Copper Mountain Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Copper Mountain Observatory clear sky chart from 2005-11-06 to 2024-01-12.

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
72%
24757
40%
74392
31%
24711
81%
24711
63%
31831

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 10thNight
62%
758
35%
2457
29%
756
72%
756
48%
1102
January11th to 20thNight
65%
726
38%
2357
32%
726
77%
726
50%
1055
January21st to endNight
53%
792
42%
2376
27%
792
71%
792
47%
1135
February1st to 10thNight
60%
720
40%
2160
30%
720
75%
720
53%
996
February11th to 20thNight
59%
700
40%
2098
29%
700
77%
700
55%
944
February21st to endNight
55%
592
40%
1776
32%
592
71%
592
52%
809
March1st to 10thNight
56%
720
34%
2160
26%
720
71%
720
49%
1012
March11th to 20thNight
64%
720
38%
2038
28%
720
77%
720
61%
918
March21st to endNight
61%
792
39%
2124
23%
792
73%
792
59%
1002
April1st to 10thNight
61%
720
39%
1800
21%
720
70%
720
60%
900
April11th to 20thNight
62%
711
43%
1779
20%
711
74%
711
71%
822
April21st to endNight
68%
704
45%
1784
23%
704
77%
704
77%
790
May1st to 10thNight
69%
540
45%
1620
31%
540
76%
540
76%
614
May11th to 20thNight
75%
531
44%
1595
31%
531
80%
531
77%
612
May21st to endNight
73%
583
41%
1746
31%
582
78%
582
80%
648
June1st to 10thNight
80%
540
38%
1620
31%
540
83%
540
78%
620
June11th to 20thNight
80%
540
39%
1620
34%
540
82%
540
84%
596
June21st to endNight
83%
540
37%
1620
32%
540
85%
540
78%
624
July1st to 10thNight
89%
525
37%
1575
33%
525
89%
525
80%
597
July11th to 20thNight
87%
522
36%
1566
31%
522
87%
522
67%
661
July21st to endNight
85%
591
37%
1674
31%
558
86%
558
59%
759
August1st to 10thNight
89%
692
38%
1757
25%
689
90%
689
77%
801
August11th to 20thNight
93%
712
42%
1780
27%
712
94%
712
82%
798
August21st to endNight
90%
792
45%
1980
31%
792
91%
792
79%
898
September1st to 10thNight
89%
720
42%
1845
32%
720
91%
720
75%
842
September11th to 20thNight
90%
720
48%
1980
41%
720
95%
720
87%
776
September21st to endNight
86%
720
47%
1980
40%
720
92%
720
85%
783
October1st to 10thNight
78%
720
45%
1980
34%
720
87%
720
73%
857
October11th to 20thNight
81%
720
51%
1980
43%
720
88%
720
81%
806
October21st to endNight
78%
792
45%
2488
41%
792
87%
792
73%
928
November1st to 10thNight
75%
740
42%
2405
38%
740
86%
740
68%
916
November11th to 20thNight
76%
760
43%
2470
39%
760
87%
760
67%
958
November21st to endNight
68%
760
41%
2470
36%
760
79%
760
55%
1057
December1st to 10thNight
67%
760
37%
2470
32%
760
77%
760
52%
1102
December11th to 20thNight
60%
759
36%
2895
28%
758
72%
758
42%
1275
December21st to endNight
55%
823
24%
4367
28%
817
69%
817
30%
1818

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
1112213346%76%
74853
Night
1112213346%76%
74898
TransparencyDay
12%35%13%26%42%
74580
Night
11%35%14%28%39%
74693
SeeingDay
412%25%33%20%7%
14403
Night
25%17%35%32%9%
24778

