Lake St. Clair Metropark Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake St. Clair Metropark Observatory clear sky chart from 2005-11-05 to 2017-09-20.

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%
15496
15%
46852
10%
15460
42%
15460
19%
32409

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
18%
895
11%
2506
5%
895
23%
895
13%
1972
January16th to endNight
20%
804
10%
2532
4%
804
27%
804
9%
1993
February1st to 15thNight
20%
701
9%
2284
3%
701
26%
701
11%
1745
February16th to endNight
25%
631
14%
1893
7%
631
32%
631
14%
1413
March1st to 15thNight
26%
720
14%
2057
8%
720
31%
720
15%
1515
March16th to endNight
32%
768
18%
2112
9%
768
39%
768
20%
1473
April1st to 15thNight
32%
619
15%
1820
8%
619
39%
619
19%
1273
April16th to endNight
37%
540
20%
1620
8%
540
46%
540
21%
1050
May1st to 15thNight
37%
540
14%
1620
8%
540
43%
540
19%
1107
May16th to endNight
44%
561
16%
1684
11%
561
50%
561
25%
1056
June1st to 15thNight
51%
360
17%
1301
14%
360
60%
360
22%
768
June16th to endNight
53%
379
19%
1279
17%
379
61%
379
24%
746
July1st to 15thNight
61%
510
17%
1360
14%
510
64%
510
37%
806
July16th to endNight
60%
564
18%
1539
15%
531
67%
531
37%
878
August1st to 15thNight
63%
539
19%
1609
15%
536
67%
536
33%
946
August16th to endNight
64%
573
24%
1719
18%
573
69%
573
35%
988
September1st to 15thNight
57%
687
22%
1932
16%
687
61%
687
31%
1192
September16th to endNight
57%
677
22%
1870
16%
677
61%
677
32%
1155
October1st to 15thNight
42%
660
19%
1917
16%
660
46%
660
25%
1246
October16th to endNight
27%
704
15%
2178
7%
704
36%
704
16%
1554
November1st to 15thNight
36%
700
21%
2276
17%
700
43%
700
21%
1478
November16th to endNight
21%
720
13%
2449
7%
720
30%
720
13%
1758
December1st to 15thNight
16%
720
7%
2520
3%
720
21%
720
9%
1986
December16th to endNight
15%
924
7%
2775
2%
924
20%
924
8%
2311

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
12%7%36%6%35%5%6%7%34%
47965
Night
15%8%36%5%3445%6%35%
47034
Cloud CoverDay
12%7%36%6%35%5%6%8%35%
47975
Night
15%8%36%5%3445%6%35%
47038
TransparencyDay
46%6%13%21%11%1
47665
Night
47%5%12%21%11%1
46852
SeeingDay
14%10%17%29%20%8%
5784
Night
16%18%21%28%14%2
15506

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
17%13%5%9%7%45%45%6%19%
1432
16th to endDay
14%17%5%9%8%46%5%5%5%15%
1689
February1st to 15thDay
15%12%6%8%7%47%5%46%21%
1577
16th to endDay
12%11%5%10%7%26%5%6%6%25%
1580
March1st to 15thDay
17%10%47%6%46%5%45%27%
1891
16th to endDay
17%9%47%6%4445%6%30%
2112
April1st to 15thDay
16%8%46%6%3346%6%32%
2139
16th to endDay
16%6%35%6%235%5%7%37%
2340
May1st to 15thDay
15%7%36%6%45%45%6%34%
2331
16th to endDay
10%5%25%6%25%45%8%41%
2431
June1st to 15thDay
8%425%5%45%6%6%9%40%
2654
16th to endDay
7%326%5%45%6%7%11%38%
2676
July1st to 15thDay
6%4145%36%5%7%7%47%
2520
16th to endDay
6%425%436%5%7%10%43%
2522
August1st to 15thDay
6%4245%35%6%8%11%40%
2340
16th to endDay
9%4245%35%5%6%9%43%
2483
September1st to 15thDay
10%5%25%5%3446%8%42%
2011
16th to endDay
11%5%245%2346%9%42%
1859
October1st to 15thDay
12%6%35%5%3435%7%40%
1713
16th to endDay
20%7%36%5%34446%32%
1691
November1st to 15thDay
13%8%25%42446%8%38%
1582
16th to endDay
17%9%48%6%25%5%5%6%27%
1509
December1st to 15thDay
18%12%5%10%7%35%5%5%5%20%
1440
16th to endDay
19%12%7%10%7%45%5%5%6%17%
1443
January1st to 15thNight
22%11%5%7%6%345%45%23%
2506
16th to endNight
14%13%8%10%7%34445%22%
2532
February1st to 15thNight
15%13%5%9%7%34435%26%
2282
16th to endNight
16%11%49%5%35%445%29%
1893
March1st to 15thNight
18%9%46%435%446%30%
2045
16th to endNight
16%7%45%5%3445%8%35%
2112
April1st to 15thNight
19%8%35%33445%6%35%
1820
16th to endNight
14%6%25%43445%7%39%
1620
May1st to 15thNight
16%6%36%5%3445%7%35%
1620
16th to endNight
11%425%6%3445%7%45%
1682
June1st to 15thNight
9%424435%5%5%8%45%
1301
16th to endNight
9%4235%35%5%5%8%46%
1279
July1st to 15thNight
7%31443335%8%53%
1440
16th to endNight
5%3143245%7%10%51%
1646
August1st to 15thNight
45%25%4245%5%9%48%
1620
16th to endNight
8%425%42345%7%52%
1719
September1st to 15thNight
10%42342445%7%49%
1932
16th to endNight
11%5%25%4145%47%48%
1870
October1st to 15thNight
15%6%35%433347%42%
1917
16th to endNight
21%7%25%5%345%46%32%
2178
November1st to 15thNight
13%7%25%5%25%447%39%
2276
16th to endNight
20%11%37%5%2445%6%28%
2449
December1st to 15thNight
21%11%5%8%6%3445%5%22%
2520
16th to endNight
22%14%7%9%7%34445%18%
2775

