Tacna Observing Station
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tacna Observing Station clear sky chart from 2005-11-05 to 2017-10-16.

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
79%
16026
40%
47269
34%
15987
84%
15987
64%
20705

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
77%
717
36%
2327
35%
716
83%
716
53%
1044
January16th to endNight
70%
768
40%
2442
38%
768
79%
768
51%
1134
February1st to 15thNight
75%
700
41%
2110
38%
699
83%
699
60%
935
February16th to endNight
67%
632
36%
1895
37%
632
73%
632
49%
955
March1st to 15thNight
71%
720
40%
2046
34%
720
80%
720
62%
940
March16th to endNight
74%
768
41%
2112
31%
768
83%
768
66%
960
April1st to 15thNight
66%
719
38%
1932
22%
719
75%
719
66%
884
April16th to endNight
71%
627
47%
1707
28%
627
82%
627
79%
695
May1st to 15thNight
73%
539
42%
1619
31%
539
81%
539
75%
630
May16th to endNight
77%
562
43%
1684
32%
561
83%
561
80%
634
June1st to 15thNight
85%
540
37%
1620
31%
540
87%
540
81%
616
June16th to endNight
92%
540
38%
1620
32%
540
92%
540
81%
617
July1st to 15thNight
89%
510
31%
1530
26%
510
90%
510
65%
664
July16th to endNight
86%
564
34%
1593
27%
531
87%
531
54%
760
August1st to 15thNight
90%
584
36%
1656
28%
581
90%
581
65%
751
August16th to endNight
87%
764
40%
1916
29%
764
88%
764
63%
979
September1st to 15thNight
87%
720
36%
1980
31%
720
89%
720
64%
935
September16th to endNight
86%
716
49%
1980
41%
716
91%
716
80%
814
October1st to 15thNight
79%
720
44%
1980
36%
720
85%
720
73%
861
October16th to endNight
86%
708
45%
2121
41%
708
91%
708
73%
861
November1st to 15thNight
83%
700
42%
2223
41%
700
89%
700
69%
890
November16th to endNight
79%
720
42%
2340
43%
720
85%
720
61%
975
December1st to 15thNight
75%
720
39%
2340
38%
720
82%
720
55%
1039
December16th to endNight
74%
768
39%
2496
38%
768
81%
768
51%
1132

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
111212335%74%
48148
Night
112212235%75%
47467
TransparencyDay
12%2411%23%45%
47843
Night
12%2310%23%46%
47273
SeeingDay
2415%30%33%13%
5778
Night
2112%38%39%5%
16035

