Vestavia Hills Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vestavia Hills Observatory clear sky chart from 2005-11-06 to 2024-02-10.

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
49%
23569
23%
79368
17%
23463
57%
23463
26%
48249

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%
754
22%
4014
10%
737
41%
737
14%
2468
January11th to 20thNight
28%
758
28%
3811
12%
740
41%
740
14%
2188
January21st to endNight
27%
833
19%
4111
12%
814
43%
814
14%
2680
February1st to 10thNight
31%
759
25%
2275
12%
759
43%
759
24%
1489
February11th to 20thNight
26%
703
21%
2098
9%
699
36%
699
23%
1386
February21st to endNight
24%
592
21%
1776
9%
592
36%
592
22%
1198
March1st to 10thNight
35%
720
24%
2160
14%
720
43%
720
28%
1338
March11th to 20thNight
32%
720
19%
2064
9%
720
40%
720
25%
1354
March21st to endNight
34%
698
24%
2084
13%
698
44%
698
27%
1299
April1st to 10thNight
40%
540
25%
1800
18%
540
50%
540
29%
1055
April11th to 20thNight
41%
533
26%
1775
18%
533
53%
533
30%
1009
April21st to endNight
48%
540
28%
1800
21%
540
59%
540
31%
999
May1st to 10thNight
52%
540
25%
1661
18%
540
60%
540
36%
947
May11th to 20thNight
56%
531
19%
1592
13%
531
61%
531
31%
982
May21st to endNight
71%
582
24%
1744
20%
582
74%
582
34%
1029
June1st to 10thNight
68%
540
17%
1620
16%
540
68%
540
27%
1038
June11th to 20thNight
77%
540
19%
1620
15%
540
79%
540
43%
868
June21st to endNight
73%
540
19%
1620
16%
540
74%
540
33%
980
July1st to 10thNight
74%
525
13%
1575
12%
525
75%
525
27%
1039
July11th to 20thNight
74%
522
15%
1566
15%
522
75%
522
30%
999
July21st to endNight
76%
591
16%
1728
16%
558
77%
558
29%
1094
August1st to 10thNight
79%
537
15%
1778
18%
534
79%
534
32%
1039
August11th to 20thNight
72%
534
16%
1776
18%
534
72%
534
26%
1139
August21st to endNight
68%
594
21%
1980
26%
594
69%
594
24%
1273
September1st to 10thNight
67%
564
23%
1824
25%
564
68%
564
29%
1108
September11th to 20thNight
64%
720
23%
1980
20%
720
65%
720
31%
1261
September21st to endNight
67%
720
30%
1980
23%
720
72%
720
41%
1145
October1st to 10thNight
62%
720
33%
1980
25%
720
67%
720
44%
1103
October11th to 20thNight
53%
720
35%
1980
24%
720
63%
720
39%
1166
October21st to endNight
50%
792
30%
2483
26%
792
57%
792
33%
1426
November1st to 10thNight
55%
740
28%
2406
25%
740
63%
740
36%
1305
November11th to 20thNight
46%
760
30%
2470
22%
760
58%
760
34%
1369
November21st to endNight
41%
760
26%
2470
18%
760
52%
760
28%
1470
December1st to 10thNight
34%
760
23%
2470
15%
760
45%
760
22%
1576
December11th to 20thNight
34%
759
24%
2902
16%
758
43%
758
21%
1740
December21st to endNight
29%
828
15%
4395
14%
817
40%
817
12%
2690

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
13%6%35%5%35%5%6%8%42%
78783
Night
13%6%25%5%3445%7%45%
80189
TransparencyDay
40%7%11%19%18%5%
78510
Night
37%6%10%20%20%7%
79981
SeeingDay
15%9%23%24%19%9%
13504
Night
14%7%23%30%21%4
23591

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
16%12%47%5%335%5%437%
2836
