Rio Vista
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rio Vista clear sky chart from 2005-11-05 to 2017-08-12.

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
61%
15169
29%
46532
22%
15133
68%
15133
45%
23886

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
19%
2422
18%
716
64%
716
30%
1403
January16th to endNight
60%
768
25%
2496
25%
768
64%
768
29%
1487
February1st to 15thNight
54%
697
23%
2283
22%
697
60%
697
27%
1388
February16th to endNight
53%
632
25%
1895
20%
632
61%
632
31%
1142
March1st to 15thNight
54%
720
19%
2030
16%
720
58%
720
31%
1289
March16th to endNight
48%
768
23%
2074
14%
768
56%
768
35%
1259
April1st to 15thNight
43%
719
24%
1799
10%
719
51%
719
37%
1129
April16th to endNight
48%
720
27%
1800
9%
720
56%
720
51%
987
May1st to 15thNight
60%
602
31%
1682
18%
602
67%
602
63%
776
May16th to endNight
57%
374
31%
1496
25%
374
71%
374
54%
551
June1st to 15thNight
55%
360
29%
1440
24%
360
71%
360
53%
543
June16th to endNight
66%
360
38%
1440
38%
360
81%
360
72%
451
July1st to 15thNight
72%
340
36%
1360
35%
340
85%
340
79%
400
July16th to endNight
75%
557
39%
1586
28%
524
83%
524
78%
608
August1st to 15thNight
72%
548
40%
1597
24%
545
80%
545
79%
624
August16th to endNight
74%
700
43%
1750
22%
700
80%
700
84%
768
September1st to 15thNight
79%
660
44%
1650
27%
660
85%
660
85%
721
September16th to endNight
74%
656
43%
1790
33%
656
81%
656
74%
773
October1st to 15thNight
66%
660
33%
1980
27%
660
77%
660
53%
933
October16th to endNight
70%
704
36%
2112
34%
704
77%
704
51%
1030
November1st to 15thNight
67%
700
30%
2215
27%
700
74%
700
45%
1116
November16th to endNight
64%
720
26%
2427
26%
720
69%
720
36%
1298
December1st to 15thNight
56%
720
20%
2520
19%
720
62%
720
25%
1535
December16th to endNight
49%
768
21%
2688
18%
768
56%
768
23%
1675

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
7%312212336%63%
47444
Night
8%312212346%62%
46716
TransparencyDay
22%39%19%25%18%
47127
Night
23%49%20%23%18%
46533
SeeingDay
8%7%24%33%17%7%
5801
Night
8%321%39%23%3
15182

