Beaver River Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Beaver River Observatory clear sky chart from 2005-11-05 to 2017-09-19.

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
29%
15025
10%
46710
7%
14989
32%
14989
14%
35538

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
7%
854
2%
2590
1%
854
9%
854
3%
2378
January16th to endNight
13%
768
3%
2496
2%
768
16%
768
4%
2222
February1st to 15thNight
12%
701
4%
2287
1%
701
16%
701
5%
1994
February16th to endNight
17%
631
8%
1994
2%
631
23%
631
8%
1629
March1st to 15thNight
18%
720
10%
2004
4%
720
23%
720
13%
1588
March16th to endNight
31%
768
18%
2112
10%
768
37%
768
20%
1523
April1st to 15thNight
24%
690
14%
1816
5%
690
29%
690
19%
1342
April16th to endNight
34%
540
18%
1620
10%
540
39%
540
19%
1133
May1st to 15thNight
43%
516
15%
1596
12%
516
48%
516
23%
1069
May16th to endNight
45%
374
15%
1497
14%
374
54%
374
22%
889
June1st to 15thNight
41%
360
11%
1347
11%
360
48%
360
19%
851
June16th to endNight
50%
360
13%
1260
14%
360
55%
360
26%
775
July1st to 15thNight
59%
340
17%
1190
21%
340
63%
340
34%
641
July16th to endNight
53%
514
15%
1540
13%
481
55%
481
27%
937
August1st to 15thNight
56%
539
15%
1609
11%
536
59%
536
29%
1005
August16th to endNight
55%
589
19%
1735
13%
589
59%
589
28%
1094
September1st to 15thNight
50%
720
17%
1851
9%
720
53%
720
31%
1224
September16th to endNight
49%
673
18%
1858
13%
673
51%
673
26%
1250
October1st to 15thNight
31%
660
14%
1978
10%
660
36%
660
17%
1438
October16th to endNight
17%
704
6%
2128
3%
704
22%
704
8%
1779
November1st to 15thNight
23%
700
12%
2378
11%
700
27%
700
11%
1828
November16th to endNight
17%
720
7%
2520
4%
720
21%
720
7%
2101
December1st to 15thNight
8%
720
2%
2520
0%
720
9%
720
3%
2286
December16th to endNight
5%
864
3%
2784
0%
864
7%
864
2%
2562

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
16%11%5%8%6%34446%27%
48096
Night
15%12%5%9%6%34445%27%
46881
Cloud CoverDay
15%11%5%8%6%3445%6%27%
48106
Night
14%12%5%9%7%34445%27%
46885
TransparencyDay
56%6%11%16%9%
47785
Night
57%6%10%15%8%
46710
SeeingDay
19%10%27%25%12%4
5723
Night
19%14%29%24%9%1
15034

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%17%9%17%9%46%3339%
1342
16th to endDay
8%19%10%15%13%47%3428%
1728
February1st to 15thDay
13%16%9%17%11%45%4429%
1575
16th to endDay
15%18%7%13%10%5%443412%
1476
March1st to 15thDay
13%12%6%12%9%45%34423%
1945
16th to endDay
13%12%5%8%7%345%46%29%
2112
April1st to 15thDay
19%13%5%6%434345%28%
2143
16th to endDay
17%11%45%42335%5%36%
2340
May1st to 15thDay
18%9%36%5%24447%35%
2355
16th to endDay
14%8%345%3445%7%38%
2618
June1st to 15thDay
18%7%25%3245%6%9%34%
2610
16th to endDay
15%6%245%35%5%6%8%35%
2700
July1st to 15thDay
13%5%25%5%35%5%6%8%37%
2700
16th to endDay
12%6%36%5%35%5%6%10%34%
2516
August1st to 15thDay
13%6%36%5%25%5%5%8%36%
2340
16th to endDay
14%6%35%6%46%5%6%8%33%
2454
September1st to 15thDay
21%7%25%5%24436%35%
2108
16th to endDay
19%6%36%5%3335%7%35%
1848
October1st to 15thDay
24%10%35%5%33345%28%
1651
16th to endDay
31%17%36%6%33345%14%
1741
November1st to 15thDay
17%18%36%6%35%435%24%
1480
16th to endDay
17%21%7%11%7%34346%12%
1440
December1st to 15thDay
16%21%14%14%7%243338%
1440
16th to endDay
16%24%13%14%7%343237%
1434
January1st to 15thNight
16%18%9%16%12%45%3337%
2590
16th to endNight
11%14%10%17%11%5%7%43310%
2496
February1st to 15thNight
11%16%10%12%11%5%6%5%4311%
2285
16th to endNight
11%15%6%13%9%445%45%18%
1994
March1st to 15thNight
14%14%6%10%7%35%44424%
1992
16th to endNight
12%10%48%5%35%33436%
2112
April1st to 15thNight
19%13%36%423346%31%
1816
16th to endNight
15%11%46%5%24435%37%
1620
May1st to 15thNight
15%8%25%42445%7%37%
1596
16th to endNight
11%5%245%35%5%5%7%43%
1495
June1st to 15thNight
14%6%25%5%35%5%5%7%37%
1347
16th to endNight
12%5%1443445%8%44%
1260
July1st to 15thNight
9%42242345%8%51%
1260
16th to endNight
9%414435%47%8%44%
1646
August1st to 15thNight
9%5%145%35%5%6%9%42%
1620
16th to endNight
9%5%26%434446%47%
1735
September1st to 15thNight
16%42432435%7%45%
1851
16th to endNight
15%7%2442435%6%43%
1858
October1st to 15thNight
21%8%36%5%3445%7%31%
1978
16th to endNight
25%16%36%7%34445%18%
2128
November1st to 15thNight
18%16%46%6%35%445%25%
2378
16th to endNight
18%16%7%10%6%44445%17%
2520
December1st to 15thNight
17%21%9%14%7%344339%
2520
16th to endNight
18%19%12%16%8%333327%
2784

