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AGS Observatory
Clear Sky Chart
History

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

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
58%
24412
31%
98682
22%
24191
70%
24191
36%
44584

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
53%
757
34%
4012
25%
736
69%
736
29%
1748
January11th to 20thNight
50%
755
43%
3899
25%
740
65%
740
40%
1239
January21st to endNight
49%
825
22%
4313
22%
814
67%
814
23%
2260
February1st to 10thNight
51%
760
34%
2470
24%
760
67%
760
46%
1106
February11th to 20thNight
40%
741
33%
2303
19%
740
57%
740
45%
1108
February21st to endNight
36%
628
40%
1775
17%
628
58%
628
46%
864
March1st to 10thNight
41%
755
46%
3322
17%
744
62%
744
40%
1189
March11th to 20thNight
48%
757
33%
3455
18%
740
64%
740
29%
1714
March21st to endNight
43%
833
26%
3626
14%
814
62%
814
40%
1329
April1st to 10thNight
42%
614
39%
1944
16%
614
67%
614
51%
843
April11th to 20thNight
38%
563
37%
1877
17%
563
65%
563
42%
807
April21st to endNight
40%
570
39%
1900
19%
570
66%
570
50%
782
May1st to 10thNight
51%
567
46%
2911
23%
559
69%
559
50%
816
May11th to 20thNight
56%
554
28%
2738
21%
541
67%
541
36%
1019
May21st to endNight
56%
607
28%
3054
23%
593
69%
593
61%
768
June1st to 10thNight
65%
570
31%
1710
25%
570
70%
570
51%
807
June11th to 20thNight
66%
570
32%
1710
25%
570
71%
570
61%
749
June21st to endNight
66%
570
21%
1710
18%
570
68%
570
38%
948
July1st to 10thNight
74%
537
25%
2434
17%
535
75%
535
24%
1228
July11th to 20thNight
74%
535
13%
2414
11%
533
74%
533
18%
1424
July21st to endNight
67%
607
8%
2847
11%
569
69%
569
15%
1705
August1st to 10thNight
77%
554
13%
2597
14%
545
78%
545
21%
1455
August11th to 20thNight
70%
548
15%
2846
20%
543
72%
543
16%
1715
August21st to endNight
77%
609
14%
3389
23%
605
78%
605
17%
2090
September1st to 10thNight
75%
570
28%
1900
30%
570
76%
570
33%
1068
September11th to 20thNight
76%
633
34%
1963
31%
633
79%
633
43%
1032
September21st to endNight
73%
760
32%
2147
22%
760
79%
760
52%
1109
October1st to 10thNight
64%
746
40%
3431
22%
740
73%
740
37%
1459
October11th to 20thNight
68%
749
30%
3474
27%
740
79%
740
40%
1493
October21st to endNight
65%
819
47%
3766
27%
813
77%
813
54%
1168
November1st to 10thNight
68%
764
45%
2292
30%
764
79%
764
63%
970
November11th to 20thNight
67%
760
43%
2280
31%
760
77%
760
62%
974
November21st to endNight
55%
760
40%
2336
27%
760
68%
760
46%
1130
December1st to 10thNight
56%
880
36%
2590
24%
880
67%
880
45%
1289
December11th to 20thNight
48%
758
34%
2918
23%
758
64%
758
34%
1431
December21st to endNight
47%
827
22%
4329
24%
817
61%
817
29%
1748

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
3425%44445%7%58%
104813
Night
241433436%7%61%
102955
TransparencyDay
23%6%9%15%27%20%
104577
Night
20%6%10%18%29%18%
102780
SeeingDay
10%16%23%26%19%7%
14461
Night
5%9%21%37%24%4
24617

