Lady Lake Astronomical Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lady Lake Astronomical Observatory clear sky chart from 2005-11-05 to 2018-11-30.

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
15%
16566
7%
51644
2%
16521
20%
16521
8%
41817

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
6%
825
5%
2864
1%
821
12%
821
4%
2428
January16th to endNight
9%
880
8%
2912
1%
880
16%
880
5%
2419
February1st to 15thNight
7%
809
6%
2522
1%
806
12%
806
5%
2119
February16th to endNight
7%
696
6%
2106
0%
696
12%
696
5%
1777
March1st to 15thNight
13%
705
9%
2265
3%
705
18%
705
7%
1863
March16th to endNight
12%
624
6%
2288
3%
624
17%
624
5%
1939
April1st to 15thNight
15%
584
9%
1866
4%
584
23%
584
8%
1497
April16th to endNight
12%
578
9%
1733
3%
578
20%
578
8%
1413
May1st to 15thNight
20%
585
6%
1729
2%
585
23%
585
9%
1416
May16th to endNight
17%
609
7%
1421
0%
608
20%
608
11%
1195
June1st to 15thNight
18%
585
4%
1365
1%
585
19%
585
10%
1166
June16th to endNight
20%
585
4%
1365
1%
585
22%
585
13%
1121
July1st to 15thNight
26%
555
6%
1295
3%
555
28%
555
16%
1037
July16th to endNight
21%
613
5%
1486
1%
580
23%
580
12%
1229
August1st to 15thNight
27%
574
7%
1674
3%
570
30%
570
13%
1309
August16th to endNight
28%
621
9%
1863
5%
621
35%
621
15%
1383
September1st to 15thNight
28%
585
10%
2015
7%
585
34%
585
14%
1443
September16th to endNight
26%
583
12%
2145
7%
583
33%
583
13%
1498
October1st to 15thNight
20%
626
12%
2277
5%
626
28%
626
10%
1694
October16th to endNight
17%
860
7%
2668
2%
860
21%
860
8%
2183
November1st to 15thNight
14%
880
7%
2762
2%
880
19%
880
8%
2211
November16th to endNight
8%
899
9%
2978
1%
899
15%
899
6%
2405
December1st to 15thNight
11%
825
6%
2925
1%
825
16%
825
5%
2383
December16th to endNight
9%
880
4%
3120
1%
880
12%
880
3%
2689

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
21%13%5%8%6%34445%21%
52668
Night
21%12%5%8%7%35%445%20%
51806
TransparencyDay
61%8%11%12%5%
52348
Night
62%8%11%11%4
51644
SeeingDay
26%24%25%16%5%1
9818
Night
25%27%25%16%4
16566

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
19%16%6%10%7%6%45%35%12%
1404
16th to endDay
20%16%6%11%8%45%435%13%
1664
February1st to 15thDay
20%12%410%9%36%5%46%14%
1667
16th to endDay
18%16%8%12%8%35%43413%
1651
March1st to 15thDay
19%14%6%10%9%45%33417%
2014
16th to endDay
23%17%8%10%7%3442313%
2288
April1st to 15thDay
20%15%5%9%7%3434419%
2410
16th to endDay
27%15%5%7%5%2334421%
2502
May1st to 15thDay
22%15%5%6%5%34345%21%
2548
16th to endDay
22%15%5%7%6%34346%20%
3045
June1st to 15thDay
25%15%6%8%6%34335%16%
2925
16th to endDay
24%12%46%6%24445%24%
2925
July1st to 15thDay
17%9%47%6%3445%7%29%
2925
16th to endDay
20%10%48%7%35%445%23%
2937
August1st to 15thDay
26%10%36%6%34445%23%
2528
16th to endDay
19%10%5%7%6%35%5%5%7%23%
2691
September1st to 15thDay
20%9%36%425%436%30%
2272
16th to endDay
17%8%47%5%34446%33%
2145
October1st to 15thDay
21%10%38%5%45%445%26%
2012
16th to endDay
24%14%5%8%7%4433418%
1905
November1st to 15thDay
20%11%5%9%6%35%346%22%
1755
16th to endDay
25%18%6%7%6%24335%15%
1634
December1st to 15thDay
21%15%7%8%6%44445%17%
1365
16th to endDay
21%16%6%10%9%45%44412%
1456
January1st to 15thNight
21%14%6%9%8%35%44315%
2864
16th to endNight
20%13%6%10%6%46%5%46%16%
2912
February1st to 15thNight
20%12%6%10%8%45%436%16%
2522
16th to endNight
17%15%7%12%7%35%5%45%15%
2106
March1st to 15thNight
16%12%7%10%8%5%6%45%5%18%
2253
16th to endNight
22%15%6%10%7%45%44314%
2288
April1st to 15thNight
23%13%5%8%6%35%345%19%
1866
16th to endNight
26%16%5%8%42332322%
1733
May1st to 15thNight
24%14%6%7%5%34347%18%
1729
16th to endNight
26%11%48%7%34445%18%
1419
June1st to 15thNight
23%13%48%7%3445%418%
1365
16th to endNight
23%13%5%8%5%33446%22%
1365
July1st to 15thNight
18%11%5%6%7%45%35%8%23%
1365
16th to endNight
20%11%49%7%35%45%5%20%
1581
August1st to 15thNight
25%12%36%5%23446%23%
1685
16th to endNight
19%10%47%6%3435%7%27%
1863
September1st to 15thNight
19%9%36%5%34447%30%
2015
16th to endNight
17%8%37%6%3335%7%31%
2145
October1st to 15thNight
21%8%47%6%35%5%5%5%26%
2277
16th to endNight
24%13%5%8%6%4445%5%18%
2668
November1st to 15thNight
23%11%47%7%34436%22%
2762
16th to endNight
21%13%5%9%6%45%445%18%
2978
December1st to 15thNight
23%13%5%8%6%4444419%
2925
16th to endNight
22%15%6%9%8%45%5%3413%
3120

