Hume Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hume Observatory clear sky chart from 2005-11-05 to 2017-10-31.

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
64%
15476
28%
47430
24%
15438
68%
15438
38%
25891

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
57%
717
19%
2386
19%
716
61%
716
26%
1444
January16th to endNight
54%
768
26%
2496
25%
768
59%
768
28%
1502
February1st to 15thNight
53%
698
23%
2288
22%
697
58%
697
24%
1445
February16th to endNight
49%
632
22%
1932
18%
632
56%
632
27%
1206
March1st to 15thNight
51%
720
15%
1986
12%
720
54%
720
26%
1338
March16th to endNight
46%
768
21%
2104
15%
768
51%
768
31%
1343
April1st to 15thNight
47%
719
24%
1799
12%
719
52%
719
32%
1147
April16th to endNight
55%
720
27%
1800
13%
720
60%
720
43%
1034
May1st to 15thNight
63%
560
29%
1640
20%
560
68%
560
49%
822
May16th to endNight
66%
396
28%
1519
26%
396
74%
396
43%
664
June1st to 15thNight
69%
360
27%
1440
30%
360
76%
360
40%
635
June16th to endNight
80%
360
35%
1440
44%
360
85%
360
58%
521
July1st to 15thNight
90%
378
33%
1398
39%
378
92%
378
68%
491
July16th to endNight
87%
564
37%
1593
34%
531
87%
531
59%
701
August1st to 15thNight
85%
538
36%
1611
30%
535
86%
535
58%
710
August16th to endNight
84%
746
39%
1892
26%
746
85%
746
62%
959
September1st to 15thNight
85%
720
39%
1800
28%
720
86%
720
69%
875
September16th to endNight
81%
716
43%
1978
37%
716
85%
716
64%
913
October1st to 15thNight
70%
720
30%
2160
30%
720
76%
720
47%
1076
October16th to endNight
73%
768
34%
2304
36%
768
76%
768
43%
1236
November1st to 15thNight
66%
700
27%
2175
25%
700
71%
700
39%
1177
November16th to endNight
59%
720
24%
2481
25%
720
63%
720
30%
1389
December1st to 15thNight
51%
720
20%
2520
17%
720
57%
720
21%
1589
December16th to endNight
47%
768
22%
2688
19%
768
54%
768
23%
1674

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
10%413313346%59%
48316
Night
11%413313346%57%
47617
TransparencyDay
27%38%21%24%15%
48003
Night
29%38%20%23%15%
47431
SeeingDay
13%9%22%31%17%4
6182
Night
13%410%30%33%7%
15487

By Month

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
19%5%2441324446%
1549
16th to endDay
17%6%24423345%44%
1728
February1st to 15thDay
19%5%25%224425%44%
1576
16th to endDay
21%7%24324347%39%
1541
March1st to 15thDay
20%7%35%5%2345%6%34%
1971
16th to endDay
20%424424446%40%
2119
April1st to 15thDay
17%6%2443445%6%40%
2149
16th to endDay
9%413313348%56%
2160
May1st to 15thDay
7%31212335%6%63%
2307
16th to endDay
6%42322335%6%59%
2592
June1st to 15thDay
6%422213337%62%
2520
16th to endDay
31112235%77%
2520
July1st to 15thDay
111212225%79%
2476
16th to endDay
1221222478%
2468
August1st to 15thDay
12212236%75%
2340
16th to endDay
112212236%75%
2309
September1st to 15thDay
1212111235%75%
2160
16th to endDay
411111236%73%
1980
October1st to 15thDay
9%212212245%65%
1800
16th to endDay
10%413213335%60%
1918
November1st to 15thDay
10%314423447%53%
1681
16th to endDay
15%5%2342334448%
1476
December1st to 15thDay
23%6%23423225%42%
1440
16th to endDay
23%8%23313246%39%
1536
January1st to 15thNight
17%41442345%8%42%
2386
16th to endNight
20%5%13313335%49%
2496
February1st to 15thNight
19%5%24424446%42%
2276
16th to endNight
17%6%14313347%44%
1932
March1st to 15thNight
17%5%3443445%6%40%
1986
16th to endNight
18%6%24312336%47%
2104
April1st to 15thNight
13%5%14323346%49%
1799
16th to endNight
8%313314235%60%
1800
May1st to 15thNight
4213421336%64%
1640
16th to endNight
4312224346%64%
1518
June1st to 15thNight
4312323336%65%
1440
16th to endNight
32111122378%
1440
July1st to 15thNight
1111122480%
1481
16th to endNight
112213236%71%
1701
August1st to 15thNight
112323246%70%
1620
16th to endNight
213412337%70%
1892
September1st to 15thNight
121212236%74%
1800
16th to endNight
311211226%74%
1978
October1st to 15thNight
6%31321333466%
2160
16th to endNight
9%313323447%58%
2304
November1st to 15thNight
11%413322349%54%
2175
16th to endNight
14%5%24313345%52%
2481
December1st to 15thNight
23%6%13323345%41%
2520
16th to endNight
24%423313346%44%
2688

