L'Assomption
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the L'Assomption clear sky chart from 2005-11-05 to 2017-03-31.

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%
14161
13%
45371
8%
14129
36%
14129
15%
32595

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
19%
720
9%
2506
5%
716
24%
716
9%
1965
January16th to endNight
23%
768
10%
2688
6%
768
30%
768
9%
2033
February1st to 15thNight
19%
704
8%
2320
5%
701
24%
701
9%
1825
February16th to endNight
24%
631
12%
1893
7%
631
31%
631
13%
1444
March1st to 15thNight
25%
720
14%
2160
9%
720
30%
720
13%
1630
March16th to endNight
30%
768
19%
2001
9%
768
36%
768
20%
1436
April1st to 15thNight
24%
658
16%
1646
6%
658
30%
658
18%
1244
April16th to endNight
25%
559
16%
1549
4%
559
35%
559
18%
1079
May1st to 15thNight
28%
366
17%
1356
13%
366
39%
366
14%
899
May16th to endNight
30%
343
12%
1369
10%
342
40%
342
15%
901
June1st to 15thNight
29%
330
8%
1320
6%
330
37%
330
11%
926
June16th to endNight
43%
330
8%
1320
10%
330
47%
330
16%
844
July1st to 15thNight
47%
310
12%
1240
17%
310
53%
310
22%
725
July16th to endNight
45%
348
10%
1306
10%
326
54%
326
20%
779
August1st to 15thNight
52%
336
14%
1317
16%
334
56%
334
18%
831
August16th to endNight
51%
681
17%
1731
9%
681
54%
681
31%
1133
September1st to 15thNight
45%
660
14%
1650
7%
660
46%
660
26%
1157
September16th to endNight
46%
657
20%
1812
13%
657
50%
657
30%
1160
October1st to 15thNight
32%
660
19%
1934
12%
660
41%
660
20%
1335
October16th to endNight
27%
704
11%
2266
7%
704
34%
704
14%
1680
November1st to 15thNight
27%
700
17%
2277
12%
700
34%
700
15%
1629
November16th to endNight
22%
720
13%
2502
8%
720
30%
720
11%
1857
December1st to 15thNight
18%
720
8%
2520
4%
720
23%
720
9%
1960
December16th to endNight
14%
768
11%
2688
4%
768
22%
768
8%
2123

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
18%8%35%5%3445%6%34%
45720
Night
19%9%46%5%34445%33%
45540
Cloud CoverDay
17%8%36%5%35%45%6%33%
45730
Night
18%9%46%5%34445%32%
45545
TransparencyDay
50%6%12%19%9%1
45407
Night
53%5%11%19%9%1
45371
SeeingDay
19%14%23%24%13%4
4912
Night
20%19%23%26%9%
14161

