Sonoita Observatories
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sonoita Observatories clear sky chart from 2005-11-05 to 2017-10-31.

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
69%
15731
34%
47407
28%
15690
77%
15690
49%
23247

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
68%
719
31%
2327
30%
716
75%
716
48%
1102
January16th to endNight
60%
768
34%
2496
29%
768
71%
768
38%
1303
February1st to 15thNight
65%
698
36%
2202
31%
696
76%
696
50%
1028
February16th to endNight
57%
632
39%
1814
30%
632
68%
632
46%
935
March1st to 15thNight
59%
720
40%
1980
27%
720
70%
720
53%
975
March16th to endNight
64%
768
37%
2112
24%
768
76%
768
55%
1047
April1st to 15thNight
58%
677
35%
1936
21%
677
70%
677
53%
938
April16th to endNight
59%
540
43%
1800
30%
540
77%
540
61%
695
May1st to 15thNight
63%
539
38%
1641
26%
539
76%
539
66%
657
May16th to endNight
69%
561
42%
1684
32%
561
78%
561
71%
668
June1st to 15thNight
77%
540
34%
1620
29%
540
79%
540
65%
688
June16th to endNight
81%
540
28%
1620
24%
540
82%
540
54%
773
July1st to 15thNight
78%
510
15%
1530
14%
510
78%
510
34%
894
July16th to endNight
79%
564
11%
1593
10%
531
79%
531
25%
1063
August1st to 15thNight
85%
539
20%
1611
19%
536
85%
536
33%
955
August16th to endNight
79%
584
26%
1883
26%
584
80%
584
34%
1073
September1st to 15thNight
73%
720
25%
1980
21%
720
74%
720
37%
1217
September16th to endNight
82%
716
42%
1980
31%
716
87%
716
65%
928
October1st to 15thNight
76%
720
38%
2100
28%
720
82%
720
63%
942
October16th to endNight
80%
768
43%
2304
36%
768
86%
768
67%
988
November1st to 15thNight
74%
700
42%
2100
33%
700
82%
700
63%
898
November16th to endNight
65%
720
39%
2258
33%
720
72%
720
48%
1082
December1st to 15thNight
67%
720
36%
2340
34%
720
74%
720
45%
1119
December16th to endNight
61%
768
34%
2496
32%
768
68%
768
39%
1279

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
331342445%6%61%
48331
Night
2213323446%65%
47609
TransparencyDay
23%46%11%27%26%
48026
Night
19%47%14%28%26%
47415
SeeingDay
7%13%26%30%17%4
5550
Night
45%15%33%34%7%
15741

