Canton de Shefford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canton de Shefford 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
27%
14649
11%
46834
7%
14618
32%
14618
13%
35227

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
13%
720
7%
2506
3%
716
17%
716
6%
2111
January16th to endNight
17%
768
7%
2688
5%
768
21%
768
7%
2208
February1st to 15thNight
13%
704
7%
2309
3%
701
19%
701
7%
1937
February16th to endNight
18%
631
8%
1893
5%
631
23%
631
9%
1541
March1st to 15thNight
22%
720
13%
2160
9%
720
27%
720
12%
1684
March16th to endNight
27%
768
18%
2007
8%
768
34%
768
18%
1487
April1st to 15thNight
22%
718
14%
1796
4%
718
27%
718
15%
1435
April16th to endNight
27%
594
16%
1674
6%
594
35%
594
19%
1183
May1st to 15thNight
26%
440
16%
1520
11%
440
35%
440
17%
1047
May16th to endNight
30%
374
11%
1497
9%
374
39%
374
15%
1013
June1st to 15thNight
31%
360
9%
1440
8%
360
40%
360
13%
1018
June16th to endNight
42%
360
9%
1440
11%
360
48%
360
18%
926
July1st to 15thNight
47%
340
11%
1360
17%
340
51%
340
19%
855
July16th to endNight
48%
376
11%
1418
14%
354
51%
354
19%
880
August1st to 15thNight
48%
398
13%
1469
14%
396
51%
396
20%
946
August16th to endNight
52%
721
19%
1867
11%
721
54%
721
33%
1213
September1st to 15thNight
44%
720
12%
1818
7%
720
45%
720
28%
1269
September16th to endNight
43%
665
19%
1836
13%
665
47%
665
29%
1187
October1st to 15thNight
29%
660
17%
1906
9%
660
37%
660
17%
1386
October16th to endNight
22%
704
9%
2282
6%
704
27%
704
10%
1786
November1st to 15thNight
23%
700
14%
2277
10%
700
30%
700
11%
1755
November16th to endNight
20%
720
12%
2463
8%
720
26%
720
10%
1923
December1st to 15thNight
11%
720
5%
2520
1%
720
15%
720
5%
2140
December16th to endNight
9%
768
7%
2688
3%
768
15%
768
4%
2297

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%36%5%34446%28%
47954
Night
20%11%47%5%34345%28%
47004
Cloud CoverDay
21%11%46%5%34445%27%
47964
Night
20%12%47%5%34445%27%
47009
TransparencyDay
57%5%10%18%7%
47642
Night
58%5%9%17%8%
46834
SeeingDay
27%13%26%19%9%3
5646
Night
26%12%26%23%9%
14650

