Melbourne
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Melbourne clear sky chart from 2005-11-05 to 2017-08-12.

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
53%
15964
18%
46523
13%
15924
59%
15924
23%
30560

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
40%
717
18%
2327
11%
716
50%
716
20%
1486
January16th to endNight
39%
768
22%
2496
16%
768
50%
768
23%
1532
February1st to 15thNight
44%
701
23%
2112
15%
698
55%
698
27%
1258
February16th to endNight
46%
631
26%
1767
14%
631
57%
631
31%
1036
March1st to 15thNight
45%
720
29%
1980
16%
720
57%
720
32%
1156
March16th to endNight
52%
768
23%
2112
16%
768
59%
768
33%
1261
April1st to 15thNight
55%
718
22%
1970
17%
718
60%
718
34%
1146
April16th to endNight
57%
720
25%
1800
14%
720
62%
720
33%
1110
May1st to 15thNight
63%
674
23%
1754
15%
674
65%
674
34%
1074
May16th to endNight
63%
561
18%
1682
13%
561
65%
561
24%
1094
June1st to 15thNight
57%
540
11%
1620
7%
540
59%
540
17%
1166
June16th to endNight
62%
540
10%
1620
8%
540
63%
540
18%
1154
July1st to 15thNight
65%
510
7%
1530
5%
510
65%
510
17%
1116
July16th to endNight
65%
564
9%
1595
8%
531
70%
531
21%
1126
August1st to 15thNight
70%
543
8%
1591
7%
540
70%
540
22%
1087
August16th to endNight
59%
700
6%
1824
4%
700
59%
700
18%
1396
September1st to 15thNight
61%
660
6%
1815
6%
660
61%
660
17%
1398
September16th to endNight
51%
657
8%
1815
5%
657
54%
657
13%
1444
October1st to 15thNight
56%
660
20%
1919
19%
660
59%
660
22%
1288
October16th to endNight
53%
704
21%
2112
17%
704
60%
704
23%
1360
November1st to 15thNight
51%
700
23%
2101
21%
700
56%
700
25%
1349
November16th to endNight
46%
720
24%
2160
16%
720
55%
720
22%
1427
December1st to 15thNight
46%
720
21%
2325
18%
720
53%
720
19%
1542
December16th to endNight
51%
768
20%
2496
16%
768
59%
768
23%
1554

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
8%5%26%6%46%6%7%10%35%
47428
Night
8%5%25%5%35%6%7%9%40%
46732
TransparencyDay
38%11%16%17%12%3
47129
Night
37%10%16%19%12%4
46535
SeeingDay
8%9%9%20%28%24%
5793
Night
9%16%10%21%28%13%
15973

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
12%6%345%35%6%7%9%35%
1611
16th to endDay
10%5%2443446%8%44%
1728
February1st to 15thDay
10%5%25%43445%8%45%
1738
16th to endDay
9%4345%25%5%5%7%47%
1704
March1st to 15thDay
6%3145%35%46%9%49%
1980
16th to endDay
7%425%5%35%6%5%9%46%
2111
April1st to 15thDay
5%3246%35%6%7%9%47%
1978
16th to endDay
6%4245%35%6%6%9%44%
2160
May1st to 15thDay
5%3145%4447%9%47%
2205
16th to endDay
8%436%6%47%7%8%9%33%
2431
June1st to 15thDay
10%7%37%6%5%7%8%7%10%24%
2340
16th to endDay
7%5%26%8%5%6%8%9%11%28%
2340
July1st to 15thDay
8%6%37%7%36%8%8%12%25%
2340
16th to endDay
9%5%26%7%47%9%9%11%26%
2465
August1st to 15thDay
6%5%26%6%37%9%8%14%28%
2258
16th to endDay
9%6%37%8%5%7%7%9%12%22%
2022
September1st to 15thDay
7%5%37%6%47%9%9%12%24%
1815
16th to endDay
11%7%38%8%49%8%8%10%19%
1815
October1st to 15thDay
10%5%36%7%47%8%6%10%30%
1710
16th to endDay
11%5%25%5%35%45%8%40%
1760
November1st to 15thDay
6%426%6%36%6%7%8%40%
1757
16th to endDay
9%435%7%45%6%6%9%37%
1800
December1st to 15thDay
12%5%36%5%46%6%6%7%36%
1632
16th to endDay
8%425%446%7%6%8%39%
1728
January1st to 15thNight
10%6%245%35%46%9%41%
2327
16th to endNight
10%5%35%425%5%6%8%42%
2496
February1st to 15thNight
11%5%24422447%50%
2112
16th to endNight
7%32332445%8%52%
1767
March1st to 15thNight
5%325%43445%8%53%
1980
16th to endNight
7%3234245%7%8%50%
2112
April1st to 15thNight
5%21441445%9%54%
1970
16th to endNight
7%2134346%5%9%49%
1800
May1st to 15thNight
6%3134235%6%7%53%
1754
16th to endNight
6%315%5%37%6%7%12%38%
1682
June1st to 15thNight
10%6%36%5%47%6%8%11%27%
1620
16th to endNight
7%425%6%47%7%9%11%33%
1620
July1st to 15thNight
9%5%27%6%45%7%8%10%31%
1620
16th to endNight
5%435%6%37%7%8%11%36%
1703
August1st to 15thNight
4415%5%45%8%11%12%35%
1602
16th to endNight
9%6%37%6%36%7%7%11%29%
1824
September1st to 15thNight
6%6%27%7%5%7%8%8%11%26%
1815
16th to endNight
9%8%310%8%5%6%7%8%9%22%
1815
October1st to 15thNight
9%6%36%5%35%5%7%9%37%
1919
16th to endNight
11%7%24425%5%6%9%40%
2112
November1st to 15thNight
6%436%6%45%6%5%7%43%
2101
16th to endNight
12%6%24425%5%6%9%39%
2160
December1st to 15thNight
8%5%36%7%45%5%6%8%38%
2325
16th to endNight
6%425%5%26%5%7%10%42%
2496

