Carlton Astronomy Campus
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carlton Astronomy Campus clear sky chart from 2005-11-06 to 2024-01-16.

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
48%
23650
22%
74531
16%
23591
55%
23591
27%
45762

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 10thNight
26%
950
23%
2458
7%
946
37%
946
26%
1635
January11th to 20thNight
31%
930
24%
2418
9%
930
40%
930
25%
1617
January21st to endNight
26%
982
23%
2566
7%
982
35%
982
25%
1735
February1st to 10thNight
24%
720
23%
2160
9%
720
35%
720
22%
1417
February11th to 20thNight
26%
703
20%
2099
7%
700
36%
700
23%
1369
February21st to endNight
18%
592
20%
1776
6%
592
28%
592
17%
1230
March1st to 10thNight
30%
563
25%
2003
14%
563
43%
563
23%
1206
March11th to 20thNight
30%
540
19%
1980
11%
540
41%
540
18%
1281
March21st to endNight
32%
594
24%
2127
14%
594
45%
594
27%
1200
April1st to 10thNight
35%
540
24%
1800
16%
540
47%
540
24%
1107
April11th to 20thNight
36%
533
24%
1775
14%
533
50%
533
26%
1063
April21st to endNight
42%
540
27%
1800
19%
540
56%
540
34%
972
May1st to 10thNight
50%
540
24%
1800
19%
540
61%
540
34%
992
May11th to 20thNight
55%
531
20%
1769
21%
531
60%
531
31%
1028
May21st to endNight
64%
584
19%
1938
21%
582
67%
582
29%
1166
June1st to 10thNight
69%
540
15%
1625
16%
540
70%
540
29%
1036
June11th to 20thNight
75%
540
18%
1620
18%
540
78%
540
37%
929
June21st to endNight
70%
540
15%
1620
15%
540
71%
540
27%
1051
July1st to 10thNight
76%
525
12%
1575
12%
525
77%
525
27%
1020
July11th to 20thNight
77%
522
15%
1566
17%
522
77%
522
27%
1012
July21st to endNight
74%
591
15%
1724
18%
558
75%
558
27%
1105
August1st to 10thNight
81%
537
12%
1778
14%
534
82%
534
33%
1002
August11th to 20thNight
78%
534
16%
1776
19%
534
78%
534
26%
1141
August21st to endNight
72%
594
16%
1980
18%
594
73%
594
24%
1281
September1st to 10thNight
73%
540
21%
1800
24%
540
74%
540
29%
1102
September11th to 20thNight
71%
540
23%
1800
25%
540
71%
540
28%
1098
September21st to endNight
65%
700
29%
1973
24%
700
67%
700
36%
1173
October1st to 10thNight
65%
720
29%
2160
23%
720
69%
720
42%
1165
October11th to 20thNight
56%
720
33%
2160
24%
720
63%
720
38%
1198
October21st to endNight
52%
792
31%
2376
25%
792
58%
792
35%
1350
November1st to 10thNight
54%
740
31%
2220
23%
740
62%
740
38%
1230
November11th to 20thNight
43%
760
31%
2280
20%
760
54%
760
33%
1317
November21st to endNight
39%
760
28%
2414
18%
760
50%
760
27%
1457
December1st to 10thNight
37%
760
26%
2470
17%
760
49%
760
25%
1539
December11th to 20thNight
30%
814
24%
2800
12%
813
40%
813
20%
1812
December21st to endNight
27%
1039
12%
4345
8%
1026
33%
1026
14%
2726

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
12%6%36%6%45%5%6%7%40%
74743
Night
12%6%25%5%345%5%8%46%
75055
TransparencyDay
42%8%11%17%17%6%
74473
Night
36%7%12%18%19%8%
74846
SeeingDay
15%9%20%24%22%10%
13807
Night
15%8%23%29%21%4
23657

