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 2017-04-07.

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%
15370
24%
45555
13%
15323
47%
15323
27%
27291

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
27%
900
23%
2327
8%
895
38%
895
28%
1459
January16th to endNight
28%
960
27%
2496
8%
960
41%
960
28%
1554
February1st to 15thNight
22%
880
18%
2288
5%
876
29%
876
22%
1552
February16th to endNight
25%
651
25%
1913
8%
651
38%
651
24%
1175
March1st to 15thNight
29%
540
22%
1980
12%
540
42%
540
20%
1181
March16th to endNight
24%
576
16%
2112
9%
576
34%
576
18%
1359
April1st to 15thNight
30%
515
22%
1777
14%
515
45%
515
22%
1031
April16th to endNight
26%
495
21%
1579
10%
495
42%
495
19%
997
May1st to 15thNight
32%
494
21%
1485
14%
494
42%
494
23%
961
May16th to endNight
38%
515
18%
1541
12%
513
47%
513
24%
952
June1st to 15thNight
49%
495
22%
1342
12%
495
56%
495
35%
779
June16th to endNight
53%
495
23%
1389
11%
495
62%
495
41%
736
July1st to 15thNight
61%
465
19%
1395
15%
465
64%
465
33%
782
July16th to endNight
60%
522
23%
1468
19%
489
71%
489
38%
773
August1st to 15thNight
69%
494
27%
1475
32%
491
72%
491
41%
783
August16th to endNight
67%
525
26%
1668
27%
525
72%
525
38%
883
September1st to 15thNight
58%
495
26%
1700
28%
495
62%
495
28%
971
September16th to endNight
59%
492
29%
1815
23%
492
69%
492
32%
925
October1st to 15thNight
45%
652
29%
1972
22%
652
50%
652
32%
1124
October16th to endNight
37%
704
30%
2112
14%
704
50%
704
35%
1168
November1st to 15thNight
36%
745
31%
2145
14%
745
50%
745
32%
1214
November16th to endNight
26%
900
25%
2467
8%
900
39%
900
28%
1516
December1st to 15thNight
25%
900
20%
2520
7%
900
35%
900
23%
1638
December16th to endNight
26%
960
23%
2589
8%
960
37%
960
22%
1778

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%
45662
Night
11%5%24423446%49%
45750
TransparencyDay
39%5%13%25%14%2
45362
Night
35%411%26%18%3
45555
SeeingDay
12%15%21%26%18%4
5125
Night
12%20%24%28%12%1
15371

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%5%2434449%
1611
16th to endDay
13%7%3442335%6%44%
1728
February1st to 15thDay
11%9%45%5%24246%42%
1575
16th to endDay
13%8%26%5%24346%41%
1569
March1st to 15thDay
12%8%46%5%345%5%5%37%
1980
16th to endDay
22%9%35%423335%35%
2110
April1st to 15thDay
16%7%35%423335%42%
1986
16th to endDay
20%7%27%5%24345%35%
2049
May1st to 15thDay
19%8%35%5%25%45%5%33%
2136
16th to endDay
14%7%45%6%3446%7%35%
2222
June1st to 15thDay
8%425%5%35%5%7%8%42%
2282
16th to endDay
4313325%5%6%10%51%
2236
July1st to 15thDay
8%325%5%35%5%6%9%44%
2145
16th to endDay
6%315%5%37%5%6%10%43%
2284
August1st to 15thDay
6%3145%35%5%7%10%45%
2145
16th to endDay
8%415%4245%6%8%47%
2182
September1st to 15thDay
12%6%25%433446%46%
1928
16th to endDay
9%31432445%8%51%
1810
October1st to 15thDay
13%6%1432434451%
1650
16th to endDay
11%5%1442343453%
1760
November1st to 15thDay
9%5%2431235%6%54%
1711
16th to endDay
16%6%23313246%49%
1491
December1st to 15thDay
15%7%35%324346%43%
1440
16th to endDay
16%7%46%423346%41%
1632
January1st to 15thNight
10%6%23424346%50%
2327
16th to endNight
8%5%25%424346%50%
2496
February1st to 15thNight
11%9%36%42445%5%42%
2278
16th to endNight
11%6%25%423446%47%
1913
March1st to 15thNight
12%6%35%423345%46%
1980
16th to endNight
17%8%25%3235%45%39%
2112
April1st to 15thNight
11%7%24323446%49%
1777
16th to endNight
15%6%25%423445%44%
1579
May1st to 15thNight
13%5%44424447%44%
1484
16th to endNight
12%5%25%42335%10%44%
1539
June1st to 15thNight
43244245%5%8%53%
1342
16th to endNight
4233135%6%8%59%
1389
July1st to 15thNight
6%314425%5%7%9%51%
1485
16th to endNight
42135%245%6%9%53%
1576
August1st to 15thNight
431433446%8%55%
1485
16th to endNight
5%31432445%6%56%
1668
September1st to 15thNight
11%4243245%5%6%50%
1700
16th to endNight
6%41433445%7%53%
1815
October1st to 15thNight
12%424322335%54%
1972
16th to endNight
10%42241323458%
2112
November1st to 15thNight
9%424323245%57%
2145
16th to endNight
15%6%2331323453%
2467
December1st to 15thNight
16%8%34313346%44%
2520
16th to endNight
15%8%35%423345%42%
2589

