Scottsdale
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Scottsdale clear sky chart from 2005-11-05 to 2017-10-06.

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
79%
15724
37%
47126
34%
15686
83%
15686
57%
21953

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
75%
718
33%
2327
34%
716
79%
716
47%
1111
January16th to endNight
70%
768
36%
2496
36%
768
76%
768
43%
1262
February1st to 15thNight
77%
698
36%
2179
37%
698
82%
698
55%
1002
February16th to endNight
71%
632
36%
1886
38%
632
74%
632
47%
968
March1st to 15thNight
73%
720
40%
1980
35%
720
78%
720
62%
936
March16th to endNight
78%
768
40%
2112
33%
768
84%
768
65%
971
April1st to 15thNight
75%
710
33%
1969
25%
710
80%
710
59%
953
April16th to endNight
74%
540
46%
1695
39%
540
82%
540
74%
650
May1st to 15thNight
79%
539
39%
1619
32%
539
84%
539
70%
669
May16th to endNight
81%
561
41%
1684
32%
561
85%
561
74%
673
June1st to 15thNight
89%
540
35%
1620
32%
540
90%
540
74%
643
June16th to endNight
92%
540
35%
1620
31%
540
92%
540
76%
640
July1st to 15thNight
86%
510
25%
1530
22%
510
86%
510
49%
765
July16th to endNight
83%
564
27%
1593
23%
531
83%
531
41%
887
August1st to 15thNight
85%
539
29%
1611
26%
536
85%
536
47%
825
August16th to endNight
84%
645
33%
1869
31%
645
84%
645
44%
1023
September1st to 15thNight
83%
720
33%
1980
29%
720
84%
720
54%
1019
September16th to endNight
85%
716
44%
1980
36%
716
89%
716
69%
885
October1st to 15thNight
82%
684
41%
1955
35%
684
85%
684
66%
874
October16th to endNight
86%
704
44%
2112
40%
704
89%
704
69%
883
November1st to 15thNight
85%
700
42%
2133
41%
700
88%
700
68%
892
November16th to endNight
78%
720
40%
2340
40%
720
82%
720
57%
1018
December1st to 15thNight
75%
720
37%
2340
39%
720
78%
720
49%
1106
December16th to endNight
71%
768
36%
2496
38%
768
74%
768
41%
1298

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
3212212346%70%
48070
Night
3212213346%69%
47323
TransparencyDay
15%25%11%24%40%
47765
Night
17%2411%22%41%
47129
SeeingDay
4314%31%33%12%
5541
Night
419%41%38%4
15735

