Aubright Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Aubright Observatory clear sky chart from 2005-11-06 to 2024-03-08.

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
53%
24595
20%
79947
15%
24500
59%
24500
26%
50098

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
33%
752
22%
4003
11%
737
48%
737
15%
2266
January11th to 20thNight
43%
755
23%
4029
18%
740
56%
740
16%
2447
January21st to endNight
29%
829
15%
4441
10%
814
44%
814
14%
2644
February1st to 10thNight
39%
760
21%
2280
14%
760
47%
760
26%
1453
February11th to 20thNight
35%
740
22%
2218
11%
739
47%
739
28%
1374
February21st to endNight
37%
628
24%
1821
14%
628
47%
628
30%
1143
March1st to 10thNight
42%
751
29%
2064
17%
751
52%
751
36%
1215
March11th to 20thNight
41%
720
25%
1980
14%
720
51%
720
33%
1214
March21st to endNight
42%
792
26%
2178
14%
792
52%
792
35%
1296
April1st to 10thNight
45%
720
24%
1980
14%
720
53%
720
34%
1195
April11th to 20thNight
43%
711
24%
1901
15%
711
49%
711
35%
1171
April21st to endNight
56%
683
29%
1763
17%
683
62%
683
44%
1024
May1st to 10thNight
65%
540
28%
1620
19%
540
70%
540
44%
853
May11th to 20thNight
66%
531
20%
1592
15%
531
69%
531
35%
941
May21st to endNight
70%
582
21%
1744
16%
582
72%
582
32%
1062
June1st to 10thNight
65%
540
13%
1620
9%
540
66%
540
24%
1081
June11th to 20thNight
72%
540
13%
1620
11%
540
72%
540
28%
1074
June21st to endNight
71%
540
11%
1620
9%
540
72%
540
26%
1104
July1st to 10thNight
72%
525
10%
1575
9%
525
72%
525
23%
1094
July11th to 20thNight
72%
522
11%
1566
11%
522
72%
522
22%
1109
July21st to endNight
76%
591
12%
1672
12%
558
77%
558
28%
1113
August1st to 10thNight
73%
537
10%
1600
9%
534
74%
534
23%
1111
August11th to 20thNight
76%
534
9%
1603
9%
534
76%
534
24%
1112
August21st to endNight
61%
772
10%
2158
10%
772
61%
772
18%
1593
September1st to 10thNight
64%
720
12%
1980
11%
720
64%
720
20%
1471
September11th to 20thNight
60%
720
9%
1980
9%
720
60%
720
17%
1495
September21st to endNight
63%
720
20%
1980
19%
720
65%
720
27%
1317
October1st to 10thNight
57%
720
23%
2003
21%
720
61%
720
28%
1318
October11th to 20thNight
63%
720
31%
2160
28%
720
70%
720
38%
1215
October21st to endNight
57%
792
29%
2376
26%
792
64%
792
33%
1394
November1st to 10thNight
51%
740
25%
2221
20%
740
59%
740
33%
1324
November11th to 20thNight
46%
760
26%
2285
18%
760
57%
760
29%
1414
November21st to endNight
44%
760
24%
2470
19%
760
54%
760
28%
1501
December1st to 10thNight
46%
760
25%
2470
18%
760
55%
760
28%
1476
December11th to 20thNight
43%
759
23%
2940
18%
758
51%
758
22%
1760
December21st to endNight
43%
829
15%
4434
17%
817
52%
817
15%
2724

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
10%6%36%6%46%6%6%8%39%
78938
Night
10%6%35%5%35%5%6%8%43%
80630
TransparencyDay
41%9%13%16%14%6%
78661
Night
37%8%14%18%15%7%
80426
SeeingDay
10%7%22%25%22%13%
14466
Night
11%6%22%32%24%5%
24628

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
11%8%35%434346%49%
2836
11th to 20thDay
