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East Valley Astronomy Club and The Saguaro Astronomy Club
,
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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 2019-05-11.

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
77%
18086
39%
53646
33%
18046
83%
18046
61%
24065

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
73%
840
36%
2717
35%
836
79%
836
48%
1268
January16th to endNight
69%
896
39%
2893
36%
896
78%
896
50%
1346
February1st to 15thNight
70%
818
40%
2468
34%
818
79%
818
54%
1154
February16th to endNight
66%
736
36%
2207
36%
736
72%
736
50%
1094
March1st to 15thNight
67%
840
41%
2377
33%
840
79%
840
59%
1115
March16th to endNight
72%
896
39%
2464
30%
896
80%
896
63%
1153
April1st to 15thNight
62%
839
36%
2263
21%
839
71%
839
60%
1084
April16th to endNight
69%
692
45%
1940
28%
692
79%
692
74%
808
May1st to 15thNight
75%
616
43%
1849
32%
616
82%
616
71%
749
May16th to endNight
79%
609
40%
1828
29%
609
84%
609
75%
719
June1st to 15thNight
86%
585
37%
1755
32%
585
87%
585
76%
689
June16th to endNight
92%
585
36%
1755
32%
585
93%
585
80%
668
July1st to 15thNight
89%
555
30%
1665
25%
555
90%
555
60%
757
July16th to endNight
85%
612
31%
1737
26%
579
87%
579
51%
864
August1st to 15thNight
89%
575
40%
1719
33%
572
89%
572
62%
769
August16th to endNight
88%
828
38%
2083
29%
828
88%
828
62%
1075
September1st to 15thNight
86%
780
38%
2145
32%
780
88%
780
61%
1027
September16th to endNight
85%
776
45%
2145
38%
776
89%
776
77%
911
October1st to 15thNight
77%
780
44%
2162
36%
780
82%
780
67%
981
October16th to endNight
84%
832
46%
2496
41%
832
90%
832
70%
1030
November1st to 15thNight
80%
820
42%
2606
40%
820
86%
820
63%
1096
November16th to endNight
77%
840
42%
2730
42%
840
83%
840
58%
1160
December1st to 15thNight
71%
840
40%
2730
38%
840
79%
840
53%
1232
December16th to endNight
68%
896
40%
2912
36%
896
78%
896
51%
1316

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%72%
54203
Night
2112212335%72%
53846
TransparencyDay
14%2311%25%42%
53898
Night
14%2312%24%43%
53652
SeeingDay
3417%31%32%11%
7764
Night
3212%35%38%7%
18095

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
3313413245%66%
1881
16th to endDay
5%22212346%67%
2033
February1st to 15thDay
3212223336%68%
2051
16th to endDay
4212313447%64%
1839
March1st to 15thDay
2111223346%70%
2241
16th to endDay
1212212235%74%
2464
April1st to 15thDay
1111212247%72%
2342
16th to endDay
11111225%82%
2623
May1st to 15thDay
1211122479%
2658
16th to endDay
1111112384%
2637
June1st to 15thDay
11112385%
2535
16th to endDay
11111186%
2535
July1st to 15thDay
1112314447%66%
2535
16th to endDay
42245%35%5%6%9%52%
2675
August1st to 15thDay
2112323448%63%
2482
16th to endDay
22222345%7%65%
2471
September1st to 15thDay
3212323446%66%
2145
16th to endDay
1111122383%
2145
October1st to 15thDay
21111222379%
2126
16th to endDay
1111123480%
2080
November1st to 15thDay
111112235%77%
1909
16th to endDay
3211111236%73%
1890
December1st to 15thDay
3313324347%63%
1890
16th to endDay
3213323347%64%
2016
January1st to 15thNight
421232335%5%66%
2717
16th to endNight
4313213335%68%
2893
February1st to 15thNight
3212312335%69%
2461
16th to endNight
5%212323335%65%
2207
March1st to 15thNight
21121235%6%69%
2377
16th to endNight
212213337%71%
2464
April1st to 15thNight
111231333473%
2263
16th to endNight
111122383%
1940
May1st to 15thNight
1111235%80%
1849
16th to endNight
11122385%
1828
June1st to 15thNight
1111122383%
1755
16th to endNight
1112386%
1755
July1st to 15thNight
111221335%7%67%
1755
16th to endNight
22133245%6%9%57%
1845
August1st to 15thNight
12232347%71%
1728
16th to endNight
311222335%8%67%
2083
September1st to 15thNight
12222345%6%69%
2145
16th to endNight
1111123283%
2145
October1st to 15thNight
211121123476%
2162
16th to endNight
1121122480%
2496
November1st to 15thNight
111221223475%
2606
16th to endNight
2112212235%73%
2730
December1st to 15thNight
3213212346%67%
2730
16th to endNight
3212313345%68%
2912

