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 2024-01-31.

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
48%
24148
26%
74439
18%
24091
55%
24091
32%
43775

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
32%
948
27%
2458
11%
946
42%
946
31%
1565
January11th to 20thNight
28%
950
26%
2470
9%
950
39%
950
30%
1585
January21st to endNight
31%
1043
29%
2711
10%
1043
42%
1043
31%
1726
February1st to 10thNight
28%
900
21%
2340
7%
900
35%
900
26%
1556
February11th to 20thNight
24%
818
20%
2213
6%
814
32%
814
24%
1482
February21st to endNight
25%
444
27%
1628
13%
444
41%
444
20%
982
March1st to 10thNight
33%
540
24%
1980
15%
540
44%
540
23%
1201
March11th to 20thNight
32%
540
21%
1980
14%
540
42%
540
21%
1229
March21st to endNight
32%
594
23%
2178
14%
594
46%
594
24%
1305
April1st to 10thNight
33%
540
26%
1890
17%
540
47%
540
27%
1088
April11th to 20thNight
34%
533
26%
1775
18%
533
48%
533
27%
1040
April21st to endNight
37%
540
25%
1800
19%
540
51%
540
29%
1039
May1st to 10thNight
45%
540
22%
1720
18%
540
55%
540
29%
1030
May11th to 20thNight
47%
531
22%
1594
20%
531
53%
531
31%
978
May21st to endNight
54%
584
22%
1746
19%
582
61%
582
31%
1085
June1st to 10thNight
73%
540
22%
1620
22%
540
76%
540
39%
913
June11th to 20thNight
73%
540
24%
1620
25%
540
75%
540
45%
845
June21st to endNight
74%
540
26%
1620
28%
540
77%
540
47%
841
July1st to 10thNight
75%
525
21%
1575
23%
525
76%
525
37%
919
July11th to 20thNight
85%
522
27%
1566
31%
522
86%
522
54%
753
July21st to endNight
79%
591
26%
1673
30%
558
79%
558
40%
931
August1st to 10thNight
82%
537
25%
1601
27%
534
84%
534
48%
819
August11th to 20thNight
74%
534
28%
1684
33%
534
76%
534
38%
927
August21st to endNight
76%
594
22%
1980
27%
594
77%
594
34%
1108
September1st to 10thNight
75%
540
28%
1800
32%
540
76%
540
39%
938
September11th to 20thNight
69%
540
27%
1950
30%
540
71%
540
32%
1082
September21st to endNight
69%
548
33%
1988
33%
548
74%
548
39%
988
October1st to 10thNight
68%
720
33%
2160
26%
720
72%
720
44%
1140
October11th to 20thNight
51%
720
34%
2160
20%
720
62%
720
40%
1190
October21st to endNight
45%
792
30%
2376
20%
792
53%
792
33%
1408
November1st to 10thNight
50%
740
31%
2220
20%
740
59%
740
37%
1254
November11th to 20thNight
44%
760
30%
2280
18%
760
55%
760
36%
1274
November21st to endNight
37%
883
29%
2403
16%
883
47%
883
30%
1525
December1st to 10thNight
36%
950
27%
2470
11%
950
46%
950
30%
1606
December11th to 20thNight
34%
948
28%
2872
12%
948
43%
948
24%
1852
December21st to endNight
30%
1039
16%
4338
10%
1026
40%
1026
19%
2571

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
15%5%25%5%3445%7%45%
75158
Night
14%5%24423447%51%
75002
TransparencyDay
39%6%10%22%19%5%
74882
Night
34%5%9%22%23%8%
74798
SeeingDay
16%9%23%26%21%6%
14184
Night
16%7%24%32%19%2
24158

