Arizona-Sonora Desert Museum
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Arizona-Sonora Desert Museum 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
77%
15577
36%
46835
33%
15539
81%
15539
56%
21893

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
74%
718
33%
2327
34%
716
78%
716
52%
1070
January16th to endNight
70%
768
35%
2496
35%
768
77%
768
43%
1260
February1st to 15thNight
74%
700
37%
2191
36%
700
80%
700
53%
1011
February16th to endNight
67%
632
38%
1844
35%
632
75%
632
53%
910
March1st to 15thNight
70%
720
40%
1980
33%
720
76%
720
61%
951
March16th to endNight
75%
768
39%
2112
30%
768
82%
768
64%
978
April1st to 15thNight
69%
695
35%
1954
25%
695
77%
695
60%
918
April16th to endNight
73%
540
46%
1770
41%
540
82%
540
74%
645
May1st to 15thNight
75%
539
40%
1619
32%
539
82%
539
74%
644
May16th to endNight
78%
561
43%
1684
35%
561
83%
561
76%
653
June1st to 15thNight
84%
540
35%
1620
29%
540
85%
540
72%
663
June16th to endNight
88%
540
33%
1620
28%
540
89%
540
66%
695
July1st to 15thNight
82%
510
21%
1530
18%
510
82%
510
43%
812
July16th to endNight
83%
564
20%
1593
17%
531
83%
531
34%
947
August1st to 15thNight
85%
539
27%
1611
25%
536
85%
536
46%
832
August16th to endNight
85%
615
32%
1884
31%
615
85%
615
43%
1007
September1st to 15thNight
80%
700
30%
1925
26%
700
80%
700
43%
1099
September16th to endNight
82%
656
42%
1815
34%
656
86%
656
69%
823
October1st to 15thNight
81%
660
41%
1908
34%
660
85%
660
67%
838
October16th to endNight
86%
704
44%
2112
41%
704
89%
704
70%
887
November1st to 15thNight
83%
700
44%
2100
40%
700
86%
700
69%
878
November16th to endNight
75%
720
39%
2304
37%
720
81%
720
54%
1048
December1st to 15thNight
74%
720
39%
2340
41%
720
78%
720
52%
1064
December16th to endNight
68%
768
36%
2496
36%
768
72%
768
43%
1260

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
3212323346%67%
47792
Night
3212213346%69%
47031
TransparencyDay
18%35%10%23%37%
47487
Night
16%36%12%25%36%
46837
SeeingDay
5%6%19%33%25%10%
5406
Night
3111%41%35%5%
15586

