Brasstown Bald
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brasstown Bald clear sky chart from 2005-11-06 to 2024-01-16.

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%
23891
20%
74492
13%
23834
51%
23834
22%
48641

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
22%
760
20%
2459
8%
757
37%
757
16%
1616
January11th to 20thNight
26%
741
19%
2406
10%
741
38%
741
15%
1666
January21st to endNight
22%
792
23%
2563
9%
792
39%
792
18%
1667
February1st to 10thNight
30%
720
22%
2160
11%
720
41%
720
21%
1421
February11th to 20thNight
19%
702
18%
2098
6%
699
32%
699
15%
1462
February21st to endNight
19%
592
19%
1776
7%
592
32%
592
15%
1287
March1st to 10thNight
27%
720
22%
2088
11%
720
36%
720
22%
1358
March11th to 20thNight
30%
720
17%
1980
8%
720
37%
720
19%
1379
March21st to endNight
31%
792
17%
2178
8%
792
37%
792
20%
1515
April1st to 10thNight
36%
712
22%
1972
12%
712
45%
712
28%
1231
April11th to 20thNight
42%
533
24%
1766
16%
533
53%
533
25%
1040
April21st to endNight
48%
540
25%
1620
18%
540
55%
540
30%
996
May1st to 10thNight
49%
540
17%
1620
9%
540
54%
540
26%
1019
May11th to 20thNight
54%
531
13%
1593
9%
531
56%
531
22%
1076
May21st to endNight
63%
582
16%
1744
12%
582
65%
582
26%
1139
June1st to 10thNight
60%
540
14%
1620
12%
540
61%
540
22%
1108
June11th to 20thNight
69%
540
13%
1620
11%
540
71%
540
32%
1006
June21st to endNight
72%
540
15%
1620
13%
540
73%
540
28%
1042
July1st to 10thNight
65%
525
11%
1575
10%
525
66%
525
20%
1119
July11th to 20thNight
64%
522
10%
1566
9%
522
64%
522
22%
1079
July21st to endNight
69%
591
13%
1672
12%
558
70%
558
24%
1153
August1st to 10thNight
67%
537
12%
1600
11%
534
67%
534
22%
1120
August11th to 20thNight
65%
534
17%
1656
17%
534
65%
534
23%
1146
August21st to endNight
62%
594
16%
1980
17%
594
64%
594
21%
1342
September1st to 10thNight
61%
709
17%
1969
16%
709
62%
709
26%
1326
September11th to 20thNight
57%
720
19%
1980
16%
720
60%
720
25%
1344
September21st to endNight
59%
720
25%
1980
20%
720
63%
720
31%
1256
October1st to 10thNight
53%
720
28%
1980
22%
720
59%
720
35%
1183
October11th to 20thNight
46%
720
25%
2114
19%
720
55%
720
28%
1315
October21st to endNight
47%
792
31%
2376
23%
792
58%
792
30%
1399
November1st to 10thNight
48%
740
27%
2377
22%
740
57%
740
31%
1354
November11th to 20thNight
40%
760
26%
2470
18%
760
52%
760
25%
1467
November21st to endNight
38%
760
23%
2470
17%
760
48%
760
22%
1553
December1st to 10thNight
29%
760
20%
2470
12%
760
40%
760
15%
1699
December11th to 20thNight
33%
759
23%
2940
14%
758
43%
758
17%
1822
December21st to endNight
28%
831
12%
4434
10%
817
38%
817
9%
2936

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
14%7%36%6%45%5%6%7%37%
74910
Night
13%7%36%5%35%5%5%7%40%
74900
TransparencyDay
44%8%11%17%16%4
74633
Night
41%8%12%18%17%4
74696
SeeingDay
18%13%23%21%16%9%
13795
Night
17%12%20%28%20%4
23900

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
16%7%38%5%3435%5%41%
1706
11th to 20thDay
