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Az-DaHut Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Az-DaHut Observatory clear sky chart from 2005-11-05 to 2017-09-10.

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
80%
15627
38%
46839
34%
15589
84%
15589
57%
21739

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
78%
718
33%
2327
36%
716
81%
716
48%
1114
January16th to endNight
72%
768
37%
2496
38%
768
77%
768
44%
1243
February1st to 15thNight
76%
699
37%
2174
37%
699
81%
699
55%
998
February16th to endNight
71%
632
37%
1885
38%
632
75%
632
47%
970
March1st to 15thNight
75%
720
41%
1980
34%
720
80%
720
61%
940
March16th to endNight
79%
768
41%
2112
33%
768
84%
768
66%
975
April1st to 15thNight
76%
713
34%
1972
26%
713
81%
713
61%
940
April16th to endNight
75%
540
46%
1697
39%
540
83%
540
75%
647
May1st to 15thNight
79%
539
40%
1619
34%
539
84%
539
69%
675
May16th to endNight
82%
561
41%
1684
33%
561
86%
561
73%
681
June1st to 15thNight
89%
540
36%
1620
32%
540
90%
540
74%
649
June16th to endNight
91%
540
36%
1620
31%
540
91%
540
76%
639
July1st to 15thNight
86%
510
26%
1530
23%
510
86%
510
51%
756
July16th to endNight
83%
564
28%
1593
24%
531
83%
531
42%
878
August1st to 15thNight
85%
539
30%
1611
27%
536
86%
536
48%
817
August16th to endNight
84%
648
34%
1872
31%
648
84%
648
45%
1007
September1st to 15thNight
82%
700
33%
1925
29%
700
83%
700
53%
997
September16th to endNight
87%
656
42%
1815
35%
656
90%
656
69%
820
October1st to 15thNight
83%
660
42%
1889
36%
660
86%
660
66%
845
October16th to endNight
88%
704
45%
2112
41%
704
90%
704
71%
874
November1st to 15thNight
87%
700
43%
2130
42%
700
88%
700
67%
899
November16th to endNight
81%
720
40%
2340
41%
720
84%
720
56%
1023
December1st to 15thNight
78%
720
38%
2340
40%
720
80%
720
49%
1089
December16th to endNight
72%
768
37%
2496
39%
768
75%
768
43%
1263

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
2212212346%70%
47785
Night
3212213346%69%
47038
TransparencyDay
16%2311%25%39%
47480
Night
17%2310%22%42%
46844
SeeingDay
3210%25%37%20%
5440
Night
418%41%39%4
15637

