Granada Hills
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Granada Hills clear sky chart from 2005-11-06 to 2024-01-12.

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
73%
24311
34%
74439
30%
24257
79%
24257
50%
36565

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%
758
28%
2646
27%
756
68%
756
38%
1330
January11th to 20thNight
62%
724
36%
2369
30%
724
74%
724
47%
1123
January21st to endNight
56%
792
39%
2420
29%
792
69%
792
42%
1246
February1st to 10thNight
64%
720
38%
2160
32%
720
73%
720
47%
1085
February11th to 20thNight
63%
700
34%
2098
31%
700
72%
700
45%
1080
February21st to endNight
58%
592
31%
1776
27%
592
67%
592
40%
962
March1st to 10thNight
60%
720
27%
2160
24%
720
68%
720
39%
1187
March11th to 20thNight
66%
720
27%
2094
24%
720
71%
720
42%
1133
March21st to endNight
65%
792
32%
1980
21%
792
72%
792
47%
1130
April1st to 10thNight
69%
720
31%
1800
21%
720
72%
720
49%
1023
April11th to 20thNight
66%
711
35%
1779
17%
711
73%
711
56%
939
April21st to endNight
69%
720
33%
1800
16%
720
75%
720
55%
955
May1st to 10thNight
69%
686
28%
1766
18%
686
70%
686
51%
979
May11th to 20thNight
74%
531
30%
1595
24%
531
76%
531
49%
807
May21st to endNight
72%
582
31%
1746
23%
582
75%
582
55%
841
June1st to 10thNight
78%
456
29%
1536
28%
456
80%
456
49%
712
June11th to 20thNight
86%
360
38%
1440
46%
360
87%
360
58%
524
June21st to endNight
91%
360
38%
1440
47%
360
91%
360
57%
527
July1st to 10thNight
93%
350
39%
1400
47%
350
93%
350
62%
490
July11th to 20thNight
93%
348
39%
1392
47%
348
93%
348
64%
485
July21st to endNight
91%
754
34%
1829
25%
713
91%
713
65%
897
August1st to 10thNight
90%
716
34%
1780
22%
712
90%
712
68%
874
August11th to 20thNight
92%
712
41%
1780
25%
712
92%
712
73%
843
August21st to endNight
91%
792
44%
1980
31%
792
91%
792
74%
931
September1st to 10thNight
87%
720
41%
1800
33%
720
87%
720
67%
890
September11th to 20thNight
91%
720
44%
1912
40%
720
91%
720
72%
856
September21st to endNight
89%
720
44%
1980
43%
720
91%
720
73%
863
October1st to 10thNight
82%
720
38%
1980
36%
720
85%
720
60%
963
October11th to 20thNight
77%
720
41%
2128
41%
720
81%
720
58%
984
October21st to endNight
76%
792
42%
2389
42%
792
82%
792
59%
1077
November1st to 10thNight
77%
740
37%
2405
38%
740
83%
740
55%
1056
November11th to 20thNight
74%
760
38%
2470
36%
760
83%
760
56%
1072
November21st to endNight
70%
760
36%
2470
35%
760
76%
760
46%
1178
December1st to 10thNight
61%
760
35%
2470
29%
760
71%
760
42%
1233
December11th to 20thNight
60%
760
30%
2970
29%
759
70%
759
27%
1770
December21st to endNight
59%
823
20%
4699
29%
817
69%
817
21%
2520

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%313323346%68%
74900
Night
6%313323346%67%
74819
TransparencyDay
19%46%17%27%27%
74625
Night
21%36%17%25%27%
74616
SeeingDay
6%7%21%34%24%8%
14432
Night
6%311%35%37%8%
24332

