Barred Owl Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Barred Owl 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
30%
16881
14%
54008
8%
16851
37%
16851
17%
38305

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
16%
840
8%
2926
3%
836
22%
836
8%
2352
January16th to endNight
19%
896
11%
3073
6%
896
25%
896
11%
2284
February1st to 15thNight
17%
822
11%
2677
4%
821
26%
821
10%
2046
February16th to endNight
23%
735
13%
2277
6%
735
32%
735
14%
1679
March1st to 15thNight
21%
840
13%
2443
7%
840
28%
840
14%
1848
March16th to endNight
31%
896
21%
2379
9%
896
39%
896
23%
1608
April1st to 15thNight
22%
838
16%
2096
5%
838
27%
838
19%
1544
April16th to endNight
31%
744
17%
1990
7%
744
37%
744
21%
1412
May1st to 15thNight
34%
420
19%
1680
17%
420
44%
420
17%
1088
May16th to endNight
34%
439
14%
1753
10%
438
48%
438
21%
1084
June1st to 15thNight
38%
420
11%
1680
11%
420
47%
420
16%
1112
June16th to endNight
41%
406
9%
1625
12%
406
46%
406
19%
1018
July1st to 15thNight
53%
370
16%
1480
22%
370
60%
370
29%
792
July16th to endNight
55%
408
14%
1546
18%
386
59%
386
26%
879
August1st to 15thNight
52%
478
15%
1619
13%
476
57%
476
25%
1015
August16th to endNight
53%
764
20%
2006
11%
764
57%
764
36%
1255
September1st to 15thNight
47%
780
18%
1950
10%
780
50%
780
30%
1327
September16th to endNight
48%
777
23%
2122
15%
777
53%
777
31%
1353
October1st to 15thNight
33%
780
17%
2340
11%
780
42%
780
19%
1631
October16th to endNight
24%
832
12%
2593
6%
832
33%
832
13%
1954
November1st to 15thNight
26%
820
17%
2737
12%
820
35%
820
15%
1938
November16th to endNight
20%
840
10%
2940
6%
840
26%
840
10%
2263
December1st to 15thNight
19%
840
8%
2940
4%
840
24%
840
8%
2341
December16th to endNight
16%
896
10%
3136
4%
896
23%
896
9%
2482

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
17%8%36%5%35%45%6%33%
54821
Night
17%9%36%5%34446%32%
54177
Cloud CoverDay
19%8%36%5%34446%33%
54830
Night
19%9%36%5%34445%33%
54183
TransparencyDay
50%6%11%19%10%1
54508
Night
51%5%11%19%10%
54008
SeeingDay
22%13%29%21%10%3
7623
Night
22%11%28%26%10%
16883

By Month

Percentage Cloud Cover NE (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
19%13%49%8%35%34421%
1672
16th to endDay
13%15%5%9%7%45%446%23%
1852
February1st to 15thDay
13%14%5%10%7%4445%424%
1845
16th to endDay
17%12%48%6%25%45%5%26%
1768
March1st to 15thDay
18%12%46%8%35%44427%
2166
16th to endDay
15%7%35%434445%40%
2548
April1st to 15thDay
23%9%36%423345%32%
2512
16th to endDay
22%8%25%5%33435%36%
2588
May1st to 15thDay
19%7%36%6%35%345%34%
2931
16th to endDay
16%5%25%6%45%45%6%36%
3066
June1st to 15thDay
20%6%35%5%35%447%32%
2940
16th to endDay
16%6%35%5%35%6%6%7%34%
2842
July1st to 15thDay
11%4245%35%5%6%8%41%
2730
16th to endDay
11%5%25%5%35%5%7%9%38%
2878
August1st to 15thDay
9%6%26%6%46%6%6%8%37%
2581
16th to endDay
10%5%25%435%5%6%8%41%
2535
September1st to 15thDay
15%5%25%5%24447%41%
2340
16th to endDay
13%5%2442445%7%44%
2165
October1st to 15thDay
20%7%36%44445%6%32%
1950
16th to endDay
24%7%37%6%35%436%27%
1982
November1st to 15thDay
17%8%35%5%45%5%5%6%31%
1778
16th to endDay
22%11%47%7%35%445%23%
1680
December1st to 15thDay
19%15%48%8%45%5%46%17%
1680
16th to endDay
22%14%5%8%7%25%335%22%
1792
January1st to 15thNight
18%14%5%10%7%35%435%19%
2926
16th to endNight
13%15%6%8%6%34345%26%
3073
February1st to 15thNight
13%13%5%11%8%35%445%24%
2675
16th to endNight
16%10%48%7%3435%5%28%
2277
March1st to 15thNight
17%12%5%8%6%34335%28%
2430
16th to endNight
15%6%35%5%2434442%
2379
April1st to 15thNight
21%8%36%5%24345%34%
2096
16th to endNight
20%8%25%5%33346%36%
1990
May1st to 15thNight
20%7%25%42345%6%36%
1680
16th to endNight
15%6%25%5%3345%7%39%
1751
June1st to 15thNight
17%6%26%6%345%6%7%35%
1680
16th to endNight
15%6%245%25%5%6%7%38%
1625
July1st to 15thNight
9%3144345%5%9%48%
1560
16th to endNight
9%5%235%35%46%9%44%
1642
August1st to 15thNight
8%5%36%5%345%6%9%41%
1629
16th to endNight
9%325%425%45%7%49%
2006
September1st to 15thNight
14%425%5%3445%6%43%
1950
16th to endNight
16%414323336%48%
2122
October1st to 15thNight
19%7%35%5%25%45%6%35%
2340
16th to endNight
23%8%36%5%34446%26%
2593
November1st to 15thNight
21%9%36%5%33445%32%
2737
16th to endNight
23%11%48%5%34446%23%
2940
December1st to 15thNight
20%14%48%6%35%5%46%19%
2940
16th to endNight
22%14%5%8%6%34335%20%
3136

