This page made possible by the sponsorship of:

Charlotte Amateur Astronomers Club
.

Charlotte
Clear Sky Chart
History

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

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%
15425
22%
45831
16%
15387
58%
15387
29%
28608

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
34%
718
23%
2327
12%
716
48%
716
25%
1427
January16th to endNight
32%
768
25%
2496
13%
768
48%
768
26%
1513
February1st to 15thNight
32%
701
23%
2251
12%
701
46%
701
28%
1349
February16th to endNight
28%
631
28%
1857
13%
631
44%
631
31%
1129
March1st to 15thNight
38%
720
27%
1980
15%
720
48%
720
33%
1210
March16th to endNight
40%
768
21%
2112
12%
768
47%
768
28%
1375
April1st to 15thNight
44%
718
23%
1913
12%
718
52%
718
35%
1188
April16th to endNight
49%
645
23%
1725
14%
645
54%
645
35%
1072
May1st to 15thNight
50%
540
17%
1620
9%
540
56%
540
28%
1032
May16th to endNight
64%
540
17%
1621
14%
540
66%
540
29%
1022
June1st to 15thNight
66%
495
16%
1485
13%
495
68%
495
26%
982
June16th to endNight
72%
495
16%
1485
13%
495
73%
495
28%
961
July1st to 15thNight
71%
465
12%
1395
9%
465
71%
465
25%
943
July16th to endNight
72%
522
13%
1469
11%
489
73%
489
27%
952
August1st to 15thNight
70%
494
16%
1474
15%
491
70%
491
27%
969
August16th to endNight
68%
616
16%
1666
13%
616
68%
616
26%
1154
September1st to 15thNight
72%
660
21%
1789
19%
660
72%
660
32%
1148
September16th to endNight
52%
657
17%
1815
14%
657
54%
657
23%
1288
October1st to 15thNight
57%
660
30%
1941
28%
660
62%
660
34%
1151
October16th to endNight
54%
704
33%
2112
26%
704
66%
704
38%
1174
November1st to 15thNight
52%
700
30%
2122
23%
700
61%
700
38%
1183
November16th to endNight
47%
720
27%
2340
21%
720
58%
720
31%
1344
December1st to 15thNight
44%
720
23%
2340
17%
720
53%
720
25%
1440
December16th to endNight
38%
768
24%
2496
18%
768
48%
768
23%
1602

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
12%5%2442445%7%44%
46435
Night
13%5%2442445%7%44%
46029
TransparencyDay
37%6%12%21%18%4
46136
Night
37%5%11%20%19%6%
45832
SeeingDay
15%417%23%23%15%
5178
Night
15%421%32%22%3
15432

