Outback Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Outback Observatory clear sky chart from 2005-11-05 to 2018-01-20.

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
32%
16677
16%
48480
8%
16631
40%
16631
23%
32596

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
20%
975
13%
2716
4%
970
29%
970
17%
1978
January16th to endNight
17%
985
15%
2757
3%
985
28%
985
17%
2041
February1st to 15thNight
21%
877
16%
2291
3%
873
30%
873
19%
1631
February16th to endNight
25%
631
15%
1893
7%
631
32%
631
16%
1368
March1st to 15thNight
29%
720
16%
2160
9%
720
35%
720
21%
1443
March16th to endNight
32%
591
19%
2003
13%
591
42%
591
21%
1309
April1st to 15thNight
27%
539
15%
1797
9%
539
38%
539
19%
1231
April16th to endNight
31%
540
17%
1716
8%
540
41%
540
20%
1174
May1st to 15thNight
29%
540
14%
1474
6%
540
35%
540
21%
1055
May16th to endNight
39%
562
13%
1498
5%
561
44%
561
29%
994
June1st to 15thNight
44%
540
10%
1440
4%
540
48%
540
29%
960
June16th to endNight
47%
540
14%
1440
6%
540
51%
540
33%
898
July1st to 15thNight
58%
510
16%
1360
8%
510
61%
510
45%
778
July16th to endNight
54%
564
19%
1417
10%
531
59%
531
43%
811
August1st to 15thNight
55%
539
21%
1452
14%
536
60%
536
36%
906
August16th to endNight
54%
573
20%
1910
19%
573
60%
573
30%
1135
September1st to 15thNight
54%
540
25%
1800
21%
540
63%
540
34%
999
September16th to endNight
46%
690
21%
1953
14%
690
52%
690
33%
1174
October1st to 15thNight
37%
720
22%
2127
13%
720
45%
720
28%
1313
October16th to endNight
29%
768
15%
2450
7%
768
38%
768
18%
1679
November1st to 15thNight
26%
760
19%
2471
10%
760
37%
760
21%
1606
November16th to endNight
23%
958
15%
2713
6%
958
32%
958
19%
1913
December1st to 15thNight
17%
975
11%
2730
3%
975
24%
975
15%
2002
December16th to endNight
18%
1040
15%
2912
3%
1040
28%
1040
14%
2198

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
13%8%36%5%35%5%5%7%34%
49059
Night
13%8%36%5%3445%7%38%
48647
Cloud CoverDay
14%8%36%5%35%45%7%35%
49069
Night
13%8%36%5%3445%7%38%
48652
Cloud CoverDay
13%8%36%5%35%45%7%35%
49067
Night
13%8%36%5%24447%38%
48652
TransparencyDay
47%413%23%10%
48744
Night
45%412%24%11%1
48480
SeeingDay
17%12%30%23%12%3
6502
Night
18%9%31%28%10%1
16678

