Area 52 Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Area 52 Observatory clear sky chart from 2005-11-06 to 2024-03-18.

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
72%
24532
31%
79992
28%
24442
77%
24442
44%
40479

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
62%
752
36%
4188
26%
736
70%
736
31%
1601
January11th to 20thNight
63%
749
33%
4038
30%
740
74%
740
26%
1996
January21st to endNight
55%
828
24%
4087
28%
814
68%
814
27%
2018
February1st to 10thNight
63%
760
36%
2280
32%
760
70%
760
41%
1229
February11th to 20thNight
62%
740
34%
2218
30%
740
71%
740
44%
1169
February21st to endNight
59%
628
28%
1884
25%
628
67%
628
40%
1017
March1st to 10thNight
60%
760
27%
2280
23%
760
68%
760
39%
1252
March11th to 20thNight
65%
752
25%
2120
22%
752
70%
752
41%
1208
March21st to endNight
68%
792
31%
2013
22%
792
74%
792
51%
1109
April1st to 10thNight
72%
720
30%
1800
21%
720
75%
720
48%
1028
April11th to 20thNight
67%
711
34%
1779
19%
711
72%
711
54%
960
April21st to endNight
73%
720
32%
1800
17%
720
76%
720
54%
981
May1st to 10thNight
71%
720
26%
1800
16%
720
73%
720
50%
1013
May11th to 20thNight
72%
563
28%
1627
21%
563
74%
563
47%
868
May21st to endNight
74%
582
28%
1746
21%
582
77%
582
53%
855
June1st to 10thNight
76%
363
27%
1443
30%
363
78%
363
34%
711
June11th to 20thNight
84%
360
30%
1440
35%
360
85%
360
46%
611
June21st to endNight
85%
360
32%
1440
39%
360
86%
360
45%
613
July1st to 10thNight
86%
350
32%
1400
39%
350
86%
350
50%
557
July11th to 20thNight
85%
428
33%
1472
33%
428
85%
428
49%
638
July21st to endNight
83%
676
30%
1755
23%
639
85%
639
52%
902
August1st to 10thNight
87%
716
31%
1780
21%
712
87%
712
57%
940
August11th to 20thNight
83%
712
33%
1780
20%
712
83%
712
55%
965
August21st to endNight
86%
792
34%
1980
24%
792
86%
792
60%
1032
September1st to 10thNight
83%
720
34%
1800
27%
720
83%
720
55%
989
September11th to 20thNight
85%
720
37%
1873
33%
720
86%
720
56%
974
September21st to endNight
84%
720
39%
1980
36%
720
86%
720
56%
978
October1st to 10thNight
82%
720
37%
2016
36%
720
85%
720
60%
960
October11th to 20thNight
78%
720
37%
2160
39%
720
81%
720
53%
1038
October21st to endNight
76%
792
40%
2376
41%
792
80%
792
55%
1115
November1st to 10thNight
76%
740
34%
2364
34%
740
82%
740
51%
1094
November11th to 20thNight
76%
760
35%
2470
35%
760
82%
760
51%
1135
November21st to endNight
67%
760
35%
2470
36%
760
73%
760
46%
1190
December1st to 10thNight
64%
760
32%
2470
31%
760
70%
760
41%
1257
December11th to 20thNight
60%
760
29%
3088
30%
759
69%
759
27%
1847
December21st to endNight
60%
826
20%
4775
31%
817
69%
817
21%
2629

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
5%31332345%8%62%
78921
Night
6%423423447%61%
80893
TransparencyDay
22%5%11%19%25%19%
78641
Night
24%48%18%25%21%
80694
SeeingDay
6%7%24%38%21%5%
14705
Night
6%212%33%36%12%
24575

