Benson
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Benson clear sky chart from 2005-11-05 to 2017-08-12.

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
76%
15379
35%
46514
31%
15341
81%
15341
52%
22370

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
74%
717
32%
2327
34%
716
77%
716
49%
1093
January16th to endNight
70%
768
35%
2496
35%
768
76%
768
42%
1285
February1st to 15thNight
75%
697
36%
2228
36%
696
82%
696
53%
1016
February16th to endNight
67%
632
40%
1802
34%
632
75%
632
53%
904
March1st to 15thNight
66%
720
40%
1980
31%
720
74%
720
59%
965
March16th to endNight
73%
768
38%
2112
27%
768
81%
768
61%
1009
April1st to 15thNight
67%
662
36%
1921
25%
662
78%
662
58%
894
April16th to endNight
71%
540
44%
1800
38%
540
82%
540
69%
673
May1st to 15thNight
75%
539
39%
1656
32%
539
82%
539
72%
654
May16th to endNight
80%
561
42%
1684
36%
561
84%
561
74%
668
June1st to 15thNight
84%
540
35%
1620
30%
540
85%
540
70%
662
June16th to endNight
85%
540
29%
1620
26%
540
86%
540
56%
750
July1st to 15thNight
83%
510
18%
1530
16%
510
83%
510
37%
862
July16th to endNight
80%
564
14%
1593
13%
531
79%
531
25%
1041
August1st to 15thNight
80%
527
22%
1575
22%
524
80%
524
35%
918
August16th to endNight
82%
525
25%
1726
27%
525
82%
525
34%
985
September1st to 15thNight
76%
641
27%
1796
24%
641
77%
641
36%
1102
September16th to endNight
86%
656
40%
1815
33%
656
89%
656
64%
858
October1st to 15thNight
82%
660
40%
1938
33%
660
87%
660
65%
860
October16th to endNight
86%
704
43%
2112
39%
704
89%
704
69%
902
November1st to 15thNight
81%
700
42%
2100
37%
700
85%
700
68%
879
November16th to endNight
73%
720
39%
2247
36%
720
78%
720
54%
1046
December1st to 15thNight
73%
720
37%
2340
38%
720
77%
720
49%
1093
December16th to endNight
68%
768
34%
2496
35%
768
72%
768
43%
1251

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
2213324446%64%
47451
Night
2212323346%67%
46714
TransparencyDay
20%47%12%26%28%
47146
Night
17%47%14%28%27%
46520
SeeingDay
5%8%20%30%24%11%
5215
Night
3212%39%36%5%
15392

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
2313313346%65%
1611
16th to endDay
4324412346%61%
1728
February1st to 15thDay
3212214235%69%
1628
16th to endDay
3312323345%65%
1669
March1st to 15thDay
2112223346%68%
1980
16th to endDay
2111213235%74%
2112
April1st to 15thDay
2111213346%71%
2027
16th to endDay
111111111483%
2160
May1st to 15thDay
11212235%77%
2291
16th to endDay
1111222481%
2429
June1st to 15thDay
1121233478%
2340
16th to endDay
2213323446%65%
2340
July1st to 15thDay
3325%6%47%7%6%11%41%
2340
16th to endDay
7%426%7%5%7%8%9%10%30%
2467
August1st to 15thDay
4426%6%48%7%8%8%36%
2290
16th to endDay
3325%6%36%6%7%10%43%
2124
September1st to 15thDay
6%5%246%46%5%6%7%45%
1832
16th to endDay
313314345%68%
1815
October1st to 15thDay
112212335%72%
1691
16th to endDay
111213235%76%
1760
November1st to 15thDay
111111335%76%
1759
16th to endDay
2212223336%69%
1710
December1st to 15thDay
4312314347%64%
1620
16th to endDay
3314313248%61%
1728
January1st to 15thNight
3213313345%66%
2327
16th to endNight
5%323423446%59%
2496
February1st to 15thNight
2213223336%69%
2221
16th to endNight
13123145%5%6%64%
1802
March1st to 15thNight
2212312345%69%
1980
16th to endNight
1212112335%73%
2112
April1st to 15thNight
1112213335%72%
1921
16th to endNight
1111222383%
1800
May1st to 15thNight
11111236%79%
1656
16th to endNight
11222384%
1684
June1st to 15thNight
21112135%79%
1620
16th to endNight
112323446%68%
1620
July1st to 15thNight
3223436%6%7%12%47%
1620
16th to endNight
23346%46%7%10%17%33%
1701
August1st to 15thNight
2324435%5%7%10%50%
1584
16th to endNight
4214435%7%8%10%47%
1726
September1st to 15thNight
6%4245%3437%8%50%
1796
16th to endNight
212212335%73%
1815
October1st to 15thNight
21212245%76%
1938
16th to endNight
1112222479%
2112
November1st to 15thNight
111112245%77%
2100
16th to endNight
4312212235%69%
2247
December1st to 15thNight
4312212347%66%
2340
16th to endNight
4224423346%61%
2496

