Lagoon Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lagoon Observatory clear sky chart from 2005-11-05 to 2017-09-22.

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
75%
15848
33%
46908
29%
15801
78%
15801
49%
23546

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
64%
719
29%
2422
27%
716
72%
716
41%
1197
January16th to endNight
59%
768
34%
2434
26%
768
71%
768
38%
1282
February1st to 15thNight
68%
698
36%
2102
32%
697
76%
697
44%
1096
February16th to endNight
62%
632
28%
1895
30%
632
64%
632
33%
1109
March1st to 15thNight
70%
720
28%
2145
28%
720
77%
720
49%
1060
March16th to endNight
73%
768
30%
1995
24%
768
77%
768
50%
1096
April1st to 15thNight
69%
719
31%
1799
19%
719
73%
719
50%
1006
April16th to endNight
75%
720
31%
1800
18%
720
77%
720
54%
963
May1st to 15thNight
75%
672
26%
1752
17%
672
76%
672
49%
967
May16th to endNight
80%
561
30%
1685
24%
561
82%
561
54%
805
June1st to 15thNight
79%
387
25%
1467
27%
387
80%
387
38%
716
June16th to endNight
87%
360
32%
1440
41%
360
87%
360
52%
564
July1st to 15thNight
88%
340
31%
1360
37%
340
89%
340
50%
542
July16th to endNight
82%
628
29%
1651
23%
589
84%
589
49%
848
August1st to 15thNight
82%
717
32%
1790
21%
713
82%
713
57%
957
August16th to endNight
88%
764
36%
1910
24%
764
88%
764
61%
978
September1st to 15thNight
83%
720
34%
1800
28%
720
83%
720
55%
988
September16th to endNight
86%
683
39%
1887
37%
683
87%
683
63%
878
October1st to 15thNight
81%
660
36%
1880
36%
660
83%
660
57%
913
October16th to endNight
80%
704
40%
2112
43%
704
82%
704
56%
990
November1st to 15thNight
78%
700
36%
2256
37%
700
83%
700
56%
988
November16th to endNight
72%
720
37%
2340
37%
720
77%
720
50%
1080
December1st to 15thNight
66%
720
35%
2340
33%
720
74%
720
40%
1184
December16th to endNight
60%
768
31%
2646
28%
768
69%
768
36%
1339

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
4312212347%64%
47954
Night
5%313213347%63%
47109
TransparencyDay
21%38%18%26%20%
47644
Night
21%27%17%26%23%
46919
SeeingDay
5%416%39%27%5%
6014
Night
6%28%28%39%15%
15858

By Month

Percentage Cloud Cover SW (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
7%313323346%61%
1513
16th to endDay
11%323212236%60%
1788
February1st to 15thDay
9%322212245%61%
1751
16th to endDay
10%313323346%56%
1579
March1st to 15thDay
431232345%7%60%
1812
16th to endDay
5%31222335%9%59%
2229
April1st to 15thDay
6%412213348%61%
2149
16th to endDay
4312211247%68%
2160
May1st to 15thDay
4412213248%63%
2196
16th to endDay
321321225%9%65%
2429
June1st to 15thDay
47%23213348%56%
2490
16th to endDay
1312212347%70%
2520
July1st to 15thDay
331221325%9%63%
2520
16th to endDay
3213222248%65%
2400
August1st to 15thDay
2312211248%66%
2160
16th to endDay
212213348%70%
2292
September1st to 15thDay
123212347%70%
2160
16th to endDay
223212237%71%
1885
October1st to 15thDay
5%32212345%68%
1748
16th to endDay
3313212346%67%
1760
November1st to 15thDay
2213212335%69%
1601
16th to endDay
4212212237%67%
1620
December1st to 15thDay
7%31322345%9%56%
1620
16th to endDay
10%214213337%59%
1572
January1st to 15thNight
6%412323347%60%
2422
16th to endNight
10%413212335%59%
2434
February1st to 15thNight
6%423312345%62%
2101
16th to endNight
13%424323225%54%
1895
March1st to 15thNight
5%31321335%7%62%
2145
16th to endNight
432322335%7%61%
1995
April1st to 15thNight
6%412212225%65%
1799
16th to endNight
4412112337%67%
1800
May1st to 15thNight
4412313237%62%
1752
16th to endNight
2322112236%70%
1684
June1st to 15thNight
342441335%8%59%
1467
16th to endNight
312322249%65%
1440
July1st to 15thNight
321222236%8%64%
1440
16th to endNight
341422345%10%57%
1764
August1st to 15thNight
23243222411%60%
1800
16th to endNight
113324448%64%
1910
September1st to 15thNight
331432435%10%58%
1800
16th to endNight
1223212245%72%
1887
October1st to 15thNight
3213113236%70%
1880
16th to endNight
4412112225%70%
2112
November1st to 15thNight
321222245%72%
2256
16th to endNight
3213313336%67%
2340
December1st to 15thNight
7%323313236%61%
2340
16th to endNight
10%412213336%60%
2646

