Auroraville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Auroraville clear sky chart from 2005-11-06 to 2024-01-10.

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
36%
24749
16%
74631
9%
24698
43%
24698
22%
50982

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
24%
950
13%
2647
5%
946
31%
946
17%
1951
January11th to 20thNight
23%
900
11%
2520
4%
900
29%
900
15%
1963
January21st to endNight
23%
990
11%
2750
3%
990
30%
990
15%
2124
February1st to 10thNight
23%
900
12%
2340
2%
900
30%
900
19%
1738
February11th to 20thNight
25%
763
18%
2162
6%
763
34%
763
20%
1511
February21st to endNight
24%
592
16%
1776
4%
592
35%
592
17%
1268
March1st to 10thNight
33%
720
16%
2160
9%
720
38%
720
20%
1475
March11th to 20thNight
32%
653
20%
2093
10%
653
42%
653
24%
1341
March21st to endNight
36%
594
19%
1994
15%
594
43%
594
19%
1375
April1st to 10thNight
26%
540
14%
1800
9%
540
35%
540
17%
1248
April11th to 20thNight
35%
533
18%
1775
15%
533
42%
533
20%
1199
April21st to endNight
36%
540
16%
1697
10%
540
43%
540
22%
1151
May1st to 10thNight
33%
540
14%
1529
8%
540
37%
540
21%
1091
May11th to 20thNight
39%
531
17%
1417
9%
531
46%
531
25%
991
May21st to endNight
48%
583
14%
1552
8%
582
53%
582
29%
1036
June1st to 10thNight
51%
540
13%
1440
7%
540
55%
540
33%
914
June11th to 20thNight
47%
540
16%
1440
8%
540
52%
540
32%
927
June21st to endNight
58%
540
17%
1440
10%
540
61%
540
37%
885
July1st to 10thNight
66%
525
18%
1400
11%
525
68%
525
45%
804
July11th to 20thNight
60%
522
19%
1392
11%
522
63%
522
39%
846
July21st to endNight
66%
591
21%
1487
14%
558
69%
558
44%
853
August1st to 10thNight
67%
537
23%
1423
17%
534
71%
534
38%
869
August11th to 20thNight
62%
534
21%
1688
19%
534
67%
534
33%
983
August21st to endNight
60%
594
22%
1980
21%
594
65%
594
34%
1107
September1st to 10thNight
56%
540
23%
1800
21%
540
61%
540
32%
1024
September11th to 20thNight
53%
593
28%
1853
23%
593
60%
593
33%
1080
September21st to endNight
47%
720
22%
1980
14%
720
53%
720
31%
1238
October1st to 10thNight
46%
720
22%
2102
15%
720
52%
720
29%
1315
October11th to 20thNight
31%
720
18%
2164
8%
720
41%
720
21%
1473
October21st to endNight
30%
792
14%
2574
9%
792
38%
792
17%
1812
November1st to 10thNight
33%
740
23%
2406
15%
740
46%
740
25%
1503
November11th to 20thNight
21%
788
15%
2498
7%
788
30%
788
15%
1771
November21st to endNight
25%
950
16%
2660
7%
950
33%
950
21%
1861
December1st to 10thNight
19%
950
11%
2660
3%
950
26%
950
16%
1977
December11th to 20thNight
19%
948
11%
3209
3%
948
27%
948
11%
2449
December21st to endNight
16%
1036
7%
4823
3%
1026
23%
1026
7%
3829

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
14%8%36%5%35%5%5%7%38%
74760
Night
14%9%46%5%3445%6%39%
74944
TransparencyDay
45%7%13%22%11%1
74460
Night
46%6%12%22%12%1
74764
SeeingDay
16%9%28%27%15%5%
14762
Night
18%8%30%31%12%1
24764

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
11%11%7%8%7%46%446%33%
1509
11th to 20thDay
