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Torrance Barrens Dark-Sky Preserve
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Torrance Barrens Dark-Sky Preserve clear sky chart from 2005-11-06 to 2024-03-23.

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
29%
22936
12%
80436
8%
22845
35%
22845
14%
58934

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
11%
751
5%
4421
4%
737
18%
737
3%
3767
January11th to 20thNight
13%
757
7%
4284
3%
740
20%
740
4%
3448
January21st to endNight
22%
828
7%
4518
7%
814
28%
814
6%
3587
February1st to 10thNight
15%
760
8%
2470
3%
760
21%
760
8%
1996
February11th to 20thNight
17%
741
12%
2405
4%
740
27%
740
11%
1834
February21st to endNight
19%
628
10%
2014
4%
628
27%
628
11%
1536
March1st to 10thNight
19%
760
16%
2090
6%
760
27%
760
17%
1522
March11th to 20thNight
22%
760
17%
2090
7%
760
32%
760
17%
1514
March21st to endNight
27%
801
18%
2201
9%
801
33%
801
21%
1523
April1st to 10thNight
21%
720
14%
1828
5%
720
26%
720
17%
1397
April11th to 20thNight
29%
630
20%
1694
9%
630
36%
630
23%
1192
April21st to endNight
30%
540
16%
1620
8%
540
36%
540
17%
1156
May1st to 10thNight
41%
513
17%
1593
12%
513
47%
513
24%
1032
May11th to 20thNight
34%
354
22%
1416
19%
354
47%
354
22%
819
May21st to endNight
46%
388
16%
1551
15%
388
56%
388
27%
842
June1st to 10thNight
35%
360
11%
1440
11%
360
44%
360
18%
901
June11th to 20thNight
47%
360
16%
1272
18%
360
54%
360
26%
738
June21st to endNight
46%
360
13%
1260
14%
360
52%
360
21%
804
July1st to 10thNight
60%
350
18%
1225
21%
350
65%
350
35%
656
July11th to 20thNight
50%
348
17%
1356
23%
348
55%
348
25%
769
July21st to endNight
53%
502
16%
1588
15%
474
58%
474
30%
938
August1st to 10thNight
58%
537
18%
1600
14%
534
61%
534
34%
926
August11th to 20thNight
59%
534
19%
1598
13%
534
64%
534
31%
984
August21st to endNight
48%
652
18%
1840
9%
652
52%
652
29%
1203
September1st to 10thNight
47%
720
16%
1800
8%
720
50%
720
33%
1165
September11th to 20thNight
49%
720
22%
1898
14%
720
53%
720
33%
1199
September21st to endNight
46%
720
21%
2018
16%
720
51%
720
25%
1364
October1st to 10thNight
33%
720
16%
2160
10%
720
40%
720
19%
1509
October11th to 20thNight
24%
720
12%
2160
6%
720
32%
720
13%
1654
October21st to endNight
17%
792
12%
2376
5%
792
25%
792
11%
1862
November1st to 10thNight
26%
740
15%
2538
12%
740
32%
740
14%
1794
November11th to 20thNight
20%
760
12%
2660
7%
760
28%
760
12%
1990
November21st to endNight
15%
760
7%
2660
4%
760
20%
760
7%
2178
December1st to 10thNight
12%
760
7%
2660
3%
760
16%
760
6%
2245
December11th to 20thNight
11%
760
7%
3276
3%
759
19%
759
6%
2657
December21st to endNight
10%
830
4%
4856
2%
817
15%
817
3%
4233

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
17%11%47%6%35%45%6%31%
79079
Night
18%13%5%8%6%34446%28%
80682
TransparencyDay
55%311%20%10%1
78785
Night
59%310%18%9%1
80512
SeeingDay
23%15%30%20%9%3
13995
Night
23%13%28%25%10%1
22965

