Maple Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Maple Ridge 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
30%
15487
12%
46756
7%
15446
35%
15446
17%
33599

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
14%
899
7%
2524
1%
895
19%
895
8%
2110
January16th to endNight
17%
948
9%
2676
2%
948
23%
948
11%
2129
February1st to 15thNight
12%
701
8%
2287
2%
701
18%
701
9%
1801
February16th to endNight
21%
631
9%
1898
3%
631
27%
631
10%
1499
March1st to 15thNight
23%
720
14%
2089
6%
720
30%
720
17%
1504
March16th to endNight
30%
768
19%
2112
10%
768
37%
768
24%
1441
April1st to 15thNight
24%
565
16%
1768
7%
565
33%
565
19%
1215
April16th to endNight
33%
540
19%
1620
10%
540
42%
540
23%
1091
May1st to 15thNight
33%
540
13%
1620
7%
540
40%
540
20%
1131
May16th to endNight
43%
468
16%
1473
10%
467
51%
467
25%
902
June1st to 15thNight
41%
360
13%
1260
10%
360
48%
360
23%
778
June16th to endNight
44%
360
12%
1260
10%
360
49%
360
26%
755
July1st to 15thNight
55%
416
15%
1266
12%
416
59%
416
36%
721
July16th to endNight
54%
564
15%
1423
10%
531
57%
531
36%
881
August1st to 15thNight
57%
539
18%
1609
12%
536
62%
536
35%
930
August16th to endNight
56%
573
20%
1719
12%
573
62%
573
33%
1030
September1st to 15thNight
48%
636
17%
1863
11%
636
52%
636
31%
1153
September16th to endNight
44%
657
16%
1815
9%
657
48%
657
28%
1202
October1st to 15thNight
35%
660
16%
1908
10%
660
42%
660
23%
1316
October16th to endNight
22%
704
9%
2241
6%
704
27%
704
12%
1704
November1st to 15thNight
25%
700
14%
2276
12%
700
31%
700
15%
1644
November16th to endNight
18%
720
8%
2511
4%
720
24%
720
8%
2024
December1st to 15thNight
13%
858
5%
2658
1%
858
17%
858
8%
2171
December16th to endNight
11%
960
6%
2880
2%
960
16%
960
7%
2467

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%6%35%45%7%31%
47908
Night
15%9%47%6%3445%6%31%
46923
Cloud CoverDay
15%9%36%6%35%45%7%32%
47918
Night
15%9%47%6%3445%6%31%
46927
TransparencyDay
51%5%12%19%9%1
47594
Night
51%6%12%19%8%
46756
SeeingDay
17%12%32%23%10%4
5920
Night
19%11%32%25%10%1
15492

