%
1900
21st to endDay
8%415%334346%57%
2090
November1st to 10thDay
11%6%25%5%3435%6%51%
1957
11th to 20thDay
14%5%2433325%454%
1895
21st to endDay
14%7%2433435%6%49%
1746
December1st to 10thDay
13%7%26%5%45%46%7%43%
1710
11th to 20thDay
16%6%25%433246%49%
2153
21st to endDay
17%10%36%444245%42%
3124
January1st to 10thNight
15%6%26%445%45%6%44%
4109
11th to 20thNight
9%6%27%5%45%46%7%45%
4120
21st to endNight
15%7%37%444346%43%
4532
February1st to 10thNight
14%5%25%44445%7%44%
2343
11th to 20thNight
17%6%35%433445%47%
2218
21st to endNight
12%6%36%435%45%6%46%
1848
March1st to 10thNight
20%11%36%433345%36%
3418
11th to 20thNight
10%5%25%335%46%7%51%
3480
21st to endNight
15%6%25%5%4445%6%44%
3817
April1st to 10thNight
10%5%2434446%7%50%
2090
11th to 20thNight
10%5%26%34435%8%51%
1969
21st to endNight
7%415%43435%7%57%
1782
May1st to 10thNight
7%426%345%47%10%48%
2813
11th to 20thNight
11%7%26%445%45%9%43%
2812
21st to endNight
6%425%4345%7%9%51%
3079
June1st to 10thNight
9%6%28%5%5%6%5%8%11%34%
1710
11th to 20thNight
6%5%26%5%5%6%5%9%11%40%
1710
21st to endNight
6%5%26%6%6%7%6%10%13%34%
1710
July1st to 10thNight
12%8%39%6%6%6%6%7%11%26%
2840
11th to 20thNight
5%5%39%7%7%8%6%9%12%29%
2840
21st to endNight
8%7%39%7%8%7%6%10%12%23%
3087
August1st to 10thNight
16%6%37%7%6%6%49%11%25%
2825
11th to 20thNight
6%5%27%6%5%6%5%7%12%39%
2785
21st to endNight
5%5%26%45%5%47%11%44%
3599
September1st to 10thNight
10%7%26%45%6%6%7%12%35%
2090
11th to 20thNight
10%6%38%5%5%5%47%9%39%
2090
21st to endNight
12%7%27%5%5%5%45%8%40%
2090
October1st to 10thNight
11%7%26%33435%6%49%
2137
11th to 20thNight
10%5%24332235%60%
2280
21st to endNight
8%6%25%443345%56%
2508
November1st to 10thNight
12%426%43435%6%52%
2341
11th to 20thNight
12%8%25%434346%50%
2500
21st to endNight
12%6%25%44335%6%50%
2529
December1st to 10thNight
14%6%26%44446%7%44%
2470
11th to 20thNight
15%7%25%343335%49%
3042
21st to endNight
16%8%37%44445%5%39%
4532

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
37%5%8%17%21%11%
2837
11th to 20thDay
32%47%20%25%11%
2840
21st to endDay
40%6%6%15%22%12%
3124
February1st to 10thDay
42%5%9%17%19%7%
1833
11th to 20thDay
38%48%14%26%9%
1858
21st to endDay
38%5%8%17%19%12%
1603
March1st to 10thDay
48%6%9%13%15%8%
3435
11th to 20thDay
28%6%11%18%22%13%
3480
21st to endDay
42%5%7%20%19%7%
3815
April1st to 10thDay
33%6%10%19%20%12%
2090
11th to 20thDay
35%5%9%18%20%12%
2159
21st to endDay
28%6%11%25%25%6%
2411
May1st to 10thDay
33%10%13%26%15%3
4120
11th to 20thDay
42%8%12%21%16%1
4085
21st to endDay
28%8%19%22%21%2
4489
June1st to 10thDay
42%12%16%16%12%1
2470
11th to 20thDay
34%11%18%24%12%1
2470
21st to endDay
39%14%19%16%10%1
2470
July1st to 10thDay
50%13%19%13%31
4055
11th to 20thDay
38%17%28%13%31
4051
21st to endDay
45%18%23%11%3
4324
August1st to 10thDay
52%13%21%12%2
4091
11th to 20thDay
35%12%18%24%10%1
4083
21st to endDay
40%11%17%27%5%1
4004
September1st to 10thDay
43%13%16%12%11%5%
2090
11th to 20thDay
43%9%12%16%15%4
2090
21st to endDay
44%5%11%18%17%5%
2090
October1st to 10thDay
40%48%13%21%14%
3393
11th to 20thDay
16%36%14%28%34%
3140
21st to endDay
22%37%18%35%16%
3428
November1st to 10thDay
33%5%9%16%23%14%
1957
11th to 20thDay
34%46%18%25%14%
1895
21st to endDay
35%5%8%20%22%10%
1746
December1st to 10thDay
39%7%12%16%18%8%
1710
11th to 20thDay
37%46%19%27%7%
2150
21st to endDay
45%46%16%25%5%
3124
January1st to 10thNight
39%5%7%15%21%13%
4109
11th to 20thNight
36%5%6%17%26%10%
4120
21st to endNight
42%6%7%11%24%11%
4532
February1st to 10thNight
39%5%10%17%20%10%
2343
11th to 20thNight
39%5%7%16%21%12%
2219
21st to endNight
37%6%8%17%17%14%
1848
March1st to 10thNight
50%6%10%13%14%7%
3418
11th to 20thNight
31%6%10%15%23%15%
3480
21st to endNight
40%6%9%17%19%10%
3817
April1st to 10thNight
32%7%11%17%20%12%
2090
11th to 20thNight
31%6%9%21%21%12%
1969
