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 2005-11-06 to 2024-01-13.

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
40%
24422
23%
74705
14%
24360
49%
24360
30%
45087

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
30%
950
22%
2458
7%
946
41%
946
31%
1562
January11th to 20thNight
25%
911
23%
2367
8%
911
35%
911
28%
1560
January21st to endNight
29%
990
25%
2574
8%
990
39%
990
29%
1679
February1st to 10thNight
22%
900
18%
2340
5%
900
30%
900
24%
1612
February11th to 20thNight
24%
879
18%
2274
6%
875
32%
875
27%
1513
February21st to endNight
24%
533
27%
1717
10%
533
39%
533
23%
1075
March1st to 10thNight
27%
540
25%
1980
11%
540
44%
540
25%
1137
March11th to 20thNight
29%
540
20%
1980
13%
540
39%
540
21%
1223
March21st to endNight
24%
594
15%
2178
8%
594
35%
594
17%
1458
April1st to 10thNight
31%
540
22%
1890
12%
540
46%
540
26%
1081
April11th to 20thNight
30%
533
23%
1775
15%
533
43%
533
25%
1072
April21st to endNight
30%
540
21%
1686
11%
540
44%
540
24%
1084
May1st to 10thNight
34%
540
18%
1620
12%
540
43%
540
24%
1077
May11th to 20thNight
42%
531
21%
1594
18%
531
48%
531
32%
978
May21st to endNight
46%
584
20%
1746
14%
582
53%
582
29%
1078
June1st to 10thNight
65%
540
23%
1476
15%
540
70%
540
45%
820
June11th to 20thNight
59%
540
23%
1440
16%
540
63%
540
42%
845
June21st to endNight
60%
540
26%
1551
19%
540
65%
540
51%
794
July1st to 10thNight
73%
525
19%
1575
18%
525
74%
525
39%
885
July11th to 20thNight
73%
522
22%
1566
21%
522
76%
522
48%
806
July21st to endNight
70%
591
24%
1673
26%
558
72%
558
39%
922
August1st to 10thNight
69%
537
23%
1601
25%
534
73%
534
41%
864
August11th to 20thNight
71%
534
29%
1600
32%
534
75%
534
41%
881
August21st to endNight
74%
594
30%
1934
35%
594
77%
594
44%
976
September1st to 10thNight
64%
540
27%
1800
28%
540
67%
540
36%
965
September11th to 20thNight
60%
540
28%
1972
26%
540
69%
540
33%
1041
September21st to endNight
59%
540
32%
1980
28%
540
66%
540
38%
963
October1st to 10thNight
51%
706
28%
2146
20%
706
57%
706
39%
1174
October11th to 20thNight
32%
720
29%
2160
14%
720
45%
720
35%
1245
October21st to endNight
34%
792
27%
2376
13%
792
45%
792
29%
1426
November1st to 10thNight
39%
740
32%
2220
16%
740
53%
740
38%
1190
November11th to 20thNight
33%
926
28%
2458
10%
926
45%
926
34%
1491
November21st to endNight
31%
950
25%
2660
10%
950
42%
950
31%
1639
December1st to 10thNight
30%
950
22%
2660
8%
950
41%
950
29%
1672
December11th to 20thNight
28%
949
23%
3120
9%
948
38%
948
23%
1942
December21st to endNight
26%
1041
15%
4558
8%
1026
38%
1026
13%
3357

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%7%35%5%3445%7%45%
74597
Night
12%6%35%42445%7%49%
75135
TransparencyDay
39%5%12%26%16%2
74320
Night
36%5%11%26%19%3
74932
SeeingDay
15%11%27%27%16%4
14456
Night
14%9%31%32%12%1
24427

