This page made possible by the sponsorship of: Esther Davenport.

Lilly Bluff Overlook
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lilly Bluff Overlook clear sky chart from 2005-11-05 to 2019-09-17.

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
46%
18008
20%
54851
15%
17965
52%
17965
24%
35430

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
23%
840
17%
2717
10%
836
33%
836
17%
1831
January16th to endNight
26%
896
19%
2887
11%
896
35%
896
17%
1958
February1st to 15thNight
23%
824
17%
2472
8%
821
32%
821
18%
1719
February16th to endNight
21%
735
18%
2205
10%
735
29%
735
15%
1603
March1st to 15thNight
26%
840
18%
2437
10%
840
33%
840
20%
1673
March16th to endNight
33%
896
16%
2464
10%
896
38%
896
22%
1706
April1st to 15thNight
39%
683
24%
2151
14%
683
51%
683
27%
1294
April16th to endNight
45%
624
22%
1952
14%
624
54%
624
27%
1210
May1st to 15thNight
50%
630
20%
1890
13%
630
56%
630
27%
1215
May16th to endNight
62%
657
17%
1971
12%
657
64%
657
28%
1272
June1st to 15thNight
68%
630
17%
1890
13%
630
70%
630
31%
1159
June16th to endNight
73%
630
18%
1890
17%
630
74%
630
32%
1139
July1st to 15thNight
71%
600
13%
1800
12%
600
72%
600
27%
1182
July16th to endNight
74%
660
18%
1883
16%
627
76%
627
30%
1155
August1st to 15thNight
72%
620
19%
1858
18%
617
73%
617
30%
1158
August16th to endNight
71%
669
18%
2230
20%
669
71%
669
28%
1360
September1st to 15thNight
63%
784
20%
2254
18%
784
65%
784
29%
1440
September16th to endNight
60%
782
27%
2159
21%
782
62%
782
33%
1356
October1st to 15thNight
59%
780
33%
2152
27%
780
63%
780
38%
1263
October16th to endNight
46%
832
29%
2551
23%
832
56%
832
31%
1502
November1st to 15thNight
44%
820
26%
2666
23%
820
52%
820
27%
1586
November16th to endNight
40%
840
25%
2730
18%
840
50%
840
24%
1693
December1st to 15thNight
31%
840
19%
2730
13%
840
39%
840
17%
1887
December16th to endNight
28%
896
17%
2912
10%
896
37%
896
16%
2069

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%7%36%5%35%5%5%7%36%
55834
Night
12%6%25%5%3445%7%41%
55049
TransparencyDay
44%7%11%19%14%2
55535
Night
40%6%11%21%16%3
54852
SeeingDay
18%9%21%21%18%10%
7915
Night
16%10%20%28%20%4
18010

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
17%9%38%5%35%435%31%
1881
16th to endDay
17%8%36%5%23445%38%
2039
February1st to 15thDay
18%10%38%5%34335%31%
2050
16th to endDay
19%8%36%5%3445%5%32%
1840
March1st to 15thDay
18%9%36%5%33346%33%
2181
16th to endDay
14%9%36%5%35%446%33%
2463
April1st to 15thDay
12%7%25%5%3445%6%42%
2469
16th to endDay
14%6%35%5%24446%41%
2611
May1st to 15thDay
14%7%35%5%35%45%7%36%
2721
16th to endDay
9%6%26%6%35%5%6%9%36%
2847
June1st to 15thDay
8%5%25%5%47%6%7%9%36%
2730
16th to endDay
6%436%7%5%6%6%8%9%36%
2730
July1st to 15thDay
11%5%36%7%5%7%7%7%9%28%
2730
16th to endDay
9%6%37%6%5%7%7%8%9%27%
2881
August1st to 15thDay
7%5%36%6%47%7%8%10%31%
2671
16th to endDay
11%5%36%6%36%6%8%9%31%
2676
September1st to 15thDay
14%5%26%6%45%5%5%8%34%
2350
16th to endDay
14%5%245%3445%7%42%
2156
October1st to 15thDay
12%415%423445%51%
2136
16th to endDay
13%5%2432235%5%50%
2024
November1st to 15thDay
14%6%34413345%46%
1852
16th to endDay
14%6%34434345%46%
1890
December1st to 15thDay
16%9%37%6%34345%33%
1890
16th to endDay
19%10%37%5%35%445%31%
2016
January1st to 15thNight
15%8%37%5%3445%6%36%
2717
16th to endNight
15%9%36%5%3445%436%
2887
February1st to 15thNight
17%7%36%5%35%446%34%
2463
16th to endNight
19%7%46%6%35%446%32%
2205
March1st to 15thNight
14%8%36%5%445%5%6%36%
2437
16th to endNight
14%7%26%5%35%446%38%
2464
April1st to 15thNight
13%41343445%8%46%
2151
16th to endNight
10%426%5%3445%7%45%
1952
May1st to 15thNight
10%6%25%5%245%5%8%43%
1889
16th to endNight
5%426%6%35%47%10%42%
1970
June1st to 15thNight
43245%36%7%6%11%43%
1890
16th to endNight
32246%35%5%7%12%44%
1890
July1st to 15thNight
8%425%5%36%7%6%10%39%
1890
16th to endNight
5%325%5%27%6%7%12%40%
1991
August1st to 15thNight
6%4145%35%5%7%10%44%
1869
16th to endNight
8%5%245%345%6%9%43%
2230
September1st to 15thNight
10%5%15%6%35%448%44%
2254
16th to endNight
10%5%26%423346%50%
2159
October1st to 15thNight
10%414222337%55%
2152
16th to endNight
11%5%25%423326%51%
2551
November1st to 15thNight
12%5%25%5%23346%47%
2666
16th to endNight
13%7%35%424435%45%
2730
December1st to 15thNight
16%9%37%6%35%345%34%
2730
16th to endNight
19%8%46%5%35%446%31%
2912

