Saddleback Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saddleback Observatory clear sky chart from 2005-11-06 to 2024-11-08.

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
51%
24207
26%
97211
20%
23995
61%
23995
27%
51127

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
34%
752
18%
4339
12%
736
44%
736
12%
2530
January11th to 20thNight
30%
754
18%
4249
10%
740
45%
740
12%
2783
January21st to endNight
33%
831
15%
4454
15%
814
48%
814
10%
3199
February1st to 10thNight
35%
760
24%
2470
15%
760
48%
760
21%
1505
February11th to 20thNight
37%
741
24%
2286
16%
740
49%
740
22%
1437
February21st to endNight
36%
628
22%
1884
15%
628
46%
628
22%
1225
March1st to 10thNight
28%
757
14%
3676
8%
744
38%
744
10%
2718
March11th to 20thNight
39%
754
23%
3461
13%
740
48%
740
18%
1702
March21st to endNight
33%
832
9%
3623
7%
814
40%
814
11%
2669
April1st to 10thNight
38%
760
22%
1900
8%
760
45%
760
26%
1301
April11th to 20thNight
43%
751
23%
1879
10%
751
48%
751
31%
1208
April21st to endNight
53%
760
22%
1900
9%
760
58%
760
42%
1126
May1st to 10thNight
44%
643
30%
2827
13%
634
53%
634
26%
1391
May11th to 20thNight
60%
368
27%
2407
23%
364
68%
364
28%
778
May21st to endNight
57%
402
19%
2713
22%
399
64%
399
27%
897
June1st to 10thNight
64%
380
24%
1520
29%
380
69%
380
34%
735
June11th to 20thNight
69%
380
33%
1520
37%
380
79%
380
51%
570
June21st to endNight
76%
380
32%
1520
40%
380
82%
380
55%
559
July1st to 10thNight
88%
362
43%
2064
48%
360
91%
360
69%
465
July11th to 20thNight
88%
364
34%
1965
49%
359
91%
359
51%
637
July21st to endNight
87%
526
35%
2195
39%
497
89%
497
63%
682
August1st to 10thNight
84%
563
40%
2349
32%
555
86%
555
47%
956
August11th to 20thNight
85%
700
36%
2419
26%
687
88%
687
73%
825
August21st to endNight
86%
821
39%
2885
27%
814
87%
814
68%
1060
September1st to 10thNight
81%
760
46%
1900
28%
760
86%
760
77%
878
September11th to 20thNight
73%
760
43%
1900
31%
760
77%
760
65%
943
September21st to endNight
61%
760
41%
2119
28%
760
74%
760
61%
987
October1st to 10thNight
59%
741
44%
3363
26%
740
70%
740
41%
1256
October11th to 20thNight
57%
749
29%
3293
30%
740
71%
740
41%
1251
October21st to endNight
53%
828
35%
3868
27%
813
68%
813
31%
1724
November1st to 10thNight
50%
770
27%
2502
21%
770
60%
770
28%
1454
November11th to 20thNight
45%
760
26%
2470
17%
760
58%
760
29%
1380
November21st to endNight
39%
760
27%
2615
19%
760
53%
760
28%
1432
December1st to 10thNight
37%
760
24%
2660
16%
760
50%
760
23%
1577
December11th to 20thNight
33%
760
19%
3224
13%
759
46%
759
13%
2266
December21st to endNight
28%
830
15%
4792
12%
817
42%
817
9%
3021

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
7%8%23222235%62%
105214
Night
9%10%24223345%57%
102612
TransparencyDay
27%36%18%25%21%
104962
Night
31%47%18%23%18%
102453
SeeingDay
17%18%31%21%10%3
15088
Night
16%10%18%31%22%3
24349