By Month

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 10thDay
20%7%24323245%47%
1707
11th to 20thDay
19%7%245%23345%46%
1710
21st to endDay
20%7%2342233449%
1872
February1st to 10thDay
25%6%245%33435%39%
1620
11th to 20thDay
22%7%35%423345%41%
1648
21st to endDay
29%7%35%323335%38%
1628
March1st to 10thDay
21%7%34323345%44%
1980
11th to 20thDay
24%6%35%5%34435%38%
1980
21st to endDay
20%7%36%434445%39%
2178
April1st to 10thDay
16%6%35%5%3445%7%43%
2070
11th to 20thDay
18%5%34435%45%6%44%
2134
21st to endDay
18%7%35%42345%6%42%
2160
May1st to 10thDay
19%6%35%5%2345%6%42%
2236
11th to 20thDay
14%6%26%6%45%5%5%8%40%
2302
21st to endDay
12%6%36%6%46%6%6%9%36%
2531
June1st to 10thDay
9%5%25%6%46%5%6%9%44%
2340
11th to 20thDay
8%5%35%5%35%6%7%9%43%
2340
21st to endDay
6%4245%36%6%6%10%48%
2340
July1st to 10thDay
8%426%8%47%7%9%10%34%
2340
11th to 20thDay
6%325%5%36%5%6%10%49%
2340
21st to endDay
7%3246%47%6%8%10%44%
2546
August1st to 10thDay
5%315%6%45%7%7%11%46%
2328
11th to 20thDay
10%425%5%35%5%7%9%46%
2215
21st to endDay
8%425%6%46%6%6%8%44%
2376
September1st to 10thDay
11%5%2443445%7%51%
2160
11th to 20thDay
12%425%445%6%6%7%46%
2006
21st to endDay
9%5%2443445%6%54%
1954
October1st to 10thDay
9%424434447%55%
1800
11th to 20thDay
16%42342234456%
1800
21st to endDay
20%6%24323335%50%
1980
November1st to 10thDay
15%5%24323346%52%
1858
11th to 20thDay
14%424332447%52%
1900
21st to endDay
22%6%3442332448%
1773
December1st to 10thDay
20%6%2442335%5%47%
1710
11th to 20thDay
17%8%35%43434443%
2161
21st to endDay
20%7%36%5%3445%6%38%
3135
January1st to 10thNight
18%6%23323345%50%
2458
11th to 20thNight
20%5%24322245%50%
2470
21st to endNight
19%6%2432333452%
2711
February1st to 10thNight
21%6%34423345%46%
2340
11th to 20thNight
21%7%25%42345%444%
2212
21st to endNight
22%6%3442233447%
1628
March1st to 10thNight
20%6%2442335%6%44%
1980
11th to 20thNight
18%7%35%424336%44%
1980
21st to endNight
18%6%35%423347%47%
2178
April1st to 10thNight
14%6%25%434346%50%
1890
11th to 20thNight
13%5%25%33445%6%49%
1775
21st to endNight
14%6%34423347%51%
1800
May1st to 10thNight
13%4344245%47%49%
1720
11th to 20thNight
13%5%45%43345%7%48%
1593
21st to endNight
9%6%25%5%435%6%10%45%
1745
June1st to 10thNight
5%32443446%9%54%
1620
11th to 20thNight
5%32433435%8%60%
1620
21st to endNight
5%325%423448%62%
1620
July1st to 10thNight
5%425%5%45%5%6%13%47%
1620
11th to 20thNight
421322348%13%60%
1620
21st to endNight
42245%46%5%6%10%53%
1772
August1st to 10thNight
332332437%13%56%
1611
11th to 20thNight
7%3144345%6%10%52%
1684
21st to endNight
5%4245%35%6%6%9%50%
1980
September1st to 10thNight
5%5%15%32435%8%58%
1800
11th to 20thNight
10%5%235%345%6%8%50%
1950
21st to endNight
8%32342345%6%60%
1988
October1st to 10thNight
9%32332345%6%61%
2160
11th to 20thNight
13%414323345%59%
2160
21st to endNight
17%5%2422323356%
2376
November1st to 10thNight
13%413323345%57%
2220
11th to 20thNight
11%5%34323345%58%
2280
21st to endNight
19%6%24323335%49%
2403
December1st to 10thNight
19%6%24324345%48%
2470
11th to 20thNight
19%5%245%35%33448%
3036
21st to endNight
19%7%25%423335%46%
4532

