Bransfield Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bransfield Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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
61%
15675
25%
47847
22%
15639
65%
15639
32%
28133

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 15thNight
60%
716
18%
2383
17%
716
64%
716
27%
1439
January16th to endNight
55%
768
24%
2496
25%
768
59%
768
26%
1552
February1st to 15thNight
54%
698
22%
2288
21%
698
59%
698
25%
1428
February16th to endNight
49%
632
22%
1903
17%
632
57%
632
26%
1235
March1st to 15thNight
51%
720
17%
2001
14%
720
54%
720
26%
1338
March16th to endNight
50%
768
20%
2092
14%
768
54%
768
28%
1372
April1st to 15thNight
46%
719
22%
1799
11%
719
51%
719
31%
1182
April16th to endNight
55%
720
24%
1800
12%
720
59%
720
41%
1072
May1st to 15thNight
65%
603
25%
1683
17%
603
67%
603
43%
931
May16th to endNight
58%
394
22%
1517
21%
394
64%
394
29%
806
June1st to 15thNight
65%
360
22%
1440
25%
360
70%
360
30%
738
June16th to endNight
77%
360
32%
1440
41%
360
80%
360
46%
600
July1st to 15thNight
80%
382
26%
1402
31%
382
82%
382
42%
659
July16th to endNight
68%
564
26%
1593
25%
531
68%
531
30%
944
August1st to 15thNight
62%
547
24%
1620
20%
544
62%
544
28%
982
August16th to endNight
69%
764
28%
1910
18%
764
69%
764
40%
1191
September1st to 15thNight
75%
720
33%
1800
24%
720
75%
720
47%
1059
September16th to endNight
76%
716
37%
1966
34%
716
79%
716
50%
1028
October1st to 15thNight
69%
720
28%
2160
28%
720
74%
720
44%
1119
October16th to endNight
67%
768
32%
2304
33%
768
71%
768
36%
1310
November1st to 15thNight
66%
760
26%
2368
26%
760
70%
760
34%
1349
November16th to endNight
59%
780
24%
2646
26%
780
63%
780
30%
1508
December1st to 15thNight
55%
728
19%
2548
17%
728
60%
728
22%
1602
December16th to endNight
47%
768
21%
2688
18%
768
54%
768
22%
1689

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
8%5%24323347%55%
48596
Night
9%5%2442335%7%49%
48034
TransparencyDay
30%38%19%23%14%
48284
Night
34%48%19%20%13%
47848
SeeingDay
10%11%27%33%14%3
6285
Night
12%411%33%30%6%
15687

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 15thDay
16%42433345%7%43%
1553
16th to endDay
17%6%25%5%33246%43%
1728
February1st to 15thDay
19%6%25%32335%5%42%
1576
16th to endDay
17%8%35%423447%37%
1568
March1st to 15thDay
16%7%25%5%2335%8%38%
1956
16th to endDay
13%6%35%5%3445%7%40%
2130
April1st to 15thDay
14%6%35%42335%7%42%
2149
16th to endDay
7%414313347%58%
2160
May1st to 15thDay
441321335%8%62%
2265
16th to endDay
6%5%24213348%55%
2593
June1st to 15thDay
5%42331335%8%58%
2520
16th to endDay
2212211246%70%
2520
July1st to 15thDay
1213212247%68%
2472
16th to endDay
312212247%69%
2468
August1st to 15thDay
1423312247%64%
2330
16th to endDay
1313312237%68%
2292
September1st to 15thDay
2313212247%67%
2160
16th to endDay
3312212236%69%
1989
October1st to 15thDay
6%312312336%64%
1800
16th to endDay
8%5%13323326%59%
1920
November1st to 15thDay
9%5%3432435%7%51%
1820
16th to endDay
14%7%25%322346%46%
1643
December1st to 15thDay
18%8%25%3235%35%41%
1448
16th to endDay
19%7%34414246%41%
1536
January1st to 15thNight
14%5%2442345%8%43%
2383
16th to endNight
17%6%24313336%46%
2496
February1st to 15thNight
16%6%25%424445%42%
2276
16th to endNight
15%6%25%424448%41%
1903
March1st to 15thNight
17%6%25%423447%40%
2001
16th to endNight
14%6%34433346%45%
2092
April1st to 15thNight
12%6%2442345%7%45%
1799
16th to endNight
7%423423347%58%
1800
May1st to 15thNight
3436%32235%7%56%
1683
16th to endNight
5%8%26%422346%53%
1516
June1st to 15thNight
4426%42347%7%52%
1440
16th to endNight
1313422337%64%
1440
July1st to 15thNight
132442435%10%57%
1485
16th to endNight
16%38%6%5%5%6%6%10%40%
1701
August1st to 15thNight
27%48%6%3447%10%39%
1629
16th to endNight
5%38%5%3447%10%45%
1910
September1st to 15thNight
25%25%42335%8%56%
1800
16th to endNight
2313323248%63%
1966
October1st to 15thNight
7%313222336%61%
2160
16th to endNight
7%5%2342345%5%54%
2304
November1st to 15thNight
9%5%23323348%52%
2368
16th to endNight
12%6%14423346%51%
2646
December1st to 15thNight
18%6%24334346%43%
2548
16th to endNight
20%5%24323336%44%
2688

