DMZ Observatories
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the DMZ Observatories clear sky chart from 2005-11-05 to 2017-09-20.

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
77%
15636
36%
46942
32%
15599
81%
15599
55%
22243

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
77%
717
34%
2327
37%
716
80%
716
53%
1052
January16th to endNight
68%
768
34%
2496
33%
768
75%
768
41%
1288
February1st to 15thNight
76%
698
37%
2173
37%
698
82%
698
56%
984
February16th to endNight
69%
632
39%
1841
35%
632
75%
632
50%
920
March1st to 15thNight
70%
720
41%
1980
33%
720
77%
720
61%
955
March16th to endNight
76%
768
38%
2112
30%
768
82%
768
62%
993
April1st to 15thNight
72%
701
36%
1960
27%
701
78%
701
60%
925
April16th to endNight
73%
540
45%
1780
40%
540
83%
540
72%
657
May1st to 15thNight
74%
539
41%
1619
32%
539
82%
539
74%
638
May16th to endNight
78%
561
44%
1684
34%
561
85%
561
76%
656
June1st to 15thNight
84%
540
35%
1620
30%
540
85%
540
71%
660
June16th to endNight
89%
540
31%
1620
27%
540
89%
540
65%
702
July1st to 15thNight
81%
510
18%
1530
15%
510
81%
510
39%
853
July16th to endNight
81%
564
15%
1593
13%
531
80%
531
28%
1021
August1st to 15thNight
87%
539
24%
1611
22%
536
87%
536
42%
865
August16th to endNight
82%
632
29%
1904
28%
632
83%
632
39%
1074
September1st to 15thNight
79%
720
28%
1980
25%
720
79%
720
42%
1155
September16th to endNight
88%
675
43%
1869
37%
675
90%
675
68%
858
October1st to 15thNight
79%
660
42%
1903
33%
660
85%
660
68%
834
October16th to endNight
87%
704
43%
2112
39%
704
90%
704
70%
884
November1st to 15thNight
84%
700
43%
2100
40%
700
86%
700
69%
878
November16th to endNight
73%
720
39%
2292
38%
720
77%
720
52%
1076
December1st to 15thNight
74%
720
38%
2340
39%
720
78%
720
51%
1060
December16th to endNight
67%
768
35%
2496
36%
768
71%
768
44%
1255

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
3213323446%64%
47887
Night
2212323346%67%
47140
TransparencyDay
20%46%10%25%32%
47582
Night
17%36%13%26%31%
46946
SeeingDay
5%7%19%31%24%11%
5463
Night
3211%37%37%8%
15648

