Starved Rock State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starved Rock State Park clear sky chart from 2005-11-05 to 2017-09-15.

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
38%
15949
18%
46830
11%
15906
45%
15906
25%
30907

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
21%
900
14%
2506
4%
895
30%
895
19%
1801
January16th to endNight
22%
960
13%
2610
4%
960
29%
960
18%
1935
February1st to 15thNight
23%
821
14%
2232
4%
821
30%
821
20%
1593
February16th to endNight
26%
631
19%
1893
7%
631
36%
631
19%
1302
March1st to 15thNight
27%
720
15%
2160
8%
720
32%
720
19%
1488
March16th to endNight
28%
585
14%
1998
8%
585
36%
585
18%
1389
April1st to 15thNight
29%
539
16%
1797
10%
539
39%
539
21%
1199
April16th to endNight
35%
540
18%
1773
12%
540
44%
540
22%
1164
May1st to 15thNight
33%
540
16%
1572
9%
540
39%
540
24%
1085
May16th to endNight
49%
563
19%
1497
10%
561
56%
561
33%
970
June1st to 15thNight
54%
540
17%
1440
11%
540
57%
540
35%
913
June16th to endNight
51%
540
18%
1440
11%
540
55%
540
34%
921
July1st to 15thNight
64%
510
18%
1360
11%
510
66%
510
40%
816
July16th to endNight
74%
564
23%
1417
18%
531
76%
531
43%
811
August1st to 15thNight
74%
539
21%
1606
20%
536
76%
536
40%
890
August16th to endNight
67%
573
22%
1910
23%
573
72%
573
35%
1070
September1st to 15thNight
63%
540
29%
1800
31%
540
68%
540
38%
956
September16th to endNight
59%
640
26%
1798
18%
640
64%
640
37%
1057
October1st to 15thNight
50%
660
29%
1930
20%
660
58%
660
35%
1128
October16th to endNight
32%
704
19%
2207
11%
704
42%
704
23%
1421
November1st to 15thNight
34%
700
24%
2276
16%
700
46%
700
26%
1375
November16th to endNight
30%
780
18%
2400
10%
780
38%
780
21%
1587
December1st to 15thNight
22%
900
13%
2520
5%
900
29%
900
17%
1866
December16th to endNight
17%
960
11%
2688
2%
960
25%
960
12%
2170

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
13%7%35%5%3445%7%37%
47910
Night
14%7%36%424446%40%
46999
Cloud CoverDay
13%7%35%5%3445%7%37%
47918
Night
14%7%35%424446%40%
47004
TransparencyDay
45%5%12%22%12%1
47596
Night
43%412%23%14%2
46831
SeeingDay
14%6%24%27%18%7%
5959
Night
17%8%28%31%13%1
15952

