North Georgia Astronomical Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the North Georgia Astronomical Observatory clear sky chart from 2005-11-06 to 2024-03-23.

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
44%
24122
22%
79955
14%
24014
53%
24014
23%
49460

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
21%
756
23%
4003
9%
737
38%
737
11%
2315
January11th to 20thNight
25%
759
26%
3948
9%
740
42%
740
12%
2230
January21st to endNight
21%
831
18%
4388
10%
814
42%
814
12%
2807
February1st to 10thNight
30%
760
25%
2280
12%
760
43%
760
24%
1433
February11th to 20thNight
21%
742
21%
2218
6%
739
35%
739
18%
1472
February21st to endNight
18%
628
20%
1884
8%
628
31%
628
18%
1285
March1st to 10thNight
27%
760
25%
2215
11%
760
40%
760
25%
1408
March11th to 20thNight
27%
760
21%
2090
8%
760
38%
760
25%
1357
March21st to endNight
32%
801
20%
2201
9%
801
41%
801
24%
1442
April1st to 10thNight
35%
694
25%
1954
12%
694
47%
694
30%
1169
April11th to 20thNight
39%
533
26%
1775
16%
533
52%
533
27%
1011
April21st to endNight
48%
540
28%
1631
18%
540
57%
540
34%
934
May1st to 10thNight
50%
540
21%
1620
11%
540
58%
540
30%
972
May11th to 20thNight
51%
531
16%
1593
10%
531
55%
531
25%
1025
May21st to endNight
61%
582
20%
1744
15%
582
63%
582
28%
1095
June1st to 10thNight
61%
540
15%
1620
11%
540
63%
540
24%
1082
June11th to 20thNight
68%
540
14%
1620
10%
540
70%
540
35%
969
June21st to endNight
71%
540
16%
1620
12%
540
73%
540
30%
1009
July1st to 10thNight
65%
525
13%
1575
12%
525
65%
525
24%
1058
July11th to 20thNight
67%
522
12%
1566
11%
522
68%
522
26%
1030
July21st to endNight
70%
591
16%
1672
13%
558
72%
558
27%
1100
August1st to 10thNight
66%
537
13%
1600
12%
534
67%
534
25%
1067
August11th to 20thNight
64%
534
19%
1692
18%
534
65%
534
24%
1122
August21st to endNight
61%
594
18%
1980
19%
594
62%
594
22%
1331
September1st to 10thNight
62%
701
19%
1961
17%
701
64%
701
30%
1273
September11th to 20thNight
56%
720
22%
1980
18%
720
59%
720
28%
1310
September21st to endNight
59%
720
26%
1980
19%
720
65%
720
34%
1227
October1st to 10thNight
53%
720
30%
1980
22%
720
61%
720
37%
1156
October11th to 20thNight
47%
720
30%
2096
21%
720
58%
720
32%
1234
October21st to endNight
48%
792
32%
2376
24%
792
60%
792
33%
1333
November1st to 10thNight
46%
740
29%
2384
21%
740
58%
740
33%
1306
November11th to 20thNight
38%
760
29%
2470
17%
760
54%
760
29%
1378
November21st to endNight
36%
760
25%
2470
15%
760
49%
760
24%
1509
December1st to 10thNight
29%
760
24%
2470
12%
760
44%
760
18%
1615
December11th to 20thNight
32%
759
27%
2904
14%
758
46%
758
20%
1653
December21st to endNight
28%
830
14%
4395
10%
817
40%
817
10%
2743

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
15%5%25%5%35%5%6%7%40%
79101
Night
15%5%25%5%345%6%7%44%
80792
TransparencyDay
41%6%11%19%18%5%
78824
Night
39%6%10%19%20%6%
80588
SeeingDay
20%11%22%22%17%8%
13989
Night
18%10%21%28%19%4
24142

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
20%7%46%4345%6%5%38%
