PACMO
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the PACMO clear sky chart from 2005-11-05 to 2017-12-04.

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
37%
16292
19%
47839
11%
16249
45%
16249
25%
31311

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
21%
900
15%
2506
5%
895
29%
895
20%
1771
January16th to endNight
22%
960
13%
2558
4%
960
28%
960
18%
1882
February1st to 15thNight
24%
869
14%
2281
3%
869
32%
869
21%
1644
February16th to endNight
25%
631
20%
1893
7%
631
37%
631
22%
1255
March1st to 15thNight
30%
670
17%
2110
10%
670
36%
670
21%
1392
March16th to endNight
27%
576
12%
2028
7%
576
34%
576
16%
1427
April1st to 15thNight
29%
539
17%
1797
12%
539
38%
539
21%
1184
April16th to endNight
37%
540
18%
1800
14%
540
46%
540
20%
1219
May1st to 15thNight
34%
540
17%
1529
9%
540
42%
540
23%
1066
May16th to endNight
43%
563
18%
1497
9%
561
50%
561
30%
994
June1st to 15thNight
54%
540
17%
1440
10%
540
57%
540
35%
895
June16th to endNight
49%
540
17%
1440
9%
540
54%
540
33%
915
July1st to 15thNight
64%
510
18%
1360
12%
510
67%
510
42%
810
July16th to endNight
69%
564
23%
1417
16%
531
72%
531
41%
830
August1st to 15thNight
73%
539
22%
1621
23%
536
75%
536
42%
865
August16th to endNight
65%
573
22%
1910
22%
573
71%
573
34%
1069
September1st to 15thNight
63%
540
28%
1800
28%
540
68%
540
38%
944
September16th to endNight
57%
660
27%
1932
19%
660
64%
660
36%
1122
October1st to 15thNight
43%
720
25%
2160
18%
720
49%
720
31%
1301
October16th to endNight
32%
768
21%
2361
12%
768
41%
768
24%
1498
November1st to 15thNight
33%
760
24%
2471
16%
760
44%
760
26%
1487
November16th to endNight
27%
910
20%
2665
10%
910
38%
910
25%
1736
December1st to 15thNight
22%
920
13%
2575
4%
920
30%
920
18%
1898
December16th to endNight
19%
960
12%
2688
4%
960
27%
960
13%
2107

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%7%35%5%3445%7%38%
48668
Night
13%7%35%424446%42%
48007
Cloud CoverDay
13%7%35%5%3445%7%38%
48676
Night
13%7%35%424446%42%
48012
TransparencyDay
44%6%13%22%12%1
48353
Night
42%5%12%23%14%2
47840
SeeingDay
14%8%27%27%16%5%
6234
Night
16%8%30%30%12%1
16295

By Month

Percentage Cloud Cover NE (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
12%12%48%6%45%445%29%
1432
16th to endDay
14%14%6%8%6%4434427%
1665
February1st to 15thDay
14%12%5%6%5%25%446%32%
1581
16th to endDay
14%8%37%6%35%346%34%
1580
March1st to 15thDay
15%10%36%43435%7%34%
1850
16th to endDay
18%9%37%5%3445%7%29%
2195
April1st to 15thDay
15%11%45%5%34445%35%
2151
16th to endDay
21%9%36%5%24436%32%
2160
May1st to 15thDay
19%7%36%6%345%5%7%30%
2421
16th to endDay
14%6%25%6%35%5%6%8%35%
2617
June1st to 15thDay
11%6%25%5%3445%8%41%
2520
16th to endDay
9%435%435%6%6%8%42%
2520
July1st to 15thDay
6%4146%45%46%10%45%
2520
16th to endDay
6%315%6%36%5%6%10%43%
2655
August1st to 15thDay
6%4245%36%7%6%10%42%
2328
16th to endDay
10%425%5%4445%7%45%
2292
September1st to 15thDay
11%5%13323448%49%
2160
16th to endDay
9%4145%345%5%7%48%
2013
October1st to 15thDay
16%6%24323346%46%
1800
16th to endDay
16%6%25%43345%6%42%
1863
November1st to 15thDay
13%9%25%425%45%6%40%
1717
16th to endDay
15%10%45%5%2334440%
1625
December1st to 15thDay
17%13%47%6%33336%29%
1467
16th to endDay
18%15%5%8%6%13345%26%
1536
January1st to 15thNight
12%10%5%6%5%24446%36%
2506
16th to endNight
12%10%6%7%5%34446%32%
2558
February1st to 15thNight
14%11%36%5%35%445%36%
2278
16th to endNight
14%9%36%424335%40%
1893
March1st to 15thNight
16%8%35%424345%41%
2097
16th to endNight
16%9%47%6%35%35%6%32%
2028
April1st to 15thNight
15%8%46%424446%39%
1797
16th to endNight
19%6%36%424346%37%
1800
May1st to 15thNight
15%6%26%6%345%46%37%
1529
16th to endNight
9%5%26%5%3446%9%42%
1496
June1st to 15thNight
10%5%2432435%7%49%
1440
16th to endNight
7%426%5%35%5%5%7%47%
1440
July1st to 15thNight
7%31342446%8%54%
1440
16th to endNight
5%214435%5%6%11%49%
1513
August1st to 15thNight
3314425%45%9%55%
1630
16th to endNight
8%32432335%6%54%
1910
September1st to 15thNight
10%32331235%7%56%
1800
16th to endNight
6%3145%245%6%8%50%
1932
October1st to 15thNight
12%5%245%23345%51%
2160
16th to endNight
15%7%25%423345%44%
2361
November1st to 15thNight
13%7%24422336%48%
2471
16th to endNight
16%7%25%423346%42%
2665
December1st to 15thNight
17%12%46%5%24335%33%
2575
16th to endNight
22%14%47%5%2433426%
2688

