Pool Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pool Observatory clear sky chart from 2005-11-06 to 2024-02-10.

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
65%
24518
25%
79796
22%
24433
69%
24433
38%
42916

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 10thNight
61%
816
18%
4156
19%
809
64%
809
21%
2339
January11th to 20thNight
58%
757
19%
4079
24%
740
64%
740
20%
2271
January21st to endNight
58%
828
17%
4396
25%
814
61%
814
21%
2375
February1st to 10thNight
57%
758
21%
2463
20%
758
62%
758
33%
1419
February11th to 20thNight
52%
701
21%
2264
18%
700
58%
700
33%
1293
February21st to endNight
48%
592
30%
1763
21%
592
60%
592
36%
1027
March1st to 10thNight
54%
720
26%
1980
18%
720
60%
720
40%
1151
March11th to 20thNight
63%
720
29%
1980
22%
720
67%
720
44%
1109
March21st to endNight
53%
792
23%
2178
15%
792
60%
792
36%
1332
April1st to 10thNight
50%
546
23%
1806
19%
546
57%
546
34%
976
April11th to 20thNight
54%
533
24%
1777
20%
533
62%
533
31%
997
April21st to endNight
54%
540
26%
1798
21%
540
63%
540
36%
966
May1st to 10thNight
58%
540
25%
1620
18%
540
64%
540
37%
903
May11th to 20thNight
69%
531
25%
1567
22%
531
72%
531
42%
835
May21st to endNight
60%
582
25%
1552
17%
582
66%
582
45%
859
June1st to 10thNight
74%
540
32%
1440
26%
540
77%
540
58%
724
June11th to 20thNight
69%
540
32%
1440
24%
540
73%
540
58%
715
June21st to endNight
81%
540
32%
1440
27%
540
84%
540
66%
686
July1st to 10thNight
82%
525
24%
1400
21%
525
83%
525
51%
753
July11th to 20thNight
86%
522
22%
1564
21%
522
86%
522
49%
785
July21st to endNight
82%
591
19%
1674
18%
558
82%
558
38%
954
August1st to 10thNight
78%
537
20%
1602
17%
534
79%
534
41%
870
August11th to 20thNight
81%
534
32%
1638
31%
534
83%
534
50%
804
August21st to endNight
82%
594
30%
1980
34%
594
83%
594
42%
1007
September1st to 10thNight
79%
540
34%
1800
37%
540
83%
540
48%
843
September11th to 20thNight
78%
571
36%
1831
36%
571
81%
571
51%
860
September21st to endNight
71%
720
36%
2047
27%
720
77%
720
55%
1001
October1st to 10thNight
68%
720
30%
2160
24%
720
73%
720
47%
1122
October11th to 20thNight
72%
720
37%
2160
27%
720
79%
720
58%
988
October21st to endNight
68%
792
37%
2376
29%
792
73%
792
48%
1199
November1st to 10thNight
69%
741
35%
2221
28%
741
73%
741
53%
1062
November11th to 20thNight
66%
950
34%
2538
23%
950
72%
950
53%
1324
November21st to endNight
63%
950
27%
2660
21%
950
66%
950
45%
1459
December1st to 10thNight
59%
950
21%
2660
15%
950
62%
950
38%
1556
December11th to 20thNight
55%
949
21%
3113
15%
949
58%
949
29%
1820
December21st to endNight
51%
1036
11%
4673
12%
1026
55%
1026
20%
2532

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
3424435%5%6%8%56%
78454
Night
45%25%4345%6%8%54%
80576
TransparencyDay
23%8%13%23%22%12%
78174
Night
24%8%13%24%21%10%
80378
SeeingDay
6%8%23%33%24%6%
14266
Night
6%419%43%25%3
24561