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 10thDay
18%7%25%433446%44%
1707
11th to 20thDay
18%8%25%5%23336%44%
1665
21st to endDay
19%8%35%42434444%
1786
February1st to 10thDay
18%7%36%5%35%45%5%39%
1800
11th to 20thDay
19%9%35%5%24445%41%
1748
21st to endDay
18%7%47%5%35%447%35%
1480
March1st to 10thDay
16%8%36%6%45%446%38%
1970
11th to 20thDay
15%7%36%7%45%45%6%37%
1980
21st to endDay
11%7%35%5%45%6%5%7%42%
2227
April1st to 10thDay
10%6%36%6%36%5%5%7%43%
2160
11th to 20thDay
16%7%25%6%35%5%5%7%40%
2134
21st to endDay
9%5%35%6%46%5%6%8%44%
2160
May1st to 10thDay
11%6%35%5%46%5%6%8%40%
2160
11th to 20thDay
11%6%27%5%35%6%6%9%40%
2124
21st to endDay
7%6%37%7%5%7%6%7%9%36%
2337
June1st to 10thDay
9%5%37%8%5%7%7%8%10%31%
2329
11th to 20thDay
7%5%36%8%5%8%7%8%10%34%
2340
21st to endDay
7%6%37%9%6%7%8%9%10%29%
2340
July1st to 10thDay
8%7%39%8%6%9%8%9%9%26%
2340
11th to 20thDay
8%6%37%8%6%7%9%9%9%29%
2340
21st to endDay
8%7%37%6%6%7%7%7%10%31%
2488
August1st to 10thDay
6%5%37%7%48%9%8%9%35%
2148
11th to 20thDay
11%5%36%7%5%6%7%9%10%31%
2125
21st to endDay
11%6%37%7%47%6%7%9%33%
2376
September1st to 10thDay
9%5%37%8%47%6%8%8%35%
2160
11th to 20thDay
12%6%36%6%45%6%6%8%39%
2160
21st to endDay
10%6%26%5%34447%50%
1962
October1st to 10thDay
7%4246%3446%7%54%
1800
11th to 20thDay
9%5%2443435%5%56%
1800
21st to endDay
12%4245%23345%56%
1980
November1st to 10thDay
11%6%24433446%54%
1858
11th to 20thDay
10%6%345%3335%5%51%
1900
21st to endDay
14%6%35%4345%45%46%
1757
December1st to 10thDay
15%8%35%4335%5%7%43%
1710
11th to 20thDay
16%8%47%5%3445%6%39%
2257
21st to endDay
16%7%35%5%3446%7%41%
3135
January1st to 10thNight
19%7%24333446%44%
2458
11th to 20thNight
17%8%245%33445%46%
2418
21st to endNight
20%8%3442444444%
2566
February1st to 10thNight
15%8%35%5%34446%42%
2160
11th to 20thNight
20%7%25%423346%43%
2098
21st to endNight
21%8%35%5%235%46%37%
1776
March1st to 10thNight
14%7%25%43445%8%43%
2003
11th to 20thNight
15%7%37%5%345%5%6%39%
1980
21st to endNight
12%7%24433447%51%
2127
April1st to 10thNight
12%6%3443446%9%45%
1800
11th to 20thNight
12%6%26%5%345%5%7%45%
1775
21st to endNight
8%425%4245%6%7%54%
1800
May1st to 10thNight
8%42443446%9%51%
1800
11th to 20thNight
7%6%25%5%246%6%8%49%
1769
21st to endNight
7%4247%35%6%7%10%45%
1938
June1st to 10thNight
6%5%26%6%45%5%7%12%42%
1625
11th to 20thNight
3314436%6%8%12%49%
1620
21st to endNight
6%425%6%46%8%8%13%38%
1620
July1st to 10thNight
5%445%5%46%6%10%12%40%
1620
11th to 20thNight
5%325%5%36%7%8%13%43%
1620
21st to endNight
6%5%35%5%46%7%7%13%41%
1826
August1st to 10thNight
33145%35%6%8%14%47%
1790
11th to 20thNight
5%415%6%5%6%6%7%15%39%
1776
21st to endNight
9%425%5%46%7%7%11%40%
1980
September1st to 10thNight
7%5%25%6%36%6%7%10%43%
1800
11th to 20thNight
8%6%25%6%35%6%7%10%44%
1800
21st to endNight
9%5%245%3445%8%51%
1973
October1st to 10thNight
7%4244235%47%60%
2160
11th to 20thNight
8%5%24423445%58%
2160
21st to endNight
11%6%245%22445%55%
2376
November1st to 10thNight
11%413424346%57%
2220
11th to 20thNight
14%5%24423435%55%
2280
21st to endNight
14%6%3443445%6%47%
2414
December1st to 10thNight
16%8%35%422337%46%
2470
11th to 20thNight
14%10%36%5%34446%42%
2925
21st to endNight
19%11%35%5%23345%41%
4532

