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 2021-07-27.

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%
20779
21%
62191
18%
20742
60%
20742
31%
38301

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
48%
956
11%
3107
10%
956
50%
956
18%
2206
January16th to endNight
47%
1024
12%
3328
12%
1024
49%
1024
16%
2449
February1st to 15thNight
44%
939
12%
3068
12%
938
46%
938
18%
2212
February16th to endNight
43%
844
17%
2553
16%
844
46%
844
20%
1781
March1st to 15thNight
52%
960
19%
2699
16%
960
56%
960
27%
1799
March16th to endNight
47%
1024
16%
2816
12%
1024
51%
1024
26%
1950
April1st to 15thNight
47%
863
19%
2475
13%
863
51%
863
27%
1606
April16th to endNight
54%
714
25%
2142
19%
714
57%
714
31%
1314
May1st to 15thNight
58%
719
23%
2159
18%
719
62%
719
33%
1268
May16th to endNight
57%
753
17%
2261
15%
753
59%
753
27%
1417
June1st to 15thNight
67%
720
26%
1956
21%
720
72%
720
49%
1043
June16th to endNight
67%
539
30%
1817
31%
539
75%
539
55%
762
July1st to 15thNight
75%
595
23%
1975
25%
595
78%
595
46%
958
July16th to endNight
79%
744
25%
2133
24%
711
79%
711
49%
1066
August1st to 15thNight
77%
665
29%
1989
24%
662
79%
662
48%
1006
August16th to endNight
76%
717
36%
2155
30%
717
79%
717
50%
1064
September1st to 15thNight
75%
855
30%
2430
26%
855
78%
855
51%
1226
September16th to endNight
70%
896
35%
2475
28%
896
74%
896
53%
1270
October1st to 15thNight
64%
900
28%
2620
23%
900
69%
900
43%
1438
October16th to endNight
62%
960
33%
2902
27%
960
68%
960
41%
1584
November1st to 15thNight
59%
940
23%
3055
22%
940
62%
940
31%
1795
November16th to endNight
55%
1080
19%
3240
18%
1080
57%
1080
28%
2042
December1st to 15thNight
46%
1200
12%
3360
9%
1200
47%
1200
22%
2395
December16th to endNight
38%
1172
11%
3476
9%
1172
40%
1172
15%
2650

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%49%
63409
Night
10%7%24423446%47%
62385
TransparencyDay
34%6%11%18%18%11%
63103
Night
36%5%11%20%16%9%
62192
SeeingDay
11%5%23%35%20%3
10725
Night
14%318%39%23%2
20791

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
15%14%37%434445%31%
2151
16th to endDay
15%16%5%5%5%345%5%5%26%
2304
February1st to 15thDay
16%16%46%5%33445%28%
2115
16th to endDay
10%16%6%7%6%3445%5%28%
2083
March1st to 15thDay
9%10%46%5%345%6%7%37%
2580
16th to endDay
15%10%36%4345%6%7%32%
2816
April1st to 15thDay
15%8%25%5%3445%7%38%
2789
16th to endDay
10%8%35%423447%45%
3083
May1st to 15thDay
8%6%25%4245%5%8%45%
3111
16th to endDay
11%5%25%5%35%5%6%8%40%
3261
June1st to 15thDay
5%31432345%8%56%
3316
16th to endDay
422211335%71%
3445
July1st to 15thDay
321322335%7%65%
3208
16th to endDay
421221345%6%64%
3240
August1st to 15thDay
3212322446%65%
2875
16th to endDay
3212313346%66%
3103
September1st to 15thDay
3212322335%68%
2518
16th to endDay
7%212222335%67%
2475
October1st to 15thDay
10%413423446%54%
2329
16th to endDay
7%5%24422447%54%
2374
November1st to 15thDay
13%8%24423447%46%
2124
16th to endDay
14%9%34423447%41%
2021
December1st to 15thDay
14%12%37%5%34445%33%
1920
16th to endDay
17%16%47%434336%26%
2168
January1st to 15thNight
16%10%36%5%23347%35%
3107
16th to endNight
15%14%36%433446%32%
3328
February1st to 15thNight
14%14%35%5%33445%34%
3057
16th to endNight
11%13%47%5%225%5%5%35%
2553
March1st to 15thNight
12%9%35%5%2335%7%40%
2699
16th to endNight
11%11%35%5%24446%39%
2816
April1st to 15thNight
13%9%35%5%2333445%
2475
16th to endNight
10%6%25%42345%5%48%
2142
May1st to 15thNight
8%5%1442446%6%49%
2159
16th to endNight
12%5%245%2445%7%44%
2260
June1st to 15thNight
6%21331345%7%60%
1956
16th to endNight
4212312336%69%
1817
July1st to 15thNight
331332446%7%58%
2064
16th to endNight
331322345%8%59%
2241
August1st to 15thNight
3213434447%60%
1998
16th to endNight
231332345%6%62%
2155
September1st to 15thNight
431231334466%
2430
16th to endNight
7%21221223467%
2475
October1st to 15thNight
9%422312345%59%
2620
16th to endNight
8%413323336%59%
2902
November1st to 15thNight
11%7%24423346%50%
3055
16th to endNight
12%8%245%34346%44%
3240
December1st to 15thNight
14%10%37%423346%37%
3360
16th to endNight
19%13%47%6%24346%27%
3476

