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

2017-09-12
.

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%
14806
15%
46683
9%
14769
42%
14769
20%
31767

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
15%
718
10%
2464
3%
716
23%
716
9%
1906
January16th to endNight
18%
768
13%
2496
4%
768
28%
768
12%
1889
February1st to 15thNight
16%
701
10%
2287
2%
701
26%
701
12%
1729
February16th to endNight
22%
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
30%
768
20%
2112
10%
768
39%
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
45%
555
27%
1050
May1st to 15thNight
46%
501
17%
1581
12%
501
54%
501
26%
1013
May16th to endNight
47%
374
17%
1497
15%
374
57%
374
26%
833
June1st to 15thNight
45%
360
13%
1440
11%
360
56%
360
22%
843
June16th to endNight
55%
360
15%
1322
16%
360
62%
360
27%
764
July1st to 15thNight
63%
340
17%
1318
23%
340
69%
340
36%
659
July16th to endNight
63%
499
17%
1531
16%
467
65%
467
33%
858
August1st to 15thNight
65%
539
18%
1609
13%
536
69%
536
37%
929
August16th to endNight
61%
618
24%
1764
16%
618
65%
618
35%
1049
September1st to 15thNight
53%
707
21%
1784
10%
707
59%
707
36%
1123
September16th to endNight
55%
657
21%
1831
15%
657
58%
657
33%
1128
October1st to 15thNight
41%
660
19%
1980
15%
660
48%
660
24%
1311
October16th to endNight
25%
704
13%
2112
6%
704
33%
704
16%
1557
November1st to 15thNight
35%
700
19%
2374
15%
700
42%
700
20%
1560
November16th to endNight
27%
720
11%
2520
7%
720
34%
720
14%
1813
December1st to 15thNight
17%
720
8%
2520
3%
720
22%
720
10%
1929
December16th to endNight
12%
768
7%
2688
2%
768
18%
768
8%
2176

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%
47960
Night
14%7%36%5%35%45%6%36%
46864
Cloud CoverDay
14%8%36%6%35%5%5%7%32%
47970
Night
14%8%36%5%3445%6%36%
46868
TransparencyDay
48%5%14%20%10%
47659
Night
47%5%12%21%11%1
46683
SeeingDay
16%8%26%26%14%6%
5462
Night
18%8%30%28%12%1
14812

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
15%15%5%8%7%445%5%6%21%
1471
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
13%6%35%6%34448%39%
2093
16th to endDay
14%5%37%5%3445%8%38%
1799
October1st to 15thDay
18%7%26%6%345%46%33%
1650
16th to endDay
24%10%46%6%3445%6%23%
1760
November1st to 15thDay
12%9%46%5%25%46%9%32%
1481
16th to endDay
16%14%5%7%5%36%45%7%23%
1440
December1st to 15thDay
17%13%7%10%8%25%5%46%17%
1440
16th to endDay
20%13%6%9%6%35%5%6%6%16%
1536
January1st to 15thNight
20%13%47%6%35%5%5%5%21%
2464
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%
1784
16th to endNight
12%424413447%48%
1831
October1st to 15thNight
17%6%26%43435%6%40%
1980
16th to endNight
19%9%27%5%25%6%5%6%28%
2112
November1st to 15thNight
16%6%26%5%35%45%7%36%
2374
16th to endNight
18%9%48%5%35%46%7%26%
2520
December1st to 15thNight
19%12%47%7%245%5%7%22%
2520
16th to endNight
20%13%6%10%6%35%5%5%6%16%
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
17%14%49%8%35%445%22%
1471
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
14%5%25%6%345%48%40%
2093
16th to endDay
13%6%36%5%3435%9%38%
1799
October1st to 15thDay
18%7%35%5%345%5%5%34%
1650
16th to endDay
24%10%46%5%345%5%6%22%
1760
November1st to 15thDay
13%9%36%5%25%45%9%33%
1481
16th to endDay
17%13%48%6%26%45%7%23%
1440
December1st to 15thDay
18%13%5%11%7%35%45%6%17%
1440
16th to endDay
20%12%5%10%6%35%5%5%6%17%
1536
January1st to 15thNight
20%13%6%8%6%345%5%421%
2464
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%47%
1784
16th to endNight
12%5%2441345%7%48%
1831
October1st to 15thNight
16%6%25%5%2445%6%40%
1980
16th to endNight
20%9%37%5%35%5%5%5%29%
2112
November1st to 15thNight
16%7%35%5%35%45%7%37%
2374
16th to endNight
19%10%47%5%35%5%6%6%26%
2520
December1st to 15thNight
19%13%48%5%35%45%5%23%
2520
16th to endNight
20%12%7%9%7%35%45%5%17%
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
63%5%12%13%5%
1472
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%
2093
16th to endDay
41%6%14%27%9%
1799
October1st to 15thDay
48%5%13%20%9%1
1650
16th to endDay
59%6%15%13%4
1760
November1st to 15thDay
47%6%17%19%8%
1481
16th to endDay
58%6%15%15%4
1440
December1st to 15thDay
65%6%14%11%1
1440
16th to endDay
65%7%12%11%2
1536
January1st to 15thNight
63%411%13%6%
2464
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
1784
16th to endNight
34%5%13%32%13%
1831
October1st to 15thNight
44%411%25%13%
1980
16th to endNight
54%5%13%18%7%
2112
November1st to 15thNight
45%5%14%21%12%1
2374
16th to endNight
54%5%17%17%4
2520
December1st to 15thNight
60%6%14%14%3
2520
16th to endNight
67%6%12%11%3
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
14%29%34%10%8%1
67
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
13%319%27%21%15%
299
16th to endDay
18%418%27%21%11%
254
October1st to 15thDay
19%5%30%21%15%6%
255
16th to endDay
27%11%29%23%7%
272
November1st to 15thDay
10%13%30%30%12%3
89
16th to endDay
25%18%26%23%6%
60
December1st to 15thDay
18%16%43%16%5%
60
16th to endDay
29%20%42%7%
64
January1st to 15thNight
26%17%33%17%3
720
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%
707
16th to endNight
14%419%31%26%3
657
October1st to 15thNight
19%5%26%27%17%2
660
16th to endNight
25%10%31%26%4
704
November1st to 15thNight
18%8%32%27%12%1
700
16th to endNight
23%13%29%25%6%
720
December1st to 15thNight
29%12%35%18%3
720
16th to endNight
26%11%37%20%2
768
Page generated at 2017-09-13 07:39:20. Version ac04

Copyright 2017 A. Danko


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