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 2017-03-14.

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%
15039
37%
45136
34%
15001
83%
15001
56%
21063

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%
716
40%
1969
35%
716
77%
716
62%
932
March16th to endNight
78%
704
38%
1936
31%
704
83%
704
64%
897
April1st to 15thNight
73%
651
34%
1805
26%
651
79%
651
57%
890
April16th to endNight
75%
495
44%
1554
38%
495
82%
495
73%
599
May1st to 15thNight
79%
494
41%
1484
34%
494
84%
494
70%
613
May16th to endNight
82%
513
38%
1540
30%
513
85%
513
73%
621
June1st to 15thNight
89%
495
37%
1485
34%
495
90%
495
73%
592
June16th to endNight
92%
495
33%
1485
29%
495
92%
495
75%
587
July1st to 15thNight
85%
465
26%
1395
23%
465
85%
465
48%
709
July16th to endNight
85%
522
28%
1467
24%
489
85%
489
44%
791
August1st to 15thNight
86%
494
31%
1476
28%
491
86%
491
48%
750
August16th to endNight
84%
591
31%
1712
29%
591
84%
591
44%
934
September1st to 15thNight
82%
660
34%
1815
30%
660
83%
660
54%
939
September16th to endNight
85%
656
41%
1815
34%
656
88%
656
68%
819
October1st to 15thNight
81%
660
42%
1889
36%
660
84%
660
65%
850
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%69%
45570
Night
3212213346%69%
45333
TransparencyDay
16%25%11%24%39%
45265
Night
17%2411%22%41%
45139
SeeingDay
4315%32%33%10%
4724
Night
419%42%38%4
15050

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%
1962
16th to endDay
321331333470%
1936
April1st to 15thDay
212213336%71%
1811
16th to endDay
21111222380%
2073
May1st to 15thDay
11111125%81%
2136
16th to endDay
21111112382%
2221
June1st to 15thDay
1111211382%
2145
16th to endDay
111112482%
2145
July1st to 15thDay
2113325%5%7%8%57%
2145
16th to endDay
4324435%5%8%10%46%
2285
August1st to 15thDay
32123145%7%9%56%
2145
16th to endDay
211232346%9%60%
2135
September1st to 15thDay
42135%13346%63%
1815
16th to endDay
21111113381%
1815
October1st to 15thDay
21122223475%
1741
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%
1969
16th to endNight
3112212335%73%
1936
April1st to 15thNight
3112313346%67%
1805
16th to endNight
211121383%
1554
May1st to 15thNight
11112245%77%
1484
16th to endNight
21111111383%
1540
June1st to 15thNight
111211482%
1485
16th to endNight
11111212482%
1485
July1st to 15thNight
1113425%47%10%56%
1485
16th to endNight
31134447%7%10%51%
1575
August1st to 15thNight
11233345%7%11%54%
1485
16th to endNight
1213435%5%6%8%55%
1712
September1st to 15thNight
2113425%35%8%60%
1815
16th to endNight
11121233376%
1815
October1st to 15thNight
2211212135%75%
1889
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%
1962
16th to endDay
17%238%29%37%
1936
April1st to 15thDay
14%228%32%39%
1811
16th to endDay
10%126%23%55%
2073
May1st to 15thDay
8%128%23%56%
2136
16th to endDay
9%126%22%58%
2224
June1st to 15thDay
9%1413%70%
2145
16th to endDay
8%12411%72%
2145
July1st to 15thDay
19%5%10%13%17%31%
2006
16th to endDay
26%7%13%21%19%11%
2130
August1st to 15thDay
19%5%11%17%18%27%
2130
16th to endDay
19%5%8%18%27%20%
2135
September1st to 15thDay
20%37%13%23%31%
1815
16th to endDay
10%126%26%52%
1815
October1st to 15thDay
12%248%25%46%
1741
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%45%
1969
16th to endNight
13%238%30%40%
1936
April1st to 15thNight
17%228%26%41%
1805
16th to endNight
8%126%20%61%
1554
May1st to 15thNight
9%136%24%53%
1485
16th to endNight
9%116%16%64%
1541
June1st to 15thNight
9%11311%72%
1485
16th to endNight
8%1246%76%
1485
July1st to 15thNight
20%5%10%14%14%33%
1395
16th to endNight
21%8%13%18%22%15%
1467
August1st to 15thNight
20%6%11%18%14%29%
1476
16th to endNight
23%6%8%14%23%23%
1712
September1st to 15thNight
19%49%17%19%29%
1815
16th to endNight
11%236%21%54%
1815
October1st to 15thNight
13%229%23%48%
1889
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
6%6%21%33%18%13%
264
16th to endDay
29%26%32%22%6%
224
April1st to 15thDay
5%11%27%31%20%3
209
16th to endDay
113%32%34%15%2
210
May1st to 15thDay
210%26%33%21%5%
228
16th to endDay
2319%43%26%5%
266
June1st to 15thDay
1418%38%30%6%
255
16th to endDay
19%35%40%12%
255
July1st to 15thDay
28%33%43%11%
245
16th to endDay
4222%46%23%
271
August1st to 15thDay
3225%45%22%
255
16th to endDay
1422%53%18%
268
September1st to 15thDay
7%110%28%40%12%
255
16th to endDay
6%111%36%35%8%
255
October1st to 15thDay
3119%29%33%13%
181
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%47%26%3
716
16th to endNight
2111%46%32%4
704
April1st to 15thNight
3313%51%26%1
651
16th to endNight
2119%48%25%3
495
May1st to 15thNight
1113%48%31%2
495
16th to endNight
212%42%38%2
515
June1st to 15thNight
116%52%35%2
495
16th to endNight
1337%53%3
495
July1st to 15thNight
25%30%56%5%
465
16th to endNight
3216%68%9%
522
August1st to 15thNight
2218%66%10%
494
16th to endNight
3219%65%9%
591
September1st to 15thNight
35%28%53%8%
660
16th to endNight
27%38%43%6%
656
October1st to 15thNight
38%45%38%2
660
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 2017-03-15 08:32:37. Version ac04

Copyright 2017 A. Danko


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