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 2018-01-20.

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%
16179
22%
48403
16%
16134
51%
16134
27%
30820

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%
975
18%
2716
8%
970
33%
970
19%
1933
January16th to endNight
23%
904
19%
2571
8%
904
33%
904
21%
1777
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
63%
717
30%
1980
23%
717
66%
717
37%
1189
October1st to 15thNight
58%
720
32%
1980
24%
720
64%
720
37%
1176
October16th to endNight
44%
768
28%
2422
21%
768
53%
768
29%
1459
November1st to 15thNight
45%
760
29%
2471
24%
760
54%
760
32%
1418
November16th to endNight
38%
780
26%
2535
20%
780
47%
780
27%
1496
December1st to 15thNight
31%
780
17%
2535
11%
780
38%
780
18%
1755
December16th to endNight
24%
1014
17%
2886
7%
1014
34%
1014
19%
2084

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%
49122
Night
14%6%24424446%44%
48587
TransparencyDay
41%6%11%22%15%2
48808
Night
39%5%10%22%17%3
48405
SeeingDay
15%6%20%24%21%11%
6092
Night
17%7%23%28%19%2
16181

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%345%4433%
1552
16th to endDay
14%9%36%5%34335%39%
1752
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%24433446%49%
1980
October1st to 15thDay
13%423323446%50%
1980
16th to endDay
15%424423335%51%
1800
November1st to 15thDay
13%5%25%423235%51%
1717
16th to endDay
16%6%23413345%46%
1755
December1st to 15thDay
20%9%35%433445%36%
1755
16th to endDay
20%11%35%433335%35%
1687
January1st to 15thNight
18%9%37%5%2433436%
2716
16th to endNight
17%9%36%5%23346%37%
2571
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
10%42332435%6%52%
1980
October1st to 15thNight
12%413323335%54%
1980
16th to endNight
16%5%1432333450%
2422
November1st to 15thNight
13%424323335%52%
2471
16th to endNight
17%5%23323336%49%
2535
December1st to 15thNight
20%10%35%424345%35%
2535
16th to endNight
21%10%45%424335%35%
2886

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%20%11%1
1553
16th to endDay
48%38%27%9%1
1752
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
34%5%8%22%23%4
1980
October1st to 15thDay
34%48%25%22%4
1980
16th to endDay
36%46%25%22%4
1800
November1st to 15thDay
37%37%22%22%6%
1717
16th to endDay
40%27%27%19%2
1755
December1st to 15thDay
49%5%11%19%12%2
1755
16th to endDay
51%411%21%9%1
1687
January1st to 15thNight
51%37%19%15%1
2716
16th to endNight
49%310%21%13%1
2571
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
32%48%19%27%6%
1980
October1st to 15thNight
31%47%21%28%5%
1980
16th to endNight
38%36%24%22%5%
2422
November1st to 15thNight
34%37%22%24%7%
2471
16th to endNight
37%38%25%21%3
2535
December1st to 15thNight
50%49%18%13%2
2535
16th to endNight
52%410%19%11%1
2886

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
27%19%33%11%6%1
135
16th to endDay
20%17%42%15%4
109
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
16%212%19%33%16%
314
October1st to 15thDay
15%220%26%24%10%
315
16th to endDay
16%8%29%27%15%2
144
November1st to 15thDay
18%8%28%23%14%5%
135
16th to endDay
21%11%32%22%8%2
135
December1st to 15thDay
15%18%36%18%8%2
135
16th to endDay
30%20%38%10%
144
January1st to 15thNight
25%14%30%24%5%
975
16th to endNight
24%13%35%24%3
904
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
12%313%28%35%6%
717
October1st to 15thNight
15%317%30%27%5%
720
16th to endNight
19%5%26%28%18%1
768
November1st to 15thNight
15%8%26%28%20%1
760
16th to endNight
21%12%24%26%14%
780
December1st to 15thNight
25%12%25%26%9%
780
16th to endNight
27%12%30%24%4
1014
Page generated at 2018-01-21 11:19:30. Version ac04

Copyright 2018 A. Danko


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