Aztalan State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Aztalan State Park clear sky chart from 2005-11-05 to 2017-09-10.

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
38%
16011
17%
46779
10%
15968
44%
15968
23%
31477

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
23%
900
13%
2506
5%
895
30%
895
17%
1865
January16th to endNight
23%
960
12%
2655
4%
960
29%
960
16%
2018
February1st to 15thNight
26%
844
14%
2256
4%
844
33%
844
21%
1597
February16th to endNight
27%
631
17%
1893
8%
631
35%
631
18%
1325
March1st to 15thNight
30%
720
15%
2160
8%
720
36%
720
20%
1462
March16th to endNight
36%
594
17%
2004
14%
594
41%
594
18%
1373
April1st to 15thNight
29%
539
15%
1797
11%
539
37%
539
19%
1230
April16th to endNight
35%
540
19%
1741
13%
540
44%
540
22%
1152
May1st to 15thNight
34%
540
15%
1530
8%
540
40%
540
22%
1085
May16th to endNight
46%
563
16%
1498
8%
561
51%
561
31%
973
June1st to 15thNight
51%
540
15%
1440
9%
540
54%
540
31%
917
June16th to endNight
52%
540
16%
1440
9%
540
55%
540
34%
914
July1st to 15thNight
66%
510
17%
1360
11%
510
68%
510
45%
779
July16th to endNight
68%
564
21%
1417
14%
531
71%
531
42%
824
August1st to 15thNight
70%
539
21%
1530
18%
536
72%
536
38%
906
August16th to endNight
62%
573
20%
1910
21%
573
66%
573
31%
1112
September1st to 15thNight
61%
525
26%
1750
26%
525
67%
525
36%
941
September16th to endNight
53%
640
24%
1798
16%
640
59%
640
35%
1085
October1st to 15thNight
43%
660
24%
1935
16%
660
50%
660
29%
1207
October16th to endNight
32%
704
17%
2230
10%
704
41%
704
21%
1464
November1st to 15thNight
35%
700
22%
2276
16%
700
44%
700
24%
1432
November16th to endNight
26%
825
15%
2445
8%
825
33%
825
18%
1729
December1st to 15thNight
19%
900
11%
2520
3%
900
26%
900
15%
1920
December16th to endNight
17%
960
11%
2688
3%
960
24%
960
12%
2167

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
14%7%36%5%3445%7%36%
47859
Night
14%8%35%5%24446%39%
46947
Cloud CoverDay
14%7%36%5%3445%7%36%
47867
Night
14%8%35%5%24446%40%
46952
TransparencyDay
46%6%13%22%11%1
47545
Night
44%5%12%22%13%1
46779
SeeingDay
16%7%27%26%16%6%
6010
Night
18%7%29%31%12%1
16014

By Month

Percentage Cloud Cover NE (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
13%12%6%7%5%345%6%7%28%
1432
16th to endDay
14%13%7%11%7%23446%22%
1566
February1st to 15thDay
14%13%6%7%424445%32%
1606
16th to endDay
14%12%36%6%35%435%32%
1580
March1st to 15thDay
15%8%37%42445%6%35%
1790
16th to endDay
18%7%36%6%34347%34%
2229
April1st to 15thDay
18%10%46%5%245%5%6%30%
2151
16th to endDay
20%7%35%433446%35%
2217
May1st to 15thDay
19%7%37%6%345%5%8%29%
2420
16th to endDay
13%426%5%345%5%8%39%
2617
June1st to 15thDay
13%425%6%35%5%6%8%38%
2520
16th to endDay
10%5%25%5%35%5%6%10%40%
2520
July1st to 15thDay
7%4244345%6%10%46%
2520
16th to endDay
7%4245%36%5%7%9%41%
2655
August1st to 15thDay
7%436%5%45%5%6%9%42%
2420
16th to endDay
11%425%435%45%7%43%
2292
September1st to 15thDay
13%41442445%8%46%
2097
16th to endDay
12%5%245%25%45%8%42%
1821
October1st to 15thDay
17%7%16%323437%42%
1694
16th to endDay
18%8%26%5%2445%7%34%
1642
November1st to 15thDay
13%8%46%424447%40%
1582
16th to endDay
15%11%47%6%33345%35%
1512
December1st to 15thDay
16%13%47%7%34345%28%
1440
16th to endDay
20%15%48%6%4445%421%
1536
January1st to 15thNight
15%12%5%7%5%24335%32%
2506
16th to endNight
13%10%6%9%6%45%446%28%
2655
February1st to 15thNight
11%14%5%6%424445%37%
2254
16th to endNight
15%11%46%5%34445%36%
1893
March1st to 15thNight
17%8%345%24447%38%
2147
16th to endNight
17%8%45%435%446%35%
2004
April1st to 15thNight
20%8%25%4235%46%34%
1797
16th to endNight
19%8%24423345%39%
1741
May1st to 15thNight
19%6%35%426%46%6%35%
1530
16th to endNight
11%425%42446%9%42%
1496
June1st to 15thNight
11%324425%5%5%7%45%
1440
16th to endNight
9%435%42446%8%46%
1440
July1st to 15thNight
6%2134235%5%10%54%
1440
16th to endNight
5%2144245%6%7%54%
1513
August1st to 15thNight
6%4134345%6%9%50%
1539
16th to endNight
10%5%1343435%7%49%
1910
September1st to 15thNight
8%32432435%6%55%
1750
16th to endNight
9%4245%2445%7%49%
1798
October1st to 15thNight
11%6%35%5%23435%48%
1935
16th to endNight
18%7%24334347%40%
2230
November1st to 15thNight
13%7%34424445%45%
2276
16th to endNight
17%8%46%5%24445%35%
2445
December1st to 15thNight
20%12%48%5%25%43429%
2520
16th to endNight
22%14%5%7%6%3333423%
2688

