Robeson Planetarium and Science Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Robeson Planetarium and Science Center clear sky chart from 2005-11-05 to 2017-10-31.

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
49%
16165
22%
47386
15%
16128
56%
16128
28%
29970

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
37%
716
21%
2327
13%
716
48%
716
23%
1455
January16th to endNight
32%
768
24%
2496
13%
768
47%
768
24%
1538
February1st to 15thNight
30%
702
21%
2287
10%
701
44%
701
25%
1380
February16th to endNight
29%
631
28%
1817
13%
631
44%
631
29%
1109
March1st to 15thNight
34%
720
25%
1980
14%
720
44%
720
32%
1223
March16th to endNight
40%
768
22%
2112
13%
768
47%
768
31%
1336
April1st to 15thNight
40%
718
24%
1854
11%
718
48%
718
34%
1155
April16th to endNight
43%
720
21%
1800
9%
720
48%
720
35%
1155
May1st to 15thNight
48%
585
17%
1665
9%
585
53%
585
30%
1058
May16th to endNight
65%
561
18%
1682
13%
561
67%
561
30%
1054
June1st to 15thNight
63%
540
15%
1620
13%
540
65%
540
27%
1070
June16th to endNight
66%
540
15%
1620
12%
540
67%
540
26%
1068
July1st to 15thNight
68%
510
11%
1530
11%
510
69%
510
24%
1051
July16th to endNight
71%
564
12%
1595
11%
531
73%
531
28%
1044
August1st to 15thNight
64%
539
15%
1609
13%
536
64%
536
23%
1090
August16th to endNight
61%
750
16%
1896
12%
750
62%
750
25%
1363
September1st to 15thNight
66%
720
22%
1839
17%
720
66%
720
30%
1249
September16th to endNight
52%
717
17%
1998
14%
717
55%
717
23%
1410
October1st to 15thNight
54%
720
27%
2160
26%
720
60%
720
32%
1309
October16th to endNight
51%
768
35%
2303
26%
768
65%
768
38%
1276
November1st to 15thNight
50%
700
29%
2101
22%
700
61%
700
36%
1192
November16th to endNight
44%
720
26%
2259
19%
720
55%
720
30%
1327
December1st to 15thNight
45%
720
22%
2340
17%
720
53%
720
24%
1457
December16th to endNight
38%
768
24%
2496
17%
768
48%
768
23%
1601

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%25%5%3445%7%42%
48359
Night
12%5%2442445%7%45%
47585
TransparencyDay
39%7%11%19%17%4
48060
Night
37%6%11%18%18%6%
47388
SeeingDay
14%5%19%25%21%13%
5994
Night
14%6%23%33%19%2
16173

