Observatoire du Lac du Moulin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire du Lac du Moulin clear sky chart from 2005-11-05 to 2017-09-19.

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%
14607
13%
46876
8%
14576
35%
14576
16%
33774

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
15%
720
6%
2506
3%
716
19%
716
7%
2034
January16th to endNight
21%
768
11%
2645
5%
768
29%
768
12%
1997
February1st to 15thNight
18%
704
10%
2287
4%
701
25%
701
10%
1778
February16th to endNight
19%
631
12%
1970
5%
631
30%
631
12%
1492
March1st to 15thNight
20%
720
13%
2088
7%
720
27%
720
13%
1601
March16th to endNight
29%
768
20%
2043
9%
768
38%
768
21%
1425
April1st to 15thNight
25%
718
16%
1796
6%
718
30%
718
19%
1315
April16th to endNight
27%
615
17%
1695
8%
615
34%
615
22%
1194
May1st to 15thNight
30%
360
17%
1440
17%
360
39%
360
16%
958
May16th to endNight
32%
374
13%
1497
10%
374
44%
374
16%
975
June1st to 15thNight
33%
360
7%
1440
6%
360
40%
360
15%
961
June16th to endNight
42%
360
8%
1440
11%
360
46%
360
18%
929
July1st to 15thNight
50%
340
12%
1360
16%
340
55%
340
24%
787
July16th to endNight
56%
376
13%
1418
17%
354
58%
354
25%
811
August1st to 15thNight
50%
440
13%
1511
11%
438
55%
438
22%
964
August16th to endNight
51%
688
19%
1834
10%
688
56%
688
36%
1143
September1st to 15thNight
41%
720
15%
1800
7%
720
44%
720
28%
1252
September16th to endNight
44%
673
20%
1840
13%
673
48%
673
30%
1196
October1st to 15thNight
27%
660
17%
1980
11%
660
36%
660
19%
1403
October16th to endNight
25%
704
11%
2197
6%
704
32%
704
14%
1680
November1st to 15thNight
25%
700
16%
2361
11%
700
34%
700
14%
1695
November16th to endNight
19%
720
8%
2520
5%
720
23%
720
9%
1964
December1st to 15thNight
15%
720
7%
2520
2%
720
21%
720
7%
2047
December16th to endNight
14%
768
10%
2688
4%
768
22%
768
8%
2173

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%10%47%6%34446%30%
47949
Night
17%10%47%5%34446%31%
47045
TransparencyDay
54%5%11%18%9%1
47636
Night
54%411%19%8%
46876
SeeingDay
23%12%29%20%9%3
5430
Night
23%11%28%24%9%
14608

