Rural Logan County Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rural Logan County Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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
35%
24957
17%
74814
9%
24898
43%
24898
25%
48839

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 10thNight
22%
950
15%
2715
4%
946
33%
946
20%
1882
January11th to 20thNight
25%
920
11%
2575
5%
920
30%
920
17%
1914
January21st to endNight
20%
990
14%
2772
4%
990
28%
990
16%
2075
February1st to 10thNight
27%
900
11%
2412
4%
900
32%
900
19%
1786
February11th to 20thNight
27%
807
16%
2203
6%
803
34%
803
22%
1535
February21st to endNight
33%
592
17%
1776
7%
592
42%
592
21%
1253
March1st to 10thNight
27%
720
11%
2160
6%
720
32%
720
16%
1595
March11th to 20thNight
29%
558
19%
1998
12%
558
39%
558
19%
1303
March21st to endNight
35%
594
14%
2164
10%
594
44%
594
19%
1436
April1st to 10thNight
33%
540
18%
1800
11%
540
45%
540
24%
1119
April11th to 20thNight
37%
533
19%
1617
16%
533
45%
533
23%
1092
April21st to endNight
37%
540
15%
1620
12%
540
43%
540
22%
1109
May1st to 10thNight
42%
540
15%
1620
9%
540
46%
540
28%
1028
May11th to 20thNight
44%
531
16%
1504
8%
531
46%
531
32%
943
May21st to endNight
39%
583
13%
1381
4%
582
41%
582
30%
946
June1st to 10thNight
51%
540
16%
1260
6%
540
55%
540
40%
807
June11th to 20thNight
41%
540
13%
1260
5%
540
44%
540
37%
833
June21st to endNight
56%
540
16%
1260
7%
540
60%
540
49%
748
July1st to 10thNight
61%
525
17%
1225
8%
525
63%
525
50%
723
July11th to 20thNight
58%
522
19%
1382
7%
522
64%
522
53%
738
July21st to endNight
63%
591
22%
1488
11%
558
65%
558
52%
793
August1st to 10thNight
62%
537
22%
1519
14%
534
67%
534
41%
856
August11th to 20thNight
58%
534
26%
1600
20%
534
67%
534
43%
872
August21st to endNight
57%
594
29%
1786
26%
594
65%
594
45%
915
September1st to 10thNight
53%
540
22%
1836
20%
540
62%
540
39%
932
September11th to 20thNight
53%
540
25%
1980
24%
540
61%
540
36%
1001
September21st to endNight
40%
540
26%
1980
19%
540
53%
540
29%
1081
October1st to 10thNight
37%
566
22%
2006
16%
566
45%
566
23%
1220
October11th to 20thNight
32%
796
21%
2236
9%
796
40%
796
29%
1421
October21st to endNight
28%
990
21%
2574
7%
990
37%
990
27%
1724
November1st to 10thNight
28%
925
21%
2405
8%
925
36%
925
25%
1632
November11th to 20thNight
27%
950
21%
2569
8%
950
36%
950
23%
1789
November21st to endNight
26%
950
18%
2720
7%
950
36%
950
24%
1788
December1st to 10thNight
25%
950
12%
2850
4%
950
33%
950
19%
2015
December11th to 20thNight
22%
949
12%
3456
5%
949
30%
949
14%
2427
December21st to endNight
20%
1040
9%
5105
4%
1026
29%
1026
9%
3508

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
10%8%47%6%35%5%6%7%39%
74611
Night
9%8%47%6%35%5%6%7%41%
75169
TransparencyDay
43%7%14%24%11%1
74307
Night
41%6%14%24%13%2
74995
SeeingDay
13%10%33%29%12%2
14894
Night
12%10%36%32%10%1
24965

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 10thDay
5%10%6%11%9%46%6%7%8%27%
1446