11th to 20thDay
15%6%36%423345%49%
2977
21st to endDay
24%9%24323336%41%
3476
February1st to 10thDay
19%10%36%434446%39%
1890
11th to 20thDay
23%7%25%424445%39%
1748
21st to endDay
20%8%37%6%24445%36%
1480
March1st to 10thDay
15%7%36%5%23346%46%
1800
11th to 20thDay
16%9%46%5%26%45%7%36%
1894
21st to endDay
14%6%36%5%345%5%8%40%
2286
April1st to 10thDay
11%5%35%4245%5%7%47%
2160
11th to 20thDay
13%5%25%6%3445%7%46%
2134
21st to endDay
9%425%5%4445%9%50%
2160
May1st to 10thDay
11%5%245%345%5%8%48%
2296
11th to 20thDay
10%5%25%6%35%5%6%10%44%
2301
21st to endDay
9%435%6%45%5%5%9%44%
2531
June1st to 10thDay
10%7%36%5%5%6%6%8%11%33%
2340
11th to 20thDay
6%3245%37%6%8%12%44%
2340
21st to endDay
7%5%25%6%46%6%7%12%39%
2340
July1st to 10thDay
9%437%7%5%8%7%9%11%31%
2340
11th to 20thDay
8%5%26%7%5%7%9%9%11%31%
2340
21st to endDay
6%436%7%5%8%9%9%12%31%
2483
August1st to 10thDay
7%325%7%48%9%9%13%32%
2148
11th to 20thDay
10%6%36%7%5%7%6%8%10%31%
2125
21st to endDay
12%6%36%7%46%7%8%9%32%
2376
September1st to 10thDay
11%426%6%36%7%6%8%41%
2116
11th to 20thDay
13%7%25%5%35%5%48%42%
1980
21st to endDay
10%5%245%3445%6%51%
1980
October1st to 10thDay
9%425%436%346%54%
1980
11th to 20thDay
10%425%42345%7%54%
1980
21st to endDay
13%5%24423436%54%
1867
November1st to 10thDay
12%6%25%423335%54%
1672
11th to 20thDay
14%5%23334346%53%
1710
21st to endDay
14%6%35%5%2445%7%45%
1710
December1st to 10thDay
21%7%35%5%3335%6%38%
1710
11th to 20thDay
18%7%35%6%3433443%
2153
21st to endDay
18%10%46%5%3435%7%35%
3124
January1st to 10thNight
17%13%34434445%41%
4109
11th to 20thNight
16%8%45%433445%45%
3978
21st to endNight
22%12%35%42333340%
4180
February1st to 10thNight
17%8%26%5%34347%42%
2275
11th to 20thNight
20%7%36%433245%44%
2098
21st to endNight
20%6%25%5%245%6%7%38%
1776
March1st to 10thNight
15%7%2442345%6%46%
2160
11th to 20thNight
15%5%35%435%5%6%7%41%
2064
21st to endNight
14%5%26%5%3445%7%45%
2084
April1st to 10thNight
11%426%5%245%6%8%47%
1800
11th to 20thNight
14%6%2442435%6%51%
1775
21st to endNight
10%4245%3445%6%53%
1800
May1st to 10thNight
8%425%425%45%9%51%
1661
11th to 20thNight
8%5%25%5%35%6%6%10%45%
1592
21st to endNight
6%424445%6%7%10%48%
1744
June1st to 10thNight
46%35%6%47%6%8%12%38%
1620
11th to 20thNight
4313335%5%9%11%53%
1620
21st to endNight
6%4246%45%6%8%11%44%
1620
July1st to 10thNight
6%426%6%37%8%9%10%38%
1620
11th to 20thNight
5%426%6%45%7%7%12%41%
1620
21st to endNight
5%426%6%47%7%8%11%41%
1830
August1st to 10thNight
5%325%5%35%7%9%14%42%
1790
11th to 20thNight
7%5%26%5%45%7%8%10%40%
1776
21st to endNight
9%6%26%6%46%5%7%8%40%
1980
September1st to 10thNight
8%437%6%45%5%6%9%43%
1824
11th to 20thNight
10%5%25%6%35%5%5%8%46%
1980
21st to endNight
6%5%25%5%3445%7%55%
1980
October1st to 10thNight
7%5%23432445%61%
1980
11th to 20thNight
11%424334446%55%
1980
21st to endNight
14%6%15%42334455%
2483
November1st to 10thNight
11%424324345%58%
2406
11th to 20thNight
12%6%2442435%5%54%
2470
21st to endNight