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 15thDay
39%5%12%17%16%8%
1553
16th to endDay
44%49%12%18%11%
1728
February1st to 15thDay
42%49%18%20%3
1576
16th to endDay
44%49%24%13%3
1568
March1st to 15thDay
43%412%19%13%5%
1956
16th to endDay
41%7%12%19%15%3
2130
April1st to 15thDay
40%5%14%19%18%2
2149
16th to endDay
27%413%26%21%6%
2160
May1st to 15thDay
21%39%29%26%8%
2265
16th to endDay
29%412%27%21%5%
2597
June1st to 15thDay
26%5%9%21%22%13%
2520
16th to endDay
17%1319%33%24%
2520
July1st to 15thDay
20%1310%24%39%
2327
16th to endDay
19%1311%25%37%
2313
August1st to 15thDay
23%1313%30%27%
2314
16th to endDay
20%317%35%21%
2292
September1st to 15thDay
20%2315%29%28%
2160
16th to endDay
19%2425%30%18%
1989
October1st to 15thDay
23%27%19%25%21%
1800
16th to endDay
28%39%22%21%14%
1920
November1st to 15thDay
32%411%29%14%7%
1820
16th to endDay
39%48%19%22%5%
1643
December1st to 15thDay
45%49%17%18%4
1448
16th to endDay
43%5%11%18%16%4
1536
January1st to 15thNight
37%5%12%19%15%8%
2383
16th to endNight
41%39%13%16%15%
2496
February1st to 15thNight
42%310%18%17%7%
2288
16th to endNight
41%5%11%23%14%2
1903
March1st to 15thNight
43%411%19%14%5%
2001
16th to endNight
40%5%11%19%18%4
2092
April1st to 15thNight
37%5%14%20%19%3
1799
16th to endNight
27%412%25%20%9%
1800
May1st to 15thNight
27%38%24%24%11%
1684
16th to endNight
33%311%25%19%6%
1517
June1st to 15thNight
29%5%9%19%23%12%
1440
16th to endNight
19%2216%33%24%
1440
July1st to 15thNight
24%219%25%35%
1402
16th to endNight
39%2310%16%27%
1593
August1st to 15thNight
40%229%24%20%
1620
16th to endNight
34%2212%27%21%
1910
September1st to 15thNight
26%4210%27%28%
1800
16th to endNight
22%2324%25%20%
1966
October1st to 15thNight
24%37%20%21%22%
2160
16th to endNight
32%36%21%20%16%
2304
November1st to 15thNight
31%411%28%15%7%
2368
16th to endNight
34%38%22%21%7%
2646
December1st to 15thNight
43%49%16%18%6%
2548
16th to endNight
42%5%11%16%17%7%
2688

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 15thDay
23%8%25%24%17%
181
16th to endDay
17%10%23%29%16%2
256
February1st to 15thDay
21%10%21%29%16%
236
16th to endDay
19%15%25%25%13%1
236
March1st to 15thDay
19%15%28%18%12%4
270
16th to endDay
15%19%33%22%7%1
288
April1st to 15thDay
18%23%28%21%6%1
269
16th to endDay
11%27%27%24%6%2
270
May1st to 15thDay
7%19%38%27%6%
288
16th to endDay
12%15%26%33%9%3
330
June1st to 15thDay
8%14%37%30%6%1
315
16th to endDay
15%32%43%14%3
315
July1st to 15thDay
2225%49%18%
305
16th to endDay
2227%48%13%6%
327
August1st to 15thDay
2328%46%13%4
315
16th to endDay
2125%46%17%6%
332
September1st to 15thDay
4423%42%18%6%
315
16th to endDay
211%24%33%21%6%
315
October1st to 15thDay
6%9%30%33%13%6%
315
16th to endDay
13%7%26%26%19%6%
336
November1st to 15thDay
10%8%24%23%28%4
236
16th to endDay
15%12%22%31%17%
109
December1st to 15thDay
24%12%33%19%8%1
62
16th to endDay
10%23%20%26%17%1
64
January1st to 15thNight
17%49%33%27%7%
720
16th to endNight
18%411%32%26%7%
768
February1st to 15thNight
17%6%12%33%25%5%
704
16th to endNight
17%7%17%30%21%5%
632
March1st to 15thNight
17%7%13%28%28%4
720
16th to endNight
16%8%16%33%22%2
768
April1st to 15thNight
13%10%20%33%18%3
719
16th to endNight
9%9%19%31%24%4
720
May1st to 15thNight
6%314%42%28%4
604
16th to endNight
11%5%15%37%24%5%
395
June1st to 15thNight
5%415%45%25%3
360
16th to endNight
419%46%35%2
360
July1st to 15thNight
45%37%45%6%
382
16th to endNight
5%2430%45%11%
564
August1st to 15thNight
10%27%32%40%6%
547
16th to endNight
5%17%37%40%7%
764
September1st to 15thNight
5%7%29%44%11%
720
16th to endNight
427%36%37%11%
716
October1st to 15thNight
8%49%35%33%8%
720
16th to endNight
10%38%27%35%13%
768
November1st to 15thNight
10%311%33%32%8%
760
16th to endNight
14%6%10%31%28%8%
780
December1st to 15thNight
20%5%11%33%21%6%
728
16th to endNight
20%8%15%31%21%2
768
Page generated at 2017-12-03 08:16:39. Version ac04

Copyright 2017 A. Danko


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