Champaign Star Gazers Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Champaign Star Gazers Observing Site 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%
15503
17%
46339
12%
15461
45%
15461
22%
31867

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
15%
869
11%
2475
5%
864
21%
864
11%
2008
January16th to endNight
20%
768
12%
2496
8%
768
27%
768
12%
1955
February1st to 15thNight
23%
701
11%
2207
5%
701
30%
701
14%
1629
February16th to endNight
22%
631
13%
1893
6%
631
28%
631
13%
1440
March1st to 15thNight
28%
720
14%
2078
9%
720
33%
720
17%
1531
March16th to endNight
30%
768
16%
2112
10%
768
36%
768
21%
1515
April1st to 15thNight
31%
593
15%
1848
8%
593
39%
593
22%
1252
April16th to endNight
38%
540
19%
1620
9%
540
47%
540
25%
1073
May1st to 15thNight
36%
540
14%
1620
7%
540
42%
540
20%
1157
May16th to endNight
55%
562
17%
1684
14%
561
57%
561
29%
1051
June1st to 15thNight
60%
540
16%
1548
12%
540
64%
540
35%
942
June16th to endNight
64%
540
17%
1440
12%
540
68%
540
36%
903
July1st to 15thNight
61%
510
17%
1360
14%
510
63%
510
33%
872
July16th to endNight
73%
564
20%
1587
17%
531
77%
531
39%
901
August1st to 15thNight
70%
527
21%
1575
19%
524
71%
524
35%
938
August16th to endNight
72%
525
19%
1641
18%
525
74%
525
35%
939
September1st to 15thNight
66%
616
28%
1771
23%
616
69%
616
37%
1028
September16th to endNight
59%
657
25%
1815
19%
657
62%
657
33%
1127
October1st to 15thNight
53%
660
25%
1874
20%
660
58%
660
32%
1158
October16th to endNight
31%
704
19%
2183
13%
704
40%
704
21%
1481
November1st to 15thNight
42%
700
25%
2276
20%
700
51%
700
27%
1368
November16th to endNight
29%
720
15%
2340
9%
720
36%
720
16%
1696
December1st to 15thNight
21%
720
10%
2340
7%
720
26%
720
11%
1818
December16th to endNight
16%
828
10%
2556
4%
828
22%
828
10%
2085

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%8%46%5%3445%7%33%
47615
Night
14%8%36%5%24446%36%
46521
Cloud CoverDay
15%8%46%5%3445%7%33%
47625
Night
14%8%36%5%34446%36%
46525
TransparencyDay
48%6%12%19%11%1
47315
Night
46%5%11%20%13%2
46339
SeeingDay
17%7%24%22%18%9%
5553
Night
18%7%26%29%15%2
15507

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
20%14%7%11%7%3433418%
1459
16th to endDay
12%15%9%11%7%3445%6%17%
1728
February1st to 15thDay
15%13%6%12%6%4335%6%22%
1654
16th to endDay
14%13%410%6%35%445%24%
1580
March1st to 15thDay
19%11%6%8%6%33345%26%
1870
16th to endDay
18%11%5%7%6%32446%28%
2112
April1st to 15thDay
18%10%46%434447%32%
2110
16th to endDay
17%7%35%5%34447%36%
2340
May1st to 15thDay
20%8%46%5%445%5%6%28%
2331
16th to endDay
12%5%25%6%36%5%6%8%37%
2431
June1st to 15thDay
11%5%25%5%35%6%6%9%38%
2409
16th to endDay
10%425%5%36%5%7%9%37%
2520
July1st to 15thDay
11%5%25%5%35%5%6%9%37%
2520
16th to endDay
9%4145%36%6%8%10%39%
2471
August1st to 15thDay
7%435%6%36%5%6%9%40%
2288
16th to endDay
8%315%5%36%6%7%12%38%
2206
September1st to 15thDay
10%6%25%5%3445%7%44%
1846
16th to endDay
15%5%25%424347%43%
1815
October1st to 15thDay
12%6%36%42445%7%42%
1755
16th to endDay
20%8%35%5%23446%35%
1686
November1st to 15thDay
12%7%3443335%7%43%
1582
16th to endDay
18%12%5%8%5%33337%27%
1620
December1st to 15thDay
20%14%8%8%6%34345%19%
1620
16th to endDay
21%15%5%9%7%35%345%17%
1662
January1st to 15thNight
20%13%5%10%7%35%42422%
2475
16th to endNight
15%17%6%9%6%3433424%
2496
February1st to 15thNight
17%13%47%6%24345%29%
2205
16th to endNight
14%12%7%9%7%34435%27%
1893
March1st to 15thNight
17%9%48%6%34435%31%
2066
16th to endNight
16%9%37%5%24346%34%
2112
April1st to 15thNight
16%7%45%5%3436%7%35%
1848
16th to endNight
14%6%26%6%35%45%6%39%
1620
May1st to 15thNight
17%7%36%5%35%5%5%8%32%
1620
16th to endNight
10%4244346%6%9%42%
1682
June1st to 15thNight
7%3245%3445%8%49%
1548
16th to endNight
8%315%3345%7%10%45%
1440
July1st to 15thNight
8%425%5%245%5%8%46%
1440
16th to endNight
7%3234246%6%8%51%
1694
August1st to 15thNight
5%415%5%35%5%6%9%46%
1586
16th to endNight
6%314435%45%9%49%
1641
September1st to 15thNight
10%41331345%7%52%
1771
16th to endNight
12%42442335%6%50%
1815
October1st to 15thNight
12%425%5%23447%47%
1874
16th to endNight
18%7%25%5%34445%38%
2183
November1st to 15thNight
13%6%25%32335%7%45%
2276
16th to endNight
19%10%47%5%3445%6%29%
2340
December1st to 15thNight
22%12%6%8%6%24336%22%
2340
16th to endNight
21%15%7%9%6%24335%19%
2556

