Observatoire Laforge-1
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire Laforge-1 clear sky chart from 2005-11-06 to 2024-01-12.

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%
23232
5%
74982
4%
23187
31%
23187
8%
63209

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
27%
1040
3%
3027
2%
1036
27%
1036
5%
2756
January11th to 20thNight
29%
975
5%
2871
3%
975
31%
975
7%
2492
January21st to endNight
40%
796
10%
2776
9%
796
43%
796
8%
2322
February1st to 10thNight
40%
720
9%
2520
7%
720
45%
720
8%
2089
February11th to 20thNight
38%
702
6%
2397
6%
699
40%
699
9%
1935
February21st to endNight
40%
592
10%
1799
8%
592
43%
592
11%
1448
March1st to 10thNight
44%
719
10%
2160
7%
719
47%
719
14%
1687
March11th to 20thNight
32%
720
9%
2115
5%
720
35%
720
12%
1712
March21st to endNight
32%
792
10%
1980
5%
792
34%
792
13%
1659
April1st to 10thNight
28%
720
8%
1800
3%
720
30%
720
11%
1533
April11th to 20thNight
39%
561
15%
1625
12%
561
42%
561
19%
1181
April21st to endNight
35%
387
11%
1467
13%
387
39%
387
13%
1118
May1st to 10thNight
33%
360
6%
1432
8%
360
36%
360
10%
1106
May11th to 20thNight
38%
354
4%
1238
1%
354
39%
354
18%
856
May21st to endNight
32%
388
0%
1274
0%
388
32%
388
15%
951
June1st to 10thNight
38%
360
0%
1080
0%
360
38%
360
20%
769
June11th to 20thNight
42%
360
0%
1080
0%
360
42%
360
20%
777
June21st to endNight
36%
360
0%
1080
0%
360
36%
360
18%
803
July1st to 10thNight
40%
350
0%
1050
0%
350
40%
350
15%
795
July11th to 20thNight
39%
348
0%
1044
0%
348
39%
348
17%
788
July21st to endNight
43%
394
2%
1323
0%
372
44%
372
11%
1049
August1st to 10thNight
41%
358
5%
1422
7%
356
41%
356
10%
1093
August11th to 20thNight
36%
356
7%
1420
8%
356
39%
356
10%
1100
August21st to endNight
38%
559
8%
1747
7%
559
40%
559
14%
1349
September1st to 10thNight
26%
720
6%
1800
4%
720
27%
720
13%
1502
September11th to 20thNight
25%
720
7%
1880
3%
720
27%
720
11%
1580
September21st to endNight
23%
720
6%
1980
3%
720
25%
720
12%
1630
October1st to 10thNight
18%
720
7%
2119
5%
720
22%
720
9%
1783
October11th to 20thNight
20%
720
5%
2340
4%
720
22%
720
6%
2072
October21st to endNight
14%
792
4%
2574
3%
792
16%
792
4%
2326
November1st to 10thNight
14%
775
2%
2619
1%
775
15%
775
3%
2419
November11th to 20thNight
11%
850
1%
2850
0%
850
12%
850
1%
2729
November21st to endNight
17%
850
3%
2850
2%
850
18%
850
3%
2628
December1st to 10thNight
19%
926
2%
2926
1%
926
19%
926
2%
2744
December11th to 20thNight
25%
1039
3%
3754
2%
1039
26%
1039
4%
3393
December21st to endNight
30%
1129
3%
5563
4%
1115
31%
1115
3%
5035

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%15%6%11%9%5%6%5%5%5%16%
74570
Night
14%15%7%12%10%5%7%6%5%5%15%
75161
TransparencyDay
69%7%9%11%4
74244
Night
70%6%8%11%4
75024
SeeingDay
24%9%24%24%13%5%
15306
Night
21%8%26%28%14%3
23251

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
11%17%7%12%11%7%10%7%9%5%4
1138
11th to 20thDay
7%13%7%15%9%5%11%10%10%5%7%
1117
