Tobermory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tobermory 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%
15125
10%
46408
8%
15084
36%
15084
14%
35338

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
9%
898
1%
2616
0%
895
9%
895
3%
2429
January16th to endNight
16%
859
5%
2587
2%
859
19%
859
5%
2310
February1st to 15thNight
16%
702
5%
2287
2%
701
20%
701
7%
1942
February16th to endNight
26%
631
9%
1964
4%
631
31%
631
10%
1585
March1st to 15thNight
27%
720
12%
2039
7%
720
32%
720
17%
1515
March16th to endNight
40%
768
19%
2112
11%
768
45%
768
24%
1470
April1st to 15thNight
34%
638
16%
1788
7%
638
39%
638
22%
1249
April16th to endNight
40%
540
18%
1620
11%
540
45%
540
23%
1100
May1st to 15thNight
50%
537
13%
1617
13%
537
52%
537
21%
1113
May16th to endNight
54%
375
14%
1470
17%
374
59%
374
22%
857
June1st to 15thNight
53%
360
13%
1260
14%
360
58%
360
23%
784
June16th to endNight
64%
360
12%
1260
14%
360
66%
360
26%
773
July1st to 15thNight
69%
340
17%
1190
20%
340
70%
340
33%
646
July16th to endNight
66%
535
15%
1465
16%
502
66%
502
33%
888
August1st to 15thNight
63%
527
18%
1575
16%
524
66%
524
32%
945
August16th to endNight
60%
525
18%
1575
13%
525
63%
525
31%
969
September1st to 15thNight
52%
641
14%
1713
9%
641
54%
641
26%
1177
September16th to endNight
49%
657
17%
1815
12%
657
51%
657
25%
1227
October1st to 15thNight
36%
660
12%
1954
10%
660
39%
660
16%
1477
October16th to endNight
21%
704
8%
2179
4%
704
26%
704
9%
1800
November1st to 15thNight
24%
700
12%
2354
12%
700
28%
700
11%
1863
November16th to endNight
17%
720
4%
2520
4%
720
19%
720
5%
2181
December1st to 15thNight
8%
768
1%
2568
0%
768
9%
768
2%
2376
December16th to endNight
8%
960
2%
2880
0%
960
9%
960
3%
2662

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
15%9%37%5%3445%6%34%
47559
Night
17%12%5%8%6%34345%27%
46575
Cloud CoverDay
15%9%36%5%34446%34%
47569
Night
17%12%48%6%34445%27%
46579
TransparencyDay
49%6%12%19%9%
47244
Night
58%6%10%15%8%
46408
SeeingDay
18%321%31%19%4
5706
Night
23%8%25%25%14%2
15129

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%20%7%13%8%5%5%4237%
1320
16th to endDay
16%20%7%13%10%5%5%5%428%
1635
February1st to 15thDay
13%17%7%13%10%5%5%34415%
1575
16th to endDay
14%14%7%8%8%36%5%45%20%
1506
March1st to 15thDay
13%9%37%7%3445%7%33%
1909
16th to endDay
13%7%37%5%245%46%38%
2112
April1st to 15thDay
20%8%26%424437%35%
2170
16th to endDay
17%7%2342335%7%41%
2340
May1st to 15thDay
18%7%24434446%39%
2331
16th to endDay
12%5%1432445%8%47%
2643
June1st to 15thDay
13%5%26%5%25%5%6%7%40%
2700
16th to endDay
10%5%35%5%35%47%9%39%
2700
July1st to 15thDay
7%42443445%7%51%
2700
16th to endDay
8%4133245%6%9%48%
2595
August1st to 15thDay
10%5%1342436%8%49%
2288
16th to endDay
9%6%245%2445%7%46%
2275
September1st to 15thDay
15%5%25%5%2435%7%43%
1903
16th to endDay
17%5%25%334448%39%
1815
October1st to 15thDay
22%8%37%434346%31%
1675
16th to endDay
29%11%49%5%34345%18%
1691
November1st to 15thDay
20%13%48%5%35%6%45%21%
1503
16th to endDay
24%20%7%10%6%3434411%
1440
December1st to 15thDay
20%22%10%14%9%333326%
1389
16th to endDay
20%24%10%15%7%242335%
1344
January1st to 15thNight
20%21%8%15%11%342226%
2616
16th to endNight
16%18%9%14%10%45%22310%
2587
February1st to 15thNight
14%18%8%14%9%5%333314%
2285
16th to endNight
14%14%7%11%8%35%44419%
1964
March1st to 15thNight
16%11%47%6%33445%31%
2027
16th to endNight
14%7%46%5%34446%39%
2112
April1st to 15thNight
22%8%25%323446%35%
1788
16th to endNight
19%6%25%43445%6%37%
1620
May1st to 15thNight
15%8%36%5%45%45%6%35%
1617
16th to endNight
11%5%35%5%3445%7%43%
1468
June1st to 15thNight
11%7%35%6%2446%8%39%
1260
16th to endNight
9%5%25%435%5%5%8%42%
1260
July1st to 15thNight
7%4245%2435%8%51%
1260
16th to endNight
8%4144245%5%9%49%
1567
August1st to 15thNight
8%5%1442436%8%49%
1586
16th to endNight
9%5%25%425%46%6%46%
1575
September1st to 15thNight
16%425%4345%5%6%40%
1713
16th to endNight
17%6%245%2445%6%40%
1815
October1st to 15thNight
24%9%37%6%34345%29%
1954
16th to endNight
29%12%47%5%24346%18%
2179
November1st to 15thNight
20%16%5%8%6%24445%21%
2354
16th to endNight
26%18%6%9%7%2433413%
2520
December1st to 15thNight
25%22%8%14%7%222227%
2568
16th to endNight
24%24%9%12%6%242226%
2880

