Useppa Island Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Useppa Island Observatory clear sky chart from 2005-11-05 to 2017-09-24.

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
58%
15992
19%
47061
15%
15953
63%
15953
26%
29708

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
49%
717
18%
2327
13%
716
56%
716
22%
1427
January16th to endNight
47%
768
25%
2373
19%
768
54%
768
25%
1438
February1st to 15thNight
50%
701
24%
2105
18%
699
57%
699
29%
1273
February16th to endNight
54%
631
28%
1836
16%
631
65%
631
33%
1040
March1st to 15thNight
55%
720
30%
1980
18%
720
65%
720
39%
1094
March16th to endNight
57%
768
27%
2112
18%
768
63%
768
35%
1202
April1st to 15thNight
63%
718
23%
1976
17%
718
68%
718
38%
1083
April16th to endNight
57%
720
26%
1890
15%
720
64%
720
33%
1128
May1st to 15thNight
68%
587
25%
1667
20%
587
71%
587
40%
900
May16th to endNight
67%
561
21%
1683
15%
561
71%
561
30%
1005
June1st to 15thNight
59%
540
8%
1620
7%
540
60%
540
18%
1160
June16th to endNight
64%
540
7%
1620
4%
540
65%
540
18%
1177
July1st to 15thNight
65%
510
5%
1530
5%
510
65%
510
17%
1163
July16th to endNight
67%
564
6%
1595
7%
531
71%
531
21%
1150
August1st to 15thNight
64%
539
5%
1697
6%
536
65%
536
19%
1204
August16th to endNight
65%
723
6%
2060
6%
723
65%
723
17%
1543
September1st to 15thNight
63%
720
6%
1980
6%
720
63%
720
17%
1482
September16th to endNight
55%
693
7%
1914
6%
693
58%
693
14%
1473
October1st to 15thNight
66%
660
23%
1845
22%
660
69%
660
28%
1157
October16th to endNight
54%
704
22%
2112
20%
704
61%
704
26%
1328
November1st to 15thNight
57%
700
29%
2101
26%
700
63%
700
32%
1209
November16th to endNight
54%
720
27%
2202
22%
720
63%
720
30%
1271
December1st to 15thNight
54%
720
23%
2340
21%
720
60%
720
26%
1404
December16th to endNight
57%
768
24%
2496
21%
768
64%
768
30%
1397

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
6%4245%35%6%7%10%43%
47850
Night
6%425%5%35%6%7%10%43%
47267
TransparencyDay
33%10%19%19%12%4
47551
Night
33%9%17%19%14%4
47070
SeeingDay
8%8%6%18%29%28%
5841
Night
7%15%9%24%28%13%
16001