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
52%10%18%14%2
2152
16th to endDay
56%9%17%12%3
2304
February1st to 15thDay
56%8%13%13%6%
2115
16th to endDay
53%8%14%15%5%1
2083
March1st to 15thDay
42%9%14%22%10%
2580
16th to endDay
48%7%14%20%7%1
2816
April1st to 15thDay
44%7%11%18%14%2
2789
16th to endDay
38%6%9%23%20%1
3083
May1st to 15thDay
33%6%9%25%20%4
3111
16th to endDay
36%8%10%22%18%3
3264
June1st to 15thDay
24%49%20%29%12%
3316
16th to endDay
15%2413%31%32%
3445
July1st to 15thDay
17%36%14%25%32%
3068
16th to endDay
18%36%11%26%33%
3085
August1st to 15thDay
17%37%13%25%32%
2860
16th to endDay
17%35%14%34%23%
3103
September1st to 15thDay
19%36%14%30%25%
2518
16th to endDay
19%38%22%34%12%
2475
October1st to 15thDay
30%5%9%25%21%8%
2329
16th to endDay
29%5%14%30%17%1
2374
November1st to 15thDay
38%6%15%22%16%1
2124
16th to endDay
42%5%18%22%10%
2021
December1st to 15thDay
52%10%16%12%6%1
1920
16th to endDay
59%7%13%13%4
2168
January1st to 15thNight
49%8%20%17%3
3107
16th to endNight
51%9%16%14%5%1
3328
February1st to 15thNight
51%7%13%18%8%
3068
16th to endNight
48%6%12%23%7%1
2553
March1st to 15thNight
43%413%25%12%
2699
16th to endNight
44%6%12%23%9%2
2816
April1st to 15thNight
42%312%22%14%5%
2475
16th to endNight
36%5%9%24%21%2
2142
May1st to 15thNight
31%6%9%22%23%5%
2160
16th to endNight
37%7%11%21%18%3
2261
June1st to 15thNight
21%410%19%32%11%
1956
16th to endNight
16%16%14%26%33%
1817
July1st to 15thNight
22%37%12%23%30%
1975
16th to endNight
20%47%12%23%31%
2133
August1st to 15thNight
22%47%13%20%32%
1989
16th to endNight
20%36%12%30%26%
2155
September1st to 15thNight
21%26%13%25%30%
2430
16th to endNight
20%26%17%32%19%
2475
October1st to 15thNight
26%48%25%26%9%
2620
16th to endNight
27%48%33%22%3
2902
November1st to 15thNight
35%411%25%19%3
3055
16th to endNight
40%414%26%11%1
3240
December1st to 15thNight
47%7%17%17%7%1
3360
16th to endNight
58%5%14%16%4
3476

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
22%421%31%15%4
270
16th to endDay
28%321%31%12%1
288
February1st to 15thDay
29%6%29%22%10%2
270
16th to endDay
15%9%39%28%7%
424
March1st to 15thDay
16%8%30%33%11%
510
16th to endDay
19%9%30%29%10%
544
April1st to 15thDay
18%11%29%26%12%
509
16th to endDay
14%11%32%22%16%2
498
May1st to 15thDay
10%9%28%32%18%1
528
16th to endDay
11%9%22%32%19%4
586
June1st to 15thDay
5%6%21%38%23%3
751
16th to endDay
4223%40%24%3
709
July1st to 15thDay
1116%46%30%3
545
16th to endDay
4112%51%27%2
565
August1st to 15thDay
5%116%49%24%3
479
16th to endDay
4112%43%32%5%
524
September1st to 15thDay
4319%32%30%9%
495
16th to endDay
9%421%33%28%3
495
October1st to 15thDay
11%5%28%28%20%5%
349
16th to endDay
9%7%22%36%22%2
288
November1st to 15thDay
15%5%16%32%20%8%
270
16th to endDay
22%8%18%30%16%3
270
December1st to 15thDay
16%322%37%14%5%
270
16th to endDay
22%422%40%8%1
288
January1st to 15thNight
21%117%37%19%2
960
16th to endNight
24%216%36%16%4
1024
February1st to 15thNight
22%321%37%14%
944
16th to endNight
16%325%39%13%1
844
March1st to 15thNight
16%319%43%15%1
960
16th to endNight
18%321%40%14%1
1024
April1st to 15thNight
18%6%23%36%14%
863
16th to endNight
12%422%38%21%
714
May1st to 15thNight
11%321%39%22%1
720
16th to endNight
14%416%32%30%1
755
June1st to 15thNight
6%5%18%40%28%1
720
16th to endNight
5%220%38%31%2
539
July1st to 15thNight
4112%44%35%1
595
16th to endNight
5%7%46%38%1
744
August1st to 15thNight
410%49%33%1
665
16th to endNight
5%111%36%42%1
717
September1st to 15thNight
5%211%41%35%3
855
16th to endNight
9%213%34%32%6%
896
October1st to 15thNight
12%216%41%25%2
900
16th to endNight
10%219%36%27%2
960
November1st to 15thNight
13%218%40%21%2
940
16th to endNight
16%318%39%18%4
1080
December1st to 15thNight
20%121%39%15%1
1200
16th to endNight
26%419%37%10%1
1172
Page generated at 2021-07-28 16:31:19. Version ac04

Copyright 2021 A. Danko


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