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 2018-01-12.

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%
16467
18%
48338
11%
16425
43%
16425
24%
32042

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%
956
13%
2662
4%
951
30%
951
18%
1923
January16th to endNight
20%
960
13%
2661
4%
960
28%
960
16%
1999
February1st to 15thNight
21%
782
14%
2193
4%
782
29%
782
19%
1557
February16th to endNight
25%
631
19%
1893
8%
631
36%
631
18%
1322
March1st to 15thNight
25%
720
13%
2160
8%
720
28%
720
17%
1528
March16th to endNight
30%
636
16%
2016
11%
636
37%
636
19%
1380
April1st to 15thNight
29%
539
16%
1797
10%
539
39%
539
21%
1189
April16th to endNight
32%
540
18%
1728
11%
540
42%
540
22%
1157
May1st to 15thNight
36%
540
17%
1614
9%
540
44%
540
23%
1098
May16th to endNight
48%
562
18%
1498
9%
561
53%
561
33%
961
June1st to 15thNight
51%
540
17%
1440
10%
540
55%
540
37%
880
June16th to endNight
50%
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
66%
573
22%
1910
22%
573
70%
573
35%
1057
September1st to 15thNight
61%
552
29%
1812
27%
552
68%
552
38%
976
September16th to endNight
60%
717
28%
1980
22%
717
64%
717
37%
1176
October1st to 15thNight
46%
720
26%
2058
18%
720
53%
720
32%
1251
October16th to endNight
29%
768
20%
2450
12%
768
39%
768
21%
1587
November1st to 15thNight
29%
760
23%
2471
15%
760
40%
760
24%
1533
November16th to endNight
25%
803
19%
2558
10%
803
36%
803
20%
1688
December1st to 15thNight
20%
975
13%
2730
4%
975
28%
975
17%
1999
December16th to endNight
15%
1040
11%
2912
3%
1040
23%
1040
11%
2358

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%
49007
Night
14%8%35%424446%39%
48506
Cloud CoverDay
14%8%36%5%35%45%7%36%
49016
Night
14%8%35%424446%39%
48511
TransparencyDay
46%412%22%12%1
48693
Night
44%411%23%14%1
48338
SeeingDay
15%9%29%25%14%5%
6337
Night
18%9%28%29%12%1
16471

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%14%37%6%25%45%6%26%
1520
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%324424446%47%
2136
16th to endDay
8%5%245%35%5%6%8%44%
1980
October1st to 15thDay
16%6%25%434336%42%
1901
16th to endDay
18%8%35%5%43335%37%
1773
November1st to 15thDay
16%7%345%1345%5%40%
1717
16th to endDay
17%8%36%5%23335%38%
1729
December1st to 15thDay
16%11%48%6%34345%29%
1560
16th to endDay
21%15%5%8%5%3433422%
1664
January1st to 15thNight
17%11%46%424435%34%
2662
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%314332347%54%
1812
16th to endNight
8%425%42447%6%50%
1980
October1st to 15thNight
14%424323347%48%
2058
16th to endNight
19%8%34323336%40%
2450
November1st to 15thNight
14%7%25%424345%44%
2471
16th to endNight
17%8%36%423247%37%
2558
December1st to 15thNight
19%10%48%423435%31%
2730
16th to endNight
23%15%5%7%6%3443422%
2912

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%26%
1520
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%
2136
16th to endDay
8%5%245%25%5%6%8%43%
1980
October1st to 15thDay
16%6%35%434345%42%
1901
16th to endDay
18%8%35%6%33345%36%
1773
November1st to 15thDay
16%7%4443335%6%40%
1717
16th to endDay
18%7%36%5%23336%38%
1729
December1st to 15thDay
17%11%48%7%35%345%28%
1560
16th to endDay
21%16%5%8%5%3343423%
1664
January1st to 15thNight
18%11%36%5%24335%34%
2662
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%
1812
16th to endNight
7%5%25%42346%7%50%
1980
October1st to 15thNight
14%5%24413347%47%
2058
16th to endNight
19%8%24323336%40%
2450
November1st to 15thNight
14%8%34433345%44%
2471
16th to endNight
17%8%36%5%33347%37%
2558
December1st to 15thNight
19%9%48%424445%31%
2730
16th to endNight
22%15%5%6%6%3433422%
2912

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
56%413%14%9%
1521
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
35%410%25%20%3
2136
16th to endDay
35%5%10%29%18%1
1980
October1st to 15thDay
43%311%25%14%2
1901
16th to endDay
49%212%23%11%1
1773
November1st to 15thDay
43%412%22%14%2
1717
16th to endDay
48%312%25%8%
1729
December1st to 15thDay
57%312%20%7%
1560
16th to endDay
64%410%12%7%
1664
January1st to 15thNight
52%311%19%11%
2662
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
1812
16th to endNight
31%49%31%20%2
1980
October1st to 15thNight
35%48%29%20%2
2058
16th to endNight
45%211%24%13%1
2450
November1st to 15thNight
42%38%25%17%3
2471
16th to endNight
47%313%25%10%
2558
December1st to 15thNight
54%310%20%9%
2730
16th to endNight
66%38%14%5%
2912

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%14%35%21%4
123
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%319%31%24%8%
315
16th to endDay
9%5%17%34%26%7%
314
October1st to 15thDay
20%5%24%28%15%5%
236
16th to endDay
22%15%35%22%3
144
November1st to 15thDay
18%8%28%28%10%5%
135
16th to endDay
25%12%40%15%5%
135
December1st to 15thDay
16%25%40%14%2
135
16th to endDay
25%23%44%5%1
144
January1st to 15thNight
22%16%34%21%4
956
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
10%417%32%28%6%
552
16th to endNight
10%5%17%35%28%3
717
October1st to 15thNight
16%6%25%32%16%1
720
16th to endNight
23%13%29%23%8%
768
November1st to 15thNight
18%12%35%21%10%1
760
16th to endNight
21%13%35%23%7%
803
December1st to 15thNight
24%14%34%21%4
975
16th to endNight
30%14%32%20%2
1040
Page generated at 2018-01-12 21:01:33. Version ac04

Copyright 2018 A. Danko


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