Avonmore
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Avonmore clear sky chart from 2005-11-06 to 2024-03-01.

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
28%
22764
12%
80816
8%
22675
35%
22675
14%
58843

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
15%
755
7%
4402
3%
737
21%
737
4%
3391
January11th to 20thNight
18%
757
6%
4423
4%
740
24%
740
4%
3526
January21st to endNight
21%
829
6%
4818
7%
814
28%
814
6%
3853
February1st to 10thNight
17%
760
10%
2470
4%
760
25%
760
9%
1951
February11th to 20thNight
18%
743
13%
2357
6%
740
28%
740
13%
1777
February21st to endNight
22%
628
14%
1884
6%
628
33%
628
13%
1430
March1st to 10thNight
21%
723
13%
2167
7%
723
29%
723
13%
1675
March11th to 20thNight
18%
720
15%
2025
6%
720
27%
720
16%
1503
March21st to endNight
27%
792
20%
2030
8%
792
34%
792
20%
1484
April1st to 10thNight
23%
720
15%
1800
5%
720
28%
720
18%
1352
April11th to 20thNight
25%
711
15%
1775
4%
711
30%
711
21%
1312
April21st to endNight
27%
630
16%
1710
6%
630
33%
630
20%
1242
May1st to 10thNight
30%
360
15%
1440
11%
360
38%
360
15%
961
May11th to 20thNight
32%
354
20%
1416
15%
354
46%
354
18%
896
May21st to endNight
35%
388
13%
1551
9%
388
48%
388
21%
913
June1st to 10thNight
36%
360
10%
1440
10%
360
43%
360
15%
968
June11th to 20thNight
38%
360
12%
1440
14%
360
46%
360
20%
871
June21st to endNight
39%
360
11%
1440
13%
360
48%
360
18%
943
July1st to 10thNight
52%
350
14%
1400
19%
350
60%
350
25%
799
July11th to 20thNight
48%
348
15%
1392
19%
348
56%
348
24%
803
July21st to endNight
48%
394
14%
1486
15%
372
54%
372
22%
904
August1st to 10thNight
53%
358
16%
1422
16%
356
60%
356
23%
855
August11th to 20thNight
53%
572
17%
1636
11%
572
57%
572
28%
1080
August21st to endNight
45%
792
17%
1980
8%
792
49%
792
31%
1334
September1st to 10thNight
45%
720
16%
1800
6%
720
48%
720
29%
1246
September11th to 20thNight
50%
720
21%
1830
12%
720
53%
720
34%
1179
September21st to endNight
39%
720
21%
1987
15%
720
44%
720
26%
1343
October1st to 10thNight
33%
720
17%
2160
11%
720
42%
720
20%
1513
October11th to 20thNight
28%
720
15%
2160
8%
720
36%
720
17%
1565
October21st to endNight
23%
792
12%
2554
6%
792
32%
792
13%
1912
November1st to 10thNight
25%
740
15%
2407
9%
740
35%
740
16%
1685
November11th to 20thNight
22%
760
16%
2598
10%
760
32%
760
14%
1844
November21st to endNight
20%
760
10%
2660
5%
760
26%
760
9%
2049
December1st to 10thNight
17%
760
7%
2660
3%
760
23%
760
7%
2199
December11th to 20thNight
14%
760
11%
3249
5%
759
22%
759
7%
2531
December21st to endNight
14%
828
5%
4847
2%
817
19%
817
4%
3954

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
18%10%47%6%35%5%5%6%32%
78293
Night
18%11%47%6%3445%6%30%
81110
TransparencyDay
52%7%11%19%10%1
77998
Night
55%6%11%18%9%1
80939
SeeingDay
23%15%29%21%9%3
13557
Night
23%12%29%26%9%1
22788

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 10thDay
18%17%5%12%7%3444421%
2517
11th to 20thDay
14%14%7%10%8%45%5%5%5%22%
