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 2005-11-05 to 2017-09-16.

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
75%
16106
39%
46956
31%
16065
82%
16065
64%
20409

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
67%
719
34%
2327
30%
716
76%
716
50%
1051
January16th to endNight
62%
768
39%
2363
29%
768
75%
768
49%
1120
February1st to 15thNight
67%
699
38%
2108
31%
698
79%
698
56%
962
February16th to endNight
61%
632
38%
1895
35%
632
72%
632
50%
918
March1st to 15thNight
66%
720
36%
2139
32%
720
77%
720
58%
950
March16th to endNight
68%
768
38%
2076
28%
768
77%
768
59%
987
April1st to 15thNight
59%
719
39%
1799
18%
719
71%
719
62%
875
April16th to endNight
66%
708
43%
1788
21%
708
76%
708
76%
792
May1st to 15thNight
72%
539
43%
1619
30%
539
79%
539
76%
614
May16th to endNight
72%
562
40%
1685
29%
561
77%
561
76%
651
June1st to 15thNight
80%
540
35%
1620
29%
540
82%
540
78%
616
June16th to endNight
84%
540
37%
1620
32%
540
85%
540
82%
605
July1st to 15thNight
88%
510
32%
1530
29%
510
88%
510
71%
619
July16th to endNight
87%
564
36%
1593
30%
531
87%
531
61%
714
August1st to 15thNight
91%
702
38%
1776
26%
699
92%
699
77%
817
August16th to endNight
92%
764
44%
1910
31%
764
92%
764
78%
872
September1st to 15thNight
91%
720
39%
1890
31%
720
93%
720
76%
840
September16th to endNight
88%
660
48%
1826
43%
660
92%
660
86%
712
October1st to 15thNight
78%
660
45%
1815
36%
660
86%
660
73%
787
October16th to endNight
82%
704
45%
2126
41%
704
88%
704
71%
845
November1st to 15thNight
77%
700
40%
2275
36%
700
88%
700
68%
886
November16th to endNight
76%
720
43%
2340
41%
720
84%
720
60%
961
December1st to 15thNight
69%
720
36%
2340
31%
720
78%
720
51%
1050
December16th to endNight
61%
768
36%
2496
30%
768
72%
768
45%
1165

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
111212235%76%
47796
Night
111112235%76%
47155
TransparencyDay
12%2413%26%40%
47491
Night
11%25%14%28%37%
46961
SeeingDay
211%22%35%20%6%
5813
Night
1415%32%35%10%
16114

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 15thDay
2212313345%68%
1611
16th to endDay
223323346%66%
1860
February1st to 15thDay
12231335%6%69%
1751
16th to endDay
11232345%8%66%
1579
March1st to 15thDay
11112347%74%
1821
16th to endDay
111212337%74%
2145
April1st to 15thDay
1112112236%73%
2149
16th to endDay
11225%83%
2169
May1st to 15thDay
111113483%
2331
16th to endDay
1123483%
2429
June1st to 15thDay
1112485%
2340
16th to endDay
111111287%
2340
July1st to 15thDay
212212346%72%
2340
16th to endDay
2112324445%67%
2467
August1st to 15thDay
11221224477%
2172
16th to endDay
111113345%75%
2292
September1st to 15thDay
1111233477%
2068
16th to endDay
111111286%
1823
October1st to 15thDay
1121223479%
1815
16th to endDay
1112125%81%
1742
November1st to 15thDay
11211223478%
1584
16th to endDay
211213247%73%
1620
December1st to 15thDay
131221335%9%64%
1620
16th to endDay
3224222347%65%
1728
January1st to 15thNight
1212223347%66%
2327
16th to endNight
211231235%6%67%
2363
February1st to 15thNight
222222346%71%
2101
16th to endNight
1122245%5%8%65%
1895
March1st to 15thNight
1111112347%71%
2139
16th to endNight
2222346%73%
2076
April1st to 15thNight
12113335%76%
1799
16th to endNight
11135%83%
1788
May1st to 15thNight
122485%
1619
16th to endNight
11112385%
1684
June1st to 15thNight
1122286%
1620
16th to endNight
1112289%
1620
July1st to 15thNight
11122235%78%
1620
16th to endNight
112312345%72%
1701
August1st to 15thNight
1111123481%
1785
16th to endNight
1111124481%
1910
September1st to 15thNight
111235%80%
1890
16th to endNight
111191%
1826
October1st to 15thNight
1112225%80%
1815
16th to endNight
111123481%
2126
November1st to 15thNight
1212335%80%
2275
16th to endNight
211112236%76%
2340
December1st to 15thNight
221221345%8%65%
2340
16th to endNight
2213323346%66%
2496

