RASC Sunshine Coast Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the RASC Sunshine Coast Observatory clear sky chart from 2005-11-05 to 2017-09-17.

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
39%
14480
9%
46738
7%
14452
41%
14452
14%
35364

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
25%
750
9%
2686
7%
746
30%
746
8%
2208
January16th to endNight
30%
787
7%
2769
6%
787
32%
787
9%
2256
February1st to 15thNight
30%
699
6%
2288
4%
699
32%
699
9%
1897
February16th to endNight
30%
632
11%
2053
8%
632
34%
632
13%
1578
March1st to 15thNight
21%
720
4%
2049
2%
720
22%
720
7%
1776
March16th to endNight
28%
768
6%
2091
3%
768
30%
768
9%
1792
April1st to 15thNight
38%
689
8%
1769
4%
689
39%
689
14%
1430
April16th to endNight
38%
519
9%
1599
7%
519
40%
519
13%
1227
May1st to 15thNight
52%
359
12%
1439
19%
359
54%
359
16%
968
May16th to endNight
49%
374
7%
1418
9%
374
51%
374
15%
1005
June1st to 15thNight
51%
360
2%
1260
2%
360
51%
360
17%
879
June16th to endNight
55%
360
5%
1260
2%
360
56%
360
16%
878
July1st to 15thNight
74%
340
8%
1190
7%
340
74%
340
33%
643
July16th to endNight
79%
376
12%
1293
18%
354
81%
354
36%
657
August1st to 15thNight
78%
449
14%
1522
18%
447
78%
447
36%
791
August16th to endNight
69%
591
19%
1737
16%
591
70%
591
33%
1040
September1st to 15thNight
72%
720
22%
1800
13%
720
74%
720
42%
1083
September16th to endNight
47%
664
16%
1840
11%
664
49%
664
22%
1312
October1st to 15thNight
46%
660
11%
1980
10%
660
48%
660
21%
1385
October16th to endNight
31%
704
6%
2211
5%
704
34%
704
11%
1763
November1st to 15thNight
19%
700
5%
2450
3%
700
21%
700
6%
2098
November16th to endNight
23%
720
6%
2520
3%
720
27%
720
8%
2071
December1st to 15thNight
25%
739
5%
2634
3%
739
27%
739
7%
2206
December16th to endNight
18%
800
6%
2880
3%
800
23%
800
7%
2421

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
22%8%35%424446%32%
48075
Night
26%8%35%424346%30%
46889
Cloud CoverDay
25%8%35%424445%31%
48075
Night
29%8%25%423345%30%
46892
TransparencyDay
55%9%13%15%5%1
47729
Night
57%7%12%15%6%1
46739
SeeingDay
26%319%27%19%3
6240
Night
32%415%23%19%4
14487

By Month

Percentage Cloud Cover NW (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
40%10%444245%3315%
1253
16th to endDay
33%11%26%6%24446%15%
1454
February1st to 15thDay
35%10%46%5%34345%17%
1576
16th to endDay
23%8%36%5%45%45%7%24%
1421
March1st to 15thDay
36%13%36%5%3433414%
1911
16th to endDay
30%10%49%6%3333321%
2133
April1st to 15thDay
24%9%46%6%35%5%5%6%22%
2176
16th to endDay
24%9%45%5%2445%5%28%
2360
May1st to 15thDay
17%7%36%5%34447%35%
2511
16th to endDay
19%7%35%6%35%6%5%7%30%
2690
June1st to 15thDay
19%6%36%5%3445%7%33%
2700
16th to endDay
17%7%35%5%346%6%7%33%
2700
July1st to 15thDay
9%424324446%54%
2700
16th to endDay
9%312323347%59%
2787
August1st to 15thDay
8%413323346%56%
2428
16th to endDay
9%5%243245%5%7%48%
2465
September1st to 15thDay
9%5%2432435%7%51%
2160
16th to endDay
24%5%24325%45%7%33%
1825
October1st to 15thDay
27%8%25%42445%6%26%
1650
16th to endDay
34%7%25%5%2345%7%19%
1660
November1st to 15thDay
43%8%25%42444417%
1408
16th to endDay
36%10%36%42233420%
1440
December1st to 15thDay
30%15%35%445%33319%
1323
16th to endDay
39%12%37%423235%14%
1344
January1st to 15thNight
38%9%25%5%23345%19%
2686
16th to endNight
32%10%35%42345%7%18%
2769
February1st to 15thNight
34%9%35%424446%19%
2276
16th to endNight
25%10%36%5%23345%29%
2053
March1st to 15thNight
37%10%37%42334417%
2049
16th to endNight
31%9%46%6%34345%19%
2087
April1st to 15thNight
23%9%47%5%35%447%24%
1769
16th to endNight
23%9%36%5%34447%27%
1599
May1st to 15thNight
17%6%35%5%35%45%7%36%
1439
16th to endNight
17%7%46%6%35%46%8%31%
1418
June1st to 15thNight
18%8%36%5%34345%35%
1260
16th to endNight
15%8%27%436%46%7%35%
1260
July1st to 15thNight
7%413423345%57%
1260
16th to endNight
7%213323446%59%
1382
August1st to 15thNight
6%223323347%59%
1530
16th to endNight
11%31333335%8%51%
1737
September1st to 15thNight
7%31232345%5%60%
1800
16th to endNight
22%7%24323446%38%
1840
October1st to 15thNight
23%7%24423346%37%
1980
16th to endNight
35%6%25%424435%24%
2211
November1st to 15thNight
41%9%35%42423417%
2450
16th to endNight
35%9%36%423336%20%
2520
December1st to 15thNight
31%13%45%425%43419%
2634
16th to endNight
39%11%35%42223320%
2880

