Macomb
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Macomb clear sky chart from 2005-11-05 to 2017-10-06.

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
40%
16001
20%
47083
12%
15956
47%
15956
27%
30130

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
24%
900
17%
2506
7%
895
33%
895
22%
1708
January16th to endNight
21%
960
16%
2520
5%
960
29%
960
21%
1791
February1st to 15thNight
24%
868
13%
2278
3%
866
31%
866
21%
1639
February16th to endNight
28%
631
22%
1893
8%
631
39%
631
25%
1208
March1st to 15thNight
28%
654
19%
2094
10%
654
37%
654
21%
1383
March16th to endNight
29%
576
14%
2039
9%
576
37%
576
17%
1400
April1st to 15thNight
32%
539
18%
1797
12%
539
42%
539
23%
1136
April16th to endNight
35%
540
18%
1800
13%
540
45%
540
21%
1179
May1st to 15thNight
36%
540
18%
1569
11%
540
44%
540
23%
1063
May16th to endNight
49%
563
19%
1497
11%
561
55%
561
31%
983
June1st to 15thNight
60%
540
18%
1440
11%
540
63%
540
41%
856
June16th to endNight
51%
540
19%
1440
11%
540
56%
540
34%
903
July1st to 15thNight
67%
510
19%
1360
13%
510
69%
510
39%
829
July16th to endNight
75%
564
24%
1450
20%
531
78%
531
44%
823
August1st to 15thNight
76%
539
23%
1634
26%
536
78%
536
42%
869
August16th to endNight
72%
573
22%
1910
25%
573
76%
573
35%
1058
September1st to 15thNight
65%
540
29%
1800
30%
540
68%
540
37%
966
September16th to endNight
61%
651
31%
1933
21%
651
68%
651
38%
1069
October1st to 15thNight
49%
684
27%
2052
20%
684
55%
684
36%
1186
October16th to endNight
36%
704
21%
2142
13%
704
45%
704
29%
1279
November1st to 15thNight
34%
700
26%
2276
15%
700
48%
700
28%
1332
November16th to endNight
28%
825
19%
2445
10%
825
38%
825
24%
1583
December1st to 15thNight
24%
900
14%
2520
5%
900
31%
900
19%
1824
December16th to endNight
20%
960
14%
2688
5%
960
29%
960
15%
2063

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%38%
48117
Night
13%7%35%424446%43%
47255
Cloud CoverDay
13%7%35%5%3445%7%39%
48125
Night
13%7%35%424346%43%
47260
TransparencyDay
43%412%23%13%1
47806
Night
41%412%24%15%2
47084
SeeingDay
13%6%24%28%20%6%
6020
Night
16%8%28%31%13%1
16002

