Lake Murray Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Murray Observatory clear sky chart from 2005-11-06 to 2024-03-28.

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
44%
24543
22%
79979
14%
24440
53%
24440
25%
49340

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 10thNight
26%
757
26%
3984
8%
737
45%
737
15%
2178
January11th to 20thNight
29%
756
27%
3946
12%
740
46%
740
16%
2128
January21st to endNight
22%
829
19%
4439
12%
814
42%
814
14%
2638
February1st to 10thNight
30%
760
23%
2423
12%
760
44%
760
24%
1506
February11th to 20thNight
22%
742
22%
2219
8%
740
37%
740
23%
1430
February21st to endNight
24%
628
24%
1848
8%
628
40%
628
24%
1184
March1st to 10thNight
31%
760
26%
2090
13%
760
42%
760
29%
1325
March11th to 20thNight
26%
760
23%
2090
9%
760
39%
760
27%
1350
March21st to endNight
27%
821
21%
2256
7%
821
39%
821
26%
1469
April1st to 10thNight
35%
720
25%
1980
12%
720
45%
720
31%
1188
April11th to 20thNight
40%
711
25%
1821
11%
711
49%
711
35%
1123
April21st to endNight
44%
590
31%
1670
16%
590
55%
590
38%
951
May1st to 10thNight
44%
540
21%
1620
9%
540
52%
540
33%
933
May11th to 20thNight
47%
531
15%
1593
8%
531
51%
531
25%
1048
May21st to endNight
63%
582
20%
1744
15%
582
66%
582
29%
1100
June1st to 10thNight
52%
540
15%
1620
11%
540
54%
540
23%
1094
June11th to 20thNight
62%
540
14%
1620
11%
540
64%
540
29%
1032
June21st to endNight
62%
540
14%
1620
11%
540
63%
540
24%
1077
July1st to 10thNight
67%
525
11%
1575
9%
525
68%
525
24%
1072
July11th to 20thNight
69%
522
10%
1566
10%
522
70%
522
24%
1045
July21st to endNight
64%
591
13%
1672
10%
558
67%
558
24%
1132
August1st to 10thNight
66%
537
12%
1600
12%
534
66%
534
21%
1142
August11th to 20thNight
63%
534
15%
1598
13%
534
63%
534
22%
1112
August21st to endNight
62%
726
14%
1958
10%
726
63%
726
22%
1399
September1st to 10thNight
67%
720
19%
1980
16%
720
68%
720
30%
1273
September11th to 20thNight
60%
720
21%
1980
17%
720
63%
720
27%
1330
September21st to endNight
56%
720
20%
1980
16%
720
60%
720
28%
1315
October1st to 10thNight
55%
720
26%
2056
22%
720
61%
720
34%
1240
October11th to 20thNight
51%
720
31%
2160
26%
720
61%
720
35%
1224
October21st to endNight
50%
792
33%
2376
25%
792
63%
792
35%
1342
November1st to 10thNight
49%
740
30%
2221
22%
740
59%
740
34%
1268
November11th to 20thNight
39%
760
28%
2410
19%
760
52%
760
30%
1389
November21st to endNight
41%
760
27%
2470
19%
760
53%
760
29%
1448
December1st to 10thNight
36%
760
25%
2470
14%
760
49%
760
21%
1574
December11th to 20thNight
39%
759
28%
2915
19%
758
51%
758
24%
1648
December21st to endNight
31%
830
15%
4409
13%
817
42%
817
13%
2633

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
12%5%25%5%35%5%6%8%43%
79177
Night
13%6%35%5%345%5%7%44%
80828
TransparencyDay
38%7%11%20%19%6%
78900
Night
38%6%10%19%20%7%
80624
SeeingDay
15%10%25%24%18%7%
14394
Night
15%9%25%31%18%3
24567

