Mound City Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mound City Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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
57%
24380
23%
74747
19%
24337
62%
24337
35%
42603

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
48%
756
17%
2457
16%
756
51%
756
23%
1616
January11th to 20thNight
49%
744
20%
2417
17%
744
54%
744
24%
1546
January21st to endNight
50%
792
18%
2574
19%
792
53%
792
23%
1682
February1st to 10thNight
47%
720
14%
2340
13%
720
51%
720
24%
1496
February11th to 20thNight
47%
700
18%
2223
17%
700
52%
700
28%
1382
February21st to endNight
47%
592
20%
1776
17%
592
53%
592
28%
1130
March1st to 10thNight
45%
720
17%
2017
14%
720
49%
720
29%
1308
March11th to 20thNight
54%
720
22%
1980
17%
720
59%
720
37%
1185
March21st to endNight
45%
792
18%
2178
11%
792
50%
792
30%
1395
April1st to 10thNight
49%
689
18%
1949
14%
689
53%
689
31%
1184
April11th to 20thNight
47%
533
22%
1662
14%
533
54%
533
34%
938
April21st to endNight
52%
540
23%
1620
16%
540
58%
540
35%
939
May1st to 10thNight
52%
540
21%
1620
15%
540
56%
540
33%
954
May11th to 20thNight
62%
531
23%
1595
19%
531
65%
531
44%
833
May21st to endNight
56%
582
17%
1746
14%
582
60%
582
36%
985
June1st to 10thNight
62%
540
25%
1494
20%
540
67%
540
44%
801
June11th to 20thNight
60%
540
30%
1440
22%
540
68%
540
54%
720
June21st to endNight
72%
540
29%
1548
26%
540
77%
540
64%
695
July1st to 10thNight
75%
525
21%
1575
19%
525
78%
525
49%
778
July11th to 20thNight
73%
522
22%
1566
23%
522
75%
522
44%
813
July21st to endNight
78%
591
24%
1674
22%
558
79%
558
43%
875
August1st to 10thNight
75%
537
27%
1602
21%
534
78%
534
47%
809
August11th to 20thNight
77%
534
31%
1602
25%
534
79%
534
49%
795
August21st to endNight
77%
594
36%
1817
33%
594
79%
594
53%
854
September1st to 10thNight
75%
640
34%
1900
29%
640
80%
640
55%
905
September11th to 20thNight
73%
720
33%
1980
26%
720
78%
720
56%
991
September21st to endNight
71%
720
37%
1980
28%
720
77%
720
55%
996
October1st to 10thNight
63%
720
28%
2080
20%
720
69%
720
46%
1110
October11th to 20thNight
66%
720
33%
2160
26%
720
72%
720
47%
1116
October21st to endNight
60%
792
32%
2376
25%
792
68%
792
47%
1198
November1st to 10thNight
59%
740
26%
2383
23%
740
64%
740
36%
1280
November11th to 20thNight
57%
760
27%
2470
22%
760
64%
760
38%
1331
November21st to endNight
52%
902
22%
2612
18%
902
57%
902
34%
1558
December1st to 10thNight
50%
950
18%
2660
13%
950
53%
950
33%
1653
December11th to 20thNight
46%
950
17%
3143
11%
949
50%
949
22%
2020
December21st to endNight
38%
892
9%
4531
11%
886
42%
886
12%
2732

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
46%36%6%35%5%6%7%49%
74624
Night
36%36%5%35%5%6%8%50%
75191
TransparencyDay
32%5%12%20%20%10%
74349
Night
31%5%14%23%19%8%
74987
SeeingDay
7%16%31%29%13%3
13947
Night
7%6%23%39%22%3
24403

