CCK's Universe
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the CCK's Universe 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
48%
15703
23%
47143
15%
15660
56%
15660
28%
29122

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
28%
719
23%
2327
10%
716
44%
716
22%
1408
January16th to endNight
28%
768
24%
2466
12%
768
43%
768
22%
1529
February1st to 15thNight
30%
704
26%
2109
10%
700
46%
700
26%
1263
February16th to endNight
26%
631
25%
1893
9%
631
42%
631
25%
1160
March1st to 15thNight
33%
720
26%
2019
11%
720
46%
720
31%
1215
March16th to endNight
38%
768
22%
2112
10%
768
47%
768
29%
1298
April1st to 15thNight
40%
718
25%
1976
14%
718
50%
718
35%
1187
April16th to endNight
49%
543
29%
1680
17%
543
61%
543
36%
947
May1st to 15thNight
49%
539
24%
1620
14%
539
58%
539
33%
946
May16th to endNight
61%
561
20%
1682
14%
561
65%
561
31%
1022
June1st to 15thNight
61%
540
15%
1620
12%
540
63%
540
27%
1062
June16th to endNight
69%
540
15%
1620
14%
540
69%
540
27%
1056
July1st to 15thNight
70%
510
11%
1530
9%
510
72%
510
26%
1032
July16th to endNight
74%
564
13%
1595
12%
531
75%
531
26%
1069
August1st to 15thNight
72%
539
15%
1609
15%
536
73%
536
25%
1077
August16th to endNight
63%
606
16%
1938
16%
606
64%
606
20%
1350
September1st to 15thNight
64%
720
17%
1980
16%
720
65%
720
27%
1331
September16th to endNight
56%
717
21%
1980
16%
717
60%
717
27%
1328
October1st to 15thNight
52%
684
30%
1914
23%
684
60%
684
36%
1140
October16th to endNight
53%
704
34%
2112
27%
704
64%
704
38%
1154
November1st to 15thNight
52%
700
31%
2185
24%
700
63%
700
37%
1182
November16th to endNight
39%
720
28%
2340
18%
720
53%
720
30%
1333
December1st to 15thNight
38%
720
25%
2340
18%
720
49%
720
26%
1402
December16th to endNight
35%
768
22%
2496
16%
768
45%
768
20%
1631

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
11%5%25%5%35%5%5%7%42%
48047
Night
11%5%2442445%7%45%
47345
TransparencyDay
38%6%11%18%17%6%
47748
Night
36%6%11%18%19%8%
47148
SeeingDay
13%7%19%24%22%12%
5574
Night
13%8%22%30%21%3
15707

