Chico Community Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chico Community Observatory clear sky chart from 2005-11-05 to 2018-02-22.

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
64%
15772
28%
48925
24%
15733
69%
15733
41%
26032

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
58%
778
19%
2680
19%
776
62%
776
27%
1607
January16th to endNight
55%
832
25%
2704
24%
832
59%
832
27%
1671
February1st to 15thNight
56%
758
26%
2483
24%
757
62%
757
29%
1481
February16th to endNight
51%
660
25%
1999
22%
660
57%
660
31%
1223
March1st to 15thNight
50%
720
15%
2037
13%
720
53%
720
26%
1363
March16th to endNight
46%
768
20%
2073
14%
768
51%
768
30%
1343
April1st to 15thNight
45%
719
22%
1799
9%
719
51%
719
33%
1165
April16th to endNight
59%
720
26%
1800
12%
720
64%
720
46%
1031
May1st to 15thNight
60%
512
28%
1592
20%
512
66%
512
52%
759
May16th to endNight
65%
375
25%
1496
27%
374
72%
374
38%
681
June1st to 15thNight
65%
360
25%
1440
27%
360
74%
360
44%
608
June16th to endNight
79%
360
34%
1440
43%
360
85%
360
63%
492
July1st to 15thNight
89%
340
34%
1360
44%
340
92%
340
76%
415
July16th to endNight
90%
497
41%
1527
40%
465
93%
465
84%
519
August1st to 15thNight
89%
538
40%
1611
32%
535
91%
535
74%
643
August16th to endNight
91%
759
46%
1905
30%
759
93%
759
85%
841
September1st to 15thNight
89%
720
43%
1800
29%
720
91%
720
81%
798
September16th to endNight
81%
716
44%
1958
37%
716
85%
716
73%
850
October1st to 15thNight
67%
720
32%
2160
29%
720
75%
720
54%
1014
October16th to endNight
72%
768
36%
2304
36%
768
77%
768
49%
1149
November1st to 15thNight
64%
760
24%
2434
23%
760
69%
760
35%
1358
November16th to endNight
57%
780
22%
2681
23%
780
61%
780
29%
1556
December1st to 15thNight
56%
780
22%
2730
21%
780
61%
780
26%
1631
December16th to endNight
46%
832
22%
2912
19%
832
54%
832
22%
1834

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%212212235%63%
49326
Night
12%312212345%60%
49108
TransparencyDay
23%38%18%24%20%
49008
Night
26%48%18%22%19%
48926
SeeingDay
11%6%18%27%26%9%
6327
Night
12%314%34%30%4
15781

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
20%41441325%6%43%
1586
16th to endDay
22%413323237%44%
1872
February1st to 15thDay
20%412223335%49%
1711
16th to endDay
21%413213337%45%
1619
March1st to 15thDay
23%413324347%41%
1920
16th to endDay
20%42332335%7%43%
2151
April1st to 15thDay
17%42432345%7%45%
2149
16th to endDay
8%322313336%61%
2160
May1st to 15thDay
5%212212237%67%
2352
16th to endDay
6%212323337%62%
2615
June1st to 15thDay
5%312313336%66%
2520
16th to endDay
21122382%
2520
July1st to 15thDay
1112386%
2520
16th to endDay
11111288%
2534
August1st to 15thDay
11112286%
2340
16th to endDay
1111389%
2296
September1st to 15thDay
11112484%
2160
16th to endDay
311111235%77%
2000
October1st to 15thDay
5%2122233470%
1800
16th to endDay
11%33212336%60%
1920
November1st to 15thDay
15%21332345%5%51%
1752
16th to endDay
19%413213345%48%
1605
December1st to 15thDay
22%5%13213335%47%
1560
16th to endDay
24%5%23322336%41%
1664
January1st to 15thNight
17%5%23313347%46%
2680
16th to endNight
20%423323235%47%
2704
February1st to 15thNight
18%413323447%47%
2471
16th to endNight
20%31222345%5%46%
1999
March1st to 15thNight
21%424324348%39%
2037
16th to endNight
18%425%322347%45%
2073
April1st to 15thNight
13%425%42435%9%45%
1799
16th to endNight
8%323313346%61%
1800
May1st to 15thNight
6%21221225%6%66%
1592
16th to endNight
431332345%7%61%
1496
June1st to 15thNight
4213212337%67%
1440
16th to endNight
211213380%
1440
July1st to 15thNight
111111286%
1440
16th to endNight
11289%
1633
August1st to 15thNight
1111112384%
1620
16th to endNight
112387%
1905
September1st to 15thNight
11112385%
1800
16th to endNight
211123479%
1958
October1st to 15thNight
6%1121223371%
2160
16th to endNight
8%212212336%65%
2304
November1st to 15thNight
13%322235%5%6%53%
2434
16th to endNight
16%413313346%50%
2681
December1st to 15thNight
23%313222346%47%
2730
16th to endNight
25%423213435%43%
2912

