Las Brisas Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Las Brisas Observatory clear sky chart from 2005-11-06 to 2024-11-11.

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
41%
25387
26%
98383
13%
25129
55%
25129
31%
48127

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 10thNight
32%
941
30%
4328
11%
926
51%
926
27%
1947
January11th to 20thNight
27%
865
37%
4127
13%
845
49%
845
32%
1551
January21st to endNight
30%
827
22%
4304
13%
814
53%
814
27%
1970
February1st to 10thNight
20%
760
29%
2470
7%
760
45%
760
37%
1207
February11th to 20thNight
24%
744
28%
2231
7%
740
45%
740
34%
1190
February21st to endNight
21%
628
35%
1884
7%
628
50%
628
39%
924
March1st to 10thNight
28%
754
31%
3642
8%
744
46%
744
27%
1668
March11th to 20thNight
37%
751
23%
3459
11%
740
47%
740
24%
1845
March21st to endNight
27%
701
20%
3482
8%
684
48%
684
24%
1534
April1st to 10thNight
28%
570
27%
1900
9%
570
51%
570
32%
946
April11th to 20thNight
32%
563
22%
1877
11%
563
49%
563
28%
1047
April21st to endNight
31%
570
21%
1900
9%
570
48%
570
29%
1078
May1st to 10thNight
37%
569
25%
2902
13%
559
48%
559
20%
1412
May11th to 20thNight
45%
553
13%
2481
10%
541
50%
541
20%
1324
May21st to endNight
41%
606
14%
2732
9%
593
51%
593
25%
1239
June1st to 10thNight
58%
570
21%
1520
15%
570
63%
570
41%
854
June11th to 20thNight
57%
570
24%
1520
16%
570
63%
570
47%
815
June21st to endNight
62%
570
21%
1520
17%
570
65%
570
40%
876
July1st to 10thNight
64%
545
24%
2170
15%
535
67%
535
23%
1235
July11th to 20thNight
70%
537
20%
2155
19%
533
71%
533
30%
1111
July21st to endNight
67%
609
14%
2345
11%
569
70%
569
19%
1350
August1st to 10thNight
64%
557
11%
2706
12%
545
66%
545
15%
1702
August11th to 20thNight
66%
551
15%
2910
23%
543
70%
543
21%
1511
August21st to endNight
66%
616
19%
3254
23%
605
71%
605
23%
1606
September1st to 10thNight
65%
570
27%
1900
25%
570
71%
570
34%
1057
September11th to 20thNight
61%
570
33%
1913
28%
570
69%
570
43%
938
September21st to endNight
54%
570
30%
2090
22%
570
67%
570
38%
1007
October1st to 10thNight
48%
734
43%
3358
14%
730
60%
730
37%
1323
October11th to 20thNight
48%
752
27%
3480
15%
740
64%
740
37%
1548
October21st to endNight
42%
846
42%
3808
15%
829
58%
829
40%
1398
November1st to 10thNight
38%
975
34%
2535
12%
975
52%
975
52%
1297
November11th to 20thNight
34%
953
37%
2477
12%
953
50%
953
49%
1266
November21st to endNight
37%
950
33%
2536
12%
950
52%
950
45%
1337
December1st to 10thNight
32%
950
29%
2660
10%
950
48%
950
40%
1365
December11th to 20thNight
26%
949
28%
3126
9%
949
44%
949
37%
1522
December21st to endNight
22%
1041
19%
4681
7%
1026
42%
1026
24%
2127

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
35%26%5%45%46%8%50%
105177
Night
25%25%44446%8%56%
102715
TransparencyDay
27%7%13%22%22%9%
104924
Night
23%7%14%26%23%8%
102558
SeeingDay
10%17%33%25%12%2
15530
Night
5%12%36%33%13%1
25554

