Gov Aker Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gov Aker Observatory 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
66%
23758
35%
74311
26%
23704
75%
23704
51%
35123

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
61%
758
35%
2457
29%
756
72%
756
48%
1158
January11th to 20thNight
63%
744
37%
2417
30%
744
76%
744
52%
1089
January21st to endNight
57%
792
37%
2574
29%
792
71%
792
43%
1276
February1st to 10thNight
63%
720
37%
2340
31%
720
76%
720
55%
1039
February11th to 20thNight
54%
700
33%
2151
23%
700
68%
700
49%
1031
February21st to endNight
52%
592
42%
1628
25%
592
69%
592
56%
785
March1st to 10thNight
50%
720
39%
1980
22%
720
66%
720
54%
983
March11th to 20thNight
57%
720
39%
1980
23%
720
71%
720
59%
941
March21st to endNight
56%
792
39%
2178
21%
792
71%
792
59%
1032
April1st to 10thNight
60%
681
39%
1941
22%
681
75%
681
66%
827
April11th to 20thNight
50%
533
41%
1777
25%
533
72%
533
59%
704
April21st to endNight
55%
540
45%
1800
31%
540
75%
540
69%
656
May1st to 10thNight
63%
540
39%
1699
28%
540
77%
540
66%
685
May11th to 20thNight
65%
531
37%
1594
27%
531
75%
531
64%
690
May21st to endNight
69%
583
42%
1746
32%
582
78%
582
78%
671
June1st to 10thNight
72%
540
34%
1620
26%
540
77%
540
61%
715
June11th to 20thNight
73%
540
37%
1620
28%
540
79%
540
75%
644
June21st to endNight
74%
540
24%
1620
20%
540
76%
540
49%
806
July1st to 10thNight
74%
525
22%
1575
18%
525
75%
525
38%
881
July11th to 20thNight
73%
522
14%
1566
13%
522
74%
522
28%
1002
July21st to endNight
76%
591
14%
1674
13%
558
76%
558
26%
1097
August1st to 10thNight
82%
537
19%
1602
16%
534
82%
534
36%
927
August11th to 20thNight
77%
534
23%
1669
22%
534
78%
534
33%
969
August21st to endNight
80%
594
26%
1980
28%
594
82%
594
36%
1092
September1st to 10thNight
73%
607
29%
1867
29%
607
76%
607
35%
1070
September11th to 20thNight
78%
720
36%
1980
29%
720
81%
720
53%
1025
September21st to endNight
77%
720
37%
1980
26%
720
83%
720
58%
981
October1st to 10thNight
73%
720
36%
2125
27%
720
79%
720
55%
1014
October11th to 20thNight
72%
720
41%
2160
29%
720
82%
720
66%
913
October21st to endNight
72%
792
45%
2376
32%
792
83%
792
70%
975
November1st to 10thNight
71%
740
44%
2220
33%
740
80%
740
69%
915
November11th to 20thNight
70%
760
43%
2280
32%
760
81%
760
63%
1001
November21st to endNight
58%
760
38%
2408
28%
760
70%
760
49%
1138
December1st to 10thNight
66%
760
39%
2470
35%
760
74%
760
49%
1160
December11th to 20thNight
55%
758
32%
2921
27%
758
67%
758
34%
1490
December21st to endNight
58%
832
23%
4336
28%
817
69%
817
32%
1741

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
221332445%7%67%
75020
Night
221332445%7%67%
74822
TransparencyDay
17%5%8%15%28%27%
74747
Night
18%5%8%14%27%29%
74617
SeeingDay
48%25%36%23%5%
13602
Night
3423%42%25%3
23771

