Port Dover
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Dover clear sky chart from 2005-11-05 to 2017-08-12.

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
33%
14795
14%
46555
9%
14758
39%
14758
17%
32407

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
13%
716
9%
2410
5%
716
19%
716
7%
1907
January16th to endNight
14%
768
9%
2496
3%
768
22%
768
9%
1962
February1st to 15thNight
17%
702
7%
2287
2%
701
23%
701
10%
1812
February16th to endNight
24%
631
11%
1988
5%
631
32%
631
13%
1491
March1st to 15thNight
24%
720
14%
1983
7%
720
30%
720
14%
1516
March16th to endNight
29%
768
19%
2112
9%
768
38%
768
20%
1450
April1st to 15thNight
27%
718
15%
1844
6%
718
32%
718
20%
1347
April16th to endNight
35%
546
20%
1626
8%
546
44%
546
22%
1039
May1st to 15thNight
35%
540
16%
1620
8%
540
42%
540
20%
1088
May16th to endNight
44%
385
18%
1508
15%
385
55%
385
21%
863
June1st to 15thNight
42%
360
14%
1440
13%
360
51%
360
18%
869
June16th to endNight
47%
360
13%
1440
12%
360
56%
360
19%
864
July1st to 15thNight
62%
340
17%
1360
22%
340
67%
340
28%
699
July16th to endNight
53%
564
15%
1595
12%
531
61%
531
31%
932
August1st to 15thNight
62%
527
18%
1575
15%
524
65%
524
31%
937
August16th to endNight
61%
561
21%
1611
13%
561
66%
561
34%
956
September1st to 15thNight
55%
660
24%
1692
14%
660
59%
660
33%
1081
September16th to endNight
54%
657
21%
1818
14%
657
59%
657
30%
1143
October1st to 15thNight
41%
660
18%
1980
18%
660
45%
660
23%
1291
October16th to endNight
23%
704
13%
2112
7%
704
30%
704
15%
1545
November1st to 15thNight
33%
700
19%
2330
16%
700
40%
700
19%
1533
November16th to endNight
18%
720
10%
2520
5%
720
25%
720
10%
1838
December1st to 15thNight
13%
720
6%
2520
3%
720
17%
720
7%
2018
December16th to endNight
12%
768
6%
2688
2%
768
18%
768
6%
2226

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%8%36%5%35%5%5%7%33%
47406
Night
15%8%36%5%3445%7%34%
46738
Cloud CoverDay
14%8%36%5%35%5%5%7%33%
47416
Night
15%8%46%5%3445%7%34%
46742
TransparencyDay
48%7%13%19%9%1
47107
Night
49%6%12%20%10%1
46555
SeeingDay
16%13%22%25%16%6%
5199
Night
17%20%22%24%12%1
14802

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
18%12%5%10%5%45%447%19%
1526
16th to endDay
14%15%6%12%8%36%446%16%
1728
February1st to 15thDay
16%16%5%10%8%45%44418%
1575
16th to endDay
17%12%6%9%8%35%5%46%21%
1482
March1st to 15thDay
16%12%48%7%35%45%6%24%
1966
16th to endDay
16%10%47%6%3435%6%31%
2112
April1st to 15thDay
18%8%37%6%3445%5%30%
2107
16th to endDay
17%7%35%423347%39%
2340
May1st to 15thDay
15%5%36%6%35%35%7%37%
2331
16th to endDay
11%5%24435%5%5%8%43%
2605
June1st to 15thDay
12%5%25%5%345%6%8%40%
2520
16th to endDay
10%4145%35%5%7%10%41%
2520
July1st to 15thDay
8%424435%5%6%9%45%
2517
16th to endDay
9%425%5%36%6%7%10%39%
2465
August1st to 15thDay
7%3245%35%7%7%9%41%
2288
16th to endDay
11%4244245%6%8%44%
2227
September1st to 15thDay
14%5%245%335%5%8%41%
1936
16th to endDay
15%425%425%45%7%41%
1812
October1st to 15thDay
17%6%25%7%3445%8%34%
1650
16th to endDay
23%9%47%5%345%5%6%24%
1760
November1st to 15thDay
13%6%26%6%445%5%8%37%
1523
16th to endDay
21%12%37%5%345%5%7%22%
1440
December1st to 15thDay
19%15%6%8%6%345%47%19%
1440
16th to endDay
21%17%7%8%5%45%5%45%15%
1536
January1st to 15thNight
21%13%5%9%5%25%445%22%
2410
16th to endNight
14%15%7%8%6%35%5%5%6%21%
2496
February1st to 15thNight
15%14%6%9%6%35%5%45%22%
2285
16th to endNight
17%11%47%6%35%45%6%25%
1988
March1st to 15thNight
19%8%47%5%45%5%46%29%
1971
16th to endNight
15%8%46%424445%38%
2112
April1st to 15thNight
20%8%345%34446%34%
1844
16th to endNight
12%6%35%5%35%45%7%42%
1626
May1st to 15thNight
16%5%26%5%3446%8%36%
1620
16th to endNight
10%5%345%235%6%8%44%
1506
June1st to 15thNight
10%5%35%5%245%6%9%40%
1440
16th to endNight
9%5%25%5%36%5%5%9%41%
1440
July1st to 15thNight
5%31442445%8%53%
1440
16th to endNight
6%324435%5%6%8%49%
1703
August1st to 15thNight
6%2145%446%6%10%47%
1586
16th to endNight
9%314424448%51%
1611
September1st to 15thNight
12%5%25%323447%48%
1692
16th to endNight
13%315%5%1436%6%47%
1818
October1st to 15thNight
16%6%2442345%7%42%
1980
16th to endNight
21%8%26%435%5%5%6%30%
2112
November1st to 15thNight
13%7%36%4345%6%7%37%
2330
16th to endNight
20%11%36%5%3445%7%27%
2520
December1st to 15thNight
23%15%5%6%5%34346%21%
2520
16th to endNight
21%14%7%9%5%35%45%5%16%
2688

