Leon Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leon Observing Site 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
40%
16095
18%
48473
12%
16057
46%
16057
22%
32919

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
19%
778
12%
2522
6%
776
27%
776
10%
1956
January16th to endNight
19%
788
15%
2560
6%
788
30%
788
13%
1875
February1st to 15thNight
23%
701
12%
2261
6%
701
31%
701
14%
1654
February16th to endNight
17%
631
13%
1893
5%
631
25%
631
13%
1428
March1st to 15thNight
26%
720
17%
2010
10%
720
32%
720
17%
1457
March16th to endNight
29%
768
14%
2112
8%
768
34%
768
18%
1544
April1st to 15thNight
30%
701
17%
1907
7%
701
38%
701
23%
1307
April16th to endNight
36%
540
20%
1620
10%
540
45%
540
25%
1061
May1st to 15thNight
36%
540
14%
1620
8%
540
41%
540
19%
1160
May16th to endNight
51%
561
17%
1684
12%
561
56%
561
26%
1095
June1st to 15thNight
60%
540
16%
1620
14%
540
64%
540
32%
995
June16th to endNight
60%
540
16%
1620
14%
540
63%
540
32%
987
July1st to 15thNight
59%
510
14%
1530
13%
510
61%
510
28%
1003
July16th to endNight
68%
564
17%
1595
14%
531
71%
531
33%
950
August1st to 15thNight
66%
539
21%
1609
16%
536
68%
536
29%
1008
August16th to endNight
70%
597
26%
1743
21%
597
72%
597
36%
1030
September1st to 15thNight
63%
720
25%
1971
19%
720
65%
720
34%
1219
September16th to endNight
57%
717
27%
1980
21%
717
61%
717
31%
1254
October1st to 15thNight
53%
720
25%
2097
23%
720
58%
720
32%
1268
October16th to endNight
38%
768
24%
2304
18%
768
47%
768
24%
1512
November1st to 15thNight
42%
760
25%
2441
19%
760
51%
760
26%
1498
November16th to endNight
34%
780
21%
2535
15%
780
43%
780
19%
1682
December1st to 15thNight
25%
780
12%
2535
8%
780
30%
780
12%
1911
December16th to endNight
23%
832
13%
2704
6%
832
31%
832
11%
2065

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
17%7%36%5%3445%7%35%
49043
Night
15%7%35%5%34446%38%
48666
Cloud CoverDay
16%7%36%5%3445%7%35%
49053
Night
15%7%36%5%24446%38%
48670
TransparencyDay
47%6%10%19%13%2
48754
Night
46%5%10%20%15%2
48473
SeeingDay
20%8%23%21%16%8%
5864
Night
20%9%23%28%16%2
16102

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%11%5%9%7%24435%23%
1746
16th to endDay
19%14%5%7%5%34445%26%
1768
February1st to 15thDay
22%11%5%7%6%23335%28%
1599
16th to endDay
19%14%47%433335%29%
1580
March1st to 15thDay
21%9%47%425%43433%
1939
16th to endDay
20%9%36%424446%32%
2112
April1st to 15thDay
18%7%34423447%38%
2050
16th to endDay
18%5%25%5%2435%6%39%
2340
May1st to 15thDay
21%7%36%6%3446%6%29%
2331
16th to endDay
13%5%26%5%35%5%5%8%38%
2431
June1st to 15thDay
11%5%145%45%5%6%9%40%
2340
16th to endDay
11%425%5%45%7%7%10%35%
2340
July1st to 15thDay
14%5%26%6%36%6%6%8%33%
2340
16th to endDay
12%426%5%37%7%7%9%33%
2465
August1st to 15thDay
12%425%6%46%6%7%11%31%
2340
16th to endDay
10%5%245%35%6%6%8%41%
2447
September1st to 15thDay
13%5%25%5%3446%6%42%
1986
16th to endDay
17%5%25%423445%43%
1980
October1st to 15thDay
14%6%25%5%2335%7%42%
1863
16th to endDay
21%6%24422236%43%
1920
November1st to 15thDay
15%7%25%423346%45%
1744
16th to endDay
18%8%35%424345%37%
1755
December1st to 15thDay
25%11%5%6%32424427%
1755
16th to endDay
23%12%5%7%5%23336%24%
1872
January1st to 15thNight
20%12%6%9%6%3443424%
2522
16th to endNight
19%13%47%5%23345%30%
2560
February1st to 15thNight
20%11%46%5%33345%30%
2259
16th to endNight
20%14%46%5%24345%27%
1893
March1st to 15thNight
18%8%36%6%34437%32%
1998
16th to endNight
18%9%36%5%24445%33%
2112
April1st to 15thNight
16%8%35%42445%6%38%
1907
16th to endNight
14%6%26%43445%7%40%
1620
May1st to 15thNight
17%7%36%5%45%35%7%34%
1620
16th to endNight
11%5%245%35%5%6%9%41%
1682
June1st to 15thNight
8%3235%25%5%6%11%45%
1620
16th to endNight
8%32442448%9%46%
1620
July1st to 15thNight
10%6%36%32445%9%42%
1620
16th to endNight
7%324445%6%6%8%45%
1703
August1st to 15thNight
7%4145%46%6%6%10%43%
1620
16th to endNight
7%32442445%8%50%
1743
September1st to 15thNight
11%41332446%7%50%
1971
16th to endNight
13%415%424446%47%
1980
October1st to 15thNight
10%5%145%3345%6%49%
2097
16th to endNight
19%5%25%5%24335%42%
2304
November1st to 15thNight
15%6%25%423345%46%
2441
16th to endNight
19%7%25%435%345%39%
2535
December1st to 15thNight
23%10%48%5%25%43426%
2535
16th to endNight
21%15%46%5%34345%25%
2704