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
12%23%35%332346%37%
2539
11th to 20thDay
12%19%37%5%5%4335%34%
2678
21st to endDay
16%17%47%434346%33%
3146
February1st to 10thDay
16%14%33232446%43%
1710
11th to 20thDay
12%17%34332345%44%
1783
21st to endDay
11%20%35%233345%43%
1570
March1st to 10thDay
11%31%8%6%33223426%
3192
11th to 20thDay
9%16%23222235%54%
3490
21st to endDay
12%26%45%343345%30%
4000
April1st to 10thDay
12%16%2433435%6%40%
2280
11th to 20thDay
10%14%2443335%6%47%
2249
21st to endDay
10%9%1433336%7%52%
2280
May1st to 10thDay
7%8%1222223466%
3995
11th to 20thDay
441322223473%
4377
21st to endDay
7%413323235%67%
4813
June1st to 10thDay
8%5%2443335%6%58%
2660
11th to 20thDay
3312222235%74%
2660
21st to endDay
311221113481%
2660
July1st to 10thDay
1111112292%
4420
11th to 20thDay
221211112384%
4420
21st to endDay
11111212287%
4587
August1st to 10thDay
321322224476%
4091
11th to 20thDay
1111112389%
3789
21st to endDay
21111112287%
4180
September1st to 10thDay
21111112386%
2280
11th to 20thDay
5%313223235%73%
2280
21st to endDay
5%31212224475%
2057
October1st to 10thDay
4313222345%72%
3180
11th to 20thDay
9%313223236%66%
3161
21st to endDay
6%7%15%343246%58%
3435
November1st to 10thDay
13%10%14323446%51%
1737
11th to 20thDay
13%7%2443435%7%49%
1710
21st to endDay
10%10%2434435%6%51%
1563
December1st to 10thDay
17%9%25%32345%7%45%
1520
11th to 20thDay
22%15%46%444335%31%
1928
21st to endDay
11%11%35%345%46%9%39%
2794
January1st to 10thNight
9%15%45%33445%6%41%
4406
11th to 20thNight
15%17%35%34445%6%35%
4282
21st to endNight
13%21%36%45%4345%30%
4521
February1st to 10thNight
15%10%2433335%6%46%
2470
11th to 20thNight
10%15%2434445%6%44%
2284
21st to endNight
13%15%36%223345%43%
1884
March1st to 10thNight
11%29%10%6%32323428%
3679
11th to 20thNight
9%15%23223245%55%
3490
21st to endNight
13%25%45%334445%28%
3653
April1st to 10thNight
12%14%26%43335%5%44%
1900
11th to 20thNight
11%12%2433335%7%48%
1879
21st to endNight
9%8%13322347%57%
1900
May1st to 10thNight
6%11%2422223462%
2973
11th to 20thNight
5%31222323472%
2516
21st to endNight
6%413322235%69%
2762
June1st to 10thNight
7%5%13332347%61%
1520
11th to 20thNight
3312222245%74%
1520
21st to endNight
321222223378%
1520
July1st to 10thNight
111111111291%
2540
11th to 20thNight
321321112282%
2540
21st to endNight
11212212385%
2969
August1st to 10thNight
431322225%472%
2848
11th to 20thNight
11111212288%
3056
21st to endNight
111211111287%
3498
September1st to 10thNight
21211223484%
1900
11th to 20thNight
4213222235%76%
1900
21st to endNight
4212222235%76%
2119
October1st to 10thNight
432421212377%
3800
11th to 20thNight
441222224474%
3777
21st to endNight
9%5%1322335%6%61%
4121
November1st to 10thNight
13%9%2422335%5%52%
2502
11th to 20thNight
10%6%2333446%8%52%
2470
21st to endNight
9%9%25%233247%53%
2615
December1st to 10thNight
17%9%2332325%6%47%
2660
11th to 20thNight
23%15%25%33335%7%31%
3276
21st to endNight
14%14%46%44445%6%36%
4862

