Vista
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vista clear sky chart from 2005-11-06 to 2024-03-18.

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
69%
25239
27%
79841
26%
25154
71%
25154
36%
45625

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 10thNight
68%
750
35%
3984
30%
736
71%
736
30%
1630
January11th to 20thNight
68%
745
30%
3855
33%
740
73%
740
24%
2004
January21st to endNight
62%
827
23%
3973
30%
814
69%
814
24%
2246
February1st to 10thNight
68%
760
33%
2280
33%
760
72%
760
41%
1256
February11th to 20thNight
62%
740
29%
2218
29%
740
67%
740
35%
1289
February21st to endNight
58%
628
26%
1884
26%
628
63%
628
32%
1133
March1st to 10thNight
62%
760
22%
2280
24%
760
64%
760
32%
1376
March11th to 20thNight
64%
752
23%
2180
24%
752
66%
752
34%
1313
March21st to endNight
67%
792
25%
2039
20%
792
69%
792
39%
1273
April1st to 10thNight
63%
720
24%
1800
18%
720
64%
720
35%
1163
April11th to 20thNight
63%
711
26%
1779
18%
711
64%
711
38%
1124
April21st to endNight
66%
720
25%
1800
16%
720
66%
720
37%
1168
May1st to 10thNight
65%
622
21%
1702
16%
622
65%
622
33%
1097
May11th to 20thNight
60%
531
18%
1595
14%
531
61%
531
26%
1093
May21st to endNight
62%
582
21%
1746
17%
582
62%
582
30%
1137
June1st to 10thNight
60%
540
15%
1620
13%
540
60%
540
23%
1166
June11th to 20thNight
72%
540
22%
1620
18%
540
72%
540
36%
984
June21st to endNight
70%
540
20%
1620
18%
540
70%
540
34%
1017
July1st to 10thNight
73%
525
21%
1575
17%
525
73%
525
37%
953
July11th to 20thNight
79%
522
22%
1566
19%
522
79%
522
39%
922
July21st to endNight
76%
714
21%
1791
15%
675
75%
675
36%
1124
August1st to 10thNight
77%
716
25%
1780
15%
712
77%
712
46%
1061
August11th to 20thNight
75%
712
29%
1780
18%
712
75%
712
46%
1071
August21st to endNight
78%
792
32%
1980
23%
792
78%
792
49%
1147
September1st to 10thNight
77%
720
32%
1804
26%
720
77%
720
44%
1085
September11th to 20thNight
82%
720
36%
1980
34%
720
82%
720
52%
1012
September21st to endNight
79%
720
37%
1980
36%
720
80%
720
50%
1034
October1st to 10thNight
80%
720
34%
1980
34%
720
81%
720
50%
1053
October11th to 20thNight
71%
720
35%
1993
34%
720
72%
720
44%
1098
October21st to endNight
75%
792
36%
2452
38%
792
77%
792
47%
1224
November1st to 10thNight
77%
740
31%
2405
35%
740
79%
740
44%
1193
November11th to 20thNight
77%
760
35%
2470
39%
760
80%
760
46%
1197
November21st to endNight
71%
760
31%
2470
33%
760
73%
760
38%
1323
December1st to 10thNight
68%
760
29%
2470
31%
760
70%
760
37%
1329
December11th to 20thNight
61%
760
28%
2951
32%
759
65%
759
27%
1750
December21st to endNight
61%
826
19%
4439
30%
817
67%
817
20%
2580

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%424323447%60%
79263
Night
7%8%35%42445%7%52%
80611
TransparencyDay
23%5%8%18%24%22%
78998
Night
30%6%8%16%20%20%
80399
SeeingDay
7%5%21%38%22%7%
14857
Night
9%39%32%37%10%
25289