18%9%35%5%35%45%5%37%
1665
21st to endDay
13%9%35%5%35%5%45%44%
1790
February1st to 10thDay
17%10%36%5%345%46%37%
1800
11th to 20thDay
19%9%46%5%34446%36%
1748
21st to endDay
21%8%37%5%33446%36%
1480
March1st to 10thDay
15%6%35%5%3446%7%43%
1872
11th to 20thDay
18%7%46%5%45%446%35%
1980
21st to endDay
14%9%47%7%35%5%5%6%37%
2178
April1st to 10thDay
12%6%26%6%446%7%7%41%
2002
11th to 20thDay
15%6%36%5%35%5%6%6%42%
2142
21st to endDay
12%6%246%35%5%5%8%43%
2340
May1st to 10thDay
13%7%35%5%45%6%46%41%
2340
11th to 20thDay
15%8%38%6%46%5%5%6%34%
2301
21st to endDay
12%6%36%7%5%6%5%6%9%33%
2531
June1st to 10thDay
12%7%47%9%5%7%6%6%9%29%
2340
11th to 20thDay
6%6%37%6%5%7%8%8%10%34%
2340
21st to endDay
8%6%37%7%5%7%7%7%11%33%
2340
July1st to 10thDay
9%7%49%8%6%8%7%8%9%24%
2340
11th to 20thDay
12%6%47%9%6%8%8%9%9%22%
2340
21st to endDay
9%6%38%10%6%9%8%8%9%25%
2547
August1st to 10thDay
10%7%29%8%5%7%8%8%10%25%
2327
11th to 20thDay
12%7%37%7%47%7%7%10%28%
2241
21st to endDay
14%7%47%7%5%8%7%6%8%27%
2368
September1st to 10thDay
12%7%38%7%46%6%6%7%33%
1980
11th to 20thDay
14%8%37%6%46%5%6%6%34%
1980
21st to endDay
13%7%26%6%4445%7%42%
1980
October1st to 10thDay
13%6%244345%45%50%
1980
11th to 20thDay
12%7%24434345%50%
1845
21st to endDay
14%6%246%23335%53%
1980
November1st to 10thDay
11%7%23324345%56%
1700
11th to 20thDay
13%5%34334437%50%
1710
21st to endDay
15%6%345%2445%7%44%
1710
December1st to 10thDay
21%8%46%5%345%5%5%35%
1710
11th to 20thDay
15%7%46%5%35%446%41%
2153
21st to endDay
19%7%5%5%6%3445%7%35%
3124
January1st to 10thNight
17%8%36%5%34445%40%
2459
11th to 20thNight
17%9%47%6%35%5%47%34%
2406
21st to endNight
14%8%47%5%35%345%42%
2563
February1st to 10thNight
14%7%47%5%345%5%7%40%
2160
11th to 20thNight
19%8%47%5%3444438%
2098
21st to endNight
21%9%47%5%35%445%33%
1776
March1st to 10thNight
14%7%45%5%35%35%6%43%
2088
11th to 20thNight
16%8%37%5%3447%6%37%
1980
21st to endNight
14%7%48%6%36%45%6%39%
2178
April1st to 10thNight
11%7%34425%45%7%47%
1972
11th to 20thNight
13%6%26%43435%7%47%
1766
21st to endNight
10%7%35%5%2446%5%49%
1620
May1st to 10thNight
11%6%35%5%35%46%9%44%
1620
11th to 20thNight
12%7%36%6%45%5%6%8%39%
1592
21st to endNight
9%7%25%5%46%6%7%10%39%
1744
June1st to 10thNight
8%6%47%7%45%6%8%10%35%
1620
11th to 20thNight
5%435%5%46%6%7%12%43%
1620
21st to endNight
8%5%245%35%7%7%12%42%
1620
July1st to 10thNight
11%6%36%7%47%7%9%10%31%
1620
11th to 20thNight
8%5%37%7%47%7%9%12%30%
1620
21st to endNight
8%6%36%6%46%8%9%10%34%
1771
August1st to 10thNight
9%7%36%7%45%7%9%11%34%
1611
11th to 20thNight
11%6%37%6%46%5%7%10%36%
1656
21st to endNight
12%6%36%6%36%5%7%10%35%
1980
September1st to 10thNight
10%6%26%6%45%6%7%10%38%
1969
11th to 20thNight
14%6%36%5%45%5%5%9%38%
1980
21st to endNight
12%6%245%3445%7%48%
1980
October1st to 10thNight
13%6%24423435%54%
1980
11th to 20thNight
12%6%35%5%345%45%47%
2114
21st to endNight
12%7%25%423345%54%
2376
November1st to 10thNight
12%5%25%434346%53%
2377
11th to 20thNight
