Blanco State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blanco State Park clear sky chart from 2005-11-05 to 2017-09-18.

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%
15424
27%
46967
18%
15377
58%
15377
34%
26872

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%
899
27%
2327
11%
895
47%
895
34%
1443
January16th to endNight
36%
870
31%
2406
12%
870
49%
870
33%
1457
February1st to 15thNight
34%
704
29%
2106
13%
698
47%
698
31%
1207
February16th to endNight
24%
632
29%
1894
9%
632
40%
632
30%
1096
March1st to 15thNight
32%
570
28%
2010
13%
570
49%
570
26%
1154
March16th to endNight
31%
576
24%
2112
15%
576
45%
576
25%
1202
April1st to 15thNight
29%
539
23%
1977
13%
539
45%
539
26%
1131
April16th to endNight
29%
540
25%
1758
13%
540
46%
540
26%
1085
May1st to 15thNight
33%
539
23%
1619
16%
539
44%
539
29%
985
May16th to endNight
47%
562
25%
1684
19%
561
58%
561
34%
1009
June1st to 15thNight
66%
540
24%
1620
23%
540
73%
540
50%
815
June16th to endNight
65%
540
22%
1620
23%
540
70%
540
40%
911
July1st to 15thNight
75%
510
20%
1530
22%
510
77%
510
41%
838
July16th to endNight
81%
564
25%
1594
28%
531
84%
531
47%
844
August1st to 15thNight
88%
539
29%
1691
34%
536
88%
536
55%
774
August16th to endNight
74%
573
21%
1961
26%
573
75%
573
34%
1103
September1st to 15thNight
75%
540
21%
1980
24%
540
76%
540
33%
1080
September16th to endNight
68%
501
26%
1848
26%
501
71%
501
29%
1042
October1st to 15thNight
67%
495
34%
1815
34%
495
71%
495
37%
912
October16th to endNight
57%
698
35%
2106
23%
698
66%
698
47%
1062
November1st to 15thNight
51%
733
29%
2133
17%
733
58%
733
37%
1217
November16th to endNight
45%
900
30%
2340
15%
900
53%
900
39%
1395
December1st to 15thNight
39%
900
29%
2340
14%
900
47%
900
32%
1487
December16th to endNight
37%
960
25%
2496
11%
960
44%
960
31%
1623

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
12%5%24434447%46%
47818
Night
11%5%23323347%52%
47170
Cloud CoverDay
11%5%2442445%6%46%
47816
Night
10%5%24323347%52%
47170
TransparencyDay
38%38%20%18%9%
47516
Night
32%310%21%19%11%
46975
SeeingDay
13%5%18%32%25%6%
5380
Night
14%6%24%35%16%1
15427

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
14%6%23423336%50%
1611
16th to endDay
14%423313335%53%
1827
February1st to 15thDay
14%5%24313335%51%
1750
16th to endDay
15%5%24213335%51%
1580
March1st to 15thDay
18%6%23322336%46%
1950
16th to endDay
16%5%33323335%48%
2112
April1st to 15thDay
14%6%24434346%45%
1971
16th to endDay
14%7%25%333346%44%
2199
May1st to 15thDay
16%6%36%5%35%45%6%36%
2331
16th to endDay
17%7%345%345%5%7%35%
2430
June1st to 15thDay
44245%36%6%6%9%45%
2340
16th to endDay
10%6%36%6%36%5%6%9%36%
2340
July1st to 15thDay
9%425%5%46%6%6%8%40%
2340
16th to endDay
7%324446%5%7%9%43%
2466
August1st to 15thDay
2213425%4410%58%
2255
16th to endDay
8%425%6%46%5%6%10%38%
2241
September1st to 15thDay
10%6%26%6%35%5%46%40%
1980
16th to endDay
10%426%5%245%6%6%44%
1837
October1st to 15thDay
11%42342435%6%50%
1808
16th to endDay
7%313323245%62%
1760
November1st to 15thDay
11%5%26%43445%5%45%
1722
16th to endDay
14%42431323455%
1620
December1st to 15thDay
16%7%35%223335%46%
1620
16th to endDay
14%7%25%5%2343446%
1728
January1st to 15thNight
15%5%23323246%50%
2327
16th to endNight
15%423323345%51%
2406
February1st to 15thNight
13%5%34212235%54%
2102
16th to endNight
12%5%24323345%51%
1894
March1st to 15thNight
16%6%24312236%49%
2010
16th to endNight
14%5%34323346%48%
2112
April1st to 15thNight
12%6%25%323346%49%
1977
16th to endNight
16%5%25%413336%46%
1758
May1st to 15thNight
13%5%34323447%47%
1619
16th to endNight
11%5%2332445%10%45%
1683
June1st to 15thNight
32232345%9%61%
1620
16th to endNight
6%413325%36%10%52%
1620
July1st to 15thNight
6%3134235%6%10%51%
1620
16th to endNight
5%21332345%11%55%
1702
August1st to 15thNight
11131345%10%65%
1701
16th to endNight
7%423435%46%10%47%
1961
September1st to 15thNight
7%4136%3346%9%49%
1980
16th to endNight
7%6%2442446%7%47%
1848
October1st to 15thNight
9%413213336%58%
1815
16th to endNight
8%312222235%65%
2106
November1st to 15thNight
9%5%24413336%54%
2133
16th to endNight
12%5%2321223457%
2340
December1st to 15thNight
15%6%24313336%49%
2340
16th to endNight
14%7%3432343448%
2496

