Corkill Astronomical Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Corkill Astronomical Observatory clear sky chart from 2005-11-06 to 2024-01-22.

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
46%
23782
26%
74452
17%
23729
55%
23729
32%
43028

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
38%
946
31%
2458
13%
946
48%
946
36%
1478
January11th to 20thNight
33%
946
27%
2466
10%
946
45%
946
33%
1528
January21st to endNight
34%
800
32%
2400
14%
800
48%
800
29%
1419
February1st to 10thNight
32%
720
28%
2160
12%
720
45%
720
29%
1257
February11th to 20thNight
28%
704
23%
2098
10%
700
39%
700
28%
1244
February21st to endNight
19%
592
27%
1776
6%
592
37%
592
27%
1071
March1st to 10thNight
26%
632
25%
2072
10%
632
41%
632
24%
1283
March11th to 20thNight
30%
540
23%
1980
15%
540
42%
540
23%
1187
March21st to endNight
26%
594
26%
2178
13%
594
44%
594
27%
1201
April1st to 10thNight
26%
540
25%
1980
12%
540
44%
540
26%
1126
April11th to 20thNight
24%
533
24%
1835
11%
533
41%
533
24%
1107
April21st to endNight
24%
540
28%
1742
13%
540
44%
540
27%
1067
May1st to 10thNight
29%
540
25%
1620
15%
540
42%
540
29%
992
May11th to 20thNight
38%
531
21%
1594
16%
531
46%
531
29%
1009
May21st to endNight
40%
583
21%
1745
15%
582
52%
582
28%
1113
June1st to 10thNight
63%
540
23%
1620
22%
540
71%
540
47%
843
June11th to 20thNight
55%
540
23%
1620
19%
540
64%
540
45%
846
June21st to endNight
61%
540
24%
1620
25%
540
66%
540
38%
920
July1st to 10thNight
66%
525
16%
1575
17%
525
68%
525
30%
982
July11th to 20thNight
77%
522
28%
1566
31%
522
82%
522
48%
797
July21st to endNight
79%
591
25%
1673
28%
558
84%
558
49%
844
August1st to 10thNight
82%
537
28%
1730
32%
534
85%
534
55%
786
August11th to 20thNight
78%
534
25%
1778
29%
534
80%
534
39%
945
August21st to endNight
73%
594
20%
2009
21%
594
75%
594
33%
1152
September1st to 10thNight
69%
540
20%
1980
24%
540
71%
540
30%
1133
September11th to 20thNight
69%
540
21%
1980
24%
540
70%
540
26%
1194
September21st to endNight
68%
540
25%
1980
26%
540
70%
540
31%
1095
October1st to 10thNight
70%
540
32%
1980
33%
540
73%
540
38%
992
October11th to 20thNight
55%
567
32%
2007
26%
567
63%
567
32%
1101
October21st to endNight
46%
792
34%
2376
19%
792
55%
792
38%
1312
November1st to 10thNight
51%
763
29%
2243
17%
763
57%
763
35%
1316
November11th to 20thNight
48%
950
27%
2470
13%
950
54%
950
39%
1467
November21st to endNight
38%
950
28%
2470
12%
950
46%
950
31%
1572
December1st to 10thNight
44%
950
32%
2470
17%
950
51%
950
37%
1498
December11th to 20thNight
33%
949
27%
2899
12%
948
42%
948
25%
1849
December21st to endNight
37%
1037
18%
4302
12%
1026
46%
1026
24%
2302

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
12%6%25%5%3445%7%48%
74936
Night
13%6%24423347%53%
75026
TransparencyDay
36%5%9%20%19%10%
74661
Night
33%5%11%20%19%12%
74821
SeeingDay
15%8%24%30%19%4
13700
Night
16%7%26%35%14%1
23796

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