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
21%13%7%11%8%2333418%
1459
16th to endDay
13%16%8%11%7%45%446%18%
1728
February1st to 15thDay
15%14%6%11%6%44346%22%
1654
16th to endDay
15%12%5%10%6%35%445%25%
1580
March1st to 15thDay
20%11%5%8%6%3345%5%26%
1881
16th to endDay
19%10%5%8%6%23346%29%
2111
April1st to 15thDay
18%9%36%5%34447%32%
2110
16th to endDay
17%6%26%43445%7%36%
2340
May1st to 15thDay
19%9%46%5%35%5%5%5%29%
2331
16th to endDay
12%5%35%6%35%6%6%8%36%
2431
June1st to 15thDay
12%435%5%35%5%6%8%39%
2409
16th to endDay
11%425%6%36%5%6%9%38%
2520
July1st to 15thDay
11%5%25%5%35%5%6%9%37%
2520
16th to endDay
9%3235%36%6%7%11%39%
2471
August1st to 15thDay
7%435%5%35%5%6%10%40%
2288
16th to endDay
9%315%5%35%6%7%10%40%
2206
September1st to 15thDay
11%5%25%6%34447%44%
1846
16th to endDay
15%5%25%5%23347%43%
1815
October1st to 15thDay
13%7%25%5%24447%42%
1755
16th to endDay
20%8%345%23446%35%
1686
November1st to 15thDay
12%7%3442345%7%44%
1582
16th to endDay
18%13%5%8%6%33336%28%
1620
December1st to 15thDay
21%15%7%9%6%25%335%19%
1620
16th to endDay
21%15%6%9%7%35%445%17%
1662
January1st to 15thNight
19%13%6%10%7%35%43422%
2475
16th to endNight
15%16%6%9%6%3443425%
2496
February1st to 15thNight
17%13%47%5%34435%29%
2198
16th to endNight
15%12%7%9%6%34445%27%
1893
March1st to 15thNight
17%8%5%7%6%44436%31%
2078
16th to endNight
16%9%37%5%34346%34%
2112
April1st to 15thNight
16%8%25%5%3445%7%35%
1848
16th to endNight
14%5%25%6%35%45%6%40%
1620
May1st to 15thNight
17%7%36%5%345%5%8%32%
1619
16th to endNight
11%4344345%6%10%41%
1682
June1st to 15thNight
7%424435%46%7%50%
1548
16th to endNight
8%314425%5%7%11%45%
1440
July1st to 15thNight
9%416%5%2446%7%46%
1440
16th to endNight
7%3133245%7%8%51%
1694
August1st to 15thNight
5%4245%35%5%6%9%47%
1586
16th to endNight
7%314435%5%5%8%50%
1641
September1st to 15thNight
11%32331345%7%52%
1771
16th to endNight
13%42432345%6%50%
1815
October1st to 15thNight
11%425%42345%7%47%
1874
16th to endNight
18%7%345%33445%38%
2183
November1st to 15thNight
13%6%24324247%45%
2276
16th to endNight
19%9%47%5%3345%6%29%
2340
December1st to 15thNight
22%11%7%8%6%24336%23%
2340
16th to endNight
22%14%7%9%5%34335%19%
2556

