Fullerton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fullerton clear sky chart from 2005-11-05 to 2017-09-20.

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%
15937
31%
46770
28%
15892
78%
15892
47%
24384

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%
2437
27%
716
76%
716
41%
1223
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%
1145
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
24%
1685
20%
561
77%
561
45%
910
June1st to 15thNight
75%
511
21%
1591
20%
511
76%
511
40%
893
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%
663
25%
1684
19%
622
83%
622
49%
923
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%
675
38%
1869
38%
675
87%
675
63%
877
October1st to 15thNight
80%
660
35%
1815
34%
660
82%
660
54%
932
October16th to endNight
80%
704
36%
2138
38%
704
81%
704
51%
1033
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
4312212336%66%
48034
Night
5%413212347%63%
46973
TransparencyDay
19%48%17%26%24%
47727
Night
22%49%15%23%24%
46781
SeeingDay
6%6%25%40%16%4
5957
Night
6%18%32%38%11%
15951

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%
1481
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%
2211
April1st to 15thDay
6%412213348%61%
2149
16th to endDay
4312212236%69%
2160
May1st to 15thDay
5%413212338%63%
2256
16th to endDay
45%12212336%65%
2429
June1st to 15thDay
6%6%23211237%62%
2364
16th to endDay
131121222476%
2520
July1st to 15thDay
3312212346%68%
2520
16th to endDay
2212213336%70%
2363
August1st to 15thDay
22121112478%
2160
16th to endDay
111212336%76%
2292
September1st to 15thDay
112212235%76%
2123
16th to endDay
22112245%77%
1860
October1st to 15thDay
5%312212336%66%
1814
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%
2437
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%65%
1800
May1st to 15thNight
5%7%1322225%9%58%
1694
16th to endNight
45%12212348%62%
1684
June1st to 15thNight
37%24312348%58%
1591
16th to endNight
25%23213347%63%
1440
July1st to 15thNight
231441235%8%61%
1440
16th to endNight
332431435%9%57%
1799
August1st to 15thNight
2413212346%66%
1800
16th to endNight
132213248%69%
1910
September1st to 15thNight
2312222235%70%
1836
16th to endNight
2212221225%75%
1869
October1st to 15thNight
3213223236%68%
1815
16th to endNight
4412212326%67%
2138
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%
1481
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%
2211
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%
2256
16th to endDay
21%5%9%28%26%8%
2432
June1st to 15thDay
24%37%15%32%15%
2364
16th to endDay
12%27%8%30%39%
2520
July1st to 15thDay
17%47%10%25%35%
2371
16th to endDay
15%410%20%30%18%
2216
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%
2123
16th to endDay
10%27%15%32%33%
1860
October1st to 15thDay
21%36%20%24%24%
1814
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%
2437
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%19%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%
1591
16th to endNight
20%213%10%23%29%
1440
July1st to 15thNight
20%29%12%24%30%
1360
16th to endNight
23%411%20%24%15%
1684
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%13%30%32%
1869
October1st to 15thNight
19%37%17%29%23%
1815
16th to endNight
19%36%11%21%36%
2138
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
19%428%32%14%
91
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
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
3224%48%14%7%
272
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%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%38%39%4
511
16th to endNight
4323%60%8%
360
July1st to 15thNight
411%66%17%
340
16th to endNight
4120%53%19%
663
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
4326%50%14%
675
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 2017-09-21 04:18:21. Version ac04

Copyright 2017 A. Danko


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