12%6%24323346%54%
1707
11th to 20thDay
16%7%24323335%51%
1730
21st to endDay
13%5%24323336%55%
1990
February1st to 10thDay
14%7%24433345%50%
1800
11th to 20thDay
17%7%25%32345%5%46%
1749
21st to endDay
16%5%24323345%52%
1480
March1st to 10thDay
19%7%2442345%6%43%
1886
11th to 20thDay
16%6%35%433346%47%
1980
21st to endDay
16%6%25%423346%49%
2178
April1st to 10thDay
14%7%35%5%24447%46%
1980
11th to 20thDay
18%5%25%424446%45%
2070
21st to endDay
15%6%35%5%33445%48%
2216
May1st to 10thDay
17%6%346%35%45%6%41%
2340
11th to 20thDay
15%8%36%5%35%447%40%
2302
21st to endDay
18%6%35%5%36%7%5%7%35%
2531
June1st to 10thDay
6%5%25%5%36%46%9%49%
2340
11th to 20thDay
7%6%25%5%35%46%9%47%
2340
21st to endDay
9%435%7%46%6%6%8%40%
2340
July1st to 10thDay
13%6%36%6%46%6%7%8%35%
2340
11th to 20thDay
6%4235%35%6%5%9%54%
2340
21st to endDay
6%3245%35%5%7%11%50%
2546
August1st to 10thDay
22135%35%45%9%62%
2194
11th to 20thDay
7%425%6%45%5%5%9%49%
2123
21st to endDay
7%5%25%5%36%6%7%10%44%
2345
September1st to 10thDay
10%7%37%7%46%45%7%41%
1980
11th to 20thDay
11%6%36%6%36%46%8%41%
1980
21st to endDay
10%5%26%5%35%5%5%9%46%
1980
October1st to 10thDay
7%426%445%5%48%51%
1980
11th to 20thDay
14%5%24424446%51%
1932
21st to endDay
13%414423335%57%
1980
November1st to 10thDay
15%7%25%5%33347%46%
1831
11th to 20thDay
11%6%25%4345%45%50%
1710
21st to endDay
16%7%35%424335%48%
1710
December1st to 10thDay
14%6%35%32335%7%49%
1710
11th to 20thDay
15%8%34434346%46%
2161
21st to endDay
14%6%2321233458%
3135
January1st to 10thNight
15%424323335%56%
2458
11th to 20thNight
15%6%24322335%54%
2466
21st to endNight
15%7%24323346%51%
2400
February1st to 10thNight
16%5%23422346%53%
2160
11th to 20thNight
16%6%2432335%5%51%
2098
21st to endNight
16%6%25%32335%6%49%
1776
March1st to 10thNight
16%7%35%423446%46%
2072
11th to 20thNight
16%6%26%324445%47%
1980
21st to endNight
14%6%23323347%52%
2178
April1st to 10thNight
13%6%3443435%6%51%
1980
11th to 20thNight
17%6%24433345%49%
1835
21st to endNight
17%6%25%41334450%
1742
May1st to 10thNight
13%7%34423448%48%
1620
11th to 20thNight
14%6%35%6%23446%47%
1593
21st to endNight
17%6%24325%45%8%44%
1745
June1st to 10thNight
5%3233245%5%10%59%
1620
11th to 20thNight
5%423323449%61%
1620
21st to endNight
6%5%2442446%9%53%
1620
July1st to 10thNight
10%5%345%35%5%7%11%44%
1620
11th to 20thNight
422232445%10%62%
1620
21st to endNight
5%31332346%9%60%
1772
August1st to 10thNight
2212313349%69%
1740
11th to 20thNight
5%42343446%12%54%
1778
21st to endNight
7%5%25%5%245%7%9%50%
2009
September1st to 10thNight
10%5%25%4445%5%7%50%
1980
11th to 20thNight
11%7%345%345%5%9%45%
1980
21st to endNight
8%6%244245%5%7%52%
1980
October1st to 10thNight
7%6%1342335%6%60%
1980
11th to 20thNight
14%41432345%6%54%
2007
21st to endNight
16%42321222461%
2376
November1st to 10thNight
14%7%23323336%54%
2243
11th to 20thNight
10%7%2432335%7%56%
2470
21st to endNight
18%5%23423346%48%
2470
