Wartburg College Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wartburg College Observatory clear sky chart from 2005-11-05 to 2017-03-22.

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
33%
15509
16%
45301
9%
15462
39%
15462
25%
29886

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
12%
2506
5%
895
33%
895
21%
1779
January16th to endNight
21%
960
12%
2511
4%
960
26%
960
19%
1862
February1st to 15thNight
21%
879
12%
2288
3%
875
26%
875
20%
1684
February16th to endNight
28%
708
17%
1970
6%
708
35%
708
24%
1312
March1st to 15thNight
29%
594
17%
2034
12%
594
36%
594
23%
1268
March16th to endNight
24%
549
11%
1988
7%
549
31%
549
16%
1378
April1st to 15thNight
25%
494
16%
1647
11%
494
34%
494
22%
1066
April16th to endNight
27%
495
14%
1598
10%
495
35%
495
23%
1066
May1st to 15thNight
29%
495
15%
1389
9%
495
35%
495
24%
980
May16th to endNight
34%
515
12%
1370
4%
513
40%
513
30%
893
June1st to 15thNight
38%
495
10%
1320
4%
495
40%
495
31%
861
June16th to endNight
44%
495
13%
1320
5%
495
46%
495
37%
816
July1st to 15thNight
58%
465
14%
1240
8%
465
60%
465
43%
716
July16th to endNight
58%
522
19%
1349
14%
489
64%
489
44%
764
August1st to 15thNight
62%
494
22%
1475
21%
491
66%
491
40%
825
August16th to endNight
57%
525
18%
1688
20%
525
61%
525
34%
970
September1st to 15thNight
54%
495
26%
1650
25%
495
61%
495
33%
913
September16th to endNight
49%
551
22%
1805
16%
551
57%
551
35%
1009
October1st to 15thNight
38%
660
23%
1980
15%
660
45%
660
31%
1195
October16th to endNight
33%
704
18%
2115
10%
704
40%
704
24%
1375
November1st to 15thNight
31%
754
22%
2330
13%
754
40%
754
28%
1413
November16th to endNight
23%
900
14%
2520
6%
900
29%
900
24%
1714
December1st to 15thNight
19%
900
9%
2520
3%
900
25%
900
16%
1903
December16th to endNight
16%
960
10%
2688
3%
960
23%
960
13%
2124

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%7%36%5%2445%7%37%
45589
Night
13%7%35%424446%41%
45474
Cloud CoverDay
27%6%25%423346%32%
45600
Night
25%6%25%423345%36%
45478
Cloud CoverDay
14%7%36%5%3445%7%37%
45598
Night
13%7%35%424446%41%
45478
TransparencyDay
45%6%13%22%10%1
45280
Night
42%5%13%23%13%1
45301
SeeingDay
16%7%27%27%16%4
5235
Night
16%7%31%31%12%1
15510

