Charleston Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Charleston Lake clear sky chart from 2005-11-05 to 2017-09-17.

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
29%
14718
13%
46855
8%
14687
35%
14687
16%
33542

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
13%
720
6%
2506
2%
716
18%
716
6%
2055
January16th to endNight
18%
768
10%
2613
5%
768
25%
768
10%
1997
February1st to 15thNight
14%
704
9%
2287
3%
701
21%
701
9%
1822
February16th to endNight
19%
631
13%
1946
6%
631
28%
631
12%
1478
March1st to 15thNight
20%
720
14%
2088
6%
720
29%
720
15%
1558
March16th to endNight
29%
768
19%
2041
8%
768
37%
768
21%
1429
April1st to 15thNight
21%
718
16%
1796
4%
718
27%
718
21%
1314
April16th to endNight
28%
675
17%
1755
7%
675
34%
675
24%
1219
May1st to 15thNight
35%
360
17%
1440
15%
360
44%
360
17%
934
May16th to endNight
34%
374
14%
1496
11%
374
45%
374
19%
921
June1st to 15thNight
36%
360
10%
1440
9%
360
45%
360
16%
957
June16th to endNight
45%
360
10%
1440
12%
360
51%
360
20%
907
July1st to 15thNight
48%
340
15%
1360
20%
340
55%
340
26%
756
July16th to endNight
51%
376
14%
1418
16%
354
56%
354
26%
804
August1st to 15thNight
49%
473
13%
1544
10%
471
53%
471
25%
973
August16th to endNight
52%
714
22%
1860
11%
714
57%
714
38%
1137
September1st to 15thNight
48%
720
17%
1800
9%
720
50%
720
32%
1197
September16th to endNight
45%
665
22%
1815
14%
665
50%
665
30%
1173
October1st to 15thNight
33%
660
16%
1980
12%
660
41%
660
18%
1404
October16th to endNight
22%
704
9%
2183
4%
704
28%
704
11%
1688
November1st to 15thNight
27%
700
17%
2319
12%
700
35%
700
16%
1611
November16th to endNight
20%
720
12%
2520
6%
720
28%
720
10%
1940
December1st to 15thNight
13%
720
6%
2520
2%
720
18%
720
7%
2035
December16th to endNight
12%
768
7%
2688
3%
768
17%
768
7%
2233

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
17%8%36%5%3445%6%33%
47928
Night
18%9%46%5%34446%32%
47025
Cloud CoverDay
18%8%36%5%34446%33%
47937
Night
18%9%36%5%34446%32%
47031
TransparencyDay
51%5%11%19%10%1
47615
Night
52%6%11%18%9%1
46856
SeeingDay
22%12%29%20%11%3
5499
Night
23%12%29%24%9%
14719

By Month

Percentage Cloud Cover NE (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
22%13%47%7%35%33423%
1432
16th to endDay
15%14%6%9%8%346%4422%
1611
February1st to 15thDay
14%14%6%11%7%45%45%420%
1575
16th to endDay
19%14%5%8%8%3423424%
1527
March1st to 15thDay
18%11%5%8%9%4434425%
1861
16th to endDay
19%8%35%5%3323440%
2182
April1st to 15thDay
23%11%45%42433433%
2152
16th to endDay
19%8%36%434445%36%
2213
May1st to 15thDay
19%8%35%5%2445%7%32%
2511
16th to endDay
16%6%25%43445%7%37%
2618
June1st to 15thDay
22%6%3443445%7%32%
2520
16th to endDay
16%6%25%435%5%6%8%34%
2520
July1st to 15thDay
12%5%25%5%245%6%8%40%
2520
16th to endDay
11%5%245%346%6%10%38%
2654
August1st to 15thDay
11%6%26%6%35%5%5%7%37%
2403
16th to endDay
11%415%5%3445%10%42%
2329
September1st to 15thDay
16%5%2442345%7%42%
2160
16th to endDay
15%6%34324346%44%
1848
October1st to 15thDay
22%7%25%423447%35%
1650
16th to endDay
27%10%36%6%3434424%
1689
November1st to 15thDay
13%8%37%7%435%5%7%32%
1537
16th to endDay
22%13%37%5%2345%5%25%
1440
December1st to 15thDay
23%16%6%8%5%24345%19%
1440
16th to endDay
24%15%6%8%6%3433419%
1536
January1st to 15thNight
20%15%6%9%6%4435%418%
2506
16th to endNight
15%15%6%9%5%345%45%24%
2613
February1st to 15thNight
16%14%6%10%8%36%44421%
2285
16th to endNight
18%12%5%8%7%34345%26%
1946
March1st to 15thNight
19%12%46%5%2333431%
2075
16th to endNight
18%9%46%423325%40%
2041
April1st to 15thNight
24%7%45%314346%34%
1796
16th to endNight
18%6%35%5%23347%38%
1755
May1st to 15thNight
21%6%25%433447%36%
1440
16th to endNight
13%5%26%5%3445%7%40%
1495
June1st to 15thNight
20%6%25%5%3446%8%33%
1440
16th to endNight
15%5%145%36%5%5%9%37%
1440
July1st to 15thNight
10%4235%246%5%8%45%
1440
16th to endNight
8%325%42447%9%45%
1514
August1st to 15thNight
10%5%35%435%5%6%9%40%
1554
16th to endNight
9%42442345%8%49%
1860
September1st to 15thNight
14%5%25%5%3345%7%45%
1800
16th to endNight
15%434423346%46%
1815
October1st to 15thNight
21%6%25%4245%5%6%34%
1980
16th to endNight
26%8%48%6%34435%26%
2183
November1st to 15thNight
18%9%35%5%25%45%6%33%
2319
16th to endNight
22%11%47%6%35%435%25%
2520
December1st to 15thNight
22%14%5%9%7%3334421%
2520
16th to endNight
26%14%6%9%5%35%33418%
2688