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
18%12%5%9%7%45%45%6%19%
1432
16th to endDay
15%16%6%9%8%46%45%5%16%
1689
February1st to 15thDay
15%12%6%8%6%47%5%5%5%21%
1577
16th to endDay
12%11%5%10%7%36%5%5%6%25%
1580
March1st to 15thDay
17%10%47%6%46%5%45%27%
1902
16th to endDay
17%9%46%6%3445%6%30%
2111
April1st to 15thDay
16%8%46%6%2446%6%32%
2139
16th to endDay
16%6%35%6%2445%7%37%
2340
May1st to 15thDay
15%7%36%5%45%45%7%34%
2331
16th to endDay
10%5%35%5%3446%8%42%
2431
June1st to 15thDay
8%425%5%35%6%7%9%40%
2654
16th to endDay
7%425%6%45%6%7%11%38%
2676
July1st to 15thDay
5%3145%36%5%7%8%47%
2520
16th to endDay
6%3245%35%6%7%10%43%
2522
August1st to 15thDay
6%4145%35%6%8%11%41%
2340
16th to endDay
9%315%5%35%5%6%9%43%
2483
September1st to 15thDay
10%5%245%3446%8%43%
2011
16th to endDay
11%5%245%2346%9%42%
1859
October1st to 15thDay
12%6%35%5%44447%40%
1713
16th to endDay
20%7%36%435%346%33%
1691
November1st to 15thDay
13%7%35%425%45%9%38%
1582
16th to endDay
17%9%5%8%6%35%5%5%6%27%
1509
December1st to 15thDay
18%12%6%9%6%36%45%5%21%
1440
16th to endDay
19%12%7%9%7%445%5%5%17%
1443
January1st to 15thNight
22%12%47%6%34445%23%
2506
16th to endNight
14%13%8%10%7%34445%22%
2532
February1st to 15thNight
15%12%5%10%6%44445%26%
2275
16th to endNight
16%11%48%6%3444429%
1893
March1st to 15thNight
18%9%47%435%45%6%30%
2057
16th to endNight
16%7%35%5%2446%7%35%
2112
April1st to 15thNight
18%8%35%33445%6%35%
1820
16th to endNight
15%6%25%5%3445%8%39%
1620
May1st to 15thNight
16%6%36%5%3445%7%35%
1619
16th to endNight
11%5%25%6%2445%7%44%
1682
June1st to 15thNight
10%425%335%5%5%8%45%
1301
16th to endNight
8%4245%35%5%5%9%46%
1279
July1st to 15thNight
8%3135%2335%8%53%
1440
16th to endNight
441442447%9%51%
1646
August1st to 15thNight
45%25%4245%6%9%48%
1620
16th to endNight
8%425%32345%7%52%
1719
September1st to 15thNight
10%5%2441445%7%48%
1932
16th to endNight
11%425%4145%5%6%48%
1870
October1st to 15thNight
14%6%35%433347%43%
1917
16th to endNight
20%7%26%5%3445%6%32%
2178
November1st to 15thNight
13%6%35%5%35%5%47%39%
2276
16th to endNight
20%11%46%5%2445%6%28%
2449
December1st to 15thNight
21%12%5%8%6%3445%5%22%
2520
16th to endNight
21%14%6%9%7%345%35%18%
2775

