Alamo Lake State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Alamo Lake 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
80%
16270
38%
48378
34%
16232
84%
16232
58%
22236

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
77%
762
33%
2471
34%
760
80%
760
46%
1189
January16th to endNight
74%
768
37%
2496
38%
768
79%
768
46%
1217
February1st to 15thNight
77%
698
37%
2115
37%
698
82%
698
53%
1004
February16th to endNight
72%
632
35%
1895
36%
632
76%
632
47%
970
March1st to 15thNight
71%
720
38%
2040
32%
720
79%
720
57%
969
March16th to endNight
75%
768
37%
2112
30%
768
80%
768
58%
1034
April1st to 15thNight
68%
719
33%
1934
21%
719
76%
719
58%
959
April16th to endNight
71%
590
45%
1670
30%
590
80%
590
74%
689
May1st to 15thNight
77%
539
40%
1619
30%
539
82%
539
67%
670
May16th to endNight
78%
561
39%
1684
30%
561
82%
561
74%
667
June1st to 15thNight
84%
540
35%
1620
30%
540
86%
540
75%
637
June16th to endNight
91%
540
37%
1620
34%
540
91%
540
82%
604
July1st to 15thNight
91%
510
28%
1530
25%
510
91%
510
58%
715
July16th to endNight
83%
564
28%
1593
24%
531
84%
531
43%
843
August1st to 15thNight
90%
539
35%
1611
30%
536
91%
536
58%
747
August16th to endNight
86%
744
39%
1899
29%
744
86%
744
57%
1002
September1st to 15thNight
86%
720
32%
1980
27%
720
88%
720
57%
982
September16th to endNight
87%
716
47%
1980
39%
716
91%
716
76%
837
October1st to 15thNight
83%
720
41%
2004
35%
720
86%
720
67%
899
October16th to endNight
86%
768
46%
2304
43%
768
90%
768
68%
971
November1st to 15thNight
85%
760
38%
2427
39%
760
88%
760
59%
1053
November16th to endNight
81%
780
42%
2535
44%
780
85%
780
59%
1071
December1st to 15thNight
77%
780
37%
2535
38%
780
81%
780
50%
1177
December16th to endNight
71%
832
38%
2704
38%
832
76%
832
45%
1330

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
2112212345%71%
48962
Night
212213345%71%
48574
TransparencyDay
15%2411%24%41%
48657
Night
15%2411%24%40%
48380
SeeingDay
36%21%36%22%8%
5957
Night
319%37%39%7%
16281

