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East Valley Astronomy Club and The Saguaro Astronomy Club
.

Antenna Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Antenna Site clear sky chart from 2005-11-05 to 2017-05-24.

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
77%
15463
39%
45859
33%
15423
82%
15423
61%
20544

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
74%
720
35%
2327
34%
716
80%
716
50%
1064
January16th to endNight
69%
768
39%
2480
37%
768
77%
768
49%
1170
February1st to 15thNight
71%
698
40%
2108
34%
698
80%
698
56%
959
February16th to endNight
67%
632
37%
1895
37%
632
73%
632
49%
946
March1st to 15thNight
68%
720
40%
2037
33%
720
78%
720
60%
941
March16th to endNight
71%
768
39%
2112
30%
768
79%
768
62%
989
April1st to 15thNight
62%
719
34%
1939
20%
719
70%
719
60%
929
April16th to endNight
69%
600
47%
1680
29%
600
80%
600
78%
680
May1st to 15thNight
75%
539
41%
1619
30%
539
82%
539
70%
659
May16th to endNight
79%
540
39%
1621
29%
540
84%
540
74%
644
June1st to 15thNight
85%
495
38%
1485
33%
495
86%
495
75%
588
June16th to endNight
92%
495
35%
1485
31%
495
93%
495
81%
564
July1st to 15thNight
89%
465
31%
1395
27%
465
90%
465
61%
628
July16th to endNight
86%
522
33%
1467
27%
489
88%
489
53%
714
August1st to 15thNight
89%
494
40%
1476
34%
491
89%
491
61%
665
August16th to endNight
87%
700
36%
1761
28%
700
87%
700
59%
933
September1st to 15thNight
86%
660
36%
1815
30%
660
88%
660
60%
873
September16th to endNight
85%
656
45%
1815
38%
656
89%
656
77%
776
October1st to 15thNight
77%
660
44%
1829
35%
660
83%
660
68%
825
October16th to endNight
84%
704
45%
2112
41%
704
89%
704
69%
883
November1st to 15thNight
80%
700
41%
2225
39%
700
86%
700
64%
928
November16th to endNight
77%
720
42%
2340
42%
720
84%
720
60%
984
December1st to 15thNight
72%
720
39%
2340
36%
720
80%
720
53%
1046
December16th to endNight
66%
768
39%
2496
35%
768
76%
768
48%
1156

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
2112212335%73%
46406
Night
2112212335%73%
46059
TransparencyDay
14%2311%25%43%
46101
Night
14%2311%24%43%
45865
SeeingDay
35%18%33%30%8%
5151
Night
3212%35%38%7%
15472