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
26%28%14%22%25%
1513
16th to endDay
27%26%18%18%25%
1788
February1st to 15thDay
24%36%16%27%21%
1751
16th to endDay
31%37%20%26%10%
1579
March1st to 15thDay
23%410%20%23%17%
1812
16th to endDay
23%5%13%23%20%12%
2229
April1st to 15thDay
23%311%27%23%9%
2149
16th to endDay
17%411%23%27%15%
2160
May1st to 15thDay
21%5%10%21%24%16%
2196
16th to endDay
19%6%11%29%26%8%
2432
June1st to 15thDay
27%5%9%17%29%12%
2490
16th to endDay
16%29%11%33%26%
2520
July1st to 15thDay
21%27%14%25%28%
2371
16th to endDay
20%49%20%27%17%
2250
August1st to 15thDay
20%17%14%34%20%
2146
16th to endDay
15%28%11%38%23%
2292
September1st to 15thDay
17%36%16%28%27%
2160
16th to endDay
18%16%16%30%25%
1885
October1st to 15thDay
18%28%23%24%23%
1748
16th to endDay
20%27%15%23%29%
1760
November1st to 15thDay
19%25%15%24%32%
1601
16th to endDay
19%39%16%21%30%
1620
December1st to 15thDay
25%5%7%16%23%20%
1620
16th to endDay
25%5%9%18%21%19%
1572
January1st to 15thNight
25%27%14%23%26%
2422
16th to endNight
28%26%14%16%31%
2434
February1st to 15thNight
24%35%16%24%25%
2112
16th to endNight
35%25%17%23%15%
1895
March1st to 15thNight
20%310%20%25%18%
2145
16th to endNight
22%312%23%22%14%
1995
April1st to 15thNight
24%28%28%24%11%
1799
16th to endNight
19%39%23%25%18%
1800
May1st to 15thNight
23%410%21%25%14%
1753
16th to endNight
17%39%28%31%9%
1685
June1st to 15thNight
25%410%18%31%9%
1467
16th to endNight
17%17%12%33%27%
1440
July1st to 15thNight
16%26%11%27%35%
1360
16th to endNight
21%48%24%23%18%
1651
August1st to 15thNight
20%15%12%34%24%
1790
16th to endNight
16%37%10%39%24%
1910
September1st to 15thNight
22%26%11%28%29%
1800
16th to endNight
16%5%12%34%29%
1887
October1st to 15thNight
16%36%19%27%25%
1880
16th to endNight
18%16%14%23%35%
2112
November1st to 15thNight
16%26%15%23%36%
2256
16th to endNight
19%25%18%21%33%
2340
December1st to 15thNight
26%28%15%21%25%
2340
16th to endNight
26%48%17%23%20%
2646

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
12%433%41%8%
141
16th to endDay
13%10%23%40%9%1
266
February1st to 15thDay
12%6%25%36%16%3
266
16th to endDay
15%7%22%36%15%1
238
March1st to 15thDay
5%9%24%39%18%2
270
16th to endDay
5%7%22%41%20%1
288
April1st to 15thDay
7%8%24%38%15%5%
269
16th to endDay
39%28%37%17%4
270
May1st to 15thDay
5%5%22%35%25%4
288
16th to endDay
35%20%39%25%4
330
June1st to 15thDay
8%320%37%24%6%
315
16th to endDay
5%39%43%9%
315
July1st to 15thDay
4334%47%9%
305
16th to endDay
3328%48%15%
327
August1st to 15thDay
25%43%40%7%
315
16th to endDay
115%37%45%9%
332
September1st to 15thDay
4111%47%28%6%
315
16th to endDay
1211%42%34%6%
280
October1st to 15thDay
5%319%43%25%2
255
16th to endDay
5%216%43%27%3
272
November1st to 15thDay
3415%37%18%19%
107
16th to endDay
412%25%36%17%3
90
December1st to 15thDay
10%7%13%42%24%2
90
16th to endDay
5%17%30%31%14%1
70
January1st to 15thNight
9%314%41%23%6%
720
16th to endNight
12%5%15%34%27%3
768
February1st to 15thNight
9%210%38%30%8%
704
16th to endNight
15%49%37%27%5%
632
March1st to 15thNight
7%310%37%32%7%
720
16th to endNight
6%211%31%40%7%
768
April1st to 15thNight
8%211%31%37%6%
719
16th to endNight
5%49%31%38%10%
720
May1st to 15thNight
7%27%29%39%13%
673
16th to endNight
218%28%44%14%
563
June1st to 15thNight
3427%45%18%
387
16th to endNight
214%60%21%
360
July1st to 15thNight
5%252%38%
340
16th to endNight
5%16%41%45%
628
August1st to 15thNight
4111%53%30%
717
16th to endNight
18%50%38%
764
September1st to 15thNight
4213%50%29%
720
16th to endNight
2219%53%22%
683
October1st to 15thNight
46%29%45%12%
660
16th to endNight
7%1430%41%14%
704
November1st to 15thNight
428%38%33%13%
700
16th to endNight
4211%35%35%9%
720
December1st to 15thNight
8%412%37%30%6%
720
16th to endNight
13%7%13%36%24%3
768
Page generated at 2017-09-23 03:43:37. Version ac04

Copyright 2017 A. Danko


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