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 10thDay
12%7%25%6%3445%5%46%
1707
11th to 20thDay
14%9%46%5%34445%42%
1638
21st to endDay
12%8%46%5%3445%7%41%
1782
February1st to 10thDay
15%10%46%5%34346%41%
1620
11th to 20thDay
14%8%36%6%35%346%41%
1574
21st to endDay
13%10%36%5%3445%7%40%
1552
March1st to 10thDay
13%7%46%6%34445%42%
1980
11th to 20thDay
20%9%36%43345%5%37%
1980
21st to endDay
20%11%46%5%24446%33%
2178
April1st to 10thDay
13%7%35%43445%6%45%
2070
11th to 20thDay
15%7%36%5%35%5%5%7%40%
2134
21st to endDay
20%7%36%6%24446%37%
2272
May1st to 10thDay
19%8%36%5%3445%6%36%
2340
11th to 20thDay
17%7%25%5%3446%7%40%
2302
21st to endDay
14%7%46%7%45%5%6%9%33%
2531
June1st to 10thDay
7%4245%45%5%7%10%49%
2474
11th to 20thDay
7%5%25%5%36%6%6%9%48%
2520
21st to endDay
6%3244345%7%10%55%
2399
July1st to 10thDay
9%425%5%46%6%7%9%44%
2340
11th to 20thDay
43245%345%6%11%54%
2340
21st to endDay
8%5%25%5%46%5%6%9%44%
2546
August1st to 10thDay
6%425%6%45%6%7%10%44%
2328
11th to 20thDay
7%4245%35%5%7%8%49%
2301
21st to endDay
7%415%4345%6%8%53%
2422
September1st to 10thDay
13%5%25%333346%53%
2160
11th to 20thDay
10%424435%5%6%8%50%
1984
21st to endDay
8%425%33445%7%56%
1974
October1st to 10thDay
11%5%25%425%45%6%52%
1800
11th to 20thDay
13%6%23323345%56%
1800
21st to endDay
17%7%24424345%48%
1980
November1st to 10thDay
10%6%2442335%6%56%
1858
11th to 20thDay
14%6%25%32335%6%51%
1714
21st to endDay
16%8%24423246%49%
1520
December1st to 10thDay
10%8%45%42435%7%47%
1520
11th to 20thDay
14%8%47%5%3333445%
1918
21st to endDay
18%15%6%7%6%34445%28%
3039
January1st to 10thNight
10%8%35%424446%49%
2458
11th to 20thNight
12%6%37%5%3445%6%44%
2367
21st to endNight
10%7%36%435%447%46%
2574
February1st to 10thNight
12%11%46%43445%7%40%
2340
11th to 20thNight
13%8%37%5%2445%6%43%
2273
21st to endNight
15%8%35%5%24445%46%
1717
March1st to 10thNight
13%5%35%424347%48%
1980
11th to 20thNight
16%7%35%5%3335%5%44%
1980
21st to endNight
20%9%36%5%345%46%35%
2178
April1st to 10thNight
10%6%35%43345%6%50%
1890
11th to 20thNight
15%8%345%24447%46%
1775
21st to endNight
17%6%26%4235%5%7%43%
1686
May1st to 10thNight
15%7%35%5%35%447%42%
1620
11th to 20thNight
14%6%25%433347%49%
1593
21st to endNight
10%6%36%5%245%7%10%43%
1745
June1st to 10thNight
5%3134346%6%10%54%
1476
11th to 20thNight
4324435%6%7%10%52%
1440
21st to endNight
432432345%8%62%
1551
July1st to 10thNight
7%3145%35%5%7%9%51%
1620
11th to 20thNight
321343446%9%60%
1620
21st to endNight
6%3245%35%5%6%10%49%
1772
August1st to 10thNight
5%4144345%8%10%52%
1611
11th to 20thNight
6%424435%45%8%56%
1600
21st to endNight
5%31432445%7%59%
1934
September1st to 10thNight
11%424324445%57%
1800
11th to 20thNight
8%5%143245%5%7%54%
1972
21st to endNight
7%42433345%7%59%
1980
October1st to 10thNight
9%5%24434446%57%
2146
11th to 20thNight
13%6%2442234456%
2160
21st to endNight
16%6%34423335%52%
2376
November1st to 10thNight
10%423322345%61%
2220
11th to 20thNight
11%5%2442335%6%53%
2458
21st to endNight
16%7%33323335%53%
2660
December1st to 10thNight
12%7%35%435%35%7%47%
2660
11th to 20thNight
13%7%35%43445%6%46%
3279
21st to endNight
19%15%5%7%5%3333432%
4624

