Dorset Wilderness Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dorset Wilderness Area clear sky chart from 2005-11-05 to 2017-09-22.

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%
15084
13%
46988
9%
15042
35%
15042
16%
34341

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
8%
718
6%
2345
2%
716
12%
716
5%
2024
January16th to endNight
9%
768
6%
2496
2%
768
13%
768
5%
2155
February1st to 15thNight
12%
704
5%
2287
3%
701
16%
701
6%
1929
February16th to endNight
15%
631
8%
1958
3%
631
21%
631
9%
1588
March1st to 15thNight
18%
720
13%
1988
7%
720
24%
720
12%
1582
March16th to endNight
24%
768
17%
2112
10%
768
30%
768
18%
1554
April1st to 15thNight
23%
718
13%
1862
4%
718
28%
718
18%
1385
April16th to endNight
34%
543
18%
1623
9%
543
42%
543
23%
1097
May1st to 15thNight
38%
540
14%
1620
9%
540
43%
540
20%
1130
May16th to endNight
43%
448
16%
1570
14%
447
48%
447
25%
945
June1st to 15thNight
49%
360
15%
1440
16%
360
57%
360
22%
852
June16th to endNight
50%
360
15%
1440
18%
360
56%
360
23%
848
July1st to 15thNight
56%
415
16%
1435
19%
415
60%
415
29%
834
July16th to endNight
62%
564
17%
1595
15%
531
63%
531
33%
940
August1st to 15thNight
64%
539
19%
1609
15%
536
66%
536
33%
966
August16th to endNight
59%
611
22%
1757
15%
611
62%
611
34%
1056
September1st to 15thNight
54%
720
21%
1875
15%
720
56%
720
32%
1223
September16th to endNight
50%
685
21%
1892
15%
685
54%
685
28%
1233
October1st to 15thNight
40%
660
18%
1969
15%
660
45%
660
24%
1302
October16th to endNight
19%
704
12%
2112
5%
704
28%
704
14%
1607
November1st to 15thNight
30%
700
17%
2275
13%
700
37%
700
17%
1595
November16th to endNight
15%
720
10%
2520
6%
720
21%
720
8%
2013
December1st to 15thNight
11%
720
5%
2520
3%
720
14%
720
6%
2126
December16th to endNight
7%
768
4%
2688
1%
768
11%
768
4%
2357

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%11%47%5%3445%6%29%
47874
Night
17%11%47%5%34446%30%
47177
Cloud CoverDay
17%11%47%5%34446%29%
47884
Night
17%11%47%5%34446%29%
47181
TransparencyDay
54%411%18%9%1
47582
Night
55%410%17%10%1
46988
SeeingDay
23%12%25%21%12%5%
5379
Night
24%13%25%23%11%1
15087