13%14%6%11%8%45%45%5%25%
1440
21st to endDay
12%14%7%11%7%45%46%6%24%
1606
February1st to 10thDay
11%12%5%8%7%35%5%5%6%33%
1620
11th to 20thDay
12%11%48%6%35%5%46%36%
1685
21st to endDay
13%10%6%8%6%45%46%6%31%
1480
March1st to 10thDay
13%10%5%7%5%35%5%5%7%35%
1800
11th to 20thDay
11%10%46%6%345%5%8%38%
1881
21st to endDay
19%10%46%6%35%45%7%31%
2362
April1st to 10thDay
17%11%46%6%446%46%32%
2160
11th to 20thDay
20%9%36%6%35%5%45%34%
2134
21st to endDay
20%9%37%6%445%46%33%
2263
May1st to 10thDay
17%7%37%5%45%5%6%7%33%
2429
11th to 20thDay
17%7%25%6%35%45%7%38%
2479
21st to endDay
14%6%26%6%35%5%6%7%39%
2725
June1st to 10thDay
12%5%25%435%5%5%8%46%
2520
11th to 20thDay
14%4345%35%46%9%42%
2520
21st to endDay
11%6%25%5%35%5%5%10%43%
2520
July1st to 10thDay
7%424436%6%8%10%47%
2520
11th to 20thDay
8%424435%5%7%10%48%
2520
21st to endDay
9%4245%45%5%6%9%49%
2743
August1st to 10thDay
7%5%246%45%7%7%9%44%
2507
11th to 20thDay
11%6%25%5%35%6%5%8%43%
2208
21st to endDay
12%5%25%5%35%5%5%7%45%
2376
September1st to 10thDay
14%436%5%35%45%7%45%
2160
11th to 20thDay
13%4245%335%5%8%48%
2088
21st to endDay
14%6%36%5%345%6%7%41%
1980
October1st to 10thDay
15%7%35%5%2445%7%43%
1854
11th to 20thDay
20%9%36%6%35%46%7%31%
1796
21st to endDay
17%10%47%5%34445%37%
1782
November1st to 10thDay
12%7%37%5%45%45%6%43%
1672
11th to 20thDay
14%10%6%8%6%45%45%6%32%
1680
21st to endDay
16%10%47%5%345%46%36%
1520
December1st to 10thDay
13%11%6%10%7%35%5%5%7%30%
1520
11th to 20thDay
13%12%5%9%7%45%5%47%27%
1918
21st to endDay
20%18%8%11%8%35%445%17%
2783
January1st to 10thNight
12%12%6%9%7%4444435%
2647
11th to 20thNight
14%13%7%9%8%35%5%45%28%
2520
21st to endNight
13%13%7%9%7%45%5%5%5%27%
2750
February1st to 10thNight
11%13%5%9%6%445%45%35%
2340
11th to 20thNight
11%10%48%6%45%5%4439%
2161
21st to endNight
16%11%48%6%34446%35%
1776
March1st to 10thNight
15%8%47%5%3446%6%38%
2160
11th to 20thNight
13%7%35%7%35%45%8%41%
2093
21st to endNight
18%9%46%5%35%446%36%
1994
April1st to 10thNight
20%8%46%6%3445%5%35%
1800
11th to 20thNight
21%7%35%43445%6%37%
1775
21st to endNight
18%7%46%5%245%5%7%38%
1697
May1st to 10thNight
19%6%36%6%35%5%5%7%34%
1529
11th to 20thNight
17%7%35%5%36%45%7%39%
1416
21st to endNight
12%425%6%35%6%6%9%41%
1551
June1st to 10thNight
10%5%25%435%6%6%8%48%
1440
11th to 20thNight
11%6%25%5%25%5%5%9%44%
1440
21st to endNight
8%4244345%5%9%51%
1440
July1st to 10thNight
7%5%133235%6%10%55%
1440
11th to 20thNight
7%325%5%35%6%5%7%52%
1440
21st to endNight
6%3144345%5%8%56%
1575
August1st to 10thNight
7%424435%6%5%10%50%
1432
11th to 20thNight
8%6%245%25%37%8%50%
1688
21st to endNight
10%42443345%7%52%
1980
September1st to 10thNight
11%5%2443446%7%51%
1800
11th to 20thNight
13%5%24424445%53%
1853
21st to endNight
12%5%25%5%245%5%7%47%
1980
October1st to 10thNight
13%6%26%42445%6%47%
2102
11th to 20thNight
17%8%35%5%445%5%6%38%
2164
21st to endNight
19%9%26%5%35%5%46%35%
2574
November1st to 10thNight
13%8%345%2445%7%45%
