AASO/Ridgemont Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the AASO/Ridgemont Observatory clear sky chart from 2005-11-06 to 2024-11-04.

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
47%
25072
21%
95573
16%
24800
53%
24800
23%
57454

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
30%
944
19%
4333
10%
926
38%
926
16%
2634
January11th to 20thNight
23%
949
20%
4194
8%
930
32%
930
14%
2698
January21st to endNight
27%
1040
14%
4483
8%
1023
36%
1023
15%
3101
February1st to 10thNight
27%
777
19%
2297
10%
777
34%
777
19%
1648
February11th to 20thNight
23%
743
20%
2219
9%
740
32%
740
22%
1481
February21st to endNight
23%
628
17%
1884
7%
628
32%
628
20%
1312
March1st to 10thNight
31%
758
19%
3707
11%
745
38%
745
13%
2493
March11th to 20thNight
31%
686
21%
3633
10%
673
39%
673
16%
1910
March21st to endNight
34%
624
12%
3330
11%
605
40%
605
12%
1949
April1st to 10thNight
39%
570
25%
1900
16%
570
53%
570
31%
1090
April11th to 20thNight
42%
563
25%
1875
20%
563
53%
563
28%
1108
April21st to endNight
38%
570
19%
1900
14%
570
47%
570
25%
1213
May1st to 10thNight
44%
564
16%
2893
12%
559
51%
559
16%
1768
May11th to 20thNight
52%
546
16%
2768
15%
541
55%
541
17%
1619
May21st to endNight
65%
606
18%
2841
17%
593
68%
593
21%
1589
June1st to 10thNight
65%
570
22%
1520
16%
570
68%
570
36%
963
June11th to 20thNight
77%
570
27%
1520
22%
570
79%
570
45%
851
June21st to endNight
76%
570
24%
1520
18%
570
77%
570
44%
858
July1st to 10thNight
73%
544
22%
2337
17%
535
75%
535
24%
1335
July11th to 20thNight
73%
538
21%
2135
20%
533
75%
533
32%
1090
July21st to endNight
72%
610
17%
2719
22%
569
75%
569
20%
1777
August1st to 10thNight
76%
550
28%
2791
24%
544
78%
544
29%
1209
August11th to 20thNight
74%
552
17%
2819
26%
543
77%
543
25%
1394
August21st to endNight
76%
606
23%
2887
29%
605
77%
605
30%
1281
September1st to 10thNight
70%
570
29%
1900
30%
570
73%
570
35%
1043
September11th to 20thNight
70%
666
30%
1996
28%
666
71%
666
36%
1157
September21st to endNight
63%
760
29%
2090
20%
760
67%
760
40%
1214
October1st to 10thNight
64%
760
30%
2128
25%
740
68%
740
40%
1223
October11th to 20thNight
50%
760
28%
2283
20%
740
59%
740
33%
1350
October21st to endNight
41%
836
22%
2852
19%
814
49%
814
24%
1826
November1st to 10thNight
49%
755
30%
2452
26%
755
58%
755
36%
1315
November11th to 20thNight
39%
760
29%
2470
20%
760
52%
760
32%
1422
November21st to endNight
38%
760
26%
2470
19%
760
49%
760
27%
1499
December1st to 10thNight
33%
779
19%
2489
12%
779
42%
779
21%
1662
December11th to 20thNight
35%
949
21%
3156
12%
948
43%
948
22%
2024
December21st to endNight
26%
1039
12%
4782
8%
1026
35%
1026
12%
3348

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%7%26%44445%7%43%
100978
Night
14%7%26%44435%7%46%
98086
TransparencyDay
38%6%11%24%18%3
104651
Night
37%6%10%24%19%4
102554
SeeingDay
14%7%22%26%20%10%
15446
Night
16%6%25%32%18%2
25224

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
