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 2017-12-04.

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%
14849
12%
47667
7%
14817
31%
14817
14%
35200

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%
720
12%
2082
6%
720
25%
720
12%
1628
March16th to endNight
25%
768
19%
2049
8%
768
33%
768
20%
1444
April1st to 15thNight
24%
718
16%
1796
6%
718
29%
718
19%
1327
April16th to endNight
26%
582
18%
1662
8%
582
33%
582
20%
1159
May1st to 15thNight
31%
360
16%
1440
15%
360
40%
360
15%
976
May16th to endNight
29%
375
12%
1497
11%
374
40%
374
15%
999
June1st to 15thNight
27%
360
7%
1440
6%
360
33%
360
13%
992
June16th to endNight
35%
360
8%
1300
7%
360
40%
360
20%
841
July1st to 15thNight
37%
340
10%
1315
11%
340
42%
340
22%
778
July16th to endNight
48%
376
12%
1418
14%
354
52%
354
23%
852
August1st to 15thNight
44%
429
13%
1500
12%
427
48%
427
23%
948
August16th to endNight
42%
669
19%
1815
8%
669
48%
669
32%
1156
September1st to 15thNight
36%
720
13%
1800
5%
720
39%
720
28%
1247
September16th to endNight
39%
717
18%
1970
11%
717
43%
717
27%
1324
October1st to 15thNight
25%
720
14%
2160
8%
720
34%
720
16%
1574
October16th to endNight
19%
768
10%
2400
6%
768
26%
768
12%
1896
November1st to 15thNight
20%
760
14%
2596
8%
760
29%
760
11%
1946
November16th to endNight
16%
780
9%
2730
6%
780
20%
780
7%
2213
December1st to 15thNight
15%
736
8%
2574
2%
736
22%
736
7%
2122
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%26%
48823
Night
18%12%47%6%34445%26%
47836
TransparencyDay
59%39%18%8%
48510
Night
58%210%19%8%
47667
SeeingDay
27%11%31%19%8%2
5789
Night
26%10%29%23%8%1
14849