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
21%14%47%6%35%33425%
1432
16th to endDay
13%14%37%6%25%446%29%
1536
February1st to 15thDay
14%14%5%8%6%34446%26%
1540
16th to endDay
17%11%5%9%5%24445%28%
1580
March1st to 15thDay
18%10%46%6%35%445%29%
1790
16th to endDay
17%8%44433345%39%
2217
April1st to 15thDay
21%8%35%5%34445%33%
1972
16th to endDay
19%7%245%25%435%39%
2079
May1st to 15thDay
20%6%36%434446%35%
2274
16th to endDay
20%5%35%5%35%448%32%
2394
June1st to 15thDay
23%6%25%5%245%5%8%30%
2310
16th to endDay
18%5%35%5%36%6%5%8%31%
2310
July1st to 15thDay
13%425%5%26%5%6%8%37%
2310
16th to endDay
13%4345%45%6%7%9%36%
2458
August1st to 15thDay
13%5%25%7%45%6%5%8%34%
2291
16th to endDay
10%414435%5%6%7%46%
2118
September1st to 15thDay
15%5%25%335%447%40%
1980
16th to endDay
14%5%24324346%48%
1818
October1st to 15thDay
21%7%25%5%3445%6%34%
1694
16th to endDay
23%8%45%5%33445%29%
1605
November1st to 15thDay
17%9%36%43445%7%33%
1581
16th to endDay
24%9%345%23445%32%
1455
December1st to 15thDay
26%12%46%6%24345%24%
1440
16th to endDay
26%13%46%5%2333425%
1536
January1st to 15thNight
18%15%5%8%6%34445%23%
2506
16th to endNight
13%12%6%8%6%36%45%5%26%
2688
February1st to 15thNight
13%13%7%11%7%45%435%23%
2318
16th to endNight
17%11%49%6%34445%28%
1893
March1st to 15thNight
21%10%46%5%35%34430%
2147
16th to endNight
16%9%45%42333440%
2001
April1st to 15thNight
25%8%36%423435%31%
1646
16th to endNight
22%6%24423446%37%
1549
May1st to 15thNight
20%6%35%6%23345%37%
1356
16th to endNight
21%6%344345%47%34%
1367
June1st to 15thNight
25%8%245%34448%29%
1320
16th to endNight
16%5%345%345%6%7%37%
1320
July1st to 15thNight
10%5%24425%48%9%40%
1320
16th to endNight
11%424425%5%7%8%41%
1402
August1st to 15thNight
13%5%36%5%25%46%7%39%
1327
16th to endNight
13%41343445%7%46%
1731
September1st to 15thNight
17%5%15%434446%41%
1650
16th to endNight
17%324414346%48%
1812
October1st to 15thNight
18%5%26%5%33445%39%
1934
16th to endNight
26%8%36%42433432%
2266
November1st to 15thNight
20%8%35%5%34445%33%
2277
16th to endNight
23%11%36%5%2433430%
2502
December1st to 15thNight
23%12%5%7%5%23335%26%
2520
16th to endNight
23%15%5%8%5%2333424%
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
21%14%48%7%3443424%
1432
16th to endDay
14%13%47%6%345%5%5%28%
1536
February1st to 15thDay
14%14%5%8%6%35%45%5%25%
1540
16th to endDay
18%12%5%8%5%25%45%428%
1580
March1st to 15thDay
18%10%47%6%35%445%28%
1800
16th to endDay
16%8%36%5%24345%39%
2217
April1st to 15thDay
20%8%36%5%25%435%33%
1972
16th to endDay
19%7%245%34435%38%
2079
May1st to 15thDay
19%6%36%5%24347%35%
2274
16th to endDay
19%6%345%36%45%8%32%
2394
June1st to 15thDay
23%6%25%42446%8%30%
2310
16th to endDay
17%5%36%5%36%5%6%8%31%
2310
July1st to 15thDay
11%5%245%36%6%6%8%38%
2310
16th to endDay
12%5%25%435%6%8%8%36%
2458
August1st to 15thDay
12%5%26%6%35%6%5%8%34%
2291
16th to endDay
9%5%23426%46%7%46%
2118
September1st to 15thDay
15%5%25%4145%6%7%41%
1980
16th to endDay
13%5%24423346%47%
1818
October1st to 15thDay
20%7%25%43446%6%33%
1694
16th to endDay
23%9%36%6%33445%28%
1605
November1st to 15thDay
16%8%46%425%5%5%7%32%
1581
16th to endDay
23%10%35%433445%31%
1455
December1st to 15thDay
26%12%48%5%2445%5%22%
1440
16th to endDay
26%13%5%6%5%2333424%
1536
January1st to 15thNight
18%15%6%9%6%34445%22%
2506
16th to endNight
13%12%5%8%7%46%445%25%
2688
February1st to 15thNight
12%14%7%10%8%45%44423%
2311
16th to endNight
17%11%5%8%6%44445%27%
1893
March1st to 15thNight
21%12%46%6%3434329%
2160
16th to endNight
16%10%5%5%5%2433439%
2000
April1st to 15thNight
24%8%45%5%24345%31%
1646
16th to endNight
22%6%25%433446%37%
1549
May1st to 15thNight
19%7%37%6%23435%36%
1356
16th to endNight
21%6%35%5%25%45%7%33%
1367
June1st to 15thNight
25%7%345%3346%7%27%
1320
16th to endNight
15%5%25%5%35%5%6%8%36%
1320
July1st to 15thNight
10%434445%5%6%9%40%
1320
16th to endNight
11%4245%25%5%6%10%40%
1402
August1st to 15thNight
13%6%35%5%346%6%7%38%
1327
16th to endNight
13%4145%3345%8%45%
1731
September1st to 15thNight
16%6%16%424445%41%
1650
16th to endNight
16%5%14313347%47%
1812
October1st to 15thNight
18%6%25%5%24446%38%