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%411%18%16%6%
1586
16th to endDay
41%5%8%14%16%12%
1872
February1st to 15thDay
35%5%12%17%23%6%
1711
16th to endDay
38%410%29%15%2
1619
March1st to 15thDay
42%5%12%18%12%7%
1920
16th to endDay
38%6%14%18%17%4
2151
April1st to 15thDay
37%5%11%20%20%4
2149
16th to endDay
24%5%11%25%24%9%
2160
May1st to 15thDay
17%310%23%32%12%
2352
16th to endDay
20%5%14%26%23%10%
2619
June1st to 15thDay
18%5%11%20%22%22%
2520
16th to endDay
7%15%15%34%35%
2520
July1st to 15thDay
41310%29%50%
2371
16th to endDay
5%1210%23%56%
2377
August1st to 15thDay
5%1311%32%44%
2324
16th to endDay
3214%34%43%
2296
September1st to 15thDay
6%1412%32%41%
2160
16th to endDay
10%26%22%33%24%
2000
October1st to 15thDay
17%36%21%26%24%
1800
16th to endDay
24%48%22%25%15%
1920
November1st to 15thDay
32%6%11%26%14%8%
1752
16th to endDay
36%5%10%20%18%8%
1605
December1st to 15thDay
41%39%16%21%8%
1560
16th to endDay
45%47%18%17%6%
1664
January1st to 15thNight
37%6%12%19%16%8%
2680
16th to endNight
40%48%14%17%14%
2704
February1st to 15thNight
36%48%19%19%11%
2483
16th to endNight
36%5%11%23%19%4
1999
March1st to 15thNight
42%6%12%15%15%7%
2037
16th to endNight
38%6%10%20%17%6%
2073
April1st to 15thNight
34%6%13%21%16%7%
1799
16th to endNight
23%5%11%22%27%10%
1800
May1st to 15thNight
18%410%21%30%15%
1593
16th to endNight
20%6%13%25%23%10%
1496
June1st to 15thNight
17%5%12%21%22%20%
1440
16th to endNight
10%25%14%30%36%
1440
July1st to 15thNight
6%211%24%53%
1360
16th to endNight
4311%19%60%
1527
August1st to 15thNight
8%1213%30%42%
1611
16th to endNight
41213%33%44%
1905
September1st to 15thNight
6%1410%33%45%
1800
16th to endNight
8%25%17%36%29%
1958
October1st to 15thNight
16%36%17%28%26%
2160
16th to endNight
20%49%21%23%21%
2304
November1st to 15thNight
28%7%13%25%16%9%
2434
16th to endNight
34%6%8%21%20%9%
2681
December1st to 15thNight
39%49%15%20%11%
2730
16th to endNight
43%48%14%20%7%
2912

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
33%6%16%27%12%4
124
16th to endDay
23%7%21%21%17%8%
304
February1st to 15thDay
22%420%26%18%6%
281
16th to endDay
21%11%20%25%15%6%
259
March1st to 15thDay
27%10%23%18%15%5%
270
16th to endDay
22%15%21%21%14%3
288
April1st to 15thDay
18%13%26%24%12%4
269
16th to endDay
11%18%22%28%15%3
270
May1st to 15thDay
6%7%34%25%22%3
288
16th to endDay
6%7%16%25%32%12%
330
June1st to 15thDay
6%8%20%32%25%6%
315
16th to endDay
2315%35%31%12%
315
July1st to 15thDay
118%36%40%11%
305
16th to endDay
10%36%40%12%
327
August1st to 15thDay
115%29%41%11%
315
16th to endDay
11%27%42%17%
332
September1st to 15thDay
213%29%35%18%
315
16th to endDay
45%20%29%28%13%
315
October1st to 15thDay
6%9%25%26%20%12%
315
16th to endDay
14%414%28%26%10%
336
November1st to 15thDay
25%413%19%30%7%
168
16th to endDay
18%424%32%20%2
100
December1st to 15thDay
31%320%17%15%12%
90
16th to endDay
12%217%30%33%4
96
January1st to 15thNight
19%311%38%24%2
780
16th to endNight
20%413%35%21%3
832
February1st to 15thNight
18%5%13%36%23%1
764
16th to endNight
20%420%31%20%2
660
March1st to 15thNight
20%7%15%30%23%3
720
16th to endNight
18%6%22%29%21%
768
April1st to 15thNight
12%8%26%30%19%2
719
16th to endNight
9%6%20%35%22%5%
720
May1st to 15thNight
6%425%34%28%1
513
16th to endNight
46%18%37%30%2
375
June1st to 15thNight
5%220%41%28%1
360
16th to endNight
2115%42%36%2
360
July1st to 15thNight
16%42%45%3
340
16th to endNight
7%34%53%4
497
August1st to 15thNight
16%34%52%4
538
16th to endNight
5%34%54%4
759
September1st to 15thNight
116%30%53%7%
720
16th to endNight
3111%32%39%11%
716
October1st to 15thNight
7%318%31%32%6%
720
16th to endNight
9%310%33%35%8%
768
November1st to 15thNight
13%314%33%31%3
760
16th to endNight
15%315%38%22%2
780
December1st to 15thNight
22%312%34%22%4
780
16th to endNight
24%417%31%20%1
832
Page generated at 2018-02-23 08:21:41. Version ac04

Copyright 2018 A. Danko


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