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
64%6%11%13%4
1433
16th to endDay
69%5%10%9%5%
1689
February1st to 15thDay
61%7%10%14%6%
1579
16th to endDay
57%5%13%16%6%
1580
March1st to 15thDay
57%7%12%15%6%
1902
16th to endDay
53%412%20%7%1
2112
April1st to 15thDay
51%5%11%19%11%
2139
16th to endDay
44%5%14%17%15%2
2340
May1st to 15thDay
48%6%10%20%11%2
2331
16th to endDay
39%6%13%25%13%1
2435
June1st to 15thDay
37%8%14%25%13%1
2654
16th to endDay
37%7%16%22%14%1
2676
July1st to 15thDay
31%6%11%28%19%2
2371
16th to endDay
31%8%18%24%14%2
2366
August1st to 15thDay
33%8%16%27%12%1
2327
16th to endDay
34%7%14%26%14%2
2483
September1st to 15thDay
36%6%14%28%13%
2011
16th to endDay
37%5%14%29%12%
1859
October1st to 15thDay
42%6%12%23%13%1
1713
16th to endDay
52%416%19%6%
1691
November1st to 15thDay
43%6%13%23%11%1
1582
16th to endDay
57%5%13%16%6%
1509
December1st to 15thDay
64%5%12%13%4
1440
16th to endDay
69%5%11%10%3
1443
January1st to 15thNight
60%5%10%15%6%
2506
16th to endNight
63%5%12%14%4
2532
February1st to 15thNight
59%7%10%15%6%
2284
16th to endNight
55%6%10%18%7%
1893
March1st to 15thNight
54%5%11%18%9%1
2057
16th to endNight
46%6%12%22%10%1
2112
April1st to 15thNight
49%410%20%13%
1820
16th to endNight
42%5%11%19%16%4
1620
May1st to 15thNight
47%412%19%13%2
1620
16th to endNight
38%5%11%24%16%3
1684
June1st to 15thNight
36%6%11%28%15%1
1301
16th to endNight
33%7%11%25%19%1
1279
July1st to 15thNight
30%410%31%20%2
1360
16th to endNight
25%8%17%24%19%3
1539
August1st to 15thNight
30%6%14%31%13%3
1609
16th to endNight
30%5%13%30%17%2
1719
September1st to 15thNight
33%7%11%28%17%1
1932
16th to endNight
34%5%13%30%15%1
1870
October1st to 15thNight
41%5%12%21%18%
1917
16th to endNight
51%5%13%21%6%
2178
November1st to 15thNight
43%5%11%24%12%1
2276
16th to endNight
55%413%19%6%
2449
December1st to 15thNight
63%6%11%12%6%
2520
16th to endNight
69%5%9%10%4
2775

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%441%22%7%2
90
16th to endDay
31%333%21%9%1
96
February1st to 15thDay
18%244%32%2
90
16th to endDay
12%7%34%35%9%
81
March1st to 15thDay
23%14%23%27%9%
192
16th to endDay
22%13%21%30%9%3
288
April1st to 15thDay
18%13%21%33%8%4
270
16th to endDay
21%12%20%25%12%7%
270
May1st to 15thDay
17%11%18%29%18%4
288
16th to endDay
13%10%18%27%22%6%
331
June1st to 15thDay
9%13%14%33%23%4
452
16th to endDay
8%13%16%35%18%6%
495
July1st to 15thDay
6%9%11%32%29%10%
475
16th to endDay
7%12%8%29%29%13%
382
August1st to 15thDay
8%6%5%32%30%16%
313
16th to endDay
11%7%7%24%32%16%
332
September1st to 15thDay
11%6%13%21%29%18%
315
16th to endDay
14%8%10%20%29%17%
270
October1st to 15thDay
15%9%20%23%21%10%
255
16th to endDay
25%8%29%28%6%1
203
November1st to 15thDay
10%7%17%35%25%3
90
16th to endDay
26%16%22%25%8%
71
December1st to 15thDay
25%141%28%3
60
16th to endDay
25%12%42%17%2
75
January1st to 15thNight
20%22%28%22%41
900
16th to endNight
17%22%25%28%6%
804
February1st to 15thNight
18%21%29%26%4
704
16th to endNight
17%19%26%29%6%
631
March1st to 15thNight
18%19%25%28%6%
720
16th to endNight
18%18%24%25%10%2
768
April1st to 15thNight
19%20%21%30%6%1
619
16th to endNight
14%19%22%29%12%2
540
May1st to 15thNight
15%18%19%30%14%1
540
16th to endNight
10%18%16%30%20%3
563
June1st to 15thNight
8%19%13%40%17%1
360
16th to endNight
9%17%11%35%22%3
379
July1st to 15thNight
8%13%8%33%30%5%
510
16th to endNight
6%16%7%39%24%4
564
August1st to 15thNight
6%10%9%35%30%7%
539
16th to endNight
7%9%9%34%33%6%
573
September1st to 15thNight
11%11%12%28%27%7%
687
16th to endNight
12%10%11%28%28%8%
677
October1st to 15thNight
17%12%19%25%20%3
660
16th to endNight
22%15%28%25%6%
704
November1st to 15thNight
13%19%25%26%13%1
700
16th to endNight
23%25%24%18%6%
720
December1st to 15thNight
24%22%27%19%4
720
16th to endNight
23%22%28%20%4
924
Page generated at 2017-09-21 07:18:20. Version ac04

Copyright 2017 A. Danko


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