Sonoran Skies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sonoran Skies Observatory clear sky chart from 2005-11-05 to 2017-09-18.

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
74%
15484
35%
46894
31%
15445
79%
15445
52%
22720

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
72%
717
32%
2327
33%
716
76%
716
48%
1110
January16th to endNight
67%
768
35%
2496
34%
768
74%
768
41%
1286
February1st to 15thNight
72%
698
36%
2233
35%
696
81%
696
53%
1014
February16th to endNight
63%
632
40%
1793
33%
632
72%
632
52%
905
March1st to 15thNight
65%
720
40%
1980
31%
720
73%
720
59%
960
March16th to endNight
69%
768
39%
2112
27%
768
79%
768
61%
1008
April1st to 15thNight
64%
653
36%
1912
25%
653
74%
653
58%
891
April16th to endNight
69%
540
44%
1800
37%
540
82%
540
68%
681
May1st to 15thNight
71%
539
38%
1673
31%
539
80%
539
72%
652
May16th to endNight
79%
561
42%
1684
35%
561
84%
561
73%
670
June1st to 15thNight
83%
540
35%
1620
30%
540
84%
540
68%
678
June16th to endNight
84%
540
28%
1620
26%
540
85%
540
54%
775
July1st to 15thNight
80%
510
17%
1530
15%
510
81%
510
36%
883
July16th to endNight
74%
564
14%
1593
12%
531
74%
531
25%
1050
August1st to 15thNight
78%
539
20%
1611
20%
536
77%
536
33%
965
August16th to endNight
81%
573
26%
1893
28%
573
81%
573
33%
1081
September1st to 15thNight
74%
683
25%
1943
22%
683
75%
683
36%
1187
September16th to endNight
85%
667
40%
1847
32%
667
88%
667
63%
884
October1st to 15thNight
80%
660
40%
1944
32%
660
85%
660
64%
870
October16th to endNight
86%
704
42%
2112
38%
704
89%
704
69%
900
November1st to 15thNight
81%
700
43%
2100
38%
700
84%
700
69%
876
November16th to endNight
71%
720
40%
2235
36%
720
77%
720
53%
1058
December1st to 15thNight
72%
720
37%
2340
37%
720
76%
720
50%
1088
December16th to endNight
67%
768
34%
2496
35%
768
71%
768
44%
1248

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
321332445%6%61%
47885
Night
3213323347%64%
47101
TransparencyDay
21%36%12%26%28%
47580
Night
19%37%14%28%27%
46907
SeeingDay
6%7%18%28%25%12%
5344
Night
4112%40%35%4
15496

