Geraldton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Geraldton 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
27%
15641
10%
46839
5%
15595
31%
15595
14%
35747

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
18%
900
7%
2580
3%
895
23%
895
9%
2143
January16th to endNight
20%
960
7%
2688
2%
960
25%
960
8%
2286
February1st to 15thNight
29%
879
10%
2439
5%
875
33%
875
16%
1887
February16th to endNight
29%
636
12%
1898
7%
636
34%
636
13%
1454
March1st to 15thNight
29%
720
15%
2160
9%
720
34%
720
16%
1577
March16th to endNight
29%
661
17%
2026
10%
661
38%
661
18%
1430
April1st to 15thNight
28%
539
12%
1785
7%
539
35%
539
16%
1292
April16th to endNight
32%
540
15%
1620
8%
540
39%
540
21%
1110
May1st to 15thNight
28%
540
10%
1441
5%
540
33%
540
19%
1071
May16th to endNight
30%
432
9%
1367
5%
431
34%
431
17%
996
June1st to 15thNight
36%
360
5%
1260
3%
360
39%
360
18%
845
June16th to endNight
32%
360
4%
1260
3%
360
34%
360
18%
839
July1st to 15thNight
40%
357
5%
1207
4%
357
43%
357
26%
732
July16th to endNight
42%
564
9%
1417
5%
531
43%
531
28%
947
August1st to 15thNight
46%
539
14%
1431
6%
536
51%
536
29%
938
August16th to endNight
37%
573
16%
1756
10%
573
42%
573
24%
1154
September1st to 15thNight
40%
549
13%
1809
7%
549
47%
549
23%
1165
September16th to endNight
29%
673
12%
1858
8%
673
33%
673
20%
1345
October1st to 15thNight
24%
660
11%
1955
5%
660
30%
660
14%
1489
October16th to endNight
21%
704
5%
2288
3%
704
24%
704
8%
1905
November1st to 15thNight
17%
735
9%
2314
4%
735
23%
735
7%
1918
November16th to endNight
18%
900
7%
2700
3%
900
21%
900
7%
2327
December1st to 15thNight
16%
900
4%
2700
1%
900
19%
900
5%
2370
December16th to endNight
17%
960
6%
2880
3%
960
19%
960
6%
2527

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
17%11%47%6%35%45%6%27%
47991
Night
15%12%48%6%45%5%5%6%26%
46998
Cloud CoverDay
17%11%47%6%35%45%6%27%
48001
Night
15%12%48%6%35%5%5%6%26%
47003
TransparencyDay
56%6%10%18%7%
47667
Night
57%6%11%17%6%
46840
SeeingDay
24%12%30%19%9%3
6147
Night
21%10%31%24%9%1
15642