By Month

Percentage Cloud Cover NE (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
9%11%6%9%7%45%5%37%28%
1432
16th to endDay
14%13%5%10%6%35%5%5%6%22%
1710
February1st to 15thDay
11%12%6%7%6%345%36%30%
1575
16th to endDay
14%9%46%5%35%45%6%33%
1503
March1st to 15thDay
15%9%37%42435%8%34%
1927
16th to endDay
16%10%37%5%34447%31%
2032
April1st to 15thDay
20%8%35%5%23447%33%
1971
16th to endDay
25%9%25%6%23345%30%
2030
May1st to 15thDay
21%8%35%5%345%5%7%28%
2231
16th to endDay
16%5%35%5%3445%7%38%
2393
June1st to 15thDay
16%5%26%425%5%5%8%36%
2310
16th to endDay
10%5%25%5%2445%8%43%
2310
July1st to 15thDay
8%5%245%345%6%9%46%
2310
16th to endDay
7%4245%25%6%7%9%43%
2411
August1st to 15thDay
9%4245%35%5%7%8%41%
2145
16th to endDay
12%5%25%4345%5%8%42%
2162
September1st to 15thDay
12%42432335%7%49%
1980
16th to endDay
13%5%2442445%6%45%
1810
October1st to 15thDay
16%6%145%23347%45%
1650
16th to endDay
19%6%25%413345%42%
1756
November1st to 15thDay
11%6%34424346%47%
1525
16th to endDay
17%8%36%424447%37%
1440
December1st to 15thDay
16%12%5%9%5%35%5%36%25%
1440
16th to endDay
20%14%6%7%7%25%42423%
1536
January1st to 15thNight
10%9%5%7%5%35%5%5%7%33%
2506
16th to endNight
12%10%5%10%6%34347%31%
2511
February1st to 15thNight
10%10%5%8%6%3445%5%33%
2285
16th to endNight
12%6%36%5%34347%42%
1970
March1st to 15thNight
14%8%34323346%44%
2022
16th to endNight
15%9%46%5%3446%6%33%
1988
April1st to 15thNight
15%7%36%423446%40%
1647
16th to endNight
22%5%24423345%40%
1598
May1st to 15thNight
16%6%24425%5%6%7%37%
1389
16th to endNight
11%5%25%4245%5%7%45%
1368
June1st to 15thNight
11%4145%25%6%6%9%41%
1320
16th to endNight
9%4145%23449%49%
1320
July1st to 15thNight
5%4124245%48%56%
1320
16th to endNight
421331446%10%55%
1449
August1st to 15thNight
6%3143245%6%8%53%
1485
16th to endNight
11%424322347%52%
1688
September1st to 15thNight
11%414323335%56%
1650
16th to endNight
9%413324347%53%
1805
October1st to 15thNight
13%425%423345%49%
1980
16th to endNight
16%7%35%324446%42%
2115
November1st to 15thNight
11%6%26%423345%48%
2330
16th to endNight
16%9%3442335%5%40%
2520
December1st to 15thNight
16%11%47%6%35%445%28%
2520
16th to endNight
20%13%5%7%6%34345%25%
2688

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 15thDay
22%8%48%6%45%436%24%
1432
16th to endDay
28%11%39%5%34445%18%
1710
February1st to 15thDay
25%10%5%7%5%33325%25%
1575
16th to endDay
26%8%26%5%34345%28%
1503
March1st to 15thDay
28%7%26%423247%30%
1938
16th to endDay
28%8%36%433345%27%
2032
April1st to 15thDay
33%7%25%422246%28%
1971
16th to endDay
38%8%25%5%23235%22%
2030
May1st to 15thDay
35%7%245%23446%23%
2231
16th to endDay
32%425%423345%31%
2393
June1st to 15thDay
32%5%25%423446%28%
2310
16th to endDay
26%415%423346%36%
2310
July1st to 15thDay
25%41343345%7%36%
2310
16th to endDay
24%3144245%6%8%33%
2411
August1st to 15thDay
17%424435%5%6%7%38%
2145
16th to endDay
18%5%2443345%7%40%
2162
September1st to 15thDay
18%414313347%45%
1980
16th to endDay
21%5%24323446%41%
1810
October1st to 15thDay
24%5%13422236%42%
1650
16th to endDay
25%5%24412335%39%
1756
November1st to 15thDay
23%5%14423345%42%
1525
16th to endDay
30%7%25%323235%33%
1440
December1st to 15thDay
30%11%48%5%2342421%
1440
16th to endDay
32%13%47%6%3332320%
1536
January1st to 15thNight
23%8%36%5%34446%30%
2506
16th to endNight
26%8%39%5%23336%26%
2511
February1st to 15thNight
24%10%47%5%2334429%
2278
16th to endNight
25%5%25%5%23346%35%
1970
March1st to 15thNight
28%7%24312235%36%
2034
16th to endNight
27%8%35%5%3335%5%28%
1988
April1st to 15thNight
30%6%25%422335%34%
1647
16th to endNight
36%5%2432233431%
1598
May1st to 15thNight
31%5%2332445%430%
1388
16th to endNight
28%425%222346%36%
1368
June1st to 15thNight
28%4144245%5%7%31%
1320
16th to endNight
25%314413347%40%
1320
July1st to 15thNight
22%312323447%44%
1320
16th to endNight
21%21231345%8%45%
1449
August1st to 15thNight
15%31332345%8%49%
1485
16th to endNight
18%313322335%50%
1688
September1st to 15thNight
18%313313235%51%
1650
16th to endNight
17%413323336%50%
1805
October1st to 15thNight
21%414423335%45%
1980
16th to endNight
23%6%24323345%40%
2115
November1st to 15thNight
23%6%15%32323443%
2330
16th to endNight
28%7%2431234437%
2520
December1st to 15thNight
31%9%36%5%23445%22%
2520
16th to endNight
34%11%37%5%2233421%
2688