15%10%39%44435%5%38%
2527
11th to 20thDay
19%8%35%444345%41%
2635
21st to endDay
24%12%37%5%34345%31%
3135
February1st to 10thDay
18%11%35%44336%6%37%
1881
11th to 20thDay
18%10%37%444345%39%
1848
21st to endDay
19%9%47%5%43446%35%
1570
March1st to 10thDay
21%13%26%45%3345%34%
3120
11th to 20thDay
16%6%35%333246%50%
3309
21st to endDay
12%8%26%5%4445%6%42%
4161
April1st to 10thDay
13%6%26%44435%8%45%
2280
11th to 20thDay
14%8%27%5%34446%41%
2254
21st to endDay
17%7%27%44435%7%40%
2280
May1st to 10thDay
17%7%26%5%45%5%7%9%33%
3978
11th to 20thDay
18%6%36%445%45%8%37%
4081
21st to endDay
12%6%27%5%5%5%46%8%41%
4684
June1st to 10thDay
9%425%45%5%5%8%9%45%
2660
11th to 20thDay
5%315%5%45%5%6%10%50%
2660
21st to endDay
5%5%25%5%5%5%5%7%10%46%
2660
July1st to 10thDay
9%426%5%5%5%5%7%10%41%
4440
11th to 20thDay
6%315%445%47%11%49%
4440
21st to endDay
10%8%49%7%6%5%5%7%8%31%
4683
August1st to 10thDay
5%41434446%9%56%
3785
11th to 20thDay
9%5%26%445%46%10%44%
3729
21st to endDay
5%315%44436%9%56%
4180
September1st to 10thDay
11%5%25%44446%7%48%
2280
11th to 20thDay
11%5%26%44445%6%49%
2164
21st to endDay
13%5%25%434348%51%
2090
October1st to 10thDay
9%415%433346%59%
2062
11th to 20thDay
14%5%25%433236%53%
1900
21st to endDay
20%6%24333345%48%
1995
November1st to 10thDay
10%5%2433435%6%54%
1699
11th to 20thDay
15%7%25%433346%48%
1710
21st to endDay
19%8%25%433345%43%
1710
December1st to 10thDay
18%9%26%33445%6%40%
1687
11th to 20thDay
16%9%37%45%445%5%36%
1918
21st to endDay
21%13%47%5%44335%31%
2783
January1st to 10thNight
19%8%25%34446%6%40%
4428
11th to 20thNight
16%9%47%44435%6%38%
4330
21st to endNight
26%10%45%32335%6%33%
4532
February1st to 10thNight
21%10%37%434345%35%
2297
11th to 20thNight
17%8%37%443345%41%
2218
21st to endNight
18%9%37%5%4434438%
1884
March1st to 10thNight
25%8%36%34434436%
3733
11th to 20thNight
14%7%25%334346%49%
3681
21st to endNight
15%7%37%5%4435%6%42%
3468
April1st to 10thNight
13%5%25%435%36%7%49%
1900
11th to 20thNight
15%6%25%43435%7%47%
1875
21st to endNight
17%7%35%5%4346%7%41%
1900
May1st to 10thNight
19%7%25%333449%40%
2916
11th to 20thNight
15%5%27%5%43347%44%
2812
21st to endNight
9%5%26%445%47%10%43%
2874
June1st to 10thNight
10%436%435%46%8%47%
1520
11th to 20thNight
4225%3435%8%8%55%
1520
21st to endNight
4214445%49%13%51%
1520
July1st to 10thNight
9%5%2445%5%5%6%8%48%
2530
11th to 20thNight
6%415%44335%10%56%
2530
21st to endNight
8%7%38%5%5%5%5%7%9%37%
2874
August1st to 10thNight
431442445%7%62%
3144
11th to 20thNight
5%415%44446%8%54%
3100
21st to endNight
5%31333336%8%62%
3476
September1st to 10thNight
9%5%25%433345%57%
1900
11th to 20thNight
9%6%25%33435%7%53%
1996
21st to endNight
11%5%14334346%55%
2090
October1st to 10thNight
8%424334247%61%
2114
11th to 20thNight
14%414343245%56%
2280
21st to endNight
18%6%26%333345%47%
2600
November1st to 10thNight
12%5%25%333246%56%
2452
11th to 20thNight
14%6%25%343346%51%
2470
21st to endNight
17%6%25%433345%49%
