Saint Leonard
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saint Leonard clear sky chart from 2005-11-05 to 2017-11-30.

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
23%
14992
12%
47723
6%
14960
30%
14960
13%
35078

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
12%
741
8%
2634
2%
737
20%
737
7%
2092
January16th to endNight
18%
768
12%
2688
5%
768
28%
768
10%
1977
February1st to 15thNight
16%
704
9%
2301
3%
701
24%
701
9%
1755
February16th to endNight
15%
631
9%
1949
3%
631
23%
631
10%
1535
March1st to 15thNight
19%
720
14%
2080
7%
720
26%
720
12%
1568
March16th to endNight
23%
768
16%
2112
7%
768
30%
768
17%
1523
April1st to 15thNight
18%
631
14%
1733
5%
631
24%
631
14%
1289
April16th to endNight
22%
540
17%
1620
6%
540
31%
540
15%
1128
May1st to 15thNight
23%
540
10%
1610
5%
540
29%
540
13%
1201
May16th to endNight
20%
405
9%
1340
4%
404
29%
404
11%
989
June1st to 15thNight
28%
360
8%
1260
4%
360
33%
360
15%
883
June16th to endNight
32%
360
5%
1260
4%
360
35%
360
12%
928
July1st to 15thNight
32%
340
9%
1190
8%
340
37%
340
17%
806
July16th to endNight
37%
376
9%
1369
8%
354
46%
354
15%
915
August1st to 15thNight
43%
515
9%
1586
8%
513
46%
513
17%
1110
August16th to endNight
39%
573
17%
1719
8%
573
45%
573
23%
1131
September1st to 15thNight
33%
661
13%
1867
6%
661
39%
661
22%
1250
September16th to endNight
37%
717
20%
1980
12%
717
44%
717
28%
1270
October1st to 15thNight
29%
720
17%
2107
9%
720
38%
720
21%
1438
October16th to endNight
21%
768
11%
2447
6%
768
27%
768
13%
1830
November1st to 15thNight
23%
780
14%
2557
9%
780
30%
780
13%
1864
November16th to endNight
21%
824
10%
2734
6%
824
27%
824
9%
2114
December1st to 15thNight
13%
750
7%
2700
2%
750
20%
750
7%
2147
December16th to endNight
13%
800
8%
2880
3%
800
20%
800
6%
2335

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%9%36%6%35%45%6%27%
48696
Night
19%9%37%5%34446%30%
47883
TransparencyDay
56%6%12%16%7%
48374
Night
54%6%12%18%7%
47723
SeeingDay
24%20%25%18%8%1
6851
Night
21%24%25%20%7%
14992

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
16%13%5%9%6%45%6%47%19%
1301
16th to endDay
13%11%5%9%6%36%6%6%6%22%
1536
February1st to 15thDay
9%14%5%8%8%6%8%7%5%6%19%
1560
16th to endDay
17%12%6%8%7%46%5%35%20%
1524
March1st to 15thDay
19%10%47%6%3445%5%26%
1868
16th to endDay
17%12%48%6%33445%30%
2112
April1st to 15thDay
23%12%46%5%23446%26%
2212
16th to endDay
24%8%36%5%23335%32%
2340
May1st to 15thDay
26%8%25%5%34445%28%
2341
16th to endDay
27%7%36%5%25%446%26%
2783
June1st to 15thDay
24%7%37%5%35%5%5%6%25%
2700
16th to endDay
25%7%37%6%345%5%7%22%
2700
July1st to 15thDay
18%6%25%6%46%5%6%9%27%
2700
16th to endDay
19%5%27%6%45%5%6%8%28%
2702
August1st to 15thDay
18%5%35%7%46%5%6%7%28%
2352
16th to endDay
13%6%36%6%46%5%6%8%32%
2483
September1st to 15thDay
21%7%34423436%38%
2091
16th to endDay
18%5%25%42435%5%43%
1980
October1st to 15thDay
20%8%36%5%34445%34%
1852
16th to endDay
27%11%46%5%23336%25%
1776
November1st to 15thDay
22%11%36%6%35%445%26%
1630
16th to endDay
24%14%47%5%2434424%
1549
December1st to 15thDay
23%12%47%5%35%436%22%
1260
16th to endDay
20%15%7%7%6%4445%419%
1344
January1st to 15thNight
17%13%5%9%8%45%445%21%
2634
16th to endNight
13%11%5%8%6%45%6%7%7%23%
2688
February1st to 15thNight
10%12%5%9%7%5%8%6%5%7%23%
2300
16th to endNight
14%17%5%8%6%3444424%
1949
March1st to 15thNight
17%9%47%6%36%5%45%29%
2068
16th to endNight
14%11%5%7%5%23446%33%
2112
April1st to 15thNight
22%10%36%42335%431%
1733
16th to endNight
24%8%24423435%36%
1620
May1st to 15thNight
23%7%36%5%35%45%429%
1610
16th to endNight
25%7%35%42445%6%28%
1338
June1st to 15thNight
23%5%35%435%446%33%
1260
16th to endNight
19%6%37%6%35%45%7%30%
1260
July1st to 15thNight
18%7%45%335%35%6%36%
1260
16th to endNight
15%6%35%6%35%6%6%7%34%
1464
August1st to 15thNight
16%426%6%45%6%6%7%34%
1596
16th to endNight
13%5%25%435%46%7%41%
1719
September1st to 15thNight
18%5%143245%46%41%
1867
16th to endNight
17%5%23323347%47%
1980
October1st to 15thNight
19%6%25%423445%40%
2107
16th to endNight
25%9%26%423447%27%
2447
November1st to 15thNight
23%9%36%5%3445%5%30%
2557
16th to endNight
23%11%48%5%3444424%
2734
December1st to 15thNight
25%12%47%7%3434422%
2700
16th to endNight
20%15%5%9%7%35%435%19%
2880

