Shired Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shired Island clear sky chart from 2005-11-05 to

2017-09-12
.

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
48%
15702
22%
46896
14%
15663
56%
15663
26%
28640

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
30%
717
20%
2327
10%
716
43%
716
20%
1431
January16th to endNight
33%
768
24%
2388
13%
768
44%
768
22%
1497
February1st to 15thNight
34%
701
26%
2107
13%
699
47%
699
26%
1259
February16th to endNight
35%
631
24%
1893
11%
631
48%
631
24%
1169
March1st to 15thNight
36%
720
28%
1995
12%
720
49%
720
31%
1166
March16th to endNight
41%
768
26%
2112
13%
768
52%
768
31%
1233
April1st to 15thNight
42%
718
23%
1976
12%
718
49%
718
32%
1161
April16th to endNight
52%
609
30%
1790
20%
609
61%
609
36%
943
May1st to 15thNight
56%
539
27%
1619
20%
539
62%
539
39%
848
May16th to endNight
61%
561
25%
1682
14%
561
69%
561
34%
913
June1st to 15thNight
58%
540
16%
1620
12%
540
61%
540
26%
1011
June16th to endNight
61%
540
13%
1620
9%
540
63%
540
25%
1036
July1st to 15thNight
66%
510
10%
1530
9%
510
67%
510
22%
1033
July16th to endNight
62%
564
7%
1595
7%
531
67%
531
20%
1117
August1st to 15thNight
65%
539
7%
1693
7%
536
66%
536
20%
1149
August16th to endNight
62%
641
12%
1978
12%
641
63%
641
20%
1369
September1st to 15thNight
59%
707
10%
1944
10%
707
59%
707
20%
1410
September16th to endNight
52%
657
17%
1815
10%
657
59%
657
20%
1282
October1st to 15thNight
58%
660
29%
1823
23%
660
64%
660
34%
1078
October16th to endNight
53%
704
30%
2112
24%
704
63%
704
34%
1192
November1st to 15thNight
45%
700
32%
2101
23%
700
59%
700
35%
1135
November16th to endNight
39%
720
28%
2340
16%
720
56%
720
29%
1303
December1st to 15thNight
39%
720
26%
2340
20%
720
50%
720
26%
1389
December16th to endNight
38%
768
24%
2496
15%
768
51%
768
22%
1516

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
9%425%435%5%6%9%42%
47745
Night
8%4244345%6%9%45%
47101
TransparencyDay
36%8%14%18%14%6%
47446
Night
34%7%14%20%16%7%
46904
SeeingDay
9%12%16%22%23%15%
5581
Night
9%19%15%26%22%7%
15711

