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 2017-09-16.

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%
15191
20%
46869
11%
15151
47%
15151
24%
29658

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%
718
21%
2443
8%
716
38%
716
17%
1542
January16th to endNight
18%
768
23%
2496
6%
768
39%
768
21%
1560
February1st to 15thNight
19%
703
19%
2287
5%
701
37%
701
20%
1419
February16th to endNight
16%
631
24%
1910
5%
631
38%
631
21%
1210
March1st to 15thNight
24%
720
21%
2019
8%
720
38%
720
23%
1323
March16th to endNight
22%
768
20%
2079
7%
768
33%
768
24%
1404
April1st to 15thNight
24%
718
19%
1796
5%
718
33%
718
27%
1205
April16th to endNight
37%
720
19%
1800
6%
720
43%
720
30%
1206
May1st to 15thNight
36%
543
18%
1623
9%
543
43%
543
22%
1100
May16th to endNight
52%
374
17%
1497
15%
374
59%
374
21%
908
June1st to 15thNight
53%
360
19%
1440
19%
360
61%
360
25%
824
June16th to endNight
57%
360
17%
1440
18%
360
63%
360
25%
835
July1st to 15thNight
57%
340
12%
1360
13%
340
59%
340
17%
892
July16th to endNight
72%
518
16%
1549
14%
485
76%
485
35%
876
August1st to 15thNight
64%
539
18%
1609
14%
536
65%
536
30%
1018
August16th to endNight
63%
761
20%
1907
12%
761
64%
761
33%
1245
September1st to 15thNight
54%
720
25%
1800
14%
720
59%
720
34%
1176
September16th to endNight
53%
658
22%
1807
18%
658
57%
658
29%
1201
October1st to 15thNight
44%
660
24%
1980
20%
660
52%
660
26%
1273
October16th to endNight
36%
704
27%
2112
15%
704
51%
704
31%
1246
November1st to 15thNight
37%
700
25%
2241
15%
700
51%
700
27%
1358
November16th to endNight
30%
720
21%
2466
11%
720
43%
720
19%
1519
December1st to 15thNight
24%
720
17%
2520
7%
720
38%
720
17%
1620
December16th to endNight
21%
768
21%
2688
6%
768
39%
768
19%
1698

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%
47867
Night
14%5%2442445%7%43%
47051
Cloud CoverDay
14%5%245%3445%7%41%
47877
Night
14%5%2442445%7%43%
47055
TransparencyDay
40%6%11%22%16%2
47567
Night
39%6%11%22%17%3
46869
SeeingDay
17%8%25%25%16%6%
5676
Night
17%10%29%28%12%1
15195

