Cerro Alto Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cerro Alto Campground clear sky chart from 2005-11-05 to 2017-12-02.

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
74%
15941
31%
47830
28%
15903
77%
15903
48%
24154

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
63%
716
24%
2374
24%
716
67%
716
36%
1280
January16th to endNight
63%
768
27%
2496
28%
768
66%
768
33%
1418
February1st to 15thNight
67%
698
29%
2192
30%
696
70%
696
37%
1224
February16th to endNight
60%
632
25%
1895
25%
632
64%
632
34%
1118
March1st to 15thNight
66%
720
23%
2057
22%
720
70%
720
41%
1172
March16th to endNight
64%
768
24%
2051
19%
768
68%
768
40%
1214
April1st to 15thNight
62%
719
28%
1799
18%
719
65%
719
44%
1058
April16th to endNight
63%
720
30%
1800
14%
720
68%
720
54%
968
May1st to 15thNight
75%
719
24%
1799
16%
719
76%
719
56%
966
May16th to endNight
73%
427
30%
1551
27%
427
78%
427
51%
659
June1st to 15thNight
81%
360
32%
1440
37%
360
85%
360
50%
571
June16th to endNight
93%
360
39%
1440
49%
360
94%
360
72%
457
July1st to 15thNight
95%
389
34%
1409
38%
389
96%
389
72%
484
July16th to endNight
91%
564
37%
1593
32%
531
92%
531
64%
682
August1st to 15thNight
92%
657
37%
1731
26%
654
92%
654
73%
779
August16th to endNight
93%
764
42%
1910
27%
764
93%
764
77%
886
September1st to 15thNight
89%
720
43%
1800
33%
720
89%
720
69%
883
September16th to endNight
89%
716
45%
1921
41%
716
91%
716
76%
830
October1st to 15thNight
77%
720
31%
2160
34%
720
80%
720
54%
1035
October16th to endNight
78%
768
38%
2304
41%
768
81%
768
52%
1128
November1st to 15thNight
76%
760
33%
2388
34%
760
80%
760
50%
1148
November16th to endNight
73%
780
31%
2535
31%
780
77%
780
44%
1257
December1st to 15thNight
65%
728
28%
2497
28%
728
70%
728
32%
1404
December16th to endNight
54%
768
25%
2688
23%
768
63%
768
30%
1533

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
5%312212336%66%
48611
Night
5%313323346%63%
48021
TransparencyDay
20%39%20%27%19%
48299
Night
22%39%20%25%18%
47834
SeeingDay
6%6%19%37%24%5%
6325
Night
6%210%33%37%9%
15953

