Lac Boswell
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac Boswell clear sky chart from 2005-11-05 to 2017-09-23.

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
25%
14598
11%
46949
6%
14566
31%
14566
13%
34967

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
12%
720
9%
2506
3%
716
19%
716
7%
2063
January16th to endNight
19%
768
11%
2688
4%
768
28%
768
10%
2059
February1st to 15thNight
19%
704
10%
2370
4%
701
28%
701
10%
1826
February16th to endNight
18%
631
11%
1893
6%
631
26%
631
11%
1490
March1st to 15thNight
17%
720
13%
2160
7%
720
25%
720
12%
1656
March16th to endNight
24%
768
18%
2012
6%
768
34%
768
18%
1445
April1st to 15thNight
22%
718
14%
1796
4%
718
28%
718
16%
1401
April16th to endNight
22%
565
15%
1645
5%
565
30%
565
16%
1164
May1st to 15thNight
27%
405
14%
1485
11%
405
36%
405
15%
1023
May16th to endNight
25%
375
10%
1497
8%
374
34%
374
12%
1035
June1st to 15thNight
29%
360
7%
1302
5%
360
34%
360
12%
947
June16th to endNight
37%
360
6%
1295
6%
360
39%
360
16%
892
July1st to 15thNight
44%
340
7%
1360
9%
340
46%
340
17%
898
July16th to endNight
44%
376
10%
1418
14%
354
47%
354
18%
925
August1st to 15thNight
47%
374
11%
1445
11%
372
51%
372
17%
973
August16th to endNight
39%
678
14%
1824
8%
678
42%
678
24%
1259
September1st to 15thNight
38%
720
12%
1818
5%
720
41%
720
26%
1281
September16th to endNight
37%
689
17%
1902
11%
689
40%
689
26%
1277
October1st to 15thNight
25%
660
16%
1923
7%
660
34%
660
17%
1391
October16th to endNight
19%
704
8%
2288
4%
704
25%
704
11%
1782
November1st to 15thNight
22%
700
15%
2277
8%
700
30%
700
13%
1683
November16th to endNight
20%
727
11%
2549
6%
727
26%
727
9%
1976
December1st to 15thNight
14%
750
5%
2700
2%
750
18%
750
7%
2197
December16th to endNight
11%
786
9%
2796
3%
786
20%
786
5%
2324

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
21%10%47%6%34446%25%
47952
Night
19%11%47%6%34445%27%
47118
TransparencyDay
59%410%16%7%
47639
Night
57%411%17%7%
46949
SeeingDay
27%14%29%18%8%2
5875
Night
26%12%29%23%7%
14598

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
19%15%7%9%8%46%44414%
1432
16th to endDay
14%14%7%11%8%445%6%6%18%
1536
February1st to 15thDay
10%15%6%11%10%5%6%5%36%18%
1489
16th to endDay
15%17%6%10%7%36%435%21%
1580
March1st to 15thDay
17%13%6%9%6%3432427%
1790
16th to endDay
15%10%5%8%7%34445%31%
2209
April1st to 15thDay
24%12%46%425%33427%
2152
16th to endDay
22%10%36%5%23235%32%
2314
May1st to 15thDay
24%8%36%5%34346%29%
2476
16th to endDay
25%7%36%6%3445%6%25%
2618
June1st to 15thDay
24%7%36%5%2445%7%26%
2655
16th to endDay
24%7%36%6%45%45%6%24%
2661
July1st to 15thDay
19%7%37%6%46%5%5%8%25%
2520
16th to endDay
17%8%37%7%36%5%5%6%26%
2654
August1st to 15thDay
21%8%37%7%46%5%5%6%21%
2492
16th to endDay
15%6%27%7%46%5%5%8%30%
2376
September1st to 15thDay
22%8%35%433336%35%
2142
16th to endDay
21%7%25%4325%46%36%
1895
October1st to 15thDay
28%9%36%5%3335%6%24%
1704
16th to endDay
29%16%36%5%2335%418%
1584
November1st to 15thDay
21%15%5%7%6%2433424%
1581
16th to endDay
22%17%6%8%5%3233321%
1407
December1st to 15thDay
25%17%5%7%5%3332418%
1260
16th to endDay
23%16%5%9%6%3434318%
1425
January1st to 15thNight
19%16%7%10%8%3444415%
2506
16th to endNight
12%15%6%9%7%45%5%5%6%19%
2688
February1st to 15thNight
10%12%7%9%9%5%5%5%46%22%
2368
16th to endNight
16%16%5%10%6%45%43423%
1893
March1st to 15thNight
19%12%5%6%6%36%435%26%
2147
16th to endNight
13%11%46%5%36%45%6%33%
2012
April1st to 15thNight
25%10%46%5%35%34427%
1796
16th to endNight
21%9%35%5%24246%35%
1645
May1st to 15thNight
22%8%36%5%3434434%
1485
16th to endNight
26%7%25%5%34246%31%
1495
June1st to 15thNight
23%8%36%5%3445%428%
1302
16th to endNight
20%6%25%5%45%46%7%32%
1295
July1st to 15thNight
15%6%26%436%5%6%9%32%
1440
16th to endNight
14%5%26%5%36%45%7%36%
1514
August1st to 15thNight
16%7%35%5%35%5%7%6%33%
1455
16th to endNight
15%5%35%6%35%5%5%7%36%
1824
September1st to 15thNight
20%7%24423445%39%
1818
16th to endNight
21%5%13423436%42%
1902
October1st to 15thNight
23%8%26%434345%31%
1923
16th to endNight
29%11%36%424445%22%
2288
November1st to 15thNight
22%11%46%5%24345%28%
2277
16th to endNight
25%13%48%5%23445%22%
2549
December1st to 15thNight
22%17%6%9%7%2434416%
2700
16th to endNight
19%19%6%10%8%4433415%
2796