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 10thDay
16%42443445%8%47%
2836
11th to 20thDay
13%5%24423346%53%
2840
21st to endDay
18%8%35%423335%45%
3124
February1st to 10thDay
14%7%35%5%345%6%7%41%
1753
11th to 20thDay
19%6%25%424446%45%
1848
21st to endDay
17%7%25%4345%46%42%
1604
March1st to 10thDay
14%5%245%24335%51%
2090
11th to 20thDay
15%5%345%35%46%7%43%
2090
21st to endDay
16%6%35%5%35%5%6%7%41%
2255
April1st to 10thDay
10%434425%5%6%7%51%
1980
11th to 20thDay
11%5%25%4345%7%7%47%
2087
21st to endDay
9%4243345%6%8%52%
2304
May1st to 10thDay
8%3245%35%5%6%9%50%
2340
11th to 20thDay
12%5%36%6%36%6%6%7%40%
2301
21st to endDay
10%6%35%5%36%6%7%9%39%
2531
June1st to 10thDay
10%6%36%6%45%6%7%10%37%
2340
11th to 20thDay
7%5%25%5%47%6%8%12%42%
2340
21st to endDay
4435%6%47%7%9%13%39%
2340
July1st to 10thDay
7%5%27%6%5%8%8%8%10%33%
2340
11th to 20thDay
7%6%36%7%5%7%7%9%13%31%
2340
21st to endDay
7%436%7%48%7%8%12%33%
2547
August1st to 10thDay
10%5%26%7%5%7%7%9%11%32%
2327
11th to 20thDay
13%6%26%6%5%6%7%8%9%31%
2303
21st to endDay
13%5%36%7%5%6%6%8%10%30%
2373
September1st to 10thDay
7%5%27%6%45%7%8%8%41%
1980
11th to 20thDay
14%6%35%5%345%5%8%42%
1980
21st to endDay
17%7%2443445%7%43%
1980
October1st to 10thDay
14%6%24423346%52%
1903
11th to 20thDay
12%424423245%58%
1800
21st to endDay
11%5%24424335%57%
1980
November1st to 10thDay
13%5%24424345%55%
1857
11th to 20thDay
13%5%23323446%54%
1767
21st to endDay
14%5%35%5%24445%49%
1710
December1st to 10thDay
18%8%35%5%245%5%6%38%
1710
11th to 20thDay
17%423334436%51%
2153
21st to endDay
18%6%26%5%2345%7%43%
3124
January1st to 10thNight
16%5%25%434446%47%
4109
11th to 20thNight
10%7%35%6%345%6%7%45%
4120
21st to endNight
17%8%35%43434345%
4532
February1st to 10thNight
16%6%25%434446%45%
2423
11th to 20thNight
19%6%35%424345%45%
2218
21st to endNight
15%5%25%5%3445%6%45%
1848
March1st to 10thNight
14%6%345%3445%7%47%
2090
11th to 20thNight
15%425%5%445%5%7%45%
2090
21st to endNight
12%6%25%5%35%5%6%7%44%
2256
April1st to 10thNight
11%5%24435%45%7%52%
1980
11th to 20thNight
12%434434446%53%
1821
21st to endNight
8%3345%2446%7%55%
1670
May1st to 10thNight
8%425%4345%7%10%48%
1620
11th to 20thNight
10%5%35%5%5%6%7%7%9%39%
1592
21st to endNight
8%435%6%45%6%7%10%43%
1744
June1st to 10thNight
11%5%46%7%46%6%7%11%33%
1620
11th to 20thNight
8%5%35%6%45%6%6%11%41%
1620
21st to endNight
6%5%37%5%36%8%9%13%35%
1620
July1st to 10thNight
6%6%36%6%5%7%7%9%12%33%
1620
11th to 20thNight
7%5%36%6%47%7%9%13%34%
1620
21st to endNight
6%6%36%8%46%7%8%11%34%
1771
August1st to 10thNight
8%5%36%7%47%8%9%12%31%
1611
11th to 20thNight
12%6%37%6%36%6%7%11%32%
1598
21st to endNight
10%6%27%7%46%6%7%11%32%
1958
September1st to 10thNight
8%6%346%36%6%8%9%42%
1980
11th to 20thNight
12%6%36%5%45%47%8%39%
1980
21st to endNight
16%5%25%4345%5%7%43%
1980
October1st to 10thNight
13%7%24423346%52%
2056
11th to 20thNight
14%425%323446%54%
2160
21st to endNight
10%5%24433446%56%
2376
November1st to 10thNight
12%6%34424235%56%
2221
11th to 20thNight
13%6%24423446%53%
2410
21st to endNight
13%5%344245%6%6%48%
2470
December1st to 10thNight
16%6%35%5%34446%43%
2470
11th to 20thNight
16%5%25%323345%52%
3042
21st to endNight
19%7%35%4345%5%6%39%
4532

