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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 2005-11-06 to 2024-01-16.

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
76%
24364
39%
74393
33%
24319
82%
24319
60%
33212

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 10thNight
72%
760
36%
2457
35%
756
79%
756
51%
1122
January11th to 20thNight
72%
740
39%
2405
36%
740
80%
740
51%
1090
January21st to endNight
62%
792
40%
2549
34%
792
75%
792
47%
1222
February1st to 10thNight
68%
720
41%
2160
34%
720
79%
720
57%
983
February11th to 20thNight
66%
700
38%
2098
33%
700
75%
700
51%
1020
February21st to endNight
60%
592
39%
1776
35%
592
70%
592
52%
857
March1st to 10thNight
63%
720
37%
2066
29%
720
75%
720
55%
987
March11th to 20thNight
70%
720
41%
1980
33%
720
79%
720
60%
948
March21st to endNight
65%
792
40%
2178
27%
792
75%
792
60%
1026
April1st to 10thNight
66%
720
35%
1980
23%
720
74%
720
62%
924
April11th to 20thNight
64%
711
40%
1810
22%
711
74%
711
67%
870
April21st to endNight
70%
541
50%
1621
33%
541
82%
541
76%
627
May1st to 10thNight
73%
540
44%
1620
32%
540
81%
540
71%
655
May11th to 20thNight
79%
531
43%
1594
33%
531
83%
531
73%
639
May21st to endNight
79%
582
41%
1746
30%
582
84%
582
78%
666
June1st to 10thNight
83%
540
38%
1620
32%
540
85%
540
76%
633
June11th to 20thNight
89%
540
41%
1620
35%
540
91%
540
81%
617
June21st to endNight
91%
540
38%
1620
33%
540
91%
540
78%
630
July1st to 10thNight
91%
525
34%
1575
29%
525
92%
525
67%
678
July11th to 20thNight
88%
522
32%
1566
27%
522
88%
522
56%
741
July21st to endNight
84%
591
33%
1674
28%
558
86%
558
49%
849
August1st to 10thNight
90%
537
39%
1602
32%
534
90%
534
64%
702
August11th to 20thNight
88%
623
38%
1691
29%
623
88%
623
59%
842
August21st to endNight
88%
792
39%
1997
31%
792
88%
792
62%
1026
September1st to 10thNight
85%
720
36%
1980
31%
720
86%
720
58%
977
September11th to 20thNight
89%
720
47%
1980
40%
720
92%
720
79%
822
September21st to endNight
84%
720
43%
1980
36%
720
88%
720
71%
889
October1st to 10thNight
78%
720
42%
1980
33%
720
83%
720
66%
905
October11th to 20thNight
83%
720
47%
2093
42%
720
89%
720
75%
853
October21st to endNight
81%
792
47%
2376
40%
792
89%
792
73%
952
November1st to 10thNight
79%
740
43%
2323
39%
740
86%
740
65%
964
November11th to 20thNight
80%
760
42%
2470
42%
760
86%
760
63%
1012
November21st to endNight
70%
760
42%
2470
38%
760
80%
760
56%
1080
December1st to 10thNight
72%
760
40%
2470
37%
760
79%
760
52%
1114
December11th to 20thNight
67%
759
37%
2923
35%
759
77%
759
39%
1429
December21st to endNight
64%
822
25%
4343
34%
817
74%
817
32%
1861

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
2212323346%73%
74936
Night
3212323345%73%
74896
TransparencyDay
14%3312%24%44%
74663
Night
15%3311%24%44%
74691
SeeingDay
35%17%32%31%12%
14087
Night
3214%38%37%6%
24385