By Month

Percentage Cloud Cover NE (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%13%5%9%6%2446%7%28%
1552
16th to endDay
13%12%5%10%8%3446%6%23%
1571
February1st to 15thDay
10%11%48%5%35%45%7%32%
1570
16th to endDay
13%11%5%7%6%346%5%7%29%
1580
March1st to 15thDay
13%9%49%6%35%45%6%31%
1790
16th to endDay
15%9%36%6%345%5%6%32%
2229
April1st to 15thDay
15%10%46%6%345%45%33%
2151
16th to endDay
18%10%35%6%35%445%31%
2243
May1st to 15thDay
17%7%36%6%3435%6%33%
2475
16th to endDay
11%5%36%6%36%5%5%7%37%
2617
June1st to 15thDay
16%5%345%36%45%7%37%
2520
16th to endDay
10%5%27%5%36%5%6%8%36%
2520
July1st to 15thDay
8%3245%36%6%6%10%42%
2520
16th to endDay
8%5%25%5%36%5%7%8%41%
2655
August1st to 15thDay
10%425%5%36%6%6%8%40%
2499
16th to endDay
15%5%245%2445%7%41%
2292
September1st to 15thDay
11%6%245%3435%7%45%
2160
16th to endDay
12%6%36%5%35%5%6%8%36%
1995
October1st to 15thDay
18%8%35%413448%38%
1830
16th to endDay
19%10%46%5%33345%31%
1773
November1st to 15thDay
14%9%37%5%35%45%7%33%
1717
16th to endDay
14%10%5%8%6%25%5%5%7%30%
1576
December1st to 15thDay
15%12%48%434447%28%
1560
16th to endDay
20%14%49%6%35%35%6%19%
1664
January1st to 15thNight
14%10%5%6%6%35%346%32%
2716
16th to endNight
10%12%6%8%6%45%5%5%6%28%
2757
February1st to 15thNight
9%11%5%7%5%35%446%36%
2288
16th to endNight
13%13%47%7%34446%31%
1893
March1st to 15thNight
13%7%36%5%34445%40%
2147
16th to endNight
14%9%45%5%3435%6%38%
2003
April1st to 15thNight
21%7%35%5%24445%35%
1797
16th to endNight
20%7%35%5%2445%7%34%
1716
May1st to 15thNight
17%9%45%5%2345%8%32%
1474
16th to endNight
12%6%245%35%5%5%9%40%
1496
June1st to 15thNight
12%6%26%5%4445%6%41%
1440
16th to endNight
10%5%24425%5%6%8%44%
1440
July1st to 15thNight
6%3133245%5%9%54%
1440
16th to endNight
6%32441446%8%53%
1513
August1st to 15thNight
7%415%5%445%48%48%
1461
16th to endNight
12%5%2433445%6%47%
1910
September1st to 15thNight
9%425%32345%6%52%
1800
16th to endNight
10%6%3442345%9%46%
1953
October1st to 15thNight
14%6%25%324347%44%
2127
16th to endNight
17%7%36%5%3445%7%33%
2450
November1st to 15thNight
15%9%45%423447%38%
2471
16th to endNight
15%9%36%5%35%45%8%31%
2713
December1st to 15thNight
14%13%47%5%34446%30%
2730
16th to endNight
17%14%5%7%5%34437%26%
2912

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 15thDay
11%12%5%9%6%345%5%7%28%
1552
16th to endDay
13%12%5%10%8%4445%6%23%
1571
February1st to 15thDay
10%11%39%5%35%5%46%33%
1570
16th to endDay
12%12%5%7%5%35%5%5%6%30%
1580
March1st to 15thDay
13%9%5%9%6%3445%6%31%
1800
16th to endDay
15%9%46%6%345%5%6%32%
2229
April1st to 15thDay
16%10%36%6%345%45%33%
2151
16th to endDay
19%10%35%6%34445%31%
2243
May1st to 15thDay
18%7%26%6%3435%6%34%
2475
16th to endDay
11%5%36%6%36%5%6%7%37%
2617
June1st to 15thDay
16%6%345%35%447%37%
2520
16th to endDay
10%5%27%5%46%5%6%8%37%
2520
July1st to 15thDay
8%4145%36%5%6%9%43%
2520
16th to endDay
8%5%25%5%36%5%7%8%41%
2655
August1st to 15thDay
10%425%5%45%6%6%8%40%
2499
16th to endDay
16%5%25%42445%7%41%
2292
September1st to 15thDay
11%6%25%5%34347%44%
2160
16th to endDay
11%6%27%5%35%5%5%8%37%
1995
October1st to 15thDay
19%8%2442335%7%38%
1830
16th to endDay
19%10%46%5%33445%31%
1773
November1st to 15thDay
14%9%36%5%35%45%7%33%
1717
16th to endDay
14%10%5%8%5%25%5%5%6%30%
1576
December1st to 15thDay
15%12%47%5%3445%6%29%
1560
16th to endDay
20%14%5%8%7%25%446%19%
1664
January1st to 15thNight
14%10%5%6%6%35%446%32%
2716
16th to endNight
10%12%5%8%6%35%5%5%6%28%
2757
February1st to 15thNight
9%11%5%8%5%35%336%36%
2281
16th to endNight
12%14%46%6%44445%32%
1893
March1st to 15thNight
13%7%46%5%2345%5%40%
2160
16th to endNight
14%9%46%5%2425%6%38%
2003
April1st to 15thNight
21%7%35%5%23445%35%
1797
16th to endNight
20%7%35%42445%7%34%
1716
May1st to 15thNight
19%7%45%5%2345%7%32%
1473
16th to endNight
12%5%245%35%5%5%9%40%
1496
June1st to 15thNight
12%5%36%6%3445%6%41%
1440
16th to endNight
10%5%14435%5%6%8%45%
1440
July1st to 15thNight
6%3134135%5%9%55%
1440
16th to endNight
5%32443346%7%54%
1513
August1st to 15thNight
7%415%5%345%47%48%
1461
16th to endNight
12%42343345%6%47%
1910
September1st to 15thNight
9%42432345%7%52%
1800
16th to endNight
10%6%2442345%8%47%
1953
October1st to 15thNight
14%7%24324447%44%
2127
16th to endNight
17%7%36%5%3445%7%33%
2450
November1st to 15thNight
15%9%45%423447%38%
2471
16th to endNight
15%9%37%5%25%46%7%31%
2713
December1st to 15thNight
15%13%47%5%24346%31%
2730
16th to endNight
17%14%5%7%5%23436%27%
2912

