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 2018-04-23.

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
56%
15607
18%
49510
17%
15581
59%
15581
25%
31632

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
43%
776
8%
2716
8%
776
46%
776
12%
2075
January16th to endNight
50%
832
10%
2912
11%
832
51%
832
16%
2077
February1st to 15thNight
43%
758
9%
2460
8%
756
46%
756
16%
1823
February16th to endNight
43%
684
10%
2051
10%
684
45%
684
15%
1565
March1st to 15thNight
42%
780
10%
2330
10%
780
44%
780
16%
1750
March16th to endNight
43%
832
12%
2217
8%
832
44%
832
20%
1643
April1st to 15thNight
47%
779
16%
1949
9%
779
49%
779
25%
1394
April16th to endNight
55%
584
23%
1700
16%
584
58%
584
33%
1028
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
69%
716
33%
1980
28%
716
71%
716
43%
1124
October1st to 15thNight
64%
720
25%
2025
22%
720
66%
720
38%
1191
October16th to endNight
61%
768
23%
2496
24%
768
64%
768
28%
1515
November1st to 15thNight
52%
760
18%
2470
19%
760
53%
760
21%
1668
November16th to endNight
46%
780
12%
2564
11%
780
48%
780
18%
1811
December1st to 15thNight
45%
780
9%
2730
7%
780
48%
780
14%
1990
December16th to endNight
36%
832
11%
2912
9%
832
39%
832
12%
2235

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%35%424446%44%
50025
Night
13%8%24424446%43%
49683
TransparencyDay
39%5%11%18%15%8%
49696
Night
41%5%12%19%14%6%
49511
SeeingDay
15%10%30%28%13%2
6030
Night
16%314%36%25%3
15619

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%345%46%26%
1552
16th to endDay
18%16%46%5%24447%25%
1664
February1st to 15thDay
16%14%47%6%35%345%26%
1729
16th to endDay
14%18%6%8%6%245%45%22%
1709
March1st to 15thDay
18%15%46%6%35%5%5%5%24%
1960
16th to endDay
18%15%47%5%25%446%25%
2358
April1st to 15thDay
13%13%46%5%46%5%5%6%28%
2329
16th to endDay
12%9%35%424346%41%
2374
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
9%413323345%57%
1980
October1st to 15thDay
10%6%14424447%49%
1932
16th to endDay
14%8%26%5%23346%42%
1728
November1st to 15thDay
17%12%35%5%3345%6%32%
1719
16th to endDay
18%12%46%5%34436%31%
1722
December1st to 15thDay
21%12%45%43445%5%29%
1560
16th to endDay
23%15%46%324335%27%
1664
January1st to 15thNight
21%12%46%433446%27%
2716
16th to endNight
17%14%34425%447%30%
2912
February1st to 15thNight
17%14%46%5%24345%31%
2449
16th to endNight
16%16%45%5%34445%28%
2051
March1st to 15thNight
18%12%46%6%24445%31%
2330
16th to endNight
16%11%35%5%25%5%5%7%31%
2217
April1st to 15thNight
14%8%35%4345%5%7%37%
1949
16th to endNight
13%5%1432335%5%51%
1700
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
10%41331233459%
1980
October1st to 15thNight
10%414423347%53%
2025
16th to endNight
13%6%1443445%6%45%
2496
November1st to 15thNight
21%8%2442345%6%36%
2470
16th to endNight
20%10%35%424445%34%
2564
December1st to 15thNight
17%12%36%6%35%5%46%29%
2730
16th to endNight
22%16%46%5%2433426%
2912

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
57%11%14%14%2
1552
16th to endDay
56%8%18%12%3
1664
February1st to 15thDay
58%9%14%14%3
1729
16th to endDay
61%7%13%14%2
1709
March1st to 15thDay
59%8%11%15%5%
1960
16th to endDay
58%8%12%15%4
2358
April1st to 15thDay
53%6%16%16%6%
2329
16th to endDay
42%413%24%13%1
2374
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
27%49%26%23%8%
1980
October1st to 15thDay
34%5%13%22%18%3
1932
16th to endDay
43%6%12%20%17%
1728
November1st to 15thDay
50%6%15%18%8%
1719
16th to endDay
54%5%14%16%7%1
1722
December1st to 15thDay
55%8%18%15%1
1560
16th to endDay
60%7%13%14%3
1664
January1st to 15thNight
58%8%15%13%3
2716
16th to endNight
51%8%17%17%6%
2912
February1st to 15thNight
54%7%15%17%4
2460
16th to endNight
57%7%13%15%5%1
2051
March1st to 15thNight
55%6%11%18%6%1
2330
16th to endNight
51%7%14%19%7%
2217
April1st to 15thNight
45%6%13%22%10%
1949
16th to endNight
34%5%13%26%18%1
1700
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
28%36%22%25%13%
1980
October1st to 15thNight
31%411%27%20%4
2025
16th to endNight
37%5%12%21%20%1
2496
November1st to 15thNight
48%413%20%12%
2470
16th to endNight
51%6%13%20%7%1
2564
December1st to 15thNight
53%8%17%14%6%
2730
16th to endNight
62%5%13%14%4
2912

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
27%113%28%18%10%
90
16th to endDay
30%5%21%26%12%4
96
February1st to 15thDay
24%327%24%16%2
206
16th to endDay
24%13%31%23%6%
290
March1st to 15thDay
26%12%32%20%7%
330
16th to endDay
26%17%31%19%5%
352
April1st to 15thDay
17%18%31%19%10%2
329
16th to endDay
18%19%34%20%6%1
288
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
12%5%28%36%16%
315
October1st to 15thDay
12%9%30%28%17%2
300
16th to endDay
22%315%33%20%3
144
November1st to 15thDay
25%5%17%30%21%
135
16th to endDay
26%11%32%17%11%1
127
December1st to 15thDay
45%221%11%11%8%
90
16th to endDay
29%7%19%31%12%
96
January1st to 15thNight
26%413%30%20%4
780
16th to endNight
25%212%31%24%4
832
February1st to 15thNight
24%317%33%19%1
764
16th to endNight
22%5%16%36%16%2
684
March1st to 15thNight
21%5%19%33%17%2
780
16th to endNight
21%7%21%35%13%
832
April1st to 15thNight
16%5%21%33%19%3
779
16th to endNight
15%419%39%20%1
584
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
11%110%31%35%8%
716
October1st to 15thNight
11%215%38%28%3
720
16th to endNight
16%113%36%28%3
768
November1st to 15thNight
24%213%34%22%2
760
16th to endNight
25%316%32%18%4
780
December1st to 15thNight
22%416%33%19%3
780
16th to endNight
31%316%32%13%1
832
Page generated at 2018-04-24 08:03:04. Version ac04

Copyright 2018 A. Danko


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