2520
21st to endDay
15%19%7%9%7%5%5%5%5%6%16%
2832
February1st to 10thDay
17%16%5%10%7%35%45%6%23%
1710
11th to 20thDay
15%13%6%11%7%3445%5%27%
1710
21st to endDay
20%14%5%7%6%45%5%45%25%
1570
March1st to 10thDay
16%13%5%10%8%35%44430%
1797
11th to 20thDay
19%11%47%7%36%446%31%
1932
21st to endDay
21%9%46%5%2445%5%36%
2326
April1st to 10thDay
22%11%46%5%23445%33%
2160
11th to 20thDay
22%8%47%5%33345%36%
2134
21st to endDay
24%10%37%5%35%45%5%31%
2262
May1st to 10thDay
20%8%36%5%35%5%5%6%35%
2520
11th to 20thDay
16%9%36%5%3445%7%39%
2478
21st to endDay
16%7%35%6%36%5%6%7%37%
2725
June1st to 10thDay
24%7%36%6%445%6%6%29%
2520
11th to 20thDay
15%5%36%5%36%6%5%9%37%
2520
21st to endDay
20%7%36%5%345%7%9%31%
2520
July1st to 10thDay
13%5%36%5%35%6%6%8%42%
2520
11th to 20thDay
12%6%35%5%36%6%7%10%37%
2520
21st to endDay
14%425%5%46%6%8%9%38%
2744
August1st to 10thDay
13%7%25%6%45%5%6%9%39%
2506
11th to 20thDay
12%6%25%5%46%6%6%8%40%
2244
21st to endDay
13%7%26%6%35%5%6%8%40%
2376
September1st to 10thDay
14%6%36%5%3447%7%42%
2160
11th to 20thDay
14%5%245%3445%7%47%
2129
21st to endDay
18%6%25%5%345%5%8%39%
1971
October1st to 10thDay
21%7%36%6%345%48%34%
1800
11th to 20thDay
20%10%48%7%45%45%5%28%
1800
21st to endDay
27%12%36%5%34445%27%
1801
November1st to 10thDay
17%9%5%7%6%35%5%5%6%32%
1671
11th to 20thDay
19%12%47%6%345%47%29%
1580
21st to endDay
21%14%5%9%7%4445%6%22%
1520
December1st to 10thDay
24%16%6%9%7%35%446%16%
1520
11th to 20thDay
22%15%5%9%6%4445%5%22%
1906
21st to endDay
26%17%6%9%6%3433320%
2772
January1st to 10thNight
18%16%6%11%7%45%345%20%
4429
11th to 20thNight
13%16%7%12%9%5%6%5%5%5%18%
4440
21st to endNight
18%18%8%10%7%4434420%
4820
February1st to 10thNight
16%14%6%12%7%5%5%45%5%22%
2470
11th to 20thNight
14%13%5%11%7%35%45%5%27%
2355
21st to endNight
16%15%6%7%7%35%44429%
1884
March1st to 10thNight
17%14%6%8%7%36%43428%
2157
11th to 20thNight
18%12%48%7%33435%32%
2025
21st to endNight
18%11%47%6%2434438%
2030
April1st to 10thNight
23%9%46%6%34346%31%
1800
11th to 20thNight
20%8%46%5%345%5%5%35%
1775
21st to endNight
23%9%36%5%33447%34%
1710
May1st to 10thNight
22%7%36%426%45%7%34%
1440
11th to 20thNight
17%9%445%34446%40%
1415
21st to endNight
13%5%35%5%345%6%8%42%
1550
June1st to 10thNight
19%7%25%7%35%6%7%10%29%
1440
11th to 20thNight
16%7%25%5%3445%9%40%
1440
21st to endNight
18%6%35%6%345%7%8%36%
1440
July1st to 10thNight
9%5%25%5%445%8%9%44%
1440
11th to 20thNight
11%6%245%25%6%7%11%41%
1440
21st to endNight
11%5%35%5%25%7%7%10%40%
1574
August1st to 10thNight
11%7%25%5%35%5%6%9%42%
1432
11th to 20thNight
11%8%25%6%36%5%5%8%41%
1636
21st to endNight
13%6%35%43446%9%42%
1980
September1st to 10thNight
12%7%36%6%45%5%6%6%43%
1800
11th to 20thNight
16%5%2432345%8%47%
1830
21st to endNight
16%5%36%5%35%45%6%41%
1987
October1st to 10thNight
20%8%25%5%35%5%46%36%
2160
11th to 20thNight
20%9%47%5%35%45%7%32%
2160
21st to endNight
24%9%46%7%3445%6%27%
2554
