Austin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Austin 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
52%
16162
26%
49079
19%
16117
59%
16117
34%
28331

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
41%
972
28%
2522
13%
970
49%
970
35%
1561
January16th to endNight
40%
988
30%
2652
14%
988
50%
988
34%
1641
February1st to 15thNight
35%
764
27%
2286
12%
758
47%
758
30%
1365
February16th to endNight
26%
684
27%
2050
9%
684
40%
684
28%
1236
March1st to 15thNight
35%
573
26%
2101
15%
573
48%
573
25%
1223
March16th to endNight
35%
576
24%
2112
17%
576
46%
576
26%
1203
April1st to 15thNight
32%
539
23%
1977
14%
539
47%
539
27%
1131
April16th to endNight
32%
540
25%
1771
14%
540
47%
540
27%
1077
May1st to 15thNight
38%
539
22%
1619
16%
539
48%
539
29%
1006
May16th to endNight
52%
562
25%
1684
21%
561
61%
561
36%
962
June1st to 15thNight
73%
540
23%
1620
24%
540
78%
540
52%
793
June16th to endNight
70%
540
22%
1620
23%
540
74%
540
38%
931
July1st to 15thNight
77%
510
22%
1530
24%
510
80%
510
47%
803
July16th to endNight
82%
564
25%
1594
29%
531
85%
531
45%
830
August1st to 15thNight
89%
539
30%
1631
34%
536
90%
536
55%
771
August16th to endNight
77%
573
21%
1988
26%
573
78%
573
32%
1121
September1st to 15thNight
77%
540
21%
1980
24%
540
77%
540
34%
1075
September16th to endNight
72%
537
26%
1980
30%
537
74%
537
29%
1111
October1st to 15thNight
73%
567
33%
2007
33%
567
75%
567
40%
1009
October16th to endNight
63%
768
37%
2304
26%
768
69%
768
49%
1153
November1st to 15thNight
54%
760
27%
2280
19%
760
58%
760
35%
1346
November16th to endNight
50%
972
32%
2532
17%
972
57%
972
40%
1502
December1st to 15thNight
44%
975
27%
2535
16%
975
48%
975
31%
1663
December16th to endNight
39%
1040
24%
2704
12%
1040
45%
1040
28%
1818

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
13%5%2442445%7%45%
49534
Night
12%413323347%52%
49282
TransparencyDay
37%49%20%18%8%
49234
Night
32%411%21%19%11%
49087
SeeingDay
13%316%27%28%10%
5920
Night
14%422%35%20%2
16167

