Cobourg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cobourg clear sky chart from 2005-11-05 to 2017-09-16.

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
31%
14778
14%
46872
8%
14746
38%
14746
16%
32952

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
12%
719
6%
2506
2%
716
17%
716
7%
2006
January16th to endNight
17%
768
10%
2522
5%
768
24%
768
8%
1998
February1st to 15thNight
14%
702
8%
2287
3%
701
20%
701
9%
1802
February16th to endNight
20%
631
12%
2003
4%
631
31%
631
12%
1500
March1st to 15thNight
23%
720
13%
2004
6%
720
30%
720
15%
1490
March16th to endNight
28%
768
21%
2099
7%
768
40%
768
22%
1410
April1st to 15thNight
28%
718
16%
1796
5%
718
34%
718
21%
1314
April16th to endNight
32%
612
19%
1692
6%
612
41%
612
23%
1109
May1st to 15thNight
38%
434
15%
1514
11%
434
45%
434
16%
1011
May16th to endNight
41%
374
17%
1497
14%
374
53%
374
20%
853
June1st to 15thNight
40%
360
12%
1440
9%
360
51%
360
18%
887
June16th to endNight
48%
360
11%
1440
14%
360
54%
360
19%
854
July1st to 15thNight
60%
340
16%
1360
24%
340
64%
340
28%
708
July16th to endNight
54%
420
15%
1459
16%
395
63%
395
27%
828
August1st to 15thNight
58%
539
16%
1609
13%
536
62%
536
28%
974
August16th to endNight
58%
660
22%
1806
11%
660
64%
660
35%
1088
September1st to 15thNight
53%
720
19%
1800
11%
720
56%
720
32%
1189
September16th to endNight
52%
661
21%
1836
15%
661
55%
661
29%
1183
October1st to 15thNight
35%
660
17%
1980
14%
660
42%
660
19%
1392
October16th to endNight
22%
704
11%
2112
5%
704
30%
704
13%
1601
November1st to 15thNight
33%
700
18%
2382
15%
700
40%
700
16%
1623
November16th to endNight
19%
720
11%
2520
5%
720
27%
720
10%
1897
December1st to 15thNight
13%
720
6%
2520
2%
720
19%
720
8%
2037
December16th to endNight
11%
768
7%
2688
1%
768
17%
768
6%
2198

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%36%5%35%5%5%7%35%
47887
Night
16%8%36%5%3445%6%35%
47046
Cloud CoverDay
14%7%36%5%35%45%7%36%
47897
Night
16%8%36%5%3445%6%35%
47051
TransparencyDay
46%7%13%20%10%1
47579
Night
48%7%12%19%11%1
46872
SeeingDay
16%12%23%26%15%4
5401
Night
17%20%24%23%12%1
14782