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 10thDay
4313413347%66%
1708
11th to 20thDay
4313223346%69%
1665
21st to endDay
5%313323446%67%
1804
February1st to 10thDay
3212223336%72%
1800
11th to 20thDay
421342345%8%65%
1750
21st to endDay
4213214335%71%
1480
March1st to 10thDay
321232345%7%68%
1892
11th to 20thDay
3212324346%70%
1980
21st to endDay
2212213335%76%
2178
April1st to 10thDay
2112222347%74%
1980
11th to 20thDay
2111112235%80%
2094
21st to endDay
11112225%83%
2336
May1st to 10thDay
112212335%81%
2340
11th to 20thDay
2111111225%84%
2301
21st to endDay
111111112387%
2530
June1st to 10thDay
111111223485%
2340
11th to 20thDay
1111112390%
2340
21st to endDay
111221222383%
2340
July1st to 10thDay
1112324346%72%
2340
11th to 20thDay
22134245%6%9%62%
2340
21st to endDay
5%325%5%36%5%7%9%49%
2545
August1st to 10thDay
221332345%8%66%
2328
11th to 20thDay
21123345%6%8%66%
2206
21st to endDay
221232446%8%66%
2358
September1st to 10thDay
3313433446%65%
1980
11th to 20thDay
21111232483%
1980
21st to endDay
211221223479%
1980
October1st to 10thDay
211122233478%
1980
11th to 20thDay
111111122385%
1865
21st to endDay
111211223483%
1980
November1st to 10thDay
1111122346%80%
1751
11th to 20thDay
1212222335%77%
1710
21st to endDay
4312313346%70%
1710
December1st to 10thDay
4323425%447%62%
1710
11th to 20thDay
32144335%8%8%58%
2169
21st to endDay
6%42442446%8%56%
3146
January1st to 10thNight
421332446%6%66%
2457
11th to 20thNight
4313323345%69%
2405
21st to endNight
5%423323345%66%
2549
February1st to 10thNight
3212422445%72%
2160
11th to 20thNight
4213423436%67%
2098
21st to endNight
5%212423345%70%
1776
March1st to 10thNight
221332346%7%66%
2066
11th to 20thNight
4212312337%71%
1980
21st to endNight
2113313447%71%
2178
April1st to 10thNight
2212313345%74%
1980
11th to 20thNight
211221232380%
1810
21st to endNight
21112235%84%
1621
May1st to 10thNight
12222235%81%
1620
11th to 20thNight
11211222384%
1594
21st to endNight
1111121388%
1746
June1st to 10thNight
11111223484%
1620
11th to 20thNight
1111122288%
1620
21st to endNight
111112235%82%
1620
July1st to 10thNight
121222335%7%73%
1620
11th to 20thNight
221332346%7%66%
1620
21st to endNight
22144346%7%10%56%
1773
August1st to 10thNight
221222235%8%72%
1611
11th to 20thNight
3212413347%69%
1691
21st to endNight
311232445%8%66%
1997
September1st to 10thNight
221232445%7%68%
1980
11th to 20thNight
11111223385%
1980
21st to endNight
211221234380%
1980
October1st to 10thNight
3212212345%75%
1980
11th to 20thNight
111221112485%
2093
21st to endNight
11121123483%
2376
November1st to 10thNight
111222223478%
2323
11th to 20thNight
2212212335%77%
2470
21st to endNight
4212213346%71%
2470
December1st to 10thNight
421332336%6%67%
2470
11th to 20thNight
432443445%7%59%
3041
21st to endNight
5%313434445%62%
4521

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 10thDay
20%2415%33%25%
1709
11th to 20thDay
17%3412%32%32%
1665
21st to endDay
20%35%16%26%30%
1804
February1st to 10thDay
16%2412%28%39%
1800
11th to 20thDay
18%3314%28%34%
1760
21st to endDay
17%2313%30%34%
1480
March1st to 10thDay
16%3213%28%36%
1892
11th to 20thDay
17%2310%28%40%
1980
21st to endDay
14%2212%31%39%
2178
April1st to 10thDay
13%2210%32%41%
1980
11th to 20thDay
9%217%27%54%
2097
21st to endDay
7%128%28%54%
2336
May1st to 10thDay
9%229%25%53%
2340
11th to 20thDay
8%128%21%60%
2304
21st to endDay
7%116%22%64%
2530
June1st to 10thDay
8%115%20%67%
2340
11th to 20thDay
411212%81%
2340
21st to endDay
10%22410%73%
2340
July1st to 10thDay
14%338%15%56%
2276
11th to 20thDay
17%5%8%19%25%25%
2271
21st to endDay
28%6%9%22%17%18%
2404
August1st to 10thDay
17%35%16%23%35%
2313
11th to 20thDay
16%5%5%14%29%30%
2206
21st to endDay
16%4414%29%33%
2358
September1st to 10thDay
20%35%11%22%38%
1980
11th to 20thDay
8%227%24%57%
1980
21st to endDay
12%327%18%58%
1980
October1st to 10thDay
12%2311%23%49%
1980
11th to 20thDay
7%227%21%61%
1865
21st to endDay
8%138%25%55%
1980
November1st to 10thDay
9%2212%31%45%
1751
11th to 20thDay
11%2212%28%45%
1710
21st to endDay
17%2310%30%38%
1710
December1st to 10thDay
23%3415%22%33%
1710
11th to 20thDay
22%46%20%27%21%
2168
21st to endDay
22%7%6%25%24%16%
3146
January1st to 10thNight
19%3416%30%28%
2457
11th to 20thNight
19%3310%31%34%
2405
21st to endNight
22%2415%23%34%
2549
February1st to 10thNight
16%2412%26%40%
2160
11th to 20thNight
21%2313%22%39%
2099
21st to endNight
19%2310%26%39%
1776
March1st to 10thNight
17%3212%28%38%
2066
11th to 20thNight
16%2212%24%44%
1980
21st to endNight
15%2311%29%39%
2178
April1st to 10thNight
15%2310%27%44%
1980
11th to 20thNight
12%127%23%54%
1810
21st to endNight
7%118%27%55%
1621
May1st to 10thNight
9%237%25%54%
1620
11th to 20thNight
8%225%22%61%
1595
21st to endNight
6%15%24%63%
1746
June1st to 10thNight
8%11319%69%
1620
11th to 20thNight
5%21310%80%
1620
21st to endNight
7%1239%77%
1620
July1st to 10thNight
12%25%10%14%58%
1575
11th to 20thNight
17%46%19%26%29%
1566
21st to endNight
19%6%9%24%19%23%
1674
August1st to 10thNight
13%3416%23%41%
1602
11th to 20thNight
15%5%417%27%32%
1691
21st to endNight
15%45%14%28%33%
1997
September1st to 10thNight
15%5%6%14%21%39%
1980
11th to 20thNight
6%228%22%60%
1980
21st to endNight
10%228%17%60%
1980
October1st to 10thNight
13%2411%21%50%
1980
11th to 20thNight
8%118%18%64%
2093
21st to endNight
8%228%20%60%
2376
November1st to 10thNight
12%218%26%50%
2323
11th to 20thNight
13%2210%24%50%
2470
21st to endNight
17%2311%27%40%
2470
December1st to 10thNight
18%3415%22%38%
2470
11th to 20thNight
24%35%13%28%27%
3041
21st to endNight
23%5%420%30%19%
4521

