Stokesville Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stokesville Observatory clear sky chart from 2005-11-06 to 2024-02-20.

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
43%
23868
21%
79936
13%
23778
53%
23778
24%
49251

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
25%
752
25%
4005
10%
737
43%
737
14%
2142
January11th to 20thNight
27%
758
28%
3963
11%
740
44%
740
14%
2234
January21st to endNight
23%
827
15%
4432
9%
814
41%
814
14%
2675
February1st to 10thNight
28%
760
21%
2470
11%
760
43%
760
23%
1521
February11th to 20thNight
18%
739
19%
2397
5%
738
36%
738
18%
1560
February21st to endNight
22%
592
25%
1713
10%
592
39%
592
22%
1118
March1st to 10thNight
29%
720
25%
1980
11%
720
43%
720
30%
1216
March11th to 20thNight
28%
720
20%
1980
9%
720
38%
720
22%
1315
March21st to endNight
33%
792
18%
2178
9%
792
40%
792
24%
1451
April1st to 10thNight
30%
720
20%
1862
7%
720
39%
720
26%
1240
April11th to 20thNight
39%
711
21%
1775
9%
711
45%
711
34%
1129
April21st to endNight
41%
650
22%
1730
10%
650
48%
650
30%
1133
May1st to 10thNight
44%
540
16%
1620
10%
540
49%
540
25%
1059
May11th to 20thNight
46%
531
13%
1592
8%
531
50%
531
22%
1115
May21st to endNight
60%
507
16%
1670
14%
507
64%
507
26%
1066
June1st to 10thNight
66%
360
18%
1440
22%
360
69%
360
26%
818
June11th to 20thNight
65%
360
15%
1440
18%
360
69%
360
23%
862
June21st to endNight
66%
360
20%
1440
19%
360
72%
360
26%
797
July1st to 10thNight
68%
514
14%
1564
14%
514
70%
514
27%
1028
July11th to 20thNight
77%
522
16%
1566
15%
522
78%
522
34%
929
July21st to endNight
70%
591
17%
1672
14%
558
71%
558
32%
1048
August1st to 10thNight
69%
537
16%
1600
15%
534
70%
534
28%
1057
August11th to 20thNight
65%
534
19%
1598
16%
534
67%
534
26%
1062
August21st to endNight
62%
776
17%
1964
11%
776
63%
776
28%
1365
September1st to 10thNight
64%
720
23%
1800
15%
720
66%
720
34%
1175
September11th to 20thNight
61%
720
26%
1921
21%
720
63%
720
32%
1231
September21st to endNight
48%
720
21%
2013
16%
720
53%
720
25%
1376
October1st to 10thNight
52%
720
20%
2160
20%
720
56%
720
27%
1376
October11th to 20thNight
44%
720
26%
2160
18%
720
56%
720
30%
1289
October21st to endNight
45%
792
29%
2376
21%
792
57%
792
31%
1411
November1st to 10thNight
47%
740
29%
2221
21%
740
57%
740
32%
1316
November11th to 20thNight
40%
760
27%
2493
18%
760
54%
760
29%
1415
November21st to endNight
40%
760
23%
2660
17%
760
52%
760
26%
1537
December1st to 10thNight
31%
760
21%
2660
11%
760
46%
760
20%
1679
December11th to 20thNight
35%
759
23%
3177
13%
759
50%
759
20%
1832
December21st to endNight
32%
824
15%
4644
11%
817
47%
817
13%
2674

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%6%35%6%35%5%6%8%41%
78443
Night
13%6%25%5%345%6%7%45%
80725
TransparencyDay
41%7%11%21%16%4
78164
Night
38%6%12%23%17%4
80523
SeeingDay
17%12%24%25%16%7%
13951
Night
16%8%26%33%15%2
23905

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%6%35%7%445%45%44%
2836
11th to 20thDay