By Month

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
15%5%145%24435%46%
1611
16th to endDay
16%4245%24337%45%
1755
February1st to 15thDay
14%5%2442345%6%45%
1750
16th to endDay
14%5%35%323346%46%
1580
March1st to 15thDay
13%434323247%48%
1941
16th to endDay
13%6%2442345%5%46%
2111
April1st to 15thDay
11%434424445%50%
1978
16th to endDay
8%42432445%8%51%
2283
May1st to 15thDay
9%5%245%3435%7%47%
2331
16th to endDay
8%425%5%46%5%6%8%41%
2431
June1st to 15thDay
9%5%25%6%46%6%7%10%34%
2340
16th to endDay
5%3346%46%7%8%11%38%
2340
July1st to 15thDay
8%5%36%7%47%8%8%10%29%
2340
16th to endDay
7%5%36%7%5%8%7%8%12%27%
2465
August1st to 15thDay
9%5%27%6%47%7%9%12%25%
2340
16th to endDay
13%6%37%6%48%6%6%7%27%
2249
September1st to 15thDay
12%5%25%5%37%5%6%9%36%
1980
16th to endDay
13%7%25%5%45%46%6%37%
1980
October1st to 15thDay
14%423222345%53%
1844
16th to endDay
10%412212445%59%
1760
November1st to 15thDay
10%424412336%54%
1670
16th to endDay
14%424413346%49%
1620
December1st to 15thDay
15%5%2342435%6%46%
1620
16th to endDay
19%8%36%433246%38%
1728
January1st to 15thNight
14%6%24323346%47%
2327
16th to endNight
16%6%25%32433447%
2466
February1st to 15thNight
15%325%423346%48%
2103
16th to endNight
13%5%245%24445%47%
1893
March1st to 15thNight
10%425%43435%6%50%
2019
16th to endNight
11%5%24424345%51%
2112
April1st to 15thNight
12%41432335%7%52%
1976
16th to endNight
7%3243245%5%8%52%
1680
May1st to 15thNight
6%5%25%42445%9%50%
1619
16th to endNight
6%414436%5%8%8%44%
1682
June1st to 15thNight
9%425%7%36%47%12%34%
1620
16th to endNight
6%4245%36%7%7%11%39%
1620
July1st to 15thNight
8%325%6%46%6%9%12%34%
1620
16th to endNight
5%425%6%47%7%10%14%32%
1703
August1st to 15thNight
6%425%5%36%7%9%14%32%
1620
16th to endNight
11%6%26%5%36%7%8%9%31%
1938
September1st to 15thNight
10%5%25%6%35%5%6%9%39%
1980
16th to endNight
10%6%26%5%345%5%8%41%
1980
October1st to 15thNight
12%5%23323335%54%
1914
16th to endNight
11%323313346%56%
2112
November1st to 15thNight
9%423322246%56%
2185
16th to endNight
12%424323336%52%
2340
December1st to 15thNight
13%435%424445%48%
2340
16th to endNight
18%7%35%433345%39%
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
39%47%16%25%7%
1612
16th to endDay
39%36%17%23%9%
1755
February1st to 15thDay
39%26%18%23%8%
1752
16th to endDay
38%35%18%25%8%
1580
March1st to 15thDay
36%38%20%20%10%
1941
16th to endDay
38%5%10%17%21%5%
2112
April1st to 15thDay
34%410%20%20%9%
1978
16th to endDay
29%411%22%22%8%
2283
May1st to 15thDay
34%5%12%20%21%5%
2331
16th to endDay
36%7%14%24%13%2
2435
June1st to 15thDay
40%8%15%21%11%1
2340
16th to endDay
35%10%18%18%15%2
2340
July1st to 15thDay
42%10%19%17%5%2
2201
16th to endDay
43%11%18%19%5%
2310
August1st to 15thDay
45%11%18%16%6%
2327
16th to endDay
51%10%13%13%9%1
2249
September1st to 15thDay
42%9%13%15%15%3
1980
16th to endDay
45%6%9%18%15%4
1980
October1st to 15thDay
34%38%20%23%10%
1844
16th to endDay
27%36%15%30%16%
1760
November1st to 15thDay
31%36%16%25%16%
1670
16th to endDay
35%37%17%23%13%
1620
December1st to 15thDay
37%311%18%19%9%
1620
16th to endDay
48%37%17%14%7%
1728
January1st to 15thNight
39%37%17%25%7%
2327
16th to endNight
42%25%13%25%10%
2466
February1st to 15thNight
37%26%18%22%12%
2112
16th to endNight
38%36%17%21%12%
1893
March1st to 15thNight
34%310%19%21%10%
2019
16th to endNight
35%411%17%21%10%
2112
April1st to 15thNight
32%48%21%22%10%
1976
16th to endNight
28%6%10%21%22%11%
1680
May1st to 15thNight
31%6%13%19%23%6%
1620
16th to endNight
32%8%15%24%16%3
1684
June1st to 15thNight
39%7%16%24%11%
1620
16th to endNight
36%10%18%17%13%2
1620
July1st to 15thNight
37%12%23%19%5%1
1530
16th to endNight
34%14%23%19%6%1
1595
August1st to 15thNight
37%11%20%21%7%
1609
16th to endNight
43%11%17%16%9%1
1938
September1st to 15thNight
38%9%15%15%15%4
1980
16th to endNight
40%7%11%18%17%4
1980
October1st to 15thNight
32%48%18%23%11%
1914
16th to endNight
28%36%16%29%16%
2112
November1st to 15thNight
28%36%16%28%16%
2185
16th to endNight
34%36%15%24%15%
2340
December1st to 15thNight
37%49%18%21%8%
2340
16th to endNight
46%37%17%16%7%
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
17%22%30%17%8%3
90
16th to endDay
17%35%34%6%6%
96
February1st to 15thDay
12%35%34%16%1
90
16th to endDay
16%25%44%13%
81
March1st to 15thDay
12%19%33%22%11%
231
16th to endDay
14%11%30%28%14%1
288
April1st to 15thDay
13%17%24%21%19%3
270
16th to endDay
9%426%29%23%6%
270
May1st to 15thDay
10%12%24%26%15%11%
288
16th to endDay
10%317%26%27%14%
331
June1st to 15thDay
13%111%25%27%19%
315
16th to endDay
6%13%30%22%25%
315
July1st to 15thDay
8%17%25%32%24%
305
16th to endDay
6%7%23%37%24%
326
August1st to 15thDay
15%27%25%27%21%
313
16th to endDay
14%19%23%33%18%
332
September1st to 15thDay
18%212%22%27%17%
315
16th to endDay
19%213%29%21%14%
314
October1st to 15thDay
17%425%27%17%6%
278
16th to endDay
10%6%19%29%25%8%
272
November1st to 15thDay
20%7%29%21%17%2
178
16th to endDay
7%16%31%30%12%2
90
December1st to 15thDay
20%14%37%20%7%
90
16th to endDay
34%13%23%20%6%1
96
January1st to 15thNight
17%19%29%24%8%
720
16th to endNight
19%18%30%26%5%
768
February1st to 15thNight
16%16%31%29%6%
704
16th to endNight
15%17%35%26%4
631
March1st to 15thNight
12%16%34%27%9%
720
16th to endNight
15%13%28%27%14%
768
April1st to 15thNight
14%10%32%27%15%
718
16th to endNight
9%8%28%33%18%1
543
May1st to 15thNight
10%5%28%31%20%2
540
16th to endNight
8%217%36%29%4
563
June1st to 15thNight
11%113%34%32%6%
540
16th to endNight
7%111%30%38%10%
540
July1st to 15thNight
10%7%33%34%14%
510
16th to endNight
6%6%35%40%9%
564
August1st to 15thNight
9%15%33%40%9%
539
16th to endNight
15%17%26%37%11%
606
September1st to 15thNight
13%18%31%36%8%
720
16th to endNight
14%215%32%30%3
717
October1st to 15thNight
16%322%29%22%4
684
16th to endNight
13%6%21%32%23%2
704
November1st to 15thNight
11%9%21%34%21%1
700
16th to endNight
14%11%29%26%15%1
720
December1st to 15thNight
14%13%28%26%15%1
720
16th to endNight
21%13%23%31%9%
768
Page generated at 2017-10-07 14:07:51. Version ac04

Copyright 2017 A. Danko


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