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
64%7%11%11%6%
1302
16th to endDay
58%6%11%15%7%
1536
February1st to 15thDay
61%7%11%13%5%
1563
16th to endDay
65%6%8%13%6%
1524
March1st to 15thDay
56%6%9%15%10%1
1879
16th to endDay
56%48%18%10%1
2112
April1st to 15thDay
58%48%15%10%2
2212
16th to endDay
54%47%18%12%2
2340
May1st to 15thDay
58%39%16%10%1
2341
16th to endDay
58%7%9%17%6%
2787
June1st to 15thDay
57%7%12%13%8%1
2700
16th to endDay
59%7%11%14%6%
2700
July1st to 15thDay
50%9%15%18%6%
2541
16th to endDay
53%8%13%17%5%
2534
August1st to 15thDay
52%8%18%17%3
2338
16th to endDay
47%8%17%20%5%
2483
September1st to 15thDay
47%5%14%23%7%
2091
16th to endDay
42%5%14%25%11%
1980
October1st to 15thDay
51%5%13%21%7%
1852
16th to endDay
61%411%16%5%
1776
November1st to 15thDay
59%6%11%15%7%
1630
16th to endDay
63%5%13%14%2
1549
December1st to 15thDay
64%5%12%12%3
1260
16th to endDay
68%5%9%11%4
1344
January1st to 15thNight
64%6%11%12%4
2634
16th to endNight
55%7%11%18%6%
2688
February1st to 15thNight
58%6%11%17%5%
2301
16th to endNight
63%5%9%13%8%
1949
March1st to 15thNight
56%5%9%17%10%
2080
16th to endNight
51%410%19%12%1
2112
April1st to 15thNight
55%49%13%13%3
1733
16th to endNight
49%5%8%18%16%1
1620
May1st to 15thNight
55%6%9%16%10%1
1610
16th to endNight
54%7%11%17%8%
1340
June1st to 15thNight
51%6%13%20%7%1
1260
16th to endNight
53%8%15%14%8%
1260
July1st to 15thNight
46%7%15%22%7%
1190
16th to endNight
47%7%16%19%8%
1369
August1st to 15thNight
47%8%17%22%4
1586
16th to endNight
39%8%17%28%6%
1719
September1st to 15thNight
42%6%13%26%9%1
1867
16th to endNight
38%5%17%25%12%1
1980
October1st to 15thNight
45%5%12%27%8%
2107
16th to endNight
57%5%13%18%4
2447
November1st to 15thNight
55%5%14%15%8%
2557
16th to endNight
60%6%12%14%4
2734
December1st to 15thNight
65%5%11%13%3
2700
16th to endNight
67%5%10%11%4
2880

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%21%28%18%1
60
16th to endDay
23%20%31%15%7%1
64
February1st to 15thDay
13%26%29%20%9%
221
16th to endDay
25%23%24%20%6%
230
March1st to 15thDay
28%24%22%17%6%
270
16th to endDay
24%24%24%14%8%3
288
April1st to 15thDay
27%28%22%13%6%1
270
16th to endDay
24%23%26%14%8%2
270
May1st to 15thDay
34%20%21%18%41
297
16th to endDay
28%26%23%16%5%
519
June1st to 15thDay
26%24%19%20%7%1
495
16th to endDay
26%21%25%15%9%1
495
July1st to 15thDay
19%16%27%22%13%1
475
16th to endDay
20%14%29%24%9%1
373
August1st to 15thDay
19%11%28%21%15%3
313
16th to endDay
21%15%22%23%13%3
332
September1st to 15thDay
21%13%27%22%10%3
315
16th to endDay
19%13%28%21%11%5%
314
October1st to 15thDay
19%22%24%18%10%4
283
16th to endDay
32%20%20%16%8%1
288
November1st to 15thDay
27%22%23%17%8%
280
16th to endDay
29%21%23%17%6%1
275
December1st to 15thDay
30%11%36%8%11%1
60
16th to endDay
39%12%37%10%
64
January1st to 15thNight
20%31%30%14%2
741
16th to endNight
16%28%29%21%4
768
February1st to 15thNight
14%30%32%16%6%
704
16th to endNight
22%28%27%15%4
631
March1st to 15thNight
20%27%27%19%4
720
16th to endNight
16%27%27%21%5%
768
April1st to 15thNight
22%28%26%16%4
631
16th to endNight
24%26%24%19%4
540
May1st to 15thNight
24%23%25%20%6%
540
16th to endNight
21%26%27%18%5%
405
June1st to 15thNight
20%21%21%28%7%
360
16th to endNight
16%20%23%26%12%
360
July1st to 15thNight
17%16%26%24%14%
340
16th to endNight
14%20%22%29%12%
376
August1st to 15thNight
16%12%19%33%16%
515
16th to endNight
14%13%25%28%15%1
573
September1st to 15thNight
19%16%27%25%9%
661
16th to endNight
18%16%24%27%12%
717
October1st to 15thNight
20%17%27%22%10%1
720
16th to endNight
29%20%25%17%7%
768
November1st to 15thNight
23%24%23%19%7%1
780
16th to endNight
25%27%21%17%6%
824
December1st to 15thNight
28%27%24%15%3
750
16th to endNight
27%28%21%15%5%
800
Page generated at 2017-12-01 13:13:40. Version ac04

Copyright 2017 A. Danko


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