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
69%11%9%7%2
1405
16th to endDay
70%8%6%7%6%
1664
February1st to 15thDay
66%9%10%8%4
1671
16th to endDay
70%8%9%6%41
1651
March1st to 15thDay
67%7%8%11%3
2025
16th to endDay
73%7%7%8%21
2288
April1st to 15thDay
64%7%10%12%5%
2410
16th to endDay
64%5%8%11%9%
2502
May1st to 15thDay
62%7%10%12%6%
2548
16th to endDay
61%8%12%12%5%
3049
June1st to 15thDay
69%8%9%9%3
2925
16th to endDay
58%8%10%13%7%
2925
July1st to 15thDay
47%11%13%18%7%
2767
16th to endDay
56%11%14%13%4
2769
August1st to 15thDay
58%8%12%16%4
2514
16th to endDay
54%10%16%14%3
2691
September1st to 15thDay
50%8%12%20%8%
2272
16th to endDay
48%7%16%17%8%
2145
October1st to 15thDay
56%7%13%14%7%
2012
16th to endDay
66%8%8%11%5%
1905
November1st to 15thDay
58%9%16%11%3
1755
16th to endDay
70%5%10%8%4
1634
December1st to 15thDay
66%8%8%11%4
1365
16th to endDay
73%7%7%7%3
1456
January1st to 15thNight
68%9%9%8%2
2864
16th to endNight
65%9%10%9%4
2912
February1st to 15thNight
68%8%9%10%3
2522
16th to endNight
67%9%10%9%3
2106
March1st to 15thNight
66%7%10%10%4
2265
16th to endNight
69%8%7%8%4
2288
April1st to 15thNight
62%8%9%12%6%
1866
16th to endNight
66%5%6%12%7%
1733
May1st to 15thNight
65%7%9%13%4
1729
16th to endNight
63%8%11%10%5%
1421
June1st to 15thNight
66%8%10%10%3
1365
16th to endNight
59%8%12%13%5%
1365
July1st to 15thNight
52%12%12%17%4
1295
16th to endNight
58%12%12%13%2
1486
August1st to 15thNight
58%8%15%12%4
1674
16th to endNight
50%10%16%17%5%
1863
September1st to 15thNight
50%10%13%18%7%
2015
16th to endNight
49%8%13%18%8%
2145
October1st to 15thNight
56%8%13%15%5%
2277
16th to endNight
65%7%11%10%4
2668
November1st to 15thNight
60%9%13%11%3
2762
16th to endNight
63%8%11%11%3
2978
December1st to 15thNight
66%7%9%11%5%
2925
16th to endNight
71%8%8%7%2
3120

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
22%38%28%9%1
285
16th to endDay
25%34%27%9%2
304
February1st to 15thDay
25%32%23%15%2
281
16th to endDay
23%39%24%9%2
251
March1st to 15thDay
24%32%26%12%21
285
16th to endDay
25%30%28%9%5%1
304
April1st to 15thDay
25%28%24%13%6%
417
16th to endDay
29%25%23%16%4
512
May1st to 15thDay
27%24%23%16%6%2
543
16th to endDay
28%24%25%16%41
599
June1st to 15thDay
36%19%20%17%5%1
570
16th to endDay
27%18%30%15%5%1
570
July1st to 15thDay
20%16%32%20%8%1
550
16th to endDay
24%17%27%20%9%
594
August1st to 15thDay
27%12%25%23%9%2
550
16th to endDay
23%15%22%27%9%1
603
September1st to 15thDay
24%15%27%22%8%2
392
16th to endDay
21%21%27%21%6%
314
October1st to 15thDay
23%18%31%19%6%
315
16th to endDay
30%26%22%14%42
336
November1st to 15thDay
22%31%27%12%5%
325
16th to endDay
31%29%27%10%1
329
December1st to 15thDay
26%33%23%10%5%
285
16th to endDay
27%34%22%12%2
304
January1st to 15thNight
24%35%27%9%2
825
16th to endNight
21%37%26%12%1
880
February1st to 15thNight
23%38%25%10%1
809
16th to endNight
24%36%24%10%3
696
March1st to 15thNight
19%34%24%16%4
705
16th to endNight
26%29%24%15%3
624
April1st to 15thNight
23%30%25%14%4
584
16th to endNight
28%27%25%14%4
578
May1st to 15thNight
28%24%23%17%5%
585
16th to endNight
28%24%25%17%4
609
June1st to 15thNight
29%23%22%19%5%
585
16th to endNight
25%21%27%18%7%
585
July1st to 15thNight
20%17%31%22%6%
555
16th to endNight
23%20%30%19%5%
613
August1st to 15thNight
31%13%22%24%8%
574
16th to endNight
21%15%27%28%7%
621
September1st to 15thNight
22%16%30%23%7%
585
16th to endNight
23%18%28%22%7%
583
October1st to 15thNight
25%22%26%19%6%
626
16th to endNight
31%24%22%16%4
860
November1st to 15thNight
26%30%24%14%3
880
16th to endNight
26%33%27%10%3
899
December1st to 15thNight
28%33%22%11%4
825
16th to endNight
26%36%21%11%2
880
Page generated at 2018-12-01 13:05:32. Version ac04

Copyright 2018 A. Danko


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