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Mar Vista
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mar Vista clear sky chart from 2005-11-05 to 2017-05-24.

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
74%
15502
33%
45766
30%
15453
78%
15453
48%
23221

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
73%
716
29%
2452
30%
716
79%
716
43%
1189
January16th to endNight
67%
768
35%
2370
33%
768
73%
768
43%
1240
February1st to 15thNight
70%
698
35%
2101
34%
696
76%
696
46%
1081
February16th to endNight
60%
632
27%
1895
27%
632
65%
632
33%
1103
March1st to 15thNight
70%
720
30%
2160
31%
720
74%
720
47%
1093
March16th to endNight
67%
768
28%
1998
22%
768
71%
768
43%
1161
April1st to 15thNight
65%
719
30%
1799
19%
719
70%
719
49%
1019
April16th to endNight
70%
720
32%
1800
17%
720
75%
720
54%
971
May1st to 15thNight
71%
638
28%
1718
19%
638
73%
638
47%
953
May16th to endNight
72%
540
28%
1622
22%
540
75%
540
51%
817
June1st to 15thNight
76%
410
27%
1400
27%
410
77%
410
44%
703
June16th to endNight
82%
330
30%
1320
36%
330
82%
330
42%
577
July1st to 15thNight
87%
310
34%
1240
42%
310
87%
310
44%
546
July16th to endNight
80%
588
26%
1523
21%
545
81%
545
47%
822
August1st to 15thNight
82%
657
36%
1640
24%
653
82%
653
58%
872
August16th to endNight
87%
700
38%
1750
26%
700
87%
700
60%
911
September1st to 15thNight
88%
660
39%
1666
32%
660
88%
660
60%
865
September16th to endNight
85%
656
41%
1815
40%
656
86%
656
62%
843
October1st to 15thNight
81%
660
38%
1842
37%
660
83%
660
57%
903
October16th to endNight
79%
704
40%
2120
43%
704
81%
704
54%
994
November1st to 15thNight
81%
700
36%
2275
39%
700
85%
700
56%
992
November16th to endNight
77%
720
38%
2340
39%
720
82%
720
52%
1062
December1st to 15thNight
68%
720
35%
2340
34%
720
74%
720
40%
1194
December16th to endNight
63%
768
32%
2580
31%
768
69%
768
38%
1310

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
4312212347%66%
46480
Night
4413313347%62%
45972
TransparencyDay
19%16%19%28%23%
46175
Night
23%25%17%26%24%
45778
SeeingDay
6%8%28%36%14%4
5505
Night
6%37%31%38%12%
15515

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%32332333462%
1483
16th to endDay
10%422222346%58%
1851
February1st to 15thDay
6%313212346%63%
1751
16th to endDay
9%313423347%55%
1579
March1st to 15thDay
331231335%7%62%
1800
16th to endDay
431332445%10%56%
2223
April1st to 15thDay
4312313348%61%
2149
16th to endDay
2212211437%69%
2160
May1st to 15thDay
3313212348%64%
2230
16th to endDay
3412211338%67%
2335
June1st to 15thDay
5%6%13312247%61%
2225
16th to endDay
1312212225%74%
2310
July1st to 15thDay
3312312347%65%
2310
16th to endDay
2212312247%69%
2215
August1st to 15thDay
122112236%74%
1980
16th to endDay
111211246%76%
2100
September1st to 15thDay
112212245%75%
1964
16th to endDay
222212235%75%
1815
October1st to 15thDay
42221215%6%68%
1785
16th to endDay
212222346%70%
1750
November1st to 15thDay
333312236%69%
1584
16th to endDay
4213312247%65%
1620
December1st to 15thDay
6%32231435%7%57%
1620
16th to endDay
9%214312336%59%
1641
January1st to 15thNight
6%312313447%60%
2452
16th to endNight
9%413312236%60%
2370
February1st to 15thNight
6%324313336%62%
2101
16th to endNight
12%4245%23336%52%
1895
March1st to 15thNight
5%313413347%60%
2160
16th to endNight
45%1342445%7%55%
1998
April1st to 15thNight
7%5%23212235%62%
1799
16th to endNight
3323323347%64%
1800
May1st to 15thNight
46%23322348%58%
1718
16th to endNight
3423312347%62%
1621
June1st to 15thNight
25%3431346%9%54%
1400
16th to endNight
15%1432345%8%58%
1320
July1st to 15thNight
2313423348%61%
1320
16th to endNight
33135%3345%10%54%
1640
August1st to 15thNight
2413312348%62%
1650
16th to endNight
132323449%65%
1750
September1st to 15thNight
222223347%67%
1666
16th to endNight
1312212236%71%
1815
October1st to 15thNight
3212412435%67%
1842
16th to endNight
4312212235%70%
2120
November1st to 15thNight
2412212136%70%
2275
16th to endNight
3312213346%66%
2340
December1st to 15thNight
6%325%323336%59%
2340
16th to endNight
11%413312235%60%
2580