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
23%18%6%10%6%45%33314%
1432
16th to endDay
13%16%6%11%7%47%5%5%418%
1536
February1st to 15thDay
13%17%8%12%7%5%6%43415%
1552
16th to endDay
16%16%7%10%6%45%34419%
1580
March1st to 15thDay
19%14%5%8%6%35%33424%
1790
16th to endDay
19%12%5%7%5%2223432%
2213
April1st to 15thDay
24%14%45%423335%28%
2152
16th to endDay
24%8%25%42343434%
2286
May1st to 15thDay
24%6%36%6%2335%6%30%
2442
16th to endDay
22%7%36%5%3445%7%30%
2618
June1st to 15thDay
29%6%245%2445%6%27%
2520
16th to endDay
23%5%36%5%35%46%7%29%
2520
July1st to 15thDay
16%425%5%35%5%6%8%33%
2520
16th to endDay
16%6%25%6%35%5%7%9%31%
2654
August1st to 15thDay
19%6%26%6%445%6%7%29%
2469
16th to endDay
14%425%5%3445%7%40%
2333
September1st to 15thDay
21%5%24423345%39%
2142
16th to endDay
18%5%14324447%42%
1830
October1st to 15thDay
27%7%2443345%6%28%
1724
16th to endDay
28%14%36%43443422%
1590
November1st to 15thDay
21%13%35%434445%29%
1581
16th to endDay
22%16%5%7%5%2423325%
1494
December1st to 15thDay
25%18%6%9%7%3423314%
1440
16th to endDay
25%22%8%8%5%25%32312%
1536
January1st to 15thNight
19%17%7%11%6%4433416%
2506
16th to endNight
14%16%7%11%7%5%5%44418%
2688
February1st to 15thNight
14%17%7%13%8%4444417%
2308
16th to endNight
15%17%7%9%7%3433422%
1893
March1st to 15thNight
21%15%5%7%5%2333427%
2147
16th to endNight
17%13%46%42333434%
2007
April1st to 15thNight
26%11%47%43433426%
1796
16th to endNight
21%7%25%423336%37%
1674
May1st to 15thNight
23%7%35%5%34246%33%
1520
16th to endNight
22%5%25%5%24447%33%
1495
June1st to 15thNight
30%6%2441445%8%27%
1440
16th to endNight
18%5%34425%46%9%35%
1440
July1st to 15thNight
14%5%246%345%7%8%36%
1440
16th to endNight
13%425%435%7%6%7%38%
1514
August1st to 15thNight
15%5%26%6%45%46%8%36%
1479
16th to endNight
14%5%24424447%45%
1867
September1st to 15thNight
20%5%245%23346%41%
1818
16th to endNight
21%323323336%46%
1836
October1st to 15thNight
22%7%35%5%24345%33%
1906
16th to endNight
30%11%35%42434424%
2282
November1st to 15thNight
21%11%35%5%35%45%5%25%
2277
16th to endNight
24%15%48%5%2333325%
2463
December1st to 15thNight
25%19%5%9%7%2432414%
2520
16th to endNight
24%22%6%8%6%2322316%
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
20%19%6%12%8%4433313%
1432
16th to endDay
12%17%6%11%8%46%5%45%16%
1536
February1st to 15thDay
13%17%9%12%8%5%6%5%3314%
1552
16th to endDay
15%17%9%10%8%35%33318%
1580
March1st to 15thDay
18%15%6%9%6%35%33423%
1800
16th to endDay
20%12%5%7%5%3222432%
2213
April1st to 15thDay
24%13%47%424235%27%
2152
16th to endDay
23%10%245%2334433%
2286
May1st to 15thDay
24%7%35%6%33447%29%
2442
16th to endDay
22%8%35%5%245%5%6%29%
2618
June1st to 15thDay
30%6%244245%5%6%27%
2520
16th to endDay
24%6%25%5%25%45%7%29%
2520
July1st to 15thDay
17%435%5%35%6%6%7%33%
2520
16th to endDay
17%7%26%5%35%6%7%8%29%
2654
August1st to 15thDay
20%6%26%6%35%5%6%8%27%
2469
16th to endDay
15%5%245%3445%8%39%
2333
September1st to 15thDay
21%6%25%423346%39%
2142
16th to endDay
19%6%24323348%41%
1830
October1st to 15thDay
28%8%34423445%29%
1724
16th to endDay
28%15%36%5%2433421%
1590
November1st to 15thDay
21%14%36%434445%27%
1581
16th to endDay
21%18%6%7%42334423%
1494
December1st to 15thDay
24%19%6%9%5%4423414%
1440
16th to endDay
23%23%8%10%5%2432312%
1536
January1st to 15thNight
19%16%8%12%6%3443315%
2506
16th to endNight
12%18%7%11%8%45%44417%
2688
February1st to 15thNight
14%16%8%14%8%35%33316%
2301
16th to endNight
14%18%7%10%7%3433321%
1893
March1st to 15thNight
21%15%5%8%6%2333425%
2160
16th to endNight
17%14%5%6%42333433%
2006
April1st to 15thNight
25%11%5%6%6%2333426%
1796
16th to endNight
21%7%25%5%23336%36%
1674
May1st to 15thNight
23%7%35%5%34336%33%
1520
16th to endNight
21%7%345%3435%7%32%
1495
June1st to 15thNight
30%7%25%32245%7%27%
1440
16th to endNight
17%6%24425%46%8%34%
1440
July1st to 15thNight
14%5%346%35%5%5%9%35%
1440
16th to endNight
14%425%5%35%6%7%7%38%
1514
August1st to 15thNight
16%5%25%5%345%6%7%36%
1479
16th to endNight
13%6%2442345%7%44%
1867
September1st to 15thNight
19%5%25%423446%40%
1818
16th to endNight
21%41332325%5%45%
1836
