Mt Potosi Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mt Potosi Observatory clear sky chart from 2005-11-06 to 2024-01-12.

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
69%
24502
37%
74429
30%
24462
77%
24462
57%
33738

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
62%
756
33%
2457
29%
756
70%
756
44%
1208
January11th to 20thNight
67%
728
37%
2366
33%
728
76%
728
52%
1065
January21st to endNight
60%
792
38%
2500
30%
792
73%
792
45%
1223
February1st to 10thNight
62%
720
36%
2160
30%
720
72%
720
51%
1048
February11th to 20thNight
58%
700
39%
2099
32%
700
70%
700
50%
1011
February21st to endNight
56%
592
36%
1776
30%
592
68%
592
49%
855
March1st to 10thNight
55%
720
31%
2160
25%
720
67%
720
49%
1044
March11th to 20thNight
58%
720
34%
2003
27%
720
68%
720
51%
1017
March21st to endNight
57%
792
35%
2178
21%
792
69%
792
56%
1054
April1st to 10thNight
55%
720
36%
1802
17%
720
65%
720
55%
942
April11th to 20thNight
54%
711
37%
1779
17%
711
65%
711
59%
899
April21st to endNight
64%
608
42%
1688
23%
608
75%
608
67%
738
May1st to 10thNight
59%
540
37%
1620
23%
540
67%
540
61%
705
May11th to 20thNight
67%
531
41%
1595
27%
531
74%
531
67%
652
May21st to endNight
66%
582
36%
1746
24%
582
74%
582
64%
724
June1st to 10thNight
74%
540
36%
1620
29%
540
79%
540
77%
622
June11th to 20thNight
70%
540
36%
1620
29%
540
76%
540
70%
647
June21st to endNight
80%
540
36%
1620
30%
540
84%
540
79%
617
July1st to 10thNight
90%
525
34%
1575
32%
525
91%
525
73%
639
July11th to 20thNight
86%
522
32%
1566
29%
522
86%
522
59%
710
July21st to endNight
83%
591
34%
1674
30%
558
84%
558
54%
811
August1st to 10thNight
83%
537
40%
1602
31%
534
85%
534
62%
708
August11th to 20thNight
90%
712
38%
1780
25%
712
91%
712
76%
831
August21st to endNight
89%
792
42%
1980
29%
792
89%
792
75%
922
September1st to 10thNight
85%
720
39%
1872
29%
720
87%
720
69%
876
September11th to 20thNight
85%
720
45%
1980
37%
720
90%
720
80%
816
September21st to endNight
81%
720
45%
1980
36%
720
88%
720
76%
836
October1st to 10thNight
74%
720
43%
1980
33%
720
82%
720
67%
886
October11th to 20thNight
77%
720
48%
2018
40%
720
84%
720
72%
866
October21st to endNight
70%
792
43%
2507
37%
792
81%
792
67%
991
November1st to 10thNight
74%
740
39%
2405
39%
740
81%
740
63%
972
November11th to 20thNight
75%
760
41%
2470
40%
760
84%
760
63%
1008
November21st to endNight
68%
760
39%
2470
36%
760
76%
760
57%
1067
December1st to 10thNight
64%
760
34%
2470
31%
760
71%
760
47%
1176
December11th to 20thNight
62%
758
34%
2902
30%
758
71%
758
37%
1439
December21st to endNight
56%
821
21%
4409
28%
817
66%
817
26%
2113

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
2213323446%69%
74885
Night
2313323446%69%
74885
TransparencyDay
15%36%14%27%35%
74612
Night
15%36%15%27%34%
74680
SeeingDay
48%22%35%25%7%
14202
Night
3418%38%31%7%
24529