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 10thDay
325%336%46%9%58%
2538
11th to 20thDay
319%445%46%8%55%
2704
21st to endDay
6%48%5%4436%7%53%
3146
February1st to 10thDay
6%37%5%3335%8%57%
1710
11th to 20thDay
32444446%10%59%
1834
21st to endDay
5%45%43445%8%58%
1570
March1st to 10thDay
17%47%443347%57%
3130
11th to 20thDay
110%5%12%6%6%5%5%6%7%39%
3483
21st to endDay
16%36%5%445%7%9%50%
4037
April1st to 10thDay
27%16%5%45%47%8%49%
2280
11th to 20thDay
49%39%6%5%445%7%45%
2251
21st to endDay
411%47%6%5%5%47%8%40%
2280
May1st to 10thDay
411%48%5%45%46%7%41%
3926
11th to 20thDay
6%8%28%6%6%6%5%8%9%38%
4343
21st to endDay
45%26%45%5%5%8%9%48%
4825
June1st to 10thDay
45%26%5%45%5%9%10%44%
2660
11th to 20thDay
45%25%445%5%7%8%51%
2660
21st to endDay
3426%6%6%7%6%8%8%44%
2660
July1st to 10thDay
4425%5%5%6%5%7%8%49%
4430
11th to 20thDay
5%5%28%6%5%6%47%10%40%
4430
21st to endDay
6%6%37%6%6%6%5%6%7%42%
4614
August1st to 10thDay
8%6%38%6%6%6%5%8%9%35%
4069
11th to 20thDay
5%416%5%6%7%5%8%8%44%
3726
21st to endDay
46%27%5%6%6%5%7%9%43%
4180
September1st to 10thDay
6%6%26%5%5%6%5%5%5%50%
2280
11th to 20thDay
6%426%5%4445%7%55%
2266
21st to endDay
5%424334346%61%
2090
October1st to 10thDay
3313223345%71%
3176
11th to 20thDay
342444446%8%58%
3150
21st to endDay
2423223346%69%
3377
November1st to 10thDay
15%2422335%7%66%
1763
11th to 20thDay
42442345%8%65%
1710
21st to endDay
435%44436%8%60%
1639
December1st to 10thDay
426%32435%9%61%
1520
11th to 20thDay
1425%43337%8%58%
1926
21st to endDay
1326%445%5%7%9%54%
2794
January1st to 10thNight
328%5%5%5%35%8%56%
4417
11th to 20thNight
2145%4446%7%63%
4293
21st to endNight
5%27%5%4435%7%57%
4521
February1st to 10thNight
436%43345%7%60%
2470
11th to 20thNight
5%27%43335%7%59%
2231
21st to endNight
5%2433435%7%64%
1884
March1st to 10thNight
18%36%33435%7%57%
3734
11th to 20thNight
18%49%5%4435%8%47%
3494
21st to endNight
15%26%44446%9%55%
3608
April1st to 10thNight
27%25%43435%7%59%
1900
11th to 20thNight
38%37%45%5%448%50%
1877
21st to endNight
49%36%44445%7%50%
1900
May1st to 10thNight
310%26%44445%7%50%
3042
11th to 20thNight
5%7%26%5%45%47%8%46%
2558
21st to endNight
3426%44446%7%58%
2762
June1st to 10thNight
25%25%3345%7%9%53%
1520
11th to 20thNight
32133445%8%8%59%
1520
21st to endNight
432445%6%5%8%8%52%
1520
July1st to 10thNight
5%5%26%45%5%5%6%8%50%
2540
11th to 20thNight
3425%445%5%8%13%49%
2540
21st to endNight
4426%5%6%5%5%8%9%46%
2945
August1st to 10thNight
8%6%37%6%6%6%6%9%11%33%
2868
11th to 20thNight
3315%46%6%5%8%11%46%
3113
21st to endNight
34145%5%6%5%9%12%45%
3487
September1st to 10thNight
5%426%5%4447%9%49%
1900
11th to 20thNight
4425%33436%8%59%
1913
21st to endNight
4425%34335%5%61%
2090
October1st to 10thNight
2313323246%70%
3790
11th to 20thNight
341433435%7%63%
3778
21st to endNight
2323222345%72%
4148
November1st to 10thNight
142322436%7%66%
2535
11th to 20thNight
214434347%68%
2477
21st to endNight
15%25%33335%7%63%
2536
December1st to 10thNight
1226%33435%9%62%
2660
11th to 20thNight
4244445%7%10%55%
3271
21st to endNight
427%445%46%8%54%
4873