11th to 20thDay
6%10%5%12%11%45%7%6%8%25%
1464
21st to endDay
7%14%6%13%10%5%6%5%7%7%20%
1584
February1st to 10thDay
8%12%5%7%7%49%6%7%8%27%
1546
11th to 20thDay
7%12%411%9%48%7%5%8%25%
1659
21st to endDay
7%12%7%12%8%46%5%7%6%27%
1480
March1st to 10thDay
10%11%6%13%10%6%5%445%26%
1800
11th to 20thDay
9%10%5%8%7%45%5%6%7%33%
1962
21st to endDay
14%11%6%11%7%345%6%8%25%
2190
April1st to 10thDay
11%10%47%7%345%6%6%38%
2160
11th to 20thDay
18%11%47%5%34445%34%
2290
21st to endDay
16%12%36%5%345%6%7%33%
2340
May1st to 10thDay
17%9%47%5%3445%6%35%
2340
11th to 20thDay
15%8%245%35%46%7%42%
2388
21st to endDay
15%8%36%6%345%6%8%37%
2892
June1st to 10thDay
13%6%35%5%35%5%6%8%41%
2700
11th to 20thDay
12%5%35%5%35%6%6%8%42%
2700
21st to endDay
8%425%6%345%6%8%48%
2700
July1st to 10thDay
5%425%5%35%5%7%9%50%
2700
11th to 20thDay
6%3234245%7%9%55%
2528
21st to endDay
5%424425%47%8%55%
2742
August1st to 10thDay
9%5%25%5%445%6%8%46%
2410
11th to 20thDay
10%5%2442445%8%50%
2301
21st to endDay
7%42442445%7%56%
2568
September1st to 10thDay
11%414434446%54%
2124
11th to 20thDay
10%5%25%425%35%7%52%
1980
21st to endDay
12%7%2442345%7%50%
1980
October1st to 10thDay
16%9%25%5%23347%44%
1936
11th to 20thDay
14%10%34434447%43%
1721
21st to endDay
12%12%36%7%3445%7%37%
1782
November1st to 10thDay
11%10%48%5%35%45%6%38%
1673
11th to 20thDay
7%10%5%10%9%46%5%46%34%
1611
21st to endDay
6%11%5%9%8%5%5%46%7%34%
1459
December1st to 10thDay
6%9%6%11%8%6%6%7%6%7%27%
1330
11th to 20thDay
7%11%6%9%7%47%36%9%30%
1683
21st to endDay
13%13%49%9%345%6%7%28%
2442
January1st to 10thNight
7%9%48%8%47%6%8%8%31%
2715
11th to 20thNight
6%12%6%10%8%46%7%7%7%28%
2575
21st to endNight
5%12%6%10%9%5%6%7%7%7%26%
2772
February1st to 10thNight
7%10%5%9%9%5%7%8%6%8%27%
2412
11th to 20thNight
6%10%48%8%45%5%6%7%36%
2202
21st to endNight
8%10%5%8%8%46%5%5%6%34%
1776
March1st to 10thNight
10%10%411%8%46%6%6%6%29%
2160
11th to 20thNight
12%11%46%7%34346%40%
1998
21st to endNight
11%8%47%7%35%5%6%8%36%
2164
April1st to 10thNight
9%7%37%6%35%5%5%8%42%
1800
11th to 20thNight
16%9%36%6%35%45%6%39%
1617
21st to endNight
14%10%46%43445%7%38%
1620
May1st to 10thNight
10%7%36%5%45%45%7%44%
1620
11th to 20thNight
11%6%25%5%3446%10%44%
1504
21st to endNight
11%7%25%5%345%6%10%42%
1381
June1st to 10thNight
10%5%2343447%10%50%
1260
11th to 20thNight
8%435%5%25%46%8%50%
1260
21st to endNight
5%312425%5%6%9%58%
1260
July1st to 10thNight
6%22443445%8%59%
1260
11th to 20thNight
3312333449%64%
1429
21st to endNight
421342446%9%61%
1576
August1st to 10thNight
5%424435%5%7%8%54%
1527
11th to 20thNight
7%41332445%7%59%
1600
21st to endNight
5%5%2342335%7%63%
1786
September1st to 10thNight
7%41433345%6%60%
1836
11th to 20thNight
8%31433435%8%56%
1980
21st to endNight
13%6%24324346%54%
1980
October1st to 10thNight
15%7%25%43445%7%44%
2006
11th to 20thNight
14%9%34423446%46%
2236
21st to endNight
11%8%35%6%3445%8%42%
2574
November1st to 10thNight
9%9%46%5%45%5%6%6%41%
2405