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
17%15%7%11%8%45%435%14%
1411
16th to endDay
13%15%7%13%11%6%6%436%11%
1548
February1st to 15thDay
13%15%6%10%10%48%445%17%
1575
16th to endDay
12%16%6%10%8%5%5%5%45%19%
1572
March1st to 15thDay
13%10%48%8%45%46%6%28%
1859
16th to endDay
16%8%46%6%3436%6%32%
2112
April1st to 15thDay
19%13%35%5%2345%6%31%
2190
16th to endDay
16%8%3442445%7%37%
2340
May1st to 15thDay
17%6%36%6%35%46%6%34%
2331
16th to endDay
13%5%14435%45%8%41%
2639
June1st to 15thDay
12%6%25%5%35%5%5%8%38%
2700
16th to endDay
13%5%25%5%35%5%5%8%38%
2700
July1st to 15thDay
11%5%245%35%46%8%42%
2615
16th to endDay
9%5%25%4345%7%9%41%
2649
August1st to 15thDay
12%5%24435%5%5%8%41%
2340
16th to endDay
12%6%36%5%346%6%7%37%
2483
September1st to 15thDay
14%5%25%43446%7%41%
2003
16th to endDay
15%6%16%5%345%5%8%36%
1815
October1st to 15thDay
20%8%37%5%24346%32%
1722
16th to endDay
22%15%48%7%345%35%17%
1630
November1st to 15thDay
15%12%47%6%3445%7%28%
1582
16th to endDay
19%16%7%9%8%35%435%16%
1449
December1st to 15thDay
16%14%7%12%9%46%445%14%
1299
16th to endDay
19%17%8%11%6%46%5%4311%
1344
January1st to 15thNight
18%13%6%10%9%45%45%5%15%
2524
16th to endNight
12%12%6%11%9%45%45%6%20%
2676
February1st to 15thNight
12%15%6%10%8%46%45%5%21%
2285
16th to endNight
15%13%5%11%8%35%5%5%6%21%
1898
March1st to 15thNight
14%9%47%6%34445%33%
2077
16th to endNight
13%10%36%423446%39%
2112
April1st to 15thNight
20%10%243245%5%6%33%
1768
16th to endNight
16%7%36%423447%38%
1620
May1st to 15thNight
14%7%35%6%46%5%5%6%34%
1620
16th to endNight
12%5%344245%6%8%43%
1471
June1st to 15thNight
13%5%15%5%345%5%8%40%
1260
16th to endNight
10%424425%5%7%9%42%
1260
July1st to 15thNight
7%313325%5%5%8%51%
1342
16th to endNight
7%3246%2346%7%49%
1519
August1st to 15thNight
8%425%42445%8%50%
1620
16th to endNight
10%42342445%7%49%
1719
September1st to 15thNight
13%42442345%7%46%
1863
16th to endNight
15%5%15%335%5%5%5%42%
1815
October1st to 15thNight
16%7%36%5%24447%37%
1908
16th to endNight
24%10%37%5%34446%25%
2241
November1st to 15thNight
15%10%46%6%35%5%5%7%27%
2276
16th to endNight
20%15%5%8%5%3445%6%19%
2511
December1st to 15thNight
17%13%7%9%8%35%45%6%17%
2658
16th to endNight
19%16%8%11%7%35%45%5%13%
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
17%14%7%13%8%45%445%14%
1411
16th to endDay
13%14%7%13%10%6%6%5%45%11%
1548
February1st to 15thDay
12%16%5%10%10%47%435%17%
1575
16th to endDay
12%15%6%10%9%46%45%5%18%
1572
March1st to 15thDay
13%10%49%7%45%46%6%28%
1870
16th to endDay
16%9%37%5%3445%7%32%
2111
April1st to 15thDay
19%12%45%423346%31%
2190
16th to endDay
17%8%2442445%7%38%
2340
May1st to 15thDay
17%6%37%43446%6%34%
2331
16th to endDay
13%5%245%245%5%8%42%
2639
June1st to 15thDay
13%6%35%5%36%5%5%7%39%
2700
16th to endDay
14%6%25%4345%5%8%38%
2700
July1st to 15thDay
11%4245%35%45%9%42%
2615
16th to endDay
10%5%24435%5%6%10%42%
2649
August1st to 15thDay
13%5%245%25%5%5%7%42%
2340
16th to endDay
12%6%35%5%345%6%8%38%
2483
September1st to 15thDay
13%5%25%5%3445%7%41%
2003
16th to endDay
16%6%15%5%445%5%8%36%
1815
October1st to 15thDay
19%8%45%6%34346%33%
1722
16th to endDay
23%13%5%7%8%45%435%16%
1630
November1st to 15thDay
15%12%47%6%4445%6%28%
1582
16th to endDay
19%16%6%9%7%34445%17%
1449
December1st to 15thDay
16%15%6%12%9%45%45%5%15%
1299
16th to endDay
20%16%8%11%5%46%5%5%5%10%
1344
January1st to 15thNight
18%12%6%11%8%45%446%16%
2524
16th to endNight
13%11%6%11%8%45%45%6%21%
2676
February1st to 15thNight
12%15%6%9%8%46%446%22%
2278
16th to endNight
14%13%5%10%7%445%5%6%21%
1898
March1st to 15thNight
14%10%47%6%345%45%33%
2089
16th to endNight
13%9%36%5%23346%40%
2112
April1st to 15thNight
20%9%2432445%6%33%
1768
16th to endNight
16%7%35%33435%6%38%
1620
May1st to 15thNight
15%6%35%6%36%5%5%7%34%
1619
16th to endNight
12%5%243345%6%8%43%
1471
June1st to 15thNight
13%6%24435%45%8%40%
1260
16th to endNight
10%5%245%345%7%9%42%
1260
July1st to 15thNight
7%3144345%6%7%52%
1342
16th to endNight
7%325%43446%8%48%
1519
August1st to 15thNight
8%415%42436%7%51%
1620
16th to endNight
10%42342445%8%49%
1719
September1st to 15thNight
12%42442345%8%45%
1863
16th to endNight
14%5%25%5%2445%6%42%
