Dunwoody
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dunwoody clear sky chart from 2005-11-06 to 2024-01-13.

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
48%
23830
22%
74430
15%
23776
56%
23776
27%
46448

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
23%
760
21%
2459
8%
757
39%
757
21%
1548
January11th to 20thNight
28%
732
23%
2378
10%
732
43%
732
21%
1542
January21st to endNight
25%
792
28%
2493
13%
792
43%
792
24%
1536
February1st to 10thNight
32%
720
23%
2160
12%
720
43%
720
24%
1397
February11th to 20thNight
24%
702
21%
2098
7%
699
38%
699
21%
1388
February21st to endNight
23%
592
21%
1776
9%
592
34%
592
21%
1195
March1st to 10thNight
33%
720
25%
2111
14%
720
43%
720
30%
1296
March11th to 20thNight
31%
720
20%
1980
9%
720
41%
720
26%
1308
March21st to endNight
38%
792
22%
2178
12%
792
45%
792
28%
1388
April1st to 10thNight
42%
680
25%
1940
15%
680
51%
680
31%
1174
April11th to 20thNight
45%
533
26%
1775
18%
533
56%
533
31%
997
April21st to endNight
53%
540
29%
1661
21%
540
61%
540
36%
930
May1st to 10thNight
53%
540
23%
1620
13%
540
61%
540
33%
958
May11th to 20thNight
56%
531
17%
1592
12%
531
59%
531
27%
1020
May21st to endNight
65%
582
20%
1744
15%
582
67%
582
30%
1094
June1st to 10thNight
71%
540
16%
1620
16%
540
72%
540
26%
1072
June11th to 20thNight
72%
540
17%
1620
14%
540
74%
540
35%
961
June21st to endNight
74%
540
15%
1620
12%
540
76%
540
30%
1012
July1st to 10thNight
70%
525
13%
1575
12%
525
70%
525
25%
1054
July11th to 20thNight
69%
522
12%
1566
10%
522
70%
522
25%
1047
July21st to endNight
69%
591
14%
1672
13%
558
70%
558
24%
1130
August1st to 10thNight
70%
537
14%
1600
14%
534
70%
534
24%
1099
August11th to 20thNight
66%
534
17%
1743
20%
534
66%
534
23%
1151
August21st to endNight
63%
594
18%
1980
19%
594
64%
594
20%
1361
September1st to 10thNight
67%
692
20%
1952
18%
692
68%
692
30%
1262
September11th to 20thNight
64%
720
22%
1980
19%
720
66%
720
29%
1301
September21st to endNight
64%
720
26%
1980
20%
720
68%
720
33%
1242
October1st to 10thNight
59%
720
29%
1980
23%
720
64%
720
38%
1161
October11th to 20thNight
54%
720
33%
2074
25%
720
63%
720
38%
1191
October21st to endNight
52%
792
32%
2376
25%
792
62%
792
37%
1338
November1st to 10thNight
51%
740
28%
2389
24%
740
60%
740
35%
1313
November11th to 20thNight
41%
760
29%
2470
19%
760
56%
760
31%
1401
November21st to endNight
42%
760
25%
2470
18%
760
53%
760
28%
1475
December1st to 10thNight
32%
760
23%
2470
13%
760
45%
760
22%
1607
December11th to 20thNight
34%
759
25%
2921
15%
758
45%
758
22%
1684
December21st to endNight
30%
828
14%
4407
13%
817
40%
817
11%
2815

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
13%6%35%5%35%5%6%8%42%
74875
Night
13%6%25%5%345%5%7%45%
74885
TransparencyDay
38%8%12%19%18%4
74598
Night
37%7%11%19%20%6%
74681
SeeingDay
15%9%21%23%21%12%
13751
Night
15%7%23%29%22%4
23842

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
18%7%35%42445%5%42%
1706
11th to 20thDay