November1st to 10thNight
20%10%46%5%3435%6%34%
2407
11th to 20thNight
18%11%36%6%45%5%46%32%
2598
21st to endNight
22%13%5%9%6%34446%24%
2660
December1st to 10thNight
21%16%7%8%7%36%5%5%5%17%
2660
11th to 20thNight
23%15%5%8%5%3443425%
3288
21st to endNight
31%16%5%10%5%2433318%
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
65%7%14%9%5%
2518
11th to 20thDay
62%8%12%11%6%1
2520
21st to endDay
68%8%11%9%41
2832
February1st to 10thDay
63%48%19%31
1710
11th to 20thDay
59%5%11%16%8%1
1719
21st to endDay
62%5%11%13%8%1
1570
March1st to 10thDay
59%49%17%9%1
1800
11th to 20thDay
56%5%10%15%11%2
1932
21st to endDay
51%5%7%17%14%4
2326
April1st to 10thDay
55%47%20%12%3
2160
11th to 20thDay
51%47%20%16%2
2134
21st to endDay
54%5%8%15%13%4
2262
May1st to 10thDay
49%6%8%19%15%3
2520
11th to 20thDay
45%5%10%22%16%2
2482
21st to endDay
46%7%12%21%13%2
2725
June1st to 10thDay
53%8%11%17%11%1
2520
11th to 20thDay
42%7%12%25%12%2
2520
21st to endDay
49%9%12%19%10%1
2520
July1st to 10thDay
38%8%13%27%14%1
2450
11th to 20thDay
39%9%16%28%9%
2445
21st to endDay
40%9%16%25%10%
2591
August1st to 10thDay
42%9%15%25%9%
2492
11th to 20thDay
39%8%18%25%10%1
2244
21st to endDay
41%7%13%28%11%1
2376
September1st to 10thDay
39%8%13%27%13%
2160
11th to 20thDay
37%6%12%32%13%
2129
21st to endDay
43%7%14%27%9%
1971
October1st to 10thDay
50%5%12%22%11%
1800
11th to 20thDay
56%8%14%16%6%
1800
21st to endDay
60%6%11%16%7%1
1801
November1st to 10thDay
51%7%13%21%7%1
1671
11th to 20thDay
56%6%11%17%9%1
1580
21st to endDay
64%8%12%12%5%
1520
December1st to 10thDay
70%6%12%10%2
1520
11th to 20thDay
64%7%11%14%3
1906
21st to endDay
71%48%14%4
2772
January1st to 10thNight
66%7%14%10%4
4429
11th to 20thNight
64%11%12%9%4
4440
21st to endNight
68%6%11%10%5%1
4820
February1st to 10thNight
65%5%9%15%6%1
2470
11th to 20thNight
58%5%9%19%7%
2357
21st to endNight
59%5%8%17%10%1
1884
March1st to 10thNight
61%5%9%14%10%2
2167
11th to 20thNight
55%5%9%18%10%3
2026
21st to endNight
51%5%6%19%15%4
2030
April1st to 10thNight
54%5%8%19%13%2
1800
11th to 20thNight
51%6%8%19%15%2
1775
21st to endNight
51%5%8%16%15%4
1710
May1st to 10thNight
49%7%8%16%16%5%
1440
11th to 20thNight
45%6%7%20%19%3
1416
21st to endNight
39%7%16%20%16%3
1551
June1st to 10thNight
48%8%13%18%11%1
1440
11th to 20thNight
41%6%12%21%17%2
1440
21st to endNight
44%9%14%20%12%
1440
July1st to 10thNight
33%9%13%26%17%1
1400
11th to 20thNight
36%8%14%30%12%
1392
21st to endNight
37%10%15%24%13%1
1486
August1st to 10thNight
38%8%19%23%11%1
1422
11th to 20thNight
40%7%14%26%12%1
1636
21st to endNight
38%8%14%27%12%1
1980
September1st to 10thNight
41%7%10%26%14%1
1800
11th to 20thNight
35%7%13%33%12%1
1830
21st to endNight
42%7%11%28%11%1
1987
October1st to 10thNight
48%7%10%23%11%1
2160
11th to 20thNight
52%7%11%21%8%
2160
21st to endNight
58%6%13%15%8%1
2554
November1st to 10thNight
51%5%14%20%9%1
2407
11th to 20thNight
53%6%12%19%9%2
2598
21st to endNight
62%6%12%15%5%