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
44%8%4443433216%
1253
16th to endDay
36%11%35%433335%18%
1454
February1st to 15thDay
37%10%45%42434417%
1576
16th to endDay
25%10%35%5%45%45%5%24%
1421
March1st to 15thDay
42%10%36%5%2332413%
1911
16th to endDay
33%13%48%42323419%
2133
April1st to 15thDay
27%10%5%6%6%25%445%19%
2176
16th to endDay
29%9%36%5%34435%25%
2360
May1st to 15thDay
19%7%36%6%2445%7%32%
2511
16th to endDay
21%8%35%6%46%5%5%6%26%
2690
June1st to 15thDay
22%7%36%5%2446%6%29%
2700
16th to endDay
21%7%36%5%35%45%6%31%
2700
July1st to 15thDay
11%423424446%52%
2700
16th to endDay
11%312313445%56%
2787
August1st to 15thDay
10%424423246%54%
2428
16th to endDay
11%5%25%4335%47%46%
2465
September1st to 15thDay
11%5%14433346%51%
2160
16th to endDay
27%5%25%423446%32%
1825
October1st to 15thDay
30%7%24425%345%28%
1650
16th to endDay
36%8%26%423347%20%
1660
November1st to 15thDay
46%8%2443233415%
1408
16th to endDay
39%9%35%42333320%
1440
December1st to 15thDay
32%14%45%425%43319%
1323
16th to endDay
44%11%35%42322315%
1344
January1st to 15thNight
41%8%25%42333419%
2685
16th to endNight
35%9%35%424445%19%
2769
February1st to 15thNight
37%8%35%424445%19%
2276
16th to endNight
29%10%35%42334428%
2053
March1st to 15thNight
40%11%35%42333416%
2049
16th to endNight
35%11%35%424345%18%
2091
April1st to 15thNight
27%9%35%5%35%446%23%
1769
16th to endNight
26%8%26%433447%27%
1599
May1st to 15thNight
18%6%35%43446%6%36%
1439
16th to endNight
19%8%35%6%25%46%7%31%
1418
June1st to 15thNight
20%8%36%5%24325%37%
1260
16th to endNight
18%6%36%335%5%46%35%
1260
July1st to 15thNight
9%323433346%57%
1260
16th to endNight
8%11322435%6%59%
1382
August1st to 15thNight
6%313313346%59%
1530
16th to endNight
11%31442335%7%51%
1737
September1st to 15thNight
9%312323345%60%
1800
16th to endNight
26%6%24313345%37%
1840
October1st to 15thNight
26%7%23323346%37%
1980
16th to endNight
38%7%2442333424%
2211
November1st to 15thNight
45%9%35%32323317%
2450
16th to endNight
37%10%35%43233322%
2520
December1st to 15thNight
34%11%36%5%3422320%
2634
16th to endNight
43%10%36%31232319%
2880