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
50%5%8%21%14%2
2539
11th to 20thDay
54%48%16%12%6%
2678
21st to endDay
53%5%8%18%14%3
3146
February1st to 10thDay
42%39%20%17%8%
1710
11th to 20thDay
43%38%19%20%6%
1792
21st to endDay
45%38%23%15%5%
1570
March1st to 10thDay
63%45%12%12%4
3192
11th to 20thDay
35%28%31%20%4
3490
21st to endDay
57%5%10%18%8%2
4000
April1st to 10thDay
45%412%21%15%3
2280
11th to 20thDay
39%5%12%24%16%5%
2252
21st to endDay
32%414%29%19%3
2280
May1st to 10thDay
24%312%25%28%8%
3995
11th to 20thDay
17%36%23%42%10%
4380
21st to endDay
22%48%40%25%3
4814
June1st to 10thDay
27%410%24%27%8%
2660
11th to 20thDay
14%37%23%36%17%
2660
21st to endDay
11%1317%37%31%
2660
July1st to 10thDay
4117%16%72%
4351
11th to 20thDay
9%29%18%61%
4345
21st to endDay
6%116%29%55%
4442
August1st to 10thDay
14%139%22%51%
4076
11th to 20thDay
5%118%43%42%
3826
21st to endDay
8%1211%44%35%
4179
September1st to 10thDay
7%1111%34%46%
2280
11th to 20thDay
16%2422%35%21%
2280
21st to endDay
15%3421%33%24%
2057
October1st to 10thDay
16%2414%33%31%
3180
11th to 20thDay
21%26%17%42%13%
3161
21st to endDay
29%26%24%26%13%
3435
November1st to 10thDay
36%37%22%20%12%
1737
11th to 20thDay
36%49%20%23%8%
1710
21st to endDay
36%37%22%22%11%
1563
December1st to 10thDay
40%48%21%20%7%
1520
11th to 20thDay
58%36%14%14%4
1928
21st to endDay
41%6%12%21%16%4
2794
January1st to 10thNight
44%5%13%23%13%3
4406
11th to 20thNight
50%6%10%13%16%6%
4282
21st to endNight
56%5%7%14%13%5%
4521
February1st to 10thNight
40%47%20%21%9%
2470
11th to 20thNight
41%47%20%20%7%
2286
21st to endNight
43%48%23%16%6%
1884
March1st to 10thNight
60%5%7%14%11%3
3679
11th to 20thNight
34%46%27%26%4
3490
21st to endNight
56%7%11%17%8%2
3653
April1st to 10thNight
42%6%11%23%16%3
1900
11th to 20thNight
36%5%12%24%17%6%
1879
21st to endNight
28%414%33%18%3
1900
May1st to 10thNight
27%5%10%24%27%7%
2973
11th to 20thNight
18%38%19%39%12%
2516
21st to endNight
19%411%39%23%5%
2762
June1st to 10thNight
24%6%12%24%24%9%
1520
11th to 20thNight
13%38%25%35%16%
1520
21st to endNight
14%2316%32%33%
1520
July1st to 10thNight
5%116%16%72%
2500
11th to 20thNight
11%119%14%63%
2492
21st to endNight
8%126%26%59%
2876
August1st to 10thNight
16%128%22%50%
2839
11th to 20thNight
6%1110%40%42%
3085
21st to endNight
8%1213%36%40%
3498
September1st to 10thNight
8%229%31%48%
1900
11th to 20thNight
14%25%20%37%22%
1900
21st to endNight
13%3422%34%25%
2119
October1st to 10thNight
17%1411%30%38%
3800
11th to 20thNight
16%25%22%42%13%
3777
21st to endNight
24%27%24%27%15%
4121
November1st to 10thNight
35%5%7%20%20%13%
2502
11th to 20thNight
31%5%10%22%22%10%
2470
21st to endNight
33%37%22%23%11%
2615
December1st to 10thNight
38%48%17%22%10%
2660
11th to 20thNight
55%3413%20%5%
3276
21st to endNight
49%5%10%17%15%4
4862