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 10thDay
8%413313336%65%
2858
11th to 20thDay
8%5%24324448%56%
3054
21st to endDay
12%5%25%43445%8%49%
3498
February1st to 10thDay
9%324424345%59%
1900
11th to 20thDay
8%42342445%8%55%
1850
21st to endDay
9%5%246%25%5%47%52%
1570
March1st to 10thDay
7%5%2443446%10%50%
1900
11th to 20thDay
7%32443345%11%54%
1944
21st to endDay
5%32442345%8%60%
2312
April1st to 10thDay
7%5%2442445%9%54%
2160
11th to 20thDay
4324424447%62%
2129
21st to endDay
5%42342245%8%63%
2160
May1st to 10thDay
5%6%345%24447%55%
2254
11th to 20thDay
5%7%34323336%61%
2301
21st to endDay
6%7%2432335%7%57%
2530
June1st to 10thDay
6%9%24323347%57%
2340
11th to 20thDay
46%23223346%65%
2340
21st to endDay
36%24323335%66%
2340
July1st to 10thDay
36%2432345%7%62%
2340
11th to 20thDay
242432445%8%63%
2340
21st to endDay
25%2433445%8%61%
2418
August1st to 10thDay
2413323445%70%
2149
11th to 20thDay
2412212336%72%
2122
21st to endDay
2313324447%68%
2376
September1st to 10thDay
3323323347%68%
2156
11th to 20thDay
3323222236%72%
1980
21st to endDay
2413313336%71%
1980
October1st to 10thDay
342432335%7%64%
1980
11th to 20thDay
5%324323346%67%
1962
21st to endDay
4313322235%71%
1901
November1st to 10thDay
431232345%7%66%
1674
11th to 20thDay
332232345%6%67%
1710
21st to endDay
5%3144235%5%8%59%
1710
December1st to 10thDay
7%42342345%8%58%
1710
11th to 20thDay
12%6%25%435%5%6%7%45%
2169
21st to endDay
10%6%25%5%45%5%5%9%43%
3146
January1st to 10thNight
6%414323346%63%
4097
11th to 20thNight
9%6%3443346%7%50%
3920
21st to endNight
15%6%2442345%6%48%
4180
February1st to 10thNight
9%5%24324445%58%
2280
11th to 20thNight
10%7%34424435%55%
2218
21st to endNight
11%6%35%5%34445%49%
1884
March1st to 10thNight
10%8%35%435%45%9%46%
2280
11th to 20thNight
11%7%34434447%48%
2180
21st to endNight
7%7%245%35%5%5%7%51%
2039
April1st to 10thNight
9%9%36%42345%8%47%
1800
11th to 20thNight
8%10%35%423336%53%
1779
21st to endNight
8%9%45%42445%7%49%
1800
May1st to 10thNight
8%11%45%3335%5%9%44%
1702
11th to 20thNight
8%16%46%5%24348%39%
1594
21st to endNight
10%14%36%423346%45%
1746
June1st to 10thNight
9%15%48%6%35%45%6%34%
1620
11th to 20thNight
5%12%44425%45%11%45%
1620
21st to endNight
5%13%46%425%46%9%43%
1620
July1st to 10thNight
414%45%423449%46%
1620
11th to 20thNight
210%46%3346%6%10%46%
1620
21st to endNight
48%36%5%45%5%6%9%46%
1896
August1st to 10thNight
38%344245%47%55%
1790
11th to 20thNight
210%35%4244410%51%
1780
21st to endNight
37%35%3245%5%7%57%
1980
September1st to 10thNight
48%34434446%57%
1804
11th to 20thNight
46%22213447%65%
1980
21st to endNight
36%33324446%63%
1980
October1st to 10thNight
3424324347%63%
1980
11th to 20thNight
7%6%24423345%61%
1993
21st to endNight
5%6%23323346%64%
2452
November1st to 10thNight
45%24323336%64%
2405
11th to 20thNight
35%23323445%64%
2470
21st to endNight
6%5%345%25%45%8%54%
2470
December1st to 10thNight
8%5%2443445%6%54%
2470
11th to 20thNight
12%7%35%5%3445%7%46%
3041
21st to endNight
10%7%26%6%345%5%7%44%
4521

