Morgan County Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morgan County Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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
37%
23423
20%
74726
11%
23376
47%
23376
22%
47323

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
20%
757
21%
2548
7%
757
37%
757
16%
1612
January11th to 20thNight
23%
735
19%
2386
7%
735
38%
735
16%
1604
January21st to endNight
19%
792
21%
2574
6%
792
36%
792
16%
1670
February1st to 10thNight
22%
720
18%
2340
8%
720
36%
720
16%
1514
February11th to 20thNight
15%
701
16%
2275
4%
700
30%
700
13%
1497
February21st to endNight
16%
592
21%
1764
7%
592
33%
592
16%
1223
March1st to 10thNight
21%
720
24%
1980
8%
720
37%
720
22%
1257
March11th to 20thNight
24%
720
21%
1980
9%
720
35%
720
20%
1308
March21st to endNight
21%
792
18%
2178
6%
792
32%
792
20%
1487
April1st to 10thNight
24%
720
17%
1810
5%
720
31%
720
21%
1278
April11th to 20thNight
33%
711
19%
1775
6%
711
39%
711
28%
1174
April21st to endNight
34%
684
21%
1764
7%
684
42%
684
25%
1178
May1st to 10thNight
40%
540
17%
1620
10%
540
46%
540
23%
1083
May11th to 20thNight
39%
478
16%
1539
10%
478
44%
478
21%
1036
May21st to endNight
52%
388
18%
1551
17%
388
58%
388
22%
910
June1st to 10thNight
53%
360
20%
1440
20%
360
62%
360
26%
804
June11th to 20thNight
52%
360
18%
1440
20%
360
57%
360
22%
857
June21st to endNight
53%
360
20%
1440
21%
360
62%
360
27%
799
July1st to 10thNight
59%
350
15%
1400
17%
350
62%
350
21%
850
July11th to 20thNight
71%
481
17%
1525
16%
481
73%
481
34%
883
July21st to endNight
64%
591
18%
1672
13%
558
68%
558
33%
1009
August1st to 10thNight
62%
537
17%
1600
11%
534
65%
534
29%
1021
August11th to 20thNight
63%
544
20%
1608
14%
544
65%
544
29%
1031
August21st to endNight
61%
792
20%
1980
12%
792
63%
792
35%
1284
September1st to 10thNight
56%
720
23%
1800
12%
720
60%
720
32%
1202
September11th to 20thNight
56%
720
30%
1839
20%
720
60%
720
38%
1130
September21st to endNight
46%
720
20%
2057
15%
720
53%
720
25%
1344
October1st to 10thNight
46%
720
20%
2160
17%
720
53%
720
27%
1373
October11th to 20thNight
42%
720
25%
2160
18%
720
54%
720
29%
1294
October21st to endNight
35%
792
27%
2376
15%
792
50%
792
28%
1438
November1st to 10thNight
38%
740
27%
2259
17%
740
50%
740
31%
1286
November11th to 20thNight
32%
760
24%
2575
13%
760
48%
760
21%
1538
November21st to endNight
31%
760
21%
2660
12%
760
45%
760
19%
1615
December1st to 10thNight
22%
760
18%
2660
6%
760
37%
760
15%
1726
December11th to 20thNight
27%
760
19%
3190
10%
759
40%
759
15%
1958
December21st to endNight
28%
826
12%
4801
9%
817
41%
817
10%
3050

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
14%6%35%5%35%5%6%8%39%
74662
Night
14%6%25%5%35%5%6%8%41%
75102
TransparencyDay
42%6%12%22%15%2
74375
Night
40%6%12%23%16%3
74908
SeeingDay
22%13%25%21%14%5%
13748
Night
20%12%25%30%13%1
23439

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
13%7%36%6%46%5%6%6%38%
1616
11th to 20thDay
