Owl Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Owl Creek Observatory clear sky chart from 2005-11-05 to 2017-09-23.

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%
15719
29%
46987
18%
15673
57%
15673
39%
25623

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 15thNight
35%
899
32%
2327
13%
895
47%
895
41%
1323
January16th to endNight
38%
960
34%
2496
15%
960
49%
960
43%
1413
February1st to 15thNight
31%
782
25%
2190
10%
778
42%
778
35%
1277
February16th to endNight
28%
632
30%
1894
10%
632
44%
632
33%
1063
March1st to 15thNight
31%
555
27%
1995
13%
555
46%
555
26%
1128
March16th to endNight
30%
576
22%
2112
13%
576
43%
576
27%
1188
April1st to 15thNight
28%
539
23%
1971
12%
539
45%
539
30%
1021
April16th to endNight
33%
540
27%
1646
14%
540
51%
540
34%
938
May1st to 15thNight
34%
539
25%
1620
15%
539
50%
539
32%
966
May16th to endNight
49%
563
28%
1684
21%
561
61%
561
41%
917
June1st to 15thNight
61%
540
24%
1620
18%
540
69%
540
46%
833
June16th to endNight
64%
540
27%
1620
23%
540
70%
540
50%
809
July1st to 15thNight
71%
510
21%
1530
22%
510
74%
510
43%
824
July16th to endNight
87%
564
31%
1594
37%
531
88%
531
58%
734
August1st to 15thNight
83%
539
32%
1610
37%
536
84%
536
50%
806
August16th to endNight
83%
573
31%
1839
35%
573
84%
573
45%
927
September1st to 15thNight
64%
540
26%
1980
27%
540
68%
540
32%
1057
September16th to endNight
65%
516
35%
1903
32%
516
74%
516
40%
914
October1st to 15thNight
48%
564
32%
1884
24%
564
57%
564
38%
996
October16th to endNight
48%
704
36%
2112
18%
704
61%
704
47%
1049
November1st to 15thNight
46%
784
32%
2184
16%
784
56%
784
45%
1159
November16th to endNight
37%
900
33%
2340
14%
900
48%
900
40%
1371
December1st to 15thNight
36%
900
31%
2340
13%
900
48%
900
39%
1380
December16th to endNight
33%
960
29%
2496
12%
960
45%
960
35%
1530

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
22%313323345%45%
47917
Night
21%312212335%50%
47183
Cloud CoverDay
9%424324447%52%
47915
Night
8%323323346%57%
47183
TransparencyDay
31%5%10%24%21%6%
47615
Night
26%49%24%25%9%
46988
SeeingDay
9%6%23%30%23%6%
5715
Night
10%7%31%33%15%1
15721

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 15thDay
25%5%1321122349%
1611
16th to endDay
23%41322223448%
1728
February1st to 15thDay
24%42331232446%
1682
16th to endDay
26%31331223346%
1580
March1st to 15thDay
30%5%13322235%39%
1963
16th to endDay
27%6%2421123443%
2112
April1st to 15thDay
25%413312225%45%
1977
16th to endDay
29%315%323335%40%
2312
May1st to 15thDay
27%6%2321223441%
2331
16th to endDay
25%314423446%36%
2430
June1st to 15thDay
23%31332335%6%43%
2340
16th to endDay
19%123235%5%8%48%
2340
July1st to 15thDay
22%2134245%6%8%38%
2340
16th to endDay
21%123235%46%48%
2466
August1st to 15thDay
12%1135%346%5%7%48%
2340
16th to endDay
12%2143345%5%8%46%
2358
September1st to 15thDay
18%31432335%6%46%
1980
16th to endDay
15%313324446%51%
1893
October1st to 15thDay
19%314312235%52%
1735
16th to endDay
15%31221222460%
1760
November1st to 15thDay
19%31322222454%
1671
16th to endDay
27%422112452%
1620
December1st to 15thDay
30%5%13323235%38%
1620
16th to endDay
28%5%1321323344%
1728
January1st to 15thNight
23%312212225%51%
2327
16th to endNight
22%31321223353%
2496
February1st to 15thNight
25%41231223447%
2180
16th to endNight
23%323212345%48%
1894
March1st to 15thNight
27%5%13322325%42%
1995
16th to endNight
25%41321223447%
2112
April1st to 15thNight
25%312212235%48%
1971
16th to endNight
26%41221233446%
1646
May1st to 15thNight
24%312322335%47%
1619
16th to endNight
23%21221235%8%47%
1683
June1st to 15thNight
20%212312337%51%
1620
16th to endNight
18%112213337%55%
1620
July1st to 15thNight
20%21332335%9%44%
1620
16th to endNight
18%12111337%56%
1702
August1st to 15thNight
11%21221345%8%56%
1620
16th to endNight
10%11232347%9%53%
1839
September1st to 15thNight
17%313313345%50%
1980
16th to endNight
14%212324347%52%
1903
October1st to 15thNight
20%31221233453%
1884
16th to endNight
15%21221223461%
2112
November1st to 15thNight
18%31222233455%
2184
16th to endNight
27%31221222349%
2340
December1st to 15thNight
28%313212245%43%
2340
16th to endNight
26%5%1322234444%
2496

