Mount Pleasant
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Pleasant clear sky chart from 2005-11-05 to 2018-08-29.

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
37%
16392
21%
50627
11%
16352
48%
16352
24%
31995

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
21%
778
21%
2648
8%
776
38%
776
18%
1648
January16th to endNight
18%
832
23%
2704
7%
832
39%
832
21%
1688
February1st to 15thNight
19%
763
18%
2482
5%
761
36%
761
19%
1564
February16th to endNight
16%
683
23%
2067
5%
683
38%
683
20%
1324
March1st to 15thNight
24%
780
22%
2187
8%
780
38%
780
23%
1421
March16th to endNight
21%
832
21%
2252
7%
832
33%
832
24%
1511
April1st to 15thNight
24%
778
19%
1946
5%
778
33%
778
27%
1302
April16th to endNight
36%
771
18%
1927
6%
771
42%
771
29%
1296
May1st to 15thNight
38%
588
18%
1758
10%
588
45%
588
23%
1184
May16th to endNight
51%
406
16%
1625
14%
406
57%
406
20%
1006
June1st to 15thNight
51%
390
19%
1560
19%
390
59%
390
24%
909
June16th to endNight
60%
390
17%
1560
19%
390
65%
390
25%
900
July1st to 15thNight
59%
370
13%
1480
15%
370
61%
370
19%
939
July16th to endNight
70%
562
16%
1689
14%
529
74%
529
34%
970
August1st to 15thNight
63%
575
17%
1715
13%
572
64%
572
29%
1103
August16th to endNight
64%
817
19%
2047
12%
817
65%
817
34%
1334
September1st to 15thNight
54%
720
25%
1800
14%
720
59%
720
34%
1176
September16th to endNight
56%
717
25%
1969
20%
717
59%
717
31%
1280
October1st to 15thNight
45%
720
23%
2160
20%
720
53%
720
26%
1392
October16th to endNight
36%
768
29%
2304
17%
768
52%
768
32%
1347
November1st to 15thNight
37%
760
24%
2433
14%
760
50%
760
26%
1483
November16th to endNight
31%
780
23%
2672
12%
780
45%
780
21%
1612
December1st to 15thNight
25%
780
17%
2730
7%
780
38%
780
16%
1764
December16th to endNight
21%
832
21%
2912
7%
832
39%
832
19%
1842

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%5%25%5%3445%7%41%
51617
Night
14%5%2442445%7%43%
50809
Cloud CoverDay
14%5%245%3445%7%41%
51627
Night
14%5%2442445%7%43%
50813
TransparencyDay
40%6%11%22%16%2
51317
Night
39%6%11%22%17%3
50627
SeeingDay
18%9%25%24%16%6%
6881
Night
17%9%29%28%12%1
16396

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
15%6%25%425%5%5%5%40%
1619
16th to endDay
13%7%345%24445%42%
1872
February1st to 15thDay
14%7%346%3445%6%38%
1710
16th to endDay
16%7%25%6%33335%40%
1691
March1st to 15thDay
14%7%345%23436%43%
2088
16th to endDay
16%6%25%5%24346%40%
2324
April1st to 15thDay
14%6%25%5%2435%7%41%
2332
16th to endDay
17%5%23424346%44%
2308
May1st to 15thDay
16%5%35%5%245%6%7%37%
2532
16th to endDay
16%5%25%5%35%45%8%37%
2842
June1st to 15thDay
12%4345%36%47%9%39%
2730
16th to endDay
10%4145%35%5%6%9%42%
2730
July1st to 15thDay
8%325%5%36%6%6%9%41%
2730
16th to endDay
9%325%5%36%6%8%10%37%
2721
August1st to 15thDay
11%5%25%5%45%7%7%8%35%
2476
16th to endDay
12%4245%35%6%6%8%41%
2449
September1st to 15thDay
13%424435%35%7%44%
2160
16th to endDay
14%5%26%42335%8%42%
1989
October1st to 15thDay
18%414423446%43%
1800
16th to endDay
15%424423445%47%
1920
November1st to 15thDay
14%6%2432346%5%45%
1752
16th to endDay
15%5%24423445%47%
1618
December1st to 15thDay
16%435%4245%5%7%41%
1560
16th to endDay
17%6%25%424347%39%
1664
January1st to 15thNight
16%5%2442445%6%42%
2648
16th to endNight
15%7%2342435%6%43%
2704
February1st to 15thNight
14%6%25%43345%7%42%
2480
16th to endNight
14%7%25%5%23347%42%
2067
March1st to 15thNight
15%6%233345%45%45%
2175
16th to endNight
14%7%35%5%2435%6%42%
2252
April1st to 15thNight
12%6%245%3446%7%42%
1946
16th to endNight
16%5%2442345%6%44%
1927
May1st to 15thNight
18%7%2442335%6%40%
1758
16th to endNight
15%6%343245%5%9%40%
1623
June1st to 15thNight
11%31443446%10%43%
1560
16th to endNight
10%3245%35%47%10%42%
1560
July1st to 15thNight
8%437%6%46%5%6%9%36%
1560
16th to endNight
6%323435%5%7%12%45%
1796
August1st to 15thNight
9%6%245%246%7%8%42%
1726
16th to endNight
10%415%4246%5%8%46%
2047
September1st to 15thNight
11%6%34423347%47%
1800
16th to endNight
13%5%25%5%24446%45%
1969
October1st to 15thNight
18%5%23324345%45%
2160
16th to endNight
14%413313347%51%
2304
November1st to 15thNight
13%6%25%323335%49%
2433
16th to endNight
15%42432445%7%45%
2672
December1st to 15thNight
16%6%25%5%35%5%5%5%38%
2730
16th to endNight
16%5%25%5%2445%7%40%
2912