21st to endDay
411%6%14%13%7%10%9%11%6%8%
1579
February1st to 10thDay
37%6%11%13%9%13%14%12%7%5%
1440
11th to 20thDay
410%5%14%13%9%10%11%10%6%6%
1449
21st to endDay
411%6%14%11%8%10%12%8%8%8%
1457
March1st to 10thDay
6%9%5%12%12%8%10%10%9%6%13%
1797
11th to 20thDay
9%14%8%13%10%5%8%8%7%5%13%
1842
21st to endDay
8%16%7%12%9%7%9%8%6%5%14%
2376
April1st to 10thDay
14%17%7%12%10%6%7%5%5%412%
2160
11th to 20thDay
10%11%6%13%10%5%5%5%5%5%27%
2284
21st to endDay
14%18%8%11%8%3434422%
2510
May1st to 10thDay
20%17%7%11%7%34445%18%
2528
11th to 20thDay
15%13%7%11%6%34447%25%
2655
21st to endDay
18%16%6%10%7%34446%22%
2999
June1st to 10thDay
20%13%46%7%345%46%29%
2880
11th to 20thDay
20%12%37%7%45%5%5%6%27%
2880
21st to endDay
22%11%38%6%45%46%6%26%
2880
July1st to 10thDay
24%9%48%7%35%5%46%24%
2880
11th to 20thDay
28%10%48%7%45%446%19%
2880
21st to endDay
27%13%49%7%5%6%5%5%5%15%
2916
August1st to 10thDay
28%11%46%6%45%6%5%6%19%
2506
11th to 20thDay
25%13%5%8%7%45%5%46%17%
2481
21st to endDay
25%14%5%8%7%45%5%5%6%17%
2588
September1st to 10thDay
28%15%5%9%7%3444416%
2160
11th to 20thDay
26%17%5%9%6%3445%5%15%
2079
21st to endDay
29%17%6%7%6%4435%5%15%
1980
October1st to 10thDay
23%23%6%10%6%4444313%
1838
11th to 20thDay
27%23%8%8%43442312%
1620
21st to endDay
25%21%10%14%8%333339%
1782
November1st to 10thDay
20%25%11%15%9%332336%
1455
11th to 20thDay
19%24%13%17%10%332224
1330
21st to endDay
12%23%10%17%11%5%5%4337%
1330
December1st to 10thDay
10%18%8%18%16%6%6%7%434
1251
11th to 20thDay
8%18%10%15%14%7%7%6%438%
1433
21st to endDay
12%17%7%11%17%6%8%8%6%34
2090
January1st to 10thNight
9%16%8%15%12%7%10%9%7%43
3027
11th to 20thNight
8%14%7%14%12%5%11%11%7%6%5%
2871
21st to endNight
5%12%7%12%13%8%11%10%8%6%8%
2776
February1st to 10thNight
39%6%12%14%9%13%12%10%6%7%
2520
11th to 20thNight
5%13%6%13%12%6%9%11%10%7%10%
2394
21st to endNight
411%6%10%11%7%10%11%10%9%11%
1799
March1st to 10thNight
310%7%12%9%6%10%11%9%7%16%
2150
11th to 20thNight
9%12%7%13%9%6%7%8%5%5%18%
2114
21st to endNight
9%15%7%11%9%6%8%7%46%19%
1980
April1st to 10thNight
13%16%7%12%9%5%7%5%5%5%17%
1800
11th to 20thNight
11%12%6%11%6%35%445%34%
1625
21st to endNight
14%13%6%9%9%4445%427%
1467
May1st to 10thNight
22%14%6%9%6%35%335%23%
1432
11th to 20thNight
14%9%5%8%7%34445%35%
1238
21st to endNight
12%13%6%9%6%45%5%5%6%27%
1274
June1st to 10thNight
19%10%26%6%35%446%34%
1080
11th to 20thNight
21%8%35%6%3345%8%33%
1080
21st to endNight
22%10%36%5%245%47%31%
1080
July1st to 10thNight
22%7%36%6%5%5%7%5%7%27%
1080
11th to 20thNight
21%9%46%6%45%45%7%29%
1080
21st to endNight
21%11%48%6%46%46%6%22%
1400
August1st to 10thNight
23%10%48%6%35%5%5%7%24%
1432
11th to 20thNight
21%12%5%8%6%3445%6%25%
1420
21st to endNight
22%10%38%7%45%45%6%26%
1747
September1st to 10thNight
25%12%410%6%35%445%22%
1800
11th to 20thNight
23%16%5%9%6%44445%20%
1880
21st to endNight
28%15%48%6%24446%20%
1980
October1st to 10thNight
25%21%48%6%33446%17%
2119
