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 2018-11-30.

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%
16115
13%
51717
8%
16084
35%
16084
16%
37213

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
16%
780
7%
2716
3%
776
21%
776
7%
2193
January16th to endNight
20%
832
10%
2865
5%
832
28%
832
11%
2171
February1st to 15thNight
18%
764
10%
2482
4%
761
26%
761
10%
1926
February16th to endNight
20%
683
12%
2132
5%
683
29%
683
12%
1607
March1st to 15thNight
19%
780
12%
2262
7%
780
25%
780
12%
1768
March16th to endNight
29%
832
21%
2213
9%
832
39%
832
22%
1525
April1st to 15thNight
25%
778
16%
1946
6%
778
30%
778
19%
1433
April16th to endNight
29%
657
17%
1813
8%
657
34%
657
21%
1284
May1st to 15thNight
32%
390
19%
1560
18%
390
42%
390
17%
1008
May16th to endNight
32%
406
13%
1625
10%
406
45%
406
17%
1036
June1st to 15thNight
33%
390
8%
1560
8%
390
41%
390
15%
1037
June16th to endNight
42%
390
9%
1560
12%
390
47%
390
18%
997
July1st to 15thNight
51%
370
14%
1480
18%
370
58%
370
26%
834
July16th to endNight
56%
408
13%
1546
17%
386
58%
386
25%
890
August1st to 15thNight
51%
468
14%
1609
12%
466
55%
466
22%
1031
August16th to endNight
51%
746
19%
1988
10%
746
56%
746
36%
1241
September1st to 15thNight
43%
780
17%
1950
8%
780
46%
780
29%
1342
September16th to endNight
44%
777
20%
2128
13%
777
48%
777
30%
1387
October1st to 15thNight
28%
780
16%
2340
10%
780
36%
780
19%
1660
October16th to endNight
23%
832
11%
2597
6%
832
31%
832
13%
1979
November1st to 15thNight
24%
820
16%
2765
10%
820
33%
820
14%
2013
November16th to endNight
19%
840
8%
2938
5%
840
23%
840
9%
2311
December1st to 15thNight
15%
780
8%
2730
3%
780
22%
780
7%
2214
December16th to endNight
15%
832
11%
2912
4%
832
23%
832
8%
2326

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%
52597
Night
17%10%47%5%34446%31%
51886
TransparencyDay
54%5%10%18%9%1
52284
Night
54%411%19%9%
51717
SeeingDay
24%13%30%20%8%3
6894
Night
23%11%28%24%10%
16116

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
21%15%6%11%6%3433419%
1552
16th to endDay
13%16%6%11%6%35%44423%
1710
February1st to 15thDay
11%15%6%12%8%45%44422%
1710
16th to endDay
17%16%6%8%5%2333426%
1627
March1st to 15thDay
17%14%5%8%6%3433425%
2015
16th to endDay
13%8%46%5%34436%39%
2363
April1st to 15thDay
23%12%46%5%23335%30%
2332
16th to endDay
22%8%36%5%23335%35%
2432
May1st to 15thDay
20%9%36%5%34345%33%
2721
16th to endDay
19%7%26%6%34446%34%
2842
June1st to 15thDay
21%7%36%7%345%5%7%27%
2730
16th to endDay
16%6%25%6%35%5%6%7%31%
2730
July1st to 15thDay
15%5%25%5%35%45%8%37%
2730
16th to endDay
12%5%36%6%46%6%6%8%33%
2878
August1st to 15thDay
12%7%37%6%45%5%6%7%32%
2593
16th to endDay
13%6%25%6%35%45%7%38%
2552
September1st to 15thDay
17%6%26%42345%7%39%
2340
16th to endDay
16%6%34424346%41%
2161
October1st to 15thDay
22%8%27%434346%32%
1950
16th to endDay
26%11%37%6%24345%23%
1978
November1st to 15thDay
17%11%37%6%2445%7%28%
1750
16th to endDay
23%16%6%9%42343421%
1677
December1st to 15thDay
21%17%5%10%6%45%5%45%13%
1560
16th to endDay
20%19%6%9%5%2332321%
1664
January1st to 15thNight
18%16%6%11%6%35%445%17%
2716
16th to endNight
13%15%6%9%6%35%445%25%
2865
February1st to 15thNight
10%15%7%11%8%36%44423%
2480
16th to endNight
15%14%48%7%35%445%26%
2132
March1st to 15thNight
18%14%5%8%7%3434424%
2249
16th to endNight
13%9%36%6%2343441%
2213
April1st to 15thNight
22%10%45%423346%32%
1946
16th to endNight
20%7%35%5%34346%36%
1813
May1st to 15thNight
20%8%36%423345%38%
1560
16th to endNight
15%6%25%5%345%5%7%36%
1623
June1st to 15thNight
18%7%25%5%25%35%8%33%
1560
16th to endNight
14%6%25%5%45%5%6%6%37%
1560
July1st to 15thNight
10%425%43447%7%46%
1560
16th to endNight
9%4244345%7%9%43%
1642
August1st to 15thNight
10%5%25%6%45%46%9%38%
1619
16th to endNight
10%4244235%5%8%48%
1988
September1st to 15thNight
15%6%25%5%2345%7%41%
1950
16th to endNight
17%5%34422337%46%
2128
October1st to 15thNight
21%8%35%5%23445%35%
2340
16th to endNight
23%9%37%6%3445%5%26%
2597
November1st to 15thNight
19%9%48%6%2445%5%29%
2765
16th to endNight
23%13%48%6%2444422%
2938
December1st to 15thNight
21%17%6%8%5%3444419%
2730
16th to endNight
21%14%6%9%7%3434420%
2912

