Wild Duck Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wild Duck Observatory clear sky chart from 2005-11-05 to 2017-09-19.

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
44%
15567
20%
46752
14%
15523
50%
15523
25%
30497

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
22%
887
14%
2493
7%
882
29%
882
16%
1875
January16th to endNight
21%
768
17%
2496
9%
768
31%
768
16%
1764
February1st to 15thNight
23%
704
14%
2112
5%
701
32%
701
17%
1523
February16th to endNight
19%
631
14%
1893
7%
631
26%
631
16%
1377
March1st to 15thNight
26%
720
16%
2115
9%
720
32%
720
19%
1482
March16th to endNight
34%
767
15%
2111
8%
767
40%
767
22%
1483
April1st to 15thNight
37%
539
21%
1797
13%
539
49%
539
26%
1096
April16th to endNight
42%
540
20%
1686
13%
540
50%
540
24%
1108
May1st to 15thNight
43%
540
15%
1620
10%
540
48%
540
20%
1127
May16th to endNight
62%
561
19%
1684
15%
561
65%
561
28%
1069
June1st to 15thNight
69%
540
20%
1551
16%
540
72%
540
39%
889
June16th to endNight
72%
540
21%
1440
16%
540
73%
540
40%
858
July1st to 15thNight
63%
510
17%
1360
14%
510
64%
510
32%
875
July16th to endNight
74%
564
21%
1578
19%
531
77%
531
38%
903
August1st to 15thNight
78%
539
24%
1609
22%
536
79%
536
37%
927
August16th to endNight
75%
573
24%
1902
26%
573
76%
573
37%
1021
September1st to 15thNight
65%
642
25%
1902
23%
642
67%
642
33%
1139
September16th to endNight
58%
673
26%
1858
21%
673
61%
673
34%
1147
October1st to 15thNight
57%
660
32%
1820
26%
660
62%
660
37%
1081
October16th to endNight
43%
704
25%
2216
20%
704
52%
704
28%
1360
November1st to 15thNight
45%
700
28%
2276
22%
700
55%
700
31%
1295
November16th to endNight
36%
720
21%
2340
16%
720
45%
720
22%
1514
December1st to 15thNight
28%
720
13%
2340
9%
720
34%
720
15%
1695
December16th to endNight
22%
825
15%
2553
8%
825
30%
825
15%
1889

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
14%7%35%5%3445%7%38%
48053
Night
14%7%35%43445%7%41%
46933
Cloud CoverDay
14%6%35%5%3445%7%38%
48062
Night
14%6%35%42445%7%41%
46938
TransparencyDay
44%6%11%21%14%2
47752
Night
42%5%11%22%15%3
46752
SeeingDay
16%5%20%24%21%11%
5645
Night
18%6%24%29%18%2
15569

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
21%9%48%5%34426%29%
1440
16th to endDay
17%9%47%6%23446%33%
1728
February1st to 15thDay
16%11%48%5%23346%33%
1747
16th to endDay
15%12%47%436%347%30%
1580
March1st to 15thDay
23%7%36%323435%35%
1835
16th to endDay
17%8%45%6%4445%7%31%
2124
April1st to 15thDay
16%7%245%25%446%39%
2151
16th to endDay
16%6%25%5%4445%5%39%
2274
May1st to 15thDay
21%8%245%25%45%7%32%
2331
16th to endDay
11%6%25%6%46%6%6%8%36%
2431
June1st to 15thDay
9%325%5%46%5%5%8%42%
2406
16th to endDay
7%425%5%26%6%6%9%42%
2520
July1st to 15thDay
14%6%25%436%5%6%10%33%
2520
16th to endDay
7%426%6%36%7%6%10%37%
2480
August1st to 15thDay
6%5%25%6%36%6%6%10%41%
2340
16th to endDay
8%5%246%35%6%6%8%42%
2297
September1st to 15thDay
13%6%25%435%5%46%42%
2046
16th to endDay
15%415%433447%46%
1848
October1st to 15thDay
11%425%424346%50%
1810
16th to endDay
17%6%1442344446%
1656
November1st to 15thDay
13%5%23423445%50%
1582
16th to endDay
18%7%34414345%41%
1620
December1st to 15thDay
24%9%46%423435%30%
1620
16th to endDay
18%13%47%423445%30%
1667
January1st to 15thNight
17%11%5%9%5%3344429%
2493
16th to endNight
17%10%46%5%24445%33%
2496
February1st to 15thNight
19%9%445%34445%32%
2110
16th to endNight
17%11%46%5%24445%31%
1893
March1st to 15thNight
18%8%36%6%24435%36%
2102
16th to endNight
16%8%26%5%2445%7%35%
2111
April1st to 15thNight
15%5%3442335%7%43%
1797
16th to endNight
15%6%35%5%34446%40%
1686
May1st to 15thNight
17%5%36%5%45%45%8%34%
1620
16th to endNight
9%4246%35%7%7%10%40%
1682
June1st to 15thNight
5%315%43436%8%52%
1551
16th to endNight
5%3234245%8%11%47%
1440
July1st to 15thNight
10%416%5%3445%8%45%
1440
16th to endNight
5%3233345%6%10%49%
1685
August1st to 15thNight
5%3135%245%6%10%51%
1620
16th to endNight
44243345%6%9%49%
1902
September1st to 15thNight
11%42332345%8%48%
1902
16th to endNight
11%6%24323445%50%
1858
October1st to 15thNight
8%5%24433337%53%
1820
16th to endNight
15%5%25%423335%47%
2216
November1st to 15thNight
12%5%23422446%50%
2276
16th to endNight
18%7%24323436%40%
2340
December1st to 15thNight
22%9%46%5%2443431%
2340
16th to endNight
23%10%36%5%33445%28%
2553

