UBarU Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the UBarU Observatory clear sky chart from 2005-11-06 to 2024-12-24.

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
44%
24859
25%
96238
17%
24559
55%
24559
28%
52050

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
34%
945
34%
3969
13%
926
46%
926
26%
2073
January11th to 20thNight
30%
943
38%
3854
10%
926
42%
926
30%
1660
January21st to endNight
32%
830
22%
4091
14%
814
49%
814
18%
2282
February1st to 10thNight
30%
760
29%
2280
11%
760
44%
760
29%
1341
February11th to 20thNight
28%
744
24%
2218
10%
740
39%
740
27%
1313
February21st to endNight
17%
628
26%
1884
5%
628
35%
628
28%
1120
March1st to 10thNight
25%
672
30%
3544
10%
659
41%
659
17%
1880
March11th to 20thNight
28%
567
22%
3454
14%
550
42%
550
13%
2157
March21st to endNight
22%
625
18%
3673
12%
605
42%
605
17%
1942
April1st to 10thNight
23%
570
27%
2090
11%
570
44%
570
27%
1158
April11th to 20thNight
21%
563
24%
1924
11%
563
40%
563
25%
1150
April21st to endNight
24%
570
28%
1838
13%
570
45%
570
29%
1086
May1st to 10thNight
25%
570
24%
2816
14%
559
41%
559
16%
1794
May11th to 20thNight
35%
558
17%
2732
15%
541
47%
541
21%
1410
May21st to endNight
36%
613
14%
3067
12%
593
51%
593
21%
1587
June1st to 10thNight
62%
570
24%
1710
22%
570
71%
570
50%
855
June11th to 20thNight
51%
570
24%
1710
18%
570
62%
570
47%
867
June21st to endNight
64%
570
24%
1710
24%
570
69%
570
41%
940
July1st to 10thNight
67%
541
23%
2593
18%
535
70%
535
27%
1210
July11th to 20thNight
77%
542
22%
2486
30%
533
83%
533
35%
1157
July21st to endNight
78%
611
18%
2843
28%
569
84%
569
26%
1620
August1st to 10thNight
84%
549
38%
2670
34%
544
87%
544
48%
938
August11th to 20thNight
75%
546
19%
2796
29%
544
78%
544
34%
1097
August21st to endNight
76%
611
15%
3198
23%
605
78%
605
24%
1634
September1st to 10thNight
69%
570
22%
2090
25%
570
72%
570
33%
1155
September11th to 20thNight
69%
570
21%
2090
24%
570
71%
570
28%
1198
September21st to endNight
68%
570
27%
2090
29%
570
71%
570
35%
1107
October1st to 10thNight
70%
570
33%
2056
34%
550
74%
550
40%
1006
October11th to 20thNight
53%
598
29%
2366
25%
578
62%
578
28%
1322
October21st to endNight
46%
836
28%
2836
18%
814
55%
814
30%
1726
November1st to 10thNight
48%
820
29%
2380
16%
820
56%
820
37%
1372
November11th to 20thNight
46%
1000
27%
2600
12%
1000
53%
1000
42%
1499
November21st to endNight
37%
1000
30%
2600
12%
1000
47%
1000
33%
1620
December1st to 10thNight
41%
1000
31%
2600
15%
1000
49%
1000
36%
1593
December11th to 20thNight
33%
1000
26%
3031
11%
999
42%
999
26%
1908
December21st to endNight
37%
1057
19%
4349
12%
1044
46%
1044
26%
2273

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
10%6%25%44435%7%50%
101425
Night
10%6%25%33335%7%54%
98817
TransparencyDay
33%410%22%21%11%
105295
Night
31%410%21%21%13%
103074
SeeingDay
13%8%25%31%19%4
14972
Night
13%8%29%35%13%1
24983

