Valle Grande Entrance Station
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Valle Grande Entrance Station clear sky chart from 2005-11-05 to 2018-02-13.

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
52%
16355
31%
48818
19%
16313
63%
16313
41%
25216

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
55%
801
34%
2545
25%
799
69%
799
49%
1157
January16th to endNight
50%
832
36%
2704
26%
832
66%
832
43%
1251
February1st to 15thNight
45%
749
30%
2396
20%
748
57%
748
40%
1151
February16th to endNight
36%
632
39%
1894
18%
632
58%
632
39%
937
March1st to 15thNight
44%
720
33%
2020
17%
720
57%
720
38%
1098
March16th to endNight
42%
732
34%
2076
16%
732
57%
732
43%
1039
April1st to 15thNight
32%
539
30%
1798
13%
539
53%
539
30%
900
April16th to endNight
35%
540
34%
1800
17%
540
59%
540
33%
842
May1st to 15thNight
42%
540
25%
1781
15%
539
58%
539
35%
915
May16th to endNight
42%
563
31%
1545
13%
561
59%
561
42%
815
June1st to 15thNight
54%
540
27%
1440
16%
540
62%
540
47%
775
June16th to endNight
60%
540
26%
1440
17%
540
65%
540
45%
789
July1st to 15thNight
66%
510
14%
1443
11%
510
68%
510
28%
949
July16th to endNight
68%
564
15%
1593
14%
531
69%
531
29%
1001
August1st to 15thNight
72%
539
15%
1686
16%
536
73%
536
30%
1013
August16th to endNight
70%
573
21%
1910
23%
573
73%
573
31%
1109
September1st to 15thNight
63%
540
23%
1800
23%
540
66%
540
29%
1070
September16th to endNight
65%
588
36%
1944
28%
588
75%
588
45%
943
October1st to 15thNight
54%
720
34%
2160
20%
720
64%
720
46%
1077
October16th to endNight
61%
768
41%
2304
25%
768
72%
768
53%
1062
November1st to 15thNight
60%
835
39%
2355
24%
835
70%
835
57%
1087
November16th to endNight
56%
975
41%
2542
23%
975
67%
975
53%
1269
December1st to 15thNight
48%
975
31%
2730
17%
975
58%
975
44%
1395
December16th to endNight
41%
1040
31%
2912
18%
1040
53%
1040
39%
1572

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
44244345%5%7%52%
49214
Night
342442445%7%57%
49012
TransparencyDay
25%49%23%25%11%
48907
Night
22%49%23%27%12%
48820
SeeingDay
7%19%27%27%15%2
6011
Night
5%13%22%33%21%3
16360

