Cameron Park Rotary Club Community Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cameron Park Rotary Club Community Observatory 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
70%
15086
28%
46507
26%
15052
72%
15052
40%
25122

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
19%
2482
21%
716
65%
716
29%
1441
January16th to endNight
55%
768
24%
2496
22%
768
61%
768
27%
1537
February1st to 15thNight
58%
696
22%
2254
23%
696
62%
696
27%
1401
February16th to endNight
57%
632
24%
1895
24%
632
60%
632
28%
1208
March1st to 15thNight
53%
720
16%
2073
16%
720
55%
720
25%
1395
March16th to endNight
56%
768
19%
2047
15%
768
59%
768
28%
1378
April1st to 15thNight
57%
719
19%
1799
12%
719
59%
719
29%
1240
April16th to endNight
66%
720
24%
1800
13%
720
68%
720
44%
1077
May1st to 15thNight
72%
572
28%
1652
22%
572
73%
572
52%
808
May16th to endNight
77%
374
26%
1496
32%
374
79%
374
41%
671
June1st to 15thNight
78%
360
27%
1440
35%
360
82%
360
45%
607
June16th to endNight
90%
360
36%
1440
51%
360
91%
360
65%
485
July1st to 15thNight
95%
340
34%
1360
47%
340
96%
340
73%
423
July16th to endNight
92%
484
39%
1515
41%
453
93%
453
71%
565
August1st to 15thNight
92%
569
38%
1618
29%
566
92%
566
73%
691
August16th to endNight
93%
700
42%
1750
27%
700
93%
700
83%
776
September1st to 15thNight
93%
660
45%
1650
32%
660
93%
660
82%
738
September16th to endNight
86%
656
42%
1774
38%
656
88%
656
69%
819
October1st to 15thNight
76%
660
31%
1980
33%
660
79%
660
49%
983
October16th to endNight
74%
704
34%
2112
36%
704
78%
704
49%
1069
November1st to 15thNight
71%
700
27%
2260
30%
700
74%
700
40%
1196
November16th to endNight
63%
720
25%
2406
26%
720
67%
720
34%
1326
December1st to 15thNight
57%
720
21%
2520
21%
720
61%
720
25%
1540
December16th to endNight
47%
768
22%
2688
20%
768
52%
768
21%
1748

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
10%31221233462%
47466
Night
12%312212335%59%
46698
TransparencyDay
25%38%18%24%19%
47147
Night
27%38%18%22%18%
46516
SeeingDay
12%8%25%33%15%4
5707
Night
13%29%33%33%8%
15100

