South Llano River State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Llano River State Park clear sky chart from 2005-11-05 to 2018-01-12.

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
49%
15946
29%
48403
18%
15902
60%
15902
40%
25977

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
37%
952
29%
2472
12%
951
48%
951
39%
1475
January16th to endNight
37%
804
35%
2340
15%
804
52%
804
38%
1291
February1st to 15thNight
36%
704
30%
2107
14%
698
50%
698
37%
1130
February16th to endNight
26%
632
33%
1894
9%
632
46%
632
38%
984
March1st to 15thNight
30%
630
29%
2070
11%
630
48%
630
33%
1135
March16th to endNight
28%
576
28%
2112
14%
576
48%
576
35%
1070
April1st to 15thNight
24%
539
28%
1902
10%
539
49%
539
35%
977
April16th to endNight
27%
540
31%
1783
12%
540
53%
540
39%
916
May1st to 15thNight
29%
539
25%
1620
13%
539
45%
539
36%
934
May16th to endNight
41%
562
25%
1684
14%
561
58%
561
38%
964
June1st to 15thNight
62%
540
24%
1620
20%
540
72%
540
58%
735
June16th to endNight
66%
540
24%
1620
24%
540
72%
540
43%
866
July1st to 15thNight
76%
510
22%
1530
22%
510
80%
510
43%
830
July16th to endNight
85%
564
29%
1594
33%
531
88%
531
57%
755
August1st to 15thNight
87%
539
29%
1789
36%
536
88%
536
50%
817
August16th to endNight
77%
573
24%
1910
28%
573
78%
573
34%
1071
September1st to 15thNight
78%
540
24%
1971
27%
540
80%
540
35%
1054
September16th to endNight
69%
537
25%
1980
26%
537
72%
537
30%
1106
October1st to 15thNight
69%
540
34%
1980
32%
540
76%
540
44%
909
October16th to endNight
56%
705
38%
2241
24%
705
66%
705
49%
1068
November1st to 15thNight
52%
890
29%
2410
14%
890
60%
890
45%
1323
November16th to endNight
47%
975
35%
2535
15%
975
57%
975
47%
1384
December1st to 15thNight
43%
975
30%
2535
14%
975
51%
975
38%
1532
December16th to endNight
37%
1040
29%
2704
12%
1040
47%
1040
37%
1651

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
8%424424446%52%
48924
Night
7%313323347%58%
48605
Cloud CoverDay
8%42442445%6%52%
48922
Night
7%313323347%58%
48605
TransparencyDay
31%5%9%20%21%11%
48623
Night
25%5%11%22%22%13%
48409
SeeingDay
10%5%22%34%21%4
5737
Night
9%6%31%37%14%
15952

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
11%5%2432333454%
1710
16th to endDay
9%413313335%58%
1893
February1st to 15thDay
8%5%13313436%58%
1750
16th to endDay
9%312323345%59%
1580
March1st to 15thDay
13%423323345%53%
1890
16th to endDay
10%423323335%56%
2112
April1st to 15thDay
8%42442335%5%55%
2042
16th to endDay
9%424423445%53%
2175
May1st to 15thDay
12%5%25%5%2445%6%44%
2331
16th to endDay
11%5%35%435%446%45%
2430
June1st to 15thDay
321342446%8%58%
2340
16th to endDay
7%425%435%6%6%9%43%
2340
July1st to 15thDay
6%325%7%36%5%6%7%45%
2340
16th to endDay
5%223435%5%6%9%50%
2463
August1st to 15thDay
1213436%5%5%8%57%
2160
16th to endDay
8%435%7%26%6%5%8%41%
2292
September1st to 15thDay
10%5%25%6%35%5%47%42%
1988
16th to endDay
11%4245%345%6%5%46%
1980
October1st to 15thDay
7%423324437%54%
1980
16th to endDay
6%313212235%67%
1971
November1st to 15thDay
9%5%14422346%55%
1775
16th to endDay
7%413212235%63%
1755
December1st to 15thDay
14%5%24213337%51%
1755
16th to endDay
11%7%25%312446%50%
1872
January1st to 15thNight
11%6%13312235%57%
2472
16th to endNight
10%412313346%57%
2340
February1st to 15thNight
8%5%23312235%60%
2102
16th to endNight
8%41221335%6%59%
1894
March1st to 15thNight
10%412323446%54%
2070
16th to endNight
6%32331445%6%58%
2112
April1st to 15thNight
6%313314347%58%
1902
16th to endNight
5%314323346%60%
1783
May1st to 15thNight
8%423414448%53%
1619
16th to endNight
7%31331345%10%54%
1683
June1st to 15thNight
111121335%10%66%
1620
16th to endNight
321232445%10%57%
1620
July1st to 15thNight
411222446%10%57%
1620
16th to endNight
211131337%11%62%
1702
August1st to 15thNight
21132345%9%65%
1800
16th to endNight
4415%4245%6%10%49%
1910
September1st to 15thNight
6%21443347%9%52%
1971
16th to endNight
8%4244245%6%8%49%
1980
October1st to 15thNight
6%222212247%64%
1980
16th to endNight
6%212212335%67%
2241
November1st to 15thNight
7%313313346%62%
2410
16th to endNight
6%312312336%64%
2535
December1st to 15thNight
12%5%13312346%54%
2535
16th to endNight
9%5%24422446%53%
2704