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
43134245%48%62%
1708
11th to 20thDay
4413323348%65%
1633
21st to endDay
442433345%7%62%
1854
February1st to 10thDay
4213435%446%65%
1800
11th to 20thDay
221442445%8%62%
1750
21st to endDay
3435%434335%63%
1480
March1st to 10thDay
231343446%8%61%
1800
11th to 20thDay
3325%5%2445%9%59%
1956
21st to endDay
2223425%5%5%7%63%
2178
April1st to 10thDay
232443445%6%65%
2154
11th to 20thDay
1224323345%72%
2129
21st to endDay
2212323346%72%
2272
May1st to 10thDay
121232345%6%71%
2340
11th to 20thDay
1112224346%73%
2301
21st to endDay
2212322346%73%
2530
June1st to 10thDay
1112212326%78%
2340
11th to 20thDay
11121223483%
2340
21st to endDay
121121223481%
2340
July1st to 10thDay
111332445%5%71%
2340
11th to 20thDay
221343345%6%66%
2340
21st to endDay
3325%6%35%5%7%10%51%
2545
August1st to 10thDay
311242435%5%70%
2325
11th to 20thDay
2212324446%72%
2122
21st to endDay
2212223446%70%
2376
September1st to 10thDay
2213332445%70%
2087
11th to 20thDay
11221223482%
1980
21st to endDay
111231224479%
1980
October1st to 10thDay
221332334472%
1980
11th to 20thDay
2111212335%79%
1940
21st to endDay
111211235%81%
1846
November1st to 10thDay
1112223346%75%
1674
11th to 20thDay
1223422236%73%
1710
21st to endDay
312332435%8%67%
1710
December1st to 10thDay
23145%2446%7%62%
1710
11th to 20thDay
4436%5%4446%11%50%
2169
21st to endDay
3425%436%6%7%7%53%
3146
January1st to 10thNight
34245%345%5%7%59%
2457
11th to 20thNight
231342445%8%64%
2366
21st to endNight
5%5%2332345%5%62%
2500
February1st to 10thNight
2424423445%66%
2160
11th to 20thNight
331442345%5%66%
2098
21st to endNight
4324423446%64%
1776
March1st to 10thNight
13244345%6%9%59%
2160
11th to 20thNight
44233235%7%8%59%
2003
21st to endNight
221343345%7%66%
2178
April1st to 10thNight
2323324346%67%
1802
11th to 20thNight
1123324448%69%
1779
21st to endNight
1112223337%75%
1688
May1st to 10thNight
221331345%7%70%
1620
11th to 20thNight
1112313345%76%
1594
21st to endNight
1212312346%76%
1746
June1st to 10thNight
111211246%81%
1620
11th to 20thNight
121122222482%
1620
21st to endNight
11111223384%
1620
July1st to 10thNight
1111223336%78%
1620
11th to 20thNight
3213323445%70%
1620
21st to endNight
33143245%6%8%60%
1773
August1st to 10thNight
2212323346%72%
1611
11th to 20thNight
122222346%76%
1780
21st to endNight
2112223345%76%
1980
September1st to 10thNight
2212212345%74%
1872
11th to 20thNight
11111222484%
1980
21st to endNight
111211222384%
1980
October1st to 10thNight
222221224477%
1980
11th to 20thNight
121222223481%
2018
21st to endNight
1212222335%78%
2507
November1st to 10thNight
1212213235%76%
2405
11th to 20thNight
1213323346%73%
2470
21st to endNight
2223323447%69%
2470
December1st to 10thNight
34235%24447%62%
2470
11th to 20thNight
4426%4345%5%9%54%
3041
21st to endNight
45%25%6%35%5%6%7%51%
4521

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
19%38%26%33%10%
1709
11th to 20thDay
19%37%27%33%13%
1633
21st to endDay
21%27%23%34%12%
1854
February1st to 10thDay
20%26%19%30%22%
1800
11th to 20thDay
19%26%15%33%24%
1760
21st to endDay
22%37%18%30%20%
1480
March1st to 10thDay
18%47%19%33%20%
1800
11th to 20thDay
20%46%18%32%20%
1956
21st to endDay
16%48%24%32%15%
2178
April1st to 10thDay
19%25%19%30%26%
2154
11th to 20thDay
15%2415%28%36%
2132
21st to endDay
13%25%15%35%31%
2272
May1st to 10thDay
12%3415%30%35%
2340
11th to 20thDay
10%2412%33%38%
2304
21st to endDay
13%25%11%32%36%
2530
June1st to 10thDay
9%1310%22%54%
2340
11th to 20thDay
7%126%18%66%
2340
21st to endDay
8%225%14%70%
2340
July1st to 10thDay
15%346%12%60%
2276
11th to 20thDay
15%47%10%21%43%
2271
21st to endDay
24%6%8%13%18%31%
2404
August1st to 10thDay
14%26%8%17%53%
2310
11th to 20thDay
13%35%8%22%49%
2122
21st to endDay
14%349%19%51%
2376
September1st to 10thDay
14%35%7%17%53%
2087
11th to 20thDay
7%237%23%58%
1980
21st to endDay
10%138%26%52%
1980
October1st to 10thDay
14%3312%25%43%
1980
11th to 20thDay
10%1411%30%44%
1940
21st to endDay
8%2310%36%41%
1846
November1st to 10thDay
11%1416%38%30%
1674
11th to 20thDay
14%15%15%36%28%
1710
21st to endDay
16%35%19%31%26%
1710
December1st to 10thDay
21%48%20%28%20%
1710
11th to 20thDay
26%5%12%22%26%9%
2168
21st to endDay
23%8%12%25%22%10%
3146
January1st to 10thNight
22%46%23%33%12%
2457
11th to 20thNight
18%36%24%32%17%
2366
21st to endNight
23%27%23%29%16%
2500
February1st to 10thNight
21%27%17%30%23%
2160
11th to 20thNight
20%35%18%26%28%
2099
21st to endNight
19%37%17%32%22%
1776
March1st to 10thNight
19%48%19%32%19%
2160
11th to 20thNight
20%46%17%30%24%
2003
21st to endNight
16%38%22%33%19%
2178
April1st to 10thNight
18%26%19%29%26%
1802
11th to 20thNight
14%3418%30%31%
1779
21st to endNight
10%1317%32%36%
1688
May1st to 10thNight
13%25%14%30%36%
1620
11th to 20thNight
10%1414%31%40%
1595
21st to endNight
10%2412%32%39%
1746
June1st to 10thNight
6%1410%23%56%
1620
11th to 20thNight
9%125%19%64%
1620
21st to endNight
6%125%12%74%
1620
July1st to 10thNight
9%238%14%65%
1575
11th to 20thNight
15%35%11%19%47%
1566
21st to endNight
18%5%7%19%18%34%
1674
August1st to 10thNight
13%349%16%55%
1602
11th to 20thNight
9%25%10%22%52%
1780
21st to endNight
10%15%8%23%53%
1980
September1st to 10thNight
11%35%9%17%55%
1872
11th to 20thNight
6%247%23%58%
1980
21st to endNight
8%227%25%57%
1980
October1st to 10thNight
12%2312%25%46%
1980
11th to 20thNight
10%239%27%49%
2018
21st to endNight
10%2411%27%46%
2507
November1st to 10thNight
12%2316%36%31%
2405
11th to 20thNight
13%25%14%34%33%
2470
21st to endNight
16%25%15%31%32%
2470
December1st to 10thNight
22%38%19%29%21%
2470
11th to 20thNight
24%5%9%19%30%13%
3041
21st to endNight
25%9%12%22%24%9%
4521