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
15%12%6%8%7%45%45%5%25%
1432
16th to endDay
14%15%7%7%6%345%5%5%24%
1612
February1st to 15thDay
15%13%5%7%5%34446%29%
1630
16th to endDay
15%10%5%8%6%24345%31%
1580
March1st to 15thDay
16%10%47%5%25%445%33%
1790
16th to endDay
17%9%46%6%35%46%7%29%
2235
April1st to 15thDay
17%10%46%424346%35%
2151
16th to endDay
20%7%25%5%345%46%34%
2186
May1st to 15thDay
19%8%35%5%35%45%7%31%
2377
16th to endDay
15%7%26%5%345%5%7%37%
2617
June1st to 15thDay
11%5%245%25%5%5%8%43%
2520
16th to endDay
8%425%5%46%5%7%9%39%
2520
July1st to 15thDay
7%434435%5%6%10%45%
2520
16th to endDay
6%424445%6%7%10%42%
2655
August1st to 15thDay
6%3245%35%6%7%9%45%
2343
16th to endDay
9%5%24435%5%5%9%45%
2292
September1st to 15thDay
12%32442345%7%49%
2148
16th to endDay
8%5%25%5%3445%7%47%
1821
October1st to 15thDay
14%5%35%422346%46%
1699
16th to endDay
16%7%35%5%34436%39%
1664
November1st to 15thDay
14%8%25%3235%5%6%43%
1582
16th to endDay
19%9%5%5%423335%37%
1560
December1st to 15thDay
18%11%46%7%44345%28%
1440
16th to endDay
22%13%6%8%6%23346%23%
1536
January1st to 15thNight
15%11%47%5%33436%34%
2506
16th to endNight
13%12%7%7%6%3445%5%30%
2610
February1st to 15thNight
15%10%5%6%5%24347%34%
2230
16th to endNight
15%10%48%434347%35%
1893
March1st to 15thNight
18%9%45%434345%36%
2147
16th to endNight
15%9%37%5%35%5%5%6%32%
1998
April1st to 15thNight
17%8%35%5%23446%38%
1797
16th to endNight
18%7%26%424346%39%
1773
May1st to 15thNight
17%7%25%5%25%35%8%34%
1572
16th to endNight
10%425%5%245%7%8%43%
1496
June1st to 15thNight
9%5%25%42445%5%49%
1440
16th to endNight
7%425%5%35%5%6%10%43%
1440
July1st to 15thNight
6%4145%2446%8%51%
1440
16th to endNight
42143347%6%9%51%
1513
August1st to 15thNight
4414325%45%9%52%
1615
16th to endNight
8%32442445%7%51%
1910
September1st to 15thNight
10%413313346%57%
1800
16th to endNight
7%4244345%5%8%50%
1798
October1st to 15thNight
11%424423246%53%
1930
16th to endNight
17%7%35%323336%42%
2207
November1st to 15thNight
12%7%25%5%23336%47%
2276
16th to endNight
17%8%35%42335%6%39%
2400
December1st to 15thNight
20%11%47%5%2334431%
2520
16th to endNight
23%13%5%9%6%2423423%
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
15%12%6%8%7%45%45%5%25%
1432
16th to endDay
14%15%7%7%6%35%446%24%
1612
February1st to 15thDay
15%13%5%7%5%34446%29%
1630
16th to endDay
15%10%5%7%6%24445%32%
1580
March1st to 15thDay
16%10%38%425%446%32%
1800
16th to endDay
17%8%46%5%35%5%5%7%29%
2233
April1st to 15thDay
17%10%46%5%24346%35%
2151
16th to endDay
20%7%35%4345%46%34%
2186
May1st to 15thDay
19%8%35%5%35%45%6%31%
2377
16th to endDay
15%6%25%5%345%5%7%37%
2617
June1st to 15thDay
11%5%25%5%25%5%5%8%43%
2520
16th to endDay
8%425%6%46%5%7%9%39%
2520
July1st to 15thDay
7%4245%35%5%6%9%45%
2520
16th to endDay
6%4245%36%6%7%10%42%
2655
August1st to 15thDay
6%3245%35%6%6%9%45%
2343
16th to endDay
9%5%244345%6%8%45%
2292
September1st to 15thDay
12%22442435%7%49%
2148
16th to endDay
8%5%25%5%345%6%6%47%
1821
October1st to 15thDay
14%5%26%412346%46%
1699
16th to endDay
16%7%35%5%34346%39%
1664
November1st to 15thDay
14%8%25%31445%6%42%
1582
16th to endDay
19%9%45%423336%37%
1560
December1st to 15thDay
18%11%5%6%7%44345%28%
1440
16th to endDay
22%12%6%7%6%23446%23%
1536
January1st to 15thNight
14%11%47%5%33436%34%
2506
16th to endNight
13%12%7%8%5%2445%5%30%
2610
February1st to 15thNight
14%10%46%5%24346%34%
2223
16th to endNight
15%9%47%5%23346%35%
1893
March1st to 15thNight
18%9%45%434345%36%
2160
16th to endNight
16%9%46%6%345%5%6%32%
1998
April1st to 15thNight
17%8%35%5%24346%37%
1797
16th to endNight
18%7%26%424347%39%
1773
May1st to 15thNight
17%7%25%5%3435%8%35%
1571
16th to endNight
10%4245%345%6%8%43%
1496
June1st to 15thNight
10%5%25%42445%6%48%
1440
16th to endNight
7%435%435%5%6%10%43%
1440
July1st to 15thNight
6%41443446%8%52%
1440
16th to endNight
4224325%6%7%9%51%
1513
August1st to 15thNight
4414425%46%9%52%
1615
16th to endNight
8%32442445%7%51%
1910
September1st to 15thNight
10%413313346%57%
1800
16th to endNight
7%3244345%5%8%50%
1798
October1st to 15thNight
11%414323246%53%
