Truman State University Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Truman State University Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
40%
15817
20%
46533
12%
15772
48%
15772
28%
29428

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 15thNight
27%
900
19%
2437
7%
895
36%
895
26%
1626
January16th to endNight
24%
960
19%
2496
6%
960
32%
960
24%
1744
February1st to 15thNight
26%
878
14%
2288
5%
876
31%
876
23%
1619
February16th to endNight
25%
684
23%
1946
6%
684
37%
684
28%
1248
March1st to 15thNight
30%
567
20%
2007
12%
567
40%
567
22%
1251
March16th to endNight
29%
576
12%
2097
9%
576
35%
576
14%
1483
April1st to 15thNight
34%
539
19%
1797
12%
539
45%
539
25%
1085
April16th to endNight
35%
540
19%
1790
14%
540
45%
540
21%
1184
May1st to 15thNight
40%
539
18%
1586
13%
539
47%
539
25%
1067
May16th to endNight
47%
563
21%
1497
12%
561
54%
561
32%
964
June1st to 15thNight
60%
540
18%
1440
11%
540
63%
540
38%
872
June16th to endNight
58%
540
21%
1440
11%
540
61%
540
39%
862
July1st to 15thNight
67%
510
19%
1360
12%
510
70%
510
41%
809
July16th to endNight
73%
564
22%
1556
20%
531
74%
531
44%
833
August1st to 15thNight
75%
527
23%
1575
25%
524
76%
524
42%
858
August16th to endNight
72%
525
21%
1714
25%
525
74%
525
37%
925
September1st to 15thNight
61%
495
29%
1650
30%
495
66%
495
34%
927
September16th to endNight
59%
547
27%
1809
20%
547
67%
547
37%
981
October1st to 15thNight
46%
660
27%
1980
19%
660
53%
660
35%
1153
October16th to endNight
37%
704
26%
2112
13%
704
48%
704
31%
1250
November1st to 15thNight
39%
700
27%
2229
15%
700
52%
700
33%
1246
November16th to endNight
30%
899
20%
2519
9%
899
39%
899
27%
1649
December1st to 15thNight
27%
900
16%
2520
7%
900
34%
900
21%
1795
December16th to endNight
22%
960
16%
2688
4%
960
32%
960
17%
1997

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%7%35%5%3445%7%40%
47439
Night
12%6%35%424446%45%
46719
TransparencyDay
42%6%12%23%13%1
47128
Night
39%5%12%24%16%2
46535
SeeingDay
13%6%25%30%17%5%
5803
Night
15%7%30%31%13%1
15820

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 15thDay
11%10%47%6%345%5%5%37%
1498
16th to endDay
14%11%5%8%435%435%33%
1728
February1st to 15thDay
14%8%46%4345%5%8%35%
1575
16th to endDay
13%9%37%5%2435%5%38%
1525
March1st to 15thDay
13%11%36%5%245%46%35%
1962
16th to endDay
16%10%48%5%35%437%29%
2125
April1st to 15thDay
17%9%36%5%2444438%
2151
16th to endDay
21%8%35%5%24445%34%
2168
May1st to 15thDay
17%7%36%5%345%5%6%32%
2363
16th to endDay
13%5%25%5%46%5%5%7%36%
2617
June1st to 15thDay
8%6%25%6%35%5%5%8%41%
2520
16th to endDay
6%4245%35%5%6%9%44%
2520
July1st to 15thDay
7%3245%35%6%7%9%44%
2520
16th to endDay
6%2245%35%6%7%10%45%
2502
August1st to 15thDay
7%4245%45%6%6%10%42%
2289
16th to endDay
10%5%25%42446%7%44%
2135
September1st to 15thDay
13%425%324447%46%
1980
16th to endDay
10%413424449%50%
1807
October1st to 15thDay
14%6%33323335%50%
1650
16th to endDay
13%6%24423346%47%
1760
November1st to 15thDay
11%6%345%14445%48%
1628
16th to endDay
18%8%4432335%6%39%
1440
December1st to 15thDay
16%11%46%5%245%5%5%32%
1440
16th to endDay
16%10%5%8%434346%33%
1536
January1st to 15thNight
10%7%35%5%345%46%41%
2437
16th to endNight
9%8%5%7%6%34446%39%
2496
February1st to 15thNight
13%10%47%5%23347%36%
2278
16th to endNight
12%8%35%413346%45%
1946
March1st to 15thNight
13%7%35%424445%44%
2007
16th to endNight
18%10%35%5%35%346%31%
2097
April1st to 15thNight
12%7%2442435%6%46%
1797
16th to endNight
18%8%25%433345%39%
1790
May1st to 15thNight
11%6%36%5%35%5%6%6%39%
1586
16th to endNight
10%5%2442445%7%45%
1496
June1st to 15thNight
6%324425%46%9%50%
1440
16th to endNight
5%413435%5%6%7%51%
1440
July1st to 15thNight
6%2243245%5%10%51%
1440
16th to endNight
431332446%9%55%
1663
August1st to 15thNight
432343445%9%56%
1585
16th to endNight
8%31332345%8%54%
1714
September1st to 15thNight
12%423423346%52%
1650
16th to endNight
8%5%24223346%56%
1809
October1st to 15thNight
13%413423345%53%
1980
16th to endNight
14%5%2431234452%
2112
November1st to 15thNight
11%5%23313335%55%
2229
16th to endNight
17%7%34323446%43%
2519
December1st to 15thNight
15%10%36%5%2445%5%35%
2520
16th to endNight
18%11%47%5%35%345%31%
2688

