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 2018-02-14.

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
40%
16611
21%
48841
12%
16566
48%
16566
28%
30801

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%
975
18%
2641
7%
970
36%
970
26%
1769
January16th to endNight
24%
1040
19%
2704
6%
1040
33%
1040
24%
1881
February1st to 15thNight
26%
948
14%
2470
5%
946
31%
946
23%
1751
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%
539
23%
1610
26%
536
77%
536
42%
872
August16th to endNight
72%
573
23%
1871
27%
573
75%
573
38%
994
September1st to 15thNight
63%
540
28%
1800
29%
540
67%
540
35%
991
September16th to endNight
59%
597
28%
1974
21%
597
68%
597
37%
1061
October1st to 15thNight
44%
720
25%
2160
17%
720
51%
720
33%
1282
October16th to endNight
38%
768
28%
2304
15%
768
49%
768
32%
1350
November1st to 15thNight
38%
760
26%
2420
15%
760
50%
760
31%
1388
November16th to endNight
30%
974
23%
2729
10%
974
41%
974
29%
1745
December1st to 15thNight
28%
975
16%
2730
6%
975
35%
975
22%
1901
December16th to endNight
22%
1040
16%
2912
4%
1040
32%
1040
18%
2158

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%
49235
Night
12%6%35%424446%45%
49027
TransparencyDay
42%6%12%23%13%1
48924
Night
38%5%11%25%16%2
48843
SeeingDay
13%6%26%29%17%5%
6408
Night
15%7%31%31%13%1
16614

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%9%37%6%345%5%6%36%
1624
16th to endDay
13%11%5%8%5%35%435%34%
1872
February1st to 15thDay
14%8%46%4345%5%7%35%
1694
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%
2340
16th to endDay
10%5%25%43446%7%45%
2330
September1st to 15thDay
12%425%324447%48%
2160
16th to endDay
10%414424449%49%
1971
October1st to 15thDay
15%6%33423335%48%
1800
16th to endDay
12%6%24423346%47%
1920
November1st to 15thDay
12%6%35%5%24445%46%
1767
16th to endDay
17%8%3432235%6%41%
1560
December1st to 15thDay
15%10%46%5%245%5%6%34%
1560
16th to endDay
16%10%48%434346%33%
1664
January1st to 15thNight
10%7%36%5%34446%41%
2641
16th to endNight
9%8%5%7%5%34446%39%
2704
February1st to 15thNight
14%10%47%5%23347%36%
2460
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%8%56%
1620
16th to endNight
8%31332345%8%55%
1871
September1st to 15thNight
11%423423346%53%
1800
16th to endNight
7%5%24223346%56%
1974
October1st to 15thNight
13%413423345%52%
2160
16th to endNight
13%5%1432234453%
2304
November1st to 15thNight
12%5%23313335%53%
2420
16th to endNight
16%6%24323446%45%
2729
December1st to 15thNight
14%9%36%5%2445%5%37%
2730
16th to endNight
17%11%47%5%34345%31%
2912

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
48%410%20%14%1
1625
16th to endDay
52%5%13%20%8%
1872
February1st to 15thDay
47%6%14%21%8%1
1695
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%
2326
16th to endDay
37%6%11%21%17%5%
2330
September1st to 15thDay
34%5%10%25%19%5%
2160
16th to endDay
32%5%13%31%15%2
1971
October1st to 15thDay
38%38%25%21%3
1800
16th to endDay
37%5%10%26%17%2
1920
November1st to 15thDay
39%49%22%21%2
1767
16th to endDay
44%413%24%13%
1560
December1st to 15thDay
49%5%13%20%9%
1560
16th to endDay
53%312%19%9%1
1664
January1st to 15thNight
42%412%24%14%
2641
16th to endNight
44%6%14%21%12%
2704
February1st to 15thNight
48%412%22%10%1
2470
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
23%7%14%32%18%2
1610
16th to endNight
26%5%13%24%21%7%
1871
September1st to 15thNight
31%38%26%22%7%
1800
16th to endNight
28%412%32%19%2
1974
October1st to 15thNight
33%49%23%22%5%
2160
16th to endNight
34%38%29%20%3
2304
November1st to 15thNight
33%411%24%20%5%
2420
16th to endNight
39%39%29%15%1
2729
December1st to 15thNight
46%5%13%22%10%
2730
16th to endNight
55%410%17%10%1
2912

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
17%8%49%18%6%
135
16th to endDay
19%9%44%23%2
144
February1st to 15thDay
17%21%37%20%3
130
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%30%9%
493
16th to endDay
11%213%33%28%11%
370
September1st to 15thDay
11%215%31%29%9%
315
16th to endDay
8%125%31%20%11%
198
October1st to 15thDay
19%5%34%22%12%4
135
16th to endDay
10%12%38%31%7%
144
November1st to 15thDay
9%5%39%22%15%8%
135
16th to endDay
28%18%30%20%2
135
December1st to 15thDay
14%18%40%19%42
135
16th to endDay
22%16%47%11%2
144
January1st to 15thNight
13%12%41%23%8%
975
16th to endNight
14%11%43%27%3
1040
February1st to 15thNight
18%10%37%29%2
950
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
539
16th to endNight
9%110%38%35%4
573
September1st to 15thNight
13%115%34%29%5%
540
16th to endNight
9%321%35%24%5%
597
October1st to 15thNight
17%430%28%17%2
720
16th to endNight
16%7%33%31%9%
768
November1st to 15thNight
15%8%35%30%10%
760
16th to endNight
19%9%37%25%7%
974
December1st to 15thNight
20%11%34%27%6%
975
16th to endNight
23%8%38%26%2
1040
Page generated at 2018-02-15 09:58:51. Version ac04

Copyright 2018 A. Danko


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