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 2018-03-11.

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
68%
16397
28%
49104
25%
16360
72%
16360
39%
27122

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%
776
26%
2573
27%
776
68%
776
34%
1413
January16th to endNight
60%
832
27%
2704
27%
832
64%
832
34%
1532
February1st to 15thNight
64%
758
31%
2348
32%
757
68%
757
38%
1285
February16th to endNight
56%
684
27%
2051
25%
684
62%
684
34%
1215
March1st to 15thNight
62%
764
22%
2199
21%
764
66%
764
34%
1329
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
80%
720
33%
1800
26%
720
81%
720
47%
1053
September16th to endNight
82%
716
38%
1929
35%
716
84%
716
56%
982
October1st to 15thNight
74%
720
31%
2142
32%
720
77%
720
49%
1078
October16th to endNight
72%
768
37%
2304
37%
768
76%
768
44%
1207
November1st to 15thNight
72%
760
31%
2394
32%
760
76%
760
43%
1226
November16th to endNight
70%
780
33%
2535
33%
780
76%
780
43%
1260
December1st to 15thNight
64%
780
29%
2639
29%
780
69%
780
35%
1420
December16th to endNight
58%
832
28%
2912
28%
832
65%
832
32%
1604

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%
49513
Night
6%5%24323448%55%
49298
TransparencyDay
24%48%18%26%18%
49200
Night
28%48%16%23%19%
49110
SeeingDay
7%7%25%35%18%4
6632
Night
7%211%32%35%10%
16410

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
9%314424446%54%
1692
16th to endDay
12%413323346%54%
1872
February1st to 15thDay
12%424323336%55%
1839
16th to endDay
13%5%14323446%49%
1709
March1st to 15thDay
8%42343245%9%51%
1994
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
2313213448%63%
2160
16th to endDay
1212212346%71%
2031
October1st to 15thDay
5%213212335%68%
1815
16th to endDay
323213336%67%
1920
November1st to 15thDay
6%313312345%63%
1792
16th to endDay
6%212312348%61%
1755
December1st to 15thDay
9%423322346%55%
1648
16th to endDay
13%31341325%6%53%
1664
January1st to 15thNight
9%5%13434346%53%
2573
16th to endNight
11%5%24323335%53%
2704
February1st to 15thNight
9%423322347%55%
2342
16th to endNight
13%6%12422336%53%
2051
March1st to 15thNight
8%5%23325%46%8%49%
2199
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%
1800
16th to endNight
131333327%68%
1929
October1st to 15thNight
5%323212245%66%
2142
16th to endNight
5%5%13212436%62%
2304
November1st to 15thNight
4413313347%62%
2394
16th to endNight
5%323313347%61%
2535
December1st to 15thNight
9%42431335%7%54%
2639
16th to endNight
13%413223346%53%
2912

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
30%47%20%22%13%
1692
16th to endDay
32%49%15%19%19%
1872
February1st to 15thDay
32%25%19%23%15%
1839
16th to endDay
35%411%21%21%5%
1709
March1st to 15thDay
30%414%20%18%11%
1994
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%26%29%
2160
16th to endDay
15%2418%34%24%
2031
October1st to 15thDay
20%26%19%28%23%
1815
16th to endDay
20%37%15%27%26%
1920
November1st to 15thDay
24%46%18%28%17%
1792
16th to endDay
22%48%17%29%17%
1755
December1st to 15thDay
30%48%15%23%17%
1648
16th to endDay
32%38%21%20%13%
1664
January1st to 15thNight
32%37%19%21%15%
2573
16th to endNight
33%38%12%20%21%
2704
February1st to 15thNight
30%37%17%25%15%
2353
16th to endNight
34%37%21%22%9%
2051
March1st to 15thNight
32%6%10%20%18%11%
2199
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%10%19%32%
1800
16th to endNight
18%25%13%32%26%
1929
October1st to 15thNight
22%35%17%26%25%
2142
16th to endNight
24%46%12%26%25%
2304
November1st to 15thNight
24%47%18%26%19%
2394
16th to endNight
23%39%17%26%18%
2535
December1st to 15thNight
30%48%14%23%19%
2639
16th to endNight
32%39%17%22%14%
2912

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
18%8%26%26%18%1
230
16th to endDay
14%8%31%28%14%1
304
February1st to 15thDay
11%10%27%25%17%6%
312
16th to endDay
13%16%31%24%11%2
290
March1st to 15thDay
12%13%33%27%12%
312
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
5%115%49%20%7%
315
16th to endDay
16%21%37%26%6%
315
October1st to 15thDay
47%32%37%13%3
315
16th to endDay
6%6%27%36%17%5%
336
November1st to 15thDay
6%6%18%31%25%11%
208
16th to endDay
8%8%19%30%28%5%
135
December1st to 15thDay
8%423%35%21%6%
110
16th to endDay
13%9%15%33%18%9%
96
January1st to 15thNight
12%213%35%26%10%
780
16th to endNight
13%215%38%21%8%
832
February1st to 15thNight
10%313%34%29%8%
764
16th to endNight
15%5%16%37%20%4
684
March1st to 15thNight
9%316%40%24%5%
764
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
41323%52%15%
720
16th to endNight
217%30%43%14%
716
October1st to 15thNight
6%210%34%37%8%
720
16th to endNight
7%112%29%37%10%
768
November1st to 15thNight
6%111%39%29%10%
760
16th to endNight
5%213%35%31%11%
780
December1st to 15thNight
10%214%37%29%6%
780
16th to endNight
14%416%38%20%5%
832
Page generated at 2018-03-12 10:28:08. Version ac04

Copyright 2018 A. Danko


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