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%46%12%4
1433
16th to endDay
64%47%15%7%
1536
February1st to 15thDay
66%310%11%7%
1491
16th to endDay
65%36%14%8%1
1580
March1st to 15thDay
61%28%14%11%1
1800
16th to endDay
54%46%18%13%2
2209
April1st to 15thDay
60%36%14%11%3
2152
16th to endDay
55%28%16%14%2
2314
May1st to 15thDay
56%39%17%12%1
2476
16th to endDay
58%5%9%16%9%1
2622
June1st to 15thDay
56%5%10%17%8%1
2655
16th to endDay
58%5%12%14%8%
2661
July1st to 15thDay
53%6%15%17%6%
2371
16th to endDay
57%7%13%16%5%
2487
August1st to 15thDay
59%7%14%14%3
2478
16th to endDay
50%5%16%21%5%
2376
September1st to 15thDay
50%415%20%8%
2142
16th to endDay
48%5%15%23%7%
1895
October1st to 15thDay
61%312%16%6%
1704
16th to endDay
68%411%13%2
1584
November1st to 15thDay
62%49%16%5%
1581
16th to endDay
66%410%14%4
1407
December1st to 15thDay
70%310%13%2
1260
16th to endDay
69%46%12%7%
1425
January1st to 15thNight
70%5%7%13%3
2506
16th to endNight
62%49%16%7%
2688
February1st to 15thNight
60%6%9%15%7%
2370
16th to endNight
63%47%14%9%
1893
March1st to 15thNight
60%47%16%10%1
2160
16th to endNight
50%49%19%13%2
2012
April1st to 15thNight
59%45%17%12%2
1796
16th to endNight
51%48%20%12%2
1645
May1st to 15thNight
52%410%17%12%2
1485
16th to endNight
55%411%18%10%1
1497
June1st to 15thNight
56%5%11%18%7%
1302
16th to endNight
50%6%12%19%10%1
1295
July1st to 15thNight
46%8%17%19%7%
1360
16th to endNight
46%6%16%23%7%
1418
August1st to 15thNight
46%8%19%22%3
1445
16th to endNight
45%6%18%24%5%
1824
September1st to 15thNight
45%5%15%26%7%
1818
16th to endNight
43%415%29%5%
1902
October1st to 15thNight
53%412%20%8%
1923
16th to endNight
62%412%16%4
2288
November1st to 15thNight
57%5%12%16%7%1
2277
16th to endNight
64%49%16%4
2549
December1st to 15thNight
70%311%11%2
2700
16th to endNight
72%36%10%5%
2796

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
33%18%36%11%
60
16th to endDay
28%12%40%12%41
64
February1st to 15thDay
21%21%39%11%5%1
89
16th to endDay
26%25%28%13%5%
239
March1st to 15thDay
27%20%30%14%6%
270
16th to endDay
21%20%27%19%8%2
288
April1st to 15thDay
34%17%26%16%41
270
16th to endDay
29%21%27%14%43
270
May1st to 15thDay
35%12%28%15%7%
288
16th to endDay
29%17%29%17%5%
331
June1st to 15thDay
28%12%29%19%8%1
450
16th to endDay
22%12%30%24%8%1
456
July1st to 15thDay
23%9%33%21%8%3
305
16th to endDay
23%6%30%27%10%1
326
August1st to 15thDay
24%7%27%23%12%5%
313
16th to endDay
19%11%29%19%14%5%
332
September1st to 15thDay
25%11%28%19%9%5%
315
16th to endDay
22%12%28%14%16%6%
283
October1st to 15thDay
28%14%26%17%9%3
252
16th to endDay
39%13%22%15%7%1
240
November1st to 15thDay
27%19%25%17%8%1
235
16th to endDay
42%17%22%16%1
75
December1st to 15thDay
33%15%33%15%11
60
16th to endDay
43%23%26%6%
64
January1st to 15thNight
27%13%36%17%3
720
16th to endNight
22%14%33%23%6%
768
February1st to 15thNight
16%17%36%22%6%
704
16th to endNight
26%15%32%20%5%
631
March1st to 15thNight
28%14%33%18%5%
720
16th to endNight
20%18%31%19%7%1
768
April1st to 15thNight
32%13%25%22%5%
718
16th to endNight
27%17%29%18%7%
565
May1st to 15thNight
28%10%30%22%7%
405
16th to endNight
29%11%27%24%5%
375
June1st to 15thNight
24%10%28%29%6%
360
16th to endNight
21%6%26%33%11%
360
July1st to 15thNight
16%5%27%33%16%
340
16th to endNight
14%427%38%13%
376
August1st to 15thNight
17%5%20%37%18%1
374
16th to endNight
18%7%25%30%15%1
678
September1st to 15thNight
24%5%26%31%10%1
720
16th to endNight
23%8%27%24%14%1
689
October1st to 15thNight
27%11%31%22%7%
660
16th to endNight
35%11%27%17%7%
704
November1st to 15thNight
28%14%29%20%6%1
700
16th to endNight
35%14%23%18%6%1
727
December1st to 15thNight
32%16%28%17%4
750
16th to endNight
33%15%29%16%4
786
Page generated at 2017-09-24 09:15:53. Version ac04

Copyright 2017 A. Danko


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