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
12%5%2432333455%
1710
16th to endDay
9%413323335%58%
1893
February1st to 15thDay
7%5%22313345%58%
1750
16th to endDay
9%322224345%59%
1580
March1st to 15thDay
13%423323345%53%
1890
16th to endDay
10%423313335%56%
2110
April1st to 15thDay
8%42441335%5%54%
2042
16th to endDay
9%424424446%53%
2175
May1st to 15thDay
12%5%25%5%2445%7%44%
2331
16th to endDay
11%5%3442445%6%45%
2430
June1st to 15thDay
321333446%8%57%
2340
16th to endDay
7%424435%6%7%8%44%
2340
July1st to 15thDay
6%325%7%36%5%7%7%45%
2340
16th to endDay
5%223435%47%9%50%
2463
August1st to 15thDay
1313435%5%5%8%57%
2160
16th to endDay
8%5%25%6%35%6%6%8%41%
2292
September1st to 15thDay
10%5%25%5%45%45%7%42%
1988
16th to endDay
11%4245%345%5%6%46%
1980
October1st to 15thDay
7%42332335%6%55%
1980
16th to endDay
6%312212235%67%
1971
November1st to 15thDay
9%5%24413346%55%
1775
16th to endDay
7%413212236%63%
1755
December1st to 15thDay
14%5%24313237%51%
1755
16th to endDay
11%7%25%312445%50%
1872
January1st to 15thNight
11%5%13312235%57%
2472
16th to endNight
10%422313236%57%
2340
February1st to 15thNight
8%5%13312336%60%
2102
16th to endNight
8%41221335%7%59%
1894
March1st to 15thNight
10%412323346%54%
2070
16th to endNight
6%32332445%7%57%
2112
April1st to 15thNight
6%322323446%58%
1902
16th to endNight
5%314323346%60%
1783
May1st to 15thNight
8%424314447%54%
1619
16th to endNight
7%31441335%9%54%
1683
June1st to 15thNight
11121235%10%66%
1620
16th to endNight
321232445%9%58%
1620
July1st to 15thNight
41132245%5%10%57%
1620
16th to endNight
211131237%11%62%
1702
August1st to 15thNight
21222345%9%65%
1800
16th to endNight
5%42442447%9%50%
1910
September1st to 15thNight
6%2134335%6%9%52%
1971
16th to endNight
9%4234235%7%7%49%
1980
October1st to 15thNight
6%213212347%64%
1980
16th to endNight
6%212212335%67%
2241
November1st to 15thNight
7%313313336%62%
2410
16th to endNight
7%313313236%64%
2535
December1st to 15thNight
13%5%12313345%54%
2535
16th to endNight
9%5%24422346%53%
2704