18%7%34324447%44%
1644
21st to endDay
19%7%35%5%2345%5%43%
1858
February1st to 10thDay
16%7%35%7%35%5%5%7%37%
1800
11th to 20thDay
20%6%345%23446%40%
1748
21st to endDay
22%7%25%5%3345%6%39%
1480
March1st to 10thDay
14%6%15%5%24448%45%
1849
11th to 20thDay
18%6%36%5%4445%7%38%
1980
21st to endDay
16%5%25%5%445%6%7%39%
2178
April1st to 10thDay
12%5%25%5%345%6%7%46%
2034
11th to 20thDay
12%5%35%6%3345%6%48%
2134
21st to endDay
10%42443446%9%51%
2299
May1st to 10thDay
10%435%43346%9%50%
2340
11th to 20thDay
11%6%25%6%45%5%6%10%41%
2301
21st to endDay
10%5%35%435%5%7%8%45%
2531
June1st to 10thDay
10%6%26%7%45%5%7%11%36%
2340
11th to 20thDay
6%4145%45%6%9%11%45%
2340
21st to endDay
7%426%6%47%7%7%10%40%
2340
July1st to 10thDay
10%435%7%6%8%8%8%11%31%
2340
11th to 20thDay
10%426%7%47%8%8%13%30%
2340
21st to endDay
7%436%7%48%8%10%11%31%
2547
August1st to 10thDay
8%5%26%7%5%9%8%9%12%30%
2327
11th to 20thDay
12%6%36%7%46%7%7%9%33%
2154
21st to endDay
12%6%36%7%47%6%7%10%31%
2376
September1st to 10thDay
10%7%35%5%45%6%6%9%40%
1990
11th to 20thDay
14%6%344336%6%8%42%
1980
21st to endDay
13%5%25%433446%50%
1980
October1st to 10thDay
13%5%14324345%55%
1980
11th to 20thDay
12%42333345%7%54%
1886
21st to endDay
13%6%24423345%54%
1980
November1st to 10thDay
13%6%13323345%56%
1686
11th to 20thDay
13%5%24333446%52%
1710
21st to endDay
14%6%35%42445%7%46%
1710
December1st to 10thDay
20%8%25%5%2445%7%37%
1710
11th to 20thDay
17%7%36%5%33445%43%
2153
21st to endDay
22%8%444345%5%7%35%
3124
January1st to 10thNight
19%7%24424435%44%
2459
11th to 20thNight
17%6%45%435%45%6%41%
2378
21st to endNight
17%6%25%423345%47%
2493
February1st to 10thNight
18%6%25%5%3435%7%43%
2160
11th to 20thNight
21%7%34433435%43%
2098
21st to endNight
22%6%36%5%2345%6%39%
1776
March1st to 10thNight
13%7%35%324345%51%
2111
11th to 20thNight
15%6%26%4245%6%7%42%
1980
21st to endNight
13%5%25%5%345%5%7%46%
2178
April1st to 10thNight
11%5%24435%5%5%8%48%
1940
11th to 20thNight
14%5%2332445%7%51%
1775
21st to endNight
8%5%2442346%8%53%
1661
May1st to 10thNight
9%5%245%3445%7%52%
1620
11th to 20thNight
10%436%6%35%5%7%8%43%
1592
21st to endNight
9%6%35%5%45%5%6%8%45%
1744
June1st to 10thNight
7%5%26%5%46%9%7%13%36%
1620
11th to 20thNight
5%4247%45%6%8%12%45%
1620
21st to endNight
6%425%6%36%7%8%12%42%
1620
July1st to 10thNight
8%6%36%6%46%7%7%13%35%
1620
11th to 20thNight
6%5%26%7%48%5%9%11%36%
1620
21st to endNight
6%5%27%7%47%8%8%11%35%
1771
August1st to 10thNight
7%5%35%7%5%6%7%9%13%34%
1611
11th to 20thNight
10%5%37%6%35%6%7%9%39%
1743
21st to endNight
13%6%36%6%46%6%7%8%34%
1980
September1st to 10thNight
9%5%35%5%45%6%7%9%43%
1952
11th to 20thNight
13%5%25%435%5%6%8%44%
1980
21st to endNight
12%5%245%3445%8%49%
1980
October1st to 10thNight
12%42432345%6%55%
1980
11th to 20thNight
12%424433345%57%
2074
21st to endNight
13%424332345%56%
2376
November1st to 10thNight
13%423423345%58%
2389
11th to 20thNight
14%5%24323336%54%
2470
21st to endNight
16%5%2443445%7%47%
