Observatorio Las Acacias
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatorio Las Acacias clear sky chart from 2005-11-05 to 2017-05-01.

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
66%
15744
35%
45682
27%
15700
73%
15700
51%
22700

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
51%
719
29%
2327
22%
716
62%
716
37%
1211
January16th to endNight
49%
768
35%
2313
22%
768
65%
768
35%
1267
February1st to 15thNight
51%
700
32%
2111
21%
700
65%
700
38%
1164
February16th to endNight
45%
632
29%
1895
25%
632
54%
632
30%
1130
March1st to 15thNight
54%
720
31%
2137
26%
720
64%
720
40%
1142
March16th to endNight
61%
768
32%
2080
25%
768
68%
768
47%
1133
April1st to 15thNight
52%
719
33%
1799
18%
719
60%
719
48%
1021
April16th to endNight
59%
720
37%
1800
19%
720
66%
720
60%
931
May1st to 15thNight
62%
520
38%
1516
24%
520
69%
520
57%
707
May16th to endNight
68%
514
35%
1541
26%
513
72%
513
61%
683
June1st to 15thNight
77%
495
38%
1485
32%
495
79%
495
74%
599
June16th to endNight
87%
495
37%
1485
32%
495
87%
495
82%
559
July1st to 15thNight
92%
465
33%
1395
27%
465
93%
465
70%
590
July16th to endNight
88%
564
33%
1506
25%
528
89%
528
61%
691
August1st to 15thNight
93%
657
38%
1640
25%
653
94%
653
75%
764
August16th to endNight
91%
700
41%
1750
29%
700
92%
700
71%
849
September1st to 15thNight
89%
660
39%
1740
33%
660
90%
660
70%
801
September16th to endNight
82%
656
45%
1815
38%
656
88%
656
75%
769
October1st to 15thNight
69%
660
39%
1815
32%
660
76%
660
54%
907
October16th to endNight
72%
704
41%
2081
34%
704
81%
704
57%
961
November1st to 15thNight
61%
700
35%
2275
29%
700
73%
700
52%
1031
November16th to endNight
58%
720
36%
2340
31%
720
70%
720
45%
1127
December1st to 15thNight
56%
720
32%
2340
27%
720
65%
720
35%
1255
December16th to endNight
44%
768
31%
2496
22%
768
58%
768
30%
1408

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
4312213335%67%
46068
Night
4412213335%66%
45882
TransparencyDay
19%2413%26%32%
45768
Night
20%2413%25%33%
45684
SeeingDay
6%13%34%30%10%4
5337
Night
6%5%17%29%31%10%
15751

