Rancho Cordova
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rancho Cordova clear sky chart from 2005-11-05 to 2017-09-17.

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
71%
15253
29%
46884
27%
15217
74%
15217
44%
24370

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
62%
716
18%
2461
20%
716
64%
716
30%
1420
January16th to endNight
62%
768
24%
2496
26%
768
65%
768
30%
1501
February1st to 15thNight
59%
697
24%
2270
26%
697
63%
697
29%
1373
February16th to endNight
58%
632
25%
1895
24%
632
63%
632
31%
1154
March1st to 15thNight
58%
720
18%
2058
18%
720
59%
720
29%
1330
March16th to endNight
57%
768
21%
2058
17%
768
60%
768
35%
1281
April1st to 15thNight
58%
719
22%
1799
12%
719
61%
719
37%
1147
April16th to endNight
67%
720
26%
1800
13%
720
70%
720
51%
1007
May1st to 15thNight
73%
578
30%
1658
22%
578
76%
578
58%
790
May16th to endNight
77%
374
28%
1496
32%
374
80%
374
52%
577
June1st to 15thNight
76%
360
28%
1440
33%
360
81%
360
51%
554
June16th to endNight
86%
360
37%
1440
49%
360
89%
360
68%
463
July1st to 15thNight
94%
340
35%
1360
46%
340
96%
340
76%
410
July16th to endNight
92%
506
39%
1535
39%
473
92%
473
74%
575
August1st to 15thNight
90%
575
39%
1648
30%
572
91%
572
73%
688
August16th to endNight
92%
764
45%
1910
29%
764
93%
764
82%
851
September1st to 15thNight
91%
720
42%
1800
30%
720
92%
720
80%
819
September16th to endNight
85%
664
43%
1800
39%
664
88%
664
72%
812
October1st to 15thNight
75%
660
32%
1980
33%
660
79%
660
52%
955
October16th to endNight
75%
704
35%
2112
37%
704
79%
704
50%
1047
November1st to 15thNight
73%
700
29%
2245
31%
700
76%
700
44%
1142
November16th to endNight
66%
720
26%
2415
27%
720
69%
720
37%
1290
December1st to 15thNight
58%
720
20%
2520
20%
720
63%
720
27%
1513
December16th to endNight
52%
768
21%
2688
20%
768
57%
768
24%
1671

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
8%312212335%63%
47892
Night
10%312212335%61%
47069
TransparencyDay
24%38%20%24%19%
47575
Night
25%39%20%23%17%
46885
SeeingDay
9%314%27%30%14%
5880
Night
10%110%36%34%6%
15266

