This page made possible by the sponsorship of: Dr. John Sohl.

Ogden
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ogden 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
58%
15525
20%
46453
18%
15488
60%
15488
30%
28853

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
49%
716
10%
2327
11%
716
50%
716
17%
1694
January16th to endNight
48%
768
12%
2496
13%
768
50%
768
16%
1820
February1st to 15thNight
49%
699
11%
2288
12%
698
51%
698
19%
1615
February16th to endNight
47%
632
17%
1911
16%
632
50%
632
22%
1294
March1st to 15thNight
55%
720
19%
2025
17%
720
58%
720
27%
1349
March16th to endNight
48%
768
17%
2112
13%
768
51%
768
26%
1455
April1st to 15thNight
48%
647
17%
1856
13%
647
51%
647
27%
1202
April16th to endNight
54%
540
24%
1620
19%
540
56%
540
28%
1032
May1st to 15thNight
58%
539
22%
1619
18%
539
61%
539
33%
954
May16th to endNight
60%
561
17%
1685
16%
561
61%
561
29%
1051
June1st to 15thNight
67%
540
22%
1467
19%
540
70%
540
46%
799
June16th to endNight
71%
404
32%
1363
35%
404
79%
404
62%
540
July1st to 15thNight
74%
439
19%
1459
21%
439
76%
439
42%
735
July16th to endNight
79%
564
26%
1593
24%
531
80%
531
49%
797
August1st to 15thNight
76%
527
29%
1575
24%
524
78%
524
47%
802
August16th to endNight
77%
525
34%
1578
28%
525
80%
525
48%
795
September1st to 15thNight
73%
627
29%
1782
25%
627
76%
627
47%
935
September16th to endNight
73%
656
35%
1815
29%
656
75%
656
53%
925
October1st to 15thNight
66%
660
28%
1922
24%
660
69%
660
40%
1087
October16th to endNight
63%
704
30%
2128
27%
704
66%
704
37%
1217
November1st to 15thNight
59%
700
22%
2275
22%
700
62%
700
29%
1368
November16th to endNight
55%
810
19%
2430
18%
810
56%
810
28%
1534
December1st to 15thNight
44%
900
10%
2520
7%
900
46%
900
20%
1829
December16th to endNight
36%
879
11%
2607
9%
879
38%
879
14%
2024

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
9%7%24423446%48%
47492
Night
11%7%24423446%47%
46647
TransparencyDay
35%6%11%18%18%10%
47186
Night
37%5%11%20%15%9%
46454
SeeingDay
11%5%23%36%20%2
5422
Night
14%217%38%24%2
15537

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
16%13%37%5%35%436%29%
1611
16th to endDay
15%14%45%5%35%5%6%5%29%
1728
February1st to 15thDay
16%14%35%4335%5%5%31%
1575
16th to endDay
12%15%5%6%5%3446%6%29%
1560
March1st to 15thDay
9%9%35%425%5%6%7%38%
1935
16th to endDay
15%10%35%435%5%6%7%31%
2112
April1st to 15thDay
14%8%245%345%5%8%38%
2089
16th to endDay
11%9%35%424447%42%
2340
May1st to 15thDay
8%6%244245%5%8%44%
2331
16th to endDay
12%424425%5%5%8%43%
2429
June1st to 15thDay
6%42442345%8%52%
2487
16th to endDay
42111123475%
2584
July1st to 15thDay
321332335%7%63%
2406
16th to endDay
421231345%6%64%
2467
August1st to 15thDay
3212323446%65%
2290
16th to endDay
4212313446%66%
2272
September1st to 15thDay
4213323335%64%
1846
16th to endDay
6%212222335%68%
1815
October1st to 15thDay
12%413423447%49%
1708
16th to endDay
9%6%14423447%50%
1741
November1st to 15thDay
14%8%24423347%45%
1584
16th to endDay
14%9%34423447%40%
1516
December1st to 15thDay
16%12%38%5%35%445%29%
1440
16th to endDay
18%17%5%7%434336%25%
1626
January1st to 15thNight
18%10%36%5%33336%36%
2327
16th to endNight
16%13%25%433445%34%
2496
February1st to 15thNight
15%11%345%34445%36%
2277
16th to endNight
11%11%45%5%2245%6%38%
1911
March1st to 15thNight
12%10%34423447%41%
2025
16th to endNight
11%11%35%5%24446%40%
2112
April1st to 15thNight
12%9%35%5%2434445%
1856
16th to endNight
12%6%25%42445%6%45%
1620
May1st to 15thNight
9%5%1442445%6%50%
1619
16th to endNight
12%42442445%7%46%
1684
June1st to 15thNight
6%21322345%7%58%
1467
16th to endNight
31221123475%
1363
July1st to 15thNight
3413425%5%6%7%56%
1548
16th to endNight
331322345%7%60%
1701
August1st to 15thNight
3214433447%60%
1584
16th to endNight
331232445%7%61%
1578
September1st to 15thNight
431341444462%
1782
16th to endNight
7%21231223468%
1815
October1st to 15thNight
10%422323346%57%
1922
16th to endNight
9%5%14323336%54%
2128
November1st to 15thNight
12%7%23423346%49%
2275
16th to endNight
11%8%246%34346%45%
2430
December1st to 15thNight
17%9%37%42335%6%35%
2520
16th to endNight
21%14%47%6%23345%26%
2607

