Brampton BrightSkies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brampton BrightSkies Observatory clear sky chart from 2005-11-05 to 2018-01-12.

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
35%
15292
15%
48259
9%
15255
42%
15255
20%
32841

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
16%
763
10%
2620
3%
761
24%
761
9%
2015
January16th to endNight
18%
768
13%
2496
4%
768
27%
768
12%
1889
February1st to 15thNight
16%
701
10%
2287
2%
701
26%
701
12%
1729
February16th to endNight
21%
631
13%
2012
4%
631
32%
631
15%
1448
March1st to 15thNight
23%
720
14%
1980
6%
720
30%
720
17%
1454
March16th to endNight
31%
768
20%
2112
10%
768
40%
768
24%
1440
April1st to 15thNight
26%
718
15%
1826
5%
718
32%
718
23%
1306
April16th to endNight
36%
555
20%
1635
8%
555
46%
555
27%
1050
May1st to 15thNight
45%
501
17%
1581
12%
501
53%
501
26%
1013
May16th to endNight
47%
374
17%
1497
15%
374
57%
374
26%
833
June1st to 15thNight
46%
360
13%
1440
11%
360
57%
360
22%
843
June16th to endNight
56%
360
15%
1322
16%
360
63%
360
27%
764
July1st to 15thNight
65%
340
17%
1318
23%
340
70%
340
36%
659
July16th to endNight
63%
499
17%
1531
16%
467
66%
467
33%
858
August1st to 15thNight
66%
539
18%
1609
13%
536
69%
536
37%
929
August16th to endNight
61%
618
24%
1764
16%
618
64%
618
35%
1049
September1st to 15thNight
54%
720
22%
1818
10%
720
60%
720
36%
1142
September16th to endNight
56%
717
24%
1998
17%
717
60%
717
34%
1222
October1st to 15thNight
40%
720
18%
2160
14%
720
47%
720
24%
1432
October16th to endNight
26%
768
14%
2304
8%
768
34%
768
17%
1679
November1st to 15thNight
34%
760
18%
2577
14%
760
41%
760
19%
1719
November16th to endNight
26%
780
12%
2730
6%
780
34%
780
14%
1951
December1st to 15thNight
16%
780
8%
2730
3%
780
22%
780
10%
2085
December16th to endNight
12%
832
7%
2912
2%
832
19%
832
8%
2332

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
13%8%36%6%35%5%5%7%32%
49062
Night
14%7%36%5%35%45%6%36%
48440
Cloud CoverDay
14%8%36%6%35%5%5%7%32%
49072
Night
14%8%36%5%3445%6%36%
48444
TransparencyDay
48%5%13%20%10%
48761
Night
47%5%12%21%11%1
48259
SeeingDay
16%8%27%26%14%6%
5813
Night
18%8%30%28%12%1
15298

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%14%5%8%7%445%5%6%20%
1559
16th to endDay
11%16%7%10%9%46%5%5%6%17%
1728
February1st to 15thDay
13%13%6%10%9%45%446%20%
1575
16th to endDay
17%13%38%6%34447%26%
1460
March1st to 15thDay
14%8%5%8%8%36%45%5%29%
1969
16th to endDay
14%8%47%6%25%45%5%35%
2112
April1st to 15thDay
18%8%36%5%2445%6%31%
2122
16th to endDay
17%8%25%5%34346%39%
2335
May1st to 15thDay
16%6%25%7%35%45%7%35%
2370
16th to endDay
10%6%25%5%35%5%5%7%41%
2618
June1st to 15thDay
14%6%25%5%3446%8%38%
2520
16th to endDay
12%425%6%35%5%6%9%37%
2631
July1st to 15thDay
7%425%6%46%6%7%8%40%
2556
16th to endDay
9%5%25%6%36%5%7%9%36%
2528
August1st to 15thDay
7%5%35%5%47%6%7%8%38%
2340
16th to endDay
9%6%26%5%35%5%6%9%39%
2426
September1st to 15thDay
12%6%25%6%34448%40%
2139
16th to endDay
13%5%37%5%3345%8%40%
1962
October1st to 15thDay
19%7%26%6%345%46%33%
1800
16th to endDay
23%10%36%6%3445%6%24%
1920
November1st to 15thDay
13%9%46%5%25%5%5%8%31%
1608
16th to endDay
15%13%5%7%5%36%46%7%23%
1560
December1st to 15thDay
16%13%7%11%8%25%5%46%18%
1560
16th to endDay
19%12%6%9%6%35%5%6%7%17%
1664
January1st to 15thNight
19%13%48%6%35%5%5%5%22%
2620
16th to endNight
12%11%6%10%8%45%5%5%6%24%
2496
February1st to 15thNight
13%11%48%8%45%6%5%6%26%
2285
16th to endNight
12%10%5%7%8%46%5%47%27%
2012
March1st to 15thNight
17%7%46%6%35%45%6%31%
1968
16th to endNight
14%8%35%5%34335%42%
2112
April1st to 15thNight
17%7%26%5%25%5%5%6%35%
1826
16th to endNight
12%6%25%5%24446%43%
1635
May1st to 15thNight
15%4245%35%45%7%40%
1581
16th to endNight
11%425%324447%49%
1495
June1st to 15thNight
12%435%435%5%5%9%42%
1440
16th to endNight
9%424425%46%8%46%
1322
July1st to 15thNight
5%21332435%7%57%
1398
16th to endNight
7%3244346%5%8%49%
1637
August1st to 15thNight
6%3145%2446%8%52%
1620
16th to endNight
8%324424446%53%
1764
September1st to 15thNight
11%32342446%7%48%
1818
16th to endNight
11%424413447%49%
1998
October1st to 15thNight
17%6%26%43435%5%40%
2160
16th to endNight
18%8%27%5%35%5%5%6%30%
2304
November1st to 15thNight
16%7%26%5%35%45%7%35%
2577
16th to endNight
18%9%47%5%35%46%7%27%
2730
December1st to 15thNight
19%12%48%7%345%5%7%22%
2730
16th to endNight
19%13%6%10%6%345%46%18%
2912