13%6%25%5%35%5%5%6%47%
2470
December1st to 10thNight
18%7%35%5%34446%41%
2470
11th to 20thNight
17%8%25%423345%47%
3042
21st to endNight
18%8%36%5%345%6%7%34%
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
49%37%14%23%5%
2837
11th to 20thDay
39%47%25%21%4
2977
21st to endDay
46%37%18%19%8%
3476
February1st to 10thDay
48%37%20%18%4
1890
11th to 20thDay
49%4418%19%7%
1758
21st to endDay
50%5%6%11%21%7%
1480
March1st to 10thDay
41%48%16%21%10%
1800
11th to 20thDay
47%6%10%15%17%5%
1894
21st to endDay
42%6%9%20%20%3
2286
April1st to 10thDay
35%7%10%21%19%8%
2160
11th to 20thDay
38%5%7%19%23%7%
2134
21st to endDay
31%6%9%26%25%3
2160
May1st to 10thDay
33%7%11%23%23%4
2296
11th to 20thDay
36%7%15%24%15%3
2305
21st to endDay
37%8%12%24%18%3
2531
June1st to 10thDay
42%9%15%19%14%1
2340
11th to 20thDay
30%10%18%25%15%2
2340
21st to endDay
35%10%17%23%11%4
2340
July1st to 10thDay
40%13%19%18%8%1
2275
11th to 20thDay
40%15%19%16%8%1
2271
21st to endDay
40%14%19%19%8%1
2344
August1st to 10thDay
37%14%20%23%7%1
2136
11th to 20thDay
44%10%17%16%9%3
2125
21st to endDay
44%11%15%17%10%4
2376
September1st to 10thDay
38%10%13%17%17%5%
2116
11th to 20thDay
39%8%10%19%19%4
1980
21st to endDay
34%6%8%22%23%7%
1980
October1st to 10thDay
32%5%10%19%25%10%
1980
11th to 20thDay
30%47%23%28%8%
1980
21st to endDay
33%36%16%31%10%
1867
November1st to 10thDay
34%36%17%28%12%
1672
11th to 20thDay
34%36%19%26%11%
1710
21st to endDay
39%5%8%17%24%8%
1710
December1st to 10thDay
47%5%7%16%19%6%
1710
11th to 20thDay
47%36%16%23%5%
2150
21st to endDay
49%38%19%19%2
3124
January1st to 10thNight
46%45%15%25%4
4109
11th to 20thNight
43%35%22%19%8%
3978
21st to endNight
51%3315%23%5%
4180
February1st to 10thNight
45%36%18%21%8%
2275
11th to 20thNight
45%45%18%19%9%
2099
21st to endNight
45%6%8%14%19%9%
1776
March1st to 10thNight
38%47%16%22%12%
2160
11th to 20thNight
41%6%11%16%19%6%
2064
21st to endNight
38%5%9%24%19%5%
2084
April1st to 10thNight
34%6%11%21%20%8%
1800
11th to 20thNight
34%47%21%22%11%
1775
21st to endNight
31%6%9%25%23%6%
1800
May1st to 10thNight
29%6%11%24%25%5%
1661
11th to 20thNight
33%9%18%20%17%3
1593
21st to endNight
29%10%12%27%18%4
1745
June1st to 10thNight
36%11%14%21%17%1
1620
11th to 20thNight
22%8%22%29%15%3
1620
21st to endNight
30%10%17%22%17%4
1620
July1st to 10thNight
35%13%20%20%10%3
1575
11th to 20thNight
31%13%24%21%9%2
1566
21st to endNight
32%13%23%22%9%1
1728
August1st to 10thNight
28%12%23%29%8%1
1778
11th to 20thNight
35%12%20%16%12%4
1776
21st to endNight
39%9%15%20%12%5%
1980
September1st to 10thNight
35%7%16%18%17%5%
1824
11th to 20thNight
35%8%11%19%21%6%
1980
21st to endNight
29%5%10%24%24%8%
1980
October1st to 10thNight
26%5%9%22%25%13%
1980
11th to 20thNight
31%5%7%21%25%12%
1980
21st to endNight
35%36%15%30%13%
2483
November1st to 10thNight
29%47%18%26%14%
2406
11th to 20thNight
33%36%18%27%13%
2470
21st to endNight
37%5%7%18%24%9%
2470
December1st to 10thNight
43%5%9%17%20%5%
2470