By Month

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 10thDay
231342435%7%67%
1708
11th to 20thDay
231231345%7%69%
1629
21st to endDay
3213424447%67%
1980
February1st to 10thDay
1313323445%72%
1800
11th to 20thDay
112323349%70%
1750
21st to endDay
1212323448%71%
1480
March1st to 10thDay
221232345%9%68%
1800
11th to 20thDay
2212223347%72%
1921
21st to endDay
1112212447%76%
2227
April1st to 10thDay
2213213237%73%
2160
11th to 20thDay
1112212235%81%
2129
21st to endDay
1111112335%82%
2173
May1st to 10thDay
1111212235%82%
2340
11th to 20thDay
1111122485%
2301
21st to endDay
111111223484%
2530
June1st to 10thDay
111112225%84%
2340
11th to 20thDay
111112390%
2340
21st to endDay
111121222384%
2340
July1st to 10thDay
1112212335%78%
2340
11th to 20thDay
3112223345%73%
2340
21st to endDay
3213435%5%6%7%62%
2545
August1st to 10thDay
1212213335%78%
2168
11th to 20thDay
11222345%6%75%
2122
21st to endDay
2111213245%78%
2376
September1st to 10thDay
2112222445%76%
2113
11th to 20thDay
11212290%
1980
21st to endDay
11211232384%
1980
October1st to 10thDay
1111213345%79%
1980
11th to 20thDay
1111122485%
1980
21st to endDay
1111222485%
1862
November1st to 10thDay
112212345%79%
1674
11th to 20thDay
121221235%6%76%
1710
21st to endDay
2112214347%73%
1710
December1st to 10thDay
222342345%9%64%
1710
11th to 20thDay
23244345%7%10%58%
2169
21st to endDay
43244345%7%9%56%
3146
January1st to 10thNight
121332446%9%65%
2457
11th to 20thNight
221332445%7%68%
2357
21st to endNight
322332245%6%68%
2376
February1st to 10thNight
2213323337%71%
2160
11th to 20thNight
221222346%5%71%
2098
21st to endNight
121222446%8%69%
1776
March1st to 10thNight
23133235%5%8%66%
2160
11th to 20thNight
111221335%8%72%
2038
21st to endNight
112323447%73%
2124
April1st to 10thNight
1213313347%72%
1800
11th to 20thNight
11121223482%
1779
21st to endNight
111111236%83%
1784
May1st to 10thNight
11111325%85%
1620
11th to 20thNight
1111223485%
1594
21st to endNight
1111111389%
1746
June1st to 10thNight
111233386%
1620
11th to 20thNight
111112389%
1620
21st to endNight
11111212386%
1620
July1st to 10thNight
11111123485%
1620
11th to 20thNight
111221235%5%76%
1620
21st to endNight
2212323346%71%
1773
August1st to 10thNight
111112335%81%
1766
11th to 20thNight
111112245%83%
1780
21st to endNight
11111123483%
1980
September1st to 10thNight
1111212235%81%
1845
11th to 20thNight
111122291%
1980
21st to endNight
11111122289%
1980
October1st to 10thNight
111213235%81%
1980
11th to 20thNight
111111112388%
1980
21st to endNight
1212335%84%
2488
November1st to 10thNight
1212235%81%
2405
11th to 20thNight
111213336%78%
2470
21st to endNight
311332335%7%71%
2470
December1st to 10thNight
222232345%8%66%
2470
11th to 20thNight
22134245%6%10%61%
3041
21st to endNight
2214435%5%6%8%60%
4521

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 10thDay
18%37%21%32%19%
1709
11th to 20thDay
16%47%16%34%24%
1629
21st to endDay
20%36%19%31%22%
1980
February1st to 10thDay
16%36%15%29%32%
1800
11th to 20thDay
14%4416%30%32%
1760
21st to endDay
15%36%17%31%27%
1480
March1st to 10thDay
14%46%19%31%27%
1800
11th to 20thDay
14%36%17%33%27%
1921
21st to endDay
10%36%22%33%26%
2227
April1st to 10thDay
14%25%17%34%28%
2160
11th to 20thDay
8%2312%33%42%
2132
21st to endDay
7%1415%33%40%
2173
May1st to 10thDay
9%2214%31%42%
2340
11th to 20thDay
6%1310%32%49%
2304
21st to endDay
7%2312%31%46%
2530
June1st to 10thDay
7%128%24%57%
2340
11th to 20thDay
3126%16%71%
2340
21st to endDay
9%12410%75%
2340
July1st to 10thDay
10%246%14%64%
2276
11th to 20thDay
13%36%13%23%42%
2271
21st to endDay
19%6%7%15%21%32%
2404
August1st to 10thDay
10%3410%20%53%
2153
11th to 20thDay
9%46%11%20%50%
2122
21st to endDay
10%349%22%51%
2376
September1st to 10thDay
12%46%8%15%55%
2113
11th to 20thDay
4125%22%67%
1980
21st to endDay
7%237%24%56%
1980
October1st to 10thDay
9%3310%27%48%
1980
11th to 20thDay
6%2310%26%54%
1980
21st to endDay
8%1310%24%54%
1862
November1st to 10thDay
9%2412%32%41%
1674
11th to 20thDay
11%2414%30%39%
1710
21st to endDay
13%26%16%30%33%
1710
December1st to 10thDay
20%37%19%25%26%
1710
11th to 20thDay
20%6%12%23%22%17%
2168
21st to endDay
21%8%10%24%25%12%
3146
January1st to 10thNight
17%47%20%31%21%
2457
11th to 20thNight
16%46%18%31%25%
2357
21st to endNight
18%37%19%27%26%
2376
February1st to 10thNight
16%35%16%26%34%
2160
11th to 20thNight
14%36%15%30%31%
2099
21st to endNight
14%45%18%30%28%
1776
March1st to 10thNight
17%36%19%30%24%
2160
11th to 20thNight
11%46%18%32%28%
2038
21st to endNight
13%37%18%37%23%
2124
April1st to 10thNight
15%25%21%31%26%
1800
11th to 20thNight
9%1414%33%38%
1779
21st to endNight
6%2414%35%39%
1784
May1st to 10thNight
5%1317%34%40%
1620
11th to 20thNight
6%1311%35%43%
1595
21st to endNight
41216%37%39%
1746
June1st to 10thNight
6%229%28%54%
1620
11th to 20thNight
4127%17%68%
1620
21st to endNight
7%115%12%73%
1620
July1st to 10thNight
6%126%17%68%
1575
11th to 20thNight
11%35%14%24%44%
1566
21st to endNight
15%36%19%24%32%
1674
August1st to 10thNight
8%3410%22%54%
1757
11th to 20thNight
6%2412%26%50%
1780
21st to endNight
8%139%25%54%
1980
September1st to 10thNight
8%35%9%20%56%
1845
11th to 20thNight
4126%22%65%
1980
21st to endNight
5%137%24%60%
1980
October1st to 10thNight
9%2310%31%45%
1980
11th to 20thNight
6%138%28%55%
1980
21st to endNight
7%25%9%22%56%
2488
November1st to 10thNight
8%3410%35%40%
2405
11th to 20thNight
10%1414%30%41%
2470
21st to endNight
15%25%15%31%32%
2470
December1st to 10thNight
18%27%19%25%30%
2470
11th to 20thNight
18%5%11%20%28%18%
3041
21st to endNight
18%8%11%23%27%13%
4521