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%19%8%14%9%45%4438%
1320
16th to endDay
15%18%8%11%11%6%5%5%4310%
1635
February1st to 15thDay
12%16%8%12%9%45%43417%
1575
16th to endDay
13%13%6%10%7%36%445%24%
1506
March1st to 15thDay
14%8%46%5%46%45%7%33%
1920
16th to endDay
12%8%37%5%2445%6%38%
2111
April1st to 15thDay
19%8%25%5%34446%36%
2170
16th to endDay
17%7%24323447%41%
2340
May1st to 15thDay
17%7%2443335%6%39%
2331
16th to endDay
12%424324448%48%
2643
June1st to 15thDay
12%5%24435%5%6%8%40%
2700
16th to endDay
11%5%25%435%5%5%9%41%
2700
July1st to 15thDay
7%4244245%5%8%51%
2700
16th to endDay
8%4234245%6%9%50%
2595
August1st to 15thDay
10%41342345%8%50%
2288
16th to endDay
10%5%25%5%2345%7%46%
2275
September1st to 15thDay
14%5%25%5%2435%6%43%
1903
16th to endDay
18%5%24334448%39%
1815
October1st to 15thDay
21%10%36%5%34345%31%
1675
16th to endDay
28%12%47%5%4443419%
1691
November1st to 15thDay
20%12%47%6%35%5%35%23%
1503
16th to endDay
22%20%6%10%7%3433312%
1440
December1st to 15thDay
20%25%8%13%9%332328%
1389
16th to endDay
20%24%8%13%8%243346%
1344
January1st to 15thNight
20%19%9%14%11%342327%
2616
16th to endNight
15%17%8%14%9%45%33313%
2587
February1st to 15thNight
13%17%8%14%9%4435%315%
2278
16th to endNight
14%14%6%9%7%36%44422%
1964
March1st to 15thNight
17%10%48%5%245%45%32%
2039
16th to endNight
13%8%37%6%34345%40%
2112
April1st to 15thNight
22%8%34423446%36%
1788
16th to endNight
17%8%35%5%24446%36%
1620
May1st to 15thNight
15%8%36%5%36%446%36%
1616
16th to endNight
12%6%25%6%3335%8%43%
1468
June1st to 15thNight
12%6%26%425%45%9%39%
1260
16th to endNight
8%5%35%5%45%6%5%8%43%
1260
July1st to 15thNight
8%314443448%51%
1260
16th to endNight
7%4234345%6%7%49%
1567
August1st to 15thNight
9%42442445%8%49%
1586
16th to endNight
11%5%25%42345%7%47%
1575
September1st to 15thNight
17%5%25%5%245%5%7%39%
1713
16th to endNight
17%6%245%33447%41%
1815
October1st to 15thNight
24%8%37%6%3433428%
1954
16th to endNight
29%12%37%5%24345%19%
2179
November1st to 15thNight
20%16%5%7%5%3335%6%22%
2354
16th to endNight
25%18%5%10%6%3433413%
2520
December1st to 15thNight
24%21%9%14%7%232227%
2568
16th to endNight
24%22%8%12%7%333237%
2880