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
232343445%7%64%
1708
11th to 20thDay
2213334446%69%
1665
21st to endDay
4323323346%66%
1782
February1st to 10thDay
2213313346%71%
1620
11th to 20thDay
33244245%5%6%63%
1692
21st to endDay
231232345%6%68%
1628
March1st to 10thDay
221332446%8%66%
1980
11th to 20thDay
221232335%7%70%
1980
21st to endDay
1112312346%76%
2178
April1st to 10thDay
111213446%76%
2016
11th to 20thDay
111121233481%
2131
21st to endDay
1111122236%81%
2160
May1st to 10thDay
11221335%5%78%
2257
11th to 20thDay
2111213346%77%
2301
21st to endDay
11111223383%
2530
June1st to 10thDay
111221245%6%75%
2340
11th to 20thDay
11222223481%
2340
21st to endDay
22134235%5%7%66%
2340
July1st to 10thDay
3223435%5%7%9%56%
2340
11th to 20thDay
22145%46%9%10%12%44%
2340
21st to endDay
4436%5%46%8%10%12%39%
2545
August1st to 10thDay
5%3245%46%6%8%10%48%
2328
11th to 20thDay
5%314435%6%8%12%49%
2232
21st to endDay
4323436%6%8%10%52%
2376
September1st to 10thDay
5%214445%5%6%8%55%
2088
11th to 20thDay
3313324447%67%
1980
21st to endDay
221221325%6%73%
1980
October1st to 10thDay
2212313446%72%
1832
11th to 20thDay
321211333479%
1800
21st to endDay
1111212245%80%
1980
November1st to 10thDay
1111112347%78%
1859
11th to 20thDay
122223446%74%
1900
21st to endDay
2313324447%67%
1767
December1st to 10thDay
3313324448%65%
1710
11th to 20thDay
3425%5%35%45%8%55%
2169
21st to endDay
2314435%6%6%7%59%
3146
January1st to 10thNight
231332445%9%64%
2457
11th to 20thNight
3312323336%71%
2417
21st to endNight
5%413433447%63%
2574
February1st to 10thNight
22122235%5%6%71%
2340
11th to 20thNight
331242345%6%66%
2150
21st to endNight
2112323446%71%
1628
March1st to 10thNight
221232345%7%69%
1980
11th to 20thNight
2212223346%72%
1980
21st to endNight
2213223346%72%
2178
April1st to 10thNight
1111212346%77%
1941
11th to 20thNight
121222233478%
1777
21st to endNight
111121213483%
1800
May1st to 10thNight
112213235%79%
1699
11th to 20thNight
212222346%77%
1594
21st to endNight
11111122485%
1746
June1st to 10thNight
2212213347%73%
1620
11th to 20thNight
1111211235%83%
1620
21st to endNight
2213425%5%6%7%64%
1620
July1st to 10thNight
2214437%7%8%10%51%
1620
11th to 20thNight
25%26%6%48%7%10%14%37%
1620
21st to endNight
4326%7%47%9%10%14%34%
1773
August1st to 10thNight
23245%47%6%7%12%49%
1611
11th to 20thNight
33245%37%6%8%11%47%
1669
21st to endNight
32245%36%6%7%11%50%
1980
September1st to 10thNight
6%425%5%345%6%9%51%
1867
11th to 20thNight
431232445%7%66%
1980
21st to endNight
221332345%5%71%
1980
October1st to 10thNight
221233335%5%70%
2125
11th to 20thNight
2212212225%80%
2160
21st to endNight
111211122384%
2376
November1st to 10thNight
211112445%78%
2220
11th to 20thNight
1212122345%77%
2280
21st to endNight
4213323445%68%
2408
December1st to 10thNight
431322345%7%66%
2470
11th to 20thNight
33145%45%6%6%8%56%
3041
21st to endNight
33134345%7%7%59%
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
21%5%8%19%34%14%
1709
11th to 20thDay
18%5%6%18%35%18%
1665
21st to endDay
21%46%17%32%20%
1782
February1st to 10thDay
17%36%14%29%30%
1620
11th to 20thDay
22%48%14%28%24%
1702
21st to endDay
18%36%13%32%28%
1628
March1st to 10thDay
18%46%13%33%25%
1980
11th to 20thDay
16%36%12%34%29%
1980
21st to endDay
12%25%15%42%25%
2178
April1st to 10thDay
10%25%10%38%34%
2016
11th to 20thDay
10%248%31%45%
2134
21st to endDay
8%1411%33%42%
2160
May1st to 10thDay
9%26%9%27%46%
2257
11th to 20thDay
11%46%11%29%40%
2304
21st to endDay
8%25%6%28%52%
2530
June1st to 10thDay
10%36%5%30%47%
2340
11th to 20thDay
8%24419%62%
2340
21st to endDay
18%48%12%19%40%
2340
July1st to 10thDay
21%7%13%18%17%25%
2276
11th to 20thDay
26%12%19%22%13%8%
2271
21st to endDay
30%13%21%20%12%4
2404
August1st to 10thDay
28%10%15%18%18%11%
2313
11th to 20thDay
27%8%16%19%19%10%
2232
21st to endDay
23%9%16%21%20%11%
2376
September1st to 10thDay
26%7%10%18%22%18%
2088
11th to 20thDay
17%47%16%29%27%
1980
21st to endDay
13%38%15%33%28%
1980
October1st to 10thDay
15%5%7%18%24%31%
1832
11th to 20thDay
12%35%9%32%39%
1800
21st to endDay
9%35%17%33%34%
1980
November1st to 10thDay
10%35%17%39%27%
1859
11th to 20thDay
15%3416%35%27%
1900
21st to endDay
19%46%17%33%21%
1767
December1st to 10thDay
19%37%23%28%18%
1710
11th to 20thDay
28%6%8%22%27%10%
2168
