Innerarity Island Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Innerarity Island Observatory clear sky chart from 2005-11-05 to 2017-03-25.

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
60%
14664
23%
45320
19%
14622
65%
14622
32%
26784

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
40%
720
23%
2192
12%
716
52%
716
27%
1348
January16th to endNight
36%
768
25%
2304
13%
768
46%
768
25%
1482
February1st to 15thNight
44%
701
29%
2107
15%
699
55%
699
33%
1246
February16th to endNight
40%
631
23%
1893
12%
631
48%
631
27%
1206
March1st to 15thNight
47%
720
23%
2160
13%
720
55%
720
31%
1308
March16th to endNight
58%
648
26%
1968
20%
648
63%
648
35%
1114
April1st to 15thNight
59%
494
26%
1647
24%
494
65%
494
32%
930
April16th to endNight
64%
495
28%
1650
27%
495
70%
495
40%
831
May1st to 15thNight
69%
494
22%
1622
22%
494
73%
494
38%
868
May16th to endNight
77%
513
23%
1538
23%
513
78%
513
41%
856
June1st to 15thNight
78%
495
16%
1485
17%
495
78%
495
38%
832
June16th to endNight
82%
495
16%
1485
16%
495
83%
495
35%
863
July1st to 15thNight
80%
465
11%
1425
12%
465
80%
465
29%
898
July16th to endNight
77%
522
9%
1632
11%
489
77%
489
28%
1004
August1st to 15thNight
82%
494
12%
1638
15%
491
82%
491
31%
972
August16th to endNight
70%
525
14%
1750
17%
525
71%
525
24%
1115
September1st to 15thNight
71%
555
16%
1710
17%
555
71%
555
26%
1086
September16th to endNight
70%
657
25%
1815
20%
657
72%
657
34%
1130
October1st to 15thNight
73%
660
34%
1815
28%
660
76%
660
45%
1012
October16th to endNight
61%
704
33%
2032
29%
704
66%
704
39%
1156
November1st to 15thNight
59%
700
31%
2276
29%
700
66%
700
36%
1234
November16th to endNight
52%
720
29%
2340
24%
720
61%
720
34%
1299
December1st to 15thNight
48%
720
25%
2340
20%
720
56%
720
28%
1386
December16th to endNight
42%
768
20%
2496
16%
768
49%
768
23%
1608

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%4244245%6%9%45%
45606
Night
9%42442445%8%48%
45540
TransparencyDay
34%7%15%20%16%5%
45323
Night
33%6%14%19%18%7%
45328
SeeingDay
10%211%22%32%20%
4457
Night
11%416%25%29%12%
14670