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%5%1332335%8%43%
1474
16th to endDay
19%6%24424335%41%
1728
February1st to 15thDay
19%5%25%414236%42%
1593
16th to endDay
18%5%25%323447%42%
1579
March1st to 15thDay
17%5%25%415%45%6%40%
1901
16th to endDay
15%5%14425%447%43%
2166
April1st to 15thDay
14%7%23424447%44%
2149
16th to endDay
8%312212345%62%
2160
May1st to 15thDay
3212212336%70%
2286
16th to endDay
5%213312346%64%
2615
June1st to 15thDay
4212312246%68%
2520
16th to endDay
11112384%
2520
July1st to 15thDay
1111387%
2520
16th to endDay
111122384%
2524
August1st to 15thDay
111112285%
2301
16th to endDay
1112385%
2292
September1st to 15thDay
11122483%
2160
16th to endDay
31211123477%
1864
October1st to 15thDay
421223346%68%
1650
16th to endDay
8%31331333463%
1760
November1st to 15thDay
9%31222336%8%54%
1612
16th to endDay
14%324323447%49%
1542
December1st to 15thDay
19%7%15%6%33325%40%
1440
16th to endDay
22%6%2332345%6%39%
1536
January1st to 15thNight
16%414313347%48%
2461
16th to endNight
16%5%23324435%47%
2496
February1st to 15thNight
18%5%13424347%45%
2259
16th to endNight
18%5%23322346%47%
1895
March1st to 15thNight
17%5%23424446%44%
2058
16th to endNight
16%414324437%48%
2058
April1st to 15thNight
11%5%34424447%47%
1799
16th to endNight
8%21322346%63%
1800
May1st to 15thNight
431212236%71%
1658
16th to endNight
5%1221226%7%67%
1496
June1st to 15thNight
321221213473%
1440
16th to endNight
1111112384%
1440
July1st to 15thNight
1112287%
1440
16th to endNight
111112384%
1642
August1st to 15thNight
121122382%
1657
16th to endNight
113286%
1910
September1st to 15thNight
111112385%
1800
16th to endNight
111112325%79%
1800
October1st to 15thNight
6%212312245%67%
1980
16th to endNight
5%213313336%65%
2112
November1st to 15thNight
9%312212347%59%
2245
16th to endNight
12%313322246%56%
2415
December1st to 15thNight
19%424323335%47%
2520
16th to endNight
23%414313336%43%
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
40%5%12%17%20%3
1474
16th to endDay
46%47%17%14%9%
1728
February1st to 15thDay
44%310%22%14%4
1593
16th to endDay
42%312%26%12%2
1579
March1st to 15thDay
42%412%20%15%4
1901
16th to endDay
40%5%13%19%16%3
2166
April1st to 15thDay
39%410%25%14%4
2149
16th to endDay
23%414%25%26%6%
2160
May1st to 15thDay
16%38%29%31%10%
2286
16th to endDay
21%312%28%25%8%
2619
June1st to 15thDay
18%310%23%24%19%
2520
16th to endDay
7%1315%38%33%
2520
July1st to 15thDay
6%1110%26%54%
2371
16th to endDay
7%1211%23%52%
2368
August1st to 15thDay
7%1112%30%46%
2285
16th to endDay
6%1113%37%39%
2292
September1st to 15thDay
7%1214%35%38%
2160
16th to endDay
12%2421%34%24%
1864
October1st to 15thDay
16%38%23%28%18%
1650
16th to endDay
26%28%23%26%12%
1760
November1st to 15thDay
26%413%30%18%5%
1612
16th to endDay
37%5%10%24%17%4
1542
December1st to 15thDay
49%310%18%14%3
1440
16th to endDay
44%6%10%18%16%4
1536
January1st to 15thNight
36%313%21%17%7%
2461
16th to endNight
38%311%16%16%14%
2496
February1st to 15thNight
39%310%23%17%7%
2270
16th to endNight
37%411%24%18%3
1895
March1st to 15thNight
40%411%19%17%6%
2058
16th to endNight
35%413%20%19%7%
2058
April1st to 15thNight
35%413%23%17%6%
1799
16th to endNight
22%313%23%26%9%
1800
May1st to 15thNight
16%39%26%30%14%
1659
16th to endNight
15%216%34%20%10%
1496
June1st to 15thNight
14%311%25%24%19%
1440
16th to endNight
8%1314%34%37%
1440
July1st to 15thNight
5%118%28%53%
1360
16th to endNight
8%1210%24%52%
1535
August1st to 15thNight
9%114%27%46%
1648
16th to endNight
5%1111%37%41%
1910
September1st to 15thNight
6%2312%35%39%
1800
16th to endNight
10%2420%34%27%
1800
October1st to 15thNight
19%36%23%26%20%
1980
16th to endNight
21%37%24%25%18%
2112
November1st to 15thNight
24%313%26%21%9%
2245
16th to endNight
30%38%25%24%7%
2415
December1st to 15thNight
39%311%19%18%6%
2520
16th to endNight
42%5%10%17%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
29%7%10%26%15%9%
102
16th to endDay
21%215%25%19%15%
256
February1st to 15thDay
20%5%13%20%26%13%
239
16th to endDay
22%5%18%21%19%11%
238
March1st to 15thDay
20%7%19%21%19%12%
270
16th to endDay
18%8%17%24%21%9%
288
April1st to 15thDay
18%8%21%23%18%9%
269
16th to endDay
8%9%22%26%21%11%
270
May1st to 15thDay
5%5%20%29%26%12%
288
16th to endDay
7%417%23%30%16%
330
June1st to 15thDay
6%422%29%27%9%
315
16th to endDay
111%28%41%15%
315
July1st to 15thDay
5%30%46%15%
305
16th to endDay
8%31%40%18%
327
August1st to 15thDay
212%35%38%11%
315
16th to endDay
7%28%41%20%
332
September1st to 15thDay
7%33%39%17%
315
16th to endDay
315%26%31%23%
260
October1st to 15thDay
4316%31%24%19%
255
16th to endDay
11%411%26%30%15%
272
November1st to 15thDay
11%26%22%37%19%
118
16th to endDay
14%5%10%36%32%1
77
December1st to 15thDay
30%8%10%33%18%
60
16th to endDay
15%412%26%29%10%
64
January1st to 15thNight
16%29%34%29%8%
720
16th to endNight
18%28%34%26%9%
768
February1st to 15thNight
19%39%33%27%5%
704
16th to endNight
20%112%37%21%5%
632
March1st to 15thNight
18%312%32%29%4
720
16th to endNight
17%215%35%26%2
768
April1st to 15thNight
11%416%37%26%2
719
16th to endNight
8%215%36%30%5%
720
May1st to 15thNight
5%116%40%31%5%
579
16th to endNight
5%111%39%40%2
375
June1st to 15thNight
413%42%37%1
360
16th to endNight
17%42%46%1
360
July1st to 15thNight
242%52%1
340
16th to endNight
234%54%7%
506
August1st to 15thNight
2439%49%5%
575
16th to endNight
338%51%5%
764
September1st to 15thNight
1432%54%7%
720
16th to endNight
29%34%43%10%
664
October1st to 15thNight
6%29%38%33%9%
660
16th to endNight
6%19%34%36%11%
704
November1st to 15thNight
10%18%37%34%7%
700
16th to endNight
12%111%38%28%7%
720
December1st to 15thNight
19%310%35%23%7%
720
16th to endNight
24%213%32%23%2
768
Page generated at 2017-09-18 05:38:28. Version ac04

Copyright 2017 A. Danko


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