2470
December1st to 10thNight
19%9%26%43435%5%39%
2489
11th to 20thNight
18%9%25%443345%44%
3279
21st to endNight
19%11%38%5%5%4445%32%
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
47%5%8%27%11%2
2528
11th to 20thDay
46%5%9%24%15%2
2635
21st to endDay
56%49%19%10%2
3135
February1st to 10thDay
48%49%24%13%2
1881
11th to 20thDay
48%410%21%13%5%
1858
21st to endDay
50%49%18%13%6%
1570
March1st to 10thDay
53%46%18%12%7%
3120
11th to 20thDay
37%49%27%17%5%
3309
21st to endDay
40%7%12%22%18%1
4161
April1st to 10thDay
37%6%11%26%18%2
2280
11th to 20thDay
42%5%9%22%18%4
2254
21st to endDay
44%6%10%25%14%2
2280
May1st to 10thDay
43%11%14%20%12%1
4014
11th to 20thDay
43%10%10%24%12%1
4085
21st to endDay
38%9%12%19%21%1
4697
June1st to 10thDay
32%9%14%22%21%2
2660
11th to 20thDay
27%8%14%27%22%3
2660
21st to endDay
31%9%16%23%16%5%
2660
July1st to 10thDay
36%7%15%27%12%3
4371
11th to 20thDay
28%8%13%37%13%2
4365
21st to endDay
48%8%13%21%9%1
4535
August1st to 10thDay
24%7%15%30%23%1
3773
11th to 20thDay
35%7%13%26%18%1
3765
21st to endDay
24%6%13%35%20%3
4179
September1st to 10thDay
34%7%10%25%20%4
2280
11th to 20thDay
35%6%9%23%24%2
2164
21st to endDay
34%5%8%24%25%5%
2090
October1st to 10thDay
17%36%18%45%10%
3426
11th to 20thDay
24%36%25%30%13%
3140
21st to endDay
30%36%27%29%5%
3272
November1st to 10thDay
31%5%9%24%25%6%
1699
11th to 20thDay
38%47%22%23%5%
1710
21st to endDay
44%37%25%17%4
1710
December1st to 10thDay
46%411%24%14%2
1687
11th to 20thDay
46%6%9%24%13%2
1915
21st to endDay
54%6%12%17%11%1
2783
January1st to 10thNight
44%5%9%29%12%1
4428
11th to 20thNight
46%6%9%23%13%2
4330
21st to endNight
51%5%9%22%11%1
4532
February1st to 10thNight
53%48%20%14%1
2297
11th to 20thNight
46%47%22%17%3
2219
21st to endNight
49%5%9%16%17%4
1884
March1st to 10thNight
51%5%7%13%18%6%
3733
11th to 20thNight
37%6%11%22%16%8%
3681
21st to endNight
42%6%9%27%15%1
3468
April1st to 10thNight
34%5%11%26%20%4
1900
11th to 20thNight
37%5%10%22%21%7%
1875
21st to endNight
41%6%10%23%18%2
1900
May1st to 10thNight
41%9%15%23%11%1
2945
11th to 20thNight
40%8%12%24%15%1
2813
21st to endNight
32%11%13%26%16%2
2882
June1st to 10thNight
32%8%12%22%22%3
1520
11th to 20thNight
23%8%15%26%23%6%
1520
21st to endNight
22%9%18%26%18%7%
1520
July1st to 10thNight
33%8%14%27%16%3
2490
11th to 20thNight
24%6%14%35%18%4
2482
21st to endNight
42%8%14%24%11%
2783
August1st to 10thNight
20%7%15%36%21%1
3132
11th to 20thNight
26%7%17%28%19%3
3130
21st to endNight
20%5%11%36%25%3
3476
September1st to 10thNight
29%6%9%28%22%5%
1900
11th to 20thNight
31%6%8%27%24%5%
1996
21st to endNight
30%410%25%23%7%
2090
October1st to 10thNight
17%35%14%46%14%
3530
11th to 20thNight
21%35%20%40%13%
3779
21st to endNight
29%36%24%27%11%
4273
November1st to 10thNight
30%39%26%27%6%
2452
11th to 20thNight
35%37%24%23%9%
2470
21st to endNight
39%47%24%23%3
2470
December1st to 10thNight
47%5%10%22%14%2
2489
11th to 20thNight
43%5%9%22%19%2