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 10thDay
7%17%22%37%14%3
270
11th to 20thDay
12%10%23%35%18%2
243
21st to endDay
9%20%28%28%13%2
462
February1st to 10thDay
6%20%28%30%13%4
420
11th to 20thDay
7%25%30%27%11%1
415
21st to endDay
9%27%28%25%10%1
346
March1st to 10thDay
8%25%29%26%11%1
420
11th to 20thDay
8%16%30%30%13%1
420
21st to endDay
8%24%30%30%6%2
462
April1st to 10thDay
8%19%23%28%17%5%
420
11th to 20thDay
424%32%21%17%3
412
21st to endDay
420%28%27%15%6%
420
May1st to 10thDay
415%30%32%13%5%
423
11th to 20thDay
115%27%35%15%6%
448
21st to endDay
214%28%34%15%7%
485
June1st to 10thDay
29%25%36%18%10%
450
11th to 20thDay
7%27%31%24%10%
450
21st to endDay
25%26%36%19%11%
450
July1st to 10thDay
1121%38%27%13%
446
11th to 20thDay
1116%40%27%15%
444
21st to endDay
4214%41%24%16%
487
August1st to 10thDay
2219%40%24%13%
447
11th to 20thDay
2115%38%29%15%
437
21st to endDay
2116%36%28%17%
495
September1st to 10thDay
3319%41%27%7%
450
11th to 20thDay
25%25%36%27%5%
450
21st to endDay
29%22%32%27%8%
450
October1st to 10thDay
29%28%35%21%4
450
11th to 20thDay
27%25%38%26%2
450
21st to endDay
27%26%34%26%5%
334
November1st to 10thDay
313%21%31%29%4
270
11th to 20thDay
311%23%33%26%4
270
21st to endDay
216%24%33%19%6%
270
December1st to 10thDay
5%11%27%33%22%2
270
11th to 20thDay
417%20%34%21%3
270
21st to endDay
9%16%32%24%16%2
297
January1st to 10thNight
49%20%35%23%9%
760
11th to 20thNight
38%20%39%23%7%
726
21st to endNight
6%10%26%33%21%5%
792
February1st to 10thNight
310%22%35%23%7%
720
11th to 20thNight
311%25%35%21%6%
704
21st to endNight
5%9%29%36%17%5%
592
March1st to 10thNight
5%11%24%37%21%3
720
11th to 20thNight
29%22%32%26%9%
720
21st to endNight
310%23%37%22%5%
792
April1st to 10thNight
29%22%36%26%5%
720
11th to 20thNight
28%26%34%24%6%
711
21st to endNight
27%21%35%27%8%
704
May1st to 10thNight
17%21%38%29%4
540
11th to 20thNight
15%17%38%34%7%
531
21st to endNight
15%20%38%31%5%
584
June1st to 10thNight
215%42%36%4
540
11th to 20thNight
217%40%36%5%
540
21st to endNight
1212%39%39%8%
540
July1st to 10thNight
16%33%48%11%
525
11th to 20thNight
27%34%47%10%
522
21st to endNight
215%33%50%9%
591
August1st to 10thNight
16%32%45%15%
692
11th to 20thNight
1325%53%18%
712
21st to endNight
2423%47%23%
792
September1st to 10thNight
125%26%51%16%
720
11th to 20thNight
18%33%44%14%
720
21st to endNight
1110%34%40%13%
720
October1st to 10thNight
2216%39%36%5%
720
11th to 20thNight
1313%37%36%10%
720
21st to endNight
16%14%34%32%14%
792
November1st to 10thNight
16%16%34%32%11%
740
11th to 20thNight
2416%36%32%10%
760
21st to endNight
36%18%37%27%8%
760
December1st to 10thNight
45%20%40%24%7%
760
11th to 20thNight
36%26%34%26%6%
760
21st to endNight
413%23%34%19%6%
836
Page generated at 2024-01-09 04:14:45. Version ac07

Copyright 2024 Attilla Danko


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