OCA Silverado
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the OCA Silverado clear sky chart from 2005-11-05 to 2017-12-04.

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
78%
16298
32%
47624
30%
16252
80%
16252
48%
24535

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
71%
718
29%
2306
29%
716
75%
716
41%
1200
January16th to endNight
65%
768
32%
2304
29%
768
70%
768
38%
1283
February1st to 15thNight
72%
697
34%
2103
34%
697
75%
697
45%
1109
February16th to endNight
64%
632
28%
1895
30%
632
66%
632
32%
1137
March1st to 15thNight
72%
720
29%
2160
32%
720
75%
720
43%
1144
March16th to endNight
75%
768
28%
2018
25%
768
77%
768
46%
1144
April1st to 15thNight
72%
719
26%
1799
18%
719
74%
719
44%
1087
April16th to endNight
78%
720
29%
1800
19%
720
79%
720
52%
997
May1st to 15thNight
76%
602
28%
1682
19%
602
76%
602
44%
942
May16th to endNight
80%
561
25%
1685
21%
561
81%
561
42%
933
June1st to 15thNight
83%
540
23%
1620
21%
540
83%
540
46%
861
June16th to endNight
92%
378
36%
1458
43%
378
92%
378
61%
529
July1st to 15thNight
89%
373
30%
1393
34%
373
89%
373
53%
565
July16th to endNight
88%
653
29%
1675
22%
613
88%
613
55%
868
August1st to 15thNight
91%
717
33%
1790
22%
713
91%
713
66%
886
August16th to endNight
92%
764
40%
1910
27%
764
92%
764
71%
921
September1st to 15thNight
88%
720
37%
1845
30%
720
88%
720
64%
910
September16th to endNight
88%
716
43%
1980
42%
716
89%
716
68%
891
October1st to 15thNight
84%
720
35%
1980
34%
720
85%
720
58%
973
October16th to endNight
80%
768
39%
2328
42%
768
82%
768
51%
1134
November1st to 15thNight
80%
760
33%
2470
37%
760
82%
760
51%
1147
November16th to endNight
76%
780
35%
2535
39%
780
78%
780
45%
1261
December1st to 15thNight
70%
736
31%
2392
31%
736
75%
736
38%
1268
December16th to endNight
60%
768
32%
2496
29%
768
68%
768
36%
1345

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
4313213346%65%
48842
Night
4313323346%62%
47829
TransparencyDay
20%37%17%26%25%
48538
Night
21%47%16%23%26%
47634
SeeingDay
6%418%38%23%7%
6229
Night
6%16%30%42%12%
16310

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
9%413222345%59%
1629
16th to endDay
10%423323345%56%
1920
February1st to 15thDay
7%32431335%5%60%
1751
16th to endDay
12%5%25%423446%49%
1579
March1st to 15thDay
5%3122245%5%9%55%
1800
16th to endDay
43234245%5%9%55%
2202
April1st to 15thDay
6%413324446%57%
2149
16th to endDay
5%312212246%66%
2160
May1st to 15thDay
4423213338%61%
2265
16th to endDay
35%13213348%61%
2429
June1st to 15thDay
45%13212248%62%
2340
16th to endDay
1111122382%
2496
July1st to 15thDay
1212223346%69%
2478
16th to endDay
2112213346%68%
2374
August1st to 15thDay
11212235%78%
2160
16th to endDay
2212235%77%
2292
September1st to 15thDay
112211235%77%
2113
16th to endDay
111121234477%
1980
October1st to 15thDay
4212323345%65%
1980
16th to endDay
431221233468%
1894
November1st to 15thDay
4313323345%65%
1719
16th to endDay
5%32431245%7%60%
1755
December1st to 15thDay
7%31342345%9%53%
1649
16th to endDay
11%423323336%54%
1728
January1st to 15thNight
6%413323446%58%
2306
16th to endNight
10%434213335%56%
2304
February1st to 15thNight
7%413313236%60%
2101
16th to endNight
12%424434335%50%
1895
March1st to 15thNight
6%42332335%8%56%
2160
16th to endNight
432432345%8%56%
2018
April1st to 15thNight
7%424323347%56%
1799
16th to endNight
4312323336%64%
1800
May1st to 15thNight
24145%2335%9%57%
1682
16th to endNight
141332335%9%58%
1684
June1st to 15thNight
23123246%5%8%57%
1620
16th to endNight
12112347%73%
1458
July1st to 15thNight
21332335%8%64%
1476
16th to endNight
22123235%6%8%60%
1790
August1st to 15thNight
112213337%71%
1800
16th to endNight
11312346%75%
1910
September1st to 15thNight
122322246%71%
1845
16th to endNight
121221122477%
1980
October1st to 15thNight
2212313237%68%
1980
16th to endNight
4213223335%66%
2328
November1st to 15thNight
2313313335%66%
2470
16th to endNight
5%313323347%60%
2535
December1st to 15thNight
7%41342345%6%55%
2392
16th to endNight
11%5%14312335%57%
2496

