Goose Island State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Goose Island State Park clear sky chart from 2005-11-05 to 2017-09-22.

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
51%
15282
22%
47013
16%
15240
56%
15240
26%
28577

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
32%
897
21%
2327
8%
895
38%
895
21%
1602
January16th to endNight
40%
900
23%
2436
10%
900
47%
900
26%
1598
February1st to 15thNight
38%
704
24%
2112
13%
700
46%
700
23%
1322
February16th to endNight
38%
578
23%
1840
12%
578
47%
578
24%
1081
March1st to 15thNight
37%
540
24%
1980
16%
540
48%
540
18%
1206
March16th to endNight
46%
576
22%
2112
17%
576
53%
576
24%
1183
April1st to 15thNight
38%
539
20%
1977
14%
539
48%
539
21%
1187
April16th to endNight
37%
540
20%
1857
17%
540
46%
540
21%
1165
May1st to 15thNight
44%
539
21%
1641
14%
539
53%
539
25%
1005
May16th to endNight
52%
561
21%
1684
19%
561
58%
561
25%
1024
June1st to 15thNight
65%
540
18%
1620
18%
540
69%
540
31%
914
June16th to endNight
63%
540
14%
1620
18%
540
65%
540
27%
1023
July1st to 15thNight
70%
510
16%
1530
19%
510
70%
510
30%
945
July16th to endNight
71%
564
20%
1594
23%
531
76%
531
37%
895
August1st to 15thNight
82%
539
26%
1628
29%
536
83%
536
48%
794
August16th to endNight
70%
573
16%
2051
21%
573
71%
573
27%
1194
September1st to 15thNight
69%
540
16%
1980
20%
540
70%
540
24%
1211
September16th to endNight
68%
513
23%
1891
24%
513
71%
513
23%
1132
October1st to 15thNight
72%
533
31%
1853
31%
533
73%
533
36%
962
October16th to endNight
68%
704
31%
2112
24%
704
71%
704
41%
1137
November1st to 15thNight
54%
700
25%
2100
19%
700
57%
700
28%
1274
November16th to endNight
45%
792
28%
2232
12%
792
57%
792
28%
1332
December1st to 15thNight
40%
900
23%
2340
12%
900
44%
900
23%
1629
December16th to endNight
31%
960
19%
2496
6%
960
38%
960
19%
1762

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
10%5%244345%6%9%42%
47859
Night
11%5%2442445%8%46%
47209
TransparencyDay
36%8%16%20%12%5%
47559
Night
35%6%14%20%15%7%
47014
SeeingDay
9%8%11%25%33%10%
5241
Night
12%17%12%26%26%5%
15288

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
20%6%344345%47%36%
1611
16th to endDay
16%6%24423446%43%
1797
February1st to 15thDay
18%6%23313346%47%
1750
16th to endDay
15%7%24424346%44%
1632
March1st to 15thDay
19%6%23423347%41%
1980
16th to endDay
11%434424447%46%
2110
April1st to 15thDay
12%5%2442446%8%43%
1971
16th to endDay
13%5%45%5%24447%43%
2100
May1st to 15thDay
9%6%34436%5%6%9%40%
2307
16th to endDay
6%5%235%35%6%7%11%41%
2430
June1st to 15thDay
3314425%5%8%14%47%
2340
16th to endDay
6%5%245%46%8%8%14%33%
2340
July1st to 15thDay
7%5%25%5%36%6%6%10%39%
2340
16th to endDay
5%314436%6%8%13%41%
2466
August1st to 15thDay
11233246%7%12%54%
2318
16th to endDay
7%3145%46%7%8%11%37%
2151
September1st to 15thDay
9%5%26%7%36%7%7%10%33%
1980
16th to endDay
9%4246%346%6%10%40%
1881
October1st to 15thDay
5%3144245%5%9%52%
1764
16th to endDay
9%323423346%57%
1760
November1st to 15thDay
10%435%5%25%45%8%44%
1758
16th to endDay
13%414424445%48%
1725
December1st to 15thDay
20%7%35%42345%7%35%
1620
16th to endDay
18%8%36%423446%37%
1728
January1st to 15thNight
21%6%25%423235%42%
2327
16th to endNight
16%6%24323437%43%
2436
February1st to 15thNight
15%6%24323336%46%
2102
16th to endNight
12%6%24424346%48%
1840
March1st to 15thNight
16%7%25%323347%43%
1980
16th to endNight
11%424423436%51%
2112
April1st to 15thNight
13%6%3442345%9%42%
1977
16th to endNight
15%6%25%42445%7%40%
1857
May1st to 15thNight
9%6%2343447%10%41%
1640
16th to endNight
7%424435%5%7%14%40%
1683
June1st to 15thNight
4313435%5%8%11%47%
1620
16th to endNight
6%424435%8%8%14%36%
1620
July1st to 15thNight
5%425%5%36%6%7%12%42%
1620
16th to endNight
431342447%13%48%
1702
August1st to 15thNight
11221447%13%59%
1638
16th to endNight
5%314435%5%6%13%44%
2051
September1st to 15thNight
7%5%15%5%35%6%6%9%43%
1980
16th to endNight
7%426%5%35%6%6%9%42%
1891
October1st to 15thNight
6%21332445%8%56%
1853
16th to endNight
7%313214346%60%
2112
November1st to 15thNight
10%42443335%9%49%
2100
16th to endNight
11%424423345%53%
2232
December1st to 15thNight
21%6%34323346%40%
2340
16th to endNight
19%8%34424345%39%
2496

