PICO
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the PICO clear sky chart from 2005-11-05 to 2017-09-24.

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
41%
15886
21%
46933
14%
15841
48%
15841
27%
29824

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
22%
899
18%
2506
7%
895
33%
895
21%
1741
January16th to endNight
22%
960
16%
2558
5%
960
30%
960
19%
1844
February1st to 15thNight
24%
790
14%
2199
4%
788
31%
788
18%
1558
February16th to endNight
24%
631
19%
1893
8%
631
33%
631
22%
1254
March1st to 15thNight
25%
720
16%
2160
8%
720
32%
720
19%
1497
March16th to endNight
32%
576
15%
1993
10%
576
40%
576
20%
1301
April1st to 15thNight
32%
539
21%
1797
13%
539
45%
539
25%
1080
April16th to endNight
37%
540
21%
1800
15%
540
47%
540
25%
1138
May1st to 15thNight
38%
540
17%
1631
11%
539
46%
539
25%
1084
May16th to endNight
51%
563
20%
1502
13%
561
55%
561
31%
991
June1st to 15thNight
63%
540
20%
1440
13%
540
66%
540
42%
844
June16th to endNight
59%
540
22%
1440
15%
540
63%
540
39%
871
July1st to 15thNight
69%
510
20%
1360
16%
510
69%
510
42%
810
July16th to endNight
75%
564
26%
1417
22%
531
77%
531
46%
797
August1st to 15thNight
75%
539
24%
1701
26%
536
77%
536
41%
897
August16th to endNight
72%
573
25%
1910
27%
573
76%
573
37%
1033
September1st to 15thNight
64%
540
28%
1800
29%
540
68%
540
35%
976
September16th to endNight
61%
675
33%
1896
25%
675
66%
675
38%
1088
October1st to 15thNight
54%
660
30%
1922
22%
660
62%
660
38%
1107
October16th to endNight
34%
704
24%
2181
16%
704
45%
704
27%
1313
November1st to 15thNight
38%
700
27%
2276
18%
700
50%
700
30%
1304
November16th to endNight
31%
723
22%
2343
14%
723
41%
723
24%
1462
December1st to 15thNight
26%
900
14%
2520
7%
900
32%
900
20%
1825
December16th to endNight
21%
960
14%
2688
5%
960
29%
960
17%
2009

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
13%6%35%5%3445%8%39%
48013
Night
13%6%35%424446%43%
47108
TransparencyDay
42%5%12%24%13%2
47691
Night
41%311%24%16%2
46935
SeeingDay
14%6%22%26%20%8%
5910
Night
16%8%27%30%15%1
15888