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
27%27%13%22%25%
1630
16th to endDay
30%37%14%16%28%
1920
February1st to 15thDay
26%25%14%25%24%
1751
16th to endDay
35%36%17%26%9%
1579
March1st to 15thDay
23%39%20%21%21%
1800
16th to endDay
23%412%24%20%13%
2202
April1st to 15thDay
27%29%25%23%11%
2149
16th to endDay
19%310%22%26%17%
2160
May1st to 15thDay
23%48%20%26%17%
2265
16th to endDay
21%49%27%27%9%
2432
June1st to 15thDay
19%46%19%31%18%
2340
16th to endDay
9%2310%28%46%
2496
July1st to 15thDay
13%46%11%26%37%
2332
16th to endDay
15%48%22%29%20%
2226
August1st to 15thDay
8%2413%36%33%
2146
16th to endDay
10%2313%35%33%
2292
September1st to 15thDay
10%25%11%34%35%
2113
16th to endDay
10%1413%33%34%
1980
October1st to 15thDay
20%3418%25%28%
1980
16th to endDay
20%3412%20%38%
1894
November1st to 15thDay
21%27%17%20%30%
1719
16th to endDay
22%46%12%22%31%
1755
December1st to 15thDay
26%310%17%17%24%
1649
16th to endDay
31%47%16%19%20%
1728
January1st to 15thNight
26%37%11%20%29%
2306
16th to endNight
31%27%12%14%31%
2304
February1st to 15thNight
25%36%15%21%27%
2112
16th to endNight
35%46%14%22%16%
1895
March1st to 15thNight
25%48%19%20%22%
2160
16th to endNight
25%411%19%22%15%
2018
April1st to 15thNight
28%410%21%21%13%
1799
16th to endNight
20%5%10%22%22%19%
1800
May1st to 15thNight
23%7%10%20%20%18%
1683
16th to endNight
24%7%10%23%21%12%
1685
June1st to 15thNight
19%8%13%16%25%16%
1620
16th to endNight
8%5%6%15%25%38%
1458
July1st to 15thNight
13%5%5%15%26%33%
1393
16th to endNight
16%6%10%21%26%18%
1675
August1st to 15thNight
10%5%5%16%34%26%
1790
16th to endNight
9%45%12%32%36%
1910
September1st to 15thNight
13%37%11%31%33%
1845
16th to endNight
12%1412%32%36%
1980
October1st to 15thNight
17%37%16%31%24%
1980
16th to endNight
20%3411%21%39%
2328
November1st to 15thNight
20%27%16%18%34%
2470
16th to endNight
23%36%14%19%33%
2535
December1st to 15thNight
28%48%14%20%24%
2392
16th to endNight
30%29%13%22%20%
2496

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
24%416%37%15%
108
16th to endDay
16%8%27%33%12%1
288
February1st to 15thDay
10%427%34%18%3
266
16th to endDay
16%11%27%29%13%2
238
March1st to 15thDay
8%11%26%29%18%4
270
16th to endDay
6%10%28%38%10%5%
288
April1st to 15thDay
7%12%33%31%11%4
269
16th to endDay
312%38%33%8%3
270
May1st to 15thDay
7%8%29%36%13%4
288
16th to endDay
6%6%25%39%16%5%
330
June1st to 15thDay
6%219%42%23%5%
315
16th to endDay
28%41%33%13%
315
July1st to 15thDay
26%37%39%13%
305
16th to endDay
2338%40%14%
327
August1st to 15thDay
6%45%37%8%
315
16th to endDay
1241%40%14%
332
September1st to 15thDay
210%52%26%6%
315
16th to endDay
2116%47%23%8%
315
October1st to 15thDay
3421%42%22%6%
315
16th to endDay
6%216%35%25%12%
294
November1st to 15thDay
4211%34%28%17%
135
16th to endDay
7%5%14%33%24%14%
135
December1st to 15thDay
11%214%24%44%5%
100
16th to endDay
14%318%39%21%2
96
January1st to 15thNight
9%19%38%28%11%
720
16th to endNight
12%210%34%29%10%
768
February1st to 15thNight
9%18%39%30%11%
704
16th to endNight
14%29%37%27%7%
632
March1st to 15thNight
7%110%41%31%8%
720
16th to endNight
5%18%38%37%8%
768
April1st to 15thNight
8%29%40%34%5%
719
16th to endNight
5%27%40%35%9%
720
May1st to 15thNight
5%110%34%41%6%
603
16th to endNight
2110%36%44%4
563
June1st to 15thNight
316%38%45%4
540
16th to endNight
1221%65%8%
378
July1st to 15thNight
2112%67%15%
373
16th to endNight
3210%63%20%
653
August1st to 15thNight
1211%64%19%
717
16th to endNight
19%62%25%
764
September1st to 15thNight
2217%57%20%
720
16th to endNight
3325%51%16%
716
October1st to 15thNight
4337%42%11%
720
16th to endNight
5%1429%39%19%
768
November1st to 15thNight
46%34%38%15%
760
16th to endNight
6%18%30%37%14%
780
December1st to 15thNight
9%28%37%31%9%
736
16th to endNight
13%314%33%26%8%
768
Page generated at 2017-12-05 07:19:04. Version ac04

Copyright 2017 A. Danko


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