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%35%44425%
1865
16th to endDay
13%9%47%5%35%45%6%33%
2175
April1st to 15thDay
23%15%45%422335%28%
2152
16th to endDay
21%10%46%423345%33%
2308
May1st to 15thDay
22%10%46%425%446%27%
2511
16th to endDay
23%7%36%5%3435%5%31%
2618
June1st to 15thDay
22%9%37%7%45%45%6%24%
2520
16th to endDay
17%6%27%5%47%5%6%8%28%
2654
July1st to 15thDay
17%6%35%6%46%45%9%29%
2559
16th to endDay
16%8%37%6%45%5%5%7%30%
2654
August1st to 15thDay
19%8%37%7%45%5%5%6%26%
2448
16th to endDay
16%7%26%6%35%45%7%32%
2375
September1st to 15thDay
22%6%26%5%24446%34%
2160
16th to endDay
21%8%2432335%6%37%
1989
October1st to 15thDay
22%13%47%414346%27%
1800
16th to endDay
29%19%37%6%3333315%
1823
November1st to 15thDay
18%17%6%8%424335%24%
1590
16th to endDay
25%16%8%10%6%2433414%
1560
December1st to 15thDay
21%20%8%10%7%35%43410%
1468
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
18%15%5%7%6%36%445%22%
2069
16th to endNight
15%10%37%5%3443436%
2049
April1st to 15thNight
21%11%45%5%23335%33%
1796
16th to endNight
19%8%35%5%34345%35%
1662
May1st to 15thNight
21%9%46%425%335%33%
1440
16th to endNight
20%8%36%434446%32%
1495
June1st to 15thNight
19%8%46%6%35%6%47%27%
1440
16th to endNight
16%6%35%5%345%5%7%36%
1300
July1st to 15thNight
14%5%346%345%5%8%38%
1395
16th to endNight
11%5%245%35%5%6%9%38%
1514
August1st to 15thNight
13%7%27%5%3445%7%37%
1510
16th to endNight
11%6%25%4245%5%7%42%
1815
September1st to 15thNight
17%8%24424446%38%
1800
16th to endNight
18%6%35%423446%40%
1970
October1st to 15thNight
22%10%46%5%2444430%
2160
16th to endNight
27%16%37%423445%20%
2400
November1st to 15thNight
21%13%5%7%6%34445%24%
2596
16th to endNight
25%17%6%8%6%2323417%
2730
December1st to 15thNight
22%18%6%9%6%34435%13%
2574
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
1875
16th to endDay
49%38%19%14%4
2175
April1st to 15thDay
59%17%17%11%2
2152
16th to endDay
54%26%19%14%2
2308
May1st to 15thDay
56%27%20%12%1
2511
16th to endDay
54%28%20%12%1
2622
June1st to 15thDay
59%38%18%9%
2520
16th to endDay
51%411%22%8%
2654
July1st to 15thDay
49%312%24%9%
2410
16th to endDay
53%312%21%8%
2487
August1st to 15thDay
58%312%19%5%
2434
16th to endDay
50%314%24%7%
2375
September1st to 15thDay
50%313%20%11%
2160
16th to endDay
48%314%26%6%
1989
October1st to 15thDay
58%212%18%8%
1800
16th to endDay
74%27%11%3
1823
November1st to 15thDay
63%311%14%7%
1590
16th to endDay
74%26%11%5%
1560
December1st to 15thDay
77%25%12%2
1468
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%
2082
16th to endNight
50%37%20%16%2
2049
April1st to 15thNight
55%16%20%14%2
1796
16th to endNight
50%27%21%14%3
1662
May1st to 15thNight
54%26%19%14%2
1440
16th to endNight
51%39%22%11%1
1497
June1st to 15thNight
55%310%20%9%
1440
16th to endNight
46%413%25%10%
1300
July1st to 15thNight
40%415%27%11%
1315
16th to endNight
41%318%27%8%
1418
August1st to 15thNight
43%418%27%5%
1500
16th to endNight
37%5%18%31%7%
1815
September1st to 15thNight
46%217%24%9%
1800
16th to endNight
44%215%30%6%
1970
October1st to 15thNight
55%311%19%10%
2160
16th to endNight
65%210%17%3
2400
November1st to 15thNight
61%211%17%6%
2596
16th to endNight
71%28%13%4
2730
December1st to 15thNight
72%27%13%3
2574
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
30%15%31%17%4
270
16th to endDay
22%13%38%16%6%1
288
April1st to 15thDay
35%17%23%15%7%1
270
16th to endDay
28%16%30%14%8%2
270
May1st to 15thDay
35%10%29%14%7%2
288
16th to endDay
29%12%30%16%8%2
331
June1st to 15thDay
31%9%34%16%6%
315
16th to endDay
18%10%34%23%10%1
449
July1st to 15thDay
17%8%36%27%6%2
344
16th to endDay
21%5%28%28%12%3
326
August1st to 15thDay
22%5%28%28%9%6%
313
16th to endDay
19%6%31%24%10%7%
332
September1st to 15thDay
25%5%31%18%13%5%
315
16th to endDay
24%7%23%24%15%4
314
October1st to 15thDay
25%16%30%17%8%
315
16th to endDay
38%12%26%17%4
311
November1st to 15thDay
27%11%36%17%5%1
154
16th to endDay
36%25%26%8%11
90
December1st to 15thDay
35%10%43%7%11
67
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
720
16th to endNight
22%13%31%22%9%
768
April1st to 15thNight
30%13%27%23%5%
718
16th to endNight
25%10%32%22%8%
582
May1st to 15thNight
25%8%28%26%10%1
360
16th to endNight
25%9%30%25%8%
375
June1st to 15thNight
27%7%26%27%10%
360
16th to endNight
19%6%31%30%11%
360
July1st to 15thNight
16%5%33%33%11%
340
16th to endNight
14%326%40%14%
376
August1st to 15thNight
17%423%30%21%2
429
16th to endNight
14%331%28%18%2
669
September1st to 15thNight
23%5%28%25%15%2
720
16th to endNight
22%5%27%27%14%1
717
October1st to 15thNight
28%10%30%21%7%1
720
16th to endNight
35%10%29%18%5%1
768
November1st to 15thNight
31%13%28%17%7%1
760
16th to endNight
38%14%23%16%6%1
780
December1st to 15thNight
35%13%27%18%4
736
16th to endNight
34%12%30%17%41
768
Page generated at 2017-12-05 10:19:00. Version ac04

Copyright 2017 A. Danko


Le Domaine Clear Sky Chart |Charts Home