Collingwood
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Collingwood clear sky chart from 2005-11-05 to 2018-03-11.

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
34%
15660
11%
48938
8%
15624
38%
15624
15%
36430

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%
893
3%
2793
1%
892
15%
892
4%
2480
January16th to endNight
19%
832
5%
2704
3%
832
21%
832
5%
2356
February1st to 15thNight
18%
761
5%
2482
1%
761
23%
761
6%
2086
February16th to endNight
25%
683
8%
2171
3%
683
31%
683
10%
1716
March1st to 15thNight
24%
764
11%
2117
6%
764
28%
764
15%
1633
March16th to endNight
38%
768
19%
2112
12%
768
42%
768
21%
1493
April1st to 15thNight
32%
700
14%
1817
6%
700
36%
700
20%
1334
April16th to endNight
42%
540
18%
1620
12%
540
47%
540
22%
1101
May1st to 15thNight
52%
501
16%
1581
15%
501
55%
501
24%
1037
May16th to endNight
53%
374
16%
1497
17%
374
61%
374
25%
838
June1st to 15thNight
50%
360
12%
1364
12%
360
56%
360
21%
839
June16th to endNight
57%
360
14%
1260
17%
360
61%
360
28%
742
July1st to 15thNight
67%
340
18%
1200
23%
340
69%
340
36%
625
July16th to endNight
61%
496
16%
1528
16%
464
63%
464
31%
887
August1st to 15thNight
65%
539
16%
1609
12%
536
68%
536
34%
943
August16th to endNight
62%
597
19%
1743
13%
597
65%
597
30%
1084
September1st to 15thNight
53%
720
17%
1836
10%
720
55%
720
31%
1231
September16th to endNight
55%
717
20%
1986
16%
717
57%
717
28%
1306
October1st to 15thNight
37%
720
14%
2160
12%
720
41%
720
20%
1543
October16th to endNight
23%
768
9%
2313
5%
768
28%
768
10%
1868
November1st to 15thNight
27%
760
12%
2598
11%
760
31%
760
12%
1956
November16th to endNight
21%
780
8%
2730
6%
780
25%
780
7%
2253
December1st to 15thNight
12%
780
2%
2730
1%
780
13%
780
4%
2400
December16th to endNight
9%
907
3%
2987
0%
907
12%
907
3%
2679

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%9%47%6%45%5%5%7%31%
49681
Night
14%9%48%6%35%5%5%6%29%
49109
Cloud CoverDay
13%9%47%6%35%5%5%7%30%
49691
Night
13%9%48%6%45%5%5%7%29%
49113
TransparencyDay
52%5%12%19%9%
49371
Night
56%6%11%16%8%
48938
SeeingDay
18%7%23%27%16%6%
6208
Night
21%10%25%27%13%2
15668

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
14%12%8%13%10%6%8%5%4411%
1470
16th to endDay
9%15%5%13%12%6%8%6%5%410%
1872
February1st to 15thDay
11%14%7%12%11%6%6%5%5%5%13%
1710
16th to endDay
14%14%6%10%9%5%5%436%19%
1584
March1st to 15thDay
12%10%6%9%9%5%445%426%
2069
16th to endDay
12%9%48%6%35%45%5%35%
2112
April1st to 15thDay
16%10%46%5%3445%6%31%
2140
16th to endDay
16%8%35%43345%7%38%
2340
May1st to 15thDay
16%8%25%5%3445%6%37%
2370
16th to endDay
12%6%24425%45%8%42%
2618
June1st to 15thDay
15%425%4345%6%8%38%
2592
16th to endDay
12%5%25%5%35%5%6%8%39%
2700
July1st to 15thDay
10%425%5%35%5%6%8%43%
2688
16th to endDay
10%5%25%5%45%5%5%9%40%
2533
August1st to 15thDay
9%5%15%5%35%5%6%9%41%
2340
16th to endDay
11%425%6%35%5%7%9%38%
2447
September1st to 15thDay
17%6%245%3445%8%36%
2121
16th to endDay
16%5%35%5%3445%7%39%
1974
October1st to 15thDay
18%8%36%6%34448%31%
1800
16th to endDay
24%14%37%5%35%5%5%5%19%
1908
November1st to 15thDay
14%12%48%6%35%45%6%26%
1590
16th to endDay
16%16%7%9%6%36%6%5%6%14%
1560
December1st to 15thDay
13%16%9%12%10%5%446%6%10%
1560
16th to endDay
17%15%8%12%7%46%5%46%10%
1583
January1st to 15thNight
14%14%6%12%10%5%7%5%5%6%12%
2793
16th to endNight
10%11%6%13%11%5%7%7%5%5%13%
2704
February1st to 15thNight
11%14%6%11%10%5%6%5%6%5%16%
2480
16th to endNight
11%10%5%12%9%46%5%6%7%21%
2171
March1st to 15thNight
14%12%5%8%7%35%445%28%
2105
16th to endNight
12%8%5%7%6%34445%38%
2112
April1st to 15thNight
17%9%36%5%44436%34%
1817
16th to endNight
15%8%25%6%35%346%38%
1620
May1st to 15thNight
15%5%245%3445%7%39%
1581
16th to endNight
12%42443445%7%46%
1495
June1st to 15thNight
13%425%5%35%5%48%40%
1364
16th to endNight
10%415%4345%6%8%45%
1260
July1st to 15thNight
7%423324348%55%
1270
16th to endNight
8%314435%5%6%8%48%
1634
August1st to 15thNight
8%3244345%6%8%48%
1620
16th to endNight
9%4145%2445%7%48%
1743
September1st to 15thNight
15%4133235%6%9%43%
1836
16th to endNight
14%5%24424447%44%
1986
October1st to 15thNight
18%5%25%5%45%447%36%
2160
16th to endNight
23%14%35%5%445%6%7%20%
2313
November1st to 15thNight
16%12%46%6%35%5%6%7%25%
2598
16th to endNight
17%14%6%9%6%35%45%6%21%
2730
December1st to 15thNight
15%15%7%11%7%46%5%6%7%13%
2730
16th to endNight
17%14%7%14%9%46%5%5%5%10%
2987