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
19%5%12223235%49%
1455
16th to endDay
22%7%2332233444%
1728
February1st to 15thDay
20%5%23323235%46%
1602
16th to endDay
24%6%33311445%40%
1579
March1st to 15thDay
20%6%2432435%6%39%
1884
16th to endDay
18%5%24325%446%41%
2176
April1st to 15thDay
18%6%2432345%6%42%
2149
16th to endDay
12%31321235%6%58%
2160
May1st to 15thDay
5%212212336%67%
2294
16th to endDay
7%313423346%60%
2615
June1st to 15thDay
5%313312236%66%
2520
16th to endDay
1111112284%
2520
July1st to 15thDay
11113285%
2520
16th to endDay
1111122284%
2547
August1st to 15thDay
1111112286%
2246
16th to endDay
1112287%
2100
September1st to 15thDay
111122284%
1980
16th to endDay
311111122379%
1853
October1st to 15thDay
6%212213446%64%
1650
16th to endDay
8%42332333461%
1760
November1st to 15thDay
10%31232435%6%54%
1598
16th to endDay
15%423314335%51%
1554
December1st to 15thDay
20%5%24413335%44%
1440
16th to endDay
25%6%23313346%40%
1536
January1st to 15thNight
18%314323348%47%
2482
16th to endNight
19%5%1342334448%
2496
February1st to 15thNight
19%5%1332335%7%43%
2251
16th to endNight
21%5%24313345%45%
1895
March1st to 15thNight
22%5%25%323345%41%
2073
16th to endNight
20%5%23313436%46%
2047
April1st to 15thNight
14%5%25%6%35%437%42%
1799
16th to endNight
10%412313346%58%
1800
May1st to 15thNight
7%212112336%67%
1652
16th to endNight
7%212212247%63%
1496
June1st to 15thNight
4212212245%69%
1440
16th to endNight
21111112283%
1440
July1st to 15thNight
11122285%
1440
16th to endNight
111122283%
1620
August1st to 15thNight
11121122380%
1627
16th to endNight
11112385%
1750
September1st to 15thNight
11112386%
1650
16th to endNight
21121122478%
1774
October1st to 15thNight
7%22212345%66%
1980
16th to endNight
7%313212346%64%
2112
November1st to 15thNight
11%312212346%58%
2260
16th to endNight
14%312323346%53%
2406
December1st to 15thNight
21%423423336%45%
2520
16th to endNight
26%6%23312335%41%
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
38%310%20%18%8%
1455
16th to endDay
43%47%15%16%12%
1728
February1st to 15thDay
41%310%18%19%6%
1602
16th to endDay
45%310%24%12%2
1579
March1st to 15thDay
45%5%11%16%15%5%
1884
16th to endDay
43%5%14%17%15%3
2176
April1st to 15thDay
41%6%12%22%13%3
2149
16th to endDay
27%5%13%24%23%5%
2160
May1st to 15thDay
19%39%29%29%7%
2294
16th to endDay
25%413%27%20%7%
2619
June1st to 15thDay
20%310%22%22%20%
2520
16th to endDay
8%1315%35%35%
2520
July1st to 15thDay
6%137%26%54%
2371
16th to endDay
8%139%24%52%
2389
August1st to 15thDay
7%1210%29%49%
2230
16th to endDay
6%1210%38%41%
2100
September1st to 15thDay
7%1410%34%42%
1980
16th to endDay
12%25%21%34%24%
1853
October1st to 15thDay
19%46%26%26%16%
1650
16th to endDay
26%46%22%24%15%
1760
November1st to 15thDay
29%313%22%21%8%
1598
16th to endDay
35%5%8%20%24%5%
1554
December1st to 15thDay
44%39%17%20%3
1440
16th to endDay
46%49%15%17%7%
1536
January1st to 15thNight
36%411%19%18%10%
2482
16th to endNight
40%47%13%19%15%
2496
February1st to 15thNight
40%49%18%18%9%
2262
16th to endNight
41%49%24%16%4
1895
March1st to 15thNight
45%310%17%16%5%
2073
16th to endNight
40%7%9%18%18%6%
2047
April1st to 15thNight
42%6%12%20%13%5%
1799
16th to endNight
26%6%13%24%21%7%
1800
May1st to 15thNight
19%312%23%28%11%
1653
16th to endNight
20%5%14%29%20%8%
1496
June1st to 15thNight
17%5%10%23%23%19%
1440
16th to endNight
10%1414%33%36%
1440
July1st to 15thNight
5%237%26%54%
1360
16th to endNight
8%129%22%54%
1515
August1st to 15thNight
9%1214%25%46%
1618
16th to endNight
6%211%33%44%
1750
September1st to 15thNight
6%149%39%39%
1650
16th to endNight
11%25%18%34%26%
1774
October1st to 15thNight
21%36%22%26%18%
1980
16th to endNight
21%36%22%27%17%
2112
November1st to 15thNight
27%412%22%20%11%
2260
16th to endNight
32%39%22%23%9%
2406
December1st to 15thNight
41%310%17%18%7%
2520
16th to endNight
46%47%14%18%8%
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
43%6%16%22%7%3
83
16th to endDay
30%321%26%14%4
256
February1st to 15thDay
25%5%23%30%14%
241
16th to endDay
29%10%21%26%10%
238
March1st to 15thDay
26%15%21%20%12%3
270
16th to endDay
21%14%30%19%12%
288
April1st to 15thDay
26%14%29%19%7%1
269
16th to endDay
15%18%28%25%10%2
270
May1st to 15thDay
9%12%35%27%10%4
288
16th to endDay
10%13%20%29%18%7%
330
June1st to 15thDay
8%11%28%35%9%5%
315
16th to endDay
15%29%37%18%7%
315
July1st to 15thDay
17%53%20%8%
305
16th to endDay
127%45%17%7%
327
August1st to 15thDay
3226%43%16%7%
300
16th to endDay
126%47%14%9%
268
September1st to 15thDay
2228%42%19%4
255
16th to endDay
38%26%38%20%3
255
October1st to 15thDay
6%9%30%34%16%3
255
16th to endDay
16%5%23%31%22%
272
November1st to 15thDay
11%315%22%36%10%
104
16th to endDay
16%6%25%35%16%
79
December1st to 15thDay
35%6%23%25%6%3
60
16th to endDay
20%415%31%17%10%
64
January1st to 15thNight
18%210%33%26%8%
720
16th to endNight
21%213%30%22%9%
768
February1st to 15thNight
22%39%34%25%5%
704
16th to endNight
22%411%34%21%5%
632
March1st to 15thNight
23%311%30%24%6%
720
16th to endNight
22%313%31%25%4
768
April1st to 15thNight
17%413%36%25%3
719
16th to endNight
12%312%33%28%9%
720
May1st to 15thNight
9%112%39%30%6%
573
16th to endNight
7%27%33%41%8%
375
June1st to 15thNight
5%8%36%42%6%
360
16th to endNight
3136%52%5%
360
July1st to 15thNight
30%61%7%
340
16th to endNight
2124%59%13%
484
August1st to 15thNight
2233%52%9%
569
16th to endNight
1231%56%8%
700
September1st to 15thNight
1327%56%11%
660
16th to endNight
316%34%38%16%
656
October1st to 15thNight
9%18%35%33%11%
660
16th to endNight
9%110%32%32%13%
704
November1st to 15thNight
12%8%35%30%12%
700
16th to endNight
15%212%36%23%9%
720
December1st to 15thNight
23%29%37%19%7%
720
16th to endNight
29%314%28%20%4
768
Page generated at 2017-08-13 11:16:34. Version ac04

Copyright 2017 A. Danko


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