11th to 20thNight
26%24%5%8%6%3434413%
2340
21st to endNight
24%22%8%13%7%3433310%
2574
November1st to 10thNight
21%23%10%15%8%443337%
2619
11th to 20thNight
19%22%11%19%11%442224
2850
21st to endNight
12%22%9%15%14%46%4337%
2850
December1st to 10thNight
9%18%10%18%14%7%8%5%325%
2926
11th to 20thNight
9%17%8%16%14%6%7%7%5%37%
3769
21st to endNight
9%17%9%13%17%8%9%6%5%35%
5588

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
77%5%8%8%2
1139
11th to 20thDay
72%6%7%11%4
1117
21st to endDay
69%6%7%11%6%1
1579
February1st to 10thDay
66%8%8%13%5%
1440
11th to 20thDay
70%8%6%11%5%
1457
21st to endDay
69%6%10%9%5%1
1457
March1st to 10thDay
64%8%8%14%5%
1800
11th to 20thDay
69%5%7%12%7%
1842
21st to endDay
70%5%8%10%6%
2376
April1st to 10thDay
72%6%7%9%5%
2160
11th to 20thDay
59%6%8%19%8%
2284
21st to endDay
67%5%9%14%6%
2510
May1st to 10thDay
70%5%8%12%5%
2528
11th to 20thDay
60%6%11%18%6%
2659
21st to endDay
64%6%10%16%4
2999
June1st to 10thDay
55%7%11%18%9%1
2880
11th to 20thDay
57%7%11%17%8%
2880
21st to endDay
58%8%11%16%7%
2880
July1st to 10thDay
60%8%11%17%5%
2801
11th to 20thDay
65%8%11%12%4
2793
21st to endDay
69%9%11%9%2
2754
August1st to 10thDay
65%9%13%11%1
2492
11th to 20thDay
67%9%11%12%2
2481
21st to endDay
67%9%11%10%3
2588
September1st to 10thDay
72%6%11%8%3
2160
11th to 20thDay
72%8%9%10%2
2079
21st to endDay
72%6%10%12%1
1980
October1st to 10thDay
76%6%7%9%2
1838
11th to 20thDay
78%5%7%7%2
1620
21st to endDay
82%5%7%5%11
1782
November1st to 10thDay
86%5%5%31
1455
11th to 20thDay
89%5%321
1330
21st to endDay
85%45%5%1
1330
December1st to 10thDay
84%7%5%31
1251
11th to 20thDay
81%5%7%5%3
1433
21st to endDay
80%6%6%43
2090
January1st to 10thNight
80%6%7%6%1
3027
11th to 20thNight
74%6%7%10%3
2871
21st to endNight
70%6%6%10%7%1
2776
February1st to 10thNight
69%7%6%14%5%
2520
11th to 20thNight
65%8%10%12%5%
2397
21st to endNight
63%8%9%12%8%
1799
March1st to 10thNight
59%7%12%13%8%
2160
11th to 20thNight
66%5%6%16%7%
2115
21st to endNight
67%5%6%14%7%
1980
April1st to 10thNight
69%6%8%11%6%1
1800
11th to 20thNight
53%6%8%20%12%1
1625
21st to endNight
60%5%9%17%8%1
1467
May1st to 10thNight
66%37%16%9%
1432
11th to 20thNight
51%5%12%22%9%
1239
21st to endNight
56%7%13%19%6%
1275
June1st to 10thNight
51%5%11%21%9%2
1080
11th to 20thNight
50%7%13%20%10%
1080
21st to endNight
53%7%11%20%9%
1080
July1st to 10thNight
55%8%12%20%5%
1050
11th to 20thNight
54%9%14%21%2
1044
21st to endNight
60%10%16%13%1
1323
August1st to 10thNight
60%9%15%15%2
1422
11th to 20thNight
60%9%13%15%2
1420
21st to endNight
58%7%14%18%2
1747
September1st to 10thNight
65%7%11%13%3
1800
11th to 20thNight
66%8%11%13%2
1880
21st to endNight
67%5%13%12%3
1980
October1st to 10thNight
69%7%11%11%2
2119
11th to 20thNight
75%8%7%7%2
2340
21st to endNight
80%6%6%6%21
2574
November1st to 10thNight
84%5%6%41
2619
11th to 20thNight
89%5%321
2850
21st to endNight
82%7%6%41
2850
December1st to 10thNight
85%6%431
2926