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
15%6%25%4245%5%5%41%
1619
16th to endDay
13%8%245%2445%5%42%
1872
February1st to 15thDay
14%7%25%7%2445%6%38%
1710
16th to endDay
16%7%35%5%33335%41%
1691
March1st to 15thDay
14%7%345%24337%43%
2099
16th to endDay
16%6%35%5%23346%41%
2323
April1st to 15thDay
14%6%25%5%2345%7%41%
2332
16th to endDay
17%5%24424346%44%
2308
May1st to 15thDay
16%6%25%425%45%7%37%
2532
16th to endDay
17%5%25%5%35%5%5%8%37%
2842
June1st to 15thDay
12%4245%35%5%7%9%40%
2730
16th to endDay
11%325%5%345%6%10%42%
2730
July1st to 15thDay
8%425%5%46%6%6%9%41%
2730
16th to endDay
9%325%5%36%7%8%9%37%
2721
August1st to 15thDay
11%5%25%5%45%8%6%7%36%
2476
16th to endDay
12%4244446%6%8%41%
2449
September1st to 15thDay
13%43443435%7%44%
2160
16th to endDay
14%5%26%42345%8%41%
1989
October1st to 15thDay
18%41342435%6%43%
1800
16th to endDay
15%414424446%48%
1920
November1st to 15thDay
14%6%2432446%5%45%
1752
16th to endDay
15%5%24423445%47%
1618
December1st to 15thDay
16%435%42445%7%41%
1560
16th to endDay
17%6%25%5%34346%39%
1664
January1st to 15thNight
16%5%3442445%6%42%
2648
16th to endNight
16%7%2332446%5%43%
2704
February1st to 15thNight
14%6%2443345%6%42%
2473
16th to endNight
14%7%25%5%23347%43%
2067
March1st to 15thNight
15%6%233245%46%45%
2187
16th to endNight
14%6%35%5%2345%6%42%
2252
April1st to 15thNight
12%6%245%345%6%6%42%
1946
16th to endNight
16%5%2442345%6%44%
1927
May1st to 15thNight
19%5%25%32345%6%39%
1757
16th to endNight
15%6%244245%5%9%40%
1623
June1st to 15thNight
11%4144345%6%10%43%
1560
16th to endNight
10%3245%35%46%11%43%
1560
July1st to 15thNight
8%436%6%47%5%6%9%37%
1560
16th to endNight
6%314436%5%7%12%45%
1796
August1st to 15thNight
10%5%15%4346%6%8%42%
1726
16th to endNight
10%425%4245%5%8%45%
2047
September1st to 15thNight
12%7%24423447%47%
1800
16th to endNight
13%5%15%5%2445%7%44%
1969
October1st to 15thNight
18%5%23424335%45%
2160
16th to endNight
14%412323347%51%
2304
November1st to 15thNight
13%6%25%323335%49%
2433
16th to endNight
15%42442445%7%45%
2672
December1st to 15thNight
16%6%25%5%35%5%5%5%39%
2730
16th to endNight
16%6%25%5%2445%7%40%
2912