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 15thDay
10%5%2422323458%
1611
16th to endDay
9%5%24223336%56%
1728
February1st to 15thDay
10%6%24323336%53%
1682
16th to endDay
13%5%2332233454%
1580
March1st to 15thDay
14%6%24423346%46%
1963
16th to endDay
14%7%34323235%47%
2110
April1st to 15thDay
10%5%23423436%53%
1977
16th to endDay
13%426%324346%48%
2312
May1st to 15thDay
13%6%34324346%46%
2331
16th to endDay
11%425%5%3446%8%43%
2430
June1st to 15thDay
8%4143245%6%7%51%
2340
16th to endDay
5%213325%5%6%8%54%
2340
July1st to 15thDay
7%3135%35%6%8%10%42%
2340
16th to endDay
4112335%6%6%9%55%
2466
August1st to 15thDay
32145%35%6%6%8%51%
2340
16th to endDay
5%314435%6%6%9%48%
2358
September1st to 15thDay
11%31442445%8%48%
1980
16th to endDay
7%313324446%58%
1893
October1st to 15thDay
10%413312235%58%
1735
16th to endDay
7%31321223465%
1760
November1st to 15thDay
5%313323236%63%
1671
16th to endDay
11%412212235%62%
1620
December1st to 15thDay
13%5%24323347%49%
1620
16th to endDay
14%6%23313335%51%
1728
January1st to 15thNight
8%423312336%61%
2327
16th to endNight
7%32321344461%
2496
February1st to 15thNight
11%5%23213345%55%
2180
16th to endNight
9%423323446%55%
1894
March1st to 15thNight
12%5%23423336%51%
1995
16th to endNight
12%5%23323346%51%
2112
April1st to 15thNight
10%413313346%56%
1971
16th to endNight
11%413313446%54%
1646
May1st to 15thNight
10%5%23433346%53%
1619
16th to endNight
8%21332336%9%55%
1683
June1st to 15thNight
4312323349%61%
1620
16th to endNight
3123214448%62%
1620
July1st to 15thNight
421342447%11%51%
1620
16th to endNight
211221245%10%65%
1702
August1st to 15thNight
22122145%7%10%58%
1620
16th to endNight
21134245%8%10%55%
1839
September1st to 15thNight
10%414313346%54%
1980
16th to endNight
6%21232435%8%58%
1903
October1st to 15thNight
11%31231333459%
1884
16th to endNight
7%21221223467%
2112
November1st to 15thNight
5%322223336%64%
2184
16th to endNight
11%41332323361%
2340
December1st to 15thNight
12%313212246%56%
2340
16th to endNight
13%5%2332334453%
2496