By Month

Percentage Cloud Cover NE (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
18%20%12%10%5%3423419%
2416
11th to 20thDay
13%17%8%16%12%45%5%4413%
2657
21st to endDay
19%21%8%11%7%3334416%
3124
February1st to 10thDay
13%20%7%14%9%5%5%32418%
1710
11th to 20thDay
15%14%7%13%6%45%33425%
1663
21st to endDay
18%16%7%10%7%46%435%21%
1436
March1st to 10thDay
15%13%5%8%7%35%5%46%29%
2087
11th to 20thDay
12%13%6%9%7%35%445%31%
2090
21st to endDay
18%10%47%5%34445%36%
2200
April1st to 10thDay
21%13%47%6%24446%30%
2132
11th to 20thDay
21%10%35%5%34445%36%
2230
21st to endDay
22%10%45%5%24445%33%
2340
May1st to 10thDay
20%7%25%5%45%5%6%7%33%
2366
11th to 20thDay
16%8%35%5%4445%6%41%
2478
21st to endDay
14%6%25%5%45%5%6%7%42%
2725
June1st to 10thDay
19%6%35%5%3445%7%38%
2520
11th to 20thDay
15%6%25%5%35%5%6%9%39%
2683
21st to endDay
18%7%26%5%35%5%5%8%37%
2700
July1st to 10thDay
12%4345%345%7%9%45%
2700
11th to 20thDay
13%7%25%5%35%5%6%8%41%
2556
21st to endDay
12%5%37%5%35%5%6%9%39%
2632
August1st to 10thDay
13%6%26%435%5%5%8%42%
2327
11th to 20thDay
13%6%25%6%35%5%7%9%39%
2303
21st to endDay
13%6%36%6%5%5%6%6%8%37%
2498
September1st to 10thDay
15%6%35%6%346%5%7%40%
2160
11th to 20thDay
15%5%35%5%3446%7%42%
2060
21st to endDay
18%7%36%5%35%6%46%35%
1941
October1st to 10thDay
22%8%36%5%35%446%33%
1800
11th to 20thDay
26%10%38%8%3445%6%22%
1800
21st to endDay
31%10%5%7%6%34445%21%
1980
November1st to 10thDay
18%14%47%6%35%46%7%26%
1538
11th to 20thDay
19%13%6%9%7%37%45%6%21%
1520
21st to endDay
20%20%5%9%8%36%5%45%15%
1520
December1st to 10thDay
18%26%8%9%6%3344415%
1520
11th to 20thDay
21%20%8%9%6%2433419%
1906
21st to endDay
26%19%7%12%6%3333413%
2761
January1st to 10thNight
18%22%11%12%7%45%43412%
4429
11th to 20thNight
15%15%7%17%9%45%445%15%
4298
21st to endNight
18%19%8%11%7%44435%17%
4532
February1st to 10thNight
13%17%7%13%10%45%345%19%
2470
11th to 20thNight
13%14%8%11%7%45%5%35%24%
2403
21st to endNight
18%15%5%9%7%45%45%5%24%
2014
March1st to 10thNight
15%12%5%7%6%44445%33%
2080
11th to 20thNight
13%13%6%8%5%35%445%33%
2089
21st to endNight
17%10%47%6%2345%5%37%
2201
April1st to 10thNight
22%12%47%5%3444430%
1828
11th to 20thNight
19%9%46%434446%37%
1694
21st to endNight
19%9%47%6%445%46%32%
1620
May1st to 10thNight
19%7%25%5%35%45%8%38%
1593
11th to 20thNight
16%7%245%2445%7%43%
1415
21st to endNight
11%6%244345%5%9%46%
1550
June1st to 10thNight
16%8%26%6%35%5%6%8%36%
1440
11th to 20thNight
12%6%25%5%35%6%49%44%
1272
21st to endNight
15%7%27%5%246%5%8%38%
1260
July1st to 10thNight
9%425%44445%7%52%
1260
11th to 20thNight
12%6%35%5%3347%8%44%
1401
21st to endNight
11%6%245%445%5%8%46%
1682
August1st to 10thNight
10%5%25%435%5%6%7%48%
1611
11th to 20thNight
10%5%35%5%45%45%7%46%
1598
21st to endNight
15%6%26%5%4445%7%43%
1840
September1st to 10thNight
12%5%26%435%45%9%45%
1800
11th to 20thNight
15%5%245%3345%7%47%
1898
21st to endNight
17%6%26%6%4435%6%40%
2018
October1st to 10thNight
19%8%35%5%45%45%7%34%
2160
11th to 20thNight
27%10%37%5%345%5%6%26%
2160
21st to endNight
26%13%48%6%35%345%23%
2376
November1st to 10thNight
20%13%46%6%34445%32%
2538
11th to 20thNight
18%17%47%6%35%45%6%25%
2660
21st to endNight
23%18%7%8%6%35%5%46%16%
2660
December1st to 10thNight
21%23%8%10%6%34445%13%
2660
11th to 20thNight
19%20%9%10%7%34445%16%
3288
21st to endNight
27%21%7%13%7%3323410%
4884