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
21%8%49%5%34336%29%
1440
16th to endDay
17%9%47%6%33446%33%
1728
February1st to 15thDay
16%10%5%8%5%24345%33%
1747
16th to endDay
16%12%5%6%436%346%30%
1580
March1st to 15thDay
23%7%36%423445%34%
1845
16th to endDay
17%8%35%5%4445%7%32%
2123
April1st to 15thDay
17%7%24425%446%39%
2151
16th to endDay
17%5%25%5%4445%5%40%
2274
May1st to 15thDay
21%7%245%35%45%7%32%
2331
16th to endDay
11%5%25%6%36%6%6%8%36%
2431
June1st to 15thDay
9%325%5%36%5%6%8%42%
2406
16th to endDay
8%4245%36%6%6%9%42%
2520
July1st to 15thDay
14%6%35%435%6%6%10%33%
2520
16th to endDay
8%5%26%6%35%6%7%10%37%
2480
August1st to 15thDay
7%5%25%6%35%6%6%10%41%
2340
16th to endDay
8%5%25%5%346%6%7%43%
2297
September1st to 15thDay
14%6%24435%5%46%42%
2046
16th to endDay
15%325%32335%7%45%
1848
October1st to 15thDay
10%425%424346%50%
1810
16th to endDay
18%5%1442334446%
1656
November1st to 15thDay
13%5%24413346%50%
1582
16th to endDay
18%8%34314345%41%
1620
December1st to 15thDay
25%9%36%5%2444430%
1620
16th to endDay
18%13%47%433435%30%
1667
January1st to 15thNight
17%11%5%9%6%2444429%
2493
16th to endNight
17%10%5%7%5%24445%33%
2496
February1st to 15thNight
19%9%45%5%345%46%32%
2103
16th to endNight
18%11%47%5%24445%31%
1893
March1st to 15thNight
18%8%35%6%2434436%
2115
16th to endNight
17%8%26%5%2435%7%35%
2111
April1st to 15thNight
15%5%2442345%7%43%
1797
16th to endNight
15%6%35%5%25%45%6%40%
1686
May1st to 15thNight
17%5%35%5%35%45%8%34%
1619
16th to endNight
9%3145%35%6%7%10%40%
1682
June1st to 15thNight
6%314435%36%9%51%
1551
16th to endNight
5%3234246%8%11%47%
1440
July1st to 15thNight
10%326%6%25%35%8%45%
1440
16th to endNight
6%3243245%6%10%50%
1685
August1st to 15thNight
5%3144245%7%10%51%
1620
16th to endNight
5%4143345%7%9%50%
1902
September1st to 15thNight
11%42342445%7%48%
1902
16th to endNight
12%5%1442345%5%50%
1858
October1st to 15thNight
8%5%24434347%53%
1820
16th to endNight
16%5%25%423335%47%
2216
November1st to 15thNight
13%5%23423347%50%
2276
16th to endNight
19%7%24323437%40%
2340
December1st to 15thNight
23%9%46%5%33435%31%
2340
16th to endNight
23%10%36%5%24345%28%
2553