2836
11th to 20thDay
17%425%424445%49%
2840
21st to endDay
27%6%2432334343%
3188
February1st to 10thDay
20%7%35%434447%39%
1900
11th to 20thDay
24%6%2442445%5%41%
1848
21st to endDay
24%6%25%5%4335%6%38%
1570
March1st to 10thDay
18%425%43445%7%44%
1963
11th to 20thDay
20%5%35%5%2445%6%39%
2090
21st to endDay
17%6%35%5%45%5%5%6%39%
2200
April1st to 10thDay
13%415%5%46%5%6%7%44%
2020
11th to 20thDay
14%6%25%6%345%5%6%45%
2134
21st to endDay
12%4144245%6%8%47%
2326
May1st to 10thDay
11%6%25%5%35%5%6%8%45%
2340
11th to 20thDay
13%5%36%7%45%6%6%8%37%
2301
21st to endDay
12%5%26%6%46%5%7%10%37%
2531
June1st to 10thDay
11%6%27%7%5%6%7%8%10%31%
2340
11th to 20thDay
6%425%7%47%7%9%12%36%
2340
21st to endDay
8%5%26%7%48%7%7%12%35%
2340
July1st to 10thDay
9%5%37%9%5%8%7%8%11%27%
2340
11th to 20thDay
10%5%37%9%6%8%9%9%11%24%
2340
21st to endDay
6%5%37%8%6%9%8%9%10%29%
2547
August1st to 10thDay
10%6%26%7%48%9%9%9%29%
2327
11th to 20thDay
11%7%36%6%47%7%7%11%31%
2205
21st to endDay
14%7%36%6%5%7%7%7%9%29%
2376
September1st to 10thDay
12%6%36%6%45%5%7%8%38%
1980
11th to 20thDay
16%5%36%6%45%6%6%7%37%
1980
21st to endDay
14%5%26%435%5%6%6%46%
1980
October1st to 10thDay
13%6%23433445%53%
1980
11th to 20thDay
13%5%23323446%55%
1862
21st to endDay
15%423423435%54%
1980
November1st to 10thDay
14%413324346%57%
1690
11th to 20thDay
16%424333346%53%
1710
21st to endDay
16%6%24424447%46%
1710
December1st to 10thDay
25%6%3442445%6%38%
1710
11th to 20thDay
18%6%24434445%46%
2153
21st to endDay
23%5%244245%5%8%37%
3124
January1st to 10thNight
19%7%25%424446%42%
4109
11th to 20thNight
15%8%35%43445%6%44%
4120
21st to endNight
27%6%35%42333439%
4464
February1st to 10thNight
16%6%24435%45%6%44%
2280
11th to 20thNight
22%5%35%5%3435%441%
2218
21st to endNight
22%5%36%5%35%45%5%38%
1884
March1st to 10thNight
17%7%24434445%47%
2215
11th to 20thNight
16%5%25%43447%7%43%
2090
21st to endNight
15%6%25%5%3445%6%43%
2201
April1st to 10thNight
14%4143345%5%7%50%
1954
11th to 20thNight
14%5%25%42335%7%49%
1775
21st to endNight
11%5%25%32436%7%52%
1631
May1st to 10thNight
12%4235%25%5%6%7%49%
1620
11th to 20thNight
12%5%36%6%35%6%6%8%42%
1592
21st to endNight
12%6%246%3445%9%44%
1744
June1st to 10thNight
10%5%25%7%47%6%8%10%35%
1620
11th to 20thNight
6%425%5%45%7%9%12%42%
1620
21st to endNight
7%4246%36%6%9%10%44%
1620
July1st to 10thNight
9%6%35%8%46%6%9%11%34%
1620
11th to 20thNight
8%6%26%6%37%7%9%12%34%
1620
21st to endNight
6%435%6%47%8%9%12%36%
1771
August1st to 10thNight
10%6%26%6%35%7%8%10%36%
1611
11th to 20thNight
11%6%36%6%345%7%10%38%
1692
21st to endNight
14%7%26%6%35%6%7%9%34%
1980
September1st to 10thNight
10%5%27%6%35%5%7%8%42%
1961
11th to 20thNight
15%5%246%25%5%6%8%42%
1980
21st to endNight
14%415%43345%6%50%
1980
October1st to 10thNight
14%5%13323336%56%
1980
11th to 20thNight
13%425%423446%53%
2096
21st to endNight
14%414423346%55%
2376
November1st to 10thNight
14%5%23323346%57%
2384
11th to 20thNight
15%42332335%5%53%
2470
