Elton Moonshine Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elton Moonshine Observatory clear sky chart from 2005-11-06 to 2024-01-11.

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
30%
23315
15%
74787
9%
23261
38%
23261
16%
53191

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
10%
757
13%
2549
4%
757
21%
757
7%
2009
January11th to 20thNight
11%
724
8%
2352
2%
724
18%
724
7%
1935
January21st to endNight
10%
792
11%
2574
4%
792
19%
792
7%
2067
February1st to 10thNight
12%
720
12%
2340
5%
720
22%
720
9%
1809
February11th to 20thNight
9%
703
10%
2275
2%
700
18%
700
7%
1794
February21st to endNight
10%
592
14%
1777
3%
592
23%
592
9%
1381
March1st to 10thNight
18%
720
17%
1980
8%
720
29%
720
16%
1425
March11th to 20thNight
20%
720
17%
1980
8%
720
29%
720
14%
1431
March21st to endNight
17%
792
17%
2178
6%
792
26%
792
16%
1589
April1st to 10thNight
19%
720
13%
1832
4%
720
25%
720
17%
1368
April11th to 20thNight
29%
711
16%
1775
7%
711
34%
711
23%
1255
April21st to endNight
28%
617
18%
1697
7%
617
34%
617
21%
1214
May1st to 10thNight
36%
540
15%
1620
8%
540
42%
540
18%
1134
May11th to 20thNight
34%
484
15%
1546
11%
484
38%
484
17%
1084
May21st to endNight
52%
388
17%
1551
16%
388
59%
388
22%
913
June1st to 10thNight
48%
360
17%
1440
18%
360
56%
360
22%
853
June11th to 20thNight
48%
360
15%
1440
17%
360
54%
360
18%
906
June21st to endNight
51%
360
17%
1440
17%
360
59%
360
24%
843
July1st to 10thNight
56%
350
15%
1400
18%
350
59%
350
22%
831
July11th to 20thNight
62%
482
18%
1526
17%
482
65%
482
34%
868
July21st to endNight
55%
591
16%
1672
11%
558
59%
558
28%
1061
August1st to 10thNight
59%
537
17%
1600
13%
534
62%
534
31%
984
August11th to 20thNight
61%
534
20%
1598
14%
534
63%
534
30%
1007
August21st to endNight
56%
758
20%
1946
12%
758
58%
758
32%
1272
September1st to 10thNight
54%
720
22%
1800
11%
720
58%
720
32%
1197
September11th to 20thNight
57%
720
28%
1880
19%
720
61%
720
37%
1145
September21st to endNight
44%
720
21%
2034
17%
720
48%
720
25%
1364
October1st to 10thNight
44%
720
17%
2160
14%
720
49%
720
25%
1411
October11th to 20thNight
30%
720
18%
2160
10%
720
42%
720
22%
1453
October21st to endNight
25%
792
20%
2376
11%
792
37%
792
17%
1686
November1st to 10thNight
35%
740
23%
2244
15%
740
46%
740
23%
1445
November11th to 20thNight
22%
760
17%
2645
10%
760
33%
760
13%
1884
November21st to endNight
19%
760
15%
2660
8%
760
29%
760
11%
1949
December1st to 10thNight
16%
760
8%
2660
4%
760
21%
760
6%
2164
December11th to 20thNight
14%
760
10%
3229
4%
759
22%
759
6%
2512
December21st to endNight
14%
831
7%
4851
4%
817
22%
817
4%
3948

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
15%10%5%8%7%45%5%5%7%30%
74621
Night
14%10%5%8%6%35%5%5%6%32%
75073
TransparencyDay
54%411%19%10%1
74334
Night
53%5%10%20%11%2
74879
SeeingDay
24%16%26%19%11%4
13634
Night
21%17%25%25%11%1
23324

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
13%13%9%14%9%45%43420%
1615
11th to 20thDay
