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 2019-06-24.

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
41%
18086
26%
54026
16%
18040
50%
18040
38%
29733

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
32%
1049
28%
2717
12%
1045
42%
1045
39%
1577
January16th to endNight
33%
1120
30%
2912
12%
1120
44%
1120
44%
1626
February1st to 15thNight
26%
915
24%
2563
9%
911
37%
911
33%
1524
February16th to endNight
24%
736
24%
2206
8%
736
36%
736
29%
1305
March1st to 15thNight
27%
648
26%
2328
13%
648
42%
648
26%
1311
March16th to endNight
27%
672
21%
2464
11%
672
40%
672
28%
1360
April1st to 15thNight
24%
629
23%
2301
12%
629
41%
629
29%
1205
April16th to endNight
28%
624
22%
1901
11%
624
42%
624
35%
1074
May1st to 15thNight
30%
629
24%
1890
13%
629
45%
629
31%
1130
May16th to endNight
40%
659
22%
1972
17%
657
51%
657
42%
1072
June1st to 15thNight
51%
630
23%
1890
18%
630
60%
630
47%
964
June16th to endNight
56%
609
22%
1827
19%
609
62%
609
50%
909
July1st to 15thNight
64%
555
20%
1665
21%
555
66%
555
42%
906
July16th to endNight
73%
612
25%
1738
30%
579
78%
579
58%
804
August1st to 15thNight
74%
575
30%
1717
35%
572
76%
572
49%
867
August16th to endNight
77%
621
28%
1993
31%
621
78%
621
46%
991
September1st to 15thNight
59%
585
24%
2145
26%
585
63%
585
30%
1171
September16th to endNight
61%
582
28%
2145
28%
582
65%
582
38%
1070
October1st to 15thNight
43%
666
29%
2226
21%
666
51%
666
36%
1197
October16th to endNight
46%
832
31%
2496
16%
832
56%
832
45%
1263
November1st to 15thNight
39%
918
29%
2558
14%
918
48%
918
42%
1396
November16th to endNight
34%
1050
28%
2730
13%
1050
43%
1050
42%
1563
December1st to 15thNight
31%
1050
27%
2730
12%
1050
40%
1050
38%
1624
December16th to endNight
28%
1120
22%
2912
9%
1120
37%
1120
33%
1824

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
21%413323345%46%
54792
Night
20%313312346%50%
54222
Cloud CoverDay
10%424324447%51%
54790
Night
8%413323347%57%
54222
TransparencyDay
32%5%10%24%21%5%
54490
Night
27%49%24%24%8%
54027
SeeingDay
12%6%25%29%20%5%
7999
Night
10%7%31%33%14%1
18088

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
24%6%1321223448%
1881
16th to endDay
21%41322223450%
2016
February1st to 15thDay
22%5%2431233444%
1971
16th to endDay
27%5%2431223343%
1840
March1st to 15thDay
27%5%13322235%41%
2290
16th to endDay
24%6%2431233443%
2464
April1st to 15thDay
23%412312226%46%
2307
16th to endDay
26%315%323335%41%
2661
May1st to 15thDay
25%5%2332334441%
2721
16th to endDay
22%31442345%7%39%
2846
June1st to 15thDay
21%31332345%6%44%
2730
16th to endDay
17%223235%5%8%48%
2640
July1st to 15thDay
21%2135%245%6%8%39%
2535
16th to endDay
19%123235%5%6%48%
2674
August1st to 15thDay
12%1135%345%5%7%48%
2486
16th to endDay
12%214325%5%5%8%47%
2556
September1st to 15thDay
19%41442335%6%43%
2145
16th to endDay
18%313313446%48%
2145
October1st to 15thDay
18%31431223452%
2051
16th to endDay
15%31231222458%
2080
November1st to 15thDay
19%413222225%52%
1957
16th to endDay
24%31221212454%
1890
December1st to 15thDay
27%5%13223236%41%
1890
16th to endDay
26%6%2421333342%
2016
January1st to 15thNight
21%413212235%50%
2717
16th to endNight
20%31321233456%
2912
February1st to 15thNight
24%5%1231233446%
2553
16th to endNight
23%5%23222335%45%
2206
March1st to 15thNight
25%5%13322325%43%
2328
16th to endNight
22%413212335%48%
2464
April1st to 15thNight
22%312212236%48%
2301
16th to endNight
24%41221233448%
1901
May1st to 15thNight
22%312322335%47%
1889
16th to endNight
20%11221235%8%48%
1971
June1st to 15thNight
17%212312338%52%
1890
16th to endNight
16%12213347%56%
1827
July1st to 15thNight
19%21332445%9%45%
1755
16th to endNight
17%12111348%55%
1846
August1st to 15thNight
11%21221345%8%56%
1727
16th to endNight
10%1232347%9%54%
1993
September1st to 15thNight
17%414313345%48%
2145
16th to endNight
15%312324347%50%
2145
October1st to 15thNight
18%31231334452%
2226
16th to endNight
14%21321223460%
2496
November1st to 15thNight
17%31332233454%
2558
16th to endNight
23%31221222353%
2730
December1st to 15thNight
25%414313245%45%
2730
16th to endNight
25%5%1332234443%
2912