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
42%6%12%21%13%3
1620
16th to endDay
42%5%12%23%13%3
1872
February1st to 15thDay
44%5%10%24%11%2
1712
16th to endDay
45%311%24%12%1
1691
March1st to 15thDay
41%411%22%17%2
2099
16th to endDay
44%5%9%18%18%2
2324
April1st to 15thDay
41%5%10%21%17%3
2332
16th to endDay
41%48%18%21%5%
2308
May1st to 15thDay
42%8%12%20%14%1
2532
16th to endDay
43%8%12%20%12%1
2846
June1st to 15thDay
38%9%12%24%14%
2730
16th to endDay
36%8%13%21%17%1
2730
July1st to 15thDay
37%10%11%21%16%3
2581
16th to endDay
36%10%14%22%12%2
2565
August1st to 15thDay
40%9%13%19%15%
2463
16th to endDay
38%8%13%21%16%2
2449
September1st to 15thDay
38%6%12%19%20%3
2160
16th to endDay
40%5%9%21%20%2
1989
October1st to 15thDay
40%5%10%22%17%2
1800
16th to endDay
36%5%9%27%20%1
1920
November1st to 15thDay
38%5%12%21%17%4
1752
16th to endDay
38%49%27%17%1
1618
December1st to 15thDay
40%6%14%24%11%2
1560
16th to endDay
45%412%23%13%
1664
January1st to 15thNight
41%5%10%20%17%4
2648
16th to endNight
40%5%10%26%15%1
2704
February1st to 15thNight
41%413%23%14%2
2482
16th to endNight
41%49%24%17%2
2067
March1st to 15thNight
39%6%10%26%14%2
2187
16th to endNight
41%5%11%20%17%3
2252
April1st to 15thNight
39%5%12%19%19%3
1946
16th to endNight
39%5%10%18%19%6%
1927
May1st to 15thNight
43%6%10%22%13%3
1758
16th to endNight
40%8%15%18%14%3
1625
June1st to 15thNight
35%8%12%25%16%
1560
16th to endNight
34%8%12%24%17%2
1560
July1st to 15thNight
42%9%14%16%13%4
1480
16th to endNight
29%8%19%23%16%2
1689
August1st to 15thNight
35%9%13%21%17%1
1715
16th to endNight
34%7%11%23%18%3
2047
September1st to 15thNight
37%5%11%20%21%3
1800
16th to endNight
38%5%8%20%22%3
1969
October1st to 15thNight
41%5%8%23%18%3
2160
16th to endNight
32%49%29%21%2
2304
November1st to 15thNight
38%48%23%18%6%
2433
16th to endNight
37%6%9%23%19%3
2672
December1st to 15thNight
45%6%11%22%12%2
2730
16th to endNight
42%5%13%22%13%1
2912

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
20%25%32%16%4
106
16th to endDay
20%23%33%20%2
144
February1st to 15thDay
27%19%45%8%
135
16th to endDay
25%13%41%18%1
272
March1st to 15thDay
19%21%30%23%4
330
16th to endDay
20%15%36%20%5%1
352
April1st to 15thDay
20%16%33%18%9%1
330
16th to endDay
21%10%30%18%14%4
319
May1st to 15thDay
24%13%27%19%10%5%
348
16th to endDay
23%418%24%23%5%
395
June1st to 15thDay
17%5%24%23%22%6%
375
16th to endDay
12%425%32%19%5%
375
July1st to 15thDay
11%218%31%24%11%
365
16th to endDay
11%114%32%28%11%
390
August1st to 15thDay
14%117%29%24%13%
358
16th to endDay
10%14%29%28%17%
384
September1st to 15thDay
14%419%21%22%17%
315
16th to endDay
19%213%33%18%13%
314
October1st to 15thDay
23%5%16%27%19%7%
315
16th to endDay
13%12%29%27%14%2
336
November1st to 15thDay
17%8%28%26%17%1
289
16th to endDay
16%13%41%18%8%1
148
December1st to 15thDay
17%24%26%16%10%4
90
16th to endDay
23%12%41%16%5%
96
January1st to 15thNight
19%16%36%22%3
780
16th to endNight
20%18%38%20%1
832
February1st to 15thNight
21%16%37%22%1
764
16th to endNight
21%19%38%18%2
683
March1st to 15thNight
20%15%36%24%3
780
16th to endNight
18%13%41%18%5%1
832
April1st to 15thNight
16%16%40%21%4
778
16th to endNight
19%8%31%28%10%
771
May1st to 15thNight
21%6%28%31%10%
588
16th to endNight
19%418%33%20%2
407
June1st to 15thNight
12%126%34%24%
390
16th to endNight
10%21%46%18%1
390
July1st to 15thNight
11%117%35%31%2
370
16th to endNight
7%13%42%31%4
562
August1st to 15thNight
13%113%41%27%2
575
16th to endNight
12%214%35%31%4
817
September1st to 15thNight
14%220%31%27%3
720
16th to endNight
16%218%31%25%5%
717
October1st to 15thNight
20%5%22%29%17%4
720
16th to endNight
18%9%32%26%12%
768
November1st to 15thNight
16%9%30%29%11%1
760
16th to endNight
18%16%28%27%7%1
780
December1st to 15thNight
21%11%36%20%9%
780
16th to endNight
19%13%40%24%1
832
Page generated at 2018-08-30 05:34:23. Version ac04

Copyright 2018 A. Danko


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