13%9%37%8%445%5%5%38%
2840
21st to endDay
14%9%47%6%3445%5%40%
3124
February1st to 10thDay
11%7%36%6%35%5%5%7%41%
1710
11th to 20thDay
13%7%46%4346%5%6%42%
1654
21st to endDay
14%7%25%5%35%5%6%7%41%
1540
March1st to 10thDay
11%5%345%3445%6%50%
1980
11th to 20thDay
13%8%346%35%5%5%7%41%
1980
21st to endDay
13%8%36%5%35%5%6%6%39%
2178
April1st to 10thDay
9%5%35%6%35%5%6%7%46%
2096
11th to 20thDay
13%5%345%345%5%7%47%
2134
21st to endDay
17%6%25%5%45%45%6%41%
2244
May1st to 10thDay
14%6%36%6%46%5%5%8%35%
2340
11th to 20thDay
19%7%36%6%35%46%7%34%
2301
21st to endDay
13%7%36%6%46%5%7%8%36%
2601
June1st to 10thDay
11%425%5%46%5%6%9%42%
2520
11th to 20thDay
10%5%36%6%47%7%7%10%36%
2520
21st to endDay
8%425%7%46%6%7%11%41%
2520
July1st to 10thDay
10%6%36%7%46%7%7%9%35%
2344
11th to 20thDay
5%426%6%5%7%7%9%12%37%
2340
21st to endDay
10%6%37%7%47%7%8%10%32%
2547
August1st to 10thDay
9%5%37%8%5%6%7%8%11%31%
2327
11th to 20thDay
13%5%27%6%5%7%6%8%8%34%
2299
21st to endDay
11%5%25%6%46%6%7%11%36%
2376
September1st to 10thDay
12%6%26%5%35%5%5%6%44%
2160
11th to 20thDay
13%6%245%35%5%5%7%44%
2035
21st to endDay
22%425%435%5%6%7%38%
1946
October1st to 10thDay
16%5%25%4345%5%7%45%
1800
11th to 20thDay
16%425%435%45%6%48%
1800
21st to endDay
14%5%245%245%46%51%
1980
November1st to 10thDay
10%6%2342435%6%55%
1857
11th to 20thDay
13%425%42446%6%50%
1682
21st to endDay
13%5%245%3335%7%50%
1520
December1st to 10thDay
14%6%37%5%36%5%5%7%39%
1520
11th to 20thDay
14%4145%33347%53%
1910
21st to endDay
16%6%36%5%45%6%6%7%35%
2882
January1st to 10thNight
11%7%245%35%6%6%7%46%
4109
11th to 20thNight
14%8%245%3435%5%45%
4120
21st to endNight
17%8%35%43445%5%42%
4532
February1st to 10thNight
11%7%25%435%5%5%8%44%
2470
11th to 20thNight
16%7%35%5%35%45%7%41%
2397
21st to endNight
14%7%25%5%345%6%8%42%
1713
March1st to 10thNight
10%425%4335%5%6%52%
1980
11th to 20thNight
15%5%35%5%3446%7%42%
1980
21st to endNight
15%7%35%5%3445%7%43%
2178
April1st to 10thNight
13%6%345%35%5%6%6%45%
1862
11th to 20thNight
11%324435%47%9%47%
1775
21st to endNight
16%4245%345%6%7%45%
1730
May1st to 10thNight
15%5%245%45%46%8%42%
1620
11th to 20thNight
19%6%36%5%345%5%8%38%
1592
21st to endNight
14%5%15%4346%6%10%42%
1669
June1st to 10thNight
10%4245%2448%13%44%
1440
11th to 20thNight
11%5%15%435%6%7%9%44%
1440
21st to endNight
8%325%426%6%7%10%47%
1440
July1st to 10thNight
9%5%26%6%35%47%9%42%
1609
11th to 20thNight
5%3245%36%7%8%12%46%
1620
21st to endNight
7%435%6%35%5%7%12%41%
1771
August1st to 10thNight
10%5%26%6%35%6%7%9%41%
1611
11th to 20thNight
11%6%36%6%346%7%7%42%
1598
21st to endNight
10%5%36%7%446%7%10%38%
1964
September1st to 10thNight
12%5%25%4345%47%49%
1800
11th to 20thNight
14%5%25%43445%7%46%
1921
21st to endNight
21%6%2442345%6%42%
2013
October1st to 10thNight
15%6%245%35%446%46%
2160
11th to 20thNight
13%5%244245%46%50%
2160
21st to endNight
14%3245%2445%6%51%
2376
November1st to 10thNight
11%6%34424445%54%
2221
11th to 20thNight
