St-Valérien-de-Milton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the St-Valérien-de-Milton 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
28%
14610
12%
46778
8%
14578
34%
14578
14%
34619

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
16%
720
7%
2506
4%
716
21%
716
7%
2066
January16th to endNight
19%
768
8%
2688
5%
768
23%
768
8%
2153
February1st to 15thNight
17%
704
7%
2315
3%
701
23%
701
9%
1889
February16th to endNight
20%
631
9%
1893
5%
631
26%
631
10%
1511
March1st to 15thNight
23%
720
14%
2160
10%
720
29%
720
13%
1658
March16th to endNight
30%
768
19%
2008
9%
768
37%
768
19%
1464
April1st to 15thNight
24%
718
13%
1796
5%
718
28%
718
16%
1412
April16th to endNight
28%
591
17%
1671
6%
591
36%
591
19%
1177
May1st to 15thNight
28%
433
16%
1513
12%
433
36%
433
17%
1039
May16th to endNight
33%
375
11%
1497
10%
374
41%
374
15%
1004
June1st to 15thNight
31%
360
8%
1440
7%
360
39%
360
12%
1016
June16th to endNight
41%
360
8%
1440
10%
360
47%
360
18%
914
July1st to 15thNight
49%
340
11%
1360
16%
340
52%
340
19%
849
July16th to endNight
49%
376
11%
1418
16%
354
52%
354
21%
873
August1st to 15thNight
49%
393
13%
1464
13%
391
52%
391
20%
923
August16th to endNight
50%
717
18%
1863
11%
717
53%
717
32%
1225
September1st to 15thNight
43%
707
13%
1783
7%
707
44%
707
27%
1238
September16th to endNight
42%
657
19%
1815
12%
657
46%
657
29%
1184
October1st to 15thNight
31%
660
18%
1907
10%
660
39%
660
19%
1369
October16th to endNight
24%
704
9%
2284
6%
704
30%
704
12%
1745
November1st to 15thNight
24%
700
16%
2277
11%
700
32%
700
13%
1705
November16th to endNight
22%
720
12%
2472
9%
720
28%
720
10%
1899
December1st to 15thNight
15%
720
6%
2520
2%
720
20%
720
6%
2088
December16th to endNight
11%
768
9%
2688
3%
768
19%
768
6%
2218

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
20%9%36%5%34446%30%
47887
Night
20%11%46%5%34345%29%
46948
TransparencyDay
54%6%11%18%7%
47575
Night
56%5%10%18%8%
46778
SeeingDay
26%11%27%21%9%3
5613
Night
26%11%27%24%9%
14610