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 10thDay
17%7%18%28%23%8%
2539
11th to 20thDay
18%8%15%30%22%6%
2704
21st to endDay
26%6%14%29%20%5%
3146
February1st to 10thDay
24%5%16%27%20%9%
1710
11th to 20thDay
19%5%13%26%29%8%
1844
21st to endDay
23%5%10%23%26%14%
1570
March1st to 10thDay
22%6%9%21%30%12%
3130
11th to 20thDay
35%8%14%27%14%3
3483
21st to endDay
23%9%16%30%19%3
4037
April1st to 10thDay
28%8%14%21%20%9%
2280
11th to 20thDay
35%7%11%22%18%7%
2254
21st to endDay
35%8%13%23%17%3
2280
May1st to 10thDay
32%10%12%20%16%10%
3926
11th to 20thDay
33%12%16%19%16%5%
4347
21st to endDay
21%12%15%19%23%10%
4825
June1st to 10thDay
28%11%16%19%18%8%
2660
11th to 20thDay
25%9%10%17%23%16%
2660
21st to endDay
29%10%12%20%19%10%
2660
July1st to 10thDay
29%8%8%14%21%20%
4361
11th to 20thDay
35%7%12%26%14%7%
4355
21st to endDay
35%9%11%17%13%14%
4468
August1st to 10thDay
41%8%19%16%13%3
4055
11th to 20thDay
33%7%15%15%18%12%
3762
21st to endDay
34%6%15%17%21%7%
4179
September1st to 10thDay
31%7%11%18%23%11%
2280
11th to 20thDay
26%6%11%19%27%12%
2266
21st to endDay
22%6%8%23%32%9%
2090
October1st to 10thDay
14%5%7%17%36%20%
3176
11th to 20thDay
24%38%32%26%8%
3150
21st to endDay
16%46%25%40%10%
3377
November1st to 10thDay
16%412%21%33%14%
1763
11th to 20thDay
15%5%10%33%28%9%
1710
21st to endDay
20%5%11%24%27%13%
1639
December1st to 10thDay
19%6%17%27%24%8%
1520
11th to 20thDay
19%5%16%26%26%7%
1924
21st to endDay
20%7%16%24%24%10%
2794
January1st to 10thNight
21%7%14%29%25%4
4417
11th to 20thNight
13%7%13%32%26%8%
4293
21st to endNight
23%7%14%29%22%4
4521
February1st to 10thNight
22%414%31%22%7%
2470
11th to 20thNight
25%5%11%27%25%7%
2231
21st to endNight
19%410%26%29%12%
1884
March1st to 10thNight
21%8%9%20%34%6%
3734
11th to 20thNight
31%7%14%27%18%2
3494
21st to endNight
22%7%17%31%21%2
3608
April1st to 10thNight
23%5%14%27%24%7%
1900
11th to 20thNight
30%6%12%26%19%5%
1877
21st to endNight
31%7%15%27%16%4
1900
May1st to 10thNight
27%9%14%24%15%10%
3042
11th to 20thNight
31%10%16%26%14%4
2559
21st to endNight
23%9%14%22%24%8%
2762
June1st to 10thNight
23%9%22%22%14%10%
1520
11th to 20thNight
17%9%14%20%22%17%
1520
21st to endNight
25%9%14%21%20%10%
1520
July1st to 10thNight
29%9%9%19%22%12%
2500
11th to 20thNight
25%7%19%34%12%4
2492
21st to endNight
28%10%16%23%8%14%
2853
August1st to 10thNight
42%8%21%16%9%4
2859
11th to 20thNight
29%9%22%18%17%5%
3143
21st to endNight
27%8%24%21%17%2
3487
September1st to 10thNight
29%8%13%22%20%8%
1900
11th to 20thNight
22%6%14%22%24%13%
1913
21st to endNight
23%6%10%25%29%8%
2090
October1st to 10thNight
16%5%9%24%34%12%
3790
11th to 20thNight
21%312%32%24%8%
3778
21st to endNight
15%36%29%36%10%
4148
November1st to 10thNight
16%5%12%26%29%13%
2535
11th to 20thNight
16%5%10%31%29%10%
2477
21st to endNight
20%5%11%24%29%12%
2536
December1st to 10thNight
18%6%16%27%25%8%
2660
11th to 20thNight
19%5%17%25%28%6%
3272
21st to endNight
22%7%15%23%24%9%
4873

