Trussville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Trussville clear sky chart from 2005-11-05 to 2017-09-24.

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
50%
15294
23%
47048
17%
15251
57%
15251
29%
28816

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
27%
720
24%
2327
10%
716
43%
716
22%
1459
January16th to endNight
26%
768
25%
2323
11%
768
40%
768
22%
1522
February1st to 15thNight
29%
704
25%
2112
9%
701
43%
701
26%
1311
February16th to endNight
27%
631
24%
1893
11%
631
38%
631
26%
1201
March1st to 15thNight
32%
720
21%
2148
12%
720
39%
720
26%
1354
March16th to endNight
38%
717
23%
2061
13%
717
47%
717
29%
1266
April1st to 15thNight
43%
539
24%
1797
18%
539
53%
539
31%
1022
April16th to endNight
47%
540
27%
1800
20%
540
58%
540
33%
986
May1st to 15thNight
53%
540
22%
1633
15%
540
60%
540
30%
1010
May16th to endNight
69%
561
23%
1682
19%
561
72%
561
35%
988
June1st to 15thNight
74%
540
16%
1620
14%
540
75%
540
32%
980
June16th to endNight
78%
540
19%
1620
18%
540
79%
540
36%
953
July1st to 15thNight
74%
510
13%
1530
12%
510
76%
510
29%
982
July16th to endNight
73%
564
16%
1614
16%
531
75%
531
28%
1037
August1st to 15thNight
77%
539
18%
1788
21%
536
78%
536
31%
1073
August16th to endNight
72%
573
19%
1910
23%
573
72%
573
25%
1241
September1st to 15thNight
63%
623
19%
1883
19%
623
65%
623
24%
1264
September16th to endNight
67%
693
28%
1914
23%
693
69%
693
35%
1156
October1st to 15thNight
57%
660
34%
1815
26%
660
64%
660
41%
1032
October16th to endNight
52%
704
33%
2126
28%
704
59%
704
37%
1204
November1st to 15thNight
51%
700
30%
2276
25%
700
61%
700
36%
1223
November16th to endNight
41%
720
27%
2340
18%
720
53%
720
29%
1376
December1st to 15thNight
35%
720
22%
2340
16%
720
45%
720
23%
1485
December16th to endNight
29%
768
20%
2496
14%
768
38%
768
19%
1691

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%5%25%5%35%5%5%7%40%
47871
Night
11%42443445%7%46%
47249
TransparencyDay
40%7%11%18%17%4
47574
Night
36%6%10%19%20%7%
47050
SeeingDay
15%6%19%23%22%12%
5204
Night
14%6%23%29%22%4
15296