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
22%17%6%10%6%35%33416%
1432
16th to endDay
15%15%6%9%6%35%446%21%
1536
February1st to 15thDay
14%16%7%11%6%47%34419%
1542
16th to endDay
16%15%7%8%6%44345%21%
1580
March1st to 15thDay
19%11%5%7%6%45%445%25%
1790
16th to endDay
19%9%47%424346%33%
2214
April1st to 15thDay
24%11%37%42433430%
2152
16th to endDay
24%7%24434345%35%
2288
May1st to 15thDay
23%7%26%5%3445%6%31%
2448
16th to endDay
21%6%36%5%345%5%7%31%
2618
June1st to 15thDay
26%6%3442445%7%29%
2520
16th to endDay
21%6%26%5%245%6%8%29%
2520
July1st to 15thDay
14%5%25%5%45%5%5%9%34%
2520
16th to endDay
15%5%35%6%345%6%9%33%
2654
August1st to 15thDay
16%6%26%6%45%6%5%9%30%
2472
16th to endDay
13%5%2442445%7%44%
2336
September1st to 15thDay
19%6%35%424446%39%
2096
16th to endDay
17%6%2432435%7%43%
1815
October1st to 15thDay
25%8%26%424347%29%
1722
16th to endDay
26%12%36%425%436%23%
1587
November1st to 15thDay
21%11%45%433445%31%
1581
16th to endDay
23%12%5%6%5%24345%26%
1488
December1st to 15thDay
28%15%5%8%6%2434415%
1440
16th to endDay
26%18%5%7%5%2333416%
1536
January1st to 15thNight
21%15%6%10%6%3433419%
2506
16th to endNight
14%17%6%8%8%45%44420%
2688
February1st to 15thNight
14%15%7%13%7%35%445%19%
2314
16th to endNight
17%14%6%10%6%3433425%
1893
March1st to 15thNight
22%13%5%6%6%3324428%
2147
16th to endNight
18%12%45%42433436%
2008
April1st to 15thNight
26%11%36%5%2434427%
1796
16th to endNight
22%8%24424346%36%
1671
May1st to 15thNight
23%7%35%5%23346%33%
1513
16th to endNight
22%6%2442446%7%33%
1495
June1st to 15thNight
29%6%1443435%6%28%
1440
16th to endNight
16%5%26%5%345%6%8%36%
1440
July1st to 15thNight
15%5%26%5%25%5%6%9%35%
1440
16th to endNight
13%5%245%25%5%6%9%39%
1514
August1st to 15thNight
15%6%35%43446%7%38%
1474
16th to endNight
13%5%24424449%43%
1863
September1st to 15thNight
20%6%25%423346%40%
1783
16th to endNight
19%413423347%45%
1815
October1st to 15thNight
19%8%27%5%24345%35%
1907
16th to endNight
29%9%46%33433427%
2284
November1st to 15thNight
21%10%36%5%35%445%28%
2277
16th to endNight
24%14%47%42333426%
2472
December1st to 15thNight
25%17%6%7%6%4433418%
2520
16th to endNight
24%19%6%8%5%2322319%
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
73%47%11%3
1433
16th to endDay
64%5%11%14%4
1536
February1st to 15thDay
69%5%9%14%1
1545
16th to endDay
65%410%12%6%
1580
March1st to 15thDay
62%410%14%6%
1800
16th to endDay
53%310%19%10%1
2214
April1st to 15thDay
58%47%18%9%1
2152
16th to endDay
51%49%18%13%2
2288
May1st to 15thDay
53%410%17%12%
2448
16th to endDay
52%7%10%18%9%1
2622
June1st to 15thDay
54%6%12%17%8%
2520
16th to endDay
51%7%12%20%7%
2520
July1st to 15thDay
43%8%14%26%7%
2371
16th to endDay
47%8%16%21%6%
2487
August1st to 15thDay
50%8%15%20%4
2458
16th to endDay
38%6%17%26%10%
2336
September1st to 15thDay
45%5%12%24%10%
2096
16th to endDay
40%5%13%29%9%
1815
October1st to 15thDay
54%5%13%20%6%
1722
16th to endDay
62%5%11%15%4
1587
November1st to 15thDay
54%6%12%18%8%
1581
16th to endDay
61%5%10%14%6%
1488
December1st to 15thDay
72%410%10%1
1440
16th to endDay
73%5%8%7%5%
1536
January1st to 15thNight
69%5%8%12%3
2506
16th to endNight
67%5%8%14%5%
2688
February1st to 15thNight
68%5%8%13%3
2315
16th to endNight
64%48%12%9%
1893
March1st to 15thNight
61%37%17%8%1
2160
16th to endNight
52%37%17%14%3
2008
April1st to 15thNight
60%35%17%11%1
1796
16th to endNight
49%48%19%15%2
1671
May1st to 15thNight
51%48%17%15%3
1513
16th to endNight
48%7%10%21%9%2
1497
June1st to 15thNight
55%5%10%20%7%1
1440
16th to endNight
44%6%13%21%12%
1440
July1st to 15thNight
40%9%13%24%11%
1360
16th to endNight
39%8%16%23%11%
1418
August1st to 15thNight
43%6%17%23%8%
1464
16th to endNight
37%6%17%27%10%
1863
September1st to 15thNight
44%5%12%25%11%
1783
16th to endNight
39%5%11%29%12%
1815
October1st to 15thNight
51%5%10%22%9%
1907
16th to endNight
61%410%16%6%
2284
November1st to 15thNight
57%5%10%17%6%2
2277
16th to endNight
62%49%16%6%
2472
December1st to 15thNight
72%49%12%2
2520
16th to endNight
72%38%9%5%
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
28%11%36%18%5%
60
16th to endDay
35%15%29%14%31
64
February1st to 15thDay
36%18%25%13%7%
111
16th to endDay
27%15%33%18%4
239
March1st to 15thDay
30%18%24%22%3
270
16th to endDay
26%13%27%20%8%3
288
April1st to 15thDay
31%15%25%20%42
270
16th to endDay
28%12%28%15%10%4
270
May1st to 15thDay
33%11%27%15%9%2
288
16th to endDay
22%13%30%20%9%2
331
June1st to 15thDay
33%8%26%22%6%1
315
16th to endDay
23%9%36%20%8%1
315
July1st to 15thDay
21%7%32%22%11%3
305
16th to endDay
18%430%33%11%2
326
August1st to 15thDay
21%7%25%25%15%3
313
16th to endDay
16%8%26%20%18%9%
332
September1st to 15thDay
21%9%23%24%13%8%
299
16th to endDay
20%11%26%20%13%7%
254
October1st to 15thDay
26%11%25%21%10%4
255
16th to endDay
34%14%23%17%11%
241
November1st to 15thDay
27%14%26%19%10%1
235
16th to endDay
26%21%17%21%11%1
108
December1st to 15thDay
45%10%21%20%3
60
16th to endDay
48%12%32%41
64
January1st to 15thNight
29%14%31%19%5%
720
16th to endNight
24%16%29%22%6%
768
February1st to 15thNight
22%14%34%23%5%
704
16th to endNight
24%14%33%21%4
631
March1st to 15thNight
29%12%28%25%3
720
16th to endNight
25%12%26%26%8%1
768
April1st to 15thNight
31%12%26%24%5%
718
16th to endNight
28%14%25%21%10%
591
May1st to 15thNight
25%8%32%21%9%1
433
16th to endNight
25%7%28%29%8%
375
June1st to 15thNight
33%5%24%25%10%
360
16th to endNight
17%431%34%10%
360
July1st to 15thNight
15%5%24%35%17%1
340
16th to endNight
16%225%40%14%
376
August1st to 15thNight
18%222%34%21%
393
16th to endNight
16%323%35%17%3
717
September1st to 15thNight
22%5%23%32%14%1
707
16th to endNight
22%5%27%26%16%1
657
October1st to 15thNight
24%9%28%23%12%1
660
16th to endNight
34%11%26%21%5%
704
November1st to 15thNight
26%13%30%19%9%
700
16th to endNight
32%17%20%18%9%1
720
December1st to 15thNight
35%14%28%17%3
720
16th to endNight
35%15%25%19%31
768
Page generated at 2017-09-13 07:39:03. Version ac04

Copyright 2017 A. Danko


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