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
2212313336%68%
1611
16th to endDay
4212213345%68%
1779
February1st to 15thDay
2212211336%72%
1751
16th to endDay
2212313447%65%
1579
March1st to 15thDay
1112212336%72%
1914
16th to endDay
111213236%75%
2112
April1st to 15thDay
11112347%76%
2013
16th to endDay
1113485%
2253
May1st to 15thDay
11223482%
2331
16th to endDay
1111388%
2429
June1st to 15thDay
1112386%
2340
16th to endDay
111122285%
2340
July1st to 15thDay
1112223346%69%
2340
16th to endDay
3113335%5%6%8%55%
2467
August1st to 15thDay
2223235%5%8%63%
2292
16th to endDay
212223446%69%
2284
September1st to 15thDay
2212224445%66%
1980
16th to endDay
11131383%
1980
October1st to 15thDay
1111125%83%
1980
16th to endDay
1111113481%
1771
November1st to 15thDay
221222479%
1634
16th to endDay
312111136%76%
1620
December1st to 15thDay
221232335%7%65%
1620
16th to endDay
221221335%8%65%
1728
January1st to 15thNight
2212323345%69%
2327
16th to endNight
331321233468%
2442
February1st to 15thNight
1112312236%72%
2101
16th to endNight
2213424447%62%
1895
March1st to 15thNight
2211112245%73%
2046
16th to endNight
111212246%74%
2112
April1st to 15thNight
1111112235%76%
1932
16th to endNight
1111387%
1707
May1st to 15thNight
111222482%
1619
16th to endNight
1112288%
1684
June1st to 15thNight
112484%
1620
16th to endNight
111287%
1620
July1st to 15thNight
111212446%73%
1620
16th to endNight
211221345%10%62%
1701
August1st to 15thNight
11221235%7%71%
1665
16th to endNight
212212346%70%
1916
September1st to 15thNight
1112213335%72%
1980
16th to endNight
111112385%
1980
October1st to 15thNight
11121122481%
1980
16th to endNight
1112235%79%
2121
November1st to 15thNight
111112235%78%
2223
16th to endNight
2212212236%74%
2340
December1st to 15thNight
223223346%68%
2340
16th to endNight
3212313336%67%
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
18%15%10%30%32%
1612
16th to endDay
18%3415%25%32%
1779
February1st to 15thDay
14%15%13%28%36%
1751
16th to endDay
18%25%17%28%28%
1579
March1st to 15thDay
14%128%26%46%
1914
16th to endDay
12%138%29%44%
2112
April1st to 15thDay
9%128%30%46%
2013
16th to endDay
6%118%23%59%
2253
May1st to 15thDay
7%127%21%60%
2331
16th to endDay
5%15%20%65%
2432
June1st to 15thDay
6%1315%72%
2340
16th to endDay
7%1228%77%
2340
July1st to 15thDay
13%36%14%18%42%
2201
16th to endDay
22%5%10%21%24%15%
2312
August1st to 15thDay
16%48%16%22%31%
2277
16th to endDay
15%37%15%30%27%
2284
September1st to 15thDay
17%45%13%24%34%
1980
16th to endDay
7%125%20%61%
1980
October1st to 15thDay
6%1310%23%54%
1980
16th to endDay
8%229%21%55%
1771
November1st to 15thDay
10%1211%27%47%
1634
16th to endDay
12%1311%25%46%
1620
December1st to 15thDay
17%25%16%28%29%
1620
16th to endDay
16%37%20%30%20%
1728
January1st to 15thNight
17%349%25%39%
2327
16th to endNight
20%1312%22%38%
2442
February1st to 15thNight
15%1314%22%41%
2112
16th to endNight
21%3412%22%35%
1895
March1st to 15thNight
14%118%24%49%
2046
16th to endNight
12%1310%25%46%
2112
April1st to 15thNight
12%128%29%45%
1932
16th to endNight
5%128%23%59%
1707
May1st to 15thNight
7%126%22%59%
1620
16th to endNight
5%15%22%64%
1685
June1st to 15thNight
6%1314%72%
1620
16th to endNight
6%136%80%
1620
July1st to 15thNight
11%25%12%23%43%
1530
16th to endNight
15%6%7%21%30%18%
1593
August1st to 15thNight
12%36%17%26%33%
1656
16th to endNight
14%36%15%26%31%
1916
September1st to 15thNight
13%2415%28%34%
1980
16th to endNight
6%127%21%60%
1980
October1st to 15thNight
10%139%22%54%
1980
16th to endNight
8%148%16%59%
2121
November1st to 15thNight
10%128%27%49%
2223
16th to endNight
14%129%23%48%
2340
December1st to 15thNight
16%25%13%27%35%
2340
16th to endNight
18%36%16%28%27%
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
5%421%36%26%5%
90
16th to endDay
46%17%29%31%9%
147
February1st to 15thDay
35%20%26%34%10%
266
16th to endDay
6%7%26%30%21%8%
238
March1st to 15thDay
27%22%24%28%14%
270
16th to endDay
210%25%25%22%14%
288
April1st to 15thDay
29%24%29%24%10%
269
16th to endDay
110%27%33%20%7%
270
May1st to 15thDay
37%23%32%21%10%
288
16th to endDay
15%19%33%35%6%
330
June1st to 15thDay
2114%40%30%8%
315
16th to endDay
18%37%34%16%
315
July1st to 15thDay
26%35%40%14%
305
16th to endDay
2326%42%23%
327
August1st to 15thDay
3331%37%23%
315
16th to endDay
2326%41%25%
332
September1st to 15thDay
4110%31%38%13%
315
16th to endDay
2112%27%39%16%
315
October1st to 15thDay
314%27%42%11%
315
16th to endDay
316%17%42%27%
102
November1st to 15thDay
5%5%41%25%22%
90
16th to endDay
6%6%18%33%25%8%
90
December1st to 15thDay
25%10%23%47%11%
90
16th to endDay
7%5%17%41%25%3
96
January1st to 15thNight
3112%46%30%5%
720
16th to endNight
6%114%44%29%3
768
February1st to 15thNight
2212%44%33%4
704
16th to endNight
4217%46%24%3
632
March1st to 15thNight
2418%38%31%4
720
16th to endNight
2317%37%33%5%
768
April1st to 15thNight
15%22%42%24%3
719
16th to endNight
15%19%41%29%2
627
May1st to 15thNight
320%39%32%2
540
16th to endNight
1316%39%36%3
563
June1st to 15thNight
1110%47%38%1
540
16th to endNight
15%39%50%2
540
July1st to 15thNight
25%31%54%5%
510
16th to endNight
26%28%59%3
564
August1st to 15thNight
2330%57%5%
584
16th to endNight
3225%56%11%
764
September1st to 15thNight
2427%55%9%
720
16th to endNight
110%34%46%7%
716
October1st to 15thNight
1114%36%41%4
720
16th to endNight
19%34%46%8%
708
November1st to 15thNight
1111%42%38%5%
700
16th to endNight
3110%39%37%8%
720
December1st to 15thNight
2113%43%34%3
720
16th to endNight
4212%47%29%3
768
Page generated at 2017-10-17 13:35:22. Version ac04

Copyright 2017 A. Danko


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