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 10thDay
25%27%7%47%6%9%11%40%
2762
11th to 20thDay
37%47%7%46%6%6%8%43%
2860
21st to endDay
36%35%6%35%46%7%52%
3146
February1st to 10thDay
36%36%6%35%5%5%9%49%
1701
11th to 20thDay
35%35%6%36%5%6%9%48%
1583
21st to endDay
37%35%6%46%6%7%7%47%
1488
March1st to 10thDay
36%36%5%35%5%5%7%52%
1980
11th to 20thDay
24344345%7%9%56%
1980
21st to endDay
25%25%6%35%6%6%8%51%
2178
April1st to 10thDay
3425%5%335%6%7%56%
2153
11th to 20thDay
35%35%5%35%6%6%7%51%
2131
21st to endDay
33144346%6%9%56%
2160
May1st to 10thDay
4325%435%6%7%9%51%
2339
11th to 20thDay
33145%35%6%6%8%55%
2326
21st to endDay
23143345%7%9%59%
2724
June1st to 10thDay
321332446%9%65%
2520
11th to 20thDay
221332346%6%67%
2520
21st to endDay
121232445%7%69%
2520
July1st to 10thDay
3213335%5%6%9%61%
2519
11th to 20thDay
2213435%6%8%10%54%
2340
21st to endDay
43135%36%7%8%14%45%
2545
August1st to 10thDay
4314446%7%8%11%47%
2328
11th to 20thDay
22224345%8%9%60%
2263
21st to endDay
2213435%7%7%10%55%
2376
September1st to 10thDay
5%3133235%5%7%63%
2160
11th to 20thDay
32133236%5%8%65%
2124
21st to endDay
4212223346%71%
1913
October1st to 10thDay
7%32232345%7%62%
1800
11th to 20thDay
3212223346%71%
1800
21st to endDay
4423323445%65%
1980
November1st to 10thDay
232331345%7%67%
1836
11th to 20thDay
341342445%7%63%
1639
21st to endDay
34244235%5%7%62%
1520
December1st to 10thDay
37%37%5%3445%7%51%
1520
11th to 20thDay
36%37%6%46%6%8%8%43%
1926
21st to endDay
37%36%5%36%6%6%8%47%
2794
January1st to 10thNight
27%38%7%5%6%6%7%8%39%
4222
11th to 20thNight
412%37%6%36%5%6%8%40%
4110
21st to endNight
5%10%47%5%35%7%5%7%43%
4521
February1st to 10thNight
36%26%5%45%5%6%7%52%
2463
11th to 20thNight
47%36%6%35%46%8%49%
2263
21st to endNight
47%35%5%35%45%7%51%
1763
March1st to 10thNight
5%6%24435%5%6%7%53%
1980
11th to 20thNight
44243346%6%7%57%
1980
21st to endNight
46%35%5%35%6%6%8%49%
2178
April1st to 10thNight
5%5%25%5%346%6%6%53%
1806
11th to 20thNight
6%6%36%5%35%46%6%51%
1777
21st to endNight
5%5%245%35%46%7%55%
1798
May1st to 10thNight
5%425%435%5%7%9%51%
1620
11th to 20thNight
5%31343447%9%58%
1567
21st to endNight
43134345%6%7%59%
1552
June1st to 10thNight
221232346%7%68%
1440
11th to 20thNight
3213313347%69%
1440
21st to endNight
112223448%70%
1440
July1st to 10thNight
3213335%5%6%9%60%
1440
11th to 20thNight
2213426%5%7%12%58%
1617
21st to endNight
42245%45%7%8%12%47%
1773
August1st to 10thNight
33145%36%6%8%11%52%
1611
11th to 20thNight
32142245%6%10%61%
1638
21st to endNight
33234345%7%11%56%
1980
September1st to 10thNight
421242446%8%63%
1800
11th to 20thNight
421232435%8%65%
1831
21st to endNight
4213314335%71%
2047
October1st to 10thNight
4413434447%63%
2160
11th to 20thNight
2213222347%72%
2160
21st to endNight
5%5%23322335%67%
2376
November1st to 10thNight
331332335%6%68%
2221
11th to 20thNight
3414323346%67%
2538
21st to endNight
45%35%32345%7%60%
2660
December1st to 10thNight
47%35%5%34346%56%
2660
11th to 20thNight
47%35%6%348%8%10%42%
3271
21st to endNight
410%37%6%36%6%6%7%43%
4873

