Casa Victoria Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Casa Victoria Observatory clear sky chart from 2005-11-06 to 2024-03-18.

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
57%
24443
30%
79913
21%
24344
67%
24344
43%
39921

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
56%
808
30%
4121
25%
791
69%
791
31%
1933
January11th to 20thNight
55%
757
40%
3952
27%
740
68%
740
38%
1475
January21st to endNight
53%
825
23%
4277
24%
814
67%
814
29%
2039
February1st to 10thNight
49%
760
32%
2440
21%
760
63%
760
46%
1184
February11th to 20thNight
44%
743
30%
2218
18%
740
56%
740
44%
1154
February21st to endNight
39%
628
37%
1884
17%
628
59%
628
49%
927
March1st to 10thNight
43%
760
35%
2186
18%
760
58%
760
50%
1116
March11th to 20thNight
46%
752
32%
2068
18%
752
55%
752
43%
1144
March21st to endNight
46%
716
33%
2102
16%
716
62%
716
45%
1093
April1st to 10thNight
40%
540
35%
1800
18%
540
61%
540
47%
811
April11th to 20thNight
42%
533
32%
1777
20%
533
60%
533
42%
850
April21st to endNight
40%
540
34%
1800
18%
540
65%
540
46%
825
May1st to 10thNight
47%
540
31%
1800
23%
540
62%
540
47%
838
May11th to 20thNight
51%
531
23%
1675
18%
531
59%
531
36%
924
May21st to endNight
52%
584
33%
1552
17%
582
66%
582
55%
780
June1st to 10thNight
59%
540
26%
1440
17%
540
66%
540
48%
780
June11th to 20thNight
63%
540
32%
1440
22%
540
70%
540
59%
706
June21st to endNight
67%
540
24%
1440
18%
540
70%
540
42%
823
July1st to 10thNight
72%
525
19%
1417
17%
525
73%
525
34%
892
July11th to 20thNight
74%
522
17%
1566
14%
522
76%
522
34%
916
July21st to endNight
71%
591
14%
1674
14%
558
71%
558
27%
1060
August1st to 10thNight
76%
537
15%
1663
15%
534
77%
534
30%
1000
August11th to 20thNight
72%
534
18%
1778
18%
534
74%
534
28%
1060
August21st to endNight
77%
594
24%
1980
27%
594
79%
594
37%
1090
September1st to 10thNight
73%
540
27%
1800
27%
540
77%
540
36%
970
September11th to 20thNight
72%
540
34%
1800
33%
540
77%
540
40%
922
September21st to endNight
66%
574
33%
1996
28%
574
73%
574
47%
905
October1st to 10thNight
62%
720
31%
2160
23%
720
67%
720
43%
1154
October11th to 20thNight
63%
720
41%
2160
25%
720
75%
720
64%
938
October21st to endNight
62%
792
40%
2376
23%
792
73%
792
58%
1071
November1st to 10thNight
65%
780
42%
2260
25%
780
76%
780
66%
977
November11th to 20thNight
64%
950
39%
2470
23%
950
72%
950
66%
1175
November21st to endNight
56%
950
36%
2470
21%
950
64%
950
51%
1351
December1st to 10thNight
51%
950
35%
2612
19%
950
63%
950
51%
1333
December11th to 20thNight
52%
949
31%
3112
21%
948
60%
948
42%
1615
December21st to endNight
45%
1038
21%
4647
17%
1026
56%
1026
33%
2090

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
33134245%6%8%61%
78872
Night
342442445%8%60%
80972
TransparencyDay
20%6%11%22%27%15%
78594
Night
22%5%11%22%27%14%
80772
SeeingDay
6%9%26%31%21%7%
14182
Night
6%5%28%43%18%1
24473

