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 2019-09-17.

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%
18286
21%
54718
18%
18249
61%
18249
30%
33921

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
50%
836
11%
2717
10%
836
52%
836
18%
1938
January16th to endNight
48%
896
12%
2912
13%
896
50%
896
16%
2126
February1st to 15thNight
48%
819
12%
2678
14%
818
49%
818
18%
1914
February16th to endNight
44%
736
15%
2226
15%
736
47%
736
19%
1573
March1st to 15thNight
53%
840
18%
2363
16%
840
56%
840
26%
1607
March16th to endNight
49%
896
16%
2464
12%
896
52%
896
26%
1698
April1st to 15thNight
47%
755
17%
2166
13%
755
50%
755
26%
1430
April16th to endNight
54%
624
23%
1872
18%
624
57%
624
29%
1168
May1st to 15thNight
60%
629
23%
1889
19%
629
63%
629
33%
1108
May16th to endNight
58%
657
15%
1973
15%
657
59%
657
27%
1263
June1st to 15thNight
69%
630
24%
1712
21%
630
72%
630
48%
921
June16th to endNight
69%
472
30%
1591
32%
472
77%
472
60%
639
July1st to 15thNight
75%
517
22%
1717
24%
517
78%
517
44%
850
July16th to endNight
79%
660
25%
1881
23%
627
79%
627
49%
940
August1st to 15thNight
76%
620
29%
1854
24%
617
78%
617
46%
952
August16th to endNight
77%
669
36%
2010
29%
669
79%
669
50%
993
September1st to 15thNight
75%
798
30%
2268
26%
798
78%
798
50%
1160
September16th to endNight
73%
780
34%
2157
28%
780
76%
780
52%
1112
October1st to 15thNight
64%
780
27%
2272
23%
780
67%
780
40%
1295
October16th to endNight
66%
832
32%
2515
28%
832
69%
832
40%
1389
November1st to 15thNight
58%
820
23%
2665
23%
820
61%
820
29%
1607
November16th to endNight
55%
945
18%
2835
18%
945
57%
945
27%
1800
December1st to 15thNight
47%
1050
11%
2940
9%
1050
48%
1050
22%
2105
December16th to endNight
39%
1025
11%
3041
9%
1025
40%
1025
15%
2333

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%2442345%7%48%
55941
Night
11%7%24423446%47%
54912
TransparencyDay
35%6%11%18%18%10%
55635
Night
37%5%11%20%16%8%
54719
SeeingDay
12%5%22%35%20%3
8232
Night
14%216%38%24%2
18298

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%435%5%46%29%
1881
16th to endDay
15%14%5%5%5%345%6%5%27%
2016
February1st to 15thDay
17%15%46%5%3345%6%28%
1845
16th to endDay
11%17%6%7%6%3445%6%26%
1816
March1st to 15thDay
10%10%46%5%25%5%6%7%35%
2257
16th to endDay
15%10%35%435%5%6%7%31%
2464
April1st to 15thDay
16%9%25%5%245%5%7%35%
2439
16th to endDay
11%8%35%423447%44%
2693
May1st to 15thDay
8%5%25%4245%5%8%44%
2721
16th to endDay
12%5%25%5%25%5%6%8%40%
2845
June1st to 15thDay
5%32432345%8%56%
2901
16th to endDay
322211235%73%
3015
July1st to 15thDay
321332335%7%63%
2808
16th to endDay
421321345%6%63%
2883
August1st to 15thDay
3212323447%65%
2680
16th to endDay
3212313346%66%
2896
September1st to 15thDay
4212323345%66%
2350
16th to endDay
6%212222345%66%
2157
October1st to 15thDay
12%5%13423446%49%
2018
16th to endDay
8%5%13323448%53%
2057
November1st to 15thDay
14%8%24423447%44%
1854
16th to endDay
15%8%34423447%40%
1768
December1st to 15thDay
15%12%37%5%35%445%32%
1680
16th to endDay
18%16%47%424336%25%
1897
January1st to 15thNight
17%9%36%5%23346%36%
2717
16th to endNight
16%13%35%433446%33%
2912
February1st to 15thNight
15%12%35%5%33445%35%
2667
16th to endNight
11%13%47%5%235%5%6%34%
2226
March1st to 15thNight
13%10%35%5%2435%7%39%
2363
16th to endNight
11%11%25%5%24446%39%
2464
April1st to 15thNight
14%9%35%5%2433443%
2166
16th to endNight
11%6%35%42345%5%47%
1872
May1st to 15thNight
8%5%145%2446%7%49%
1889
16th to endNight
13%5%25%5%2445%7%43%
1972
June1st to 15thNight
6%21322345%7%60%
1712
16th to endNight
322211245%72%
1591
July1st to 15thNight
331332446%7%56%
1806
16th to endNight
331322345%8%60%
1989
August1st to 15thNight
32144345%5%7%58%
1863
16th to endNight
331232345%7%62%
2010
September1st to 15thNight
4312323445%64%
2268
16th to endNight
7%21231233467%
2157
October1st to 15thNight
10%423323346%56%
2272
16th to endNight
8%414323336%57%
2515
November1st to 15thNight
12%7%24423346%49%
2665
16th to endNight
12%7%245%34346%44%
2835
December1st to 15thNight
15%10%37%42335%6%37%
2940
16th to endNight
21%13%46%5%23345%26%
3041