21st to endNight
18%5%2443445%7%45%
2470
December1st to 10thNight
21%7%35%43445%6%39%
2470
11th to 20thNight
18%5%24323446%48%
3042
21st to endNight
23%6%25%5%35%5%6%7%34%
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
47%45%17%21%7%
2837
11th to 20thDay
38%46%19%25%8%
2840
21st to endDay
47%3417%22%7%
3188
February1st to 10thDay
45%47%18%21%5%
1900
11th to 20thDay
45%35%19%20%7%
1858
21st to endDay
48%36%15%19%8%
1570
March1st to 10thDay
41%49%16%21%10%
1963
11th to 20thDay
46%49%16%18%7%
2090
21st to endDay
45%5%9%22%17%3
2200
April1st to 10thDay
38%5%10%22%20%6%
2020
11th to 20thDay
39%47%18%24%7%
2134
21st to endDay
33%6%11%27%19%4
2326
May1st to 10thDay
37%5%13%23%18%4
2340
11th to 20thDay
43%7%15%19%14%2
2305
21st to endDay
40%8%13%21%15%2
2531
June1st to 10thDay
44%8%18%20%8%2
2340
11th to 20thDay
37%9%19%22%11%2
2340
21st to endDay
39%10%17%19%12%3
2340
July1st to 10thDay
47%10%19%16%7%2
2275
11th to 20thDay
48%12%19%11%7%3
2271
21st to endDay
42%12%20%18%8%
2405
August1st to 10thDay
44%11%18%21%5%1
2314
11th to 20thDay
44%10%17%19%8%2
2205
21st to endDay
48%10%14%17%9%2
2376
September1st to 10thDay
42%8%13%17%16%4
1980
11th to 20thDay
45%6%10%17%20%1
1980
21st to endDay
38%6%10%17%23%7%
1980
October1st to 10thDay
34%49%17%28%8%
1980
11th to 20thDay
31%49%23%24%10%
1862
21st to endDay
34%35%19%28%11%
1980
November1st to 10thDay
31%37%16%33%11%
1690
11th to 20thDay
34%36%20%26%11%
1710
21st to endDay
38%47%17%27%7%
1710
December1st to 10thDay
48%46%18%18%6%
1710
11th to 20thDay
42%36%16%25%9%
2150
21st to endDay
44%5%7%19%22%4
3124
January1st to 10thNight
42%45%15%27%6%
4109
11th to 20thNight
40%5%7%19%19%10%
4120
21st to endNight
49%3414%23%7%
4464
February1st to 10thNight
41%38%19%21%7%
2280
11th to 20thNight
47%3418%21%7%
2219
21st to endNight
47%5%6%15%19%8%
1884
March1st to 10thNight
40%47%17%22%10%
2215
11th to 20thNight
39%6%11%18%20%6%
2090
21st to endNight
42%49%23%19%2
2201
April1st to 10thNight
33%5%12%21%24%6%
1954
11th to 20thNight
35%47%23%21%10%
1775
21st to endNight
31%5%12%28%21%3
1631
May1st to 10thNight
34%6%13%22%22%2
1620
11th to 20thNight
39%8%16%23%13%1
1593
21st to endNight
38%7%12%28%13%3
1745
June1st to 10thNight
40%10%17%20%10%2
1620
11th to 20thNight
29%9%24%24%12%1
1620
21st to endNight
33%10%19%22%13%3
1620
July1st to 10thNight
41%9%19%19%11%1
1575
11th to 20thNight
37%11%25%16%8%3
1566
21st to endNight
36%12%22%21%8%2
1672
August1st to 10thNight
39%11%23%20%7%1
1600
11th to 20thNight
40%10%16%18%15%1
1692
21st to endNight
44%9%16%19%10%2
1980
September1st to 10thNight
37%8%15%19%16%5%
1961
11th to 20thNight
39%8%12%19%20%2
1980
21st to endNight
34%6%12%21%20%8%
1980
October1st to 10thNight
31%410%19%28%7%
1980
11th to 20thNight
33%5%9%21%23%10%
2096
21st to endNight
31%35%21%28%12%
2376
November1st to 10thNight
31%47%20%27%12%
2384
11th to 20thNight
33%36%20%26%13%
2470
21st to endNight
39%45%20%23%7%
2470
December1st to 10thNight
46%47%19%18%6%
2470
11th to 20thNight