15%17%9%14%8%45%435%16%
1620
21st to endDay
16%14%10%13%9%44345%18%
1782
February1st to 10thDay
15%17%6%10%9%5%5%446%19%
1620
11th to 20thDay
15%12%8%13%9%35%5%45%20%
1573
21st to endDay
17%14%6%11%7%35%345%24%
1472
March1st to 10thDay
13%11%6%9%7%35%5%46%31%
1980
11th to 20thDay
18%12%5%10%6%35%45%6%25%
1980
21st to endDay
18%13%5%7%6%4445%6%27%
2178
April1st to 10thDay
13%13%5%8%6%35%5%5%7%29%
2128
11th to 20thDay
16%11%5%6%6%4445%6%33%
2134
21st to endDay
20%9%47%5%35%45%7%30%
2276
May1st to 10thDay
19%9%37%7%46%5%5%7%28%
2340
11th to 20thDay
21%8%36%6%445%5%8%30%
2344
21st to endDay
14%6%36%6%36%5%6%9%35%
2725
June1st to 10thDay
15%7%45%7%46%5%6%8%33%
2520
11th to 20thDay
14%8%37%6%46%7%8%8%31%
2520
21st to endDay
14%5%36%6%46%5%7%10%34%
2520
July1st to 10thDay
11%7%36%6%5%7%6%6%7%37%
2520
11th to 20thDay
10%6%36%6%45%5%7%10%37%
2378
21st to endDay
13%7%37%6%46%6%6%8%33%
2547
August1st to 10thDay
10%8%37%7%5%7%7%7%9%30%
2327
11th to 20thDay
13%7%37%8%35%6%7%8%32%
2303
21st to endDay
14%6%26%6%45%6%8%9%33%
2390
September1st to 10thDay
16%6%26%6%45%45%7%38%
2160
11th to 20thDay
13%5%36%5%345%5%8%43%
2077
21st to endDay
19%9%37%6%35%5%46%35%
1926
October1st to 10thDay
15%9%36%6%4446%7%36%
1800
11th to 20thDay
18%11%37%5%35%5%5%5%34%
1800
21st to endDay
17%15%47%6%43446%31%
1980
November1st to 10thDay
11%10%5%7%5%345%46%40%
1831
11th to 20thDay
14%12%7%8%6%45%5%5%6%29%
1533
21st to endDay
16%14%8%10%7%45%446%24%
1520
December1st to 10thDay
16%16%9%14%7%45%34417%
1520
11th to 20thDay
16%16%8%13%6%23446%22%
1910
21st to endDay
21%18%10%11%6%3443416%
2772
January1st to 10thNight
12%12%8%14%9%5%6%5%4420%
2549
11th to 20thNight
16%16%6%14%8%5%6%33418%
2352
21st to endNight
13%14%9%13%9%45%445%20%
2574
February1st to 10thNight
15%11%7%11%9%45%5%5%5%24%
2340
11th to 20thNight
15%12%6%11%9%5%6%5%5%6%20%
2273
21st to endNight
14%13%8%11%7%46%445%25%
1777
March1st to 10thNight
12%9%6%8%6%445%5%7%32%
1980
11th to 20thNight
17%11%48%6%25%35%6%33%
1980
21st to endNight
16%12%6%8%6%24446%32%
2178
April1st to 10thNight
15%14%48%6%35%446%32%
1832
11th to 20thNight
15%9%36%5%36%5%5%7%36%
1775
21st to endNight
15%9%38%6%44447%35%
1697
May1st to 10thNight
17%10%36%5%35%5%6%7%33%
1620
11th to 20thNight
17%9%37%6%25%5%5%7%34%
1545
21st to endNight
9%7%35%6%346%6%10%41%
1550
June1st to 10thNight
12%7%35%5%35%5%5%8%42%
1440
11th to 20thNight
11%6%35%7%37%5%7%8%37%
1440
21st to endNight
11%5%26%5%35%5%7%10%42%
1440
July1st to 10thNight
10%7%36%5%25%5%7%8%43%
1440
11th to 20thNight
8%435%4345%6%10%49%
1577
21st to endNight
9%6%25%7%45%6%7%9%40%
1771
August1st to 10thNight
8%5%35%6%45%6%7%11%42%
1611
11th to 20thNight
9%6%36%6%45%5%5%7%44%
1598
21st to endNight
11%6%35%5%25%5%6%8%43%
1946
September1st to 10thNight
13%7%34435%46%6%45%
1800
11th to 20thNight
10%7%244335%6%8%50%
1880
21st to endNight
15%8%36%5%4445%7%40%
2034
October1st to 10thNight
15%8%25%5%36%45%7%41%
2160
11th to 20thNight
15%9%36%5%4445%7%37%
2160