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
33%35%19%25%13%
1711
16th to endDay
29%37%13%28%18%
1893
February1st to 15thDay
27%37%15%23%22%
1751
16th to endDay
27%26%17%28%17%
1580
March1st to 15thDay
33%38%15%20%18%
1890
16th to endDay
30%47%19%23%14%
2112
April1st to 15thDay
30%5%7%16%21%18%
2042
16th to endDay
32%46%20%20%15%
2175
May1st to 15thDay
39%5%9%14%20%9%
2331
16th to endDay
38%6%9%18%21%5%
2434
June1st to 15thDay
22%6%12%26%25%6%
2340
16th to endDay
34%7%13%22%17%4
2340
July1st to 15thDay
33%8%14%27%14%2
2201
16th to endDay
25%8%19%30%14%1
2308
August1st to 15thDay
23%6%13%35%19%1
2147
16th to endDay
38%7%15%24%12%2
2292
September1st to 15thDay
39%7%10%20%16%4
1988
16th to endDay
36%7%9%20%17%8%
1980
October1st to 15thDay
28%6%11%21%22%10%
1980
16th to endDay
20%26%16%30%23%
1971
November1st to 15thDay
30%48%22%21%11%
1775
16th to endDay
24%35%16%25%23%
1755
December1st to 15thDay
35%37%16%26%11%
1755
16th to endDay
35%46%17%24%11%
1872
January1st to 15thNight
31%25%17%24%18%
2472
16th to endNight
29%25%17%25%20%
2340
February1st to 15thNight
27%37%14%22%24%
2112
16th to endNight
24%35%18%27%19%
1894
March1st to 15thNight
29%5%9%14%23%17%
2070
16th to endNight
25%5%11%20%21%15%
2112
April1st to 15thNight
25%5%10%18%19%21%
1902
16th to endNight
24%5%10%23%21%15%
1783
May1st to 15thNight
30%5%10%23%19%11%
1620
16th to endNight
27%7%15%24%20%5%
1685
June1st to 15thNight
12%5%15%31%28%5%
1620
16th to endNight
22%7%16%28%19%5%
1620
July1st to 15thNight
20%10%19%30%17%2
1530
16th to endNight
13%6%25%35%18%1
1594
August1st to 15thNight
14%7%16%36%22%1
1789
16th to endNight
27%8%19%27%13%2
1910
September1st to 15thNight
25%8%14%25%19%5%
1971
16th to endNight
31%7%14%20%17%8%
1980
October1st to 15thNight
20%414%27%21%11%
1980
16th to endNight
19%37%16%27%24%
2241
November1st to 15thNight
23%49%24%24%13%
2410
16th to endNight
22%37%16%25%23%
2535
December1st to 15thNight
31%47%17%24%14%
2535
16th to endNight
32%46%16%24%15%
2704

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
14%13%35%26%8%
123
16th to endDay
13%12%41%23%8%
96
February1st to 15thDay
10%8%40%26%14%
90
16th to endDay
12%6%51%24%4
81
March1st to 15thDay
18%10%32%24%14%
90
16th to endDay
5%7%42%27%16%1
96
April1st to 15thDay
15%21%42%18%11
161
16th to endDay
10%17%41%22%7%
285
May1st to 15thDay
16%13%39%24%5%
468
16th to endDay
16%7%29%34%9%
517
June1st to 15thDay
4220%50%19%3
495
16th to endDay
5%18%43%28%3
495
July1st to 15thDay
5%18%45%33%5%
475
16th to endDay
35%41%38%10%
512
August1st to 15thDay
5%440%38%11%
315
16th to endDay
12%8%37%28%12%
332
September1st to 15thDay
5%330%40%19%
143
16th to endDay
19%325%39%11%
135
October1st to 15thDay
8%5%37%37%11%
135
16th to endDay
9%5%22%31%27%3
144
November1st to 15thDay
23%5%22%29%16%2
135
16th to endDay
12%14%27%20%20%4
135
December1st to 15thDay
19%5%25%33%11%4
135
16th to endDay
17%13%36%27%5%
144
January1st to 15thNight
15%8%35%31%9%
956
16th to endNight
13%6%39%32%7%
804
February1st to 15thNight
12%11%37%33%5%
704
16th to endNight
10%13%48%25%2
632
March1st to 15thNight
13%10%43%26%5%
630
16th to endNight
6%11%50%27%2
576
April1st to 15thNight
7%12%53%23%2
539
16th to endNight
5%9%54%25%4
540
May1st to 15thNight
8%9%50%26%4
540
16th to endNight
6%5%42%33%11%
563
June1st to 15thNight
232%53%11%
540
16th to endNight
2123%49%20%1
540
July1st to 15thNight
413%56%24%1
510
16th to endNight
35%59%29%1
564
August1st to 15thNight
21253%36%3
539
16th to endNight
5%7%49%32%3
573
September1st to 15thNight
6%7%44%36%3
540
16th to endNight
10%12%46%28%1
537
October1st to 15thNight
8%116%47%25%
540
16th to endNight
5%6%28%39%19%1
705
November1st to 15thNight
9%430%38%15%1
890
16th to endNight
9%6%32%34%15%1
975
December1st to 15thNight
15%6%31%37%8%
975
16th to endNight
13%10%35%33%7%
1040
Page generated at 2018-01-12 21:01:34. Version ac04

Copyright 2018 A. Danko


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