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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 2019-01-28.

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
81%
17497
38%
52494
35%
17459
84%
17459
57%
24326

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%
838
34%
2717
37%
836
79%
836
45%
1337
January16th to endNight
74%
881
37%
2863
38%
881
79%
881
47%
1391
February1st to 15thNight
76%
759
37%
2359
37%
759
81%
759
55%
1087
February16th to endNight
71%
684
37%
2040
38%
684
75%
684
47%
1052
March1st to 15thNight
75%
780
40%
2145
34%
780
81%
780
60%
1023
March16th to endNight
79%
832
40%
2288
33%
832
84%
832
65%
1062
April1st to 15thNight
76%
773
36%
2137
27%
773
82%
773
62%
1011
April16th to endNight
74%
579
45%
1817
37%
579
83%
579
72%
708
May1st to 15thNight
79%
584
41%
1754
35%
584
84%
584
69%
727
May16th to endNight
83%
609
40%
1828
33%
609
86%
609
74%
731
June1st to 15thNight
89%
585
37%
1755
33%
585
90%
585
74%
703
June16th to endNight
91%
585
35%
1755
31%
585
91%
585
76%
691
July1st to 15thNight
85%
555
26%
1665
21%
555
85%
555
49%
844
July16th to endNight
83%
612
27%
1737
23%
579
84%
579
43%
946
August1st to 15thNight
86%
575
32%
1719
28%
572
87%
572
49%
857
August16th to endNight
84%
702
33%
2029
30%
702
84%
702
46%
1081
September1st to 15thNight
83%
780
37%
2145
32%
780
85%
780
56%
1084
September16th to endNight
88%
776
43%
2145
36%
776
90%
776
71%
955
October1st to 15thNight
82%
780
41%
2233
35%
780
85%
780
64%
1007
October16th to endNight
87%
832
45%
2496
41%
832
90%
832
71%
1030
November1st to 15thNight
85%
820
44%
2495
43%
820
88%
820
65%
1076
November16th to endNight
82%
840
40%
2730
42%
840
84%
840
55%
1200
December1st to 15thNight
77%
840
39%
2730
41%
840
79%
840
49%
1283
December16th to endNight
74%
896
38%
2912
40%
896
77%
896
45%
1440

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%
53090
Night
3212213346%69%
52693
TransparencyDay
16%2312%25%39%
52785
Night
16%2311%23%42%
52499
SeeingDay
329%25%36%21%
7198
Night
418%41%39%4
17507

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
4414413336%62%
1881
16th to endDay
6%212222337%65%
1980
February1st to 15thDay
3313311246%67%
1830
16th to endDay
5%313323336%63%
1719
March1st to 15thDay
4112212345%68%
2145
16th to endDay
2112313245%69%
2288
April1st to 15thDay
212213346%72%
2141
16th to endDay
111111225%80%
2415
May1st to 15thDay
1111225%81%
2526
16th to endDay
211112483%
2637
June1st to 15thDay
1111212383%
2535
16th to endDay
111121384%
2535
July1st to 15thDay
22133245%6%10%58%
2535
16th to endDay
33235%35%6%7%12%46%
2675
August1st to 15thDay
22132245%6%8%58%
2485
16th to endDay
22123245%5%9%61%
2520
September1st to 15thDay
321331244467%
2145
16th to endDay
1112222381%
2145
October1st to 15thDay
311213225%74%
2057
16th to endDay
12111235%78%
2080
November1st to 15thDay
1112211235%76%
2020
16th to endDay
5%212211235%72%
1890
December1st to 15thDay
5%314323345%61%
1890
16th to endDay
5%414313446%60%
2016
January1st to 15thNight
5%413324346%61%
2717
16th to endNight
7%213323235%65%
2863
February1st to 15thNight
3312212236%69%
2351
16th to endNight
6%312423336%62%
2040
March1st to 15thNight
4212212346%69%
2145
16th to endNight
3111212246%73%
2288
April1st to 15thNight
2112213346%70%
2137
16th to endNight
1111113382%
1817
May1st to 15thNight
1111224478%
1754
16th to endNight
1111122284%
1828
June1st to 15thNight
111222481%
1755
16th to endNight
1111112482%
1755
July1st to 15thNight
1213325%5%6%9%57%
1755
16th to endNight
4213336%7%7%13%46%
1845
August1st to 15thNight
21124245%7%11%55%
1728
16th to endNight
1213435%5%6%9%55%
2029
September1st to 15thNight
2212324449%63%
2145
16th to endNight
11121222478%
2145
October1st to 15thNight
2212212135%74%
2233
16th to endNight
11211213480%
2496
November1st to 15thNight
112212225%75%
2495
16th to endNight
321321222472%
2730
December1st to 15thNight
5%313312346%64%
2730
16th to endNight
6%313324345%61%
2912

