Observatoire de Leclercville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de Leclercville clear sky chart from 2005-11-05 to 2017-09-23.

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
27%
14640
12%
46970
7%
14608
33%
14608
14%
34765

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
14%
720
8%
2506
4%
716
20%
716
8%
2027
January16th to endNight
21%
768
10%
2688
6%
768
28%
768
9%
2096
February1st to 15thNight
18%
704
9%
2348
4%
701
25%
701
10%
1857
February16th to endNight
18%
631
11%
1893
5%
631
26%
631
11%
1488
March1st to 15thNight
19%
720
14%
2160
7%
720
27%
720
14%
1624
March16th to endNight
29%
768
17%
2016
7%
768
37%
768
21%
1454
April1st to 15thNight
23%
718
14%
1796
5%
718
28%
718
18%
1387
April16th to endNight
26%
561
15%
1641
6%
561
33%
561
18%
1151
May1st to 15thNight
27%
435
13%
1515
10%
435
35%
435
15%
1060
May16th to endNight
26%
375
10%
1497
8%
374
36%
374
13%
1054
June1st to 15thNight
31%
360
7%
1329
6%
360
37%
360
14%
942
June16th to endNight
38%
360
8%
1326
8%
360
41%
360
17%
918
July1st to 15thNight
43%
340
8%
1360
11%
340
48%
340
19%
882
July16th to endNight
47%
376
10%
1418
14%
354
49%
354
17%
928
August1st to 15thNight
48%
398
11%
1469
11%
396
51%
396
16%
985
August16th to endNight
43%
675
15%
1821
10%
675
45%
675
27%
1224
September1st to 15thNight
41%
720
13%
1830
7%
720
43%
720
27%
1285
September16th to endNight
42%
689
19%
1902
12%
689
47%
689
29%
1243
October1st to 15thNight
31%
660
17%
1911
10%
660
39%
660
20%
1378
October16th to endNight
22%
704
9%
2288
5%
704
28%
704
12%
1746
November1st to 15thNight
25%
700
15%
2277
10%
700
33%
700
14%
1669
November16th to endNight
24%
725
12%
2504
8%
725
31%
725
10%
1911
December1st to 15thNight
14%
750
6%
2700
2%
750
19%
750
7%
2175
December16th to endNight
15%
783
9%
2775
4%
783
21%
783
7%
2281

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
20%8%36%5%3445%6%30%
47933
Night
20%10%47%5%34445%29%
47140
TransparencyDay
54%6%11%18%8%
47621
Night
56%5%11%17%8%
46970
SeeingDay
25%11%27%22%10%2
5865
Night
25%10%29%25%8%
14640

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%14%49%6%3433420%
1432
16th to endDay
13%15%7%8%8%25%5%45%23%
1536
February1st to 15thDay
11%15%5%11%7%45%35%5%23%
1509
16th to endDay
17%14%5%8%7%25%445%24%
1580
March1st to 15thDay
20%10%5%7%5%24335%31%
1790
16th to endDay
16%10%36%5%35%446%33%
2208
April1st to 15thDay
24%9%45%5%23335%32%
2152
16th to endDay
22%7%26%325%345%35%
2318
May1st to 15thDay
23%7%25%5%3345%6%31%
2445
16th to endDay
21%7%36%5%3446%6%28%
2618
June1st to 15thDay
22%6%35%6%35%5%5%8%27%
2628
16th to endDay
20%7%36%6%35%5%7%6%27%
2628
July1st to 15thDay
14%5%26%6%45%5%7%9%31%
2520
16th to endDay
16%6%25%6%46%6%6%8%29%
2654
August1st to 15thDay
17%6%26%6%46%5%6%10%28%
2469
16th to endDay
13%5%25%5%335%5%7%41%
2381
September1st to 15thDay
20%5%24424446%39%
2130
16th to endDay
20%42342335%6%44%
1895
October1st to 15thDay
25%7%35%5%34446%29%
1718
16th to endDay
27%10%36%7%2344423%
1584
November1st to 15thDay
21%9%46%5%3444430%
1581
16th to endDay
24%13%5%7%5%2323427%
1451
December1st to 15thDay
29%13%47%5%2232423%
1260
16th to endDay
26%14%5%7%5%2333422%
1446
January1st to 15thNight
23%15%5%8%6%3344420%
2506
16th to endNight
14%15%5%9%6%46%44423%
2688
February1st to 15thNight
10%12%7%13%9%45%44423%
2347
16th to endNight
18%12%6%10%6%25%33325%
1893
March1st to 15thNight
20%10%47%5%35%33430%
2147
16th to endNight
15%11%36%42345%437%
2016
April1st to 15thNight
26%10%35%42345%5%27%
1796
16th to endNight
23%7%25%323346%36%
1641
May1st to 15thNight
24%7%35%424346%33%
1515
16th to endNight
25%7%25%425%35%6%30%
1495
June1st to 15thNight
24%7%46%42346%6%28%
1329
16th to endNight
20%6%36%5%35%5%5%7%30%
1326
July1st to 15thNight
15%5%36%5%345%5%8%34%
1440
16th to endNight
13%5%35%5%36%6%48%37%
1514
August1st to 15thNight
14%6%26%5%45%5%7%9%32%
1479
16th to endNight
13%5%26%6%3446%7%40%
1821
September1st to 15thNight
20%6%2442335%7%39%
1830
16th to endNight
20%5%14323237%45%
1902
October1st to 15thNight
20%7%345%345%46%34%
1911
16th to endNight
29%9%25%5%3334428%
2288
November1st to 15thNight
20%9%37%6%2435%5%31%
2277
16th to endNight
25%13%47%42423426%
2504
December1st to 15thNight
25%14%5%8%6%2333421%
2700
16th to endNight
24%16%5%9%6%3433419%
2775