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
42%212%19%14%9%
1549
16th to endDay
43%27%13%20%12%
1728
February1st to 15thDay
44%27%19%20%4
1576
16th to endDay
45%310%24%12%3
1541
March1st to 15thDay
49%310%17%13%4
1971
16th to endDay
44%411%19%16%3
2119
April1st to 15thDay
43%412%19%16%3
2149
16th to endDay
27%314%26%21%6%
2160
May1st to 15thDay
21%37%34%25%7%
2307
16th to endDay
25%313%30%21%6%
2596
June1st to 15thDay
23%311%24%24%12%
2520
16th to endDay
11%1419%38%23%
2520
July1st to 15thDay
9%2211%33%40%
2330
16th to endDay
11%3311%28%41%
2313
August1st to 15thDay
11%3217%36%29%
2324
16th to endDay
10%3217%39%26%
2309
September1st to 15thDay
11%2216%35%30%
2160
16th to endDay
14%15%27%31%18%
1980
October1st to 15thDay
21%26%20%27%20%
1800
16th to endDay
27%37%24%24%12%
1918
November1st to 15thDay
29%411%31%13%8%
1681
16th to endDay
39%39%21%17%7%
1476
December1st to 15thDay
46%38%15%20%4
1440
16th to endDay
47%29%17%15%7%
1536
January1st to 15thNight
39%411%19%14%9%
2386
16th to endNight
39%28%15%18%15%
2496
February1st to 15thNight
43%39%18%17%7%
2288
16th to endNight
40%312%23%16%3
1932
March1st to 15thNight
44%414%15%16%5%
1986
16th to endNight
40%211%21%19%5%
2104
April1st to 15thNight
35%414%22%18%4
1799
16th to endNight
26%311%28%22%8%
1800
May1st to 15thNight
21%36%25%30%12%
1641
16th to endNight
19%412%32%22%8%
1519
June1st to 15thNight
19%5%8%25%24%16%
1440
16th to endNight
12%1315%37%28%
1440
July1st to 15thNight
8%2110%34%43%
1398
16th to endNight
13%4311%24%42%
1593
August1st to 15thNight
14%3215%31%33%
1611
16th to endNight
14%4115%34%29%
1892
September1st to 15thNight
12%2312%35%33%
1800
16th to endNight
14%1324%33%23%
1978
October1st to 15thNight
21%36%20%25%23%
2160
16th to endNight
25%46%22%25%15%
2304
November1st to 15thNight
28%413%29%15%8%
2175
16th to endNight
34%38%22%20%10%
2481
December1st to 15thNight
44%48%17%19%6%
2520
16th to endNight
43%39%15%19%7%
2688

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
36%6%19%23%11%2
177
16th to endDay
22%9%22%26%16%2
256
February1st to 15thDay
25%9%25%24%13%2
236
16th to endDay
22%13%24%23%14%1
231
March1st to 15thDay
29%14%21%18%12%3
270
16th to endDay
22%18%28%21%7%1
288
April1st to 15thDay
25%23%22%20%6%2
269
16th to endDay
19%19%29%21%7%2
270
May1st to 15thDay
14%16%29%28%9%2
288
16th to endDay
10%13%21%31%17%6%
330
June1st to 15thDay
8%13%28%34%11%2
315
16th to endDay
4425%39%20%5%
315
July1st to 15thDay
2217%45%24%6%
305
16th to endDay
117%50%22%7%
327
August1st to 15thDay
2318%47%22%5%
315
16th to endDay
1220%39%29%7%
332
September1st to 15thDay
3321%38%24%8%
315
16th to endDay
5%7%21%33%24%7%
315
October1st to 15thDay
8%9%26%30%18%6%
315
16th to endDay
13%7%20%28%24%5%
336
November1st to 15thDay
13%7%17%22%33%5%
187
16th to endDay
15%13%28%21%16%4
66
December1st to 15thDay
45%10%25%8%11%
60
16th to endDay
23%10%21%23%14%6%
64
January1st to 15thNight
19%39%35%25%6%
720
16th to endNight
21%5%10%30%24%7%
768
February1st to 15thNight
21%5%8%34%24%4
704
16th to endNight
21%6%15%31%19%5%
632
March1st to 15thNight
19%6%13%28%26%4
720
16th to endNight
20%5%20%28%22%3
768
April1st to 15thNight
16%9%17%31%20%4
719
16th to endNight
10%11%17%27%25%6%
720
May1st to 15thNight
6%318%29%35%5%
561
16th to endNight
45%17%29%35%7%
397
June1st to 15thNight
6%6%12%36%35%2
360
16th to endNight
429%36%42%5%
360
July1st to 15thNight
2324%59%9%
378
16th to endNight
31126%53%14%
564
August1st to 15thNight
11228%53%12%
538
16th to endNight
11431%52%8%
746
September1st to 15thNight
215%28%49%12%
720
16th to endNight
426%31%40%14%
716
October1st to 15thNight
8%5%9%32%34%10%
720
16th to endNight
10%27%27%38%12%
768
November1st to 15thNight
12%311%30%33%9%
700
16th to endNight
16%5%10%31%27%8%
720
December1st to 15thNight
25%6%9%29%22%7%
720
16th to endNight
25%5%14%32%19%2
768
Page generated at 2017-11-01 14:23:33. Version ac04

Copyright 2017 A. Danko


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