Anaheim
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Anaheim clear sky chart from 2005-11-05 to 2017-04-26.

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
75%
15473
31%
45406
28%
15428
78%
15428
47%
23666

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
70%
716
28%
2417
27%
716
76%
716
41%
1217
January16th to endNight
64%
768
33%
2304
28%
768
71%
768
40%
1261
February1st to 15thNight
71%
697
33%
2102
33%
697
75%
697
44%
1110
February16th to endNight
64%
632
26%
1895
28%
632
67%
632
32%
1128
March1st to 15thNight
73%
720
29%
2160
30%
720
77%
720
45%
1137
March16th to endNight
73%
768
26%
2010
22%
768
75%
768
46%
1144
April1st to 15thNight
68%
719
27%
1799
18%
719
71%
719
46%
1059
April16th to endNight
73%
704
28%
1760
17%
704
74%
704
51%
978
May1st to 15thNight
72%
563
27%
1553
19%
563
72%
563
43%
894
May16th to endNight
76%
513
23%
1541
19%
513
76%
513
45%
831
June1st to 15thNight
76%
473
23%
1463
21%
473
76%
473
41%
816
June16th to endNight
84%
330
26%
1320
30%
330
85%
330
45%
562
July1st to 15thNight
84%
310
30%
1240
36%
310
84%
310
45%
525
July16th to endNight
84%
615
24%
1552
19%
574
84%
574
50%
845
August1st to 15thNight
84%
657
32%
1640
21%
653
84%
653
60%
856
August16th to endNight
88%
700
34%
1750
23%
700
88%
700
66%
865
September1st to 15thNight
85%
660
34%
1683
28%
660
85%
660
59%
873
September16th to endNight
86%
656
38%
1815
38%
656
87%
656
64%
844
October1st to 15thNight
80%
660
35%
1815
34%
660
82%
660
54%
932
October16th to endNight
80%
704
36%
2136
38%
704
81%
704
51%
1032
November1st to 15thNight
82%
700
35%
2275
38%
700
85%
700
53%
1025
November16th to endNight
77%
720
35%
2340
38%
720
80%
720
46%
1145
December1st to 15thNight
70%
720
32%
2340
31%
720
75%
720
37%
1256
December16th to endNight
62%
768
32%
2496
29%
768
69%
768
37%
1331

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
5%312212336%66%
46211
Night
5%413212346%63%
45609
TransparencyDay
19%48%17%26%23%
45905
Night
22%49%15%23%24%
45417
SeeingDay
6%6%26%40%16%3
5384
Night
6%18%33%38%10%
15487