11th to 20thNight
7%8%5%10%8%45%446%38%
2569
21st to endNight
8%7%48%6%35%5%6%9%40%
2720
December1st to 10thNight
7%10%5%9%8%46%6%7%6%31%
2850
11th to 20thNight
8%11%5%10%7%5%5%5%5%8%31%
3514
21st to endNight
15%11%49%8%345%5%6%29%
5225

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 10thDay
52%5%16%16%9%1
1447
11th to 20thDay
56%5%14%15%8%1
1464
21st to endDay
61%6%12%13%7%
1584
February1st to 10thDay
52%7%12%18%10%1
1546
11th to 20thDay
55%8%12%17%7%2
1668
21st to endDay
56%6%13%17%8%1
1480
March1st to 10thDay
60%6%11%15%7%
1800
11th to 20thDay
50%5%13%21%11%
1962
21st to endDay
57%8%15%16%5%
2190
April1st to 10thDay
45%7%15%21%11%1
2160
11th to 20thDay
52%5%10%20%11%1
2293
21st to endDay
49%7%16%23%6%1
2340
May1st to 10thDay
49%6%11%22%11%1
2340
11th to 20thDay
41%7%14%26%13%
2392
21st to endDay
44%7%17%24%8%1
2892
June1st to 10thDay
39%9%16%27%9%1
2700
11th to 20thDay
38%9%16%25%11%1
2700
21st to endDay
32%8%20%28%12%1
2700
July1st to 10thDay
27%8%17%32%14%2
2626
11th to 20thDay
24%8%16%30%18%4
2452
21st to endDay
25%8%17%31%17%2
2590
August1st to 10thDay
34%8%16%26%13%3
2394
11th to 20thDay
31%8%16%31%13%1
2301
21st to endDay
27%7%13%32%17%3
2568
September1st to 10thDay
31%5%14%34%16%2
2124
11th to 20thDay
32%6%16%31%14%1
1980
21st to endDay
33%6%14%31%14%1
1980
October1st to 10thDay
42%5%14%26%13%1
1936
11th to 20thDay
42%5%11%28%12%2
1721
21st to endDay
46%7%14%21%11%1
1782
November1st to 10thDay
46%6%12%23%13%1
1673
11th to 20thDay
50%6%13%21%8%1
1611
21st to endDay
48%7%15%21%8%2
1459
December1st to 10thDay
53%8%14%18%7%1
1330
11th to 20thDay
49%7%15%20%8%
1680
21st to endDay
56%5%11%20%8%
2442
January1st to 10thNight
47%7%13%22%11%
2715
11th to 20thNight
53%7%15%14%10%1
2575
21st to endNight
54%7%13%17%9%1
2772
February1st to 10thNight
51%7%13%17%11%1
2412
11th to 20thNight
46%6%12%22%12%2
2203
21st to endNight
49%6%13%18%12%2
1776
March1st to 10thNight
54%7%13%18%9%
2160
11th to 20thNight
47%5%10%24%14%1
1998
21st to endNight
46%7%17%20%9%1
2164
April1st to 10thNight
40%6%12%23%17%2
1800
11th to 20thNight
47%410%23%14%2
1617
21st to endNight
46%7%12%23%11%1
1620
May1st to 10thNight
38%7%15%22%16%2
1620
11th to 20thNight
35%7%16%26%16%1
1505
21st to endNight
38%9%19%24%11%1
1381
June1st to 10thNight
29%8%19%32%10%2
1260
11th to 20thNight
33%8%16%26%13%3
1260
21st to endNight
21%8%22%30%16%2
1260
July1st to 10thNight
22%7%16%34%17%4
1225
11th to 20thNight
18%6%15%34%21%5%
1382
21st to endNight
20%6%16%33%22%4
1488
August1st to 10thNight
24%8%15%33%15%4
1519
11th to 20thNight
23%7%16%34%17%3
1600
21st to endNight
21%6%12%35%23%3
1786
September1st to 10thNight
25%5%14%31%22%2
1836
11th to 20thNight
26%6%19%30%19%1
1980
21st to endNight
33%5%12%31%17%2
1980
October1st to 10thNight
39%6%13%25%14%2
2006
11th to 20thNight
39%412%29%14%3
2236
21st to endNight
40%6%13%26%12%1
2574
November1st to 10thNight
41%6%11%22%17%2
2405
11th to 20thNight
46%5%13%21%12%2
2569
21st to endNight
40%7%17%26%9%1