1934
16th to endNight
25%9%36%5%24335%31%
2266
November1st to 15thNight
20%8%35%5%34445%32%
2277
16th to endNight
23%11%47%5%3433429%
2502
December1st to 15thNight
23%12%5%8%5%23335%24%
2520
16th to endNight
23%16%6%7%5%2333423%
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
65%5%8%14%5%
1433
16th to endDay
57%5%11%16%7%
1536
February1st to 15thDay
61%5%10%17%3
1542
16th to endDay
59%410%15%9%1
1580
March1st to 15thDay
58%5%11%16%8%1
1800
16th to endDay
48%410%18%13%3
2217
April1st to 15thDay
54%47%19%11%2
1972
16th to endDay
47%48%20%14%3
2079
May1st to 15thDay
48%5%10%19%14%1
2274
16th to endDay
48%7%12%18%11%1
2398
June1st to 15thDay
50%7%11%17%10%1
2310
16th to endDay
47%7%12%22%8%
2310
July1st to 15thDay
39%8%14%25%11%
2161
16th to endDay
41%9%18%22%7%
2291
August1st to 15thDay
45%8%16%22%6%
2277
16th to endDay
33%8%19%26%12%
2118
September1st to 15thDay
40%6%14%26%11%
1980
16th to endDay
37%5%13%30%12%
1818
October1st to 15thDay
49%7%13%20%8%
1694
16th to endDay
57%5%12%17%6%
1605
November1st to 15thDay
50%6%13%19%9%
1581
16th to endDay
54%6%13%17%8%
1455
December1st to 15thDay
64%5%12%14%3
1440
16th to endDay
65%411%10%7%
1536
January1st to 15thNight
63%5%11%14%4
2506
16th to endNight
59%6%9%16%7%
2688
February1st to 15thNight
64%49%15%5%
2320
16th to endNight
59%49%14%10%
1893
March1st to 15thNight
58%49%17%8%1
2160
16th to endNight
49%49%17%15%3
2001
April1st to 15thNight
56%35%19%13%1
1646
16th to endNight
48%48%18%16%4
1549
May1st to 15thNight
48%48%17%14%4
1356
16th to endNight
49%410%20%12%2
1369
June1st to 15thNight
55%5%10%17%10%1
1320
16th to endNight
43%8%12%19%15%1
1320
July1st to 15thNight
36%7%14%27%13%1
1240
16th to endNight
37%8%18%22%12%
1306
August1st to 15thNight
42%7%16%22%10%
1317
16th to endNight
36%5%16%27%12%
1731
September1st to 15thNight
43%6%11%25%12%
1650
16th to endNight
37%5%11%30%13%
1812
October1st to 15thNight
47%5%10%24%11%
1934
16th to endNight
57%5%11%18%7%
2266
November1st to 15thNight
53%412%18%8%2
2277
16th to endNight
59%310%18%6%
2502
December1st to 15thNight
64%412%15%3
2520
16th to endNight
66%49%12%6%
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
18%13%25%28%15%
60
16th to endDay
28%6%34%21%7%1
64
February1st to 15thDay
31%16%27%19%4
91
16th to endDay
23%15%26%26%6%
239
March1st to 15thDay
21%20%26%25%6%
270
16th to endDay
20%14%29%24%10%1
286
April1st to 15thDay
19%23%22%22%8%2
210
16th to endDay
13%21%21%27%10%3
210
May1st to 15thDay
21%16%23%20%13%4
228
16th to endDay
18%19%23%19%16%3
267
June1st to 15thDay
25%18%20%21%10%2
255
16th to endDay
15%15%17%33%15%3
255
July1st to 15thDay
14%10%22%26%20%6%
245
16th to endDay
12%12%17%32%19%5%
270
August1st to 15thDay
15%9%18%23%24%9%
253
16th to endDay
9%7%20%26%19%15%
268
September1st to 15thDay
15%9%17%26%19%11%
255
16th to endDay
15%13%25%18%15%11%
254
October1st to 15thDay
20%11%24%24%16%3
255
16th to endDay
26%12%25%22%13%
243
November1st to 15thDay
19%16%26%24%11%1
235
16th to endDay
29%12%25%21%12%
75
December1st to 15thDay
28%333%25%6%3
60
16th to endDay
42%10%37%9%
64
January1st to 15thNight
20%24%25%23%6%
720
16th to endNight
17%22%28%25%5%
768
February1st to 15thNight
18%21%29%23%6%
704
16th to endNight
21%19%26%26%5%
631
March1st to 15thNight
24%21%24%23%5%
720
16th to endNight
19%19%25%26%8%
768
April1st to 15thNight
23%23%23%25%4
658
16th to endNight
20%24%25%21%7%
559
May1st to 15thNight
17%22%23%25%9%1
366
16th to endNight
17%22%25%28%6%
343
June1st to 15thNight
26%20%17%27%8%
330
16th to endNight
14%19%18%34%12%
330
July1st to 15thNight
10%15%23%29%20%
310
16th to endNight
12%18%16%37%13%
348
August1st to 15thNight
11%11%13%38%22%1
336
16th to endNight
13%11%17%34%22%1
681
September1st to 15thNight
16%11%18%36%15%1
660
16th to endNight
19%11%18%29%18%1
657
October1st to 15thNight
19%14%28%26%10%1
660
16th to endNight
26%16%24%24%8%
704
November1st to 15thNight
19%18%27%23%10%
700
16th to endNight
23%22%25%17%9%
720
December1st to 15thNight
27%21%23%21%4
720
16th to endNight
28%22%26%17%4
768
Page generated at 2017-04-01 08:23:15. Version ac04

Copyright 2017 A. Danko


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