16%8%37%6%33447%39%
2840
21st to endDay
11%7%36%5%35%5%5%7%45%
3134
February1st to 10thDay
16%7%35%6%335%46%43%
1900
11th to 20thDay
13%5%25%43445%6%49%
1848
21st to endDay
11%6%25%4345%5%7%48%
1632
March1st to 10thDay
8%5%25%32445%8%53%
2057
11th to 20thDay
9%5%35%6%245%6%7%49%
1980
21st to endDay
10%5%25%5%345%48%49%
2178
April1st to 10thDay
9%5%35%5%345%5%8%48%
1980
11th to 20thDay
10%7%36%5%45%5%6%7%41%
2006
21st to endDay
5%425%5%45%5%6%8%52%
2210
May1st to 10thDay
7%3245%345%5%9%53%
2340
11th to 20thDay
9%335%6%5%6%7%7%10%39%
2301
21st to endDay
9%426%7%5%7%7%7%10%37%
2531
June1st to 10thDay
12%6%28%8%5%7%7%7%10%28%
2340
11th to 20thDay
6%5%37%7%5%8%8%9%11%30%
2340
21st to endDay
8%5%48%9%5%7%7%9%11%27%
2340
July1st to 10thDay
8%6%47%9%5%8%8%9%9%27%
2340
11th to 20thDay
8%6%48%8%6%9%8%9%11%23%
2340
21st to endDay
7%5%38%8%5%8%9%8%12%27%
2547
August1st to 10thDay
9%6%37%9%6%8%7%8%11%25%
2327
11th to 20thDay
11%6%38%8%6%8%9%9%11%22%
2293
21st to endDay
12%7%38%9%6%8%7%8%9%24%
2178
September1st to 10thDay
10%7%48%9%6%7%9%8%8%24%
1980
11th to 20thDay
14%7%38%8%6%8%7%7%9%23%
1980
21st to endDay
13%7%37%6%46%7%6%7%34%
1980
October1st to 10thDay
11%5%37%7%46%6%7%8%35%
1955
11th to 20thDay
8%5%25%5%35%6%47%50%
1800
21st to endDay
9%5%345%3446%8%49%
1980
November1st to 10thDay
10%5%25%5%345%5%9%46%
1857
11th to 20thDay
10%6%35%6%25%46%8%44%
1891
21st to endDay
12%5%35%7%4345%6%45%
1710
December1st to 10thDay
10%5%25%5%36%5%7%9%44%
1710
11th to 20thDay
14%6%35%5%245%5%7%44%
2153
21st to endDay
15%8%36%5%34346%41%
3124
January1st to 10thNight
13%8%35%5%3446%6%43%
4109
11th to 20thNight
12%8%37%6%35%5%6%8%38%
4120
21st to endNight
12%7%36%5%35%46%7%41%
4518
February1st to 10thNight
14%6%26%6%3435%6%45%
2280
11th to 20thNight
13%6%25%5%34446%48%
2218
21st to endNight
11%6%25%5%34447%48%
1821
March1st to 10thNight
9%5%25%5%34437%55%
2064
11th to 20thNight
9%5%25%5%345%5%8%49%
1980
21st to endNight
8%5%245%2445%6%54%
2178
April1st to 10thNight
8%5%245%35%5%5%8%51%
1980
11th to 20thNight
9%5%35%43435%7%51%
1901
21st to endNight
6%323435%5%7%9%54%
1763
May1st to 10thNight
5%214425%5%5%8%60%
1620
11th to 20thNight
5%424435%6%8%11%48%
1592
21st to endNight
6%425%6%47%6%7%10%45%
1744
June1st to 10thNight
11%5%26%5%45%7%8%12%35%
1620
11th to 20thNight
6%325%6%5%6%7%10%12%38%
1620
21st to endNight
7%425%7%5%5%7%8%13%36%
1620
July1st to 10thNight
6%436%7%37%7%8%13%36%
1620
11th to 20thNight
5%6%36%7%5%7%6%9%13%34%
1620
21st to endNight
4436%6%46%7%10%11%38%
1771
August1st to 10thNight
5%6%36%6%47%6%10%14%33%
1611
11th to 20thNight
5%425%7%47%7%10%12%37%
1603
21st to endNight
9%7%38%8%5%6%7%8%11%28%
2158
September1st to 10thNight
10%6%36%7%5%7%8%7%11%30%
1980
11th to 20thNight
11%6%37%8%5%6%6%9%9%28%
1980
21st to endNight
9%6%27%6%46%5%6%10%40%
1980
October1st to 10thNight
10%5%27%5%35%5%6%7%44%
2003
11th to 20thNight
7%425%5%3435%6%55%
2160
21st to endNight
9%5%25%5%345%5%8%50%
2376
November1st to 10thNight
11%4245%2446%8%49%
2221
