Old Town Pasadena
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Old Town Pasadena clear sky chart from 2005-11-06 to 2024-01-16.

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
72%
24391
32%
74413
28%
24335
76%
24335
46%
38328

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 10thNight
61%
756
28%
2646
26%
756
68%
756
37%
1340
January11th to 20thNight
63%
740
35%
2417
29%
740
75%
740
45%
1190
January21st to endNight
57%
792
38%
2376
29%
792
69%
792
42%
1258
February1st to 10thNight
64%
720
36%
2160
32%
720
72%
720
45%
1121
February11th to 20thNight
61%
700
33%
2098
28%
700
71%
700
45%
1083
February21st to endNight
57%
592
28%
1776
26%
592
64%
592
38%
987
March1st to 10thNight
59%
720
26%
2160
23%
720
66%
720
38%
1216
March11th to 20thNight
64%
720
25%
2109
23%
720
69%
720
40%
1180
March21st to endNight
62%
792
30%
1980
20%
792
69%
792
46%
1142
April1st to 10thNight
66%
720
28%
1800
19%
720
69%
720
43%
1076
April11th to 20thNight
64%
711
32%
1779
17%
711
69%
711
51%
981
April21st to endNight
65%
720
29%
1800
15%
720
69%
720
49%
1019
May1st to 10thNight
64%
662
26%
1742
16%
662
66%
662
43%
1021
May11th to 20thNight
70%
531
28%
1595
22%
531
71%
531
43%
874
May21st to endNight
67%
582
30%
1746
24%
582
69%
582
51%
882
June1st to 10thNight
75%
520
25%
1600
22%
520
76%
520
46%
839
June11th to 20thNight
86%
360
35%
1440
42%
360
86%
360
47%
590
June21st to endNight
88%
360
33%
1440
41%
360
88%
360
46%
608
July1st to 10thNight
90%
350
35%
1400
44%
350
90%
350
50%
562
July11th to 20thNight
92%
370
35%
1414
39%
370
92%
370
51%
592
July21st to endNight
89%
755
30%
1829
22%
713
89%
713
56%
967
August1st to 10thNight
88%
716
33%
1780
21%
712
88%
712
63%
907
August11th to 20thNight
90%
712
37%
1780
24%
712
90%
712
66%
894
August21st to endNight
90%
792
39%
1980
28%
792
90%
792
63%
1008
September1st to 10thNight
85%
720
38%
1800
29%
720
86%
720
60%
941
September11th to 20thNight
86%
720
42%
1930
38%
720
87%
720
66%
906
September21st to endNight
86%
720
41%
1980
39%
720
88%
720
64%
920
October1st to 10thNight
78%
720
36%
1980
33%
720
82%
720
54%
1018
October11th to 20thNight
77%
720
40%
2092
39%
720
81%
720
54%
1019
October21st to endNight
75%
792
40%
2412
39%
792
81%
792
57%
1107
November1st to 10thNight
76%
740
35%
2405
36%
740
82%
740
53%
1079
November11th to 20thNight
76%
760
37%
2470
37%
760
83%
760
53%
1119
November21st to endNight
69%
760
34%
2470
34%
760
74%
760
43%
1238
December1st to 10thNight
63%
760
31%
2470
28%
760
71%
760
38%
1304
December11th to 20thNight
58%
760
29%
2968
30%
759
65%
759
27%
1769
December21st to endNight
55%
826
20%
4589
27%
817
66%
817
21%
2571

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
6%313323346%68%
75029
Night
6%413323346%66%
74778
TransparencyDay
19%5%7%17%27%26%
74754
Night
21%6%7%17%25%25%
74574
SeeingDay
6%9%27%37%16%4
14465
Night
6%315%37%33%7%
24411