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
12%11%5%10%6%346%46%29%
1432
16th to endDay
15%14%6%7%6%24445%28%
1701
February1st to 15thDay
12%11%5%7%5%3445%6%32%
1583
16th to endDay
12%10%5%7%6%3445%5%34%
1580
March1st to 15thDay
14%11%46%435%446%34%
1868
16th to endDay
15%11%47%6%3445%7%29%
2184
April1st to 15thDay
16%8%45%5%24345%38%
2151
16th to endDay
19%7%26%5%345%5%6%33%
2160
May1st to 15thDay
19%7%36%435%45%6%32%
2379
16th to endDay
14%7%26%5%45%35%7%36%
2617
June1st to 15thDay
10%5%35%7%35%45%7%41%
2520
16th to endDay
8%4246%36%5%6%8%42%
2520
July1st to 15thDay
7%4245%45%5%7%9%44%
2520
16th to endDay
6%3245%46%6%7%10%42%
2616
August1st to 15thDay
8%4245%35%6%7%9%42%
2316
16th to endDay
9%5%245%3445%8%45%
2292
September1st to 15thDay
12%415%32345%7%49%
2160
16th to endDay
7%5%14425%5%5%7%48%
2012
October1st to 15thDay
15%5%14324335%47%
1706
16th to endDay
17%6%25%413346%45%
1730
November1st to 15thDay
14%7%34423346%46%
1582
16th to endDay
17%9%46%42335%439%
1512
December1st to 15thDay
19%11%47%5%2445%5%29%
1440
16th to endDay
19%14%5%6%5%23445%27%
1536
January1st to 15thNight
13%8%46%5%35%346%38%
2506
16th to endNight
12%10%5%8%6%34346%34%
2520
February1st to 15thNight
14%9%37%5%34446%34%
2275
16th to endNight
13%8%46%323346%43%
1893
March1st to 15thNight
15%8%35%5%23445%40%
2081
16th to endNight
17%10%45%5%3445%6%33%
2039
April1st to 15thNight
14%8%25%42435%6%41%
1797
16th to endNight
18%7%25%5%34346%39%
1800
May1st to 15thNight
16%7%35%434347%38%
1569
16th to endNight
9%4246%35%5%5%8%43%
1496
June1st to 15thNight
9%3245%24348%51%
1440
16th to endNight
7%425%6%25%45%8%46%
1440
July1st to 15thNight
6%314425%5%5%8%50%
1440
16th to endNight
43144245%7%10%51%
1549
August1st to 15thNight
5%21243445%8%56%
1644
16th to endNight
8%32442445%7%54%
1910
September1st to 15thNight
11%424312246%56%
1800
16th to endNight
6%3144245%5%8%52%
1933
October1st to 15thNight
11%413423346%52%
2052
16th to endNight
15%5%24313445%48%
2142
November1st to 15thNight
12%7%34323235%50%
2276
16th to endNight
16%8%2342345%7%40%
2445
December1st to 15thNight
19%10%46%424346%33%
2520
16th to endNight
20%12%5%8%42344428%
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
12%11%410%6%346%36%29%
1432
16th to endDay
14%14%6%7%6%34445%28%
1701
February1st to 15thDay
12%11%5%7%435%45%5%32%
1583
16th to endDay
12%11%5%7%6%3445%5%35%
1580
March1st to 15thDay
14%11%46%5%35%435%34%
1878
16th to endDay
15%10%47%7%3445%7%30%
2182
April1st to 15thDay
17%8%45%5%23345%38%
2151
16th to endDay
19%6%26%5%335%5%6%33%
2160
May1st to 15thDay
19%8%36%5%35%45%6%32%
2379
16th to endDay
14%6%26%6%35%35%7%36%
2617
June1st to 15thDay
10%5%26%7%35%45%7%41%
2520
16th to endDay
8%425%5%35%5%6%9%42%
2520
July1st to 15thDay
6%4245%35%5%6%10%44%
2520
16th to endDay
5%4245%46%5%7%10%42%
2616
August1st to 15thDay
7%4246%35%6%6%9%42%
2316
16th to endDay
10%425%5%35%45%7%46%
2292
September1st to 15thDay
12%42432345%8%49%
2160
16th to endDay
7%4144345%5%8%48%
2012
October1st to 15thDay
16%5%23324345%47%
1706
16th to endDay
17%6%34423335%45%
1730
November1st to 15thDay
14%7%24423346%46%
1582
16th to endDay
17%9%45%423345%39%
1512
December1st to 15thDay
19%11%5%7%5%245%5%5%29%
1440
16th to endDay
19%14%47%5%23445%27%
1536
January1st to 15thNight
13%8%46%5%35%346%38%
2506
16th to endNight
12%10%5%7%6%34347%34%
2520
February1st to 15thNight
14%9%46%5%35%35%6%34%
2268
16th to endNight
13%8%46%423336%43%
1893
March1st to 15thNight
16%9%25%424345%40%
2094
16th to endNight
17%10%45%43445%6%32%
2039
April1st to 15thNight
14%8%25%425%35%6%41%
1797
16th to endNight
18%6%25%6%34346%39%
1800
May1st to 15thNight
16%6%35%43345%6%38%
1568
16th to endNight
10%325%5%35%6%48%43%
1496
June1st to 15thNight
9%3245%24348%51%
1440
16th to endNight
7%425%5%25%46%8%46%
1440
July1st to 15thNight
6%323426%46%8%50%
1440
16th to endNight
42145%245%6%10%52%
1549
August1st to 15thNight
5%31343445%8%56%
1644
16th to endNight
8%31443435%7%53%
1910
September1st to 15thNight
11%414322246%56%
1800
16th to endNight
6%3135%335%5%8%52%
1933
October1st to 15thNight
11%5%14324346%52%
2052