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 10thDay
21%47%23%26%19%
2859
11th to 20thDay
27%5%12%24%16%15%
3054
21st to endDay
33%5%8%14%24%16%
3498
February1st to 10thDay
28%46%14%21%27%
1900
11th to 20thDay
27%5%9%13%28%19%
1860
21st to endDay
32%5%9%18%21%16%
1570
March1st to 10thDay
29%5%9%21%18%18%
1900
11th to 20thDay
26%5%10%21%23%16%
1944
21st to endDay
23%5%12%25%21%13%
2312
April1st to 10thDay
27%5%11%25%21%10%
2160
11th to 20thDay
21%6%8%20%26%18%
2132
21st to endDay
21%411%24%29%11%
2160
May1st to 10thDay
28%5%11%19%23%14%
2254
11th to 20thDay
26%47%23%28%11%
2304
21st to endDay
27%410%26%27%7%
2530
June1st to 10thDay
27%6%7%21%28%13%
2340
11th to 20thDay
20%45%12%32%26%
2340
21st to endDay
21%35%8%23%40%
2340
July1st to 10thDay
20%6%6%11%22%36%
2276
11th to 20thDay
18%6%9%20%25%21%
2271
21st to endDay
20%6%12%24%26%12%
2284
August1st to 10thDay
15%46%15%29%31%
2135
11th to 20thDay
13%36%19%29%29%
2122
21st to endDay
16%5%5%13%31%30%
2376
September1st to 10thDay
16%46%10%32%31%
2156
11th to 20thDay
14%35%11%33%34%
1980
21st to endDay
17%35%12%33%30%
1980
October1st to 10thDay
19%46%19%21%30%
1980
11th to 20thDay
19%46%13%24%34%
1962
21st to endDay
18%3413%22%41%
1901
November1st to 10thDay
17%48%19%19%33%
1674
11th to 20thDay
19%37%15%20%37%
1710
21st to endDay
22%5%9%14%20%31%
1710
December1st to 10thDay
25%410%18%17%26%
1710
11th to 20thDay
36%6%9%13%20%15%
2168
21st to endDay
37%7%9%22%14%11%
3146
January1st to 10thNight
22%6%7%17%29%19%
4097
11th to 20thNight
31%7%12%21%13%16%
3920
21st to endNight
36%5%8%12%21%18%
4180
February1st to 10thNight
29%47%15%21%25%
2280
11th to 20thNight
33%46%13%22%22%
2219
21st to endNight
35%5%6%15%22%17%
1884
March1st to 10thNight
36%5%9%17%16%18%
2280
11th to 20thNight
34%6%9%17%19%15%
2180
21st to endNight
31%6%11%20%19%12%
2039
April1st to 10thNight
35%6%9%22%16%12%
1800
11th to 20thNight
32%6%8%16%21%17%
1779
21st to endNight
34%7%9%20%20%11%
1800
May1st to 10thNight
35%8%12%16%16%14%
1702
11th to 20thNight
44%7%8%16%14%11%
1595
21st to endNight
40%5%9%22%16%8%
1746
June1st to 10thNight
45%9%8%9%18%10%
1620
11th to 20thNight
31%8%8%11%24%19%
1620
21st to endNight
35%6%6%9%18%26%
1620
July1st to 10thNight
31%6%6%12%17%27%
1575
11th to 20thNight
27%9%10%18%22%15%
1566
21st to endNight
31%8%12%22%20%7%
1791
August1st to 10thNight
25%7%7%15%25%22%
1780
11th to 20thNight
27%6%7%18%25%18%
1780
21st to endNight
23%6%7%14%25%24%
1980
September1st to 10thNight
28%5%411%23%28%
1804
11th to 20thNight
20%45%10%32%30%
1980
21st to endNight
22%45%14%31%23%
1980
October1st to 10thNight
22%5%6%19%21%27%
1980
11th to 20thNight
26%5%6%13%20%30%
1993
21st to endNight
23%4412%21%37%
2452
November1st to 10thNight
22%5%7%15%17%33%
2405
11th to 20thNight
23%36%13%18%38%
2470
21st to endNight
29%48%15%15%29%
2470
December1st to 10thNight
29%410%15%16%26%
2470
11th to 20thNight
37%48%14%20%16%
3041
21st to endNight
36%9%12%18%12%13%
4521

