Lake San Antonio
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake San Antonio 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
76%
15567
32%
46860
29%
15530
80%
15530
51%
23038

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%
716
23%
2377
23%
716
71%
716
34%
1318
January16th to endNight
69%
768
27%
2496
30%
768
70%
768
34%
1413
February1st to 15thNight
67%
698
28%
2213
28%
697
72%
697
36%
1239
February16th to endNight
63%
632
26%
1895
26%
632
68%
632
36%
1103
March1st to 15thNight
70%
720
23%
2049
21%
720
73%
720
41%
1161
March16th to endNight
66%
768
25%
2058
19%
768
71%
768
44%
1168
April1st to 15thNight
62%
719
30%
1799
18%
719
67%
719
48%
1026
April16th to endNight
66%
720
31%
1800
14%
720
72%
720
58%
936
May1st to 15thNight
76%
719
29%
1799
18%
719
78%
719
65%
893
May16th to endNight
74%
401
36%
1525
32%
401
82%
401
60%
559
June1st to 15thNight
81%
360
34%
1440
37%
360
89%
360
58%
512
June16th to endNight
92%
360
42%
1440
52%
360
94%
360
82%
412
July1st to 15thNight
97%
385
36%
1405
42%
385
98%
385
85%
435
July16th to endNight
93%
564
41%
1593
37%
531
94%
531
74%
634
August1st to 15thNight
94%
639
40%
1713
29%
636
95%
636
80%
724
August16th to endNight
95%
764
45%
1910
30%
764
95%
764
83%
843
September1st to 15thNight
93%
706
44%
1765
34%
706
94%
706
78%
807
September16th to endNight
90%
656
46%
1768
41%
656
92%
656
78%
752
October1st to 15thNight
79%
660
34%
1980
36%
660
83%
660
53%
949
October16th to endNight
81%
704
39%
2112
41%
704
84%
704
56%
994
November1st to 15thNight
80%
700
35%
2199
37%
700
84%
700
53%
1033
November16th to endNight
76%
720
29%
2340
29%
720
79%
720
43%
1168
December1st to 15thNight
69%
720
27%
2496
28%
720
73%
720
32%
1403
December16th to endNight
59%
768
24%
2688
24%
768
64%
768
29%
1556

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
4213313336%66%
47797
Night
4212223336%66%
47049
TransparencyDay
20%37%18%27%23%
47485
Night
20%38%19%27%20%
46862
SeeingDay
5%5%16%30%27%13%
6018
Night
5%210%33%39%8%
15579