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
21%2412%29%29%
1882
16th to endDay
19%25%15%26%30%
2033
February1st to 15thDay
18%2413%29%32%
2051
16th to endDay
19%2415%30%27%
1839
March1st to 15thDay
15%2212%30%36%
2241
16th to endDay
15%1211%30%38%
2464
April1st to 15thDay
13%1210%31%40%
2342
16th to endDay
7%18%28%53%
2623
May1st to 15thDay
10%119%25%51%
2658
16th to endDay
8%16%20%62%
2640
June1st to 15thDay
7%415%71%
2535
16th to endDay
7%1127%79%
2535
July1st to 15thDay
16%45%13%17%43%
2396
16th to endDay
24%49%24%20%16%
2520
August1st to 15thDay
18%3417%22%32%
2467
16th to endDay
16%35%12%31%29%
2471
September1st to 15thDay
18%25%12%23%37%
2145
16th to endDay
8%11422%60%
2145
October1st to 15thDay
11%1210%23%50%
2126
16th to endDay
9%238%24%52%
2080
November1st to 15thDay
11%1214%29%41%
1909
16th to endDay
13%1213%30%38%
1890
December1st to 15thDay
21%35%15%25%29%
1890
16th to endDay
19%27%19%32%19%
2016
January1st to 15thNight
20%3414%25%32%
2717
16th to endNight
20%1413%25%34%
2893
February1st to 15thNight
18%2413%24%36%
2472
16th to endNight
21%2312%26%33%
2207
March1st to 15thNight
15%2212%26%41%
2377
16th to endNight
14%1311%28%40%
2464
April1st to 15thNight
15%139%27%41%
2263
16th to endNight
8%118%24%55%
1940
May1st to 15thNight
9%127%26%52%
1850
16th to endNight
7%115%22%61%
1829
June1st to 15thNight
8%1413%71%
1755
16th to endNight
6%1127%81%
1755
July1st to 15thNight
15%26%14%16%43%
1665
16th to endNight
19%5%8%26%20%21%
1737
August1st to 15thNight
13%3217%26%36%
1719
16th to endNight
16%35%15%28%30%
2083
September1st to 15thNight
14%45%14%24%37%
2145
16th to endNight
8%115%19%63%
2145
October1st to 15thNight
12%139%22%50%
2162
16th to endNight
9%129%19%57%
2496
November1st to 15thNight
13%1110%27%45%
2606
16th to endNight
15%1211%27%41%
2730
December1st to 15thNight
18%2415%26%33%
2730
16th to endNight
18%2417%30%25%
2912

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%122%32%28%3
180
16th to endDay
4418%27%32%12%
209
February1st to 15thDay
6%6%24%28%25%7%
386
16th to endDay
7%11%28%30%18%3
342
March1st to 15thDay
310%24%32%23%5%
390
16th to endDay
39%23%32%24%6%
416
April1st to 15thDay
210%25%31%20%8%
389
16th to endDay
211%28%32%17%8%
378
May1st to 15thDay
25%25%31%26%9%
389
16th to endDay
2222%40%26%5%
394
June1st to 15thDay
2217%39%28%9%
375
16th to endDay
118%36%36%17%
375
July1st to 15thDay
16%34%42%14%
365
16th to endDay
3222%48%22%
391
August1st to 15thDay
1431%44%18%
359
16th to endDay
2226%47%21%
396
September1st to 15thDay
311%34%36%13%
375
16th to endDay
318%29%37%11%
375
October1st to 15thDay
4323%33%28%5%
356
16th to endDay
3432%38%19%
192
November1st to 15thDay
212%30%44%8%
180
16th to endDay
5%321%22%31%16%
180
December1st to 15thDay
4218%33%36%5%
180
16th to endDay
35%16%29%36%8%
192
January1st to 15thNight
6%112%41%30%6%
840
16th to endNight
6%215%39%30%5%
896
February1st to 15thNight
5%214%40%31%4
824
16th to endNight
6%219%41%26%4
736
March1st to 15thNight
3421%38%27%5%
840
16th to endNight
2316%40%31%5%
896
April1st to 15thNight
25%23%36%27%4
839
16th to endNight
1422%41%25%4
692
May1st to 15thNight
1316%40%33%4
617
16th to endNight
1213%42%36%3
611
June1st to 15thNight
118%42%42%3
585
16th to endNight
1435%51%6%
585
July1st to 15thNight
2128%60%6%
555
16th to endNight
3219%61%11%
612
August1st to 15thNight
2220%63%11%
575
16th to endNight
3218%60%14%
828
September1st to 15thNight
25%25%53%11%
780
16th to endNight
29%28%48%10%
776
October1st to 15thNight
2113%38%39%4
780
16th to endNight
118%33%41%12%
832
November1st to 15thNight
211%42%34%8%
820
16th to endNight
4110%35%35%11%
840
December1st to 15thNight
5%214%42%32%3
840
16th to endNight
5%216%40%29%5%
896
Page generated at 2019-05-11 21:31:09. Version ac04

Copyright 2019 A. Danko


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