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
46%14%24%13%31
180
11th to 20thDay
31%17%25%22%5%
266
21st to endDay
28%16%25%20%10%1
407
February1st to 10thDay
29%19%27%17%7%1
370
11th to 20thDay
30%24%27%14%4
423
21st to endDay
27%23%29%16%5%
382
March1st to 10thDay
40%26%19%9%5%
460
11th to 20thDay
32%21%23%15%8%1
460
21st to endDay
32%28%24%11%4
506
April1st to 10thDay
27%25%27%13%7%1
460
11th to 20thDay
29%22%26%18%41
452
21st to endDay
18%23%28%18%10%2
460
May1st to 10thDay
19%27%30%17%5%2
463
11th to 20thDay
19%19%31%20%7%5%
488
21st to endDay
15%18%29%24%9%4
529
June1st to 10thDay
12%18%33%23%10%4
490
11th to 20thDay
9%21%39%18%9%3
490
21st to endDay
414%38%27%11%5%
490
July1st to 10thDay
211%47%25%12%5%
486
11th to 20thDay
29%45%26%14%4
484
21st to endDay
26%44%27%16%6%
531
August1st to 10thDay
410%41%25%15%6%
487
11th to 20thDay
312%37%28%16%5%
477
21st to endDay
411%41%27%16%2
539
September1st to 10thDay
312%40%26%16%2
490
11th to 20thDay
10%15%33%27%13%2
490
21st to endDay
8%17%39%26%9%2
490
October1st to 10thDay
7%21%29%28%14%2
490
11th to 20thDay
12%16%27%29%14%2
490
21st to endDay
18%17%26%24%12%2
538
November1st to 10thDay
23%19%19%23%15%3
291
11th to 20thDay
17%13%27%23%18%1
270
21st to endDay
16%19%28%22%11%3
201
December1st to 10thDay
28%17%24%14%12%4
180
11th to 20thDay
28%24%15%19%12%2
180
21st to endDay
27%21%21%18%12%1
198
January1st to 10thNight
27%12%23%24%11%4
760
11th to 20thNight
23%13%27%27%9%1
760
21st to endNight
26%15%20%24%14%1
836
February1st to 10thNight
24%15%21%28%11%1
760
11th to 20thNight
25%12%20%27%14%2
744
21st to endNight
26%13%21%31%7%2
628
March1st to 10thNight
32%15%18%21%13%2
760
11th to 20thNight
26%13%16%24%19%2
760
21st to endNight
29%15%19%24%13%1
836
April1st to 10thNight
22%12%21%29%16%1
760
11th to 20thNight
20%12%20%29%15%3
751
21st to endNight
15%9%20%33%20%4
760
May1st to 10thNight
14%14%23%26%20%3
644
11th to 20thNight
13%6%14%33%30%4
374
21st to endNight
13%6%16%29%31%4
411
June1st to 10thNight
9%5%15%31%35%5%
380
11th to 20thNight
5%7%17%37%32%3
380
21st to endNight
4212%39%37%4
380
July1st to 10thNight
216%41%47%2
370
11th to 20thNight
118%44%42%4
368
21st to endNight
115%33%52%8%
536
August1st to 10thNight
415%37%45%7%
567
11th to 20thNight
219%41%39%8%
706
21st to endNight
127%47%38%4
836
September1st to 10thNight
2212%41%38%4
760
11th to 20thNight
5%414%35%33%9%
760
21st to endNight
6%6%23%31%26%8%
760
October1st to 10thNight
9%7%18%34%27%4
760
11th to 20thNight
11%8%19%31%27%4
760
21st to endNight
13%11%21%27%23%5%
836
November1st to 10thNight
19%10%17%28%22%3
770
11th to 20thNight
15%14%21%33%15%3
760
21st to endNight
17%12%26%26%17%3
760
December1st to 10thNight
25%14%20%29%11%1
760
11th to 20thNight
30%12%20%26%11%1
760
21st to endNight
28%17%21%27%7%1
836
Page generated at 2024-11-05 05:15:52. Version ac07

Copyright © 2024 Attilla Danko.


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