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
44245%26%5%6%8%49%
1558
16th to endDay
12%4245%24347%48%
1728
February1st to 15thDay
9%5%35%423347%50%
1648
16th to endDay
12%5%26%4245%47%43%
1579
March1st to 15thDay
5%3245%35%6%6%8%48%
1910
16th to endDay
7%4245%25%447%51%
2166
April1st to 15thDay
7%5%24324447%53%
2149
16th to endDay
4212323446%64%
2160
May1st to 15thDay
1212212246%71%
2151
16th to endDay
2211212236%74%
2583
June1st to 15thDay
111112236%75%
2520
16th to endDay
111488%
2520
July1st to 15thDay
1112484%
2467
16th to endDay
1111123480%
2468
August1st to 15thDay
1111112482%
2238
16th to endDay
111122483%
2292
September1st to 15thDay
111222482%
2114
16th to endDay
112223479%
1859
October1st to 15thDay
2212214446%65%
1650
16th to endDay
22332335%6%67%
1760
November1st to 15thDay
4424324346%59%
1660
16th to endDay
3325%42435%5%58%
1620
December1st to 15thDay
8%6%35%5%34348%45%
1461
16th to endDay
10%5%35%424448%46%
1536
January1st to 15thNight
7%415%433347%52%
2377
16th to endNight
10%42332335%6%53%
2496
February1st to 15thNight
7%414424447%52%
2203
16th to endNight
9%424323347%53%
1895
March1st to 15thNight
5%324323447%57%
2049
16th to endNight
432342345%9%57%
2058
April1st to 15thNight
6%213323447%61%
1799
16th to endNight
2212213337%70%
1800
May1st to 15thNight
12212337%72%
1799
16th to endNight
11112147%76%
1523
June1st to 15thNight
211112236%77%
1440
16th to endNight
11390%
1440
July1st to 15thNight
112487%
1489
16th to endNight
111123481%
1701
August1st to 15thNight
11112385%
1722
16th to endNight
1122485%
1910
September1st to 15thNight
1222483%
1765
16th to endNight
111112484%
1768
October1st to 15thNight
3322213245%68%
1980
16th to endNight
2212212446%69%
2112
November1st to 15thNight
3213213336%69%
2199
16th to endNight
421232445%7%60%
2340
December1st to 15thNight
6%5%25%42445%7%51%
2496
16th to endNight
9%5%25%424346%50%
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
31%5%10%20%21%10%
1558
16th to endDay
35%410%14%19%15%
1728
February1st to 15thDay
35%38%21%21%9%
1648
16th to endDay
39%6%9%21%18%4
1579
March1st to 15thDay
31%5%14%22%18%9%
1910
16th to endDay
33%412%23%18%6%
2166
April1st to 15thDay
31%410%23%22%6%
2149
16th to endDay
20%5%10%24%28%10%
2160
May1st to 15thDay
15%37%24%35%13%
2151
16th to endDay
14%28%28%34%11%
2587
June1st to 15thDay
12%29%17%32%25%
2520
16th to endDay
5%1210%36%45%
2520
July1st to 15thDay
6%27%24%57%
2322
16th to endDay
9%1410%26%46%
2313
August1st to 15thDay
8%129%30%48%
2222
16th to endDay
7%29%38%40%
2292
September1st to 15thDay
8%1312%30%43%
2114
16th to endDay
10%1217%40%27%
1859
October1st to 15thDay
19%36%22%25%22%
1650
16th to endDay
18%27%21%28%21%
1760
November1st to 15thDay
25%39%19%30%11%
1660
16th to endDay
26%5%7%21%27%11%
1620
December1st to 15thDay
38%5%8%18%20%9%
1461
16th to endDay
36%5%12%18%19%7%
1536
January1st to 15thNight
32%39%21%22%10%
2377
16th to endNight
32%5%11%13%22%15%
2496
February1st to 15thNight
31%49%22%23%9%
2214
16th to endNight
32%410%26%21%5%
1895
March1st to 15thNight
26%5%15%23%20%9%
2049
16th to endNight
24%6%16%22%22%7%
2058
April1st to 15thNight
24%312%30%21%7%
1799
16th to endNight
16%411%29%28%10%
1800
May1st to 15thNight
13%211%23%34%15%
1800
16th to endNight
11%29%28%34%13%
1525
June1st to 15thNight
11%29%18%30%26%
1440
16th to endNight
31211%34%46%
1440
July1st to 15thNight
427%27%57%
1405
16th to endNight
8%1211%27%48%
1593
August1st to 15thNight
6%118%32%48%
1713
16th to endNight
6%19%34%47%
1910
September1st to 15thNight
7%2311%25%50%
1765
16th to endNight
7%1318%38%30%
1768
October1st to 15thNight
19%26%23%27%20%
1980
16th to endNight
17%37%20%31%20%
2112
November1st to 15thNight
18%210%21%33%12%
2199
16th to endNight
22%412%19%26%13%
2340
December1st to 15thNight
31%6%9%17%24%10%
2496
16th to endNight
35%5%12%19%18%8%
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
13%6%18%30%20%9%
186
16th to endDay
11%6%20%25%24%11%
256
February1st to 15thDay
13%8%19%24%22%12%
249
16th to endDay
15%11%21%28%17%5%
238
March1st to 15thDay
7%11%22%28%25%4
270
16th to endDay
9%10%25%31%18%5%
288
April1st to 15thDay
14%12%26%28%10%7%
269
16th to endDay
5%13%31%31%13%4
270
May1st to 15thDay
5%6%26%39%16%5%
288
16th to endDay
38%19%35%21%11%
330
June1st to 15thDay
16%19%36%24%11%
315
16th to endDay
12%34%28%23%
315
July1st to 15thDay
16%33%35%22%
305
16th to endDay
5%34%34%24%
327
August1st to 15thDay
25%30%41%20%
315
16th to endDay
1324%42%28%
332
September1st to 15thDay
29%29%35%23%
300
16th to endDay
211%29%37%18%
255
October1st to 15thDay
35%21%34%28%7%
255
16th to endDay
5%419%31%33%6%
272
November1st to 15thDay
4415%15%34%25%
166
16th to endDay
5%5%18%35%28%5%
90
December1st to 15thDay
15%7%20%26%26%1
63
16th to endDay
9%7%10%29%28%14%
64
January1st to 15thNight
10%110%40%29%7%
720
16th to endNight
12%11%38%31%5%
768
February1st to 15thNight
9%212%38%31%5%
704
16th to endNight
11%314%43%22%4
632
March1st to 15thNight
7%213%41%29%5%
720
16th to endNight
6%216%35%34%3
768
April1st to 15thNight
6%5%19%37%26%3
719
16th to endNight
2322%32%31%7%
720
May1st to 15thNight
1214%38%35%8%
720
16th to endNight
2217%33%36%7%
402
June1st to 15thNight
2310%39%39%5%
360
16th to endNight
5%33%53%6%
360
July1st to 15thNight
117%63%18%
385
16th to endNight
19%61%26%
564
August1st to 15thNight
20%61%16%
639
16th to endNight
116%65%16%
764
September1st to 15thNight
223%57%15%
706
16th to endNight
427%51%14%
656
October1st to 15thNight
5%18%34%39%10%
660
16th to endNight
418%33%41%11%
704
November1st to 15thNight
419%37%41%6%
700
16th to endNight
5%28%39%36%7%
720
December1st to 15thNight
9%39%41%31%4
720
16th to endNight
11%215%40%26%2
768
Page generated at 2017-09-13 04:39:21. Version ac04

Copyright 2017 A. Danko


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