By Month

Percentage Cloud Cover SW (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
211%5%7%9%35%7%7%7%37%
1708
11th to 20thDay
29%6%9%8%45%447%41%
1665
21st to endDay
310%8%8%7%46%6%5%6%39%
1782
February1st to 10thDay
312%5%9%6%45%7%7%7%36%
1620
11th to 20thDay
412%48%8%446%6%7%36%
1620
21st to endDay
310%6%10%7%47%6%6%8%33%
1480
March1st to 10thDay
29%6%10%7%45%5%8%8%37%
1941
11th to 20thDay
38%46%7%45%7%7%10%40%
1980
21st to endDay
412%49%8%46%5%7%8%33%
2178
April1st to 10thDay
39%46%6%46%5%6%8%41%
2011
11th to 20thDay
5%9%48%6%46%5%7%7%40%
2243
21st to endDay
5%7%45%6%45%5%6%7%45%
2340
May1st to 10thDay
5%6%35%6%46%6%7%9%41%
2340
11th to 20thDay
45%35%5%46%6%7%9%47%
2301
21st to endDay
5%6%36%6%46%8%8%10%39%
2530
June1st to 10thDay
43235%35%5%6%8%56%
2456
11th to 20thDay
4423425%446%64%
2520
21st to endDay
22122245%5%5%69%
2403
July1st to 10thDay
22133245%6%9%63%
2340
11th to 20thDay
33244346%7%7%57%
2340
21st to endDay
43235%45%6%7%8%53%
2545
August1st to 10thDay
43144346%7%9%56%
2328
11th to 20thDay
3223335%45%7%62%
2299
21st to endDay
32134345%6%8%60%
2538
September1st to 10thDay
321332445%7%67%
2056
11th to 20thDay
431342446%7%63%
1980
21st to endDay
5%313423346%67%
1980
October1st to 10thDay
6%6%35%5%35%45%5%53%
1878
11th to 20thDay
6%5%23423447%60%
1800
21st to endDay
27%244345%6%6%57%
1980
November1st to 10thDay
5%7%35%5%45%5%6%7%48%
1692
11th to 20thDay
5%7%445%35%46%7%49%
1710
21st to endDay
27%47%7%45%5%6%7%46%
1544
December1st to 10thDay
48%37%6%45%5%6%8%43%
1520
11th to 20thDay
39%410%6%47%7%8%7%35%
1926
21st to endDay
28%6%10%9%35%5%5%8%39%
3050
January1st to 10thNight
310%49%7%46%6%7%8%37%
2457
11th to 20thNight
39%48%8%46%5%5%6%41%
2417
21st to endNight
311%5%8%7%45%5%7%8%36%
2574
February1st to 10thNight
39%47%6%46%6%7%10%38%
2340
11th to 20thNight
29%47%6%35%5%7%7%43%
2222
21st to endNight
27%48%7%5%6%7%7%9%38%
1776
March1st to 10thNight
210%5%8%6%5%5%6%7%8%38%
2017
11th to 20thNight
27%35%437%7%7%9%46%
1980
21st to endNight
38%35%7%46%6%7%7%43%
2178
April1st to 10thNight
5%10%45%435%45%7%48%
1949
11th to 20thNight
36%245%36%7%7%7%49%
1662
21st to endNight
5%7%25%5%345%6%7%50%
1620
May1st to 10thNight
5%5%36%6%346%7%9%45%
1620
11th to 20thNight
3425%5%345%6%9%54%
1594
21st to endNight
5%5%25%6%346%7%10%47%
1746
June1st to 10thNight
4313435%5%6%8%59%
1494
11th to 20thNight
32133235%46%69%
1440
21st to endNight
11123235%48%70%
1548
July1st to 10thNight
21135%36%5%7%8%58%
1620
11th to 20thNight
33245%36%6%6%9%54%
1620
21st to endNight
22245%45%7%6%10%53%
1773
August1st to 10thNight
3313445%5%6%9%58%
1611
11th to 20thNight
22145%35%46%9%60%
1602
21st to endNight
23134345%6%8%62%
1817
September1st to 10thNight
331332345%6%69%
1900
11th to 20thNight
421232445%8%65%
1980
21st to endNight
5%312323335%70%
1980
October1st to 10thNight
5%5%243235%5%7%59%
2080
11th to 20thNight
45%2343446%6%61%
2160
21st to endNight
36%2432346%7%61%
2376
November1st to 10thNight
45%25%5%345%5%8%54%
2383
11th to 20thNight
47%24425%5%5%11%52%
2470
21st to endNight
26%37%5%46%46%9%47%
2612
December1st to 10thNight
28%48%6%345%5%9%46%
2660
11th to 20thNight
5%8%47%6%46%6%7%11%36%
3271
21st to endNight
27%411%9%46%6%8%10%31%
4642