By Month

Percentage Cloud Cover SW (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%343245%5%7%60%
2793
11th to 20thDay
341221345%6%69%
2860
21st to endDay
35%245%245%7%9%54%
3146
February1st to 10thDay
25%245%2335%7%62%
1738
11th to 20thDay
342342336%8%61%
1849
21st to endDay
35%23322348%64%
1570
March1st to 10thDay
33132245%7%8%61%
1990
11th to 20thDay
37%3442335%7%59%
2058
21st to endDay
34233245%5%8%61%
2253
April1st to 10thDay
221332346%8%67%
2160
11th to 20thDay
341443445%6%63%
2131
21st to endDay
3312423448%66%
2160
May1st to 10thDay
22133235%5%8%67%
2160
11th to 20thDay
34234345%6%8%60%
2212
21st to endDay
22123235%48%68%
2724
June1st to 10thDay
11123245%7%11%65%
2520
11th to 20thDay
2112213446%73%
2520
21st to endDay
43134246%5%8%60%
2520
July1st to 10thDay
34146%46%8%8%11%47%
2498
11th to 20thDay
2323446%7%9%13%49%
2340
21st to endDay
3325%5%48%8%10%12%39%
2545
August1st to 10thDay
33245%45%7%8%12%47%
2265
11th to 20thDay
33145%36%8%8%10%50%
2123
21st to endDay
3214446%6%8%11%51%
2376
September1st to 10thDay
6%3134345%7%9%54%
2160
11th to 20thDay
43133345%5%8%61%
2160
21st to endDay
321332335%7%71%
1960
October1st to 10thDay
6%32443345%6%61%
1800
11th to 20thDay
321322223478%
1800
21st to endDay
331332223473%
1980
November1st to 10thDay
211221245%7%73%
1798
11th to 20thDay
221222345%6%72%
1710
21st to endDay
35%2342335%7%65%
1710
December1st to 10thDay
24224235%46%66%
1563
11th to 20thDay
342443445%8%59%
1926
21st to endDay
3413423347%66%
2794
January1st to 10thNight
26%46%5%24346%56%
4191
11th to 20thNight
3313324346%68%
4110
21st to endNight
47%244245%5%9%53%
4521
February1st to 10thNight
26%34323347%63%
2440
11th to 20thNight
46%2432435%8%60%
2218
21st to endNight
35%23322346%65%
1884
March1st to 10thNight
45%2332445%7%62%
2186
11th to 20thNight
46%2442345%7%58%
2068
21st to endNight
5%424424446%63%
2102
April1st to 10thNight
331233436%8%64%
1800
11th to 20thNight
3415%424447%61%
1777
21st to endNight
331332445%6%67%
1800
May1st to 10thNight
331343335%7%65%
1800
11th to 20thNight
5%5%24435%5%5%9%54%
1675
21st to endNight
32123235%5%8%66%
1552
June1st to 10thNight
13135%35%5%7%10%57%
1440
11th to 20thNight
211332345%7%69%
1440
21st to endNight
43145%35%6%7%9%54%
1440
July1st to 10thNight
33247%45%7%9%11%45%
1457
11th to 20thNight
33245%47%6%10%12%43%
1620
21st to endNight
5%426%6%48%7%10%14%36%
1773
August1st to 10thNight
3325%5%47%8%11%10%43%
1672
11th to 20thNight
4425%6%5%6%9%10%12%38%
1778
21st to endNight
32145%46%7%9%12%48%
1980
September1st to 10thNight
43245%36%7%8%11%49%
1800
11th to 20thNight
4323435%5%6%8%58%
1800
21st to endNight
4323323446%67%
1996
October1st to 10thNight
6%42432445%5%62%
2160
11th to 20thNight
3212212335%77%
2160
21st to endNight
421232225%6%72%
2376
November1st to 10thNight
2211222236%77%
2260
11th to 20thNight
1212312345%75%
2470
21st to endNight
5%424423336%65%
2470
December1st to 10thNight
441232335%6%66%
2612
11th to 20thNight
44144245%5%8%59%
3271
21st to endNight
46%24423346%62%
4873