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
19%13%5%9%8%3444422%
1672
16th to endDay
14%14%5%8%6%45%5%45%24%
1852
February1st to 15thDay
14%13%410%7%45%44424%
1845
16th to endDay
18%12%37%6%25%5%46%26%
1768
March1st to 15thDay
24%10%45%6%3443427%
2176
16th to endDay
21%7%34424345%39%
2547
April1st to 15thDay
22%8%36%5%23345%34%
2512
16th to endDay
21%6%25%424435%38%
2588
May1st to 15thDay
24%6%35%5%34345%34%
2931
16th to endDay
22%5%25%5%34446%36%
3066
June1st to 15thDay
25%5%345%35%5%46%30%
2940
16th to endDay
20%6%25%5%35%5%6%6%32%
2842
July1st to 15thDay
11%5%245%25%5%6%7%42%
2730
16th to endDay
11%5%25%435%5%6%9%38%
2878
August1st to 15thDay
21%415%5%3445%6%35%
2581
16th to endDay
19%41442445%7%40%
2535
September1st to 15thDay
15%5%25%5%2445%7%41%
2340
16th to endDay
13%5%2443445%7%44%
2165
October1st to 15thDay
20%6%26%5%345%5%6%32%
1950
16th to endDay
23%8%37%5%345%45%27%
1982
November1st to 15thDay
20%8%35%5%345%5%6%30%
1778
16th to endDay
24%11%37%5%35%445%23%
1680
December1st to 15thDay
19%13%49%7%446%45%18%
1680
16th to endDay
22%14%6%7%6%24335%23%
1792
January1st to 15thNight
18%13%6%10%7%345%4420%
2926
16th to endNight
13%16%6%7%6%34346%26%
3073
February1st to 15thNight
14%13%5%11%6%44445%25%
2668
16th to endNight
16%10%48%7%3435%5%30%
2277
March1st to 15thNight
25%11%46%6%3333428%
2443
16th to endNight
22%5%3442333441%
2379
April1st to 15thNight
22%8%35%5%24335%35%
2096
16th to endNight
20%7%25%423346%38%
1990
May1st to 15thNight
23%6%24423446%36%
1680
16th to endNight
17%5%35%42345%7%40%
1751
June1st to 15thNight
20%5%26%5%3445%6%33%
1680
16th to endNight
17%5%25%5%345%5%7%37%
1625
July1st to 15thNight
9%3134345%5%8%48%
1560
16th to endNight
9%4245%26%46%8%45%
1642
August1st to 15thNight
13%436%324448%43%
1629
16th to endNight
15%314334345%49%
2006
September1st to 15thNight
13%5%25%43446%6%43%
1950
16th to endNight
15%5%24423345%49%
2122
October1st to 15thNight
18%8%35%434445%36%
2340
16th to endNight
23%9%36%6%34446%27%
2593
November1st to 15thNight
25%8%35%5%2434432%
2737
16th to endNight
26%11%47%5%34345%24%
2940
December1st to 15thNight
21%14%47%5%345%5%5%21%
2940
16th to endNight
22%14%47%7%34335%22%
3136