December1st to 10thNight
14%6%23313346%54%
2470
11th to 20thNight
16%8%35%423335%48%
3036
21st to endNight
18%6%23222225%56%
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
32%3420%23%18%
1708
11th to 20thDay
38%25%15%22%17%
1730
21st to endDay
32%47%13%26%17%
1990
February1st to 10thDay
38%46%12%23%17%
1800
11th to 20thDay
41%45%18%18%15%
1759
21st to endDay
35%47%17%20%18%
1480
March1st to 10thDay
43%48%14%18%13%
1886
11th to 20thDay
39%47%15%18%17%
1980
21st to endDay
38%38%18%19%13%
2178
April1st to 10thDay
40%5%8%17%19%12%
1980
11th to 20thDay
41%46%17%19%13%
2070
21st to endDay
40%5%6%18%19%12%
2216
May1st to 10thDay
43%6%7%16%20%7%
2340
11th to 20thDay
45%5%8%19%18%4
2306
21st to endDay
46%8%10%20%14%2
2531
June1st to 10thDay
31%6%12%27%20%3
2340
11th to 20thDay
33%7%12%25%17%6%
2340
21st to endDay
41%7%11%22%15%4
2340
July1st to 10thDay
43%9%13%24%10%1
2276
11th to 20thDay
26%8%15%29%20%2
2271
21st to endDay
23%9%21%33%13%
2405
August1st to 10thDay
19%7%14%39%19%1
2180
11th to 20thDay
32%7%16%29%12%3
2123
21st to endDay
35%9%15%25%13%3
2345
September1st to 10thDay
43%6%9%18%16%6%
1980
11th to 20thDay
39%8%11%20%16%5%
1980
21st to endDay
34%6%11%20%18%10%
1980
October1st to 10thDay
31%5%10%21%25%8%
1980
11th to 20thDay
35%5%8%14%22%16%
1932
21st to endDay
32%35%15%24%20%
1980
November1st to 10thDay
39%38%20%19%11%
1831
11th to 20thDay
36%47%16%20%16%
1710
21st to endDay
41%45%15%21%15%
1710
December1st to 10thDay
37%38%18%24%10%
1710
11th to 20thDay
40%47%11%22%17%
2159
21st to endDay
32%25%15%29%17%
3135
January1st to 10thNight
32%35%15%24%21%
2458
11th to 20thNight
36%35%17%22%18%
2466
21st to endNight
37%35%14%22%19%
2400
February1st to 10thNight
35%37%12%22%20%
2160
11th to 20thNight
37%36%17%20%17%
2098
21st to endNight
38%47%12%21%18%
1776
March1st to 10thNight
41%48%16%19%12%
2072
11th to 20thNight
40%5%7%13%16%18%
1980
21st to endNight
34%411%18%17%16%
2178
April1st to 10thNight
36%410%18%16%16%
1980
11th to 20thNight
39%5%8%15%17%17%
1835
21st to endNight
39%48%18%19%12%
1742
May1st to 10thNight
37%5%10%22%16%11%
1620
11th to 20thNight
39%5%10%24%16%5%
1594
21st to endNight
38%7%14%26%13%2
1746
June1st to 10thNight
21%6%18%32%19%3
1620
11th to 20thNight
22%6%16%29%21%5%
1620
21st to endNight
28%7%18%28%16%4
1620
July1st to 10thNight
32%11%19%28%9%1
1575
11th to 20thNight
19%7%18%32%22%2
1566
21st to endNight
18%7%26%36%11%1
1673
August1st to 10thNight
15%5%20%41%18%1
1730
11th to 20thNight
24%8%22%28%15%3
1778
21st to endNight
30%9%21%24%14%3
2009
September1st to 10thNight
33%6%13%22%18%7%
1980
11th to 20thNight
36%9%16%20%15%5%
1980
21st to endNight
31%7%12%20%19%11%
1980
October1st to 10thNight
26%413%25%21%11%
1980
11th to 20thNight
32%410%16%21%16%
2007
21st to endNight
30%25%17%24%22%
2376
November1st to 10thNight
33%47%20%23%13%
2243
11th to 20thNight
30%48%21%20%17%
2470
21st to endNight
37%47%15%21%15%
2470
December1st to 10thNight
32%49%19%22%13%
