Black Hills State University
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Black Hills State University 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
36%
24866
21%
74459
11%
24815
45%
24815
28%
45195

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
25%
950
20%
2647
8%
946
35%
946
23%
1713
January11th to 20thNight
25%
920
20%
2575
6%
920
36%
920
21%
1683
January21st to endNight
19%
990
17%
2772
4%
990
31%
990
18%
1907
February1st to 10thNight
20%
734
15%
2354
7%
734
30%
734
16%
1592
February11th to 20thNight
26%
700
18%
2164
9%
700
36%
700
20%
1425
February21st to endNight
28%
592
18%
1776
6%
592
39%
592
23%
1174
March1st to 10thNight
30%
720
20%
2160
7%
720
41%
720
25%
1347
March11th to 20thNight
31%
720
20%
2100
10%
720
41%
720
27%
1340
March21st to endNight
37%
601
16%
1987
11%
601
44%
601
20%
1324
April1st to 10thNight
31%
540
16%
1800
10%
540
41%
540
22%
1158
April11th to 20thNight
29%
533
17%
1777
10%
533
40%
533
20%
1161
April21st to endNight
35%
540
17%
1682
12%
540
43%
540
24%
1079
May1st to 10thNight
42%
540
17%
1519
12%
540
47%
540
30%
956
May11th to 20thNight
43%
531
18%
1418
10%
531
47%
531
29%
943
May21st to endNight
38%
583
14%
1552
6%
582
42%
582
26%
1049
June1st to 10thNight
48%
540
14%
1440
7%
540
51%
540
34%
885
June11th to 20thNight
36%
540
14%
1440
5%
540
41%
540
34%
891
June21st to endNight
50%
540
18%
1440
9%
540
54%
540
44%
821
July1st to 10thNight
58%
525
17%
1400
10%
525
62%
525
47%
786
July11th to 20thNight
52%
522
23%
1392
12%
522
58%
522
49%
767
July21st to endNight
61%
591
26%
1488
17%
558
66%
558
52%
788
August1st to 10thNight
58%
537
26%
1424
17%
534
64%
534
43%
824
August11th to 20thNight
62%
534
28%
1663
23%
534
69%
534
45%
845
August21st to endNight
61%
594
29%
1980
27%
594
70%
594
46%
929
September1st to 10thNight
57%
540
28%
1800
26%
540
68%
540
43%
890
September11th to 20thNight
52%
540
31%
1857
24%
540
65%
540
38%
939
September21st to endNight
47%
540
29%
1980
26%
540
56%
540
34%
999
October1st to 10thNight
41%
660
24%
2100
17%
660
48%
660
28%
1254
October11th to 20thNight
37%
720
28%
2160
13%
720
48%
720
31%
1248
October21st to endNight
32%
990
24%
2574
8%
990
41%
990
32%
1593
November1st to 10thNight
32%
925
22%
2405
8%
925
41%
925
30%
1537
November11th to 20thNight
26%
950
27%
2510
7%
950
40%
950
28%
1592
November21st to endNight
27%
950
25%
2660
8%
950
41%
950
30%
1580
December1st to 10thNight
22%
950
20%
2660
6%
950
34%
950
22%
1753
December11th to 20thNight
26%
948
25%
3095
8%
948
39%
948
24%
1743
December21st to endNight
23%
1036
13%
4708
4%
1026
37%
1026
14%
2680

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
8%7%35%4345%6%8%48%
74806
Night
7%8%35%5%3445%8%47%
74982
TransparencyDay
34%7%14%26%16%4
74509
Night
34%6%13%25%17%4
74801
SeeingDay
13%16%33%25%11%2
14753
Night
12%15%32%30%10%1
24882