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
12%7%25%4245%47%44%
1611
16th to endDay
13%5%2442345%7%46%
1833
February1st to 15thDay
16%5%25%32243449%
1750
16th to endDay
12%423433346%50%
1580
March1st to 15thDay
8%31331335%8%54%
1963
16th to endDay
8%41432445%6%54%
2111
April1st to 15thDay
7%31442446%9%50%
1972
16th to endDay
6%2133235%49%57%
2178
May1st to 15thDay
5%31442345%9%55%
2331
16th to endDay
6%213435%5%7%9%48%
2431
June1st to 15thDay
8%425%5%36%7%9%13%33%
2340
16th to endDay
8%415%5%38%7%9%11%33%
2340
July1st to 15thDay
7%425%6%48%7%10%14%28%
2340
16th to endDay
7%5%27%6%5%9%9%9%13%23%
2465
August1st to 15thDay
11%425%6%47%9%10%13%23%
2252
16th to endDay
9%6%17%6%47%7%8%12%27%
2211
September1st to 15thDay
10%426%7%5%8%7%8%11%27%
1936
16th to endDay
10%5%27%6%45%6%7%10%32%
1815
October1st to 15thDay
7%41443446%8%49%
1804
16th to endDay
8%31432345%7%54%
1760
November1st to 15thDay
6%32431345%7%56%
1754
16th to endDay
9%324434348%52%
1620
December1st to 15thDay
10%5%25%5%3445%7%46%
1620
16th to endDay
9%6%35%4245%5%9%43%
1728
January1st to 15thNight
12%6%2442445%8%43%
2327
16th to endNight
15%5%2442345%6%43%
2388
February1st to 15thNight
13%5%345%22335%51%
2103
16th to endNight
12%6%35%324346%46%
1893
March1st to 15thNight
7%5%2432335%8%52%
1995
16th to endNight
8%314423446%55%
2112
April1st to 15thNight
7%42442445%7%51%
1976
16th to endNight
5%21442335%8%58%
1790
May1st to 15thNight
5%31331335%11%56%
1619
16th to endNight
44134235%6%10%53%
1682
June1st to 15thNight
9%5%244345%6%12%40%
1620
16th to endNight
6%4245%35%6%6%14%39%
1620
July1st to 15thNight
5%325%5%47%7%10%15%33%
1620
16th to endNight
4415%7%49%10%10%13%28%
1703
August1st to 15thNight
7%425%5%47%7%10%13%29%
1704
16th to endNight
7%5%26%5%47%8%7%10%34%
1978
September1st to 15thNight
8%5%37%6%5%6%6%8%11%29%
1944
16th to endNight
11%6%26%6%46%6%7%10%32%
1815
October1st to 15thNight
6%315%5%3445%7%52%
1823
16th to endNight
8%32442445%6%53%
2112
November1st to 15thNight
6%323423447%56%
2101
16th to endNight
7%5%244235%5%6%52%
2340
December1st to 15thNight
12%6%34323348%46%
2340
16th to endNight
9%6%25%5%3445%8%44%
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
39%410%18%17%9%
1612
16th to endDay
37%38%18%21%10%
1833
February1st to 15thDay
38%35%15%20%15%
1752
16th to endDay
35%311%13%23%11%
1580
March1st to 15thDay
27%5%12%22%23%8%
1963
16th to endDay
29%413%21%19%10%
2112
April1st to 15thDay
30%7%10%20%21%9%
1972
16th to endDay
25%7%11%23%22%9%
2178
May1st to 15thDay
27%6%12%25%21%7%
2331
16th to endDay
31%9%16%24%15%2
2435
June1st to 15thDay
39%12%19%22%5%
2340
16th to endDay
41%12%19%19%6%
2340
July1st to 15thDay
42%16%25%13%1
2201
16th to endDay
46%15%23%11%3
2310
August1st to 15thDay
46%17%23%11%1
2239
16th to endDay
48%14%21%12%3
2211
September1st to 15thDay
48%15%18%11%5%1
1936
16th to endDay
45%12%13%16%8%3
1815
October1st to 15thDay
34%7%11%16%16%13%
1804
16th to endDay
28%6%8%16%25%14%
1760
November1st to 15thDay
26%411%22%22%12%
1754
16th to endDay
31%38%19%22%12%
1620
December1st to 15thDay
36%5%10%23%17%7%
1620
16th to endDay
36%5%12%23%13%8%
1728
January1st to 15thNight
39%49%19%18%7%
2327
16th to endNight
40%47%13%23%10%
2388
February1st to 15thNight
35%37%16%22%14%
2112
16th to endNight
37%48%14%23%10%
1893
March1st to 15thNight
30%312%23%19%9%
1995
16th to endNight
29%411%22%20%12%
2112
April1st to 15thNight
30%412%20%22%8%
1976
16th to endNight
24%411%29%22%7%
1790
May1st to 15thNight
22%5%14%27%20%9%
1620
16th to endNight
24%6%19%27%19%2
1684
June1st to 15thNight
33%8%22%28%5%
1620
16th to endNight
33%10%24%23%6%
1620
July1st to 15thNight
35%14%29%17%3
1530
16th to endNight
36%18%30%11%3
1595
August1st to 15thNight
38%13%32%13%2
1693
16th to endNight
40%14%23%17%3
1978
September1st to 15thNight
43%13%23%13%5%
1944
16th to endNight
43%9%16%17%8%3
1815
October1st to 15thNight
30%5%13%18%20%12%
1823
16th to endNight
30%47%17%25%14%
2112
November1st to 15thNight
27%48%23%25%10%
2101
16th to endNight
30%5%9%20%18%16%
2340
December1st to 15thNight
36%410%26%15%7%
2340
16th to endNight
38%49%24%15%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
14%18%38%11%10%6%
90
16th to endDay
15%17%45%16%4
96
February1st to 15thDay
11%26%31%21%10%
90
16th to endDay
425%41%20%6%
81
March1st to 15thDay
9%22%33%21%11%2
253
16th to endDay
11%20%23%26%17%2
288
April1st to 15thDay
8%22%23%23%20%1
270
16th to endDay
5%15%21%30%19%7%
270
May1st to 15thDay
7%14%21%26%19%10%
288
16th to endDay
6%12%8%21%29%21%
331
June1st to 15thDay
10%12%6%19%26%24%
315
16th to endDay
9%10%222%25%28%
315
July1st to 15thDay
5%6%217%30%37%
305
16th to endDay
8%10%415%30%30%
326
August1st to 15thDay
19%6%413%27%29%
313
16th to endDay
9%5%419%31%29%
332
September1st to 15thDay
17%7%420%27%23%
299
16th to endDay
14%6%8%20%34%15%
254
October1st to 15thDay
9%7%13%35%25%7%
255
16th to endDay
7%9%25%29%22%5%
272
November1st to 15thDay
8%13%21%32%19%4
262
16th to endDay
8%341%26%16%3
90
December1st to 15thDay
314%46%25%8%1
90
16th to endDay
15%5%34%28%12%4
96
January1st to 15thNight
13%27%23%24%11%
720
16th to endNight
15%25%21%26%10%
768
February1st to 15thNight
11%26%24%26%10%1
704
16th to endNight
13%25%20%33%6%
631
March1st to 15thNight
7%26%25%27%10%1
720
16th to endNight
9%23%22%28%15%1
768
April1st to 15thNight
8%22%22%29%16%
718
16th to endNight
5%20%17%32%22%1
609
May1st to 15thNight
7%19%13%35%20%3
540
16th to endNight
5%19%6%26%34%7%
563
June1st to 15thNight
10%17%322%34%12%
540
16th to endNight
7%17%217%30%24%
540
July1st to 15thNight
412%211%35%33%
510
16th to endNight
417%19%43%23%
564
August1st to 15thNight
9%10%112%41%25%
539
16th to endNight
8%9%5%18%36%20%
641
September1st to 15thNight
9%10%6%20%35%16%
707
16th to endNight
13%11%10%29%28%6%
657
October1st to 15thNight
8%12%14%35%26%3
660
16th to endNight
8%13%19%33%23%2
704
November1st to 15thNight
7%18%23%32%15%2
700
16th to endNight
8%20%25%27%15%1
720
December1st to 15thNight
11%23%21%26%16%1
720
16th to endNight
10%24%21%28%14%
768
Page generated at 2017-09-13 07:39:17. Version ac04

Copyright 2017 A. Danko


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