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Limber Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Limber Observatory clear sky chart from 2005-11-06 to 2024-01-22.

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
45%
23750
25%
74442
17%
23694
54%
23694
31%
43533

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
39%
946
30%
2458
13%
946
49%
946
35%
1502
January11th to 20thNight
34%
950
26%
2470
10%
950
44%
950
31%
1573
January21st to endNight
34%
809
31%
2409
14%
809
48%
809
26%
1469
February1st to 10thNight
31%
720
28%
2160
11%
720
45%
720
27%
1274
February11th to 20thNight
28%
704
23%
2098
9%
700
39%
700
25%
1286
February21st to endNight
20%
592
26%
1776
6%
592
37%
592
23%
1098
March1st to 10thNight
25%
609
24%
2049
9%
609
39%
609
22%
1268
March11th to 20thNight
28%
540
22%
1980
13%
540
40%
540
21%
1203
March21st to endNight
27%
594
25%
2178
12%
594
43%
594
25%
1228
April1st to 10thNight
26%
540
24%
1980
11%
540
44%
540
24%
1136
April11th to 20thNight
21%
533
23%
1880
11%
533
38%
533
22%
1138
April21st to endNight
25%
540
27%
1725
13%
540
42%
540
25%
1082
May1st to 10thNight
28%
540
25%
1620
15%
540
41%
540
29%
1007
May11th to 20thNight
36%
531
21%
1594
16%
531
45%
531
29%
988
May21st to endNight
38%
583
21%
1745
13%
582
51%
582
27%
1108
June1st to 10thNight
61%
540
24%
1620
21%
540
69%
540
46%
853
June11th to 20thNight
51%
540
23%
1620
18%
540
62%
540
45%
862
June21st to endNight
58%
540
22%
1620
23%
540
64%
540
36%
961
July1st to 10thNight
64%
525
16%
1575
15%
525
67%
525
32%
949
July11th to 20thNight
76%
522
27%
1566
28%
522
80%
522
47%
811
July21st to endNight
75%
591
23%
1673
24%
558
80%
558
49%
851
August1st to 10thNight
81%
537
28%
1708
30%
534
84%
534
56%
770
August11th to 20thNight
76%
534
23%
1778
27%
534
78%
534
38%
946
August21st to endNight
73%
594
18%
2034
21%
594
75%
594
33%
1136
September1st to 10thNight
69%
540
19%
1980
22%
540
70%
540
29%
1151
September11th to 20thNight
66%
540
21%
1980
24%
540
68%
540
25%
1205
September21st to endNight
66%
540
26%
1980
28%
540
68%
540
32%
1079
October1st to 10thNight
70%
540
33%
1980
33%
540
73%
540
38%
984
October11th to 20thNight
53%
584
32%
2024
24%
584
61%
584
32%
1140
October21st to endNight
48%
792
34%
2376
20%
792
56%
792
38%
1312
November1st to 10thNight
53%
740
29%
2220
19%
740
58%
740
33%
1325
November11th to 20thNight
49%
931
27%
2451
14%
931
55%
931
35%
1484
November21st to endNight
38%
950
27%
2470
12%
950
46%
950
29%
1597
December1st to 10thNight
43%
950
31%
2470
16%
950
50%
950
34%
1523
December11th to 20thNight
34%
950
26%
2892
12%
948
41%
948
24%
1875
December21st to endNight
38%
1039
17%
4303
13%
1026
46%
1026
23%
2359

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%5%25%43445%7%46%
74941
Night
14%5%24423447%51%
75022
TransparencyDay
39%49%21%18%9%
74666
Night
35%410%20%19%12%
74817
SeeingDay
15%9%24%31%18%3
13671
Night
16%8%26%35%14%1
23761