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
12%12%5%8%6%45%5%45%30%
1432
16th to endDay
14%14%6%9%6%4444427%
1665
February1st to 15thDay
14%12%46%5%25%437%32%
1581
16th to endDay
13%9%47%6%34446%34%
1580
March1st to 15thDay
15%10%46%5%2435%6%34%
1860
16th to endDay
19%9%37%6%2445%7%30%
2193
April1st to 15thDay
15%11%45%6%34345%35%
2151
16th to endDay
21%9%36%5%24436%33%
2160
May1st to 15thDay
19%7%36%6%345%5%7%30%
2421
16th to endDay
14%5%25%6%35%5%6%8%35%
2617
June1st to 15thDay
11%5%35%5%35%45%8%41%
2520
16th to endDay
9%5%35%435%6%6%8%42%
2520
July1st to 15thDay
7%4246%345%6%9%45%
2520
16th to endDay
6%325%6%36%5%7%10%43%
2655
August1st to 15thDay
6%4245%45%7%7%10%42%
2328
16th to endDay
9%425%5%35%45%7%45%
2292
September1st to 15thDay
11%413333448%49%
2160
16th to endDay
9%4145%345%5%7%48%
2013
October1st to 15thDay
16%6%24323346%46%
1800
16th to endDay
16%6%2442345%5%42%
1863
November1st to 15thDay
13%9%25%435%45%6%40%
1717
16th to endDay
16%10%35%422345%40%
1625
December1st to 15thDay
18%13%47%6%24336%29%
1467
16th to endDay
18%15%5%8%6%1334427%
1536
January1st to 15thNight
12%10%5%6%6%33446%36%
2506
16th to endNight
12%10%6%7%5%34446%32%
2558
February1st to 15thNight
14%11%46%5%25%445%36%
2271
16th to endNight
15%8%36%423436%40%
1893
March1st to 15thNight
16%8%35%424345%41%
2110
16th to endNight
16%9%46%7%25%35%5%32%
2028
April1st to 15thNight
15%8%36%424346%39%
1797
16th to endNight
19%7%36%42435%5%37%
1800
May1st to 15thNight
15%6%25%6%3445%6%37%
1528
16th to endNight
9%426%5%2446%9%42%
1496
June1st to 15thNight
10%5%2442435%8%49%
1440
16th to endNight
7%425%5%346%5%7%47%
1440
July1st to 15thNight
7%31342446%9%53%
1440
16th to endNight
4214435%5%6%11%49%
1513
August1st to 15thNight
321443446%8%56%
1630
16th to endNight
8%42442345%6%53%
1910
September1st to 15thNight
9%41331235%7%56%
1800
16th to endNight
6%3235%245%6%7%50%
1932
October1st to 15thNight
12%5%245%23345%51%
2160
16th to endNight
15%7%25%423345%44%
2361
November1st to 15thNight
13%7%24423336%48%
2471
16th to endNight
16%7%35%423246%42%
2665
December1st to 15thNight
17%12%46%5%3433433%
2575
16th to endNight
22%14%47%5%2433426%
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
56%5%12%15%10%
1433
16th to endDay
60%412%14%7%
1665
February1st to 15thDay
53%415%20%5%
1582
16th to endDay
50%6%13%21%7%
1580
March1st to 15thDay
49%5%15%20%8%
1860
16th to endDay
52%6%13%20%5%
2195
April1st to 15thDay
51%5%10%21%11%
2151
16th to endDay
52%5%9%17%12%2
2160
May1st to 15thDay
52%6%13%20%8%
2421
16th to endDay
44%8%12%18%13%1
2621
June1st to 15thDay
40%6%12%23%15%1
2520
16th to endDay
36%8%13%21%17%2
2520
July1st to 15thDay
35%7%14%25%14%3
2371
16th to endDay
34%8%15%24%14%2
2488
August1st to 15thDay
33%8%14%25%16%1
2313
16th to endDay
35%6%12%26%15%2
2292
September1st to 15thDay
32%5%9%26%21%4
2160
16th to endDay
33%5%12%27%18%1
2013
October1st to 15thDay
39%49%27%17%1
1800
16th to endDay
42%414%23%12%1
1863
November1st to 15thDay
43%5%11%24%12%2
1717
16th to endDay
47%415%22%9%
1625