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 10thDay
6%8%21%36%25%5%
270
11th to 20thDay
9%418%34%29%5%
255
21st to endDay
36%25%34%21%12%
286
February1st to 10thDay
6%7%23%31%25%8%
420
11th to 20thDay
7%12%28%30%20%3
415
21st to endDay
7%12%30%34%16%2
346
March1st to 10thDay
411%29%35%18%3
420
11th to 20thDay
6%8%23%29%26%9%
420
21st to endDay
5%12%31%30%19%3
462
April1st to 10thDay
38%23%35%21%10%
420
11th to 20thDay
39%31%33%18%6%
412
21st to endDay
111%24%31%21%12%
420
May1st to 10thDay
2423%35%26%10%
423
11th to 20thDay
2324%33%28%10%
448
21st to endDay
2322%38%26%9%
485
June1st to 10thDay
2214%36%34%11%
450
11th to 20thDay
1318%33%30%16%
450
21st to endDay
110%36%39%14%
450
July1st to 10thDay
7%35%43%14%
446
11th to 20thDay
3327%43%24%
444
21st to endDay
32320%46%25%
487
August1st to 10thDay
2431%42%21%
447
11th to 20thDay
21324%44%26%
437
21st to endDay
3224%45%26%
495
September1st to 10thDay
429%27%38%20%
450
11th to 20thDay
211%34%38%15%
450
21st to endDay
3217%28%36%14%
450
October1st to 10thDay
2318%32%31%13%
450
11th to 20thDay
2215%35%32%13%
335
21st to endDay
1415%28%39%14%
297
November1st to 10thDay
1316%37%33%10%
270
11th to 20thDay
2413%32%35%13%
270
21st to endDay
4420%31%26%14%
270
December1st to 10thDay
6%117%37%30%8%
270
11th to 20thDay
1320%37%32%7%
270
21st to endDay
7%9%22%33%25%4
297
January1st to 10thNight
5%216%44%28%5%
760
11th to 20thNight
5%415%42%29%5%
740
21st to endNight
7%320%42%23%3
792
February1st to 10thNight
4318%40%30%4
720
11th to 20thNight
6%418%45%24%3
704
21st to endNight
5%424%42%21%4
592
March1st to 10thNight
3426%44%21%2
720
11th to 20thNight
5%417%36%31%7%
720
21st to endNight
35%22%42%24%4
792
April1st to 10thNight
25%22%43%25%4
720
11th to 20thNight
26%24%39%25%3
711
21st to endNight
1423%44%25%3
541
May1st to 10thNight
1319%45%29%3
540
11th to 20thNight
1214%45%34%4
531
21st to endNight
2215%45%33%3
584
June1st to 10thNight
1211%41%42%3
540
11th to 20thNight
19%47%41%2
540
21st to endNight
115%38%49%6%
540
July1st to 10thNight
21234%57%5%
525
11th to 20thNight
2222%65%8%
522
21st to endNight
21323%61%11%
591
August1st to 10thNight
2223%62%11%
537
11th to 20thNight
31321%60%12%
623
21st to endNight
31221%60%12%
792
September1st to 10thNight
316%26%56%9%
720
11th to 20thNight
27%31%51%9%
720
21st to endNight
210%34%45%9%
720
October1st to 10thNight
3113%41%38%4
720
11th to 20thNight
1111%41%41%6%
720
21st to endNight
2311%37%36%11%
792
November1st to 10thNight
2113%42%34%8%
740
11th to 20thNight
3211%41%35%9%
760
21st to endNight
5%217%40%29%7%
760
December1st to 10thNight
5%214%45%30%3
760
11th to 20thNight
6%317%45%28%2
760
21st to endNight
6%320%44%23%5%
836
Page generated at 2024-01-12 23:38:12. Version ac07

Copyright 2024 Attilla Danko


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