1930
16th to endNight
17%7%35%313345%42%
2207
November1st to 15thNight
12%7%345%23336%47%
2276
16th to endNight
17%8%35%423446%39%
2400
December1st to 15thNight
20%11%47%5%2334431%
2520
16th to endNight
23%12%5%9%6%3423423%
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
60%411%13%9%
1433
16th to endDay
59%412%15%6%
1612
February1st to 15thDay
56%414%17%6%1
1632
16th to endDay
54%311%21%6%1
1580
March1st to 15thDay
52%414%21%6%
1800
16th to endDay
52%6%14%20%41
2235
April1st to 15thDay
51%311%22%10%
2151
16th to endDay
49%5%13%17%11%3
2186
May1st to 15thDay
51%6%11%23%6%
2377
16th to endDay
44%6%11%20%15%1
2621
June1st to 15thDay
36%7%12%25%16%1
2520
16th to endDay
38%7%12%22%16%2
2520
July1st to 15thDay
34%6%13%27%15%2
2371
16th to endDay
32%7%18%25%13%2
2488
August1st to 15thDay
31%6%16%26%17%1
2328
16th to endDay
34%6%12%26%16%3
2292
September1st to 15thDay
33%410%25%20%5%
2148
16th to endDay
35%410%29%18%2
1821
October1st to 15thDay
38%410%28%16%1
1699
16th to endDay
46%412%23%10%2
1664
November1st to 15thDay
40%411%26%14%2
1582
16th to endDay
51%313%24%7%
1560
December1st to 15thDay
58%313%18%6%
1440
16th to endDay
63%411%12%7%
1536
January1st to 15thNight
51%412%18%12%
2506
16th to endNight
54%415%16%8%
2610
February1st to 15thNight
50%412%21%10%
2232
16th to endNight
50%312%23%9%
1893
March1st to 15thNight
50%313%20%9%2
2160
16th to endNight
50%5%13%19%9%1
1998
April1st to 15thNight
47%39%22%13%2
1797
16th to endNight
46%311%22%11%4
1773
May1st to 15thNight
46%412%21%12%
1572
16th to endNight
35%7%14%22%17%3
1498
June1st to 15thNight
34%5%11%25%19%3
1440
16th to endNight
35%6%13%21%18%4
1440
July1st to 15thNight
30%5%12%29%19%3
1360
16th to endNight
25%7%15%28%19%4
1417
August1st to 15thNight
26%6%15%29%18%2
1606
16th to endNight
31%411%27%19%4
1910
September1st to 15thNight
28%48%28%25%5%
1800
16th to endNight
30%411%28%20%3
1798
October1st to 15thNight
33%39%28%23%2
1930
16th to endNight
43%39%25%14%1
2207
November1st to 15thNight
39%39%25%17%4
2276
16th to endNight
46%312%24%12%
2400
December1st to 15thNight
55%311%20%8%
2520
16th to endNight
65%39%14%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
27%10%34%18%8%
90
16th to endDay
20%8%40%18%11%
96
February1st to 15thDay
16%14%44%20%4
90
16th to endDay
16%13%34%20%14%
81
March1st to 15thDay
34%21%23%18%2
90
16th to endDay
26%10%31%19%9%1
219
April1st to 15thDay
22%9%34%22%11%1
270
16th to endDay
21%7%25%27%13%3
270
May1st to 15thDay
19%11%30%25%10%3
334
16th to endDay
18%10%27%24%14%5%
517
June1st to 15thDay
10%5%24%33%21%5%
495
16th to endDay
11%7%31%28%17%4
495
July1st to 15thDay
8%5%21%30%22%11%
475
16th to endDay
6%19%31%28%13%
515
August1st to 15thDay
6%212%33%28%15%
424
16th to endDay
11%312%28%30%12%
332
September1st to 15thDay
10%113%32%30%10%
311
16th to endDay
8%5%19%32%23%10%
254
October1st to 15thDay
12%7%23%24%23%7%
139
16th to endDay
26%437%27%5%
96
November1st to 15thDay
7%7%26%33%14%10%
90
16th to endDay
40%10%24%17%7%
90
December1st to 15thDay
21%12%31%26%7%1
90
16th to endDay
30%20%41%5%2
96
January1st to 15thNight
21%13%37%22%5%
900
16th to endNight
17%13%35%28%4
960
February1st to 15thNight
20%10%36%26%5%
824
16th to endNight
19%10%36%27%5%
631
March1st to 15thNight
23%10%32%26%6%
720
16th to endNight
22%8%35%25%7%1
585
April1st to 15thNight
23%10%32%28%5%
539
16th to endNight
22%7%30%29%9%
540
May1st to 15thNight
20%7%32%28%10%
540
16th to endNight
12%426%40%14%
563
June1st to 15thNight
12%223%46%14%
540
16th to endNight
8%427%40%18%
540
July1st to 15thNight
8%116%40%29%3
510
16th to endNight
4210%47%31%3
564
August1st to 15thNight
5%18%44%34%5%
539
16th to endNight
9%212%39%33%3
573
September1st to 15thNight
11%413%37%29%4
540
16th to endNight
9%420%35%27%2
640
October1st to 15thNight
13%5%25%33%20%1
660
16th to endNight
22%9%31%27%8%
704
November1st to 15thNight
16%8%35%27%11%
700
16th to endNight
22%10%32%26%7%
780
December1st to 15thNight
26%11%30%24%6%
900
16th to endNight
29%12%31%21%4
960
Page generated at 2017-09-15 23:58:31. Version ac04

Copyright 2017 A. Danko


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