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%16%9%18%10%5%43348%
1342
16th to endDay
8%20%10%16%13%5%7%4338%
1728
February1st to 15thDay
13%16%9%17%12%45%4439%
1575
16th to endDay
14%19%7%13%9%5%433413%
1476
March1st to 15thDay
13%11%7%12%9%45%33423%
1956
16th to endDay
12%11%6%8%7%3445%5%29%
2111
April1st to 15thDay
19%13%47%434346%28%
2143
16th to endDay
17%10%45%5%23345%36%
2340
May1st to 15thDay
17%9%26%42445%6%34%
2355
16th to endDay
14%7%345%3445%7%38%
2618
June1st to 15thDay
17%7%25%325%5%6%9%34%
2610
16th to endDay
15%7%245%35%5%6%8%34%
2700
July1st to 15thDay
12%5%25%5%35%5%6%9%37%
2700
16th to endDay
11%6%36%5%35%5%6%10%34%
2516
August1st to 15thDay
12%6%36%5%35%46%8%36%
2340
16th to endDay
13%6%35%7%45%6%5%8%32%
2454
September1st to 15thDay
20%7%25%5%34346%35%
2108
16th to endDay
18%7%36%43335%7%36%
1848
October1st to 15thDay
22%12%36%5%33346%28%
1651
16th to endDay
30%16%37%5%3434414%
1741
November1st to 15thDay
16%17%5%6%5%45%435%24%
1480
16th to endDay
17%20%7%12%7%3445%5%12%
1440
December1st to 15thDay
15%21%12%16%7%243248%
1440
16th to endDay
16%23%13%14%7%35%2246%
1434
January1st to 15thNight
16%16%9%17%12%45%3337%
2590
16th to endNight
10%14%8%17%12%5%7%5%3310%
2496
February1st to 15thNight
10%16%10%12%11%46%44311%
2278
16th to endNight
11%14%7%13%10%45%446%18%
1994
March1st to 15thNight
14%13%6%10%7%35%5%3424%
2004
16th to endNight
12%10%49%6%2443436%
2112
April1st to 15thNight
19%13%46%423346%31%
1816
16th to endNight
15%10%46%5%24426%37%
1620
May1st to 15thNight
14%9%36%42445%7%37%
1595
16th to endNight
11%6%25%4345%5%7%43%
1495
June1st to 15thNight
14%5%345%36%5%5%7%37%
1347
16th to endNight
11%5%245%3445%8%44%
1260
July1st to 15thNight
9%5%1342445%7%52%
1260
16th to endNight
8%415%435%5%6%8%45%
1646
August1st to 15thNight
8%5%245%35%6%6%8%42%
1620
16th to endNight
9%5%26%5%34447%46%
1735
September1st to 15thNight
16%42432345%8%44%
1851
16th to endNight
15%7%2342435%6%42%
1858
October1st to 15thNight
20%8%36%5%3435%7%31%
1978
16th to endNight
24%16%47%6%445%45%18%
2128
November1st to 15thNight
17%16%47%6%35%445%25%
2378
16th to endNight
18%15%8%10%7%3445%5%17%
2520
December1st to 15thNight
17%21%10%14%7%344339%
2520
16th to endNight
17%19%11%17%9%333327%
2784

