This page made possible by the sponsorship of: Emilio Robau
Robau and Associates.

Caxambas Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Caxambas Observatory clear sky chart from 2005-11-05 to 2017-03-26.

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
67%
15477
19%
45285
16%
15435
70%
15435
30%
28436

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
60%
718
19%
2327
17%
716
65%
716
28%
1391
January16th to endNight
55%
768
26%
2384
21%
768
62%
768
33%
1406
February1st to 15thNight
54%
702
25%
2103
20%
698
60%
698
35%
1223
February16th to endNight
66%
631
30%
1800
23%
631
72%
631
42%
997
March1st to 15thNight
64%
720
29%
1980
20%
720
71%
720
48%
1067
March16th to endNight
67%
748
27%
2057
23%
748
70%
748
43%
1147
April1st to 15thNight
71%
658
26%
1811
20%
658
74%
658
47%
965
April16th to endNight
67%
660
24%
1719
17%
660
70%
660
45%
990
May1st to 15thNight
83%
602
26%
1592
19%
602
84%
602
52%
867
May16th to endNight
73%
513
14%
1539
11%
513
73%
513
30%
987
June1st to 15thNight
65%
495
7%
1485
5%
495
65%
495
19%
1077
June16th to endNight
72%
495
5%
1485
5%
495
72%
495
19%
1111
July1st to 15thNight
73%
465
5%
1395
6%
465
73%
465
16%
1100
July16th to endNight
82%
522
6%
1469
7%
489
82%
489
25%
1032
August1st to 15thNight
75%
494
5%
1532
6%
491
75%
491
20%
1108
August16th to endNight
67%
697
3%
1922
3%
697
67%
697
16%
1475
September1st to 15thNight
70%
660
4%
1815
4%
660
70%
660
18%
1364
September16th to endNight
60%
657
4%
1815
4%
657
60%
657
12%
1480
October1st to 15thNight
72%
660
19%
1862
20%
660
73%
660
30%
1198
October16th to endNight
59%
704
22%
2112
21%
704
63%
704
27%
1333
November1st to 15thNight
65%
700
29%
2101
28%
700
71%
700
39%
1175
November16th to endNight
64%
720
28%
2160
26%
720
69%
720
35%
1269
December1st to 15thNight
63%
720
23%
2324
22%
720
68%
720
33%
1334
December16th to endNight
67%
768
24%
2496
27%
768
70%
768
38%
1340

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%425%5%36%7%8%10%39%
45671
Night
6%425%5%35%5%7%10%43%
45493
TransparencyDay
34%12%18%18%11%3
45372
Night
33%10%18%20%13%3
45296
SeeingDay
7%110%24%32%23%
5218
Night
8%112%30%32%13%
15484