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%13%5%8%6%3446%6%28%
1552
16th to endDay
13%12%5%10%8%345%5%6%23%
1571
February1st to 15thDay
10%11%49%5%35%5%36%34%
1570
16th to endDay
13%12%47%5%345%47%30%
1580
March1st to 15thDay
13%9%5%9%5%35%45%6%31%
1800
16th to endDay
15%9%46%6%35%447%31%
2227
April1st to 15thDay
15%10%36%6%345%46%32%
2151
16th to endDay
18%10%36%5%44445%31%
2243
May1st to 15thDay
17%7%36%6%3435%6%34%
2475
16th to endDay
11%6%36%5%36%5%5%7%37%
2617
June1st to 15thDay
15%6%35%5%35%45%7%37%
2520
16th to endDay
9%5%36%5%46%5%5%9%36%
2520
July1st to 15thDay
7%4145%36%6%6%10%42%
2520
16th to endDay
8%5%25%6%36%5%6%8%41%
2655
August1st to 15thDay
9%425%6%45%6%6%8%40%
2499
16th to endDay
15%5%25%4245%5%6%41%
2292
September1st to 15thDay
11%6%245%34447%44%
2160
16th to endDay
12%5%37%5%35%5%6%8%37%
1995
October1st to 15thDay
18%8%25%42335%7%38%
1830
16th to endDay
20%10%36%5%2345%5%31%
1773
November1st to 15thDay
14%10%35%5%35%447%33%
1717
16th to endDay
14%10%5%7%5%245%5%6%30%
1576
December1st to 15thDay
16%12%47%5%3445%5%29%
1560
16th to endDay
21%14%48%7%25%35%6%19%
1664
January1st to 15thNight
14%10%6%6%5%35%446%32%
2716
16th to endNight
10%13%49%6%35%45%6%28%
2757
February1st to 15thNight
9%12%5%7%5%35%346%36%
2281
16th to endNight
13%13%47%7%34345%31%
1893
March1st to 15thNight
13%7%46%5%3445%440%
2160
16th to endNight
14%9%46%424347%38%
2003
April1st to 15thNight
20%8%35%5%23446%35%
1797
16th to endNight
20%8%25%5%2345%6%34%
1716
May1st to 15thNight
18%8%45%5%235%5%7%32%
1473
16th to endNight
12%5%25%5%45%45%9%40%
1496
June1st to 15thNight
12%6%27%6%35%45%6%41%
1440
16th to endNight
10%5%244245%6%8%45%
1440
July1st to 15thNight
6%3133145%5%10%54%
1440
16th to endNight
5%4235%235%5%8%53%
1513
August1st to 15thNight
6%5%15%5%35%5%48%48%
1461
16th to endNight
12%42442445%6%47%
1910
September1st to 15thNight
8%5%2431445%7%52%
1800
16th to endNight
10%6%2442335%8%47%
1953
October1st to 15thNight
14%7%24324347%44%
2127
16th to endNight
17%7%36%6%3445%7%32%
2450
November1st to 15thNight
15%9%35%5%23447%38%
2471
16th to endNight
15%9%46%5%35%45%8%31%
2713
December1st to 15thNight
15%13%47%5%24446%31%
2730
16th to endNight
18%14%5%7%5%34336%27%
2912

