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 2017-04-09.

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
62%
15222
28%
45443
24%
15184
67%
15184
40%
24819

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%
695
26%
1739
15%
695
55%
695
37%
1086
April16th to endNight
55%
660
27%
1650
11%
660
60%
660
45%
950
May1st to 15thNight
59%
659
21%
1649
11%
659
61%
659
43%
985
May16th to endNight
55%
438
22%
1466
14%
437
61%
437
34%
784
June1st to 15thNight
61%
330
26%
1320
26%
330
66%
330
29%
679
June16th to endNight
76%
330
26%
1320
31%
330
78%
330
45%
553
July1st to 15thNight
75%
367
26%
1297
27%
367
76%
367
41%
628
July16th to endNight
66%
522
26%
1467
22%
489
68%
489
37%
801
August1st to 15thNight
62%
629
23%
1613
15%
626
63%
626
44%
930
August16th to endNight
76%
700
29%
1750
18%
700
76%
700
56%
948
September1st to 15thNight
78%
660
35%
1650
27%
660
79%
660
54%
913
September16th to endNight
74%
656
36%
1767
31%
656
78%
656
56%
888
October1st to 15thNight
69%
660
32%
1965
32%
660
74%
660
48%
998
October16th to endNight
65%
704
37%
2112
37%
704
70%
704
46%
1084
November1st to 15thNight
68%
700
33%
2198
33%
700
74%
700
45%
1102
November16th to endNight
66%
720
33%
2340
30%
720
74%
720
41%
1171
December1st to 15thNight
59%
720
29%
2427
27%
720
65%
720
32%
1357
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%56%
45827
Night
5%5%25%42445%8%50%
45636
TransparencyDay
24%38%18%27%17%
45516
Night
28%38%16%23%18%
45448
SeeingDay
7%9%27%33%16%4
5439
Night
7%414%30%33%10%
15232

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%54%
2072
16th to endDay
6%32321335%7%60%
1980
May1st to 15thDay
35%2332325%9%58%
1971
16th to endDay
35%23423347%59%
2291
June1st to 15thDay
36%24324448%56%
2310
16th to endDay
1313423348%63%
2310
July1st to 15thDay
26%234244410%54%
2244
16th to endDay
35%2442435%9%54%
2286
August1st to 15thDay
28%25%32435%9%52%
2005
16th to endDay
16%24214448%59%
2100
September1st to 15thDay
24235%2435%8%58%
1980
16th to endDay
15%23312346%66%
1862
October1st to 15thDay
5%213313345%64%
1662
16th to endDay
3313213446%63%
1760
November1st to 15thDay
5%32332334463%
1660
16th to endDay
6%324412347%60%
1620
December1st to 15thDay
9%425%42345%5%52%
1530
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%4245%345%37%49%
1739
16th to endNight
5%5%24224449%55%
1650
May1st to 15thNight
26%27%5%3446%11%44%
1649
16th to endNight
5%7%36%43445%9%45%
1464
June1st to 15thNight
17%47%7%45%46%10%40%
1320
16th to endNight
1325%7%25%5%6%9%48%
1320
July1st to 15thNight
15%26%6%47%5%7%12%39%
1382
16th to endNight
16%48%7%47%5%6%11%35%
1575
August1st to 15thNight
8%5%7%8%35%6%6%11%35%
1622
16th to endNight
6%36%6%4446%9%45%
1750
September1st to 15thNight
2425%6%45%47%10%46%
1650
16th to endNight
142342335%8%58%
1767
October1st to 15thNight
5%414423347%59%
1965
16th to endNight
5%7%14413347%57%
2112
November1st to 15thNight
6%413323335%61%
2198
16th to endNight
442432435%7%57%
2340
December1st to 15thNight
8%5%35%424347%49%
2427
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%312%27%21%6%
2072
16th to endDay
21%410%27%27%9%
1980
May1st to 15thDay
21%39%24%28%12%
1971
16th to endDay
21%410%29%27%6%
2294
June1st to 15thDay
23%410%18%29%13%
2310
16th to endDay
16%16%9%35%30%
2310
July1st to 15thDay
23%25%12%26%29%
2101
16th to endDay
25%38%14%27%20%
2131
August1st to 15thDay
25%17%11%32%21%
1989
16th to endDay
18%16%11%36%24%
2100
September1st to 15thDay
19%35%13%29%29%
1980
16th to endDay
17%1417%32%25%
1862
October1st to 15thDay
20%37%21%29%17%
1662
16th to endDay
20%35%16%29%23%
1760
November1st to 15thDay
23%26%17%29%20%
1660
16th to endDay
24%37%16%28%19%
1620
December1st to 15thDay
31%410%15%24%13%
1530
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%17%7%
1739
16th to endNight
23%5%9%24%25%11%
1650
May1st to 15thNight
27%5%11%20%21%14%
1650
16th to endNight
29%410%22%25%9%
1466
June1st to 15thNight
30%5%9%15%24%14%
1320
16th to endNight
20%28%10%28%29%
1320
July1st to 15thNight
26%27%14%18%31%
1297
16th to endNight
31%28%16%19%21%
1467
August1st to 15thNight
30%17%10%23%26%
1613
16th to endNight
22%9%9%28%28%
1750
September1st to 15thNight
22%29%12%21%32%
1650
16th to endNight
19%26%13%30%28%
1767
October1st to 15thNight
23%25%19%28%21%
1965
16th to endNight
24%26%13%27%25%
2112
November1st to 15thNight
24%26%16%26%23%
2198
16th to endNight
25%37%18%25%19%
2340
December1st to 15thNight
33%38%15%22%15%
2427
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%18%37%18%11%3
244
16th to endDay
321%41%22%7%2
210
May1st to 15thDay
6%12%36%33%8%2
228
16th to endDay
6%15%34%31%9%2
266
June1st to 15thDay
6%7%33%36%12%3
255
16th to endDay
130%39%21%7%
255
July1st to 15thDay
6%217%44%25%4
245
16th to endDay
410%46%28%9%
271
August1st to 15thDay
6%316%51%18%3
255
16th to endDay
5%112%47%25%7%
268
September1st to 15thDay
5%116%48%20%7%
255
16th to endDay
15%23%36%24%8%
255
October1st to 15thDay
410%29%36%17%2
255
16th to endDay
5%8%30%35%15%4
272
November1st to 15thDay
6%6%18%24%26%17%
166
16th to endDay
7%12%26%26%22%4
90
December1st to 15thDay
13%5%26%36%18%
75
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%32%22%4
695
16th to endNight
6%8%23%27%27%7%
660
May1st to 15thNight
35%18%33%32%6%
660
16th to endNight
5%8%17%32%29%7%
439
June1st to 15thNight
4313%33%41%3
330
16th to endNight
215%37%50%3
330
July1st to 15thNight
25%17%55%16%
367
16th to endNight
37%12%51%23%
522
August1st to 15thNight
2110%28%44%13%
629
16th to endNight
15%21%53%16%
700
September1st to 15thNight
35%23%54%13%
660
16th to endNight
329%27%42%13%
656
October1st to 15thNight
5%312%30%37%10%
660
16th to endNight
9%211%28%34%13%
704
November1st to 15thNight
8%210%32%32%12%
700
16th to endNight
6%413%34%28%12%
720
December1st to 15thNight
11%314%35%25%9%
720
16th to endNight
13%7%17%34%22%5%
768
Page generated at 2017-04-10 06:00:37. Version ac04

Copyright 2017 A. Danko


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