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%14%48%6%34446%23%
1432
16th to endDay
12%14%7%10%8%46%5%45%21%
1701
February1st to 15thDay
12%13%6%11%8%46%5%45%21%
1575
16th to endDay
18%11%5%7%6%34435%27%
1469
March1st to 15thDay
16%10%47%6%35%5%5%5%29%
1942
16th to endDay
16%8%35%5%33345%40%
2124
April1st to 15thDay
19%7%36%5%2345%6%33%
2152
16th to endDay
17%5%25%434446%39%
2277
May1st to 15thDay
13%6%36%5%35%5%5%7%37%
2436
16th to endDay
12%5%245%35%5%5%8%42%
2618
June1st to 15thDay
16%6%25%5%3445%10%34%
2520
16th to endDay
12%5%245%245%6%9%41%
2520
July1st to 15thDay
8%324425%5%6%10%46%
2520
16th to endDay
8%325%5%36%7%6%10%40%
2608
August1st to 15thDay
7%5%25%436%6%6%8%43%
2340
16th to endDay
10%4234245%6%9%46%
2384
September1st to 15thDay
13%5%234245%5%7%45%
2160
16th to endDay
13%5%25%434447%45%
1811
October1st to 15thDay
18%7%26%5%335%46%35%
1650
16th to endDay
23%8%36%6%2345%5%27%
1759
November1st to 15thDay
13%7%36%6%45%45%7%34%
1473
16th to endDay
19%11%46%7%35%447%26%
1440
December1st to 15thDay
18%14%5%8%5%35%446%21%
1440
16th to endDay
21%12%6%8%5%25%446%19%
1536
January1st to 15thNight
21%14%5%7%5%34445%22%
2506
16th to endNight
15%13%6%8%7%35%435%24%
2522
February1st to 15thNight
14%14%6%9%5%35%446%24%
2285
16th to endNight
15%9%37%8%3445%6%30%
2003
March1st to 15thNight
19%8%46%6%43345%32%
1992
16th to endNight
15%6%36%42334444%
2099
April1st to 15thNight
20%8%25%424446%36%
1796
16th to endNight
15%6%2442245%6%43%
1692
May1st to 15thNight
15%5%16%5%46%45%7%36%
1514
16th to endNight
11%5%26%32345%6%46%
1495
June1st to 15thNight
12%6%46%5%2446%7%39%
1440
16th to endNight
12%435%5%2346%9%42%
1440
July1st to 15thNight
5%3134345%49%53%
1440
16th to endNight
8%42343445%8%49%
1558
August1st to 15thNight
7%42443446%9%47%
1620
16th to endNight
6%424415%45%7%52%
1806
September1st to 15thNight
14%41342345%7%46%
1800
16th to endNight
15%424413336%48%
1836
October1st to 15thNight
20%7%26%424446%37%
1980
16th to endNight
22%7%37%435%5%5%5%29%
2112
November1st to 15thNight
16%6%25%5%25%45%7%37%
2382
16th to endNight
23%10%35%425%45%7%27%
2520
December1st to 15thNight
22%13%46%5%4445%6%23%
2520
16th to endNight
21%13%6%8%5%4446%6%18%
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%14%5%7%6%35%36%6%22%
1432
16th to endDay
12%14%6%9%8%47%5%45%20%
1701
February1st to 15thDay
12%12%5%12%8%36%5%5%5%20%
1575
16th to endDay
19%10%5%8%6%34446%26%
1469
March1st to 15thDay
16%9%46%7%35%5%5%6%29%
1953
16th to endDay
16%8%25%5%23435%40%
2123
April1st to 15thDay
19%6%36%5%2435%6%33%
2152
16th to endDay
17%5%25%5%24446%40%
2277
May1st to 15thDay
13%6%36%5%35%5%5%7%37%
2436
16th to endDay
12%5%244345%5%8%43%
2618
June1st to 15thDay
16%5%25%5%35%45%9%35%
2520
16th to endDay
12%4245%25%5%5%9%42%
2520
July1st to 15thDay
7%224435%46%10%47%
2520
16th to endDay
8%3245%26%7%7%10%41%
2608
August1st to 15thDay
7%4245%35%5%6%8%44%
2340
16th to endDay
11%41432446%10%47%
2384
September1st to 15thDay
13%42342445%7%45%
2160
16th to endDay
12%5%2442445%6%45%
1811
October1st to 15thDay
18%6%35%5%34447%35%
1650
16th to endDay
23%8%26%5%3345%6%28%
1759
November1st to 15thDay
13%7%36%6%4445%6%35%
1473
16th to endDay
19%11%46%6%35%5%36%26%
1440
December1st to 15thDay
18%15%6%7%6%35%446%20%
1440
16th to endDay
21%13%6%7%7%35%446%18%
1536
January1st to 15thNight
22%14%5%7%6%34346%21%
2506
16th to endNight
15%14%6%8%7%35%445%23%
2522
February1st to 15thNight
15%14%6%8%6%35%446%23%
2278
16th to endNight
16%9%47%7%445%5%5%29%
2003
March1st to 15thNight
20%8%36%6%44346%32%
2004
16th to endNight
15%6%36%423345%44%
2099
April1st to 15thNight
20%7%25%424446%36%
1796
16th to endNight
15%6%1442345%6%44%
1692
May1st to 15thNight
15%5%25%5%36%5%6%6%36%
1514
16th to endNight
12%426%424447%46%
1495
June1st to 15thNight
12%7%35%4345%6%8%38%
1440
16th to endNight
12%425%5%3446%9%42%
1440
July1st to 15thNight
5%3145%335%5%9%52%
1440
16th to endNight
8%5%14425%46%8%48%
1558
August1st to 15thNight
8%4245%3446%9%47%
1620
16th to endNight
7%424424447%52%
1806
September1st to 15thNight
14%41442435%6%47%
1800
16th to endNight
16%424423336%48%
1836
October1st to 15thNight
20%6%25%5%24446%37%
1980
16th to endNight