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
2213313335%68%
1611
16th to endDay
6%22212345%67%
1743
February1st to 15thDay
212223336%69%
1751
16th to endDay
4112313347%64%
1579
March1st to 15thDay
2111212345%72%
1921
16th to endDay
1212212225%74%
2112
April1st to 15thDay
211112246%73%
2006
16th to endDay
11125%83%
2278
May1st to 15thDay
1211122480%
2331
16th to endDay
111111384%
2335
June1st to 15thDay
11112385%
2145
16th to endDay
11221185%
2145
July1st to 15thDay
1112314447%65%
2145
16th to endDay
4223435%5%6%9%52%
2285
August1st to 15thDay
211332345%8%63%
2142
16th to endDay
22222345%7%65%
2089
September1st to 15thDay
3112323446%66%
1815
16th to endDay
1111122382%
1815
October1st to 15thDay
11111232380%
1799
16th to endDay
1121123480%
1760
November1st to 15thDay
111111235%78%
1631
16th to endDay
3111111235%75%
1620
December1st to 15thDay
3212324347%64%
1620
16th to endDay
321332335%7%64%
1728
January1st to 15thNight
3212323345%68%
2327
16th to endNight
5%31321223467%
2480
February1st to 15thNight
2212312335%71%
2101
16th to endNight
4212323335%65%
1895
March1st to 15thNight
221212346%71%
2037
16th to endNight
212213337%71%
2112
April1st to 15thNight
211231233374%
1939
16th to endNight
1112386%
1680
May1st to 15thNight
1111235%79%
1619
16th to endNight
111122384%
1621
June1st to 15thNight
1111122383%
1485
16th to endNight
1112386%
1485
July1st to 15thNight
121221335%7%69%
1485
16th to endNight
221232447%9%58%
1575
August1st to 15thNight
22222347%70%
1485
16th to endNight
311232335%8%64%
1761
September1st to 15thNight
1212235%5%6%67%
1815
16th to endNight
1111123382%
1815
October1st to 15thNight
1111211245%76%
1829
16th to endNight
1121123479%
2112
November1st to 15thNight
11221223476%
2225
16th to endNight
311221222475%
2340
December1st to 15thNight
311221235%6%67%
2340
16th to endNight
4212323345%66%
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
18%2412%30%30%
1612
16th to endDay
19%2415%25%31%
1743
February1st to 15thDay
16%1413%29%32%
1751
16th to endDay
19%1415%30%27%
1579
March1st to 15thDay
14%1110%30%40%
1921
16th to endDay
14%1210%30%39%
2112
April1st to 15thDay
12%119%32%41%
2006
16th to endDay
7%18%27%54%
2278
May1st to 15thDay
10%118%25%53%
2331
16th to endDay
8%16%21%61%
2338
June1st to 15thDay
7%415%70%
2145
16th to endDay
8%1137%77%
2145
July1st to 15thDay
16%45%11%17%44%
2006
16th to endDay
23%48%23%20%19%
2130
August1st to 15thDay
18%3418%22%32%
2127
16th to endDay
17%45%12%31%29%
2089
September1st to 15thDay
18%25%13%24%35%
1815
16th to endDay
9%215%19%62%
1815
October1st to 15thDay
10%1210%25%50%
1799
16th to endDay
9%238%22%54%
1760
November1st to 15thDay
10%1113%30%42%
1631
16th to endDay
12%1112%29%41%
1620
December1st to 15thDay
19%25%15%27%28%
1620
16th to endDay
19%27%19%31%18%
1728
January1st to 15thNight
18%3413%25%35%
2327
16th to endNight
22%1313%25%33%
2480
February1st to 15thNight
17%1315%24%37%
2112
16th to endNight
22%2312%26%33%
1895
March1st to 15thNight
14%119%25%45%
2037
16th to endNight
14%1311%28%40%
2112
April1st to 15thNight
15%138%28%42%
1939
16th to endNight
6%19%26%55%
1680
May1st to 15thNight
9%126%25%54%
1620
16th to endNight
8%116%23%60%
1622
June1st to 15thNight
8%1413%70%
1485
16th to endNight
6%138%80%
1485
July1st to 15thNight
14%27%13%17%44%
1395
16th to endNight
18%47%26%19%24%
1467
August1st to 15thNight
13%3317%26%35%
1476
16th to endNight
18%35%15%27%29%
1761
September1st to 15thNight
14%46%15%26%33%
1815
16th to endNight
8%116%19%62%
1815
October1st to 15thNight
12%139%23%49%
1829
16th to endNight
10%128%18%57%
2112
November1st to 15thNight
12%1110%26%47%
2225
16th to endNight
14%1110%26%44%
2340
December1st to 15thNight
17%2414%28%32%
2340
16th to endNight
20%2419%27%24%
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
7%228%42%17%1
90
16th to endDay
45%26%22%29%11%
111
February1st to 15thDay
47%24%30%28%4
266
16th to endDay
7%12%27%31%17%3
238
March1st to 15thDay
211%22%30%25%7%
270
16th to endDay
212%26%28%21%7%
288
April1st to 15thDay
311%24%33%18%8%
269
16th to endDay
115%31%32%12%5%
270
May1st to 15thDay
26%29%31%22%7%
288
16th to endDay
2222%39%27%4
301
June1st to 15thDay
3220%38%27%6%
255
16th to endDay
110%43%31%12%
255
July1st to 15thDay
18%38%45%5%
245
16th to endDay
3226%48%18%
271
August1st to 15thDay
1436%45%12%
255
16th to endDay
2228%49%17%
268
September1st to 15thDay
313%36%35%10%
255
16th to endDay
420%32%32%9%
255
October1st to 15thDay
1423%33%30%6%
239
16th to endDay
15%333%44%12%
96
November1st to 15thDay
413%28%40%13%
90
16th to endDay
5%427%26%26%8%
90
December1st to 15thDay
2417%25%42%7%
90
16th to endDay
6%7%18%33%32%2
96
January1st to 15thNight
5%213%41%30%7%
720
16th to endNight
7%315%39%29%5%
768
February1st to 15thNight
4214%41%32%4
704
16th to endNight
5%218%43%25%4
632
March1st to 15thNight
25%21%34%29%6%
720
16th to endNight
2416%38%31%6%
768
April1st to 15thNight
25%24%36%26%4
719
16th to endNight
15%22%41%25%5%
600
May1st to 15thNight
1316%41%31%4
540
16th to endNight
1213%40%37%4
542
June1st to 15thNight
119%43%41%3
495
16th to endNight
438%50%6%
495
July1st to 15thNight
1129%60%6%
465
16th to endNight
3319%61%11%
522
August1st to 15thNight
2221%63%10%
494
16th to endNight
4218%60%14%
700
September1st to 15thNight
25%26%52%12%
660
16th to endNight
29%29%47%10%
656
October1st to 15thNight
2113%36%40%4
660
16th to endNight
118%33%41%12%
704
November1st to 15thNight
212%40%35%9%
700
16th to endNight
4111%36%33%11%
720
December1st to 15thNight
4214%41%32%3
720
16th to endNight
6%217%39%28%5%
768
Page generated at 2017-05-25 10:27:40. Version ac04

Copyright 2017 A. Danko


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