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
15%6%34322336%52%
1707
11th to 20thDay
18%7%34333335%48%
1716
21st to endDay
15%5%24323346%51%
1990
February1st to 10thDay
17%8%33424435%46%
1800
11th to 20thDay
20%7%2442445%444%
1749
21st to endDay
18%6%33314335%50%
1480
March1st to 10thDay
20%7%25%424345%43%
1908
11th to 20thDay
17%7%2442445%5%46%
1980
21st to endDay
18%5%25%323346%46%
2178
April1st to 10thDay
16%7%35%5%23447%45%
1980
11th to 20thDay
19%6%25%5%245%45%43%
2026
21st to endDay
16%6%35%5%2345%5%45%
2232
May1st to 10thDay
17%5%35%6%25%5%5%6%41%
2340
11th to 20thDay
15%7%35%5%45%45%7%39%
2302
21st to endDay
17%6%35%6%45%6%6%7%36%
2531
June1st to 10thDay
8%415%5%36%6%7%9%47%
2340
11th to 20thDay
8%425%6%46%5%6%8%46%
2340
21st to endDay
10%5%36%6%37%7%7%9%38%
2340
July1st to 10thDay
13%6%27%5%46%5%6%8%37%
2340
11th to 20thDay
6%325%5%445%6%10%51%
2340
21st to endDay
6%314435%5%7%9%51%
2546
August1st to 10thDay
2212425%5%5%11%60%
2216
11th to 20thDay
6%4245%45%5%7%11%48%
2123
21st to endDay
7%5%26%6%46%6%7%11%42%
2322
September1st to 10thDay
12%6%35%7%45%5%6%7%40%
1980
11th to 20thDay
10%6%25%6%45%5%7%7%40%
1980
21st to endDay
8%4246%35%6%7%8%47%
1980
October1st to 10thDay
7%5%25%425%5%5%7%53%
1980
11th to 20thDay
15%5%24324447%50%
1916
21st to endDay
13%42442334458%
1980
November1st to 10thDay
16%7%35%43335%5%45%
1858
11th to 20thDay
15%6%35%334345%49%
1725
21st to endDay
19%7%3443343446%
1710
December1st to 10thDay
17%6%34423447%47%
1710
11th to 20thDay
19%6%24433446%45%
2161
21st to endDay
17%5%1332332456%
3135
January1st to 10thNight
16%423323336%54%
2458
11th to 20thNight
17%6%24323345%51%
2470
21st to endNight
19%5%24423345%49%
2409
February1st to 10thNight
17%7%24323346%51%
2160
11th to 20thNight
18%6%2433333450%
2098
21st to endNight
18%6%33433347%47%
1776
March1st to 10thNight
18%6%25%5%2445%6%44%
2049
11th to 20thNight
18%7%34424245%46%
1980
21st to endNight
18%6%23323446%50%
2178
April1st to 10thNight
13%6%2443435%7%48%
1980
11th to 20thNight
18%6%25%423445%48%
1880
21st to endNight
20%5%24423345%48%
1725
May1st to 10thNight
13%7%35%5%23348%46%
1620
11th to 20thNight
14%5%345%345%48%46%
1593
21st to endNight
15%6%2442346%9%43%
1745
June1st to 10thNight
6%31233446%9%60%
1620
11th to 20thNight
6%3143334410%59%
1620
21st to endNight
7%434425%6%6%10%49%
1620
July1st to 10thNight
9%6%246%345%7%10%45%
1620
11th to 20thNight
33133245%5%8%62%
1620
21st to endNight
6%31332447%10%58%
1772
August1st to 10thNight
321232235%8%68%
1718
11th to 20thNight
5%3234345%6%11%54%
1778
21st to endNight
7%4245%35%5%6%10%49%
2034
September1st to 10thNight
8%435%5%45%46%8%47%
1980
11th to 20thNight
10%6%35%5%25%5%6%8%45%
1980
21st to endNight
8%5%26%43446%8%50%
1980
October1st to 10thNight
7%42432445%6%59%
1980
11th to 20thNight
14%5%23323446%53%
2024
21st to endNight
15%413312225%61%
2376
November1st to 10thNight
13%7%25%423336%54%
2220
11th to 20thNight
12%5%24333446%54%
2451
21st to endNight
