Santa Maria
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Santa Maria clear sky chart from 2005-11-05 to

2017-09-12
.

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
68%
15675
28%
46850
25%
15638
71%
15638
39%
25953

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
64%
716
27%
2374
27%
716
69%
716
36%
1272
January16th to endNight
60%
768
28%
2496
28%
768
64%
768
33%
1421
February1st to 15thNight
62%
698
29%
2164
30%
697
66%
697
36%
1212
February16th to endNight
55%
632
25%
1895
24%
632
60%
632
31%
1160
March1st to 15thNight
63%
720
23%
2070
22%
720
67%
720
36%
1220
March16th to endNight
60%
768
24%
2042
19%
768
65%
768
38%
1254
April1st to 15thNight
59%
719
24%
1799
15%
719
62%
719
39%
1128
April16th to endNight
61%
720
28%
1800
13%
720
66%
720
46%
1044
May1st to 15thNight
66%
719
19%
1799
11%
719
67%
719
41%
1124
May16th to endNight
66%
460
24%
1584
19%
460
69%
460
32%
878
June1st to 15thNight
73%
360
25%
1440
28%
360
75%
360
30%
739
June16th to endNight
83%
360
28%
1440
34%
360
83%
360
40%
644
July1st to 15thNight
84%
389
25%
1409
28%
389
84%
389
41%
659
July16th to endNight
74%
564
28%
1593
24%
531
76%
531
34%
897
August1st to 15thNight
76%
684
23%
1758
15%
681
76%
681
41%
1054
August16th to endNight
81%
764
30%
1910
20%
764
81%
764
49%
1097
September1st to 15thNight
81%
706
33%
1765
26%
706
81%
706
48%
1031
September16th to endNight
82%
656
36%
1768
33%
656
84%
656
56%
904
October1st to 15thNight
73%
660
31%
1963
33%
660
76%
660
47%
1010
October16th to endNight
72%
704
35%
2112
36%
704
76%
704
45%
1096
November1st to 15thNight
72%
700
32%
2205
33%
700
76%
700
46%
1099
November16th to endNight
69%
720
32%
2340
31%
720
75%
720
43%
1166
December1st to 15thNight
63%
720
28%
2436
28%
720
68%
720
33%
1350
December16th to endNight
57%
768
27%
2688
27%
768
64%
768
32%
1494

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
5%413313347%60%
47799
Night
6%5%24323448%55%
47044
TransparencyDay
24%48%18%26%17%
47486
Night
28%48%16%23%18%
46856
SeeingDay
8%7%25%36%17%4
6030
Night
7%211%32%35%10%
15688

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%314423446%56%
1561
16th to endDay
13%413323345%54%
1728
February1st to 15thDay
13%5%24213335%54%
1694
16th to endDay
14%5%24423446%46%
1579
March1st to 15thDay
7%32343245%9%52%
1887
16th to endDay
8%5%24323348%52%
2181
April1st to 15thDay
9%32432235%6%56%
2149
16th to endDay
7%312212348%62%
2160
May1st to 15thDay
4313213348%63%
2151
16th to endDay
35%23312337%62%
2525
June1st to 15thDay
35%13223348%61%
2520
16th to endDay
212213337%70%
2520
July1st to 15thDay
1413223448%61%
2464
16th to endDay
232331445%8%59%
2468
August1st to 15thDay
26%2421235%9%58%
2192
16th to endDay
131321345%8%63%
2292
September1st to 15thDay
23132135%48%63%
2114
16th to endDay
1212212346%70%
1862
October1st to 15thDay
5%313212335%65%
1664
16th to endDay
3213213336%67%
1760
November1st to 15thDay
7%31331234465%
1651
16th to endDay
7%312422337%62%
1620
December1st to 15thDay
10%5%24422446%53%
1521
16th to endDay
14%413413245%53%
1536
January1st to 15thNight
9%413423345%56%
2374
16th to endNight
12%5%24323335%53%
2496
February1st to 15thNight
9%424323347%54%
2158
16th to endNight
14%7%13423336%50%
1895
March1st to 15thNight
7%42332436%8%52%
2070
16th to endNight
8%5%2432445%9%50%
2042
April1st to 15thNight
8%5%24323346%55%
1799
16th to endNight
5%5%22213338%60%
1800
May1st to 15thNight
38%35%423349%51%
1799
16th to endNight
5%7%25%323348%51%
1583
June1st to 15thNight
16%35%2345%5%10%51%
1440
16th to endNight
325%3245%411%56%
1440
July1st to 15thNight
14143145%6%12%53%
1493
16th to endNight
1336%5%25%8%5%10%44%
1701
August1st to 15thNight
7%36%335%5%5%11%46%
1767
16th to endNight
5%2432346%9%55%
1910
September1st to 15thNight
24243246%5%8%55%
1765
16th to endNight
1313213437%67%
1768
October1st to 15thNight
5%323312245%63%
1963
16th to endNight
5%5%12212336%63%
2112
November1st to 15thNight
5%413212236%65%
2205
16th to endNight
5%323313347%61%
2340
December1st to 15thNight
9%425%313346%52%
2436
16th to endNight
14%413223336%53%
2688

