Le Domaine
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Le Domaine clear sky chart from 2005-11-05 to 2017-03-14.

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
24%
14020
12%
45050
7%
13988
31%
13988
14%
33362

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
14%
720
7%
2506
4%
716
18%
716
6%
2072
January16th to endNight
19%
768
10%
2655
5%
768
26%
768
9%
2072
February1st to 15thNight
19%
704
10%
2287
5%
701
27%
701
10%
1805
February16th to endNight
17%
631
10%
1987
4%
631
24%
631
9%
1566
March1st to 15thNight
18%
716
12%
2071
6%
716
26%
716
12%
1617
March16th to endNight
25%
704
18%
1878
8%
704
32%
704
19%
1329
April1st to 15thNight
23%
658
17%
1646
6%
658
29%
658
19%
1205
April16th to endNight
27%
533
18%
1523
8%
533
34%
533
21%
1051
May1st to 15thNight
32%
330
17%
1320
17%
330
42%
330
16%
871
May16th to endNight
29%
343
12%
1369
11%
342
40%
342
16%
898
June1st to 15thNight
26%
330
7%
1320
6%
330
33%
330
12%
921
June16th to endNight
36%
330
8%
1192
6%
330
41%
330
21%
765
July1st to 15thNight
37%
310
10%
1199
11%
310
42%
310
23%
700
July16th to endNight
47%
348
10%
1306
12%
326
52%
326
23%
785
August1st to 15thNight
43%
393
14%
1374
12%
391
47%
391
23%
867
August16th to endNight
42%
613
17%
1663
7%
613
47%
613
32%
1061
September1st to 15thNight
34%
660
13%
1650
5%
660
37%
660
26%
1159
September16th to endNight
36%
657
16%
1805
10%
657
41%
657
26%
1227
October1st to 15thNight
22%
660
15%
1980
7%
660
32%
660
15%
1471
October16th to endNight
20%
704
9%
2200
6%
704
25%
704
11%
1761
November1st to 15thNight
20%
700
15%
2391
9%
700
29%
700
11%
1779
November16th to endNight
15%
720
9%
2520
6%
720
19%
720
7%
2046
December1st to 15thNight
16%
720
8%
2520
2%
720
23%
720
7%
2071
December16th to endNight
13%
768
9%
2688
5%
768
19%
768
6%
2263

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%12%47%6%34446%25%
45656
Night
18%12%47%6%34445%26%
45219
TransparencyDay
59%29%18%8%
45343
Night
59%210%18%8%
45050
SeeingDay
26%11%32%19%8%2
4793
Night
27%10%29%22%8%1
14020