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 10thDay
28%12%20%31%9%
2763
11th to 20thDay
25%16%23%26%9%1
2860
21st to endDay
27%8%19%33%11%2
3146
February1st to 10thDay
30%8%19%25%15%2
1701
11th to 20thDay
31%8%13%26%19%3
1592
21st to endDay
32%9%11%24%19%4
1488
March1st to 10thDay
30%8%10%26%23%3
1980
11th to 20thDay
23%8%12%34%19%4
1980
21st to endDay
28%10%12%26%20%5%
2178
April1st to 10thDay
25%7%12%22%23%11%
2153
11th to 20thDay
28%8%12%21%23%8%
2134
21st to endDay
22%8%11%26%26%7%
2160
May1st to 10thDay
26%9%12%20%26%8%
2339
11th to 20thDay
23%8%13%23%25%8%
2329
21st to endDay
20%8%11%18%28%16%
2724
June1st to 10thDay
15%5%8%19%30%23%
2520
11th to 20thDay
15%5%7%10%22%39%
2520
21st to endDay
13%5%6%14%26%37%
2520
July1st to 10thDay
18%7%11%14%19%31%
2450
11th to 20thDay
19%8%14%20%20%20%
2271
21st to endDay
26%13%18%19%14%11%
2404
August1st to 10thDay
26%11%16%17%15%16%
2313
11th to 20thDay
19%8%11%17%24%21%
2263
21st to endDay
21%8%12%18%22%18%
2376
September1st to 10thDay
21%7%8%13%24%27%
2160
11th to 20thDay
16%8%11%17%27%21%
2124
21st to endDay
16%5%6%17%39%18%
1913
October1st to 10thDay
22%6%10%22%30%11%
1800
11th to 20thDay
16%47%25%37%12%
1800
21st to endDay
21%5%11%28%30%6%
1980
November1st to 10thDay
14%6%13%27%34%7%
1836
11th to 20thDay
19%5%12%35%25%3
1639
21st to endDay
23%6%13%32%24%3
1520
December1st to 10thDay
31%8%16%28%15%2
1520
11th to 20thDay
31%10%13%33%13%
1924
21st to endDay
30%7%17%22%22%2
2794
January1st to 10thNight
32%12%17%28%11%
4222
11th to 20thNight
25%19%22%25%8%1
4110
21st to endNight
32%9%19%28%10%1
4521
February1st to 10thNight
31%8%17%28%15%2
2463
11th to 20thNight
30%8%13%27%19%3
2264
21st to endNight
28%8%9%29%22%4
1763
March1st to 10thNight
26%8%12%27%25%2
1980
11th to 20thNight
24%7%9%30%26%5%
1980
21st to endNight
31%8%12%26%20%4
2178
April1st to 10thNight
28%7%13%20%23%10%
1806
11th to 20thNight
29%8%10%19%22%12%
1777
21st to endNight
24%9%9%23%27%8%
1798
May1st to 10thNight
25%8%11%19%27%9%
1620
11th to 20thNight
21%9%14%23%26%7%
1568
21st to endNight
22%6%12%17%27%15%
1552
June1st to 10thNight
15%5%8%18%28%26%
1440
11th to 20thNight
15%5%8%13%18%41%
1440
21st to endNight
12%47%16%22%39%
1440
July1st to 10thNight
19%7%12%12%18%31%
1400
11th to 20thNight
17%8%14%21%18%22%
1564
21st to endNight
25%11%21%19%14%12%
1674
August1st to 10thNight
22%10%20%18%16%15%
1602
11th to 20thNight
19%6%13%18%20%24%
1638
21st to endNight
22%7%11%16%22%22%
1980
September1st to 10thNight
19%5%10%15%20%31%
1800
11th to 20thNight
17%6%12%18%22%26%
1831
21st to endNight
17%46%16%37%20%
2047
October1st to 10thNight
21%6%9%21%26%16%
2160
11th to 20thNight
14%5%8%21%35%17%
2160
21st to endNight
21%46%29%32%7%
2376
November1st to 10thNight
16%5%11%28%31%8%
2221
11th to 20thNight
19%5%9%34%28%4
2538
21st to endNight
24%6%10%28%28%4
2660
December1st to 10thNight
29%7%16%28%19%2
2660
11th to 20thNight
29%10%15%32%13%1
3272
21st to endNight
33%8%16%23%19%1
4873

