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 2018-03-11.

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
76%
16634
31%
48882
28%
16589
78%
16589
47%
25404

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%
776
28%
2619
28%
776
75%
776
40%
1335
January16th to endNight
65%
832
34%
2496
29%
832
72%
832
42%
1338
February1st to 15thNight
71%
757
33%
2282
33%
757
76%
757
44%
1198
February16th to endNight
64%
684
28%
2051
29%
684
68%
684
35%
1191
March1st to 15thNight
72%
764
28%
2292
29%
764
76%
764
44%
1220
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
72%
720
29%
1800
17%
720
74%
720
51%
994
May1st to 15thNight
71%
614
26%
1694
18%
614
72%
614
42%
980
May16th to endNight
76%
561
25%
1685
20%
561
77%
561
45%
910
June1st to 15thNight
75%
516
21%
1596
20%
516
76%
516
40%
898
June16th to endNight
84%
360
28%
1440
33%
360
84%
360
45%
610
July1st to 15thNight
84%
340
29%
1360
35%
340
84%
340
45%
575
July16th to endNight
83%
666
25%
1687
19%
625
83%
625
49%
926
August1st to 15thNight
83%
717
30%
1790
19%
713
83%
713
59%
940
August16th to endNight
88%
764
36%
1910
24%
764
88%
764
66%
950
September1st to 15thNight
85%
720
33%
1836
27%
720
85%
720
60%
947
September16th to endNight
86%
716
40%
1980
40%
716
87%
716
63%
923
October1st to 15thNight
82%
720
34%
1980
33%
720
83%
720
56%
1007
October16th to endNight
80%
768
38%
2331
40%
768
81%
768
51%
1127
November1st to 15thNight
82%
760
33%
2470
36%
760
85%
760
52%
1134
November16th to endNight
77%
780
36%
2535
40%
780
80%
780
46%
1239
December1st to 15thNight
70%
780
32%
2535
32%
780
75%
780
39%
1333
December16th to endNight
63%
832
33%
2704
30%
832
71%
832
38%
1426

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
4312212336%66%
49702
Night
5%413312347%63%
49085
TransparencyDay
19%48%17%26%24%
49396
Night
22%49%15%23%24%
48893
SeeingDay
5%6%24%39%17%5%
6562
Night
6%18%33%38%11%
16648

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%423313336%60%
1625
16th to endDay
10%423312245%58%
2080
February1st to 15thDay
6%23313347%62%
1901
16th to endDay
10%413323438%55%
1709
March1st to 15thDay
5%31222345%7%60%
1904
16th to endDay
432332345%8%59%
2210
April1st to 15thDay
6%412213348%61%
2149
16th to endDay
4312212236%69%
2160
May1st to 15thDay
5%413212338%63%
2255
16th to endDay
45%12212336%65%
2429
June1st to 15thDay
6%6%23211236%62%
2359
16th to endDay
131121222476%
2520
July1st to 15thDay
3312212346%68%
2519
16th to endDay
2212213336%70%
2360
August1st to 15thDay
22121112478%
2160
16th to endDay
111212336%76%
2292
September1st to 15thDay
112212235%76%
2122
16th to endDay
211111235%77%
1980
October1st to 15thDay
5%312212235%67%
1980
16th to endDay
4213221345%69%
1887
November1st to 15thDay
3212222345%69%
1719
16th to endDay
5%212312347%64%
1755
December1st to 15thDay
6%31321335%8%58%
1755
16th to endDay
10%413312338%59%
1872
January1st to 15thNight
6%32332335%7%58%
2619
16th to endNight
10%322312235%61%
2496
February1st to 15thNight
6%413313235%62%
2281
16th to endNight
10%423423335%55%
2051
March1st to 15thNight
5%41322336%8%58%
2292
16th to endNight
5%413223349%57%
2010
April1st to 15thNight
7%424312347%60%
1799
16th to endNight
5%412222336%65%
1800
May1st to 15thNight
5%7%1322225%9%58%
1694
16th to endNight
45%12212348%62%
1684
June1st to 15thNight
37%24312348%58%
1596
16th to endNight
25%23213347%63%
1440
July1st to 15thNight
231441235%8%61%
1440
16th to endNight
332331435%9%57%
1802
August1st to 15thNight
2413212346%66%
1800
16th to endNight
132213248%69%
1910
September1st to 15thNight
2312222235%70%
1836
16th to endNight
2212221225%76%
1980
October1st to 15thNight
2213223236%69%
1980
16th to endNight
4412212226%67%
2331
November1st to 15thNight
2222212235%69%
2470
16th to endNight
4313312346%64%
2535
December1st to 15thNight
7%314322347%59%
2535
16th to endNight
10%412212335%60%
2704