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
21%411%31%30%4
2794
11th to 20thDay
16%412%39%25%4
2860
21st to endDay
25%6%12%23%29%6%
3146
February1st to 10thDay
22%412%25%27%10%
1738
11th to 20thDay
21%48%27%28%13%
1859
21st to endDay
20%37%20%33%17%
1570
March1st to 10thDay
19%49%21%31%16%
1990
11th to 20thDay
25%49%19%31%13%
2058
21st to endDay
20%410%22%31%14%
2253
April1st to 10thDay
16%49%19%34%19%
2160
11th to 20thDay
21%48%18%30%19%
2134
21st to endDay
18%48%22%33%16%
2160
May1st to 10thDay
15%5%9%18%33%21%
2160
11th to 20thDay
24%6%10%19%25%16%
2215
21st to endDay
16%5%11%17%25%27%
2724
June1st to 10thDay
13%6%12%21%25%23%
2520
11th to 20thDay
13%46%13%23%41%
2520
21st to endDay
21%6%10%18%22%23%
2520
July1st to 10thDay
29%10%15%14%17%15%
2430
11th to 20thDay
22%9%20%25%15%9%
2271
21st to endDay
30%14%21%25%9%1
2404
August1st to 10thDay
25%12%20%20%14%9%
2250
11th to 20thDay
25%11%15%22%18%8%
2123
21st to endDay
25%10%15%23%22%6%
2376
September1st to 10thDay
25%8%13%21%21%11%
2160
11th to 20thDay
21%6%11%19%24%19%
2160
21st to endDay
15%47%23%34%18%
1960
October1st to 10thDay
24%6%8%20%25%18%
1800
11th to 20thDay
13%2414%36%30%
1800
21st to endDay
16%37%20%37%17%
1980
November1st to 10thDay
12%27%21%42%16%
1798
11th to 20thDay
13%48%25%38%12%
1710
21st to endDay
21%36%21%34%15%
1710
December1st to 10thDay
18%5%12%32%24%9%
1563
11th to 20thDay
25%5%10%22%29%9%
1924
21st to endDay
19%310%21%33%14%
2794
January1st to 10thNight
27%410%27%25%6%
4191
11th to 20thNight
18%410%36%25%7%
4110
21st to endNight
26%6%12%24%28%5%
4521
February1st to 10thNight
22%411%25%27%12%
2440
11th to 20thNight
24%48%24%27%13%
2218
21st to endNight
21%26%16%34%20%
1884
March1st to 10thNight
21%37%22%31%16%
2186
11th to 20thNight
25%5%7%20%30%13%
2068
21st to endNight
24%38%18%34%13%
2102
April1st to 10thNight
18%48%20%31%20%
1800
11th to 20thNight
21%39%18%26%21%
1777
21st to endNight
19%410%19%34%15%
1800
May1st to 10thNight
20%49%15%32%21%
1800
11th to 20thNight
27%8%11%18%20%17%
1676
21st to endNight
16%5%13%18%22%27%
1552
June1st to 10thNight
20%7%16%18%19%21%
1440
11th to 20thNight
15%48%13%21%39%
1440
21st to endNight
24%8%13%15%17%23%
1440
July1st to 10thNight
30%12%15%18%12%13%
1417
11th to 20thNight
26%12%22%20%13%8%
1566
21st to endNight
32%14%26%20%7%1
1674
August1st to 10thNight
28%13%21%18%11%8%
1663
11th to 20thNight
29%13%21%17%13%7%
1778
21st to endNight
23%11%17%26%15%7%
1980
September1st to 10thNight
26%8%17%21%18%9%
1800
11th to 20thNight
23%8%14%16%22%18%
1800
21st to endNight
18%5%9%18%30%19%
1996
October1st to 10thNight
24%6%8%19%21%22%
2160
11th to 20thNight
12%36%15%35%30%
2160
21st to endNight
15%27%20%37%18%
2376
November1st to 10thNight
11%36%23%40%17%
2260
11th to 20thNight
12%27%24%40%14%
2470
21st to endNight
23%36%20%32%17%
2470
December1st to 10thNight
19%410%31%29%8%
2612
11th to 20thNight
23%5%10%25%29%8%
3272
21st to endNight
24%48%22%31%11%
4873