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
8%424434448%57%
1519
11th to 20thDay
8%413323345%64%
1611
21st to endDay
11%423323336%60%
1931
February1st to 10thDay
8%323312345%64%
1800
11th to 20thDay
9%31221345%7%62%
1750
21st to endDay
8%42442335%6%59%
1480
March1st to 10thDay
8%5%244335%46%54%
1800
11th to 20thDay
7%42433345%9%56%
1862
21st to endDay
7%3133345%5%6%61%
2376
April1st to 10thDay
7%323323447%62%
2160
11th to 20thDay
4323323346%68%
2129
21st to endDay
5%313313346%68%
2160
May1st to 10thDay
5%423322347%64%
2191
11th to 20thDay
3424323347%66%
2301
21st to endDay
5%32432325%6%66%
2530
June1st to 10thDay
4423222348%66%
2418
11th to 20thDay
3412212246%74%
2520
21st to endDay
221221223480%
2520
July1st to 10thDay
121322323476%
2520
11th to 20thDay
221221223478%
2517
21st to endDay
211221235%6%74%
2381
August1st to 10thDay
2211122235%79%
2149
11th to 20thDay
111111235%83%
2122
21st to endDay
111221233481%
2376
September1st to 10thDay
221121123480%
2160
11th to 20thDay
221211222382%
2048
21st to endDay
211221222480%
1980
October1st to 10thDay
4212312346%72%
1980
11th to 20thDay
421221323476%
1828
21st to endDay
321321333474%
1964
November1st to 10thDay
3212223335%72%
1674
11th to 20thDay
4313322346%70%
1710
21st to endDay
5%323324447%64%
1710
December1st to 10thDay
7%313325%45%7%60%
1710
11th to 20thDay
16%5%2443445%7%45%
2169
21st to endDay
13%5%247%45%45%6%46%
2844
January1st to 10thNight
10%413324347%58%
2646
11th to 20thNight
7%31332235%8%63%
2369
21st to endNight
10%5%14322246%63%
2420
February1st to 10thNight
7%423313336%65%
2160
11th to 20thNight
8%413323435%64%
2098
21st to endNight
11%423323436%59%
1776
March1st to 10thNight
8%6%2333345%8%54%
2160
11th to 20thNight
7%423424447%58%
2094
21st to endNight
7%413424447%61%
1980
April1st to 10thNight
7%324333346%63%
1800
11th to 20thNight
4423213336%68%
1779
21st to endNight
5%41322325%8%68%
1800
May1st to 10thNight
5%5%24423247%61%
1766
11th to 20thNight
35%23323345%67%
1594
21st to endNight
35%13313235%70%
1746
June1st to 10thNight
2423423349%64%
1536
11th to 20thNight
2312212226%77%
1440
21st to endNight
121221222479%
1440
July1st to 10thNight
1212212235%79%
1440
11th to 20thNight
1112313345%77%
1440
21st to endNight
2112222346%74%
1936
August1st to 10thNight
321222333476%
1790
11th to 20thNight
213212235%79%
1780
21st to endNight
11221223480%
1980
September1st to 10thNight
3313211235%77%
1800
11th to 20thNight
221211232382%
1912
21st to endNight
111211222482%
1980
October1st to 10thNight
321322334373%
1980
11th to 20thNight
431321232474%
2128
21st to endNight
331222223475%
2389
November1st to 10thNight
4212213345%72%
2405
11th to 20thNight
4212222335%73%
2470
21st to endNight
5%3133235%5%6%64%
2470
December1st to 10thNight
7%425%32335%7%60%
2470
11th to 20thNight
17%5%2442345%7%47%
3041
21st to endNight
13%7%25%435%5%46%47%
4804

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%46%18%23%23%
1519
11th to 20thDay
24%37%13%25%27%
1611
21st to endDay
27%46%17%18%28%
1931
February1st to 10thDay
23%35%14%25%30%
1800
11th to 20thDay
21%46%16%27%26%
1760
21st to endDay
25%5%7%17%24%21%
1480
March1st to 10thDay
29%5%8%19%17%21%
1800
11th to 20thDay
24%5%9%20%22%19%
1862
21st to endDay
22%6%11%22%22%16%
2376
April1st to 10thDay
22%5%12%25%22%14%
2160
11th to 20thDay
18%5%8%21%30%19%
2132
21st to endDay
18%48%25%31%14%
2160
May1st to 10thDay
20%5%10%23%28%15%
2191
11th to 20thDay
19%410%24%29%13%
2304
21st to endDay
20%49%29%29%8%
2530
June1st to 10thDay
19%310%20%32%15%
2418
11th to 20thDay
14%26%16%33%29%
2520
21st to endDay
12%2311%36%36%
2520
July1st to 10thDay
13%3312%27%43%
2451
11th to 20thDay
12%26%18%33%29%
2442
21st to endDay
12%37%23%34%20%
2249
August1st to 10thDay
12%2311%33%39%
2135
11th to 20thDay
7%2215%37%37%
2122
21st to endDay
9%2311%36%39%
2376
September1st to 10thDay
10%3310%32%41%
2160
11th to 20thDay
10%2313%33%39%
2048
21st to endDay
11%2216%37%32%
1980
October1st to 10thDay
15%35%19%24%34%
1980
11th to 20thDay
14%3413%28%37%
1828
21st to endDay
14%3412%22%44%
1964
November1st to 10thDay
17%3416%25%35%
1674
11th to 20thDay
17%36%14%21%39%
1710
21st to endDay
22%36%13%24%33%
1710
December1st to 10thDay
25%46%16%21%27%
1710
11th to 20thDay
38%5%6%14%20%16%
2168
21st to endDay
37%5%8%23%15%13%
2844
January1st to 10thNight
27%47%15%25%22%
2646
11th to 20thNight
22%38%15%22%31%
2369
21st to endNight
25%37%16%19%31%
2420
February1st to 10thNight
24%26%14%25%30%
2160
11th to 20thNight
24%35%16%25%27%
2099
21st to endNight
28%36%16%22%24%
1776
March1st to 10thNight
29%48%20%20%20%
2160
11th to 20thNight
25%5%8%18%23%20%
2094
21st to endNight
24%49%23%23%16%
1980
April1st to 10thNight
24%411%25%20%16%
1800
11th to 20thNight
19%38%25%25%20%
1779
21st to endNight
18%49%25%31%13%
1800
May1st to 10thNight
22%5%10%24%25%15%
1766
11th to 20thNight
19%6%9%26%26%13%
1595
21st to endNight
17%411%30%27%11%
1746
June1st to 10thNight
17%6%13%22%27%15%
1536
11th to 20thNight
13%27%17%35%26%
1440
21st to endNight
14%2411%34%35%
1440
July1st to 10thNight
12%1214%30%42%
1400
11th to 20thNight
11%27%21%29%31%
1392
21st to endNight
14%27%26%31%20%
1829
August1st to 10thNight
13%2312%35%35%
1780
11th to 20thNight
11%1212%38%36%
1780
21st to endNight
10%2212%38%36%
1980
September1st to 10thNight
14%249%29%42%
1800
11th to 20thNight
10%2312%33%40%
1912
21st to endNight
10%2315%35%35%
1980
October1st to 10thNight
17%35%18%23%35%
1980
11th to 20thNight
16%35%15%24%37%
2128
21st to endNight
14%3411%21%46%
2389
November1st to 10thNight
16%35%15%24%36%
2405
11th to 20thNight
16%27%13%22%40%
2470
21st to endNight
22%36%17%19%33%
2470
December1st to 10thNight
25%36%15%20%31%
2470
11th to 20thNight
38%36%13%22%17%
3041
21st to endNight
35%5%9%21%16%13%
4804