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
9%11%6%9%7%45%447%28%
1432
16th to endDay
14%13%5%10%6%36%5%5%6%22%
1710
February1st to 15thDay
11%12%6%7%6%35%5%36%30%
1575
16th to endDay
14%9%37%5%35%45%6%33%
1503
March1st to 15thDay
15%8%47%42435%8%34%
1938
16th to endDay
17%10%46%5%34447%31%
2030
April1st to 15thDay
20%8%35%43335%7%33%
1971
16th to endDay
25%8%36%5%23445%30%
2030
May1st to 15thDay
21%7%35%6%35%5%5%8%27%
2231
16th to endDay
15%5%35%5%35%45%7%38%
2393
June1st to 15thDay
16%5%35%425%5%5%8%36%
2310
16th to endDay
10%426%5%345%5%8%42%
2310
July1st to 15thDay
8%42443446%8%46%
2310
16th to endDay
7%4245%35%6%7%10%42%
2411
August1st to 15thDay
8%5%24435%6%7%9%41%
2145
16th to endDay
12%5%25%5%345%5%8%42%
2162
September1st to 15thDay
12%42441345%7%49%
1980
16th to endDay
14%5%2443445%6%45%
1810
October1st to 15thDay
16%5%14423346%45%
1650
16th to endDay
19%6%24413345%42%
1756
November1st to 15thDay
11%7%34434446%47%
1525
16th to endDay
17%9%36%424347%37%
1440
December1st to 15thDay
16%13%410%6%345%45%25%
1440
16th to endDay
19%14%6%8%6%3442423%
1536
January1st to 15thNight
10%9%5%7%5%35%5%5%7%33%
2506
16th to endNight
11%10%5%10%6%34447%31%
2511
February1st to 15thNight
10%11%5%8%7%25%45%5%33%
2278
16th to endNight
12%6%36%6%24347%42%
1970
March1st to 15thNight
15%8%34323336%44%
2034
16th to endNight
15%9%47%5%245%5%6%32%
1988
April1st to 15thNight
15%8%36%423446%40%
1647
16th to endNight
23%5%25%323335%39%
1598
May1st to 15thNight
16%6%34425%5%7%7%36%
1388
16th to endNight
11%435%4245%5%7%45%
1368
June1st to 15thNight
12%424435%6%6%9%41%
1320
16th to endNight
9%42442445%8%50%
1320
July1st to 15thNight
44123245%48%56%
1320
16th to endNight
421332346%11%55%
1449
August1st to 15thNight
6%32432445%9%52%
1485
16th to endNight
11%424313347%52%
1688
September1st to 15thNight
12%314322336%56%
1650
16th to endNight
9%423324347%53%
1805
October1st to 15thNight
13%5%14423445%50%
1980
16th to endNight
16%7%25%423446%42%
2115
November1st to 15thNight
11%6%25%423345%48%
2330
16th to endNight
16%9%35%42335%5%40%
2520
December1st to 15thNight
16%11%47%6%345%45%28%
2520
16th to endNight
20%14%47%6%34345%24%
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
55%414%15%10%
1433
16th to endDay
60%414%14%4
1710
February1st to 15thDay
54%5%13%19%6%
1576
16th to endDay
50%5%12%22%7%1
1503
March1st to 15thDay
48%5%15%20%8%
1938
16th to endDay
52%6%13%21%5%
2032
April1st to 15thDay
50%5%12%22%8%
1971
16th to endDay
54%5%12%18%7%1
2030
May1st to 15thDay
53%6%13%19%6%
2231
16th to endDay
44%6%13%22%11%2
2397
June1st to 15thDay
43%6%14%23%11%
2310
16th to endDay
38%8%12%24%14%1
2310
July1st to 15thDay
35%7%14%27%13%2
2161
16th to endDay
32%9%19%23%13%1
2248
August1st to 15thDay
36%8%13%26%12%1
2131
16th to endDay
38%6%11%25%15%1
2162
September1st to 15thDay
33%6%13%27%18%1
1980
16th to endDay
39%5%12%28%12%1
1810
October1st to 15thDay
39%312%24%18%
1650
16th to endDay
43%415%24%11%
1756
November1st to 15thDay
38%412%28%14%1
1525
16th to endDay
48%5%18%22%5%
1440