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
2313423445%64%
1611
16th to endDay
432331335%5%62%
1728
February1st to 15thDay
5%212213235%68%
1685
16th to endDay
4313324435%62%
1631
March1st to 15thDay
221232335%5%67%
1980
16th to endDay
2211212335%74%
2112
April1st to 15thDay
212212346%71%
1985
16th to endDay
11111112482%
2178
May1st to 15thDay
1212135%79%
2331
16th to endDay
111123384%
2429
June1st to 15thDay
2112235%79%
2340
16th to endDay
212213335%71%
2340
July1st to 15thDay
4326%7%47%7%7%9%38%
2340
16th to endDay
8%6%38%8%47%8%9%9%25%
2467
August1st to 15thDay
5%425%6%46%7%7%9%38%
2340
16th to endDay
4425%5%46%6%6%8%45%
2291
September1st to 15thDay
6%425%6%35%6%48%47%
1980
16th to endDay
3112233345%68%
1860
October1st to 15thDay
111213335%75%
1726
16th to endDay
11212235%77%
1760
November1st to 15thDay
111212325%76%
1759
16th to endDay
3213222326%70%
1666
December1st to 15thDay
5%312323346%62%
1620
16th to endDay
5%31231335%7%61%
1728
January1st to 15thNight
3212213345%68%
2327
16th to endNight
5%2134245%45%58%
2496
February1st to 15thNight
321122245%5%69%
2164
16th to endNight
131233335%5%64%
1841
March1st to 15thNight
221322346%70%
1980
16th to endNight
111222234472%
2112
April1st to 15thNight
1112223335%72%
1960
16th to endNight
11111211483%
1780
May1st to 15thNight
111246%79%
1619
16th to endNight
11122285%
1684
June1st to 15thNight
11111213480%
1620
16th to endNight
1111112337%73%
1620
July1st to 15thNight
32135%35%5%8%11%48%
1620
16th to endNight
3315%447%8%10%17%32%
1701
August1st to 15thNight
21123245%7%11%54%
1620
16th to endNight
4313425%5%7%10%52%
1904
September1st to 15thNight
5%4235%3445%7%54%
1980
16th to endNight
112212345%76%
1869
October1st to 15thNight
11121232379%
1903
16th to endNight
121122480%
2112
November1st to 15thNight
111112335%77%
2100
16th to endNight
4213322235%68%
2292
December1st to 15thNight
4213212346%67%
2340
16th to endNight
4313423346%62%
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
21%26%11%26%31%
1612
16th to endDay
23%2416%25%27%
1728
February1st to 15thDay
19%1411%28%34%
1685
16th to endDay
22%3412%28%27%
1631
March1st to 15thDay
17%237%30%38%
1980
16th to endDay
14%139%33%36%
2112
April1st to 15thDay
13%226%38%36%
1985
16th to endDay
9%126%27%52%
2178
May1st to 15thDay
9%127%23%54%
2331
16th to endDay
6%125%29%53%
2432
June1st to 15thDay
8%12424%59%
2340
16th to endDay
15%345%19%51%
2340
July1st to 15thDay
35%10%13%14%14%12%
2201
16th to endDay
47%13%17%15%5%1
2312
August1st to 15thDay
37%11%12%14%15%8%
2325
16th to endDay
33%8%12%18%14%13%
2291
September1st to 15thDay
33%6%9%16%18%15%
1980
16th to endDay
18%25%11%34%27%
1860
October1st to 15thDay
13%35%10%31%36%
1726
16th to endDay
10%149%28%45%
1760
November1st to 15thDay
11%1310%35%37%
1759
16th to endDay
17%2410%27%38%
1666
December1st to 15thDay
22%35%15%30%23%
1620
16th to endDay
22%28%15%31%19%
1728
January1st to 15thNight
18%25%13%29%31%
2327
16th to endNight
25%4413%29%22%
2496
February1st to 15thNight
16%26%14%25%34%
2175
16th to endNight
20%3413%33%25%
1841
March1st to 15thNight
16%2311%29%38%
1980
16th to endNight
14%25%10%32%35%
2112
April1st to 15thNight
15%2310%35%33%
1960
16th to endNight
8%28%26%52%
1780
May1st to 15thNight
7%138%29%49%
1620
16th to endNight
7%116%29%53%
1685
June1st to 15thNight
9%12421%59%
1620
16th to endNight
12%25%5%21%52%
1620
July1st to 15thNight
23%9%19%16%16%14%
1530
16th to endNight
30%15%24%20%7%1
1593
August1st to 15thNight
20%10%16%23%18%11%
1611
16th to endNight
24%9%15%18%20%11%
1904
September1st to 15thNight
27%6%11%20%21%12%
1980
16th to endNight
11%2414%36%29%
1869
October1st to 15thNight
11%26%15%28%36%
1903
16th to endNight
10%1411%25%46%
2112
November1st to 15thNight
10%1415%32%35%
2100
16th to endNight
20%239%26%37%
2292
December1st to 15thNight
18%2416%30%27%
2340
16th to endNight
23%36%18%28%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
11%6%18%35%25%2
90
16th to endDay
48%17%34%21%13%
96
February1st to 15thDay
5%10%20%29%30%4
200
16th to endDay
6%18%29%27%14%3
238
March1st to 15thDay
5%15%25%30%13%9%
270
16th to endDay
214%29%30%13%9%
288
April1st to 15thDay
412%36%24%14%7%
269
16th to endDay
216%34%28%12%5%
270
May1st to 15thDay
315%31%29%11%7%
288
16th to endDay
18%30%39%15%5%
330
June1st to 15thDay
35%26%40%18%6%
315
16th to endDay
2113%43%27%12%
315
July1st to 15thDay
7%17%33%34%14%
305
16th to endDay
12%5%25%32%23%
327
August1st to 15thDay
7%5%26%39%20%
315
16th to endDay
6%5%26%37%22%
332
September1st to 15thDay
13%9%34%32%10%
315
16th to endDay
5%414%37%27%11%
272
October1st to 15thDay
18%24%30%23%12%
166
16th to endDay
3111%18%43%21%
96
November1st to 15thDay
18%17%30%28%13%
90
16th to endDay
112%20%35%18%12%
90
December1st to 15thDay
6%218%20%36%15%
90
16th to endDay
14%422%33%18%6%
96
January1st to 15thNight
4210%45%30%6%
720
16th to endNight
7%213%43%27%5%
768
February1st to 15thNight
3212%45%30%4
704
16th to endNight
45%17%49%20%2
632
March1st to 15thNight
2320%41%25%5%
720
16th to endNight
1314%42%33%5%
768
April1st to 15thNight
2416%49%24%2
701
16th to endNight
1319%45%27%3
540
May1st to 15thNight
219%41%31%3
540
16th to endNight
1215%41%35%3
563
June1st to 15thNight
218%46%36%4
540
16th to endNight
2434%52%5%
540
July1st to 15thNight
3321%61%10%
510
16th to endNight
4213%61%17%
564
August1st to 15thNight
2112%62%19%
539
16th to endNight
4312%61%18%
632
September1st to 15thNight
5%223%50%16%
720
16th to endNight
25%34%45%11%
675
October1st to 15thNight
1113%37%36%9%
660
16th to endNight
17%35%43%12%
704
November1st to 15thNight
110%40%38%8%
700
16th to endNight
5%212%37%32%8%
720
December1st to 15thNight
5%411%41%28%8%
720
16th to endNight
6%215%43%24%6%
768
Page generated at 2017-09-21 04:18:12. Version ac04

Copyright 2017 A. Danko


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