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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 2017-10-06.

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%
15934
33%
47019
30%
15885
78%
15885
48%
23918

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%
561
28%
1685
23%
561
74%
561
50%
860
June1st to 15thNight
75%
447
26%
1527
26%
447
76%
447
42%
781
June16th to endNight
82%
360
31%
1440
38%
360
82%
360
41%
633
July1st to 15thNight
85%
340
32%
1360
39%
340
85%
340
43%
604
July16th to endNight
80%
634
27%
1653
22%
591
81%
591
46%
903
August1st to 15thNight
81%
717
34%
1790
23%
713
81%
713
55%
969
August16th to endNight
85%
764
39%
1910
26%
764
85%
764
58%
1009
September1st to 15thNight
87%
720
37%
1818
30%
720
88%
720
60%
950
September16th to endNight
85%
716
43%
1980
42%
716
86%
716
63%
916
October1st to 15thNight
82%
684
37%
1908
36%
684
84%
684
58%
931
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%
48150
Night
4413313347%62%
47225
TransparencyDay
19%16%19%28%23%
47845
Night
23%25%17%26%24%
47031
SeeingDay
5%8%27%37%15%5%
6037
Night
6%37%31%38%12%
15947

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
3412212338%66%
2429
June1st to 15thDay
5%6%13312247%61%
2428
16th to endDay
1312212225%74%
2520
July1st to 15thDay
3312312347%66%
2520
16th to endDay
2212322347%68%
2392
August1st to 15thDay
2312112227%74%
2160
16th to endDay
111211346%76%
2292
September1st to 15thDay
112212246%74%
2142
16th to endDay
222212235%75%
1980
October1st to 15thDay
422212146%69%
1846
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
35%23312347%62%
1684
June1st to 15thNight
26%3432346%8%54%
1527
16th to endNight
14133235%5%8%57%
1440
July1st to 15thNight
2314324347%60%
1440
16th to endNight
44135%3445%10%53%
1770
August1st to 15thNight
2423312348%61%
1800
16th to endNight
1313312449%64%
1910
September1st to 15thNight
222223347%67%
1818
16th to endNight
1312212236%72%
1980
October1st to 15thNight
3212312435%67%
1908
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%32%29%8%
2432
June1st to 15thDay
24%17%17%33%15%
2428
16th to endDay
15%129%35%35%
2520
July1st to 15thDay
18%1211%30%34%
2371
16th to endDay
15%27%22%33%18%
2247
August1st to 15thDay
13%116%38%29%
2146
16th to endDay
11%1113%43%27%
2292
September1st to 15thDay
12%2215%33%33%
2142
16th to endDay
13%1116%36%31%
1980
October1st to 15thDay
17%1424%26%25%
1846
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
22%29%29%26%10%
1685
June1st to 15thNight
25%39%16%32%12%
1527
16th to endNight
22%3310%32%28%
1440
July1st to 15thNight
22%3112%28%32%
1360
16th to endNight
25%35%22%26%16%
1653
August1st to 15thNight
21%111%39%24%
1790
16th to endNight
19%211%40%25%
1910
September1st to 15thNight
18%239%35%31%
1818
16th to endNight
15%1116%33%32%
1980
October1st to 15thNight
18%1421%30%23%
1908
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
5%11%38%30%11%2
330
June1st to 15thDay
8%8%26%39%14%2
315
16th to endDay
119%50%17%10%
315
July1st to 15thDay
3213%48%24%7%
305
16th to endDay
1210%50%22%12%
327
August1st to 15thDay
2116%52%20%6%
315
16th to endDay
213%52%22%8%
332
September1st to 15thDay
4127%44%16%5%
315
16th to endDay
1430%41%14%7%
315
October1st to 15thDay
5%9%32%36%14%2
278
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%
563
June1st to 15thNight
438%32%42%8%
447
16th to endNight
3319%61%11%
360
July1st to 15thNight
32464%24%
340
16th to endNight
43112%50%27%
634
August1st to 15thNight
42219%50%20%
717
16th to endNight
22213%52%26%
764
September1st to 15thNight
41121%49%22%
720
16th to endNight
42223%54%13%
716
October1st to 15thNight
45%35%41%11%
684
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 2017-10-07 11:07:45. Version ac04

Copyright 2017 A. Danko


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