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
7%4344246%6%10%45%
1611
16th to endDay
7%5%15%43446%9%46%
1839
February1st to 15thDay
9%5%232245%48%50%
1750
16th to endDay
43342445%9%57%
1673
March1st to 15thDay
22132245%7%9%59%
1980
16th to endDay
431442346%9%55%
2053
April1st to 15thDay
311332446%11%57%
1807
16th to endDay
431342445%10%55%
1910
May1st to 15thDay
31122245%7%12%57%
2034
16th to endDay
7%425%5%37%6%8%10%38%
2223
June1st to 15thDay
10%5%26%6%47%7%11%13%24%
2145
16th to endDay
6%6%26%7%5%8%10%9%12%24%
2145
July1st to 15thDay
7%5%28%9%5%11%9%11%12%16%
2145
16th to endDay
5%326%7%7%11%12%11%13%18%
2283
August1st to 15thDay
4427%8%6%10%12%11%11%21%
2073
16th to endDay
6%5%37%9%5%9%10%11%10%19%
1925
September1st to 15thDay
4428%9%6%8%9%9%12%22%
1815
16th to endDay
10%7%38%8%5%8%8%10%9%18%
1815
October1st to 15thDay
4427%6%46%6%8%10%37%
1767
16th to endDay
9%5%26%5%3445%9%42%
1760
November1st to 15thDay
4315%425%46%8%52%
1757
16th to endDay
7%2135%345%7%7%50%
1800
December1st to 15thDay
8%5%244245%6%10%45%
1633
16th to endDay
44133246%6%9%52%
1728
January1st to 15thNight
7%4246%35%47%11%41%
2327
16th to endNight
5%425%5%35%46%9%47%
2384
February1st to 15thNight
9%6%3432335%7%50%
2103
16th to endNight
321442445%9%55%
1800
March1st to 15thNight
431432336%8%57%
1980
16th to endNight
331332445%9%56%
2057
April1st to 15thNight
331332445%10%58%
1811
16th to endNight
5%31432446%9%53%
1719
May1st to 15thNight
2113245%6%11%59%
1592
16th to endNight
7%4336%35%6%8%9%40%
1538
June1st to 15thNight
10%6%36%7%45%6%9%12%27%
1485
16th to endNight
6%5%27%7%48%6%9%12%28%
1485
July1st to 15thNight
5%5%37%7%5%8%8%9%12%25%
1485
16th to endNight
32247%5%7%8%12%14%31%
1577
August1st to 15thNight
5%426%5%47%7%10%13%31%
1543
16th to endNight
7%6%37%7%47%7%9%12%27%
1922
September1st to 15thNight
45%36%7%48%8%9%14%26%
1815
16th to endNight
8%7%38%9%6%7%7%8%10%21%
1815
October1st to 15thNight
5%425%5%45%7%8%10%40%
1862
16th to endNight
10%5%25%6%3445%8%42%
2112
November1st to 15thNight
5%424424448%53%
2101
16th to endNight
7%423436%46%8%49%
2160
December1st to 15thNight
6%5%2443446%10%47%
2324
16th to endNight
431442446%10%52%
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
32%8%16%24%13%5%
1612
16th to endDay
32%6%12%24%18%5%
1839
February1st to 15thDay
30%5%11%23%19%9%
1752
16th to endDay
21%6%15%27%20%6%
1673
March1st to 15thDay
20%7%15%30%22%4
1980
16th to endDay
24%6%15%26%19%7%
2054
April1st to 15thDay
20%7%22%28%17%3
1807
16th to endDay
23%6%18%26%21%3
1910
May1st to 15thDay
18%8%21%29%17%4
2034
16th to endDay
35%12%20%22%8%
2227
June1st to 15thDay
44%16%23%13%2
2145
16th to endDay
46%19%21%10%2
2145
July1st to 15thDay
52%20%20%6%
2006
16th to endDay
45%23%23%7%
2128
August1st to 15thDay
44%22%22%9%
2060
16th to endDay
49%20%22%5%
1925
September1st to 15thDay
45%22%23%7%
1815
16th to endDay
53%16%17%9%2
1815
October1st to 15thDay
36%12%17%16%12%3
1767
16th to endDay
36%6%13%18%17%7%
1760
November1st to 15thDay
28%6%12%22%22%8%
1757
16th to endDay
29%7%14%19%18%10%
1800
December1st to 15thDay
33%7%16%20%17%4
1633
16th to endDay
25%7%16%25%20%4
1728
January1st to 15thNight
34%7%16%24%13%3
2327
16th to endNight
31%7%13%25%17%5%
2384
February1st to 15thNight
32%48%24%20%9%
2112
16th to endNight
25%6%14%24%21%8%
1800
March1st to 15thNight
22%414%31%20%5%
1980
16th to endNight
24%6%14%27%21%5%
2057
April1st to 15thNight
21%6%18%32%16%4
1811
16th to endNight
24%6%15%25%23%3
1719
May1st to 15thNight
18%7%20%31%18%3
1593
16th to endNight
34%10%20%22%12%
1540
June1st to 15thNight
45%12%26%13%2
1485
16th to endNight
43%16%26%10%2
1485
July1st to 15thNight
45%20%24%7%1
1395
16th to endNight
35%17%33%13%
1469
August1st to 15thNight
37%20%30%11%
1532
16th to endNight
43%20%28%7%
1922
September1st to 15thNight
41%19%28%8%1
1815
16th to endNight
51%20%17%9%1
1815
October1st to 15thNight
33%11%20%18%13%2
1862
16th to endNight
38%6%12%18%18%5%
2112
November1st to 15thNight
28%5%11%23%23%7%
2101
16th to endNight
30%6%11%21%20%8%
2160
December1st to 15thNight
30%7%16%22%17%4
2324
16th to endNight
26%6%16%25%20%3
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
16%328%26%22%2
90
16th to endDay
13%10%27%31%13%4
96
February1st to 15thDay
5%5%21%35%24%7%
90
16th to endDay
5%125%45%21%
174
March1st to 15thDay
2219%46%26%1
270
16th to endDay
5%220%37%28%4
267
April1st to 15thDay
2419%35%31%5%
210
16th to endDay
5%112%41%34%4
210
May1st to 15thDay
47%37%33%16%
228
16th to endDay
6%5%20%38%28%
267
June1st to 15thDay
13%2315%31%32%
255
16th to endDay
436%30%54%
255
July1st to 15thDay
5%17%29%55%
245
16th to endDay
8%37%34%45%
270
August1st to 15thDay
8%16%34%48%
253
16th to endDay
9%48%31%45%
268
September1st to 15thDay
7%38%34%46%
255
16th to endDay
8%310%38%38%
254
October1st to 15thDay
6%5%29%41%17%
255
16th to endDay
14%213%31%25%13%
272
November1st to 15thDay
7%110%29%39%12%
265
16th to endDay
5%119%36%32%4
270
December1st to 15thDay
20%116%30%26%4
103
16th to endDay
112%32%44%9%
96
January1st to 15thNight
9%417%37%30%1
720
16th to endNight
7%425%39%20%1
768
February1st to 15thNight
11%225%40%19%1
704
16th to endNight
6%119%46%24%1
631
March1st to 15thNight
5%221%43%25%1
720
16th to endNight
6%118%44%25%2
748
April1st to 15thNight
5%213%42%32%2
658
16th to endNight
8%16%42%30%1
660
May1st to 15thNight
28%43%38%5%
603
16th to endNight
7%7%30%40%13%
515
June1st to 15thNight
12%1415%44%20%
495
16th to endNight
6%29%41%39%
495
July1st to 15thNight
6%18%40%42%
465
16th to endNight
316%39%48%
522
August1st to 15thNight
8%16%41%42%
494
16th to endNight
11%310%38%36%
697
September1st to 15thNight
8%311%37%38%
660
16th to endNight
13%314%41%25%
657
October1st to 15thNight
7%16%32%39%13%
660
16th to endNight
13%114%31%29%9%
704
November1st to 15thNight
7%117%37%31%4
700
16th to endNight
8%217%40%29%2
720
December1st to 15thNight
7%217%38%30%3
720
16th to endNight
6%117%36%34%4
768
Page generated at 2017-03-27 11:15:18. Version ac04

Copyright 2017 A. Danko


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