Land of Oz Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Land of Oz Observatory clear sky chart from 2005-11-05 to 2018-11-30.

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
38%
17483
24%
51881
14%
17436
48%
17436
28%
30965

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
28%
975
22%
2522
8%
970
38%
970
28%
1582
January16th to endNight
28%
1040
28%
2704
9%
1040
41%
1040
29%
1668
February1st to 15thNight
22%
955
17%
2483
5%
951
29%
951
23%
1682
February16th to endNight
24%
705
24%
2071
8%
705
36%
705
23%
1301
March1st to 15thNight
29%
585
23%
2145
12%
585
43%
585
21%
1262
March16th to endNight
24%
624
16%
2288
9%
624
35%
624
17%
1482
April1st to 15thNight
30%
584
22%
2012
13%
584
44%
584
22%
1168
April16th to endNight
27%
579
21%
1844
11%
579
41%
579
20%
1176
May1st to 15thNight
35%
584
20%
1755
14%
584
44%
584
25%
1116
May16th to endNight
42%
611
20%
1829
14%
609
51%
609
26%
1104
June1st to 15thNight
54%
585
23%
1586
14%
585
60%
585
38%
897
June16th to endNight
54%
585
24%
1641
12%
585
62%
585
42%
870
July1st to 15thNight
66%
555
19%
1665
17%
555
68%
555
36%
915
July16th to endNight
64%
612
24%
1738
20%
579
74%
579
40%
913
August1st to 15thNight
69%
575
25%
1717
30%
572
72%
572
40%
918
August16th to endNight
66%
621
27%
1973
28%
621
71%
621
38%
1055
September1st to 15thNight
60%
585
26%
2010
28%
585
64%
585
30%
1119
September16th to endNight
60%
582
29%
2145
25%
582
69%
582
33%
1087
October1st to 15thNight
42%
771
27%
2331
19%
771
47%
771
29%
1392
October16th to endNight
39%
832
31%
2496
16%
832
51%
832
36%
1361
November1st to 15thNight
35%
873
29%
2513
14%
873
47%
873
30%
1470
November16th to endNight
29%
1050
25%
2878
9%
1050
41%
1050
29%
1748
December1st to 15thNight
26%
975
20%
2730
8%
975
37%
975
24%
1734
December16th to endNight
25%
1040
22%
2805
8%
1040
36%
1040
21%
1945

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
12%6%25%42445%7%44%
52402
Night
10%5%24423446%50%
52076
TransparencyDay
38%5%13%25%14%2
52102
Night
34%411%26%18%3
51881
SeeingDay
13%12%23%27%18%5%
7446
Night
12%18%25%29%12%1
17484

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
11%5%15%6%24445%48%
1746
16th to endDay
12%7%34423346%46%
1872
February1st to 15thDay
11%9%45%5%23246%42%
1710
16th to endDay
14%9%26%5%24346%40%
1698
March1st to 15thDay
12%8%46%5%345%5%5%39%
2145
16th to endDay
22%9%35%423335%35%
2286
April1st to 15thDay
15%7%35%424346%41%
2266
16th to endDay
20%6%27%5%24335%36%
2388
May1st to 15thDay
17%7%25%5%2445%6%37%
2526
16th to endDay
13%6%35%6%3446%8%37%
2638
June1st to 15thDay
7%4245%35%5%6%8%46%
2697
16th to endDay
5%3133245%6%10%51%
2642
July1st to 15thDay
7%3245%35%5%6%8%47%
2535
16th to endDay
6%3245%36%5%6%10%45%
2674
August1st to 15thDay
6%4245%35%5%6%10%45%
2486
16th to endDay
8%415%435%5%6%8%47%
2580
September1st to 15thDay
12%5%25%433445%48%
2278
16th to endDay
8%41432445%8%51%
2139
October1st to 15thDay
14%6%14324345%48%
1950
16th to endDay
11%5%1441343455%
2080
November1st to 15thDay
11%7%2431235%6%50%
2003
16th to endDay
15%5%14313245%51%
1735
December1st to 15thDay
14%6%35%324446%44%
1560
16th to endDay
15%7%46%424346%40%
1768
January1st to 15thNight
10%6%24424346%50%
2522
16th to endNight
8%5%25%434346%51%
2704
February1st to 15thNight
11%9%35%42445%5%42%
2473
16th to endNight
13%7%25%423345%46%
2071
March1st to 15thNight
12%5%25%423345%48%
2145
16th to endNight
18%7%25%3235%45%38%
2288
April1st to 15thNight
10%7%2432345%6%48%
2012
16th to endNight
16%6%25%5%23446%43%
1844
May1st to 15thNight
12%5%34424347%46%
1754
16th to endNight
10%425%42335%10%46%
1827
June1st to 15thNight
43144245%5%9%54%
1586
16th to endNight
32133235%5%8%59%
1641
July1st to 15thNight
6%2134245%6%9%53%
1755
16th to endNight
42135%245%6%9%54%
1846
August1st to 15thNight
431333446%9%55%
1727
16th to endNight
5%31432445%7%55%
1973
September1st to 15thNight
11%4142245%5%5%53%
2010
16th to endNight
6%41433446%7%54%
2145
October1st to 15thNight
14%6%24323335%51%
2331
16th to endNight
10%422413335%59%
2496
November1st to 15thNight
12%424323346%54%
2513
16th to endNight
13%6%23313235%53%
2878
December1st to 15thNight
15%7%24313347%46%
2730
16th to endNight
15%9%35%5%23346%41%
2805