2720
December1st to 10thNight
50%6%17%18%8%1
2850
11th to 20thNight
51%7%16%18%7%1
3516
21st to endNight
55%6%10%19%11%1
5225

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 10thDay
11%12%38%29%8%2
270
11th to 20thDay
10%15%39%27%8%2
249
21st to endDay
11%16%39%25%8%1
264
February1st to 10thDay
11%16%44%24%5%
240
11th to 20thDay
15%12%45%23%31
240
21st to endDay
12%12%40%32%4
198
March1st to 10thDay
18%11%38%20%12%2
240
11th to 20thDay
13%12%35%28%9%2
240
21st to endDay
12%11%34%24%16%4
276
April1st to 10thDay
15%16%40%22%7%
420
11th to 20thDay
27%14%28%22%8%1
571
21st to endDay
21%12%28%28%9%2
600
May1st to 10thDay
16%12%30%28%12%1
603
11th to 20thDay
19%9%30%27%12%3
625
21st to endDay
16%12%29%25%15%3
679
June1st to 10thDay
10%9%27%33%15%6%
630
11th to 20thDay
11%10%42%26%10%1
630
21st to endDay
11%9%30%34%13%3
630
July1st to 10thDay
6%428%40%19%3
621
11th to 20thDay
7%6%35%37%14%1
618
21st to endDay
5%427%43%17%4
684
August1st to 10thDay
9%322%41%20%3
626
11th to 20thDay
13%5%23%31%22%7%
615
21st to endDay
9%7%26%35%21%3
687
September1st to 10thDay
11%10%30%35%13%1
414
11th to 20thDay
16%6%31%36%10%
270
21st to endDay
18%13%33%26%8%2
270
October1st to 10thDay
22%11%30%25%10%2
270
11th to 20thDay
19%14%32%28%7%
270
21st to endDay
19%19%40%17%5%1
297
November1st to 10thDay
19%11%36%26%7%1
270
11th to 20thDay
11%19%39%23%7%1
270
21st to endDay
12%17%45%18%8%
270
December1st to 10thDay
11%14%39%26%8%1
270
11th to 20thDay
13%14%46%24%3
270
21st to endDay
17%14%40%21%6%1
297
January1st to 10thNight
11%13%44%25%7%1
950
11th to 20thNight
12%14%38%28%7%1
920
21st to endNight
11%12%44%26%6%
990
February1st to 10thNight
13%12%39%29%6%1
900
11th to 20thNight
11%11%41%26%9%2
808
21st to endNight
11%9%37%29%11%3
592
March1st to 10thNight
16%11%35%28%9%1
720
11th to 20thNight
15%12%36%25%10%1
558
21st to endNight
13%7%37%30%12%1
594
April1st to 10thNight
12%11%37%31%7%
540
11th to 20thNight
19%9%29%33%9%
533
21st to endNight
17%11%29%30%13%
540
May1st to 10thNight
13%7%33%36%11%
540
11th to 20thNight
12%7%33%36%12%
531
21st to endNight
14%8%33%35%10%
584
June1st to 10thNight
12%6%27%39%15%1
540
11th to 20thNight
9%8%38%35%10%
540
21st to endNight
5%6%30%46%12%1
540
July1st to 10thNight
6%226%48%16%
525
11th to 20thNight
4232%48%13%1
522
21st to endNight
5%226%52%15%1
591
August1st to 10thNight
5%324%51%15%1
537
11th to 20thNight
8%327%42%18%2
534
21st to endNight
8%5%27%45%15%1
594
September1st to 10thNight
9%430%40%15%2
540
11th to 20thNight
8%432%40%14%1
540
21st to endNight
14%9%34%31%11%1
540
October1st to 10thNight
17%11%30%34%7%
566
11th to 20thNight
19%11%33%28%9%
796
21st to endNight
17%13%38%25%7%1
990
November1st to 10thNight
13%14%38%27%7%
925
11th to 20thNight
10%13%42%25%8%1
950
21st to endNight
12%14%42%27%5%
950
December1st to 10thNight
11%11%43%27%7%1
950
11th to 20thNight
15%14%37%28%6%1
950
21st to endNight
18%12%38%25%5%1
1045
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