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
22145%2335%5%61%
1611
16th to endDay
442331345%6%59%
1728
February1st to 15thDay
4322213235%67%
1652
16th to endDay
3423313345%63%
1658
March1st to 15thDay
2213313446%65%
1980
16th to endDay
2212213345%71%
2112
April1st to 15thDay
1112213336%70%
2011
16th to endDay
11121112480%
2160
May1st to 15thDay
11211223477%
2305
16th to endDay
1111212381%
2429
June1st to 15thDay
11121222477%
2340
16th to endDay
322324446%65%
2340
July1st to 15thDay
4425%7%5%8%7%10%9%34%
2340
16th to endDay
9%6%37%9%6%9%7%7%9%22%
2467
August1st to 15thDay
7%5%38%7%46%8%7%7%32%
2340
16th to endDay
5%325%6%47%7%7%9%40%
2312
September1st to 15thDay
7%425%6%5%5%6%6%6%42%
1980
16th to endDay
4212323445%64%
1980
October1st to 15thDay
221312245%72%
1860
16th to endDay
112122235%76%
1918
November1st to 15thDay
11222245%75%
1759
16th to endDay
3312213235%69%
1701
December1st to 15thDay
4313413347%62%
1620
16th to endDay
341432336%7%59%
1728
January1st to 15thNight
231332245%5%65%
2327
16th to endNight
5%31343445%5%57%
2496
February1st to 15thNight
2212323347%66%
2197
16th to endNight
121342435%5%64%
1814
March1st to 15thNight
2213322246%69%
1980
16th to endNight
121232333471%
2112
April1st to 15thNight
1212323335%69%
1936
16th to endNight
1111122382%
1800
May1st to 15thNight
1112346%78%
1641
16th to endNight
211122383%
1684
June1st to 15thNight
211112125%78%
1620
16th to endNight
211121445%6%68%
1620
July1st to 15thNight
23245%35%6%9%14%43%
1620
16th to endNight
3325%5%47%8%10%15%31%
1701
August1st to 15thNight
2313435%6%8%10%50%
1620
16th to endNight
5%323435%5%7%9%49%
1883
September1st to 15thNight
5%42443446%9%50%
1980
16th to endNight
212112336%74%
1980
October1st to 15thNight
11121233476%
2100
16th to endNight
1121122478%
2304
November1st to 15thNight
112111235%76%
2100
16th to endNight
3313312335%67%
2258
December1st to 15thNight
4212323346%64%
2340
16th to endNight
3314423446%60%
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
24%35%11%29%26%
1612
16th to endDay
25%4315%27%22%
1728
February1st to 15thDay
21%1312%31%29%
1652
16th to endDay
23%2313%29%26%
1658
March1st to 15thDay
20%237%36%28%
1980
16th to endDay
17%139%37%29%
2112
April1st to 15thDay
16%237%40%29%
2011
16th to endDay
11%127%30%46%
2160
May1st to 15thDay
11%138%29%44%
2305
16th to endDay
9%226%32%45%
2432
June1st to 15thDay
12%125%26%51%
2340
16th to endDay
20%35%9%21%38%
2340
July1st to 15thDay
38%13%14%12%12%8%
2201
16th to endDay
52%16%15%10%4
2312
August1st to 15thDay
46%10%12%13%14%2
2325
16th to endDay
38%10%13%15%12%8%
2312
September1st to 15thDay
39%7%11%14%17%9%
1980
16th to endDay
22%37%12%33%20%
1980
October1st to 15thDay
15%46%13%30%30%
1860
16th to endDay
13%2410%31%37%
1918
November1st to 15thDay
12%3312%37%30%
1759
16th to endDay
18%2412%28%32%
1701
December1st to 15thDay
23%25%15%33%19%
1620
16th to endDay
23%38%17%30%16%
1728
January1st to 15thNight
20%35%11%31%27%
2327
16th to endNight
27%35%15%29%19%
2496
February1st to 15thNight
18%35%14%26%31%
2208
16th to endNight
21%3414%32%23%
1814
March1st to 15thNight
17%2311%30%33%
1980
16th to endNight
17%2410%35%29%
2112
April1st to 15thNight
18%2410%40%24%
1936
16th to endNight
10%229%30%45%
1800
May1st to 15thNight
9%249%34%40%
1642
16th to endNight
7%239%36%41%
1685
June1st to 15thNight
12%12428%50%
1620
16th to endNight
15%5%5%9%23%40%
1620
July1st to 15thNight
26%11%22%17%12%9%
1530
16th to endNight
36%13%29%15%31
1593
August1st to 15thNight
25%13%16%20%19%4
1611
16th to endNight
28%8%17%18%18%8%
1883
September1st to 15thNight
29%8%12%19%21%8%
1980
16th to endNight
12%27%15%40%20%
1980
October1st to 15thNight
12%27%17%31%28%
2100
16th to endNight
11%25%13%29%38%
2304
November1st to 15thNight
12%2417%33%30%
2100
16th to endNight
21%2312%28%31%
2258
December1st to 15thNight
21%3415%34%20%
2340
16th to endNight
25%46%18%26%18%
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
8%21%26%36%6%
90
16th to endDay
6%14%26%38%10%4
96
February1st to 15thDay
9%14%26%32%13%2
167
16th to endDay
10%35%25%20%7%
238
March1st to 15thDay
8%24%31%17%12%4
270
16th to endDay
6%29%31%18%9%4
288
April1st to 15thDay
7%22%37%21%7%2
269
16th to endDay
7%26%38%17%7%1
270
May1st to 15thDay
7%22%36%19%11%1
288
16th to endDay
5%16%42%26%7%1
330
June1st to 15thDay
47%43%32%10%1
315
16th to endDay
4129%39%21%2
315
July1st to 15thDay
7%17%45%24%2
305
16th to endDay
11%13%39%26%8%
327
August1st to 15thDay
9%12%32%34%10%
315
16th to endDay
7%19%37%33%9%
332
September1st to 15thDay
12%216%40%21%5%
315
16th to endDay
6%8%27%33%19%5%
315
October1st to 15thDay
39%26%32%21%7%
195
16th to endDay
2421%34%28%8%
144
November1st to 15thDay
420%24%36%10%4
90
16th to endDay
6%25%25%27%14%
90
December1st to 15thDay
6%12%21%27%30%2
90
16th to endDay
12%21%25%32%7%1
96
January1st to 15thNight
4319%38%29%4
720
16th to endNight
8%6%19%37%24%3
768
February1st to 15thNight
27%19%36%27%5%
704
16th to endNight
311%24%39%18%2
632
March1st to 15thNight
410%22%33%24%4
720
16th to endNight
37%20%34%29%4
768
April1st to 15thNight
29%25%40%19%2
677
16th to endNight
210%26%37%19%2
540
May1st to 15thNight
17%26%34%27%2
540
16th to endNight
15%21%40%29%2
563
June1st to 15thNight
3213%45%32%2
540
16th to endNight
39%36%45%5%
540
July1st to 15thNight
45%23%56%9%
510
16th to endNight
5%218%54%18%
564
August1st to 15thNight
4215%55%21%
539
16th to endNight
7%1316%52%19%
584
September1st to 15thNight
6%18%20%49%13%
720
16th to endNight
2110%36%39%8%
716
October1st to 15thNight
1414%34%36%8%
720
16th to endNight
1212%31%41%10%
768
November1st to 15thNight
26%13%35%34%7%
700
16th to endNight
5%6%18%30%30%7%
720
December1st to 15thNight
6%7%14%36%29%6%
720
16th to endNight
6%9%17%37%22%6%
768
Page generated at 2017-11-01 14:23:32. Version ac04

Copyright 2017 A. Danko


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