11th to 20thNight
10%6%35%435%45%7%48%
2285
21st to endNight
12%6%25%5%35%5%5%7%46%
2470
December1st to 10thNight
11%6%25%5%3445%9%46%
2470
11th to 20thNight
14%7%25%5%3435%6%47%
3042
21st to endNight
14%8%36%5%35%45%6%40%
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
38%38%17%21%13%
2837
11th to 20thDay
46%46%14%17%14%
2840
21st to endDay
38%7%9%18%17%12%
3134
February1st to 10thDay
42%5%10%13%19%10%
1900
11th to 20thDay
36%5%8%15%23%13%
1858
21st to endDay
37%5%11%16%19%12%
1632
March1st to 10thDay
30%5%10%21%23%10%
2057
11th to 20thDay
33%6%13%20%17%11%
1980
21st to endDay
34%6%10%20%20%9%
2178
April1st to 10thDay
34%7%10%18%18%12%
1980
11th to 20thDay
40%8%8%17%20%8%
2006
21st to endDay
28%7%12%22%23%8%
2210
May1st to 10thDay
27%8%10%23%24%9%
2340
11th to 20thDay
36%11%15%19%15%4
2305
21st to endDay
39%10%14%18%17%2
2531
June1st to 10thDay
47%12%16%15%8%1
2340
11th to 20thDay
41%16%19%20%5%
2340
21st to endDay
46%15%20%12%6%
2340
July1st to 10thDay
45%17%20%15%2
2275
11th to 20thDay
48%18%21%10%4
2271
21st to endDay
43%17%21%17%2
2405
August1st to 10thDay
47%16%23%13%2
2314
11th to 20thDay
48%19%21%10%1
2293
21st to endDay
53%14%18%13%3
2178
September1st to 10thDay
52%15%14%10%7%1
1980
11th to 20thDay
54%13%14%13%6%
1980
21st to endDay
47%8%13%15%13%3
1980
October1st to 10thDay
43%9%10%14%14%9%
1955
11th to 20thDay
33%5%9%19%27%6%
1800
21st to endDay
33%5%9%16%22%14%
1980
November1st to 10thDay
35%7%10%19%18%11%
1857
11th to 20thDay
37%6%9%16%21%10%
1891
21st to endDay
39%5%10%17%22%7%
1710
December1st to 10thDay
35%8%13%22%15%6%
1710
11th to 20thDay
40%6%10%17%19%9%
2150
21st to endDay
45%47%17%19%8%
3124
January1st to 10thNight
40%5%7%13%21%14%
4109
11th to 20thNight
44%48%15%18%10%
4120
21st to endNight
41%8%10%14%16%12%
4518
February1st to 10thNight
40%6%9%16%17%12%
2280
11th to 20thNight
37%5%8%18%18%13%
2219
21st to endNight
37%5%9%19%18%12%
1821
March1st to 10thNight
31%5%11%23%20%10%
2064
11th to 20thNight
32%7%15%21%15%10%
1980
21st to endNight
30%6%12%24%18%10%
2178
April1st to 10thNight
32%6%14%19%18%11%
1980
11th to 20thNight
32%6%9%23%21%8%
1901
21st to endNight
25%7%15%27%21%6%
1763
May1st to 10thNight
22%6%13%28%23%7%
1620
11th to 20thNight
27%11%21%23%15%3
1593
21st to endNight
32%9%17%24%17%2
1745
June1st to 10thNight
37%13%22%20%8%
1620
11th to 20thNight
35%13%25%23%5%
1620
21st to endNight
36%14%25%18%6%1
1620
July1st to 10thNight
37%16%26%18%2
1575
11th to 20thNight
39%16%26%14%5%
1566
21st to endNight
32%16%29%21%2
1672
August1st to 10thNight
36%17%30%14%3
1600
11th to 20thNight
35%18%30%17%1
1603
21st to endNight
46%14%23%14%3
2158
September1st to 10thNight
45%15%20%14%6%1
1980
11th to 20thNight
47%15%16%15%7%
1980
21st to endNight
38%10%17%18%14%3
1980
October1st to 10thNight
38%8%12%17%15%9%
2003
11th to 20thNight
29%5%9%24%26%6%
2160
21st to endNight
32%6%10%17%22%13%
2376
November1st to 10thNight
33%6%13%19%17%13%
2221
11th to 20thNight
36%7%9%17%20%11%
2285
21st to endNight
