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 2017-09-19.

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%
15859
24%
47051
13%
15812
48%
15812
28%
28098

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%
539
21%
1857
13%
539
44%
539
23%
1072
April16th to endNight
26%
540
21%
1722
11%
540
41%
540
19%
1101
May1st to 15thNight
33%
539
20%
1620
13%
539
43%
539
24%
1038
May16th to endNight
38%
563
20%
1685
13%
561
48%
561
25%
1029
June1st to 15thNight
51%
540
21%
1464
11%
540
58%
540
36%
845
June16th to endNight
53%
540
24%
1515
12%
540
62%
540
42%
807
July1st to 15thNight
63%
510
18%
1530
15%
510
66%
510
35%
847
July16th to endNight
62%
564
24%
1594
21%
531
72%
531
39%
836
August1st to 15thNight
70%
539
25%
1610
30%
536
72%
536
40%
861
August16th to endNight
67%
573
28%
1821
30%
573
72%
573
38%
962
September1st to 15thNight
60%
540
25%
1855
27%
540
63%
540
30%
1030
September16th to endNight
59%
504
29%
1857
22%
504
69%
504
31%
952
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%
47746
Night
10%5%24423446%50%
47246
TransparencyDay
39%5%13%25%14%2
47446
Night
34%411%26%18%3
47051
SeeingDay
12%13%22%27%19%4
5886
Night
12%20%24%28%12%1
15860

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
15%7%35%424346%42%
2091
16th to endDay
20%7%27%5%24335%35%
2235
May1st to 15thDay
18%8%35%5%2445%5%36%
2331
16th to endDay
14%6%35%6%3446%7%36%
2430
June1st to 15thDay
8%425%5%35%5%6%8%44%
2490
16th to endDay
5%3133245%6%10%51%
2439
July1st to 15thDay
8%325%5%35%5%6%8%46%
2340
16th to endDay
6%315%5%36%5%6%10%45%
2466
August1st to 15thDay
6%4145%35%5%7%10%45%
2340
16th to endDay
7%415%4345%6%8%48%
2381
September1st to 15thDay
11%5%25%433346%49%
2103
16th to endDay
8%31432445%8%51%
1843
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%6%24323446%49%
1857
16th to endNight
16%6%25%5%23446%42%
1722
May1st to 15thNight
13%5%34424347%45%
1619
16th to endNight
11%5%2442335%9%45%
1683
June1st to 15thNight
43144246%5%8%53%
1464
16th to endNight
32133135%6%8%59%
1515
July1st to 15thNight
6%2144245%6%9%52%
1620
16th to endNight
42135%245%6%9%53%
1702
August1st to 15thNight
431433446%8%55%
1620
16th to endNight
5%314324446%56%
1821
September1st to 15thNight
10%4142245%5%5%53%
1855
16th to endNight
6%41433446%7%53%
1857
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
43%411%24%14%
2091
16th to endDay
50%5%11%20%11%
2235
May1st to 15thDay
48%5%11%21%12%
2331
16th to endDay
46%5%15%21%10%
2434
June1st to 15thDay
34%8%13%25%16%1
2490
16th to endDay
25%6%16%32%17%2
2439
July1st to 15thDay
34%6%15%28%13%2
2201
16th to endDay
30%6%15%31%14%1
2311
August1st to 15thDay
32%7%15%26%16%1
2326
16th to endDay
31%6%13%25%16%6%
2381
September1st to 15thDay
36%410%25%17%5%
2103
16th to endDay
31%5%11%29%19%3
1843
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
35%49%24%22%3
1857
16th to endNight
43%39%24%17%1
1722
May1st to 15thNight
40%5%13%23%16%1
1620
16th to endNight
35%6%16%26%13%1
1685
June1st to 15thNight
26%6%17%30%16%3
1464
16th to endNight
21%5%15%32%21%3
1515
July1st to 15thNight
27%5%14%32%16%4
1530
16th to endNight
23%5%15%30%22%2
1594
August1st to 15thNight
24%5%14%33%17%3
1610
16th to endNight
25%5%10%26%24%6%
1821
September1st to 15thNight
31%5%10%24%20%7%
1855
16th to endNight
28%5%10%28%23%3
1857
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
14%23%30%22%9%
210
16th to endDay
22%18%31%18%8%
345
May1st to 15thDay
17%20%27%22%10%1
468
16th to endDay
17%17%26%23%11%3
517
June1st to 15thDay
8%14%20%31%18%6%
495
16th to endDay
5%14%25%30%20%3
495
July1st to 15thDay
10%10%14%32%25%6%
475
16th to endDay
6%13%7%28%37%7%
515
August1st to 15thDay
7%7%8%34%33%7%
493
16th to endDay
7%7%12%29%34%8%
421
September1st to 15thDay
10%6%10%29%32%9%
258
16th to endDay
8%123%42%13%12%
99
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%
539
16th to endNight
17%22%29%22%7%
540
May1st to 15thNight
14%21%26%26%9%1
540
16th to endNight
14%19%22%26%14%1
563
June1st to 15thNight
5%17%20%34%21%1
540
16th to endNight
218%22%40%15%1
540
July1st to 15thNight
6%12%12%40%26%2
510
16th to endNight
5%17%7%31%35%2
564
August1st to 15thNight
6%10%7%39%33%3
539
16th to endNight
7%8%9%37%34%2
573
September1st to 15thNight
12%9%12%35%25%3
540
16th to endNight
7%9%16%34%24%6%
504
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 2017-09-20 03:49:44. Version ac04

Copyright 2017 A. Danko


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