Vale
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vale clear sky chart from 2005-11-05 to 2018-10-27.

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
57%
16142
19%
51229
16%
16116
61%
16116
28%
31665

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
43%
776
6%
2716
5%
776
45%
776
11%
2156
January16th to endNight
47%
832
7%
2912
7%
832
49%
832
13%
2209
February1st to 15thNight
50%
758
9%
2459
7%
756
54%
756
18%
1784
February16th to endNight
47%
684
13%
2051
11%
684
52%
684
19%
1464
March1st to 15thNight
47%
780
12%
2340
10%
780
51%
780
21%
1631
March16th to endNight
44%
832
15%
2191
9%
832
48%
832
25%
1546
April1st to 15thNight
48%
779
18%
1949
8%
779
52%
779
30%
1309
April16th to endNight
54%
639
23%
1797
13%
639
59%
639
38%
1059
May1st to 15thNight
56%
532
22%
1702
18%
532
63%
532
40%
888
May16th to endNight
60%
406
17%
1624
23%
406
64%
406
26%
921
June1st to 15thNight
53%
390
15%
1560
18%
390
62%
390
27%
848
June16th to endNight
61%
390
23%
1560
30%
390
72%
390
42%
679
July1st to 15thNight
75%
370
25%
1480
34%
370
83%
370
58%
540
July16th to endNight
72%
408
34%
1544
39%
386
83%
386
63%
531
August1st to 15thNight
75%
469
33%
1613
30%
467
81%
467
55%
673
August16th to endNight
78%
793
36%
2035
23%
793
81%
793
68%
980
September1st to 15thNight
79%
780
38%
1973
23%
780
83%
780
67%
968
September16th to endNight
72%
776
33%
2145
28%
776
74%
776
48%
1151
October1st to 15thNight
61%
780
27%
2223
22%
780
67%
780
40%
1260
October16th to endNight
67%
816
25%
2633
26%
816
71%
816
33%
1505
November1st to 15thNight
56%
760
19%
2470
20%
760
58%
760
24%
1603
November16th to endNight
50%
780
12%
2610
10%
780
53%
780
20%
1766
December1st to 15thNight
48%
780
10%
2730
8%
780
51%
780
15%
1993
December16th to endNight
44%
832
10%
2912
9%
832
47%
832
13%
2201

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
8%5%25%42445%6%50%
52337
Night
10%6%25%42445%6%47%
51402
TransparencyDay
34%6%12%19%17%10%
52008
Night
36%6%13%19%15%8%
51230
SeeingDay
9%417%28%26%12%
6806
Night
12%219%37%24%3
16154

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
15%12%49%8%45%5%5%5%22%
1552
16th to endDay
14%13%6%12%7%45%46%6%18%
1664
February1st to 15thDay
13%11%48%7%35%35%6%30%
1729
16th to endDay
11%7%36%7%35%5%6%8%33%
1709
March1st to 15thDay
11%8%47%6%46%5%7%7%30%
1950
16th to endDay
11%8%36%5%35%5%6%7%35%
2382
April1st to 15thDay
8%7%36%5%35%5%6%7%39%
2329
16th to endDay
7%5%244245%5%7%50%
2438
May1st to 15thDay
5%42342345%8%55%
2575
16th to endDay
7%5%25%5%35%5%6%8%44%
2839
June1st to 15thDay
7%4245%35%46%8%48%
2730
16th to endDay
4212313345%67%
2730
July1st to 15thDay
222213335%71%
2730
16th to endDay
1111223381%
2881
August1st to 15thDay
2111112246%72%
2592
16th to endDay
12121123477%
2516
September1st to 15thDay
21221333474%
2316
16th to endDay
5%213323346%61%
2145
October1st to 15thDay
8%424323346%54%
2064
16th to endDay
9%5%25%6%3445%7%44%
1846
November1st to 15thDay
15%7%35%5%35%46%7%36%
1719
16th to endDay
13%8%410%7%45%5%5%5%30%
1677
December1st to 15thDay
19%9%49%6%35%46%6%24%
1560
16th to endDay
20%11%6%10%7%44345%23%
1664
January1st to 15thNight
15%11%5%10%7%35%445%25%
2716
16th to endNight
13%11%49%7%3445%6%29%
2912
February1st to 15thNight
12%9%47%5%345%6%6%34%
2448
16th to endNight
11%8%37%5%35%6%6%6%34%
2051
March1st to 15thNight
12%9%35%6%35%35%7%36%
2340
16th to endNight
9%8%36%6%35%5%5%8%36%
2191
April1st to 15thNight
10%5%35%6%2445%6%43%
1949
16th to endNight
9%5%14324447%52%
1797
May1st to 15thNight
5%314325%45%7%57%
1702
16th to endNight
5%5%35%5%3447%9%43%
1624
June1st to 15thNight
7%425%5%35%35%8%50%
1560
16th to endNight
3213313346%64%
1560
July1st to 15thNight
11121325%6%72%
1560
16th to endNight
11121223378%
1640
August1st to 15thNight
12231335%6%68%
1621
16th to endNight
122222245%74%
2035
September1st to 15thNight
3112211235%75%
1973
16th to endNight
7%312323345%62%
2145
October1st to 15thNight
8%414323346%56%
2223
16th to endNight
8%4144345%5%6%51%
2633
November1st to 15thNight
14%5%25%425%45%6%40%
2470
16th to endNight
16%7%345%35%45%5%39%
2610
December1st to 15thNight
16%9%48%5%34446%33%
2730
16th to endNight
19%12%37%5%3435%5%28%
2912