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%17%7%12%7%2433415%
1590
16th to endDay
16%20%8%14%10%3433311%
1728
February1st to 15thDay
16%20%10%11%10%3332313%
1575
16th to endDay
16%17%7%12%7%3334419%
1512
March1st to 15thDay
20%16%8%8%422345%22%
1960
16th to endDay
19%12%5%6%5%23445%29%
2112
April1st to 15thDay
23%11%35%423446%28%
2092
16th to endDay
20%9%35%5%22445%37%
2340
May1st to 15thDay
18%9%35%6%35%5%5%6%30%
2331
16th to endDay
14%6%245%35%46%7%39%
2542
June1st to 15thDay
15%6%36%5%35%5%5%6%36%
2520
16th to endDay
16%425%4345%6%10%35%
2520
July1st to 15thDay
11%5%25%5%35%5%6%8%39%
2436
16th to endDay
12%5%25%5%45%6%5%9%37%
2465
August1st to 15thDay
10%6%25%6%36%6%6%8%36%
2340
16th to endDay
11%6%246%35%5%6%8%37%
2432
September1st to 15thDay
16%7%26%6%36%45%7%33%
2083
16th to endDay
18%7%36%42435%7%36%
1881
October1st to 15thDay
22%6%25%6%34446%33%
1661
16th to endDay
30%10%26%5%24445%23%
1760
November1st to 15thDay
14%13%45%5%3445%6%32%
1578
16th to endDay
20%23%47%5%24345%17%
1440
December1st to 15thDay
21%22%10%10%5%2332312%
1440
16th to endDay
21%25%9%12%5%332229%
1536
January1st to 15thNight
23%18%9%12%5%3322314%
2345
16th to endNight
17%20%8%12%10%3432413%
2496
February1st to 15thNight
17%17%6%12%9%45%33316%
2285
16th to endNight
17%14%8%11%6%2444420%
1958
March1st to 15thNight
19%12%5%10%6%2435%424%
1976
16th to endNight
17%10%5%6%6%24445%32%
2112
April1st to 15thNight
20%13%35%433445%30%
1862
16th to endNight
12%8%346%346%5%7%37%
1623
May1st to 15thNight
17%7%35%5%34448%33%
1620
16th to endNight
12%5%25%43345%10%41%
1568
June1st to 15thNight
7%6%26%5%35%6%5%7%42%
1440
16th to endNight
10%5%25%5%45%5%5%8%42%
1440
July1st to 15thNight
7%4246%35%448%47%
1521
16th to endNight
7%425%425%46%9%46%
1703
August1st to 15thNight
8%325%4445%6%9%46%
1620
16th to endNight
10%4244345%6%7%47%
1757
September1st to 15thNight
15%5%24323447%45%
1875
16th to endNight
17%4245%3445%7%41%
1892
October1st to 15thNight
17%7%25%324447%39%
1969
16th to endNight
27%8%26%434446%25%
2112
November1st to 15thNight
18%10%36%5%34446%32%
2275
16th to endNight
22%18%48%5%24345%19%
2520
December1st to 15thNight
22%21%8%8%42433415%
2520
16th to endNight
23%21%9%9%6%3333410%
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
20%18%7%12%7%3433414%
1590
16th to endDay
15%20%9%14%9%3433410%
1728
February1st to 15thDay
15%20%10%12%10%3332313%
1575
16th to endDay
16%17%7%12%7%2433419%
1512
March1st to 15thDay
20%16%7%9%422245%22%
1971
16th to endDay
19%12%6%6%423445%29%
2111
April1st to 15thDay
23%10%34433446%29%
2092
16th to endDay
20%9%25%422346%37%
2340
May1st to 15thDay
18%9%36%5%45%5%5%6%30%
2331
16th to endDay
14%5%245%35%45%7%39%
2542
June1st to 15thDay
16%6%26%435%5%5%7%36%
2520
16th to endDay
15%5%244345%5%11%36%
2520
July1st to 15thDay
11%5%25%5%35%5%6%8%39%
2436
16th to endDay
12%425%5%45%5%6%9%38%
2465
August1st to 15thDay
10%5%26%6%36%5%7%8%36%
2340
16th to endDay
12%6%25%5%45%5%6%7%38%
2432
September1st to 15thDay
17%7%36%6%35%45%7%33%
2083
16th to endDay
18%6%36%5%23447%36%
1881
October1st to 15thDay
22%6%25%6%335%45%33%
1661
16th to endDay
30%10%26%423445%23%
1760
November1st to 15thDay
14%14%46%5%34446%31%
1578
16th to endDay
20%22%5%7%5%34335%17%
1440
December1st to 15thDay
20%24%9%10%5%2332312%
1440
16th to endDay
21%25%9%12%5%232239%
1536
January1st to 15thNight
23%18%9%13%6%2332214%
2345
16th to endNight
16%20%8%12%9%3332313%
2496
February1st to 15thNight
16%17%6%13%8%45%33316%
2278
16th to endNight
17%14%8%12%7%2444419%
1958
March1st to 15thNight
18%13%6%9%6%24445%24%
1988
16th to endNight
17%10%6%6%6%24445%32%
2112
April1st to 15thNight
20%13%35%42335%5%30%
1862
16th to endNight
12%7%35%6%35%5%5%7%37%
1623
May1st to 15thNight
17%7%36%5%35%348%33%
1619
16th to endNight
12%5%25%5%3435%10%41%
1568
June1st to 15thNight
8%5%26%6%35%5%6%7%42%
1440
16th to endNight
11%425%5%25%448%42%
1440
July1st to 15thNight
8%4246%3445%9%46%
1521
16th to endNight
7%425%425%5%6%9%46%
1703
August1st to 15thNight
7%315%5%345%6%9%46%
1620
16th to endNight
10%4244245%6%7%47%
1757
September1st to 15thNight
15%5%2332435%6%45%
1875
16th to endNight
16%425%433447%42%