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%6%5%5%1
1343
16th to endDay
81%5%6%5%2
1728
February1st to 15thDay
77%6%6%7%
1577
16th to endDay
74%5%7%7%5%
1476
March1st to 15thDay
63%410%13%7%
1956
16th to endDay
53%6%10%15%12%1
2112
April1st to 15thDay
56%49%18%9%
2143
16th to endDay
48%5%9%20%14%1
2340
May1st to 15thDay
48%5%10%21%13%1
2355
16th to endDay
43%6%12%21%14%1
2622
June1st to 15thDay
44%7%12%21%13%
2610
16th to endDay
43%8%14%20%12%
2700
July1st to 15thDay
40%7%14%21%14%1
2541
16th to endDay
44%8%13%22%10%1
2359
August1st to 15thDay
42%8%14%19%13%
2327
16th to endDay
45%9%14%20%9%1
2454
September1st to 15thDay
49%6%12%21%9%1
2108
16th to endDay
47%6%13%24%8%
1848
October1st to 15thDay
56%5%9%16%10%
1651
16th to endDay
72%6%9%7%3
1741
November1st to 15thDay
61%6%12%12%6%
1480
16th to endDay
74%7%8%7%1
1440
December1st to 15thDay
81%6%7%4
1440
16th to endDay
83%5%6%4
1434
January1st to 15thNight
81%6%6%4
2590
16th to endNight
76%7%8%5%1
2496
February1st to 15thNight
75%6%7%8%1
2287
16th to endNight
65%7%9%10%6%
1994
March1st to 15thNight
61%5%10%14%6%
2004
16th to endNight
50%5%8%18%14%1
2112
April1st to 15thNight
54%39%19%12%
1816
16th to endNight
49%5%7%16%18%2
1620
May1st to 15thNight
46%5%10%20%15%1
1596
16th to endNight
37%7%12%26%13%2
1497
June1st to 15thNight
43%6%12%21%14%1
1347
16th to endNight
37%7%14%25%14%
1260
July1st to 15thNight
29%5%13%28%20%2
1190
16th to endNight
36%7%12%26%16%1
1540
August1st to 15thNight
35%8%16%23%14%
1609
16th to endNight
36%8%13%26%13%1
1735
September1st to 15thNight
37%8%15%27%11%
1851
16th to endNight
40%8%12%26%11%
1858
October1st to 15thNight
51%7%11%18%11%
1978
16th to endNight
67%7%11%9%3
2128
November1st to 15thNight
59%6%12%13%6%1
2378
16th to endNight
68%7%11%9%2
2520
December1st to 15thNight
79%7%8%31
2520
16th to endNight
82%5%6%4
2784

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
11%33%37%15%1
69
16th to endDay
20%18%39%19%1
96
February1st to 15thDay
24%33%28%13%
90
16th to endDay
24%23%37%13%1
81
March1st to 15thDay
17%20%35%19%6%
246
16th to endDay
22%10%31%25%8%1
288
April1st to 15thDay
22%13%34%18%8%1
270
16th to endDay
25%11%25%19%11%5%
270
May1st to 15thDay
25%6%28%22%12%4
288
16th to endDay
17%8%28%26%14%3
331
June1st to 15thDay
19%10%25%25%16%2
405
16th to endDay
15%7%29%32%11%3
495
July1st to 15thDay
13%6%25%33%14%5%
475
16th to endDay
9%426%32%20%6%
328
August1st to 15thDay
15%220%32%18%9%
313
16th to endDay
17%5%18%32%18%8%
332
September1st to 15thDay
16%423%25%20%10%
315
16th to endDay
17%6%22%25%20%7%
266
October1st to 15thDay
22%9%28%27%9%2
255
16th to endDay
34%21%24%15%3
253
November1st to 15thDay
21%12%27%27%8%2
73
16th to endDay
30%20%33%15%1
60
December1st to 15thDay
13%45%25%16%
60
16th to endDay
23%45%29%1
64
January1st to 15thNight
21%27%32%14%4
859
16th to endNight
15%18%38%21%4
768
February1st to 15thNight
18%21%36%20%3
704
16th to endNight
18%16%34%24%5%
631
March1st to 15thNight
19%19%35%20%4
720
16th to endNight
17%10%33%26%9%1
768
April1st to 15thNight
23%13%32%24%5%
690
16th to endNight
20%12%27%26%11%1
540
May1st to 15thNight
19%6%23%33%13%2
516
16th to endNight
15%430%34%15%
375
June1st to 15thNight
15%5%28%35%13%
360
16th to endNight
14%424%38%17%1
360
July1st to 15thNight
9%322%42%21%
340
16th to endNight
10%326%38%20%1
514
August1st to 15thNight
12%219%37%25%2
539
16th to endNight
13%420%34%24%3
589
September1st to 15thNight
17%5%21%30%16%7%
720
16th to endNight
17%7%20%33%16%4
673
October1st to 15thNight
24%11%28%22%11%1
660
16th to endNight
33%19%26%17%3
704
November1st to 15thNight
23%18%29%19%8%
700
16th to endNight
23%23%29%17%4
720
December1st to 15thNight
26%26%32%12%2
720
16th to endNight
24%23%35%13%1
864
Page generated at 2017-09-20 04:49:55. Version ac04

Copyright 2017 A. Danko


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