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 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%
16244
17%
48608
12%
16202
45%
16202
22%
33389

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
17%
941
10%
2682
5%
936
23%
936
11%
2174
January16th to endNight
19%
832
13%
2704
7%
832
27%
832
12%
2105
February1st to 15thNight
23%
757
10%
2383
5%
757
29%
757
14%
1770
February16th to endNight
23%
631
13%
1893
6%
631
29%
631
13%
1440
March1st to 15thNight
27%
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
37%
540
19%
1620
9%
540
46%
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
58%
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
67%
540
36%
903
July1st to 15thNight
60%
510
17%
1360
14%
510
62%
510
33%
872
July16th to endNight
72%
564
20%
1587
17%
531
75%
531
39%
901
August1st to 15thNight
71%
539
21%
1609
19%
536
71%
536
34%
960
August16th to endNight
73%
573
21%
1791
19%
573
75%
573
35%
1024
September1st to 15thNight
64%
672
26%
1932
22%
672
68%
672
36%
1138
September16th to endNight
61%
717
27%
1980
21%
717
64%
717
35%
1211
October1st to 15thNight
52%
720
24%
2045
20%
720
57%
720
32%
1274
October16th to endNight
32%
768
21%
2382
15%
768
41%
768
22%
1602
November1st to 15thNight
41%
760
23%
2471
19%
760
49%
760
26%
1505
November16th to endNight
28%
780
17%
2535
10%
780
37%
780
17%
1801
December1st to 15thNight
22%
780
10%
2535
6%
780
27%
780
12%
1937
December16th to endNight
16%
897
10%
2769
4%
897
23%
897
10%
2251

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%
49448
Night
14%8%36%5%34446%36%
48790
Cloud CoverDay
15%8%46%5%3445%7%33%
49458
Night
14%8%36%5%34446%36%
48794
TransparencyDay
49%6%11%19%11%1
49148
Night
46%5%11%20%13%1
48608
SeeingDay
17%7%25%22%18%9%
6186
Night
18%7%26%29%15%2
16248

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%3443417%
1581
16th to endDay
13%15%8%11%7%4445%6%19%
1872
February1st to 15thDay
16%13%5%11%6%44446%21%
1779
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%425%6%36%5%6%9%41%
2340
16th to endDay
8%425%5%36%6%6%11%38%
2408
September1st to 15thDay
11%5%25%5%3445%7%43%
2014
16th to endDay
14%5%24423347%45%
1980
October1st to 15thDay
13%7%36%42445%7%40%
1914
16th to endDay
19%8%35%5%23446%35%
1839
November1st to 15thDay
13%8%35%43335%7%41%
1717
16th to endDay
17%12%5%7%5%33337%29%
1755
December1st to 15thDay
19%14%7%9%6%45%34419%
1755
16th to endDay
21%16%5%10%6%35%445%17%
1800
January1st to 15thNight
20%12%5%10%7%45%42421%
2682
16th to endNight
14%16%6%9%7%3433425%
2704
February1st to 15thNight
17%12%47%6%34345%29%
2381
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%
1620
16th to endNight
6%314435%45%10%49%
1791
September1st to 15thNight
11%41331345%8%50%
1932
16th to endNight
12%424323346%51%
1980
October1st to 15thNight
12%425%5%23447%46%
2045
16th to endNight
18%7%25%5%34445%39%
2382
November1st to 15thNight
14%6%25%32335%7%44%
2471
16th to endNight
18%10%37%5%2445%6%30%
2535
December1st to 15thNight
20%12%6%8%6%24336%24%
2535
16th to endNight
20%15%7%9%6%34335%19%
2769