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
43%8%17%21%10%1
1709
11th to 20thDay
45%5%14%19%14%3
1665
21st to endDay
45%6%17%21%8%3
1782
February1st to 10thDay
45%8%16%18%11%2
1620
11th to 20thDay
46%5%14%21%12%2
1629
21st to endDay
48%6%14%20%10%1
1480
March1st to 10thDay
44%6%14%24%10%2
1941
11th to 20thDay
38%6%18%23%12%3
1980
21st to endDay
48%5%16%21%7%2
2178
April1st to 10thDay
41%6%16%19%14%5%
2011
11th to 20thDay
43%5%14%22%16%1
2246
21st to endDay
38%5%11%26%18%2
2340
May1st to 10thDay
37%5%11%24%20%3
2340
11th to 20thDay
32%5%12%26%21%4
2304
21st to endDay
37%6%14%21%19%3
2530
June1st to 10thDay
23%6%10%22%29%10%
2456
11th to 20thDay
22%37%18%29%20%
2520
21st to endDay
16%25%11%31%34%
2403
July1st to 10thDay
18%5%7%14%25%31%
2276
11th to 20thDay
23%49%14%24%27%
2271
21st to endDay
25%7%8%14%23%22%
2404
August1st to 10thDay
23%5%9%19%22%23%
2313
11th to 20thDay
20%48%14%29%25%
2299
21st to endDay
22%38%17%31%19%
2538
September1st to 10thDay
19%36%16%27%29%
2056
11th to 20thDay
21%48%19%26%22%
1980
21st to endDay
20%37%21%37%13%
1980
October1st to 10thDay
31%48%21%26%9%
1878
11th to 20thDay
26%28%31%25%7%
1800
21st to endDay
26%414%29%22%3
1980
November1st to 10thDay
34%5%14%23%20%4
1692
11th to 20thDay
33%414%27%19%2
1710
21st to endDay
37%5%14%24%15%5%
1544
December1st to 10thDay
37%8%20%21%10%4
1520
11th to 20thDay
44%7%14%21%13%1
1924
21st to endDay
42%5%15%15%21%3
3050
January1st to 10thNight
43%7%16%23%9%2
2457
11th to 20thNight
42%6%16%22%11%3
2417
21st to endNight
43%6%17%22%8%3
2574
February1st to 10thNight
40%7%19%21%10%2
2340
11th to 20thNight
39%5%14%23%17%2
2223
21st to endNight
39%6%16%25%12%2
1776
March1st to 10thNight
40%5%18%25%11%
2017
11th to 20thNight
31%6%17%30%15%2
1980
21st to endNight
37%6%17%27%10%3
2178
April1st to 10thNight
36%417%20%18%5%
1949
11th to 20thNight
30%5%17%26%20%2
1662
21st to endNight
31%5%15%27%20%1
1620
May1st to 10thNight
33%5%15%24%21%2
1620
11th to 20thNight
25%415%30%20%5%
1595
21st to endNight
29%5%17%29%16%3
1746
June1st to 10thNight
24%411%25%28%9%
1494
11th to 20thNight
17%47%20%30%21%
1440
21st to endNight
13%26%13%30%35%
1548
July1st to 10thNight
21%39%16%23%28%
1575
11th to 20thNight
24%5%10%16%21%24%
1566
21st to endNight
24%5%13%18%18%21%
1674
August1st to 10thNight
22%5%13%20%19%21%
1602
11th to 20thNight
22%39%16%27%24%
1602
21st to endNight
18%310%18%30%21%
1817
September1st to 10thNight
17%46%18%25%30%
1900
11th to 20thNight
17%411%21%25%22%
1980
21st to endNight
19%36%20%38%15%
1980
October1st to 10thNight
25%310%25%27%9%
2080
11th to 20thNight
24%38%30%28%7%
2160
21st to endNight
22%415%30%26%4
2376
November1st to 10thNight
28%5%14%28%21%5%
2383
11th to 20thNight
28%5%15%31%18%3
2470
21st to endNight
34%5%14%26%18%4
2612
December1st to 10thNight
35%6%18%25%12%3
2660
11th to 20thNight
41%7%18%22%12%1
3272
21st to endNight
44%7%17%17%13%1
4642

