Copper Harbor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Copper Harbor clear sky chart from 2005-11-05 to 2017-08-12.

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
28%
15846
9%
46533
6%
15800
31%
15800
13%
35384

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
10%
900
1%
2506
0%
895
12%
895
2%
2298
January16th to endNight
13%
960
3%
2688
1%
960
15%
960
5%
2417
February1st to 15thNight
18%
878
2%
2373
1%
874
19%
874
8%
2067
February16th to endNight
26%
631
8%
1893
5%
631
29%
631
11%
1518
March1st to 15thNight
30%
720
13%
2160
9%
720
33%
720
17%
1531
March16th to endNight
33%
633
16%
2016
11%
633
40%
633
16%
1380
April1st to 15thNight
29%
539
11%
1797
7%
539
36%
539
14%
1281
April16th to endNight
32%
540
15%
1655
8%
540
39%
540
17%
1138
May1st to 15thNight
33%
540
10%
1461
7%
540
36%
540
18%
1070
May16th to endNight
38%
562
12%
1498
6%
561
42%
561
21%
1046
June1st to 15thNight
44%
423
8%
1323
6%
423
46%
423
19%
881
June16th to endNight
41%
417
8%
1317
5%
417
44%
417
18%
874
July1st to 15thNight
51%
510
9%
1360
6%
510
52%
510
31%
853
July16th to endNight
51%
564
16%
1417
9%
531
57%
531
35%
849
August1st to 15thNight
57%
527
20%
1400
14%
524
61%
524
37%
826
August16th to endNight
45%
525
16%
1682
11%
525
52%
525
27%
976
September1st to 15thNight
47%
495
17%
1650
13%
495
53%
495
23%
988
September16th to endNight
40%
651
11%
1809
8%
651
42%
651
24%
1220
October1st to 15thNight
32%
660
14%
1932
9%
660
37%
660
18%
1378
October16th to endNight
24%
704
6%
2288
4%
704
27%
704
10%
1790
November1st to 15thNight
20%
707
11%
2283
7%
707
27%
707
11%
1759
November16th to endNight
16%
900
6%
2547
3%
900
19%
900
6%
2223
December1st to 15thNight
6%
900
1%
2700
0%
900
7%
900
3%
2477
December16th to endNight
8%
960
3%
2778
1%
960
10%
960
3%
2544

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%10%48%7%35%446%31%
47434
Night
14%11%5%9%8%45%445%26%
46700
Cloud CoverDay
13%9%48%7%35%446%31%
47444
Night
14%11%5%9%8%45%5%5%5%25%
46705
Cloud CoverDay
13%9%48%7%35%446%31%
47443
Night
14%11%5%9%8%45%445%25%
46705
TransparencyDay
53%412%20%8%
47119
Night
59%411%16%6%
46533
SeeingDay
17%14%24%27%13%2
5987
Night
16%22%23%23%12%1
15847