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
26%46%14%22%25%
1625
16th to endDay
28%46%16%16%27%
2080
February1st to 15thDay
22%46%14%25%25%
1901
16th to endDay
29%48%19%26%11%
1709
March1st to 15thDay
22%5%9%21%19%21%
1904
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%17%
2160
May1st to 15thDay
21%5%9%20%27%15%
2255
16th to endDay
21%5%9%28%26%8%
2432
June1st to 15thDay
24%37%15%32%15%
2359
16th to endDay
12%27%8%30%39%
2520
July1st to 15thDay
17%47%10%25%35%
2370
16th to endDay
15%410%20%30%18%
2214
August1st to 15thDay
11%1414%36%31%
2146
16th to endDay
10%26%12%38%30%
2292
September1st to 15thDay
11%27%12%32%32%
2122
16th to endDay
10%26%15%32%33%
1980
October1st to 15thDay
20%25%19%24%26%
1980
16th to endDay
18%36%13%19%38%
1887
November1st to 15thDay
18%38%17%19%31%
1719
16th to endDay
20%47%13%21%31%
1755
December1st to 15thDay
23%5%9%16%17%27%
1755
16th to endDay
27%47%16%21%22%
1872
January1st to 15thNight
26%48%12%21%26%
2619
16th to endNight
26%38%15%15%30%
2496
February1st to 15thNight
23%47%15%20%27%
2292
16th to endNight
32%47%13%24%16%
2051
March1st to 15thNight
23%5%10%19%21%19%
2292
16th to endNight
23%6%15%20%20%13%
2010
April1st to 15thNight
25%5%10%24%21%12%
1799
16th to endNight
20%5%13%21%21%17%
1800
May1st to 15thNight
25%8%10%19%22%14%
1695
16th to endNight
21%7%13%24%22%10%
1685
June1st to 15thNight
26%6%13%13%26%13%
1596
16th to endNight
20%213%10%23%29%
1440
July1st to 15thNight
20%29%12%24%30%
1360
16th to endNight
23%412%19%24%16%
1687
August1st to 15thNight
19%28%13%34%21%
1790
16th to endNight
14%210%12%31%28%
1910
September1st to 15thNight
17%210%9%30%28%
1836
16th to endNight
14%26%12%31%32%
1980
October1st to 15thNight
18%37%17%28%24%
1980
16th to endNight
19%36%11%19%38%
2331
November1st to 15thNight
18%37%17%18%34%
2470
16th to endNight
21%46%16%19%31%
2535
December1st to 15thNight
26%5%7%14%18%27%
2535
16th to endNight
27%48%13%23%22%
2704

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%419%33%22%3
131
16th to endDay
11%10%26%32%15%3
352
February1st to 15thDay
8%7%23%34%17%7%
326
16th to endDay
12%14%28%30%12%2
290
March1st to 15thDay
9%10%30%30%15%3
312
16th to endDay
7%10%37%32%10%1
288
April1st to 15thDay
7%13%38%27%8%3
269
16th to endDay
413%45%28%43
270
May1st to 15thDay
6%12%32%35%10%3
288
16th to endDay
5%8%36%35%12%2
330
June1st to 15thDay
7%5%28%41%14%2
315
16th to endDay
1115%49%22%8%
315
July1st to 15thDay
411%50%24%7%
305
16th to endDay
38%48%29%9%
327
August1st to 15thDay
3112%56%21%5%
315
16th to endDay
211%53%22%9%
332
September1st to 15thDay
1122%53%14%6%
315
16th to endDay
3323%47%14%6%
315
October1st to 15thDay
5%6%28%39%15%4
315
16th to endDay
4422%39%21%7%
303
November1st to 15thDay
35%18%30%29%12%
135
16th to endDay
45%20%29%28%11%
135
December1st to 15thDay
27%17%34%30%8%
135
16th to endDay
8%7%15%31%27%9%
144
January1st to 15thNight
7%212%40%28%8%
780
16th to endNight
12%212%32%33%6%
832
February1st to 15thNight
8%110%37%31%10%
764
16th to endNight
11%311%39%27%5%
684
March1st to 15thNight
7%112%40%30%7%
764
16th to endNight
6%111%36%35%7%
768
April1st to 15thNight
8%213%42%27%5%
719
16th to endNight
6%212%38%32%7%
720
May1st to 15thNight
6%114%34%36%5%
615
16th to endNight
4112%40%35%5%
563
June1st to 15thNight
5%110%39%39%4
516
16th to endNight
4323%60%8%
360
July1st to 15thNight
411%66%17%
340
16th to endNight
4120%53%19%
666
August1st to 15thNight
5%221%52%17%
717
16th to endNight
3115%54%25%
764
September1st to 15thNight
4222%50%19%
720
16th to endNight
4327%49%14%
716
October1st to 15thNight
36%36%43%9%
720
16th to endNight
5%6%30%39%16%
768
November1st to 15thNight
37%37%37%13%
760
16th to endNight
5%18%36%35%13%
780
December1st to 15thNight
9%29%37%32%8%
780
16th to endNight
11%215%34%27%6%
832
Page generated at 2018-03-12 10:28:09. Version ac04

Copyright 2018 A. Danko


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