1892
October1st to 15thNight
18%7%25%424347%39%
1969
16th to endNight
27%8%36%5%34445%26%
2112
November1st to 15thNight
18%11%36%5%24446%32%
2275
16th to endNight
21%19%5%8%5%24335%19%
2520
December1st to 15thNight
22%20%9%8%5%2433314%
2520
16th to endNight
22%22%8%9%7%3342410%
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
73%39%10%3
1591
16th to endDay
78%38%8%1
1728
February1st to 15thDay
77%26%9%3
1577
16th to endDay
68%39%12%4
1512
March1st to 15thDay
63%410%15%4
1971
16th to endDay
56%48%20%8%1
2112
April1st to 15thDay
55%412%17%10%
2092
16th to endDay
48%310%19%13%3
2340
May1st to 15thDay
52%5%10%19%10%1
2331
16th to endDay
43%413%24%11%1
2546
June1st to 15thDay
45%5%12%24%11%
2520
16th to endDay
41%5%13%22%14%1
2520
July1st to 15thDay
41%5%10%24%16%1
2294
16th to endDay
41%5%12%24%14%1
2310
August1st to 15thDay
42%6%14%24%11%
2327
16th to endDay
41%5%12%23%13%2
2432
September1st to 15thDay
48%5%12%21%10%1
2083
16th to endDay
47%410%21%14%1
1881
October1st to 15thDay
51%412%19%11%
1661
16th to endDay
61%413%14%4
1760
November1st to 15thDay
52%5%9%18%10%3
1578
16th to endDay
69%38%11%6%
1440
December1st to 15thDay
77%47%7%1
1440
16th to endDay
82%36%5%1
1536
January1st to 15thNight
76%36%8%4
2345
16th to endNight
76%37%9%2
2496
February1st to 15thNight
73%48%10%3
2287
16th to endNight
67%48%14%4
1958
March1st to 15thNight
62%48%16%7%
1988
16th to endNight
54%48%19%11%1
2112
April1st to 15thNight
54%310%18%12%
1862
16th to endNight
45%5%10%20%14%4
1623
May1st to 15thNight
49%411%21%10%2
1620
16th to endNight
39%5%14%23%14%2
1570
June1st to 15thNight
39%6%11%26%15%1
1440
16th to endNight
38%6%14%21%16%2
1440
July1st to 15thNight
35%5%8%26%20%2
1435
16th to endNight
33%5%14%24%19%3
1595
August1st to 15thNight
33%6%12%30%14%2
1609
16th to endNight
33%5%12%27%17%3
1757
September1st to 15thNight
38%5%13%23%16%2
1875
16th to endNight
40%5%11%24%16%1
1892
October1st to 15thNight
44%411%20%17%1
1969
16th to endNight
58%5%12%16%6%
2112
November1st to 15thNight
52%410%17%10%4
2275
16th to endNight
67%48%14%4
2520
December1st to 15thNight
75%29%9%2
2520
16th to endNight
78%49%7%
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
36%32%14%11%4
87
16th to endDay
36%35%19%7%1
96
February1st to 15thDay
37%25%35%1
90
16th to endDay
25%28%39%6%
81
March1st to 15thDay
31%18%29%16%3
261
16th to endDay
30%19%24%18%5%1
288
April1st to 15thDay
33%14%27%15%8%
270
16th to endDay
23%16%27%15%11%5%
270
May1st to 15thDay
30%11%24%22%7%2
288
16th to endDay
17%10%29%24%10%6%
331
June1st to 15thDay
20%8%29%24%14%2
315
16th to endDay
19%10%29%25%11%3
315
July1st to 15thDay
16%6%24%29%16%7%
305
16th to endDay
12%5%25%30%15%10%
326
August1st to 15thDay
15%422%27%19%10%
313
16th to endDay
14%6%21%25%18%14%
332
September1st to 15thDay
16%5%20%23%22%12%
315
16th to endDay
19%5%19%19%23%12%
278
October1st to 15thDay
22%8%25%22%18%2
255
16th to endDay
35%16%29%14%4
272
November1st to 15thDay
27%9%17%31%13%
107
16th to endDay
26%28%28%16%
60
December1st to 15thDay
40%20%26%6%5%1
60
16th to endDay
40%29%26%3
64
January1st to 15thNight
34%22%29%10%2
720
16th to endNight
30%22%31%13%2
768
February1st to 15thNight
29%22%29%16%2
704
16th to endNight
28%19%30%18%2
631
March1st to 15thNight
27%18%30%18%4
720
16th to endNight
23%16%29%22%7%
768
April1st to 15thNight
29%14%29%21%5%
718
16th to endNight
17%11%32%28%9%1
543
May1st to 15thNight
21%7%23%34%11%
540
16th to endNight
14%6%28%28%19%3
449
June1st to 15thNight
9%428%41%15%
360
16th to endNight
13%5%24%40%16%
360
July1st to 15thNight
8%321%38%23%3
415
16th to endNight
9%415%40%28%1
564
August1st to 15thNight
10%215%41%25%5%
539
16th to endNight
12%317%28%33%3
611
September1st to 15thNight
17%415%31%25%4
720
16th to endNight
18%6%19%25%22%6%
685
October1st to 15thNight
23%7%23%27%16%2
660
16th to endNight
33%13%30%19%3
704
November1st to 15thNight
24%14%27%22%10%1
700
16th to endNight
35%20%24%13%6%
720
December1st to 15thNight
37%20%26%11%4
720
16th to endNight
34%23%28%11%2
768
Page generated at 2017-09-23 06:43:43. Version ac04

Copyright 2017 A. Danko


Dorset Wilderness Area Clear Sky Chart | Charts Home