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
62%11%13%10%1
1552
16th to endDay
65%11%10%8%2
1664
February1st to 15thDay
52%12%16%13%4
1729
16th to endDay
45%10%19%18%5%
1709
March1st to 15thDay
49%10%15%18%5%
1950
16th to endDay
45%7%16%20%8%
2382
April1st to 15thDay
41%6%17%23%9%1
2329
16th to endDay
32%6%13%26%17%3
2438
May1st to 15thDay
26%410%31%21%4
2575
16th to endDay
35%8%15%22%14%3
2843
June1st to 15thDay
33%6%11%22%21%5%
2730
16th to endDay
17%37%22%31%16%
2730
July1st to 15thDay
14%25%14%27%34%
2581
16th to endDay
8%1311%27%47%
2714
August1st to 15thDay
13%26%14%31%30%
2575
16th to endDay
12%16%16%37%24%
2516
September1st to 15thDay
13%35%19%35%21%
2316
16th to endDay
24%49%28%27%6%
2145
October1st to 15thDay
30%6%14%25%21%2
2064
16th to endDay
36%7%17%28%10%
1846
November1st to 15thDay
44%9%20%18%6%
1719
16th to endDay
52%9%16%15%4
1677
December1st to 15thDay
58%11%16%10%3
1560
16th to endDay
63%8%11%12%4
1664
January1st to 15thNight
58%11%14%11%3
2716
16th to endNight
54%10%17%13%3
2912
February1st to 15thNight
47%11%20%14%5%
2459
16th to endNight
46%10%17%18%5%1
2051
March1st to 15thNight
46%7%12%23%7%2
2340
16th to endNight
44%7%15%23%8%
2191
April1st to 15thNight
39%6%14%24%14%1
1949
16th to endNight
30%5%11%26%21%3
1797
May1st to 15thNight
24%5%11%27%26%4
1703
16th to endNight
34%7%13%27%13%4
1624
June1st to 15thNight
32%6%12%22%20%5%
1560
16th to endNight
20%36%21%33%13%
1560
July1st to 15thNight
11%36%17%28%32%
1480
16th to endNight
11%1310%25%48%
1544
August1st to 15thNight
15%37%13%26%33%
1613
16th to endNight
12%2415%31%32%
2035
September1st to 15thNight
13%15%17%32%29%
1973
16th to endNight
23%36%22%27%15%
2145
October1st to 15thNight
29%410%26%23%5%
2223
16th to endNight
31%6%14%27%19%
2633
November1st to 15thNight
41%7%15%23%11%
2470
16th to endNight
45%8%18%20%7%
2610
December1st to 15thNight
51%10%16%17%4
2730
16th to endNight
56%8%15%15%3
2912

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
23%16%22%30%16%
90
16th to endDay
33%411%22%20%7%
96
February1st to 15thDay
17%119%28%25%6%
239
16th to endDay
13%6%26%34%13%5%
290
March1st to 15thDay
16%8%24%29%17%3
330
16th to endDay
15%13%26%28%14%1
352
April1st to 15thDay
11%13%26%26%13%8%
329
16th to endDay
9%7%27%28%19%6%
318
May1st to 15thDay
9%9%21%26%24%8%
348
16th to endDay
9%413%31%24%15%
394
June1st to 15thDay
7%5%24%26%23%13%
375
16th to endDay
4318%33%25%13%
375
July1st to 15thDay
4210%32%34%16%
365
16th to endDay
110%35%39%13%
391
August1st to 15thDay
311%31%37%14%
359
16th to endDay
3111%28%31%24%
396
September1st to 15thDay
2111%25%33%26%
375
16th to endDay
6%312%23%37%17%
375
October1st to 15thDay
11%417%29%26%11%
375
16th to endDay
12%213%22%31%18%
196
November1st to 15thDay
15%415%28%35%
135
16th to endDay
24%422%29%17%1
117
December1st to 15thDay
27%214%25%13%16%
90
16th to endDay
29%412%26%22%5%
96
January1st to 15thNight
18%215%34%23%5%
780
16th to endNight
17%214%34%25%6%
832
February1st to 15thNight
16%118%37%22%2
764
16th to endNight
14%224%39%17%1
684
March1st to 15thNight
14%323%35%19%2
780
16th to endNight
12%5%27%40%12%1
832
April1st to 15thNight
11%424%35%20%1
779
16th to endNight
11%425%35%20%2
639
May1st to 15thNight
6%427%37%21%2
533
16th to endNight
6%318%36%28%5%
407
June1st to 15thNight
8%426%33%24%2
390
16th to endNight
4424%39%25%1
390
July1st to 15thNight
217%54%23%1
370
16th to endNight
122%49%23%1
408
August1st to 15thNight
3116%40%36%2
469
16th to endNight
2113%41%36%4
793
September1st to 15thNight
4112%35%38%7%
780
16th to endNight
8%112%35%34%7%
776
October1st to 15thNight
10%218%37%25%5%
780
16th to endNight
10%113%36%31%6%
816
November1st to 15thNight
15%216%40%23%2
760
16th to endNight
18%220%33%20%5%
780
December1st to 15thNight
19%115%37%21%3
780
16th to endNight
23%316%38%16%1
832
Page generated at 2018-10-28 06:41:04. Version ac04

Copyright 2018 A. Danko


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