Ketchum
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ketchum clear sky chart from 2005-11-05 to 2017-09-18.

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%
15110
22%
46939
18%
15083
63%
15083
34%
26625

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
53%
716
17%
2506
14%
716
58%
716
24%
1497
January16th to endNight
55%
768
22%
2667
21%
768
61%
768
29%
1529
February1st to 15thNight
47%
697
14%
2261
11%
696
53%
696
24%
1435
February16th to endNight
44%
632
16%
1895
12%
632
52%
632
25%
1232
March1st to 15thNight
47%
720
16%
2103
12%
720
52%
720
26%
1365
March16th to endNight
44%
768
16%
2112
10%
768
49%
768
28%
1359
April1st to 15thNight
47%
695
20%
1781
9%
695
52%
695
29%
1165
April16th to endNight
48%
540
23%
1620
13%
540
55%
540
36%
897
May1st to 15thNight
55%
539
21%
1619
15%
539
61%
539
40%
853
May16th to endNight
59%
462
14%
1586
15%
462
63%
462
28%
927
June1st to 15thNight
61%
360
18%
1338
21%
360
67%
360
31%
717
June16th to endNight
76%
360
27%
1355
36%
360
83%
360
49%
565
July1st to 15thNight
80%
340
23%
1360
34%
340
86%
340
49%
549
July16th to endNight
81%
394
30%
1433
39%
371
84%
371
52%
570
August1st to 15thNight
77%
539
29%
1611
24%
536
79%
536
52%
776
August16th to endNight
78%
615
37%
1761
28%
615
80%
615
58%
839
September1st to 15thNight
78%
720
32%
1899
23%
720
81%
720
59%
949
September16th to endNight
72%
667
34%
1847
28%
667
75%
667
48%
976
October1st to 15thNight
65%
660
30%
1872
23%
660
71%
660
45%
999
October16th to endNight
61%
704
25%
2249
20%
704
68%
704
37%
1211
November1st to 15thNight
59%
700
24%
2275
24%
700
63%
700
33%
1259
November16th to endNight
49%
759
19%
2379
13%
759
57%
759
28%
1423
December1st to 15thNight
45%
900
13%
2635
8%
900
51%
900
26%
1721
December16th to endNight
42%
855
18%
2775
11%
855
51%
855
22%
1812

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
5%7%35%5%3445%7%47%
47859
Night
46%2442445%7%52%
47113
TransparencyDay
34%6%12%21%17%7%
47532
Night
30%6%14%24%17%7%
46940
SeeingDay
12%20%32%22%9%2
5466
Night
8%6%19%38%21%5%
15124

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
210%25%5%3445%9%45%
1432
16th to endDay
211%5%6%42445%8%43%
1557
February1st to 15thDay
39%46%425%5%5%9%42%
1601
16th to endDay
413%6%9%6%35%45%6%32%
1579
March1st to 15thDay
413%48%5%35%5%6%8%32%
1857
16th to endDay
8%14%37%6%35%46%7%32%
2112
April1st to 15thDay
6%10%5%9%7%35%5%5%7%32%
2164
16th to endDay
6%10%37%5%245%5%8%40%
2340
May1st to 15thDay
5%7%37%5%345%6%7%41%
2331
16th to endDay
8%10%48%8%5%7%6%5%6%29%
2525
June1st to 15thDay
10%5%35%6%25%5%6%8%39%
2616
16th to endDay
3213224346%65%
2598
July1st to 15thDay
331333345%7%60%
2520
16th to endDay
331433334464%
2639
August1st to 15thDay
3213435%5%5%6%57%
2340
16th to endDay
2213324335%65%
2441
September1st to 15thDay
4422223335%62%
2061
16th to endDay
8%31331335%6%58%
1838
October1st to 15thDay
7%7%34425%446%49%
1757
16th to endDay
5%5%24435%47%7%48%
1620
November1st to 15thDay
6%7%25%5%345%6%8%45%
1584
16th to endDay
48%46%43446%8%44%
1566
December1st to 15thDay
413%35%6%345%5%7%38%
1323
16th to endDay
5%15%36%6%4445%8%35%
1458
January1st to 15thNight
37%35%5%2446%9%47%
2506
16th to endNight
211%4432335%8%49%
2667
February1st to 15thNight
27%37%5%36%5%6%9%41%
2250
16th to endNight
410%47%5%2445%7%41%
1895
March1st to 15thNight
49%45%5%247%7%8%40%
2103
16th to endNight
7%10%344235%6%8%43%
2112
April1st to 15thNight
48%45%425%6%6%8%43%
1781
16th to endNight
5%6%233235%5%9%52%
1620
May1st to 15thNight
3313335%46%7%57%
1619
16th to endNight
6%5%244246%8%9%43%
1585
June1st to 15thNight
8%313435%5%5%8%50%
1338
16th to endNight
2211313345%70%
1355
July1st to 15thNight
2314447%68%
1440
16th to endNight
111232333473%
1530
August1st to 15thNight
2113323347%65%
1620
16th to endNight
112312346%70%
1761
September1st to 15thNight
3212222325%71%
1899
16th to endNight
6%313322345%63%
1847
October1st to 15thNight
7%31232335%6%61%
1872
16th to endNight
6%3143245%6%8%53%
2249
November1st to 15thNight
6%5%13325%47%8%49%
2275
16th to endNight
38%244345%7%7%46%
2379
December1st to 15thNight
5%8%26%6%35%6%5%9%39%
2635
16th to endNight
413%5%6%5%245%5%6%39%
2775