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
9%5%25%4245%5%8%44%
1611
16th to endDay
8%5%23425%5%48%48%
1848
February1st to 15thDay
9%5%2442245%5%52%
1750
16th to endDay
5%41332346%8%55%
1636
March1st to 15thDay
22133245%6%9%59%
1980
16th to endDay
5%31442447%6%55%
2111
April1st to 15thDay
421332337%10%56%
1972
16th to endDay
5%312425%36%10%55%
2067
May1st to 15thDay
211222345%10%62%
2292
16th to endDay
5%213425%6%7%10%46%
2431
June1st to 15thDay
10%6%37%5%35%6%8%11%30%
2340
16th to endDay
6%5%25%6%37%7%10%13%32%
2340
July1st to 15thDay
6%437%7%48%9%10%13%25%
2340
16th to endDay
5%425%6%49%10%12%15%22%
2465
August1st to 15thDay
4426%7%48%9%9%13%27%
2248
16th to endDay
8%427%8%48%7%10%12%26%
2129
September1st to 15thDay
6%5%35%6%5%7%7%11%11%29%
1980
16th to endDay
8%7%26%7%5%7%6%8%12%27%
1905
October1st to 15thDay
5%4145%45%5%6%9%45%
1785
16th to endDay
8%415%4346%5%7%47%
1760
November1st to 15thDay
6%423325%46%8%53%
1757
16th to endDay
6%3244335%5%9%51%
1755
December1st to 15thDay
8%5%35%43445%8%45%
1620
16th to endDay
5%42442445%10%50%
1728
January1st to 15thNight
7%5%25%6%35%6%7%8%40%
2327
16th to endNight
9%4245%35%5%6%8%44%
2373
February1st to 15thNight
9%5%25%435%345%49%
2103
16th to endNight
5%3135%245%6%9%51%
1836
March1st to 15thNight
4212325%5%6%9%55%
1980
16th to endNight
332343446%9%54%
2112
April1st to 15thNight
331332446%10%55%
1976
16th to endNight
43145%3346%9%51%
1890
May1st to 15thNight
2234245%5%10%57%
1667
16th to endNight
6%3146%3446%8%48%
1682
June1st to 15thNight
9%5%25%7%45%8%9%10%31%
1620
16th to endNight
5%426%7%46%7%10%15%30%
1620
July1st to 15thNight
45%36%8%5%7%7%9%13%28%
1620
16th to endNight
34246%38%8%11%15%31%
1703
August1st to 15thNight
5%5%27%6%46%7%9%12%32%
1708
16th to endNight
9%426%7%5%7%8%8%12%28%
2060
September1st to 15thNight
7%5%27%7%47%8%9%12%26%
1980
16th to endNight
9%8%27%6%5%6%8%9%11%23%
1914
October1st to 15thNight
5%4245%35%6%8%11%43%
1845
16th to endNight
11%5%15%5%35%6%5%7%42%
2112
November1st to 15thNight
6%425%4335%5%6%51%
2101
16th to endNight
7%325%4335%5%9%49%
2202
December1st to 15thNight
7%5%25%5%35%46%8%45%
2340
16th to endNight
5%4235%245%5%10%49%
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
35%6%12%24%16%3
1612
16th to endDay
32%6%11%23%20%6%
1848
February1st to 15thDay
30%5%10%22%19%11%
1752
16th to endDay
24%7%14%22%23%7%
1636
March1st to 15thDay
20%5%15%30%21%7%
1980
16th to endDay
26%6%12%25%20%7%
2112
April1st to 15thDay
21%5%22%26%18%4
1972
16th to endDay
25%6%15%24%24%4
2067
May1st to 15thDay
17%7%17%30%20%5%
2292
16th to endDay
29%10%19%26%12%
2435
June1st to 15thDay
43%12%25%15%2
2340
16th to endDay
39%16%27%13%2
2340
July1st to 15thDay
45%19%26%7%1
2201
16th to endDay
43%20%25%10%
2310
August1st to 15thDay
41%19%30%8%
2235
16th to endDay
45%18%26%8%1
2129
September1st to 15thDay
42%16%28%10%1
1980
16th to endDay
46%14%22%11%4
1905
October1st to 15thDay
34%9%14%20%16%4
1785
16th to endDay
33%7%12%17%19%9%
1760
November1st to 15thDay
27%6%11%24%21%9%
1757
16th to endDay
28%8%12%20%18%11%
1755
December1st to 15thDay
36%5%15%22%15%4
1620
16th to endDay
28%6%16%25%17%5%
1728
January1st to 15thNight
36%7%14%24%13%3
2327
16th to endNight
35%6%10%22%19%5%
2373
February1st to 15thNight
34%5%9%19%20%11%
2112
16th to endNight
27%6%12%24%20%8%
1836
March1st to 15thNight
22%6%14%29%21%5%
1980
16th to endNight
25%6%13%26%21%6%
2112
April1st to 15thNight
22%6%18%30%17%4
1976
16th to endNight
27%6%13%22%25%4
1890
May1st to 15thNight
20%7%18%27%20%5%
1668
16th to endNight
30%7%18%27%15%
1684
June1st to 15thNight
42%13%23%15%4
1620
16th to endNight
38%19%25%13%3
1620
July1st to 15thNight
42%19%28%7%1
1530
16th to endNight
35%20%30%13%
1595
August1st to 15thNight
38%17%33%9%
1697
16th to endNight
44%17%27%9%
2060
September1st to 15thNight
45%15%26%10%1
1980
16th to endNight
45%18%21%10%3
1914
October1st to 15thNight
31%10%16%16%19%5%
1845
16th to endNight
38%6%10%16%20%7%
2112
November1st to 15thNight
30%5%10%22%22%8%
2101
16th to endNight
30%6%11%21%19%10%
2202
December1st to 15thNight
35%5%13%23%16%4
2340
16th to endNight
30%6%14%22%21%4
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
15%5%15%32%18%12%
90
16th to endDay
14%9%20%28%21%5%
96
February1st to 15thDay
5%6%13%32%27%14%
90
16th to endDay
7%8%16%38%27%2
137
March1st to 15thDay
311%14%38%27%4
270
16th to endDay
5%12%13%36%26%5%
288
April1st to 15thDay
411%11%32%33%7%
270
16th to endDay
8%11%6%30%37%5%
270
May1st to 15thDay
411%428%36%14%
288
16th to endDay
39%411%37%32%
331
June1st to 15thDay
13%10%5%10%27%32%
315
16th to endDay
5%9%15%21%56%
315
July1st to 15thDay
46%1321%62%
305
16th to endDay
7%9%16%24%49%
326
August1st to 15thDay
7%6%15%24%54%
313
16th to endDay
12%426%28%45%
332
September1st to 15thDay
10%5%27%24%49%
315
16th to endDay
10%5%26%32%43%
287
October1st to 15thDay
9%6%5%20%37%21%
255
16th to endDay
12%6%6%29%31%13%
272
November1st to 15thDay
8%10%8%22%33%16%
265
16th to endDay
7%10%12%26%35%8%
225
December1st to 15thDay
13%17%27%36%4
90
16th to endDay
6%8%13%46%25%
96
January1st to 15thNight
10%20%13%29%24%2
720
16th to endNight
9%20%17%32%19%
768
February1st to 15thNight
7%18%16%36%18%1
704
16th to endNight
6%17%16%37%21%
631
March1st to 15thNight
5%17%17%32%24%2
720
16th to endNight
418%14%34%25%2
768
April1st to 15thNight
317%11%36%28%2
718
16th to endNight
6%17%11%33%28%2
720
May1st to 15thNight
216%6%32%36%5%
588
16th to endNight
417%321%42%11%
563
June1st to 15thNight
9%17%210%38%20%
540
16th to endNight
5%16%18%27%40%
540
July1st to 15thNight
412%15%28%47%
510
16th to endNight
416%6%25%45%
564
August1st to 15thNight
7%10%26%30%43%
539
16th to endNight
11%8%39%32%34%
723
September1st to 15thNight
8%9%310%35%32%
720
16th to endNight
14%9%314%35%22%
693
October1st to 15thNight
7%9%5%27%36%12%
660
16th to endNight
14%10%10%26%30%7%
704
November1st to 15thNight
9%15%10%34%26%4
700
16th to endNight
7%17%14%32%24%3
720
December1st to 15thNight
9%18%12%29%26%3
720
16th to endNight
417%13%27%31%4
768
Page generated at 2017-09-25 09:02:20. Version ac04

Copyright 2017 A. Danko


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