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 10thDay
10%22%34%24%10%
270
11th to 20thDay
14%23%39%21%31
270
21st to endDay
422%44%22%8%1
297
February1st to 10thDay
11%35%37%15%11
270
11th to 20thDay
11%32%42%11%4
270
21st to endDay
18%31%36%12%2
225
March1st to 10thDay
15%23%37%20%6%
270
11th to 20thDay
13%26%36%18%7%
453
21st to endDay
18%32%35%13%2
506
April1st to 10thDay
15%32%35%15%31
460
11th to 20thDay
20%33%32%13%21
452
21st to endDay
17%32%31%16%31
460
May1st to 10thDay
15%26%35%18%5%1
537
11th to 20thDay
11%17%33%29%10%2
675
21st to endDay
9%19%29%28%13%2
734
June1st to 10thDay
5%14%30%29%19%3
680
11th to 20thDay
9%12%34%28%14%3
680
21st to endDay
310%37%28%17%4
680
July1st to 10thDay
6%6%24%33%26%5%
671
11th to 20thDay
7%320%38%26%7%
668
21st to endDay
10%321%33%27%6%
626
August1st to 10thDay
12%5%27%35%17%4
487
11th to 20thDay
7%6%30%35%17%6%
477
21st to endDay
9%6%33%32%16%3
539
September1st to 10thDay
8%10%28%32%18%5%
490
11th to 20thDay
8%11%38%28%13%2
476
21st to endDay
7%13%22%33%22%4
300
October1st to 10thDay
8%11%29%26%19%6%
300
11th to 20thDay
8%20%32%23%15%3
300
21st to endDay
11%21%34%23%10%1
330
November1st to 10thDay
12%17%37%21%10%2
300
11th to 20thDay
9%18%39%24%8%1
270
21st to endDay
7%19%44%21%8%1
270
December1st to 10thDay
10%24%39%20%7%
270
11th to 20thDay
7%23%49%15%6%
270
21st to endDay
11%29%37%17%5%1
297
January1st to 10thNight
419%39%28%9%1
950
11th to 20thNight
423%42%22%7%1
865
21st to endNight
213%49%30%6%1
836
February1st to 10thNight
417%55%20%4
760
11th to 20thNight
418%50%25%3
744
21st to endNight
323%49%23%2
628
March1st to 10thNight
317%47%28%4
760
11th to 20thNight
5%13%40%35%8%
760
21st to endNight
5%17%47%27%4
706
April1st to 10thNight
8%19%42%28%3
570
11th to 20thNight
9%19%38%29%6%1
563
21st to endNight
10%15%39%29%7%
570
May1st to 10thNight
11%11%35%36%7%1
570
11th to 20thNight
9%9%30%40%12%1
561
21st to endNight
6%11%34%34%14%1
617
June1st to 10thNight
5%5%26%44%18%3
570
11th to 20thNight
46%30%46%14%1
570
21st to endNight
5%321%45%25%2
570
July1st to 10thNight
5%315%44%31%2
555
11th to 20thNight
6%112%43%35%3
552
21st to endNight
6%110%40%39%4
624
August1st to 10thNight
8%312%43%31%3
567
11th to 20thNight
6%215%45%29%3
564
21st to endNight
6%316%41%31%3
627
September1st to 10thNight
6%219%42%26%4
570
11th to 20thNight
6%323%44%21%3
570
21st to endNight
5%7%29%39%18%2
570
October1st to 10thNight
5%8%34%39%14%2
750
11th to 20thNight
37%39%35%14%3
760
21st to endNight
6%9%38%32%12%2
852
November1st to 10thNight
412%42%32%10%1
975
11th to 20thNight
416%42%29%7%1
953
21st to endNight
5%15%40%32%8%
950
December1st to 10thNight
320%41%30%6%
950
11th to 20thNight
417%48%24%6%
950
21st to endNight
6%22%44%23%5%
1045
Page generated at 2024-11-08 04:44:46. Version ac07

Copyright © 2024 Attilla Danko.


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