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
53%11%18%12%3
1882
16th to endDay
54%10%19%11%3
2016
February1st to 15thDay
56%9%13%13%6%
1845
16th to endDay
56%8%14%15%4
1816
March1st to 15thDay
44%9%15%20%9%
2257
16th to endDay
49%7%15%19%7%1
2464
April1st to 15thDay
46%7%12%19%12%1
2439
16th to endDay
39%6%10%22%20%1
2693
May1st to 15thDay
33%6%9%26%18%4
2721
16th to endDay
38%8%9%21%18%3
2848
June1st to 15thDay
25%5%9%20%29%10%
2901
16th to endDay
14%2412%31%34%
3015
July1st to 15thDay
19%36%15%26%28%
2668
16th to endDay
19%46%11%26%32%
2728
August1st to 15thDay
17%37%14%26%30%
2665
16th to endDay
17%35%15%33%23%
2896
September1st to 15thDay
20%36%15%30%23%
2350
16th to endDay
19%38%21%34%11%
2157
October1st to 15thDay
34%5%10%25%19%4
2018
16th to endDay
29%6%14%30%17%1
2057
November1st to 15thDay
39%6%15%22%15%
1854
16th to endDay
43%5%19%22%9%
1768
December1st to 15thDay
53%9%17%13%5%
1680
16th to endDay
60%8%14%12%3
1897
January1st to 15thNight
49%8%20%16%4
2717
16th to endNight
50%9%17%15%5%1
2912
February1st to 15thNight
50%8%14%18%8%
2678
16th to endNight
50%6%12%24%5%
2226
March1st to 15thNight
44%5%13%24%11%
2363
16th to endNight
44%6%12%23%9%2
2464
April1st to 15thNight
44%313%24%11%2
2166
16th to endNight
37%5%9%23%20%2
1872
May1st to 15thNight
31%6%9%24%22%5%
1890
16th to endNight
38%7%11%20%17%3
1973
June1st to 15thNight
21%5%10%20%32%10%
1712
16th to endNight
14%16%13%27%37%
1591
July1st to 15thNight
23%37%13%23%27%
1717
16th to endNight
21%46%12%23%31%
1881
August1st to 15thNight
22%47%13%21%29%
1854
16th to endNight
20%46%12%30%25%
2010
September1st to 15thNight
22%36%13%26%28%
2268
16th to endNight
21%26%17%32%20%
2157
October1st to 15thNight
29%49%26%23%6%
2272
16th to endNight
28%48%32%23%2
2515
November1st to 15thNight
37%412%24%17%3
2665
16th to endNight
40%5%15%25%11%1
2835
December1st to 15thNight
48%7%18%18%6%
2940
16th to endNight
59%5%14%16%3
3041

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
26%215%30%19%6%
180
16th to endDay
29%216%34%14%1
192
February1st to 15thDay
30%6%22%23%14%3
180
16th to endDay
18%8%36%26%8%
319
March1st to 15thDay
17%7%30%33%11%
390
16th to endDay
19%7%31%30%9%
416
April1st to 15thDay
21%9%29%26%12%
389
16th to endDay
15%11%33%21%16%1
378
May1st to 15thDay
11%8%28%31%18%1
408
16th to endDay
13%7%21%33%20%4
458
June1st to 15thDay
5%5%21%38%25%3
606
16th to endDay
3224%39%26%3
570
July1st to 15thDay
2116%45%30%3
425
16th to endDay
5%114%51%23%2
455
August1st to 15thDay
5%118%48%23%2
419
16th to endDay
3113%44%31%5%
460
September1st to 15thDay
5%121%33%29%8%
435
16th to endDay
8%419%35%28%3
380
October1st to 15thDay
14%429%28%17%4
248
16th to endDay
9%218%38%27%4
192
November1st to 15thDay
15%5%20%31%17%10%
180
16th to endDay
23%9%14%30%17%4
180
December1st to 15thDay
16%320%42%12%5%
180
16th to endDay
27%217%43%8%1
192
January1st to 15thNight
22%114%37%21%2
840
16th to endNight
23%215%35%18%4
896
February1st to 15thNight
21%318%38%16%1
824
16th to endNight
16%323%40%15%1
736
March1st to 15thNight
17%317%42%16%2
840
16th to endNight
18%320%40%15%1
896
April1st to 15thNight
19%6%21%35%16%
755
16th to endNight
13%421%37%22%
624
May1st to 15thNight
11%219%39%24%1
630
16th to endNight
14%215%30%33%2
659
June1st to 15thNight
6%416%40%30%1
630
16th to endNight
5%119%36%34%2
472
July1st to 15thNight
4111%41%39%2
517
16th to endNight
6%7%45%39%1
660
August1st to 15thNight
410%48%34%1
620
16th to endNight
5%111%36%42%2
669
September1st to 15thNight
5%112%40%36%4
798
16th to endNight
9%211%32%36%7%
780
October1st to 15thNight
13%314%39%27%2
780
16th to endNight
11%215%37%31%3
832
November1st to 15thNight
14%218%39%22%2
820
16th to endNight
15%318%38%19%4
945
December1st to 15thNight
20%220%40%16%1
1050
16th to endNight
27%417%37%11%1
1025
Page generated at 2019-09-17 19:12:16. Version ac04

Copyright 2019 A. Danko


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