15%7%47%5%46%5%6%8%33%
1647
21st to endDay
14%9%47%7%45%45%7%36%
1782
February1st to 10thDay
15%10%5%7%5%35%5%5%6%35%
1620
11th to 20thDay
14%9%36%7%445%5%7%37%
1573
21st to endDay
16%8%48%5%34446%37%
1490
March1st to 10thDay
13%6%36%43445%7%46%
1980
11th to 20thDay
16%8%26%5%445%5%7%38%
1980
21st to endDay
16%8%36%6%35%5%6%6%36%
2178
April1st to 10thDay
11%8%36%6%45%45%9%38%
2150
11th to 20thDay
14%6%35%6%45%5%5%7%42%
2134
21st to endDay
20%6%25%5%35%45%5%39%
2210
May1st to 10thDay
17%7%46%6%35%5%6%8%35%
2340
11th to 20thDay
21%5%25%6%46%5%5%7%35%
2354
21st to endDay
14%6%36%5%45%5%5%9%39%
2725
June1st to 10thDay
13%5%24435%6%7%10%41%
2520
11th to 20thDay
11%6%26%6%46%5%7%9%37%
2520
21st to endDay
10%325%5%46%6%7%10%42%
2520
July1st to 10thDay
9%5%35%7%45%5%7%9%41%
2520
11th to 20thDay
8%425%5%36%6%8%10%43%
2379
21st to endDay
10%6%26%6%47%6%6%9%37%
2547
August1st to 10thDay
10%5%25%7%45%7%7%11%35%
2327
11th to 20thDay
11%5%25%5%46%5%7%9%39%
2273
21st to endDay
11%426%5%35%5%6%8%44%
2376
September1st to 10thDay
17%6%244345%5%8%43%
2160
11th to 20thDay
12%5%25%5%2445%8%47%
2118
21st to endDay
18%7%25%4345%5%7%39%
1902
October1st to 10thDay
16%6%24425%45%7%45%
1800
11th to 20thDay
17%5%24435%5%5%7%44%
1800
21st to endDay
15%5%25%4335%5%6%46%
1980
November1st to 10thDay
11%5%23434448%51%
1818
11th to 20thDay
16%5%344245%6%7%45%
1601
21st to endDay
16%5%245%45%5%6%8%41%
1520
December1st to 10thDay
17%8%36%6%35%6%7%6%32%
1520
11th to 20thDay
15%6%26%6%45%5%5%7%38%
1910
21st to endDay
17%6%36%7%46%7%8%7%29%
2772
January1st to 10thNight
13%8%25%5%36%5%6%7%39%
2548
11th to 20thNight
17%8%35%5%35%5%6%8%34%
2386
21st to endNight
14%8%46%5%35%5%5%7%38%
2574
February1st to 10thNight
15%7%35%5%35%46%8%38%
2340
11th to 20thNight
15%8%45%5%45%5%6%6%36%
2273
21st to endNight
17%10%36%5%35%45%7%35%
1764
March1st to 10thNight
13%6%245%25%5%5%6%47%
1980
11th to 20thNight
17%6%25%5%3446%6%42%
1980
21st to endNight
15%7%46%5%4445%6%41%
2178
April1st to 10thNight
16%7%35%6%35%6%6%6%38%
1810
11th to 20thNight
13%5%35%5%345%6%8%43%
1775
21st to endNight
19%425%4345%6%7%42%
1764
May1st to 10thNight
18%5%36%5%26%5%5%8%38%
1620
11th to 20thNight
19%6%35%5%25%5%47%39%
1539
21st to endNight
13%5%245%35%6%7%10%41%
1550
June1st to 10thNight
12%4243345%7%9%47%
1440
11th to 20thNight
11%5%35%6%35%6%6%9%41%
1440
21st to endNight
9%335%435%6%7%12%43%
1440
July1st to 10thNight
10%5%25%5%46%5%6%10%42%
1440
11th to 20thNight
6%325%5%445%7%10%48%
1576
21st to endNight
9%4235%47%6%9%11%41%
1771
August1st to 10thNight
9%6%27%5%36%5%7%9%41%
1611
11th to 20thNight
10%5%36%5%35%6%5%9%44%
1608
21st to endNight
12%5%145%345%7%9%44%
1980
September1st to 10thNight
16%5%24425%45%7%46%
1800
11th to 20thNight
11%6%35%433447%51%
1839
21st to endNight
19%425%445%446%43%
2057
October1st to 10thNight
19%6%2443245%6%44%
2160
11th to 20thNight
15%41433445%7%49%
2160
21st to endNight
16%5%2442445%6%48%
2376
November1st to 10thNight
10%6%245%2445%7%52%
2259
11th to 20thNight
