Vista Hill
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vista Hill clear sky chart from 2005-11-05 to 2017-09-19.

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
66%
15435
26%
46937
23%
15399
69%
15399
39%
25777

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
60%
716
18%
2368
18%
716
63%
716
28%
1431
January16th to endNight
58%
768
24%
2496
25%
768
61%
768
26%
1561
February1st to 15thNight
55%
700
23%
2288
22%
700
60%
700
25%
1425
February16th to endNight
50%
632
21%
1898
17%
632
56%
632
26%
1215
March1st to 15thNight
54%
720
18%
1998
16%
720
58%
720
28%
1315
March16th to endNight
52%
768
19%
2093
14%
768
57%
768
29%
1363
April1st to 15thNight
48%
719
20%
1799
10%
719
52%
719
32%
1190
April16th to endNight
56%
720
24%
1800
12%
720
61%
720
44%
1048
May1st to 15thNight
66%
617
25%
1697
17%
617
69%
617
52%
875
May16th to endNight
67%
408
23%
1531
20%
408
73%
408
38%
736
June1st to 15thNight
70%
360
25%
1440
25%
360
78%
360
43%
619
June16th to endNight
85%
360
35%
1440
45%
360
88%
360
64%
486
July1st to 15thNight
90%
400
33%
1420
38%
400
92%
400
72%
496
July16th to endNight
87%
564
35%
1593
33%
531
87%
531
64%
676
August1st to 15thNight
85%
556
33%
1629
26%
553
86%
553
60%
726
August16th to endNight
86%
764
38%
1910
25%
764
87%
764
70%
913
September1st to 15thNight
87%
720
39%
1800
28%
720
88%
720
71%
862
September16th to endNight
79%
671
38%
1838
34%
671
81%
671
62%
876
October1st to 15thNight
73%
660
27%
1980
28%
660
77%
660
46%
1016
October16th to endNight
70%
704
31%
2112
32%
704
73%
704
41%
1141
November1st to 15thNight
68%
700
27%
2172
28%
700
71%
700
39%
1186
November16th to endNight
64%
720
24%
2427
26%
720
67%
720
33%
1348
December1st to 15thNight
55%
720
21%
2520
19%
720
61%
720
24%
1553
December16th to endNight
46%
768
19%
2688
16%
768
53%
768
21%
1720

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
6%424323347%56%
47876
Night
6%42442445%8%53%
47126
TransparencyDay
26%410%20%23%14%
47565
Night
28%411%20%21%14%
46938
SeeingDay
7%10%25%33%17%5%
6052
Night
8%414%32%32%7%
15445