12%5%25%424447%51%
2493
21st to endNight
14%4244245%5%6%50%
2660
December1st to 10thNight
14%6%36%5%35%5%5%6%43%
2660
11th to 20thNight
13%6%35%435%446%47%
3285
21st to endNight
16%425%6%35%5%7%9%38%
4756

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
42%48%22%18%6%
2837
11th to 20thDay
47%48%17%18%7%
2840
21st to endDay
47%47%21%18%3
3124
February1st to 10thDay
43%5%10%21%17%4
1710
11th to 20thDay
42%5%11%19%18%5%
1663
21st to endDay
42%6%11%17%18%6%
1540
March1st to 10thDay
37%411%22%22%5%
1980
11th to 20thDay
43%7%10%18%16%6%
1980
21st to endDay
46%6%10%20%13%6%
2178
April1st to 10thDay
36%7%12%20%19%8%
2096
11th to 20thDay
37%6%11%20%21%5%
2134
21st to endDay
43%7%11%21%13%5%
2244
May1st to 10thDay
47%8%11%19%12%3
2340
11th to 20thDay
49%8%13%19%9%2
2305
21st to endDay
45%8%14%23%10%1
2601
June1st to 10thDay
39%8%14%24%15%1
2520
11th to 20thDay
41%10%15%19%14%2
2520
21st to endDay
37%9%15%25%12%1
2520
July1st to 10thDay
43%10%12%19%14%3
2279
11th to 20thDay
36%11%16%24%11%2
2271
21st to endDay
43%10%12%20%13%1
2405
August1st to 10thDay
44%10%16%21%9%1
2314
11th to 20thDay
44%9%13%21%11%1
2299
21st to endDay
41%10%15%21%10%3
2376
September1st to 10thDay
40%7%13%18%18%4
2160
11th to 20thDay
40%6%8%24%19%4
2035
21st to endDay
45%7%9%19%18%3
1946
October1st to 10thDay
40%6%9%25%16%5%
1800
11th to 20thDay
37%49%25%20%4
1800
21st to endDay
36%49%24%21%6%
1980
November1st to 10thDay
32%49%24%26%5%
1857
11th to 20thDay
35%5%9%20%22%9%
1682
21st to endDay
36%410%24%23%3
1520
December1st to 10thDay
44%6%11%21%15%3
1520
11th to 20thDay
33%49%27%20%7%
1906
21st to endDay
45%6%13%22%12%2
2882
January1st to 10thNight
37%5%11%21%22%4
4109
11th to 20thNight
41%48%22%19%6%
4120
21st to endNight
44%47%24%17%4
4532
February1st to 10thNight
38%6%12%25%17%2
2470
11th to 20thNight
44%5%8%19%17%6%
2399
21st to endNight
41%6%12%21%14%6%
1713
March1st to 10thNight
33%6%10%26%19%5%
1980
11th to 20thNight
41%6%10%21%18%4
1980
21st to endNight
40%7%12%19%16%5%
2178
April1st to 10thNight
39%7%11%20%19%5%
1862
11th to 20thNight
33%6%16%20%20%5%
1775
21st to endNight
38%6%13%25%15%3
1730
May1st to 10thNight
40%8%15%21%12%4
1620
11th to 20thNight
45%9%13%21%11%1
1593
21st to endNight
38%8%18%26%9%1
1670
June1st to 10thNight
33%9%16%28%14%
1440
11th to 20thNight
35%10%17%22%13%2
1440
21st to endNight
30%10%18%22%17%2
1440
July1st to 10thNight
37%11%15%22%13%3
1564
11th to 20thNight
28%10%21%26%13%1
1566
21st to endNight
34%8%20%25%13%
1672
August1st to 10thNight
37%10%18%23%11%1
1600
11th to 20thNight
40%9%13%25%12%1
1598
21st to endNight
41%9%16%23%9%3
1964
September1st to 10thNight
35%8%15%21%18%4
1800
11th to 20thNight
38%5%9%27%17%3
1921
21st to endNight
44%6%9%20%18%2
2013
October1st to 10thNight
40%5%10%25%17%3
2160
11th to 20thNight
35%5%10%26%21%4
2160
21st to endNight
34%5%10%22%25%4
2376
November1st to 10thNight
35%48%22%24%7%
2221
11th to 20thNight
34%49%23%25%6%
2493
21st to endNight
35%5%10%24%21%5%
2660