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
81%7%6%4
1321
16th to endDay
78%8%6%42
1635
February1st to 15thDay
72%5%8%10%2
1577
16th to endDay
64%5%11%13%5%
1506
March1st to 15thDay
49%7%14%18%9%
1920
16th to endDay
45%6%12%19%13%2
2112
April1st to 15thDay
49%410%22%11%1
2170
16th to endDay
41%5%12%23%14%2
2340
May1st to 15thDay
44%5%10%21%15%2
2331
16th to endDay
35%6%15%24%16%1
2647
June1st to 15thDay
40%6%12%27%12%
2700
16th to endDay
38%9%13%25%12%
2700
July1st to 15thDay
29%6%15%29%16%1
2541
16th to endDay
31%9%15%28%14%1
2434
August1st to 15thDay
32%7%18%27%13%
2275
16th to endDay
36%7%16%27%10%
2275
September1st to 15thDay
39%7%16%27%8%
1903
16th to endDay
43%6%15%25%8%
1815
October1st to 15thDay
55%5%11%17%10%
1675
16th to endDay
68%6%12%9%4
1691
November1st to 15thDay
62%8%10%13%5%
1503
16th to endDay
76%5%9%6%2
1440
December1st to 15thDay
83%6%421
1389
16th to endDay
84%46%3
1344
January1st to 15thNight
83%5%5%31
2616
16th to endNight
77%7%6%6%2
2587
February1st to 15thNight
73%5%8%10%2
2287
16th to endNight
65%7%9%11%6%
1964
March1st to 15thNight
53%6%13%18%6%
2039
16th to endNight
46%5%9%19%16%2
2112
April1st to 15thNight
49%48%23%12%1
1788
16th to endNight
47%48%18%18%2
1620
May1st to 15thNight
48%5%9%20%13%2
1617
16th to endNight
39%5%12%22%17%2
1470
June1st to 15thNight
40%6%11%22%17%1
1260
16th to endNight
37%7%15%24%14%
1260
July1st to 15thNight
30%5%13%28%20%2
1190
16th to endNight
32%7%15%25%18%
1465
August1st to 15thNight
33%7%15%27%14%1
1575
16th to endNight
35%6%16%28%11%1
1575
September1st to 15thNight
42%7%14%24%8%1
1713
16th to endNight
43%6%13%26%9%
1815
October1st to 15thNight
57%5%9%17%9%
1954
16th to endNight
66%8%9%11%4
2179
November1st to 15thNight
62%7%10%14%4
2354
16th to endNight
74%7%10%5%1
2520
December1st to 15thNight
85%45%31
2568
16th to endNight
83%46%31
2880

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
25%8%36%25%4
71
16th to endDay
40%125%23%8%1
96
February1st to 15thDay
33%8%34%22%1
90
16th to endDay
24%11%28%32%3
81
March1st to 15thDay
20%7%33%29%7%
210
16th to endDay
22%325%32%11%3
288
April1st to 15thDay
25%326%31%11%2
270
16th to endDay
21%5%27%27%12%5%
270
May1st to 15thDay
23%219%29%21%4
288
16th to endDay
15%316%35%23%5%
356
June1st to 15thDay
15%118%37%21%4
495
16th to endDay
14%17%37%26%4
495
July1st to 15thDay
9%113%43%24%7%
475
16th to endDay
13%15%34%29%5%
428
August1st to 15thDay
14%15%28%31%9%
297
16th to endDay
14%214%30%29%7%
268
September1st to 15thDay
16%118%26%25%10%
255
16th to endDay
18%121%27%21%8%
254
October1st to 15thDay
24%7%21%29%12%3
255
16th to endDay
30%12%27%20%8%
203
November1st to 15thDay
11%6%32%37%10%1
77
16th to endDay
30%6%40%21%1
60
December1st to 15thDay
31%18%35%10%5%
60
16th to endDay
37%26%29%6%
64
January1st to 15thNight
28%15%31%19%4
900
16th to endNight
22%10%33%24%7%1
859
February1st to 15thNight
22%10%35%24%6%
704
16th to endNight
21%7%30%28%10%
631
March1st to 15thNight
22%8%33%26%8%1
720
16th to endNight
16%429%30%16%2
768
April1st to 15thNight
24%7%28%29%8%1
638
16th to endNight
23%424%27%17%2
540
May1st to 15thNight
19%217%33%22%4
537
16th to endNight
15%216%36%24%4
375
June1st to 15thNight
15%417%36%23%3
360
16th to endNight
11%112%40%28%4
360
July1st to 15thNight
8%214%40%28%6%
340
16th to endNight
10%113%37%32%4
535
August1st to 15thNight
12%114%33%30%6%
527
16th to endNight
13%216%29%31%7%
525
September1st to 15thNight
18%218%27%21%11%
641
16th to endNight
19%419%25%22%8%
657
October1st to 15thNight
28%5%22%24%15%3
660
16th to endNight
35%10%26%21%5%
704
November1st to 15thNight
27%12%29%19%10%1
700
16th to endNight
34%14%25%17%7%
720
December1st to 15thNight
34%16%31%12%5%
768
16th to endNight
34%16%29%14%4
960
Page generated at 2017-08-13 14:16:43. Version ac04

Copyright 2017 A. Danko


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