21st to endNight
26%6%13%25%23%7%
1782
May1st to 10thNight
28%9%16%28%14%4
2840
11th to 20thNight
36%9%14%24%15%2
2813
21st to endNight
25%11%14%28%19%3
3087
June1st to 10thNight
38%12%19%20%10%1
1710
11th to 20thNight
33%12%19%26%9%1
1710
21st to endNight
36%15%24%16%9%1
1710
July1st to 10thNight
48%12%20%15%31
2795
11th to 20thNight
42%15%28%13%3
2786
21st to endNight
49%17%19%13%2
2988
August1st to 10thNight
50%12%24%11%2
2814
11th to 20thNight
35%13%20%25%6%1
2812
21st to endNight
31%10%20%34%4
3599
September1st to 10thNight
40%12%19%14%12%4
2090
11th to 20thNight
39%10%16%18%13%3
2090
21st to endNight
41%8%14%15%19%3
2090
October1st to 10thNight
38%5%10%14%23%10%
3566
11th to 20thNight
17%3412%26%38%
3779
21st to endNight
23%46%17%32%18%
4120
November1st to 10thNight
33%5%10%14%24%15%
2341
11th to 20thNight
35%48%17%23%14%
2500
21st to endNight
35%48%19%23%11%
2529
December1st to 10thNight
38%6%13%16%20%6%
2470
11th to 20thNight
39%47%16%26%8%
3044
21st to endNight
45%5%7%16%22%4
4532

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%19%48%15%5%
270
11th to 20thDay
11%19%37%20%11%2
270
21st to endDay
22%26%39%10%4
297
February1st to 10thDay
16%22%38%17%7%
270
11th to 20thDay
26%15%32%24%2
270
21st to endDay
14%19%43%17%7%
258
March1st to 10thDay
14%17%30%25%12%1
460
11th to 20thDay
12%12%40%26%8%1
460
21st to endDay
17%14%31%27%9%2
506
April1st to 10thDay
16%15%30%26%12%2
460
11th to 20thDay
11%13%30%22%17%7%
452
21st to endDay
7%10%23%32%20%9%
460
May1st to 10thDay
7%12%29%25%19%9%
463
11th to 20thDay
11%321%28%24%14%
487
21st to endDay
10%315%29%25%18%
529
June1st to 10thDay
9%218%24%30%17%
490
11th to 20thDay
7%414%23%26%27%
490
21st to endDay
5%410%29%28%24%
490
July1st to 10thDay
7%26%19%39%28%
485
11th to 20thDay
6%15%18%37%34%
484
21st to endDay
7%26%23%37%26%
532
August1st to 10thDay
12%210%22%30%24%
486
11th to 20thDay
7%35%20%34%31%
479
21st to endDay
12%19%24%30%23%
539
September1st to 10thDay
11%38%29%30%19%
490
11th to 20thDay
15%414%29%28%11%
490
21st to endDay
14%213%28%32%11%
490
October1st to 10thDay
13%6%22%31%19%9%
490
11th to 20thDay
10%5%24%31%21%9%
490
21st to endDay
11%5%25%29%24%6%
539
November1st to 10thDay
16%7%24%28%20%5%
495
11th to 20thDay
18%9%36%23%11%3
395
21st to endDay
12%15%28%31%13%1
282
December1st to 10thDay
17%14%35%23%9%1
270
11th to 20thDay
19%17%33%21%8%2
270
21st to endDay
28%9%34%17%11%1
297
January1st to 10thNight
16%12%36%29%6%
760
11th to 20thNight
15%13%31%32%9%
760
21st to endNight
19%13%39%25%4
836
February1st to 10thNight
15%11%34%33%7%
760
11th to 20thNight
21%11%36%29%3
743
21st to endNight
14%13%39%30%4
628
March1st to 10thNight
13%10%33%38%6%
760
11th to 20thNight
14%12%33%32%8%1
760
21st to endNight
11%11%36%32%9%
836
April1st to 10thNight
12%10%34%33%10%1
760
11th to 20thNight
11%9%32%34%14%
751
21st to endNight
7%7%29%40%17%
642
May1st to 10thNight
7%6%23%46%17%1
570
11th to 20thNight
7%423%41%20%4
561
21st to endNight
9%313%37%35%3
617
June1st to 10thNight
10%213%37%34%3
570
11th to 20thNight
7%211%35%34%11%
570
21st to endNight
6%110%38%38%8%
570
July1st to 10thNight
9%17%28%46%9%
555
11th to 20thNight
8%1425%50%11%
552
21st to endNight
7%16%34%46%5%
624
August1st to 10thNight
8%28%29%43%10%
567
11th to 20thNight
8%26%27%47%10%
564
21st to endNight
11%110%27%39%11%
774
September1st to 10thNight
11%28%28%44%6%
760
11th to 20thNight
11%213%32%39%3
760
21st to endNight
15%213%35%31%4
760
October1st to 10thNight
13%419%35%25%4
760
11th to 20thNight
13%5%22%35%23%3
760
21st to endNight
10%6%22%38%24%2
836
November1st to 10thNight
14%6%20%36%22%2
780
11th to 20thNight
16%8%28%32%15%1
800
21st to endNight
14%8%28%32%17%
779
December1st to 10thNight
16%8%29%33%13%1
760
11th to 20thNight
16%10%30%30%12%1
760
21st to endNight
21%11%29%30%10%
836
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