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
41%311%26%17%1
1708
11th to 20thDay
45%411%25%13%1
1638
21st to endDay
43%315%25%12%1
1782
February1st to 10thDay
48%5%11%24%9%2
1620
11th to 20thDay
45%314%21%14%3
1583
21st to endDay
45%49%24%14%4
1552
March1st to 10thDay
45%311%20%16%4
1980
11th to 20thDay
51%410%21%12%3
1980
21st to endDay
54%414%19%8%2
2178
April1st to 10thDay
40%5%12%25%17%1
2070
11th to 20thDay
43%5%12%24%15%1
2134
21st to endDay
49%411%24%11%
2272
May1st to 10thDay
49%6%11%21%13%1
2340
11th to 20thDay
43%6%14%24%12%
2306
21st to endDay
47%7%14%22%9%1
2531
June1st to 10thDay
29%8%17%27%16%1
2474
11th to 20thDay
32%7%14%29%16%2
2520
21st to endDay
24%6%15%33%18%3
2399
July1st to 10thDay
36%7%14%25%15%3
2276
11th to 20thDay
25%7%16%30%19%4
2271
21st to endDay
34%7%14%30%15%
2405
August1st to 10thDay
32%9%17%27%14%1
2314
11th to 20thDay
31%6%12%32%16%2
2301
21st to endDay
28%7%12%26%20%7%
2422
September1st to 10thDay
33%412%28%16%6%
2160
11th to 20thDay
31%5%10%25%26%2
1984
21st to endDay
29%5%9%28%25%4
1974
October1st to 10thDay
33%411%27%22%3
1800
11th to 20thDay
33%47%28%24%5%
1800
21st to endDay
41%39%22%19%6%
1980
November1st to 10thDay
30%5%11%29%20%4
1858
11th to 20thDay
36%39%26%22%4
1714
21st to endDay
39%39%28%19%2
1520
December1st to 10thDay
38%411%33%13%1
1520
11th to 20thDay
45%310%26%14%2
1915
21st to endDay
58%411%19%7%2
3039
January1st to 10thNight
37%413%26%17%2
2458
11th to 20thNight
41%411%27%16%1
2367
21st to endNight
39%5%12%28%13%3
2574
February1st to 10thNight
45%5%11%23%15%1
2340
11th to 20thNight
41%412%24%16%3
2274
21st to endNight
43%37%23%18%6%
1717
March1st to 10thNight
38%39%23%21%5%
1980
11th to 20thNight
43%410%22%17%4
1980
21st to endNight
50%412%21%11%2
2178
April1st to 10thNight
35%5%10%23%23%4
1890
11th to 20thNight
39%49%25%19%4
1775
21st to endNight
43%410%26%16%1
1686
May1st to 10thNight
44%5%11%23%15%1
1620
11th to 20thNight
36%5%14%27%16%1
1594
21st to endNight
36%7%16%28%11%1
1746
June1st to 10thNight
23%6%18%32%17%3
1476
11th to 20thNight
26%8%16%29%19%2
1440
21st to endNight
21%415%34%22%5%
1551
July1st to 10thNight
28%6%15%31%16%4
1575
11th to 20thNight
19%7%14%31%24%4
1566
21st to endNight
27%6%14%31%20%2
1673
August1st to 10thNight
25%7%16%35%14%3
1601
11th to 20thNight
26%6%10%32%25%2
1600
21st to endNight
22%6%12%27%25%7%
1934
September1st to 10thNight
28%6%10%28%20%7%
1800
11th to 20thNight
29%5%9%24%26%5%
1972
21st to endNight
25%49%28%29%5%
1980
October1st to 10thNight
29%49%27%26%6%
2146
11th to 20thNight
33%36%28%24%7%
2160
21st to endNight
37%37%23%24%5%
2376
November1st to 10thNight
27%411%28%24%6%
2220
11th to 20thNight
33%48%25%26%4
2458
21st to endNight
37%38%27%21%3
2660
December1st to 10thNight
38%5%12%27%17%1
2660
11th to 20thNight
40%48%29%17%2
3281
21st to endNight
58%48%19%10%2
4624