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 10thDay
35%6%6%23%23%7%
2837
11th to 20thDay
34%45%18%29%11%
2840
21st to endDay
44%3416%25%8%
3124
February1st to 10thDay
42%49%20%19%6%
1753
11th to 20thDay
42%45%18%24%6%
1858
21st to endDay
43%5%8%14%21%9%
1604
March1st to 10thDay
37%36%22%21%10%
2090
11th to 20thDay
40%6%10%18%19%7%
2090
21st to endDay
43%5%10%18%19%5%
2255
April1st to 10thDay
32%5%11%19%27%6%
1980
11th to 20thDay
35%5%10%19%21%10%
2087
21st to endDay
30%7%9%27%23%4
2304
May1st to 10thDay
31%6%14%23%21%4
2340
11th to 20thDay
41%8%15%18%17%1
2305
21st to endDay
39%9%12%23%15%1
2531
June1st to 10thDay
40%10%16%21%10%2
2340
11th to 20thDay
33%10%16%26%13%1
2340
21st to endDay
34%12%16%22%13%2
2340
July1st to 10thDay
41%12%18%17%9%3
2275
11th to 20thDay
40%12%21%18%7%2
2271
21st to endDay
37%14%20%20%8%1
2405
August1st to 10thDay
42%13%16%21%8%1
2314
11th to 20thDay
46%11%15%18%9%1
2303
21st to endDay
46%10%17%17%8%2
2373
September1st to 10thDay
37%9%14%17%18%4
1980
11th to 20thDay
40%8%10%19%20%4
1980
21st to endDay
42%5%8%21%17%7%
1980
October1st to 10thDay
35%5%7%21%24%8%
1903
11th to 20thDay
30%48%25%25%8%
1800
21st to endDay
31%45%18%30%12%
1980
November1st to 10thDay
33%46%18%27%12%
1857
11th to 20thDay
33%47%21%25%11%
1767
21st to endDay
38%5%7%19%23%9%
1710
December1st to 10thDay
45%5%8%18%17%7%
1710
11th to 20thDay
36%37%22%22%11%
2150
21st to endDay
42%47%21%24%3
3124
January1st to 10thNight
38%5%5%19%26%7%
4109
11th to 20thNight
37%47%20%24%8%
4120
21st to endNight
43%5%415%26%8%
4532
February1st to 10thNight
41%47%18%21%9%
2423
11th to 20thNight
42%46%18%21%9%
2219
21st to endNight
40%5%9%17%19%10%
1848
March1st to 10thNight
38%47%17%22%12%
2090
11th to 20thNight
38%6%11%16%21%8%
2090
21st to endNight
39%6%9%20%19%6%
2256
April1st to 10thNight
33%411%20%24%8%
1980
11th to 20thNight
34%48%20%23%11%
1821
21st to endNight
28%6%10%27%25%5%
1670
May1st to 10thNight
30%7%15%24%19%5%
1620
11th to 20thNight
39%10%16%19%16%1
1593
21st to endNight
35%9%12%25%16%3
1745
June1st to 10thNight
42%9%15%21%11%1
1620
11th to 20thNight
36%9%18%24%12%2
1620
21st to endNight
37%13%17%20%11%2
1620
July1st to 10thNight
39%13%22%13%10%3
1575
11th to 20thNight
37%13%25%16%6%2
1566
21st to endNight
39%12%23%18%7%1
1672
August1st to 10thNight
42%14%18%19%6%1
1600
11th to 20thNight
43%11%20%17%8%1
1598
21st to endNight
44%11%17%17%9%2
1958
September1st to 10thNight
35%9%16%20%15%5%
1980
11th to 20thNight
41%8%11%18%18%4
1980
21st to endNight
40%7%11%17%19%5%
1980
October1st to 10thNight
35%49%19%27%6%
2056
11th to 20thNight
31%48%23%23%10%
2160
21st to endNight
31%45%20%28%13%
2376
November1st to 10thNight
32%47%16%27%14%
2221
11th to 20thNight
35%36%18%25%14%
2410
21st to endNight
36%48%18%24%10%
2470
December1st to 10thNight
42%5%9%19%19%7%
2470
11th to 20thNight
36%47%18%27%9%
3044
21st to endNight
45%46%20%20%4
4532