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
42%28%21%19%7%
1708
11th to 20thDay
41%37%24%20%4
1710
21st to endDay
40%25%21%25%6%
1872
February1st to 10thDay
49%47%17%18%5%
1620
11th to 20thDay
47%46%19%18%5%
1657
21st to endDay
51%36%11%20%8%
1628
March1st to 10thDay
43%37%17%19%10%
1980
11th to 20thDay
49%47%19%17%4
1980
21st to endDay
47%48%21%17%3
2178
April1st to 10thDay
41%5%8%22%18%6%
2070
11th to 20thDay
41%5%9%21%18%6%
2134
21st to endDay
42%5%10%20%20%3
2160
May1st to 10thDay
43%5%9%22%18%4
2236
11th to 20thDay
41%7%13%22%15%1
2306
21st to endDay
42%8%13%22%13%1
2531
June1st to 10thDay
36%7%14%26%15%2
2340
11th to 20thDay
34%9%13%26%16%2
2340
21st to endDay
29%8%12%29%20%2
2340
July1st to 10thDay
39%11%17%22%10%1
2276
11th to 20thDay
28%7%18%28%18%1
2271
21st to endDay
31%9%19%31%9%1
2405
August1st to 10thDay
28%10%17%29%15%1
2314
11th to 20thDay
32%8%15%28%15%2
2215
21st to endDay
34%8%16%26%13%3
2376
September1st to 10thDay
33%6%12%21%20%8%
2160
11th to 20thDay
36%7%11%21%19%7%
2006
21st to endDay
29%6%10%21%24%10%
1954
October1st to 10thDay
29%6%10%20%25%11%
1800
11th to 20thDay
33%36%17%27%14%
1800
21st to endDay
38%46%18%24%11%
1980
November1st to 10thDay
34%47%23%24%8%
1858
11th to 20thDay
33%47%19%28%9%
1900
21st to endDay
44%3418%25%7%
1773
December1st to 10thDay
40%49%21%20%7%
1710
11th to 20thDay
45%35%18%21%8%
2159
21st to endDay
47%47%17%20%5%
3135
January1st to 10thNight
38%36%18%28%7%
2458
11th to 20thNight
39%39%20%22%6%
2470
21st to endNight
38%35%17%29%7%
2711
February1st to 10thNight
42%48%18%21%7%
2340
11th to 20thNight
44%46%19%20%7%
2213
21st to endNight
43%36%15%22%11%
1628
March1st to 10thNight
42%47%15%19%12%
1980
11th to 20thNight
43%48%17%20%7%
1980
21st to endNight
39%5%8%21%22%4
2178
April1st to 10thNight
36%49%21%18%11%
1890
11th to 20thNight
35%6%8%21%21%9%
1775
21st to endNight
35%48%24%24%4
1800
May1st to 10thNight
34%7%10%24%17%8%
1720
11th to 20thNight
36%5%13%25%18%3
1594
21st to endNight
34%8%14%26%17%2
1746
June1st to 10thNight
25%9%13%31%18%4
1620
11th to 20thNight
24%5%12%32%24%3
1620
21st to endNight
22%5%12%30%26%5%
1620
July1st to 10thNight
28%9%19%28%16%2
1575
11th to 20thNight
16%6%20%33%23%3
1566
21st to endNight
25%8%16%33%17%1
1673
August1st to 10thNight
19%7%18%33%21%2
1601
11th to 20thNight
26%8%13%29%20%4
1684
21st to endNight
28%9%15%26%19%4
1980
September1st to 10thNight
25%6%11%23%25%9%
1800
11th to 20thNight
31%6%10%22%22%8%
1950
21st to endNight
25%5%9%21%27%14%
1988
October1st to 10thNight
24%5%9%24%24%14%
2160
11th to 20thNight
29%36%16%28%18%
2160
21st to endNight
35%35%19%26%12%
2376
November1st to 10thNight
30%5%8%19%27%11%
2220
11th to 20thNight
31%47%19%28%12%
2280
21st to endNight
39%45%18%27%8%
2403
December1st to 10thNight
39%48%19%21%8%
2470
11th to 20thNight
41%45%17%23%10%
3037
21st to endNight
41%37%23%22%5%
4532