2660
December1st to 10thNight
69%6%9%13%3
2660
11th to 20thNight
64%6%9%15%6%1
3288
21st to endNight
72%5%8%13%3
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%13%25%23%4
180
11th to 20thDay
27%27%28%13%41
180
21st to endDay
22%17%38%17%5%
214
February1st to 10thDay
31%27%29%11%2
270
11th to 20thDay
24%26%38%11%1
317
21st to endDay
31%19%34%15%2
382
March1st to 10thDay
27%18%30%21%4
420
11th to 20thDay
25%21%34%17%31
420
21st to endDay
31%18%26%17%7%1
462
April1st to 10thDay
29%19%29%17%5%1
420
11th to 20thDay
30%19%24%18%7%2
412
21st to endDay
32%14%28%17%7%1
420
May1st to 10thDay
27%15%31%17%8%2
423
11th to 20thDay
19%17%33%18%11%2
447
21st to endDay
19%15%33%21%12%1
485
June1st to 10thDay
30%10%28%22%8%3
450
11th to 20thDay
16%13%30%28%10%3
450
21st to endDay
24%13%28%20%13%2
450
July1st to 10thDay
14%8%25%33%16%4
445
11th to 20thDay
13%10%30%30%15%3
444
21st to endDay
16%7%32%31%12%2
488
August1st to 10thDay
15%8%24%33%16%4
446
11th to 20thDay
16%6%22%32%17%8%
439
21st to endDay
16%10%28%24%14%8%
495
September1st to 10thDay
14%10%29%23%15%8%
450
11th to 20thDay
14%9%25%24%19%10%
450
21st to endDay
18%12%31%19%14%5%
450
October1st to 10thDay
26%12%25%20%12%5%
450
11th to 20thDay
25%19%29%19%7%2
450
21st to endDay
33%15%26%20%6%
405
November1st to 10thDay
26%19%28%20%7%1
365
11th to 20thDay
25%21%35%13%7%
240
21st to endDay
28%24%27%16%41
180
December1st to 10thDay
31%19%27%18%4
180
11th to 20thDay
31%27%29%12%11
180
21st to endDay
32%28%23%12%41
198
January1st to 10thNight
28%18%31%19%4
760
11th to 20thNight
30%15%28%21%5%1
760
21st to endNight
21%14%33%26%6%
836
February1st to 10thNight
23%17%35%23%3
760
11th to 20thNight
23%17%36%19%4
743
21st to endNight
25%17%29%26%3
628
March1st to 10thNight
25%16%30%23%5%
723
11th to 20thNight
26%15%34%20%4
720
21st to endNight
25%13%29%27%7%
792
April1st to 10thNight
29%12%29%25%4
720
11th to 20thNight
23%15%33%21%7%
711
21st to endNight
27%11%29%24%7%1
630
May1st to 10thNight
28%8%30%26%8%2
360
11th to 20thNight
22%7%33%28%8%1
354
21st to endNight
14%8%38%28%12%
389
June1st to 10thNight
21%7%28%36%8%
360
11th to 20thNight
19%7%28%32%13%1
360
21st to endNight
18%430%32%15%1
360
July1st to 10thNight
11%6%25%41%16%1
350
11th to 20thNight
14%426%37%18%1
348
21st to endNight
11%5%29%42%12%1
394
August1st to 10thNight
14%5%20%44%16%1
358
11th to 20thNight
13%5%19%38%23%2
572
21st to endNight
16%5%26%33%18%2
792
September1st to 10thNight
14%7%27%34%17%1
720
11th to 20thNight
18%6%22%31%19%3
720
21st to endNight
19%8%29%22%19%2
720
October1st to 10thNight
24%7%29%25%13%1
720
11th to 20thNight
25%11%31%24%9%
720
21st to endNight
29%13%29%23%5%
792
November1st to 10thNight
26%15%28%22%8%1
740
11th to 20thNight
24%17%31%19%8%1
760
21st to endNight
28%16%27%21%7%
760
December1st to 10thNight
30%17%29%20%3
760
11th to 20thNight
30%16%32%17%5%1
760
21st to endNight
35%15%28%18%3
836
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