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 2017-12-02.

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%
15498
23%
47915
19%
15456
65%
15456
32%
28264

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%
666
26%
2028
21%
666
64%
666
36%
1147
April1st to 15thNight
60%
539
26%
1797
24%
539
66%
539
34%
988
April16th to endNight
65%
540
30%
1800
28%
540
71%
540
41%
895
May1st to 15thNight
69%
539
22%
1769
21%
539
73%
539
39%
935
May16th to endNight
75%
561
23%
1682
22%
561
76%
561
39%
953
June1st to 15thNight
77%
540
15%
1620
15%
540
77%
540
35%
938
June16th to endNight
80%
540
16%
1620
17%
540
80%
540
33%
966
July1st to 15thNight
80%
510
11%
1563
12%
510
80%
510
30%
969
July16th to endNight
77%
564
10%
1772
12%
531
77%
531
28%
1093
August1st to 15thNight
80%
539
11%
1788
14%
536
80%
536
30%
1081
August16th to endNight
70%
573
15%
1910
17%
573
70%
573
23%
1224
September1st to 15thNight
70%
606
16%
1866
16%
606
70%
606
27%
1169
September16th to endNight
72%
717
26%
1980
22%
717
73%
717
35%
1216
October1st to 15thNight
71%
720
32%
1980
26%
720
74%
720
43%
1119
October16th to endNight
61%
768
34%
2217
30%
768
66%
768
39%
1259
November1st to 15thNight
61%
760
30%
2471
28%
760
68%
760
37%
1328
November16th to endNight
54%
780
30%
2535
25%
780
63%
780
35%
1386
December1st to 15thNight
49%
728
25%
2365
20%
728
57%
728
28%
1400
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%
48504
Night
9%42442445%8%48%
48135
TransparencyDay
33%7%15%20%16%5%
48221
Night
33%6%14%20%18%7%
47923
SeeingDay
11%211%22%32%20%
5414
Night
11%416%25%30%12%
15504