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
24%2415%28%24%
1882
16th to endDay
20%2315%27%30%
1980
February1st to 15thDay
19%1416%28%29%
1830
16th to endDay
22%2314%31%25%
1719
March1st to 15thDay
18%219%30%37%
2145
16th to endDay
17%128%34%35%
2288
April1st to 15thDay
12%219%33%39%
2141
16th to endDay
9%116%24%55%
2415
May1st to 15thDay
8%117%23%56%
2526
16th to endDay
8%115%22%60%
2640
June1st to 15thDay
9%1314%70%
2535
16th to endDay
8%1311%74%
2535
July1st to 15thDay
19%5%9%15%17%33%
2396
16th to endDay
26%7%13%24%19%9%
2520
August1st to 15thDay
20%48%18%19%28%
2470
16th to endDay
19%47%18%27%23%
2520
September1st to 15thDay
18%4413%25%33%
2145
16th to endDay
10%115%28%53%
2145
October1st to 15thDay
14%228%25%46%
2057
16th to endDay
9%239%28%46%
2080
November1st to 15thDay
12%1113%31%39%
2020
16th to endDay
17%1110%28%39%
1890
December1st to 15thDay
25%3315%27%23%
1890
16th to endDay
24%35%21%29%16%
2016
January1st to 15thNight
23%2412%24%31%
2717
16th to endNight
23%1212%26%32%
2863
February1st to 15thNight
18%1413%25%35%
2362
16th to endNight
24%2212%26%32%
2040
March1st to 15thNight
16%229%24%45%
2145
16th to endNight
13%127%31%41%
2288
April1st to 15thNight
15%127%27%45%
2137
16th to endNight
8%11421%62%
1817
May1st to 15thNight
9%225%23%56%
1755
16th to endNight
8%15%15%67%
1829
June1st to 15thNight
8%11312%73%
1755
16th to endNight
8%1137%78%
1755
July1st to 15thNight
21%38%16%14%34%
1665
16th to endNight
24%6%11%22%20%13%
1737
August1st to 15thNight
19%5%9%19%16%29%
1719
16th to endNight
23%47%15%23%25%
2029
September1st to 15thNight
18%36%17%20%33%
2145
16th to endNight
10%116%21%57%
2145
October1st to 15thNight
14%129%22%50%
2233
16th to endNight
10%129%19%56%
2496
November1st to 15thNight
13%119%27%45%
2495
16th to endNight
16%229%24%43%
2730
December1st to 15thNight
21%2315%26%30%
2730
16th to endNight
23%2416%30%21%
2912

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
12%110%32%32%10%
180
16th to endDay
5%18%33%35%15%
180
February1st to 15thDay
7%210%27%37%14%
255
16th to endDay
6%5%19%35%26%6%
290
March1st to 15thDay
5%5%14%35%22%16%
330
16th to endDay
15%19%27%30%15%
352
April1st to 15thDay
45%15%29%29%15%
329
16th to endDay
26%22%31%23%12%
318
May1st to 15thDay
2318%33%27%14%
348
16th to endDay
2211%34%38%12%
394
June1st to 15thDay
127%32%35%20%
375
16th to endDay
11317%44%31%
375
July1st to 15thDay
2417%44%30%
365
16th to endDay
2110%41%42%
391
August1st to 15thDay
3111%45%37%
359
16th to endDay
1112%46%38%
396
September1st to 15thDay
46%18%45%23%
375
16th to endDay
49%25%37%22%
375
October1st to 15thDay
6%112%28%35%16%
287
16th to endDay
115%20%44%26%
192
November1st to 15thDay
111%31%40%16%
180
16th to endDay
8%25%23%43%16%
180
December1st to 15thDay
6%15%38%40%8%
180
16th to endDay
6%114%32%31%14%
192
January1st to 15thNight
7%7%53%29%2
840
16th to endNight
9%19%49%28%2
881
February1st to 15thNight
5%110%49%29%3
764
16th to endNight
8%113%51%23%1
684
March1st to 15thNight
5%113%49%26%4
780
16th to endNight
3110%45%34%4
832
April1st to 15thNight
3213%50%27%2
773
16th to endNight
2118%46%27%2
579
May1st to 15thNight
1114%46%32%3
585
16th to endNight
111%44%38%2
611
June1st to 15thNight
26%45%43%2
585
16th to endNight
1331%59%3
585
July1st to 15thNight
2329%56%7%
555
16th to endNight
4313%66%11%
612
August1st to 15thNight
2117%65%12%
575
16th to endNight
2217%63%13%
702
September1st to 15thNight
36%24%57%7%
780
16th to endNight
25%37%47%7%
776
October1st to 15thNight
318%46%39%1
780
16th to endNight
16%41%44%6%
832
November1st to 15thNight
26%49%37%3
820
16th to endNight
46%44%39%3
840
December1st to 15thNight
7%16%49%34%1
840
16th to endNight
7%19%49%29%3
896
Page generated at 2019-01-28 19:54:00. Version ac04

Copyright 2019 A. Danko


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