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
7%413313336%61%
1499
16th to endDay
11%423312245%57%
1920
February1st to 15thDay
7%313413347%61%
1751
16th to endDay
11%413323438%53%
1579
March1st to 15thDay
431222345%8%60%
1800
16th to endDay
432332345%8%59%
2210
April1st to 15thDay
6%412213348%61%
2149
16th to endDay
4312212236%69%
2111
May1st to 15thDay
5%313212338%64%
2066
16th to endDay
45%13212236%65%
2221
June1st to 15thDay
6%6%13211236%62%
2162
16th to endDay
1311212225%76%
2310
July1st to 15thDay
4312212346%67%
2309
16th to endDay
2212212236%70%
2187
August1st to 15thDay
221111125%78%
1980
16th to endDay
111212336%76%
2100
September1st to 15thDay
112212235%77%
1945
16th to endDay
1112245%77%
1815
October1st to 15thDay
5%312212336%66%
1815
16th to endDay
4212211345%69%
1730
November1st to 15thDay
321221234471%
1584
16th to endDay
5%212312337%64%
1620
December1st to 15thDay
7%31332336%8%56%
1620
16th to endDay
10%413212337%58%
1728
January1st to 15thNight
6%323322346%60%
2417
16th to endNight
11%323312235%60%
2304
February1st to 15thNight
6%414313235%63%
2101
16th to endNight
11%423424335%53%
1895
March1st to 15thNight
5%41222225%8%60%
2160
16th to endNight
5%413223349%57%
2010
April1st to 15thNight
7%424312347%60%
1799
16th to endNight
5%412222336%64%
1760
May1st to 15thNight
5%7%1221225%9%58%
1553
16th to endNight
45%1222338%63%
1540
June1st to 15thNight
37%23312348%59%
1463
16th to endNight
25%13213347%63%
1320
July1st to 15thNight
341441235%9%60%
1320
16th to endNight
432331435%8%58%
1667
August1st to 15thNight
3312212346%67%
1650
16th to endNight
1312213248%70%
1750
September1st to 15thNight
2312222235%70%
1683
16th to endNight
2212221225%76%
1815
October1st to 15thNight
3213223236%68%
1815
16th to endNight
4412212326%67%
2136
November1st to 15thNight
2212212235%72%
2275
16th to endNight
4313312346%65%
2340
December1st to 15thNight
8%314322347%58%
2340
16th to endNight
11%423212235%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
25%46%12%23%27%
1499
16th to endDay
29%46%15%16%27%
1920
February1st to 15thDay
23%5%7%15%25%24%
1751
16th to endDay
31%5%8%19%26%9%
1579
March1st to 15thDay
21%5%9%21%20%21%
1800
16th to endDay
23%5%13%24%18%14%
2210
April1st to 15thDay
23%5%10%25%22%11%
2149
16th to endDay
17%411%22%27%16%
2111
May1st to 15thDay
21%5%10%20%26%15%
2066
16th to endDay
21%5%9%29%27%7%
2224
June1st to 15thDay
25%47%15%32%15%
2162
16th to endDay
12%27%8%32%36%
2310
July1st to 15thDay
17%48%10%25%34%
2160
16th to endDay
16%410%20%29%18%
2041
August1st to 15thDay
11%1415%37%30%
1966
16th to endDay
10%26%12%38%29%
2100
September1st to 15thDay
11%27%11%32%34%
1945
16th to endDay
9%27%14%32%33%
1815
October1st to 15thDay
21%36%20%24%24%
1815
16th to endDay
19%36%13%19%37%
1730
November1st to 15thDay
17%38%17%20%34%
1584
16th to endDay
20%48%14%21%31%
1620
December1st to 15thDay
25%5%10%16%17%23%
1620
16th to endDay
27%48%17%20%21%
1728
January1st to 15thNight
25%48%11%21%28%
2417
16th to endNight
28%38%14%14%30%
2304
February1st to 15thNight
24%46%15%21%27%
2112
16th to endNight
34%47%14%23%14%
1895
March1st to 15thNight
23%5%9%19%22%20%
2160
16th to endNight
23%6%15%20%20%13%
2010
April1st to 15thNight
25%5%10%24%21%12%
1799
16th to endNight
21%5%13%21%21%16%
1760
May1st to 15thNight
24%8%10%19%22%15%
1554
16th to endNight
21%7%13%24%23%9%
1541
June1st to 15thNight
25%6%13%12%28%12%
1463
16th to endNight
20%214%10%25%26%
1320
July1st to 15thNight
20%210%12%23%30%
1240
16th to endNight
22%412%19%24%16%
1552
August1st to 15thNight
18%28%13%35%22%
1640
16th to endNight
14%211%11%32%28%
1750
September1st to 15thNight
18%210%8%29%30%
1683
16th to endNight
14%26%12%31%33%
1815
October1st to 15thNight
19%37%17%29%23%
1815
16th to endNight
19%36%11%20%36%
2136
November1st to 15thNight
17%36%16%19%36%
2275
16th to endNight
21%46%16%18%32%
2340
December1st to 15thNight
27%5%8%14%19%24%
2340
16th to endNight
28%48%14%22%21%
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
20%427%34%13%
95
16th to endDay
13%10%29%32%12%1
288
February1st to 15thDay
10%8%25%36%17%2
266
16th to endDay
13%13%30%30%11%1
238
March1st to 15thDay
7%11%30%30%15%4
270
16th to endDay
7%10%37%32%10%1
288
April1st to 15thDay
7%13%38%27%8%3
269
16th to endDay
412%44%29%43
254
May1st to 15thDay
6%12%31%38%9%1
228
16th to endDay
5%9%36%34%12%1
266
June1st to 15thDay
7%5%30%42%11%1
255
16th to endDay
1118%48%23%6%
255
July1st to 15thDay
4114%53%21%4
245
16th to endDay
219%51%28%7%
271
August1st to 15thDay
3114%55%21%3
255
16th to endDay
210%54%22%8%
268
September1st to 15thDay
1122%54%14%4
255
16th to endDay
2225%48%14%6%
255
October1st to 15thDay
5%7%31%38%14%2
255
16th to endDay
4326%40%20%3
242
November1st to 15thDay
1413%30%32%18%
90
16th to endDay
36%27%30%27%4
90
December1st to 15thDay
4416%38%32%3
90
16th to endDay
11%5%21%37%20%3
96
January1st to 15thNight
7%212%40%27%9%
720
16th to endNight
13%213%32%32%6%
768
February1st to 15thNight
8%110%38%31%8%
704
16th to endNight
12%311%39%27%5%
632
March1st to 15thNight
6%112%40%30%7%
720
16th to endNight
6%111%36%35%7%
768
April1st to 15thNight
8%213%42%27%5%
719
16th to endNight
6%211%38%33%7%
704
May1st to 15thNight
6%114%35%37%4
564
16th to endNight
4113%39%36%5%
515
June1st to 15thNight
419%39%40%4
473
16th to endNight
4323%59%8%
330
July1st to 15thNight
411%66%16%
310
16th to endNight
4119%55%18%
615
August1st to 15thNight
5%121%52%18%
657
16th to endNight
3115%54%25%
700
September1st to 15thNight
3221%51%20%
660
16th to endNight
3326%50%14%
656
October1st to 15thNight
37%37%41%9%
660
16th to endNight
6%6%30%39%16%
704
November1st to 15thNight
37%35%38%14%
700
16th to endNight
5%18%37%34%13%
720
December1st to 15thNight
10%19%37%31%8%
720
16th to endNight
12%315%35%27%6%
768
Page generated at 2017-04-27 14:48:59. Version ac04

Copyright 2017 A. Danko


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