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
18%26%19%31%22%
1612
16th to endDay
20%25%19%28%23%
1860
February1st to 15thDay
16%26%17%29%27%
1751
16th to endDay
18%47%18%32%18%
1579
March1st to 15thDay
10%2420%31%30%
1821
16th to endDay
12%25%21%32%24%
2145
April1st to 15thDay
13%2415%35%28%
2149
16th to endDay
7%1316%33%38%
2169
May1st to 15thDay
8%1210%33%43%
2331
16th to endDay
7%1311%30%45%
2432
June1st to 15thDay
6%128%18%63%
2340
16th to endDay
6%139%77%
2340
July1st to 15thDay
13%248%19%51%
2201
16th to endDay
17%46%13%22%35%
2312
August1st to 15thDay
10%239%20%52%
2157
16th to endDay
12%25%8%22%48%
2292
September1st to 15thDay
11%35%8%21%50%
2068
16th to endDay
7%12425%58%
1823
October1st to 15thDay
9%339%31%42%
1815
16th to endDay
9%1312%26%46%
1742
November1st to 15thDay
12%1413%33%34%
1584
16th to endDay
12%15%16%30%32%
1620
December1st to 15thDay
18%38%22%25%21%
1620
16th to endDay
21%38%24%25%17%
1728
January1st to 15thNight
17%36%18%28%25%
2327
16th to endNight
19%36%19%25%26%
2363
February1st to 15thNight
15%25%17%29%28%
2112
16th to endNight
18%45%20%30%20%
1895
March1st to 15thNight
13%25%18%32%27%
2139
16th to endNight
14%26%18%35%23%
2076
April1st to 15thNight
12%15%18%34%26%
1799
16th to endNight
6%415%36%36%
1788
May1st to 15thNight
5%1214%36%39%
1620
16th to endNight
6%1314%37%36%
1685
June1st to 15thNight
5%1110%20%59%
1620
16th to endNight
5%15%12%74%
1620
July1st to 15thNight
9%128%19%57%
1530
16th to endNight
14%36%14%26%35%
1593
August1st to 15thNight
8%2210%25%51%
1776
16th to endNight
8%139%26%50%
1910
September1st to 15thNight
7%25%10%21%52%
1890
16th to endNight
416%26%60%
1826
October1st to 15thNight
9%1310%34%40%
1815
16th to endNight
8%15%10%25%49%
2126
November1st to 15thNight
9%2413%36%34%
2275
16th to endNight
12%2317%30%33%
2340
December1st to 15thNight
17%39%17%26%25%
2340
16th to endNight
19%211%19%26%19%
2496

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
5%16%21%46%10%
90
16th to endDay
320%30%30%11%3
228
February1st to 15thDay
317%28%30%16%3
266
16th to endDay
7%26%25%24%15%
238
March1st to 15thDay
420%22%32%18%2
270
16th to endDay
320%27%34%12%1
288
April1st to 15thDay
7%24%27%21%14%4
269
16th to endDay
225%31%24%12%2
270
May1st to 15thDay
214%26%37%13%5%
288
16th to endDay
112%26%35%16%7%
330
June1st to 15thDay
18%28%33%21%6%
315
16th to endDay
1425%32%24%11%
315
July1st to 15thDay
115%42%28%11%
305
16th to endDay
1115%41%22%16%
327
August1st to 15thDay
1116%46%22%11%
315
16th to endDay
211%41%26%16%
332
September1st to 15thDay
1219%43%27%4
315
16th to endDay
28%18%35%29%5%
258
October1st to 15thDay
111%29%38%18%1
255
16th to endDay
28%20%32%33%1
173
November1st to 15thDay
17%11%24%40%6%
90
16th to endDay
216%27%32%16%4
90
December1st to 15thDay
314%12%31%35%3
90
16th to endDay
413%23%38%19%
96
January1st to 15thNight
35%17%37%24%11%
720
16th to endNight
46%21%33%25%8%
768
February1st to 15thNight
26%19%36%27%8%
704
16th to endNight
27%25%35%21%7%
632
March1st to 15thNight
27%19%36%26%7%
720
16th to endNight
9%17%35%27%8%
768
April1st to 15thNight
110%25%30%26%5%
719
16th to endNight
7%23%32%27%8%
708
May1st to 15thNight
6%18%35%32%6%
540
16th to endNight
420%33%33%6%
563
June1st to 15thNight
216%40%37%4
540
16th to endNight
12%36%43%6%
540
July1st to 15thNight
2431%50%11%
510
16th to endNight
1331%53%8%
564
August1st to 15thNight
1425%53%15%
702
16th to endNight
1217%53%25%
764
September1st to 15thNight
425%51%17%
720
16th to endNight
117%30%42%17%
660
October1st to 15thNight
1215%33%36%10%
660
16th to endNight
310%29%37%17%
704
November1st to 15thNight
217%30%36%12%
700
16th to endNight
35%12%31%32%14%
720
December1st to 15thNight
35%17%36%28%8%
720
16th to endNight
49%19%33%24%7%
768
Page generated at 2017-09-17 09:05:40. Version ac04

Copyright 2017 A. Danko


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