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%7%11%7%22336%13%
1432
16th to endDay
15%15%6%10%8%35%5%5%5%16%
1566
February1st to 15thDay
8%17%7%13%11%46%446%15%
1575
16th to endDay
16%19%6%9%6%3442421%
1485
March1st to 15thDay
17%15%5%8%6%25%445%26%
1848
16th to endDay
13%10%47%5%35%5%5%6%33%
1994
April1st to 15thDay
23%15%46%422335%28%
1972
16th to endDay
21%10%46%423345%34%
2116
May1st to 15thDay
20%10%46%425%447%29%
2301
16th to endDay
22%7%36%5%3435%5%31%
2394
June1st to 15thDay
22%8%37%7%45%5%5%6%23%
2310
16th to endDay
16%6%26%5%47%5%6%8%29%
2433
July1st to 15thDay
18%6%45%6%46%46%9%29%
2346
16th to endDay
16%8%37%6%45%5%5%7%29%
2458
August1st to 15thDay
20%8%47%6%45%5%5%5%26%
2244
16th to endDay
17%7%26%6%35%45%7%32%
2176
September1st to 15thDay
22%7%26%5%24446%32%
1980
16th to endDay
22%8%25%42335%6%36%
1824
October1st to 15thDay
23%14%47%424346%25%
1650
16th to endDay
30%19%47%5%3332314%
1671
November1st to 15thDay
19%15%6%8%424425%25%
1465
16th to endDay
25%16%8%10%5%2433415%
1440
December1st to 15thDay
21%20%8%10%7%35%43410%
1440
16th to endDay
22%19%8%9%7%3443312%
1536
January1st to 15thNight
19%18%7%12%7%3434413%
2506
16th to endNight
14%15%6%10%8%45%46%6%16%
2655
February1st to 15thNight
11%12%6%10%12%6%6%445%18%
2285
16th to endNight
13%17%6%9%8%35%44320%
1987
March1st to 15thNight
17%15%5%7%6%36%445%22%
2058
16th to endNight
15%10%37%5%35%43336%
1878
April1st to 15thNight
21%10%45%433335%33%
1646
16th to endNight
19%8%35%5%34345%36%
1523
May1st to 15thNight
20%8%36%425%345%35%
1320
16th to endNight
19%8%35%434446%33%
1367
June1st to 15thNight
20%8%46%6%35%5%46%26%
1320
16th to endNight
16%6%35%4345%5%7%36%
1192
July1st to 15thNight
15%5%235%245%5%8%39%
1279
16th to endNight
11%5%245%35%5%6%9%38%
1402
August1st to 15thNight
13%7%26%5%25%5%6%7%37%
1384
16th to endNight
11%6%25%4245%6%7%42%
1663
September1st to 15thNight
18%9%25%424446%37%
1650
16th to endNight
19%6%35%423445%39%
1805
October1st to 15thNight
23%11%46%5%2444428%
1980
16th to endNight
28%16%47%423445%19%
2200
November1st to 15thNight
21%12%5%7%5%34445%25%
2391
16th to endNight
26%16%6%8%6%2323417%
2520
December1st to 15thNight
22%18%6%9%6%345%35%13%
2520
16th to endNight
20%19%7%11%7%4432413%
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%26%11%4
1433
16th to endDay
67%26%14%8%
1566
February1st to 15thDay
69%27%13%7%
1577
16th to endDay
66%15%16%9%
1485
March1st to 15thDay
61%37%16%9%1
1858
16th to endDay
50%39%18%14%3
1994
April1st to 15thDay
59%17%16%11%2
1972
16th to endDay
53%26%19%15%2
2116
May1st to 15thDay
54%27%21%13%1
2301
16th to endDay
53%28%21%12%1
2398
June1st to 15thDay
60%39%18%8%
2310
16th to endDay
50%411%23%9%
2433
July1st to 15thDay
50%312%23%9%
2197
16th to endDay
54%312%20%8%
2291
August1st to 15thDay
58%312%19%5%
2230
16th to endDay
50%314%23%8%
2176
September1st to 15thDay
51%313%20%10%
1980
16th to endDay
49%314%25%6%
1824
October1st to 15thDay
60%211%16%8%
1650
16th to endDay
75%26%10%3
1671
November1st to 15thDay
61%212%15%7%
1465
16th to endDay
73%27%11%5%
1440
December1st to 15thDay
77%25%12%2
1440
16th to endDay
75%25%10%4
1536
January1st to 15thNight
74%27%11%3
2506
16th to endNight
65%36%15%8%
2655
February1st to 15thNight
66%27%16%6%
2287
16th to endNight
66%26%13%9%
1987
March1st to 15thNight
63%37%17%8%
2071
16th to endNight
50%37%20%15%2
1878
April1st to 15thNight
54%16%20%14%2
1646
16th to endNight
50%27%21%15%3
1523
May1st to 15thNight
51%27%20%15%2
1320
16th to endNight
51%28%23%12%1
1369
June1st to 15thNight
56%310%19%9%
1320
16th to endNight
45%412%26%10%
1192
July1st to 15thNight
39%416%28%11%
1199
16th to endNight
41%319%27%8%
1306
August1st to 15thNight
43%418%27%5%
1374
16th to endNight
37%5%18%30%7%
1663
September1st to 15thNight
47%217%23%8%
1650
16th to endNight
46%215%29%6%
1805
October1st to 15thNight
58%310%17%9%
1980
16th to endNight
67%210%15%3
2200
November1st to 15thNight
61%210%18%6%
2391
16th to endNight
71%28%13%4
2520
December1st to 15thNight
71%28%13%3
2520
16th to endNight
75%25%10%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
31%18%38%10%1
60
16th to endDay
33%8%39%8%10%
69
February1st to 15thDay
26%17%43%11%1
90
16th to endDay
35%15%33%12%2
144
March1st to 15thDay
28%16%32%18%4
264
16th to endDay
20%13%38%17%7%1
224
April1st to 15thDay
32%15%25%16%8%1
210
16th to endDay
24%14%30%16%10%3
210
May1st to 15thDay
30%8%32%16%9%2
228
16th to endDay
27%12%30%17%8%2
267
June1st to 15thDay
32%8%34%15%8%
255
16th to endDay
15%10%34%26%10%2
378
July1st to 15thDay
18%8%36%27%6%2
281
16th to endDay
20%431%27%12%3
270
August1st to 15thDay
24%428%25%9%7%
253
16th to endDay
19%5%33%23%8%7%
268
September1st to 15thDay
26%5%30%17%13%6%
255
16th to endDay
25%9%25%22%12%4
254
October1st to 15thDay
27%16%29%16%8%1
255
16th to endDay
39%12%24%18%41
255
November1st to 15thDay
26%10%37%17%6%
119
16th to endDay
38%16%28%13%11
60
December1st to 15thDay
35%11%43%6%11
60
16th to endDay
39%21%34%4
64
January1st to 15thNight
32%12%31%20%2
720
16th to endNight
24%11%33%23%7%1
768
February1st to 15thNight
20%14%35%21%6%
704
16th to endNight
25%14%32%21%4
631
March1st to 15thNight
28%16%29%21%3
716
16th to endNight
22%13%31%22%9%
704
April1st to 15thNight
29%13%28%23%4
658
16th to endNight
25%10%31%23%8%
533
May1st to 15thNight
23%8%29%26%10%1
330
16th to endNight
25%8%31%25%9%
343
June1st to 15thNight
28%7%26%26%10%
330
16th to endNight
18%6%30%31%12%
330
July1st to 15thNight
17%5%33%32%10%
310
16th to endNight
13%427%39%14%
348
August1st to 15thNight
17%424%30%20%2
393
16th to endNight
15%331%29%17%2
613
September1st to 15thNight
24%5%29%24%14%2
660
16th to endNight
23%5%28%26%13%1
657
October1st to 15thNight
29%10%31%20%6%1
660
16th to endNight
36%9%28%18%5%1
704
November1st to 15thNight
31%14%28%17%7%1
700
16th to endNight
38%14%23%15%6%1
720
December1st to 15thNight
35%14%27%18%4
720
16th to endNight
34%12%30%17%41
768
Page generated at 2017-03-15 11:32:34. Version ac04

Copyright 2017 A. Danko


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