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
10%7%27%40%13%3
270
11th to 20thDay
10%7%23%35%20%4
245
21st to endDay
413%21%35%24%4
336
February1st to 10thDay
5%12%26%34%18%5%
420
11th to 20thDay
6%14%29%34%14%3
415
21st to endDay
8%16%32%32%12%1
346
March1st to 10thDay
8%18%30%31%13%
420
11th to 20thDay
5%15%30%31%16%2
420
21st to endDay
6%17%35%30%11%1
462
April1st to 10thDay
7%13%29%30%16%4
420
11th to 20thDay
6%17%34%26%15%2
412
21st to endDay
5%18%25%30%17%5%
420
May1st to 10thDay
412%31%30%17%5%
423
11th to 20thDay
311%26%34%19%7%
448
21st to endDay
5%9%22%35%21%8%
485
June1st to 10thDay
36%22%36%23%10%
450
11th to 20thDay
18%21%31%28%11%
450
21st to endDay
1322%37%28%9%
450
July1st to 10thDay
1113%41%32%12%
446
11th to 20thDay
417%37%37%14%
444
21st to endDay
317%37%38%16%
487
August1st to 10thDay
3115%38%29%13%
447
11th to 20thDay
2211%38%32%16%
437
21st to endDay
4112%34%38%12%
495
September1st to 10thDay
1314%36%37%8%
450
11th to 20thDay
6%19%42%28%5%
450
21st to endDay
35%20%32%34%6%
450
October1st to 10thDay
36%20%39%28%4
450
11th to 20thDay
25%22%34%32%5%
410
21st to endDay
1422%33%32%8%
297
November1st to 10thDay
19%22%32%30%5%
270
11th to 20thDay
3420%40%23%9%
270
21st to endDay
26%23%31%29%8%
270
December1st to 10thDay
4321%42%26%4
270
11th to 20thDay
2324%39%24%8%
270
21st to endDay
6%8%29%32%21%3
297
January1st to 10thNight
5%5%19%37%24%10%
760
11th to 20thNight
35%18%41%26%7%
728
21st to endNight
8%5%20%40%22%5%
792
February1st to 10thNight
4323%41%23%7%
720
11th to 20thNight
37%25%40%19%5%
704
21st to endNight
7%9%25%37%18%5%
592
March1st to 10thNight
28%28%41%18%3
720
11th to 20thNight
5%6%24%34%24%7%
720
21st to endNight
39%27%40%19%3
792
April1st to 10thNight
49%25%36%21%5%
720
11th to 20thNight
29%30%36%19%4
711
21st to endNight
28%22%39%23%6%
608
May1st to 10thNight
3428%41%20%3
540
11th to 20thNight
26%21%35%32%5%
531
21st to endNight
18%20%37%30%4
584
June1st to 10thNight
1418%42%33%3
540
11th to 20thNight
2421%37%33%3
540
21st to endNight
1115%43%36%3
540
July1st to 10thNight
2440%48%5%
525
11th to 20thNight
4436%52%4
522
21st to endNight
41331%57%4
591
August1st to 10thNight
27%41%45%4
537
11th to 20thNight
2429%57%8%
712
21st to endNight
21431%48%15%
792
September1st to 10thNight
227%30%48%12%
720
11th to 20thNight
110%40%39%10%
720
21st to endNight
1211%34%39%13%
720
October1st to 10thNight
3316%42%31%5%
720
11th to 20thNight
2215%39%32%11%
720
21st to endNight
2320%31%32%12%
792
November1st to 10thNight
1416%37%33%8%
740
11th to 20thNight
1216%41%33%7%
760
21st to endNight
3420%39%28%7%
760
December1st to 10thNight
6%319%38%28%5%
760
11th to 20thNight
6%420%39%26%5%
760
21st to endNight
5%6%24%38%22%5%
836
Page generated at 2024-01-09 13:24:23. Version ac07

Copyright 2024 Attilla Danko


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