Rue de Renard Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rue de Renard Observatory clear sky chart from 2005-11-05 to 2017-09-17.

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
45%
15645
22%
46807
16%
15600
51%
15600
27%
29831

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
24%
900
18%
2506
9%
895
33%
895
19%
1784
January16th to endNight
22%
879
19%
2502
7%
879
32%
879
21%
1733
February1st to 15thNight
21%
704
16%
2112
7%
701
29%
701
17%
1510
February16th to endNight
19%
631
19%
1893
7%
631
29%
631
19%
1327
March1st to 15thNight
28%
720
18%
2160
10%
720
35%
720
21%
1471
March16th to endNight
33%
672
16%
2028
11%
672
39%
672
21%
1393
April1st to 15thNight
41%
539
23%
1797
16%
539
52%
539
29%
1045
April16th to endNight
44%
540
21%
1773
18%
540
52%
540
26%
1102
May1st to 15thNight
45%
540
19%
1619
13%
539
50%
539
25%
1080
May16th to endNight
62%
561
20%
1683
16%
561
64%
561
30%
1045
June1st to 15thNight
68%
540
22%
1458
17%
540
71%
540
41%
865
June16th to endNight
76%
540
24%
1440
18%
540
78%
540
43%
832
July1st to 15thNight
70%
510
18%
1360
14%
510
70%
510
35%
865
July16th to endNight
75%
564
23%
1494
20%
531
78%
531
39%
884
August1st to 15thNight
75%
539
23%
1732
25%
536
76%
536
36%
970
August16th to endNight
75%
573
24%
1910
27%
573
77%
573
35%
1049
September1st to 15thNight
64%
588
24%
1848
25%
588
67%
588
31%
1095
September16th to endNight
61%
665
28%
1837
22%
665
64%
665
35%
1123
October1st to 15thNight
58%
660
34%
1815
25%
660
64%
660
38%
1068
October16th to endNight
44%
704
26%
2220
21%
704
53%
704
29%
1347
November1st to 15thNight
46%
700
30%
2276
25%
700
56%
700
33%
1273
November16th to endNight
36%
720
24%
2340
18%
720
45%
720
26%
1406
December1st to 15thNight
29%
720
16%
2340
12%
720
36%
720
17%
1643
December16th to endNight
25%
936
18%
2664
8%
936
34%
936
19%
1921

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
13%6%25%5%3445%7%40%
47966
Night
14%6%24424446%44%
46991
TransparencyDay
41%6%11%22%15%2
47652
Night
40%5%10%22%17%3
46809
SeeingDay
15%6%20%24%22%11%
5688
Night
17%7%23%28%19%2
15647

By Month

Percentage Cloud Cover SE (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
20%7%47%5%235%4433%
1432
16th to endDay
14%9%36%5%34335%39%
1717
February1st to 15thDay
15%10%5%6%6%3325%436%
1750
16th to endDay
14%10%46%5%2445%7%33%
1580
March1st to 15thDay
21%8%35%5%23345%36%
1800
16th to endDay
17%7%26%6%345%5%6%33%
2202
April1st to 15thDay
13%6%25%5%2445%7%41%
2151
16th to endDay
14%6%25%5%34346%42%
2186
May1st to 15thDay
18%5%25%6%3445%7%35%
2331
16th to endDay
10%435%5%35%6%7%8%38%
2431
June1st to 15thDay
7%315%5%345%6%8%46%
2499
16th to endDay
5%3245%46%6%6%11%42%
2520
July1st to 15thDay
10%5%25%5%36%6%6%9%37%
2520
16th to endDay
7%3246%45%7%8%11%38%
2568
August1st to 15thDay
7%5%246%36%5%6%10%41%
2214
16th to endDay
8%4146%35%5%6%10%42%
2292
September1st to 15thDay
12%5%25%6%35%5%5%9%38%
2100
16th to endDay
11%5%24432445%49%
1829
October1st to 15thDay
13%323323445%52%
1815
16th to endDay
16%414423335%50%
1650
November1st to 15thDay
12%426%323236%53%
1582
16th to endDay
17%6%23414345%46%
1620
December1st to 15thDay
21%9%35%43344434%
1620
16th to endDay
19%10%35%333435%36%
1557
January1st to 15thNight
18%9%47%5%2333436%
2506
16th to endNight
17%10%35%5%23346%36%
2502
February1st to 15thNight
21%9%46%5%3323435%
2103
16th to endNight
16%8%47%423445%36%
1893
March1st to 15thNight
17%9%35%41435%5%39%
2160
16th to endNight
16%8%35%424447%37%
2028
April1st to 15thNight
13%5%142235%5%6%48%
1797
16th to endNight
13%5%35%42345%8%43%
1773
May1st to 15thNight
16%5%36%43335%7%40%
1619
16th to endNight
6%3246%36%5%6%10%45%
1682
June1st to 15thNight
7%32333446%9%51%
1458
16th to endNight
42133245%7%13%49%
1440
July1st to 15thNight
9%3234345%6%10%45%
1440
16th to endNight
7%313435%47%9%49%
1597
August1st to 15thNight
5%42442446%9%50%
1743
16th to endNight
6%2244245%5%9%51%
1910
September1st to 15thNight
13%32333435%7%48%
1848
16th to endNight
11%42442435%6%51%
1837
October1st to 15thNight
12%412323335%55%
1815
16th to endNight
17%5%1432333449%
2220
November1st to 15thNight
12%423323235%54%
2276
16th to endNight
18%5%23323336%47%
2340
December1st to 15thNight
22%10%45%423345%33%
2340
16th to endNight
21%10%45%42433435%
2664