2406
11th to 20thNight
15%10%48%6%35%5%45%34%
2498
21st to endNight
15%9%46%6%34446%38%
2660
December1st to 10thNight
13%13%5%8%6%35%5%47%31%
2660
11th to 20thNight
13%14%6%9%7%45%445%29%
3279
21st to endNight
23%17%6%9%6%33445%21%
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
54%6%13%18%9%1
1510
11th to 20thDay
61%7%11%12%8%1
1440
21st to endDay
60%7%13%13%7%
1606
February1st to 10thDay
52%6%13%20%9%1
1620
11th to 20thDay
48%7%12%21%10%2
1694
21st to endDay
54%7%10%17%10%2
1480
March1st to 10thDay
48%7%14%20%9%2
1800
11th to 20thDay
43%9%13%20%13%2
1881
21st to endDay
52%6%12%21%7%1
2362
April1st to 10thDay
52%7%12%18%11%1
2160
11th to 20thDay
51%7%8%21%11%2
2134
21st to endDay
52%7%11%18%10%2
2263
May1st to 10thDay
48%8%14%21%8%1
2429
11th to 20thDay
43%8%13%23%11%2
2483
21st to endDay
42%8%13%23%13%2
2725
June1st to 10thDay
36%7%14%27%15%1
2520
11th to 20thDay
37%9%13%26%15%1
2520
21st to endDay
36%9%15%26%13%2
2520
July1st to 10thDay
29%9%16%30%13%2
2451
11th to 20thDay
30%9%16%28%15%2
2445
21st to endDay
30%9%16%27%16%3
2591
August1st to 10thDay
32%9%18%28%11%1
2492
11th to 20thDay
37%8%14%28%12%1
2208
21st to endDay
36%8%13%25%17%1
2376
September1st to 10thDay
38%7%12%25%17%1
2160
11th to 20thDay
34%7%16%31%11%1
2088
21st to endDay
41%7%13%29%10%
1980
October1st to 10thDay
40%7%12%28%12%
1854
11th to 20thDay
51%7%13%20%9%1
1796
21st to endDay
49%7%13%20%10%
1782
November1st to 10thDay
41%6%14%23%14%2
1672
11th to 20thDay
54%6%13%19%8%1
1680
21st to endDay
50%6%14%22%7%
1520
December1st to 10thDay
55%6%14%18%6%1
1520
11th to 20thDay
56%5%15%16%6%2
1915
21st to endDay
71%7%8%10%4
2783
January1st to 10thNight
55%411%18%11%1
2647
11th to 20thNight
59%6%13%15%7%1
2520
21st to endNight
58%6%10%16%9%
2750
February1st to 10thNight
53%6%10%21%9%2
2340
11th to 20thNight
47%6%11%23%10%2
2162
21st to endNight
52%5%12%19%11%2
1776
March1st to 10thNight
46%6%14%22%10%2
2160
11th to 20thNight
42%6%14%23%14%2
2093
21st to endNight
50%5%9%23%11%2
1994
April1st to 10thNight
51%5%9%18%16%2
1800
11th to 20thNight
48%5%9%20%15%3
1775
21st to endNight
44%8%12%21%14%1
1697
May1st to 10thNight
47%8%13%18%12%1
1529
11th to 20thNight
44%7%12%23%12%2
1417
21st to endNight
39%8%14%22%15%1
1552
June1st to 10thNight
34%7%14%27%17%1
1440
11th to 20thNight
36%7%11%26%19%1
1440
21st to endNight
30%8%16%29%13%3
1440
July1st to 10thNight
25%6%15%32%19%3
1400
11th to 20thNight
28%8%15%28%18%3
1392
21st to endNight
24%8%18%30%15%5%
1487
August1st to 10thNight
28%9%17%29%15%2
1423
11th to 20thNight
31%8%15%30%16%1
1688
21st to endNight
30%7%14%27%20%3
1980
September1st to 10thNight
31%7%12%25%23%1
1800
11th to 20thNight
32%7%12%34%15%1
1853
21st to endNight
35%6%12%31%14%1
1980
October1st to 10thNight
37%6%10%30%16%2
2102
11th to 20thNight
45%7%14%20%13%1
2164
21st to endNight
50%7%11%20%11%
2574
November1st to 10thNight
39%6%12%26%15%2
2406
11th to 20thNight
52%7%13%17%11%1
2498
21st to endNight
48%5%16%24%7%1