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
12%13%8%10%9%5%8%6%9%5%12%
1356
16th to endDay
13%13%410%8%5%9%9%7%7%10%
1536
February1st to 15thDay
7%13%5%9%8%5%7%7%7%7%20%
1422
16th to endDay
6%12%6%11%8%48%5%5%6%24%
1575
March1st to 15thDay
13%13%5%7%7%35%6%46%26%
1790
16th to endDay
14%12%5%7%6%34446%30%
2208
April1st to 15thDay
13%13%46%7%3445%5%30%
2163
16th to endDay
17%12%5%6%423345%33%
2340
May1st to 15thDay
24%8%36%6%34446%26%
2508
16th to endDay
23%8%25%5%3445%7%28%
2747
June1st to 15thDay
22%8%25%6%3345%5%32%
2700
16th to endDay
18%6%26%5%3445%7%34%
2700
July1st to 15thDay
19%5%36%43435%8%34%
2679
16th to endDay
17%5%245%35%46%8%35%
2655
August1st to 15thDay
16%5%26%6%35%5%6%8%32%
2520
16th to endDay
18%6%26%43445%7%35%
2442
September1st to 15thDay
20%8%26%5%34445%35%
2139
16th to endDay
24%10%35%424336%30%
1848
October1st to 15thDay
21%17%36%4135%46%25%
1672
16th to endDay
24%21%6%6%6%3433414%
1584
November1st to 15thDay
19%18%7%12%6%3343417%
1543
16th to endDay
19%18%6%9%8%45%35%414%
1260
December1st to 15thDay
12%16%6%13%11%6%6%6%5%5%8%
1260
16th to endDay
14%18%9%14%8%46%35%5%10%
1344
January1st to 15thNight
12%16%5%11%8%48%7%7%5%12%
2580
16th to endNight
11%14%5%10%9%5%10%8%7%5%10%
2688
February1st to 15thNight
7%10%48%7%6%9%8%6%7%22%
2436
16th to endNight
8%12%6%9%8%5%7%6%6%5%23%
1898
March1st to 15thNight
10%10%48%7%46%45%7%30%
2147
16th to endNight
11%10%47%7%34435%36%
2026
April1st to 15thNight
14%11%47%6%35%5%6%5%28%
1785
16th to endNight
18%10%345%2335%6%36%
1620
May1st to 15thNight
23%8%35%424446%31%
1441
16th to endNight
23%8%26%433346%33%
1366
June1st to 15thNight
20%5%24325%5%5%6%36%
1260
16th to endNight
17%6%35%435%45%6%37%
1260
July1st to 15thNight
13%5%2433346%8%43%
1278
16th to endNight
10%425%425%46%9%42%
1513
August1st to 15thNight
9%5%26%425%5%5%8%43%
1440
16th to endNight
13%5%26%42445%7%42%
1756
September1st to 15thNight
15%6%25%5%2345%6%43%
1809
16th to endNight
24%5%34423446%36%
1858
October1st to 15thNight
20%15%35%5%33235%30%
1955
16th to endNight
22%17%49%5%3445%5%17%
2288
November1st to 15thNight
21%16%6%8%7%3444417%
2314
16th to endNight
18%16%6%11%9%5%443314%
2700
December1st to 15thNight
12%18%7%12%9%6%8%6%449%
2700
16th to endNight
16%18%6%11%9%5%7%5%3410%
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
12%14%7%10%9%48%5%8%5%12%
1356
16th to endDay
13%14%410%8%5%9%9%7%7%10%
1536
February1st to 15thDay
7%12%5%9%9%5%8%6%7%7%21%
1422
16th to endDay
6%12%6%11%8%48%5%5%6%24%
1575
March1st to 15thDay
13%13%47%7%35%6%46%26%
1800
16th to endDay
14%12%5%7%6%34445%30%
2208
April1st to 15thDay
13%13%5%6%7%3445%5%30%
2163
16th to endDay
18%12%46%423246%33%
2340
May1st to 15thDay
24%9%36%7%34446%26%
2508
16th to endDay
23%9%35%5%2445%6%28%
2747
June1st to 15thDay
22%8%25%5%34445%33%
2700
16th to endDay
19%6%36%6%245%47%34%
2700
July1st to 15thDay
19%5%25%5%3445%8%34%
2679
16th to endDay
16%5%25%5%35%46%8%35%
2655
August1st to 15thDay
16%5%35%5%45%6%6%8%32%
2520
16th to endDay
18%6%25%5%3445%7%35%
2442
September1st to 15thDay
20%8%25%5%34446%34%
2139
16th to endDay
24%11%35%424336%30%
1848
October1st to 15thDay
21%16%26%41345%6%25%
1672
16th to endDay
25%21%6%7%5%33345%14%
1584
November1st to 15thDay
19%18%7%12%6%24335%17%
1543
16th to endDay
19%18%6%9%8%45%345%14%
1260
December1st to 15thDay
11%17%7%13%11%5%7%6%45%8%
1260
16th to endDay
14%18%8%14%8%46%35%410%
1344
January1st to 15thNight
12%16%6%10%8%48%7%7%5%12%
2580
16th to endNight
12%14%5%10%9%5%10%7%6%5%10%
2688
February1st to 15thNight
7%11%48%7%6%9%7%6%7%22%
2429
16th to endNight
7%13%6%9%8%47%7%5%6%23%
1898
March1st to 15thNight
11%10%5%8%7%35%45%6%30%
2160
16th to endNight
12%10%48%7%34435%35%
2026
April1st to 15thNight
14%12%46%6%35%5%6%5%29%
1785
16th to endNight
17%10%3441435%6%37%
1620
May1st to 15thNight
23%8%25%42435%6%31%
1440
16th to endNight
23%8%25%5%24347%33%
1366
June1st to 15thNight
20%6%24325%5%6%6%36%
1260
16th to endNight
17%6%26%4245%6%6%36%
1260
July1st to 15thNight
14%42432446%8%43%
1278
16th to endNight
10%5%25%435%5%6%8%42%
1513
August1st to 15thNight
9%5%26%435%45%9%43%
1440
16th to endNight
13%5%26%42345%8%41%
1756
September1st to 15thNight
16%6%245%2335%6%42%