37%6%11%19%19%8%
2470
December1st to 10thNight
35%7%15%23%15%6%
2470
11th to 20thNight
39%5%10%16%21%9%
3044
21st to endNight
44%6%11%16%18%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
10%19%46%19%41
270
11th to 20thDay
8%15%40%26%9%1
270
21st to endDay
15%20%47%15%3
297
February1st to 10thDay
13%19%38%21%8%1
270
11th to 20thDay
17%16%40%20%8%
270
21st to endDay
12%16%38%26%8%
287
March1st to 10thDay
10%14%36%28%12%
448
11th to 20thDay
13%12%33%25%13%4
420
21st to endDay
12%13%33%26%14%2
462
April1st to 10thDay
12%15%29%24%16%3
420
11th to 20thDay
11%13%30%24%14%7%
412
21st to endDay
6%8%31%27%18%11%
420
May1st to 10thDay
5%7%29%30%20%9%
423
11th to 20thDay
8%221%30%24%14%
447
21st to endDay
10%212%26%31%19%
485
June1st to 10thDay
13%212%29%25%18%
450
11th to 20thDay
8%213%22%29%26%
450
21st to endDay
6%39%22%33%28%
450
July1st to 10thDay
7%15%20%32%35%
445
11th to 20thDay
5%15%14%36%39%
444
21st to endDay
7%28%20%36%26%
488
August1st to 10thDay
9%29%17%33%30%
446
11th to 20thDay
8%25%18%32%36%
439
21st to endDay
9%27%23%32%26%
495
September1st to 10thDay
10%48%19%31%28%
450
11th to 20thDay
13%214%27%26%19%
450
21st to endDay
12%310%23%33%18%
450
October1st to 10thDay
14%423%32%20%6%
450
11th to 20thDay
7%6%19%32%29%7%
450
21st to endDay
9%6%24%36%20%5%
495
November1st to 10thDay
14%8%27%27%19%5%
455
11th to 20thDay
14%11%31%26%15%3
451
21st to endDay
11%11%39%27%11%
270
December1st to 10thDay
8%16%33%27%15%2
270
11th to 20thDay
16%14%33%30%6%
270
21st to endDay
15%10%34%31%8%2
297
January1st to 10thNight
15%12%33%31%9%1
760
11th to 20thNight
13%12%27%35%12%1
760
21st to endNight
18%12%36%29%6%
836
February1st to 10thNight
17%9%30%35%9%
760
11th to 20thNight
16%12%31%34%7%
743
21st to endNight
14%10%34%36%6%
628
March1st to 10thNight
10%11%32%38%9%
751
11th to 20thNight
10%10%34%33%11%1
720
21st to endNight
10%10%33%35%11%1
792
April1st to 10thNight
10%9%31%38%11%
720
11th to 20thNight
10%10%31%33%16%
711
21st to endNight
7%429%42%17%1
683
May1st to 10thNight
5%421%47%20%2
540
11th to 20thNight
7%217%38%33%3
531
21st to endNight
7%110%36%39%7%
584
June1st to 10thNight
12%211%34%35%6%
540
11th to 20thNight
6%18%30%40%15%
540
21st to endNight
7%29%23%43%16%
540
July1st to 10thNight
6%17%23%44%18%
525
11th to 20thNight
6%419%50%21%
522
21st to endNight
5%6%23%53%13%
591
August1st to 10thNight
7%15%23%49%16%
537
11th to 20thNight
6%1418%51%20%
534
21st to endNight
11%210%22%39%16%
772
September1st to 10thNight
12%27%22%45%12%
720
11th to 20thNight
13%210%29%38%8%
720
21st to endNight
11%212%29%37%9%
720
October1st to 10thNight
13%220%32%30%3
720
11th to 20thNight
8%417%37%31%3
720
21st to endNight
10%421%36%27%2
792
November1st to 10thNight
12%5%25%34%22%1
740
11th to 20thNight
14%7%26%33%19%2
760
21st to endNight
14%7%29%33%17%1
760
December1st to 10thNight
14%8%26%31%20%1
760
11th to 20thNight
15%8%26%34%15%2
760
21st to endNight
15%9%27%35%14%
836
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