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%16%10%16%13%7%7%3216%
1432
16th to endDay
10%14%8%15%14%8%7%4329%
1536
February1st to 15thDay
9%13%6%14%17%8%7%5%2211%
1485
16th to endDay
10%14%7%14%12%5%6%45%5%13%
1580
March1st to 15thDay
11%10%6%11%9%45%445%25%
1790
16th to endDay
16%10%6%8%5%35%446%27%
2216
April1st to 15thDay
14%10%46%6%34446%32%
2151
16th to endDay
18%9%25%5%3445%7%32%
2304
May1st to 15thDay
15%9%35%5%34446%36%
2490
16th to endDay
12%7%36%5%35%45%8%36%
2617
June1st to 15thDay
12%6%35%435%447%42%
2631
16th to endDay
13%5%35%6%2446%8%39%
2637
July1st to 15thDay
9%42442445%7%48%
2520
16th to endDay
8%315%5%24449%50%
2655
August1st to 15thDay
9%41433446%7%50%
2465
16th to endDay
11%6%144345%5%8%44%
2168
September1st to 15thDay
13%7%245%2445%7%42%
1975
16th to endDay
19%8%35%6%34447%33%
1815
October1st to 15thDay
17%13%37%6%33446%29%
1697
16th to endDay
23%17%6%11%6%4433314%
1584
November1st to 15thDay
17%19%5%8%435%5%4420%
1573
16th to endDay
16%18%7%15%11%5%5%32310%
1410
December1st to 15thDay
11%18%10%20%14%45%3323
1260
16th to endDay
18%20%12%16%9%35%3224
1443
January1st to 15thNight
13%13%8%16%14%6%9%5%326%
2506
16th to endNight
10%13%9%15%14%9%6%4436%
2688
February1st to 15thNight
10%12%6%13%13%8%9%5%3412%
2370
16th to endNight
11%13%7%10%10%5%6%45%5%17%
1893
March1st to 15thNight
10%11%37%8%45%446%32%
2147
16th to endNight
13%10%47%5%34447%33%
2016
April1st to 15thNight
16%9%35%7%46%5%45%30%
1797
16th to endNight
19%9%25%424446%34%
1655
May1st to 15thNight
19%7%37%8%345%5%6%29%
1461
16th to endNight
12%6%36%6%25%5%6%6%37%
1496
June1st to 15thNight
14%6%25%6%36%5%8%6%34%
1323
16th to endNight
14%6%25%6%35%5%6%8%35%
1317
July1st to 15thNight
10%5%245%3446%7%45%
1440
16th to endNight
7%324315%6%6%9%49%
1513
August1st to 15thNight
8%4134245%5%8%52%
1409
16th to endNight
10%5%25%43345%7%46%
1682
September1st to 15thNight
10%7%25%5%2445%6%45%
1650
16th to endNight
16%7%25%6%2335%6%39%
1809
October1st to 15thNight
18%10%36%5%24445%33%
1932
16th to endNight
20%13%48%8%34445%21%
2288
November1st to 15thNight
17%17%7%8%5%25%34423%
2283
16th to endNight
18%17%7%14%8%2444413%
2547
December1st to 15thNight
13%16%9%21%13%5%43226%
2700
16th to endNight
15%21%11%16%10%443226%
2778

Percentage Cloud Cover SW (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%16%8%16%13%6%9%4326%
1432
16th to endDay
10%14%7%16%17%7%6%3338%
1536
February1st to 15thDay
9%13%5%16%15%9%8%5%329%
1485
16th to endDay
10%12%7%13%12%5%7%5%46%13%
1580
March1st to 15thDay
12%10%6%11%10%45%445%25%
1800
16th to endDay
15%8%5%10%6%34446%28%
2216
April1st to 15thDay
14%10%46%5%45%447%32%
2151
16th to endDay
16%9%36%435%45%7%33%
2304
May1st to 15thDay
15%8%35%5%3445%6%37%
2490
16th to endDay
11%7%26%5%345%5%9%37%
2617
June1st to 15thDay
12%5%25%5%3345%8%42%
2631
16th to endDay
12%5%25%5%345%5%8%39%
2637
July1st to 15thDay
9%4244345%5%6%48%
2520
16th to endDay
7%31442345%8%52%
2655
August1st to 15thDay
8%4133245%5%9%50%
2465
16th to endDay
11%5%244345%5%8%45%
2168
September1st to 15thDay
13%6%25%5%2335%8%42%
1975
16th to endDay
19%7%25%5%2445%7%34%
1815
October1st to 15thDay
18%11%26%7%3445%6%28%
1697
16th to endDay
22%17%6%10%6%45%33314%
1584
November1st to 15thDay
18%15%7%9%6%45%445%19%
1573
16th to endDay
17%19%7%13%11%45%43310%
1410
December1st to 15thDay
12%17%9%20%13%45%4414
1260
16th to endDay
19%18%11%16%10%444224
1443
January1st to 15thNight
14%13%8%16%13%6%9%5%326%
2506
16th to endNight
10%14%7%14%14%8%7%6%437%
2688
February1st to 15thNight
9%13%7%13%11%8%9%7%4410%
2363
16th to endNight
11%12%5%10%10%5%6%5%5%6%18%
1893
March1st to 15thNight
11%11%47%6%45%5%5%6%31%
2160
16th to endNight
12%10%47%6%35%447%32%
2016
April1st to 15thNight
17%8%36%7%45%5%5%6%30%
1797
16th to endNight
19%9%25%42345%7%34%
1655
May1st to 15thNight
18%7%37%7%345%46%30%
1460
16th to endNight
11%6%35%6%45%46%6%37%
1496
June1st to 15thNight
14%5%36%6%345%7%8%34%
1323
16th to endNight
16%5%25%436%46%8%36%
1317
July1st to 15thNight
11%4245%345%5%8%43%
1440
16th to endNight
6%5%243245%6%8%49%
1513
August1st to 15thNight
7%4243345%5%7%51%
1409
16th to endNight
10%425%43436%7%46%
1682
September1st to 15thNight
12%6%25%434446%44%
1650
16th to endNight
15%7%345%2445%6%39%
1809
October1st to 15thNight
18%9%36%5%34445%34%
1932
16th to endNight
19%15%38%7%45%45%5%21%
2288
November1st to 15thNight
18%16%47%6%445%45%23%
2283
16th to endNight
17%18%8%11%9%35%5%4412%
2547
December1st to 15thNight
14%18%9%19%11%45%3336%
2700
16th to endNight
17%20%9%15%9%45%3326%
2778

