Banks
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Banks clear sky chart from 2005-11-05 to 2017-09-16.

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%
14743
18%
46814
17%
14717
59%
14717
26%
29719

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
42%
716
9%
2506
8%
716
45%
716
12%
1921
January16th to endNight
50%
768
10%
2688
12%
768
52%
768
17%
1900
February1st to 15thNight
42%
698
8%
2267
7%
696
45%
696
16%
1683
February16th to endNight
43%
632
11%
1895
11%
632
45%
632
15%
1438
March1st to 15thNight
42%
720
9%
2151
8%
720
44%
720
16%
1624
March16th to endNight
42%
768
12%
2046
8%
768
44%
768
20%
1517
April1st to 15thNight
48%
719
17%
1799
9%
719
50%
719
26%
1273
April16th to endNight
55%
564
22%
1644
16%
564
58%
564
32%
1001
May1st to 15thNight
59%
537
20%
1617
16%
537
64%
537
36%
910
May16th to endNight
65%
374
16%
1496
24%
374
66%
374
24%
863
June1st to 15thNight
64%
360
16%
1440
22%
360
69%
360
26%
813
June16th to endNight
77%
360
23%
1440
36%
360
81%
360
42%
631
July1st to 15thNight
85%
340
22%
1360
35%
340
88%
340
52%
517
July16th to endNight
86%
376
34%
1416
49%
354
89%
354
59%
511
August1st to 15thNight
82%
476
31%
1549
31%
474
83%
474
53%
689
August16th to endNight
83%
683
36%
1829
26%
683
84%
683
64%
869
September1st to 15thNight
84%
720
33%
1851
23%
720
85%
720
61%
940
September16th to endNight
70%
660
34%
1826
28%
660
72%
660
45%
1014
October1st to 15thNight
64%
660
26%
1856
22%
660
67%
660
38%
1095
October16th to endNight
59%
704
21%
2288
21%
704
63%
704
26%
1424
November1st to 15thNight
54%
700
18%
2275
19%
700
55%
700
22%
1508
November16th to endNight
47%
720
13%
2367
11%
720
49%
720
18%
1659
December1st to 15thNight
43%
720
8%
2520
6%
720
46%
720
13%
1861
December16th to endNight
36%
768
10%
2688
9%
768
39%
768
12%
2058

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
11%8%34424446%45%
47963
Night
13%8%24424446%44%
46987
TransparencyDay
39%5%11%18%16%9%
47634
Night
40%5%12%19%14%7%
46815
SeeingDay
14%11%30%29%13%2
5354
Night
16%314%36%25%3
14755