By Month

Percentage Cloud Cover SE (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
16%9%5%11%7%35%34427%
1432
16th to endDay
14%11%5%7%5%34446%32%
1665
February1st to 15thDay
13%10%5%7%7%2445%6%31%
1663
16th to endDay
12%11%48%5%35%45%7%31%
1580
March1st to 15thDay
16%9%36%5%33446%34%
1809
16th to endDay
18%10%46%5%34447%30%
2228
April1st to 15thDay
16%6%35%5%2445%7%38%
2151
16th to endDay
18%7%25%5%34346%37%
2160
May1st to 15thDay
19%6%245%3436%8%34%
2319
16th to endDay
10%5%35%5%45%45%9%38%
2611
June1st to 15thDay
7%4235%345%6%9%45%
2520
16th to endDay
9%325%5%35%5%6%10%42%
2520
July1st to 15thDay
9%3245%36%5%7%8%42%
2520
16th to endDay
5%214435%7%7%12%44%
2655
August1st to 15thDay
8%3144346%6%10%45%
2247
16th to endDay
7%425%5%345%5%10%44%
2292
September1st to 15thDay
12%42443445%6%45%
2160
16th to endDay
9%424334347%50%
1911
October1st to 15thDay
13%5%24323446%49%
1706
16th to endDay
14%5%2442345%6%46%
1689
November1st to 15thDay
13%5%23324347%48%
1582
16th to endDay
17%8%44423345%40%
1617
December1st to 15thDay
20%10%5%7%5%24446%28%
1440
16th to endDay
18%12%6%6%334447%27%
1536
January1st to 15thNight
14%8%47%6%34345%37%
2506
16th to endNight
14%9%5%7%6%34445%34%
2558
February1st to 15thNight
15%9%47%5%35%445%34%
2190
16th to endNight
16%7%37%423436%40%
1893
March1st to 15thNight
19%8%35%5%34345%36%
2160
16th to endNight
16%9%35%4245%5%6%35%
1993
April1st to 15thNight
14%8%24423446%45%
1797
16th to endNight
17%6%35%424346%41%
1800
May1st to 15thNight
17%6%35%433446%39%
1631
16th to endNight
9%5%146%36%5%5%9%42%
1501
June1st to 15thNight
6%314425%47%9%50%
1440
16th to endNight
8%42443346%9%48%
1440
July1st to 15thNight
9%31342447%8%49%
1440
16th to endNight
431332345%10%56%
1513
August1st to 15thNight
5%3133335%7%11%51%
1710
16th to endNight
5%2135%35%45%8%53%
1910
September1st to 15thNight
10%425%223447%52%
1800
16th to endNight
8%425%32345%7%53%
1896
October1st to 15thNight
11%314423337%52%
1922
16th to endNight
17%6%23423345%48%
2181
November1st to 15thNight
10%6%24324445%52%
2276
16th to endNight
16%8%34413336%42%
2343
December1st to 15thNight
21%9%36%423446%31%
2520
16th to endNight
20%10%47%5%34445%29%
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
58%39%18%9%
1433
16th to endDay
52%313%23%7%
1665
February1st to 15thDay
52%313%21%7%
1665
16th to endDay
51%412%22%8%
1580
March1st to 15thDay
49%5%13%22%7%
1809
16th to endDay
52%5%13%21%6%
2230
April1st to 15thDay
44%411%25%13%1
2151
16th to endDay
47%312%22%11%1
2160
May1st to 15thDay
47%5%14%22%9%
2319
16th to endDay
41%6%14%18%15%2
2615
June1st to 15thDay
33%6%14%25%18%2
2520
16th to endDay
36%6%13%23%16%3
2520
July1st to 15thDay
36%6%12%25%15%3
2371
16th to endDay
29%8%15%29%16%1
2488
August1st to 15thDay
31%6%14%29%15%1
2232
16th to endDay
33%6%13%22%18%6%
2292
September1st to 15thDay
37%48%24%20%4
2160
16th to endDay
33%48%29%20%3
1911
October1st to 15thDay
35%311%27%19%2
1706
16th to endDay
37%311%28%18%1
1689
November1st to 15thDay
35%412%23%19%5%
1582
16th to endDay
46%112%26%11%1
1617
December1st to 15thDay
55%313%17%9%
1440
16th to endDay
56%410%21%6%1
1536
January1st to 15thNight
49%29%24%13%
2506
16th to endNight
51%312%22%9%
2558
February1st to 15thNight
51%312%20%11%1
2199
16th to endNight
46%312%26%10%
1893
March1st to 15thNight
50%310%21%11%1
2160
16th to endNight
47%313%24%10%1
1993
April1st to 15thNight
39%310%27%17%2
1797
16th to endNight
43%310%22%15%3
1800
May1st to 15thNight
45%312%22%14%
1632
16th to endNight
38%6%13%19%17%3
1503
June1st to 15thNight
28%413%29%20%2
1440
16th to endNight
31%5%11%25%19%6%
1440
July1st to 15thNight
30%312%28%17%6%
1360
16th to endNight
24%5%14%31%20%2
1417
August1st to 15thNight
25%5%13%28%23%3
1701
16th to endNight
28%5%11%26%22%6%
1910
September1st to 15thNight
31%38%25%23%7%
1800
16th to endNight
30%47%26%25%5%
1896
October1st to 15thNight
31%39%28%21%5%
1922
16th to endNight
39%28%28%17%3
2181
November1st to 15thNight
34%39%24%21%7%
2276
16th to endNight
42%210%26%16%
2343
December1st to 15thNight
53%311%20%10%
2520
16th to endNight
56%311%18%8%1
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
30%11%38%12%7%
90
16th to endDay
12%25%36%23%2
96
February1st to 15thDay
22%17%38%18%2
90
16th to endDay
9%19%37%28%4
81
March1st to 15thDay
32%13%30%15%7%1
90
16th to endDay
23%15%27%24%8%
214
April1st to 15thDay
19%11%30%27%10%1
270
16th to endDay
21%6%27%25%14%4
270
May1st to 15thDay
20%9%27%27%10%3
288
16th to endDay
12%7%33%25%14%6%
511
June1st to 15thDay
9%320%31%27%7%
495
16th to endDay
10%427%32%17%6%
495
July1st to 15thDay
13%216%31%23%13%
475
16th to endDay
6%112%29%35%14%
515
August1st to 15thDay
11%110%24%31%20%
388
16th to endDay
8%11%27%37%15%
332
September1st to 15thDay
12%312%25%29%15%
315
16th to endDay
11%412%21%31%18%
287
October1st to 15thDay
11%6%22%28%24%5%
146
16th to endDay
10%12%33%33%8%2
96
November1st to 15thDay
10%5%21%25%26%11%
90
16th to endDay
37%18%23%13%5%1
90
December1st to 15thDay
17%13%33%25%5%4
90
16th to endDay
27%18%42%9%2
96
January1st to 15thNight
18%15%37%23%4
900
16th to endNight
18%14%38%25%3
960
February1st to 15thNight
19%14%35%27%3
791
16th to endNight
20%12%38%27%2
631
March1st to 15thNight
24%11%34%25%4
720
16th to endNight
21%9%31%28%8%
576
April1st to 15thNight
18%11%33%26%9%
539
16th to endNight
18%7%31%31%10%1
540
May1st to 15thNight
20%5%27%32%12%1
540
16th to endNight
10%326%34%20%3
563
June1st to 15thNight
8%120%44%24%
540
16th to endNight
10%121%39%25%1
540
July1st to 15thNight
10%111%40%34%2
510
16th to endNight
6%9%40%37%5%
564
August1st to 15thNight
7%18%40%37%4
539
16th to endNight
5%110%36%39%5%
573
September1st to 15thNight
12%213%34%31%5%
540
16th to endNight
9%416%30%33%6%
675
October1st to 15thNight
13%322%32%22%4
660
16th to endNight
21%9%30%28%9%
704
November1st to 15thNight
13%8%35%29%12%
700
16th to endNight
21%11%32%26%8%
723
December1st to 15thNight
26%10%31%24%7%
900
16th to endNight
25%10%35%24%3
960
Page generated at 2017-09-25 08:02:25. Version ac04

Copyright 2017 A. Danko


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