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
2313335%446%63%
1733
16th to endDay
35%23433335%62%
1872
February1st to 15thDay
25%36%5%12446%56%
1730
16th to endDay
16%2443446%7%54%
1580
March1st to 15thDay
26%25%42445%7%53%
1938
16th to endDay
36%25%42445%6%56%
2148
April1st to 15thDay
3325%5%245%47%54%
2150
16th to endDay
35%25%43445%5%54%
2160
May1st to 15thDay
44145%345%5%5%53%
2166
16th to endDay
5%324423446%57%
2565
June1st to 15thDay
22134345%6%6%59%
2520
16th to endDay
221332446%9%57%
2520
July1st to 15thDay
6%5%27%5%46%7%8%10%35%
2425
16th to endDay
6%427%8%5%8%9%9%10%28%
2467
August1st to 15thDay
7%5%48%8%47%6%8%8%29%
2265
16th to endDay
7%425%5%46%7%8%9%36%
2292
September1st to 15thDay
9%5%25%436%6%7%8%39%
2160
16th to endDay
5%31342445%7%59%
2013
October1st to 15thDay
7%22442334460%
1800
16th to endDay
321331233469%
1920
November1st to 15thDay
22332245%6%65%
1821
16th to endDay
3412222345%66%
1745
December1st to 15thDay
242442345%5%60%
1560
16th to endDay
26%26%42445%8%50%
1664
January1st to 15thNight
1313223446%65%
2545
16th to endNight
331232435%6%63%
2704
February1st to 15thNight
25%24413346%61%
2386
16th to endNight
25%13323346%61%
1894
March1st to 15thNight
26%14433446%57%
2020
16th to endNight
3313313346%63%
2076
April1st to 15thNight
342442435%7%56%
1798
16th to endNight
4413323336%63%
1800
May1st to 15thNight
5%6%2332345%7%55%
1781
16th to endNight
5%21342435%6%60%
1545
June1st to 15thNight
221333445%8%58%
1440
16th to endNight
2215%425%6%5%8%55%
1440
July1st to 15thNight
6%435%6%5%8%7%8%8%35%
1530
16th to endNight
4437%6%47%7%9%11%32%
1701
August1st to 15thNight
6%425%5%37%7%8%12%37%
1695
16th to endNight
6%435%446%6%10%10%37%
1910
September1st to 15thNight
7%426%6%45%5%7%8%39%
1800
16th to endNight
6%313323346%61%
1944
October1st to 15thNight
6%323223335%64%
2160
16th to endNight
421221324469%
2304
November1st to 15thNight
112323336%70%
2355
16th to endNight
2313213345%67%
2542
December1st to 15thNight
3413423347%61%
2730
16th to endNight
36%2442435%7%56%
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
17%410%34%29%3
1734
16th to endDay
20%37%29%30%8%
1872
February1st to 15thDay
26%39%28%22%9%
1731
16th to endDay
23%35%25%30%10%
1580
March1st to 15thDay
24%35%25%32%8%
1938
16th to endDay
24%36%24%31%9%
2148
April1st to 15thDay
24%46%25%28%11%
2150
16th to endDay
25%46%22%28%13%
2160
May1st to 15thDay
26%48%19%30%10%
2166
16th to endDay
23%48%20%26%16%
2568
June1st to 15thDay
20%39%15%24%27%
2520
16th to endDay
18%48%18%26%24%
2520
July1st to 15thDay
35%7%16%15%12%12%
2283
16th to endDay
36%9%25%22%6%
2312
August1st to 15thDay
40%8%16%18%10%5%
2250
16th to endDay
34%7%14%22%15%5%
2292
September1st to 15thDay
34%6%13%22%16%6%
2160
16th to endDay
20%46%23%33%12%
2013
October1st to 15thDay
23%25%20%31%15%
1800
16th to endDay
16%26%22%37%14%
1920
November1st to 15thDay
14%37%29%33%11%
1821
16th to endDay
17%25%26%35%12%
1745
December1st to 15thDay
20%412%33%21%7%
1560
16th to endDay
26%5%12%28%23%4
1664
January1st to 15thNight
16%39%30%31%7%
2545
16th to endNight
18%47%25%34%10%
2704
February1st to 15thNight
21%39%28%25%11%
2396
16th to endNight
20%35%24%33%13%
1894
March1st to 15thNight
25%3425%33%8%
2020
16th to endNight
19%35%21%36%12%
2076
April1st to 15thNight
24%37%23%27%13%
1798
16th to endNight
20%35%22%32%14%
1800
May1st to 15thNight
25%48%19%30%12%
1782
16th to endNight
22%49%19%25%19%
1546
June1st to 15thNight
21%38%16%20%28%
1440
16th to endNight
23%5%9%14%19%29%
1440
July1st to 15thNight
37%10%16%14%8%12%
1443
16th to endNight
35%8%24%21%8%
1593
August1st to 15thNight
31%10%20%18%11%8%
1686
16th to endNight
32%7%18%21%12%6%
1910
September1st to 15thNight
34%7%16%18%14%9%
1800
16th to endNight
20%47%18%30%18%
1944
October1st to 15thNight
21%36%18%30%19%
2160
16th to endNight
15%3420%37%18%
2304
November1st to 15thNight
13%26%26%38%11%
2355
16th to endNight
16%2423%36%16%
2542
December1st to 15thNight
20%310%31%25%8%
2730
16th to endNight
24%311%27%27%4
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
427%31%24%12%
135
16th to endDay
227%29%25%13%2
144
February1st to 15thDay
28%31%31%7%
126
16th to endDay
334%28%23%9%
81
March1st to 15thDay
7%30%40%16%4
228
16th to endDay
9%44%29%12%3
288
April1st to 15thDay
11%36%34%12%4
269
16th to endDay
10%42%35%10%1
270
May1st to 15thDay
9%31%37%17%4
288
16th to endDay
9%22%31%22%11%1
466
June1st to 15thDay
414%27%29%22%1
495
16th to endDay
35%24%33%27%5%
495
July1st to 15thDay
8%321%33%27%5%
387
16th to endDay
11%310%38%28%8%
327
August1st to 15thDay
10%5%16%40%20%5%
315
16th to endDay
12%216%41%21%4
332
September1st to 15thDay
10%5%26%37%16%3
315
16th to endDay
7%13%39%24%13%2
222
October1st to 15thDay
8%22%31%20%11%5%
135
16th to endDay
11%12%25%30%15%4
144
November1st to 15thDay
5%22%30%28%12%
135
16th to endDay
431%31%20%10%
135
December1st to 15thDay
426%29%30%6%2
135
16th to endDay
6%30%34%26%2
144
January1st to 15thNight
311%23%38%18%3
803
16th to endNight
317%24%34%16%3
832
February1st to 15thNight
5%14%29%36%13%1
752
16th to endNight
323%33%31%7%
632
March1st to 15thNight
5%20%25%33%14%1
720
16th to endNight
5%21%27%33%12%
732
April1st to 15thNight
428%30%29%6%
539
16th to endNight
7%24%28%30%9%
540
May1st to 15thNight
7%15%28%34%12%
540
16th to endNight
6%15%29%28%19%
563
June1st to 15thNight
39%25%37%20%1
540
16th to endNight
3422%36%30%2
540
July1st to 15thNight
7%28%32%45%4
510
16th to endNight
6%2423%51%11%
564
August1st to 15thNight
5%25%25%47%12%
539
16th to endNight
7%17%29%46%7%
573
September1st to 15thNight
8%311%34%35%6%
540
16th to endNight
7%416%37%29%4
588
October1st to 15thNight
6%9%25%36%19%3
720
16th to endNight
5%9%19%35%22%6%
768
November1st to 15thNight
212%21%37%23%2
835
16th to endNight
414%20%34%21%4
975
December1st to 15thNight
5%17%24%37%12%2
975
16th to endNight
5%17%29%32%12%1
1040
Page generated at 2018-02-13 18:45:57. Version ac04

Copyright 2018 A. Danko


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