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%16%9%16%13%6%8%5%216%
1432
16th to endDay
10%14%8%16%17%7%6%4238%
1536
February1st to 15thDay
9%13%6%16%15%10%7%5%329%
1485
16th to endDay
10%13%7%13%13%6%7%45%5%13%
1580
March1st to 15thDay
12%10%6%11%10%45%445%25%
1800
16th to endDay
15%9%5%9%7%34447%27%
2215
April1st to 15thDay
14%9%37%5%35%45%5%33%
2151
16th to endDay
16%9%36%5%25%447%34%
2304
May1st to 15thDay
15%8%35%5%35%45%6%37%
2490
16th to endDay
11%7%36%5%35%5%5%9%36%
2617
June1st to 15thDay
11%6%35%5%2445%8%42%
2631
16th to endDay
12%5%35%5%35%46%9%39%
2637
July1st to 15thDay
9%4244245%5%7%48%
2520
16th to endDay
7%314324448%53%
2655
August1st to 15thDay
8%3143245%5%8%50%
2465
16th to endDay
10%5%2433445%8%45%
2168
September1st to 15thDay
13%7%245%2345%7%42%
1975
16th to endDay
18%7%36%5%2445%6%34%
1815
October1st to 15thDay
17%11%47%7%245%46%28%
1697
16th to endDay
23%17%6%10%8%3333414%
1584
November1st to 15thDay
18%17%6%10%6%245%45%19%
1573
16th to endDay
17%18%8%13%11%444339%
1410
December1st to 15thDay
12%16%11%21%12%5%6%3313
1260
16th to endDay
19%20%11%16%10%35%3224
1443
January1st to 15thNight
13%13%8%16%14%6%9%5%226%
2506
16th to endNight
11%14%7%15%15%9%8%5%337%
2688
February1st to 15thNight
9%12%7%13%14%7%9%7%4310%
2363
16th to endNight
12%13%6%10%11%5%7%45%5%18%
1893
March1st to 15thNight
11%11%48%7%35%5%5%5%30%
2160
16th to endNight
12%10%48%6%35%5%47%32%
2016
April1st to 15thNight
16%8%46%7%45%45%6%30%
1797
16th to endNight
19%9%35%33345%7%34%
1655
May1st to 15thNight
18%7%37%7%35%45%6%30%
1460
16th to endNight
11%7%36%6%36%5%6%6%37%
1496
June1st to 15thNight
14%6%26%6%345%7%8%34%
1323
16th to endNight
15%6%25%5%345%6%8%35%
1317
July1st to 15thNight
11%425%5%245%6%7%43%
1440
16th to endNight
6%5%24325%5%6%9%49%
1513
August1st to 15thNight
7%3244245%5%7%51%
1409
16th to endNight
9%43444446%7%46%
1682
September1st to 15thNight
11%7%25%44435%6%43%
1650
16th to endNight
15%8%246%23446%39%
1809
October1st to 15thNight
18%10%36%6%24345%34%
1932
16th to endNight
19%15%48%7%44445%20%
2288
November1st to 15thNight
18%16%5%7%6%44335%23%
2283
16th to endNight
17%18%8%13%9%4433311%
2547
December1st to 15thNight
14%19%9%20%11%5%43225%
2700
16th to endNight
17%21%10%14%10%46%3226%
2778