December1st to 15thDay
57%414%17%5%
1467
16th to endDay
60%5%12%12%8%
1536
January1st to 15thNight
48%5%14%18%12%
2506
16th to endNight
51%6%15%16%9%
2558
February1st to 15thNight
49%5%13%20%10%
2281
16th to endNight
46%313%24%11%
1893
March1st to 15thNight
46%414%23%9%2
2110
16th to endNight
52%5%12%19%8%1
2028
April1st to 15thNight
45%49%23%13%2
1797
16th to endNight
47%5%8%20%13%3
1800
May1st to 15thNight
45%6%11%22%12%
1529
16th to endNight
36%8%12%21%17%2
1498
June1st to 15thNight
33%6%12%25%19%3
1440
16th to endNight
34%7%12%20%21%3
1440
July1st to 15thNight
27%6%14%29%17%3
1360
16th to endNight
26%7%15%29%17%3
1417
August1st to 15thNight
24%6%15%33%17%3
1621
16th to endNight
29%6%11%26%20%5%
1910
September1st to 15thNight
27%410%26%26%4
1800
16th to endNight
29%6%12%27%21%2
1932
October1st to 15thNight
35%49%24%21%4
2160
16th to endNight
41%410%24%16%1
2361
November1st to 15thNight
38%410%23%18%4
2471
16th to endNight
43%312%27%12%
2665
December1st to 15thNight
54%411%21%8%
2575
16th to endNight
61%49%15%7%
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%14%33%18%3
90
16th to endDay
20%16%38%14%8%1
96
February1st to 15thDay
18%18%41%14%6%
90
16th to endDay
20%14%35%18%7%2
81
March1st to 15thDay
22%24%34%14%31
90
16th to endDay
30%16%25%17%7%1
179
April1st to 15thDay
17%14%34%21%11%
270
16th to endDay
26%8%27%21%13%2
270
May1st to 15thDay
19%11%31%25%9%2
402
16th to endDay
16%11%29%26%12%3
517
June1st to 15thDay
11%428%33%16%5%
495
16th to endDay
10%7%31%28%14%6%
495
July1st to 15thDay
9%326%28%21%10%
475
16th to endDay
6%121%33%28%7%
515
August1st to 15thDay
6%219%37%24%9%
475
16th to endDay
9%415%32%26%12%
332
September1st to 15thDay
9%317%32%28%9%
315
16th to endDay
7%5%20%32%25%8%
302
October1st to 15thDay
19%8%28%24%13%5%
135
16th to endDay
18%14%34%23%9%
144
November1st to 15thDay
14%12%37%17%11%7%
135
16th to endDay
34%11%32%17%3
135
December1st to 15thDay
20%19%29%24%6%2
100
16th to endDay
29%26%37%6%1
96
January1st to 15thNight
17%16%39%21%5%
900
16th to endNight
17%12%38%26%5%
960
February1st to 15thNight
19%12%37%25%5%
872
16th to endNight
19%11%39%24%4
631
March1st to 15thNight
21%11%32%28%5%
670
16th to endNight
20%10%36%25%7%
576
April1st to 15thNight
20%12%32%27%5%
539
16th to endNight
22%7%27%33%7%
540
May1st to 15thNight
20%6%34%29%8%1
540
16th to endNight
11%433%35%14%
563
June1st to 15thNight
12%424%44%14%
540
16th to endNight
8%330%38%17%1
540
July1st to 15thNight
9%219%40%26%2
510
16th to endNight
5%116%42%31%2
564
August1st to 15thNight
3112%44%33%5%
539
16th to endNight
9%115%40%29%3
573
September1st to 15thNight
11%217%37%24%5%
540
16th to endNight
7%5%22%34%26%2
660
October1st to 15thNight
15%5%31%29%17%1
720
16th to endNight
20%11%31%26%9%
768
November1st to 15thNight
18%8%35%26%9%1
760
16th to endNight
20%13%35%24%6%
910
December1st to 15thNight
23%11%35%24%4
920
16th to endNight
27%12%32%22%3
960
Page generated at 2017-12-05 09:18:58. Version ac04

Copyright 2017 A. Danko


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