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 2017-09-19.

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%
14895
7%
46812
2%
14850
20%
14850
8%
37929

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
7%
750
6%
2643
1%
746
13%
746
4%
2245
January16th to endNight
10%
800
8%
2688
1%
800
17%
800
5%
2228
February1st to 15thNight
7%
734
6%
2324
1%
731
12%
731
5%
1943
February16th to endNight
7%
640
6%
1946
0%
640
12%
640
4%
1652
March1st to 15thNight
13%
651
8%
2091
3%
651
18%
651
7%
1713
March16th to endNight
11%
576
6%
2112
2%
576
17%
576
5%
1787
April1st to 15thNight
15%
539
9%
1722
3%
539
23%
539
8%
1382
April16th to endNight
12%
540
8%
1620
3%
540
20%
540
8%
1324
May1st to 15thNight
21%
540
5%
1596
2%
540
23%
540
9%
1318
May16th to endNight
18%
561
6%
1309
1%
560
20%
560
10%
1106
June1st to 15thNight
17%
540
3%
1260
1%
540
19%
540
10%
1077
June16th to endNight
20%
540
4%
1260
1%
540
22%
540
13%
1029
July1st to 15thNight
27%
510
6%
1190
3%
510
29%
510
17%
944
July16th to endNight
22%
565
5%
1363
1%
532
24%
532
12%
1125
August1st to 15thNight
25%
539
7%
1573
3%
535
28%
535
12%
1232
August16th to endNight
28%
573
10%
1719
4%
573
35%
573
15%
1277
September1st to 15thNight
26%
540
9%
1860
7%
540
31%
540
13%
1349
September16th to endNight
26%
505
13%
1857
8%
505
34%
505
14%
1280
October1st to 15thNight
20%
516
13%
1927
6%
516
30%
516
9%
1440
October16th to endNight
16%
706
7%
2258
2%
706
20%
706
7%
1864
November1st to 15thNight
15%
730
7%
2358
2%
730
19%
730
8%
1883
November16th to endNight
8%
750
8%
2556
1%
750
15%
750
6%
2058
December1st to 15thNight
11%
750
7%
2700
1%
750
17%
750
5%
2189
December16th to endNight
8%
800
4%
2880
1%
800
11%
800
3%
2484

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
22%13%5%8%6%34445%20%
48012
Night
22%12%5%8%6%35%445%20%
46974
TransparencyDay
62%8%11%12%5%
47692
Night
63%8%11%11%4
46812
SeeingDay
26%24%24%16%5%1
8229
Night
25%28%25%15%4
14895