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
14%5%22423335%50%
1611
16th to endDay
14%5%13323335%53%
1827
February1st to 15thDay
13%6%24313246%51%
1750
16th to endDay
14%5%2431334451%
1580
March1st to 15thDay
18%6%24323335%46%
1950
16th to endDay
14%6%34323336%48%
2110
April1st to 15thDay
13%6%25%434346%45%
1971
16th to endDay
14%6%25%433346%45%
2199
May1st to 15thDay
15%7%36%5%3445%6%37%
2331
16th to endDay
16%7%345%3446%7%35%
2430
June1st to 15thDay
44245%37%6%6%8%46%
2340
16th to endDay
9%6%35%6%46%5%5%9%37%
2340
July1st to 15thDay
9%425%5%36%6%7%8%40%
2340
16th to endDay
7%3245%35%6%7%10%43%
2466
August1st to 15thDay
21124344410%58%
2255
16th to endDay
8%425%7%46%6%6%9%38%
2241
September1st to 15thDay
10%5%26%6%45%45%6%40%
1980
16th to endDay
10%425%5%345%5%6%44%
1837
October1st to 15thDay
10%5%23424446%51%
1808
16th to endDay
8%214312345%62%
1760
November1st to 15thDay
10%6%26%5%24446%45%
1722
16th to endDay
13%5%1431333455%
1620
December1st to 15thDay
15%8%34323235%46%
1620
16th to endDay
12%8%25%5%2444446%
1728
January1st to 15thNight
15%423223246%50%
2327
16th to endNight
15%423323345%51%
2406
February1st to 15thNight
12%5%25%22223455%
2102
16th to endNight
11%5%25%322345%51%
1894
March1st to 15thNight
14%7%24323236%49%
2010
16th to endNight
13%5%33323446%48%
2112
April1st to 15thNight
10%6%35%5%23346%49%
1977
16th to endNight
14%5%35%423336%46%
1758
May1st to 15thNight
12%6%23423447%47%
1619
16th to endNight
10%5%2432445%10%46%
1683
June1st to 15thNight
321223345%9%62%
1620
16th to endNight
6%323315%36%10%53%
1620
July1st to 15thNight
6%21342446%11%52%
1620
16th to endNight
5%21231445%12%55%
1702
August1st to 15thNight
11221345%10%65%
1701
16th to endNight
7%414425%46%11%47%
1961
September1st to 15thNight
7%4145%3445%9%49%
1980
16th to endNight
7%6%3442446%7%47%
1848
October1st to 15thNight
8%323324246%59%
1815
16th to endNight
8%312223235%65%
2106
November1st to 15thNight
8%5%25%323346%54%
2133
16th to endNight
11%5%2321223458%
2340
December1st to 15thNight
13%7%24313335%49%
2340
16th to endNight
13%8%24324335%47%
2496