2470
December1st to 10thNight
17%7%25%5%3445%6%41%
2470
11th to 20thNight
17%7%24423346%48%
3042
21st to endNight
21%7%36%6%35%45%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
42%5%9%18%21%4
1707
11th to 20thDay
42%49%19%23%4
1644
21st to endDay
43%5%6%20%20%6%
1858
February1st to 10thDay
46%49%17%20%4
1800
11th to 20thDay
45%5%8%19%19%6%
1758
21st to endDay
47%5%8%14%19%7%
1480
March1st to 10thDay
38%5%9%18%21%9%
1849
11th to 20thDay
45%6%11%15%17%6%
1980
21st to endDay
41%7%12%22%16%3
2178
April1st to 10thDay
36%6%11%22%20%5%
2034
11th to 20thDay
37%5%8%19%23%7%
2134
21st to endDay
30%6%12%28%21%3
2299
May1st to 10thDay
31%6%14%23%22%3
2340
11th to 20thDay
37%11%15%22%13%1
2305
21st to endDay
34%8%13%26%17%1
2531
June1st to 10thDay
39%10%17%22%9%2
2340
11th to 20thDay
28%11%22%26%12%1
2340
21st to endDay
35%12%17%23%11%2
2340
July1st to 10thDay
40%14%20%16%8%2
2275
11th to 20thDay
40%14%21%15%8%2
2271
21st to endDay
38%16%20%18%7%
2405
August1st to 10thDay
40%15%20%19%5%1
2314
11th to 20thDay
44%12%16%17%9%2
2154
21st to endDay
45%12%15%16%10%2
2376
September1st to 10thDay
38%10%16%16%17%4
1990
11th to 20thDay
38%10%11%17%22%1
1980
21st to endDay
36%6%10%19%23%7%
1980
October1st to 10thDay
31%6%9%18%28%7%
1980
11th to 20thDay
29%5%9%23%25%8%
1886
21st to endDay
33%5%6%17%29%10%
1980
November1st to 10thDay
31%48%15%32%10%
1686
11th to 20thDay
34%47%18%27%10%
1710
21st to endDay
37%6%7%19%24%7%
1710
December1st to 10thDay
46%6%6%19%16%6%
1710
11th to 20thDay
44%46%15%23%7%
2150
21st to endDay
44%8%9%19%17%3
3124
January1st to 10thNight
42%48%18%23%5%
2459
11th to 20thNight
44%49%18%20%5%
2378
21st to endNight
39%45%19%26%6%
2493
February1st to 10thNight
42%5%9%18%20%8%
2160
11th to 20thNight
45%45%17%21%7%
2099
21st to endNight
45%6%7%16%18%8%
1776
March1st to 10thNight
37%48%19%20%12%
2111
11th to 20thNight
39%8%11%15%20%7%
1980
21st to endNight
38%5%10%22%20%4
2178
April1st to 10thNight
34%5%10%20%23%7%
1940
11th to 20thNight
33%5%9%19%24%10%
1775
21st to endNight
29%7%11%27%21%5%
1661
May1st to 10thNight
31%8%13%22%22%4
1620
11th to 20thNight
37%9%15%22%15%2
1593
21st to endNight
34%9%12%24%18%3
1745
June1st to 10thNight
35%14%18%20%12%2
1620
11th to 20thNight
28%10%22%26%12%2
1620
21st to endNight
31%12%20%21%13%3
1620
July1st to 10thNight
38%12%20%20%9%2
1575
11th to 20thNight
35%15%23%16%9%3
1566
21st to endNight
37%14%22%18%7%2
1672
August1st to 10thNight
37%15%18%24%6%1
1600
11th to 20thNight
38%12%18%16%14%1
1743
21st to endNight
43%12%16%17%10%2
1980
September1st to 10thNight
35%10%17%17%17%4
1952
11th to 20thNight
36%10%11%20%19%3
1980
21st to endNight
33%8%12%17%21%9%
1980
October1st to 10thNight
30%5%12%18%27%7%
1980
11th to 20thNight
30%5%8%21%27%9%
2074
21st to endNight
30%46%18%30%13%
2376
November1st to 10thNight
30%5%7%18%28%13%
2389
11th to 20thNight
33%45%18%28%13%
2470
21st to endNight
36%5%7%19%25%8%
2470
December1st to 10thNight
43%6%8%19%18%5%
2470
11th to 20thNight