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 15thDay
20%6%2442333443%
1611
16th to endDay
19%5%24323435%45%
1899
February1st to 15thDay
17%8%34423346%41%
1750
16th to endDay
19%5%25%424335%41%
1580
March1st to 15thDay
17%6%35%6%24346%40%
1811
16th to endDay
14%6%25%435%447%41%
2171
April1st to 15thDay
13%5%25%5%3445%6%44%
2151
16th to endDay
10%4345%35%5%5%7%45%
2160
May1st to 15thDay
12%5%245%3446%7%43%
2316
16th to endDay
9%5%26%5%346%6%9%40%
2431
June1st to 15thDay
8%426%7%37%7%7%10%32%
2340
16th to endDay
6%3246%46%5%8%11%41%
2340
July1st to 15thDay
9%426%7%5%8%7%8%10%27%
2340
16th to endDay
7%5%26%6%5%8%8%9%10%29%
2442
August1st to 15thDay
8%4247%5%7%8%9%11%30%
2160
16th to endDay
11%6%37%6%47%6%6%9%28%
2292
September1st to 15thDay
12%6%26%6%45%5%5%7%36%
2064
16th to endDay
13%5%145%2445%6%45%
1905
October1st to 15thDay
11%32443345%6%50%
1815
16th to endDay
11%42441222458%
1743
November1st to 15thDay
13%5%23223245%54%
1582
16th to endDay
15%5%23424445%48%
1620
December1st to 15thDay
18%8%25%424345%40%
1620
16th to endDay
24%9%35%433345%34%
1728
January1st to 15thNight
16%6%24423345%44%
2327
16th to endNight
17%6%25%42445%440%
2323
February1st to 15thNight
15%6%24424335%47%
2103
16th to endNight
16%4245%33335%45%
1893
March1st to 15thNight
17%5%14423448%43%
2148
16th to endNight
12%42442435%6%47%
2061
April1st to 15thNight
12%31442445%8%48%
1797
16th to endNight
9%424333446%53%
1800
May1st to 15thNight
9%3245%35%5%6%7%46%
1632
16th to endNight
5%3145%35%5%6%10%48%
1682
June1st to 15thNight
43145%46%6%8%12%42%
1620
16th to endNight
4314436%5%7%12%46%
1620
July1st to 15thNight
7%325%6%46%6%6%11%39%
1620
16th to endNight
5%425%6%35%6%8%12%39%
1723
August1st to 15thNight
5%3145%36%6%8%12%43%
1800
16th to endNight
9%5%25%436%6%5%9%40%
1910
September1st to 15thNight
10%5%25%6%45%5%6%7%41%
1883
16th to endNight
8%3245%3445%6%51%
1914
October1st to 15thNight
9%414422346%56%
1815
16th to endNight
11%415%31233457%
2126
November1st to 15thNight
11%413223246%55%
2276
16th to endNight
13%5%14433335%51%
2340
December1st to 15thNight
16%6%25%423345%42%
2340
16th to endNight
22%6%35%5%24335%37%
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
45%37%14%25%4
1612
16th to endDay
41%35%21%20%6%
1899
February1st to 15thDay
44%37%21%18%3
1752
16th to endDay
45%46%15%23%5%
1580
March1st to 15thDay
45%410%14%19%5%
1811
16th to endDay
42%5%11%20%17%2
2172
April1st to 15thDay
40%410%18%18%7%
2151
16th to endDay
36%6%9%21%22%3
2160
May1st to 15thDay
38%7%12%18%18%4
2316
16th to endDay
37%7%14%23%13%2
2435
June1st to 15thDay
41%10%16%18%12%1
2340
16th to endDay
33%9%16%22%14%3
2340
July1st to 15thDay
42%13%17%16%7%1
2201
16th to endDay
42%13%18%16%8%
2288
August1st to 15thDay
40%13%16%16%9%2
2148
16th to endDay
48%11%12%16%9%1
2292
September1st to 15thDay
44%8%12%17%12%4
2064
16th to endDay
37%6%11%20%18%5%
1905
October1st to 15thDay
32%5%9%18%23%10%
1815
16th to endDay
31%3416%33%11%
1743
November1st to 15thDay
32%35%17%29%10%
1582
16th to endDay
36%5%6%16%26%8%
1620
December1st to 15thDay
46%48%18%16%6%
1620
16th to endDay
52%37%18%12%4
1728
January1st to 15thNight
42%46%17%24%5%
2327
16th to endNight
44%46%17%19%7%
2323
February1st to 15thNight
40%36%20%20%9%
2112
16th to endNight
41%35%18%24%6%
1893
March1st to 15thNight
39%410%18%19%7%
2148
16th to endNight
36%5%9%23%21%3
2061
April1st to 15thNight
34%410%22%19%9%
1797
16th to endNight
30%5%10%22%23%7%
1800
May1st to 15thNight
34%8%11%18%23%4
1633
16th to endNight
28%8%14%27%14%5%
1684
June1st to 15thNight
29%10%18%23%16%1
1620
16th to endNight
27%10%17%23%18%2
1620
July1st to 15thNight
34%11%21%19%9%3
1530
16th to endNight
33%12%21%19%12%
1614
August1st to 15thNight
29%11%18%24%12%3
1788
16th to endNight
37%11%15%20%12%3
1910
September1st to 15thNight
40%10%13%16%13%5%
1883
16th to endNight
32%6%10%22%20%7%
1914
October1st to 15thNight
28%48%20%23%13%
1815
16th to endNight
31%3411%32%15%
2126
November1st to 15thNight
29%36%18%27%14%
2276
16th to endNight
35%46%16%25%11%
2340
December1st to 15thNight
42%48%17%20%5%
2340
16th to endNight
49%37%17%16%5%
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
21%20%33%20%32
90
16th to endDay
22%22%43%7%3
96
February1st to 15thDay
22%28%35%12%1
90
16th to endDay
35%12%35%14%1
81
March1st to 15thDay
27%21%31%13%4
101
16th to endDay
18%10%33%22%14%
288
April1st to 15thDay
20%8%28%25%16%
270
16th to endDay
12%11%22%28%22%3
270
May1st to 15thDay
14%5%26%26%17%9%
288
16th to endDay
12%421%23%23%14%
331
June1st to 15thDay
11%112%23%29%22%
315
16th to endDay
10%111%22%27%25%
315
July1st to 15thDay
6%9%23%32%26%
305
16th to endDay
10%5%17%32%33%
326
August1st to 15thDay
13%7%24%31%22%
313
16th to endDay
13%18%25%34%17%
332
September1st to 15thDay
14%210%25%28%18%
315
16th to endDay
12%213%30%29%11%
287
October1st to 15thDay
14%5%20%31%23%5%
255
16th to endDay
15%420%31%24%2
170
November1st to 15thDay
21%15%22%35%41
90
16th to endDay
16%12%41%18%10%1
90
December1st to 15thDay
22%21%34%20%2
90
16th to endDay
34%12%37%10%5%
96
January1st to 15thNight
21%13%34%23%7%
720
16th to endNight
19%14%37%24%4
768
February1st to 15thNight
20%12%34%28%4
704
16th to endNight
18%13%37%27%3
631
March1st to 15thNight
20%12%32%28%6%
720
16th to endNight
14%10%32%27%13%
717
April1st to 15thNight
12%10%30%29%15%1
539
16th to endNight
11%7%29%32%18%1
540
May1st to 15thNight
10%325%30%24%4
540
16th to endNight
8%14%36%34%5%
563
June1st to 15thNight
6%9%33%40%10%
540
16th to endNight
37%29%44%15%
540
July1st to 15thNight
6%6%26%44%15%
510
16th to endNight
6%6%23%42%19%
564
August1st to 15thNight
7%5%24%47%14%
539
16th to endNight
11%5%31%39%11%
573
September1st to 15thNight
13%19%26%39%9%
623
16th to endNight
9%112%36%35%4
693
October1st to 15thNight
12%321%33%24%4
660
16th to endNight
12%6%22%30%23%3
704
November1st to 15thNight
14%6%24%32%19%3
700
16th to endNight
14%11%29%30%12%
720
December1st to 15thNight
20%10%28%29%9%1
720
16th to endNight
24%12%30%24%7%
768
Page generated at 2017-09-25 08:02:16. Version ac04

Copyright 2017 A. Danko


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