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
18%13%5%9%7%45%447%19%
1526
16th to endDay
14%14%6%12%8%46%446%16%
1728
February1st to 15thDay
16%15%6%10%7%46%44418%
1575
16th to endDay
17%11%5%9%7%3445%6%21%
1482
March1st to 15thDay
17%11%48%7%35%45%5%25%
1977
16th to endDay
16%9%46%6%34446%31%
2111
April1st to 15thDay
18%8%46%6%35%45%5%30%
2107
16th to endDay
17%7%26%423447%39%
2340
May1st to 15thDay
15%435%7%35%35%8%36%
2331
16th to endDay
10%5%24435%5%6%7%43%
2605
June1st to 15thDay
11%5%25%5%25%5%6%8%40%
2520
16th to endDay
10%424435%5%6%10%40%
2520
July1st to 15thDay
8%4244346%6%10%44%
2517
16th to endDay
8%5%246%36%6%8%10%38%
2465
August1st to 15thDay
7%4145%36%7%7%9%41%
2288
16th to endDay
10%5%2442447%8%44%
2227
September1st to 15thDay
13%5%344345%5%7%40%
1936
16th to endDay
14%425%5%345%6%7%40%
1812
October1st to 15thDay
16%6%26%6%3445%8%34%
1650
16th to endDay
23%9%47%5%25%5%5%6%23%
1760
November1st to 15thDay
13%5%26%7%345%48%37%
1523
16th to endDay
21%12%46%5%35%46%7%23%
1440
December1st to 15thDay
19%14%6%8%6%3445%7%19%
1440
16th to endDay
21%16%8%8%6%345%45%14%
1536
January1st to 15thNight
21%14%5%9%5%24445%21%
2410
16th to endNight
14%14%7%8%7%35%5%5%6%21%
2496
February1st to 15thNight
15%14%6%9%6%45%445%23%
2278
16th to endNight
17%11%48%6%35%45%7%25%
1988
March1st to 15thNight
19%8%47%6%45%446%28%
1983
16th to endNight
15%9%36%424445%38%
2112
April1st to 15thNight
20%7%35%5%34446%34%
1844
16th to endNight
11%6%35%5%35%45%7%42%
1626
May1st to 15thNight
16%5%26%6%25%5%6%7%35%
1619
16th to endNight
10%5%2442446%8%45%
1506
June1st to 15thNight
10%5%35%5%25%5%6%9%39%
1440
16th to endNight
8%6%25%5%35%5%6%8%42%
1440
July1st to 15thNight
5%31343445%8%53%
1440
16th to endNight
6%415%435%5%5%8%49%
1703
August1st to 15thNight
6%2145%346%7%9%47%
1586
16th to endNight
9%3442445%7%51%
1611
September1st to 15thNight
12%5%25%32335%7%48%
1692
16th to endNight
13%425%42345%6%47%
1818
October1st to 15thNight
16%6%2442335%7%41%
1980
16th to endNight
20%8%35%4345%6%6%29%
2112
November1st to 15thNight
13%7%36%4245%6%7%37%
2330
16th to endNight
20%12%35%5%2445%6%27%
2520
December1st to 15thNight
22%15%6%7%5%33447%20%
2520
16th to endNight
21%13%7%8%6%3445%5%16%
2688

