Observatoire de Labelle Etoile
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de Labelle Etoile clear sky chart from 2005-11-06 to 2024-01-14.

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
28%
22469
12%
74743
8%
22427
34%
22427
14%
55168

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 10thNight
11%
760
7%
2649
1%
757
17%
757
6%
2219
January11th to 20thNight
17%
735
7%
2569
3%
735
22%
735
7%
2073
January21st to endNight
22%
792
11%
2772
7%
792
29%
792
11%
2083
February1st to 10thNight
15%
720
10%
2349
4%
720
23%
720
9%
1857
February11th to 20thNight
16%
703
11%
2240
4%
700
25%
700
9%
1752
February21st to endNight
22%
592
11%
1776
6%
592
29%
592
13%
1340
March1st to 10thNight
20%
720
12%
2160
8%
720
26%
720
13%
1658
March11th to 20thNight
23%
720
13%
2040
6%
720
31%
720
14%
1557
March21st to endNight
28%
792
19%
2021
8%
792
35%
792
19%
1463
April1st to 10thNight
24%
720
13%
1800
5%
720
28%
720
17%
1368
April11th to 20thNight
28%
711
16%
1775
6%
711
34%
711
22%
1256
April21st to endNight
26%
573
15%
1653
8%
573
32%
573
17%
1180
May1st to 10thNight
33%
360
16%
1440
13%
360
43%
360
16%
957
May11th to 20thNight
33%
354
19%
1416
19%
354
44%
354
17%
926
May21st to endNight
32%
389
12%
1551
10%
388
44%
388
18%
983
June1st to 10thNight
34%
360
8%
1440
9%
360
41%
360
15%
986
June11th to 20thNight
41%
360
10%
1440
13%
360
47%
360
18%
912
June21st to endNight
46%
360
9%
1440
13%
360
49%
360
16%
963
July1st to 10thNight
51%
350
11%
1400
17%
350
56%
350
22%
830
July11th to 20thNight
52%
348
13%
1392
20%
348
54%
348
21%
847
July21st to endNight
53%
394
12%
1486
15%
372
56%
372
21%
915
August1st to 10thNight
52%
358
13%
1422
15%
356
57%
356
20%
895
August11th to 20thNight
53%
507
15%
1571
12%
507
56%
507
26%
1030
August21st to endNight
43%
792
15%
1980
7%
792
46%
792
27%
1362
September1st to 10thNight
44%
720
15%
1800
6%
720
46%
720
30%
1219
September11th to 20thNight
49%
720
18%
1836
11%
720
52%
720
31%
1211
September21st to endNight
43%
720
19%
1983
14%
720
47%
720
26%
1328
October1st to 10thNight
35%
720
17%
2160
12%
720
42%
720
19%
1521
October11th to 20thNight
26%
720
11%
2166
6%
720
31%
720
15%
1643
October21st to endNight
23%
792
9%
2574
6%
792
29%
792
11%
2013
November1st to 10thNight
26%
740
12%
2407
8%
740
32%
740
13%
1778
November11th to 20thNight
20%
760
13%
2627
9%
760
26%
760
10%
2028
November21st to endNight
18%
760
7%
2660
5%
760
21%
760
7%
2189
December1st to 10thNight
15%
760
6%
2660
3%
760
18%
760
6%
2258
December11th to 20thNight
14%
760
8%
3246
5%
759
18%
759
6%
2600
December21st to endNight
13%
827
6%
4842
3%
817
18%
817
4%
3968

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%12%48%6%35%45%6%28%
74749
Night
19%13%5%8%6%34445%28%
74998
TransparencyDay
57%411%18%9%1
74454
Night
58%411%17%8%1
74827
SeeingDay
26%17%28%18%8%2
13345
Night
26%13%26%25%10%1
22478