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 15thDay
31%37%23%28%6%
1612
16th to endDay
31%26%25%27%7%
1728
February1st to 15thDay
33%37%26%23%5%
1683
16th to endDay
33%46%23%24%7%
1580
March1st to 15thDay
38%47%22%18%8%
1963
16th to endDay
41%48%22%19%4
2112
April1st to 15thDay
32%411%23%19%7%
1977
16th to endDay
37%5%8%22%20%6%
2312
May1st to 15thDay
39%5%10%19%21%4
2331
16th to endDay
37%8%12%25%15%1
2434
June1st to 15thDay
30%7%13%25%19%2
2340
16th to endDay
25%7%13%25%21%5%
2340
July1st to 15thDay
31%9%15%27%14%1
2201
16th to endDay
21%7%15%29%23%2
2311
August1st to 15thDay
25%8%14%24%19%8%
2326
16th to endDay
28%8%12%29%15%4
2358
September1st to 15thDay
32%6%11%21%18%9%
1980
16th to endDay
25%5%9%25%25%8%
1893
October1st to 15thDay
29%39%24%23%9%
1735
16th to endDay
23%37%22%30%11%
1760
November1st to 15thDay
24%210%25%28%8%
1671
16th to endDay
27%25%22%30%11%
1620
December1st to 15thDay
36%39%25%22%3
1620
16th to endDay
36%28%21%24%5%
1728
January1st to 15thNight
25%37%22%32%8%
2327
16th to endNight
26%37%21%30%9%
2496
February1st to 15thNight
32%37%24%24%8%
2190
16th to endNight
29%48%24%23%9%
1894
March1st to 15thNight
34%47%21%20%10%
1995
16th to endNight
33%5%11%23%20%5%
2112
April1st to 15thNight
29%412%22%19%12%
1971
16th to endNight
30%5%10%23%21%9%
1646
May1st to 15thNight
33%5%9%20%22%9%
1620
16th to endNight
24%7%15%31%17%4
1685
June1st to 15thNight
21%5%13%32%22%4
1620
16th to endNight
19%5%13%28%26%7%
1620
July1st to 15thNight
23%6%12%31%22%2
1530
16th to endNight
13%5%13%33%28%4
1594
August1st to 15thNight
17%7%14%25%26%8%
1610
16th to endNight
20%6%11%30%23%7%
1839
September1st to 15thNight
30%5%8%21%21%11%
1980
16th to endNight
23%47%25%27%10%
1903
October1st to 15thNight
28%311%21%22%13%
1884
16th to endNight
21%36%21%32%14%
2112
November1st to 15thNight
23%37%24%28%12%
2184
16th to endNight
29%26%20%29%11%
2340
December1st to 15thNight
29%38%25%24%7%
2340
16th to endNight
34%37%20%25%8%
2496

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 15thDay
20%14%34%21%8%1
90
16th to endDay
9%17%40%23%7%1
96
February1st to 15thDay
11%16%43%26%2
90
16th to endDay
11%16%48%19%4
81
March1st to 15thDay
18%17%42%16%4
90
16th to endDay
10%17%36%22%10%2
96
April1st to 15thDay
11%12%31%38%6%
96
16th to endDay
18%12%38%22%5%1
422
May1st to 15thDay
13%12%36%26%9%1
468
16th to endDay
13%8%33%25%14%3
517
June1st to 15thDay
7%322%38%22%5%
495
16th to endDay
7%218%36%26%8%
495
July1st to 15thDay
6%16%37%32%7%
475
16th to endDay
4429%49%12%
515
August1st to 15thDay
6%15%34%46%6%
493
16th to endDay
7%11%37%33%9%
398
September1st to 15thDay
41431%38%20%
135
16th to endDay
5%15%46%22%18%
111
October1st to 15thDay
4424%37%18%10%
90
16th to endDay
13%325%33%19%5%
96
November1st to 15thDay
13%327%27%24%3
90
16th to endDay
25%12%37%16%5%2
90
December1st to 15thDay
12%6%47%21%11%1
90
16th to endDay
15%14%46%19%3
96
January1st to 15thNight
11%13%36%31%7%
900
16th to endNight
9%9%39%35%6%
960
February1st to 15thNight
15%11%38%28%5%
782
16th to endNight
11%15%41%26%4
632
March1st to 15thNight
15%14%35%31%3
555
16th to endNight
15%10%40%26%6%
576
April1st to 15thNight
12%13%43%24%5%
539
16th to endNight
13%10%41%26%7%
540
May1st to 15thNight
10%8%42%26%10%1
540
16th to endNight
7%336%33%17%2
563
June1st to 15thNight
5%225%42%21%1
540
16th to endNight
3224%45%21%3
540
July1st to 15thNight
5%15%46%30%2
510
16th to endNight
2445%43%3
564
August1st to 15thNight
26%46%39%4
539
16th to endNight
29%45%37%4
573
September1st to 15thNight
12%213%36%33%2
540
16th to endNight
8%118%40%24%6%
516
October1st to 15thNight
12%430%30%19%2
564
16th to endNight
10%8%31%33%15%
704
November1st to 15thNight
7%9%33%33%14%1
784
16th to endNight
13%10%37%28%9%
900
December1st to 15thNight
15%10%34%30%8%
900
16th to endNight
16%9%37%28%7%
960
Page generated at 2017-09-24 08:15:49. Version ac04

Copyright 2017 A. Danko


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