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%41443435%7%50%
2204
April1st to 15thDay
12%32342435%7%49%
2151
16th to endDay
6%41442346%8%54%
2160
May1st to 15thDay
6%313325%6%6%9%51%
2181
16th to endDay
5%3134245%6%10%50%
2431
June1st to 15thDay
6%325%5%35%5%8%12%40%
2340
16th to endDay
7%315%5%35%6%9%14%37%
2340
July1st to 15thDay
6%425%7%47%8%10%13%27%
2301
16th to endDay
6%6%26%6%37%7%9%12%30%
2276
August1st to 15thDay
8%5%246%36%8%9%15%28%
2160
16th to endDay
12%425%435%6%6%9%39%
2292
September1st to 15thDay
9%6%25%435%6%7%10%38%
2082
16th to endDay
6%315%435%6%5%8%47%
1980
October1st to 15thDay
6%31222347%8%56%
1980
16th to endDay
8%314313345%59%
2001
November1st to 15thDay
9%314314446%57%
1717
16th to endDay
7%41333335%7%55%
1755
December1st to 15thDay
10%6%25%42445%7%46%
1632
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%
2028
April1st to 15thNight
8%42433446%9%50%
1797
16th to endNight
7%312423347%60%
1800
May1st to 15thNight
7%3133234410%53%
1769
16th to endNight
5%323325%5%5%9%52%
1682
June1st to 15thNight
5%4245%2447%12%46%
1620
16th to endNight
5%223325%7%9%13%43%
1620
July1st to 15thNight
4224435%7%10%14%40%
1655
16th to endNight
5%3245%37%7%8%14%37%
1892
August1st to 15thNight
43145%36%6%8%14%40%
1800
16th to endNight
9%5%344345%6%11%40%
1910
September1st to 15thNight
7%5%25%5%35%6%7%12%38%
1866
16th to endNight
8%4244245%5%9%47%
1980
October1st to 15thNight
6%31243345%8%56%
1980
16th to endNight
8%4135%2334458%
2217
November1st to 15thNight
8%5%14332246%55%
2471
16th to endNight
8%424324345%55%
2535
December1st to 15thNight
10%6%2442445%6%48%
2365
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%21%18%7%
2205
April1st to 15thDay
34%410%24%20%6%
2151
16th to endDay
26%5%14%26%20%6%
2160
May1st to 15thDay
27%7%16%23%19%6%
2181
16th to endDay
26%8%17%27%17%2
2435
June1st to 15thDay
31%9%20%28%8%
2340
16th to endDay
33%11%21%22%10%1
2340
July1st to 15thDay
39%16%23%15%3
2165
16th to endDay
39%14%25%17%3
2133
August1st to 15thDay
38%13%26%16%4
2148
16th to endDay
39%12%21%17%6%2
2292
September1st to 15thDay
36%11%18%18%11%3
2082
16th to endDay
32%10%14%18%18%5%
1980
October1st to 15thDay
23%6%14%21%20%12%
1980
16th to endDay
27%46%15%27%18%
2001
November1st to 15thDay
28%49%22%26%9%
1717
16th to endDay
27%5%8%21%23%13%
1755
December1st to 15thDay
36%6%12%21%19%4
1632
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%
2028
April1st to 15thNight
30%412%19%23%9%
1797
16th to endNight
25%311%31%20%7%
1800
May1st to 15thNight
28%316%22%21%7%
1770
16th to endNight
26%7%19%22%21%2
1684
June1st to 15thNight
28%8%25%23%13%
1620
16th to endNight
28%11%25%23%10%
1620
July1st to 15thNight
28%14%32%18%5%
1563
16th to endNight
31%12%32%19%3
1772
August1st to 15thNight
29%12%33%20%3
1788
16th to endNight
38%10%23%19%5%2
1910
September1st to 15thNight
37%8%21%17%12%3
1866
16th to endNight
32%7%16%20%17%5%
1980
October1st to 15thNight
25%6%8%23%21%14%
1980
16th to endNight
30%35%13%27%19%
2217
November1st to 15thNight
29%37%21%27%10%
2471
16th to endNight
30%37%19%22%15%
2535
December1st to 15thNight
37%49%23%19%5%
2365
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%321%30%25%3
270
April1st to 15thDay
14%323%32%23%2
270
16th to endDay
5%317%30%36%5%
270
May1st to 15thDay
6%410%34%35%7%
288
16th to endDay
7%16%25%40%18%
331
June1st to 15thDay
12%220%38%24%
315
16th to endDay
11%1313%35%33%
315
July1st to 15thDay
5%26%34%50%
305
16th to endDay
9%38%35%42%
326
August1st to 15thDay
13%27%36%39%
313
16th to endDay
9%49%32%41%
332
September1st to 15thDay
14%16%14%33%29%
315
16th to endDay
10%5%23%43%16%
314
October1st to 15thDay
6%13%32%31%14%
315
16th to endDay
10%317%30%27%11%
228
November1st to 15thDay
15%10%37%33%2
135
16th to endDay
7%321%30%33%3
135
December1st to 15thDay
15%319%45%10%5%
94
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
666
April1st to 15thNight
10%418%38%26%2
539
16th to endNight
8%215%32%34%5%
540
May1st to 15thNight
10%111%34%34%7%
540
16th to endNight
6%7%22%46%15%
563
June1st to 15thNight
7%320%48%19%
540
16th to endNight
7%39%46%32%
540
July1st to 15thNight
426%42%43%
510
16th to endNight
417%43%42%
564
August1st to 15thNight
5%2441%45%
539
16th to endNight
10%1310%41%32%
573
September1st to 15thNight
9%25%16%39%26%
606
16th to endNight
11%7%23%42%14%
717
October1st to 15thNight
8%112%31%37%8%
720
16th to endNight
10%417%28%32%6%
768
November1st to 15thNight
11%316%35%27%5%
760
16th to endNight
11%5%23%33%22%4
780
December1st to 15thNight
12%7%26%27%21%4
728
16th to endNight
18%6%25%29%17%2
768
Page generated at 2017-12-03 10:16:46. Version ac04

Copyright 2017 A. Danko


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