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
41%9%10%18%15%4
1612
16th to endDay
35%6%9%18%21%7%
1728
February1st to 15thDay
34%6%9%17%22%9%
1740
16th to endDay
33%8%14%17%19%7%
1704
March1st to 15thDay
30%6%13%27%16%5%
1980
16th to endDay
32%7%15%19%19%5%
2112
April1st to 15thDay
29%9%15%22%19%3
1978
16th to endDay
31%7%13%20%21%4
2160
May1st to 15thDay
29%8%13%23%18%6%
2205
16th to endDay
38%12%15%19%12%
2435
June1st to 15thDay
47%13%17%17%3
2340
16th to endDay
42%14%24%15%3
2340
July1st to 15thDay
42%18%25%12%
2201
16th to endDay
42%17%23%14%1
2310
August1st to 15thDay
38%19%30%11%
2245
16th to endDay
46%18%23%9%
2022
September1st to 15thDay
44%17%22%12%3
1815
16th to endDay
51%15%17%10%4
1815
October1st to 15thDay
42%11%12%15%13%3
1710
16th to endDay
38%6%12%14%23%5%
1760
November1st to 15thDay
36%7%11%21%18%5%
1757
16th to endDay
40%8%11%14%15%9%
1800
December1st to 15thDay
44%7%11%18%13%4
1632
16th to endDay
35%10%12%21%14%5%
1728
January1st to 15thNight
39%8%13%19%14%5%
2327
16th to endNight
37%5%11%21%15%7%
2496
February1st to 15thNight
33%5%10%18%21%10%
2121
16th to endNight
28%7%15%22%20%6%
1767
March1st to 15thNight
28%6%10%29%19%5%
1980
16th to endNight
28%8%15%22%18%7%
2112
April1st to 15thNight
26%7%16%24%19%5%
1970
16th to endNight
30%6%15%21%21%4
1800
May1st to 15thNight
27%8%11%26%18%7%
1755
16th to endNight
34%12%17%22%12%
1684
June1st to 15thNight
45%11%20%17%4
1620
16th to endNight
39%16%21%18%3
1620
July1st to 15thNight
42%16%23%15%1
1530
16th to endNight
36%18%28%15%
1595
August1st to 15thNight
33%18%34%13%
1591
16th to endNight
45%16%26%11%
1824
September1st to 15thNight
45%18%22%11%2
1815
16th to endNight
52%14%14%12%31
1815
October1st to 15thNight
40%9%14%16%14%3
1919
16th to endNight
39%7%10%14%20%6%
2112
November1st to 15thNight
38%7%10%18%19%5%
2101
16th to endNight
41%6%9%17%16%8%
2160
December1st to 15thNight
43%7%11%21%11%4
2325
16th to endNight
34%9%15%20%13%6%
2496

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
21%321%27%17%8%
90
16th to endDay
14%12%23%26%19%3
96
February1st to 15thDay
4227%30%27%7%
90
16th to endDay
10%12%18%37%20%
205
March1st to 15thDay
7%15%20%34%17%5%
270
16th to endDay
8%13%17%28%25%6%
288
April1st to 15thDay
312%14%34%29%5%
270
16th to endDay
6%11%9%28%35%8%
270
May1st to 15thDay
5%11%6%29%31%14%
288
16th to endDay
6%9%6%13%34%29%
331
June1st to 15thDay
9%10%411%34%29%
315
16th to endDay
310%17%25%51%
315
July1st to 15thDay
6%6%1323%59%
305
16th to endDay
7%9%17%28%44%
326
August1st to 15thDay
6%6%2431%49%
297
16th to endDay
10%6%27%23%49%
268
September1st to 15thDay
6%7%312%28%41%
255
16th to endDay
12%5%5%11%25%38%
254
October1st to 15thDay
12%6%8%21%36%13%
255
16th to endDay
10%8%12%30%29%8%
272
November1st to 15thDay
6%11%10%27%30%13%
265
16th to endDay
10%11%17%30%24%5%
270
December1st to 15thDay
10%219%32%31%2
102
16th to endDay
9%39%22%45%9%
96
January1st to 15thNight
12%21%19%23%19%3
720
16th to endNight
9%22%22%27%17%
768
February1st to 15thNight
9%20%18%30%18%2
704
16th to endNight
9%17%19%33%18%
631
March1st to 15thNight
5%20%21%30%17%4
720
16th to endNight
5%19%16%28%26%2
768
April1st to 15thNight
5%19%13%29%27%4
718
16th to endNight
6%17%11%30%30%3
720
May1st to 15thNight
7%17%6%27%35%5%
675
16th to endNight
6%17%317%36%18%
563
June1st to 15thNight
10%16%310%37%21%
540
16th to endNight
5%16%26%33%34%
540
July1st to 15thNight
7%12%16%32%39%
510
16th to endNight
5%16%1436%36%
564
August1st to 15thNight
5%9%15%36%41%
543
16th to endNight
11%9%37%31%36%
700
September1st to 15thNight
10%9%49%35%31%
660
16th to endNight
14%10%311%32%26%
657
October1st to 15thNight
13%10%6%21%39%9%
660
16th to endNight
14%10%11%21%32%8%
704
November1st to 15thNight
8%16%12%29%25%7%
700
16th to endNight
12%18%15%28%20%4
720
December1st to 15thNight
9%19%15%25%25%5%
720
16th to endNight
7%20%13%25%27%5%
768
Page generated at 2017-08-13 14:16:16. Version ac04

Copyright 2017 A. Danko


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