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 10thDay
9%423423447%58%
1519
11th to 20thDay
8%412323347%62%
1644
21st to endDay
11%423422335%60%
1980
February1st to 10thDay
9%333312236%65%
1800
11th to 20thDay
10%313223346%62%
1750
21st to endDay
10%5%13423347%58%
1480
March1st to 10thDay
9%5%25%5%3446%7%51%
1800
11th to 20thDay
8%5%2232336%7%58%
1845
21st to endDay
6%41343445%7%58%
2376
April1st to 10thDay
6%42332335%8%61%
2160
11th to 20thDay
5%413324346%67%
2129
21st to endDay
6%413222336%68%
2160
May1st to 10thDay
7%5%23322447%62%
2218
11th to 20thDay
5%423423347%64%
2301
21st to endDay
6%423323346%64%
2530
June1st to 10thDay
5%412423248%65%
2354
11th to 20thDay
3312222236%74%
2520
21st to endDay
2112212335%78%
2520
July1st to 10thDay
2212223236%76%
2520
11th to 20thDay
2112312235%79%
2494
21st to endDay
211221345%8%72%
2378
August1st to 10thDay
211221223481%
2149
11th to 20thDay
2121222484%
2122
21st to endDay
111213335%80%
2376
September1st to 10thDay
3211212235%79%
2160
11th to 20thDay
211211235%82%
2029
21st to endDay
2211212245%78%
1980
October1st to 10thDay
4212323345%72%
1980
11th to 20thDay
421221222477%
1864
21st to endDay
4312212335%74%
1941
November1st to 10thDay
4213322345%72%
1674
11th to 20thDay
5%312313346%70%
1710
21st to endDay
5%223434347%64%
1710
December1st to 10thDay
8%324323446%60%
1710
11th to 20thDay
17%5%2442345%9%45%
2169
21st to endDay
14%6%245%3445%7%47%
2977
January1st to 10thNight
10%413223447%59%
2646
11th to 20thNight
8%313323346%65%
2417
21st to endNight
10%423322335%64%
2376
February1st to 10thNight
8%424322235%66%
2160
11th to 20thNight
8%423323335%63%
2098
21st to endNight
12%41332443459%
1776
March1st to 10thNight
10%5%2322445%8%54%
2160
11th to 20thNight
8%42332346%7%58%
2109
21st to endNight
7%41333445%7%59%
1980
April1st to 10thNight
7%424333337%61%
1800
11th to 20thNight
5%6%12223336%67%
1779
21st to endNight
4422433346%66%
1800
May1st to 10thNight
5%6%145%22447%61%
1742
11th to 20thNight
45%13433347%63%
1594
21st to endNight
4423322235%70%
1746
June1st to 10thNight
241342435%7%65%
1600
11th to 20thNight
231232223475%
1440
21st to endNight
2212212345%75%
1440
July1st to 10thNight
1311212325%79%
1440
11th to 20thNight
1112223346%74%
1462
21st to endNight
311231345%7%70%
1937
August1st to 10thNight
1322212235%77%
1790
11th to 20thNight
1211212236%79%
1780
21st to endNight
112212345%80%
1980
September1st to 10thNight
321322222477%
1800
11th to 20thNight
22221222383%
1930
21st to endNight
122211225%81%
1980
October1st to 10thNight
331233323472%
1980
11th to 20thNight
5%21222233476%
2092
21st to endNight
431221223475%
2412
November1st to 10thNight
4312322336%72%
2405
11th to 20thNight
4312223236%72%
2470
21st to endNight
6%32332445%7%62%
2470
December1st to 10thNight
8%314423347%61%
2470
11th to 20thNight
17%434433447%48%
3041
21st to endNight
13%7%2442445%6%49%
4676