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
16%13%49%8%35%5%5%5%21%
1559
16th to endDay
12%15%6%11%8%46%5%5%5%17%
1728
February1st to 15thDay
14%13%6%10%9%4445%5%20%
1575
16th to endDay
17%12%48%7%2445%6%27%
1460
March1st to 15thDay
15%8%5%8%6%4445%6%28%
1980
16th to endDay
15%9%47%5%35%35%5%34%
2111
April1st to 15thDay
18%9%46%5%3445%6%31%
2122
16th to endDay
17%8%26%5%24345%39%
2335
May1st to 15thDay
15%6%25%6%345%47%35%
2370
16th to endDay
11%5%25%5%25%6%5%7%41%
2618
June1st to 15thDay
14%5%25%5%35%46%8%38%
2520
16th to endDay
11%5%246%45%5%6%10%36%
2631
July1st to 15thDay
7%425%5%35%7%7%9%40%
2556
16th to endDay
9%436%6%46%6%7%9%36%
2528
August1st to 15thDay
7%5%26%6%45%7%7%8%38%
2340
16th to endDay
9%5%26%6%35%5%5%9%40%
2426
September1st to 15thDay
13%5%25%6%345%48%40%
2139
16th to endDay
12%5%35%5%3435%8%40%
1962
October1st to 15thDay
19%7%35%5%3445%6%34%
1800
16th to endDay
23%10%36%5%345%5%6%23%
1920
November1st to 15thDay
14%10%36%5%25%45%8%32%
1608
16th to endDay
16%13%47%5%36%45%7%24%
1560
December1st to 15thDay
17%13%5%12%7%35%45%6%19%
1560
16th to endDay
20%12%5%10%6%35%5%5%6%17%
1664
January1st to 15thNight
20%12%6%8%6%345%5%5%22%
2620
16th to endNight
14%11%6%9%8%35%5%46%24%
2496
February1st to 15thNight
12%12%5%9%7%45%5%5%5%25%
2278
16th to endNight
13%11%48%7%45%45%6%28%
2012
March1st to 15thNight
18%8%37%6%3445%7%30%
1980
16th to endNight
14%8%46%42423442%
2112
April1st to 15thNight
17%7%35%5%35%35%6%35%
1826
16th to endNight
12%6%35%424446%43%
1635
May1st to 15thNight
15%4245%345%5%7%40%
1580
16th to endNight
12%4235%2445%6%48%
1495
June1st to 15thNight
12%4344345%5%9%42%
1440
16th to endNight
9%5%245%2446%8%45%
1322
July1st to 15thNight
6%21342445%8%56%
1398
16th to endNight
7%3244346%5%8%49%
1637
August1st to 15thNight
7%2145%3446%7%51%
1620
16th to endNight
8%324435%445%53%
1764
September1st to 15thNight
11%3244245%6%6%48%
1818
16th to endNight
11%5%245%13447%49%
1998
October1st to 15thNight
17%6%25%5%2345%6%40%
2160
16th to endNight
19%8%37%5%35%5%5%5%30%
2304
November1st to 15thNight
16%7%35%5%35%45%7%36%
2577
16th to endNight
18%10%46%5%35%46%6%27%
2730
December1st to 15thNight
19%13%48%6%35%45%6%23%
2730
16th to endNight
20%13%7%9%7%3445%5%18%
2912