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 10thDay
18%19%8%15%10%3422315%
1517
11th to 20thDay
18%18%8%11%6%3445%5%19%
1464
21st to endDay
13%15%7%11%8%46%46%5%23%
1584
February1st to 10thDay
11%19%8%12%12%35%345%19%
1606
11th to 20thDay
13%19%7%11%7%35%435%23%
1606
21st to endDay
15%18%7%9%8%445%4422%
1480
March1st to 10thDay
15%13%7%10%7%44446%26%
1797
11th to 20thDay
15%15%5%9%7%45%445%26%
1916
21st to endDay
19%10%5%8%6%34345%33%
2335
April1st to 10thDay
22%15%5%8%5%3334428%
2160
11th to 20thDay
21%12%46%5%34345%33%
2134
21st to endDay
21%12%48%6%3444430%
2321
May1st to 10thDay
22%11%36%5%3445%6%31%
2520
11th to 20thDay
21%9%36%6%35%45%5%34%
2478
21st to endDay
20%8%36%5%35%5%5%7%34%
2725
June1st to 10thDay
25%9%35%6%45%5%5%7%27%
2520
11th to 20thDay
18%6%36%6%46%6%5%7%33%
2520
21st to endDay
22%8%36%6%45%5%6%6%28%
2520
July1st to 10thDay
17%7%35%6%35%5%6%9%34%
2520
11th to 20thDay
15%7%36%6%35%6%7%9%32%
2520
21st to endDay
15%8%36%6%46%6%6%8%33%
2744
August1st to 10thDay
17%9%37%6%46%6%6%8%28%
2506
11th to 20thDay
16%7%36%6%46%5%6%7%35%
2307
21st to endDay
16%7%36%5%45%6%6%8%35%
2376
September1st to 10thDay
19%5%25%6%35%5%5%7%39%
2160
11th to 20thDay
18%8%35%5%25%5%6%7%38%
2124
21st to endDay
23%6%35%5%335%47%37%
1976
October1st to 10thDay
24%9%35%6%35%447%30%
1800
11th to 20thDay
28%15%47%5%34345%24%
1793
21st to endDay
29%16%46%433445%22%
1782
November1st to 10thDay
17%16%47%433447%29%
1671
11th to 20thDay
22%16%7%9%7%2344419%
1549
21st to endDay
23%17%7%11%7%4343418%
1520
December1st to 10thDay
23%20%7%10%6%34335%15%
1520
11th to 20thDay
21%16%8%13%7%3435%416%
1906
21st to endDay
22%19%6%11%7%35%34416%
2772
January1st to 10thNight
18%20%8%12%8%34435%14%
2649
11th to 20thNight
19%18%6%10%8%45%5%5%5%17%
2569
21st to endNight
12%14%6%9%8%46%6%5%6%24%
2772
February1st to 10thNight
13%16%6%12%9%45%5%4421%
2349
11th to 20thNight
14%15%7%12%9%45%45%421%
2238
21st to endNight
15%15%7%8%7%45%446%24%
1776
March1st to 10thNight
17%12%6%10%8%5%5%445%24%
2150
11th to 20thNight
19%14%5%7%6%33446%27%
2039
21st to endNight
16%10%48%5%3443437%
2021
April1st to 10thNight
24%12%5%6%5%24445%30%
1800
11th to 20thNight
20%9%45%5%3346%5%36%
1775
21st to endNight
20%12%47%5%34436%33%
1653
May1st to 10thNight
21%10%36%425%447%35%
1440
11th to 20thNight
18%9%36%6%24447%37%
1415
21st to endNight
17%8%26%5%4446%7%38%
1550
June1st to 10thNight
20%7%46%5%45%5%6%8%31%
1440
11th to 20thNight
17%7%346%35%5%5%7%38%
1440
21st to endNight
19%7%25%6%35%5%6%7%35%
1440
July1st to 10thNight
12%7%36%4445%7%8%41%
1440
11th to 20thNight
14%6%25%5%35%5%6%9%40%
1440
21st to endNight
12%6%35%446%6%7%9%39%
1574
August1st to 10thNight
13%6%36%6%45%6%6%7%38%
1432
11th to 20thNight
13%6%36%6%35%5%6%7%41%
1571
21st to endNight
17%5%36%435%45%7%40%
1980
September1st to 10thNight
18%7%25%43346%6%43%
1800
11th to 20thNight
19%6%3433345%6%45%
1836
21st to endNight
19%7%35%42335%7%41%
1983
October1st to 10thNight
22%9%35%435%446%36%
2160
11th to 20thNight
25%14%37%6%24345%27%
2166
21st to endNight
26%14%47%5%34445%24%
2574
November1st to 10thNight
21%13%5%7%5%24446%28%
2407
11th to 20thNight
20%16%6%10%6%35%445%22%
2627
21st to endNight
23%18%6%10%6%3434417%
2660
December1st to 10thNight
21%20%8%11%8%3434314%
2660
11th to 20thNight
21%18%7%10%7%3433321%
3288
21st to endNight
22%22%6%10%8%3433316%
4884