37%47%18%27%7%
3044
21st to endNight
47%5%7%19%18%3
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
29%26%35%8%2
270
11th to 20thDay
31%21%30%14%4
270
21st to endDay
28%27%33%9%3
297
February1st to 10thDay
29%22%31%16%2
270
11th to 20thDay
43%20%28%9%
270
21st to endDay
40%20%33%6%1
225
March1st to 10thDay
27%17%31%18%7%
333
11th to 20thDay
28%19%28%19%5%1
460
21st to endDay
24%17%33%18%6%1
470
April1st to 10thDay
23%15%26%24%11%1
420
11th to 20thDay
15%19%32%21%11%2
412
21st to endDay
20%13%26%21%15%5%
420
May1st to 10thDay
19%11%29%22%12%7%
423
11th to 20thDay
17%7%20%28%17%11%
447
21st to endDay
17%7%16%29%18%14%
485
June1st to 10thDay
15%5%18%28%22%13%
450
11th to 20thDay
9%317%24%25%21%
450
21st to endDay
10%6%20%29%21%14%
450
July1st to 10thDay
12%49%24%29%21%
445
11th to 20thDay
11%29%23%34%21%
444
21st to endDay
6%38%25%33%25%
488
August1st to 10thDay
17%5%13%21%24%20%
446
11th to 20thDay
15%310%26%30%17%
439
21st to endDay
18%39%23%30%17%
495
September1st to 10thDay
12%411%31%29%14%
450
11th to 20thDay
18%6%10%26%31%9%
450
21st to endDay
15%420%25%28%8%
450
October1st to 10thDay
19%5%21%28%18%9%
450
11th to 20thDay
16%11%23%29%17%4
450
21st to endDay
20%9%27%26%14%3
495
November1st to 10thDay
23%11%26%26%13%3
288
11th to 20thDay
19%20%36%21%31
270
21st to endDay
16%18%39%18%9%1
270
December1st to 10thDay
35%18%26%17%31
270
11th to 20thDay
28%17%33%18%4
270
21st to endDay
36%17%29%13%41
297
January1st to 10thNight
28%20%25%22%5%
760
11th to 20thNight
24%18%28%24%7%
760
21st to endNight
23%18%33%23%2
836
February1st to 10thNight
20%15%32%27%7%
760
11th to 20thNight
28%18%29%22%2
743
21st to endNight
25%17%35%20%3
628
March1st to 10thNight
23%15%32%26%5%
760
11th to 20thNight
19%15%33%24%8%1
760
21st to endNight
21%14%27%29%9%
801
April1st to 10thNight
17%16%28%27%11%1
694
11th to 20thNight
17%13%25%28%16%1
533
21st to endNight
14%7%25%32%21%1
540
May1st to 10thNight
13%11%20%33%21%1
540
11th to 20thNight
15%6%16%34%25%4
531
21st to endNight
16%211%30%33%7%
584
June1st to 10thNight
11%312%36%31%7%
540
11th to 20thNight
8%114%29%34%14%
540
21st to endNight
8%28%38%35%9%
540
July1st to 10thNight
11%35%27%44%10%
525
11th to 20thNight
9%46%23%45%13%
522
21st to endNight
6%39%23%46%13%
591
August1st to 10thNight
15%26%23%39%15%
537
11th to 20thNight
14%19%24%41%10%
534
21st to endNight
19%26%25%39%9%
594
September1st to 10thNight
11%411%27%38%9%
701
11th to 20thNight
17%313%29%33%4
720
21st to endNight
16%413%36%29%3
720
October1st to 10thNight
17%6%19%30%22%7%
720
11th to 20thNight
15%9%22%32%20%3
720
21st to endNight
17%11%20%32%18%2
792
November1st to 10thNight
17%9%24%29%19%2
740
11th to 20thNight
18%12%28%29%12%1
760
21st to endNight
21%14%25%27%13%1
760
December1st to 10thNight
25%16%24%27%7%1
760
11th to 20thNight
22%13%28%28%8%1
760
21st to endNight
31%12%25%27%6%
836
Page generated at 2024-03-19 23:31:02. Version ac07

Copyright © 2024 Attilla Danko.


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