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
37%2320%22%13%
1612
16th to endDay
34%3415%26%15%
1827
February1st to 15thDay
36%2415%22%17%
1751
16th to endDay
37%1419%21%14%
1580
March1st to 15thDay
42%17%13%21%13%
1950
16th to endDay
38%37%18%20%11%
2112
April1st to 15thDay
40%27%16%19%13%
1971
16th to endDay
42%2421%16%11%
2199
May1st to 15thDay
47%38%14%18%6%
2331
16th to endDay
47%48%18%16%4
2434
June1st to 15thDay
32%410%24%21%5%
2340
16th to endDay
43%5%10%21%15%3
2340
July1st to 15thDay
38%5%14%25%13%1
2201
16th to endDay
32%419%30%11%
2311
August1st to 15thDay
21%316%40%17%1
2241
16th to endDay
39%5%15%25%10%2
2241
September1st to 15thDay
42%5%9%21%16%5%
1980
16th to endDay
37%49%19%18%9%
1837
October1st to 15thDay
34%39%19%19%13%
1808
16th to endDay
24%3318%29%20%
1760
November1st to 15thDay
41%26%21%17%11%
1722
16th to endDay
35%2414%21%21%
1620
December1st to 15thDay
41%26%18%20%10%
1620
16th to endDay
41%37%15%21%11%
1728
January1st to 15thNight
36%2418%20%18%
2327
16th to endNight
35%2315%24%18%
2406
February1st to 15thNight
34%2413%23%21%
2112
16th to endNight
35%3417%22%16%
1894
March1st to 15thNight
38%28%15%20%15%
2010
16th to endNight
37%38%17%20%11%
2112
April1st to 15thNight
36%38%16%17%16%
1977
16th to endNight
40%38%17%17%11%
1758
May1st to 15thNight
37%310%20%17%9%
1620
16th to endNight
34%414%26%16%3
1685
June1st to 15thNight
20%413%30%26%4
1620
16th to endNight
27%5%18%29%16%3
1620
July1st to 15thNight
25%6%21%31%13%1
1530
16th to endNight
21%6%27%33%10%1
1594
August1st to 15thNight
14%5%21%40%16%1
1691
16th to endNight
31%5%21%27%10%3
1961
September1st to 15thNight
31%5%17%23%17%5%
1980
16th to endNight
34%5%12%20%17%9%
1848
October1st to 15thNight
27%39%26%19%13%
1815
16th to endNight
23%25%18%28%22%
2106
November1st to 15thNight
31%38%23%20%13%
2133
16th to endNight
32%26%15%20%23%
2340
December1st to 15thNight
38%26%18%22%11%
2340
16th to endNight
40%25%14%23%13%
2496

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
16%8%35%28%10%
90
16th to endDay
17%10%39%22%8%1
96
February1st to 15thDay
11%20%27%30%11%
90
16th to endDay
17%13%48%19%1
81
March1st to 15thDay
24%7%38%17%11%
90
16th to endDay
12%6%37%33%9%1
96
April1st to 15thDay
14%14%42%24%4
90
16th to endDay
17%11%36%26%7%
309
May1st to 15thDay
17%13%36%25%6%
468
16th to endDay
23%6%22%32%14%1
517
June1st to 15thDay
6%213%47%26%3
495
16th to endDay
12%210%37%29%7%
495
July1st to 15thDay
7%210%40%33%6%
475
16th to endDay
6%1430%46%10%
515
August1st to 15thDay
5%234%44%13%
409
16th to endDay
13%434%32%14%
281
September1st to 15thDay
5%220%52%19%
135
16th to endDay
5%215%54%22%
96
October1st to 15thDay
216%33%41%15%
90
16th to endDay
18%312%28%33%4
96
November1st to 15thDay
33%5%20%26%7%6%
90
16th to endDay
30%8%23%25%8%3
90
December1st to 15thDay
21%8%20%26%15%7%
90
16th to endDay
21%14%35%22%5%
96
January1st to 15thNight
19%10%28%32%8%
900
16th to endNight
18%9%32%31%7%
870
February1st to 15thNight
18%13%30%30%7%
704
16th to endNight
18%11%43%24%2
632
March1st to 15thNight
20%8%33%30%6%
570
16th to endNight
17%9%37%31%3
576
April1st to 15thNight
15%11%39%30%2
539
16th to endNight
18%8%39%25%8%
540
May1st to 15thNight
15%8%36%33%5%
540
16th to endNight
13%429%37%13%
563
June1st to 15thNight
4222%48%21%1
540
16th to endNight
7%217%48%20%3
540
July1st to 15thNight
6%29%51%28%2
510
16th to endNight
6%1449%32%4
564
August1st to 15thNight
2348%38%6%
539
16th to endNight
10%5%41%37%4
573
September1st to 15thNight
9%15%40%36%6%
540
16th to endNight
11%19%34%38%5%
501
October1st to 15thNight
10%314%40%28%3
495
16th to endNight
10%6%22%32%25%2
698
November1st to 15thNight
13%5%24%35%19%2
733
16th to endNight
14%9%25%34%13%1
900
December1st to 15thNight
21%8%27%31%9%1
900
16th to endNight
20%9%27%33%8%
960
Page generated at 2017-09-19 06:32:33. Version ac04

Copyright 2017 A. Danko


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