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
6%10%40%33%11%
270
11th to 20thDay
10%9%39%32%11%
270
21st to endDay
5%5%38%35%13%4
297
February1st to 10thDay
5%14%40%30%10%1
270
11th to 20thDay
6%16%40%29%8%
270
21st to endDay
12%18%41%23%5%
225
March1st to 10thDay
420%33%33%9%1
360
11th to 20thDay
11%19%34%26%8%3
449
21st to endDay
11%27%34%19%8%
462
April1st to 10thDay
9%20%37%23%8%2
420
11th to 20thDay
10%23%38%18%10%1
412
21st to endDay
9%21%40%23%7%1
420
May1st to 10thDay
6%16%42%26%9%1
423
11th to 20thDay
6%12%33%31%14%4
483
21st to endDay
5%10%32%35%16%2
679
June1st to 10thDay
25%21%41%25%6%
630
11th to 20thDay
27%22%38%26%5%
630
21st to endDay
5%5%18%36%29%7%
630
July1st to 10thDay
4212%34%36%13%
600
11th to 20thDay
315%30%37%23%
444
21st to endDay
415%22%43%25%
487
August1st to 10thDay
438%25%40%20%
447
11th to 20thDay
5%313%33%34%13%
437
21st to endDay
5%110%33%35%16%
495
September1st to 10thDay
7%214%30%32%15%
450
11th to 20thDay
4222%36%27%9%
450
21st to endDay
5%420%33%30%8%
288
October1st to 10thDay
6%8%25%30%23%7%
270
11th to 20thDay
7%9%26%28%24%7%
270
21st to endDay
8%10%26%29%20%6%
297
November1st to 10thDay
5%11%32%36%14%1
270
11th to 20thDay
36%27%42%20%2
270
21st to endDay
9%14%32%29%16%1
270
December1st to 10thDay
7%7%37%33%14%1
270
11th to 20thDay
6%8%38%37%11%1
270
21st to endDay
10%10%40%34%6%
297
January1st to 10thNight
5%431%45%14%1
815
11th to 20thNight
6%331%46%12%1
760
21st to endNight
7%5%31%44%12%2
836
February1st to 10thNight
6%6%36%43%9%1
760
11th to 20thNight
8%7%38%39%8%
744
21st to endNight
7%6%46%38%3
628
March1st to 10thNight
7%6%41%39%7%1
760
11th to 20thNight
8%9%33%38%11%
752
21st to endNight
6%9%35%42%7%
716
April1st to 10thNight
411%41%39%5%
540
11th to 20thNight
7%12%35%38%8%
533
21st to endNight
6%9%42%35%7%
540
May1st to 10thNight
47%36%41%11%
540
11th to 20thNight
8%7%30%40%15%1
531
21st to endNight
5%7%33%43%12%
584
June1st to 10thNight
36%26%44%20%1
540
11th to 20thNight
2228%51%16%1
540
21st to endNight
4318%50%24%1
540
July1st to 10thNight
4112%47%32%3
525
11th to 20thNight
319%34%47%4
522
21st to endNight
6%27%30%49%6%
591
August1st to 10thNight
5%27%31%49%7%
537
11th to 20thNight
4211%45%34%4
534
21st to endNight
3110%42%40%5%
594
September1st to 10thNight
5%213%49%29%2
540
11th to 20thNight
5%214%47%30%1
540
21st to endNight
5%323%47%21%2
574
October1st to 10thNight
7%422%47%20%1
720
11th to 20thNight
5%326%48%16%2
720
21st to endNight
5%425%42%20%3
792
November1st to 10thNight
4326%47%20%1
780
11th to 20thNight
25%26%49%17%2
950
21st to endNight
7%6%27%41%17%2
950
December1st to 10thNight
6%6%32%43%12%1
950
11th to 20thNight
8%5%31%45%11%
950
21st to endNight
9%5%36%43%8%
1045
Page generated at 2024-03-15 12:01:40. Version ac07

Copyright © 2024 Attilla Danko.


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