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
17%7%24423346%42%
1513
16th to endDay
16%6%24434335%43%
1728
February1st to 15thDay
17%5%36%5%2434443%
1582
16th to endDay
17%5%2341445%6%43%
1579
March1st to 15thDay
13%6%25%42446%8%40%
1929
16th to endDay
10%5%25%5%35%45%6%45%
2148
April1st to 15thDay
13%42442445%7%45%
2149
16th to endDay
6%212312336%64%
2160
May1st to 15thDay
3112211346%71%
2262
16th to endDay
3112213337%68%
2615
June1st to 15thDay
3212213237%69%
2520
16th to endDay
111125%83%
2520
July1st to 15thDay
122485%
2520
16th to endDay
11125%85%
2474
August1st to 15thDay
111121484%
2267
16th to endDay
111125%83%
2100
September1st to 15thDay
1111125%83%
1980
16th to endDay
221112235%76%
1837
October1st to 15thDay
4112213236%69%
1650
16th to endDay
6%312323236%63%
1760
November1st to 15thDay
8%422334347%54%
1642
16th to endDay
12%6%25%422346%48%
1533
December1st to 15thDay
17%7%26%413336%41%
1440
16th to endDay
18%7%34323348%40%
1536
January1st to 15thNight
14%414323347%49%
2422
16th to endNight
15%424313446%49%
2496
February1st to 15thNight
15%424423446%45%
2271
16th to endNight
15%4133135%5%7%49%
1895
March1st to 15thNight
13%5%14424347%47%
2030
16th to endNight
12%323224347%52%
2074
April1st to 15thNight
10%41333445%7%51%
1799
16th to endNight
6%212312347%65%
1800
May1st to 15thNight
311211237%72%
1682
16th to endNight
311112347%72%
1496
June1st to 15thNight
212112245%75%
1440
16th to endNight
11112385%
1440
July1st to 15thNight
1112386%
1440
16th to endNight
1111237%78%
1693
August1st to 15thNight
1111237%78%
1606
16th to endNight
2148%80%
1750
September1st to 15thNight
1137%82%
1650
16th to endNight
11112236%78%
1790
October1st to 15thNight
41221335%6%68%
1980
16th to endNight
423313347%65%
2112
November1st to 15thNight
7%312212449%60%
2215
16th to endNight
9%314323346%56%
2427
December1st to 15thNight
16%5%14323347%45%
2520
16th to endNight
20%423323345%46%
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
42%5%14%14%19%3
1513
16th to endDay
42%5%8%16%20%6%
1728
February1st to 15thDay
43%5%9%21%16%3
1582
16th to endDay
39%6%12%24%12%3
1579
March1st to 15thDay
40%5%13%19%15%4
1929
16th to endDay
38%6%14%18%18%3
2148
April1st to 15thDay
36%6%12%21%19%3
2149
16th to endDay
20%413%26%26%8%
2160
May1st to 15thDay
13%38%28%35%11%
2262
16th to endDay
17%312%30%25%10%
2619
June1st to 15thDay
15%410%22%27%18%
2520
16th to endDay
6%1415%36%35%
2520
July1st to 15thDay
41310%26%54%
2371
16th to endDay
41410%25%53%
2318
August1st to 15thDay
6%312%31%44%
2251
16th to endDay
5%1214%38%37%
2100
September1st to 15thDay
6%1411%36%39%
1980
16th to endDay
12%25%20%35%23%
1837
October1st to 15thDay
16%49%22%27%19%
1650
16th to endDay
23%310%23%26%12%
1760
November1st to 15thDay
29%5%13%28%17%5%
1642
16th to endDay
36%6%11%21%19%4
1533
December1st to 15thDay
44%5%11%18%16%3
1440
16th to endDay
42%5%13%18%15%4
1536
January1st to 15thNight
34%5%13%23%16%6%
2422
16th to endNight
35%5%11%16%17%13%
2496
February1st to 15thNight
38%410%21%17%7%
2283
16th to endNight
34%5%12%25%18%3
1895
March1st to 15thNight
36%6%12%21%16%6%
2030
16th to endNight
32%5%12%22%20%7%
2074
April1st to 15thNight
31%5%14%22%18%6%
1799
16th to endNight
19%5%15%23%26%10%
1800
May1st to 15thNight
12%39%24%34%15%
1683
16th to endNight
11%413%33%25%12%
1496
June1st to 15thNight
11%5%9%24%27%21%
1440
16th to endNight
6%2314%33%40%
1440
July1st to 15thNight
5%28%23%59%
1360
16th to endNight
6%2311%22%54%
1586
August1st to 15thNight
6%313%27%47%
1597
16th to endNight
5%1311%35%43%
1750
September1st to 15thNight
415%9%33%44%
1650
16th to endNight
8%15%21%34%27%
1790
October1st to 15thNight
16%49%22%26%20%
1980
16th to endNight
18%47%24%26%17%
2112
November1st to 15thNight
22%413%29%20%9%
2215
16th to endNight
29%49%23%25%7%
2427
December1st to 15thNight
39%5%11%18%18%6%
2520
16th to endNight
40%6%11%17%18%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
25%417%24%15%12%
141
16th to endDay
18%7%16%20%21%15%
256
February1st to 15thDay
21%5%20%18%21%13%
237
16th to endDay
17%10%20%25%16%9%
238
March1st to 15thDay
17%9%24%20%14%13%
270
16th to endDay
12%13%30%26%12%4
288
April1st to 15thDay
15%14%30%19%13%6%
269
16th to endDay
8%18%30%24%13%5%
270
May1st to 15thDay
6%9%34%32%14%2
288
16th to endDay
5%6%26%33%22%4
330
June1st to 15thDay
5%13%32%36%10%1
315
16th to endDay
1326%46%19%2
315
July1st to 15thDay
23%54%18%1
305
16th to endDay
125%49%19%3
327
August1st to 15thDay
2325%50%16%1
300
16th to endDay
1125%54%14%2
268
September1st to 15thDay
1315%44%27%6%
255
16th to endDay
27%18%35%17%18%
255
October1st to 15thDay
7%7%22%27%20%15%
255
16th to endDay
11%5%21%29%18%14%
272
November1st to 15thDay
9%420%9%33%22%
148
16th to endDay
10%5%18%33%25%6%
75
December1st to 15thDay
26%10%23%25%13%1
60
16th to endDay
20%7%12%28%26%4
64
January1st to 15thNight
16%213%32%31%5%
720
16th to endNight
16%313%33%26%7%
768
February1st to 15thNight
16%413%35%25%3
704
16th to endNight
15%5%19%34%21%3
632
March1st to 15thNight
14%5%20%33%23%3
720
16th to endNight
13%6%26%35%17%
768
April1st to 15thNight
10%7%32%32%15%1
719
16th to endNight
7%7%34%30%17%2
720
May1st to 15thNight
3231%42%17%1
603
16th to endNight
3432%48%12%
375
June1st to 15thNight
3236%48%8%
360
16th to endNight
129%54%14%
360
July1st to 15thNight
125%58%14%
340
16th to endNight
119%55%21%1
557
August1st to 15thNight
222%51%21%1
548
16th to endNight
22%52%22%
700
September1st to 15thNight
118%49%28%1
660
16th to endNight
2119%40%29%5%
656
October1st to 15thNight
4321%38%26%5%
660
16th to endNight
5%317%34%31%8%
704
November1st to 15thNight
6%219%32%34%4
700
16th to endNight
10%215%37%27%6%
720
December1st to 15thNight
17%413%35%22%5%
720
16th to endNight
19%5%18%32%21%2
768
Page generated at 2017-08-13 11:16:48. Version ac04

Copyright 2017 A. Danko


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