21st to endNight
21%13%36%433446%33%
2376
November1st to 10thNight
10%11%46%5%3445%6%43%
2244
11th to 20thNight
15%12%5%8%7%35%35%6%31%
2645
21st to endNight
15%13%7%9%6%44446%28%
2660
December1st to 10thNight
18%15%9%12%7%46%435%18%
2660
11th to 20thNight
16%12%8%13%8%45%44422%
3285
21st to endNight
18%17%10%11%8%445%45%14%
4884

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
68%5%8%13%5%1
1616
11th to 20thDay
73%39%11%4
1620
21st to endDay
70%38%12%6%1
1782
February1st to 10thDay
68%49%12%6%1
1620
11th to 20thDay
66%5%8%14%6%
1582
21st to endDay
64%49%13%8%2
1472
March1st to 10thDay
55%5%11%21%9%1
1980
11th to 20thDay
59%48%18%8%1
1980
21st to endDay
58%39%18%10%2
2178
April1st to 10thDay
54%411%18%11%2
2128
11th to 20thDay
53%311%15%16%2
2134
21st to endDay
54%49%21%10%2
2276
May1st to 10thDay
56%49%19%11%1
2340
11th to 20thDay
54%5%11%16%11%2
2348
21st to endDay
46%6%17%21%9%1
2725
June1st to 10thDay
49%5%12%24%10%1
2520
11th to 20thDay
48%6%13%21%11%1
2520
21st to endDay
44%6%12%26%11%
2520
July1st to 10thDay
46%6%10%22%13%3
2450
11th to 20thDay
41%5%14%24%15%1
2306
21st to endDay
47%6%10%23%14%1
2405
August1st to 10thDay
47%6%14%25%8%
2314
11th to 20thDay
48%5%12%24%11%1
2303
21st to endDay
45%5%12%23%12%3
2390
September1st to 10thDay
45%6%10%21%15%3
2160
11th to 20thDay
40%410%29%16%2
2077
21st to endDay
51%412%20%13%1
1926
October1st to 10thDay
48%411%22%13%2
1800
11th to 20thDay
53%49%25%11%
1800
21st to endDay
55%39%18%12%2
1980
November1st to 10thDay
46%411%19%16%4
1831
11th to 20thDay
56%410%17%11%3
1533
21st to endDay
63%49%17%7%
1520
December1st to 10thDay
72%39%11%4
1520
11th to 20thDay
66%38%19%5%
1906
21st to endDay
74%38%12%4
2772
January1st to 10thNight
66%5%7%15%7%1
2549
11th to 20thNight
70%5%8%13%41
2352
21st to endNight
68%47%14%6%1
2574
February1st to 10thNight
62%49%17%7%1
2340
11th to 20thNight
64%6%7%15%7%
2275
21st to endNight
62%48%16%9%2
1777
March1st to 10thNight
52%410%21%12%1
1980
11th to 20thNight
53%311%21%11%2
1980
21st to endNight
54%48%18%14%3
2178
April1st to 10thNight
55%310%18%13%1
1832
11th to 20thNight
47%411%20%15%3
1775
21st to endNight
50%48%23%11%3
1697
May1st to 10thNight
50%5%9%21%11%3
1620
11th to 20thNight
50%6%10%18%14%2
1546
21st to endNight
38%7%17%26%11%1
1551
June1st to 10thNight
40%5%12%29%13%1
1440
11th to 20thNight
44%7%13%25%10%2
1440
21st to endNight
37%8%15%26%14%1
1440
July1st to 10thNight
38%7%14%24%13%4
1400
11th to 20thNight
31%6%16%27%18%1
1526
21st to endNight
38%7%16%23%13%3
1672
August1st to 10thNight
35%7%18%27%13%
1600
11th to 20thNight
39%5%15%26%14%1
1598
21st to endNight
38%6%13%27%14%3
1946
September1st to 10thNight
40%412%25%16%3
1800
11th to 20thNight
33%411%31%19%1
1880
21st to endNight
44%410%24%16%1
2034
October1st to 10thNight
43%413%24%14%2
2160
11th to 20thNight
47%410%25%13%1
2160
21st to endNight
53%38%22%11%2
2376
November1st to 10thNight
43%310%21%18%4
2244
11th to 20thNight
55%48%19%12%3
2645
21st to endNight