3281
21st to endNight
52%7%9%17%11%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
25%13%34%22%6%1
270
11th to 20thDay
26%16%35%19%4
270
21st to endDay
19%15%40%21%5%
297
February1st to 10thDay
26%13%36%19%42
270
11th to 20thDay
27%17%38%16%31
270
21st to endDay
29%13%35%17%5%
225
March1st to 10thDay
20%12%42%19%6%1
270
11th to 20thDay
22%17%35%21%41
270
21st to endDay
24%15%32%21%7%1
502
April1st to 10thDay
17%13%33%27%10%1
460
11th to 20thDay
18%14%28%26%12%2
452
21st to endDay
19%10%30%27%9%4
460
May1st to 10thDay
16%13%26%28%12%4
463
11th to 20thDay
19%6%20%27%20%8%
487
21st to endDay
11%322%29%22%13%
646
June1st to 10thDay
10%5%16%27%26%17%
680
11th to 20thDay
7%114%34%30%14%
680
21st to endDay
7%216%35%26%14%
680
July1st to 10thDay
9%111%28%26%25%
671
11th to 20thDay
6%211%27%36%17%
668
21st to endDay
7%212%29%32%19%
733
August1st to 10thDay
10%110%27%31%21%
486
11th to 20thDay
12%212%27%30%16%
479
21st to endDay
10%15%23%37%25%
539
September1st to 10thDay
8%311%25%34%19%
490
11th to 20thDay
11%18%24%35%21%
490
21st to endDay
15%5%18%25%24%13%
490
October1st to 10thDay
10%216%35%29%9%
462
11th to 20thDay
14%8%31%27%14%7%
300
21st to endDay
24%13%26%23%12%2
330
November1st to 10thDay
14%6%29%31%14%6%
279
11th to 20thDay
12%14%29%29%14%2
270
21st to endDay
20%14%26%28%11%2
270
December1st to 10thDay
17%14%33%22%11%3
270
11th to 20thDay
24%13%27%24%12%
270
21st to endDay
27%16%33%21%3
297
January1st to 10thNight
23%11%32%28%6%
950
11th to 20thNight
25%11%37%22%5%
950
21st to endNight
21%8%39%29%2
1045
February1st to 10thNight
25%9%35%27%3
777
11th to 20thNight
21%12%40%25%2
743
21st to endNight
22%14%37%24%2
628
March1st to 10thNight
22%12%30%31%6%
760
11th to 20thNight
21%9%35%28%7%
693
21st to endNight
20%11%29%32%8%
627
April1st to 10thNight
14%8%35%35%8%1
570
11th to 20thNight
16%10%28%32%13%1
563
21st to endNight
17%6%33%31%12%1
570
May1st to 10thNight
17%6%26%35%14%2
570
11th to 20thNight
16%318%38%23%2
561
21st to endNight
7%316%40%29%4
617
June1st to 10thNight
11%313%39%30%4
570
11th to 20thNight
5%10%46%36%2
570
21st to endNight
4112%45%33%5%
570
July1st to 10thNight
7%27%29%45%10%
555
11th to 20thNight
7%39%28%45%9%
552
21st to endNight
7%110%33%41%8%
624
August1st to 10thNight
6%18%33%45%7%
567
11th to 20thNight
9%18%38%39%6%
564
21st to endNight
8%16%27%49%9%
627
September1st to 10thNight
11%110%31%41%6%
570
11th to 20thNight
10%110%32%40%7%
666
21st to endNight
12%217%34%30%5%
760
October1st to 10thNight
8%318%36%29%5%
760
11th to 20thNight
16%5%25%34%18%2
760
21st to endNight
21%8%26%31%13%1
836
November1st to 10thNight
13%6%26%38%15%1
755
11th to 20thNight
15%7%34%31%12%
760
21st to endNight
19%9%29%30%12%1
760
December1st to 10thNight
23%9%28%31%8%1
779
11th to 20thNight
23%6%30%33%7%
950
21st to endNight
27%9%31%28%4
1045
Page generated at 2024-11-01 21:47:38. Version ac07

Copyright © 2024 Attilla Danko.


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