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
71%211%9%6%
2417
11th to 20thDay
75%28%9%6%1
2657
21st to endDay
75%17%9%6%1
3124
February1st to 10thDay
74%26%14%41
1710
11th to 20thDay
65%28%14%9%1
1672
21st to endDay
69%27%15%7%
1436
March1st to 10thDay
58%313%16%10%
2090
11th to 20thDay
57%29%19%11%2
2090
21st to endDay
53%28%19%15%3
2200
April1st to 10thDay
58%29%19%11%1
2132
11th to 20thDay
52%27%24%14%1
2230
21st to endDay
54%38%20%12%3
2340
May1st to 10thDay
51%39%22%13%2
2366
11th to 20thDay
46%37%28%14%1
2482
21st to endDay
42%415%23%14%3
2725
June1st to 10thDay
48%210%26%14%
2520
11th to 20thDay
41%412%26%16%1
2683
21st to endDay
47%314%23%12%1
2700
July1st to 10thDay
36%415%29%15%1
2626
11th to 20thDay
41%413%30%11%1
2479
21st to endDay
43%412%29%12%1
2485
August1st to 10thDay
41%316%26%12%1
2314
11th to 20thDay
42%416%28%10%1
2303
21st to endDay
44%415%26%10%1
2498
September1st to 10thDay
45%312%28%11%1
2160
11th to 20thDay
42%313%30%11%
2060
21st to endDay
50%5%12%26%8%
1941
October1st to 10thDay
53%411%20%11%1
1800
11th to 20thDay
65%312%14%6%1
1800
21st to endDay
67%210%14%7%
1980
November1st to 10thDay
59%313%19%6%
1538
11th to 20thDay
64%413%12%6%1
1520
21st to endDay
73%39%12%3
1520
December1st to 10thDay
74%38%11%4
1520
11th to 20thDay
72%27%12%7%
1906
21st to endDay
79%17%10%3
2761
January1st to 10thNight
80%26%8%4
4429
11th to 20thNight
74%210%10%41
4298
21st to endNight
72%110%10%6%1
4532
February1st to 10thNight
70%27%15%5%1
2470
11th to 20thNight
64%39%16%8%
2405
21st to endNight
64%210%17%7%
2014
March1st to 10thNight
55%212%17%12%2
2090
11th to 20thNight
55%29%21%11%2
2090
21st to endNight
50%28%22%15%3
2201
April1st to 10thNight
59%27%19%11%2
1828
11th to 20thNight
50%36%24%16%2
1694
21st to endNight
55%38%17%16%2
1620
May1st to 10thNight
46%39%21%18%3
1593
11th to 20thNight
42%39%25%20%2
1416
21st to endNight
35%316%25%17%3
1551
June1st to 10thNight
47%410%23%15%1
1440
11th to 20thNight
39%313%25%20%1
1272
21st to endNight
45%5%13%24%12%1
1260
July1st to 10thNight
32%313%27%22%3
1225
11th to 20thNight
38%313%30%15%1
1356
21st to endNight
38%313%30%15%1
1588
August1st to 10thNight
34%318%30%14%1
1600
11th to 20thNight
38%415%27%15%1
1598
21st to endNight
42%413%29%11%1
1840
September1st to 10thNight
38%416%27%14%2
1800
11th to 20thNight
39%314%33%12%
1898
21st to endNight
47%312%29%10%
2018
October1st to 10thNight
52%410%22%12%
2160
11th to 20thNight
61%410%20%5%
2160
21st to endNight
64%39%14%9%1
2376
November1st to 10thNight
56%311%21%8%
2538
11th to 20thNight
62%311%16%7%1
2660
21st to endNight
71%410%12%3
2660
December1st to 10thNight
76%28%10%3
2660
11th to 20thNight
72%310%11%4
3288
21st to endNight
82%25%9%3
4884