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
13%12%5%7%6%345%5%7%28%
1432
16th to endDay
14%13%7%11%7%3345%6%23%
1566
February1st to 15thDay
14%13%6%7%43444432%
1606
16th to endDay
13%12%46%6%35%436%32%
1580
March1st to 15thDay
15%8%47%42445%6%35%
1800
16th to endDay
18%8%36%6%34347%34%
2227
April1st to 15thDay
18%10%46%5%345%5%5%30%
2151
16th to endDay
20%7%35%433446%35%
2217
May1st to 15thDay
19%7%36%6%345%5%8%29%
2420
16th to endDay
13%436%6%3445%8%39%
2617
June1st to 15thDay
13%425%6%35%5%6%8%38%
2520
16th to endDay
10%425%5%35%5%6%10%40%
2520
July1st to 15thDay
8%4144345%6%10%45%
2520
16th to endDay
7%435%5%35%5%7%9%41%
2655
August1st to 15thDay
7%426%5%35%46%8%42%
2420
16th to endDay
11%5%25%5%35%45%7%43%
2292
September1st to 15thDay
13%31443445%8%45%
2097
16th to endDay
11%5%245%25%45%8%42%
1821
October1st to 15thDay
17%6%25%323347%42%
1694
16th to endDay
18%8%26%5%2445%7%34%
1642
November1st to 15thDay
13%8%45%424347%40%
1582
16th to endDay
16%11%47%6%23245%35%
1512
December1st to 15thDay
17%12%38%7%34435%29%
1440
16th to endDay
20%15%5%8%6%3444421%
1536
January1st to 15thNight
15%12%5%7%5%24435%32%
2506
16th to endNight
13%10%6%9%6%35%446%28%
2655
February1st to 15thNight
11%14%5%6%424445%37%
2247
16th to endNight
15%11%36%5%24345%35%
1893
March1st to 15thNight
17%8%335%23447%38%
2160
16th to endNight
17%9%35%425%5%46%35%
2004
April1st to 15thNight
20%9%25%5%2345%6%34%
1797
16th to endNight
19%7%34323345%40%
1741
May1st to 15thNight
19%5%35%426%5%5%6%35%
1529
16th to endNight
11%435%425%46%9%42%
1496
June1st to 15thNight
12%3245%25%5%5%7%45%
1440
16th to endNight
9%426%42446%8%46%
1440
July1st to 15thNight
6%2134245%5%10%54%
1440
16th to endNight
5%21442446%7%54%
1513
August1st to 15thNight
5%4134345%6%9%51%
1539
16th to endNight
10%5%13434447%49%
1910
September1st to 15thNight
9%314324346%56%
1750
16th to endNight
9%425%5%2345%7%49%
1798
October1st to 15thNight
11%6%25%5%2443448%
1935
16th to endNight
18%6%24424347%39%
2230
November1st to 15thNight
13%8%24423445%45%
2276
16th to endNight
17%8%36%5%34445%35%
2445
December1st to 15thNight
19%12%47%5%3443429%
2520
16th to endNight
22%14%5%7%6%3433423%
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
54%5%14%17%7%
1433
16th to endDay
61%5%12%14%6%
1566
February1st to 15thDay
55%411%20%7%1
1608
16th to endDay
53%5%10%20%8%1
1580
March1st to 15thDay
48%6%14%20%9%1
1800
16th to endDay
50%6%14%21%7%
2229
April1st to 15thDay
53%5%11%18%9%
2151
16th to endDay
48%6%11%20%10%1
2217
May1st to 15thDay
52%6%13%20%7%
2420
16th to endDay
42%7%11%24%13%1
2621
June1st to 15thDay
41%7%13%23%13%
2520
16th to endDay
37%8%15%21%15%1
2520
July1st to 15thDay
33%8%14%26%15%1
2371
16th to endDay
35%8%16%22%13%2
2488
August1st to 15thDay
37%7%12%27%13%1
2405
16th to endDay
38%7%12%24%15%1
2292
September1st to 15thDay
35%6%11%26%18%
2097
16th to endDay
38%5%13%28%13%
1821
October1st to 15thDay
42%410%27%14%
1694
16th to endDay
48%5%12%22%9%
1642
November1st to 15thDay
43%5%12%24%12%1
1582
16th to endDay
52%416%21%4
1512