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
53%5%10%19%8%1
1553
16th to endDay
59%412%17%5%
1571
February1st to 15thDay
50%5%13%20%8%1
1571
16th to endDay
53%5%12%20%7%
1580
March1st to 15thDay
52%413%19%8%1
1800
16th to endDay
51%414%20%6%1
2229
April1st to 15thDay
51%410%20%12%
2151
16th to endDay
53%39%19%12%1
2243
May1st to 15thDay
50%312%22%10%
2475
16th to endDay
44%5%11%24%12%1
2621
June1st to 15thDay
46%414%26%8%
2520
16th to endDay
43%5%16%23%11%
2520
July1st to 15thDay
35%415%29%12%1
2371
16th to endDay
38%5%13%26%14%1
2488
August1st to 15thDay
38%5%13%28%11%1
2484
16th to endDay
40%5%13%25%13%1
2292
September1st to 15thDay
38%313%31%12%
2160
16th to endDay
42%5%15%27%8%
1995
October1st to 15thDay
44%414%27%8%
1830
16th to endDay
53%411%22%7%
1773
November1st to 15thDay
50%411%21%11%
1717
16th to endDay
52%415%21%4
1576
December1st to 15thDay
55%410%22%7%
1560
16th to endDay
65%210%13%7%
1664
January1st to 15thNight
53%410%20%10%
2716
16th to endNight
54%411%22%7%
2757
February1st to 15thNight
49%411%22%9%2
2291
16th to endNight
54%411%20%8%1
1893
March1st to 15thNight
45%412%23%12%1
2160
16th to endNight
46%312%25%11%
2003
April1st to 15thNight
50%38%20%15%2
1797
16th to endNight
48%410%20%13%2
1716
May1st to 15thNight
50%411%22%10%
1474
16th to endNight
40%413%25%13%
1498
June1st to 15thNight
41%316%25%12%
1440
16th to endNight
36%415%28%12%3
1440
July1st to 15thNight
24%6%13%34%17%2
1360
16th to endNight
27%418%29%16%3
1417
August1st to 15thNight
34%5%12%28%17%1
1452
16th to endNight
36%413%25%17%2
1910
September1st to 15thNight
31%410%35%17%
1800
16th to endNight
34%314%36%9%
1953
October1st to 15thNight
39%312%31%11%1
2127
16th to endNight
50%414%20%10%
2450
November1st to 15thNight
45%312%23%13%
2471
16th to endNight
50%416%19%8%1
2713
December1st to 15thNight
54%413%20%7%
2730
16th to endNight
58%312%16%8%
2912

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
22%16%33%24%3
135
16th to endDay
24%17%37%15%4
109
February1st to 15thDay
13%33%37%13%2
90
16th to endDay
19%16%49%11%21
81
March1st to 15thDay
21%20%33%17%6%1
90
16th to endDay
26%12%26%22%8%2
219
April1st to 15thDay
22%13%28%25%10%1
270
16th to endDay
25%13%28%18%11%1
270
May1st to 15thDay
21%16%34%17%7%2
432
16th to endDay
16%12%34%22%9%4
517
June1st to 15thDay
16%11%29%27%12%3
495
16th to endDay
13%10%31%26%13%4
495
July1st to 15thDay
11%7%27%28%18%6%
475
16th to endDay
8%8%27%31%16%7%
515
August1st to 15thDay
13%425%30%21%5%
490
16th to endDay
20%5%20%25%20%6%
332
September1st to 15thDay
12%6%25%26%20%9%
315
16th to endDay
12%8%28%29%18%2
314
October1st to 15thDay
21%15%27%23%10%1
165
16th to endDay
24%16%40%17%1
144
November1st to 15thDay
13%20%35%20%8%2
135
16th to endDay
25%20%34%11%5%1
135
December1st to 15thDay
21%23%39%10%5%
135
16th to endDay
33%26%29%9%
144
January1st to 15thNight
20%13%36%23%5%1
975
16th to endNight
17%13%41%22%5%
985
February1st to 15thNight
14%16%36%25%6%
877
16th to endNight
21%11%31%27%6%
631
March1st to 15thNight
18%12%34%24%9%
720
16th to endNight
19%9%32%27%10%1
591
April1st to 15thNight
27%8%31%26%6%
539
16th to endNight
26%7%30%28%6%
540
May1st to 15thNight
22%8%33%26%7%
540
16th to endNight
14%6%33%32%11%1
563
June1st to 15thNight
15%6%26%39%12%
540
16th to endNight
13%427%38%14%1
540
July1st to 15thNight
8%224%42%20%
510
16th to endNight
8%225%41%20%1
564
August1st to 15thNight
10%123%38%24%1
539
16th to endNight
16%320%33%24%2
573
September1st to 15thNight
10%326%32%21%6%
540
16th to endNight
15%6%25%33%17%2
690
October1st to 15thNight
18%10%29%26%14%1
720
16th to endNight
21%10%29%25%11%
768
November1st to 15thNight
21%10%36%22%8%1
760
16th to endNight
20%14%34%23%6%
958
December1st to 15thNight
23%16%34%20%5%
975
16th to endNight
23%14%32%24%4
1040
Page generated at 2018-01-21 11:19:26. Version ac04

Copyright 2018 A. Danko


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