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
4213222345%67%
1710
16th to endDay
6%113313326%65%
1728
February1st to 15thDay
3213213336%68%
1747
16th to endDay
5%223313337%63%
1579
March1st to 15thDay
311212345%71%
1920
16th to endDay
221123235%72%
2112
April1st to 15thDay
2112213346%69%
2011
16th to endDay
11112225%81%
2289
May1st to 15thDay
11111132479%
2331
16th to endDay
111113382%
2429
June1st to 15thDay
11111386%
2340
16th to endDay
1112485%
2340
July1st to 15thDay
2122245%47%66%
2340
16th to endDay
4214435%6%7%8%51%
2467
August1st to 15thDay
221332345%7%62%
2340
16th to endDay
221322345%7%64%
2300
September1st to 15thDay
2113314446%67%
1980
16th to endDay
11111123480%
1980
October1st to 15thDay
11221123478%
1956
16th to endDay
1112133478%
1920
November1st to 15thDay
1111112345%74%
1761
16th to endDay
3212212336%72%
1755
December1st to 15thDay
3213324248%61%
1755
16th to endDay
6%21232225%6%63%
1872
January1st to 15thNight
3313324346%64%
2471
16th to endNight
6%213213345%65%
2496
February1st to 15thNight
2313313245%68%
2104
16th to endNight
6%213323337%62%
1895
March1st to 15thNight
3212213345%69%
2040
16th to endNight
311231335%6%69%
2112
April1st to 15thNight
2112313335%72%
1934
16th to endNight
1111235%81%
1670
May1st to 15thNight
11111223479%
1619
16th to endNight
11123481%
1684
June1st to 15thNight
111113483%
1620
16th to endNight
11112487%
1620
July1st to 15thNight
1231445%7%67%
1620
16th to endNight
3313325%6%6%9%54%
1701
August1st to 15thNight
21122345%8%67%
1620
16th to endNight
323323447%65%
1899
September1st to 15thNight
21232445%7%65%
1980
16th to endNight
1111112383%
1980
October1st to 15thNight
21121223477%
2004
16th to endNight
1111322478%
2304
November1st to 15thNight
1112212335%73%
2427
16th to endNight
22121223475%
2535
December1st to 15thNight
4212322345%67%
2535
16th to endNight
6%312323345%63%
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
20%3413%29%28%
1711
16th to endDay
22%26%16%24%28%
1728
February1st to 15thDay
17%25%16%27%31%
1747
16th to endDay
22%3415%28%25%
1579
March1st to 15thDay
14%2310%31%37%
1920
16th to endDay
16%2411%31%34%
2112
April1st to 15thDay
15%2311%30%37%
2011
16th to endDay
8%229%28%49%
2289
May1st to 15thDay
10%1310%25%48%
2331
16th to endDay
8%128%23%55%
2432
June1st to 15thDay
7%1416%70%
2340
16th to endDay
7%239%77%
2340
July1st to 15thDay
17%46%11%16%43%
2201
16th to endDay
25%7%10%20%17%18%
2312
August1st to 15thDay
18%5%7%15%21%31%
2325
16th to endDay
19%47%13%25%30%
2300
September1st to 15thDay
18%45%13%21%37%
1980
16th to endDay
10%125%20%59%
1980
October1st to 15thDay
11%238%24%49%
1956
16th to endDay
10%248%22%50%
1920
November1st to 15thDay
12%2313%30%36%
1761
16th to endDay
15%1410%27%40%
1755
December1st to 15thDay
22%36%16%22%28%
1755
16th to endDay
22%27%18%30%18%
1872
January1st to 15thNight
21%4413%25%31%
2471
16th to endNight
23%2414%24%30%
2496
February1st to 15thNight
18%26%13%24%33%
2115
16th to endNight
23%35%12%26%28%
1895
March1st to 15thNight
16%2411%27%38%
2040
16th to endNight
17%2411%30%33%
2112
April1st to 15thNight
16%2210%29%37%
1934
16th to endNight
7%139%27%50%
1670
May1st to 15thNight
10%129%27%47%
1620
16th to endNight
7%139%23%54%
1685
June1st to 15thNight
8%125%15%67%
1620
16th to endNight
5%139%78%
1620
July1st to 15thNight
14%48%12%14%45%
1530
16th to endNight
22%7%10%20%16%22%
1593
August1st to 15thNight
15%45%14%24%36%
1611
16th to endNight
18%36%13%25%32%
1899
September1st to 15thNight
16%46%17%20%34%
1980
16th to endNight
8%12418%64%
1980
October1st to 15thNight
12%139%23%48%
2004
16th to endNight
11%147%20%54%
2304
November1st to 15thNight
15%2310%29%38%
2427
16th to endNight
14%1310%27%41%
2535
December1st to 15thNight
19%3414%26%31%
2535
16th to endNight
23%35%18%28%21%
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
11%7%14%38%23%4
123
16th to endDay
5%6%14%28%27%18%
96
February1st to 15thDay
48%28%33%23%3
262
16th to endDay
7%17%31%28%10%4
238
March1st to 15thDay
415%24%32%16%6%
270
16th to endDay
318%29%28%13%6%
288
April1st to 15thDay
7%14%33%25%8%10%
269
16th to endDay
421%33%25%9%4
270
May1st to 15thDay
410%30%34%15%5%
288
16th to endDay
36%31%35%18%3
330
June1st to 15thDay
1431%42%16%4
315
16th to endDay
1215%44%25%10%
315
July1st to 15thDay
11%48%29%7%
305
16th to endDay
5%441%33%14%
327
August1st to 15thDay
311%46%26%10%
315
16th to endDay
37%40%33%14%
332
September1st to 15thDay
3120%41%24%7%
315
16th to endDay
2423%40%20%8%
315
October1st to 15thDay
25%29%35%21%5%
291
16th to endDay
3111%24%34%25%
144
November1st to 15thDay
138%27%48%9%
135
16th to endDay
2420%28%27%16%
135
December1st to 15thDay
1214%32%36%13%
135
16th to endDay
7%411%29%34%11%
144
January1st to 15thNight
4110%43%30%8%
764
16th to endNight
6%111%41%31%7%
768
February1st to 15thNight
438%44%33%5%
704
16th to endNight
7%212%49%23%5%
632
March1st to 15thNight
3317%37%31%5%
720
16th to endNight
3412%42%31%6%
768
April1st to 15thNight
25%19%39%29%4
719
16th to endNight
2419%42%26%5%
590
May1st to 15thNight
2414%40%34%4
540
16th to endNight
1314%42%33%4
563
June1st to 15thNight
219%43%40%3
540
16th to endNight
6%35%50%6%
540
July1st to 15thNight
1327%61%6%
510
16th to endNight
4316%65%10%
564
August1st to 15thNight
3220%66%7%
539
16th to endNight
4217%61%13%
744
September1st to 15thNight
2324%57%11%
720
16th to endNight
27%33%46%9%
716
October1st to 15thNight
219%42%38%5%
720
16th to endNight
117%33%44%12%
768
November1st to 15thNight
216%47%35%7%
760
16th to endNight
318%38%38%9%
780
December1st to 15thNight
5%19%43%32%7%
780
16th to endNight
7%212%39%29%8%
832
Page generated at 2018-01-12 20:01:32. Version ac04

Copyright 2018 A. Danko


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