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
11%6%1322433455%
1881
16th to endDay
9%5%24223335%56%
2016
February1st to 15thDay
10%6%25%323336%50%
1971
16th to endDay
15%6%3432333450%
1840
March1st to 15thDay
13%5%24423346%48%
2290
16th to endDay
14%7%35%423345%46%
2462
April1st to 15thDay
11%5%23423336%53%
2307
16th to endDay
13%426%324436%48%
2661
May1st to 15thDay
13%6%3432435%6%45%
2721
16th to endDay
10%425%5%345%6%8%45%
2846
June1st to 15thDay
8%4143245%6%8%50%
2730
16th to endDay
5%213325%5%6%8%53%
2640
July1st to 15thDay
7%3146%35%7%8%10%42%
2535
16th to endDay
4113335%6%6%9%55%
2674
August1st to 15thDay
32145%35%6%6%8%51%
2486
16th to endDay
4314435%6%6%9%49%
2556
September1st to 15thDay
12%41442446%7%46%
2145
16th to endDay
11%313323446%55%
2145
October1st to 15thDay
11%413412335%57%
2051
16th to endDay
8%31332223463%
2080
November1st to 15thDay
7%424323236%59%
1957
16th to endDay
11%412212235%62%
1890
December1st to 15thDay
13%5%24323347%50%
1890
16th to endDay
14%7%2431333448%
2016
January1st to 15thNight
8%413312346%58%
2717
16th to endNight
7%32321334462%
2912
February1st to 15thNight
11%6%23313345%54%
2553
16th to endNight
11%6%24323446%51%
2206
March1st to 15thNight
11%5%24323336%51%
2328
16th to endNight
11%5%23322347%52%
2464
April1st to 15thNight
10%413313347%55%
2301
16th to endNight
10%413323446%55%
1901
May1st to 15thNight
10%5%23433347%51%
1889
16th to endNight
7%21332346%9%55%
1971
June1st to 15thNight
4212323449%61%
1890
16th to endNight
312321445%9%62%
1827
July1st to 15thNight
42134245%7%11%51%
1755
16th to endNight
211221245%11%64%
1846
August1st to 15thNight
22123145%7%10%58%
1727
16th to endNight
2133245%8%10%56%
1993
September1st to 15thNight
10%424414346%52%
2145
16th to endNight
8%31232435%8%56%
2145
October1st to 15thNight
11%413323345%57%
2226
16th to endNight
7%212222335%65%
2496
November1st to 15thNight
6%423323335%61%
2558
16th to endNight
10%31331323462%
2730
December1st to 15thNight
11%414322246%56%
2730
16th to endNight
14%6%2332334451%
2912