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
38%312%26%17%1
1612
16th to endDay
41%315%25%13%1
1728
February1st to 15thDay
44%5%15%24%9%1
1576
16th to endDay
43%313%24%13%1
1569
March1st to 15thDay
47%412%20%12%2
1980
16th to endDay
53%313%19%9%1
2112
April1st to 15thDay
44%410%25%14%
1986
16th to endDay
49%412%21%11%
2049
May1st to 15thDay
50%5%12%20%11%
2136
16th to endDay
47%5%15%20%9%
2226
June1st to 15thDay
35%8%14%25%14%1
2282
16th to endDay
25%7%16%31%16%2
2236
July1st to 15thDay
35%6%16%26%13%2
2006
16th to endDay
30%7%15%31%14%1
2129
August1st to 15thDay
32%7%15%26%17%1
2131
16th to endDay
32%6%13%25%15%6%
2182
September1st to 15thDay
39%49%22%17%6%
1928
16th to endDay
30%5%11%29%19%3
1810
October1st to 15thDay
35%310%23%21%4
1650
16th to endDay
34%310%27%18%5%
1760
November1st to 15thDay
30%5%10%27%20%5%
1711
16th to endDay
37%210%28%20%
1491
December1st to 15thDay
43%313%29%10%
1440
16th to endDay
46%314%22%10%3
1632
January1st to 15thNight
35%313%26%19%1
2327
16th to endNight
34%413%28%16%2
2496
February1st to 15thNight
43%412%24%13%1
2288
16th to endNight
37%311%27%17%2
1913
March1st to 15thNight
40%310%23%16%4
1980
16th to endNight
45%412%22%12%1
2112
April1st to 15thNight
36%48%24%22%3
1777
16th to endNight
42%310%24%17%1
1579
May1st to 15thNight
40%5%14%24%14%1
1485
16th to endNight
36%6%16%26%12%1
1541
June1st to 15thNight
26%6%17%29%16%2
1342
16th to endNight
21%5%16%32%21%3
1389
July1st to 15thNight
28%5%14%31%14%4
1395
16th to endNight
23%5%15%30%22%2
1468
August1st to 15thNight
24%5%14%33%18%4
1475
16th to endNight
25%5%11%26%23%7%
1668
September1st to 15thNight
33%5%10%22%20%7%
1700
16th to endNight
27%410%28%24%3
1815
October1st to 15thNight
32%38%24%24%6%
1972
16th to endNight
29%38%30%22%5%
2112
November1st to 15thNight
29%310%24%24%7%
2145
16th to endNight
36%27%28%21%3
2467
December1st to 15thNight
41%313%27%13%
2520
16th to endNight
45%411%22%12%3
2589

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%13%32%21%3
90
16th to endDay
17%16%37%19%7%1
96
February1st to 15thDay
6%26%41%18%6%
90
16th to endDay
16%20%39%17%41
81
March1st to 15thDay
24%16%43%11%4
90
16th to endDay
26%16%29%21%5%1
96
April1st to 15thDay
16%26%28%22%7%
175
16th to endDay
18%20%32%17%8%
279
May1st to 15thDay
18%22%27%19%10%1
393
16th to endDay
19%18%23%22%11%4
437
June1st to 15thDay
8%16%20%31%17%6%
420
16th to endDay
5%16%20%30%23%3
420
July1st to 15thDay
10%12%16%31%23%5%
400
16th to endDay
6%15%8%28%34%7%
445
August1st to 15thDay
7%8%8%34%33%7%
418
16th to endDay
8%8%12%27%34%9%
350
September1st to 15thDay
12%7%10%33%29%6%
203
16th to endDay
6%122%42%14%13%
90
October1st to 15thDay
8%230%34%11%13%
90
16th to endDay
10%6%38%33%10%1
96
November1st to 15thDay
10%5%21%30%23%10%
90
16th to endDay
32%18%26%14%6%1
90
December1st to 15thDay
15%13%41%20%5%4
90
16th to endDay
19%18%36%20%4
96
January1st to 15thNight
12%25%31%24%5%1
900
16th to endNight
10%25%32%27%4
960
February1st to 15thNight
14%25%33%23%2
880
16th to endNight
15%24%32%24%3
651
March1st to 15thNight
15%22%29%26%5%
540
16th to endNight
17%25%29%22%4
576
April1st to 15thNight
13%24%28%26%6%
515
16th to endNight
16%24%29%22%7%
495
May1st to 15thNight
14%23%26%27%8%
495
16th to endNight
14%20%22%25%15%1
515
June1st to 15thNight
5%18%20%33%20%1
495
16th to endNight
219%20%39%16%1
495
July1st to 15thNight
6%13%13%38%25%2
465
16th to endNight
5%18%8%32%33%2
522
August1st to 15thNight
6%10%6%38%33%3
494
16th to endNight
7%9%8%35%35%2
525
September1st to 15thNight
13%10%13%35%23%3
495
16th to endNight
7%10%16%35%24%6%
492
October1st to 15thNight
15%12%21%28%19%2
652
16th to endNight
10%16%32%28%11%
704
November1st to 15thNight
11%21%26%26%13%
745
16th to endNight
16%25%28%21%7%
900
December1st to 15thNight
20%23%27%25%3
900
16th to endNight
16%24%28%27%3
960
Page generated at 2017-04-08 04:35:21. Version ac04

Copyright 2017 A. Danko


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