By Month

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
17%423312335%50%
1746
16th to endDay
16%5%23323235%52%
1934
February1st to 15thDay
17%5%24322335%49%
1900
16th to endDay
20%6%2342333445%
1710
March1st to 15thDay
21%6%24313235%43%
2092
16th to endDay
17%5%24313335%47%
2110
April1st to 15thDay
15%6%25%5%24446%43%
1971
16th to endDay
15%6%35%434346%43%
2185
May1st to 15thDay
17%6%35%425%446%37%
2331
16th to endDay
16%6%25%5%36%5%5%8%34%
2430
June1st to 15thDay
6%3146%25%5%6%9%45%
2340
16th to endDay
10%5%25%7%36%6%7%9%35%
2340
July1st to 15thDay
8%3245%46%5%7%10%40%
2340
16th to endDay
7%3246%35%5%6%9%44%
2466
August1st to 15thDay
221132446%10%60%
2316
16th to endDay
7%426%5%36%6%6%10%39%
2212
September1st to 15thDay
9%436%5%25%6%5%7%41%
1980
16th to endDay
10%5%25%435%5%5%7%44%
1980
October1st to 15thDay
10%5%13424347%52%
1941
16th to endDay
8%31222224465%
1920
November1st to 15thDay
13%5%25%5%24445%45%
1908
16th to endDay
15%5%1321333455%
1755
December1st to 15thDay
18%7%24323236%44%
1755
16th to endDay
18%7%34324346%41%
1872
January1st to 15thNight
16%5%13212326%51%
2522
16th to endNight
17%413313346%50%
2652
February1st to 15thNight
17%5%2431223451%
2282
16th to endNight
16%6%23323346%47%
2050
March1st to 15thNight
17%6%13324436%46%
2101
16th to endNight
15%5%23223446%48%
2112
April1st to 15thNight
14%5%24313346%48%
1977
16th to endNight
17%5%23324346%45%
1771
May1st to 15thNight
12%5%24424448%45%
1619
16th to endNight
11%41332446%11%47%
1683
June1st to 15thNight
321122435%9%63%
1620
16th to endNight
5%32332446%8%53%
1620
July1st to 15thNight
5%31321347%11%55%
1620
16th to endNight
421332436%11%55%
1702
August1st to 15thNight
211121345%10%65%
1641
16th to endNight
6%214425%5%6%10%47%
1988
September1st to 15thNight
7%325%42445%9%51%
1980
16th to endNight
8%42442445%6%49%
1980
October1st to 15thNight
9%212313247%60%
2007
16th to endNight
9%212212335%66%
2304
November1st to 15thNight
11%414423446%51%
2280
16th to endNight
14%413312235%57%
2532
December1st to 15thNight
16%7%2432334447%
2535
16th to endNight
19%7%2432333445%
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
38%25%19%22%11%
1747
16th to endDay
36%25%14%26%14%
1934
February1st to 15thDay
39%36%15%20%14%
1901
16th to endDay
43%25%17%18%12%
1710
March1st to 15thDay
43%37%12%21%11%
2092
16th to endDay
39%37%17%22%9%
2112
April1st to 15thDay
42%36%16%17%12%
1971
16th to endDay
42%45%18%17%11%
2185
May1st to 15thDay
46%48%15%17%7%
2331
16th to endDay
46%5%10%17%16%3
2434
June1st to 15thDay
32%6%11%22%21%5%
2340
16th to endDay
42%8%10%21%15%2
2340
July1st to 15thDay
35%6%15%26%13%1
2201
16th to endDay
32%6%19%28%12%
2311
August1st to 15thDay
18%5%17%38%18%1
2302
16th to endDay
37%8%15%24%11%3
2212
September1st to 15thDay
39%7%10%21%15%6%
1980
16th to endDay
37%6%9%18%18%9%
1980
October1st to 15thDay
31%410%21%18%13%
1941
16th to endDay
22%25%17%30%21%
1920
November1st to 15thDay
40%48%20%17%9%
1908
16th to endDay
34%25%15%23%19%
1755
December1st to 15thDay
44%27%17%19%9%
1755
16th to endDay
44%38%15%18%9%
1872
January1st to 15thNight
35%25%18%21%16%
2522
16th to endNight
36%2415%22%17%
2652
February1st to 15thNight
37%25%15%20%18%
2292
16th to endNight
38%36%17%19%15%
2050
March1st to 15thNight
39%39%13%20%13%
2101
16th to endNight
36%410%15%22%10%
2112
April1st to 15thNight
37%39%16%17%15%
1977
16th to endNight
40%310%18%16%11%
1771
May1st to 15thNight
37%410%20%17%8%
1620
16th to endNight
30%5%16%28%15%3
1685
June1st to 15thNight
17%5%16%28%27%4
1620
16th to endNight
26%8%16%29%16%2
1620
July1st to 15thNight
21%6%24%33%13%
1530
16th to endNight
21%6%26%35%9%
1594
August1st to 15thNight
14%6%22%37%17%1
1631
16th to endNight
29%8%21%26%10%3
1988
September1st to 15thNight
30%5%18%25%14%6%
1980
16th to endNight
32%7%12%21%17%9%
1980
October1st to 15thNight
25%410%25%19%13%
2007
16th to endNight
22%25%17%27%24%
2304
November1st to 15thNight
33%410%20%18%12%
2280
16th to endNight
31%26%16%22%20%
2532
December1st to 15thNight
41%26%19%18%10%
2535
16th to endNight
43%35%14%21%12%
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
17%431%30%13%2
135
16th to endDay
17%9%33%27%9%2
144
February1st to 15thDay
19%7%34%28%10%
135
16th to endDay
29%9%36%19%5%
120
March1st to 15thDay
25%9%32%20%9%2
121
16th to endDay
15%6%28%35%9%5%
96
April1st to 15thDay
11%8%35%30%12%2
90
16th to endDay
16%8%34%26%13%
295
May1st to 15thDay
16%6%35%27%12%1
468
16th to endDay
19%421%32%18%2
517
June1st to 15thDay
8%8%40%34%8%
495
16th to endDay
8%37%33%33%13%
495
July1st to 15thDay
6%17%33%41%9%
475
16th to endDay
6%222%49%18%
515
August1st to 15thDay
4218%55%18%
469
16th to endDay
12%426%31%23%
252
September1st to 15thDay
2218%45%31%
135
16th to endDay
15%214%36%30%
135
October1st to 15thDay
25%22%45%23%
135
16th to endDay
13%314%22%30%14%
144
November1st to 15thDay
27%214%29%20%5%
135
16th to endDay
16%5%22%32%16%7%
135
December1st to 15thDay
20%425%23%16%9%
135
16th to endDay
31%9%27%22%7%1
144
January1st to 15thNight
20%7%25%33%12%
975
16th to endNight
19%6%29%35%8%
988
February1st to 15thNight
20%10%30%31%7%
764
16th to endNight
22%8%40%25%2
684
March1st to 15thNight
19%7%34%33%5%
573
16th to endNight
15%9%37%32%4
576
April1st to 15thNight
15%7%40%33%2
539
16th to endNight
17%7%39%27%7%
540
May1st to 15thNight
13%7%35%35%7%
540
16th to endNight
11%228%37%19%
563
June1st to 15thNight
4118%48%25%1
540
16th to endNight
6%113%47%27%3
540
July1st to 15thNight
5%9%44%35%3
510
16th to endNight
5%443%41%4
564
August1st to 15thNight
3245%42%6%
539
16th to endNight
7%436%46%5%
573
September1st to 15thNight
7%5%34%46%6%
540
16th to endNight
9%6%32%44%5%
537
October1st to 15thNight
10%19%38%34%5%
567
16th to endNight
10%320%32%30%2
768
November1st to 15thNight
12%323%34%23%2
760
16th to endNight
17%423%34%18%1
972
December1st to 15thNight
20%6%24%35%11%
975
16th to endNight
23%5%26%34%9%
1040
Page generated at 2018-03-12 12:28:02. Version ac04

Copyright 2018 A. Danko


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