20%42443335%6%46%
2470
December1st to 10thNight
16%6%23322347%52%
2470
11th to 20thNight
19%7%25%423345%47%
3036
21st to endNight
19%6%13223335%54%
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
36%4319%21%18%
1708
11th to 20thDay
42%25%14%20%18%
1716
21st to endDay
36%36%14%24%16%
1990
February1st to 10thDay
43%3413%21%17%
1800
11th to 20thDay
43%35%18%18%13%
1759
21st to endDay
40%26%17%19%16%
1480
March1st to 10thDay
45%37%14%19%12%
1908
11th to 20thDay
41%37%15%16%17%
1980
21st to endDay
40%37%18%18%13%
2178
April1st to 10thDay
43%38%18%18%11%
1980
11th to 20thDay
45%35%18%17%12%
2026
21st to endDay
43%36%19%18%11%
2232
May1st to 10thDay
45%48%17%19%7%
2340
11th to 20thDay
45%49%20%18%4
2306
21st to endDay
48%5%10%22%15%1
2531
June1st to 10thDay
33%5%13%26%19%3
2340
11th to 20thDay
36%412%26%17%4
2340
21st to endDay
42%7%10%24%14%3
2340
July1st to 10thDay
44%5%15%25%10%1
2276
11th to 20thDay
29%5%17%29%18%2
2271
21st to endDay
26%5%21%34%13%1
2405
August1st to 10thDay
20%416%40%19%1
2202
11th to 20thDay
30%5%20%31%12%3
2123
21st to endDay
36%6%17%25%13%3
2322
September1st to 10thDay
42%5%11%20%16%6%
1980
11th to 20thDay
41%6%10%20%17%5%
1980
21st to endDay
35%410%22%18%10%
1980
October1st to 10thDay
32%49%20%26%9%
1980
11th to 20thDay
36%48%17%19%16%
1916
21st to endDay
32%2417%24%20%
1980
November1st to 10thDay
42%36%21%17%11%
1858
11th to 20thDay
39%37%16%20%15%
1725
21st to endDay
43%35%16%19%14%
1710
December1st to 10thDay
40%27%21%20%10%
1710
11th to 20thDay
44%27%10%21%16%
2159
21st to endDay
35%2416%28%15%
3135
January1st to 10thNight
35%25%16%23%20%
2458
11th to 20thNight
38%2417%21%18%
2470
21st to endNight
40%2314%21%20%
2409
February1st to 10thNight
38%26%14%21%19%
2160
11th to 20thNight
40%35%16%20%17%
2098
21st to endNight
41%36%15%18%17%
1776
March1st to 10thNight
43%39%16%19%11%
2049
11th to 20thNight
43%37%13%16%18%
1980
21st to endNight
38%311%17%17%15%
2178
April1st to 10thNight
39%310%18%17%14%
1980
11th to 20thNight
42%38%14%17%16%
1880
21st to endNight
42%48%19%16%11%
1725
May1st to 10thNight
40%311%20%15%10%
1620
11th to 20thNight
38%411%24%16%5%
1594
21st to endNight
40%6%14%26%13%2
1746
June1st to 10thNight
24%417%32%21%3
1620
11th to 20thNight
25%5%15%30%20%5%
1620
21st to endNight
32%6%18%27%14%3
1620
July1st to 10thNight
34%7%20%28%9%2
1575
11th to 20thNight
20%7%20%32%19%2
1566
21st to endNight
20%6%28%34%10%1
1673
August1st to 10thNight
16%423%40%16%1
1708
11th to 20thNight
25%8%23%30%12%2
1778
21st to endNight
31%6%24%24%12%3
2034
September1st to 10thNight
35%6%15%21%17%6%
1980
11th to 20thNight
38%7%15%21%15%4
1980
21st to endNight
32%5%12%22%18%11%
1980
October1st to 10thNight
27%311%26%21%11%
1980
11th to 20thNight
33%49%17%20%17%
2024
21st to endNight
30%25%16%25%22%
2376
November1st to 10thNight
36%36%20%22%14%
2220
11th to 20thNight
33%38%19%20%16%
2451
21st to endNight
40%37%16%19%15%
2470
December1st to 10thNight