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
46%6%7%15%14%8%
1612
16th to endDay
42%5%8%16%17%10%
1797
February1st to 15thDay
39%49%16%16%13%
1751
16th to endDay
40%5%9%18%17%8%
1632
March1st to 15thDay
43%5%11%14%16%7%
1980
16th to endDay
36%7%12%17%16%8%
2112
April1st to 15thDay
37%6%14%18%14%8%
1971
16th to endDay
40%6%12%21%10%8%
2100
May1st to 15thDay
37%7%17%20%9%7%
2307
16th to endDay
31%10%18%22%14%1
2434
June1st to 15thDay
23%10%19%29%16%
2340
16th to endDay
37%11%20%24%6%
2340
July1st to 15thDay
35%11%21%24%6%
2201
16th to endDay
28%12%30%27%1
2311
August1st to 15thDay
20%9%29%34%6%
2304
16th to endDay
35%13%24%21%4
2151
September1st to 15thDay
40%13%16%19%7%1
1980
16th to endDay
36%10%16%18%13%4
1881
October1st to 15thDay
28%6%14%24%18%7%
1764
16th to endDay
28%49%20%23%13%
1760
November1st to 15thDay
37%7%13%17%15%7%
1758
16th to endDay
36%5%10%15%18%13%
1725
December1st to 15thDay
47%6%10%14%14%6%
1620
16th to endDay
47%5%9%16%13%7%
1728
January1st to 15thNight
46%37%13%18%11%
2327
16th to endNight
41%47%17%16%12%
2436
February1st to 15thNight
38%5%11%11%17%15%
2112
16th to endNight
36%410%17%20%9%
1840
March1st to 15thNight
41%411%15%17%10%
1980
16th to endNight
34%5%12%17%20%9%
2112
April1st to 15thNight
38%6%11%16%18%9%
1977
16th to endNight
41%5%11%18%13%8%
1857
May1st to 15thNight
34%7%16%19%12%8%
1641
16th to endNight
32%9%18%23%15%1
1685
June1st to 15thNight
26%7%17%27%19%1
1620
16th to endNight
32%11%20%26%8%
1620
July1st to 15thNight
32%9%23%29%5%
1530
16th to endNight
23%9%32%30%3
1594
August1st to 15thNight
15%7%28%42%4
1628
16th to endNight
29%11%27%24%6%
2051
September1st to 15thNight
35%10%20%21%9%2
1980
16th to endNight
35%9%14%21%14%4
1891
October1st to 15thNight
24%7%12%25%19%10%
1853
16th to endNight
25%48%19%27%15%
2112
November1st to 15thNight
33%6%14%20%17%7%
2100
16th to endNight
33%411%17%18%15%
2232
December1st to 15thNight
46%410%17%14%7%
2340
16th to endNight
47%5%7%14%15%9%
2496

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
22%423%37%12%
90
16th to endDay
19%7%32%25%15%
96
February1st to 15thDay
7%227%40%20%2
90
16th to endDay
9%38%39%12%
81
March1st to 15thDay
22%132%31%13%
90
16th to endDay
10%429%43%12%
96
April1st to 15thDay
8%238%30%20%
90
16th to endDay
12%11%25%31%17%1
210
May1st to 15thDay
12%13%27%36%9%
444
16th to endDay
11%14%16%37%17%2
517
June1st to 15thDay
412%428%41%7%
495
16th to endDay
9%12%222%42%10%
495
July1st to 15thDay
48%322%44%15%
475
16th to endDay
412%111%50%19%
515
August1st to 15thDay
17%8%56%26%
471
16th to endDay
14%3316%40%22%
191
September1st to 15thDay
4320%55%15%
135
16th to endDay
5%12%52%28%
108
October1st to 15thDay
3230%46%17%
90
16th to endDay
14%46%31%38%5%
96
November1st to 15thDay
26%16%42%21%2
90
16th to endDay
21%221%34%13%7%
90
December1st to 15thDay
37%213%24%18%3
90
16th to endDay
27%6%29%26%9%2
96
January1st to 15thNight
20%23%18%27%10%
900
16th to endNight
13%21%19%33%12%
900
February1st to 15thNight
17%22%16%31%12%
704
16th to endNight
12%21%21%34%9%
578
March1st to 15thNight
19%20%17%32%10%
540
16th to endNight
11%20%18%36%12%
576
April1st to 15thNight
14%19%22%33%10%
539
16th to endNight
17%18%21%28%13%
540
May1st to 15thNight
11%18%21%37%11%
540
16th to endNight
7%18%13%35%23%1
563
June1st to 15thNight
5%16%326%43%3
540
16th to endNight
417%424%39%9%
540
July1st to 15thNight
5%11%119%44%16%
510
16th to endNight
316%114%48%15%
564
August1st to 15thNight
19%15%61%20%
539
16th to endNight
6%8%111%50%21%
573
September1st to 15thNight
8%8%212%48%19%
540
16th to endNight
7%9%220%44%15%
513
October1st to 15thNight
6%9%6%22%45%9%
533
16th to endNight
7%10%10%30%35%5%
704
November1st to 15thNight
12%16%10%27%29%4
700
16th to endNight
14%18%15%28%20%2
792
December1st to 15thNight
19%19%16%25%17%2
900
16th to endNight
21%22%18%24%12%
960
Page generated at 2017-09-23 05:43:42. Version ac04

Copyright 2017 A. Danko


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