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
20%16%6%10%7%6%45%3412%
1295
16th to endDay
19%16%6%10%8%5%4436%13%
1536
February1st to 15thDay
20%12%5%9%8%37%5%46%14%
1535
16th to endDay
19%16%8%12%8%46%43412%
1525
March1st to 15thDay
18%13%6%10%9%46%33417%
1858
16th to endDay
23%16%8%10%7%35%43313%
2112
April1st to 15thDay
20%15%5%9%7%3444419%
2224
16th to endDay
28%15%47%5%2333421%
2340
May1st to 15thDay
23%16%5%6%5%34345%19%
2352
16th to endDay
22%14%5%7%6%34346%20%
2805
June1st to 15thDay
25%15%6%8%6%34335%16%
2700
16th to endDay
23%12%46%6%24445%25%
2700
July1st to 15thDay
17%9%5%7%5%3445%7%29%
2700
16th to endDay
20%10%48%6%45%445%24%
2708
August1st to 15thDay
27%10%35%6%34445%22%
2376
16th to endDay
19%10%5%7%6%35%5%5%7%23%
2483
September1st to 15thDay
22%9%37%425%446%29%
2097
16th to endDay
16%8%36%5%34446%34%
1848
October1st to 15thDay
24%10%38%5%35%345%26%
1702
16th to endDay
25%14%47%7%44435%18%
1612
November1st to 15thDay
21%11%5%9%6%35%346%21%
1499
16th to endDay
25%18%6%7%6%23335%14%
1401
December1st to 15thDay
20%15%7%7%6%445%46%17%
1260
16th to endDay
22%16%6%9%8%45%44413%
1344
January1st to 15thNight
21%15%6%9%8%35%44415%
2643
16th to endNight
20%12%6%10%6%36%5%46%16%
2688
February1st to 15thNight
20%12%5%10%8%46%446%16%
2324
16th to endNight
18%15%7%13%7%35%445%15%
1946
March1st to 15thNight
16%11%6%10%9%5%6%45%5%18%
2079
16th to endNight
22%15%6%9%7%45%44315%
2112
April1st to 15thNight
23%13%5%8%6%35%345%19%
1722
16th to endNight
27%16%48%42332322%
1620
May1st to 15thNight
25%14%6%7%5%34347%17%
1596
16th to endNight
26%11%48%7%35%445%17%
1307
June1st to 15thNight
24%13%49%7%3445%418%
1260
16th to endNight
23%12%5%7%6%34446%22%
1260
July1st to 15thNight
17%10%46%7%36%35%8%24%
1260
16th to endNight
20%11%5%8%7%36%45%5%20%
1458
August1st to 15thNight
26%12%46%5%23436%23%
1584
16th to endNight
19%9%47%6%3435%7%27%
1719
September1st to 15thNight
21%10%36%5%34346%30%
1860
16th to endNight
16%8%47%5%3435%7%32%
1857
October1st to 15thNight
22%9%37%6%35%445%25%
1927
16th to endNight
26%13%5%8%6%3445%5%17%
2258
November1st to 15thNight
23%11%5%7%7%35%436%22%
2358
16th to endNight
22%13%5%9%6%45%445%18%
2556
December1st to 15thNight
23%13%5%8%6%4444420%
2700
16th to endNight
23%16%6%9%7%45%5%3413%
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
70%11%8%7%2
1296
16th to endDay
70%8%6%7%6%
1536
February1st to 15thDay
66%9%9%8%4
1539
16th to endDay
70%8%10%6%3
1525
March1st to 15thDay
67%7%8%11%3
1869
16th to endDay
72%7%7%8%3
2112
April1st to 15thDay
64%7%10%12%5%
2224
16th to endDay
65%5%8%11%9%
2340
May1st to 15thDay
64%7%10%12%4
2352
16th to endDay
61%8%12%12%5%
2809
June1st to 15thDay
70%8%9%8%3
2700
16th to endDay
58%8%10%13%8%
2700
July1st to 15thDay
48%11%13%19%7%
2542
16th to endDay
56%11%14%13%4
2540
August1st to 15thDay
59%7%12%15%4
2362
16th to endDay
54%10%16%14%3
2483
September1st to 15thDay
51%8%12%20%7%
2097
16th to endDay
46%7%18%18%9%
1848
October1st to 15thDay
58%6%13%13%6%
1702
16th to endDay
66%8%8%11%5%
1612
November1st to 15thDay
59%9%16%11%3
1499
16th to endDay
71%410%8%3
1401
December1st to 15thDay
65%8%8%11%4
1260
16th to endDay
73%6%7%8%3
1344
January1st to 15thNight
69%9%9%8%2
2643
16th to endNight
65%10%10%9%4
2688
February1st to 15thNight
67%8%10%10%3
2324
16th to endNight
68%9%10%8%2
1946
March1st to 15thNight
65%8%10%10%4
2091
16th to endNight
70%8%8%8%3
2112
April1st to 15thNight
63%7%9%13%5%
1722
16th to endNight
67%5%7%11%7%
1620
May1st to 15thNight
66%7%10%12%3
1596
16th to endNight
64%8%10%11%4
1309
June1st to 15thNight
66%7%11%10%3
1260
16th to endNight
58%9%11%13%5%
1260
July1st to 15thNight
51%12%12%18%4
1190
16th to endNight
58%12%12%14%2
1363
August1st to 15thNight
59%7%15%12%4
1573
16th to endNight
50%10%16%17%4
1719
September1st to 15thNight
51%10%13%18%6%
1860
16th to endNight
48%8%13%19%9%
1857
October1st to 15thNight
58%7%12%15%6%
1927
16th to endNight
67%7%10%10%3
2258
November1st to 15thNight
60%9%14%10%4
2358
16th to endNight
64%8%12%10%3
2556
December1st to 15thNight
65%7%8%12%5%
2700
16th to endNight
72%7%8%7%2
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
23%37%26%10%1
240
16th to endDay
23%35%26%10%2
256
February1st to 15thDay
25%31%22%16%2
236
16th to endDay
23%39%23%10%2
212
March1st to 15thDay
23%35%24%13%21
240
16th to endDay
24%33%26%8%5%1
256
April1st to 15thDay
24%27%25%14%6%
351
16th to endDay
32%25%23%14%4
450
May1st to 15thDay
27%23%21%16%7%2
468
16th to endDay
28%24%24%16%41
519
June1st to 15thDay
36%20%18%17%5%1
495
16th to endDay
26%20%28%15%6%2
495
July1st to 15thDay
21%16%30%21%8%1
475
16th to endDay
25%18%24%21%9%
514
August1st to 15thDay
29%13%24%21%8%2
493
16th to endDay
24%16%21%27%9%1
523
September1st to 15thDay
26%17%25%21%6%2
337
16th to endDay
20%21%25%24%7%
233
October1st to 15thDay
27%19%27%17%8%
225
16th to endDay
31%25%22%15%31
240
November1st to 15thDay
21%29%28%13%5%
235
16th to endDay
31%30%25%10%2
240
December1st to 15thDay
24%33%26%11%4
240
16th to endDay
28%35%22%10%2
256
January1st to 15thNight
24%35%26%10%2
750
16th to endNight
20%38%26%12%2
800
February1st to 15thNight
22%38%26%10%1
734
16th to endNight
24%37%23%10%4
640
March1st to 15thNight
18%36%24%16%4
651
16th to endNight
25%31%24%14%3
576
April1st to 15thNight
23%30%25%14%4
539
16th to endNight
29%26%24%13%4
540
May1st to 15thNight
29%24%20%18%6%
540
16th to endNight
27%25%24%16%4
561
June1st to 15thNight
29%23%22%18%5%
540
16th to endNight
24%21%27%18%7%
540
July1st to 15thNight
20%17%30%23%7%
510
16th to endNight
23%21%29%19%6%
565
August1st to 15thNight
32%14%22%22%8%
539
16th to endNight
21%16%27%27%6%
573
September1st to 15thNight
23%17%29%22%6%
540
16th to endNight
21%18%28%23%7%
505
October1st to 15thNight
25%23%24%18%7%
516
16th to endNight
33%25%21%15%2
706
November1st to 15thNight
25%30%25%14%3
730
16th to endNight
25%32%27%10%3
750
December1st to 15thNight
27%34%22%11%3
750
16th to endNight
27%37%21%11%21
800
Page generated at 2017-09-20 06:19:48. Version ac04

Copyright 2017 A. Danko


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