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
64%5%8%13%6%1
1673
16th to endDay
61%413%12%7%
1852
February1st to 15thDay
61%5%10%17%4
1847
16th to endDay
57%5%10%15%9%1
1768
March1st to 15thDay
59%5%10%16%7%
2176
16th to endDay
44%410%19%16%5%
2548
April1st to 15thDay
54%37%18%13%2
2512
16th to endDay
50%47%18%15%3
2588
May1st to 15thDay
51%5%7%20%14%2
2931
16th to endDay
46%7%11%21%11%1
3070
June1st to 15thDay
50%7%9%20%11%1
2940
16th to endDay
47%6%12%20%11%1
2842
July1st to 15thDay
35%7%14%28%13%1
2581
16th to endDay
40%8%15%24%10%
2711
August1st to 15thDay
43%8%16%21%10%
2567
16th to endDay
37%7%14%27%11%
2535
September1st to 15thDay
40%5%13%26%12%
2340
16th to endDay
38%6%12%31%10%
2165
October1st to 15thDay
50%6%13%20%8%
1950
16th to endDay
59%5%13%14%5%
1982
November1st to 15thDay
51%6%14%18%8%
1778
16th to endDay
62%6%11%12%6%1
1680
December1st to 15thDay
66%7%10%12%3
1680
16th to endDay
65%410%12%6%
1792
January1st to 15thNight
66%5%9%11%5%
2926
16th to endNight
59%410%16%8%
3073
February1st to 15thNight
61%5%10%17%5%
2677
16th to endNight
56%49%19%9%
2277
March1st to 15thNight
59%410%18%7%
2443
16th to endNight
45%39%19%17%4
2379
April1st to 15thNight
52%47%19%15%
2096
16th to endNight
47%5%7%17%17%3
1990
May1st to 15thNight
47%5%7%20%15%3
1680
16th to endNight
42%5%12%21%15%2
1753
June1st to 15thNight
47%6%10%20%12%1
1680
16th to endNight
42%7%12%21%16%
1625
July1st to 15thNight
31%6%12%29%18%1
1480
16th to endNight
35%6%15%26%16%
1546
August1st to 15thNight
38%8%16%23%11%
1619
16th to endNight
32%6%15%32%12%
2006
September1st to 15thNight
39%7%10%29%11%
1950
16th to endNight
37%5%11%34%10%
2122
October1st to 15thNight
48%6%10%22%11%
2340
16th to endNight
57%6%12%17%6%
2593
November1st to 15thNight
53%5%13%17%10%
2737
16th to endNight
62%5%11%15%4
2940
December1st to 15thNight
63%7%12%12%3
2940
16th to endNight
66%49%12%6%
3136

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
26%19%31%17%4
120
16th to endDay
27%20%34%15%1
146
February1st to 15thDay
33%25%31%10%
180
16th to endDay
32%23%23%15%3
271
March1st to 15thDay
29%14%31%19%4
390
16th to endDay
24%16%29%18%9%1
416
April1st to 15thDay
32%18%27%14%6%1
390
16th to endDay
27%17%24%17%9%3
379
May1st to 15thDay
27%13%30%18%6%3
408
16th to endDay
19%15%33%20%9%1
459
June1st to 15thDay
25%9%30%23%8%2
435
16th to endDay
16%11%33%24%11%2
407
July1st to 15thDay
12%5%28%33%16%4
365
16th to endDay
14%428%28%18%5%
390
August1st to 15thDay
12%6%27%29%17%6%
358
16th to endDay
13%5%25%28%15%11%
396
September1st to 15thDay
17%6%25%17%20%12%
375
16th to endDay
14%9%26%21%17%10%
374
October1st to 15thDay
24%10%28%21%11%2
375
16th to endDay
27%20%26%19%5%
369
November1st to 15thDay
25%15%28%20%8%1
252
16th to endDay
31%19%35%11%1
120
December1st to 15thDay
20%19%40%17%2
120
16th to endDay
33%20%28%14%2
128
January1st to 15thNight
26%16%32%19%5%
840
16th to endNight
22%14%34%23%5%
896
February1st to 15thNight
22%14%37%20%4
824
16th to endNight
24%15%31%22%5%
735
March1st to 15thNight
25%13%31%25%3
840
16th to endNight
20%14%28%26%9%
896
April1st to 15thNight
27%14%29%23%4
838
16th to endNight
25%13%25%26%8%
744
May1st to 15thNight
24%7%26%30%10%
420
16th to endNight
17%6%35%27%12%
439
June1st to 15thNight
20%6%27%33%11%
420
16th to endNight
18%327%34%13%
406
July1st to 15thNight
10%225%44%16%1
370
16th to endNight
10%223%43%17%1
408
August1st to 15thNight
12%220%39%23%1
478
16th to endNight
10%423%35%22%2
764
September1st to 15thNight
16%5%25%29%20%3
780
16th to endNight
17%8%23%25%22%3
777
October1st to 15thNight
22%10%27%26%12%1
780
16th to endNight
28%13%25%24%7%
832
November1st to 15thNight
28%10%28%21%10%
820
16th to endNight
30%15%25%20%8%
840
December1st to 15thNight
30%13%29%22%3
840
16th to endNight
31%13%29%20%41
896
Page generated at 2019-06-24 20:41:28. Version ac04

Copyright 2019 A. Danko


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