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
62%5%12%13%6%
1560
16th to endDay
66%5%9%12%5%
1728
February1st to 15thDay
64%412%14%3
1577
16th to endDay
56%5%13%15%7%1
1460
March1st to 15thDay
56%413%17%8%
1980
16th to endDay
50%310%20%13%1
2112
April1st to 15thDay
52%411%19%11%
2122
16th to endDay
47%310%21%14%2
2335
May1st to 15thDay
46%5%12%22%12%
2370
16th to endDay
40%6%15%22%14%1
2622
June1st to 15thDay
41%5%13%25%12%
2520
16th to endDay
39%7%16%23%13%
2631
July1st to 15thDay
35%6%14%24%16%2
2407
16th to endDay
40%7%15%22%11%2
2371
August1st to 15thDay
38%7%17%20%14%1
2327
16th to endDay
37%6%16%27%10%
2426
September1st to 15thDay
41%6%15%24%11%
2139
16th to endDay
40%6%14%28%9%
1962
October1st to 15thDay
49%5%13%20%9%1
1800
16th to endDay
58%6%15%14%4
1920
November1st to 15thDay
49%6%16%19%7%
1608
16th to endDay
57%6%16%15%4
1560
December1st to 15thDay
64%5%14%12%2
1560
16th to endDay
64%7%12%12%3
1664
January1st to 15thNight
62%5%11%13%6%
2620
16th to endNight
59%5%12%16%5%
2496
February1st to 15thNight
58%6%11%17%6%
2287
16th to endNight
55%314%18%7%
2012
March1st to 15thNight
53%5%12%20%7%
1980
16th to endNight
45%49%22%16%2
2112
April1st to 15thNight
48%5%10%19%14%
1826
16th to endNight
40%411%21%17%3
1635
May1st to 15thNight
40%6%11%23%15%1
1581
16th to endNight
35%5%13%26%15%3
1497
June1st to 15thNight
38%6%12%23%17%1
1440
16th to endNight
35%6%12%26%17%1
1322
July1st to 15thNight
25%5%11%27%25%2
1318
16th to endNight
31%5%15%26%17%3
1531
August1st to 15thNight
29%6%17%30%13%2
1609
16th to endNight
32%5%10%31%18%1
1764
September1st to 15thNight
33%5%15%28%15%1
1818
16th to endNight
33%5%12%33%13%
1998
October1st to 15thNight
44%411%24%13%
2160
16th to endNight
53%5%13%19%7%
2304
November1st to 15thNight
46%5%13%20%11%1
2577
16th to endNight
54%5%17%17%4
2730
December1st to 15thNight
60%6%14%14%4
2730
16th to endNight
65%6%11%11%4
2912

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
14%26%33%16%6%1
89
16th to endDay
33%25%25%16%
96
February1st to 15thDay
18%26%41%10%3
90
16th to endDay
22%13%44%17%2
86
March1st to 15thDay
21%14%31%24%8%
270
16th to endDay
23%10%31%23%8%2
288
April1st to 15thDay
20%13%33%24%7%
270
16th to endDay
19%10%30%22%11%5%
270
May1st to 15thDay
20%326%26%13%8%
288
16th to endDay
14%6%29%26%17%5%
331
June1st to 15thDay
16%6%22%33%18%2
315
16th to endDay
14%6%27%32%15%3
426
July1st to 15thDay
8%421%36%19%9%
341
16th to endDay
7%224%35%20%8%
326
August1st to 15thDay
7%219%30%23%15%
313
16th to endDay
13%416%26%20%18%
332
September1st to 15thDay
12%218%26%22%16%
315
16th to endDay
15%417%23%24%15%
314
October1st to 15thDay
21%6%30%20%14%6%
315
16th to endDay
25%11%29%23%8%
336
November1st to 15thDay
19%12%30%23%10%2
126
16th to endDay
22%16%35%20%5%
90
December1st to 15thDay
16%20%41%18%3
90
16th to endDay
28%16%43%10%1
96
January1st to 15thNight
26%17%34%17%4
765
16th to endNight
20%11%38%23%6%
768
February1st to 15thNight
20%15%39%19%4
704
16th to endNight
20%13%36%24%5%
631
March1st to 15thNight
23%11%37%24%4
720
16th to endNight
19%10%32%27%9%
768
April1st to 15thNight
22%8%37%26%5%
718
16th to endNight
14%8%33%31%10%1
555
May1st to 15thNight
16%425%34%17%1
501
16th to endNight
12%429%32%20%
375
June1st to 15thNight
13%5%28%35%17%
360
16th to endNight
9%223%45%18%
360
July1st to 15thNight
7%220%46%23%
340
16th to endNight
8%218%46%22%2
499
August1st to 15thNight
7%115%44%27%3
539
16th to endNight
10%118%35%29%3
618
September1st to 15thNight
13%5%21%29%24%5%
720
16th to endNight
13%418%30%28%5%
717
October1st to 15thNight
20%5%26%27%17%2
720
16th to endNight
24%11%31%27%5%
768
November1st to 15thNight
19%8%31%27%12%1
760
16th to endNight
23%13%30%25%6%
780
December1st to 15thNight
29%13%36%17%3
780
16th to endNight
26%12%38%19%2
832
Page generated at 2018-01-12 22:01:30. Version ac04

Copyright 2018 A. Danko


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