McKim Alpena County Observation Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the McKim Alpena County Observation Site 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
30%
15620
13%
47030
7%
15578
36%
15578
18%
33571

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
15%
900
6%
2506
2%
895
19%
895
8%
2081
January16th to endNight
16%
948
9%
2676
2%
948
22%
948
11%
2155
February1st to 15thNight
13%
701
8%
2284
3%
701
19%
701
10%
1786
February16th to endNight
21%
631
10%
1893
4%
631
27%
631
11%
1487
March1st to 15thNight
22%
720
14%
2093
7%
720
29%
720
17%
1499
March16th to endNight
29%
768
19%
2112
10%
768
36%
768
23%
1438
April1st to 15thNight
25%
560
16%
1770
7%
560
33%
560
18%
1232
April16th to endNight
34%
540
18%
1620
9%
540
41%
540
22%
1109
May1st to 15thNight
32%
540
13%
1620
7%
540
38%
540
21%
1117
May16th to endNight
41%
490
16%
1497
9%
489
49%
489
28%
924
June1st to 15thNight
40%
360
12%
1260
10%
360
46%
360
23%
790
June16th to endNight
47%
360
13%
1260
12%
360
51%
360
26%
760
July1st to 15thNight
56%
440
15%
1290
11%
440
60%
440
37%
735
July16th to endNight
55%
564
14%
1423
10%
531
57%
531
36%
878
August1st to 15thNight
56%
539
18%
1609
13%
536
62%
536
35%
922
August16th to endNight
55%
573
20%
1719
14%
573
60%
573
34%
1014
September1st to 15thNight
51%
646
18%
1906
12%
646
56%
646
31%
1164
September16th to endNight
48%
717
19%
1980
14%
717
51%
717
30%
1282
October1st to 15thNight
35%
684
16%
1969
11%
684
42%
684
23%
1348
October16th to endNight
23%
704
11%
2244
7%
704
29%
704
13%
1671
November1st to 15thNight
25%
700
15%
2276
11%
700
31%
700
16%
1613
November16th to endNight
20%
720
9%
2491
5%
720
27%
720
11%
1900
December1st to 15thNight
14%
855
5%
2655
1%
855
18%
855
8%
2207
December16th to endNight
12%
960
6%
2877
1%
960
17%
960
7%
2459

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%9%47%6%35%45%7%31%
48167
Night
14%9%47%6%35%45%6%32%
47199
Cloud CoverDay
14%9%47%6%35%5%5%7%31%
48176
Night
14%9%47%6%35%45%6%33%
47204
TransparencyDay
51%6%12%18%9%1
47854
Night
50%6%13%19%9%
47030
SeeingDay
18%12%31%22%9%4
6019
Night
19%11%32%26%9%1
15624

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
16%14%6%12%8%45%5%35%16%
1432
16th to endDay
12%14%8%14%11%5%6%45%313%
1548
February1st to 15thDay
13%14%7%10%11%5%6%43418%
1577
16th to endDay
12%16%5%11%9%35%5%45%19%
1580
March1st to 15thDay
13%10%49%8%45%45%6%27%
1856
16th to endDay
15%11%36%6%35%446%31%
2112
April1st to 15thDay
19%12%46%423345%31%
2187
16th to endDay
16%10%25%42345%7%36%
2340
May1st to 15thDay
18%6%36%5%25%5%5%6%33%
2331
16th to endDay
13%5%25%5%35%447%41%
2614
June1st to 15thDay
12%5%27%6%35%5%5%8%36%
2700
16th to endDay
13%6%26%6%36%5%6%8%35%
2700
July1st to 15thDay
11%425%5%35%5%6%9%39%
2588
16th to endDay
10%5%35%5%46%5%7%9%37%
2649
August1st to 15thDay
11%5%26%6%35%5%7%8%37%
2340
16th to endDay
12%7%26%6%25%46%8%37%
2481
September1st to 15thDay
13%6%35%5%245%5%7%40%
2040
16th to endDay
15%6%25%435%45%7%38%
1980
October1st to 15thDay
19%8%37%5%34346%34%
1789
16th to endDay
23%12%5%8%7%35%446%17%
1628
November1st to 15thDay
14%12%47%6%35%5%5%6%28%
1582
16th to endDay
18%16%6%9%6%4445%5%19%
1467
December1st to 15thDay
15%17%6%11%8%36%345%16%
1302
16th to endDay
19%17%8%11%8%4443412%
1344
January1st to 15thNight
18%12%5%10%8%46%5%5%5%16%
2506
16th to endNight
12%13%6%11%9%46%445%19%
2676
February1st to 15thNight
11%14%5%10%10%46%5%5%5%20%
2282
16th to endNight
13%14%7%12%7%35%5%45%21%
1893
March1st to 15thNight
13%11%47%5%35%435%34%
2080
16th to endNight
14%9%45%414446%39%
2112
April1st to 15thNight
19%10%344235%6%6%32%
1770
16th to endNight
15%10%35%43445%5%38%
1620
May1st to 15thNight
13%6%26%7%25%6%5%7%34%
1620
16th to endNight
12%6%13425%5%5%8%43%
1495
June1st to 15thNight
11%6%25%5%345%6%7%40%
1260
16th to endNight
8%5%235%35%46%10%44%
1260
July1st to 15thNight
7%323425%46%8%50%
1369
16th to endNight
7%4234245%6%9%48%
1519
August1st to 15thNight
7%425%32445%8%51%
1620
16th to endNight
10%5%24434347%51%
1719
September1st to 15thNight
11%5%24424446%48%
1906
16th to endNight
14%5%2442346%6%44%
1980
October1st to 15thNight
16%6%36%5%2434440%
1969
16th to endNight
22%9%46%5%24446%28%
2244
November1st to 15thNight
14%11%37%6%35%5%6%8%28%
2276
16th to endNight
17%13%5%7%6%35%5%47%22%
2491
December1st to 15thNight
17%13%5%11%8%46%45%5%17%
2655
16th to endNight
18%15%8%11%6%46%44414%
2877