21st to endDay
22%5%9%18%36%10%
3146
January1st to 10thNight
20%47%20%34%16%
2457
11th to 20thNight
18%35%17%35%23%
2417
21st to endNight
24%35%15%33%20%
2574
February1st to 10thNight
15%46%16%26%33%
2340
11th to 20thNight
19%37%15%28%26%
2151
21st to endNight
15%46%12%32%31%
1628
March1st to 10thNight
17%46%14%29%31%
1980
11th to 20thNight
15%35%13%30%35%
1980
21st to endNight
14%36%14%35%28%
2178
April1st to 10thNight
10%15%11%39%33%
1941
11th to 20thNight
12%249%27%46%
1777
21st to endNight
8%1411%32%44%
1800
May1st to 10thNight
11%25%7%27%49%
1699
11th to 20thNight
11%46%11%23%45%
1595
21st to endNight
6%147%24%57%
1746
June1st to 10thNight
14%36%423%51%
1620
11th to 20thNight
8%24416%66%
1620
21st to endNight
19%6%10%9%15%42%
1620
July1st to 10thNight
24%10%11%18%13%23%
1575
11th to 20thNight
33%12%19%19%9%7%
1566
21st to endNight
34%14%25%16%8%3
1674
August1st to 10thNight
27%10%16%20%13%13%
1602
11th to 20thNight
27%11%19%14%17%11%
1669
21st to endNight
26%9%16%20%20%9%
1980
September1st to 10thNight
30%7%10%16%19%18%
1867
11th to 20thNight
19%5%8%16%26%27%
1980
21st to endNight
17%45%11%33%30%
1980
October1st to 10thNight
16%48%16%22%34%
2125
11th to 20thNight
11%3412%27%44%
2160
21st to endNight
9%2414%31%40%
2376
November1st to 10thNight
10%25%12%40%30%
2220
11th to 20thNight
12%3418%28%34%
2280
21st to endNight
20%36%16%32%23%
2408
December1st to 10thNight
20%45%22%30%20%
2470
11th to 20thNight
26%48%19%30%11%
3041
21st to endNight
20%5%11%17%31%15%
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%11%35%39%9%
270
11th to 20thDay
6%9%30%38%15%3
255
21st to endDay
39%38%34%14%2
264
February1st to 10thDay
25%32%40%18%3
240
11th to 20thDay
8%18%36%30%8%
345
21st to endDay
7%21%40%25%6%1
346
March1st to 10thDay
5%20%36%28%10%2
420
11th to 20thDay
7%16%31%31%12%4
420
21st to endDay
5%26%31%28%9%2
462
April1st to 10thDay
313%34%35%13%3
420
11th to 20thDay
320%34%29%10%3
412
21st to endDay
219%33%31%12%4
420
May1st to 10thDay
113%34%33%17%1
423
11th to 20thDay
27%30%38%20%2
448
21st to endDay
27%29%44%18%1
485
June1st to 10thDay
1421%45%25%3
450
11th to 20thDay
15%24%37%28%5%
450
21st to endDay
4121%41%28%4
450
July1st to 10thDay
2212%46%33%5%
446
11th to 20thDay
316%37%40%12%
444
21st to endDay
5%18%30%42%14%
487
August1st to 10thDay
427%31%41%15%
447
11th to 20thDay
427%37%40%10%
437
21st to endDay
317%30%45%14%
495
September1st to 10thDay
4214%41%32%6%
450
11th to 20thDay
3114%40%35%7%
450
21st to endDay
4419%41%25%7%
450
October1st to 10thDay
35%23%37%26%7%
302
11th to 20thDay
6%6%26%34%20%8%
270
21st to endDay
36%22%35%27%8%
297
November1st to 10thDay
36%33%37%18%3
270
11th to 20thDay
15%30%38%22%3
270
21st to endDay
39%38%33%15%2
270
December1st to 10thDay
5%7%27%47%14%
270
11th to 20thDay
48%40%36%11%
270
21st to endDay
7%10%36%35%10%1
297
January1st to 10thNight
35%28%46%17%1
760
11th to 20thNight
46%24%44%19%3
744
21st to endNight
6%6%27%41%18%2
792
February1st to 10thNight
35%28%39%22%3
720
11th to 20thNight
5%7%31%43%13%
704
21st to endNight
37%35%40%15%
592
March1st to 10thNight
47%37%36%16%1
720
11th to 20thNight
37%29%37%20%4
720
21st to endNight
18%32%37%21%1
792
April1st to 10thNight
17%29%43%18%2
681
11th to 20thNight
28%38%35%16%2
533
21st to endNight
17%35%40%14%3
540
May1st to 10thNight
15%29%47%16%2
540
11th to 20thNight
2129%47%18%2
531
21st to endNight
2325%49%21%1
584
June1st to 10thNight
2121%48%26%1
540
11th to 20thNight
1122%53%21%2
540
21st to endNight
3215%47%31%2
540
July1st to 10thNight
3213%43%35%5%
525
11th to 20thNight
328%41%40%7%
522
21st to endNight
325%35%46%9%
591
August1st to 10thNight
31433%49%10%
537
11th to 20thNight
426%34%45%9%
534
21st to endNight
316%33%48%9%
594
September1st to 10thNight
6%210%35%42%5%
607
11th to 20thNight
4111%40%38%6%
720
21st to endNight
3212%46%33%3
720
October1st to 10thNight
2218%45%29%3
720
11th to 20thNight
2319%45%27%3
720
21st to endNight
1420%41%28%6%
792
November1st to 10thNight
2222%41%27%5%
740
11th to 20thNight
1322%45%26%2
760
21st to endNight
5%5%28%39%19%3
760
December1st to 10thNight
6%322%47%20%2
760
11th to 20thNight
5%7%28%40%17%3
760
21st to endNight
45%29%43%16%3
836
Page generated at 2024-01-13 07:37:55. Version ac07

Copyright 2024 Attilla Danko


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