1809
16th to endNight
24%6%34413446%35%
1858
October1st to 15thNight
20%14%35%6%33335%30%
1955
16th to endNight
22%17%5%9%5%3445%6%16%
2288
November1st to 15thNight
21%16%6%9%7%3444417%
2314
16th to endNight
18%17%6%11%9%4443314%
2700
December1st to 15thNight
13%17%7%11%10%6%7%6%449%
2700
16th to endNight
16%18%6%11%9%5%7%5%349%
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
70%310%12%2
1357
16th to endDay
67%7%9%11%4
1536
February1st to 15thDay
59%5%9%18%6%
1423
16th to endDay
59%410%19%6%
1575
March1st to 15thDay
57%5%9%15%10%
1800
16th to endDay
54%5%9%19%9%1
2208
April1st to 15thDay
54%5%9%20%8%1
2163
16th to endDay
52%5%7%18%14%1
2340
May1st to 15thDay
58%5%8%16%9%1
2508
16th to endDay
54%6%12%17%8%
2751
June1st to 15thDay
52%5%8%18%13%
2700
16th to endDay
48%6%11%24%7%
2700
July1st to 15thDay
45%6%13%23%10%
2521
16th to endDay
45%7%13%25%6%
2488
August1st to 15thDay
46%9%15%20%6%
2505
16th to endDay
46%8%12%22%8%
2442
September1st to 15thDay
50%7%14%21%6%
2139
16th to endDay
55%5%12%20%5%
1848
October1st to 15thDay
57%6%14%17%3
1672
16th to endDay
73%5%9%10%
1584
November1st to 15thDay
71%5%9%11%2
1543
16th to endDay
73%5%10%6%3
1260
December1st to 15thDay
75%6%7%9%1
1260
16th to endDay
76%47%8%3
1344
January1st to 15thNight
68%5%9%13%2
2580
16th to endNight
70%6%7%11%4
2688
February1st to 15thNight
57%6%10%18%6%
2439
16th to endNight
59%5%10%18%6%
1898
March1st to 15thNight
54%5%9%20%9%
2160
16th to endNight
50%5%9%20%11%2
2026
April1st to 15thNight
53%6%8%18%11%1
1785
16th to endNight
47%5%11%19%14%2
1620
May1st to 15thNight
52%5%7%21%11%1
1441
16th to endNight
51%7%10%19%9%
1368
June1st to 15thNight
45%7%9%24%12%
1260
16th to endNight
45%8%13%24%8%
1260
July1st to 15thNight
35%8%15%25%14%
1207
16th to endNight
38%8%15%28%8%
1417
August1st to 15thNight
36%9%18%28%6%
1431
16th to endNight
39%9%15%26%9%
1756
September1st to 15thNight
41%7%17%26%7%
1809
16th to endNight
49%6%16%21%5%
1858
October1st to 15thNight
57%5%15%17%3
1955
16th to endNight
68%7%10%12%1
2288
November1st to 15thNight
69%6%9%11%3
2314
16th to endNight
73%6%8%8%3
2700
December1st to 15thNight
76%5%8%7%2
2700
16th to endNight
76%46%8%3
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%12%40%18%10%1
77
16th to endDay
27%8%37%16%7%3
96
February1st to 15thDay
21%15%34%25%3
90
16th to endDay
22%23%37%16%1
81
March1st to 15thDay
18%18%30%22%8%1
90
16th to endDay
20%11%39%15%8%3
267
April1st to 15thDay
20%14%30%23%7%2
270
16th to endDay
26%11%30%20%6%4
270
May1st to 15thDay
29%14%30%14%7%2
465
16th to endDay
29%14%29%17%6%2
517
June1st to 15thDay
30%12%25%16%11%3
495
16th to endDay
21%14%30%20%10%3
495
July1st to 15thDay
19%10%34%22%10%2
475
16th to endDay
14%11%34%24%11%4
515
August1st to 15thDay
17%9%31%24%11%6%
493
16th to endDay
22%7%29%21%13%5%
345
September1st to 15thDay
22%10%24%23%14%5%
315
16th to endDay
31%12%26%16%11%2
266
October1st to 15thDay
32%11%21%23%8%2
156
16th to endDay
33%12%41%8%22
96
November1st to 15thDay
34%14%31%17%1
89
16th to endDay
40%8%16%26%8%
60
December1st to 15thDay
41%5%33%10%5%5%
60
16th to endDay
23%18%40%9%7%
64
January1st to 15thNight
21%14%33%22%6%1
900
16th to endNight
18%13%34%24%7%1
960
February1st to 15thNight
13%9%38%29%8%1
880
16th to endNight
14%8%35%30%10%1
636
March1st to 15thNight
17%15%30%25%10%1
720
16th to endNight
17%12%34%22%11%1
661
April1st to 15thNight
20%11%34%25%7%1
539
16th to endNight
22%8%31%27%8%1
540
May1st to 15thNight
28%8%29%25%7%
540
16th to endNight
27%7%28%27%6%1
432
June1st to 15thNight
23%7%28%27%11%
360
16th to endNight
20%8%34%26%10%
360
July1st to 15thNight
15%7%33%30%11%1
357
16th to endNight
13%6%33%30%15%
564
August1st to 15thNight
12%6%28%32%17%2
539
16th to endNight
15%7%32%27%15%
573
September1st to 15thNight
19%6%28%30%13%1
549
16th to endNight
28%9%29%22%9%
673
October1st to 15thNight
29%12%28%22%6%
660
16th to endNight
31%9%27%17%11%1
704
November1st to 15thNight
30%14%30%18%5%
735
16th to endNight
28%13%28%22%6%
900
December1st to 15thNight
22%13%32%21%8%1
900
16th to endNight
25%11%31%18%9%3
960
Page generated at 2017-09-20 04:49:51. Version ac04

Copyright 2017 A. Danko


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