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
65%6%12%12%3
1527
16th to endDay
68%5%12%10%2
1728
February1st to 15thDay
68%5%10%11%3
1577
16th to endDay
62%6%12%13%4
1482
March1st to 15thDay
59%7%12%16%4
1977
16th to endDay
52%6%9%21%8%1
2112
April1st to 15thDay
53%6%11%18%10%
2107
16th to endDay
44%5%10%20%15%2
2340
May1st to 15thDay
45%8%11%21%12%
2331
16th to endDay
37%8%14%24%13%1
2609
June1st to 15thDay
40%8%13%23%12%1
2520
16th to endDay
35%10%16%22%14%
2520
July1st to 15thDay
32%8%13%25%18%1
2368
16th to endDay
36%11%16%22%12%1
2310
August1st to 15thDay
33%12%15%24%12%1
2275
16th to endDay
34%10%15%25%12%2
2227
September1st to 15thDay
40%8%13%25%11%
1936
16th to endDay
41%7%14%25%10%
1812
October1st to 15thDay
47%8%13%18%10%1
1650
16th to endDay
58%7%14%14%4
1760
November1st to 15thDay
44%7%18%19%8%1
1523
16th to endDay
59%6%14%14%4
1440
December1st to 15thDay
65%6%16%10%1
1440
16th to endDay
71%6%11%9%
1536
January1st to 15thNight
65%5%10%11%6%
2410
16th to endNight
63%6%12%13%4
2496
February1st to 15thNight
63%6%12%12%5%
2287
16th to endNight
57%5%13%17%5%
1988
March1st to 15thNight
56%6%10%19%6%
1983
16th to endNight
46%411%21%13%2
2112
April1st to 15thNight
50%5%9%20%13%
1844
16th to endNight
40%410%21%18%4
1626
May1st to 15thNight
44%5%12%24%10%2
1620
16th to endNight
36%6%12%24%16%3
1508
June1st to 15thNight
39%7%11%26%13%2
1440
16th to endNight
38%7%12%22%17%1
1440
July1st to 15thNight
28%6%11%26%23%3
1360
16th to endNight
31%6%16%25%17%3
1595
August1st to 15thNight
28%9%15%30%13%1
1575
16th to endNight
31%6%13%30%15%2
1611
September1st to 15thNight
35%5%12%28%15%2
1692
16th to endNight
36%5%12%29%14%1
1818
October1st to 15thNight
42%5%13%22%15%1
1980
16th to endNight
52%7%14%18%6%
2112
November1st to 15thNight
43%7%13%21%12%1
2330
16th to endNight
56%5%16%16%4
2520
December1st to 15thNight
64%7%14%10%3
2520
16th to endNight
68%8%11%9%2
2688

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
23%22%38%6%7%1
76
16th to endDay
27%13%44%12%2
96
February1st to 15thDay
17%13%52%16%
90
16th to endDay
17%18%33%29%1
81
March1st to 15thDay
20%18%25%27%7%
267
16th to endDay
21%17%26%25%7%1
288
April1st to 15thDay
20%18%27%22%9%1
270
16th to endDay
16%15%23%25%11%7%
270
May1st to 15thDay
19%14%21%25%14%5%
288
16th to endDay
12%12%21%32%16%4
331
June1st to 15thDay
11%11%22%36%16%2
315
16th to endDay
12%11%20%32%17%5%
315
July1st to 15thDay
9%9%16%25%29%9%
305
16th to endDay
9%9%17%30%23%9%
326
August1st to 15thDay
9%6%13%29%28%12%
297
16th to endDay
11%8%10%23%29%16%
268
September1st to 15thDay
10%7%13%23%29%16%
255
16th to endDay
18%9%14%21%23%12%
254
October1st to 15thDay
19%9%23%22%18%6%
255
16th to endDay
24%14%30%23%6%
272
November1st to 15thDay
8%15%25%33%13%4
96
16th to endDay
33%13%21%21%10%
60
December1st to 15thDay
23%33%26%10%6%
60
16th to endDay
28%31%31%9%
64
January1st to 15thNight
23%27%27%15%4
720
16th to endNight
17%28%30%19%3
768
February1st to 15thNight
21%25%27%21%3
704
16th to endNight
19%21%27%25%5%
631
March1st to 15thNight
21%21%25%22%8%
720
16th to endNight
19%19%26%25%8%
768
April1st to 15thNight
20%22%24%25%6%
718
16th to endNight
13%20%23%30%10%1
546
May1st to 15thNight
15%18%21%27%15%1
540
16th to endNight
12%18%18%28%19%2
386
June1st to 15thNight
13%18%18%31%16%
360
16th to endNight
11%16%16%35%18%
360
July1st to 15thNight
5%12%16%36%26%3
340
16th to endNight
7%16%14%35%21%4
564
August1st to 15thNight
7%10%11%36%28%4
527
16th to endNight
10%10%11%30%31%5%
561
September1st to 15thNight
11%12%14%26%27%6%
660
16th to endNight
13%12%13%26%27%6%
657
October1st to 15thNight
20%13%19%25%18%3
660
16th to endNight
24%18%29%23%4
704
November1st to 15thNight
16%20%25%24%12%1
700
16th to endNight
24%28%25%16%5%1
720
December1st to 15thNight
29%27%25%13%3
720
16th to endNight
24%28%28%15%3
768
Page generated at 2017-08-13 14:16:43. Version ac04

Copyright 2017 A. Danko


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