21%8%36%435%45%6%29%
2112
November1st to 15thNight
16%6%25%5%3445%7%37%
2382
16th to endNight
24%9%45%435%447%26%
2520
December1st to 15thNight
22%13%46%6%35%5%46%21%
2520
16th to endNight
21%14%5%8%6%35%45%5%18%
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
60%9%12%12%5%
1433
16th to endDay
65%9%8%10%5%
1701
February1st to 15thDay
63%9%10%13%3
1577
16th to endDay
59%6%10%13%8%
1469
March1st to 15thDay
54%6%14%16%6%1
1953
16th to endDay
45%5%9%21%15%2
2124
April1st to 15thDay
50%5%10%19%12%1
2152
16th to endDay
44%410%21%16%2
2277
May1st to 15thDay
44%8%11%20%13%1
2436
16th to endDay
39%7%16%22%12%1
2622
June1st to 15thDay
45%5%15%22%10%
2520
16th to endDay
37%8%17%21%14%
2520
July1st to 15thDay
29%8%13%31%15%
2371
16th to endDay
35%9%17%26%9%
2444
August1st to 15thDay
35%10%17%22%13%1
2327
16th to endDay
32%7%16%29%12%1
2384
September1st to 15thDay
36%8%15%26%12%
2160
16th to endDay
36%9%13%28%11%
1811
October1st to 15thDay
48%7%12%21%9%1
1650
16th to endDay
55%8%15%13%5%
1759
November1st to 15thDay
47%9%15%16%9%1
1473
16th to endDay
58%8%13%12%6%
1440
December1st to 15thDay
62%10%14%9%2
1440
16th to endDay
65%8%10%11%3
1536
January1st to 15thNight
64%7%12%11%3
2506
16th to endNight
62%8%9%13%6%
2522
February1st to 15thNight
62%7%11%13%4
2287
16th to endNight
54%8%12%17%7%
2003
March1st to 15thNight
54%5%11%19%8%
2004
16th to endNight
43%5%8%22%17%2
2099
April1st to 15thNight
48%6%9%18%15%1
1796
16th to endNight
39%6%11%19%19%3
1692
May1st to 15thNight
45%7%10%18%14%3
1514
16th to endNight
36%5%13%24%16%2
1497
June1st to 15thNight
42%5%13%21%15%1
1440
16th to endNight
38%7%14%21%16%1
1440
July1st to 15thNight
27%8%11%27%24%
1360
16th to endNight
31%7%13%26%17%2
1459
August1st to 15thNight
32%8%17%27%13%1
1609
16th to endNight
30%7%14%31%16%
1806
September1st to 15thNight
36%7%14%25%13%1
1800
16th to endNight
38%5%9%30%15%
1836
October1st to 15thNight
48%6%10%21%12%
1980
16th to endNight
54%9%13%14%7%
2112
November1st to 15thNight
45%9%12%18%12%1
2382
16th to endNight
56%9%14%14%5%
2520
December1st to 15thNight
61%11%13%11%3
2520
16th to endNight
65%9%11%9%4
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
18%21%38%15%33
60
16th to endDay
25%14%34%23%3
91
February1st to 15thDay
15%24%48%10%1
90
16th to endDay
29%18%29%18%3
128
March1st to 15thDay
21%21%28%22%5%
270
16th to endDay
23%16%28%23%6%1
288
April1st to 15thDay
21%17%29%22%8%1
270
16th to endDay
17%14%29%23%9%4
270
May1st to 15thDay
22%13%22%24%10%5%
288
16th to endDay
15%10%24%30%15%3
331
June1st to 15thDay
17%13%18%31%16%1
315
16th to endDay
17%10%18%32%16%5%
315
July1st to 15thDay
8%7%12%34%27%8%
305
16th to endDay
8%11%18%35%19%6%
326
August1st to 15thDay
8%6%13%32%29%9%
313
16th to endDay
11%6%14%27%29%10%
332
September1st to 15thDay
11%7%19%24%25%12%
315
16th to endDay
15%9%19%28%19%8%
257
October1st to 15thDay
16%11%24%25%16%4
255
16th to endDay
23%16%31%22%5%
271
November1st to 15thDay
14%12%29%28%12%2
127
16th to endDay
28%8%18%33%11%
60
December1st to 15thDay
13%26%31%21%5%1
60
16th to endDay
32%26%34%6%
64
January1st to 15thNight
21%30%29%13%5%
720
16th to endNight
18%26%29%20%3
768
February1st to 15thNight
19%25%35%16%2
704
16th to endNight
19%23%29%21%5%
631
March1st to 15thNight
21%24%26%23%4
720
16th to endNight
18%20%27%23%8%1
768
April1st to 15thNight
20%21%26%23%7%
718
16th to endNight
14%22%25%23%12%1
612
May1st to 15thNight
18%19%16%29%14%2
434
16th to endNight
12%18%19%30%18%
375
June1st to 15thNight
14%18%21%29%14%2
360
16th to endNight
11%17%15%34%20%
360
July1st to 15thNight
5%12%15%40%22%2
340
16th to endNight
7%16%14%36%21%1
420
August1st to 15thNight
9%10%10%35%28%4
539
16th to endNight
9%10%14%30%30%4
660
September1st to 15thNight
13%10%16%27%26%5%
720
16th to endNight
15%12%15%24%24%7%
661
October1st to 15thNight
22%14%23%22%15%2
660
16th to endNight
23%17%31%22%5%
704
November1st to 15thNight
15%20%24%25%11%2
700
16th to endNight
23%26%25%17%6%
720
December1st to 15thNight
26%27%28%13%3
720
16th to endNight
25%25%30%14%3
768
Page generated at 2017-09-17 12:05:40. Version ac04

Copyright 2017 A. Danko


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