13%6%445%34436%49%
2470
21st to endNight
14%7%36%5%35%5%5%6%41%
2470
December1st to 10thNight
19%8%37%5%3445%6%35%
2470
11th to 20thNight
14%8%47%5%33445%42%
3042
21st to endNight
19%8%48%7%45%45%7%29%
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
45%48%17%20%5%
1707
11th to 20thDay
48%5%8%16%18%5%
1665
21st to endDay
42%5%7%19%20%7%
1790
February1st to 10thDay
49%5%7%17%18%5%
1800
11th to 20thDay
49%5%7%17%17%5%
1758
21st to endDay
50%5%8%12%18%6%
1480
March1st to 10thDay
40%5%10%16%21%8%
1872
11th to 20thDay
49%7%9%14%16%6%
1980
21st to endDay
48%6%11%19%14%2
2178
April1st to 10thDay
40%7%10%21%18%4
2002
11th to 20thDay
42%6%8%16%22%5%
2142
21st to endDay
38%6%11%26%16%3
2340
May1st to 10thDay
42%7%13%21%15%3
2340
11th to 20thDay
48%10%12%17%12%1
2305
21st to endDay
44%9%14%20%12%1
2531
June1st to 10thDay
48%10%16%19%6%1
2340
11th to 20thDay
41%12%18%18%10%1
2340
21st to endDay
42%12%16%17%11%2
2340
July1st to 10thDay
50%14%15%15%5%1
2275
11th to 20thDay
50%15%16%10%7%2
2271
21st to endDay
49%13%16%15%6%
2405
August1st to 10thDay
48%14%17%16%4
2314
11th to 20thDay
48%12%16%15%8%1
2241
21st to endDay
51%12%12%15%8%2
2368
September1st to 10thDay
45%11%11%16%13%3
1980
11th to 20thDay
46%8%12%16%16%2
1980
21st to endDay
41%6%12%16%20%6%
1980
October1st to 10thDay
34%6%9%17%27%7%
1980
11th to 20thDay
35%6%9%19%21%10%
1845
21st to endDay
34%46%20%25%10%
1980
November1st to 10thDay
32%47%15%31%11%
1700
11th to 20thDay
35%47%18%27%10%
1710
21st to endDay
40%5%7%16%26%6%
1710
December1st to 10thDay
50%5%7%16%17%5%
1710
11th to 20thDay
42%5%8%13%23%8%
2150
21st to endDay
45%7%7%20%17%3
3124
January1st to 10thNight
47%48%15%20%6%
2459
11th to 20thNight
50%5%9%13%18%4
2406
21st to endNight
45%47%18%21%5%
2563
February1st to 10thNight
44%49%19%18%5%
2160
11th to 20thNight
50%5%6%16%18%5%
2099
21st to endNight
53%5%7%14%16%5%
1776
March1st to 10thNight
41%5%9%15%20%9%
2088
11th to 20thNight
45%7%11%16%16%5%
1980
21st to endNight
46%6%10%21%16%2
2178
April1st to 10thNight
36%5%13%20%22%4
1972
11th to 20thNight
37%410%21%21%7%
1766
21st to endNight
35%7%13%27%17%2
1620
May1st to 10thNight
36%9%15%21%17%2
1620
11th to 20thNight
42%10%17%20%11%1
1593
21st to endNight
38%10%16%25%10%2
1745
June1st to 10thNight
41%12%18%20%7%1
1620
11th to 20thNight
30%12%23%25%9%1
1620
21st to endNight
32%13%19%20%12%3
1620
July1st to 10thNight
43%13%18%17%8%1
1575
11th to 20thNight
39%14%24%14%7%2
1566
21st to endNight
37%16%21%19%7%1
1672
August1st to 10thNight
40%14%20%19%6%
1600
11th to 20thNight
40%13%17%17%13%1
1656
21st to endNight
42%11%19%19%7%2
1980
September1st to 10thNight
38%11%16%17%14%4
1969
11th to 20thNight
40%10%13%19%17%1
1980
21st to endNight
35%8%11%22%18%6%
1980
October1st to 10thNight
32%6%11%18%28%6%
1980
11th to 20thNight
36%7%10%19%20%9%
2114
21st to endNight
34%5%5%20%26%10%
2376
November1st to 10thNight
34%47%20%25%11%
2377
11th to 20thNight
37%5%6%17%24%11%
2470
21st to endNight
41%5%7%20%22%6%
2470