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
32%38%23%26%5%
1882
16th to endDay
30%26%25%26%7%
2016
February1st to 15thDay
35%38%25%22%5%
1972
16th to endDay
38%35%22%22%7%
1840
March1st to 15thDay
38%47%22%18%9%
2290
16th to endDay
40%49%23%17%4
2464
April1st to 15thDay
32%411%24%19%7%
2307
16th to endDay
37%5%8%23%20%5%
2661
May1st to 15thDay
40%6%10%20%19%3
2721
16th to endDay
35%8%12%26%16%1
2850
June1st to 15thDay
29%7%14%27%18%2
2730
16th to endDay
26%7%14%25%21%5%
2640
July1st to 15thDay
31%9%16%27%14%1
2396
16th to endDay
22%7%16%28%23%2
2519
August1st to 15thDay
26%8%13%23%20%7%
2472
16th to endDay
27%8%13%30%15%4
2556
September1st to 15thDay
35%6%11%20%17%8%
2145
16th to endDay
29%49%24%24%7%
2145
October1st to 15thDay
30%49%23%22%9%
2051
16th to endDay
25%37%21%29%11%
2080
November1st to 15thDay
27%210%24%26%7%
1957
16th to endDay
26%16%24%30%9%
1890
December1st to 15thDay
34%39%24%21%5%
1890
16th to endDay
39%28%20%22%5%
2016
January1st to 15thNight
27%37%22%30%7%
2717
16th to endNight
24%37%23%30%10%
2912
February1st to 15thNight
33%38%23%23%7%
2563
16th to endNight
34%47%22%22%9%
2206
March1st to 15thNight
34%47%20%20%11%
2328
16th to endNight
32%5%11%25%19%5%
2464
April1st to 15thNight
30%411%23%19%11%
2301
16th to endNight
30%410%24%21%8%
1901
May1st to 15thNight
32%6%10%22%20%7%
1890
16th to endNight
23%7%14%32%18%4
1973
June1st to 15thNight
20%6%13%33%22%4
1890
16th to endNight
18%5%13%28%26%6%
1827
July1st to 15thNight
24%7%13%31%20%2
1665
16th to endNight
13%5%13%33%28%4
1738
August1st to 15thNight
17%7%13%24%27%8%
1717
16th to endNight
19%6%11%31%23%6%
1993
September1st to 15thNight
32%5%9%21%21%10%
2145
16th to endNight
26%47%25%26%9%
2145
October1st to 15thNight
29%411%21%21%12%
2226
16th to endNight
22%36%21%31%14%
2496
November1st to 15thNight
25%38%24%27%11%
2558
16th to endNight
27%25%22%30%10%
2730
December1st to 15thNight
29%38%24%24%8%
2730
16th to endNight
36%37%20%23%7%
2912

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
22%9%35%22%9%
180
16th to endDay
11%15%39%22%8%2
192
February1st to 15thDay
15%17%42%21%2
180
16th to endDay
27%14%40%14%3
159
March1st to 15thDay
18%21%38%16%5%
180
16th to endDay
13%15%37%21%10%1
192
April1st to 15thDay
15%16%31%30%5%
186
16th to endDay
17%12%37%22%7%1
553
May1st to 15thDay
13%11%35%27%9%1
618
16th to endDay
11%8%34%26%14%4
677
June1st to 15thDay
8%222%40%21%4
645
16th to endDay
6%220%38%25%6%
611
July1st to 15thDay
7%13%33%32%12%
550
16th to endDay
4430%47%12%
595
August1st to 15thDay
7%5%34%44%6%
549
16th to endDay
6%10%36%35%10%
468
September1st to 15thDay
11%15%27%35%20%
180
16th to endDay
22%16%33%21%13%
180
October1st to 15thDay
13%6%25%32%16%6%
180
16th to endDay
15%5%27%31%17%2
192
November1st to 15thDay
18%6%36%20%13%3
180
16th to endDay
19%10%35%21%11%2
180
December1st to 15thDay
11%10%45%22%9%
180
16th to endDay
21%16%38%19%4
192
January1st to 15thNight
12%12%35%30%7%
1050
16th to endNight
8%10%39%34%6%
1120
February1st to 15thNight
15%12%39%27%5%
915
16th to endNight
14%14%40%25%4
736
March1st to 15thNight
14%14%35%30%4
648
16th to endNight
14%10%41%26%6%
672
April1st to 15thNight
12%13%43%24%5%
629
16th to endNight
13%10%41%26%7%
624
May1st to 15thNight
10%7%42%27%10%1
630
16th to endNight
6%337%33%17%1
659
June1st to 15thNight
5%225%44%20%1
630
16th to endNight
3125%46%19%3
609
July1st to 15thNight
5%14%43%32%3
555
16th to endNight
26%44%42%3
612
August1st to 15thNight
37%47%38%4
575
16th to endNight
29%45%37%4
621
September1st to 15thNight
12%213%35%33%2
585
16th to endNight
10%117%40%24%6%
582
October1st to 15thNight
13%429%32%17%2
666
16th to endNight
10%7%31%35%14%
832
November1st to 15thNight
9%9%33%32%13%1
918
16th to endNight
11%10%36%29%11%
1050
December1st to 15thNight
15%10%34%31%8%
1050
16th to endNight
17%9%36%28%7%
1120
Page generated at 2019-06-24 19:41:31. Version ac04

Copyright 2019 A. Danko


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