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
26%2414%24%27%
1483
16th to endDay
28%26%17%17%27%
1851
February1st to 15thDay
22%2418%26%24%
1751
16th to endDay
29%26%22%29%10%
1579
March1st to 15thDay
20%19%22%24%20%
1800
16th to endDay
23%211%27%20%14%
2223
April1st to 15thDay
21%210%27%25%12%
2149
16th to endDay
15%19%26%28%18%
2160
May1st to 15thDay
20%29%23%28%15%
2230
16th to endDay
19%18%31%29%9%
2338
June1st to 15thDay
24%17%17%34%14%
2225
16th to endDay
15%310%37%32%
2310
July1st to 15thDay
19%1312%30%33%
2161
16th to endDay
16%27%21%33%19%
2070
August1st to 15thDay
12%117%38%28%
1966
16th to endDay
10%1114%43%27%
2100
September1st to 15thDay
12%1114%33%35%
1964
16th to endDay
13%1116%35%31%
1815
October1st to 15thDay
18%1424%26%25%
1785
16th to endDay
16%1417%23%36%
1750
November1st to 15thDay
17%25%16%24%33%
1584
16th to endDay
21%17%14%23%31%
1620
December1st to 15thDay
25%28%17%22%23%
1620
16th to endDay
26%28%17%23%21%
1641
January1st to 15thNight
24%26%15%22%28%
2452
16th to endNight
26%26%16%16%30%
2370
February1st to 15thNight
25%15%16%24%25%
2112
16th to endNight
35%26%15%25%14%
1895
March1st to 15thNight
24%17%21%25%20%
2160
16th to endNight
28%310%21%21%14%
1998
April1st to 15thNight
25%18%27%24%12%
1799
16th to endNight
21%18%25%23%18%
1800
May1st to 15thNight
26%29%21%26%13%
1719
16th to endNight
21%29%29%26%10%
1622
June1st to 15thNight
24%310%16%34%11%
1400
16th to endNight
23%2311%34%25%
1320
July1st to 15thNight
21%2113%27%32%
1240
16th to endNight
25%25%21%26%17%
1523
August1st to 15thNight
20%112%41%24%
1640
16th to endNight
18%212%40%26%
1750
September1st to 15thNight
18%238%33%33%
1666
16th to endNight
15%116%33%32%
1815
October1st to 15thNight
18%1421%30%23%
1842
16th to endNight
18%2315%23%36%
2120
November1st to 15thNight
16%15%17%21%37%
2275
16th to endNight
19%15%18%22%31%
2340
December1st to 15thNight
27%27%16%21%25%
2340
16th to endNight
27%28%15%24%21%
2580

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
17%7%34%31%9%
111
16th to endDay
12%9%35%32%7%1
277
February1st to 15thDay
11%11%30%26%15%4
266
16th to endDay
13%17%35%22%8%2
238
March1st to 15thDay
7%15%35%22%14%3
270
16th to endDay
7%14%38%26%9%3
288
April1st to 15thDay
8%15%41%21%8%4
269
16th to endDay
418%42%27%24
270
May1st to 15thDay
414%35%32%10%3
288
16th to endDay
412%38%31%10%1
301
June1st to 15thDay
7%9%28%39%13%1
255
16th to endDay
121%50%16%9%
255
July1st to 15thDay
4216%51%21%3
245
16th to endDay
1211%50%23%9%
271
August1st to 15thDay
2118%53%18%5%
255
16th to endDay
113%56%20%7%
268
September1st to 15thDay
4125%48%16%4
255
16th to endDay
1232%45%11%6%
255
October1st to 15thDay
5%9%32%36%13%2
255
16th to endDay
37%29%39%16%4
262
November1st to 15thDay
45%8%25%31%24%
90
16th to endDay
5%5%17%37%31%2
90
December1st to 15thDay
38%14%34%34%4
90
16th to endDay
13%16%14%32%19%3
81
January1st to 15thNight
8%38%40%29%8%
720
16th to endNight
13%210%36%29%8%
768
February1st to 15thNight
8%28%35%34%9%
704
16th to endNight
13%5%10%35%28%5%
632
March1st to 15thNight
6%310%43%28%7%
720
16th to endNight
7%411%37%32%7%
768
April1st to 15thNight
10%5%11%36%29%5%
719
16th to endNight
5%6%10%38%31%7%
720
May1st to 15thNight
7%49%35%35%7%
639
16th to endNight
4313%37%34%6%
542
June1st to 15thNight
338%32%43%8%
410
16th to endNight
3320%62%9%
330
July1st to 15thNight
32463%25%
310
16th to endNight
43112%50%27%
588
August1st to 15thNight
42318%50%21%
657
16th to endNight
21212%54%26%
700
September1st to 15thNight
41119%50%23%
660
16th to endNight
42122%55%13%
656
October1st to 15thNight
45%35%41%11%
660
16th to endNight
6%2428%40%15%
704
November1st to 15thNight
425%33%38%15%
700
16th to endNight
5%37%32%37%13%
720
December1st to 15thNight
9%38%37%33%8%
720
16th to endNight
13%5%10%39%24%6%
768
Page generated at 2017-05-25 10:27:32. Version ac04

Copyright 2017 A. Danko


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