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 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
64%
14996
28%
46517
24%
14957
69%
14957
41%
24783

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
59%
718
19%
2473
19%
716
63%
716
28%
1453
January16th to endNight
55%
768
26%
2496
26%
768
60%
768
28%
1521
February1st to 15thNight
54%
698
24%
2288
22%
697
59%
697
26%
1410
February16th to endNight
50%
632
24%
1914
21%
632
57%
632
30%
1181
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
88%
526
40%
1575
32%
523
91%
523
74%
629
August16th to endNight
91%
695
44%
1745
28%
695
92%
695
84%
774
September1st to 15thNight
89%
660
45%
1650
30%
660
91%
660
83%
724
September16th to endNight
80%
656
42%
1795
35%
656
85%
656
72%
781
October1st to 15thNight
68%
660
32%
1980
30%
660
75%
660
52%
953
October16th to endNight
70%
704
34%
2112
34%
704
75%
704
48%
1072
November1st to 15thNight
65%
700
26%
2242
24%
700
71%
700
37%
1223
November16th to endNight
58%
720
22%
2475
23%
720
62%
720
30%
1418
December1st to 15thNight
53%
720
20%
2520
19%
720
59%
720
23%
1558
December16th to endNight
45%
768
21%
2688
18%
768
53%
768
22%
1710

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%64%
47458
Night
12%312212335%60%
46700
TransparencyDay
23%38%18%24%20%
47140
Night
26%48%18%22%19%
46518
SeeingDay
11%6%18%27%26%9%
5711
Night
12%315%34%30%3
15005

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%31431325%6%45%
1463
16th to endDay
22%413323236%46%
1728
February1st to 15thDay
22%412223335%47%
1576
16th to endDay
22%413213338%44%
1559
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
111112286%
2291
16th to endDay
11289%
2104
September1st to 15thDay
11111385%
1980
16th to endDay
3111112478%
1834
October1st to 15thDay
6%3222233468%
1650
16th to endDay
12%33212336%59%
1760
November1st to 15thDay
13%21332345%5%52%
1614
16th to endDay
19%413213345%50%
1482
December1st to 15thDay
23%5%1321433445%
1440
16th to endDay
26%5%23222335%41%
1536
January1st to 15thNight
17%5%23213347%48%
2473
16th to endNight
20%42332223449%
2496
February1st to 15thNight
20%5%23323447%43%
2276
16th to endNight
21%322223445%46%
1914
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
11111112384%
1584
16th to endNight
1112386%
1745
September1st to 15thNight
11111387%
1650
16th to endNight
31111123480%
1795
October1st to 15thNight
7%21121234369%
1980
16th to endNight
9%212212346%63%
2112
November1st to 15thNight
12%222235%5%7%54%
2242
16th to endNight
16%413313346%51%
2475
December1st to 15thNight
25%313222346%44%
2520
16th to endNight
26%423213335%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%411%19%17%7%
1463
16th to endDay
40%5%8%14%17%13%
1728
February1st to 15thDay
37%5%13%16%21%5%
1576
16th to endDay
39%410%28%14%2
1559
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
6%1310%32%45%
2275
16th to endDay
3214%34%43%
2104
September1st to 15thDay
6%1311%33%43%
1980
16th to endDay
10%16%22%32%25%
1834
October1st to 15thDay
18%47%22%27%19%
1650
16th to endDay
26%48%22%25%13%
1760
November1st to 15thDay
30%7%11%25%15%8%
1614
16th to endDay
35%5%9%20%19%8%
1482
December1st to 15thDay
43%39%17%20%5%
1440
16th to endDay
47%47%16%17%6%
1536
January1st to 15thNight
35%6%12%19%17%8%
2473
16th to endNight
39%37%15%18%15%
2496
February1st to 15thNight
39%49%19%17%9%
2288
16th to endNight
37%5%11%23%18%4
1914
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%43%
1575
16th to endNight
5%1212%33%44%
1745
September1st to 15thNight
5%138%34%46%
1650
16th to endNight
8%25%16%36%30%
1795
October1st to 15thNight
18%46%19%29%21%
1980
16th to endNight
21%49%22%23%19%
2112
November1st to 15thNight
26%7%13%25%17%9%
2242
16th to endNight
33%6%7%21%20%10%
2475
December1st to 15thNight
41%5%9%15%20%7%
2520
16th to endNight
44%48%14%19%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
34%8%17%27%9%2
91
16th to endDay
23%7%19%21%17%9%
256
February1st to 15thDay
26%5%19%25%19%4
236
16th to endDay
23%11%18%25%14%6%
235
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
1115%29%41%11%
300
16th to endDay
13%31%39%14%
268
September1st to 15thDay
313%25%36%20%
255
16th to endDay
45%16%29%27%15%
255
October1st to 15thDay
7%7%24%27%20%14%
255
16th to endDay
17%5%17%30%22%6%
272
November1st to 15thDay
18%313%18%36%10%
120
16th to endDay
16%428%29%20%
67
December1st to 15thDay
45%128%16%8%
60
16th to endDay
17%120%29%28%3
64
January1st to 15thNight
18%312%40%23%2
720
16th to endNight
21%413%36%21%4
768
February1st to 15thNight
20%5%13%36%23%1
704
16th to endNight
21%5%19%31%20%2
632
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%33%52%4
526
16th to endNight
6%35%52%3
695
September1st to 15thNight
116%30%53%7%
660
16th to endNight
4211%29%40%12%
656
October1st to 15thNight
7%316%31%33%6%
660
16th to endNight
9%311%34%33%7%
704
November1st to 15thNight
12%314%33%32%4
700
16th to endNight
15%416%39%21%3
720
December1st to 15thNight
24%312%35%21%2
720
16th to endNight
25%418%31%19%1
768
Page generated at 2017-08-13 11:16:47. Version ac04

Copyright 2017 A. Danko


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