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
10%8%35%222345%56%
2847
11th to 20thDay
11%8%1422325%458%
2882
21st to endDay
13%7%25%333247%50%
3487
February1st to 10thDay
14%7%25%333346%50%
1900
11th to 20thDay
13%7%25%43435%6%48%
1849
21st to endDay
13%7%2433335%5%54%
1570
March1st to 10thDay
14%8%26%443246%47%
3275
11th to 20thDay
17%10%37%444346%37%
3480
21st to endDay
10%6%25%44446%6%49%
3814
April1st to 10thDay
12%7%26%44436%7%47%
2090
11th to 20thDay
15%6%26%443346%47%
2202
21st to endDay
12%7%36%5%33345%50%
2340
May1st to 10thDay
17%8%27%5%4435%6%38%
4082
11th to 20thDay
14%7%26%44445%5%45%
4082
21st to endDay
11%6%26%5%5%5%46%8%42%
4477
June1st to 10thDay
5%5%25%45%5%46%9%51%
2470
11th to 20thDay
5%5%25%45%446%9%50%
2470
21st to endDay
7%5%16%6%5%6%5%6%10%43%
2470
July1st to 10thDay
7%425%5%5%5%46%8%47%
4120
11th to 20thDay
4414445%47%9%55%
4120
21st to endDay
8%5%15%5%5%5%5%8%9%44%
4465
August1st to 10thDay
121333335%8%68%
3859
11th to 20thDay
421334336%9%61%
3726
21st to endDay
4425%5%5%5%46%10%50%
4130
September1st to 10thDay
10%6%28%5%6%5%347%44%
2090
11th to 20thDay
9%7%27%45%6%46%7%41%
2090
21st to endDay
10%426%44446%7%49%
2090
October1st to 10thDay
6%4245%3445%7%56%
2090
11th to 20thDay
12%5%25%443245%55%
2042
21st to endDay
12%5%25%333235%59%
2090
November1st to 10thDay
14%7%25%43435%6%49%
1913
11th to 20thDay
9%6%15%43425%7%54%
1800
21st to endDay
14%7%35%333246%51%
1800
December1st to 10thDay
14%8%25%33235%6%50%
1800
11th to 20thDay
12%7%26%344346%48%
2251
21st to endDay
12%6%2433323458%
3162
January1st to 10thNight
13%6%36%222235%56%
4108
11th to 20thNight
11%5%2322122467%
4116
21st to endNight
16%7%26%333246%47%
4180
February1st to 10thNight
13%7%25%333245%53%
2280
11th to 20thNight
14%6%25%333346%51%
2218
21st to endNight
14%7%25%33335%6%50%
1884
March1st to 10thNight
10%9%26%34445%6%47%
3584
11th to 20thNight
16%12%26%444445%38%
3480
21st to endNight
11%9%26%433346%50%
3817
April1st to 10thNight
9%6%25%44435%6%51%
2090
11th to 20thNight
14%7%26%434345%48%
1924
21st to endNight
14%7%24333246%51%
1838
May1st to 10thNight
21%11%25%333346%39%
2823
11th to 20thNight
9%7%25%43335%7%50%
2823
21st to endNight
12%7%25%33445%8%48%
3090
June1st to 10thNight
331322447%10%60%
1710
11th to 20thNight
441433336%8%61%
1710
21st to endNight
7%5%1434445%10%54%
1710
July1st to 10thNight
442444446%10%55%
2850
11th to 20thNight
331433436%9%62%
2850
21st to endNight
8%7%26%44446%9%46%
3098
August1st to 10thNight
1212222248%73%
3076
11th to 20thNight
321333337%10%62%
3113
21st to endNight
45%1434447%10%53%
3535
September1st to 10thNight
8%6%26%33436%7%52%
2090
11th to 20thNight
9%6%26%445%35%7%48%
2090
21st to endNight
7%6%15%44435%7%54%
2090
October1st to 10thNight
5%42423335%7%63%
2090
11th to 20thNight
12%415%33325%5%58%
2118
21st to endNight
13%5%2432223362%
2508
November1st to 10thNight
13%6%25%332246%55%
2380
11th to 20thNight
9%6%24333346%59%
2600
21st to endNight
15%7%24333345%52%
2600
December1st to 10thNight
14%6%25%433246%52%
2600
11th to 20thNight
13%9%35%433335%49%
3166
21st to endNight
15%6%24222235%57%
4578