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 10thDay
78%25%11%4
1518
11th to 20thDay
67%38%11%9%1
1464
21st to endDay
62%38%15%9%2
1584
February1st to 10thDay
69%26%14%7%2
1606
11th to 20thDay
65%210%11%10%1
1615
21st to endDay
66%38%13%9%1
1480
March1st to 10thDay
60%39%17%9%2
1800
11th to 20thDay
60%49%14%11%2
1916
21st to endDay
54%39%19%12%3
2335
April1st to 10thDay
61%28%16%10%3
2160
11th to 20thDay
55%39%19%12%2
2134
21st to endDay
58%48%15%12%3
2321
May1st to 10thDay
55%47%19%12%3
2520
11th to 20thDay
52%49%18%15%2
2482
21st to endDay
51%5%11%18%13%2
2725
June1st to 10thDay
56%6%11%16%10%1
2520
11th to 20thDay
49%6%12%20%10%2
2520
21st to endDay
56%6%12%17%9%
2520
July1st to 10thDay
45%6%14%24%10%
2450
11th to 20thDay
46%7%15%23%9%
2445
21st to endDay
48%7%14%22%8%
2591
August1st to 10thDay
51%8%16%21%5%
2492
11th to 20thDay
47%6%18%22%7%
2307
21st to endDay
47%6%13%22%11%1
2376
September1st to 10thDay
46%414%24%12%
2160
11th to 20thDay
44%5%14%28%9%1
2124
21st to endDay
47%5%14%24%9%
1976
October1st to 10thDay
56%412%20%8%1
1800
11th to 20thDay
65%5%11%14%41
1793
21st to endDay
66%411%14%5%1
1782
November1st to 10thDay
55%5%13%20%6%1
1671
11th to 20thDay
69%410%11%6%1
1549
21st to endDay
71%5%9%10%41
1520
December1st to 10thDay
74%38%10%4
1520
11th to 20thDay
71%49%11%5%
1906
21st to endDay
73%27%13%5%
2772
January1st to 10thNight
75%39%10%4
2649
11th to 20thNight
70%49%9%7%1
2569
21st to endNight
61%49%13%12%1
2772
February1st to 10thNight
66%38%15%6%1
2349
11th to 20thNight
65%39%14%7%1
2240
21st to endNight
61%211%15%10%1
1776
March1st to 10thNight
62%29%16%8%2
2160
11th to 20thNight
59%410%14%11%1
2040
21st to endNight
51%48%20%13%4
2021
April1st to 10thNight
57%310%16%11%2
1800
11th to 20thNight
48%410%22%14%2
1775
21st to endNight
54%39%18%13%3
1653
May1st to 10thNight
50%5%8%20%14%3
1440
11th to 20thNight
49%5%8%19%16%3
1416
21st to endNight
46%5%13%22%13%2
1551
June1st to 10thNight
50%7%13%20%10%
1440
11th to 20thNight
45%6%13%22%11%3
1440
21st to endNight
48%7%12%21%11%1
1440
July1st to 10thNight
40%6%17%24%12%1
1400
11th to 20thNight
41%7%15%27%9%1
1392
21st to endNight
39%9%18%25%9%
1486
August1st to 10thNight
41%9%17%26%6%
1422
11th to 20thNight
40%7%18%24%10%
1571
21st to endNight
44%5%17%25%9%1
1980
September1st to 10thNight
42%5%15%25%13%1
1800
11th to 20thNight
41%415%31%8%1
1836
21st to endNight
43%5%14%29%9%
1983
October1st to 10thNight
51%5%10%23%11%1
2160
11th to 20thNight
59%414%16%6%1
2166
21st to endNight
64%410%15%6%1
2574
November1st to 10thNight
58%415%16%5%
2407
11th to 20thNight
64%312%13%6%1
2627
21st to endNight
72%39%12%3
2660
December1st to 10thNight
75%39%9%3
2660
11th to 20thNight
70%38%13%5%1
3288
21st to endNight
75%36%12%4
4884