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
17%6%24423445%43%
1611
16th to endDay
16%5%1332345%449%
1728
February1st to 15thDay
15%5%22324446%46%
1607
16th to endDay
15%5%14323346%48%
1614
March1st to 15thDay
14%5%2331435%6%49%
1980
16th to endDay
17%423324447%44%
2111
April1st to 15thDay
11%41332445%8%51%
2033
16th to endDay
14%423424445%47%
2244
May1st to 15thDay
11%435%5%35%46%8%41%
2331
16th to endDay
10%5%145%35%45%7%45%
2337
June1st to 15thDay
9%425%5%25%6%7%10%41%
2145
16th to endDay
4324435%6%6%11%45%
2145
July1st to 15thDay
10%6%35%6%35%7%7%10%34%
2145
16th to endDay
7%3245%47%7%8%12%35%
2283
August1st to 15thDay
12%5%24437%6%9%10%34%
2145
16th to endDay
11%5%26%6%45%6%7%11%31%
2173
September1st to 15thDay
9%414435%5%6%10%44%
1838
16th to endDay
18%6%245%24446%39%
1815
October1st to 15thDay
15%41322233456%
1689
16th to endDay
12%41431233358%
1760
November1st to 15thDay
13%413312336%57%
1733
16th to endDay
15%423423335%50%
1620
December1st to 15thDay
16%7%1432345%7%43%
1620
16th to endDay
19%8%23424445%41%
1728
January1st to 15thNight
16%5%24324335%48%
2327
16th to endNight
16%5%24323445%47%
2496
February1st to 15thNight
15%5%25%423345%48%
2243
16th to endNight
14%42342345%6%47%
1857
March1st to 15thNight
14%42432345%7%49%
1980
16th to endNight
16%425%33445%6%43%
2112
April1st to 15thNight
11%5%13425%347%50%
1913
16th to endNight
13%424425%45%6%48%
1725
May1st to 15thNight
10%5%36%5%345%5%8%41%
1619
16th to endNight
10%425%5%35%5%5%9%42%
1619
June1st to 15thNight
10%325%6%37%5%8%11%35%
1485
16th to endNight
4325%6%5%7%7%8%11%38%
1485
July1st to 15thNight
8%5%35%5%46%7%10%11%32%
1485
16th to endNight
5%435%6%37%6%9%11%35%
1577
August1st to 15thNight
8%5%25%6%45%6%7%11%35%
1485
16th to endNight
8%5%37%5%45%6%8%9%34%
1666
September1st to 15thNight
8%4245%26%6%6%10%41%
1789
16th to endNight
20%5%25%5%2435%6%36%
1815
October1st to 15thNight
15%5%23223335%52%
1941
16th to endNight
12%41231333457%
2112
November1st to 15thNight
12%413213346%55%
2122
16th to endNight
13%414424346%50%
2340
December1st to 15thNight
16%6%24424445%45%
2340
16th to endNight
20%6%24324346%40%
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
43%47%20%20%4
1612
16th to endDay
37%37%22%21%8%
1728
February1st to 15thDay
38%29%21%22%5%
1609
16th to endDay
37%37%25%19%5%
1614
March1st to 15thDay
35%5%7%23%22%6%
1980
16th to endDay
39%5%11%22%18%3
2112
April1st to 15thDay
30%410%26%22%5%
2033
16th to endDay
37%49%20%20%7%
2244
May1st to 15thDay
38%6%14%22%16%1
2331
16th to endDay
37%6%14%24%14%2
2341
June1st to 15thDay
35%8%16%25%11%
2145
16th to endDay
30%8%19%24%15%2
2145
July1st to 15thDay
40%10%16%18%10%3
2006
16th to endDay
35%11%20%21%10%
2128
August1st to 15thDay
40%9%16%20%11%1
2132
16th to endDay
43%9%16%18%10%1
2173
September1st to 15thDay
33%9%15%20%17%3
1838
16th to endDay
45%6%8%18%17%4
1815
October1st to 15thDay
33%38%24%25%5%
1689
16th to endDay
30%25%21%29%8%
1760
November1st to 15thDay
30%37%19%30%8%
1733
16th to endDay
36%37%20%25%6%
1620
December1st to 15thDay
40%310%22%18%5%
1620
16th to endDay
44%410%18%17%5%
1728
January1st to 15thNight
39%48%16%24%7%
2327
16th to endNight
39%35%20%23%7%
2496
February1st to 15thNight
38%27%20%23%6%
2252
16th to endNight
37%29%23%22%4
1857
March1st to 15thNight
34%49%20%22%7%
1980
16th to endNight
40%410%20%18%5%
2112
April1st to 15thNight
34%48%22%23%6%
1913
16th to endNight
35%411%19%20%9%
1725
May1st to 15thNight
38%6%14%21%16%3
1620
16th to endNight
37%6%15%25%13%1
1621
June1st to 15thNight
40%8%17%24%8%1
1485
16th to endNight
34%11%15%22%11%4
1485
July1st to 15thNight
38%11%16%19%9%3
1395
16th to endNight
36%10%21%19%9%2
1469
August1st to 15thNight
37%9%19%19%11%1
1474
16th to endNight
39%10%17%20%9%1
1666
September1st to 15thNight
34%8%16%19%15%5%
1789
16th to endNight
46%7%10%13%17%4
1815
October1st to 15thNight
34%49%21%25%5%
1941
16th to endNight
30%26%20%26%12%
2112
November1st to 15thNight
31%27%16%27%14%
2122
16th to endNight
34%36%19%26%8%
2340
December1st to 15thNight
40%48%18%20%7%
2340
16th to endNight
44%39%17%18%6%
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
23%11%24%33%7%
90
16th to endDay
19%19%39%13%6%1
96
February1st to 15thDay
17%11%56%13%1
90
16th to endDay
17%9%38%24%9%
115
March1st to 15thDay
13%8%34%30%12%
270
16th to endDay
19%5%30%30%12%1
288
April1st to 15thDay
15%8%24%27%19%5%
270
16th to endDay
18%318%28%21%9%
270
May1st to 15thDay
16%325%26%19%8%
288
16th to endDay
15%19%18%29%26%
302
June1st to 15thDay
13%27%24%28%23%
255
16th to endDay
7%10%20%34%27%
255
July1st to 15thDay
11%19%18%33%26%
245
16th to endDay
8%15%14%35%34%
270
August1st to 15thDay
16%1415%30%31%
253
16th to endDay
14%6%19%27%32%
268
September1st to 15thDay
14%1318%34%27%
255
16th to endDay
24%312%21%24%13%
254
October1st to 15thDay
20%215%29%23%9%
255
16th to endDay
12%416%30%23%12%
272
November1st to 15thDay
19%317%29%21%7%
241
16th to endDay
10%7%18%34%24%4
90
December1st to 15thDay
21%5%34%24%13%1
90
16th to endDay
23%9%36%18%11%
96
January1st to 15thNight
19%7%32%32%8%
720
16th to endNight
19%7%36%33%3
768
February1st to 15thNight
18%7%37%34%2
704
16th to endNight
16%8%41%29%4
631
March1st to 15thNight
15%8%32%35%7%
720
16th to endNight
18%6%27%35%11%
768
April1st to 15thNight
15%7%29%31%14%
718
16th to endNight
17%424%32%21%
645
May1st to 15thNight
12%423%40%18%1
540
16th to endNight
11%111%32%38%3
542
June1st to 15thNight
13%18%34%33%7%
495
16th to endNight
6%8%28%47%8%
495
July1st to 15thNight
11%1431%42%8%
465
16th to endNight
7%1425%49%11%
522
August1st to 15thNight
11%425%50%7%
494
16th to endNight
10%5%26%49%8%
616
September1st to 15thNight
11%1428%46%8%
660
16th to endNight
24%11%28%30%3
657
October1st to 15thNight
17%217%31%26%5%
660
16th to endNight
13%421%33%23%3
704
November1st to 15thNight
14%325%34%19%3
700
16th to endNight
15%5%27%33%17%1
720
December1st to 15thNight
18%5%24%38%11%
720
16th to endNight
23%5%25%36%8%
768
Page generated at 2017-05-25 13:27:38. Version ac04

Copyright 2017 A. Danko


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