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
16%6%25%425%5%5%5%40%
1494
16th to endDay
14%7%345%2445%5%42%
1728
February1st to 15thDay
13%7%347%2446%6%39%
1575
16th to endDay
14%7%25%6%43336%41%
1562
March1st to 15thDay
14%7%345%23437%43%
1927
16th to endDay
16%6%25%5%24346%40%
2145
April1st to 15thDay
14%5%25%5%2435%7%42%
2152
16th to endDay
17%5%24424346%44%
2160
May1st to 15thDay
16%5%35%5%245%6%7%37%
2337
16th to endDay
14%425%5%35%45%8%37%
2618
June1st to 15thDay
11%4345%36%47%9%39%
2520
16th to endDay
10%4145%35%5%6%9%43%
2520
July1st to 15thDay
9%425%5%36%6%6%9%39%
2520
16th to endDay
7%325%5%37%7%8%10%37%
2509
August1st to 15thDay
11%5%25%5%45%6%7%8%36%
2330
16th to endDay
12%4245%35%6%6%8%41%
2292
September1st to 15thDay
13%424435%35%7%44%
2160
16th to endDay
16%5%26%423348%41%
1824
October1st to 15thDay
18%414423446%44%
1650
16th to endDay
15%424423445%46%
1760
November1st to 15thDay
14%6%2432346%5%46%
1614
16th to endDay
17%5%24423445%44%
1494
December1st to 15thDay
16%435%4245%5%7%41%
1440
16th to endDay
17%6%25%424347%39%
1536
January1st to 15thNight
16%5%3442445%6%41%
2443
16th to endNight
16%6%2342445%6%43%
2496
February1st to 15thNight
14%6%2443345%7%43%
2285
16th to endNight
13%6%35%5%23347%44%
1910
March1st to 15thNight
15%6%233345%45%44%
2007
16th to endNight
14%6%36%5%2445%6%42%
2079
April1st to 15thNight
12%6%2443446%7%42%
1796
16th to endNight
16%5%2442345%6%44%
1800
May1st to 15thNight
19%7%2442335%6%39%
1623
16th to endNight
13%6%343245%5%9%41%
1495
June1st to 15thNight
11%31443447%10%44%
1440
16th to endNight
10%3245%35%47%10%42%
1440
July1st to 15thNight
9%437%6%46%6%6%9%34%
1440
16th to endNight
5%323335%5%7%12%46%
1656
August1st to 15thNight
9%5%15%4245%7%8%44%
1620
16th to endNight
10%425%4246%5%7%46%
1907
September1st to 15thNight
11%6%34423347%47%
1800
16th to endNight
14%5%25%5%34447%43%
1807
October1st to 15thNight
18%5%23324345%45%
1980
16th to endNight
14%413313337%51%
2112
November1st to 15thNight
12%6%25%32333450%
2241
16th to endNight
16%42442445%7%43%
2466
December1st to 15thNight
16%5%25%5%35%5%5%5%39%
2520
16th to endNight
16%5%25%5%2445%7%40%
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
16%6%24425%5%5%5%41%
1494
16th to endDay
14%7%245%2445%5%42%
1728
February1st to 15thDay
13%7%25%7%245%5%6%39%
1575
16th to endDay
14%7%35%5%33336%42%
1562
March1st to 15thDay
14%6%345%23337%43%
1938
16th to endDay
16%6%345%23346%41%
2144
April1st to 15thDay
14%5%25%5%2345%7%42%
2152
16th to endDay
17%5%34424346%44%
2160
May1st to 15thDay
17%6%26%425%45%7%37%
2337
16th to endDay
15%425%5%35%5%5%8%38%
2618
June1st to 15thDay
11%4245%35%5%7%9%40%
2520
16th to endDay
11%4244345%6%9%43%
2520
July1st to 15thDay
9%425%5%46%6%6%9%39%
2520
16th to endDay
7%325%5%37%7%8%10%38%
2509
August1st to 15thDay
12%5%25%5%45%7%6%7%36%
2330
16th to endDay
12%424435%6%6%8%41%
2292
September1st to 15thDay
13%43443435%7%44%
2160
16th to endDay
16%5%36%423448%40%
1824
October1st to 15thDay
18%414424346%44%
1650
16th to endDay
15%5%24424446%46%
1760
November1st to 15thDay
14%6%2332445%5%46%
1614
16th to endDay
17%5%24423445%44%
1494
December1st to 15thDay
16%425%42445%7%41%
1440
16th to endDay
17%6%25%5%24346%39%
1536
January1st to 15thNight
16%5%3442445%6%41%
2443
16th to endNight
16%6%2332446%5%43%
2496
February1st to 15thNight
14%6%2443335%6%43%
2278
16th to endNight
13%7%25%5%23347%44%
1910
March1st to 15thNight
15%6%233245%46%44%
2019
16th to endNight
14%6%36%5%23446%42%
2079
April1st to 15thNight
13%6%245%345%6%6%42%
1796
16th to endNight
16%5%2442345%6%44%
1800
May1st to 15thNight
20%5%25%32345%6%38%
1622
16th to endNight
13%6%243245%5%10%41%
1495
June1st to 15thNight
11%3134345%6%10%43%
1440
16th to endNight
10%3245%35%46%11%42%
1440
July1st to 15thNight
9%5%36%6%47%5%6%9%35%
1440
16th to endNight
5%313336%5%7%12%46%
1656
August1st to 15thNight
10%5%15%4346%6%8%43%
1620
16th to endNight
10%425%425%5%5%7%46%
1907
September1st to 15thNight
12%7%24423447%47%
1800
16th to endNight
14%5%15%5%2435%7%42%
1807
October1st to 15thNight
18%5%23324345%45%
1980
16th to endNight
14%413323347%51%
2112
November1st to 15thNight