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
14%12%8%12%10%6%9%5%4410%
1470
16th to endDay
9%14%5%14%12%7%8%6%5%5%10%
1872
February1st to 15thDay
11%13%7%13%10%6%6%6%5%5%13%
1710
16th to endDay
14%14%5%10%7%5%5%5%46%19%
1584
March1st to 15thDay
12%9%6%9%9%45%45%5%26%
2080
16th to endDay
12%9%48%6%35%45%5%35%
2111
April1st to 15thDay
16%10%47%5%3445%6%31%
2140
16th to endDay
16%8%45%424447%38%
2340
May1st to 15thDay
16%7%25%5%3445%6%37%
2370
16th to endDay
11%6%245%35%45%8%42%
2618
June1st to 15thDay
15%5%245%25%5%6%7%38%
2592
16th to endDay
12%5%25%5%35%5%6%8%39%
2700
July1st to 15thDay
9%425%5%35%5%6%9%42%
2688
16th to endDay
9%5%35%5%35%5%6%9%39%
2533
August1st to 15thDay
8%5%25%5%346%6%10%41%
2340
16th to endDay
10%5%16%6%35%5%7%9%38%
2447
September1st to 15thDay
16%6%26%5%345%47%36%
2121
16th to endDay
14%5%35%6%245%5%7%39%
1974
October1st to 15thDay
17%8%37%6%345%47%31%
1800
16th to endDay
23%13%48%5%35%5%5%5%19%
1908
November1st to 15thDay
13%14%38%7%35%45%7%25%
1590
16th to endDay
16%15%6%11%7%36%5%5%6%14%
1560
December1st to 15thDay
13%17%9%13%10%445%6%6%9%
1560
16th to endDay
17%15%8%13%8%45%5%46%10%
1583
January1st to 15thNight
14%13%6%12%10%5%6%5%5%7%11%
2793
16th to endNight
11%11%6%13%12%47%7%5%6%12%
2704
February1st to 15thNight
10%13%6%11%10%5%7%6%5%6%15%
2473
16th to endNight
11%10%412%8%46%5%6%6%21%
2171
March1st to 15thNight
14%11%6%9%6%36%44428%
2117
16th to endNight
12%8%47%5%34445%38%
2112
April1st to 15thNight
17%9%36%5%35%345%34%
1817
16th to endNight
14%8%25%6%35%346%38%
1620
May1st to 15thNight
15%5%344345%5%7%39%
1580
16th to endNight
12%41442445%7%46%
1495
June1st to 15thNight
14%4146%346%48%40%
1364
16th to endNight
10%425%425%46%8%45%
1260
July1st to 15thNight
7%42342435%8%55%
1270
16th to endNight
8%3135%35%5%6%8%47%
1634
August1st to 15thNight
7%3134345%6%9%48%
1620
16th to endNight
8%5%145%3445%8%48%
1743
September1st to 15thNight
14%42442345%9%43%
1836
16th to endNight
13%6%2443445%6%44%
1986
October1st to 15thNight
17%6%25%6%35%35%7%35%
2160
16th to endNight
22%12%37%5%45%46%7%20%
2313
November1st to 15thNight
16%11%47%6%45%5%6%8%25%
2598
16th to endNight
17%14%6%9%6%35%5%5%6%19%
2730
December1st to 15thNight
15%15%7%11%8%46%6%6%6%12%
2730
16th to endNight
17%13%7%15%9%5%5%5%5%49%
2987