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
332332335%6%62%
1611
16th to endDay
5%324323346%59%
1728
February1st to 15thDay
4313212235%68%
1616
16th to endDay
4423323346%62%
1681
March1st to 15thDay
3213322347%65%
1980
16th to endDay
2212212225%72%
2112
April1st to 15thDay
221221334470%
2036
16th to endDay
11111112481%
2160
May1st to 15thDay
111211223475%
2274
16th to endDay
111111223378%
2429
June1st to 15thDay
112212235%76%
2340
16th to endDay
2213424445%62%
2340
July1st to 15thDay
4325%6%47%6%8%10%38%
2340
16th to endDay
6%438%8%5%8%7%8%10%27%
2467
August1st to 15thDay
5%5%27%7%47%8%7%8%34%
2340
16th to endDay
4415%5%36%7%7%8%42%
2307
September1st to 15thDay
6%426%6%45%5%6%7%44%
2013
16th to endDay
41331345%6%64%
1838
October1st to 15thDay
1212313235%71%
1684
16th to endDay
212212335%74%
1760
November1st to 15thDay
1111212336%74%
1759
16th to endDay
333313345%68%
1722
December1st to 15thDay
431332335%6%62%
1620
16th to endDay
5%42332335%7%59%
1728
January1st to 15thNight
4323223346%63%
2327
16th to endNight
6%423334436%58%
2496
February1st to 15thNight
2212223337%66%
2233
16th to endNight
2313324445%63%
1793
March1st to 15thNight
221331225%5%68%
1980
16th to endNight
2212212235%72%
2112
April1st to 15thNight
2113313335%70%
1912
16th to endNight
11111322480%
1800
May1st to 15thNight
21112246%76%
1673
16th to endNight
1112125%81%
1684
June1st to 15thNight
211212235%77%
1620
16th to endNight
21232445%6%65%
1620
July1st to 15thNight
3314445%7%8%14%42%
1620
16th to endNight
3425%7%47%8%9%16%28%
1701
August1st to 15thNight
2425%6%35%5%8%11%43%
1620
16th to endNight
4324435%7%7%10%45%
1893
September1st to 15thNight
6%4244345%6%8%47%
1943
16th to endNight
2212212335%71%
1847
October1st to 15thNight
1112212235%74%
1944
16th to endNight
11121223477%
2112
November1st to 15thNight
111212236%75%
2100
16th to endNight
4313212235%68%
2235
December1st to 15thNight
5%313213445%64%
2340
16th to endNight
5%424323336%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%36%14%32%22%
1612
16th to endDay
26%1415%28%23%
1728
February1st to 15thDay
19%1313%30%31%
1616
16th to endDay
22%1312%32%26%
1681
March1st to 15thDay
19%129%33%33%
1980
16th to endDay
15%39%34%35%
2112
April1st to 15thDay
15%128%38%34%
2036
16th to endDay
10%117%28%51%
2160
May1st to 15thDay
11%128%25%50%
2274
16th to endDay
11%127%26%49%
2432
June1st to 15thDay
12%125%21%56%
2340
16th to endDay
21%447%20%41%
2340
July1st to 15thDay
33%10%16%14%14%10%
2201
16th to endDay
46%12%18%14%6%1
2312
August1st to 15thDay
41%10%12%16%15%4
2325
16th to endDay
33%8%14%16%16%10%
2307
September1st to 15thDay
35%6%11%16%17%12%
2013
16th to endDay
18%36%13%33%24%
1838
October1st to 15thDay
15%26%13%26%34%
1684
16th to endDay
13%2311%29%39%
1760
November1st to 15thDay
11%1313%37%32%
1759
16th to endDay
19%2313%30%30%
1722
December1st to 15thDay
20%26%17%34%18%
1620
16th to endDay
23%37%21%32%13%
1728
January1st to 15thNight
21%25%12%31%25%
2327
16th to endNight
27%2415%30%19%
2496
February1st to 15thNight
17%2415%29%30%
2244
16th to endNight
21%2413%35%23%
1793
March1st to 15thNight
17%1311%30%34%
1980
16th to endNight
15%2311%35%31%
2112
April1st to 15thNight
17%1211%37%29%
1912
16th to endNight
9%128%28%49%
1800
May1st to 15thNight
9%148%30%45%
1674
16th to endNight
8%139%32%45%
1685
June1st to 15thNight
11%12425%54%
1620
16th to endNight
17%45%8%22%42%
1620
July1st to 15thNight
27%9%20%19%12%10%
1530
16th to endNight
36%12%27%17%41
1593
August1st to 15thNight
30%9%17%19%17%4
1611
16th to endNight
29%8%16%18%16%10%
1893
September1st to 15thNight
31%7%12%20%18%10%
1943
16th to endNight
14%36%17%35%22%
1847
October1st to 15thNight
13%26%18%27%31%
1944
16th to endNight
11%15%14%26%41%
2112
November1st to 15thNight
10%1417%34%31%
2100
16th to endNight
19%1312%29%32%
2235
December1st to 15thNight
20%26%19%32%19%
2340
16th to endNight
25%27%18%32%13%
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%5%15%41%20%1
90
16th to endDay
7%5%18%34%26%8%
96
February1st to 15thDay
6%9%15%27%37%4
131
16th to endDay
8%20%28%22%14%5%
238
March1st to 15thDay
6%13%27%23%20%7%
270
16th to endDay
318%28%22%17%9%
288
April1st to 15thDay
6%12%31%26%17%5%
269
16th to endDay
319%34%23%14%4
270
May1st to 15thDay
314%32%28%13%6%
288
16th to endDay
27%28%37%18%6%
330
June1st to 15thDay
3224%38%16%14%
315
16th to endDay
4111%35%30%16%
315
July1st to 15thDay
8%8%30%36%15%
305
16th to endDay
9%16%24%33%24%
327
August1st to 15thDay
11%5%22%33%25%
315
16th to endDay
9%320%38%28%
332
September1st to 15thDay
11%19%30%33%14%
315
16th to endDay
6%5%14%29%32%10%
264
October1st to 15thDay
4218%25%32%16%
124
16th to endDay
5%5%26%36%27%
96
November1st to 15thDay
47%15%30%33%8%
90
16th to endDay
5%7%23%32%28%2
90
December1st to 15thDay
5%316%30%27%16%
90
16th to endDay
11%13%19%30%22%2
96
January1st to 15thNight
7%113%49%26%2
720
16th to endNight
10%214%47%23%1
768
February1st to 15thNight
4216%46%28%2
704
16th to endNight
4324%49%18%
632
March1st to 15thNight
4322%42%24%2
720
16th to endNight
3220%42%29%1
768
April1st to 15thNight
2422%50%18%1
653
16th to endNight
1323%48%21%1
540
May1st to 15thNight
1121%47%26%
540
16th to endNight
1213%49%31%1
563
June1st to 15thNight
38%50%34%
540
16th to endNight
25%37%52%1
540
July1st to 15thNight
5%226%57%7%
510
16th to endNight
5%119%60%12%
564
August1st to 15thNight
5%214%64%13%
539
16th to endNight
7%17%62%11%
573
September1st to 15thNight
9%421%57%7%
683
16th to endNight
35%38%46%5%
667
October1st to 15thNight
213%45%33%5%
660
16th to endNight
17%39%44%5%
704
November1st to 15thNight
212%41%37%5%
700
16th to endNight
6%215%39%31%4
720
December1st to 15thNight
7%114%45%27%3
720
16th to endNight
7%216%46%22%4
768
Page generated at 2017-09-19 04:32:29. Version ac04

Copyright 2017 A. Danko


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