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
31%3316%25%22%
2848
11th to 20thDay
31%25%14%31%16%
2882
21st to endDay
36%35%14%29%13%
3487
February1st to 10thDay
37%38%13%22%18%
1900
11th to 20thDay
38%36%18%19%16%
1859
21st to endDay
33%37%16%23%18%
1570
March1st to 10thDay
39%46%14%21%17%
3275
11th to 20thDay
50%47%12%17%10%
3480
21st to endDay
34%48%17%19%16%
3814
April1st to 10thDay
37%48%18%19%14%
2090
11th to 20thDay
39%47%17%20%12%
2202
21st to endDay
38%27%21%20%12%
2340
May1st to 10thDay
47%410%14%17%8%
4120
11th to 20thDay
40%5%7%19%21%9%
4086
21st to endDay
38%5%12%28%12%4
4489
June1st to 10thDay
30%5%12%29%21%3
2470
11th to 20thDay
31%5%12%27%20%6%
2470
21st to endDay
36%7%12%23%18%5%
2470
July1st to 10thDay
32%7%17%37%8%
4056
11th to 20thDay
24%6%14%35%17%3
4051
21st to endDay
32%8%17%30%13%1
4325
August1st to 10thDay
14%5%11%40%30%1
3845
11th to 20thDay
20%422%38%13%2
3762
21st to endDay
29%8%17%26%19%2
4129
September1st to 10thDay
40%5%10%20%17%8%
2090
11th to 20thDay
39%6%10%20%19%6%
2090
21st to endDay
34%410%21%19%13%
2090
October1st to 10thDay
17%26%13%26%35%
3480
11th to 20thDay
27%35%19%24%22%
3373
21st to endDay
26%3417%37%13%
3428
November1st to 10thDay
38%38%20%20%12%
1913
11th to 20thDay
32%37%18%22%19%
1800
21st to endDay
38%35%17%22%15%
1800
December1st to 10thDay
37%28%20%24%10%
1800
11th to 20thDay
37%48%12%23%16%
2249
21st to endDay
32%2416%28%18%
3162
January1st to 10thNight
33%2313%26%22%
4108
11th to 20thNight
25%1318%26%26%
4116
21st to endNight
40%3412%27%14%
4180
February1st to 10thNight
36%37%12%22%20%
2280
11th to 20thNight
36%35%17%21%17%
2218
21st to endNight
37%36%13%22%19%
1884
March1st to 10thNight
38%47%14%23%14%
3584
11th to 20thNight
49%48%12%16%12%
3480
21st to endNight
37%39%17%17%16%
3817
April1st to 10thNight
34%410%18%16%17%
2090
11th to 20thNight
39%48%15%18%17%
1924
21st to endNight
38%29%20%20%11%
1838
May1st to 10thNight
48%48%18%13%10%
2850
11th to 20thNight
33%5%11%23%18%10%
2824
21st to endNight
35%5%14%29%11%6%
3099
June1st to 10thNight
19%5%19%34%20%3
1710
11th to 20thNight
22%416%29%23%5%
1710
21st to endNight
27%5%17%28%19%4
1710
July1st to 10thNight
24%7%23%39%6%1
2805
11th to 20thNight
20%7%18%36%18%2
2796
21st to endNight
32%7%21%29%10%1
2999
August1st to 10thNight
12%414%46%24%1
3066
11th to 20thNight
17%5%28%37%11%2
3143
21st to endNight
25%10%20%25%18%2
3535
September1st to 10thNight
32%5%14%23%19%9%
2090
11th to 20thNight
35%6%15%22%16%6%
2090
21st to endNight
30%412%21%19%13%
2090
October1st to 10thNight
15%28%15%23%37%
3480
11th to 20thNight
24%38%16%30%19%
3513
21st to endNight
25%3420%34%15%
4120
November1st to 10thNight
33%28%20%22%15%
2380
11th to 20thNight
28%37%22%21%18%
2600
21st to endNight
37%27%17%21%16%
2600
December1st to 10thNight
35%28%19%23%13%
2600
11th to 20thNight
40%25%14%19%20%
3167
21st to endNight
33%2415%29%17%
4578