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
17%13%7%11%7%445%45%17%
1432
16th to endDay
11%14%7%14%10%5%6%5%45%13%
1548
February1st to 15thDay
13%14%6%10%11%47%44419%
1577
16th to endDay
12%14%5%9%10%5%5%5%45%20%
1580
March1st to 15thDay
13%10%5%9%8%45%5%46%26%
1866
16th to endDay
15%10%47%6%3445%5%31%
2111
April1st to 15thDay
19%12%46%423445%31%
2187
16th to endDay
16%10%245%23447%37%
2340
May1st to 15thDay
17%6%36%5%35%45%6%34%
2331
16th to endDay
13%5%25%5%25%45%8%41%
2614
June1st to 15thDay
12%6%26%5%35%5%5%7%37%
2700
16th to endDay
13%6%36%5%36%5%5%9%35%
2700
July1st to 15thDay
10%425%5%36%5%5%8%40%
2588
16th to endDay
10%5%35%5%36%5%6%9%38%
2649
August1st to 15thDay
12%425%6%35%6%6%8%38%
2340
16th to endDay
12%7%36%6%345%6%8%37%
2481
September1st to 15thDay
13%6%245%345%5%8%40%
2040
16th to endDay
15%6%245%35%45%8%38%
1980
October1st to 15thDay
18%8%27%5%34436%34%
1789
16th to endDay
22%13%47%8%45%445%18%
1628
November1st to 15thDay
14%11%47%5%346%47%29%
1582
16th to endDay
17%15%5%9%7%3445%5%19%
1467
December1st to 15thDay
16%15%6%11%8%25%5%47%17%
1302
16th to endDay
18%17%8%11%7%45%435%13%
1344
January1st to 15thNight
18%13%5%9%8%46%445%18%
2506
16th to endNight
12%12%6%12%9%45%5%5%5%21%
2676
February1st to 15thNight
11%14%5%10%9%46%46%6%22%
2275
16th to endNight
13%14%6%11%7%34446%21%
1893
March1st to 15thNight
13%10%48%6%35%445%34%
2093
16th to endNight
14%10%36%423336%41%
2112
April1st to 15thNight
20%10%3442346%7%33%
1770
16th to endNight
15%8%35%5%24446%38%
1620
May1st to 15thNight
13%6%36%7%25%6%5%7%34%
1619
16th to endNight
12%6%143345%5%8%44%
1495
June1st to 15thNight
12%5%25%5%26%6%6%7%40%
1260
16th to endNight
8%5%145%35%46%10%44%
1260
July1st to 15thNight
7%324425%45%8%51%
1369
16th to endNight
7%3144245%6%9%48%
1519
August1st to 15thNight
7%32443445%8%51%
1620
16th to endNight
10%5%14423347%51%
1719
September1st to 15thNight
11%4245%3445%6%49%
1906
16th to endNight
14%4245%2445%6%45%
1980
October1st to 15thNight
16%7%26%5%34445%39%
1969
16th to endNight
22%9%36%5%2435%6%28%
2244
November1st to 15thNight
14%10%36%5%35%5%5%9%29%
2276
16th to endNight
17%12%5%7%6%35%45%6%24%
2491
December1st to 15thNight
16%13%6%10%8%46%5%45%18%
2655
16th to endNight
19%15%7%10%6%45%44415%
2877