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%6%29%34%14%1
180
11th to 20thDay
11%10%30%32%14%2
325
21st to endDay
11%14%32%29%12%1
441
February1st to 10thDay
9%11%30%30%17%3
420
11th to 20thDay
12%14%32%31%8%2
415
21st to endDay
10%14%36%30%10%
346
March1st to 10thDay
14%15%33%26%10%2
420
11th to 20thDay
12%15%28%30%13%2
420
21st to endDay
11%15%34%28%12%2
462
April1st to 10thDay
10%10%30%28%17%5%
420
11th to 20thDay
6%15%35%30%10%4
412
21st to endDay
412%31%30%15%7%
420
May1st to 10thDay
6%12%26%36%15%5%
423
11th to 20thDay
8%6%26%34%22%5%
448
21st to endDay
6%7%29%34%19%6%
485
June1st to 10thDay
4418%37%27%10%
450
11th to 20thDay
5%412%39%29%11%
450
21st to endDay
4213%36%33%13%
450
July1st to 10thDay
3436%42%15%
446
11th to 20thDay
1329%46%21%
444
21st to endDay
1333%45%18%
487
August1st to 10thDay
218%35%38%15%
447
11th to 20thDay
25%32%45%15%
437
21st to endDay
25%39%39%15%
495
September1st to 10thDay
2211%41%30%14%
450
11th to 20thDay
3216%41%30%8%
450
21st to endDay
2320%37%28%10%
450
October1st to 10thDay
27%20%41%24%6%
450
11th to 20thDay
45%24%40%24%4
450
21st to endDay
6%7%24%31%25%6%
479
November1st to 10thDay
46%19%35%29%7%
270
11th to 20thDay
48%20%42%19%6%
270
21st to endDay
6%7%26%34%23%4
270
December1st to 10thDay
11%5%25%35%22%2
270
11th to 20thDay
7%7%20%39%23%3
270
21st to endDay
18%13%22%34%11%1
210
January1st to 10thNight
11%415%44%20%5%
760
11th to 20thNight
9%320%42%23%4
724
21st to endNight
12%6%19%39%21%3
792
February1st to 10thNight
9%315%40%27%6%
720
11th to 20thNight
9%5%16%40%23%7%
704
21st to endNight
13%5%17%41%21%3
592
March1st to 10thNight
10%5%17%43%22%3
720
11th to 20thNight
9%5%12%38%30%6%
720
21st to endNight
7%6%16%43%23%5%
792
April1st to 10thNight
8%411%44%29%4
720
11th to 20thNight
6%5%16%40%29%4
711
21st to endNight
6%6%14%37%29%8%
720
May1st to 10thNight
8%213%40%32%5%
686
11th to 20thNight
5%212%39%37%5%
531
21st to endNight
5%215%38%37%4
584
June1st to 10thNight
219%37%46%5%
456
11th to 20thNight
4332%55%6%
360
21st to endNight
21130%60%7%
360
July1st to 10thNight
2112%75%10%
350
11th to 20thNight
19%75%14%
348
21st to endNight
21113%64%20%
754
August1st to 10thNight
41122%57%15%
716
11th to 20thNight
21113%63%21%
712
21st to endNight
2117%59%21%
792
September1st to 10thNight
41222%52%18%
720
11th to 20thNight
21328%53%13%
720
21st to endNight
215%31%49%13%
720
October1st to 10thNight
416%41%41%6%
720
11th to 20thNight
6%29%34%40%9%
720
21st to endNight
4313%34%33%13%
792
November1st to 10thNight
4411%40%32%10%
740
11th to 20thNight
5%212%39%32%9%
760
21st to endNight
7%314%42%27%7%
760
December1st to 10thNight
10%416%38%26%6%
760
11th to 20thNight
14%5%16%40%23%4
760
21st to endNight
12%6%17%42%18%5%
836
Page generated at 2024-01-08 19:31:24. Version ac07

Copyright 2024 Attilla Danko


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