16th to endNight
15%42431335%5%48%
2142
November1st to 15thNight
12%7%34323236%50%
2276
16th to endNight
17%8%2342345%7%40%
2445
December1st to 15thNight
20%10%46%434345%33%
2520
16th to endNight
20%13%5%7%5%2334428%
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
55%411%17%10%
1433
16th to endDay
57%214%17%6%
1701
February1st to 15thDay
53%315%21%5%
1584
16th to endDay
49%413%21%10%
1580
March1st to 15thDay
51%414%21%7%
1878
16th to endDay
53%313%21%5%1
2184
April1st to 15thDay
48%310%24%12%1
2151
16th to endDay
48%411%21%11%1
2160
May1st to 15thDay
51%411%22%9%
2379
16th to endDay
46%5%12%19%14%1
2621
June1st to 15thDay
39%5%11%24%16%1
2520
16th to endDay
35%6%13%24%17%3
2520
July1st to 15thDay
34%7%14%26%13%3
2371
16th to endDay
32%7%16%26%15%1
2452
August1st to 15thDay
35%6%14%26%15%1
2302
16th to endDay
34%6%12%23%17%4
2292
September1st to 15thDay
33%49%27%19%5%
2160
16th to endDay
33%411%31%17%2
2012
October1st to 15thDay
38%29%25%20%2
1706
16th to endDay
41%212%26%14%2
1730
November1st to 15thDay
40%211%23%18%2
1582
16th to endDay
47%313%24%9%
1512
December1st to 15thDay
55%414%18%7%
1440
16th to endDay
58%310%16%8%1
1536
January1st to 15thNight
47%312%22%13%
2506
16th to endNight
50%215%21%9%
2520
February1st to 15thNight
50%313%20%10%1
2278
16th to endNight
42%312%28%12%1
1893
March1st to 15thNight
47%310%25%10%2
2094
16th to endNight
50%5%13%20%8%1
2039
April1st to 15thNight
43%39%25%14%3
1797
16th to endNight
46%310%20%14%3
1800
May1st to 15thNight
45%5%13%20%15%
1569
16th to endNight
37%6%13%17%21%2
1498
June1st to 15thNight
30%414%27%20%3
1440
16th to endNight
34%6%11%23%20%3
1440
July1st to 15thNight
30%6%11%30%16%4
1360
16th to endNight
25%5%15%30%20%2
1450
August1st to 15thNight
25%413%33%18%3
1634
16th to endNight
29%5%11%25%20%6%
1910
September1st to 15thNight
30%29%26%23%7%
1800
16th to endNight
28%410%28%24%3
1933
October1st to 15thNight
32%39%26%22%4
2052
16th to endNight
37%311%26%19%2
2142
November1st to 15thNight
36%310%23%20%5%
2276
16th to endNight
43%411%26%14%
2445
December1st to 15thNight
53%312%22%7%
2520
16th to endNight
59%310%17%8%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
28%12%32%17%8%
90
16th to endDay
18%17%37%17%8%
96
February1st to 15thDay
17%16%38%18%7%
90
16th to endDay
8%14%38%27%9%1
81
March1st to 15thDay
28%10%43%13%4
90
16th to endDay
24%17%27%22%6%1
168
April1st to 15thDay
18%13%30%25%12%
270
16th to endDay
18%6%30%27%14%2
270
May1st to 15thDay
21%12%27%26%8%2
390
16th to endDay
18%7%28%28%12%5%
517
June1st to 15thDay
9%324%33%22%6%
495
16th to endDay
9%6%30%29%18%6%
495
July1st to 15thDay
11%318%32%24%10%
475
16th to endDay
5%116%33%35%7%
515
August1st to 15thDay
8%114%32%31%11%
469
16th to endDay
8%13%27%36%13%
332
September1st to 15thDay
10%214%30%33%9%
315
16th to endDay
4416%33%30%9%
293
October1st to 15thDay
13%8%23%26%20%8%
107
16th to endDay
18%6%35%33%6%
96
November1st to 15thDay
26%33%26%22%8%
90
16th to endDay
41%15%22%13%5%2
90
December1st to 15thDay
18%16%30%23%10%1
90
16th to endDay
27%17%44%7%3
96
January1st to 15thNight
16%13%41%21%7%
900
16th to endNight
17%14%37%26%3
960
February1st to 15thNight
18%12%37%27%4
869
16th to endNight
19%11%37%27%3
631
March1st to 15thNight
21%10%36%25%5%
654
16th to endNight
21%9%33%27%7%
576
April1st to 15thNight
19%12%31%28%6%
539
16th to endNight
21%7%28%30%10%
540
May1st to 15thNight
19%432%30%10%1
540
16th to endNight
11%428%36%18%1
563
June1st to 15thNight
10%320%45%19%1
540
16th to endNight
7%327%39%21%1
540
July1st to 15thNight
8%14%47%26%2
510
16th to endNight
5%19%48%32%2
564
August1st to 15thNight
6%17%47%33%4
539
16th to endNight
9%10%36%38%3
573
September1st to 15thNight
13%312%35%28%5%
540
16th to endNight
8%419%35%26%5%
651
October1st to 15thNight
14%427%30%20%2
684
16th to endNight
18%10%31%30%9%
704
November1st to 15thNight
16%9%34%27%11%1
700
16th to endNight
21%11%34%24%6%
825
December1st to 15thNight
25%10%34%24%5%
900
16th to endNight
27%11%33%23%3
960
Page generated at 2017-10-07 13:07:55. Version ac04

Copyright 2017 A. Danko


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