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%15%6%10%6%3433420%
1432
16th to endDay
13%16%5%11%6%345%4423%
1578
February1st to 15thDay
11%15%6%13%8%45%44422%
1575
16th to endDay
16%17%6%8%5%2334426%
1503
March1st to 15thDay
16%13%5%8%7%3433427%
1859
16th to endDay
14%8%46%5%23436%39%
2181
April1st to 15thDay
23%11%35%5%22335%31%
2152
16th to endDay
22%8%36%6%23335%35%
2274
May1st to 15thDay
20%9%36%5%34446%31%
2511
16th to endDay
19%7%26%6%35%446%32%
2618
June1st to 15thDay
21%7%36%7%35%5%5%7%26%
2520
16th to endDay
17%6%26%7%45%5%6%8%30%
2520
July1st to 15thDay
16%5%25%5%36%45%8%34%
2520
16th to endDay
12%5%36%6%36%6%6%8%33%
2654
August1st to 15thDay
12%6%37%6%45%5%6%7%32%
2438
16th to endDay
13%5%26%5%45%45%8%38%
2355
September1st to 15thDay
17%6%36%423447%38%
2160
16th to endDay
17%6%25%424336%41%
1865
October1st to 15thDay
22%8%26%433345%33%
1650
16th to endDay
28%12%37%6%24345%22%
1674
November1st to 15thDay
16%10%47%6%235%5%7%30%
1494
16th to endDay
23%16%6%8%42343421%
1440
December1st to 15thDay
22%17%5%10%6%345%45%13%
1440
16th to endDay
21%20%6%8%5%3332319%
1536
January1st to 15thNight
18%16%6%11%7%35%345%17%
2506
16th to endNight
12%15%6%8%6%35%5%45%25%
2645
February1st to 15thNight
11%15%7%11%8%36%44423%
2285
16th to endNight
15%14%5%8%7%35%44426%
1970
March1st to 15thNight
17%13%5%8%6%34345%26%
2075
16th to endNight
13%9%47%6%2333440%
2043
April1st to 15thNight
22%9%45%423346%32%
1796
16th to endNight
19%8%35%5%34346%36%
1695
May1st to 15thNight
22%9%37%422245%35%
1440
16th to endNight
15%7%36%5%35%5%5%7%34%
1495
June1st to 15thNight
18%7%25%5%26%348%33%
1440
16th to endNight
15%5%25%5%45%5%6%7%35%
1440
July1st to 15thNight
10%425%435%47%7%44%
1440
16th to endNight
10%5%2433447%9%43%
1514
August1st to 15thNight
11%5%25%5%35%5%6%9%39%
1521
16th to endNight
9%4244235%5%8%48%
1834
September1st to 15thNight
16%6%35%5%2345%7%40%
1800
16th to endNight
17%5%33422336%47%
1840
October1st to 15thNight
21%8%35%5%22445%36%
1980
16th to endNight
24%9%37%5%3445%5%26%
2197
November1st to 15thNight
18%9%48%5%24445%30%
2361
16th to endNight
23%13%48%5%25%44423%
2520
December1st to 15thNight
21%17%6%8%5%3444419%
2520
16th to endNight
22%15%6%9%7%3433419%
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
70%38%12%5%
1433
16th to endDay
62%310%14%7%
1578
February1st to 15thDay
65%310%15%4
1577
16th to endDay
62%29%14%10%
1503
March1st to 15thDay
60%310%16%8%1
1869
16th to endDay
46%310%19%14%4
2181
April1st to 15thDay
57%26%19%11%2
2152
16th to endDay
53%36%20%13%3
2274
May1st to 15thDay
55%46%18%14%1
2511
16th to endDay
51%6%10%17%12%1
2622
June1st to 15thDay
56%7%9%19%8%
2520
16th to endDay
49%7%12%20%9%1
2520
July1st to 15thDay
44%5%13%25%10%
2371
16th to endDay
47%7%15%21%9%
2487
August1st to 15thDay
48%7%15%21%6%
2424
16th to endDay
42%6%16%24%8%
2355
September1st to 15thDay
45%5%12%24%11%
2160
16th to endDay
43%5%12%29%8%
1865
October1st to 15thDay
52%413%19%9%
1650
16th to endDay
64%5%11%13%4
1674
November1st to 15thDay
51%6%14%19%8%
1494
16th to endDay
67%410%12%6%
1440
December1st to 15thDay
72%5%9%10%2
1440
16th to endDay
70%310%10%5%
1536
January1st to 15thNight
69%410%10%3
2506
16th to endNight
60%410%16%7%
2645
February1st to 15thNight
64%39%17%4
2287
16th to endNight
60%39%17%8%
1970
March1st to 15thNight
60%48%18%7%
2088
16th to endNight
47%38%20%16%3
2043
April1st to 15thNight
53%27%19%14%1
1796
16th to endNight
49%38%19%15%3
1695
May1st to 15thNight
51%36%19%15%3
1440
16th to endNight
47%6%11%21%11%2
1497
June1st to 15thNight
50%5%14%21%7%1
1440
16th to endNight
44%7%11%22%13%
1440
July1st to 15thNight
36%6%14%26%15%
1360
16th to endNight
35%6%16%29%11%
1418
August1st to 15thNight
40%8%16%24%9%
1511
16th to endNight
32%6%19%32%8%
1834
September1st to 15thNight
43%5%13%25%11%
1800
16th to endNight
40%413%33%7%
1840
October1st to 15thNight
50%411%21%11%
1980
16th to endNight
59%5%13%17%5%
2197
November1st to 15thNight
54%5%12%17%9%
2361
16th to endNight
64%412%14%3
2520
December1st to 15thNight
68%5%10%12%3
2520
16th to endNight
69%38%11%6%
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
30%21%26%18%3
60
16th to endDay
32%5%35%21%41
71
February1st to 15thDay
23%23%43%7%11
90
16th to endDay
32%19%29%16%2
162
March1st to 15thDay
24%20%31%20%4
270
16th to endDay
22%15%31%18%9%2
288
April1st to 15thDay
32%17%26%15%7%1
270
16th to endDay
27%21%22%16%10%1
270
May1st to 15thDay
33%9%27%18%7%3
288
16th to endDay
27%14%31%18%7%1
331
June1st to 15thDay
25%12%34%20%6%1
315
16th to endDay
13%11%34%27%9%2
315
July1st to 15thDay
16%6%35%28%9%3
305
16th to endDay
14%6%29%28%16%3
326
August1st to 15thDay
19%326%29%15%5%
313
16th to endDay
15%7%29%24%13%9%
332
September1st to 15thDay
20%8%24%22%13%10%
315
16th to endDay
19%10%26%21%15%7%
266
October1st to 15thDay
26%13%27%20%10%2
255
16th to endDay
33%15%28%14%8%
256
November1st to 15thDay
20%12%34%20%9%2
148
16th to endDay
40%10%28%18%3
60
December1st to 15thDay
33%16%35%13%1
60
16th to endDay
39%23%32%4
64
January1st to 15thNight
29%13%31%20%5%
720
16th to endNight
22%12%32%24%7%
768
February1st to 15thNight
19%14%37%21%6%
704
16th to endNight
25%15%32%21%5%
631
March1st to 15thNight
25%16%30%23%3
720
16th to endNight
17%18%27%24%10%
768
April1st to 15thNight
28%15%26%24%5%
718
16th to endNight
26%12%29%24%7%
615
May1st to 15thNight
27%6%28%26%10%
360
16th to endNight
20%8%33%28%9%
375
June1st to 15thNight
19%9%31%31%8%
360
16th to endNight
18%5%26%35%13%
360
July1st to 15thNight
10%5%26%38%18%
340
16th to endNight
11%422%42%17%2
376
August1st to 15thNight
14%322%35%22%2
440
16th to endNight
12%5%26%32%21%2
688
September1st to 15thNight
20%427%27%17%2
720
16th to endNight
19%6%25%27%18%2
673
October1st to 15thNight
27%11%27%21%11%1
660
16th to endNight
31%11%27%20%8%
704
November1st to 15thNight
24%14%28%22%9%1
700
16th to endNight
33%14%25%17%7%
720
December1st to 15thNight
32%15%29%18%3
720
16th to endNight
33%11%30%17%41
768
Page generated at 2017-09-20 04:49:58. Version ac04

Copyright 2017 A. Danko


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