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 10thDay
20%21%40%17%3
180
11th to 20thDay
29%16%33%13%8%1
166
21st to endDay
24%19%33%19%5%1
176
February1st to 10thDay
34%29%29%6%1
234
11th to 20thDay
30%28%31%11%
273
21st to endDay
31%24%29%14%3
346
March1st to 10thDay
26%20%33%17%31
420
11th to 20thDay
29%23%27%17%41
420
21st to endDay
31%21%25%16%6%2
462
April1st to 10thDay
31%18%27%16%7%1
420
11th to 20thDay
33%16%25%12%11%3
412
21st to endDay
28%22%28%15%5%1
420
May1st to 10thDay
31%18%29%13%6%2
423
11th to 20thDay
26%18%29%18%7%2
447
21st to endDay
24%19%30%18%7%1
485
June1st to 10thDay
30%14%32%17%5%1
450
11th to 20thDay
22%17%31%19%10%1
450
21st to endDay
25%15%29%19%9%2
450
July1st to 10thDay
17%11%36%26%9%3
445
11th to 20thDay
16%14%32%27%9%2
444
21st to endDay
15%11%34%26%11%2
488
August1st to 10thDay
20%11%25%30%13%2
446
11th to 20thDay
18%7%28%25%14%8%
439
21st to endDay
21%15%27%17%14%7%
495
September1st to 10thDay
21%13%26%19%14%7%
450
11th to 20thDay
19%12%27%20%16%7%
450
21st to endDay
24%15%23%19%12%7%
450
October1st to 10thDay
29%16%21%18%13%3
450
11th to 20thDay
36%20%22%14%7%2
446
21st to endDay
40%14%22%17%6%
396
November1st to 10thDay
32%15%26%20%5%1
365
11th to 20thDay
29%26%28%9%8%1
209
21st to endDay
33%24%26%13%31
180
December1st to 10thDay
35%16%29%14%6%
180
11th to 20thDay
31%27%26%14%21
180
21st to endDay
35%20%27%12%5%2
198
January1st to 10thNight
29%18%31%16%5%
760
11th to 20thNight
31%16%25%21%6%
735
21st to endNight
19%15%34%24%7%1
792
February1st to 10thNight
22%18%35%20%5%1
720
11th to 20thNight
23%22%32%19%4
703
21st to endNight
24%19%28%25%4
592
March1st to 10thNight
24%18%31%23%5%
720
11th to 20thNight
28%18%26%21%6%1
720
21st to endNight
25%14%27%25%8%1
792
April1st to 10thNight
31%15%23%24%6%
720
11th to 20thNight
27%15%27%23%8%1
711
21st to endNight
25%17%26%22%9%1
573
May1st to 10thNight
25%11%24%27%11%2
360
11th to 20thNight
24%10%27%29%11%
354
21st to endNight
20%8%34%28%9%
389
June1st to 10thNight
22%7%31%31%9%1
360
11th to 20thNight
20%7%24%31%17%1
360
21st to endNight
21%5%18%38%18%1
360
July1st to 10thNight
15%5%23%43%14%
350
11th to 20thNight
16%420%40%20%1
348
21st to endNight
13%5%23%38%19%2
394
August1st to 10thNight
15%417%39%24%1
358
11th to 20thNight
15%418%35%26%2
507
21st to endNight
19%8%22%30%18%3
792
September1st to 10thNight
22%6%22%32%17%1
720
11th to 20thNight
22%7%18%32%21%1
720
21st to endNight
22%10%21%28%18%2
720
October1st to 10thNight
26%11%23%24%15%1
720
11th to 20thNight
33%11%23%22%9%1
720
21st to endNight
33%13%24%24%6%
792
November1st to 10thNight
29%13%25%23%8%1
740
11th to 20thNight
28%17%27%18%9%1
760
21st to endNight
35%16%23%19%6%1
760
December1st to 10thNight
31%17%27%18%6%1
760
11th to 20thNight
30%18%27%18%6%1
760
21st to endNight
35%16%26%17%6%
836
Page generated at 2024-01-11 04:22:43. Version ac07

Copyright 2024 Attilla Danko


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