La Sarre
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the La Sarre clear sky chart from 2005-11-05 to 2018-03-21.

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
30%
15805
9%
49194
6%
15773
33%
15773
12%
38627

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
21%
974
6%
2910
4%
970
23%
970
7%
2513
January16th to endNight
30%
950
7%
2952
4%
950
33%
950
9%
2465
February1st to 15thNight
34%
764
8%
2482
8%
761
37%
761
11%
1989
February16th to endNight
26%
683
8%
2220
5%
683
30%
683
9%
1810
March1st to 15thNight
29%
780
10%
2197
8%
780
31%
780
13%
1776
March16th to endNight
37%
792
18%
2172
11%
792
41%
792
21%
1572
April1st to 15thNight
29%
682
12%
1760
6%
682
32%
682
17%
1348
April16th to endNight
35%
540
15%
1620
10%
540
40%
540
20%
1156
May1st to 15thNight
36%
366
13%
1446
14%
366
41%
366
15%
1012
May16th to endNight
37%
375
8%
1428
7%
374
42%
374
15%
996
June1st to 15thNight
39%
360
6%
1260
5%
360
41%
360
17%
882
June16th to endNight
43%
360
7%
1260
4%
360
44%
360
22%
810
July1st to 15thNight
48%
340
6%
1190
6%
340
48%
340
21%
786
July16th to endNight
51%
376
10%
1298
13%
354
51%
354
17%
889
August1st to 15thNight
45%
482
8%
1553
6%
480
47%
480
18%
1111
August16th to endNight
45%
585
14%
1731
10%
585
47%
585
23%
1188
September1st to 15thNight
37%
720
9%
1800
4%
720
39%
720
21%
1344
September16th to endNight
40%
717
14%
1999
9%
717
42%
717
22%
1408
October1st to 15thNight
30%
720
10%
2160
9%
720
33%
720
14%
1663
October16th to endNight
22%
768
7%
2403
5%
768
25%
768
8%
2042
November1st to 15thNight
19%
760
6%
2662
5%
760
22%
760
7%
2246
November16th to endNight
15%
780
5%
2730
3%
780
18%
780
6%
2340
December1st to 15thNight
19%
891
3%
2841
1%
891
21%
891
5%
2513
December16th to endNight
21%
1040
6%
3120
4%
1040
22%
1040
5%
2768

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
19%11%47%6%35%45%6%24%
49673
Night
17%13%5%8%6%35%445%23%
49347
TransparencyDay
59%6%10%15%6%
49344
Night
62%6%10%14%6%
49194
SeeingDay
24%7%25%26%13%3
6449
Night
24%6%27%29%10%1
15806

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
19%17%7%9%8%45%6%6%5%9%
1358
16th to endDay
13%18%7%8%8%47%6%6%7%11%
1619
February1st to 15thDay
8%12%7%9%9%5%10%6%7%7%15%
1710
16th to endDay
11%16%7%11%8%45%445%19%
1539
March1st to 15thDay
13%11%5%10%9%36%435%24%
2081
16th to endDay
12%11%5%6%5%45%5%45%32%
2180
April1st to 15thDay
22%12%46%5%2444426%
2197
16th to endDay
18%11%37%5%24445%32%
2340
May1st to 15thDay
19%10%45%5%245%5%6%28%
2504
16th to endDay
24%9%35%5%24347%29%
2684
June1st to 15thDay
20%8%36%6%345%5%7%29%
2700
16th to endDay
18%7%35%5%35%5%6%7%31%
2700
July1st to 15thDay
19%7%36%5%35%5%5%7%28%
2700
16th to endDay
16%8%36%7%36%5%5%7%29%
2781
August1st to 15thDay
19%9%37%6%35%5%5%7%26%
2395
16th to endDay
17%7%36%6%35%5%5%8%29%
2459
September1st to 15thDay
22%7%36%5%2445%7%30%
2160
16th to endDay
21%9%46%5%34335%32%
1957
October1st to 15thDay
24%13%36%433445%28%
1800
16th to endDay
31%17%5%7%424335%14%
1821
November1st to 15thDay
24%16%6%9%6%3344315%
1526
16th to endDay
25%19%8%10%7%3333311%
1560
December1st to 15thDay
19%21%8%10%7%26%45%5%9%
1446
16th to endDay
16%21%7%12%10%46%4339%
1456
January1st to 15thNight
18%17%7%11%8%35%5%5%412%
2910
16th to endNight
13%15%7%9%9%5%6%6%5%6%13%
2952
February1st to 15thNight
8%13%7%10%9%5%8%5%5%8%17%
2480
16th to endNight
12%18%6%10%7%47%5%4417%
2220
March1st to 15thNight
16%11%6%10%8%47%34323%
2185
16th to endNight
12%10%46%6%45%447%33%
2172
April1st to 15thNight
21%11%47%5%2443429%
1760
16th to endNight
20%9%36%424436%34%
1620
May1st to 15thNight
16%10%25%6%35%5%45%31%
1446
16th to endNight
21%7%35%5%35%45%8%30%
1426
June1st to 15thNight
20%7%45%5%2445%6%33%
1260
16th to endNight
14%5%35%5%35%45%8%38%
1260
July1st to 15thNight
16%5%345%35%6%6%8%34%
1260
16th to endNight
14%6%26%6%25%5%6%7%35%
1387
August1st to 15thNight
14%9%45%6%3446%7%32%
1563
16th to endNight
15%6%26%425%448%38%
1731
September1st to 15thNight
19%7%36%6%34446%33%
1800
16th to endNight
20%7%25%423446%37%
1999
October1st to 15thNight
21%11%37%5%33446%27%
2160
16th to endNight
25%18%48%5%34345%16%
2403
November1st to 15thNight
22%17%7%9%6%3443417%
2662
16th to endNight
23%18%6%9%6%2433415%
2730
December1st to 15thNight
18%19%7%11%8%46%5%4410%
2841
16th to endNight
18%18%8%11%8%46%44310%
3120