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
1427%33435%6%61%
2858
11th to 20thDay
2324223347%68%
2860
21st to endDay
49%35%5%45%45%7%50%
3146
February1st to 10thDay
1435%433347%63%
1710
11th to 20thDay
25%24343346%64%
1763
21st to endDay
26%2323346%7%64%
1674
March1st to 10thDay
142434446%8%59%
3444
11th to 20thDay
5%11%36%445%45%8%45%
3490
21st to endDay
143444446%6%61%
3825
April1st to 10thDay
231433335%7%65%
2234
11th to 20thDay
2414434345%66%
2251
21st to endDay
2315%33335%6%66%
2280
May1st to 10thDay
1313333345%72%
3800
11th to 20thDay
3425%5%5%445%5%59%
4070
21st to endDay
211222223478%
4477
June1st to 10thDay
341444435%7%62%
2470
11th to 20thDay
231323335%6%69%
2470
21st to endDay
45%26%6%6%5%46%6%49%
2470
July1st to 10thDay
4426%5%5%5%45%6%55%
4110
11th to 20thDay
4427%7%8%7%6%7%9%38%
4110
21st to endDay
6%6%39%7%7%8%7%9%9%29%
4454
August1st to 10thDay
5%428%7%6%7%6%8%10%37%
4092
11th to 20thDay
4426%5%6%6%5%8%9%45%
3784
21st to endDay
5%6%28%7%7%8%6%8%8%36%
4180
September1st to 10thDay
8%5%27%45%5%5%6%7%45%
2280
11th to 20thDay
6%426%5%4445%6%54%
2213
21st to endDay
3414334346%63%
2031
October1st to 10thDay
4414333235%69%
3170
11th to 20thDay
4315%333237%65%
3150
21st to endDay
11211212483%
3438
November1st to 10thDay
231322225%7%72%
1909
11th to 20thDay
221432325%6%69%
1900
21st to endDay
35%2444335%5%64%
1832
December1st to 10thDay
332432335%6%67%
1553
11th to 20thDay
37%37%45%435%6%54%
2169
21st to endDay
1425%345%46%6%60%
3146
January1st to 10thNight
1428%44435%7%58%
4097
11th to 20thNight
2312222246%73%
4110
21st to endNight
37%37%45%5%46%7%49%
4521
February1st to 10thNight
141423335%8%65%
2470
11th to 20thNight
341433335%7%63%
2302
21st to endNight
2313332348%68%
1775
March1st to 10thNight
1224323346%71%
3430
11th to 20thNight
6%9%25%33335%6%54%
3490
21st to endNight
131423336%9%66%
3828
April1st to 10thNight
131332335%7%70%
1944
11th to 20thNight
2313233335%71%
1877
21st to endNight
1213223346%73%
1900
May1st to 10thNight
2212222235%79%
3154
11th to 20thNight
231443345%6%65%
2834
21st to endNight
111221113484%
3110
June1st to 10thNight
341333336%8%63%
1710
11th to 20thNight
321222425%6%71%
1710
21st to endNight
3425%5%5%5%5%7%8%51%
1710
July1st to 10thNight
3325%5%5%5%46%8%56%
2860
11th to 20thNight
3426%5%6%8%5%10%12%38%
2860
21st to endNight
45%27%6%7%7%6%10%13%34%
3109
August1st to 10thNight
2326%5%6%6%7%11%13%40%
2847
11th to 20thNight
35%37%6%6%7%6%9%10%37%
3052
21st to endNight
4427%7%7%8%8%11%13%31%
3487
September1st to 10thNight
5%426%5%5%6%47%10%47%
1900
11th to 20thNight
4316%344447%59%
1963
21st to endNight
4414334246%66%
2147
October1st to 10thNight
341433335%5%65%
3800
11th to 20thNight
4413223246%67%
3778
21st to endNight
1112123245%79%
4120
November1st to 10thNight
222123346%75%
2292
11th to 20thNight
121322325%5%76%
2280
21st to endNight
45%13323247%65%
2336
December1st to 10thNight
4313234347%65%
2590
11th to 20thNight