December1st to 10thNight
43%5%10%24%14%4
2660
11th to 20thNight
38%410%21%20%6%
3288
21st to endNight
40%7%13%21%17%2
4756

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
21%29%29%17%5%1
270
11th to 20thDay
25%29%29%16%2
270
21st to endDay
24%25%32%16%2
297
February1st to 10thDay
21%25%33%16%4
270
11th to 20thDay
31%26%34%8%1
267
21st to endDay
26%19%34%17%4
300
March1st to 10thDay
17%24%32%22%5%
420
11th to 20thDay
20%22%32%18%6%2
420
21st to endDay
20%17%33%22%7%1
462
April1st to 10thDay
20%21%25%22%10%1
420
11th to 20thDay
17%14%27%24%14%4
412
21st to endDay
24%13%28%22%9%3
420
May1st to 10thDay
20%16%28%22%10%4
423
11th to 20thDay
22%9%27%23%14%5%
447
21st to endDay
17%5%19%26%22%10%
485
June1st to 10thDay
14%324%27%23%8%
450
11th to 20thDay
13%8%20%29%18%12%
450
21st to endDay
8%425%35%22%6%
450
July1st to 10thDay
12%315%25%31%13%
445
11th to 20thDay
3215%33%32%15%
444
21st to endDay
12%214%33%25%14%
488
August1st to 10thDay
11%5%14%28%24%17%
446
11th to 20thDay
14%315%26%27%15%
439
21st to endDay
11%212%29%28%18%
495
September1st to 10thDay
16%5%15%24%23%17%
450
11th to 20thDay
15%315%26%30%12%
450
21st to endDay
25%8%18%25%19%6%
450
October1st to 10thDay
19%6%19%27%24%6%
450
11th to 20thDay
14%12%27%29%17%2
450
21st to endDay
17%12%30%28%10%2
495
November1st to 10thDay
17%9%28%30%14%3
455
11th to 20thDay
19%16%30%23%11%1
290
21st to endDay
18%17%33%22%9%1
180
December1st to 10thDay
19%19%33%23%5%1
180
11th to 20thDay
21%19%29%22%8%1
180
21st to endDay
19%20%34%16%10%1
231
January1st to 10thNight
17%17%36%26%4
760
11th to 20thNight
19%15%33%29%4
760
21st to endNight
17%13%41%27%3
836
February1st to 10thNight
15%14%38%30%4
760
11th to 20thNight
24%15%38%22%1
742
21st to endNight
21%14%38%24%3
592
March1st to 10thNight
15%13%38%30%4
720
11th to 20thNight
20%15%32%25%8%1
720
21st to endNight
20%10%32%30%7%1
792
April1st to 10thNight
18%15%33%28%7%
720
11th to 20thNight
14%10%33%30%12%1
711
21st to endNight
19%6%28%36%9%1
650
May1st to 10thNight
16%7%25%35%16%1
540
11th to 20thNight
20%423%34%16%2
531
21st to endNight
16%214%38%29%2
509
June1st to 10thNight
11%116%48%23%2
360
11th to 20thNight
11%314%45%26%2
360
21st to endNight
9%117%46%25%2
360
July1st to 10thNight
13%28%36%36%5%
514
11th to 20thNight
6%17%38%41%7%
522
21st to endNight
8%210%40%36%5%
591
August1st to 10thNight
12%18%42%32%4
537
11th to 20thNight
12%210%37%34%5%
534
21st to endNight
12%213%33%35%5%
776
September1st to 10thNight
14%111%35%31%8%
720
11th to 20thNight
16%211%34%31%6%
720
21st to endNight
23%317%33%22%2
720
October1st to 10thNight
18%5%18%32%23%4
720
11th to 20thNight
16%8%28%32%16%1
720
21st to endNight
17%9%24%36%12%2
792
November1st to 10thNight
15%6%26%37%13%2
740
11th to 20thNight
16%11%28%35%10%1
760
21st to endNight
17%11%29%34%8%1
760
December1st to 10thNight
18%11%33%31%6%
760
11th to 20thNight
14%9%35%36%6%
760
21st to endNight
18%12%32%35%4
836
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