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
71%38%11%5%
1553
16th to endDay
63%410%14%6%
1710
February1st to 15thDay
65%39%15%4
1712
16th to endDay
62%29%14%10%
1627
March1st to 15thDay
63%39%15%8%1
2025
16th to endDay
46%39%20%14%4
2363
April1st to 15thDay
58%26%18%11%2
2332
16th to endDay
53%26%20%13%3
2432
May1st to 15thDay
53%46%18%15%1
2721
16th to endDay
50%6%10%18%12%1
2846
June1st to 15thDay
55%6%8%19%9%
2730
16th to endDay
49%6%12%20%10%1
2730
July1st to 15thDay
42%5%12%26%11%
2581
16th to endDay
46%7%14%21%9%
2711
August1st to 15thDay
49%7%15%20%6%
2579
16th to endDay
42%6%15%25%9%
2552
September1st to 15thDay
44%5%12%24%12%
2340
16th to endDay
43%5%12%29%8%
2161
October1st to 15thDay
52%5%13%19%8%
1950
16th to endDay
62%5%12%14%4
1978
November1st to 15thDay
54%6%13%17%7%
1750
16th to endDay
68%39%11%6%
1677
December1st to 15thDay
71%5%9%10%3
1560
16th to endDay
69%39%11%6%
1664
January1st to 15thNight
68%411%10%3
2716
16th to endNight
61%410%15%7%
2865
February1st to 15thNight
64%39%17%4
2482
16th to endNight
59%39%18%8%
2132
March1st to 15thNight
62%38%17%7%
2262
16th to endNight
46%38%21%16%3
2213
April1st to 15thNight
53%27%19%14%1
1946
16th to endNight
49%38%18%16%3
1813
May1st to 15thNight
49%36%20%17%3
1560
16th to endNight
44%6%11%21%13%2
1625
June1st to 15thNight
49%5%13%21%7%1
1560
16th to endNight
44%7%11%21%14%
1560
July1st to 15thNight
34%6%13%26%17%1
1480
16th to endNight
35%7%15%30%10%
1546
August1st to 15thNight
41%8%16%24%8%
1609
16th to endNight
32%6%19%31%9%
1988
September1st to 15thNight
41%6%12%26%12%
1950
16th to endNight
40%414%32%7%
2128
October1st to 15thNight
50%5%11%22%10%
2340
16th to endNight
58%5%12%17%5%
2597
November1st to 15thNight
56%5%12%16%8%
2765
16th to endNight
65%411%13%3
2938
December1st to 15thNight
68%5%10%11%4
2730
16th to endNight
67%38%12%7%
2912

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
26%20%33%14%5%
90
16th to endDay
31%11%34%18%2
107
February1st to 15thDay
23%22%44%8%
135
16th to endDay
33%22%27%14%1
208
March1st to 15thDay
28%18%31%17%3
330
16th to endDay
22%15%34%18%8%1
352
April1st to 15thDay
33%16%26%16%6%
330
16th to endDay
29%20%22%15%11%
319
May1st to 15thDay
32%11%28%16%7%3
348
16th to endDay
25%15%31%18%7%1
395
June1st to 15thDay
24%12%33%22%5%1
375
16th to endDay
15%12%33%26%9%2
375
July1st to 15thDay
15%6%35%30%9%3
365
16th to endDay
14%7%28%30%15%3
390
August1st to 15thDay
19%328%27%15%5%
358
16th to endDay
16%7%28%23%13%9%
396
September1st to 15thDay
19%8%25%22%13%10%
375
16th to endDay
17%12%27%21%14%7%
374
October1st to 15thDay
27%13%29%18%9%2
375
16th to endDay
31%19%29%13%6%
368
November1st to 15thDay
29%13%30%18%6%1
224
16th to endDay
36%21%28%10%1
119
December1st to 15thDay
30%16%38%13%1
90
16th to endDay
33%23%35%5%2
96
January1st to 15thNight
29%13%31%20%6%
780
16th to endNight
23%12%32%23%7%
832
February1st to 15thNight
19%14%37%21%6%
764
16th to endNight
25%15%32%21%4
683
March1st to 15thNight
27%16%30%22%3
780
16th to endNight
17%17%29%24%10%
832
April1st to 15thNight
28%15%26%23%6%
778
16th to endNight
27%12%27%24%8%
657
May1st to 15thNight
26%7%28%27%9%
390
16th to endNight
19%8%34%28%9%
407
June1st to 15thNight
19%9%32%30%8%
390
16th to endNight
18%6%25%35%13%1
390
July1st to 15thNight
10%5%26%38%19%
370
16th to endNight
10%423%41%18%2
408
August1st to 15thNight
13%322%36%22%2
468
16th to endNight
12%5%25%32%21%2
746
September1st to 15thNight
19%426%27%18%2
780
16th to endNight
19%7%25%27%18%2
777
October1st to 15thNight
26%10%28%21%11%1
780
16th to endNight
30%11%29%20%7%
832
November1st to 15thNight
26%14%27%21%8%
820
16th to endNight
34%13%25%17%7%
840
December1st to 15thNight
31%15%29%18%3
780
16th to endNight
31%11%31%18%41
832
Page generated at 2018-12-01 11:35:37. Version ac04

Copyright 2018 A. Danko


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