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 2017-04-01.

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
77%
15421
32%
45106
29%
15375
80%
15375
48%
23290

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
70%
663
27%
1659
19%
663
72%
663
43%
1018
April16th to endNight
77%
660
27%
1650
17%
660
78%
660
50%
928
May1st to 15thNight
76%
552
29%
1542
20%
552
77%
552
45%
858
May16th to endNight
80%
513
24%
1541
20%
513
80%
513
42%
848
June1st to 15thNight
84%
495
25%
1485
22%
495
84%
495
47%
783
June16th to endNight
91%
347
33%
1337
39%
347
92%
347
59%
495
July1st to 15thNight
88%
340
32%
1270
35%
340
88%
340
51%
524
July16th to endNight
88%
603
28%
1541
21%
563
88%
563
55%
798
August1st to 15thNight
91%
657
36%
1640
23%
653
91%
653
66%
812
August16th to endNight
92%
700
38%
1750
26%
700
92%
700
72%
838
September1st to 15thNight
88%
660
38%
1691
31%
660
88%
660
64%
838
September16th to endNight
89%
656
42%
1815
42%
656
89%
656
70%
800
October1st to 15thNight
83%
660
36%
1815
35%
660
84%
660
56%
905
October16th to endNight
79%
704
38%
2133
40%
704
81%
704
50%
1048
November1st to 15thNight
81%
700
35%
2275
38%
700
83%
700
53%
1026
November16th to endNight
75%
720
34%
2340
37%
720
78%
720
45%
1160
December1st to 15thNight
69%
720
32%
2340
32%
720
74%
720
37%
1249
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%64%
45972
Night
5%313323346%62%
45311
TransparencyDay
20%37%17%26%25%
45668
Night
22%47%16%23%26%
45116
SeeingDay
6%5%20%39%22%5%
5287
Night
6%17%31%41%12%
15433

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%413424446%56%
1974
16th to endDay
5%313222236%66%
1980
May1st to 15thDay
4423213338%62%
2075
16th to endDay
35%13212348%62%
2221
June1st to 15thDay
45%13212247%62%
2145
16th to endDay
11111223380%
2288
July1st to 15thDay
1212223346%68%
2272
16th to endDay
2112213346%69%
2200
August1st to 15thDay
1212335%78%
1980
16th to endDay
2213235%77%
2100
September1st to 15thDay
111211235%78%
1937
16th to endDay
1112233378%
1815
October1st to 15thDay
5%21332335%5%63%
1815
16th to endDay
431231233467%
1737
November1st to 15thDay
421231234469%
1584
16th to endDay
5%31331245%7%61%
1620
December1st to 15thDay
7%31342345%9%53%
1620
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%434323347%55%
1659
16th to endNight
4312323336%63%
1650
May1st to 15thNight
241442335%9%57%
1542
16th to endNight
141332335%10%58%
1540
June1st to 15thNight
2322315%6%6%7%58%
1485
16th to endNight
12212347%71%
1337
July1st to 15thNight
121332336%8%62%
1353
16th to endNight
22133235%6%8%61%
1656
August1st to 15thNight
212213337%71%
1650
16th to endNight
11212346%75%
1750
September1st to 15thNight
1212322246%71%
1691
16th to endNight
121111122479%
1815
October1st to 15thNight
3213313236%68%
1815
16th to endNight
4213223345%65%
2133
November1st to 15thNight
2213312235%69%
2275
16th to endNight
5%313423346%61%
2340
December1st to 15thNight
7%41342345%6%55%
2340
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
29%29%25%21%11%
1974
16th to endDay
20%39%22%26%17%
1980
May1st to 15thDay
22%48%20%26%17%
2075
16th to endDay
21%410%28%28%8%
2224
June1st to 15thDay
20%46%19%31%18%
2145
16th to endDay
9%2310%29%43%
2288
July1st to 15thDay
13%47%11%25%37%
2126
16th to endDay
14%48%22%28%21%
2052
August1st to 15thDay
8%2414%37%32%
1966
16th to endDay
10%2414%35%33%
2100
September1st to 15thDay
10%2410%34%37%
1937
16th to endDay
10%15%13%34%35%
1815
October1st to 15thDay
21%3420%25%25%
1815
16th to endDay
21%3412%20%37%
1737
November1st to 15thDay
19%27%16%21%32%
1584
16th to endDay
22%46%13%21%31%
1620
December1st to 15thDay
27%310%17%17%24%
1620
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
30%49%21%19%14%
1659
16th to endNight
22%5%10%21%21%18%
1650
May1st to 15thNight
23%6%10%19%20%18%
1543
16th to endNight
24%7%11%24%22%10%
1541
June1st to 15thNight
18%8%13%15%26%16%
1485
16th to endNight
8%6%6%17%25%36%
1337
July1st to 15thNight
14%5%5%16%24%32%
1270
16th to endNight
16%6%10%21%25%19%
1541
August1st to 15thNight
11%5%5%17%34%25%
1640
16th to endNight
9%45%12%31%36%
1750
September1st to 15thNight
13%37%9%30%35%
1691
16th to endNight
10%1412%32%37%
1815
October1st to 15thNight
18%37%16%31%23%
1815
16th to endNight
20%3411%22%37%
2133
November1st to 15thNight
18%16%15%20%37%
2275
16th to endNight
23%36%14%17%33%
2340
December1st to 15thNight
28%48%13%19%24%
2340
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
8%15%36%28%7%3
211
16th to endDay
413%39%34%6%2
210
May1st to 15thDay
6%10%31%36%13%1
228
16th to endDay
6%8%28%37%15%3
266
June1st to 15thDay
7%220%47%20%2
255
16th to endDay
310%45%32%9%
255
July1st to 15thDay
28%42%38%6%
245
16th to endDay
2342%38%12%
271
August1st to 15thDay
8%49%34%5%
255
16th to endDay
1243%39%12%
268
September1st to 15thDay
1110%55%25%6%
255
16th to endDay
1116%48%24%7%
255
October1st to 15thDay
35%24%41%20%4
255
16th to endDay
7%318%36%26%8%
234
November1st to 15thDay
1410%30%27%26%
90
16th to endDay
6%7%18%35%25%5%
90
December1st to 15thDay
12%213%24%42%5%
90
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%33%4
663
16th to endNight
5%28%39%35%9%
660
May1st to 15thNight
5%110%35%41%5%
553
16th to endNight
2111%34%44%5%
515
June1st to 15thNight
217%40%44%4
495
16th to endNight
1222%65%7%
347
July1st to 15thNight
2113%67%14%
340
16th to endNight
3210%64%19%
603
August1st to 15thNight
1212%64%19%
657
16th to endNight
19%62%25%
700
September1st to 15thNight
1215%58%21%
660
16th to endNight
2325%52%16%
656
October1st to 15thNight
4438%40%11%
660
16th to endNight
5%1428%39%19%
704
November1st to 15thNight
46%32%39%16%
700
16th to endNight
6%28%30%36%15%
720
December1st to 15thNight
9%28%37%31%9%
720
16th to endNight
13%314%33%26%8%
768
Page generated at 2017-04-02 04:39:10. Version ac04

Copyright 2017 A. Danko


OCA Silverado Clear Sky Chart | Charts Home