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 10thDay
27%5%6%19%22%21%
1519
11th to 20thDay
24%5%7%12%25%27%
1644
21st to endDay
28%28%17%17%27%
1980
February1st to 10thDay
25%35%14%24%29%
1800
11th to 20thDay
22%46%16%28%25%
1760
21st to endDay
26%39%18%25%19%
1480
March1st to 10thDay
30%5%10%18%18%20%
1800
11th to 20thDay
24%6%11%20%23%17%
1845
21st to endDay
23%6%12%22%22%15%
2376
April1st to 10thDay
23%5%12%26%22%12%
2160
11th to 20thDay
18%410%21%29%18%
2132
21st to endDay
18%48%26%31%13%
2160
May1st to 10thDay
23%7%10%20%28%13%
2218
11th to 20thDay
21%6%7%22%31%12%
2304
21st to endDay
22%6%8%27%29%8%
2530
June1st to 10thDay
21%6%9%19%30%15%
2354
11th to 20thDay
15%46%13%32%31%
2520
21st to endDay
14%448%31%39%
2520
July1st to 10thDay
13%5%5%9%22%45%
2451
11th to 20thDay
12%5%6%17%31%29%
2419
21st to endDay
12%6%8%22%33%19%
2246
August1st to 10thDay
11%3313%32%39%
2135
11th to 20thDay
8%4312%37%36%
2122
21st to endDay
9%45%10%36%36%
2376
September1st to 10thDay
10%35%9%34%39%
2160
11th to 20thDay
9%4212%36%37%
2029
21st to endDay
10%45%14%34%33%
1980
October1st to 10thDay
16%45%18%24%32%
1980
11th to 20thDay
13%5%5%15%28%35%
1864
21st to endDay
14%45%12%22%43%
1941
November1st to 10thDay
15%45%18%25%33%
1674
11th to 20thDay
17%36%15%20%38%
1710
21st to endDay
21%5%8%12%24%31%
1710
December1st to 10thDay
26%5%6%17%19%26%
1710
11th to 20thDay
37%48%15%19%16%
2168
21st to endDay
36%6%8%23%14%12%
2977
January1st to 10thNight
26%5%7%17%25%20%
2646
11th to 20thNight
23%48%16%20%30%
2417
21st to endNight
26%37%16%18%29%
2376
February1st to 10thNight
25%36%14%22%29%
2160
11th to 20thNight
23%47%17%24%26%
2099
21st to endNight
29%5%7%15%22%22%
1776
March1st to 10thNight
29%5%8%21%19%18%
2160
11th to 20thNight
26%7%10%16%24%17%
2109
21st to endNight
24%6%12%23%23%13%
1980
April1st to 10thNight
27%6%10%24%19%14%
1800
11th to 20thNight
19%7%10%22%24%18%
1779
21st to endNight
21%7%10%23%29%10%
1800
May1st to 10thNight
24%9%10%21%24%12%
1742
11th to 20thNight
23%8%8%25%25%11%
1595
21st to endNight
17%7%10%30%27%8%
1746
June1st to 10thNight
20%8%13%19%27%13%
1600
11th to 20thNight
15%7%6%15%35%23%
1440
21st to endNight
17%5%7%8%31%33%
1440
July1st to 10thNight
13%7%49%27%40%
1400
11th to 20thNight
14%7%7%20%27%26%
1414
21st to endNight
15%8%9%23%29%16%
1829
August1st to 10thNight
14%5%5%9%36%32%
1780
11th to 20thNight
11%6%413%36%30%
1780
21st to endNight
12%7%410%35%32%
1980
September1st to 10thNight
16%5%5%8%30%37%
1800
11th to 20thNight
9%7%311%33%36%
1930
21st to endNight
11%5%413%36%30%
1980
October1st to 10thNight
18%5%417%23%32%
1980
11th to 20thNight
16%6%415%26%33%
2092
21st to endNight
15%5%5%11%23%42%
2412
November1st to 10thNight
16%5%6%15%25%33%
2405
11th to 20thNight
17%47%14%20%38%
2470
21st to endNight
23%5%7%17%18%31%
2470
December1st to 10thNight
25%7%7%14%18%28%
2470
11th to 20thNight
37%47%14%21%15%
3041
21st to endNight
33%10%10%20%15%12%
4676