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
33%10%20%23%9%2
1432
16th to endDay
38%6%16%23%9%4
1557
February1st to 15thDay
37%9%21%21%7%2
1601
16th to endDay
49%8%15%19%6%1
1579
March1st to 15thDay
46%8%16%21%6%1
1857
16th to endDay
47%9%15%18%7%1
2112
April1st to 15thDay
48%7%15%17%10%
2164
16th to endDay
40%5%15%23%15%1
2340
May1st to 15thDay
40%6%11%26%14%1
2331
16th to endDay
50%6%12%19%8%1
2528
June1st to 15thDay
39%7%10%24%14%3
2616
16th to endDay
19%35%23%38%9%
2598
July1st to 15thDay
19%3419%30%21%
2371
16th to endDay
20%3312%24%35%
2473
August1st to 15thDay
22%45%18%27%20%
2325
16th to endDay
20%35%22%29%18%
2441
September1st to 15thDay
22%47%20%30%15%
2061
16th to endDay
25%39%29%24%6%
1838
October1st to 15thDay
34%6%16%25%14%3
1757
16th to endDay
31%7%15%27%16%
1620
November1st to 15thDay
35%6%18%24%13%2
1584
16th to endDay
35%6%19%22%12%3
1566
December1st to 15thDay
43%7%20%23%5%
1323
16th to endDay
45%7%16%20%8%2
1458
January1st to 15thNight
34%9%20%21%11%2
2506
16th to endNight
32%6%14%26%14%4
2667
February1st to 15thNight
38%8%19%21%10%1
2261
16th to endNight
40%6%18%24%7%1
1895
March1st to 15thNight
37%8%16%24%11%1
2103
16th to endNight
37%6%18%26%9%1
2112
April1st to 15thNight
36%7%14%27%12%1
1781
16th to endNight
28%418%30%17%
1620
May1st to 15thNight
24%413%38%17%
1620
16th to endNight
34%6%17%27%12%1
1586
June1st to 15thNight
30%5%12%31%17%2
1338
16th to endNight
16%45%21%37%15%
1355
July1st to 15thNight
16%35%18%31%24%
1360
16th to endNight
15%2311%25%41%
1433
August1st to 15thNight
19%37%17%25%27%
1611
16th to endNight
15%35%18%31%25%
1761
September1st to 15thNight
16%37%20%36%16%
1899
16th to endNight
23%38%29%25%9%
1847
October1st to 15thNight
24%314%35%17%5%
1872
16th to endNight
26%6%14%31%19%1
2249
November1st to 15thNight
29%6%17%25%18%3
2275
16th to endNight
32%8%17%22%15%3
2379
December1st to 15thNight
38%8%22%21%8%
2635
16th to endNight
43%5%14%23%9%2
2775

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
15%10%23%25%13%13%
60
16th to endDay
14%11%25%22%20%4
67
February1st to 15thDay
16%18%28%13%18%4
116
16th to endDay
21%23%32%18%31
238
March1st to 15thDay
15%28%35%18%1
270
16th to endDay
20%28%35%14%1
288
April1st to 15thDay
16%28%28%16%6%2
269
16th to endDay
17%27%32%16%41
270
May1st to 15thDay
11%25%32%21%7%1
288
16th to endDay
16%20%21%26%12%3
330
June1st to 15thDay
12%20%24%26%12%2
411
16th to endDay
7%18%34%21%14%3
393
July1st to 15thDay
5%18%34%27%12%1
305
16th to endDay
5%20%40%21%8%2
327
August1st to 15thDay
5%18%37%26%10%2
315
16th to endDay
416%37%25%10%5%
332
September1st to 15thDay
11%14%32%23%12%5%
315
16th to endDay
10%15%35%25%9%1
264
October1st to 15thDay
12%20%29%27%7%2
197
16th to endDay
18%10%29%29%10%2
96
November1st to 15thDay
8%6%21%32%27%3
90
16th to endDay
11%15%35%26%10%1
90
December1st to 15thDay
23%14%29%26%5%
71
16th to endDay
15%14%28%25%14%3
64
January1st to 15thNight
7%7%21%41%18%3
720
16th to endNight
11%6%19%37%21%4
768
February1st to 15thNight
8%8%25%39%14%3
704
16th to endNight
12%7%24%37%13%3
632
March1st to 15thNight
10%8%24%37%15%3
720
16th to endNight
13%15%20%34%13%1
768
April1st to 15thNight
9%11%23%34%15%5%
695
16th to endNight
7%10%27%36%15%2
540
May1st to 15thNight
5%10%24%31%25%2
540
16th to endNight
9%317%34%26%7%
464
June1st to 15thNight
10%315%42%24%3
360
16th to endNight
3413%45%28%5%
360
July1st to 15thNight
19%41%41%4
340
16th to endNight
2110%41%38%6%
394
August1st to 15thNight
3112%44%32%5%
539
16th to endNight
2211%42%35%6%
615
September1st to 15thNight
419%35%36%11%
720
16th to endNight
7%310%32%31%13%
667
October1st to 15thNight
9%416%36%24%8%
660
16th to endNight
8%5%17%40%18%8%
704
November1st to 15thNight
9%6%19%40%21%3
700
16th to endNight
9%6%25%37%14%5%
759
December1st to 15thNight
11%8%24%41%11%2
900
16th to endNight
13%9%23%37%13%2
855
Page generated at 2017-09-19 05:32:26. Version ac04

Copyright 2017 A. Danko


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