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
53%5%7%21%11%
1433
16th to endDay
48%48%27%9%1
1717
February1st to 15thDay
51%38%23%10%1
1752
16th to endDay
49%412%17%12%1
1580
March1st to 15thDay
51%48%21%13%2
1800
16th to endDay
50%5%10%24%7%
2203
April1st to 15thDay
41%49%22%19%2
2151
16th to endDay
42%5%10%24%14%2
2186
May1st to 15thDay
47%7%11%20%12%
2331
16th to endDay
40%9%14%20%12%2
2435
June1st to 15thDay
33%8%12%23%19%2
2499
16th to endDay
32%8%13%22%19%3
2520
July1st to 15thDay
39%8%12%21%13%4
2371
16th to endDay
33%10%18%23%11%2
2408
August1st to 15thDay
36%8%13%23%16%1
2201
16th to endDay
36%8%11%21%17%4
2292
September1st to 15thDay
41%7%11%20%16%3
2100
16th to endDay
36%5%7%20%24%5%
1829
October1st to 15thDay
33%47%24%24%4
1815
16th to endDay
37%36%25%21%4
1650
November1st to 15thDay
35%37%21%24%7%
1582
16th to endDay
41%27%27%17%3
1620
December1st to 15thDay
51%5%10%18%11%2
1620
16th to endDay
50%411%22%9%1
1557
January1st to 15thNight
51%37%19%15%1
2506
16th to endNight
49%310%21%13%1
2502
February1st to 15thNight
53%38%21%11%1
2112
16th to endNight
49%5%9%21%12%1
1893
March1st to 15thNight
46%5%9%19%14%4
2160
16th to endNight
47%5%12%22%11%1
2028
April1st to 15thNight
33%5%11%23%20%5%
1797
16th to endNight
39%5%8%24%17%4
1773
May1st to 15thNight
43%5%10%24%14%1
1620
16th to endNight
32%10%15%22%16%3
1684
June1st to 15thNight
28%6%15%25%21%2
1458
16th to endNight
24%8%16%24%21%5%
1440
July1st to 15thNight
31%9%12%25%15%5%
1360
16th to endNight
27%8%17%27%16%2
1494
August1st to 15thNight
29%6%14%25%22%2
1732
16th to endNight
27%7%13%26%20%4
1910
September1st to 15thNight
35%5%9%24%19%5%
1848
16th to endNight
34%47%18%28%7%
1837
October1st to 15thNight
31%47%21%29%6%
1815
16th to endNight
38%36%24%21%6%
2220
November1st to 15thNight
33%36%23%25%8%
2276
16th to endNight
39%38%25%19%3
2340
December1st to 15thNight
52%49%17%13%2
2340
16th to endNight
52%310%19%11%1
2664

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
33%16%32%8%7%1
90
16th to endDay
20%17%44%13%3
96
February1st to 15thDay
21%32%30%14%2
90
16th to endDay
23%18%38%11%8%
81
March1st to 15thDay
31%22%34%10%2
90
16th to endDay
20%11%32%23%10%1
274
April1st to 15thDay
16%14%23%30%12%1
270
16th to endDay
19%6%28%23%17%4
270
May1st to 15thDay
19%10%27%22%12%6%
288
16th to endDay
14%6%20%30%16%12%
331
June1st to 15thDay
8%218%24%30%14%
474
16th to endDay
6%317%33%25%13%
495
July1st to 15thDay
13%115%31%23%13%
475
16th to endDay
6%7%25%32%27%
428
August1st to 15thDay
15%6%25%31%20%
313
16th to endDay
12%9%23%35%17%
332
September1st to 15thDay
15%110%18%35%18%
315
16th to endDay
18%311%21%30%15%
259
October1st to 15thDay
15%121%24%25%10%
255
16th to endDay
18%6%23%32%16%2
96
November1st to 15thDay
11%11%26%24%18%7%
90
16th to endDay
26%14%32%15%8%2
90
December1st to 15thDay
17%15%37%17%7%3
90
16th to endDay
23%17%45%11%1
96
January1st to 15thNight
25%15%30%24%5%
900
16th to endNight
24%13%35%23%2
879
February1st to 15thNight
26%14%32%24%2
704
16th to endNight
22%14%40%20%2
631
March1st to 15thNight
24%12%30%29%3
720
16th to endNight
20%9%30%28%9%
672
April1st to 15thNight
16%9%30%32%10%
539
16th to endNight
16%429%33%14%
540
May1st to 15thNight
18%5%24%32%15%2
540
16th to endNight
7%318%35%31%4
563
June1st to 15thNight
8%115%36%34%3
540
16th to endNight
5%110%40%38%3
540
July1st to 15thNight
10%9%32%41%5%
510
16th to endNight
7%8%27%44%10%
564
August1st to 15thNight
7%8%30%44%9%
539
16th to endNight
6%9%32%44%6%
573
September1st to 15thNight
15%210%27%37%7%
588
16th to endNight
13%313%28%33%6%
665
October1st to 15thNight
15%317%30%27%5%
660
16th to endNight
19%5%25%29%18%1
704
November1st to 15thNight
14%8%26%28%20%1
700
16th to endNight
22%12%25%25%13%
720
December1st to 15thNight
27%12%25%24%9%
720
16th to endNight
27%12%30%25%4
936
Page generated at 2017-09-18 07:38:21. Version ac04

Copyright 2017 A. Danko


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