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
22%14%47%7%35%34323%
1432
16th to endDay
15%14%6%9%8%345%3422%
1611
February1st to 15thDay
15%14%5%11%7%45%45%420%
1575
16th to endDay
19%14%5%9%6%3323425%
1527
March1st to 15thDay
19%12%5%9%7%4433425%
1871
16th to endDay
19%8%35%5%3323440%
2181
April1st to 15thDay
23%10%45%333335%33%
2152
16th to endDay
20%7%36%424445%37%
2213
May1st to 15thDay
19%7%25%5%3445%6%33%
2511
16th to endDay
17%6%25%4345%48%37%
2618
June1st to 15thDay
23%6%34425%448%32%
2520
16th to endDay
17%6%244345%6%7%36%
2520
July1st to 15thDay
13%5%244245%6%8%40%
2520
16th to endDay
12%5%245%35%6%6%9%39%
2654
August1st to 15thDay
11%5%35%5%35%5%6%7%39%
2403
16th to endDay
12%415%5%3446%9%43%
2329
September1st to 15thDay
16%6%2443335%7%42%
2160
16th to endDay
16%6%24424346%44%
1848
October1st to 15thDay
23%6%24423346%36%
1650
16th to endDay
28%9%36%6%35%34425%
1689
November1st to 15thDay
14%8%27%6%45%6%5%6%33%
1537
16th to endDay
22%13%37%4335%45%25%
1440
December1st to 15thDay
24%15%5%8%5%3334420%
1440
16th to endDay
25%16%5%6%6%35%43419%
1536
January1st to 15thNight
21%16%5%9%7%3434419%
2506
16th to endNight
16%15%6%9%6%34445%24%
2613
February1st to 15thNight
16%14%6%11%7%35%34421%
2278
16th to endNight
18%11%5%8%6%34445%27%
1946
March1st to 15thNight
20%12%46%5%2333431%
2088
16th to endNight
18%8%46%42323440%
2041
April1st to 15thNight
24%8%25%323345%35%
1796
16th to endNight
18%6%345%33347%38%
1755
May1st to 15thNight
21%6%25%423447%36%
1440
16th to endNight
13%5%26%5%35%45%7%40%
1495
June1st to 15thNight
19%6%26%5%3346%8%33%
1440
16th to endNight
15%424435%5%6%8%37%
1440
July1st to 15thNight
10%423435%5%6%8%45%
1440
16th to endNight
9%414425%47%9%46%
1514
August1st to 15thNight
10%6%24435%5%7%9%40%
1554
16th to endNight
10%42432345%8%50%
1860
September1st to 15thNight
14%5%245%2335%7%45%
1800
16th to endNight
15%42442335%6%46%
1815
October1st to 15thNight
22%5%25%42445%6%34%
1980
16th to endNight
27%8%37%6%33435%26%
2183
November1st to 15thNight
19%8%26%5%2445%6%33%
2319
16th to endNight
22%11%36%5%35%445%26%
2520
December1st to 15thNight
23%14%5%9%6%33335%21%
2520
16th to endNight
26%14%5%8%6%3434418%
2688