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
19%46%14%32%22%
1612
16th to endDay
23%3416%29%23%
1728
February1st to 15thDay
18%2412%30%30%
1628
16th to endDay
21%3412%33%24%
1669
March1st to 15thDay
17%248%34%32%
1980
16th to endDay
14%248%37%33%
2112
April1st to 15thDay
14%236%39%33%
2027
16th to endDay
8%127%29%49%
2160
May1st to 15thDay
10%147%26%48%
2291
16th to endDay
9%137%28%49%
2432
June1st to 15thDay
10%235%21%56%
2340
16th to endDay
18%35%8%19%43%
2340
July1st to 15thDay
31%11%14%14%15%11%
2201
16th to endDay
43%15%19%14%6%1
2312
August1st to 15thDay
39%11%12%14%16%4
2275
16th to endDay
31%9%15%18%15%9%
2124
September1st to 15thDay
35%6%11%16%17%11%
1832
16th to endDay
17%35%13%33%26%
1815
October1st to 15thDay
13%36%13%28%34%
1691
16th to endDay
11%2411%30%39%
1760
November1st to 15thDay
10%2313%37%32%
1759
16th to endDay
18%2412%30%31%
1710
December1st to 15thDay
20%25%17%33%19%
1620
16th to endDay
22%37%20%32%13%
1728
January1st to 15thNight
20%26%13%31%25%
2327
16th to endNight
25%45%15%30%19%
2496
February1st to 15thNight
17%35%15%28%30%
2232
16th to endNight
18%35%13%34%23%
1802
March1st to 15thNight
16%2410%30%34%
1980
16th to endNight
14%3410%35%31%
2112
April1st to 15thNight
16%239%39%28%
1921
16th to endNight
9%128%29%48%
1800
May1st to 15thNight
7%248%31%44%
1657
16th to endNight
7%137%32%46%
1685
June1st to 15thNight
10%13424%55%
1620
16th to endNight
15%35%7%22%44%
1620
July1st to 15thNight
24%10%19%20%13%12%
1530
16th to endNight
32%15%25%19%41
1593
August1st to 15thNight
25%11%15%20%19%6%
1575
16th to endNight
27%10%18%18%15%10%
1726
September1st to 15thNight
29%9%11%20%19%9%
1796
16th to endNight
13%25%17%36%23%
1815
October1st to 15thNight
12%36%17%28%32%
1938
16th to endNight
10%2413%27%41%
2112
November1st to 15thNight
10%2417%33%31%
2100
16th to endNight
18%2412%28%33%
2247
December1st to 15thNight
19%35%18%32%20%
2340
16th to endNight
24%38%18%31%13%
2496

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
413%17%48%13%2
90
16th to endDay
5%6%18%37%25%7%
96
February1st to 15thDay
6%11%17%24%33%5%
143
16th to endDay
7%22%28%23%14%2
238
March1st to 15thDay
7%15%27%24%15%9%
270
16th to endDay
222%25%28%12%9%
288
April1st to 15thDay
5%13%34%23%16%5%
269
16th to endDay
5%20%32%24%12%4
270
May1st to 15thDay
216%32%27%13%7%
288
16th to endDay
17%31%35%18%5%
330
June1st to 15thDay
3326%38%16%12%
315
16th to endDay
4113%38%26%15%
315
July1st to 15thDay
6%8%34%36%14%
305
16th to endDay
8%10%26%32%22%
327
August1st to 15thDay
6%6%28%34%23%
300
16th to endDay
47%32%32%22%
268
September1st to 15thDay
15%19%32%29%10%
255
16th to endDay
6%420%27%29%12%
255
October1st to 15thDay
1323%32%22%16%
131
16th to endDay
1429%44%20%
96
November1st to 15thDay
38%17%28%36%4
90
16th to endDay
5%10%27%28%25%2
90
December1st to 15thDay
3417%31%36%6%
90
16th to endDay
10%11%26%32%18%1
96
January1st to 15thNight
4212%50%27%2
720
16th to endNight
7%213%49%24%1
768
February1st to 15thNight
2413%47%28%2
704
16th to endNight
3322%50%19%
632
March1st to 15thNight
35%20%42%26%2
720
16th to endNight
2317%42%30%2
768
April1st to 15thNight
3420%51%19%1
662
16th to endNight
2322%45%24%2
540
May1st to 15thNight
1219%45%29%1
540
16th to endNight
214%47%34%1
563
June1st to 15thNight
229%47%37%2
540
16th to endNight
26%34%53%2
540
July1st to 15thNight
3225%59%9%
510
16th to endNight
3216%61%14%
564
August1st to 15thNight
4211%62%18%
527
16th to endNight
5%215%61%13%
525
September1st to 15thNight
7%1419%55%10%
641
16th to endNight
26%35%47%7%
656
October1st to 15thNight
211%44%36%5%
660
16th to endNight
117%39%44%6%
704
November1st to 15thNight
1112%40%38%5%
700
16th to endNight
5%114%41%32%4
720
December1st to 15thNight
6%313%45%28%3
720
16th to endNight
5%316%47%21%5%
768
Page generated at 2017-08-13 11:16:46. Version ac04

Copyright 2017 A. Danko


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