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
57%48%18%9%
1441
16th to endDay
51%5%10%23%7%1
1728
February1st to 15thDay
53%48%23%8%1
1749
16th to endDay
54%5%11%21%8%
1580
March1st to 15thDay
51%411%18%12%1
1845
16th to endDay
51%5%11%22%8%
2124
April1st to 15thDay
45%5%9%23%15%1
2151
16th to endDay
44%5%9%22%13%4
2274
May1st to 15thDay
50%6%11%18%11%
2331
16th to endDay
43%8%14%18%12%1
2435
June1st to 15thDay
37%7%12%22%17%1
2406
16th to endDay
35%8%12%20%18%4
2520
July1st to 15thDay
43%7%12%17%13%4
2371
16th to endDay
38%8%15%22%12%2
2324
August1st to 15thDay
36%8%12%22%17%2
2327
16th to endDay
35%7%13%22%16%4
2297
September1st to 15thDay
40%5%11%18%17%6%
2046
16th to endDay
38%49%20%24%2
1848
October1st to 15thDay
34%47%26%22%3
1810
16th to endDay
40%49%26%16%3
1656
November1st to 15thDay
36%37%25%19%7%
1582
16th to endDay
45%37%24%17%1
1620
December1st to 15thDay
56%410%18%8%1
1620
16th to endDay
56%5%10%19%7%1
1667
January1st to 15thNight
57%48%16%11%1
2493
16th to endNight
53%49%21%9%1
2496
February1st to 15thNight
52%5%10%22%7%1
2112
16th to endNight
55%411%18%10%
1893
March1st to 15thNight
50%48%21%13%2
2115
16th to endNight
47%5%14%21%9%1
2111
April1st to 15thNight
39%410%21%20%3
1797
16th to endNight
43%5%9%22%12%6%
1686
May1st to 15thNight
47%7%11%21%10%1
1620
16th to endNight
35%9%14%21%14%4
1684
June1st to 15thNight
29%5%13%27%19%4
1551
16th to endNight
27%7%18%21%19%6%
1440
July1st to 15thNight
38%411%22%16%5%
1360
16th to endNight
26%8%15%27%18%2
1578
August1st to 15thNight
26%8%16%23%19%4
1609
16th to endNight
27%6%15%26%20%4
1902
September1st to 15thNight
33%6%11%21%20%6%
1902
16th to endNight
35%5%8%21%24%4
1858
October1st to 15thNight
31%47%26%24%5%
1820
16th to endNight
39%38%26%18%3
2216
November1st to 15thNight
34%39%22%23%7%
2276
16th to endNight
45%48%22%17%1
2340
December1st to 15thNight
56%410%18%9%1
2340
16th to endNight
56%411%17%8%1
2553

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
34%8%36%11%6%2
90
16th to endDay
16%21%45%12%3
96
February1st to 15thDay
14%20%46%14%4
90
16th to endDay
22%17%33%19%7%
81
March1st to 15thDay
24%13%31%25%5%
135
16th to endDay
20%9%33%25%10%1
288
April1st to 15thDay
21%10%24%25%15%3
270
16th to endDay
19%7%25%26%12%8%
270
May1st to 15thDay
26%7%22%22%13%7%
288
16th to endDay
17%319%25%21%13%
331
June1st to 15thDay
10%211%30%30%14%
381
16th to endDay
9%322%29%24%10%
495
July1st to 15thDay
19%115%27%24%11%
475
16th to endDay
11%18%19%32%27%
340
August1st to 15thDay
11%9%21%28%27%
313
16th to endDay
11%18%27%28%23%
332
September1st to 15thDay
18%112%21%29%17%
315
16th to endDay
17%212%18%32%16%
266
October1st to 15thDay
12%421%28%23%9%
255
16th to endDay
17%6%25%29%19%1
168
November1st to 15thDay
11%11%23%25%17%11%
90
16th to endDay
26%7%30%27%6%1
90
December1st to 15thDay
24%10%31%24%6%3
90
16th to endDay
32%15%36%12%3
96
January1st to 15thNight
23%13%33%24%5%
887
16th to endNight
25%12%35%23%1
768
February1st to 15thNight
25%9%35%27%1
704
16th to endNight
23%11%39%23%1
631
March1st to 15thNight
23%12%32%25%5%
720
16th to endNight
20%7%31%29%10%1
767
April1st to 15thNight
17%8%33%29%10%
539
16th to endNight
17%6%27%34%12%2
540
May1st to 15thNight
19%5%23%32%17%1
540
16th to endNight
12%314%38%24%6%
563
June1st to 15thNight
7%114%41%30%4
540
16th to endNight
7%12%42%34%2
540
July1st to 15thNight
13%110%32%38%3
510
16th to endNight
8%7%32%39%10%
564
August1st to 15thNight
7%6%33%45%7%
539
16th to endNight
7%6%34%43%6%
573
September1st to 15thNight
13%110%29%37%6%
642
16th to endNight
14%314%26%35%5%
673
October1st to 15thNight
10%5%20%32%25%6%
660
16th to endNight
18%5%27%32%14%
704
November1st to 15thNight
15%7%27%27%20%2
700
16th to endNight
23%8%27%29%10%
720
December1st to 15thNight
28%10%28%24%8%1
720
16th to endNight
31%9%32%23%4
825
Page generated at 2017-09-20 04:49:52. Version ac04

Copyright 2017 A. Danko


Wild Duck Observatory Clear Sky Chart | Charts Home