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
73%5%8%7%41
1253
16th to endDay
71%7%10%7%11
1454
February1st to 15thDay
70%7%9%6%32
1576
16th to endDay
61%10%12%12%3
1421
March1st to 15thDay
76%7%8%5%2
1911
16th to endDay
71%6%9%11%1
2133
April1st to 15thDay
66%10%8%12%2
2176
16th to endDay
62%9%10%11%5%
2360
May1st to 15thDay
52%9%12%18%6%
2511
16th to endDay
57%11%12%16%2
2694
June1st to 15thDay
54%10%16%13%41
2700
16th to endDay
53%10%14%15%4
2700
July1st to 15thDay
34%9%17%24%11%2
2541
16th to endDay
28%10%19%29%10%1
2613
August1st to 15thDay
32%9%17%28%10%1
2411
16th to endDay
35%10%19%26%6%1
2465
September1st to 15thDay
34%8%16%22%14%2
2160
16th to endDay
53%10%12%14%6%1
1825
October1st to 15thDay
57%9%14%12%6%
1650
16th to endDay
65%9%14%8%2
1660
November1st to 15thDay
73%7%8%6%21
1408
16th to endDay
67%7%7%11%5%
1440
December1st to 15thDay
70%6%7%9%42
1323
16th to endDay
75%6%6%7%21
1344
January1st to 15thNight
68%6%7%11%4
2686
16th to endNight
67%6%9%11%31
2769
February1st to 15thNight
68%7%9%9%22
2288
16th to endNight
59%6%11%15%5%
2053
March1st to 15thNight
73%6%9%8%2
2049
16th to endNight
69%7%8%12%1
2091
April1st to 15thNight
60%8%10%16%3
1769
16th to endNight
56%9%11%17%5%
1599
May1st to 15thNight
47%8%14%20%7%
1440
16th to endNight
50%9%16%18%4
1418
June1st to 15thNight
51%5%19%16%5%1
1260
16th to endNight
49%8%14%20%5%1
1260
July1st to 15thNight
29%6%19%27%14%3
1190
16th to endNight
23%8%20%30%15%2
1293
August1st to 15thNight
24%8%22%26%14%3
1522
16th to endNight
31%8%19%28%9%2
1737
September1st to 15thNight
26%8%15%26%19%4
1800
16th to endNight
48%6%13%20%8%2
1840
October1st to 15thNight
48%6%16%18%9%
1980
16th to endNight
64%5%13%11%4
2211
November1st to 15thNight
73%6%8%6%21
2450
16th to endNight
67%7%8%9%6%
2520
December1st to 15thNight
71%5%7%8%5%1
2634
16th to endNight
72%5%7%9%4
2880

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
16%126%23%21%10%
60
16th to endDay
62%317%12%4
94
February1st to 15thDay
44%5%18%19%11%
236
16th to endDay
34%8%24%16%15%1
211
March1st to 15thDay
52%8%21%11%5%
269
16th to endDay
41%7%26%15%7%1
288
April1st to 15thDay
36%6%21%21%13%1
269
16th to endDay
30%5%27%24%11%1
270
May1st to 15thDay
25%424%27%18%1
288
16th to endDay
20%318%29%23%4
405
June1st to 15thDay
20%422%28%22%2
495
16th to endDay
18%222%35%19%2
495
July1st to 15thDay
12%214%35%32%3
475
16th to endDay
7%15%38%33%4
456
August1st to 15thDay
9%112%33%34%9%
315
16th to endDay
12%215%37%28%3
332
September1st to 15thDay
16%321%31%22%4
315
16th to endDay
30%220%22%16%6%
260
October1st to 15thDay
37%418%21%16%2
255
16th to endDay
41%5%15%22%10%3
208
November1st to 15thDay
61%6%15%13%3
60
16th to endDay
46%310%13%15%11%
60
December1st to 15thDay
53%5%15%18%8%
60
16th to endDay
43%126%18%9%
64
January1st to 15thNight
42%5%19%20%11%1
750
16th to endNight
40%417%22%14%
787
February1st to 15thNight
40%417%24%11%
704
16th to endNight
34%7%19%23%12%2
632
March1st to 15thNight
46%6%17%17%9%1
720
16th to endNight
40%6%17%20%13%2
768
April1st to 15thNight
30%415%29%15%4
689
16th to endNight
29%318%28%17%2
519
May1st to 15thNight
20%315%28%25%6%
360
16th to endNight
21%312%27%30%5%
375
June1st to 15thNight
22%39%28%28%7%
360
16th to endNight
22%29%31%29%5%
360
July1st to 15thNight
11%8%25%41%13%
340
16th to endNight
7%15%20%49%15%
376
August1st to 15thNight
10%220%49%16%
449
16th to endNight
14%17%23%44%9%
591
September1st to 15thNight
10%10%27%37%13%
720
16th to endNight
31%212%21%25%6%
664
October1st to 15thNight
30%215%28%20%2
660
16th to endNight
41%5%16%22%12%2
704
November1st to 15thNight
47%7%21%18%5%
700
16th to endNight
41%6%21%19%9%1
720
December1st to 15thNight
39%5%20%26%6%
739
16th to endNight
46%8%22%17%5%
800
Page generated at 2017-09-18 05:38:24. Version ac04

Copyright 2017 A. Danko


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