Ojai
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ojai clear sky chart from 2005-11-05 to 2017-10-31.

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
77%
15943
36%
47371
31%
15898
82%
15898
57%
22033

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
66%
716
31%
2424
30%
716
73%
716
43%
1186
January16th to endNight
58%
768
35%
2463
29%
768
70%
768
40%
1264
February1st to 15thNight
67%
700
37%
2101
33%
696
76%
696
49%
1050
February16th to endNight
59%
632
31%
1895
29%
632
66%
632
41%
1033
March1st to 15thNight
67%
720
30%
2136
26%
720
75%
720
52%
1040
March16th to endNight
71%
768
32%
2001
24%
768
77%
768
54%
1056
April1st to 15thNight
68%
719
33%
1799
20%
719
73%
719
53%
979
April16th to endNight
72%
720
34%
1800
17%
720
78%
720
61%
919
May1st to 15thNight
78%
672
31%
1752
19%
672
81%
672
61%
873
May16th to endNight
80%
555
32%
1679
25%
555
83%
555
64%
728
June1st to 15thNight
90%
360
34%
1440
39%
360
92%
360
58%
524
June16th to endNight
97%
360
42%
1440
52%
360
97%
360
76%
439
July1st to 15thNight
94%
340
35%
1360
42%
340
94%
340
64%
464
July16th to endNight
93%
600
37%
1625
31%
563
93%
563
69%
697
August1st to 15thNight
94%
717
38%
1790
25%
713
94%
713
79%
809
August16th to endNight
95%
764
45%
1910
30%
764
95%
764
82%
853
September1st to 15thNight
92%
720
43%
1800
34%
720
92%
720
74%
849
September16th to endNight
91%
716
48%
1970
45%
716
94%
716
81%
812
October1st to 15thNight
81%
720
37%
2065
36%
720
85%
720
63%
943
October16th to endNight
80%
768
45%
2304
46%
768
84%
768
60%
1038
November1st to 15thNight
75%
700
37%
2255
36%
700
83%
700
60%
961
November16th to endNight
74%
720
39%
2340
39%
720
81%
720
56%
1027
December1st to 15thNight
68%
720
37%
2340
33%
720
76%
720
45%
1142
December16th to endNight
59%
768
32%
2682
29%
768
69%
768
38%
1347

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
3212223235%70%
48364
Night
4212212235%71%
47571
TransparencyDay
17%26%18%28%24%
48052
Night
16%25%18%28%27%
47383
SeeingDay
5%6%28%40%15%3
6165
Night
5%111%33%36%11%
15954

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%213312346%63%
1513
16th to endDay
11%312312146%60%
1760
February1st to 15thDay
7%322213247%61%
1751
16th to endDay
11%313323337%55%
1579
March1st to 15thDay
5%112225%5%46%60%
1821
16th to endDay
4223223448%60%
2223
April1st to 15thDay
6%214323237%61%
2149
16th to endDay
322122337%70%
2160
May1st to 15thDay
3312213336%69%
2196
16th to endDay
2211212236%72%
2432
June1st to 15thDay
2223222236%68%
2520
16th to endDay
1222382%
2520
July1st to 15thDay
111222235%76%
2520
16th to endDay
211112325%75%
2426
August1st to 15thDay
1111223478%
2160
16th to endDay
11213482%
2292
September1st to 15thDay
11111223480%
2160
16th to endDay
11111212382%
1989
October1st to 15thDay
312212235%73%
1893
16th to endDay
12242223473%
1918
November1st to 15thDay
311221233473%
1603
16th to endDay
3212323236%67%
1620
December1st to 15thDay
6%31222345%8%59%
1620
16th to endDay
9%323223246%59%
1539
January1st to 15thNight
6%312324346%61%
2424
16th to endNight
9%313313326%60%
2463
February1st to 15thNight
6%313213336%65%
2101
16th to endNight
12%313313335%58%
1895
March1st to 15thNight
421231335%6%65%
2136
16th to endNight
321232435%8%63%
2001
April1st to 15thNight
6%21221224468%
1799
16th to endNight
211223235%73%
1800
May1st to 15thNight
1212212246%72%
1752
16th to endNight
111112245%76%
1678
June1st to 15thNight
112123236%74%
1440
16th to endNight
11112387%
1440
July1st to 15thNight
11121223479%
1440
16th to endNight
111112235%78%
1736
August1st to 15thNight
111112385%
1800
16th to endNight
111112385%
1910
September1st to 15thNight
11111213382%
1800
16th to endNight
11212484%
1970
October1st to 15thNight
31111323476%
2065
16th to endNight
121221222475%
2304
November1st to 15thNight
22121222475%
2255
16th to endNight
4212212335%70%
2340
December1st to 15thNight
6%213313346%63%
2340
16th to endNight
9%312222336%61%
2682