2425%445%46%10%54%
3041
21st to endNight
2425%44335%7%61%
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
22%5%6%21%35%11%
2859
11th to 20thDay
16%49%28%34%10%
2860
21st to endDay
28%6%8%17%32%9%
3146
February1st to 10thDay
20%38%19%28%23%
1710
11th to 20thDay
21%36%19%30%21%
1772
21st to endDay
18%37%14%33%26%
1674
March1st to 10thDay
17%5%8%12%37%20%
3444
11th to 20thDay
30%7%10%15%26%12%
3490
21st to endDay
19%5%8%17%39%12%
3825
April1st to 10thDay
16%36%15%37%23%
2234
11th to 20thDay
20%3412%32%29%
2254
21st to endDay
18%36%16%37%20%
2280
May1st to 10thDay
12%35%10%36%34%
3800
11th to 20thDay
22%6%7%10%32%22%
4073
21st to endDay
10%347%22%55%
4477
June1st to 10thDay
21%5%6%12%26%30%
2470
11th to 20thDay
15%35%8%23%46%
2470
21st to endDay
31%6%9%13%21%19%
2470
July1st to 10thDay
27%7%9%9%14%33%
4046
11th to 20thDay
35%11%14%23%13%4
4041
21st to endDay
41%14%21%17%6%1
4314
August1st to 10thDay
34%13%19%19%12%3
4078
11th to 20thDay
29%10%13%20%21%7%
3821
21st to endDay
38%12%16%15%16%4
4179
September1st to 10thDay
35%8%10%14%22%12%
2280
11th to 20thDay
28%6%8%16%24%18%
2213
21st to endDay
19%6%7%17%28%22%
2031
October1st to 10thDay
16%45%13%29%33%
3170
11th to 20thDay
19%4413%37%23%
3150
21st to endDay
8%2314%35%38%
3438
November1st to 10thDay
12%3421%36%23%
1909
11th to 20thDay
15%26%17%36%24%
1900
21st to endDay
22%45%14%33%21%
1832
December1st to 10thDay
18%46%23%33%16%
1553
11th to 20thDay
30%49%17%25%15%
2168
21st to endDay
21%6%9%16%26%23%
3146
January1st to 10thNight
23%6%8%19%32%12%
4097
11th to 20thNight
12%49%27%40%9%
4110
21st to endNight
30%7%9%17%30%8%
4521
February1st to 10thNight
16%410%21%29%20%
2470
11th to 20thNight
19%36%23%28%20%
2303
21st to endNight
17%3420%31%24%
1775
March1st to 10thNight
14%37%17%43%16%
3430
11th to 20thNight
26%6%8%19%30%11%
3490
21st to endNight
13%49%27%38%9%
3828
April1st to 10thNight
13%35%22%37%20%
1944
11th to 20thNight
16%3414%36%27%
1877
21st to endNight
12%47%17%39%21%
1900
May1st to 10thNight
9%2410%50%24%
3154
11th to 20thNight
16%6%9%14%36%19%
2835
21st to endNight
7%248%22%57%
3110
June1st to 10thNight
18%47%15%27%29%
1710
11th to 20thNight
13%36%11%23%45%
1710
21st to endNight
25%9%12%13%17%23%
1710
July1st to 10thNight
24%9%11%12%13%30%
2815
11th to 20thNight
28%13%20%23%11%4
2806
21st to endNight
33%15%30%18%41
3011
August1st to 10thNight
28%12%27%20%9%3
2838
11th to 20thNight
33%14%17%19%11%7%
3081
21st to endNight
35%15%22%15%11%3
3487
September1st to 10thNight
29%8%14%16%20%12%
1900
11th to 20thNight
23%7%10%17%27%17%
1963
21st to endNight
19%5%6%17%32%21%
2147
October1st to 10thNight
18%6%7%14%28%28%
3800
11th to 20thNight
17%6%6%18%32%22%
3778
21st to endNight
10%2315%39%30%
4120
November1st to 10thNight
11%3423%37%21%
2292
11th to 20thNight
11%36%22%34%24%
2280
21st to endNight
20%36%18%35%18%
2336
December1st to 10thNight
20%47%24%30%16%
2590
11th to 20thNight
22%6%10%19%29%13%
3041
21st to endNight