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
24%17%32%22%5%
270
11th to 20thDay
30%17%36%15%1
246
21st to endDay
15%17%48%17%3
264
February1st to 10thDay
25%23%35%13%21
240
11th to 20thDay
19%24%40%12%5%
240
21st to endDay
26%26%33%13%21
198
March1st to 10thDay
23%19%40%16%2
240
11th to 20thDay
28%17%31%20%5%
240
21st to endDay
31%27%28%11%2
264
April1st to 10thDay
18%19%42%15%6%1
330
11th to 20thDay
23%17%34%20%6%
412
21st to endDay
22%16%33%23%5%1
532
May1st to 10thDay
20%16%34%21%8%1
603
11th to 20thDay
19%12%30%25%12%2
625
21st to endDay
17%8%30%25%15%5%
679
June1st to 10thDay
7%419%38%24%8%
630
11th to 20thDay
8%427%37%20%3
630
21st to endDay
6%7%31%34%20%2
630
July1st to 10thDay
9%413%35%29%10%
621
11th to 20thDay
5%220%35%30%7%
618
21st to endDay
9%214%34%33%8%
684
August1st to 10thDay
7%317%40%28%5%
626
11th to 20thDay
7%316%39%30%5%
615
21st to endDay
9%313%32%35%8%
541
September1st to 10thDay
14%415%33%28%7%
450
11th to 20thDay
5%222%40%25%6%
274
21st to endDay
12%8%24%37%14%5%
270
October1st to 10thDay
13%10%32%24%16%6%
270
11th to 20thDay
15%17%40%23%41
270
21st to endDay
25%18%31%21%5%
297
November1st to 10thDay
13%15%37%22%9%4
270
11th to 20thDay
19%21%29%23%8%1
270
21st to endDay
24%16%32%22%6%
270
December1st to 10thDay
14%13%45%17%7%3
270
11th to 20thDay
22%18%31%23%6%
270
21st to endDay
20%28%37%14%1
297
January1st to 10thNight
15%13%38%27%6%
950
11th to 20thNight
17%13%39%25%5%1
911
21st to endNight
13%14%41%28%4
990
February1st to 10thNight
18%15%41%23%3
900
11th to 20thNight
19%13%40%26%2
879
21st to endNight
22%15%37%23%4
533
March1st to 10thNight
17%11%42%26%4
540
11th to 20thNight
19%12%35%27%6%1
540
21st to endNight
23%13%35%25%3
594
April1st to 10thNight
14%14%39%29%5%
540
11th to 20thNight
19%13%35%26%7%
533
21st to endNight
19%11%36%27%7%
540
May1st to 10thNight
18%7%35%31%9%
540
11th to 20thNight
15%8%30%32%15%1
531
21st to endNight
12%5%30%32%18%3
584
June1st to 10thNight
5%320%41%29%1
540
11th to 20thNight
6%326%46%18%2
540
21st to endNight
5%229%46%16%1
540
July1st to 10thNight
7%311%42%34%3
525
11th to 20thNight
3216%43%34%2
522
21st to endNight
7%211%41%37%2
591
August1st to 10thNight
5%214%47%30%2
537
11th to 20thNight
8%212%48%28%3
534
21st to endNight
7%111%41%37%3
594
September1st to 10thNight
11%317%43%22%4
540
11th to 20thNight
11%220%37%26%4
540
21st to endNight
8%5%23%40%21%4
540
October1st to 10thNight
11%429%34%20%2
706
11th to 20thNight
16%9%38%28%8%1
720
21st to endNight
19%11%32%29%8%1
792
November1st to 10thNight
11%11%36%30%11%1
740
11th to 20thNight
14%14%36%27%9%
926
21st to endNight
20%11%35%29%5%
950
December1st to 10thNight
16%12%38%27%6%1
950
11th to 20thNight
20%11%36%28%4
950
21st to endNight
21%15%34%26%4
1045
Page generated at 2024-01-10 00:25:05. Version ac07

Copyright 2024 Attilla Danko


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