October1st to 15thNight
23%8%36%5%24335%32%
1906
16th to endNight
30%11%35%5%2434423%
2282
November1st to 15thNight
21%12%37%6%35%445%25%
2277
16th to endNight
22%16%5%8%5%3333325%
2463
December1st to 15thNight
23%20%7%11%6%2332314%
2520
16th to endNight
23%22%8%9%6%2322314%
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
76%46%9%3
1433
16th to endDay
67%6%10%11%3
1536
February1st to 15thDay
73%5%7%12%1
1555
16th to endDay
69%47%10%6%
1580
March1st to 15thDay
64%49%14%6%1
1800
16th to endDay
57%38%18%10%1
2213
April1st to 15thDay
60%36%17%10%1
2152
16th to endDay
53%48%18%11%3
2286
May1st to 15thDay
54%49%18%11%
2442
16th to endDay
53%7%10%18%9%1
2622
June1st to 15thDay
55%6%12%17%7%
2520
16th to endDay
53%5%10%21%7%
2520
July1st to 15thDay
44%7%14%26%6%
2371
16th to endDay
49%7%15%21%5%
2487
August1st to 15thDay
51%7%15%20%4
2455
16th to endDay
42%6%15%25%10%
2333
September1st to 15thDay
46%5%11%25%10%
2142
16th to endDay
42%5%11%30%10%
1830
October1st to 15thDay
55%6%11%19%6%
1724
16th to endDay
66%410%13%5%
1590
November1st to 15thDay
57%6%10%15%8%1
1581
16th to endDay
64%49%13%7%
1494
December1st to 15thDay
73%5%9%10%1
1440
16th to endDay
79%45%6%4
1536
January1st to 15thNight
73%47%10%3
2506
16th to endNight
69%5%7%12%4
2688
February1st to 15thNight
71%47%12%3
2309
16th to endNight
67%48%10%8%
1893
March1st to 15thNight
62%47%17%7%1
2160
16th to endNight
54%37%16%14%3
2007
April1st to 15thNight
62%3416%12%1
1796
16th to endNight
49%48%19%14%2
1674
May1st to 15thNight
52%46%18%15%2
1520
16th to endNight
51%5%11%21%9%1
1497
June1st to 15thNight
55%5%10%20%7%1
1440
16th to endNight
45%7%13%22%10%
1440
July1st to 15thNight
41%9%13%26%10%
1360
16th to endNight
41%8%15%25%9%
1418
August1st to 15thNight
44%6%17%22%8%
1469
16th to endNight
38%417%27%11%
1867
September1st to 15thNight
44%5%12%25%10%
1818
16th to endNight
40%413%28%12%
1836
October1st to 15thNight
53%5%9%21%9%
1906
16th to endNight
63%5%9%15%5%
2282
November1st to 15thNight
60%6%9%15%6%2
2277
16th to endNight
64%38%15%6%
2463
December1st to 15thNight
75%37%10%1
2520
16th to endNight
75%47%8%4
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
26%15%33%15%10%
60
16th to endDay
32%21%28%12%4
64
February1st to 15thDay
26%29%26%13%3
117
16th to endDay
27%21%28%18%3
239
March1st to 15thDay
29%18%29%18%4
270
16th to endDay
27%17%27%13%11%3
288
April1st to 15thDay
35%14%24%17%5%1
270
16th to endDay
30%13%27%15%8%4
270
May1st to 15thDay
33%11%26%15%9%3
288
16th to endDay
22%17%30%20%7%2
331
June1st to 15thDay
35%8%25%19%8%1
315
16th to endDay
26%9%34%20%6%2
315
July1st to 15thDay
21%6%33%24%10%2
305
16th to endDay
19%7%26%32%11%2
326
August1st to 15thDay
25%7%23%23%15%3
313
16th to endDay
20%8%21%20%19%8%
332
September1st to 15thDay
21%8%25%20%16%7%
315
16th to endDay
17%10%21%27%14%8%
259
October1st to 15thDay
25%14%21%20%12%4
255
16th to endDay
39%13%20%19%6%
241
November1st to 15thDay
26%18%28%16%8%1
235
16th to endDay
28%22%21%16%7%2
114
December1st to 15thDay
40%18%21%16%11
60
16th to endDay
48%20%26%4
64
January1st to 15thNight
27%18%32%16%4
720
16th to endNight
23%18%30%20%5%
768
February1st to 15thNight
23%16%34%21%3
704
16th to endNight
25%15%33%21%3
631
March1st to 15thNight
30%15%26%23%4
720
16th to endNight
24%15%27%22%8%1
768
April1st to 15thNight
31%14%26%22%5%
718
16th to endNight
27%14%26%21%10%
594
May1st to 15thNight
26%10%30%21%9%1
440
16th to endNight
26%5%31%27%8%
375
June1st to 15thNight
33%8%17%30%10%
360
16th to endNight
19%5%27%34%12%
360
July1st to 15thNight
14%5%26%34%18%
340
16th to endNight
16%323%37%18%
376
August1st to 15thNight
19%5%19%32%21%1
398
16th to endNight
17%5%19%33%22%2
721
September1st to 15thNight
22%6%22%31%14%2
720
16th to endNight
23%6%25%24%19%2
665
October1st to 15thNight
26%10%27%20%12%2
660
16th to endNight
39%11%23%18%6%
704
November1st to 15thNight
27%14%28%18%9%1
700
16th to endNight
32%17%22%16%9%1
720
December1st to 15thNight
35%17%29%13%3
720
16th to endNight
34%18%26%15%41
768
Page generated at 2017-09-18 08:38:18. Version ac04

Copyright 2017 A. Danko


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