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
8%5%13213445%58%
1611
16th to endDay
9%5%13323446%55%
1908
February1st to 15thDay
6%5%1332335%6%57%
1751
16th to endDay
10%6%235%24346%48%
1579
March1st to 15thDay
6%412313347%60%
1821
16th to endDay
5%412324436%61%
2142
April1st to 15thDay
7%41331435%460%
2149
16th to endDay
4311112236%71%
2160
May1st to 15thDay
2212112235%73%
2113
16th to endDay
2211235%78%
2221
June1st to 15thDay
111223479%
2145
16th to endDay
1111111286%
2145
July1st to 15thDay
1212212346%71%
2145
16th to endDay
22122245%5%8%62%
2240
August1st to 15thDay
11213335%75%
1980
16th to endDay
212223445%70%
2100
September1st to 15thDay
2111222335%71%
1889
16th to endDay
11221122281%
1815
October1st to 15thDay
3312212235%69%
1815
16th to endDay
231321213473%
1787
November1st to 15thDay
4313222335%66%
1584
16th to endDay
5%41232334464%
1620
December1st to 15thDay
8%423424447%53%
1620
16th to endDay
9%6%24414436%53%
1728
January1st to 15thNight
6%41242435%5%58%
2327
16th to endNight
9%5%13324336%56%
2313
February1st to 15thNight
5%6%145%24336%56%
2101
16th to endNight
9%7%24434445%47%
1895
March1st to 15thNight
7%5%23323446%57%
2137
16th to endNight
45%1432335%7%59%
2080
April1st to 15thNight
5%5%23323336%59%
1799
16th to endNight
4422212225%69%
1800
May1st to 15thNight
2312223237%68%
1516
16th to endNight
15%1221223474%
1540
June1st to 15thNight
21111112380%
1485
16th to endNight
1111388%
1485
July1st to 15thNight
112112245%76%
1485
16th to endNight
2112213347%70%
1617
August1st to 15thNight
1112247%76%
1650
16th to endNight
21111123478%
1750
September1st to 15thNight
11222222379%
1740
16th to endNight
2111112284%
1815
October1st to 15thNight
341311233469%
1815
16th to endNight
1312213335%69%
2081
November1st to 15thNight
4213312235%68%
2275
16th to endNight
45%1322234463%
2340
December1st to 15thNight
8%6%13313446%54%
2340
16th to endNight
9%8%23424335%53%
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
27%2411%26%26%
1612
16th to endDay
28%37%11%23%25%
1908
February1st to 15thDay
27%1412%24%28%
1751
16th to endDay
35%25%15%23%17%
1579
March1st to 15thDay
23%3313%28%27%
1821
16th to endDay
24%26%14%32%19%
2142
April1st to 15thDay
24%35%16%33%17%
2149
16th to endDay
15%1419%30%26%
2160
May1st to 15thDay
14%1415%28%35%
2113
16th to endDay
10%1419%37%26%
2224
June1st to 15thDay
9%1312%23%48%
2145
16th to endDay
7%11416%67%
2145
July1st to 15thDay
14%4410%22%43%
2006
16th to endDay
16%6%10%23%24%19%
2089
August1st to 15thDay
11%5%414%28%35%
1966
16th to endDay
16%45%11%31%30%
2100
September1st to 15thDay
15%46%8%26%38%
1889
16th to endDay
11%127%29%48%
1815
October1st to 15thDay
18%1315%25%35%
1815
16th to endDay
16%249%22%44%
1787
November1st to 15thDay
20%1412%23%37%
1584
16th to endDay
22%2412%22%34%
1620
December1st to 15thDay
30%35%15%19%25%
1620
16th to endDay
33%36%15%22%18%
1728
January1st to 15thNight
26%35%12%22%29%
2327
16th to endNight
29%35%12%19%30%
2313
February1st to 15thNight
29%3311%20%31%
2112
16th to endNight
37%2412%21%21%
1895
March1st to 15thNight
26%3414%24%27%
2137
16th to endNight
24%35%15%29%22%
2080
April1st to 15thNight
24%2416%32%18%
1799
16th to endNight
18%316%31%29%
1800
May1st to 15thNight
15%2411%29%35%
1517
16th to endNight
14%1416%33%29%
1541
June1st to 15thNight
9%311%23%51%
1485
16th to endNight
5%115%14%72%
1485
July1st to 15thNight
9%2411%22%48%
1395
16th to endNight
13%38%22%28%22%
1506
August1st to 15thNight
8%3418%27%37%
1640
16th to endNight
10%3312%33%35%
1750
September1st to 15thNight
11%238%31%43%
1740
16th to endNight
8%117%33%47%
1815
October1st to 15thNight
18%2314%26%34%
1815
16th to endNight
16%2410%23%43%
2081
November1st to 15thNight
19%1312%27%35%
2275
16th to endNight
22%2413%23%33%
2340
December1st to 15thNight
29%35%14%22%24%
2340
16th to endNight
34%26%15%19%21%
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
31%11%24%27%5%
90
16th to endDay
14%21%31%26%4
276
February1st to 15thDay
8%17%45%22%6%
266
16th to endDay
13%28%30%19%7%
238
March1st to 15thDay
11%21%33%21%10%2
270
16th to endDay
6%21%41%18%7%3
288
April1st to 15thDay
11%23%40%15%6%3
269
16th to endDay
5%24%40%21%5%2
270
May1st to 15thDay
6%23%40%23%41
229
16th to endDay
6%16%43%24%6%3
266
June1st to 15thDay
111%46%29%7%3
255
16th to endDay
2336%34%14%8%
255
July1st to 15thDay
1131%46%13%6%
245
16th to endDay
219%48%18%10%
271
August1st to 15thDay
129%43%12%12%
255
16th to endDay
2118%49%16%11%
268
September1st to 15thDay
4234%40%12%5%
255
16th to endDay
5%10%32%37%9%3
255
October1st to 15thDay
118%41%27%8%
255
16th to endDay
5%8%33%35%16%1
195
November1st to 15thDay
7%13%31%18%21%7%
90
16th to endDay
15%18%30%26%8%
90
December1st to 15thDay
412%22%35%25%
90
16th to endDay
14%20%33%25%6%
96
January1st to 15thNight
9%9%24%35%15%6%
720
16th to endNight
13%12%19%33%18%3
768
February1st to 15thNight
9%7%25%30%22%4
704
16th to endNight
13%11%24%30%16%4
632
March1st to 15thNight
8%10%24%31%20%4
720
16th to endNight
5%7%19%33%26%6%
768
April1st to 15thNight
8%8%26%32%19%4
719
16th to endNight
5%8%25%29%24%7%
720
May1st to 15thNight
25%24%34%25%6%
521
16th to endNight
25%19%34%30%8%
515
June1st to 15thNight
1115%40%34%6%
495
16th to endNight
19%32%46%9%
495
July1st to 15thNight
1221%60%13%
465
16th to endNight
11218%57%18%
564
August1st to 15thNight
115%56%25%
657
16th to endNight
2212%48%33%
700
September1st to 15thNight
1321%53%20%
660
16th to endNight
3111%27%41%15%
656
October1st to 15thNight
47%15%35%30%6%
660
16th to endNight
3215%30%33%12%
704
November1st to 15thNight
6%322%32%25%8%
700
16th to endNight
7%6%21%31%24%8%
720
December1st to 15thNight
12%8%17%33%23%5%
720
16th to endNight
14%11%24%30%14%4
768
Page generated at 2017-05-02 05:43:25. Version ac04

Copyright 2017 A. Danko


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