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
12%6%2442445%6%44%
1568
16th to endDay
14%6%35%424347%42%
1728
February1st to 15thDay
11%8%45%5%3345%6%40%
1576
16th to endDay
14%8%37%42345%7%37%
1576
March1st to 15thDay
11%6%47%5%246%6%10%34%
1959
16th to endDay
10%5%37%6%4445%6%40%
2130
April1st to 15thDay
12%7%35%42435%8%41%
2149
16th to endDay
6%5%23414347%56%
2160
May1st to 15thDay
332322335%9%61%
2250
16th to endDay
5%7%2442325%7%55%
2578
June1st to 15thDay
5%422213447%60%
2520
16th to endDay
111112246%75%
2520
July1st to 15thDay
111212337%74%
2452
16th to endDay
1111112246%74%
2468
August1st to 15thDay
22213348%70%
2320
16th to endDay
1111235%8%72%
2292
September1st to 15thDay
112212337%73%
2160
16th to endDay
3312212246%69%
1864
October1st to 15thDay
6%314223347%60%
1650
16th to endDay
5%5%1343345%7%55%
1760
November1st to 15thDay
7%4345%2445%7%49%
1687
16th to endDay
9%6%45%5%33346%47%
1533
December1st to 15thDay
11%7%47%6%25%5%45%38%
1440
16th to endDay
14%8%47%5%24347%37%
1536
January1st to 15thNight
12%6%25%5%2446%8%41%
2368
16th to endNight
13%6%35%5%24446%44%
2496
February1st to 15thNight
8%7%45%5%35%45%7%41%
2276
16th to endNight
12%8%35%43446%8%39%
1898
March1st to 15thNight
11%7%36%5%33447%42%
1998
16th to endNight
9%6%35%5%34447%44%
2093
April1st to 15thNight
9%6%345%25%5%6%8%43%
1799
16th to endNight
5%313324448%57%
1800
May1st to 15thNight
131332347%9%58%
1697
16th to endNight
23243145%7%9%53%
1530
June1st to 15thNight
231321435%9%62%
1440
16th to endNight
11212247%74%
1440
July1st to 15thNight
1212249%73%
1505
16th to endNight
1123135%7%11%61%
1701
August1st to 15thNight
121232247%13%58%
1638
16th to endNight
1121337%11%65%
1910
September1st to 15thNight
11121245%9%69%
1800
16th to endNight
212313347%68%
1838
October1st to 15thNight
431432445%6%59%
1980
16th to endNight
5%42442245%7%56%
2112
November1st to 15thNight
6%42432335%8%54%
2172
16th to endNight
6%6%24434447%51%
2427
December1st to 15thNight
10%6%25%5%35%45%6%43%
2520
16th to endNight
14%7%35%5%34445%41%
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
37%5%12%18%15%10%
1568
16th to endDay
41%6%8%12%18%12%
1728
February1st to 15thDay
43%49%18%20%4
1576
16th to endDay
45%5%9%22%13%3
1576
March1st to 15thDay
43%6%11%18%14%5%
1959
16th to endDay
42%7%13%18%16%1
2130
April1st to 15thDay
40%5%14%19%18%2
2149
16th to endDay
27%413%25%21%6%
2160
May1st to 15thDay
19%413%26%27%7%
2250
16th to endDay
27%416%24%21%5%
2582
June1st to 15thDay
22%5%13%22%22%14%
2520
16th to endDay
10%27%19%34%25%
2520
July1st to 15thDay
9%16%15%24%42%
2308
16th to endDay
9%25%15%29%37%
2313
August1st to 15thDay
12%18%16%31%29%
2304
16th to endDay
8%17%22%35%24%
2292
September1st to 15thDay
11%17%18%29%30%
2160
16th to endDay
16%26%25%29%19%
1864
October1st to 15thDay
23%410%20%24%16%
1650
16th to endDay
27%310%22%22%12%
1760
November1st to 15thDay
33%411%25%17%7%
1687
16th to endDay
37%5%10%16%26%4
1533
December1st to 15thDay
45%5%10%15%18%5%
1440
16th to endDay
46%412%15%16%5%
1536
January1st to 15thNight
38%412%19%16%8%
2368
16th to endNight
39%6%8%12%16%15%
2496
February1st to 15thNight
40%49%19%18%7%
2288
16th to endNight
41%5%13%25%12%2
1898
March1st to 15thNight
40%5%13%19%15%6%
1998
16th to endNight
38%6%13%18%17%5%
2093
April1st to 15thNight
36%6%16%21%16%2
1799
16th to endNight
24%6%14%26%20%8%
1800
May1st to 15thNight
19%413%23%25%12%
1698
16th to endNight
23%5%18%25%21%6%
1531
June1st to 15thNight
16%6%14%24%22%15%
1440
16th to endNight
10%16%17%33%31%
1440
July1st to 15thNight
7%1414%30%40%
1420
16th to endNight
12%28%19%25%30%
1593
August1st to 15thNight
15%28%18%28%26%
1629
16th to endNight
11%27%20%30%27%
1910
September1st to 15thNight
11%27%18%25%34%
1800
16th to endNight
14%36%22%29%22%
1838
October1st to 15thNight
23%311%21%21%18%
1980
16th to endNight
27%38%22%23%14%
2112
November1st to 15thNight
28%413%25%19%7%
2172
16th to endNight
31%410%23%20%8%
2427
December1st to 15thNight
39%6%9%16%20%7%
2520
16th to endNight
43%5%11%15%17%6%
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
18%12%22%27%14%3
197
16th to endDay
16%10%28%24%17%3
256
February1st to 15thDay
13%17%24%27%13%2
236
16th to endDay
18%15%28%24%10%1
237
March1st to 15thDay
17%18%28%19%12%3
270
16th to endDay
9%19%38%23%6%1
288
April1st to 15thDay
15%20%34%20%7%1
269
16th to endDay
7%25%32%24%8%1
270
May1st to 15thDay
5%13%36%30%10%2
288
16th to endDay
8%13%26%32%14%4
330
June1st to 15thDay
313%33%33%12%2
315
16th to endDay
324%43%21%6%
315
July1st to 15thDay
217%48%25%5%
305
16th to endDay
114%48%26%8%
327
August1st to 15thDay
121%42%26%7%
315
16th to endDay
118%44%26%9%
332
September1st to 15thDay
1117%42%27%9%
315
16th to endDay
47%18%36%23%9%
268
October1st to 15thDay
6%9%21%38%18%5%
255
16th to endDay
10%8%29%29%19%3
272
November1st to 15thDay
8%7%22%23%27%10%
193
16th to endDay
5%16%25%32%18%2
75
December1st to 15thDay
10%18%31%26%13%
60
16th to endDay
12%15%15%26%21%7%
64
January1st to 15thNight
15%410%33%28%7%
720
16th to endNight
16%413%30%23%10%
768
February1st to 15thNight
11%8%14%33%25%6%
704
16th to endNight
16%7%19%30%20%4
632
March1st to 15thNight
13%8%16%28%28%5%
720
16th to endNight
12%6%20%35%21%2
768
April1st to 15thNight
11%10%21%33%19%2
719
16th to endNight
7%7%23%31%22%7%
720
May1st to 15thNight
2321%37%28%6%
618
16th to endNight
4319%35%32%5%
409
June1st to 15thNight
2218%43%30%1
360
16th to endNight
10%43%42%2
360
July1st to 15thNight
434%54%6%
400
16th to endNight
1327%54%13%
564
August1st to 15thNight
25%31%51%8%
556
16th to endNight
16%32%49%9%
764
September1st to 15thNight
26%31%47%12%
720
16th to endNight
319%30%41%13%
671
October1st to 15thNight
5%311%32%36%10%
660
16th to endNight
7%39%31%32%15%
704
November1st to 15thNight
8%115%32%33%9%
700
16th to endNight
9%412%35%28%9%
720
December1st to 15thNight
12%5%17%32%24%7%
720
16th to endNight
17%7%20%30%20%3
768
Page generated at 2017-09-20 01:49:56. Version ac04

Copyright 2017 A. Danko


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