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
39%311%26%17%1
1747
16th to endDay
40%314%25%14%1
1872
February1st to 15thDay
45%5%15%23%8%1
1711
16th to endDay
45%312%23%13%2
1698
March1st to 15thDay
46%411%20%13%2
2145
16th to endDay
54%313%19%8%1
2288
April1st to 15thDay
44%412%24%13%
2266
16th to endDay
49%411%21%11%
2388
May1st to 15thDay
47%5%11%22%12%
2526
16th to endDay
43%6%15%22%11%
2642
June1st to 15thDay
33%7%13%27%16%1
2697
16th to endDay
25%6%16%31%16%1
2642
July1st to 15thDay
32%6%15%28%13%2
2396
16th to endDay
30%6%15%31%14%1
2519
August1st to 15thDay
32%7%15%26%16%1
2472
16th to endDay
32%7%14%25%15%5%
2580
September1st to 15thDay
37%410%24%17%5%
2278
16th to endDay
30%5%11%29%19%3
2139
October1st to 15thDay
37%311%22%19%4
1950
16th to endDay
33%39%27%20%5%
2080
November1st to 15thDay
34%410%26%19%4
2003
16th to endDay
37%210%29%20%1
1735
December1st to 15thDay
41%312%29%11%
1560
16th to endDay
46%314%21%10%3
1768
January1st to 15thNight
35%313%27%18%1
2522
16th to endNight
33%413%29%16%3
2704
February1st to 15thNight
42%413%24%13%1
2483
16th to endNight
40%310%25%17%3
2071
March1st to 15thNight
39%39%23%18%5%
2145
16th to endNight
46%412%22%12%1
2288
April1st to 15thNight
35%5%9%24%21%3
2012
16th to endNight
43%39%25%16%1
1844
May1st to 15thNight
38%5%13%24%16%1
1755
16th to endNight
34%6%15%28%13%1
1829
June1st to 15thNight
24%6%16%31%18%3
1586
16th to endNight
21%5%15%33%21%3
1641
July1st to 15thNight
25%6%14%32%16%4
1665
16th to endNight
22%6%15%31%22%2
1738
August1st to 15thNight
24%5%14%33%18%3
1717
16th to endNight
26%5%11%26%23%6%
1973
September1st to 15thNight
31%5%10%23%20%7%
2010
16th to endNight
27%410%29%23%4
2145
October1st to 15thNight
36%38%23%21%6%
2331
16th to endNight
28%38%30%23%6%
2496
November1st to 15thNight
32%410%23%22%6%
2513
16th to endNight
35%37%29%21%2
2878
December1st to 15thNight
38%313%28%14%
2730
16th to endNight
46%411%21%12%3
2805

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
28%11%28%25%4
135
16th to endDay
14%13%41%22%7%
144
February1st to 15thDay
11%23%42%18%4
135
16th to endDay
24%20%35%14%4
120
March1st to 15thDay
19%19%40%17%3
135
16th to endDay
29%15%32%18%3
144
April1st to 15thDay
17%23%33%18%7%
265
16th to endDay
22%16%30%22%9%
400
May1st to 15thDay
16%19%29%22%10%2
543
16th to endDay
15%15%25%23%14%6%
597
June1st to 15thDay
7%12%18%33%20%7%
570
16th to endDay
6%12%24%33%19%2
570
July1st to 15thDay
9%9%12%30%26%11%
550
16th to endDay
7%11%8%30%36%7%
595
August1st to 15thDay
8%6%10%34%33%6%
549
16th to endDay
8%6%14%29%32%7%
492
September1st to 15thDay
13%5%9%28%31%11%
313
16th to endDay
8%117%42%18%10%
180
October1st to 15thDay
17%333%31%6%7%
180
16th to endDay
11%8%38%33%7%
192
November1st to 15thDay
18%10%25%26%14%5%
180
16th to endDay
22%14%29%21%11%1
178
December1st to 15thDay
11%14%43%20%5%3
135
16th to endDay
18%20%39%18%3
144
January1st to 15thNight
12%23%32%24%5%1
975
16th to endNight
10%25%32%27%4
1040
February1st to 15thNight
14%24%34%23%2
955
16th to endNight
17%23%31%24%2
705
March1st to 15thNight
15%21%30%25%5%
585
16th to endNight
17%23%30%22%4
624
April1st to 15thNight
13%24%29%26%6%
584
16th to endNight
17%21%29%23%8%
579
May1st to 15thNight
13%20%27%28%9%1
585
16th to endNight
13%18%21%27%17%1
611
June1st to 15thNight
5%15%19%35%22%1
585
16th to endNight
216%22%42%15%1
585
July1st to 15thNight
6%11%11%38%28%3
555
16th to endNight
415%7%33%35%2
612
August1st to 15thNight
6%9%8%39%33%3
575
16th to endNight
7%8%11%36%33%2
621
September1st to 15thNight
12%9%12%35%25%4
585
16th to endNight
8%8%16%35%25%6%
582
October1st to 15thNight
17%11%23%28%17%1
771
16th to endNight
10%14%32%32%10%
832
November1st to 15thNight
14%19%27%25%12%
873
16th to endNight
15%22%30%24%7%
1050
December1st to 15thNight
18%22%27%25%4
975
16th to endNight
16%23%29%26%3
1040
Page generated at 2018-12-01 10:35:35. Version ac04

Copyright 2018 A. Danko


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