Moraine Valley Community College Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Moraine Valley Community College Observatory clear sky chart from 2005-11-05 to

2017-09-12
.

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
36%
15939
18%
46781
11%
15897
43%
15897
24%
31042

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
19%
900
13%
2506
4%
895
28%
895
17%
1825
January16th to endNight
20%
960
13%
2661
4%
960
28%
960
16%
1999
February1st to 15thNight
22%
782
14%
2193
4%
782
30%
782
19%
1557
February16th to endNight
25%
631
19%
1893
8%
631
35%
631
18%
1322
March1st to 15thNight
25%
720
13%
2160
8%
720
29%
720
17%
1528
March16th to endNight
30%
636
16%
2016
10%
636
37%
636
19%
1380
April1st to 15thNight
30%
539
15%
1797
10%
539
39%
539
21%
1189
April16th to endNight
32%
540
18%
1728
11%
540
41%
540
22%
1157
May1st to 15thNight
36%
540
16%
1614
9%
540
43%
540
23%
1098
May16th to endNight
47%
562
18%
1498
9%
561
53%
561
33%
961
June1st to 15thNight
50%
540
17%
1440
10%
540
55%
540
37%
880
June16th to endNight
51%
540
17%
1440
10%
540
55%
540
33%
937
July1st to 15thNight
61%
510
17%
1360
11%
510
64%
510
41%
802
July16th to endNight
67%
564
23%
1417
17%
531
70%
531
45%
820
August1st to 15thNight
76%
539
23%
1578
22%
536
78%
536
44%
864
August16th to endNight
67%
573
22%
1910
22%
573
71%
573
35%
1057
September1st to 15thNight
60%
541
29%
1778
27%
541
67%
541
38%
953
September16th to endNight
57%
657
26%
1815
20%
657
62%
657
36%
1092
October1st to 15thNight
47%
660
27%
1886
19%
660
54%
660
33%
1129
October16th to endNight
28%
704
18%
2246
11%
704
38%
704
21%
1457
November1st to 15thNight
30%
700
24%
2276
16%
700
42%
700
25%
1393
November16th to endNight
26%
741
17%
2361
10%
741
35%
741
19%
1583
December1st to 15thNight
19%
900
13%
2520
4%
900
27%
900
17%
1868
December16th to endNight
14%
960
11%
2688
2%
960
22%
960
11%
2191

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%36%5%3445%7%36%
47886
Night
14%8%35%424446%39%
46949
Cloud CoverDay
13%8%36%5%35%45%7%36%
47895
Night
14%8%35%424446%39%
46954
TransparencyDay
46%412%22%12%1
47572
Night
44%411%23%13%1
46781
SeeingDay
14%9%29%26%14%5%
5944
Night
18%10%28%29%12%1
15943