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
6%212223345%69%
2607
11th to 20thDay
9%423423449%56%
2860
21st to endDay
11%4233245%6%8%53%
3244
February1st to 10thDay
9%5%23212346%63%
1900
11th to 20thDay
6%22332346%8%61%
1850
21st to endDay
8%214324347%62%
1570
March1st to 10thDay
7%4244245%5%7%56%
1900
11th to 20thDay
6%3135%2346%9%56%
2001
21st to endDay
5%21332445%7%64%
2341
April1st to 10thDay
5%32441345%8%60%
2160
11th to 20thDay
331332245%8%67%
2129
21st to endDay
3223324447%66%
2160
May1st to 10thDay
341343345%8%62%
2160
11th to 20thDay
342342345%8%62%
2269
21st to endDay
3313423448%66%
2530
June1st to 10thDay
5%5%2443345%9%56%
2511
11th to 20thDay
3413423447%64%
2520
21st to endDay
231343345%8%64%
2520
July1st to 10thDay
321442346%8%62%
2520
11th to 20thDay
221331346%8%66%
2435
21st to endDay
22134346%7%9%59%
2459
August1st to 10thDay
231332347%9%61%
2149
11th to 20thDay
22123235%6%10%65%
2122
21st to endDay
221242445%9%67%
2376
September1st to 10thDay
221232445%9%66%
2160
11th to 20thDay
221231345%8%70%
2085
21st to endDay
1213433347%70%
1980
October1st to 10thDay
331212245%7%70%
1940
11th to 20thDay
3312422336%70%
1800
21st to endDay
2222323446%71%
1980
November1st to 10thDay
221242335%7%69%
1712
11th to 20thDay
331332345%6%67%
1710
21st to endDay
321343335%7%66%
1710
December1st to 10thDay
6%3134345%5%7%59%
1710
11th to 20thDay
16%5%24424347%49%
2047
21st to endDay
11%5%245%246%5%8%48%
2794
January1st to 10thNight
7%324322335%66%
4335
11th to 20thNight
9%5%2442335%7%55%
4110
21st to endNight
12%5%23323447%54%
4423
February1st to 10thNight
9%5%23323336%62%
2280
11th to 20thNight
7%424422435%63%
2218
21st to endNight
10%41343334460%
1884
March1st to 10thNight
7%5%25%42445%8%54%
2280
11th to 20thNight
6%42443446%6%57%
2120
21st to endNight
6%423324347%63%
2013
April1st to 10thNight
6%32343345%8%59%
1800
11th to 20thNight
441332325%7%66%
1779
21st to endNight
3333324447%65%
1800
May1st to 10thNight
45%24434347%61%
1800
11th to 20thNight
35%25%423446%63%
1626
21st to endNight
2423323346%69%
1746
June1st to 10thNight
26%245%24448%58%
1443
11th to 20thNight
14135%24446%67%
1440
21st to endNight
241433345%10%62%
1440
July1st to 10thNight
32145%2336%10%61%
1440
11th to 20thNight
13144245%6%11%60%
1520
21st to endNight
13146%35%5%7%11%54%
1858
August1st to 10thNight
2212325%6%6%11%59%
1790
11th to 20thNight
13146%345%6%8%59%
1780
21st to endNight
13134245%5%9%62%
1980
September1st to 10thNight
4413323349%63%
1800
11th to 20thNight
2313433447%67%
1873
21st to endNight
2135%34345%70%
1980
October1st to 10thNight
321231345%5%71%
2016
11th to 20thNight
4323322336%68%
2160
21st to endNight
2413322335%72%
2376
November1st to 10thNight
3323223347%68%
2364
11th to 20thNight
4322323436%70%
2470
21st to endNight
4323424436%65%
2470
December1st to 10thNight
7%414424346%61%
2470
11th to 20thNight
18%6%2432335%8%46%
3147
21st to endNight
14%4245%3445%7%48%
4862