December1st to 15thDay
58%5%12%18%5%
1440
16th to endDay
65%5%11%10%6%
1536
January1st to 15thNight
54%5%9%19%10%
2506
16th to endNight
55%5%13%16%7%
2655
February1st to 15thNight
49%412%21%10%1
2256
16th to endNight
50%5%12%21%9%1
1893
March1st to 15thNight
46%5%13%19%13%1
2160
16th to endNight
48%6%12%23%7%1
2004
April1st to 15thNight
50%48%20%15%
1797
16th to endNight
46%410%20%14%2
1741
May1st to 15thNight
47%6%11%21%11%
1530
16th to endNight
36%7%15%22%14%3
1498
June1st to 15thNight
34%8%11%27%17%
1440
16th to endNight
34%7%14%21%20%2
1440
July1st to 15thNight
25%5%15%29%20%2
1360
16th to endNight
25%7%14%30%16%4
1417
August1st to 15thNight
28%8%13%28%19%1
1530
16th to endNight
34%5%13%26%17%2
1910
September1st to 15thNight
28%5%11%27%25%1
1750
16th to endNight
33%5%12%32%15%
1798
October1st to 15thNight
38%410%25%19%1
1935
16th to endNight
44%5%13%24%11%
2230
November1st to 15thNight
41%5%10%24%16%2
2276
16th to endNight
50%5%15%19%8%
2445
December1st to 15thNight
58%411%17%7%
2520
16th to endNight
65%410%13%5%
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
22%10%31%34%2
90
16th to endDay
21%10%31%30%5%1
96
February1st to 15thDay
17%18%43%12%7%
90
16th to endDay
28%11%38%16%41
81
March1st to 15thDay
26%13%40%14%5%
90
16th to endDay
28%7%26%23%11%2
222
April1st to 15thDay
24%10%28%26%9%
270
16th to endDay
21%11%24%25%11%4
270
May1st to 15thDay
24%9%29%24%9%3
377
16th to endDay
15%9%31%23%14%5%
517
June1st to 15thDay
13%6%26%31%17%4
495
16th to endDay
11%7%32%26%15%6%
495
July1st to 15thDay
8%324%30%21%10%
475
16th to endDay
8%226%30%23%9%
515
August1st to 15thDay
10%219%29%26%11%
451
16th to endDay
15%5%13%29%23%12%
332
September1st to 15thDay
13%317%30%24%10%
294
16th to endDay
14%422%25%24%9%
254
October1st to 15thDay
19%7%18%29%20%4
134
16th to endDay
27%10%33%25%4
96
November1st to 15thDay
7%11%30%30%18%2
90
16th to endDay
35%10%34%11%7%1
90
December1st to 15thDay
18%12%50%15%3
90
16th to endDay
26%18%44%8%2
96
January1st to 15thNight
19%12%35%22%8%
900
16th to endNight
18%10%38%28%4
960
February1st to 15thNight
20%9%34%29%6%
847
16th to endNight
20%10%33%28%6%
631
March1st to 15thNight
21%9%32%27%8%
720
16th to endNight
19%8%30%31%8%1
594
April1st to 15thNight
25%7%34%28%4
539
16th to endNight
23%6%31%29%8%
540
May1st to 15thNight
22%5%33%29%8%
540
16th to endNight
12%331%38%14%
563
June1st to 15thNight
14%326%41%14%
540
16th to endNight
10%228%41%15%
540
July1st to 15thNight
7%19%42%26%3
510
16th to endNight
6%117%48%24%1
564
August1st to 15thNight
8%113%48%26%2
539
16th to endNight
12%116%38%25%4
573
September1st to 15thNight
8%321%34%26%6%
525
16th to endNight
11%423%31%26%2
640
October1st to 15thNight
16%7%27%31%16%1
660
16th to endNight
20%10%30%28%9%
704
November1st to 15thNight
17%8%34%27%12%
700
16th to endNight
21%11%33%24%7%
825
December1st to 15thNight
25%11%35%21%5%
900
16th to endNight
29%9%32%23%4
960
Page generated at 2017-09-11 18:35:14. Version ac04

Copyright 2017 A. Danko


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