Lake Granby (North Shore)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Granby (North Shore) clear sky chart from 2005-11-05 to 2017-09-17.

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
36%
15962
19%
46877
10%
15916
44%
15916
27%
29469

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
22%
900
13%
2506
6%
895
28%
895
18%
1795
January16th to endNight
18%
789
19%
2517
8%
789
31%
789
19%
1706
February1st to 15thNight
14%
701
9%
2281
3%
698
22%
698
14%
1684
February16th to endNight
13%
632
17%
1894
3%
632
28%
632
19%
1314
March1st to 15thNight
24%
720
19%
2082
6%
720
36%
720
26%
1320
March16th to endNight
24%
701
18%
2045
6%
701
36%
701
25%
1312
April1st to 15thNight
27%
539
16%
1798
7%
539
38%
539
21%
1128
April16th to endNight
31%
540
19%
1800
12%
540
42%
540
22%
1129
May1st to 15thNight
37%
540
15%
1579
7%
540
45%
540
23%
1060
May16th to endNight
47%
563
15%
1498
9%
561
52%
561
31%
940
June1st to 15thNight
51%
540
21%
1440
13%
540
57%
540
47%
768
June16th to endNight
67%
540
28%
1440
22%
540
72%
540
58%
708
July1st to 15thNight
72%
510
17%
1360
13%
510
75%
510
39%
807
July16th to endNight
76%
564
20%
1467
19%
531
77%
531
40%
837
August1st to 15thNight
72%
539
18%
1632
16%
536
74%
536
38%
893
August16th to endNight
72%
573
25%
1910
26%
573
76%
573
37%
1044
September1st to 15thNight
63%
540
26%
1800
22%
540
72%
540
38%
931
September16th to endNight
60%
524
32%
1798
28%
524
68%
524
44%
883
October1st to 15thNight
39%
660
24%
1980
13%
660
48%
660
32%
1188
October16th to endNight
34%
712
26%
2120
10%
712
48%
712
35%
1201
November1st to 15thNight
26%
875
24%
2275
9%
875
37%
875
33%
1394
November16th to endNight
25%
900
23%
2447
8%
900
37%
900
30%
1528
December1st to 15thNight
14%
900
10%
2520
2%
900
21%
900
17%
1836
December16th to endNight
15%
960
13%
2688
4%
960
23%
960
14%
2063

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
5%10%48%5%3445%7%40%
47915
Night
39%5%7%5%23347%47%
47053
TransparencyDay
42%5%13%20%13%3
47593
Night
37%6%15%23%14%3
46877
SeeingDay
14%18%33%20%11%2
5859
Night
11%12%34%26%13%1
15965