14%6%35%434447%46%
2575
21st to endNight
13%5%35%6%35%5%5%7%42%
2660
December1st to 10thNight
16%7%36%6%35%5%5%7%37%
2660
11th to 20thNight
16%6%25%5%35%5%6%7%39%
3285
21st to endNight
17%6%35%6%46%6%7%10%31%
4884

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
45%5%10%24%14%2
1617
11th to 20thDay
47%6%12%21%12%1
1647
21st to endDay
48%412%21%13%2
1782
February1st to 10thDay
50%313%21%10%2
1620
11th to 20thDay
47%412%23%12%2
1582
21st to endDay
49%411%20%13%3
1490
March1st to 10thDay
40%411%25%19%2
1980
11th to 20thDay
46%410%18%17%5%
1980
21st to endDay
48%5%10%19%15%3
2178
April1st to 10thDay
44%5%12%18%17%4
2150
11th to 20thDay
40%5%11%21%18%5%
2134
21st to endDay
46%5%9%21%15%3
2210
May1st to 10thDay
46%6%12%19%15%2
2340
11th to 20thDay
47%6%12%19%12%3
2358
21st to endDay
42%6%14%23%12%2
2725
June1st to 10thDay
36%8%14%24%16%2
2520
11th to 20thDay
41%9%15%20%14%2
2520
21st to endDay
35%7%15%26%15%1
2520
July1st to 10thDay
39%8%12%23%15%3
2450
11th to 20thDay
34%7%15%23%18%2
2307
21st to endDay
40%8%12%21%16%3
2405
August1st to 10thDay
40%8%16%24%12%
2314
11th to 20thDay
39%7%15%24%14%1
2273
21st to endDay
36%7%15%25%14%3
2376
September1st to 10thDay
40%6%12%19%20%4
2160
11th to 20thDay
36%5%9%28%20%3
2118
21st to endDay
45%410%21%19%2
1902
October1st to 10thDay
40%5%12%24%17%3
1800
11th to 20thDay
38%6%11%25%19%2
1800
21st to endDay
38%5%10%26%18%3
1980
November1st to 10thDay
34%413%25%21%4
1818
11th to 20thDay
39%5%11%21%21%3
1601
21st to endDay
41%413%28%13%1
1520
December1st to 10thDay
49%7%14%21%9%1
1520
11th to 20thDay
44%5%14%27%8%2
1906
21st to endDay
48%9%14%17%10%1
2772
January1st to 10thNight
42%6%11%23%15%3
2548
11th to 20thNight
47%6%14%21%11%2
2386
21st to endNight
44%5%10%26%13%2
2574
February1st to 10thNight
44%5%14%24%12%2
2340
11th to 20thNight
47%411%19%16%3
2275
21st to endNight
48%5%10%20%12%4
1764
March1st to 10thNight
38%5%11%27%17%2
1980
11th to 20thNight
42%5%12%22%17%3
1980
21st to endNight
44%6%11%20%15%4
2178
April1st to 10thNight
45%5%10%19%17%4
1810
11th to 20thNight
39%5%12%22%17%5%
1775
21st to endNight
40%6%11%25%14%4
1764
May1st to 10thNight
43%7%10%23%13%4
1620
11th to 20thNight
46%6%11%18%17%2
1540
21st to endNight
37%7%16%25%13%1
1551
June1st to 10thNight
33%7%11%28%18%3
1440
11th to 20thNight
38%8%14%26%12%2
1440
21st to endNight
33%7%14%28%17%2
1440
July1st to 10thNight
37%11%14%21%13%4
1400
11th to 20thNight
30%8%18%24%18%3
1525
21st to endNight
32%8%18%22%17%2
1672
August1st to 10thNight
37%8%16%23%15%1
1600
11th to 20thNight
38%7%14%22%18%1
1608
21st to endNight
35%6%15%25%16%3
1980
September1st to 10thNight
38%6%11%22%19%4
1800
11th to 20thNight
34%39%28%23%2
1839
21st to endNight
42%5%10%22%18%2
2057
October1st to 10thNight
41%411%25%17%2
2160
11th to 20thNight
35%410%27%21%2
2160
21st to endNight
37%310%27%21%2
2376
November1st to 10thNight
33%412%27%20%5%
2259
11th to 20thNight
39%48%25%19%5%
2575
21st to endNight
40%5%12%24%17%2
2660
December1st to 10thNight
