Cima
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cima clear sky chart from 2005-11-05 to 2018-02-14.

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
66%
16569
37%
48813
27%
16529
75%
16529
55%
22566

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
55%
779
32%
2522
24%
776
68%
776
43%
1219
January16th to endNight
52%
832
35%
2632
25%
832
67%
832
41%
1306
February1st to 15thNight
57%
754
36%
2280
27%
754
70%
754
50%
1093
February16th to endNight
52%
632
33%
1895
29%
632
63%
632
42%
974
March1st to 15thNight
55%
720
33%
2112
26%
720
68%
720
46%
1056
March16th to endNight
56%
768
34%
2112
23%
768
66%
768
49%
1061
April1st to 15thNight
47%
719
35%
1805
14%
719
59%
719
50%
930
April16th to endNight
55%
654
40%
1734
18%
654
68%
654
60%
787
May1st to 15thNight
61%
540
38%
1619
22%
539
70%
539
64%
664
May16th to endNight
59%
561
36%
1685
22%
561
69%
561
62%
688
June1st to 15thNight
70%
540
32%
1620
26%
540
75%
540
67%
663
June16th to endNight
78%
540
37%
1620
29%
540
83%
540
80%
613
July1st to 15thNight
87%
510
30%
1530
26%
510
89%
510
64%
662
July16th to endNight
81%
564
31%
1593
27%
531
82%
531
51%
798
August1st to 15thNight
87%
616
38%
1689
27%
613
89%
613
67%
765
August16th to endNight
87%
764
42%
1910
29%
764
89%
764
71%
928
September1st to 15thNight
83%
720
36%
1914
27%
720
87%
720
63%
927
September16th to endNight
80%
716
49%
1980
38%
716
88%
716
79%
811
October1st to 15thNight
73%
720
42%
1980
33%
720
80%
720
64%
903
October16th to endNight
73%
768
45%
2337
38%
768
84%
768
64%
984
November1st to 15thNight
67%
760
37%
2470
32%
760
78%
760
56%
1059
November16th to endNight
67%
780
41%
2535
37%
780
78%
780
53%
1100
December1st to 15thNight
59%
780
34%
2535
27%
780
71%
780
44%
1214
December16th to endNight
53%
832
36%
2704
27%
832
66%
832
38%
1361

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
2212223335%69%
49259
Night
2212213345%70%
49008
TransparencyDay
16%25%14%26%34%
48954
Night
16%25%15%27%33%
48814
SeeingDay
412%26%36%16%3
6209
Night
37%18%31%30%8%
16578

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
2413212338%64%
1746
16th to endDay
3413433336%61%
1942
February1st to 15thDay
3312223445%65%
1883
16th to endDay
35%245%23346%58%
1579
March1st to 15thDay
2312212347%66%
1847
16th to endDay
2312223347%65%
2112
April1st to 15thDay
321231434466%
2140
16th to endDay
211121123475%
2223
May1st to 15thDay
12112236%76%
2331
16th to endDay
1311212235%74%
2429
June1st to 15thDay
1121225%80%
2340
16th to endDay
111111285%
2340
July1st to 15thDay
3212323446%64%
2340
16th to endDay
4214435%5%47%56%
2467
August1st to 15thDay
1212323345%70%
2259
16th to endDay
3212223336%67%
2292
September1st to 15thDay
211323445%71%
2046
16th to endDay
111222381%
1980
October1st to 15thDay
221221123475%
1980
16th to endDay
11121223478%
1882
November1st to 15thDay
1312213345%71%
1719
16th to endDay
2212212347%68%
1755
December1st to 15thDay
24143225%5%8%59%
1755
16th to endDay
4424324447%58%
1872
January1st to 15thNight
221442445%6%61%
2522
16th to endNight
3424323346%61%
2632
February1st to 15thNight
2313312337%65%
2269
16th to endNight
4423423345%60%
1895
March1st to 15thNight
13133245%6%6%61%
2112
16th to endNight
2213223448%64%
2112
April1st to 15thNight
2213322245%69%
1805
16th to endNight
111112235%76%
1734
May1st to 15thNight
11212246%75%
1619
16th to endNight
11112225%78%
1684
June1st to 15thNight
1112122480%
1620
16th to endNight
112288%
1620
July1st to 15thNight
111131335%5%71%
1620
16th to endNight
6%21231446%7%59%
1701
August1st to 15thNight
111213345%74%
1698
16th to endNight
112212335%74%
1910
September1st to 15thNight
122213345%71%
1914
16th to endNight
111111286%
1980
October1st to 15thNight
21121223477%
1980
16th to endNight
11121223477%
2337
November1st to 15thNight
1222212345%72%
2470
16th to endNight
2312213336%69%
2535
December1st to 15thNight
2313324447%62%
2535
16th to endNight
4325%423347%58%
2704