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 10thDay
16%5%15%41%19%3
270
11th to 20thDay
13%421%37%20%4
386
21st to endDay
10%6%28%36%15%5%
506
February1st to 10thDay
12%7%28%31%16%6%
460
11th to 20thDay
9%9%29%35%16%2
455
21st to endDay
10%11%35%32%10%2
382
March1st to 10thDay
12%10%32%32%11%3
460
11th to 20thDay
12%6%29%35%14%3
449
21st to endDay
7%11%33%33%13%3
462
April1st to 10thDay
10%8%32%28%16%5%
420
11th to 20thDay
6%9%33%34%13%4
412
21st to endDay
6%8%30%33%16%7%
420
May1st to 10thDay
9%7%29%35%16%4
423
11th to 20thDay
9%6%26%39%17%4
448
21st to endDay
9%8%27%36%17%4
485
June1st to 10thDay
8%221%38%26%6%
450
11th to 20thDay
6%318%42%22%8%
450
21st to endDay
7%113%43%27%9%
450
July1st to 10thDay
5%16%45%33%10%
446
11th to 20thDay
4441%34%16%
444
21st to endDay
415%43%32%15%
487
August1st to 10thDay
327%46%30%13%
447
11th to 20thDay
48%44%30%13%
437
21st to endDay
5%19%40%34%12%
495
September1st to 10thDay
6%12%49%26%7%
450
11th to 20thDay
5%318%45%22%7%
450
21st to endDay
5%419%40%24%8%
450
October1st to 10thDay
6%5%21%39%24%5%
450
11th to 20thDay
4425%37%23%6%
450
21st to endDay
6%318%36%27%10%
416
November1st to 10thDay
6%414%36%31%9%
270
11th to 20thDay
3319%38%28%9%
270
21st to endDay
5%5%22%39%21%8%
270
December1st to 10thDay
10%121%38%23%7%
270
11th to 20thDay
7%219%38%26%9%
270
21st to endDay
15%6%20%34%21%4
297
January1st to 10thNight
10%313%42%26%8%
760
11th to 20thNight
9%310%43%29%7%
760
21st to endNight
13%214%41%25%5%
836
February1st to 10thNight
11%411%38%28%8%
760
11th to 20thNight
12%412%39%27%6%
744
21st to endNight
13%416%39%24%4
628
March1st to 10thNight
12%414%43%24%3
760
11th to 20thNight
14%39%37%29%8%
752
21st to endNight
10%310%42%29%5%
792
April1st to 10thNight
12%5%9%40%30%5%
720
11th to 20thNight
10%413%37%28%7%
711
21st to endNight
11%310%35%33%8%
720
May1st to 10thNight
10%5%10%35%34%6%
622
11th to 20thNight
12%411%31%35%6%
531
21st to endNight
13%5%10%32%35%4
584
June1st to 10thNight
13%49%33%34%6%
540
11th to 20thNight
9%3433%46%5%
540
21st to endNight
9%26%29%48%6%
540
July1st to 10thNight
9%1417%54%16%
525
11th to 20thNight
5%2211%59%21%
522
21st to endNight
7%1210%55%24%
714
August1st to 10thNight
6%2316%51%22%
716
11th to 20thNight
7%3211%54%24%
712
21st to endNight
6%2211%54%26%
792
September1st to 10thNight
8%2315%54%18%
720
11th to 20thNight
7%2320%55%12%
720
21st to endNight
425%30%45%14%
720
October1st to 10thNight
5%16%38%43%8%
720
11th to 20thNight
9%36%34%39%9%
720
21st to endNight
8%28%33%35%15%
792
November1st to 10thNight
437%39%36%11%
740
11th to 20thNight
5%37%38%35%13%
760
21st to endNight
7%312%39%29%10%
760
December1st to 10thNight
10%212%41%29%6%
760
11th to 20thNight
14%313%41%24%5%
760
21st to endNight
11%416%38%23%8%
836
Page generated at 2024-03-15 11:01:39. Version ac07

Copyright © 2024 Attilla Danko.


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