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%15%37%6%25%5%5%6%25%
1432
16th to endDay
13%15%8%9%6%33435%25%
1560
February1st to 15thDay
16%13%5%9%5%45%435%27%
1669
16th to endDay
16%11%48%6%24346%31%
1580
March1st to 15thDay
15%13%48%5%35%345%28%
1790
16th to endDay
17%10%46%5%345%5%6%30%
2217
April1st to 15thDay
19%9%47%5%34345%32%
2151
16th to endDay
20%7%25%5%24446%35%
2232
May1st to 15thDay
18%9%36%5%35%46%7%29%
2334
16th to endDay
13%5%36%5%35%45%7%39%
2617
June1st to 15thDay
11%435%5%345%5%7%43%
2520
16th to endDay
10%425%6%36%6%7%8%36%
2520
July1st to 15thDay
7%426%5%35%5%6%9%42%
2520
16th to endDay
6%425%6%36%6%7%10%39%
2655
August1st to 15thDay
7%425%6%45%6%7%8%42%
2370
16th to endDay
10%4246%345%7%10%41%
2292
September1st to 15thDay
13%324424447%48%
2090
16th to endDay
9%5%245%35%5%6%8%42%
1815
October1st to 15thDay
15%6%25%434336%43%
1743
16th to endDay
18%8%35%5%43345%36%
1625
November1st to 15thDay
15%7%345%2345%6%42%
1582
16th to endDay
18%8%37%5%23336%36%
1596
December1st to 15thDay
17%12%49%6%34345%27%
1440
16th to endDay
22%15%5%8%5%3433422%
1536
January1st to 15thNight
18%11%46%5%24435%33%
2506
16th to endNight
13%12%6%9%5%34445%29%
2661
February1st to 15thNight
16%12%46%5%24336%34%
2191
16th to endNight
16%10%5%6%5%34345%34%
1893
March1st to 15thNight
17%11%46%5%2433435%
2147
16th to endNight
16%7%36%5%35%5%47%34%
2016
April1st to 15thNight
16%8%46%423447%36%
1797
16th to endNight
19%7%25%434345%38%
1728
May1st to 15thNight
18%6%25%5%345%6%7%35%
1614
16th to endNight
10%3245%335%5%9%44%
1496
June1st to 15thNight
10%4245%3335%7%49%
1440
16th to endNight
9%424435%6%5%11%41%
1440
July1st to 15thNight
6%4235%25%47%7%51%
1440
16th to endNight
442433446%9%51%
1513
August1st to 15thNight
33135%25%45%9%55%
1587
16th to endNight
9%31342435%8%52%
1910
September1st to 15thNight
10%314322347%54%
1778
16th to endNight
8%425%42446%6%49%
1815
October1st to 15thNight
13%424323347%49%
1886
16th to endNight
20%8%34323336%40%
2246
November1st to 15thNight
13%7%25%423335%46%
2276
16th to endNight
18%8%36%423346%36%
2361
December1st to 15thNight
20%10%48%423435%30%
2520
16th to endNight
24%15%5%7%5%3443421%
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%14%37%6%26%45%6%25%
1432
16th to endDay
13%16%7%9%6%34346%24%
1560
February1st to 15thDay
16%13%5%8%5%35%445%27%
1669
16th to endDay
15%11%47%6%24447%30%
1580
March1st to 15thDay
15%13%48%5%25%446%28%
1800
16th to endDay
18%9%46%6%35%446%30%
2216
April1st to 15thDay
19%10%38%434345%32%
2151
16th to endDay
19%7%25%5%3345%7%34%
2232
May1st to 15thDay
18%8%36%6%35%5%5%7%29%
2334
16th to endDay
13%5%26%5%35%45%8%38%
2617
June1st to 15thDay
10%5%345%35%45%7%44%
2520
16th to endDay
9%5%26%6%35%6%8%9%35%
2520
July1st to 15thDay
7%425%5%35%5%6%9%43%
2520
16th to endDay
7%325%5%37%5%8%9%40%
2655
August1st to 15thDay
6%425%6%45%6%6%8%42%
2370
16th to endDay
9%425%5%35%5%7%9%42%
2292
September1st to 15thDay
13%3145%24447%47%
2090
16th to endDay
9%5%245%36%5%6%8%41%
1815
October1st to 15thDay
14%5%35%435%346%43%
1743
16th to endDay
18%8%35%6%33345%36%
1625
November1st to 15thDay
14%7%4443335%6%42%
1582
16th to endDay
19%8%36%5%23336%35%
1596
December1st to 15thDay
18%11%48%7%35%335%27%
1440
16th to endDay
22%15%5%8%43343423%
1536
January1st to 15thNight
18%12%36%5%24335%33%
2506
16th to endNight
14%12%7%8%5%34445%29%
2661
February1st to 15thNight
16%11%5%5%5%34446%34%
2184
16th to endNight
16%11%46%5%24345%33%
1893
March1st to 15thNight
17%11%46%5%2443435%
2160
16th to endNight
16%8%35%5%35%45%7%33%
2016
April1st to 15thNight
16%7%45%5%2445%6%36%
1797
16th to endNight
19%7%36%434345%38%
1728
May1st to 15thNight
18%5%25%5%345%6%6%34%
1613
16th to endNight
10%4246%245%5%8%44%
1496
June1st to 15thNight
9%5%25%423447%49%
1440
16th to endNight
10%434436%46%11%40%
1440
July1st to 15thNight
6%3135%25%5%7%7%51%
1440
16th to endNight
44243245%6%9%51%
1513
August1st to 15thNight
33134445%5%9%54%
1587
16th to endNight
8%31433345%7%52%
1910
September1st to 15thNight
10%314423348%54%
1778
16th to endNight
8%5%25%42345%7%49%
1815
October1st to 15thNight
12%5%24413347%48%
1886