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
20%27%33%13%7%
180
11th to 20thDay
24%25%34%11%5%1
220
21st to endDay
29%15%35%18%4
297
February1st to 10thDay
29%27%32%6%5%
270
11th to 20thDay
26%24%39%10%1
270
21st to endDay
41%22%31%6%
227
March1st to 10thDay
25%20%36%16%3
460
11th to 20thDay
23%21%33%18%4
460
21st to endDay
33%13%31%17%6%
470
April1st to 10thDay
27%20%28%15%8%1
420
11th to 20thDay
33%17%23%17%8%3
412
21st to endDay
31%14%31%16%6%2
420
May1st to 10thDay
28%12%28%22%7%3
423
11th to 20thDay
21%13%30%21%11%3
447
21st to endDay
18%14%29%23%12%4
485
June1st to 10thDay
20%14%29%29%7%1
450
11th to 20thDay
18%13%31%24%11%3
613
21st to endDay
20%10%35%24%9%2
630
July1st to 10thDay
12%9%33%28%16%3
621
11th to 20thDay
15%11%26%29%14%5%
478
21st to endDay
13%8%32%30%12%5%
488
August1st to 10thDay
15%7%25%30%15%9%
446
11th to 20thDay
15%5%25%30%15%10%
439
21st to endDay
16%10%29%22%16%7%
495
September1st to 10thDay
15%9%29%26%13%8%
450
11th to 20thDay
14%8%29%24%19%7%
450
21st to endDay
20%12%26%24%14%3
450
October1st to 10thDay
25%15%25%18%11%5%
450
11th to 20thDay
29%20%30%17%5%
450
21st to endDay
35%19%28%14%4
495
November1st to 10thDay
29%18%32%16%5%
211
11th to 20thDay
28%22%33%14%2
180
21st to endDay
30%21%37%11%1
180
December1st to 10thDay
29%23%31%15%3
180
11th to 20thDay
34%29%20%12%31
180
21st to endDay
34%23%31%9%2
198
January1st to 10thNight
30%16%31%18%41
760
11th to 20thNight
30%16%31%17%5%1
760
21st to endNight
22%11%33%25%7%1
836
February1st to 10thNight
24%20%32%22%3
760
11th to 20thNight
22%18%34%21%6%
743
21st to endNight
27%19%29%20%4
628
March1st to 10thNight
23%18%34%22%4
760
11th to 20thNight
23%16%33%22%5%1
760
21st to endNight
21%13%32%25%9%
801
April1st to 10thNight
28%15%29%23%5%
720
11th to 20thNight
27%12%28%23%10%1
630
21st to endNight
24%10%28%28%9%1
540
May1st to 10thNight
22%6%24%33%13%1
513
11th to 20thNight
20%9%29%31%11%
354
21st to endNight
13%5%31%35%15%
389
June1st to 10thNight
18%6%31%33%10%1
360
11th to 20thNight
13%10%26%39%12%
360
21st to endNight
17%7%24%37%15%
360
July1st to 10thNight
11%419%46%19%1
350
11th to 20thNight
14%6%24%34%21%1
348
21st to endNight
13%326%35%23%1
502
August1st to 10thNight
12%418%38%25%3
537
11th to 20thNight
10%5%18%37%28%2
534
21st to endNight
16%7%24%30%21%2
652
September1st to 10thNight
13%7%26%31%19%4
720
11th to 20thNight
16%7%24%30%19%5%
720
21st to endNight
20%8%19%33%17%2
720
October1st to 10thNight
22%12%28%24%13%2
720
11th to 20thNight
32%14%25%21%8%1
720
21st to endNight
31%17%29%19%31
792
November1st to 10thNight
29%14%26%23%8%1
740
11th to 20thNight
27%18%31%18%5%1
760
21st to endNight
35%13%30%18%3
760
December1st to 10thNight
35%20%28%14%4
760
11th to 20thNight
29%19%34%15%41
760
21st to endNight
34%16%30%18%2
836
Page generated at 2024-03-19 23:31:09. Version ac07

Copyright © 2024 Attilla Danko.


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