By Month

Percentage Cloud Cover SW (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
112%8%15%7%44246%31%
1432
16th to endDay
114%8%14%8%23235%35%
1719
February1st to 15thDay
216%10%15%6%32235%29%
1581
16th to endDay
113%9%15%9%33336%30%
1580
March1st to 15thDay
212%8%9%7%23336%40%
1875
16th to endDay
413%7%9%5%24347%35%
2178
April1st to 15thDay
5%14%5%9%5%3345%7%35%
2150
16th to endDay
6%16%5%9%6%35%6%5%7%28%
2160
May1st to 15thDay
10%12%35%6%35%5%6%8%32%
2367
16th to endDay
8%11%36%5%35%7%7%9%31%
2616
June1st to 15thDay
6%4245%35%5%7%9%46%
2520
16th to endDay
321333446%7%58%
2520
July1st to 15thDay
8%5%24435%6%6%7%44%
2520
16th to endDay
7%5%25%7%46%6%8%7%38%
2598
August1st to 15thDay
10%6%26%6%445%6%8%37%
2319
16th to endDay
8%5%25%5%36%5%7%7%40%
2292
September1st to 15thDay
9%42443335%5%52%
2160
16th to endDay
8%7%24312336%56%
1866
October1st to 15thDay
7%11%44323346%48%
1650
16th to endDay
6%11%46%322337%48%
1741
November1st to 15thDay
312%5%8%312247%47%
1583
16th to endDay
112%6%7%412148%47%
1512
December1st to 15thDay
117%8%15%7%44235%29%
1440
16th to endDay
115%10%16%10%5%322427%
1536
January1st to 15thNight
112%10%13%6%43235%35%
2506
16th to endNight
114%7%12%6%3222441%
2517
February1st to 15thNight
212%8%18%7%33226%31%
2270
16th to endNight
114%8%12%6%13336%37%
1894
March1st to 15thNight
19%6%7%6%23247%47%
2082
16th to endNight
211%5%8%423236%47%
2045
April1st to 15thNight
310%6%6%5%34346%45%
1798
16th to endNight
414%35%5%23347%45%
1800
May1st to 15thNight
5%9%35%435%5%6%8%42%
1578
16th to endNight
5%7%24424448%50%
1497
June1st to 15thNight
211232335%8%64%
1440
16th to endNight
22221347%7%66%
1440
July1st to 15thNight
32134246%6%10%52%
1440
16th to endNight
42235%345%6%7%54%
1567
August1st to 15thNight
3314425%5%5%10%53%
1641
16th to endNight
42234345%6%7%54%
1910
September1st to 15thNight
6%31332445%8%56%
1800
16th to endNight
45%2321235%6%61%
1798
October1st to 15thNight
5%9%34323346%51%
1980
16th to endNight
5%8%45%212247%55%
2120
November1st to 15thNight
212%5%5%312246%52%
2275
16th to endNight
110%5%7%5%22337%49%
2447
December1st to 15thNight
216%6%12%7%44235%34%
2520
16th to endNight
112%9%16%10%43235%30%
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
54%416%15%6%2
1433
16th to endDay
51%316%18%9%
1719
February1st to 15thDay
57%415%15%6%1
1581
16th to endDay
56%411%17%9%1
1580
March1st to 15thDay
44%415%20%13%
1875
16th to endDay
47%5%13%23%7%2
2178
April1st to 15thDay
46%5%14%17%12%3
2150
16th to endDay
52%6%13%18%7%
2160
May1st to 15thDay
48%8%13%19%10%
2367
16th to endDay
45%7%15%19%10%1
2620
June1st to 15thDay
30%7%15%18%21%6%
2520
16th to endDay
21%5%11%23%27%10%
2520
July1st to 15thDay
36%7%12%17%16%9%
2371
16th to endDay
38%7%15%20%12%5%
2435
August1st to 15thDay
41%7%13%16%14%6%
2304
16th to endDay
38%6%14%20%17%3
2292
September1st to 15thDay
32%411%20%22%8%
2160
16th to endDay
29%312%28%23%2
1866
October1st to 15thDay
37%411%26%17%2
1650
16th to endDay
36%5%12%29%14%2
1741
November1st to 15thDay
37%5%15%20%17%3
1583
16th to endDay
36%417%27%11%2
1512
December1st to 15thDay
57%316%16%5%
1440
16th to endDay
62%48%16%6%2
1536
January1st to 15thNight
50%5%16%17%8%1
2506
16th to endNight
49%313%21%11%1
2517
February1st to 15thNight
56%5%14%16%6%
2281
16th to endNight
48%412%21%10%2
1894
March1st to 15thNight
37%6%16%25%12%1
2082
16th to endNight
39%5%14%29%9%1
2045
April1st to 15thNight
39%6%14%23%13%2
1798
16th to endNight
40%6%14%24%13%
1800
May1st to 15thNight
38%11%15%24%10%
1579
16th to endNight
30%10%19%25%12%1
1498
June1st to 15thNight
17%8%18%24%23%7%
1440
16th to endNight
14%412%28%26%13%
1440
July1st to 15thNight
25%10%18%18%17%9%
1360
16th to endNight
25%8%20%22%15%7%
1467
August1st to 15thNight
24%8%22%19%16%8%
1632
16th to endNight
25%8%14%23%23%4
1910
September1st to 15thNight
24%6%15%19%22%10%
1800
16th to endNight
22%411%35%22%3
1798
October1st to 15thNight
33%5%12%26%17%3
1980
16th to endNight
30%316%29%17%1
2120
November1st to 15thNight
33%314%24%19%4
2275
16th to endNight
35%415%27%14%2
2447
December1st to 15thNight
52%5%16%16%7%
2520
16th to endNight
58%5%10%17%6%1
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
23%12%31%16%15%1
90
16th to endDay
10%22%36%25%5%
96
February1st to 15thDay
27%18%37%12%3
90
16th to endDay
18%23%38%14%4
81
March1st to 15thDay
23%26%33%13%2
165
16th to endDay
21%42%27%6%2
288
April1st to 15thDay
21%32%31%10%3
269
16th to endDay
27%34%27%8%1
270
May1st to 15thDay
19%21%32%17%7%1
399
16th to endDay
15%17%30%22%12%1
517
June1st to 15thDay
9%14%31%25%16%3
495
16th to endDay
315%36%21%20%2
495
July1st to 15thDay
10%6%29%28%19%5%
475
16th to endDay
8%5%29%28%21%5%
457
August1st to 15thDay
16%10%39%24%8%1
315
16th to endDay
12%7%37%29%10%3
332
September1st to 15thDay
13%17%35%24%6%2
315
16th to endDay
11%12%37%20%13%3
158
October1st to 15thDay
8%14%35%24%13%3
90
16th to endDay
23%13%33%20%7%1
96
November1st to 15thDay
6%17%28%21%18%6%
90
16th to endDay
18%34%37%8%
90
December1st to 15thDay
18%28%45%6%
90
16th to endDay
13%28%44%10%3
96
January1st to 15thNight
16%19%37%18%7%1
900
16th to endNight
14%18%42%17%5%
789
February1st to 15thNight
13%18%47%16%4
704
16th to endNight
14%20%44%16%3
632
March1st to 15thNight
9%16%45%18%9%
720
16th to endNight
9%16%45%22%4
701
April1st to 15thNight
10%17%40%25%5%
539
16th to endNight
13%16%36%24%8%
540
May1st to 15thNight
11%10%35%28%12%
540
16th to endNight
11%7%28%35%16%1
563
June1st to 15thNight
46%32%37%17%1
540
16th to endNight
4420%45%24%1
540
July1st to 15thNight
5%110%42%35%4
510
16th to endNight
47%39%40%6%
564
August1st to 15thNight
412%46%34%1
539
16th to endNight
4113%36%38%5%
573
September1st to 15thNight
7%221%40%24%4
540
16th to endNight
5%324%36%24%5%
524
October1st to 15thNight
14%7%35%26%13%2
660
16th to endNight
12%10%39%23%10%2
712
November1st to 15thNight
15%15%39%20%7%
875
16th to endNight
12%19%39%23%3
900
December1st to 15thNight
16%21%43%14%3
900
16th to endNight
16%18%41%17%5%
960
Page generated at 2017-09-18 06:38:20. Version ac04

Copyright 2017 A. Danko


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