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
23%37%16%23%24%
1513
16th to endDay
27%28%17%18%26%
1760
February1st to 15thDay
24%3418%28%21%
1751
16th to endDay
30%27%20%28%9%
1579
March1st to 15thDay
23%311%21%22%17%
1821
16th to endDay
23%312%25%22%12%
2223
April1st to 15thDay
25%39%25%25%10%
2149
16th to endDay
17%210%25%30%14%
2160
May1st to 15thDay
19%39%21%27%18%
2196
16th to endDay
15%29%30%31%10%
2435
June1st to 15thDay
18%37%20%32%17%
2520
16th to endDay
8%1410%37%37%
2520
July1st to 15thDay
11%2315%27%39%
2371
16th to endDay
13%27%21%29%25%
2274
August1st to 15thDay
10%2215%36%32%
2146
16th to endDay
7%2114%39%33%
2292
September1st to 15thDay
9%2413%31%39%
2160
16th to endDay
9%1214%36%36%
1989
October1st to 15thDay
16%25%18%26%30%
1893
16th to endDay
17%3413%25%36%
1918
November1st to 15thDay
16%2416%30%29%
1603
16th to endDay
19%35%17%23%30%
1620
December1st to 15thDay
22%5%9%16%24%21%
1620
16th to endDay
27%38%20%21%17%
1539
January1st to 15thNight
24%25%17%24%24%
2424
16th to endNight
26%35%14%20%29%
2463
February1st to 15thNight
22%2419%27%24%
2112
16th to endNight
29%26%20%27%13%
1895
March1st to 15thNight
19%38%22%26%19%
2136
16th to endNight
19%311%24%23%16%
2001
April1st to 15thNight
20%48%26%27%13%
1799
16th to endNight
15%36%23%31%19%
1800
May1st to 15thNight
15%39%23%27%20%
1753
16th to endNight
12%210%27%32%14%
1679
June1st to 15thNight
12%210%22%32%19%
1440
16th to endNight
5%1214%34%41%
1440
July1st to 15thNight
9%2313%25%44%
1360
16th to endNight
11%15%22%28%29%
1625
August1st to 15thNight
7%1213%35%39%
1790
16th to endNight
6%1110%44%35%
1910
September1st to 15thNight
10%239%32%42%
1800
16th to endNight
6%213%38%38%
1970
October1st to 15thNight
14%2316%30%32%
2065
16th to endNight
14%3314%23%41%
2304
November1st to 15thNight
14%2414%31%32%
2255
16th to endNight
16%25%18%24%32%
2340
December1st to 15thNight
22%37%17%22%25%
2340
16th to endNight
25%47%19%23%19%
2682

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
14%7%43%29%4
141
16th to endDay
13%14%35%29%6%1
261
February1st to 15thDay
10%8%35%37%6%2
266
16th to endDay
17%10%37%25%8%
238
March1st to 15thDay
7%12%37%30%12%
270
16th to endDay
7%9%39%31%9%2
288
April1st to 15thDay
11%12%39%24%7%4
269
16th to endDay
5%12%45%27%7%2
270
May1st to 15thDay
9%8%32%34%9%4
288
16th to endDay
6%8%33%36%13%2
330
June1st to 15thDay
5%6%29%37%16%3
315
16th to endDay
20%48%19%8%
315
July1st to 15thDay
111%51%26%8%
305
16th to endDay
316%51%29%8%
327
August1st to 15thDay
114%57%17%8%
315
16th to endDay
19%53%26%8%
332
September1st to 15thDay
2120%51%17%5%
315
16th to endDay
1424%51%15%2
315
October1st to 15thDay
36%37%38%13%
315
16th to endDay
35%30%39%17%2
336
November1st to 15thDay
15%23%36%28%3
109
16th to endDay
6%6%36%37%11%1
90
December1st to 15thDay
45%25%40%24%
90
16th to endDay
6%15%38%29%9%1
65
January1st to 15thNight
8%117%44%18%9%
720
16th to endNight
10%419%39%20%5%
768
February1st to 15thNight
8%316%39%25%6%
704
16th to endNight
14%118%37%22%6%
632
March1st to 15thNight
4120%40%26%5%
720
16th to endNight
4116%42%29%4
768
April1st to 15thNight
6%414%42%26%5%
719
16th to endNight
3217%39%29%7%
720
May1st to 15thNight
2212%38%35%7%
673
16th to endNight
2112%36%38%7%
557
June1st to 15thNight
25%33%51%8%
360
16th to endNight
28%58%12%
360
July1st to 15thNight
28%67%20%
340
16th to endNight
27%61%28%
600
August1st to 15thNight
1116%61%18%
717
16th to endNight
110%61%26%
764
September1st to 15thNight
2120%54%20%
720
16th to endNight
5%29%47%16%
716
October1st to 15thNight
311%36%39%7%
720
16th to endNight
319%37%34%12%
768
November1st to 15thNight
4114%38%29%11%
700
16th to endNight
5%114%40%28%9%
720
December1st to 15thNight
7%215%42%26%5%
720
16th to endNight
12%319%40%17%6%
768
Page generated at 2017-11-01 14:23:33. Version ac04

Copyright 2017 A. Danko


Ojai Clear Sky Chart |Charts Home