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%6%7%10%1
1359
16th to endDay
69%6%7%10%6%
1619
February1st to 15thDay
63%7%10%12%6%
1712
16th to endDay
66%5%8%15%4
1539
March1st to 15thDay
62%48%13%10%
2092
16th to endDay
52%48%21%10%2
2180
April1st to 15thDay
59%48%16%9%1
2197
16th to endDay
53%5%10%15%14%1
2340
May1st to 15thDay
53%7%9%17%10%1
2504
16th to endDay
54%6%10%19%9%
2688
June1st to 15thDay
52%5%11%19%10%
2700
16th to endDay
50%8%12%19%9%
2700
July1st to 15thDay
50%7%15%19%6%
2541
16th to endDay
53%8%12%20%5%
2607
August1st to 15thDay
56%8%15%16%2
2381
16th to endDay
51%8%16%17%5%
2459
September1st to 15thDay
51%7%14%18%6%
2160
16th to endDay
55%6%12%21%4
1957
October1st to 15thDay
59%5%12%15%7%
1800
16th to endDay
75%5%6%9%2
1821
November1st to 15thDay
73%6%9%7%3
1526
16th to endDay
79%47%6%1
1560
December1st to 15thDay
75%6%6%9%2
1446
16th to endDay
78%5%6%6%3
1456
January1st to 15thNight
74%5%7%10%1
2910
16th to endNight
70%5%8%10%4
2952
February1st to 15thNight
65%5%11%11%6%
2482
16th to endNight
68%47%14%4
2220
March1st to 15thNight
65%47%12%9%1
2197
16th to endNight
51%47%20%12%2
2172
April1st to 15thNight
58%47%16%12%1
1760
16th to endNight
51%47%19%15%1
1620
May1st to 15thNight
52%6%9%16%13%1
1446
16th to endNight
51%7%10%18%10%1
1428
June1st to 15thNight
51%6%8%19%13%1
1260
16th to endNight
42%6%11%26%10%1
1260
July1st to 15thNight
43%8%15%24%7%
1190
16th to endNight
47%8%14%24%5%
1298
August1st to 15thNight
49%9%16%21%4
1553
16th to endNight
43%8%19%23%5%
1731
September1st to 15thNight
50%7%16%18%7%
1800
16th to endNight
48%6%15%24%5%
1999
October1st to 15thNight
58%6%12%15%5%
2160
16th to endNight
72%5%10%8%3
2403
November1st to 15thNight
71%6%10%8%2
2662
16th to endNight
74%5%9%8%1
2730
December1st to 15thNight
77%5%7%7%1
2841
16th to endNight
78%5%5%6%3
3120

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%432%20%11%3
90
16th to endDay
29%127%28%10%2
113
February1st to 15thDay
11%439%37%7%
135
16th to endDay
26%8%39%20%5%
120
March1st to 15thDay
19%6%28%29%13%2
310
16th to endDay
18%7%27%32%11%2
311
April1st to 15thDay
23%10%23%29%11%2
270
16th to endDay
22%5%29%24%14%4
270
May1st to 15thDay
28%6%20%20%19%4
288
16th to endDay
30%6%24%23%12%2
397
June1st to 15thDay
26%9%21%24%14%2
495
16th to endDay
17%7%27%27%16%3
495
July1st to 15thDay
22%7%23%29%12%4
475
16th to endDay
19%324%32%15%4
452
August1st to 15thDay
23%418%25%19%9%
313
16th to endDay
26%5%19%22%17%9%
332
September1st to 15thDay
23%5%21%27%14%7%
315
16th to endDay
23%7%21%29%12%5%
314
October1st to 15thDay
29%9%26%23%9%1
315
16th to endDay
33%13%22%22%6%1
273
November1st to 15thDay
36%11%30%15%6%
90
16th to endDay
42%10%31%12%22
90
December1st to 15thDay
28%7%28%23%8%2
90
16th to endDay
20%7%40%14%13%3
96
January1st to 15thNight
28%5%28%26%9%1
975
16th to endNight
21%5%25%30%14%2
950
February1st to 15thNight
14%6%27%38%12%1
764
16th to endNight
22%432%28%10%1
683
March1st to 15thNight
21%7%29%31%8%
780
16th to endNight
17%5%30%35%10%
792
April1st to 15thNight
27%9%26%28%7%
682
16th to endNight
25%5%27%29%9%1
540
May1st to 15thNight
24%428%29%11%
366
16th to endNight
25%426%32%9%
375
June1st to 15thNight
22%5%25%32%11%1
360
16th to endNight
15%328%35%14%1
360
July1st to 15thNight
18%424%38%12%1
340
16th to endNight
17%219%41%18%1
376
August1st to 15thNight
19%322%29%22%2
482
16th to endNight
19%424%33%16%1
585
September1st to 15thNight
25%426%26%15%2
720
16th to endNight
24%6%23%29%12%2
717
October1st to 15thNight
26%8%28%26%8%1
720
16th to endNight
36%9%24%20%7%1
768
November1st to 15thNight
31%9%30%20%7%
760
16th to endNight
34%7%29%23%5%
780
December1st to 15thNight
29%6%29%25%7%1
891
16th to endNight
27%6%25%26%9%3
1040
Page generated at 2018-03-22 11:34:22. Version ac04

Copyright 2018 A. Danko


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