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
20%13%7%12%7%24335%17%
1581
16th to endDay
13%16%8%10%7%45%346%19%
1872
February1st to 15thDay
16%14%5%11%6%44346%21%
1779
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%425%5%35%5%6%10%41%
2340
16th to endDay
8%325%5%35%6%7%10%39%
2408
September1st to 15thDay
12%5%25%6%34447%43%
2014
16th to endDay
14%5%25%5%2335%7%45%
1980
October1st to 15thDay
14%7%26%5%24347%41%
1914
16th to endDay
19%8%35%5%23446%35%
1839
November1st to 15thDay
12%8%35%43335%7%41%
1717
16th to endDay
17%13%47%5%33337%29%
1755
December1st to 15thDay
19%14%7%9%6%25%435%20%
1755
16th to endDay
21%15%6%9%7%35%445%17%
1800
January1st to 15thNight
19%12%6%10%7%45%43421%
2682
16th to endNight
14%16%5%9%7%3443425%
2704
February1st to 15thNight
17%13%47%5%34435%29%
2374
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%6%6%9%47%
1620
16th to endNight
6%314435%5%5%8%49%
1791
September1st to 15thNight
11%42331345%7%51%
1932
16th to endNight
12%42432345%6%51%
1980
October1st to 15thNight
12%425%42345%7%46%
2045
16th to endNight
18%7%345%24445%39%
2382
November1st to 15thNight
14%6%24324247%44%
2471
16th to endNight
18%9%46%5%3345%6%30%
2535
December1st to 15thNight
21%11%6%8%6%24336%24%
2535
16th to endNight
21%14%7%9%6%34335%20%
2769

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%
1582
16th to endDay
65%412%12%4
1872
February1st to 15thDay
63%5%10%12%7%
1781
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
35%8%13%24%14%2
2327
16th to endDay
35%8%13%25%13%3
2408
September1st to 15thDay
39%5%10%21%19%3
2014
16th to endDay
39%49%20%24%
1980
October1st to 15thDay
42%6%10%21%16%2
1914
16th to endDay
47%5%13%21%10%
1839
November1st to 15thDay
41%5%9%22%16%3
1717
16th to endDay
55%411%19%8%1
1755
December1st to 15thDay
66%49%14%4
1755
16th to endDay
69%5%8%13%3
1800
January1st to 15thNight
66%47%14%7%
2682
16th to endNight
62%5%9%16%6%
2704
February1st to 15thNight
57%412%15%8%1
2383
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
1609
16th to endNight
30%6%15%22%22%3
1791
September1st to 15thNight
31%5%12%24%21%4
1932
16th to endNight
33%6%8%24%25%2
1980
October1st to 15thNight
36%5%11%22%22%1
2045
16th to endNight
45%5%8%25%13%1
2382
November1st to 15thNight
39%410%22%19%3
2471
16th to endNight
53%410%21%9%
2535
December1st to 15thNight
61%49%16%7%
2535
16th to endNight
67%48%14%4
2769

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%12%38%14%8%
135
16th to endDay
34%12%35%15%1
144
February1st to 15thDay
26%21%39%11%
130
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
11%11%21%32%21%
313
16th to endDay
8%214%22%33%18%
332
September1st to 15thDay
13%314%20%30%16%
315
16th to endDay
14%413%19%28%19%
314
October1st to 15thDay
14%6%21%25%23%8%
315
16th to endDay
18%10%34%24%10%1
255
November1st to 15thDay
20%10%22%22%17%6%
135
16th to endDay
23%11%40%19%5%
135
December1st to 15thDay
17%22%37%11%9%1
135
16th to endDay
35%15%40%7%1
144
January1st to 15thNight
25%14%34%20%4
941
16th to endNight
21%15%36%24%2
832
February1st to 15thNight
25%11%33%27%2
760
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%10%40%34%6%
539
16th to endNight
7%19%35%39%6%
573
September1st to 15thNight
13%311%34%30%6%
672
16th to endNight
13%215%30%31%5%
717
October1st to 15thNight
14%6%21%31%20%4
720
16th to endNight
22%8%33%24%10%
768
November1st to 15thNight
18%9%27%29%14%1
760
16th to endNight
24%10%30%25%8%1
780
December1st to 15thNight
27%11%30%24%5%
780
16th to endNight
28%11%35%21%3
897
Page generated at 2018-02-15 10:58:45. Version ac04

Copyright 2018 A. Danko


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