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
19%38%26%33%11%
2607
11th to 20thDay
28%7%16%15%19%14%
2860
21st to endDay
28%5%7%22%24%13%
3244
February1st to 10thDay
25%46%17%25%23%
1900
11th to 20thDay
23%6%8%17%27%20%
1860
21st to endDay
24%410%22%24%17%
1570
March1st to 10thDay
28%5%11%20%19%18%
1900
11th to 20thDay
24%6%14%20%21%15%
2001
21st to endDay
21%6%12%25%24%12%
2341
April1st to 10thDay
23%6%16%24%20%11%
2160
11th to 20thDay
18%5%9%26%28%15%
2132
21st to endDay
18%6%11%24%31%10%
2160
May1st to 10thDay
19%7%15%22%25%13%
2160
11th to 20thDay
21%6%11%24%26%11%
2272
21st to endDay
18%6%16%29%25%6%
2530
June1st to 10thDay
26%7%12%19%26%9%
2511
11th to 20thDay
19%5%12%15%31%18%
2520
21st to endDay
21%310%10%30%25%
2520
July1st to 10thDay
20%49%12%24%30%
2451
11th to 20thDay
17%410%20%28%20%
2360
21st to endDay
23%6%12%20%25%14%
2322
August1st to 10thDay
22%412%11%29%22%
2135
11th to 20thDay
17%211%16%31%22%
2122
21st to endDay
17%312%11%32%25%
2376
September1st to 10thDay
18%310%11%30%28%
2160
11th to 20thDay
17%410%16%28%25%
2085
21st to endDay
17%38%17%30%25%
1980
October1st to 10thDay
14%410%20%22%29%
1940
11th to 20thDay
19%310%14%25%30%
1800
21st to endDay
17%47%15%23%35%
1980
November1st to 10thDay
19%48%17%22%31%
1712
11th to 20thDay
17%48%15%20%35%
1710
21st to endDay
19%37%17%24%29%
1710
December1st to 10thDay
25%5%8%18%23%21%
1710
11th to 20thDay
36%5%8%16%21%13%
2046
21st to endDay
34%7%10%23%15%10%
2794
January1st to 10thNight
22%37%17%35%15%
4335
11th to 20thNight
31%410%24%15%16%
4110
21st to endNight
30%38%20%23%15%
4423
February1st to 10thNight
27%45%15%24%25%
2280
11th to 20thNight
25%46%20%22%23%
2219
21st to endNight
28%38%18%24%19%
1884
March1st to 10thNight
28%5%9%20%25%14%
2280
11th to 20thNight
26%6%11%18%22%16%
2120
21st to endNight
22%411%24%25%14%
2013
April1st to 10thNight
24%5%12%26%21%11%
1800
11th to 20thNight
19%49%24%27%16%
1779
21st to endNight
19%5%10%22%31%13%
1800
May1st to 10thNight
24%312%21%27%13%
1800
11th to 20thNight
24%49%25%26%12%
1627
21st to endNight
18%411%30%30%7%
1746
June1st to 10thNight
26%6%13%19%26%10%
1443
11th to 20thNight
19%48%17%36%16%
1440
21st to endNight
20%37%12%31%26%
1440
July1st to 10thNight
17%38%12%24%37%
1400
11th to 20thNight
18%47%21%28%23%
1472
21st to endNight
21%49%25%27%15%
1755
August1st to 10thNight
19%36%13%31%28%
1780
11th to 20thNight
21%37%11%34%24%
1780
21st to endNight
17%36%13%34%26%
1980
September1st to 10thNight
22%27%10%27%31%
1800
11th to 20thNight
21%16%13%33%26%
1873
21st to endNight
19%2414%32%29%
1980
October1st to 10thNight
15%36%18%26%31%
2016
11th to 20thNight
20%37%15%24%32%
2160
21st to endNight
18%36%12%24%38%
2376
November1st to 10thNight
18%47%15%25%31%
2364
11th to 20thNight
19%39%12%21%36%
2470
21st to endNight
22%46%18%20%31%
2470
December1st to 10thNight
26%47%16%21%27%
2470
11th to 20thNight
38%48%14%22%14%
3147
21st to endNight
36%6%9%22%16%10%
4862