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
67%6%8%12%5%
1433
16th to endDay
61%6%8%16%5%
1536
February1st to 15thDay
63%5%10%14%5%
1512
16th to endDay
62%5%7%15%6%1
1580
March1st to 15thDay
57%5%10%14%10%1
1800
16th to endDay
52%5%9%17%12%2
2208
April1st to 15thDay
55%48%17%10%3
2152
16th to endDay
51%48%18%13%2
2318
May1st to 15thDay
53%6%9%17%12%1
2445
16th to endDay
55%7%9%16%10%
2622
June1st to 15thDay
53%7%11%16%9%1
2628
16th to endDay
54%8%10%17%8%
2628
July1st to 15thDay
45%9%16%21%7%
2371
16th to endDay
51%10%14%17%6%
2487
August1st to 15thDay
50%10%18%16%4
2455
16th to endDay
40%7%16%26%8%
2381
September1st to 15thDay
45%6%14%23%10%
2130
16th to endDay
41%5%14%28%9%
1895
October1st to 15thDay
54%5%12%20%6%
1718
16th to endDay
63%6%8%17%3
1584
November1st to 15thDay
56%5%11%17%8%
1581
16th to endDay
62%5%10%17%4
1451
December1st to 15thDay
66%410%14%3
1260
16th to endDay
67%6%7%12%6%
1446
January1st to 15thNight
67%6%8%12%4
2506
16th to endNight
63%5%9%14%5%
2688
February1st to 15thNight
64%5%9%13%5%
2348
16th to endNight
62%5%7%13%10%
1893
March1st to 15thNight
58%49%15%10%1
2160
16th to endNight
49%5%10%17%14%2
2016
April1st to 15thNight
58%36%17%11%2
1796
16th to endNight
48%6%9%17%14%3
1641
May1st to 15thNight
53%410%15%14%2
1515
16th to endNight
54%6%10%16%11%1
1497
June1st to 15thNight
55%413%17%7%1
1329
16th to endNight
50%6%12%18%11%
1326
July1st to 15thNight
44%7%16%20%9%1
1360
16th to endNight
44%9%15%20%10%
1418
August1st to 15thNight
45%10%17%21%5%
1469
16th to endNight
41%6%17%26%7%
1821
September1st to 15thNight
44%5%13%24%10%
1830
16th to endNight
40%5%15%27%11%
1902
October1st to 15thNight
50%6%10%22%9%
1911
16th to endNight
59%5%11%17%5%
2288
November1st to 15thNight
55%5%13%16%8%
2277
16th to endNight
62%49%17%6%
2504
December1st to 15thNight
68%410%12%3
2700
16th to endNight
70%47%10%5%
2775

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%15%28%25%1
60
16th to endDay
32%17%32%9%6%1
64
February1st to 15thDay
24%20%40%11%3
110
16th to endDay
25%13%32%22%5%
239
March1st to 15thDay
26%18%25%23%5%
270
16th to endDay
24%11%28%18%12%4
288
April1st to 15thDay
30%17%24%21%5%1
270
16th to endDay
23%15%31%18%8%2
270
May1st to 15thDay
34%10%28%16%8%2
288
16th to endDay
24%13%31%22%7%1
331
June1st to 15thDay
27%8%30%21%9%1
423
16th to endDay
22%10%28%28%9%1
423
July1st to 15thDay
18%9%30%26%13%2
305
16th to endDay
20%330%30%13%1
326
August1st to 15thDay
22%7%22%27%15%6%
313
16th to endDay
20%9%25%18%17%6%
332
September1st to 15thDay
24%6%21%27%14%6%
315
16th to endDay
17%12%24%20%18%7%
283
October1st to 15thDay
29%7%27%20%11%2
251
16th to endDay
36%13%21%20%8%
240
November1st to 15thDay
28%13%25%21%9%1
235
16th to endDay
35%14%20%21%7%
105
December1st to 15thDay
40%11%26%20%1
60
16th to endDay
45%20%28%41
64
January1st to 15thNight
28%14%34%20%3
720
16th to endNight
22%13%31%26%6%
768
February1st to 15thNight
17%13%38%24%6%
704
16th to endNight
25%13%34%20%5%
631
March1st to 15thNight
26%10%36%21%3
720
16th to endNight
19%13%31%26%7%1
768
April1st to 15thNight
30%11%29%23%4
718
16th to endNight
27%13%29%22%7%
561
May1st to 15thNight
25%9%28%28%7%
435
16th to endNight
31%6%30%25%5%
375
June1st to 15thNight
30%326%32%7%
360
16th to endNight
20%7%26%33%12%
360
July1st to 15thNight
16%5%26%36%15%
340
16th to endNight
17%324%43%10%
376
August1st to 15thNight
17%421%36%18%1
398
16th to endNight
16%5%27%31%16%1
675
September1st to 15thNight
23%424%33%11%1
720
16th to endNight
20%6%26%28%16%1
689
October1st to 15thNight
24%9%29%28%7%1
660
16th to endNight
33%10%27%22%5%
704
November1st to 15thNight
26%13%27%23%8%
700
16th to endNight
31%13%23%21%8%1
725
December1st to 15thNight
32%14%29%19%4
750
16th to endNight
33%14%27%17%41
783
Page generated at 2017-09-24 09:15:52. Version ac04

Copyright 2017 A. Danko


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