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
5%212322336%66%
1611
16th to endDay
7%313212245%65%
1728
February1st to 15thDay
3313212237%67%
1682
16th to endDay
6%323222346%61%
1588
March1st to 15thDay
4212213335%68%
1980
16th to endDay
3213313335%70%
2112
April1st to 15thDay
212213347%70%
1977
16th to endDay
11111213480%
2262
May1st to 15thDay
11111125%81%
2331
16th to endDay
21111122482%
2429
June1st to 15thDay
1111211383%
2340
16th to endDay
111112482%
2340
July1st to 15thDay
21133245%7%8%59%
2340
16th to endDay
4324435%6%8%10%45%
2467
August1st to 15thDay
32123145%7%9%57%
2340
16th to endDay
211232345%8%61%
2330
September1st to 15thDay
3212413346%64%
1980
16th to endDay
11111112382%
1980
October1st to 15thDay
21121223476%
1802
16th to endDay
1221123480%
1760
November1st to 15thDay
1111212235%76%
1723
16th to endDay
5%222123473%
1620
December1st to 15thDay
6%3332234463%
1620
16th to endDay
6%414223346%60%
1728
January1st to 15thNight
5%31322334465%
2327
16th to endNight
8%21331323462%
2496
February1st to 15thNight
4312212335%69%
2169
16th to endNight
7%212423325%63%
1886
March1st to 15thNight
4212212246%70%
1980
16th to endNight
2111212335%74%
2112
April1st to 15thNight
3112313336%68%
1969
16th to endNight
111121384%
1695
May1st to 15thNight
111212245%77%
1619
16th to endNight
1111111384%
1684
June1st to 15thNight
11112225%81%
1620
16th to endNight
1111212482%
1620
July1st to 15thNight
1113425%47%10%57%
1620
16th to endNight
32144447%7%10%48%
1701
August1st to 15thNight
22224345%7%10%54%
1620
16th to endNight
1212435%5%6%8%55%
1869
September1st to 15thNight
2112325%45%8%61%
1980
16th to endNight
21121223377%
1980
October1st to 15thNight
2211212135%76%
1955
16th to endNight
121121122479%
2112
November1st to 15thNight
211112235%75%
2133
16th to endNight
42221222472%
2340
December1st to 15thNight
7%212223346%64%
2340
16th to endNight
8%314323335%59%
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
20%25%14%27%28%
1612
16th to endDay
22%2316%25%30%
1728
February1st to 15thDay
18%26%17%27%28%
1682
16th to endDay
23%2415%30%24%
1588
March1st to 15thDay
17%238%29%38%
1980
16th to endDay
17%238%32%35%
2112
April1st to 15thDay
13%229%33%38%
1977
16th to endDay
9%127%23%55%
2262
May1st to 15thDay
8%129%23%55%
2331
16th to endDay
9%126%21%59%
2432
June1st to 15thDay
8%1315%70%
2340
16th to endDay
8%12311%73%
2340
July1st to 15thDay
18%5%10%14%18%32%
2201
16th to endDay
26%7%14%22%17%10%
2312
August1st to 15thDay
19%5%11%16%18%28%
2325
16th to endDay
18%5%8%17%26%24%
2330
September1st to 15thDay
19%37%13%24%31%
1980
16th to endDay
9%125%27%53%
1980
October1st to 15thDay
12%248%25%47%
1802
16th to endDay
10%147%27%48%
1760
November1st to 15thDay
11%1311%31%40%
1723
16th to endDay
16%1210%26%42%
1620
December1st to 15thDay
24%2416%28%23%
1620
16th to endDay
24%36%19%28%16%
1728
January1st to 15thNight
21%35%11%24%33%
2327
16th to endNight
25%2312%26%29%
2496
February1st to 15thNight
18%25%14%25%34%
2180
16th to endNight
24%1312%26%30%
1886
March1st to 15thNight
16%147%24%46%
1980
16th to endNight
13%238%31%41%
2112
April1st to 15thNight
16%227%27%43%
1969
16th to endNight
8%125%20%62%
1695
May1st to 15thNight
10%137%24%53%
1620
16th to endNight
9%17%15%64%
1685
June1st to 15thNight
8%11312%71%
1620
16th to endNight
8%1246%76%
1620
July1st to 15thNight
19%5%10%15%14%34%
1530
16th to endNight
24%8%13%19%20%14%
1593
August1st to 15thNight
21%5%10%17%14%30%
1611
16th to endNight
23%6%7%13%22%25%
1869
September1st to 15thNight
19%49%18%20%29%
1980
16th to endNight
11%126%21%56%
1980
October1st to 15thNight
12%129%22%50%
1955
16th to endNight
10%138%17%57%
2112
November1st to 15thNight
11%139%27%46%
2133
16th to endNight
16%149%22%45%
2340
December1st to 15thNight
21%2414%27%29%
2340
16th to endNight
26%35%15%28%20%
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
26%16%41%21%3
90
16th to endDay
8%39%36%28%14%
96
February1st to 15thDay
4216%35%36%5%
197
16th to endDay
8%426%35%19%5%
238
March1st to 15thDay
5%6%21%32%18%15%
270
16th to endDay
28%26%29%23%10%
288
April1st to 15thDay
49%23%30%23%8%
269
16th to endDay
113%29%34%16%4
270
May1st to 15thDay
29%26%31%23%6%
288
16th to endDay
2220%42%26%5%
330
June1st to 15thDay
1317%35%32%9%
315
16th to endDay
17%32%42%15%
315
July1st to 15thDay
27%31%43%15%
305
16th to endDay
4320%43%28%
327
August1st to 15thDay
4222%46%23%
315
16th to endDay
2320%51%21%
332
September1st to 15thDay
5%9%29%41%13%
315
16th to endDay
5%112%34%36%10%
315
October1st to 15thDay
2118%30%34%11%
204
16th to endDay
4415%57%18%
96
November1st to 15thDay
1210%33%37%15%
90
16th to endDay
10%211%40%33%3
90
December1st to 15thDay
4334%45%12%
90
16th to endDay
15%217%36%25%3
96
January1st to 15thNight
7%10%50%27%3
720
16th to endNight
10%111%47%25%3
768
February1st to 15thNight
5%110%51%28%2
704
16th to endNight
9%12%52%23%1
632
March1st to 15thNight
4116%46%26%3
720
16th to endNight
2211%45%32%4
768
April1st to 15thNight
3313%50%27%1
710
16th to endNight
2120%46%26%3
540
May1st to 15thNight
1214%47%32%2
540
16th to endNight
2113%42%38%2
563
June1st to 15thNight
116%52%36%2
540
16th to endNight
1237%54%3
540
July1st to 15thNight
2430%57%4
510
16th to endNight
4215%68%9%
564
August1st to 15thNight
3218%64%11%
539
16th to endNight
2218%65%9%
645
September1st to 15thNight
35%29%52%8%
720
16th to endNight
27%39%43%6%
716
October1st to 15thNight
38%46%38%2
684
16th to endNight
17%39%45%5%
704
November1st to 15thNight
27%46%38%4
700
16th to endNight
5%9%44%36%3
720
December1st to 15thNight
9%9%44%34%1
720
16th to endNight
10%19%48%26%3
768
Page generated at 2017-10-07 11:07:53. Version ac04

Copyright 2017 A. Danko


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