Central-Clemson
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Central-Clemson clear sky chart from 2005-11-05 to 2017-12-20.

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%
15991
22%
48075
16%
15950
57%
15950
28%
30298

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%
720
24%
2327
12%
716
48%
716
26%
1424
January16th to endNight
29%
768
25%
2496
14%
768
44%
768
24%
1541
February1st to 15thNight
36%
701
26%
2148
12%
700
50%
700
29%
1282
February16th to endNight
31%
631
25%
1893
12%
631
45%
631
29%
1156
March1st to 15thNight
38%
720
24%
2016
14%
720
47%
720
31%
1260
March16th to endNight
42%
768
20%
2112
12%
768
47%
768
28%
1369
April1st to 15thNight
46%
713
24%
1971
15%
713
54%
713
34%
1187
April16th to endNight
50%
540
25%
1638
17%
540
56%
540
30%
1016
May1st to 15thNight
52%
540
18%
1620
10%
540
57%
540
26%
1045
May16th to endNight
61%
561
18%
1683
13%
561
63%
561
28%
1083
June1st to 15thNight
66%
540
14%
1620
12%
540
68%
540
26%
1085
June16th to endNight
74%
540
14%
1620
13%
540
75%
540
29%
1041
July1st to 15thNight
67%
510
9%
1530
8%
510
68%
510
21%
1094
July16th to endNight
73%
564
14%
1595
12%
531
74%
531
25%
1074
August1st to 15thNight
67%
539
13%
1609
11%
536
68%
536
23%
1122
August16th to endNight
65%
603
16%
1861
16%
603
66%
603
21%
1282
September1st to 15thNight
63%
720
16%
1980
14%
720
64%
720
26%
1334
September16th to endNight
55%
717
21%
1980
17%
717
58%
717
27%
1323
October1st to 15thNight
53%
720
30%
2045
25%
720
59%
720
34%
1235
October16th to endNight
57%
768
34%
2304
28%
768
68%
768
40%
1259
November1st to 15thNight
53%
760
29%
2398
25%
760
61%
760
36%
1346
November16th to endNight
48%
780
28%
2535
22%
780
58%
780
31%
1449
December1st to 15thNight
42%
780
24%
2535
16%
780
53%
780
25%
1585
December16th to endNight
35%
788
22%
2559
15%
788
45%
788
21%
1706

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%42443445%8%43%
48766
Night
14%42442445%7%45%
48273
TransparencyDay
37%7%12%20%17%4
48467
Night
37%6%11%18%19%6%
48076
SeeingDay
16%418%24%21%14%
5807
Night
15%421%31%22%4
15996

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
18%5%13433335%46%
1611
16th to endDay
17%423322346%48%
1728
February1st to 15thDay
15%41342345%6%47%
1714
16th to endDay
17%424423336%47%
1580
March1st to 15thDay
17%323423436%48%
1944
16th to endDay
17%324325%45%7%43%
2111
April1st to 15thDay
13%313325%45%7%48%
1987
16th to endDay
11%3244245%47%49%
2322
May1st to 15thDay
11%424425%45%8%44%
2331
16th to endDay
10%4145%35%6%6%10%42%
2431
June1st to 15thDay
8%4246%46%6%8%12%34%
2340
16th to endDay
5%3245%46%6%8%11%41%
2340
July1st to 15thDay
9%5%35%6%5%7%7%7%10%32%
2340
16th to endDay
6%425%6%5%7%7%8%11%34%
2465
August1st to 15thDay
11%426%6%36%7%8%10%32%
2340
16th to endDay
12%5%35%5%36%6%7%10%33%
2327
September1st to 15thDay
10%4246%45%6%6%9%39%
1980
16th to endDay
15%5%2442345%8%44%
1980
October1st to 15thDay
13%5%13312335%57%
1914
16th to endDay
12%41321213462%
1920
November1st to 15thDay
13%42222325%6%54%
1787
16th to endDay
17%32431225%5%50%
1755
December1st to 15thDay
20%5%25%31335%5%43%
1755
16th to endDay
24%6%1342333441%
1764
January1st to 15thNight
18%32442334448%
2327
16th to endNight
18%424422445%46%
2496
February1st to 15thNight
15%323424335%51%
2139
16th to endNight
15%324334445%48%
1893
March1st to 15thNight
15%42332445%6%47%
2016
16th to endNight
15%42343435%6%46%
2112
April1st to 15thNight
13%314324346%52%
1971
16th to endNight
12%415%424446%48%
1638
May1st to 15thNight
12%5%25%43445%8%42%
1619
16th to endNight
10%315%5%45%5%6%8%42%
1682
June1st to 15thNight
9%425%6%36%5%8%11%36%
1620
16th to endNight
6%325%426%8%7%10%41%
1620
July1st to 15thNight
9%5%35%6%5%6%6%9%10%30%
1620
16th to endNight
7%3346%36%7%11%11%33%
1703
August1st to 15thNight
11%425%6%46%7%8%11%32%
1620
16th to endNight
11%6%35%436%6%7%10%33%
1861
September1st to 15thNight
12%425%6%35%5%6%9%37%
1980
16th to endNight
16%425%5%34447%41%
1980
October1st to 15thNight
13%42341334453%
2045
16th to endNight
10%31322334459%
2304
November1st to 15thNight
13%414312235%56%
2398
16th to endNight
17%312323345%52%
2535
December1st to 15thNight
18%5%24424345%45%
2535
16th to endNight
22%5%24424345%39%
2559