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
83%346%1
1433
16th to endDay
78%5%8%6%1
1536
February1st to 15thDay
78%310%7%
1486
16th to endDay
71%48%11%3
1580
March1st to 15thDay
59%411%14%8%
1800
16th to endDay
56%413%18%6%1
2216
April1st to 15thDay
51%411%20%11%1
2151
16th to endDay
51%49%23%9%1
2304
May1st to 15thDay
48%312%22%11%1
2490
16th to endDay
45%5%12%24%12%
2621
June1st to 15thDay
41%417%24%11%
2631
16th to endDay
40%5%17%27%8%
2637
July1st to 15thDay
33%5%13%31%15%1
2371
16th to endDay
30%416%30%15%
2488
August1st to 15thDay
30%6%18%31%12%
2450
16th to endDay
36%5%18%27%11%
2168
September1st to 15thDay
41%417%30%6%
1975
16th to endDay
49%417%22%5%
1815
October1st to 15thDay
55%413%21%5%
1697
16th to endDay
74%49%8%3
1584
November1st to 15thDay
64%412%14%4
1573
16th to endDay
79%48%5%2
1410
December1st to 15thDay
86%26%3
1260
16th to endDay
86%26%4
1443
January1st to 15thNight
83%47%5%
2506
16th to endNight
79%48%6%
2688
February1st to 15thNight
74%412%8%
2373
16th to endNight
66%312%14%2
1893
March1st to 15thNight
51%413%19%9%
2160
16th to endNight
50%412%21%9%1
2016
April1st to 15thNight
53%49%20%9%1
1797
16th to endNight
49%39%22%13%
1655
May1st to 15thNight
52%410%18%11%
1461
16th to endNight
44%6%11%23%13%
1498
June1st to 15thNight
45%5%11%22%13%1
1323
16th to endNight
43%7%15%21%11%
1317
July1st to 15thNight
35%415%29%15%
1360
16th to endNight
29%6%15%31%14%2
1417
August1st to 15thNight
28%5%17%32%12%2
1400
16th to endNight
35%416%26%14%1
1682
September1st to 15thNight
39%415%32%9%
1650
16th to endNight
45%417%28%4
1809
October1st to 15thNight
51%415%20%7%
1932
16th to endNight
63%413%12%4
2288
November1st to 15thNight
62%411%15%6%
2283
16th to endNight
75%49%8%2
2547
December1st to 15thNight
83%47%3
2700
16th to endNight
83%46%5%
2778

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
21%8%33%27%8%
90
16th to endDay
13%7%32%33%12%1
96
February1st to 15thDay
25%13%33%21%6%
90
16th to endDay
23%14%34%22%4
81
March1st to 15thDay
15%20%22%30%12%
90
16th to endDay
20%17%25%22%10%2
248
April1st to 15thDay
22%16%22%28%8%1
270
16th to endDay
23%14%27%22%9%3
270
May1st to 15thDay
17%19%27%24%10%2
447
16th to endDay
19%17%23%26%10%2
517
June1st to 15thDay
14%14%26%33%8%2
495
16th to endDay
16%15%22%25%16%3
495
July1st to 15thDay
12%11%22%32%17%3
475
16th to endDay
8%15%22%31%16%4
515
August1st to 15thDay
13%8%21%32%20%3
474
16th to endDay
15%10%19%32%17%4
271
September1st to 15thDay
14%12%19%27%20%5%
255
16th to endDay
20%11%25%22%16%3
254
October1st to 15thDay
23%9%24%20%18%3
142
16th to endDay
31%13%34%17%3
96
November1st to 15thDay
15%18%28%22%12%2
90
16th to endDay
30%11%27%20%8%2
85
December1st to 15thDay
25%8%40%23%3
60
16th to endDay
25%24%35%12%1
81
January1st to 15thNight
14%29%31%18%5%
900
16th to endNight
13%27%30%21%6%
960
February1st to 15thNight
14%28%25%22%6%1
878
16th to endNight
16%20%25%28%8%1
631
March1st to 15thNight
13%25%24%23%10%2
720
16th to endNight
12%24%23%24%13%2
633
April1st to 15thNight
16%20%26%25%8%1
539
16th to endNight
22%19%20%23%10%3
540
May1st to 15thNight
17%20%20%25%14%2
540
16th to endNight
13%20%19%25%17%3
563
June1st to 15thNight
13%20%12%37%13%3
423
16th to endNight
17%19%13%28%18%3
417
July1st to 15thNight
11%14%14%30%23%4
510
16th to endNight
9%17%16%29%23%3
564
August1st to 15thNight
8%12%15%26%33%3
527
16th to endNight
13%13%20%26%22%3
525
September1st to 15thNight
13%13%20%23%23%5%
495
16th to endNight
16%14%21%28%16%2
651
October1st to 15thNight
21%16%22%22%15%1
660
16th to endNight
24%18%25%23%7%
704
November1st to 15thNight
20%24%25%20%7%
707
16th to endNight
22%28%23%19%6%
900
December1st to 15thNight
20%32%28%15%3
900
16th to endNight
21%29%25%16%5%1
960
Page generated at 2017-08-13 14:16:58. Version ac04

Copyright 2017 A. Danko


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