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
16%7%29%36%11%1
222
11th to 20thDay
13%9%27%38%12%1
370
21st to endDay
10%11%32%34%11%2
436
February1st to 10thDay
12%9%33%33%10%3
460
11th to 20thDay
9%11%35%32%11%1
455
21st to endDay
12%13%35%29%10%1
382
March1st to 10thDay
14%15%37%25%10%
460
11th to 20thDay
10%12%35%29%13%1
449
21st to endDay
9%15%33%34%8%
462
April1st to 10thDay
7%9%33%31%16%3
420
11th to 20thDay
415%34%32%10%4
412
21st to endDay
49%32%31%17%6%
420
May1st to 10thDay
10%8%26%39%13%5%
423
11th to 20thDay
410%24%35%23%4
448
21st to endDay
6%8%27%35%19%4
485
June1st to 10thDay
6%420%37%27%6%
450
11th to 20thDay
3319%40%26%8%
450
21st to endDay
3217%42%28%8%
450
July1st to 10thDay
38%46%34%9%
446
11th to 20thDay
26%36%41%15%
444
21st to endDay
26%43%35%14%
487
August1st to 10thDay
2113%41%32%12%
447
11th to 20thDay
37%42%34%14%
437
21st to endDay
3111%42%32%10%
495
September1st to 10thDay
2214%46%26%9%
450
11th to 20thDay
2220%50%20%5%
450
21st to endDay
16%17%43%27%6%
450
October1st to 10thDay
3426%43%21%3
450
11th to 20thDay
2430%43%19%3
450
21st to endDay
46%24%40%22%4
495
November1st to 10thDay
36%23%44%22%3
308
11th to 20thDay
4431%38%20%3
270
21st to endDay
49%30%35%17%4
270
December1st to 10thDay
10%6%29%36%19%2
270
11th to 20thDay
7%8%28%35%18%4
234
21st to endDay
16%12%33%25%11%4
198
January1st to 10thNight
11%217%42%19%8%
760
11th to 20thNight
8%220%42%23%4
760
21st to endNight
11%423%41%17%4
836
February1st to 10thNight
10%416%40%24%6%
760
11th to 20thNight
10%218%40%23%7%
744
21st to endNight
11%420%40%21%4
628
March1st to 10thNight
11%419%39%24%4
760
11th to 20thNight
8%416%39%27%6%
752
21st to endNight
7%216%41%30%4
792
April1st to 10thNight
6%213%42%31%6%
720
11th to 20thNight
6%316%36%33%6%
711
21st to endNight
4312%39%31%10%
720
May1st to 10thNight
5%213%38%35%7%
720
11th to 20thNight
4211%30%41%12%
563
21st to endNight
3115%35%38%9%
584
June1st to 10thNight
317%29%47%13%
363
11th to 20thNight
115%24%55%14%
360
21st to endNight
1322%56%19%
360
July1st to 10thNight
215%65%26%
350
11th to 20thNight
21452%40%
428
21st to endNight
228%53%35%
676
August1st to 10thNight
11216%55%25%
716
11th to 20thNight
21210%57%29%
712
21st to endNight
2113%55%28%
792
September1st to 10thNight
31317%51%24%
720
11th to 20thNight
22424%52%17%
720
21st to endNight
215%28%45%19%
720
October1st to 10thNight
316%36%46%8%
720
11th to 20thNight
319%36%42%9%
720
21st to endNight
4210%36%37%12%
792
November1st to 10thNight
4212%39%33%11%
740
11th to 20thNight
6%110%38%36%8%
760
21st to endNight
7%218%41%27%6%
760
December1st to 10thNight
9%317%40%27%5%
760
11th to 20thNight
13%218%41%21%4
760
21st to endNight
11%418%41%19%7%
836
Page generated at 2024-03-15 11:01:44. Version ac07

Copyright © 2024 Attilla Danko.


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