59%49%19%8%1
2660
December1st to 10thNight
70%48%12%5%1
2660
11th to 20thNight
65%5%7%17%5%
3288
21st to endNight
73%39%11%4
4884

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
35%27%24%9%5%
227
11th to 20thDay
39%26%28%5%2
240
21st to endDay
35%21%33%9%1
264
February1st to 10thDay
33%30%31%6%1
240
11th to 20thDay
38%30%28%5%
240
21st to endDay
37%27%24%11%1
289
March1st to 10thDay
32%25%27%14%2
420
11th to 20thDay
31%26%24%15%41
420
21st to endDay
31%25%27%12%41
462
April1st to 10thDay
29%21%28%16%41
420
11th to 20thDay
23%20%30%14%8%5%
412
21st to endDay
32%17%30%13%7%1
420
May1st to 10thDay
32%16%25%15%8%4
423
11th to 20thDay
25%17%30%17%8%4
447
21st to endDay
18%12%27%22%14%7%
485
June1st to 10thDay
19%16%25%22%14%3
450
11th to 20thDay
22%10%25%23%16%4
450
21st to endDay
16%13%31%23%14%3
450
July1st to 10thDay
13%7%23%27%19%11%
445
11th to 20thDay
10%7%30%28%17%8%
444
21st to endDay
16%8%26%28%15%7%
488
August1st to 10thDay
12%7%23%28%22%9%
446
11th to 20thDay
17%7%21%26%17%12%
439
21st to endDay
13%8%23%28%18%10%
495
September1st to 10thDay
21%8%19%23%18%12%
450
11th to 20thDay
15%322%31%20%9%
450
21st to endDay
24%12%24%19%15%6%
450
October1st to 10thDay
20%12%22%25%18%3
450
11th to 20thDay
25%18%26%20%10%1
450
21st to endDay
26%21%30%17%6%1
495
November1st to 10thDay
20%19%29%20%11%2
442
11th to 20thDay
27%24%29%15%5%1
193
21st to endDay
29%26%31%13%2
180
December1st to 10thDay
30%33%23%11%21
180
11th to 20thDay
39%22%28%9%2
180
21st to endDay
35%25%23%12%4
198
January1st to 10thNight
25%31%29%11%3
760
11th to 20thNight
29%26%28%15%2
724
21st to endNight
23%29%31%14%1
792
February1st to 10thNight
26%27%28%16%2
720
11th to 20thNight
26%33%29%11%1
703
21st to endNight
30%25%29%14%2
592
March1st to 10thNight
22%26%30%21%2
720
11th to 20thNight
27%24%24%17%6%1
720
21st to endNight
25%20%32%17%5%1
792
April1st to 10thNight
26%20%31%18%5%
720
11th to 20thNight
21%18%27%24%9%1
711
21st to endNight
22%14%30%29%6%
617
May1st to 10thNight
26%10%22%31%10%1
540
11th to 20thNight
23%10%26%31%10%
484
21st to endNight
12%7%20%38%20%3
389
June1st to 10thNight
14%7%25%35%18%1
360
11th to 20thNight
13%8%22%38%18%1
360
21st to endNight
13%6%26%40%15%1
360
July1st to 10thNight
13%418%39%23%2
350
11th to 20thNight
10%417%38%28%4
482
21st to endNight
10%5%19%40%23%3
591
August1st to 10thNight
10%317%40%28%2
537
11th to 20thNight
11%5%14%39%28%4
534
21st to endNight
13%419%35%24%5%
758
September1st to 10thNight
16%5%16%35%24%4
720
11th to 20thNight
12%6%18%33%26%4
720
21st to endNight
20%9%21%26%20%3
720
October1st to 10thNight
19%7%23%30%18%2
720
11th to 20thNight
21%15%31%24%8%2
720
21st to endNight
27%19%25%23%6%1
792
November1st to 10thNight
18%16%27%28%10%1
740
11th to 20thNight
26%22%25%21%6%1
760
21st to endNight
25%21%30%18%5%
760
December1st to 10thNight
31%26%23%17%3
760
11th to 20thNight
24%30%25%18%3
760
21st to endNight
26%25%28%18%2
836
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