1815
October1st to 15thNight
16%7%35%5%34447%38%
1908
16th to endNight
23%11%47%5%33446%25%
2241
November1st to 15thNight
16%11%36%6%35%46%7%28%
2276
16th to endNight
20%14%5%9%6%35%45%5%20%
2511
December1st to 15thNight
18%13%6%9%8%35%45%6%17%
2658
16th to endNight
20%15%7%10%8%35%45%5%13%
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
71%6%9%10%1
1412
16th to endDay
73%7%8%8%2
1548
February1st to 15thDay
67%5%11%11%4
1577
16th to endDay
65%6%10%11%5%
1572
March1st to 15thDay
55%5%12%17%6%
1870
16th to endDay
51%413%20%8%1
2112
April1st to 15thDay
53%49%19%12%
2190
16th to endDay
45%414%18%15%2
2340
May1st to 15thDay
48%5%9%21%12%2
2331
16th to endDay
39%6%14%24%13%2
2643
June1st to 15thDay
41%7%12%24%12%2
2700
16th to endDay
42%6%13%23%12%1
2700
July1st to 15thDay
36%6%12%26%16%1
2463
16th to endDay
38%6%16%22%14%1
2482
August1st to 15thDay
39%5%15%26%12%
2327
16th to endDay
42%7%14%23%11%1
2483
September1st to 15thDay
41%6%12%29%10%
2003
16th to endDay
44%5%17%23%8%
1815
October1st to 15thDay
52%5%10%21%9%
1722
16th to endDay
69%6%10%10%3
1630
November1st to 15thDay
56%413%18%7%
1582
16th to endDay
69%5%13%9%2
1449
December1st to 15thDay
69%6%12%8%2
1299
16th to endDay
74%6%9%6%2
1344
January1st to 15thNight
68%6%10%11%3
2524
16th to endNight
62%6%13%13%3
2676
February1st to 15thNight
63%5%11%15%4
2287
16th to endNight
62%7%12%12%5%
1898
March1st to 15thNight
52%5%11%21%8%
2089
16th to endNight
44%413%23%11%2
2112
April1st to 15thNight
49%49%22%12%1
1768
16th to endNight
45%5%9%20%16%3
1620
May1st to 15thNight
47%7%10%18%14%2
1620
16th to endNight
37%6%11%26%14%3
1473
June1st to 15thNight
40%5%12%23%15%1
1260
16th to endNight
35%7%16%24%14%1
1260
July1st to 15thNight
28%7%13%28%19%1
1266
16th to endNight
32%5%17%26%16%1
1423
August1st to 15thNight
31%5%16%30%13%1
1609
16th to endNight
33%6%17%29%12%1
1719
September1st to 15thNight
36%5%14%30%11%1
1863
16th to endNight
41%5%16%25%10%
1815
October1st to 15thNight
46%5%12%24%10%
1908
16th to endNight
59%5%13%16%4
2241
November1st to 15thNight
52%7%13%19%6%
2276
16th to endNight
64%8%12%11%3
2511
December1st to 15thNight
66%6%13%10%2
2658
16th to endNight
71%7%9%8%3
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
22%17%39%14%41
87
16th to endDay
29%8%38%14%7%2
96
February1st to 15thDay
26%24%41%7%
90
16th to endDay
24%29%28%17%
81
March1st to 15thDay
23%18%29%21%5%1
160
16th to endDay
26%10%32%19%8%2
288
April1st to 15thDay
25%12%27%22%11%1
270
16th to endDay
21%15%34%14%10%4
270
May1st to 15thDay
19%17%30%20%6%5%
288
16th to endDay
14%12%37%22%8%3
446
June1st to 15thDay
16%12%38%22%7%2
495
16th to endDay
15%12%36%24%8%2
495
July1st to 15thDay
13%7%35%29%10%3
475
16th to endDay
10%7%33%32%12%4
509
August1st to 15thDay
13%5%22%31%16%10%
313
16th to endDay
13%6%24%26%21%7%
332
September1st to 15thDay
11%6%28%27%15%10%
299
16th to endDay
17%10%25%25%11%8%
254
October1st to 15thDay
23%9%31%23%9%1
255
16th to endDay
21%27%32%11%5%
142
November1st to 15thDay
17%14%38%22%6%
90
16th to endDay
24%21%27%22%11
61
December1st to 15thDay
21%35%28%11%11
60
16th to endDay
26%29%35%7%
64
January1st to 15thNight
24%15%36%18%4
900
16th to endNight
17%15%37%22%6%1
948
February1st to 15thNight
19%17%38%20%5%
704
16th to endNight
23%13%34%23%5%
631
March1st to 15thNight
19%15%34%23%5%
720
16th to endNight
18%12%32%26%8%
768
April1st to 15thNight
23%11%36%22%41
565
16th to endNight
20%10%32%24%11%1
540
May1st to 15thNight
18%7%33%27%11%2
540
16th to endNight
14%9%26%36%12%
469
June1st to 15thNight
15%5%31%31%14%
360
16th to endNight
12%8%30%35%13%1
360
July1st to 15thNight
9%325%39%20%
416
16th to endNight
8%228%36%21%2
564
August1st to 15thNight
9%223%39%21%4
539
16th to endNight
12%224%34%24%1
573
September1st to 15thNight
15%5%24%28%19%5%
636
16th to endNight
18%5%26%28%15%5%
657
October1st to 15thNight
18%9%30%29%10%
660
16th to endNight
30%14%28%21%4
704
November1st to 15thNight
21%14%32%20%9%1
700
16th to endNight
27%15%32%18%4
720
December1st to 15thNight
23%17%38%16%4
858
16th to endNight
25%16%36%16%4
960
Page generated at 2017-09-13 07:39:10. Version ac04

Copyright 2017 A. Danko


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