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
19%16%40%19%41
270
11th to 20thDay
24%14%34%21%6%
270
21st to endDay
19%14%40%22%5%
297
February1st to 10thDay
25%14%35%20%6%
270
11th to 20thDay
25%16%38%17%31
270
21st to endDay
21%19%41%17%2
225
March1st to 10thDay
20%19%43%16%2
270
11th to 20thDay
20%21%37%17%6%
270
21st to endDay
17%19%44%16%31
297
April1st to 10thDay
20%20%41%17%3
270
11th to 20thDay
19%20%39%16%5%1
400
21st to endDay
17%15%44%18%5%
520
May1st to 10thDay
16%11%42%26%5%
653
11th to 20thDay
20%7%34%28%9%1
675
21st to endDay
16%7%32%34%10%
734
June1st to 10thDay
6%422%44%21%4
680
11th to 20thDay
7%322%48%18%3
680
21st to endDay
7%316%42%28%5%
680
July1st to 10thDay
10%48%40%31%8%
671
11th to 20thDay
326%44%38%7%
668
21st to endDay
425%42%37%10%
739
August1st to 10thDay
2441%42%11%
535
11th to 20thDay
9%1438%38%11%
477
21st to endDay
6%25%35%39%14%
515
September1st to 10thDay
9%18%34%34%14%
300
11th to 20thDay
7%1434%43%11%
300
21st to endDay
11%15%38%37%9%
300
October1st to 10thDay
7%215%39%30%7%
300
11th to 20thDay
11%326%40%16%3
300
21st to endDay
18%12%29%27%12%2
330
November1st to 10thDay
22%5%33%30%8%3
300
11th to 20thDay
21%9%32%22%10%5%
300
21st to endDay
23%20%30%19%7%2
300
December1st to 10thDay
19%10%34%28%8%2
300
11th to 20thDay
18%15%38%20%8%1
300
21st to endDay
18%13%36%25%8%
306
January1st to 10thNight
16%11%35%30%8%
950
11th to 20thNight
17%11%36%30%5%
946
21st to endNight
18%11%34%31%6%
836
February1st to 10thNight
20%13%33%28%6%
760
11th to 20thNight
19%14%37%26%4
744
21st to endNight
18%14%48%19%1
628
March1st to 10thNight
18%13%39%26%3
675
11th to 20thNight
18%11%38%29%4
570
21st to endNight
14%14%48%21%3
627
April1st to 10thNight
10%15%49%24%3
570
11th to 20thNight
16%17%44%21%3
563
21st to endNight
17%11%45%23%41
570
May1st to 10thNight
15%12%45%24%4
570
11th to 20thNight
14%6%39%33%7%
561
21st to endNight
13%6%39%32%9%1
617
June1st to 10thNight
4228%48%16%1
570
11th to 20thNight
5%337%46%9%
570
21st to endNight
7%319%49%20%2
570
July1st to 10thNight
8%312%48%27%2
555
11th to 20thNight
3111%55%27%2
552
21st to endNight
5%18%56%26%3
624
August1st to 10thNight
218%54%32%2
567
11th to 20thNight
5%18%51%32%3
564
21st to endNight
5%37%44%37%4
627
September1st to 10thNight
10%310%41%33%3
570
11th to 20thNight
12%26%42%36%2
570
21st to endNight
10%211%44%31%2
570
October1st to 10thNight
6%215%47%28%2
570
11th to 20thNight
13%425%41%16%2
598
21st to endNight
16%8%27%29%18%2
836
November1st to 10thNight
15%6%26%38%14%1
820
11th to 20thNight
12%7%31%35%13%2
1000
21st to endNight
19%10%30%30%11%1
1000
December1st to 10thNight
17%8%30%36%9%1
1000
11th to 20thNight
20%10%32%31%7%
1000
21st to endNight
16%11%32%34%7%
1063
Page generated at 2024-12-21 03:13:52. Version ac07

Copyright © 2024 Attilla Danko.


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