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
21%10%5%9%7%34335%23%
1746
16th to endDay
19%14%6%6%5%24345%25%
1768
February1st to 15thDay
21%11%5%8%6%24335%28%
1599
16th to endDay
18%14%47%5%23445%29%
1580
March1st to 15thDay
21%9%47%5%2343432%
1950
16th to endDay
19%9%37%423445%32%
2111
April1st to 15thDay
18%7%25%423446%39%
2050
16th to endDay
17%6%25%5%2435%6%38%
2340
May1st to 15thDay
21%7%36%5%35%5%5%6%29%
2331
16th to endDay
13%5%26%6%35%46%8%38%
2431
June1st to 15thDay
11%425%5%35%5%6%10%40%
2340
16th to endDay
11%4246%46%6%7%9%35%
2340
July1st to 15thDay
14%5%26%7%36%5%6%8%33%
2340
16th to endDay
11%435%5%47%7%7%10%32%
2465
August1st to 15thDay
11%5%26%6%46%7%7%11%31%
2340
16th to endDay
10%5%245%346%6%7%41%
2447
September1st to 15thDay
13%4246%345%6%7%42%
1986
16th to endDay
17%5%25%425%44443%
1980
October1st to 15thDay
15%6%25%42335%7%42%
1863
16th to endDay
20%6%24423235%44%
1920
November1st to 15thDay
15%7%25%423346%45%
1744
16th to endDay
17%9%35%434335%38%
1755
December1st to 15thDay
24%11%5%6%5%13345%27%
1755
16th to endDay
23%12%5%8%424336%24%
1872
January1st to 15thNight
19%12%6%9%6%25%34423%
2522
16th to endNight
20%12%5%7%5%2333430%
2560
February1st to 15thNight
19%12%46%5%34335%30%
2252
16th to endNight
20%13%47%5%25%345%27%
1893
March1st to 15thNight
18%8%37%5%44436%32%
2010
16th to endNight
19%9%36%5%2445%5%33%
2112
April1st to 15thNight
16%8%35%424446%38%
1907
16th to endNight
14%6%36%4245%5%6%40%
1620
May1st to 15thNight
16%8%36%5%35%35%6%34%
1619
16th to endNight
11%5%145%25%6%6%9%41%
1682
June1st to 15thNight
8%3234346%7%11%44%
1620
16th to endNight
8%324425%5%6%11%45%
1620
July1st to 15thNight
11%5%36%315%5%5%8%43%
1620
16th to endNight
7%3245%35%5%6%10%44%
1703
August1st to 15thNight
7%415%5%36%5%6%10%42%
1620
16th to endNight
7%425%42446%8%50%
1743
September1st to 15thNight
11%3143245%5%7%50%
1971
16th to endNight
14%315%5%34446%47%
1980
October1st to 15thNight
10%415%5%34347%48%
2097
16th to endNight
19%5%25%5%33335%42%
2304
November1st to 15thNight
14%7%25%423346%46%
2441
16th to endNight
19%7%25%425%336%39%
2535
December1st to 15thNight
22%10%48%6%25%43426%
2535
16th to endNight
21%15%46%5%34335%25%
2704