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
69%37%13%5%
1460
16th to endDay
66%412%11%3
1728
February1st to 15thDay
63%5%10%12%7%
1656
16th to endDay
60%5%12%16%5%
1580
March1st to 15thDay
59%6%12%15%5%
1881
16th to endDay
55%5%12%20%5%
2112
April1st to 15thDay
51%5%13%18%10%
2110
16th to endDay
46%5%12%18%13%3
2340
May1st to 15thDay
54%7%12%17%7%1
2331
16th to endDay
42%9%12%21%11%1
2435
June1st to 15thDay
41%6%12%23%14%1
2409
16th to endDay
40%8%15%18%15%1
2520
July1st to 15thDay
42%7%11%20%15%2
2371
16th to endDay
35%9%17%24%12%1
2315
August1st to 15thDay
36%8%13%24%14%2
2275
16th to endDay
34%8%13%24%13%4
2206
September1st to 15thDay
38%5%10%21%20%3
1846
16th to endDay
41%49%19%23%
1815
October1st to 15thDay
41%6%10%22%17%2
1755
16th to endDay
48%5%13%21%10%1
1686
November1st to 15thDay
39%5%9%23%17%4
1582
16th to endDay
57%411%18%7%
1620
December1st to 15thDay
67%49%13%4
1620
16th to endDay
69%5%8%13%3
1662
January1st to 15thNight
66%47%13%7%
2475
16th to endNight
62%5%9%16%6%
2496
February1st to 15thNight
57%412%16%7%1
2207
16th to endNight
59%410%17%7%
1893
March1st to 15thNight
54%5%10%20%7%1
2078
16th to endNight
50%5%10%23%8%1
2112
April1st to 15thNight
46%5%12%19%14%1
1848
16th to endNight
43%5%12%19%15%5%
1620
May1st to 15thNight
48%7%11%21%8%2
1620
16th to endNight
35%8%12%25%14%3
1684
June1st to 15thNight
31%7%13%24%20%1
1548
16th to endNight
30%9%18%21%16%3
1440
July1st to 15thNight
35%7%11%21%19%3
1360
16th to endNight
26%7%16%29%15%2
1587
August1st to 15thNight
30%8%14%24%20%1
1575
16th to endNight
30%6%14%23%21%3
1641
September1st to 15thNight
30%5%12%24%22%4
1771
16th to endNight
34%6%8%23%25%2
1815
October1st to 15thNight
35%5%11%23%22%2
1874
16th to endNight
46%5%8%25%11%2
2183
November1st to 15thNight
38%49%22%20%4
2276
16th to endNight
55%410%19%9%
2340
December1st to 15thNight
63%410%15%6%
2340
16th to endNight
67%48%14%4
2556

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
25%16%38%11%6%1
90
16th to endDay
35%13%33%15%11
96
February1st to 15thDay
23%26%38%10%1
90
16th to endDay
16%14%50%12%41
81
March1st to 15thDay
27%15%29%24%3
171
16th to endDay
23%11%35%19%7%1
288
April1st to 15thDay
20%14%29%22%11%1
270
16th to endDay
18%8%30%24%11%6%
270
May1st to 15thDay
27%9%24%22%10%5%
288
16th to endDay
16%426%23%15%12%
331
June1st to 15thDay
11%220%33%23%8%
384
16th to endDay
13%5%27%26%19%7%
495
July1st to 15thDay
16%221%26%21%11%
475
16th to endDay
10%111%22%27%25%
331
August1st to 15thDay
12%111%20%31%22%
297
16th to endDay
8%212%21%33%21%
268
September1st to 15thDay
10%211%19%36%18%
255
16th to endDay
17%313%19%29%16%
254
October1st to 15thDay
12%5%22%27%23%8%
255
16th to endDay
20%10%34%24%8%1
198
November1st to 15thDay
12%10%21%24%23%8%
90
16th to endDay
27%12%40%15%4
90
December1st to 15thDay
25%16%36%12%6%2
90
16th to endDay
34%16%41%5%2
96
January1st to 15thNight
25%15%36%18%3
869
16th to endNight
21%15%35%25%2
768
February1st to 15thNight
24%11%33%27%2
704
16th to endNight
20%13%35%26%3
631
March1st to 15thNight
21%11%31%27%7%
720
16th to endNight
21%8%34%24%9%1
768
April1st to 15thNight
21%10%33%26%7%
593
16th to endNight
15%7%35%27%12%2
540
May1st to 15thNight
21%5%31%27%14%
540
16th to endNight
13%122%33%23%5%
563
June1st to 15thNight
9%121%42%24%
540
16th to endNight
9%218%41%27%1
540
July1st to 15thNight
11%116%39%26%3
510
16th to endNight
9%19%37%37%4
564
August1st to 15thNight
7%11%39%34%6%
527
16th to endNight
8%19%34%39%6%
525
September1st to 15thNight
12%310%34%31%6%
616
16th to endNight
14%315%33%29%4
657
October1st to 15thNight
13%6%22%32%19%4
660
16th to endNight
22%8%33%25%9%
704
November1st to 15thNight
17%9%27%29%14%1
700
16th to endNight
25%10%29%25%8%1
720
December1st to 15thNight
28%11%30%24%5%
720
16th to endNight
28%11%34%21%3
828
Page generated at 2017-08-13 14:16:48. Version ac04

Copyright 2017 A. Danko


Champaign Star Gazers Observing Site Clear Sky Chart | Charts Home