2470
11th to 20thNight
41%35%13%19%20%
3037
21st to endNight
34%3414%28%17%
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
24%14%37%19%6%1
270
11th to 20thDay
28%11%32%22%6%1
270
21st to endDay
21%16%38%19%5%
267
February1st to 10thDay
25%13%34%21%6%
240
11th to 20thDay
27%20%34%15%31
240
21st to endDay
26%22%36%15%2
198
March1st to 10thDay
23%18%40%17%2
240
11th to 20thDay
20%23%37%15%5%
240
21st to endDay
21%19%41%17%21
264
April1st to 10thDay
25%17%42%14%2
240
11th to 20thDay
20%20%38%20%3
348
21st to endDay
21%15%41%20%4
476
May1st to 10thDay
17%13%40%24%5%
603
11th to 20thDay
23%8%30%30%8%1
625
21st to endDay
21%6%32%30%11%
679
June1st to 10thDay
8%419%44%22%3
630
11th to 20thDay
10%221%48%17%2
630
21st to endDay
10%216%39%27%7%
630
July1st to 10thDay
12%312%36%30%8%
621
11th to 20thDay
5%7%44%37%7%
618
21st to endDay
6%16%37%42%9%
684
August1st to 10thDay
36%41%38%11%
492
11th to 20thDay
9%6%35%39%11%
437
21st to endDay
7%16%31%39%15%
464
September1st to 10thDay
8%9%29%40%14%
270
11th to 20thDay
7%15%33%43%11%
270
21st to endDay
11%19%33%36%10%
270
October1st to 10thDay
6%220%37%29%6%
270
11th to 20thDay
13%6%22%38%18%3
270
21st to endDay
20%14%26%26%12%2
297
November1st to 10thDay
19%7%33%28%11%3
270
11th to 20thDay
21%13%25%27%10%4
270
21st to endDay
24%20%32%13%8%2
270
December1st to 10thDay
17%11%31%29%11%2
270
11th to 20thDay
21%17%35%19%7%
270
21st to endDay
20%14%36%23%7%1
297
January1st to 10thNight
18%9%31%32%9%
950
11th to 20thNight
21%11%31%31%6%
946
21st to endNight
22%10%30%30%7%
800
February1st to 10thNight
22%11%31%29%7%
720
11th to 20thNight
23%13%34%26%4
704
21st to endNight
24%11%43%20%1
592
March1st to 10thNight
23%12%36%26%3
632
11th to 20thNight
20%11%35%29%5%
540
21st to endNight
17%11%43%25%4
594
April1st to 10thNight
15%13%44%26%3
540
11th to 20thNight
20%12%41%25%2
533
21st to endNight
19%11%44%21%5%
540
May1st to 10thNight
15%13%41%26%5%
540
11th to 20thNight
16%6%36%34%8%1
531
21st to endNight
17%7%32%35%9%
584
June1st to 10thNight
5%126%48%19%1
540
11th to 20thNight
7%232%47%11%
540
21st to endNight
7%322%45%21%2
540
July1st to 10thNight
10%210%50%25%3
525
11th to 20thNight
5%11%53%28%2
522
21st to endNight
5%18%54%28%3
591
August1st to 10thNight
219%53%33%3
537
11th to 20thNight
6%17%50%35%2
534
21st to endNight
7%27%41%38%5%
594
September1st to 10thNight
10%19%41%35%4
540
11th to 20thNight
13%18%39%37%2
540
21st to endNight
10%213%39%33%4
540
October1st to 10thNight
9%115%44%29%2
540
11th to 20thNight
15%5%21%40%17%2
567
21st to endNight
17%8%26%27%21%2
792
November1st to 10thNight
17%6%22%36%18%1
763
11th to 20thNight
14%8%25%37%14%1
950
21st to endNight
23%9%26%30%11%1
950
December1st to 10thNight
18%8%27%37%10%1
950
11th to 20thNight
22%10%30%31%7%
950
21st to endNight
18%12%29%34%7%
1045
Page generated at 2024-01-19 08:28:34. Version ac07

Copyright 2024 Attilla Danko


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