Vandenberg Village
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vandenberg Village clear sky chart from 2005-11-05 to 2017-12-02.

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
63%
16039
28%
47831
24%
16001
67%
16001
40%
26136

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
61%
716
28%
2363
25%
716
67%
716
36%
1274
January16th to endNight
59%
768
29%
2496
29%
768
63%
768
33%
1414
February1st to 15thNight
59%
700
30%
2161
30%
699
64%
699
37%
1203
February16th to endNight
49%
632
26%
1895
23%
632
56%
632
31%
1160
March1st to 15thNight
58%
720
23%
2067
21%
720
63%
720
36%
1206
March16th to endNight
55%
768
25%
2043
19%
768
61%
768
38%
1232
April1st to 15thNight
50%
719
26%
1799
14%
719
55%
719
37%
1116
April16th to endNight
53%
720
28%
1800
11%
720
59%
720
43%
1041
May1st to 15thNight
58%
719
20%
1799
11%
719
60%
719
42%
1078
May16th to endNight
55%
479
23%
1603
17%
478
60%
478
34%
863
June1st to 15thNight
62%
360
25%
1440
25%
360
67%
360
31%
728
June16th to endNight
76%
360
27%
1440
32%
360
77%
360
44%
613
July1st to 15thNight
76%
403
24%
1423
26%
403
77%
403
42%
677
July16th to endNight
67%
564
28%
1593
24%
531
69%
531
38%
860
August1st to 15thNight
62%
687
22%
1761
14%
684
62%
684
42%
1041
August16th to endNight
75%
764
30%
1910
19%
764
75%
764
54%
1047
September1st to 15thNight
76%
720
33%
1800
26%
720
76%
720
51%
1021
September16th to endNight
74%
716
38%
1928
33%
716
78%
716
56%
969
October1st to 15thNight
70%
720
32%
2144
32%
720
75%
720
50%
1066
October16th to endNight
66%
768
37%
2304
38%
768
71%
768
45%
1197
November1st to 15thNight
68%
760
32%
2386
31%
760
73%
760
42%
1226
November16th to endNight
67%
780
34%
2535
32%
780
74%
780
41%
1266
December1st to 15thNight
60%
728
28%
2453
27%
728
66%
728
32%
1365
December16th to endNight
55%
768
28%
2688
27%
768
63%
768
31%
1473

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%424323347%57%
48606
Night
5%5%25%42445%8%50%
48024
TransparencyDay
24%38%18%27%17%
48295
Night
28%38%16%23%19%
47836
SeeingDay
7%9%26%33%18%5%
6353
Night
7%414%30%33%9%
16049

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%42442345%7%53%
1572
16th to endDay
12%5%13223346%52%
1728
February1st to 15thDay
12%5%23313346%52%
1697
16th to endDay
12%5%244245%5%6%46%
1579
March1st to 15thDay
7%4245%2435%9%51%
1891
16th to endDay
7%5%24434448%51%
2181
April1st to 15thDay
7%42433335%6%55%
2149
16th to endDay
6%32331335%7%60%
2160
May1st to 15thDay
35%23323249%58%
2151
16th to endDay
25%23413347%59%
2506
June1st to 15thDay
25%24324448%57%
2520
16th to endDay
1313423348%62%
2520
July1st to 15thDay
25%23434449%55%
2448
16th to endDay
35%2442435%9%54%
2468
August1st to 15thDay
28%25%32445%9%52%
2187
16th to endDay
16%24224448%59%
2292
September1st to 15thDay
33135%2435%8%58%
2160
16th to endDay
15%12312336%67%
2031
October1st to 15thDay
5%213212345%67%
1813
16th to endDay
3313213446%64%
1920
November1st to 15thDay
5%32432334461%
1802
16th to endDay
5%324412348%59%
1755
December1st to 15thDay
9%425%42345%5%52%
1540
16th to endDay
12%423413336%52%
1536
January1st to 15thNight
8%425%324346%53%
2363
16th to endNight
10%6%24413336%52%
2496
February1st to 15thNight
9%425%42435%7%51%
2154
16th to endNight
12%7%26%423336%46%
1895
March1st to 15thNight
6%5%335%25%36%9%47%
2067
16th to endNight
8%6%25%42446%8%46%
2043
April1st to 15thNight
7%4345%345%37%49%
1799
16th to endNight
5%5%24224449%54%
1800
May1st to 15thNight
26%27%5%3446%11%45%
1799
16th to endNight
48%36%5%2445%9%44%
1601
June1st to 15thNight
16%47%6%45%46%10%41%
1440
16th to endNight
1435%6%25%5%6%9%48%
1440
July1st to 15thNight
5%26%5%47%5%7%12%41%
1508
16th to endNight
15%48%7%47%5%6%12%36%
1701
August1st to 15thNight
9%6%7%8%25%5%6%11%34%
1770
16th to endNight
6%36%6%4446%9%45%
1910
September1st to 15thNight
25%25%6%45%46%10%46%
1800
16th to endNight
242342335%8%59%
1928
October1st to 15thNight
4413423347%61%
2144
16th to endNight
47%14413347%56%
2304
November1st to 15thNight
5%413323446%58%
2386
16th to endNight
5%42332435%8%56%
2535
December1st to 15thNight
8%5%35%414347%50%
2453
16th to endNight
12%423324336%52%
2688