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
55%11%18%12%2
1612
16th to endDay
53%10%19%11%3
1728
February1st to 15thDay
53%10%14%14%7%
1575
16th to endDay
52%8%15%17%41
1560
March1st to 15thDay
41%10%15%21%10%
1935
16th to endDay
49%6%14%19%7%1
2112
April1st to 15thDay
42%7%13%21%13%1
2089
16th to endDay
40%6%8%23%18%1
2340
May1st to 15thDay
33%7%9%25%19%4
2331
16th to endDay
36%7%9%22%20%3
2432
June1st to 15thDay
27%5%8%19%28%9%
2487
16th to endDay
13%249%31%38%
2584
July1st to 15thDay
19%36%14%23%31%
2266
16th to endDay
19%46%11%24%34%
2312
August1st to 15thDay
17%37%14%24%32%
2275
16th to endDay
18%36%15%31%24%
2272
September1st to 15thDay
22%46%15%29%21%
1846
16th to endDay
19%37%21%36%10%
1815
October1st to 15thDay
33%6%11%27%16%4
1708
16th to endDay
32%6%12%31%17%
1741
November1st to 15thDay
39%7%14%21%15%1
1584
16th to endDay
43%5%18%22%9%
1516
December1st to 15thDay
56%9%17%12%3
1440
16th to endDay
61%8%14%11%31
1626
January1st to 15thNight
51%8%19%16%31
2327
16th to endNight
50%9%15%16%5%1
2496
February1st to 15thNight
48%8%15%19%8%
2288
16th to endNight
45%6%13%26%6%
1911
March1st to 15thNight
42%5%13%25%12%
2025
16th to endNight
44%5%12%23%10%2
2112
April1st to 15thNight
42%312%25%13%3
1856
16th to endNight
39%6%9%23%19%3
1620
May1st to 15thNight
32%6%8%22%23%6%
1620
16th to endNight
36%7%10%21%19%4
1685
June1st to 15thNight
23%411%19%30%9%
1467
16th to endNight
13%15%11%27%41%
1363
July1st to 15thNight
24%47%11%21%30%
1459
16th to endNight
21%46%11%22%33%
1593
August1st to 15thNight
22%47%13%20%31%
1575
16th to endNight
20%46%11%29%25%
1578
September1st to 15thNight
23%36%13%25%26%
1782
16th to endNight
20%26%17%32%20%
1815
October1st to 15thNight
28%410%28%22%6%
1922
16th to endNight
30%46%31%23%2
2128
November1st to 15thNight
37%411%24%17%4
2275
16th to endNight
40%415%25%11%1
2430
December1st to 15thNight
49%7%18%18%4
2520
16th to endNight
60%5%14%15%3
2607

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
31%24%25%11%7%
90
16th to endDay
28%312%36%16%3
96
February1st to 15thDay
32%211%24%24%5%
90
16th to endDay
19%9%35%25%9%1
219
March1st to 15thDay
15%7%27%35%12%
270
16th to endDay
19%7%33%29%9%
288
April1st to 15thDay
14%10%33%23%17%1
269
16th to endDay
17%11%35%21%14%
270
May1st to 15thDay
10%10%33%29%14%
288
16th to endDay
11%7%21%34%20%4
330
June1st to 15thDay
6%5%22%39%23%2
462
16th to endDay
4120%39%29%4
430
July1st to 15thDay
217%47%29%2
305
16th to endDay
3215%53%22%2
327
August1st to 15thDay
4219%51%19%3
300
16th to endDay
5%213%45%28%4
268
September1st to 15thDay
4227%39%22%3
255
16th to endDay
6%215%36%32%5%
255
October1st to 15thDay
13%421%32%21%6%
148
16th to endDay
16%121%35%21%3
96
November1st to 15thDay
11%313%30%25%16%
90
16th to endDay
22%15%21%30%7%3
90
December1st to 15thDay
18%328%38%10%
90
16th to endDay
21%419%40%11%2
96
January1st to 15thNight
22%116%36%20%3
720
16th to endNight
23%215%33%19%4
768
February1st to 15thNight
20%218%38%18%1
704
16th to endNight
16%323%39%15%1
632
March1st to 15thNight
15%317%43%16%2
720
16th to endNight
17%322%40%15%1
768
April1st to 15thNight
16%6%23%34%17%
647
16th to endNight
14%420%37%22%
540
May1st to 15thNight
12%320%40%22%2
540
16th to endNight
14%215%32%33%2
563
June1st to 15thNight
7%5%17%41%27%
540
16th to endNight
4117%36%36%2
404
July1st to 15thNight
4112%40%39%2
439
16th to endNight
6%7%43%40%1
564
August1st to 15thNight
410%47%35%1
527
16th to endNight
5%111%36%43%1
525
September1st to 15thNight
5%113%41%34%2
627
16th to endNight
9%311%29%38%9%
656
October1st to 15thNight
13%213%37%30%2
660
16th to endNight
12%216%34%30%2
704
November1st to 15thNight
14%217%38%24%3
700
16th to endNight
14%319%38%19%4
810
December1st to 15thNight
21%221%38%15%
900
16th to endNight
28%418%34%12%1
879
Page generated at 2017-08-13 12:16:34. Version ac04

Copyright 2017 A. Danko


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