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
41%48%17%23%5%
1612
16th to endDay
37%37%21%20%8%
1728
February1st to 15thDay
36%49%21%23%5%
1716
16th to endDay
39%38%22%19%6%
1580
March1st to 15thDay
37%47%21%20%7%
1944
16th to endDay
39%6%11%21%17%3
2112
April1st to 15thDay
33%5%11%21%21%5%
1987
16th to endDay
33%5%10%22%20%6%
2322
May1st to 15thDay
37%7%13%19%18%3
2331
16th to endDay
35%10%16%22%14%1
2435
June1st to 15thDay
37%12%19%21%7%1
2340
16th to endDay
32%11%17%22%12%3
2340
July1st to 15thDay
40%13%16%18%8%2
2201
16th to endDay
37%13%20%18%8%2
2310
August1st to 15thDay
42%11%16%18%10%
2327
16th to endDay
43%10%17%17%8%1
2327
September1st to 15thDay
37%10%14%17%16%2
1980
16th to endDay
38%6%12%19%18%4
1980
October1st to 15thDay
30%410%20%27%6%
1914
16th to endDay
28%25%21%30%11%
1920
November1st to 15thDay
31%38%17%28%9%
1787
16th to endDay
36%27%20%25%7%
1755
December1st to 15thDay
43%47%19%18%7%
1755
16th to endDay
47%38%18%16%6%
1764
January1st to 15thNight
39%48%16%24%7%
2327
16th to endNight
40%45%18%23%8%
2496
February1st to 15thNight
36%37%20%23%7%
2148
16th to endNight
37%48%20%23%6%
1893
March1st to 15thNight
36%49%17%22%8%
2016
16th to endNight
39%5%10%19%20%5%
2112
April1st to 15thNight
33%38%23%23%6%
1971
16th to endNight
36%6%8%20%20%7%
1638
May1st to 15thNight
38%8%12%20%17%2
1620
16th to endNight
37%8%13%26%11%2
1684
June1st to 15thNight
37%11%17%23%8%1
1620
16th to endNight
33%12%18%19%13%3
1620
July1st to 15thNight
43%12%19%15%7%1
1530
16th to endNight
34%15%21%18%7%2
1595
August1st to 15thNight
41%12%17%16%10%
1609
16th to endNight
42%12%17%16%9%1
1861
September1st to 15thNight
40%9%17%17%12%3
1980
16th to endNight
41%6%12%17%15%5%
1980
October1st to 15thNight
33%5%9%19%25%6%
2045
16th to endNight
27%46%19%28%13%
2304
November1st to 15thNight
32%26%18%28%10%
2398
16th to endNight
33%47%17%27%10%
2535
December1st to 15thNight
41%38%19%19%7%
2535
16th to endNight
46%5%8%14%18%6%
2559

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%7%33%30%5%
90
16th to endDay
12%26%41%16%3
96
February1st to 15thDay
14%14%55%14%1
90
16th to endDay
19%16%35%24%3
81
March1st to 15thDay
16%10%32%30%9%
234
16th to endDay
20%6%28%27%15%1
288
April1st to 15thDay
15%8%22%25%22%4
270
16th to endDay
15%221%30%19%10%
270
May1st to 15thDay
13%427%22%18%12%
288
16th to endDay
16%314%22%22%20%
331
June1st to 15thDay
11%39%24%25%25%
315
16th to endDay
11%12%25%22%29%
315
July1st to 15thDay
11%10%23%27%25%
305
16th to endDay
7%6%18%35%31%
326
August1st to 15thDay
18%17%20%26%25%
313
16th to endDay
15%8%22%25%27%
332
September1st to 15thDay
15%111%19%30%21%
315
16th to endDay
20%111%23%26%15%
314
October1st to 15thDay
21%316%28%22%7%
315
16th to endDay
14%5%18%28%27%5%
336
November1st to 15thDay
21%5%19%30%18%4
205
16th to endDay
12%223%34%21%5%
135
December1st to 15thDay
28%8%23%31%6%
135
16th to endDay
33%11%36%13%4
108
January1st to 15thNight
21%8%32%31%7%
720
16th to endNight
20%8%35%31%2
768
February1st to 15thNight
17%8%32%38%3
704
16th to endNight
16%8%39%30%4
631
March1st to 15thNight
17%8%33%32%8%
720
16th to endNight
16%6%29%34%13%
768
April1st to 15thNight
14%9%26%33%15%
713
16th to endNight
14%324%35%20%1
540
May1st to 15thNight
14%321%36%21%2
540
16th to endNight
11%115%29%36%5%
563
June1st to 15thNight
11%9%30%36%11%
540
16th to endNight
8%19%29%40%12%
540
July1st to 15thNight
12%6%29%41%9%
510
16th to endNight
8%6%23%45%14%
564
August1st to 15thNight
13%7%26%41%10%
539
16th to endNight
14%15%26%41%9%
603
September1st to 15thNight
13%10%26%38%10%
720
16th to endNight
18%113%30%31%4
717
October1st to 15thNight
14%5%20%26%27%5%
720
16th to endNight
13%321%33%24%3
768
November1st to 15thNight
14%322%36%19%4
760
16th to endNight
17%5%24%33%17%1
780
December1st to 15thNight
20%5%24%34%13%1
780
16th to endNight
25%429%32%8%
788
Page generated at 2017-12-21 07:04:48. Version ac04

Copyright 2017 A. Danko


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