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
20%26%22%32%16%
1747
16th to endDay
24%26%19%29%17%
1942
February1st to 15thDay
19%27%17%29%24%
1883
16th to endDay
27%26%15%32%15%
1579
March1st to 15thDay
16%25%19%32%23%
1847
16th to endDay
18%27%20%32%18%
2112
April1st to 15thDay
20%2417%32%23%
2140
16th to endDay
13%1417%31%31%
2223
May1st to 15thDay
10%1416%31%35%
2331
16th to endDay
14%1411%30%37%
2432
June1st to 15thDay
9%138%18%59%
2340
16th to endDay
8%11312%72%
2340
July1st to 15thDay
18%25%10%16%47%
2201
16th to endDay
21%38%15%20%30%
2312
August1st to 15thDay
15%3410%23%42%
2244
16th to endDay
17%3410%24%39%
2292
September1st to 15thDay
13%36%12%21%42%
2046
16th to endDay
8%137%28%50%
1980
October1st to 15thDay
14%1310%29%41%
1980
16th to endDay
10%2412%27%41%
1882
November1st to 15thDay
16%1417%33%26%
1719
16th to endDay
16%25%16%30%27%
1755
December1st to 15thDay
23%38%18%24%21%
1755
16th to endDay
27%27%21%25%14%
1872
January1st to 15thNight
22%36%20%28%19%
2522
16th to endNight
23%26%20%23%23%
2632
February1st to 15thNight
19%27%17%27%24%
2280
16th to endNight
24%26%17%31%16%
1895
March1st to 15thNight
20%35%18%30%22%
2112
16th to endNight
18%27%20%31%18%
2112
April1st to 15thNight
17%25%19%34%21%
1805
16th to endNight
10%1418%30%33%
1734
May1st to 15thNight
10%15%16%33%32%
1620
16th to endNight
9%25%14%35%32%
1685
June1st to 15thNight
10%129%18%57%
1620
16th to endNight
6%16%12%71%
1620
July1st to 15thNight
12%25%10%18%50%
1530
16th to endNight
20%47%13%23%31%
1593
August1st to 15thNight
11%2414%22%44%
1689
16th to endNight
12%1411%25%44%
1910
September1st to 15thNight
14%26%12%23%39%
1914
16th to endNight
6%18%28%53%
1980
October1st to 15thNight
11%2310%30%41%
1980
16th to endNight
11%1410%25%46%
2337
November1st to 15thNight
15%1314%36%27%
2470
16th to endNight
16%15%15%28%32%
2535
December1st to 15thNight
22%27%16%28%23%
2535
16th to endNight
25%28%19%27%16%
2704

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
17%11%29%27%13%1
135
16th to endDay
7%15%27%30%14%4
214
February1st to 15thDay
5%14%37%23%14%4
320
16th to endDay
7%24%33%22%10%
238
March1st to 15thDay
5%20%30%29%14%1
270
16th to endDay
5%23%31%27%9%1
288
April1st to 15thDay
8%26%33%19%8%4
269
16th to endDay
5%32%28%22%10%1
270
May1st to 15thDay
214%34%34%12%2
288
16th to endDay
212%39%31%11%2
330
June1st to 15thDay
18%37%35%13%2
315
16th to endDay
15%22%46%20%4
315
July1st to 15thDay
219%51%20%4
305
16th to endDay
6%10%53%22%6%
327
August1st to 15thDay
2418%51%17%5%
315
16th to endDay
415%46%24%8%
332
September1st to 15thDay
2225%47%19%2
315
16th to endDay
28%23%43%19%2
315
October1st to 15thDay
313%33%36%12%
315
16th to endDay
49%20%34%26%5%
184
November1st to 15thDay
317%17%28%25%6%
135
16th to endDay
7%17%22%29%20%2
135
December1st to 15thDay
6%19%19%28%25%1
135
16th to endDay
8%15%19%28%22%5%
144
January1st to 15thNight
47%26%31%22%7%
780
16th to endNight
7%9%23%31%22%6%
832
February1st to 15thNight
46%24%33%24%5%
760
16th to endNight
7%9%25%33%17%6%
632
March1st to 15thNight
411%23%32%22%5%
720
16th to endNight
312%22%31%23%5%
768
April1st to 15thNight
416%26%27%18%5%
719
16th to endNight
115%24%31%20%5%
654
May1st to 15thNight
28%26%32%25%4
540
16th to endNight
12%23%30%29%3
563
June1st to 15thNight
16%18%40%30%2
540
16th to endNight
118%37%39%2
540
July1st to 15thNight
25%35%51%5%
510
16th to endNight
6%5%28%53%5%
564
August1st to 15thNight
26%31%51%8%
616
16th to endNight
2423%49%19%
764
September1st to 15thNight
36%28%45%14%
720
16th to endNight
2212%28%34%18%
716
October1st to 15thNight
35%14%39%30%6%
720
16th to endNight
15%15%29%32%14%
768
November1st to 15thNight
2420%34%30%7%
760
16th to endNight
5%7%15%31%29%10%
780
December1st to 15thNight
6%8%20%33%25%6%
780
16th to endNight
7%11%21%30%21%6%
832
Page generated at 2018-02-15 07:58:39. Version ac04

Copyright 2018 A. Danko


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