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 10thDay
16%428%35%14%2
180
11th to 20thDay
11%12%33%31%11%2
322
21st to endDay
10%15%30%33%12%1
462
February1st to 10thDay
11%11%30%31%13%4
420
11th to 20thDay
11%17%31%32%7%2
415
21st to endDay
11%20%31%29%8%
346
March1st to 10thDay
13%18%34%24%10%1
420
11th to 20thDay
13%14%34%27%10%2
420
21st to endDay
11%19%34%28%8%1
462
April1st to 10thDay
9%14%34%26%14%2
420
11th to 20thDay
7%20%38%25%8%3
412
21st to endDay
5%17%33%28%14%3
420
May1st to 10thDay
12%14%34%27%10%3
423
11th to 20thDay
8%12%31%33%13%3
448
21st to endDay
9%11%35%29%13%2
485
June1st to 10thDay
47%29%40%15%5%
450
11th to 20thDay
5%5%26%40%17%7%
450
21st to endDay
2326%43%17%8%
450
July1st to 10thDay
2116%50%25%7%
446
11th to 20thDay
1110%49%26%13%
444
21st to endDay
213%49%25%11%
487
August1st to 10thDay
2218%51%19%8%
447
11th to 20thDay
2214%49%24%10%
437
21st to endDay
1118%50%25%5%
495
September1st to 10thDay
3224%45%19%6%
450
11th to 20thDay
2430%42%18%4
450
21st to endDay
26%30%36%20%6%
450
October1st to 10thDay
49%30%34%19%3
450
11th to 20thDay
310%29%39%17%3
450
21st to endDay
5%8%25%36%21%5%
456
November1st to 10thDay
47%21%39%23%6%
270
11th to 20thDay
7%6%21%39%23%5%
270
21st to endDay
5%7%27%37%18%6%
270
December1st to 10thDay
10%5%23%41%19%3
270
11th to 20thDay
6%6%27%37%21%4
270
21st to endDay
17%9%27%34%12%1
248
January1st to 10thNight
11%320%42%20%4
760
11th to 20thNight
9%220%43%23%2
740
21st to endNight
13%421%42%18%3
792
February1st to 10thNight
8%418%41%24%4
720
11th to 20thNight
8%5%22%38%23%5%
704
21st to endNight
12%422%40%19%3
592
March1st to 10thNight
9%5%23%42%19%3
720
11th to 20thNight
9%417%38%26%6%
720
21st to endNight
8%5%21%42%22%3
792
April1st to 10thNight
8%415%46%24%3
720
11th to 20thNight
5%7%19%39%27%3
711
21st to endNight
46%20%37%27%6%
720
May1st to 10thNight
6%421%39%26%4
662
11th to 20thNight
5%317%39%31%5%
531
21st to endNight
4322%38%29%4
584
June1st to 10thNight
2216%38%40%3
520
11th to 20thNight
216%32%53%5%
360
21st to endNight
21436%50%6%
360
July1st to 10thNight
31316%67%11%
350
11th to 20thNight
1315%67%13%
370
21st to endNight
31226%53%15%
755
August1st to 10thNight
21429%50%13%
716
11th to 20thNight
115%20%55%19%
712
21st to endNight
215%23%53%17%
792
September1st to 10thNight
317%27%47%15%
720
11th to 20thNight
218%33%45%11%
720
21st to endNight
227%33%47%9%
720
October1st to 10thNight
4210%42%38%4
720
11th to 20thNight
5%213%37%36%8%
720
21st to endNight
4315%35%32%11%
792
November1st to 10thNight
5%212%42%30%8%
740
11th to 20thNight
4312%44%30%7%
760
21st to endNight
6%218%44%25%5%
760
December1st to 10thNight
8%418%42%23%4
760
11th to 20thNight
12%5%17%44%19%3
760
21st to endNight
10%6%23%40%17%4
836
Page generated at 2024-01-12 22:38:10. Version ac07

Copyright 2024 Attilla Danko


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