16th to endNight
20%8%34323346%39%
2246
November1st to 15thNight
13%8%34433345%45%
2276
16th to endNight
18%8%36%5%33346%36%
2361
December1st to 15thNight
20%9%48%424435%30%
2520
16th to endNight
24%15%5%6%6%3433421%
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
57%414%13%9%
1433
16th to endDay
61%311%15%6%
1560
February1st to 15thDay
59%311%15%8%1
1671
16th to endDay
54%412%21%6%1
1580
March1st to 15thDay
57%410%19%7%
1800
16th to endDay
53%414%20%5%
2217
April1st to 15thDay
53%48%21%11%
2151
16th to endDay
48%413%17%11%3
2232
May1st to 15thDay
52%412%22%7%
2334
16th to endDay
43%5%12%21%15%2
2621
June1st to 15thDay
38%411%25%18%1
2520
16th to endDay
40%7%13%22%14%2
2520
July1st to 15thDay
36%6%11%27%15%2
2371
16th to endDay
35%7%15%24%14%2
2488
August1st to 15thDay
36%5%13%27%14%1
2355
16th to endDay
35%6%12%26%15%2
2292
September1st to 15thDay
34%410%25%20%3
2090
16th to endDay
37%410%29%16%1
1815
October1st to 15thDay
41%311%26%15%1
1743
16th to endDay
49%212%23%10%1
1625
November1st to 15thDay
41%312%23%15%2
1582
16th to endDay
50%312%24%8%
1596
December1st to 15thDay
59%212%19%6%
1440
16th to endDay
65%410%11%7%
1536
January1st to 15thNight
53%312%19%9%
2506
16th to endNight
56%413%17%8%
2661
February1st to 15thNight
52%312%21%9%1
2193
16th to endNight
52%211%23%9%1
1893
March1st to 15thNight
52%311%19%10%2
2160
16th to endNight
48%414%21%8%1
2016
April1st to 15thNight
47%310%22%13%1
1797
16th to endNight
47%39%21%13%3
1728
May1st to 15thNight
47%412%24%11%
1614
16th to endNight
36%6%14%21%18%3
1498
June1st to 15thNight
34%312%26%19%2
1440
16th to endNight
36%7%13%22%18%1
1440
July1st to 15thNight
29%5%14%28%19%3
1360
16th to endNight
26%5%16%27%18%4
1417
August1st to 15thNight
25%416%30%19%2
1578
16th to endNight
30%5%12%27%18%4
1910
September1st to 15thNight
29%310%27%25%3
1778
16th to endNight
33%48%31%19%2
1815
October1st to 15thNight
34%39%29%21%1
1886
16th to endNight
46%211%25%12%1
2246
November1st to 15thNight
41%38%25%18%3
2276
16th to endNight
48%313%23%10%
2361
December1st to 15thNight
56%310%19%9%
2520
16th to endNight
67%38%14%5%1
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
23%15%37%18%4
90
16th to endDay
19%15%36%21%6%
96
February1st to 15thDay
17%27%43%11%
90
16th to endDay
16%17%40%14%8%2
81
March1st to 15thDay
30%18%33%15%2
90
16th to endDay
27%12%28%20%9%1
251
April1st to 15thDay
24%14%28%20%11%
270
16th to endDay
21%13%30%20%10%3
270
May1st to 15thDay
21%14%28%19%10%4
291
16th to endDay
15%10%35%23%11%3
517
June1st to 15thDay
12%8%33%27%14%4
495
16th to endDay
10%10%37%25%10%5%
495
July1st to 15thDay
9%5%30%29%15%8%
475
16th to endDay
7%5%26%30%19%9%
515
August1st to 15thDay
6%318%36%22%13%
388
16th to endDay
10%315%33%24%12%
332
September1st to 15thDay
11%420%32%24%7%
299
16th to endDay
11%5%16%35%24%5%
254
October1st to 15thDay
15%5%26%27%18%6%
183
16th to endDay
22%14%37%23%1
96
November1st to 15thDay
7%11%26%36%12%5%
90
16th to endDay
31%14%35%13%5%
90
December1st to 15thDay
20%23%37%16%2
90
16th to endDay
26%25%42%42
96
January1st to 15thNight
22%16%34%20%4
900
16th to endNight
19%15%34%27%2
960
February1st to 15thNight
21%12%37%23%4
785
16th to endNight
20%16%31%25%5%
631
March1st to 15thNight
23%11%35%22%6%
720
16th to endNight
18%11%32%27%8%1
636
April1st to 15thNight
20%13%30%26%7%
539
16th to endNight
23%7%32%25%10%
540
May1st to 15thNight
20%6%30%29%11%
540
16th to endNight
12%427%36%18%
563
June1st to 15thNight
11%424%44%14%
540
16th to endNight
10%427%37%19%
540
July1st to 15thNight
8%320%39%26%2
510
16th to endNight
5%216%46%26%3
564
August1st to 15thNight
4110%49%29%4
539
16th to endNight
10%213%36%32%4
573
September1st to 15thNight
11%417%33%28%5%
541
16th to endNight
10%5%17%35%27%3
657
October1st to 15thNight
15%6%25%32%17%1
660
16th to endNight
24%13%29%23%8%
704
November1st to 15thNight
17%13%34%22%10%2
700
16th to endNight
21%13%33%23%7%
741
December1st to 15thNight
25%14%34%21%4
900
16th to endNight
31%14%31%19%2
960
Page generated at 2017-09-13 06:39:25. Version ac04

Copyright 2017 A. Danko


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