December1st to 10thNight
50%5%8%15%16%6%
2470
11th to 20thNight
40%7%8%13%25%6%
3044
21st to endNight
50%8%10%16%14%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%27%34%9%2
270
11th to 20thDay
34%23%26%13%4
255
21st to endDay
28%31%29%8%3
264
February1st to 10thDay
31%27%33%8%1
240
11th to 20thDay
42%30%24%31
240
21st to endDay
39%25%29%6%1
198
March1st to 10thDay
28%17%33%17%5%
312
11th to 20thDay
27%22%27%18%5%1
420
21st to endDay
26%22%27%19%6%1
462
April1st to 10thDay
23%16%27%22%11%1
420
11th to 20thDay
17%25%24%21%12%1
412
21st to endDay
20%14%23%24%14%5%
420
May1st to 10thDay
19%18%25%19%13%6%
423
11th to 20thDay
16%10%21%28%12%11%
447
21st to endDay
14%8%21%24%19%14%
485
June1st to 10thDay
14%5%20%26%22%12%
450
11th to 20thDay
8%5%22%23%25%16%
450
21st to endDay
11%424%25%20%15%
450
July1st to 10thDay
10%413%25%29%19%
445
11th to 20thDay
8%412%25%27%24%
444
21st to endDay
8%210%27%28%24%
488
August1st to 10thDay
15%6%15%23%20%22%
446
11th to 20thDay
11%5%14%22%31%17%
439
21st to endDay
13%414%22%29%18%
495
September1st to 10thDay
10%5%14%25%33%13%
450
11th to 20thDay
16%5%16%21%32%10%
450
21st to endDay
12%7%20%27%27%8%
450
October1st to 10thDay
16%7%23%28%18%8%
450
11th to 20thDay
17%12%24%26%18%3
450
21st to endDay
19%12%27%25%15%2
495
November1st to 10thDay
16%16%32%25%9%3
298
11th to 20thDay
22%23%32%18%5%
270
21st to endDay
16%23%37%16%7%1
270
December1st to 10thDay
33%21%29%14%3
270
11th to 20thDay
26%20%35%13%5%1
270
21st to endDay
29%24%31%12%31
297
January1st to 10thNight
26%19%28%21%5%1
760
11th to 20thNight
22%22%25%23%8%
741
21st to endNight
21%21%31%24%3
792
February1st to 10thNight
21%19%26%28%6%
720
11th to 20thNight
27%21%29%21%2
703
21st to endNight
29%21%28%19%4
592
March1st to 10thNight
20%18%32%26%4
720
11th to 20thNight
21%18%25%26%8%1
720
21st to endNight
20%16%28%25%10%
792
April1st to 10thNight
17%17%27%29%10%1
712
11th to 20thNight
17%14%22%29%16%2
533
21st to endNight
13%10%23%35%18%2
540
May1st to 10thNight
15%9%19%33%21%2
540
11th to 20thNight
13%7%18%32%25%5%
531
21st to endNight
12%412%32%33%8%
584
June1st to 10thNight
10%411%34%35%6%
540
11th to 20thNight
6%213%30%35%15%
540
21st to endNight
8%210%32%38%10%
540
July1st to 10thNight
10%19%24%46%10%
525
11th to 20thNight
9%39%21%44%14%
522
21st to endNight
8%17%22%47%15%
591
August1st to 10thNight
9%47%23%44%14%
537
11th to 20thNight
11%110%28%40%9%
534
21st to endNight
14%28%24%41%11%
594
September1st to 10thNight
10%312%28%37%10%
709
11th to 20thNight
16%413%28%35%4
720
21st to endNight
13%6%13%33%32%3
720
October1st to 10thNight
15%7%19%29%24%7%
720
11th to 20thNight
16%10%21%31%21%2
720
21st to endNight
16%14%17%35%16%3
792
November1st to 10thNight
14%9%24%31%19%3
740
11th to 20thNight
18%15%23%29%13%2
760
21st to endNight
18%17%21%29%14%1
760
December1st to 10thNight
25%18%23%26%7%1
760
11th to 20thNight
21%16%25%30%7%1
760
21st to endNight
27%15%25%28%5%
836
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