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 10thDay
42%35%17%23%8%
1708
11th to 20thDay
44%3413%25%9%
1665
21st to endDay
45%35%14%23%11%
1786
February1st to 10thDay
48%5%7%13%17%10%
1800
11th to 20thDay
47%46%14%21%8%
1758
21st to endDay
49%5%7%14%15%9%
1480
March1st to 10thDay
46%6%7%15%17%9%
1970
11th to 20thDay
47%7%8%11%20%6%
1980
21st to endDay
39%7%8%18%22%5%
2227
April1st to 10thDay
39%7%9%18%19%7%
2160
11th to 20thDay
44%5%8%17%18%8%
2134
21st to endDay
37%7%10%19%23%4
2160
May1st to 10thDay
41%7%10%19%17%6%
2160
11th to 20thDay
41%8%11%24%15%2
2128
21st to endDay
41%9%13%23%13%1
2337
June1st to 10thDay
43%12%13%20%11%1
2329
11th to 20thDay
42%10%14%20%11%2
2340
21st to endDay
46%12%16%17%8%1
2340
July1st to 10thDay
48%14%17%14%6%1
2276
11th to 20thDay
45%16%17%16%41
2271
21st to endDay
45%12%18%17%7%1
2350
August1st to 10thDay
41%13%19%18%8%
2136
11th to 20thDay
44%13%18%18%6%2
2125
21st to endDay
46%11%14%16%10%3
2376
September1st to 10thDay
43%10%15%15%12%4
2160
11th to 20thDay
42%8%12%15%16%7%
2160
21st to endDay
35%6%10%20%20%9%
1962
October1st to 10thDay
29%6%10%18%24%13%
1800
11th to 20thDay
30%5%7%14%30%14%
1800
21st to endDay
32%37%14%30%14%
1980
November1st to 10thDay
32%48%17%28%11%
1858
11th to 20thDay
34%5%6%14%27%13%
1900
21st to endDay
40%47%18%21%10%
1757
December1st to 10thDay
42%5%8%18%18%8%
1710
11th to 20thDay
46%47%13%23%8%
2255
21st to endDay
41%5%8%18%24%3
3135
January1st to 10thNight
42%46%14%25%9%
2458
11th to 20thNight
42%5%6%17%21%10%
2418
21st to endNight
45%36%13%23%9%
2566
February1st to 10thNight
44%47%16%20%9%
2160
11th to 20thNight
43%5%6%15%20%11%
2099
21st to endNight
49%6%7%13%14%11%
1776
March1st to 10thNight
38%6%9%16%21%10%
2003
11th to 20thNight
45%6%10%13%18%7%
1980
21st to endNight
35%5%12%19%24%6%
2127
April1st to 10thNight
37%7%9%18%19%9%
1800
11th to 20thNight
37%6%11%18%18%10%
1775
21st to endNight
27%7%13%21%27%6%
1800
May1st to 10thNight
30%6%12%25%21%7%
1800
11th to 20thNight
31%8%16%25%18%2
1770
21st to endNight
31%12%15%26%16%1
1939
June1st to 10thNight
34%11%18%22%14%1
1625
11th to 20thNight
25%11%19%28%15%2
1620
21st to endNight
34%13%19%23%11%
1620
July1st to 10thNight
32%15%26%18%7%2
1575
11th to 20thNight
30%17%26%21%5%2
1566
21st to endNight
32%14%23%22%9%1
1724
August1st to 10thNight
25%12%33%21%9%
1778
11th to 20thNight
32%15%23%20%7%2
1776
21st to endNight
35%14%20%16%12%3
1980
September1st to 10thNight
33%10%19%19%13%6%
1800
11th to 20thNight
35%9%17%16%15%9%
1800
21st to endNight
31%6%11%23%18%10%
1973
October1st to 10thNight
25%6%10%19%25%15%
2160
11th to 20thNight
29%5%7%19%27%14%
2160
21st to endNight
31%46%15%26%18%
2376
November1st to 10thNight
29%49%18%25%15%
2220
11th to 20thNight
33%46%14%28%15%
2280
21st to endNight
38%5%7%18%21%12%
2414
December1st to 10thNight
40%5%7%21%20%7%
2470
11th to 20thNight
45%46%11%22%13%
2926
21st to endNight
46%46%17%19%7%
4532