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
18%12%47%6%34446%26%
1432
16th to endDay
18%15%36%5%2445%8%26%
1536
February1st to 15thDay
16%13%47%6%35%35%6%26%
1592
16th to endDay
14%17%5%7%6%245%5%5%23%
1579
March1st to 15thDay
18%14%46%6%35%5%5%5%24%
1809
16th to endDay
19%14%46%5%25%446%25%
2177
April1st to 15thDay
12%12%5%6%5%45%45%7%30%
2149
16th to endDay
13%9%35%5%24346%41%
2316
May1st to 15thDay
8%7%25%5%2446%7%44%
2331
16th to endDay
11%7%36%6%3446%6%36%
2615
June1st to 15thDay
13%6%245%35%5%5%7%38%
2520
16th to endDay
7%313223445%62%
2520
July1st to 15thDay
3212212445%69%
2520
16th to endDay
211221233473%
2657
August1st to 15thDay
3213223335%68%
2401
16th to endDay
2212212335%71%
2372
September1st to 15thDay
421221233471%
2109
16th to endDay
8%412323436%58%
1823
October1st to 15thDay
11%5%144245%47%49%
1771
16th to endDay
14%8%36%5%24345%40%
1584
November1st to 15thDay
16%12%345%2345%6%34%
1584
16th to endDay
17%12%36%5%34335%32%
1590
December1st to 15thDay
22%12%45%32345%5%29%
1440
16th to endDay
24%14%46%224335%27%
1536
January1st to 15thNight
21%12%46%433446%27%
2506
16th to endNight
17%14%24425%447%31%
2688
February1st to 15thNight
17%14%46%5%24345%30%
2256
16th to endNight
17%15%44434446%28%
1895
March1st to 15thNight
18%13%45%6%2444430%
2151
16th to endNight
17%11%25%425%45%7%31%
2046
April1st to 15thNight
12%8%35%435%5%5%7%38%
1799
16th to endNight
13%5%2432445%5%50%
1644
May1st to 15thNight
7%413335%5%46%53%
1617
16th to endNight
9%5%36%435%5%5%8%42%
1496
June1st to 15thNight
11%5%143235%5%8%48%
1440
16th to endNight
5%31232345%5%62%
1440
July1st to 15thNight
11221346%7%67%
1440
16th to endNight
221112223475%
1512
August1st to 15thNight
31221345%6%67%
1557
16th to endNight
223112335%73%
1829
September1st to 15thNight
21322234472%
1851
16th to endNight
9%41331233461%
1826
October1st to 15thNight
10%414423347%53%
1856
16th to endNight
14%7%1443445%6%42%
2288
November1st to 15thNight
20%7%2442345%7%37%
2275
16th to endNight
19%10%25%434445%35%
2367
December1st to 15thNight
18%13%35%6%35%5%45%28%
2520
16th to endNight
22%16%46%42433426%
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
58%11%13%14%2
1432
16th to endDay
55%8%19%13%3
1536
February1st to 15thDay
57%9%14%14%3
1592
16th to endDay
60%8%13%14%2
1579
March1st to 15thDay
59%8%11%14%5%
1809
16th to endDay
57%7%12%16%4
2177
April1st to 15thDay
52%6%16%18%6%
2149
16th to endDay
42%413%24%13%1
2316
May1st to 15thDay
36%5%11%30%13%2
2331
16th to endDay
44%6%14%20%12%2
2619
June1st to 15thDay
41%7%11%19%16%3
2520
16th to endDay
21%47%20%31%14%
2520
July1st to 15thDay
16%37%15%29%28%
2371
16th to endDay
12%249%27%43%
2490
August1st to 15thDay
17%37%14%29%27%
2384
16th to endDay
15%35%17%36%22%
2372
September1st to 15thDay
17%36%18%33%21%
2109
16th to endDay
26%49%26%24%8%
1823
October1st to 15thDay
34%5%14%22%19%3
1771
16th to endDay
44%6%11%19%16%
1584
November1st to 15thDay
48%7%16%19%8%
1584
16th to endDay
53%5%15%16%7%1
1590
December1st to 15thDay
55%8%18%15%2
1440
16th to endDay
60%7%14%13%3
1536
January1st to 15thNight
59%8%14%13%4
2506
16th to endNight
50%8%17%17%6%
2688
February1st to 15thNight
55%6%14%17%4
2267
16th to endNight
56%7%14%15%41
1895
March1st to 15thNight
56%7%12%17%5%1
2151
16th to endNight
51%6%14%19%8%
2046
April1st to 15thNight
44%6%13%23%11%
1799
16th to endNight
34%5%13%26%18%1
1644
May1st to 15thNight
29%5%13%29%21%1
1618
16th to endNight
36%6%11%28%14%2
1496
June1st to 15thNight
33%7%11%27%15%4
1440
16th to endNight
21%39%20%29%15%
1440
July1st to 15thNight
13%37%14%31%28%
1360
16th to endNight
12%1411%27%42%
1416
August1st to 15thNight
16%37%14%27%29%
1549
16th to endNight
14%25%15%31%29%
1829
September1st to 15thNight
16%26%15%33%24%
1851
16th to endNight
26%36%21%26%14%
1826
October1st to 15thNight
31%412%26%20%4
1856
16th to endNight
39%5%13%20%19%1
2288
November1st to 15thNight
45%5%14%21%12%
2275
16th to endNight
50%6%12%20%7%1
2367
December1st to 15thNight
54%8%16%14%5%
2520
16th to endNight
61%413%14%4
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
28%15%31%16%8%
60
16th to endDay
29%418%25%17%4
64
February1st to 15thDay
26%323%23%20%3
159
16th to endDay
24%13%31%23%6%
238
March1st to 15thDay
27%14%31%20%7%
270
16th to endDay
27%17%30%19%5%
288
April1st to 15thDay
14%19%31%19%12%2
269
16th to endDay
18%20%34%20%5%1
270
May1st to 15thDay
10%17%35%26%8%1
288
16th to endDay
15%10%26%27%16%4
330
June1st to 15thDay
11%13%34%25%12%2
315
16th to endDay
7%13%33%29%13%2
315
July1st to 15thDay
48%28%39%15%3
305
16th to endDay
8%39%37%11%1
327
August1st to 15thDay
46%40%37%10%
315
16th to endDay
28%27%36%21%3
332
September1st to 15thDay
7%7%23%39%19%2
315
16th to endDay
8%6%28%37%17%
258
October1st to 15thDay
11%9%29%29%17%2
241
16th to endDay
27%5%16%32%16%2
96
November1st to 15thDay
17%415%32%30%
90
16th to endDay
22%12%37%16%8%2
85
December1st to 15thDay
60%326%6%3
60
16th to endDay
31%417%31%15%
64
January1st to 15thNight
27%5%13%30%19%4
720
16th to endNight
24%212%30%25%4
768
February1st to 15thNight
25%316%31%20%2
704
16th to endNight
22%6%17%35%15%2
632
March1st to 15thNight
21%5%19%33%17%2
720
16th to endNight
21%7%22%34%13%
768
April1st to 15thNight
15%5%20%33%21%3
719
16th to endNight
15%418%39%20%1
564
May1st to 15thNight
8%5%20%38%26%1
538
16th to endNight
8%314%34%34%3
375
June1st to 15thNight
11%213%40%29%3
360
16th to endNight
5%29%45%37%
360
July1st to 15thNight
116%47%41%2
340
16th to endNight
35%47%40%1
376
August1st to 15thNight
5%16%42%42%2
476
16th to endNight
218%41%41%4
683
September1st to 15thNight
27%43%41%4
720
16th to endNight
10%210%31%35%9%
660
October1st to 15thNight
11%215%38%29%3
660
16th to endNight
16%113%35%27%3
704
November1st to 15thNight
23%213%34%23%2
700
16th to endNight
23%417%32%18%4
720
December1st to 15thNight
23%5%17%34%17%2
720
16th to endNight
31%416%32%14%1
768
Page generated at 2017-09-17 10:05:42. Version ac04

Copyright 2017 A. Danko


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