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
64%49%14%6%1
1433
16th to endDay
64%6%10%10%8%
1611
February1st to 15thDay
66%48%15%4
1577
16th to endDay
64%48%11%9%1
1527
March1st to 15thDay
63%310%13%6%1
1871
16th to endDay
48%48%18%15%4
2182
April1st to 15thDay
55%37%18%13%2
2152
16th to endDay
49%48%19%14%3
2213
May1st to 15thDay
50%5%9%18%14%1
2511
16th to endDay
45%6%13%22%11%1
2622
June1st to 15thDay
50%5%11%21%9%
2520
16th to endDay
45%7%13%21%11%
2520
July1st to 15thDay
37%7%13%27%12%
2371
16th to endDay
40%8%18%23%9%
2487
August1st to 15thDay
42%8%16%21%10%
2389
16th to endDay
36%6%15%28%12%
2329
September1st to 15thDay
41%5%13%26%12%
2160
16th to endDay
41%5%9%30%12%
1848
October1st to 15thDay
49%413%20%10%
1650
16th to endDay
63%5%10%15%5%
1689
November1st to 15thDay
49%8%13%18%8%
1537
16th to endDay
59%7%11%13%7%
1440
December1st to 15thDay
68%6%11%11%2
1440
16th to endDay
70%5%9%9%4
1536
January1st to 15thNight
67%7%9%10%4
2506
16th to endNight
60%6%10%15%6%
2613
February1st to 15thNight
65%5%10%13%4
2287
16th to endNight
59%5%10%16%8%
1946
March1st to 15thNight
56%410%19%7%
2088
16th to endNight
48%38%19%16%3
2041
April1st to 15thNight
50%48%19%15%1
1796
16th to endNight
46%410%19%16%3
1755
May1st to 15thNight
46%5%9%18%13%4
1440
16th to endNight
41%6%14%19%14%2
1497
June1st to 15thNight
48%6%13%20%10%
1440
16th to endNight
42%7%13%21%14%
1440
July1st to 15thNight
33%7%12%30%15%1
1360
16th to endNight
33%8%17%26%13%1
1418
August1st to 15thNight
37%8%17%21%13%
1544
16th to endNight
31%5%15%32%14%
1860
September1st to 15thNight
38%6%12%29%12%1
1800
16th to endNight
38%5%10%31%12%
1815
October1st to 15thNight
49%6%11%20%11%
1980
16th to endNight
60%6%12%14%6%
2183
November1st to 15thNight
49%6%14%17%10%1
2319
16th to endNight
60%6%9%16%5%
2520
December1st to 15thNight
66%6%11%12%3
2520
16th to endNight
69%6%9%9%3
2688

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%26%30%10%11%
60
16th to endDay
35%14%32%14%3
77
February1st to 15thDay
32%27%32%7%
90
16th to endDay
32%16%33%13%4
186
March1st to 15thDay
25%18%27%23%5%
270
16th to endDay
25%17%30%15%9%2
288
April1st to 15thDay
31%17%27%13%9%
270
16th to endDay
23%15%31%14%9%4
270
May1st to 15thDay
25%11%30%22%9%2
288
16th to endDay
19%15%32%17%12%3
331
June1st to 15thDay
25%10%32%21%8%2
315
16th to endDay
21%10%29%23%13%2
315
July1st to 15thDay
15%7%27%28%16%4
305
16th to endDay
13%7%29%30%15%4
326
August1st to 15thDay
12%429%30%16%6%
313
16th to endDay
11%6%30%24%16%11%
332
September1st to 15thDay
16%7%27%20%14%12%
315
16th to endDay
21%9%26%16%19%7%
259
October1st to 15thDay
24%11%25%20%13%3
255
16th to endDay
34%16%26%18%2
259
November1st to 15thDay
18%14%35%21%8%1
191
16th to endDay
31%10%23%23%11%
60
December1st to 15thDay
23%28%30%6%11%
60
16th to endDay
46%28%20%4
64
January1st to 15thNight
30%17%30%17%4
720
16th to endNight
22%16%34%21%5%
768
February1st to 15thNight
24%19%35%18%3
704
16th to endNight
24%13%34%21%6%
631
March1st to 15thNight
28%15%32%20%3
720
16th to endNight
22%13%30%23%9%
768
April1st to 15thNight
26%14%33%20%4
718
16th to endNight
23%13%30%21%10%
675
May1st to 15thNight
23%6%29%31%8%1
360
16th to endNight
14%7%37%28%11%
375
June1st to 15thNight
21%8%26%31%10%1
360
16th to endNight
15%5%27%35%15%
360
July1st to 15thNight
11%229%39%17%
340
16th to endNight
8%328%40%17%1
376
August1st to 15thNight
12%5%23%35%21%2
473
16th to endNight
11%5%24%34%21%2
714
September1st to 15thNight
17%424%30%20%2
720
16th to endNight
17%8%24%26%20%3
665
October1st to 15thNight
24%10%27%22%14%
660
16th to endNight
31%14%26%23%5%
704
November1st to 15thNight
24%12%31%22%9%
700
16th to endNight
31%16%26%17%8%
720
December1st to 15thNight
32%20%28%14%3
720
16th to endNight
34%14%31%16%2
768
Page generated at 2017-09-18 08:38:27. Version ac04

Copyright 2017 A. Danko


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