37%5%9%15%27%7%
3044
21st to endNight
47%7%8%20%16%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
24%19%40%16%1
270
11th to 20thDay
23%21%28%19%7%2
248
21st to endDay
20%24%36%14%5%1
264
February1st to 10thDay
20%20%34%21%4
240
11th to 20thDay
34%19%31%15%1
240
21st to endDay
28%18%37%14%21
198
March1st to 10thDay
20%17%32%25%7%1
289
11th to 20thDay
20%17%32%23%8%
420
21st to endDay
17%15%35%24%8%1
462
April1st to 10thDay
16%15%28%26%13%1
420
11th to 20thDay
12%14%30%24%18%2
412
21st to endDay
15%10%22%28%21%4
420
May1st to 10thDay
12%9%28%28%18%6%
423
11th to 20thDay
11%421%28%23%14%
447
21st to endDay
14%413%24%29%16%
485
June1st to 10thDay
13%212%24%31%18%
450
11th to 20thDay
7%313%23%24%31%
450
21st to endDay
10%212%28%26%22%
450
July1st to 10thDay
10%2421%32%31%
445
11th to 20thDay
10%18%17%29%36%
444
21st to endDay
7%17%17%39%29%
488
August1st to 10thDay
12%310%20%29%26%
446
11th to 20thDay
11%37%21%36%23%
439
21st to endDay
14%210%23%27%24%
495
September1st to 10thDay
10%410%23%32%20%
450
11th to 20thDay
16%412%21%34%14%
450
21st to endDay
15%216%23%33%11%
450
October1st to 10thDay
16%417%32%23%9%
450
11th to 20thDay
11%9%25%23%25%6%
450
21st to endDay
18%8%20%30%20%4
495
November1st to 10thDay
20%6%27%24%18%5%
284
11th to 20thDay
16%16%36%22%9%2
270
21st to endDay
9%14%37%27%10%1
270
December1st to 10thDay
27%16%33%16%6%1
270
11th to 20thDay
22%17%31%22%7%1
270
21st to endDay
30%13%32%18%6%
297
January1st to 10thNight
24%16%33%22%6%1
760
11th to 20thNight
20%15%32%25%8%
732
21st to endNight
20%14%38%25%4
792
February1st to 10thNight
20%13%31%30%7%
720
11th to 20thNight
24%13%36%25%2
703
21st to endNight
24%13%36%24%3
592
March1st to 10thNight
16%11%36%33%4
720
11th to 20thNight
17%10%36%26%11%1
720
21st to endNight
17%12%29%32%10%
792
April1st to 10thNight
14%12%29%33%13%1
680
11th to 20thNight
16%9%27%33%15%1
533
21st to endNight
11%6%26%35%21%1
540
May1st to 10thNight
10%8%23%35%23%1
540
11th to 20thNight
12%321%33%26%5%
531
21st to endNight
11%211%32%36%8%
584
June1st to 10thNight
9%9%38%36%7%
540
11th to 20thNight
6%112%28%39%14%
540
21st to endNight
6%19%32%41%11%
540
July1st to 10thNight
9%26%23%46%14%
525
11th to 20thNight
8%18%16%53%15%
522
21st to endNight
7%17%24%49%13%
591
August1st to 10thNight
10%18%23%47%11%
537
11th to 20thNight
10%18%26%45%9%
534
21st to endNight
15%28%25%40%10%
594
September1st to 10thNight
10%18%26%43%11%
692
11th to 20thNight
15%211%27%41%4
720
21st to endNight
15%213%33%36%3
720
October1st to 10thNight
13%317%34%25%8%
720
11th to 20thNight
14%5%23%33%22%3
720
21st to endNight
14%8%22%35%19%3
792
November1st to 10thNight
14%6%23%34%22%1
740
11th to 20thNight
17%9%30%29%15%1
760
21st to endNight
19%8%28%31%14%
760
December1st to 10thNight
19%12%31%29%8%1
760
11th to 20thNight
23%9%30%29%9%1
760
21st to endNight
27%11%26%28%7%
836
Page generated at 2024-01-10 19:35:19. Version ac07

Copyright 2024 Attilla Danko


Dunwoody Clear Sky Chart |Charts Home