36%27%19%21%13%
2470
11th to 20thNight
43%2414%18%20%
3037
21st to endNight
37%2414%28%15%
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
23%16%36%21%5%
270
11th to 20thDay
26%15%32%21%6%
270
21st to endDay
20%18%36%21%5%
267
February1st to 10thDay
28%17%28%22%5%
240
11th to 20thDay
30%21%32%13%4
240
21st to endDay
28%22%35%13%2
198
March1st to 10thDay
26%19%40%13%1
240
11th to 20thDay
20%22%43%13%3
240
21st to endDay
22%21%38%16%2
264
April1st to 10thDay
23%20%40%15%2
240
11th to 20thDay
20%21%35%20%3
304
21st to endDay
20%16%42%19%3
492
May1st to 10thDay
19%13%39%25%4
603
11th to 20thDay
17%12%31%32%6%1
625
21st to endDay
19%5%30%33%12%
679
June1st to 10thDay
8%322%44%20%3
630
11th to 20thDay
9%224%46%17%2
630
21st to endDay
11%317%39%26%5%
630
July1st to 10thDay
12%313%36%29%7%
621
11th to 20thDay
6%8%41%41%3
618
21st to endDay
418%39%40%8%
684
August1st to 10thDay
35%44%39%9%
514
11th to 20thDay
8%17%42%35%8%
437
21st to endDay
5%26%38%39%10%
441
September1st to 10thDay
12%19%29%37%12%
270
11th to 20thDay
7%16%35%46%6%
270
21st to endDay
9%215%31%35%8%
270
October1st to 10thDay
6%419%40%27%4
270
11th to 20thDay
14%423%40%17%2
270
21st to endDay
20%15%27%24%12%2
297
November1st to 10thDay
17%10%34%24%11%2
270
11th to 20thDay
23%11%30%26%8%2
270
21st to endDay
26%18%34%14%7%1
270
December1st to 10thDay
17%13%33%28%8%1
270
11th to 20thDay
24%17%33%22%4
270
21st to endDay
24%12%36%23%5%1
297
January1st to 10thNight
20%11%26%35%8%
950
11th to 20thNight
21%12%31%29%7%
950
21st to endNight
23%11%27%32%7%
809
February1st to 10thNight
23%14%28%27%7%1
720
11th to 20thNight
25%13%31%26%5%
704
21st to endNight
26%13%39%21%2
592
March1st to 10thNight
23%14%35%26%3
609
11th to 20thNight
22%12%34%29%3
540
21st to endNight
20%13%38%25%4
594
April1st to 10thNight
15%14%43%26%3
540
11th to 20thNight
20%14%43%22%2
533
21st to endNight
21%12%40%21%6%1
540
May1st to 10thNight
16%11%41%28%3
540
11th to 20thNight
17%8%35%32%7%1
531
21st to endNight
18%6%35%32%9%
584
June1st to 10thNight
6%228%46%18%1
540
11th to 20thNight
6%138%44%11%
540
21st to endNight
8%325%40%22%1
540
July1st to 10thNight
10%216%48%23%2
525
11th to 20thNight
3112%56%25%2
522
21st to endNight
5%112%54%25%3
591
August1st to 10thNight
2111%52%33%1
537
11th to 20thNight
6%19%52%29%2
534
21st to endNight
6%28%45%35%4
594
September1st to 10thNight
9%111%44%31%4
540
11th to 20thNight
12%211%40%33%3
540
21st to endNight
11%213%40%30%4
540
October1st to 10thNight
8%214%50%24%3
540
11th to 20thNight
15%5%23%38%18%1
584
21st to endNight
18%7%25%29%19%3
792
November1st to 10thNight
14%7%21%37%19%2
740
11th to 20thNight
15%8%23%38%14%1
931
21st to endNight
23%10%25%30%11%1
950
December1st to 10thNight
21%8%25%35%11%1
950
11th to 20thNight
26%10%25%30%8%
950
21st to endNight
22%9%26%34%8%
1045
Page generated at 2024-01-19 08:28:35. Version ac07

Copyright 2024 Attilla Danko


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