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 10thDay
10%8%21%34%20%7%
270
11th to 20thDay
7%7%27%39%19%2
270
21st to endDay
6%5%21%45%18%6%
297
February1st to 10thDay
8%8%32%38%12%2
267
11th to 20thDay
9%8%33%35%13%2
240
21st to endDay
8%14%29%35%12%2
206
March1st to 10thDay
10%15%31%28%13%2
420
11th to 20thDay
7%14%29%30%17%3
420
21st to endDay
9%21%34%26%9%1
462
April1st to 10thDay
9%17%33%25%13%3
420
11th to 20thDay
12%21%34%20%10%2
412
21st to endDay
6%19%35%26%13%1
420
May1st to 10thDay
8%17%33%30%10%2
423
11th to 20thDay
6%10%27%31%22%4
473
21st to endDay
5%11%25%32%23%5%
679
June1st to 10thDay
47%22%33%28%6%
630
11th to 20thDay
47%25%34%25%5%
630
21st to endDay
15%20%40%30%4
630
July1st to 10thDay
2211%35%40%10%
620
11th to 20thDay
429%36%40%10%
444
21st to endDay
6%18%34%39%11%
487
August1st to 10thDay
5%213%35%36%9%
447
11th to 20thDay
1312%39%35%10%
437
21st to endDay
2211%37%37%11%
495
September1st to 10thDay
6%216%33%30%12%
450
11th to 20thDay
45%20%36%28%6%
450
21st to endDay
5%9%20%25%31%11%
383
October1st to 10thDay
9%7%20%24%27%13%
270
11th to 20thDay
38%18%33%26%11%
270
21st to endDay
8%5%21%31%29%5%
297
November1st to 10thDay
5%7%29%32%19%8%
270
11th to 20thDay
27%25%38%19%9%
270
21st to endDay
7%5%27%34%19%9%
270
December1st to 10thDay
7%7%26%38%17%5%
270
11th to 20thDay
7%5%24%38%19%7%
270
21st to endDay
9%9%23%42%13%4
297
January1st to 10thNight
7%420%45%21%3
833
11th to 20thNight
7%422%43%22%3
760
21st to endNight
8%5%20%46%19%2
836
February1st to 10thNight
7%326%47%14%2
758
11th to 20thNight
5%5%29%46%14%1
704
21st to endNight
8%432%48%9%
592
March1st to 10thNight
6%6%30%43%14%2
720
11th to 20thNight
5%424%44%22%1
720
21st to endNight
6%7%28%44%15%1
792
April1st to 10thNight
6%7%32%43%11%
546
11th to 20thNight
9%7%26%42%14%2
533
21st to endNight
7%5%29%39%17%3
540
May1st to 10thNight
7%7%24%44%16%1
540
11th to 20thNight
7%5%14%45%25%4
531
21st to endNight
5%7%23%38%24%3
584
June1st to 10thNight
3217%44%31%3
540
11th to 20thNight
25%20%46%24%3
540
21st to endNight
2113%44%38%3
540
July1st to 10thNight
37%37%47%5%
525
11th to 20thNight
2438%50%5%
522
21st to endNight
5%1333%53%5%
591
August1st to 10thNight
417%36%49%3
537
11th to 20thNight
418%38%44%5%
534
21st to endNight
318%40%41%7%
594
September1st to 10thNight
419%44%38%4
540
11th to 20thNight
5%211%42%36%4
571
21st to endNight
6%215%36%35%6%
720
October1st to 10thNight
5%5%18%42%29%2
720
11th to 20thNight
4318%43%28%4
720
21st to endNight
8%317%40%27%4
792
November1st to 10thNight
4419%44%26%3
741
11th to 20thNight
5%422%46%20%4
950
21st to endNight
7%5%22%40%24%3
950
December1st to 10thNight
7%421%48%19%1
950
11th to 20thNight
8%5%23%41%21%2
950
21st to endNight
10%6%21%47%13%2
1045
Page generated at 2024-02-07 04:11:53. Version ac07

Copyright 2024 Attilla Danko


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