11th to 20thNight
79%7%7%6%1
3769
21st to endNight
81%6%5%6%2
5588

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
12%6%30%28%21%4
180
11th to 20thDay
12%10%30%38%7%1
162
21st to endDay
7%5%27%32%22%8%
176
February1st to 10thDay
5%8%25%39%18%5%
160
11th to 20thDay
45%37%32%16%6%
183
21st to endDay
6%11%30%31%18%4
323
March1st to 10thDay
10%6%21%33%22%8%
420
11th to 20thDay
12%7%31%30%18%4
420
21st to endDay
12%11%32%27%13%4
462
April1st to 10thDay
18%6%27%30%15%4
420
11th to 20thDay
13%10%29%25%15%8%
412
21st to endDay
21%11%24%25%14%5%
420
May1st to 10thDay
21%8%24%26%14%7%
431
11th to 20thDay
21%8%22%25%17%6%
624
21st to endDay
25%11%27%25%11%2
760
June1st to 10thDay
29%5%26%22%13%5%
810
11th to 20thDay
26%11%18%29%12%4
810
21st to endDay
25%9%23%22%16%4
810
July1st to 10thDay
26%7%20%26%14%7%
796
11th to 20thDay
31%8%20%27%11%3
792
21st to endDay
31%8%17%18%17%9%
660
August1st to 10thDay
31%8%15%21%16%9%
446
11th to 20thDay
26%8%23%18%15%10%
439
21st to endDay
28%8%21%23%12%7%
495
September1st to 10thDay
37%12%22%18%9%3
450
11th to 20thDay
30%15%24%20%9%3
450
21st to endDay
33%13%25%17%8%4
450
October1st to 10thDay
31%14%24%20%9%2
447
11th to 20thDay
36%13%21%20%7%4
360
21st to endDay
31%11%22%20%11%4
396
November1st to 10thDay
33%16%27%17%5%3
224
11th to 20thDay
24%11%33%23%8%1
180
21st to endDay
12%17%30%23%15%3
180
December1st to 10thDay
13%12%25%18%22%9%
180
11th to 20thDay
18%8%35%24%12%2
180
21st to endDay
13%7%31%33%11%6%
198
January1st to 10thNight
15%7%26%31%18%4
1040
11th to 20thNight
12%8%31%29%16%4
975
21st to endNight
9%424%37%21%5%
796
February1st to 10thNight
6%7%26%38%17%6%
720
11th to 20thNight
11%327%37%19%3
703
21st to endNight
9%427%34%21%5%
592
March1st to 10thNight
6%5%28%33%24%4
720
11th to 20thNight
13%9%29%30%17%3
720
21st to endNight
14%8%31%33%12%3
792
April1st to 10thNight
21%7%30%26%14%2
720
11th to 20thNight
16%5%26%34%17%2
561
21st to endNight
16%10%28%32%13%1
387
May1st to 10thNight
26%8%21%31%12%2
360
11th to 20thNight
19%8%23%32%15%3
354
21st to endNight
20%9%30%33%7%1
389
June1st to 10thNight
24%425%32%14%1
360
11th to 20thNight
23%9%19%36%13%1
360
21st to endNight
26%7%23%28%15%1
360
July1st to 10thNight
25%5%22%32%14%2
350
11th to 20thNight
24%7%22%31%14%1
348
21st to endNight
22%6%20%25%23%4
394
August1st to 10thNight
25%418%30%20%3
358
11th to 20thNight
25%5%20%25%22%2
356
21st to endNight
27%5%21%31%15%2
559
September1st to 10thNight
31%9%27%23%9%1
720
11th to 20thNight
30%11%26%25%8%
720
21st to endNight
34%11%26%20%7%2
720
October1st to 10thNight
36%10%28%18%7%1
720
11th to 20thNight
38%9%22%22%8%1
720
21st to endNight
34%9%26%17%11%3
792
November1st to 10thNight
33%12%25%21%8%2
775
11th to 20thNight
29%13%26%19%10%3
850
21st to endNight
22%10%30%25%9%4
850
December1st to 10thNight
16%12%28%26%15%3
926
11th to 20thNight
15%8%30%30%15%3
1040
21st to endNight
16%7%25%32%16%3
1144
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