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
11%16%31%24%13%4
270
11th to 20thDay
6%16%32%31%13%2
255
21st to endDay
6%15%30%33%13%3
264
February1st to 10thDay
10%19%40%21%8%2
240
11th to 20thDay
7%20%38%26%7%2
285
21st to endDay
10%25%36%23%6%1
346
March1st to 10thDay
9%23%39%22%7%1
420
11th to 20thDay
10%24%33%26%7%1
420
21st to endDay
14%29%32%21%4
462
April1st to 10thDay
10%25%32%21%9%2
420
11th to 20thDay
15%28%34%16%6%1
412
21st to endDay
12%28%27%23%10%1
420
May1st to 10thDay
10%22%37%21%9%1
423
11th to 20thDay
9%19%33%25%10%4
448
21st to endDay
9%17%34%24%12%4
485
June1st to 10thDay
7%14%30%29%16%4
566
11th to 20thDay
7%15%30%29%18%2
630
21st to endDay
314%29%37%14%3
513
July1st to 10thDay
27%34%41%12%3
446
11th to 20thDay
46%38%36%13%4
444
21st to endDay
3430%38%19%6%
487
August1st to 10thDay
49%34%33%17%3
447
11th to 20thDay
37%28%39%17%6%
437
21st to endDay
37%31%35%19%5%
495
September1st to 10thDay
410%28%32%18%8%
450
11th to 20thDay
6%14%29%29%17%5%
450
21st to endDay
7%16%22%32%19%4
450
October1st to 10thDay
7%16%28%25%16%7%
348
11th to 20thDay
8%15%23%26%22%6%
270
21st to endDay
7%16%34%30%11%2
297
November1st to 10thDay
14%16%26%23%17%5%
270
11th to 20thDay
6%18%27%31%13%5%
270
21st to endDay
7%11%26%29%22%5%
270
December1st to 10thDay
6%15%31%30%14%5%
270
11th to 20thDay
6%12%35%36%9%2
270
21st to endDay
12%16%30%31%10%1
297
January1st to 10thNight
8%7%28%34%20%3
760
11th to 20thNight
8%7%27%40%16%3
744
21st to endNight
8%6%27%40%16%3
792
February1st to 10thNight
8%432%41%11%2
720
11th to 20thNight
7%6%31%38%15%2
704
21st to endNight
6%10%29%42%13%1
592
March1st to 10thNight
8%9%31%39%11%2
720
11th to 20thNight
5%7%28%40%18%2
720
21st to endNight
9%11%30%36%13%1
792
April1st to 10thNight
12%12%23%39%13%1
689
11th to 20thNight
7%11%32%37%13%
533
21st to endNight
10%9%26%33%20%2
540
May1st to 10thNight
8%7%26%41%16%1
540
11th to 20thNight
7%422%37%27%3
531
21st to endNight
9%6%22%37%22%4
584
June1st to 10thNight
5%9%19%39%25%2
540
11th to 20thNight
5%10%21%43%21%
540
21st to endNight
1321%41%32%2
540
July1st to 10thNight
3314%35%41%4
525
11th to 20thNight
4311%47%32%3
522
21st to endNight
219%36%50%2
591
August1st to 10thNight
5%213%44%35%1
537
11th to 20thNight
3112%45%36%3
534
21st to endNight
4112%45%35%2
594
September1st to 10thNight
4314%40%34%5%
640
11th to 20thNight
5%5%14%39%32%6%
720
21st to endNight
7%415%32%35%7%
720
October1st to 10thNight
9%5%21%37%25%3
720
11th to 20thNight
6%418%42%25%4
720
21st to endNight
7%6%23%37%23%4
792
November1st to 10thNight
7%8%22%38%23%3
740
11th to 20thNight
9%5%25%41%16%4
760
21st to endNight
6%8%29%35%19%4
902
December1st to 10thNight
7%7%32%38%15%1
950
11th to 20thNight
10%7%29%41%11%1
950
21st to endNight
10%11%29%37%10%1
905
Page generated at 2024-01-13 07:37:55. Version ac07

Copyright 2024 Attilla Danko


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