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 2018-02-14.

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%
16105
35%
48756
32%
16067
81%
16067
52%
23394

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%
777
32%
2522
33%
776
77%
776
49%
1190
January16th to endNight
71%
832
36%
2704
37%
832
77%
832
44%
1356
February1st to 15thNight
76%
753
37%
2406
36%
752
83%
752
54%
1087
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%
539
22%
1611
21%
536
80%
536
35%
935
August16th to endNight
82%
573
27%
1884
30%
573
82%
573
35%
1059
September1st to 15thNight
76%
699
26%
1959
23%
699
77%
699
37%
1198
September16th to endNight
86%
716
43%
1980
35%
716
90%
716
66%
919
October1st to 15thNight
83%
720
39%
2114
32%
720
88%
720
66%
930
October16th to endNight
86%
768
44%
2304
40%
768
89%
768
69%
980
November1st to 15thNight
81%
760
41%
2280
36%
760
85%
760
65%
978
November16th to endNight
74%
780
41%
2435
38%
780
79%
780
54%
1127
December1st to 15thNight
71%
780
36%
2535
37%
780
75%
780
47%
1207
December16th to endNight
69%
832
36%
2704
36%
832
73%
832
44%
1346

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%
49312
Night
2212323346%67%
48956
TransparencyDay
20%46%12%27%28%
49007
Night
17%47%14%28%27%
48762
SeeingDay
5%7%19%30%25%12%
5831
Night
3212%39%36%5%
16118

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
2313323446%64%
1746
16th to endDay
4324413346%63%
1872
February1st to 15thDay
3212214235%69%
1750
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%37%
2340
16th to endDay
3325%6%36%6%7%10%45%
2318
September1st to 15thDay
6%4236%46%5%6%7%46%
1998
16th to endDay
312213345%69%
1980
October1st to 15thDay
111212345%73%
1845
16th to endDay
111213335%76%
1920
November1st to 15thDay
111112446%74%
1909
16th to endDay
2212222335%70%
1852
December1st to 15thDay
5%312314347%62%
1755
16th to endDay
4314313248%62%
1872
January1st to 15thNight
3213313345%65%
2522
16th to endNight
5%213323346%62%
2704
February1st to 15thNight
2213223336%70%
2399
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%
1620
16th to endNight
4214425%6%8%10%48%
1884
September1st to 15thNight
6%4245%3446%8%50%
1959
16th to endNight
212212335%75%
1980
October1st to 15thNight
1121224477%
2114
16th to endNight
1112222480%
2304
November1st to 15thNight
111213245%74%
2280
16th to endNight
3312212336%69%
2435
December1st to 15thNight
5%312312347%64%
2535
16th to endNight
4214423335%62%
2704

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
20%46%14%32%21%
1747
16th to endDay
22%3315%30%23%
1872
February1st to 15thDay
18%3412%30%30%
1750
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%17%4
2325
16th to endDay
31%8%14%16%16%10%
2318
September1st to 15thDay
34%6%11%16%17%13%
1998
16th to endDay
16%35%13%34%26%
1980
October1st to 15thDay
13%36%12%28%34%
1845
16th to endDay
10%25%11%30%39%
1920
November1st to 15thDay
11%3315%36%30%
1909
16th to endDay
17%2412%31%31%
1852
December1st to 15thDay
22%25%17%33%18%
1755
16th to endDay
22%37%19%32%13%
1872
January1st to 15thNight
20%36%13%32%23%
2522
16th to endNight
23%35%15%31%21%
2704
February1st to 15thNight
16%35%15%27%31%
2410
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%16%21%19%6%
1611
16th to endNight
26%9%17%17%17%11%
1884
September1st to 15thNight
29%8%11%19%20%10%
1959
16th to endNight
12%25%17%37%24%
1980
October1st to 15thNight
11%36%16%29%33%
2114
16th to endNight
10%2413%28%40%
2304
November1st to 15thNight
11%3418%32%29%
2280
16th to endNight
18%2411%29%33%
2435
December1st to 15thNight
20%35%18%32%19%
2535
16th to endNight
23%37%17%31%15%
2704

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
311%13%42%25%4
135
16th to endDay
35%18%39%22%9%
144
February1st to 15thDay
5%11%16%24%34%8%
187
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%
315
16th to endDay
6%6%28%32%25%
332
September1st to 15thDay
12%17%34%30%12%
315
16th to endDay
5%420%27%31%10%
315
October1st to 15thDay
1319%32%27%15%
180
16th to endDay
16%27%41%23%
144
November1st to 15thDay
27%16%28%40%4
135
16th to endDay
37%21%28%30%8%
135
December1st to 15thDay
8%421%31%30%4
135
16th to endDay
10%9%20%25%25%9%
144
January1st to 15thNight
4212%49%28%2
780
16th to endNight
7%213%50%25%1
832
February1st to 15thNight
2313%46%30%3
760
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%
539
16th to endNight
5%215%62%13%
573
September1st to 15thNight
7%1420%56%9%
699
16th to endNight
26%37%45%6%
716
October1st to 15thNight
210%44%37%5%
720
16th to endNight
117%37%45%6%
768
November1st to 15thNight
1111%41%38%5%
760
16th to endNight
5%113%40%33%4
780
December1st to 15thNight
6%214%45%27%3
780
16th to endNight
5%315%47%22%5%
832
Page generated at 2018-02-15 08:58:41. Version ac04

Copyright 2018 A. Danko


Benson Clear Sky Chart |Charts Home