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 10thDay
17%28%39%14%3
270
11th to 20thDay
22%24%33%19%1
270
21st to endDay
22%27%38%12%2
297
February1st to 10thDay
17%27%38%14%4
270
11th to 20thDay
32%19%35%13%1
270
21st to endDay
25%23%34%13%4
259
March1st to 10thDay
19%20%32%21%8%
460
11th to 20thDay
19%17%42%16%5%
460
21st to endDay
20%18%38%15%8%
490
April1st to 10thDay
18%16%33%21%10%
420
11th to 20thDay
14%16%32%20%15%3
412
21st to endDay
11%12%32%24%17%4
420
May1st to 10thDay
9%12%36%27%13%3
423
11th to 20thDay
15%5%20%32%18%9%
447
21st to endDay
13%6%15%27%27%12%
485
June1st to 10thDay
12%416%31%26%11%
450
11th to 20thDay
10%420%24%28%14%
450
21st to endDay
8%316%34%27%13%
450
July1st to 10thDay
10%29%26%32%22%
445
11th to 20thDay
8%212%25%36%17%
444
21st to endDay
6%211%32%36%13%
488
August1st to 10thDay
13%312%26%32%14%
446
11th to 20thDay
14%5%10%26%29%18%
439
21st to endDay
13%410%28%28%16%
495
September1st to 10thDay
8%410%30%34%14%
450
11th to 20thDay
16%314%26%29%12%
450
21st to endDay
20%316%28%26%7%
450
October1st to 10thDay
16%5%22%30%18%9%
450
11th to 20thDay
12%8%24%28%22%6%
450
21st to endDay
13%9%28%28%17%5%
495
November1st to 10thDay
17%10%27%26%14%6%
455
11th to 20thDay
19%13%37%24%6%2
327
21st to endDay
11%14%40%23%11%1
270
December1st to 10thDay
25%19%33%18%4
270
11th to 20thDay
23%14%41%15%6%1
270
21st to endDay
26%20%32%15%42
297
January1st to 10thNight
20%17%33%25%6%
760
11th to 20thNight
18%15%33%28%6%
760
21st to endNight
20%18%37%22%3
836
February1st to 10thNight
19%14%34%28%4
760
11th to 20thNight
22%17%35%24%2
743
21st to endNight
18%17%37%24%4
628
March1st to 10thNight
17%13%35%29%6%
760
11th to 20thNight
18%13%39%23%7%
760
21st to endNight
16%15%36%24%7%
821
April1st to 10thNight
15%16%32%28%9%
720
11th to 20thNight
13%13%30%32%12%
711
21st to endNight
11%9%33%36%12%
590
May1st to 10thNight
11%8%33%35%12%
540
11th to 20thNight
11%330%34%19%3
531
21st to endNight
9%316%39%28%4
584
June1st to 10thNight
12%220%38%23%5%
540
11th to 20thNight
10%215%33%30%9%
540
21st to endNight
8%215%39%30%6%
540
July1st to 10thNight
9%19%36%36%7%
525
11th to 20thNight
10%18%35%38%8%
522
21st to endNight
7%211%37%39%5%
591
August1st to 10thNight
10%29%32%40%7%
537
11th to 20thNight
15%27%34%38%4
534
21st to endNight
13%210%31%39%5%
726
September1st to 10thNight
10%39%35%38%5%
720
11th to 20thNight
14%214%29%36%5%
720
21st to endNight
18%314%33%27%5%
720
October1st to 10thNight
16%5%19%31%26%4
720
11th to 20thNight
16%6%22%30%23%3
720
21st to endNight
11%9%24%32%21%2
792
November1st to 10thNight
14%8%24%32%19%3
740
11th to 20thNight
15%11%31%30%12%1
760
21st to endNight
15%9%30%30%14%1
760
December1st to 10thNight
18%14%27%32%9%1
760
11th to 20thNight
20%9%27%33%10%1
760
21st to endNight
26%14%26%27%7%1
836
Page generated at 2024-03-24 23:37:03. Version ac07

Copyright © 2024 Attilla Danko.


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