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 10thDay
24%23%31%17%41
270
11th to 20thDay
24%15%38%18%4
255
21st to endDay
26%25%36%11%2
264
February1st to 10thDay
28%21%33%14%3
240
11th to 20thDay
38%15%30%12%4
240
21st to endDay
26%27%39%7%1
198
March1st to 10thDay
25%19%38%14%3
240
11th to 20thDay
28%21%37%13%1
240
21st to endDay
19%21%31%23%5%1
313
April1st to 10thDay
17%15%35%23%8%1
420
11th to 20thDay
24%14%30%19%11%2
412
21st to endDay
13%13%32%29%11%2
420
May1st to 10thDay
15%9%30%31%13%3
423
11th to 20thDay
14%424%31%19%9%
447
21st to endDay
9%5%18%34%24%11%
485
June1st to 10thDay
9%315%33%29%11%
619
11th to 20thDay
8%315%34%31%9%
630
21st to endDay
9%312%29%29%17%
630
July1st to 10thDay
6%45%28%39%18%
621
11th to 20thDay
6%2424%41%23%
618
21st to endDay
8%36%23%42%18%
626
August1st to 10thDay
6%36%18%41%26%
446
11th to 20thDay
10%1315%44%27%
439
21st to endDay
13%47%21%29%25%
495
September1st to 10thDay
11%36%24%36%20%
450
11th to 20thDay
12%311%22%36%16%
450
21st to endDay
14%39%28%34%12%
432
October1st to 10thDay
8%6%21%39%21%6%
270
11th to 20thDay
10%7%21%36%20%5%
270
21st to endDay
21%10%26%28%12%3
297
November1st to 10thDay
16%6%29%33%13%3
270
11th to 20thDay
16%14%34%23%11%
270
21st to endDay
18%15%36%20%9%2
270
December1st to 10thDay
21%13%36%22%7%1
270
11th to 20thDay
23%14%36%21%6%
270
21st to endDay
29%17%31%17%41
297
January1st to 10thNight
24%15%32%23%6%
950
11th to 20thNight
22%14%30%25%8%1
930
21st to endNight
24%14%33%24%5%
982
February1st to 10thNight
20%16%36%24%4
720
11th to 20thNight
26%16%30%24%5%
703
21st to endNight
25%20%33%19%3
592
March1st to 10thNight
19%14%33%27%6%
563
11th to 20thNight
18%13%34%29%6%
540
21st to endNight
16%11%39%27%8%
594
April1st to 10thNight
16%10%37%27%9%1
540
11th to 20thNight
17%10%33%29%11%1
533
21st to endNight
9%9%36%31%14%1
540
May1st to 10thNight
10%5%31%39%15%1
540
11th to 20thNight
10%424%37%22%3
531
21st to endNight
7%317%40%27%6%
584
June1st to 10thNight
7%210%39%36%5%
540
11th to 20thNight
3111%42%35%8%
540
21st to endNight
6%28%32%36%16%
540
July1st to 10thNight
5%25%26%48%14%
525
11th to 20thNight
5%25%25%45%18%
522
21st to endNight
7%15%25%49%12%
591
August1st to 10thNight
5%1424%48%18%
537
11th to 20thNight
6%1324%49%17%
534
21st to endNight
10%16%25%41%17%
594
September1st to 10thNight
8%3426%46%13%
540
11th to 20thNight
10%37%30%43%8%
540
21st to endNight
10%212%31%39%6%
700
October1st to 10thNight
8%318%35%33%4
720
11th to 20thNight
9%6%23%35%23%3
720
21st to endNight
16%8%21%31%22%2
792
November1st to 10thNight
13%6%22%34%23%2
740
11th to 20thNight
16%9%28%32%14%1
760
21st to endNight
19%9%30%28%14%1
760
December1st to 10thNight
19%12%29%30%10%
760
11th to 20thNight
22%10%32%28%8%
815
21st to endNight
27%13%27%26%6%
1045
Page generated at 2024-01-13 08:37:53. Version ac07

Copyright 2024 Attilla Danko


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