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%41442445%6%52%
1561
16th to endDay
13%5%23423335%51%
1728
February1st to 15thDay
12%5%24213336%52%
1667
16th to endDay
14%6%3332345%6%45%
1579
March1st to 15thDay
7%5%15%32446%9%48%
1902
16th to endDay
9%423434347%50%
2172
April1st to 15thDay
10%6%24313346%54%
2149
16th to endDay
6%312312346%64%
2160
May1st to 15thDay
3212222346%69%
2151
16th to endDay
3312112237%71%
2557
June1st to 15thDay
1211212346%72%
2520
16th to endDay
11112485%
2520
July1st to 15thDay
11121236%77%
2464
16th to endDay
111112336%75%
2468
August1st to 15thDay
11112236%78%
2219
16th to endDay
111211226%79%
2292
September1st to 15thDay
111112125%81%
2160
16th to endDay
12111235%77%
2035
October1st to 15thDay
4213212235%69%
1800
16th to endDay
2213322435%68%
1920
November1st to 15thDay
6%32241334463%
1798
16th to endDay
5%424423346%59%
1755
December1st to 15thDay
10%5%25%424446%49%
1498
16th to endDay
15%5%24322337%50%
1536
January1st to 15thNight
9%5%25%322346%54%
2374
16th to endNight
11%5%14313335%53%
2496
February1st to 15thNight
9%5%23324346%54%
2184
16th to endNight
12%5%13423346%52%
1895
March1st to 15thNight
6%5%23323447%55%
2057
16th to endNight
7%31442445%7%52%
2051
April1st to 15thNight
7%423314236%60%
1799
16th to endNight
4423212237%66%
1800
May1st to 15thNight
2313322349%63%
1799
16th to endNight
2323212337%68%
1549
June1st to 15thNight
221223349%67%
1440
16th to endNight
111136%81%
1440
July1st to 15thNight
11112337%76%
1493
16th to endNight
111213348%70%
1701
August1st to 15thNight
111122238%74%
1740
16th to endNight
2212236%77%
1910
September1st to 15thNight
121221222476%
1800
16th to endNight
1111235%80%
1921
October1st to 15thNight
431321223470%
2160
16th to endNight
3313224245%66%
2304
November1st to 15thNight
4313323345%65%
2388
16th to endNight
4323324447%60%
2535
December1st to 15thNight
9%5%23423447%51%
2497
16th to endNight
12%6%23323337%50%
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
31%48%21%21%12%
1561
16th to endDay
34%311%14%18%16%
1728
February1st to 15thDay
33%37%21%21%11%
1667
16th to endDay
38%5%11%23%17%4
1579
March1st to 15thDay
30%5%13%21%17%10%
1902
16th to endDay
32%415%22%18%6%
2172
April1st to 15thDay
31%412%25%20%5%
2149
16th to endDay
21%5%12%25%25%9%
2160
May1st to 15thDay
17%211%25%31%11%
2151
16th to endDay
15%213%30%30%8%
2561
June1st to 15thDay
14%310%23%28%18%
2520
16th to endDay
6%1416%34%35%
2520
July1st to 15thDay
9%1414%28%41%
2319
16th to endDay
10%37%15%29%33%
2313
August1st to 15thDay
10%1416%33%33%
2203
16th to endDay
9%1316%38%29%
2292
September1st to 15thDay
9%25%18%30%33%
2160
16th to endDay
10%16%20%38%23%
2035
October1st to 15thDay
18%27%21%24%24%
1800
16th to endDay
18%38%19%26%23%
1920
November1st to 15thDay
24%310%19%30%12%
1798
16th to endDay
25%39%21%26%14%
1755
December1st to 15thDay
35%410%16%21%11%
1498
16th to endDay
35%49%21%20%8%
1536
January1st to 15thNight
30%39%19%23%12%
2374
16th to endNight
33%410%11%21%18%
2496
February1st to 15thNight
31%38%22%24%10%
2195
16th to endNight
34%39%24%20%5%
1895
March1st to 15thNight
28%414%24%18%10%
2057
16th to endNight
28%5%16%19%21%7%
2051
April1st to 15thNight
27%312%27%21%7%
1799
16th to endNight
20%312%27%26%10%
1800
May1st to 15thNight
19%214%23%27%12%
1800
16th to endNight
17%213%27%28%9%
1551
June1st to 15thNight
16%310%24%28%16%
1440
16th to endNight
7%1414%33%38%
1440
July1st to 15thNight
8%417%28%40%
1409
16th to endNight
12%26%15%31%30%
1593
August1st to 15thNight
10%319%36%28%
1731
16th to endNight
9%417%34%32%
1910
September1st to 15thNight
13%1416%25%38%
1800
16th to endNight
8%16%19%36%27%
1921
October1st to 15thNight
19%26%21%24%25%
2160
16th to endNight
20%37%18%28%22%
2304
November1st to 15thNight
21%210%23%26%15%
2388
16th to endNight
22%412%19%25%16%
2535
December1st to 15thNight
32%5%8%17%22%13%
2497
16th to endNight
34%411%19%19%9%
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
17%7%23%34%15%1
189
16th to endDay
14%8%24%32%18%2
256
February1st to 15thDay
15%7%23%28%20%3
252
16th to endDay
17%13%26%28%10%2
238
March1st to 15thDay
7%14%28%36%12%
270
16th to endDay
8%15%25%35%13%1
288
April1st to 15thDay
13%12%32%28%8%3
269
16th to endDay
6%13%34%31%12%1
270
May1st to 15thDay
5%6%29%40%14%2
288
16th to endDay
5%10%23%39%17%4
330
June1st to 15thDay
25%21%41%23%5%
315
16th to endDay
14%39%33%10%
315
July1st to 15thDay
16%40%38%10%
305
16th to endDay
15%36%41%14%
327
August1st to 15thDay
112%45%34%6%
315
16th to endDay
1439%41%12%
332
September1st to 15thDay
2111%40%35%9%
315
16th to endDay
1411%43%33%5%
315
October1st to 15thDay
36%26%41%21%1
315
16th to endDay
45%20%38%27%2
336
November1st to 15thDay
6%317%34%31%6%
214
16th to endDay
6%7%20%37%26%1
135
December1st to 15thDay
12%425%48%9%
72
16th to endDay
15%9%18%39%17%
64
January1st to 15thNight
12%213%38%26%5%
720
16th to endNight
13%214%39%24%6%
768
February1st to 15thNight
12%310%38%28%6%
704
16th to endNight
14%5%14%39%22%4
632
March1st to 15thNight
8%316%39%26%6%
720
16th to endNight
7%416%38%29%4
768
April1st to 15thNight
8%5%15%38%27%3
719
16th to endNight
5%421%29%31%8%
720
May1st to 15thNight
3210%37%38%8%
720
16th to endNight
3115%34%36%8%
428
June1st to 15thNight
38%35%45%6%
360
16th to endNight
1228%57%10%
360
July1st to 15thNight
11%63%22%
389
16th to endNight
16%62%28%
564
August1st to 15thNight
1220%59%15%
657
16th to endNight
18%61%18%
764
September1st to 15thNight
1221%55%17%
720
16th to endNight
6%28%49%14%
716
October1st to 15thNight
5%17%35%42%7%
720
16th to endNight
5%17%35%38%10%
768
November1st to 15thNight
5%110%44%33%4
760
16th to endNight
5%211%39%32%7%
780
December1st to 15thNight
10%311%41%28%3
728
16th to endNight
14%419%39%19%3
768
Page generated at 2017-12-03 08:16:38. Version ac04

Copyright 2017 A. Danko


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