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
11%425%43435%8%46%
1743
16th to endDay
16%6%25%5%235%4444%
1920
February1st to 15thDay
12%5%1342435%7%48%
1750
16th to endDay
13%5%24424447%48%
1580
March1st to 15thDay
12%5%24423447%48%
1800
16th to endDay
10%41443445%7%49%
2131
April1st to 15thDay
12%42442435%7%47%
1971
16th to endDay
6%41442345%8%54%
1980
May1st to 15thDay
6%313325%6%6%9%49%
1998
16th to endDay
43134245%6%10%52%
2223
June1st to 15thDay
5%325%435%6%9%12%41%
2145
16th to endDay
5%315%5%35%7%9%14%38%
2145
July1st to 15thDay
7%5%25%7%47%8%10%13%26%
2109
16th to endDay
6%5%26%6%38%8%9%12%30%
2108
August1st to 15thDay
7%5%346%36%8%9%16%29%
1980
16th to endDay
12%5%25%4246%6%9%39%
2100
September1st to 15thDay
9%6%25%435%6%7%11%36%
1909
16th to endDay
7%415%5%45%5%6%8%46%
1815
October1st to 15thDay
6%31221346%8%58%
1815
16th to endDay
8%314313345%58%
1834
November1st to 15thDay
9%324314446%56%
1582
16th to endDay
7%42333445%8%54%
1620
December1st to 15thDay
10%5%25%42445%7%46%
1620
16th to endDay
18%8%37%433446%35%
1728
January1st to 15thNight
11%6%35%424447%45%
2192
16th to endNight
15%7%34423345%43%
2304
February1st to 15thNight
13%413323346%52%
2103
16th to endNight
14%6%2442433446%
1893
March1st to 15thNight
11%5%25%424447%47%
2160
16th to endNight
9%414424448%52%
1968
April1st to 15thNight
8%42443446%8%48%
1647
16th to endNight
7%322423347%58%
1650
May1st to 15thNight
7%3133244410%52%
1622
16th to endNight
4313325%5%5%10%53%
1538
June1st to 15thNight
43145%2447%12%48%
1485
16th to endNight
4223325%7%9%13%44%
1485
July1st to 15thNight
4224435%7%10%14%38%
1517
16th to endNight
43245%37%7%8%14%37%
1752
August1st to 15thNight
42145%36%6%8%15%41%
1650
16th to endNight
9%5%34435%5%6%11%40%
1750
September1st to 15thNight
8%5%25%5%35%5%7%13%37%
1710
16th to endNight
8%4244245%6%9%46%
1815
October1st to 15thNight
5%31343335%8%57%
1815
16th to endNight
8%41342334457%
2032
November1st to 15thNight
9%5%14332246%55%
2276
16th to endNight
9%424434345%54%
2340
December1st to 15thNight
10%6%2442445%5%48%
2340
16th to endNight
16%6%25%5%2446%6%39%
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
37%410%17%23%7%
1744
16th to endDay
42%5%6%15%21%8%
1920
February1st to 15thDay
36%310%18%22%8%
1752
16th to endDay
35%7%8%18%22%7%
1580
March1st to 15thDay
35%311%23%20%5%
1800
16th to endDay
33%5%14%20%18%7%
2132
April1st to 15thDay
36%410%23%18%7%
1971
16th to endDay
27%413%27%20%6%
1980
May1st to 15thDay
27%7%17%24%16%6%
1998
16th to endDay
25%7%18%28%17%1
2227
June1st to 15thDay
29%9%21%29%8%
2145
16th to endDay
31%11%22%23%10%1
2145
July1st to 15thDay
41%16%23%15%2
1973
16th to endDay
39%14%26%15%3
1965
August1st to 15thDay
36%12%27%17%5%
1968
16th to endDay
39%11%22%17%7%2
2100
September1st to 15thDay
37%12%19%18%10%2
1909
16th to endDay
33%9%13%18%18%5%
1815
October1st to 15thDay
22%5%14%21%22%14%
1815
16th to endDay
28%45%15%27%18%
1834
November1st to 15thDay
29%48%20%27%10%
1582
16th to endDay
28%5%8%21%22%13%
1620
December1st to 15thDay
35%6%12%21%19%5%
1620
16th to endDay
49%5%7%19%13%4
1728
January1st to 15thNight
38%49%13%25%8%
2192
16th to endNight
42%37%14%22%9%
2304
February1st to 15thNight
34%36%19%24%12%
2112
16th to endNight
40%47%13%21%11%
1893
March1st to 15thNight
36%411%18%22%6%
2160
16th to endNight
31%310%23%20%10%
1968
April1st to 15thNight
32%5%13%19%21%8%
1647
16th to endNight
26%310%30%20%7%
1650
May1st to 15thNight
28%417%23%19%7%
1623
16th to endNight
25%7%19%24%21%2
1540
June1st to 15thNight
26%8%26%24%14%
1485
16th to endNight
26%10%27%24%10%
1485
July1st to 15thNight
29%14%32%17%4
1425
16th to endNight
31%12%32%19%3
1632
August1st to 15thNight
28%12%34%21%3
1638
16th to endNight
37%10%23%19%5%2
1750
September1st to 15thNight
38%8%22%17%11%2
1710
16th to endNight
33%7%16%19%17%5%
1815
October1st to 15thNight
24%5%8%23%22%16%
1815
16th to endNight
30%36%13%27%19%
2032
November1st to 15thNight
30%26%20%28%10%
2276
16th to endNight
31%37%17%22%16%
2340
December1st to 15thNight
37%49%23%20%5%
2340
16th to endNight
44%48%21%15%5%
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
11%10%27%33%16%1
90
16th to endDay
20%11%30%28%9%
96
February1st to 15thDay
11%8%32%22%23%2
90
16th to endDay
8%338%35%13%
81
March1st to 15thDay
18%234%33%11%
90
16th to endDay
15%421%28%26%3
246
April1st to 15thDay
15%422%34%20%2
210
16th to endDay
6%218%32%34%5%
210
May1st to 15thDay
6%310%34%36%7%
228
16th to endDay
5%15%18%46%23%
267
June1st to 15thDay
8%318%40%28%
255
16th to endDay
7%310%37%40%
255
July1st to 15thDay
6%28%37%44%
245
16th to endDay
8%137%34%45%
270
August1st to 15thDay
11%38%34%41%
253
16th to endDay
9%48%33%42%
268
September1st to 15thDay
14%412%35%32%
255
16th to endDay
11%16%24%40%16%
254
October1st to 15thDay
5%12%32%36%12%
255
16th to endDay
10%112%32%29%12%
173
November1st to 15thDay
21%110%36%27%3
90
16th to endDay
7%426%31%25%4
90
December1st to 15thDay
15%320%47%7%5%
90
16th to endDay
29%7%23%15%23%
96
January1st to 15thNight
14%8%29%31%13%2
720
16th to endNight
17%10%29%27%14%
768
February1st to 15thNight
15%6%28%31%15%1
704
16th to endNight
16%7%30%29%15%
631
March1st to 15thNight
12%6%26%33%19%1
720
16th to endNight
12%418%31%28%4
648
April1st to 15thNight
10%419%38%24%2
494
16th to endNight
9%215%34%33%4
495
May1st to 15thNight
10%11%34%35%7%
495
16th to endNight
5%7%20%48%16%
515
June1st to 15thNight
5%1420%49%18%
495
16th to endNight
5%28%47%34%
495
July1st to 15thNight
426%45%39%
465
16th to endNight
416%43%42%
522
August1st to 15thNight
425%41%46%
494
16th to endNight
10%1311%41%31%
525
September1st to 15thNight
10%2314%41%28%
555
16th to endNight
11%7%24%41%13%
657
October1st to 15thNight
7%111%33%38%8%
660
16th to endNight
10%416%27%32%7%
704
November1st to 15thNight
11%417%34%26%6%
700
16th to endNight
12%5%24%34%19%4
720
December1st to 15thNight
12%7%26%27%21%4
720
16th to endNight
18%6%25%29%17%2
768
Page generated at 2017-03-26 12:16:37. Version ac04

Copyright 2017 A. Danko


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