2660
December1st to 10thNight
54%6%13%20%6%1
2660
11th to 20thNight
59%6%11%17%7%1
3281
21st to endNight
66%6%9%14%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
16%10%32%30%10%2
267
11th to 20thDay
23%10%31%28%7%1
240
21st to endDay
19%8%30%32%10%
264
February1st to 10thDay
11%13%44%25%6%
240
11th to 20thDay
17%15%38%20%8%1
240
21st to endDay
17%15%43%23%11
198
March1st to 10thDay
22%12%38%18%9%1
240
11th to 20thDay
20%14%31%22%8%4
240
21st to endDay
26%8%29%25%11%1
448
April1st to 10thDay
24%11%32%25%8%
420
11th to 20thDay
25%13%30%18%12%3
412
21st to endDay
21%11%27%25%13%3
420
May1st to 10thDay
18%11%34%24%11%2
512
11th to 20thDay
20%10%27%26%12%5%
625
21st to endDay
17%7%26%26%17%7%
679
June1st to 10thDay
10%7%28%33%18%5%
630
11th to 20thDay
17%5%27%30%16%6%
630
21st to endDay
12%8%25%31%17%6%
630
July1st to 10thDay
7%318%29%28%14%
621
11th to 20thDay
9%6%22%30%23%9%
618
21st to endDay
9%423%34%22%8%
684
August1st to 10thDay
9%420%32%24%11%
626
11th to 20thDay
13%5%16%24%28%15%
495
21st to endDay
12%5%20%32%20%11%
495
September1st to 10thDay
16%7%19%29%21%8%
450
11th to 20thDay
14%319%34%21%8%
450
21st to endDay
17%10%26%22%19%6%
450
October1st to 10thDay
19%9%25%24%19%5%
324
11th to 20thDay
20%16%32%24%8%1
270
21st to endDay
24%12%35%21%8%1
297
November1st to 10thDay
14%14%34%25%11%2
270
11th to 20thDay
14%19%37%20%8%1
270
21st to endDay
21%13%38%21%6%
270
December1st to 10thDay
16%16%39%22%7%1
270
11th to 20thDay
20%16%36%21%7%1
270
21st to endDay
26%13%39%18%4
297
January1st to 10thNight
17%12%34%27%8%1
950
11th to 20thNight
20%10%34%28%7%1
900
21st to endNight
20%9%33%29%8%
990
February1st to 10thNight
18%10%37%28%7%
900
11th to 20thNight
15%12%39%25%8%
766
21st to endNight
22%11%34%27%5%
592
March1st to 10thNight
19%9%31%30%10%1
720
11th to 20thNight
18%8%36%30%8%1
653
21st to endNight
21%7%29%33%9%1
594
April1st to 10thNight
24%9%34%27%6%
540
11th to 20thNight
23%9%29%31%7%1
533
21st to endNight
20%9%29%33%8%1
540
May1st to 10thNight
20%7%32%33%7%1
540
11th to 20thNight
19%7%30%34%9%1
531
21st to endNight
14%5%24%37%19%1
584
June1st to 10thNight
11%6%23%42%16%1
540
11th to 20thNight
15%328%40%13%1
540
21st to endNight
10%422%46%17%1
540
July1st to 10thNight
8%218%42%27%2
525
11th to 20thNight
9%320%42%24%2
522
21st to endNight
7%217%47%24%2
591
August1st to 10thNight
8%315%47%25%2
537
11th to 20thNight
10%416%37%29%4
534
21st to endNight
12%218%42%24%2
594
September1st to 10thNight
12%423%37%20%5%
540
11th to 20thNight
15%323%31%23%4
593
21st to endNight
13%9%24%32%19%2
720
October1st to 10thNight
16%7%26%30%20%1
720
11th to 20thNight
21%11%32%27%8%
720
21st to endNight
25%10%29%28%9%1
792
November1st to 10thNight
17%8%36%27%10%1
740
11th to 20thNight
20%14%38%22%5%
788
21st to endNight
20%12%36%25%7%
950
December1st to 10thNight
20%11%40%22%7%
950
11th to 20thNight
23%11%34%24%7%1
950
21st to endNight
28%12%31%25%4
1045
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