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 15thDay
47%411%20%14%1
1499
16th to endDay
52%5%13%19%7%
1728
February1st to 15thDay
46%6%14%22%8%1
1576
16th to endDay
47%412%21%13%
1525
March1st to 15thDay
47%7%12%22%8%1
1962
16th to endDay
55%5%11%19%7%
2127
April1st to 15thDay
48%5%8%24%12%
2151
16th to endDay
52%5%10%19%11%
2168
May1st to 15thDay
50%7%10%21%9%
2363
16th to endDay
45%8%11%22%11%1
2621
June1st to 15thDay
38%7%13%24%13%1
2520
16th to endDay
33%8%14%26%15%2
2520
July1st to 15thDay
34%7%14%26%13%2
2371
16th to endDay
31%7%14%28%16%1
2346
August1st to 15thDay
33%9%14%24%16%
2275
16th to endDay
37%6%11%22%16%5%
2135
September1st to 15thDay
36%5%10%23%18%5%
1980
16th to endDay
32%412%31%16%2
1807
October1st to 15thDay
36%38%26%22%3
1650
16th to endDay
38%5%11%26%16%2
1760
November1st to 15thDay
37%410%22%22%2
1628
16th to endDay
45%414%23%12%
1440
December1st to 15thDay
52%5%13%20%8%
1440
16th to endDay
52%313%19%9%1
1536
January1st to 15thNight
42%412%24%15%
2437
16th to endNight
44%6%14%21%12%
2496
February1st to 15thNight
48%413%22%10%1
2288
16th to endNight
39%5%12%25%16%1
1946
March1st to 15thNight
41%5%12%25%13%2
2007
16th to endNight
53%6%11%18%8%1
2097
April1st to 15thNight
38%410%25%17%2
1797
16th to endNight
46%410%21%14%2
1790
May1st to 15thNight
42%7%13%22%14%
1587
16th to endNight
36%7%13%24%16%2
1498
June1st to 15thNight
29%7%15%27%18%1
1440
16th to endNight
28%7%13%26%20%3
1440
July1st to 15thNight
28%6%12%30%17%5%
1360
16th to endNight
24%5%15%32%20%2
1556
August1st to 15thNight
24%7%14%32%18%2
1575
16th to endNight
27%5%13%23%21%8%
1714
September1st to 15thNight
33%37%26%21%7%
1650
16th to endNight
28%411%32%19%2
1809
October1st to 15thNight
32%49%24%23%5%
1980
16th to endNight
35%38%29%18%3
2112
November1st to 15thNight
31%311%25%21%5%
2229
16th to endNight
41%49%28%14%1
2519
December1st to 15thNight
49%5%13%22%9%
2520
16th to endNight
55%410%17%10%1
2688

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 15thDay
20%5%51%17%5%
90
16th to endDay
23%10%40%20%4
96
February1st to 15thDay
14%21%35%24%4
90
16th to endDay
11%20%33%20%11%2
81
March1st to 15thDay
20%15%47%15%1
90
16th to endDay
32%14%29%18%31
111
April1st to 15thDay
17%11%34%25%9%
270
16th to endDay
25%6%30%26%8%2
278
May1st to 15thDay
19%9%35%22%10%1
468
16th to endDay
17%8%28%28%12%4
517
June1st to 15thDay
9%5%21%37%20%5%
495
16th to endDay
9%430%31%18%5%
495
July1st to 15thDay
9%217%38%22%8%
475
16th to endDay
5%115%39%31%6%
515
August1st to 15thDay
7%112%38%31%9%
474
16th to endDay
13%210%33%29%10%
303
September1st to 15thDay
13%315%34%26%6%
255
16th to endDay
6%228%26%22%14%
148
October1st to 15thDay
14%430%30%14%6%
90
16th to endDay
12%9%35%35%7%
96
November1st to 15thDay
36%33%26%17%12%
90
16th to endDay
36%22%24%13%21
90
December1st to 15thDay
17%20%34%20%34
90
16th to endDay
22%20%43%9%3
96
January1st to 15thNight
13%13%41%23%8%
900
16th to endNight
14%11%43%27%3
960
February1st to 15thNight
18%10%38%29%2
880
16th to endNight
18%8%42%25%5%
684
March1st to 15thNight
19%9%34%29%7%
567
16th to endNight
24%8%32%27%7%
576
April1st to 15thNight
16%10%36%29%7%
539
16th to endNight
21%7%29%32%8%
540
May1st to 15thNight
14%5%31%36%10%
540
16th to endNight
12%5%29%34%17%1
563
June1st to 15thNight
7%220%46%21%1
540
16th to endNight
6%226%41%21%1
540
July1st to 15thNight
7%115%41%30%3
510
16th to endNight
6%13%42%34%3
564
August1st to 15thNight
5%10%44%35%3
527
16th to endNight
10%110%38%35%4
525
September1st to 15thNight
14%116%34%28%5%
495
16th to endNight
9%322%34%24%5%
547
October1st to 15thNight
15%330%30%17%2
660
16th to endNight
17%7%33%30%9%
704
November1st to 15thNight
14%8%34%31%11%
700
16th to endNight
20%10%35%25%8%
899
December1st to 15thNight
21%11%34%27%5%
900
16th to endNight
23%8%37%26%3
960
Page generated at 2017-08-13 13:16:14. Version ac04

Copyright 2017 A. Danko


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