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
28%14%33%21%3
270
11th to 20thDay
26%18%38%14%4
270
21st to endDay
25%20%37%13%5%
294
February1st to 10thDay
31%16%33%15%5%
240
11th to 20thDay
34%23%34%8%2
240
21st to endDay
42%19%30%7%3
198
March1st to 10thDay
30%17%33%16%4
240
11th to 20thDay
33%21%33%12%2
240
21st to endDay
26%24%33%15%2
264
April1st to 10thDay
20%17%36%18%8%
330
11th to 20thDay
25%14%33%20%8%2
412
21st to endDay
21%14%32%22%9%2
420
May1st to 10thDay
18%10%33%30%9%1
499
11th to 20thDay
14%6%31%32%14%3
625
21st to endDay
12%6%24%34%19%5%
679
June1st to 10thDay
11%415%31%29%9%
630
11th to 20thDay
8%317%37%29%6%
630
21st to endDay
6%318%35%27%11%
630
July1st to 10thDay
5%212%32%38%10%
621
11th to 20thDay
4210%30%40%15%
618
21st to endDay
5%19%30%40%15%
684
August1st to 10thDay
4110%32%42%11%
626
11th to 20thDay
13%28%30%36%12%
529
21st to endDay
9%17%23%41%18%
495
September1st to 10thDay
9%39%22%42%14%
450
11th to 20thDay
6%313%28%38%11%
296
21st to endDay
12%414%33%29%8%
270
October1st to 10thDay
6%329%36%23%4
270
11th to 20thDay
15%10%33%26%13%3
270
21st to endDay
29%12%26%23%8%2
297
November1st to 10thDay
19%12%29%24%14%3
270
11th to 20thDay
17%14%36%24%7%1
270
21st to endDay
29%15%25%23%7%2
270
December1st to 10thDay
24%17%33%19%6%2
270
11th to 20thDay
27%18%31%18%6%
270
21st to endDay
24%21%37%12%5%1
297
January1st to 10thNight
23%12%31%29%6%
950
11th to 20thNight
23%13%33%25%5%1
950
21st to endNight
22%12%33%28%5%
1043
February1st to 10thNight
24%14%31%26%5%
900
11th to 20thNight
24%16%34%23%4
818
21st to endNight
26%14%32%25%4
444
March1st to 10thNight
24%11%31%29%5%
540
11th to 20thNight
21%14%30%29%6%
540
21st to endNight
20%11%35%29%5%
594
April1st to 10thNight
16%11%37%29%7%
540
11th to 20thNight
14%13%35%26%12%1
533
21st to endNight
15%10%34%30%11%
540
May1st to 10thNight
15%5%30%38%12%1
540
11th to 20thNight
14%5%28%33%18%2
531
21st to endNight
11%224%35%26%2
584
June1st to 10thNight
5%211%42%37%3
540
11th to 20thNight
6%213%44%34%2
540
21st to endNight
4211%38%39%7%
540
July1st to 10thNight
5%8%31%49%7%
525
11th to 20thNight
416%30%49%10%
522
21st to endNight
317%31%48%9%
591
August1st to 10thNight
417%34%46%8%
537
11th to 20thNight
9%19%34%39%8%
534
21st to endNight
6%17%34%45%8%
594
September1st to 10thNight
7%28%33%43%7%
540
11th to 20thNight
11%111%36%37%4
540
21st to endNight
9%214%36%35%4
548
October1st to 10thNight
10%214%40%29%4
720
11th to 20thNight
14%5%26%35%18%1
720
21st to endNight
21%7%24%28%18%2
792
November1st to 10thNight
15%426%37%16%1
740
11th to 20thNight
14%9%29%36%11%
760
21st to endNight
21%11%27%27%13%1
883
December1st to 10thNight
22%10%29%31%7%
950
11th to 20thNight
27%9%26%32%6%
950
21st to endNight
23%11%31%27%7%
1045
Page generated at 2024-01-28 04:26:36. Version ac07

Copyright 2024 Attilla Danko


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