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
77%6%7%6%1
1471
16th to endDay
75%8%6%7%1
1872
February1st to 15thDay
72%5%8%10%1
1712
16th to endDay
68%310%10%5%
1584
March1st to 15thDay
58%412%16%7%
2080
16th to endDay
49%5%10%18%14%1
2112
April1st to 15thDay
52%410%22%10%
2140
16th to endDay
45%411%22%13%2
2340
May1st to 15thDay
45%411%22%14%1
2370
16th to endDay
39%5%13%24%14%2
2622
June1st to 15thDay
41%6%14%24%12%
2592
16th to endDay
39%6%16%24%12%
2700
July1st to 15thDay
34%6%15%25%15%2
2530
16th to endDay
39%6%14%27%10%1
2376
August1st to 15thDay
36%6%18%23%14%1
2327
16th to endDay
38%7%17%26%9%
2447
September1st to 15thDay
46%415%24%8%
2121
16th to endDay
43%5%14%28%8%
1974
October1st to 15thDay
52%5%11%19%9%1
1800
16th to endDay
66%6%12%10%4
1908
November1st to 15thDay
60%6%12%14%6%
1590
16th to endDay
71%7%11%8%1
1560
December1st to 15thDay
78%5%9%5%
1560
16th to endDay
78%5%8%5%
1583
January1st to 15thNight
76%6%8%6%1
2793
16th to endNight
71%9%9%6%2
2704
February1st to 15thNight
71%6%10%10%1
2482
16th to endNight
63%6%11%12%5%
2171
March1st to 15thNight
60%410%16%7%
2117
16th to endNight
48%5%8%20%15%1
2112
April1st to 15thNight
52%5%9%18%13%
1817
16th to endNight
47%410%18%17%2
1620
May1st to 15thNight
43%5%11%19%16%2
1581
16th to endNight
36%413%28%14%2
1497
June1st to 15thNight
41%6%11%23%16%
1364
16th to endNight
35%6%16%26%15%
1260
July1st to 15thNight
27%5%13%30%21%2
1200
16th to endNight
32%7%14%29%15%1
1528
August1st to 15thNight
30%7%20%26%14%
1609
16th to endNight
36%6%13%28%13%1
1743
September1st to 15thNight
37%8%14%27%12%
1836
16th to endNight
40%6%13%27%11%
1986
October1st to 15thNight
51%5%11%20%10%
2160
16th to endNight
63%7%11%12%4
2313
November1st to 15thNight
58%6%13%14%5%1
2598
16th to endNight
67%7%12%10%1
2730
December1st to 15thNight
77%5%10%41
2730
16th to endNight
80%5%8%5%
2987

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
17%16%40%19%7%
99
16th to endDay
34%7%29%23%4
144
February1st to 15thDay
22%13%48%15%
135
16th to endDay
23%16%35%24%
120
March1st to 15thDay
18%11%34%26%8%1
296
16th to endDay
21%7%28%26%13%2
288
April1st to 15thDay
22%7%32%23%11%2
270
16th to endDay
21%10%22%23%14%7%
270
May1st to 15thDay
21%6%18%26%18%7%
288
16th to endDay
13%424%29%19%8%
331
June1st to 15thDay
16%6%23%26%22%4
387
16th to endDay
13%320%38%18%5%
495
July1st to 15thDay
11%417%33%23%9%
464
16th to endDay
10%216%34%23%11%
326
August1st to 15thDay
11%114%29%25%17%
313
16th to endDay
11%414%29%28%11%
332
September1st to 15thDay
16%316%23%24%15%
315
16th to endDay
17%6%13%24%24%13%
314
October1st to 15thDay
23%5%22%26%16%4
315
16th to endDay
33%15%22%21%6%
324
November1st to 15thDay
23%11%21%29%11%2
106
16th to endDay
36%14%36%11%1
90
December1st to 15thDay
18%27%31%16%5%
90
16th to endDay
23%22%41%10%1
96
January1st to 15thNight
24%18%31%18%6%
897
16th to endNight
20%12%32%27%6%1
832
February1st to 15thNight
20%13%35%23%5%
764
16th to endNight
21%10%32%27%7%
683
March1st to 15thNight
21%12%32%25%7%
764
16th to endNight
18%8%26%30%14%2
768
April1st to 15thNight
25%8%27%30%8%
700
16th to endNight
20%8%21%30%17%1
540
May1st to 15thNight
17%317%38%19%3
501
16th to endNight
14%321%37%22%
375
June1st to 15thNight
15%6%16%36%22%1
360
16th to endNight
12%216%41%24%2
360
July1st to 15thNight
8%213%43%27%3
340
16th to endNight
7%319%39%27%2
496
August1st to 15thNight
11%213%39%29%4
539
16th to endNight
13%313%34%30%4
597
September1st to 15thNight
20%216%31%20%9%
720
16th to endNight
17%5%14%32%22%7%
717
October1st to 15thNight
25%6%24%28%12%2
720
16th to endNight
35%14%22%21%5%
768
November1st to 15thNight
27%12%25%21%11%1
760
16th to endNight
29%18%25%19%6%
780
December1st to 15thNight
29%17%33%15%3
780
16th to endNight
28%16%33%17%3
907
Page generated at 2018-03-12 13:28:11. Version ac04

Copyright 2018 A. Danko


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