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
28%47%20%23%15%
1561
16th to endDay
33%38%14%19%20%
1728
February1st to 15thDay
33%26%20%22%14%
1694
16th to endDay
37%411%21%20%5%
1579
March1st to 15thDay
29%415%20%18%12%
1887
16th to endDay
30%414%23%20%6%
2181
April1st to 15thDay
29%413%25%21%6%
2149
16th to endDay
22%313%25%26%9%
2160
May1st to 15thDay
21%410%23%29%11%
2151
16th to endDay
22%410%29%26%5%
2528
June1st to 15thDay
22%49%18%29%15%
2520
16th to endDay
15%45%8%34%32%
2520
July1st to 15thDay
20%35%11%26%32%
2319
16th to endDay
22%5%8%11%28%23%
2313
August1st to 15thDay
23%45%10%30%26%
2176
16th to endDay
18%3410%36%25%
2292
September1st to 15thDay
19%45%14%25%30%
2114
16th to endDay
16%3417%33%24%
1862
October1st to 15thDay
21%27%20%28%18%
1664
16th to endDay
20%37%15%28%24%
1760
November1st to 15thDay
22%46%17%29%19%
1651
16th to endDay
23%48%16%28%18%
1620
December1st to 15thDay
32%49%15%23%13%
1521
16th to endDay
34%48%22%18%12%
1536
January1st to 15thNight
30%37%18%23%16%
2374
16th to endNight
34%38%11%19%22%
2496
February1st to 15thNight
31%37%18%24%13%
2169
16th to endNight
37%37%20%22%8%
1895
March1st to 15thNight
30%5%11%21%18%11%
2070
16th to endNight
31%5%12%17%23%8%
2042
April1st to 15thNight
31%5%11%25%18%7%
1799
16th to endNight
25%5%9%24%23%12%
1800
May1st to 15thNight
31%5%9%18%23%12%
1800
16th to endNight
31%5%8%21%24%9%
1584
June1st to 15thNight
28%6%7%16%22%17%
1440
16th to endNight
23%37%7%27%31%
1440
July1st to 15thNight
21%5%9%10%17%35%
1409
16th to endNight
30%6%8%11%18%24%
1593
August1st to 15thNight
29%5%7%9%20%27%
1758
16th to endNight
24%47%6%28%28%
1910
September1st to 15thNight
24%5%8%9%19%32%
1765
16th to endNight
19%35%13%31%27%
1768
October1st to 15thNight
23%35%19%26%20%
1963
16th to endNight
24%36%13%28%23%
2112
November1st to 15thNight
22%46%17%27%21%
2205
16th to endNight
23%410%18%25%18%
2340
December1st to 15thNight
32%48%15%23%15%
2436
16th to endNight
33%410%18%21%13%
2688

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
19%10%27%28%13%2
189
16th to endDay
16%8%32%28%12%1
256
February1st to 15thDay
13%12%29%25%16%3
257
16th to endDay
14%16%33%24%8%2
238
March1st to 15thDay
10%14%34%27%13%
270
16th to endDay
9%15%34%31%7%1
288
April1st to 15thDay
12%15%37%21%8%3
269
16th to endDay
8%18%38%25%6%2
270
May1st to 15thDay
9%10%34%35%9%2
288
16th to endDay
9%9%30%37%10%3
330
June1st to 15thDay
6%6%27%40%15%3
315
16th to endDay
119%46%23%8%
315
July1st to 15thDay
4112%45%28%7%
305
16th to endDay
311%40%33%10%
327
August1st to 15thDay
6%114%49%22%4
315
16th to endDay
319%48%28%8%
332
September1st to 15thDay
4115%50%20%8%
300
16th to endDay
15%21%37%26%6%
255
October1st to 15thDay
5%9%32%38%12%2
255
16th to endDay
5%6%29%40%14%2
272
November1st to 15thDay
7%5%14%31%26%14%
157
16th to endDay
8%11%24%31%21%3
90
December1st to 15thDay
12%5%26%35%20%
73
16th to endDay
17%12%21%31%15%1
64
January1st to 15thNight
11%213%35%25%10%
720
16th to endNight
14%215%37%21%8%
768
February1st to 15thNight
11%314%34%28%7%
704
16th to endNight
16%5%15%37%20%5%
632
March1st to 15thNight
8%315%41%25%5%
720
16th to endNight
9%417%37%27%4
768
April1st to 15thNight
9%419%36%25%4
719
16th to endNight
7%421%29%31%6%
720
May1st to 15thNight
7%311%36%34%6%
720
16th to endNight
7%412%33%35%7%
462
June1st to 15thNight
5%8%33%45%6%
360
16th to endNight
231%56%6%
360
July1st to 15thNight
314%59%20%
389
16th to endNight
4212%52%28%
564
August1st to 15thNight
21326%50%15%
684
16th to endNight
2216%56%20%
764
September1st to 15thNight
3322%52%15%
706
16th to endNight
217%30%43%14%
656
October1st to 15thNight
6%210%34%37%8%
660
16th to endNight
7%111%30%36%10%
704
November1st to 15thNight
7%112%37%30%11%
700
16th to endNight
5%214%35%30%12%
720
December1st to 15thNight
10%214%38%27%6%
720
16th to endNight
15%417%39%18%5%
768
Page generated at 2017-09-13 04:39:04. Version ac04

Copyright 2017 A. Danko


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