21%49%18%26%21%
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
10%19%33%25%11%1
270
11th to 20thDay
14%21%24%23%14%3
270
21st to endDay
7%21%27%28%15%3
297
February1st to 10thDay
7%23%31%24%11%4
270
11th to 20thDay
15%22%29%27%7%
270
21st to endDay
19%34%23%17%5%1
329
March1st to 10thDay
14%27%31%20%6%1
460
11th to 20thDay
18%22%30%16%12%2
460
21st to endDay
15%35%26%16%6%1
506
April1st to 10thDay
10%25%34%18%9%4
460
11th to 20thDay
17%29%29%15%8%2
452
21st to endDay
12%27%31%18%9%2
460
May1st to 10thDay
10%24%34%21%10%2
463
11th to 20thDay
8%20%30%23%13%6%
488
21st to endDay
7%21%34%25%11%2
529
June1st to 10thDay
5%9%30%31%21%4
490
11th to 20thDay
5%11%27%29%22%6%
490
21st to endDay
7%7%26%32%22%7%
490
July1st to 10thDay
7%410%36%34%9%
486
11th to 20thDay
7%2432%35%20%
484
21st to endDay
9%5%326%36%22%
531
August1st to 10thDay
7%47%28%34%19%
487
11th to 20thDay
8%47%31%32%18%
477
21st to endDay
7%5%7%31%32%18%
539
September1st to 10thDay
11%410%34%29%12%
490
11th to 20thDay
8%421%35%22%10%
490
21st to endDay
6%10%20%33%22%9%
431
October1st to 10thDay
9%10%22%26%20%14%
300
11th to 20thDay
11%9%23%27%19%10%
300
21st to endDay
10%12%18%29%23%8%
330
November1st to 10thDay
8%19%24%27%16%5%
285
11th to 20thDay
5%10%23%30%24%8%
270
21st to endDay
7%24%27%24%14%4
270
December1st to 10thDay
10%14%28%29%18%2
270
11th to 20thDay
5%24%27%27%15%1
270
21st to endDay
12%23%28%27%9%1
297
January1st to 10thNight
5%11%24%38%17%4
760
11th to 20thNight
7%13%25%36%17%2
760
21st to endNight
5%15%25%36%17%3
836
February1st to 10thNight
416%26%36%15%3
760
11th to 20thNight
5%14%35%35%9%1
744
21st to endNight
6%18%37%29%9%
628
March1st to 10thNight
419%32%33%11%1
760
11th to 20thNight
8%13%27%35%15%1
760
21st to endNight
417%31%36%11%1
836
April1st to 10thNight
217%34%36%10%
614
11th to 20thNight
421%33%32%10%1
563
21st to endNight
317%37%30%13%
570
May1st to 10thNight
310%32%42%13%1
570
11th to 20thNight
5%7%24%43%19%2
561
21st to endNight
36%28%44%17%1
617
June1st to 10thNight
45%19%49%22%2
570
11th to 20thNight
3323%49%22%1
570
21st to endNight
4215%38%38%2
570
July1st to 10thNight
42341%42%7%
555
11th to 20thNight
6%2326%54%9%
552
21st to endNight
7%3419%57%12%
624
August1st to 10thNight
5%2220%57%15%
567
11th to 20thNight
5%2427%52%10%
564
21st to endNight
5%2326%54%8%
627
September1st to 10thNight
7%2436%44%6%
570
11th to 20thNight
6%17%42%40%5%
633
21st to endNight
5%312%37%39%4
760
October1st to 10thNight
5%5%18%43%25%3
760
11th to 20thNight
5%319%48%21%4
760
21st to endNight
48%18%35%29%5%
836
November1st to 10thNight
46%19%43%24%4
764
11th to 20thNight
27%22%41%25%4
760
21st to endNight
7%11%22%34%21%4
760
December1st to 10thNight
6%14%20%39%18%3
880
11th to 20thNight
5%13%27%38%17%1
760
21st to endNight
5%13%28%40%13%2
836
Page generated at 2024-11-03 11:18:59. Version ac07

Copyright © 2024 Attilla Danko.


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