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
68%5%11%11%3
1433
16th to endDay
73%49%9%2
1548
February1st to 15thDay
69%5%9%11%3
1579
16th to endDay
64%6%10%11%5%
1580
March1st to 15thDay
56%6%12%17%6%
1866
16th to endDay
51%6%12%18%8%1
2112
April1st to 15thDay
54%5%9%18%12%
2187
16th to endDay
46%5%14%16%15%2
2340
May1st to 15thDay
49%6%9%20%11%2
2331
16th to endDay
41%6%13%22%14%2
2618
June1st to 15thDay
44%6%11%22%12%1
2700
16th to endDay
44%7%13%21%12%1
2700
July1st to 15thDay
39%6%11%23%16%1
2438
16th to endDay
41%8%13%20%14%1
2482
August1st to 15thDay
41%7%14%22%12%1
2327
16th to endDay
43%6%14%22%11%1
2481
September1st to 15thDay
41%6%11%26%12%
2040
16th to endDay
43%6%16%24%10%
1980
October1st to 15thDay
51%49%22%10%
1789
16th to endDay
66%7%11%10%3
1628
November1st to 15thDay
54%7%12%18%6%
1582
16th to endDay
66%5%14%10%2
1467
December1st to 15thDay
67%7%12%9%2
1302
16th to endDay
75%5%9%7%1
1344
January1st to 15thNight
67%6%11%11%3
2506
16th to endNight
64%5%14%11%3
2676
February1st to 15thNight
63%5%11%15%4
2284
16th to endNight
62%5%13%13%5%
1893
March1st to 15thNight
51%5%12%20%8%
2093
16th to endNight
45%412%23%12%2
2112
April1st to 15thNight
49%5%9%21%12%1
1770
16th to endNight
45%5%10%19%15%3
1620
May1st to 15thNight
46%6%12%19%11%2
1620
16th to endNight
36%6%13%25%14%3
1497
June1st to 15thNight
40%6%13%23%14%
1260
16th to endNight
34%8%14%26%14%1
1260
July1st to 15thNight
29%6%14%28%19%1
1290
16th to endNight
31%7%18%26%15%1
1423
August1st to 15thNight
28%8%17%30%14%1
1609
16th to endNight
32%5%17%29%14%1
1719
September1st to 15thNight
35%6%13%31%13%1
1906
16th to endNight
38%6%15%29%10%
1980
October1st to 15thNight
46%411%24%11%
1969
16th to endNight
55%7%13%18%5%
2244
November1st to 15thNight
51%6%15%18%6%
2276
16th to endNight
60%6%15%14%3
2491
December1st to 15thNight
66%8%12%9%2
2655
16th to endNight
71%6%10%8%3
2877

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%17%45%11%3
90
16th to endDay
30%6%37%17%7%1
96
February1st to 15thDay
36%22%32%8%
90
16th to endDay
23%29%34%11%1
81
March1st to 15thDay
25%17%33%16%6%
156
16th to endDay
27%9%30%21%9%1
288
April1st to 15thDay
24%14%28%21%10%1
270
16th to endDay
22%14%34%13%10%4
270
May1st to 15thDay
22%13%32%16%8%6%
288
16th to endDay
15%14%34%24%7%3
445
June1st to 15thDay
15%15%36%22%8%2
495
16th to endDay
15%12%35%25%7%3
495
July1st to 15thDay
13%9%35%28%9%4
475
16th to endDay
11%8%34%29%10%5%
509
August1st to 15thDay
12%225%31%14%13%
313
16th to endDay
18%5%23%24%17%9%
332
September1st to 15thDay
15%6%20%28%15%13%
315
16th to endDay
16%8%23%28%14%8%
314
October1st to 15thDay
22%12%33%19%10%1
278
16th to endDay
24%22%32%15%5%
140
November1st to 15thDay
11%21%35%25%5%1
90
16th to endDay
26%20%35%15%11
65
December1st to 15thDay
30%26%35%331
60
16th to endDay
34%29%31%4
64
January1st to 15thNight
24%17%34%18%4
900
16th to endNight
18%14%38%22%5%
948
February1st to 15thNight
19%17%37%21%3
704
16th to endNight
23%14%31%26%4
631
March1st to 15thNight
20%17%33%22%5%
720
16th to endNight
19%12%34%25%7%1
768
April1st to 15thNight
24%11%34%22%41
560
16th to endNight
18%11%30%28%8%1
540
May1st to 15thNight
16%9%34%28%9%1
540
16th to endNight
14%9%29%33%12%
491
June1st to 15thNight
15%7%30%36%9%
360
16th to endNight
9%7%29%36%15%
360
July1st to 15thNight
9%326%41%16%2
440
16th to endNight
9%325%40%19%2
564
August1st to 15thNight
8%126%36%23%2
539
16th to endNight
14%221%35%22%2
573
September1st to 15thNight
15%325%28%20%6%
646
16th to endNight
16%5%24%29%19%4
717
October1st to 15thNight
19%8%30%28%11%
684
16th to endNight
27%12%31%22%5%
704
November1st to 15thNight
20%14%36%18%9%1
700
16th to endNight
23%14%35%21%4
720
December1st to 15thNight
22%17%38%18%3
855
16th to endNight
26%14%37%16%4
960
Page generated at 2017-10-07 14:07:44. Version ac04

Copyright 2017 A. Danko


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