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
3313223246%66%
1611
16th to endDay
6%313323336%61%
1728
February1st to 15thDay
6%312212225%69%
1670
16th to endDay
7%212222235%65%
1629
March1st to 15thDay
3212213336%68%
1980
16th to endDay
31122223474%
2112
April1st to 15thDay
211122345%73%
1994
16th to endDay
11111112383%
2187
May1st to 15thDay
11121213480%
2331
16th to endDay
11112384%
2429
June1st to 15thDay
21111125%80%
2340
16th to endDay
1112212245%74%
2340
July1st to 15thDay
32145%46%8%8%10%45%
2340
16th to endDay
6%426%8%46%8%8%11%32%
2467
August1st to 15thDay
5%425%5%35%5%7%8%45%
2340
16th to endDay
32145%36%6%7%6%51%
2315
September1st to 15thDay
5%3144345%6%6%53%
1922
16th to endDay
321112335%72%
1815
October1st to 15thDay
111212335%75%
1722
16th to endDay
1211113479%
1760
November1st to 15thDay
111111236%78%
1759
16th to endDay
321221223472%
1653
December1st to 15thDay
6%22212246%65%
1620
16th to endDay
6%3232235%6%64%
1728
January1st to 15thNight
5%312213335%68%
2327
16th to endNight
6%313424435%61%
2496
February1st to 15thNight
4213212335%69%
2180
16th to endNight
5%212323345%64%
1844
March1st to 15thNight
4211212335%71%
1980
16th to endNight
22121323475%
2112
April1st to 15thNight
2112313245%71%
1954
16th to endNight
2111111286%
1770
May1st to 15thNight
111336%79%
1619
16th to endNight
111112385%
1684
June1st to 15thNight
1111222381%
1620
16th to endNight
111111222477%
1620
July1st to 15thNight
32134246%7%11%52%
1620
16th to endNight
32145%45%7%10%15%39%
1701
August1st to 15thNight
21134246%7%9%56%
1620
16th to endNight
321343447%11%53%
1884
September1st to 15thNight
42234345%5%8%55%
1925
16th to endNight
22121223476%
1815
October1st to 15thNight
11112224477%
1908
16th to endNight
12121122480%
2112
November1st to 15thNight
111211235%77%
2100
16th to endNight
5%212113335%69%
2304
December1st to 15thNight
5%212212345%67%
2340
16th to endNight
7%313423335%61%
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
19%3413%26%32%
1612
16th to endDay
22%25%14%24%29%
1728
February1st to 15thDay
19%1312%27%35%
1670
16th to endDay
22%1313%30%28%
1629
March1st to 15thDay
16%236%29%40%
1980
16th to endDay
14%237%29%43%
2112
April1st to 15thDay
13%115%34%42%
1994
16th to endDay
9%125%22%58%
2187
May1st to 15thDay
9%126%20%59%
2331
16th to endDay
7%126%22%60%
2432
June1st to 15thDay
9%11317%66%
2340
16th to endDay
13%23414%60%
2340
July1st to 15thDay
28%9%12%13%16%19%
2201
16th to endDay
40%11%16%19%9%2
2312
August1st to 15thDay
33%7%11%13%17%15%
2325
16th to endDay
28%7%11%18%17%16%
2315
September1st to 15thDay
26%6%9%17%17%21%
1922
16th to endDay
15%248%32%37%
1815
October1st to 15thDay
12%25%10%25%43%
1722
16th to endDay
9%138%25%51%
1760
November1st to 15thDay
9%129%34%41%
1759
16th to endDay
15%239%28%39%
1653
December1st to 15thDay
20%2414%31%25%
1620
16th to endDay
20%46%18%31%18%
1728
January1st to 15thNight
18%35%13%27%32%
2327
16th to endNight
24%3413%29%24%
2496
February1st to 15thNight
18%25%14%25%34%
2191
16th to endNight
20%2413%31%27%
1844
March1st to 15thNight
15%239%26%41%
1980
16th to endNight
13%2410%30%39%
2112
April1st to 15thNight
15%138%32%38%
1954
16th to endNight
7%16%24%58%
1770
May1st to 15thNight
7%137%23%55%
1620
16th to endNight
7%126%22%60%
1685
June1st to 15thNight
9%12318%64%
1620
16th to endNight
12%13316%61%
1620
July1st to 15thNight
22%7%16%15%15%22%
1530
16th to endNight
27%11%22%22%12%3
1593
August1st to 15thNight
19%7%14%21%17%18%
1611
16th to endNight
23%6%12%19%19%17%
1884
September1st to 15thNight
25%6%8%21%18%18%
1925
16th to endNight
12%1410%33%37%
1815
October1st to 15thNight
11%2413%25%42%
1908
16th to endNight
10%1310%24%49%
2112
November1st to 15thNight
10%2311%31%40%
2100
16th to endNight
18%2310%24%40%
2304
December1st to 15thNight
18%2417%29%27%
2340
16th to endNight
24%36%17%29%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
14%320%41%20%1
90
16th to endDay
5%5%11%38%28%11%
96
February1st to 15thDay
5%10%14%41%25%2
185
16th to endDay
10%11%34%27%13%2
238
March1st to 15thDay
6%12%28%27%16%8%
270
16th to endDay
212%32%27%15%10%
288
April1st to 15thDay
5%14%28%27%15%7%
269
16th to endDay
117%33%28%14%4
270
May1st to 15thDay
313%30%32%12%6%
288
16th to endDay
27%27%37%20%4
330
June1st to 15thDay
5%125%41%17%8%
315
16th to endDay
212%43%27%13%
315
July1st to 15thDay
6%9%34%35%13%
305
16th to endDay
6%8%29%30%24%
327
August1st to 15thDay
7%5%29%40%16%
315
16th to endDay
415%29%38%20%
332
September1st to 15thDay
10%114%35%28%10%
294
16th to endDay
7%318%33%27%9%
255
October1st to 15thDay
26%22%35%20%12%
162
16th to endDay
35%26%54%11%
96
November1st to 15thDay
28%17%31%31%8%
90
16th to endDay
5%5%23%36%25%3
90
December1st to 15thDay
327%30%51%5%
90
16th to endDay
15%321%33%25%1
96
January1st to 15thNight
6%113%47%27%3
720
16th to endNight
7%214%46%26%3
768
February1st to 15thNight
4312%46%27%5%
704
16th to endNight
5%319%49%19%1
632
March1st to 15thNight
4218%43%26%3
720
16th to endNight
3215%45%29%4
768
April1st to 15thNight
3417%51%22%1
695
16th to endNight
1320%50%21%2
540
May1st to 15thNight
220%45%29%1
540
16th to endNight
1216%49%29%1
563
June1st to 15thNight
1110%50%34%1
540
16th to endNight
15%40%50%1
540
July1st to 15thNight
4425%59%6%
510
16th to endNight
4219%60%13%
564
August1st to 15thNight
2218%61%13%
539
16th to endNight
3321%62%9%
615
September1st to 15thNight
5%6%27%49%11%
700
16th to endNight
29%37%43%7%
656
October1st to 15thNight
1111%43%36%5%
660
16th to endNight
16%43%39%7%
704
November1st to 15thNight
1110%44%36%5%
700
16th to endNight
6%114%40%32%4
720
December1st to 15thNight
6%212%43%30%4
720
16th to endNight
7%312%47%23%4
768
Page generated at 2017-09-11 16:35:29. Version ac04

Copyright 2017 A. Danko


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