11th to 20thNight
41%37%14%29%6%
3044
21st to endNight
47%48%19%19%3
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%24%29%19%4
270
11th to 20thDay
26%20%31%15%7%
270
21st to endDay
25%25%37%11%21
297
February1st to 10thDay
26%22%36%13%2
267
11th to 20thDay
40%16%30%13%
240
21st to endDay
28%21%40%11%1
198
March1st to 10thDay
24%21%33%18%31
240
11th to 20thDay
21%17%38%16%7%1
334
21st to endDay
22%17%32%21%9%
462
April1st to 10thDay
19%12%33%24%11%1
420
11th to 20thDay
17%14%31%22%14%1
412
21st to endDay
12%10%32%30%13%2
420
May1st to 10thDay
13%9%26%30%15%5%
423
11th to 20thDay
9%427%28%23%9%
447
21st to endDay
12%318%30%20%16%
485
June1st to 10thDay
13%315%30%25%13%
450
11th to 20thDay
6%412%26%29%22%
450
21st to endDay
9%5%9%27%30%20%
450
July1st to 10thDay
7%28%26%34%23%
445
11th to 20thDay
7%28%21%32%30%
444
21st to endDay
7%29%21%35%26%
488
August1st to 10thDay
7%29%24%33%24%
446
11th to 20thDay
10%27%28%36%18%
439
21st to endDay
15%29%24%31%19%
495
September1st to 10thDay
9%49%33%32%14%
450
11th to 20thDay
12%413%27%34%10%
450
21st to endDay
11%316%31%31%8%
450
October1st to 10thDay
11%6%25%29%24%6%
450
11th to 20thDay
13%6%26%32%20%2
450
21st to endDay
19%13%25%28%13%2
315
November1st to 10thDay
17%10%33%26%10%3
270
11th to 20thDay
18%13%41%21%6%
270
21st to endDay
15%17%38%20%9%1
270
December1st to 10thDay
29%16%30%22%3
270
11th to 20thDay
24%16%38%17%41
270
21st to endDay
27%20%31%18%4
297
January1st to 10thNight
20%15%35%24%5%1
760
11th to 20thNight
22%17%29%25%7%
760
21st to endNight
20%14%36%26%4
836
February1st to 10thNight
22%11%33%30%4
759
11th to 20thNight
24%13%34%25%4
703
21st to endNight
22%14%36%25%2
592
March1st to 10thNight
18%12%32%32%6%
720
11th to 20thNight
17%11%37%25%10%1
720
21st to endNight
17%12%33%28%9%
698
April1st to 10thNight
13%10%34%29%13%
540
11th to 20thNight
15%9%32%29%14%2
533
21st to endNight
11%10%26%34%17%2
540
May1st to 10thNight
9%6%28%32%21%3
540
11th to 20thNight
10%324%32%26%5%
531
21st to endNight
7%212%36%37%7%
584
June1st to 10thNight
8%29%39%35%6%
540
11th to 20thNight
5%19%28%43%14%
540
21st to endNight
5%19%29%44%12%
540
July1st to 10thNight
6%16%28%45%14%
525
11th to 20thNight
6%15%22%44%21%
522
21st to endNight
6%17%25%47%14%
591
August1st to 10thNight
6%1425%50%15%
537
11th to 20thNight
9%17%30%44%10%
534
21st to endNight
10%27%28%41%11%
594
September1st to 10thNight
10%29%32%38%9%
564
11th to 20thNight
12%312%29%39%6%
720
21st to endNight
8%114%33%40%4
720
October1st to 10thNight
9%321%34%27%6%
720
11th to 20thNight
11%6%24%34%21%3
720
21st to endNight
16%7%21%34%19%2
792
November1st to 10thNight
13%6%19%39%19%3
740
11th to 20thNight
14%8%29%34%13%1
760
21st to endNight
16%9%30%32%12%1
760
December1st to 10thNight
21%11%27%31%8%1
760
11th to 20thNight
24%9%29%29%9%
760
21st to endNight
25%11%30%27%7%
836
Page generated at 2024-02-07 05:11:54. Version ac07

Copyright 2024 Attilla Danko


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