December1st to 15thDay
60%5%12%13%6%
1440
16th to endDay
65%411%12%6%
1536
January1st to 15thNight
49%5%15%19%10%
2506
16th to endNight
53%415%18%8%
2511
February1st to 15thNight
51%5%13%20%9%
2288
16th to endNight
43%413%25%11%1
1970
March1st to 15thNight
41%412%28%11%1
2034
16th to endNight
50%6%15%19%6%
1988
April1st to 15thNight
45%412%23%13%1
1647
16th to endNight
46%411%23%11%2
1598
May1st to 15thNight
44%8%12%22%11%1
1389
16th to endNight
36%7%14%24%15%2
1370
June1st to 15thNight
35%8%17%24%12%
1320
16th to endNight
31%6%11%25%19%4
1320
July1st to 15thNight
26%6%17%29%17%3
1240
16th to endNight
21%9%17%30%17%2
1349
August1st to 15thNight
27%6%14%30%18%2
1475
16th to endNight
32%5%13%24%18%5%
1688
September1st to 15thNight
30%5%7%28%25%2
1650
16th to endNight
30%412%31%19%1
1805
October1st to 15thNight
36%311%24%20%2
1980
16th to endNight
42%5%14%22%14%1
2115
November1st to 15thNight
37%412%25%17%2
2330
16th to endNight
45%416%25%7%
2520
December1st to 15thNight
56%5%13%17%6%
2520
16th to endNight
62%412%13%6%
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
24%11%33%24%5%1
90
16th to endDay
20%8%33%28%7%2
96
February1st to 15thDay
12%18%37%23%7%
90
16th to endDay
22%12%33%18%13%
81
March1st to 15thDay
22%14%40%16%6%
90
16th to endDay
26%8%35%20%6%2
92
April1st to 15thDay
20%12%27%30%9%
210
16th to endDay
30%10%27%18%10%2
260
May1st to 15thDay
26%11%29%19%9%2
393
16th to endDay
15%9%29%27%15%3
437
June1st to 15thDay
15%6%25%33%15%3
420
16th to endDay
9%5%31%30%19%4
420
July1st to 15thDay
8%224%34%20%10%
400
16th to endDay
8%223%32%26%6%
445
August1st to 15thDay
10%122%34%25%5%
418
16th to endDay
15%218%35%21%6%
330
September1st to 15thDay
14%224%26%22%9%
255
16th to endDay
12%10%28%25%17%5%
156
October1st to 15thDay
12%7%30%24%18%6%
90
16th to endDay
22%7%33%29%7%
96
November1st to 15thDay
5%7%35%32%12%6%
90
16th to endDay
41%12%27%10%8%
90
December1st to 15thDay
21%15%36%20%6%
90
16th to endDay
29%13%38%15%3
96
January1st to 15thNight
15%10%35%29%9%
900
16th to endNight
16%10%38%29%4
960
February1st to 15thNight
16%9%37%27%8%
880
16th to endNight
15%10%36%28%8%1
708
March1st to 15thNight
19%9%31%28%10%1
594
16th to endNight
17%8%37%26%8%1
549
April1st to 15thNight
19%9%37%27%6%
494
16th to endNight
24%433%28%7%2
495
May1st to 15thNight
19%6%34%28%9%
495
16th to endNight
13%5%31%34%15%
515
June1st to 15thNight
14%328%40%13%
495
16th to endNight
10%327%42%15%1
495
July1st to 15thNight
6%119%43%27%2
465
16th to endNight
417%48%25%3
522
August1st to 15thNight
6%118%42%28%1
494
16th to endNight
13%216%38%25%4
525
September1st to 15thNight
14%317%37%22%5%
495
16th to endNight
10%5%27%33%22%1
551
October1st to 15thNight
17%6%31%27%15%1
660
16th to endNight
19%8%30%31%9%
704
November1st to 15thNight
14%8%37%30%8%
754
16th to endNight
18%12%37%23%7%
900
December1st to 15thNight
22%9%37%23%5%
900
16th to endNight
26%8%31%24%7%
960
Page generated at 2017-03-23 06:36:15. Version ac04

Copyright 2017 A. Danko


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