12%6%25%323335%50%
2241
16th to endNight
16%42442445%7%43%
2466
December1st to 15thNight
16%5%25%5%35%45%5%39%
2520
16th to endNight
16%6%25%5%2345%7%40%
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
42%6%12%21%12%3
1495
16th to endDay
41%5%12%23%12%3
1728
February1st to 15thDay
43%5%10%25%12%2
1577
16th to endDay
44%312%25%12%1
1562
March1st to 15thDay
42%411%23%15%2
1938
16th to endDay
44%5%10%18%18%2
2145
April1st to 15thDay
40%5%10%21%18%3
2152
16th to endDay
41%5%8%17%21%5%
2160
May1st to 15thDay
43%7%11%20%14%1
2337
16th to endDay
42%8%13%21%12%1
2622
June1st to 15thDay
38%9%12%25%14%
2520
16th to endDay
36%8%13%21%17%1
2520
July1st to 15thDay
38%10%11%21%14%2
2371
16th to endDay
35%11%14%23%13%2
2353
August1st to 15thDay
41%8%13%19%16%
2317
16th to endDay
38%7%12%22%16%2
2292
September1st to 15thDay
38%6%12%19%20%3
2160
16th to endDay
41%5%8%20%21%2
1824
October1st to 15thDay
39%5%11%23%17%3
1650
16th to endDay
37%5%9%26%19%1
1760
November1st to 15thDay
37%5%12%21%18%5%
1614
16th to endDay
41%5%9%26%16%1
1494
December1st to 15thDay
40%6%15%23%11%2
1440
16th to endDay
45%411%23%13%
1536
January1st to 15thNight
42%5%10%20%16%3
2443
16th to endNight
40%5%11%26%15%1
2496
February1st to 15thNight
40%412%24%15%2
2287
16th to endNight
40%49%25%17%2
1910
March1st to 15thNight
39%6%11%26%13%2
2019
16th to endNight
42%6%11%19%17%3
2079
April1st to 15thNight
39%5%11%19%19%3
1796
16th to endNight
38%5%10%18%19%6%
1800
May1st to 15thNight
44%6%9%22%14%2
1623
16th to endNight
38%9%15%19%14%3
1497
June1st to 15thNight
33%9%12%27%16%
1440
16th to endNight
35%8%12%24%16%2
1440
July1st to 15thNight
44%9%14%15%11%4
1360
16th to endNight
27%8%19%24%17%2
1549
August1st to 15thNight
34%9%12%22%18%1
1609
16th to endNight
35%7%10%24%18%3
1907
September1st to 15thNight
37%5%11%20%21%3
1800
16th to endNight
40%5%8%19%22%3
1807
October1st to 15thNight
40%5%8%23%18%3
1980
16th to endNight
33%5%9%27%21%2
2112
November1st to 15thNight
37%48%22%19%7%
2241
16th to endNight
39%6%10%22%17%3
2466
December1st to 15thNight
44%6%11%22%12%1
2520
16th to endNight
42%5%13%22%13%1
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
23%25%35%12%11
71
16th to endDay
22%22%30%21%2
96
February1st to 15thDay
25%21%42%11%
90
16th to endDay
19%16%43%19%
221
March1st to 15thDay
19%17%30%25%5%
270
16th to endDay
20%15%38%18%5%2
288
April1st to 15thDay
18%15%32%20%11%2
270
16th to endDay
21%8%29%19%15%5%
270
May1st to 15thDay
26%15%28%15%9%5%
288
16th to endDay
19%5%20%26%22%5%
331
June1st to 15thDay
15%5%25%23%23%6%
315
16th to endDay
13%427%33%16%6%
315
July1st to 15thDay
13%221%32%22%7%
305
16th to endDay
7%114%34%29%12%
326
August1st to 15thDay
14%117%28%24%12%
313
16th to endDay
11%12%30%30%15%
332
September1st to 15thDay
14%419%21%22%17%
315
16th to endDay
21%114%33%15%12%
254
October1st to 15thDay
22%6%18%28%18%5%
255
16th to endDay
15%12%29%30%11%1
272
November1st to 15thDay
17%10%27%23%18%2
241
16th to endDay
20%13%37%19%7%1
114
December1st to 15thDay
20%25%26%15%8%5%
60
16th to endDay
29%12%34%18%4
64
January1st to 15thNight
20%16%35%23%3
720
16th to endNight
20%18%39%19%1
768
February1st to 15thNight
21%17%37%23%1
704
16th to endNight
20%20%38%18%1
631
March1st to 15thNight
20%14%36%24%3
720
16th to endNight
18%14%40%18%6%1
768
April1st to 15thNight
16%16%40%21%5%
718
16th to endNight
19%8%31%28%10%
720
May1st to 15thNight
23%6%29%30%9%
543
16th to endNight
17%5%19%34%21%2
375
June1st to 15thNight
12%126%35%24%
360
16th to endNight
10%22%46%18%1
360
July1st to 15thNight
12%118%37%29%
340
16th to endNight
6%13%43%31%4
518
August1st to 15thNight
13%112%42%26%2
539
16th to endNight
12%214%36%29%4
761
September1st to 15thNight
14%220%31%27%3
720
16th to endNight
17%218%32%24%4
658
October1st to 15thNight
20%6%23%29%17%3
660
16th to endNight
18%10%31%28%10%
704
November1st to 15thNight
16%10%31%28%11%2
700
16th to endNight
19%17%28%26%7%1
720
December1st to 15thNight
21%12%36%20%9%
720
16th to endNight
20%14%39%24%2
768
Page generated at 2017-09-16 17:06:59. Version ac04

Copyright 2017 A. Danko


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