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
29%37%19%23%15%
1572
16th to endDay
32%38%15%18%21%
1728
February1st to 15thDay
31%36%20%22%14%
1697
16th to endDay
35%410%23%20%5%
1579
March1st to 15thDay
28%413%21%19%12%
1891
16th to endDay
30%412%25%21%6%
2181
April1st to 15thDay
28%311%27%22%5%
2149
16th to endDay
21%411%26%25%10%
2160
May1st to 15thDay
21%39%24%28%11%
2151
16th to endDay
21%410%29%27%6%
2509
June1st to 15thDay
22%49%18%30%14%
2520
16th to endDay
16%16%8%34%32%
2520
July1st to 15thDay
22%26%11%26%30%
2305
16th to endDay
24%37%13%28%21%
2313
August1st to 15thDay
26%17%10%32%21%
2171
16th to endDay
19%26%11%37%24%
2292
September1st to 15thDay
20%35%13%29%27%
2160
16th to endDay
17%1317%34%25%
2031
October1st to 15thDay
18%37%19%28%22%
1813
16th to endDay
20%35%16%28%26%
1920
November1st to 15thDay
25%26%18%27%18%
1802
16th to endDay
23%37%17%29%18%
1755
December1st to 15thDay
31%410%15%25%13%
1540
16th to endDay
34%47%21%19%13%
1536
January1st to 15thNight
29%36%19%23%17%
2363
16th to endNight
33%47%11%20%23%
2496
February1st to 15thNight
31%38%17%24%15%
2165
16th to endNight
37%46%19%22%8%
1895
March1st to 15thNight
30%5%11%21%18%12%
2067
16th to endNight
31%412%17%24%9%
2043
April1st to 15thNight
31%5%10%27%18%7%
1799
16th to endNight
24%5%9%23%24%12%
1800
May1st to 15thNight
27%5%10%20%22%13%
1800
16th to endNight
29%410%21%24%9%
1603
June1st to 15thNight
29%5%9%16%24%15%
1440
16th to endNight
21%29%10%26%30%
1440
July1st to 15thNight
25%17%13%17%33%
1423
16th to endNight
30%28%15%20%22%
1593
August1st to 15thNight
32%16%10%21%27%
1761
16th to endNight
23%19%9%28%27%
1910
September1st to 15thNight
24%28%12%20%30%
1800
16th to endNight
19%25%12%32%27%
1928
October1st to 15thNight
22%25%17%27%25%
2144
16th to endNight
24%26%13%25%27%
2304
November1st to 15thNight
25%36%17%25%21%
2386
16th to endNight
24%37%17%27%19%
2535
December1st to 15thNight
32%38%15%23%15%
2453
16th to endNight
32%410%18%21%13%
2688

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%10%30%25%14%
201
16th to endDay
15%11%31%24%15%1
256
February1st to 15thDay
12%14%27%21%17%6%
257
16th to endDay
14%18%31%25%7%2
238
March1st to 15thDay
7%15%33%26%14%1
270
16th to endDay
7%19%35%26%7%2
288
April1st to 15thDay
9%17%38%18%12%3
269
16th to endDay
423%40%20%8%2
270
May1st to 15thDay
6%11%36%31%9%3
288
16th to endDay
5%13%34%32%11%2
330
June1st to 15thDay
5%8%30%35%15%3
315
16th to endDay
326%39%23%6%
315
July1st to 15thDay
5%115%40%28%8%
305
16th to endDay
4110%42%30%10%
327
August1st to 15thDay
6%215%49%21%4
315
16th to endDay
6%111%45%27%7%
332
September1st to 15thDay
6%117%46%21%6%
315
16th to endDay
16%22%36%25%8%
315
October1st to 15thDay
38%29%36%17%4
315
16th to endDay
5%7%29%33%17%7%
336
November1st to 15thDay
6%6%22%25%25%13%
218
16th to endDay
6%9%22%25%28%8%
135
December1st to 15thDay
12%5%25%36%20%
79
16th to endDay
18%12%20%29%15%3
64
January1st to 15thNight
10%315%30%27%12%
720
16th to endNight
12%415%35%22%8%
768
February1st to 15thNight
11%316%29%29%8%
704
16th to endNight
15%6%19%31%21%5%
632
March1st to 15thNight
9%5%16%37%25%5%
720
16th to endNight
9%5%20%35%24%5%
768
April1st to 15thNight
8%9%22%31%23%4
719
16th to endNight
6%9%23%27%26%6%
720
May1st to 15thNight
45%18%32%31%6%
720
16th to endNight
6%7%17%32%28%7%
480
June1st to 15thNight
4313%33%41%3
360
16th to endNight
31435%50%3
360
July1st to 15thNight
25%16%56%18%
403
16th to endNight
37%12%52%23%
564
August1st to 15thNight
219%28%44%12%
687
16th to endNight
25%21%54%16%
764
September1st to 15thNight
415%23%52%12%
720
16th to endNight
329%28%42%13%
716
October1st to 15thNight
5%311%32%36%10%
720
16th to endNight
9%211%28%34%14%
768
November1st to 15thNight
8%211%34%31%11%
760
16th to endNight
6%312%34%29%12%
780
December1st to 15thNight
11%314%35%25%9%
728
16th to endNight
13%7%17%34%22%5%
768
Page generated at 2017-12-03 08:16:46. Version ac04

Copyright 2017 A. Danko


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