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
63%39%14%7%
1747
16th to endDay
60%410%17%5%1
1768
February1st to 15thDay
60%311%15%8%
1601
16th to endDay
56%5%9%20%7%
1580
March1st to 15thDay
54%48%22%8%1
1950
16th to endDay
52%5%10%19%10%1
2112
April1st to 15thDay
44%6%9%21%14%3
2050
16th to endDay
45%5%10%19%13%5%
2340
May1st to 15thDay
52%6%12%15%10%1
2331
16th to endDay
42%8%13%20%13%1
2435
June1st to 15thDay
37%9%13%22%16%
2340
16th to endDay
41%10%13%16%15%2
2340
July1st to 15thDay
46%8%11%16%13%2
2201
16th to endDay
42%10%13%19%12%2
2310
August1st to 15thDay
44%10%12%20%11%1
2327
16th to endDay
37%7%12%24%14%3
2447
September1st to 15thDay
39%7%10%18%19%4
1986
16th to endDay
42%6%7%20%23%1
1980
October1st to 15thDay
40%411%23%17%1
1863
16th to endDay
43%38%26%16%1
1920
November1st to 15thDay
41%38%24%18%4
1744
16th to endDay
48%39%21%16%
1755
December1st to 15thDay
59%410%17%6%1
1755
16th to endDay
61%411%16%6%
1872
January1st to 15thNight
63%38%12%9%1
2522
16th to endNight
57%310%19%7%1
2560
February1st to 15thNight
56%39%19%9%
2261
16th to endNight
59%49%17%9%
1893
March1st to 15thNight
52%49%20%10%1
2010
16th to endNight
52%5%10%18%12%
2112
April1st to 15thNight
44%5%8%19%17%3
1907
16th to endNight
41%5%10%18%16%7%
1620
May1st to 15thNight
50%6%9%17%12%2
1620
16th to endNight
37%10%12%22%15%1
1684
June1st to 15thNight
30%10%15%22%19%2
1620
16th to endNight
31%9%14%20%20%2
1620
July1st to 15thNight
38%8%11%20%17%2
1530
16th to endNight
30%9%17%24%16%3
1595
August1st to 15thNight
35%8%13%23%16%2
1609
16th to endNight
31%6%11%24%21%4
1743
September1st to 15thNight
32%8%11%19%21%6%
1971
16th to endNight
37%5%8%20%26%
1980
October1st to 15thNight
35%5%12%24%19%3
2097
16th to endNight
43%48%24%17%1
2304
November1st to 15thNight
40%39%20%21%5%
2441
16th to endNight
47%47%22%16%1
2535
December1st to 15thNight
60%48%17%7%1
2535
16th to endNight
61%411%16%5%
2704

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
28%17%36%10%5%2
135
16th to endDay
39%22%28%7%2
109
February1st to 15thDay
34%27%28%7%1
90
16th to endDay
34%17%37%9%1
81
March1st to 15thDay
30%14%29%19%7%
240
16th to endDay
22%17%34%16%7%1
288
April1st to 15thDay
22%14%30%22%10%
270
16th to endDay
24%7%30%18%12%7%
270
May1st to 15thDay
27%12%26%18%11%4
288
16th to endDay
16%6%25%23%16%11%
331
June1st to 15thDay
11%5%19%29%24%9%
315
16th to endDay
13%7%27%22%19%9%
315
July1st to 15thDay
22%122%26%13%12%
305
16th to endDay
14%112%22%30%18%
326
August1st to 15thDay
15%214%26%27%14%
313
16th to endDay
12%115%26%27%16%
332
September1st to 15thDay
15%314%23%28%13%
315
16th to endDay
20%215%22%23%15%
314
October1st to 15thDay
17%6%20%27%21%6%
315
16th to endDay
22%11%25%22%14%3
336
November1st to 15thDay
26%10%25%22%12%2
162
16th to endDay
20%19%28%24%6%
135
December1st to 15thDay
25%22%27%14%6%2
135
16th to endDay
37%18%33%8%2
144
January1st to 15thNight
28%16%29%21%4
780
16th to endNight
29%15%31%20%2
788
February1st to 15thNight
27%13%30%26%1
704
16th to endNight
27%17%32%20%2
631
March1st to 15thNight
26%14%26%26%5%
720
16th to endNight
23%13%27%24%8%
768
April1st to 15thNight
22%14%29%25%8%
701
16th to endNight
16%8%33%27%12%1
540
May1st to 15thNight
18%8%29%29%12%1
540
16th to endNight
14%323%28%26%3
563
June1st to 15thNight
10%122%35%27%3
540
16th to endNight
9%118%40%26%2
540
July1st to 15thNight
14%116%35%27%4
510
16th to endNight
9%112%31%37%8%
564
August1st to 15thNight
9%112%35%37%4
539
16th to endNight
10%19%36%35%6%
597
September1st to 15thNight
13%214%29%35%4
720
16th to endNight
16%216%27%30%6%
717
October1st to 15thNight
12%6%21%30%26%3
720
16th to endNight
21%9%26%25%15%1
768
November1st to 15thNight
17%10%24%28%17%1
760
16th to endNight
23%12%23%28%10%
780
December1st to 15thNight
29%12%25%24%7%
780
16th to endNight
30%14%26%27%1
832
Page generated at 2018-01-21 12:19:28. Version ac04

Copyright 2018 A. Danko


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