46%5%12%25%11%1
2660
11th to 20thNight
43%5%12%23%15%2
3288
21st to endNight
45%9%17%18%10%
4884

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
40%21%26%9%4
227
11th to 20thDay
34%23%28%13%2
249
21st to endDay
34%30%23%10%3
264
February1st to 10thDay
36%25%27%8%3
240
11th to 20thDay
40%24%30%5%
240
21st to endDay
36%20%26%17%2
332
March1st to 10thDay
31%22%25%19%4
420
11th to 20thDay
29%24%25%15%5%2
420
21st to endDay
28%22%28%15%6%2
462
April1st to 10thDay
27%23%24%18%7%1
420
11th to 20thDay
21%17%29%18%10%5%
412
21st to endDay
34%14%26%15%8%2
420
May1st to 10thDay
27%15%29%15%9%4
423
11th to 20thDay
24%16%27%17%12%4
447
21st to endDay
19%9%23%22%17%9%
485
June1st to 10thDay
17%10%30%20%18%5%
450
11th to 20thDay
16%9%30%23%16%5%
450
21st to endDay
13%8%28%28%15%7%
450
July1st to 10thDay
14%5%20%28%21%13%
445
11th to 20thDay
6%323%30%25%13%
444
21st to endDay
15%419%34%19%9%
488
August1st to 10thDay
15%5%18%26%23%13%
446
11th to 20thDay
14%320%29%23%11%
439
21st to endDay
11%422%26%24%13%
495
September1st to 10thDay
19%7%18%21%23%11%
450
11th to 20thDay
16%5%17%28%25%9%
450
21st to endDay
24%9%23%22%17%5%
450
October1st to 10thDay
23%5%20%28%19%5%
450
11th to 20thDay
22%13%24%25%14%2
450
21st to endDay
22%15%30%21%10%2
495
November1st to 10thDay
20%10%28%24%14%4
436
11th to 20thDay
25%16%27%22%9%1
261
21st to endDay
26%19%29%18%7%1
180
December1st to 10thDay
32%20%28%15%5%1
180
11th to 20thDay
29%21%24%21%5%
180
21st to endDay
27%18%28%17%10%
198
January1st to 10thNight
21%21%33%22%4
760
11th to 20thNight
26%14%30%27%3
735
21st to endNight
22%22%31%23%2
792
February1st to 10thNight
23%20%29%26%2
720
11th to 20thNight
26%25%29%18%2
703
21st to endNight
29%18%32%19%3
592
March1st to 10thNight
24%18%33%22%4
720
11th to 20thNight
27%18%27%22%6%
720
21st to endNight
21%16%35%21%5%1
792
April1st to 10thNight
25%19%30%20%6%
720
11th to 20thNight
19%13%31%27%9%1
711
21st to endNight
23%13%25%32%7%
684
May1st to 10thNight
23%7%24%31%14%1
540
11th to 20thNight
23%8%24%33%12%
478
21st to endNight
16%5%19%37%21%2
389
June1st to 10thNight
12%425%33%26%
360
11th to 20thNight
13%6%19%38%23%2
360
21st to endNight
10%223%44%20%1
360
July1st to 10thNight
13%314%35%32%3
350
11th to 20thNight
8%39%41%35%5%
481
21st to endNight
10%216%39%30%3
591
August1st to 10thNight
12%213%40%29%3
537
11th to 20thNight
12%310%39%31%5%
544
21st to endNight
13%314%36%30%4
792
September1st to 10thNight
18%315%33%27%4
720
11th to 20thNight
14%5%17%33%28%4
720
21st to endNight
20%6%18%33%20%3
720
October1st to 10thNight
22%6%18%30%20%3
720
11th to 20thNight
18%12%23%33%13%1
720
21st to endNight
21%13%27%29%10%
792
November1st to 10thNight
15%10%29%33%12%1
740
11th to 20thNight
21%17%24%29%8%1
760
21st to endNight
19%16%27%31%7%
760
December1st to 10thNight
23%17%29%24%7%
760
11th to 20thNight
22%14%31%30%4
760
21st to endNight
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836
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