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%25%413345%45%
1611
16th to endDay
14%6%25%423346%45%
1728
February1st to 15thDay
18%5%2432445%5%43%
1575
16th to endDay
16%5%24323336%48%
1652
March1st to 15thDay
12%424424346%49%
1980
16th to endDay
14%5%2442445%6%44%
2111
April1st to 15thDay
10%31342445%6%52%
2092
16th to endDay
10%425%42445%6%47%
2160
May1st to 15thDay
10%5%36%6%45%45%7%40%
2295
16th to endDay
7%6%26%6%46%5%6%7%39%
2431
June1st to 15thDay
10%5%245%35%6%7%8%40%
2340
16th to endDay
7%426%6%46%6%8%11%35%
2340
July1st to 15thDay
8%435%7%46%5%8%11%32%
2340
16th to endDay
6%5%35%6%47%8%8%12%31%
2465
August1st to 15thDay
11%6%35%6%46%6%7%9%29%
2340
16th to endDay
12%6%36%6%46%6%7%9%29%
2294
September1st to 15thDay
10%5%245%35%5%6%8%41%
2118
16th to endDay
15%8%36%5%345%46%35%
1962
October1st to 15thDay
15%6%24323235%49%
1800
16th to endDay
9%5%24312335%59%
1920
November1st to 15thDay
14%5%14212335%54%
1757
16th to endDay
12%5%24323446%50%
1700
December1st to 15thDay
16%7%36%434335%42%
1620
16th to endDay
19%6%24422345%42%
1728
January1st to 15thNight
14%6%24424346%45%
2327
16th to endNight
15%6%24423445%44%
2496
February1st to 15thNight
16%5%1331435%5%47%
2278
16th to endNight
13%325%424446%48%
1817
March1st to 15thNight
12%425%324347%49%
1980
16th to endNight
12%5%2442446%7%45%
2112
April1st to 15thNight
11%424424447%50%
1854
16th to endNight
10%424425%36%8%47%
1800
May1st to 15thNight
9%425%5%345%6%7%44%
1664
16th to endNight
9%5%14435%5%6%8%44%
1682
June1st to 15thNight
10%434435%5%7%11%37%
1620
16th to endNight
6%435%5%36%7%7%11%39%
1620
July1st to 15thNight
6%436%6%46%7%7%10%35%
1620
16th to endNight
5%325%6%45%6%8%13%36%
1703
August1st to 15thNight
8%6%35%6%36%5%7%9%36%
1620
16th to endNight
10%6%26%6%35%5%7%10%33%
1896
September1st to 15thNight
9%4246%35%5%6%8%42%
1839
16th to endNight
15%6%36%5%35%45%6%37%
1998
October1st to 15thNight
15%5%24323346%49%
2160
16th to endNight
10%31432224458%
2303
November1st to 15thNight
12%423312335%56%
2101
16th to endNight
15%5%23313346%50%
2259
December1st to 15thNight
15%6%24424446%43%
2340
16th to endNight
17%6%24424345%43%
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
41%5%9%17%20%6%
1612
16th to endDay
39%37%17%24%8%
1728
February1st to 15thDay
41%37%19%21%5%
1577
16th to endDay
39%36%23%20%6%
1652
March1st to 15thDay
35%410%20%21%7%
1980
16th to endDay
39%6%9%19%20%4
2112
April1st to 15thDay
31%5%10%22%23%6%
2092
16th to endDay
35%6%10%18%20%8%
2160
May1st to 15thDay
41%8%12%19%15%2
2295
16th to endDay
40%8%14%20%15%
2435
June1st to 15thDay
38%8%15%22%12%1
2340
16th to endDay
38%12%16%19%11%2
2340
July1st to 15thDay
42%10%17%17%9%3
2201
16th to endDay
38%14%18%18%7%2
2310
August1st to 15thDay
47%10%12%16%11%
2327
16th to endDay
47%9%15%17%8%1
2294
September1st to 15thDay
39%7%14%17%15%5%
2118
16th to endDay
47%7%9%14%17%3
1962
October1st to 15thDay
38%38%21%23%3
1800
16th to endDay
28%37%19%30%10%
1920
November1st to 15thDay
32%46%17%28%9%
1757
16th to endDay
34%48%18%23%10%
1700
December1st to 15thDay
45%49%17%16%5%
1620
16th to endDay
44%38%19%17%6%
1728
January1st to 15thNight
40%5%10%12%23%7%
2327
16th to endNight
40%46%19%20%9%
2496
February1st to 15thNight
38%47%16%24%8%
2287
16th to endNight
36%49%20%21%7%
1817
March1st to 15thNight
34%5%10%19%22%7%
1980
16th to endNight
35%6%12%20%19%5%
2112
April1st to 15thNight
33%5%9%20%23%7%
1854
16th to endNight
34%6%12%19%18%8%
1800
May1st to 15thNight
34%9%14%19%18%2
1665
16th to endNight
34%8%16%25%13%1
1684
June1st to 15thNight
38%9%15%26%9%
1620
16th to endNight
37%10%17%20%11%2
1620
July1st to 15thNight
39%13%18%19%8%1
1530
16th to endNight
34%12%22%17%11%1
1595
August1st to 15thNight
41%10%19%18%8%1
1609
16th to endNight
42%11%16%20%8%
1896
September1st to 15thNight
37%9%14%17%14%6%
1839
16th to endNight
46%7%10%16%15%3
1998
October1st to 15thNight
36%49%19%24%5%
2160
16th to endNight
29%47%18%27%13%
2303
November1st to 15thNight
31%28%15%27%14%
2101
16th to endNight
35%48%15%25%11%
2259
December1st to 15thNight
40%5%10%17%19%6%
2340
16th to endNight
42%5%8%17%18%7%
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
21%17%32%20%8%
90
16th to endDay
17%25%35%16%5%
96
February1st to 15thDay
21%20%41%16%1
90
16th to endDay
16%15%35%28%3
194
March1st to 15thDay
13%11%32%29%11%1
270
16th to endDay
15%11%30%29%12%2
288
April1st to 15thDay
17%12%23%21%17%7%
270
16th to endDay
12%422%28%22%8%
270
May1st to 15thDay
12%6%26%29%18%6%
288
16th to endDay
10%314%23%24%23%
331
June1st to 15thDay
14%19%26%27%20%
315
16th to endDay
9%18%26%29%24%
315
July1st to 15thDay
8%10%24%39%17%
305
16th to endDay
7%6%25%40%20%
326
August1st to 15thDay
17%18%16%30%24%
313
16th to endDay
14%10%17%27%29%
332
September1st to 15thDay
13%14%26%19%25%
315
16th to endDay
21%116%25%24%10%
314
October1st to 15thDay
22%415%29%18%9%
315
16th to endDay
8%6%24%27%24%9%
336
November1st to 15thDay
18%5%23%30%15%6%
265
16th to endDay
11%9%22%35%18%2
170
December1st to 15thDay
23%12%35%18%10%
90
16th to endDay
28%15%31%15%9%
96
January1st to 15thNight
15%12%29%32%9%
720
16th to endNight
18%11%33%33%3
768
February1st to 15thNight
20%11%34%28%3
704
16th to endNight
14%12%38%30%3
631
March1st to 15thNight
13%10%38%29%7%
720
16th to endNight
14%8%30%34%10%
768
April1st to 15thNight
12%12%31%32%10%
718
16th to endNight
13%6%31%36%11%
720
May1st to 15thNight
9%429%38%16%
585
16th to endNight
11%214%38%29%3
563
June1st to 15thNight
12%212%42%25%5%
540
16th to endNight
7%14%38%31%6%
540
July1st to 15thNight
8%110%39%35%5%
510
16th to endNight
7%7%40%41%3
564
August1st to 15thNight
13%7%31%42%4
539
16th to endNight
13%111%29%37%7%
750
September1st to 15thNight
11%19%34%37%4
720
16th to endNight
19%315%31%27%2
717
October1st to 15thNight
18%219%28%27%3
720
16th to endNight
10%6%26%31%21%3
768
November1st to 15thNight
14%423%35%18%2
700
16th to endNight
18%7%25%29%17%1
720
December1st to 15thNight
16%9%24%38%10%
720
16th to endNight
21%8%25%33%10%
768
Page generated at 2017-11-01 17:23:40. Version ac04

Copyright 2017 A. Danko


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