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
4313312336%66%
1611
16th to endDay
6%322222336%64%
1728
February1st to 15thDay
3223311246%67%
1685
16th to endDay
5%313323346%63%
1588
March1st to 15thDay
4112212345%68%
1980
16th to endDay
2112313245%70%
2112
April1st to 15thDay
212213346%71%
1976
16th to endDay
111111125%81%
2261
May1st to 15thDay
1111225%81%
2331
16th to endDay
211122482%
2429
June1st to 15thDay
1111112384%
2340
16th to endDay
111122383%
2340
July1st to 15thDay
21133245%6%9%58%
2340
16th to endDay
43235%35%6%8%11%45%
2467
August1st to 15thDay
3213225%5%6%8%57%
2340
16th to endDay
22123245%5%8%61%
2325
September1st to 15thDay
321332345%5%64%
1922
16th to endDay
1112222380%
1815
October1st to 15thDay
211213226%75%
1741
16th to endDay
12111135%79%
1760
November1st to 15thDay
1112111235%77%
1726
16th to endDay
5%212211235%73%
1620
December1st to 15thDay
5%313223335%64%
1620
16th to endDay
5%414313346%60%
1728
January1st to 15thNight
4313323346%64%
2327
16th to endNight
8%213323235%63%
2496
February1st to 15thNight
3312212236%69%
2166
16th to endNight
6%212424336%62%
1885
March1st to 15thNight
3212212346%70%
1980
16th to endNight
211122245%74%
2112
April1st to 15thNight
3112213346%69%
1972
16th to endNight
1111112384%
1697
May1st to 15thNight
1121224477%
1619
16th to endNight
1121122283%
1684
June1st to 15thNight
1111222482%
1620
16th to endNight
1111112482%
1620
July1st to 15thNight
12133245%6%9%58%
1620
16th to endNight
4213336%7%6%12%47%
1701
August1st to 15thNight
22124245%7%11%54%
1620
16th to endNight
1214435%5%6%8%55%
1872
September1st to 15thNight
2213324449%60%
1925
16th to endNight
11221233476%
1815
October1st to 15thNight
2111212235%75%
1889
16th to endNight
1211113380%
2112
November1st to 15thNight
111212226%76%
2130
16th to endNight
421221222473%
2340
December1st to 15thNight
6%213212346%65%
2340
16th to endNight
7%314424345%60%
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%2416%28%26%
1612
16th to endDay
22%2316%26%29%
1728
February1st to 15thDay
18%1417%28%28%
1685
16th to endDay
22%2315%31%24%
1588
March1st to 15thDay
17%228%30%39%
1980
16th to endDay
17%128%33%35%
2112
April1st to 15thDay
13%219%33%39%
1976
16th to endDay
9%116%25%55%
2261
May1st to 15thDay
8%117%23%56%
2331
16th to endDay
8%116%23%58%
2432
June1st to 15thDay
8%1315%70%
2340
16th to endDay
8%11311%73%
2340
July1st to 15thDay
19%5%9%15%17%33%
2201
16th to endDay
27%7%12%23%19%9%
2312
August1st to 15thDay
21%48%18%18%28%
2325
16th to endDay
19%46%17%27%24%
2325
September1st to 15thDay
20%45%14%25%30%
1922
16th to endDay
10%115%26%53%
1815
October1st to 15thDay
13%228%26%46%
1741
16th to endDay
9%148%27%48%
1760
November1st to 15thDay
11%1111%32%41%
1726
16th to endDay
16%1110%28%41%
1620
December1st to 15thDay
24%2415%29%23%
1620
16th to endDay
24%35%20%30%15%
1728
January1st to 15thNight
21%2412%24%33%
2327
16th to endNight
25%2212%26%30%
2496
February1st to 15thNight
17%2414%25%35%
2177
16th to endNight
24%2112%26%32%
1885
March1st to 15thNight
16%118%24%47%
1980
16th to endNight
13%127%31%42%
2112
April1st to 15thNight
16%126%28%44%
1972
16th to endNight
7%115%20%63%
1697
May1st to 15thNight
10%225%24%55%
1620
16th to endNight
9%15%16%66%
1685
June1st to 15thNight
8%11313%72%
1620
16th to endNight
8%1237%77%
1620
July1st to 15thNight
20%39%17%14%34%
1530
16th to endNight
25%6%11%20%21%14%
1593
August1st to 15thNight
20%5%9%18%15%29%
1611
16th to endNight
24%46%14%23%26%
1872
September1st to 15thNight
19%47%18%20%30%
1925
16th to endNight
11%116%22%55%
1815
October1st to 15thNight
13%129%22%50%
1889
16th to endNight
10%138%17%58%
2112
November1st to 15thNight
12%119%26%48%
2130
16th to endNight
16%228%23%46%
2340
December1st to 15thNight
21%2313%28%30%
2340
16th to endNight
25%25%15%29%21%
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
16%110%36%31%4
90
16th to endDay
7%29%32%29%19%
96
February1st to 15thDay
5%212%30%40%9%
200
16th to endDay
7%421%30%28%7%
238
March1st to 15thDay
5%5%16%33%18%19%
270
16th to endDay
26%19%27%29%14%
288
April1st to 15thDay
46%16%30%28%13%
269
16th to endDay
27%24%32%21%10%
270
May1st to 15thDay
1420%32%27%13%
288
16th to endDay
2212%33%36%13%
330
June1st to 15thDay
137%33%33%20%
315
16th to endDay
1319%45%29%
315
July1st to 15thDay
1417%46%27%
305
16th to endDay
3111%43%39%
327
August1st to 15thDay
3113%48%33%
315
16th to endDay
1113%46%35%
332
September1st to 15thDay
6%17%18%47%19%
294
16th to endDay
5%10%28%40%14%
255
October1st to 15thDay
3212%28%34%18%
181
16th to endDay
1117%54%26%
96
November1st to 15thDay
111%30%38%18%
90
16th to endDay
8%47%28%41%8%
90
December1st to 15thDay
31324%51%16%
90
16th to endDay
8%219%37%27%5%
96
January1st to 15thNight
6%7%53%28%2
720
16th to endNight
10%19%49%26%2
768
February1st to 15thNight
4110%50%28%3
704
16th to endNight
8%213%51%23%1
632
March1st to 15thNight
4114%48%26%4
720
16th to endNight
2111%44%33%4
768
April1st to 15thNight
3213%51%27%1
713
16th to endNight
2119%47%26%2
540
May1st to 15thNight
1115%46%31%3
540
16th to endNight
112%41%40%2
563
June1st to 15thNight
16%46%42%2
540
16th to endNight
1332%60%3
540
July1st to 15thNight
1329%57%6%
510
16th to endNight
4313%66%12%
564
August1st to 15thNight
2117%64%12%
539
16th to endNight
2218%63%12%
648
September1st to 15thNight
36%24%56%8%
700
16th to endNight
25%38%44%7%
656
October1st to 15thNight
218%45%39%1
660
16th to endNight
15%43%43%5%
704
November1st to 15thNight
26%47%38%4
700
16th to endNight
5%17%46%36%3
720
December1st to 15thNight
7%16%47%35%1
720
16th to endNight
8%110%49%27%3
768
Page generated at 2017-09-11 16:35:23. Version ac04

Copyright 2017 A. Danko


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