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%48%17%14%2
1882
16th to endDay
46%410%20%15%1
2039
February1st to 15thDay
54%47%18%12%2
2052
16th to endDay
51%5%10%17%12%2
1840
March1st to 15thDay
51%38%17%13%4
2181
16th to endDay
49%6%11%19%12%
2464
April1st to 15thDay
41%5%11%21%17%2
2469
16th to endDay
42%5%10%22%16%2
2611
May1st to 15thDay
45%7%12%23%10%1
2721
16th to endDay
42%9%14%20%10%1
2851
June1st to 15thDay
40%9%16%20%12%1
2730
16th to endDay
39%10%15%18%12%3
2730
July1st to 15thDay
46%11%14%15%8%2
2591
16th to endDay
45%10%14%17%10%1
2726
August1st to 15thDay
43%11%16%16%10%1
2658
16th to endDay
43%11%13%17%12%1
2676
September1st to 15thDay
45%7%12%17%12%4
2350
16th to endDay
40%5%11%20%18%3
2156
October1st to 15thDay
34%410%21%22%6%
2136
16th to endDay
34%38%23%24%4
2024
November1st to 15thDay
40%36%20%23%5%
1852
16th to endDay
40%37%23%21%3
1890
December1st to 15thDay
51%46%21%12%3
1890
16th to endDay
54%412%15%11%1
2016
January1st to 15thNight
48%411%16%15%3
2717
16th to endNight
48%49%19%15%2
2887
February1st to 15thNight
49%410%20%11%2
2472
16th to endNight
52%5%8%18%11%2
2205
March1st to 15thNight
47%411%17%15%4
2437
16th to endNight
45%6%11%23%12%1
2464
April1st to 15thNight
35%5%11%24%18%3
2151
16th to endNight
38%5%10%24%17%3
1952
May1st to 15thNight
38%8%13%27%11%2
1890
16th to endNight
36%10%16%23%12%1
1972
June1st to 15thNight
31%10%18%25%13%1
1890
16th to endNight
30%10%16%26%12%3
1890
July1st to 15thNight
37%10%17%19%13%2
1800
16th to endNight
30%11%19%22%13%3
1883
August1st to 15thNight
32%10%17%22%14%2
1858
16th to endNight
35%7%17%23%14%1
2230
September1st to 15thNight
37%7%15%19%15%4
2254
16th to endNight
35%6%8%21%25%3
2159
October1st to 15thNight
29%5%10%23%23%7%
2152
16th to endNight
35%25%22%25%7%
2551
November1st to 15thNight
37%37%19%22%8%
2666
16th to endNight
41%36%23%21%3
2730
December1st to 15thNight
50%48%18%13%3
2730
16th to endNight
53%49%16%14%1
2912

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
29%26%30%10%21
180
16th to endDay
24%31%30%9%3
192
February1st to 15thDay
35%27%27%8%1
180
16th to endDay
42%15%35%6%
159
March1st to 15thDay
30%27%26%13%1
261
16th to endDay
19%19%30%20%9%
416
April1st to 15thDay
21%14%27%24%11%1
390
16th to endDay
20%9%25%24%16%3
379
May1st to 15thDay
17%12%25%20%14%8%
408
16th to endDay
17%5%22%23%14%15%
459
June1st to 15thDay
11%215%25%25%18%
435
16th to endDay
9%219%24%23%19%
435
July1st to 15thDay
14%112%22%26%23%
425
16th to endDay
12%212%22%28%22%
454
August1st to 15thDay
13%13%26%23%22%
418
16th to endDay
14%38%24%31%17%
460
September1st to 15thDay
13%39%21%35%16%
435
16th to endDay
19%113%24%28%13%
378
October1st to 15thDay
13%6%22%22%25%9%
375
16th to endDay
18%11%22%23%20%3
344
November1st to 15thDay
25%13%35%17%6%1
180
16th to endDay
16%15%34%23%7%1
180
December1st to 15thDay
27%23%28%15%4
180
16th to endDay
34%22%30%9%2
192
January1st to 15thNight
22%21%29%20%6%
840
16th to endNight
24%17%28%26%3
896
February1st to 15thNight
23%17%32%24%2
824
16th to endNight
25%20%29%22%1
735
March1st to 15thNight
21%17%29%27%3
840
16th to endNight
20%14%25%26%10%1
896
April1st to 15thNight
16%13%26%30%11%
683
16th to endNight
12%9%25%35%15%
624
May1st to 15thNight
12%7%21%33%21%3
630
16th to endNight
8%215%32%33%7%
659
June1st to 15thNight
6%112%36%34%8%
630
16th to endNight
6%16%34%39%10%
630
July1st to 15thNight
12%5%27%42%12%
600
16th to endNight
7%16%24%47%13%
660
August1st to 15thNight
10%15%26%46%9%
620
16th to endNight
11%16%27%44%8%
669
September1st to 15thNight
12%19%26%39%9%
784
16th to endNight
14%213%26%37%4
782
October1st to 15thNight
13%6%16%25%29%8%
780
16th to endNight
15%9%24%28%19%2
832
November1st to 15thNight
15%12%21%29%17%3
820
16th to endNight
18%16%21%29%13%
840
December1st to 15thNight
21%17%24%27%7%
840
16th to endNight
27%14%25%26%6%
896
Page generated at 2019-09-17 21:12:15. Version ac04

Copyright 2019 A. Danko


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