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
48%47%5%345%7%9%43%
1518
11th to 20thDay
5%13%6%8%5%35%347%41%
1464
21st to endDay
5%12%6%9%6%3446%7%38%
1584
February1st to 10thDay
5%16%5%8%7%5%6%445%34%
1620
11th to 20thDay
6%13%6%8%6%3445%7%38%
1684
21st to endDay
411%5%9%6%35%6%5%8%38%
1480
March1st to 10thDay
410%48%4445%5%7%44%
1800
11th to 20thDay
7%7%36%5%2345%8%48%
1858
21st to endDay
9%13%47%6%45%5%6%8%33%
2368
April1st to 10thDay
11%10%45%5%35%45%8%40%
2160
11th to 20thDay
14%12%5%7%6%345%5%7%32%
2131
21st to endDay
16%11%35%435%5%5%8%34%
2277
May1st to 10thDay
13%9%36%6%36%5%6%7%36%
2438
11th to 20thDay
15%8%35%425%5%6%9%36%
2478
21st to endDay
15%6%36%5%347%7%11%34%
2724
June1st to 10thDay
8%424436%5%8%10%47%
2520
11th to 20thDay
9%3233346%8%10%49%
2520
21st to endDay
5%4133345%6%9%59%
2520
July1st to 10thDay
5%313425%5%6%9%56%
2520
11th to 20thDay
311232446%9%65%
2520
21st to endDay
5%3133245%6%9%59%
2742
August1st to 10thDay
5%2145%35%5%7%10%53%
2507
11th to 20thDay
6%3133245%5%8%59%
2233
21st to endDay
332232445%7%64%
2376
September1st to 10thDay
7%413323446%63%
2160
11th to 20thDay
9%31232345%6%62%
2102
21st to endDay
11%413323447%57%
1980
October1st to 10thDay
11%9%24323346%52%
1857
11th to 20thDay
12%8%24323447%52%
1782
21st to endDay
9%8%35%42445%8%49%
1782
November1st to 10thDay
7%7%344345%7%7%48%
1673
11th to 20thDay
5%8%36%6%335%48%49%
1668
21st to endDay
5%8%245%335%5%10%50%
1520
December1st to 10thDay
310%5%8%6%45%5%6%7%42%
1520
11th to 20thDay
46%35%5%3446%10%51%
1926
21st to endDay
7%10%47%5%245%5%7%46%
2794
January1st to 10thNight
49%47%5%46%5%6%7%43%
2647
11th to 20thNight
7%11%47%5%3445%8%42%
2575
21st to endNight
6%14%5%7%6%3445%7%37%
2772
February1st to 10thNight
7%13%6%7%6%35%5%5%6%36%
2354
11th to 20thNight
5%12%6%8%6%35%46%6%40%
2163
21st to endNight
5%10%5%8%6%45%46%7%40%
1776
March1st to 10thNight
6%9%46%5%25%5%5%8%46%
2160
11th to 20thNight
7%8%37%7%3445%8%44%
2100
21st to endNight
10%10%47%435%5%6%9%37%
1987
April1st to 10thNight
13%10%45%43446%8%39%
1800
11th to 20thNight
13%9%47%5%34446%40%
1777
21st to endNight
13%9%345%35%45%8%41%
1682
May1st to 10thNight
11%7%25%43446%7%47%
1519
11th to 20thNight
13%8%26%5%3346%8%43%
1417
21st to endNight
13%6%245%35%5%6%11%40%
1552
June1st to 10thNight
9%4145%345%6%11%48%
1440
11th to 20thNight
8%4245%36%6%7%11%45%
1440
21st to endNight
6%32442346%7%58%
1440
July1st to 10thNight
5%3235%345%7%11%55%
1440
11th to 20thNight
5%31332437%8%61%
1440
21st to endNight
32143245%7%9%59%
1576
August1st to 10thNight
43244347%7%9%53%
1432
11th to 20thNight
5%3133345%6%8%60%
1663
21st to endNight
33133245%5%7%63%
1980
September1st to 10thNight
6%313423448%61%
1800
11th to 20thNight
8%41332345%7%59%
1857
21st to endNight
11%313323445%59%
1980
October1st to 10thNight
14%7%3342345%6%48%
2100
11th to 20thNight
10%6%2433445%7%52%
2160
21st to endNight
11%7%3442345%7%50%
2574
November1st to 10thNight
8%7%35%43446%9%46%
2405
11th to 20thNight
7%8%47%5%4446%6%47%
2510
21st to endNight
6%8%35%43446%8%50%
2660
December1st to 10thNight
5%9%5%10%6%35%45%7%42%
2660
11th to 20thNight
37%46%5%245%6%10%49%
3271
21st to endNight
7%12%35%5%35%5%5%6%45%
4873

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
37%5%21%23%12%2
1519
11th to 20thDay
43%6%16%24%9%3
1464
21st to endDay
44%7%16%20%11%2
1584
February1st to 10thDay
52%5%11%20%9%2
1620
11th to 20thDay
44%7%15%19%11%4
1693
21st to endDay
44%7%12%21%12%4
1480
March1st to 10thDay
37%8%17%24%13%1
1800
11th to 20thDay
33%6%15%31%14%2
1858
21st to endDay
49%7%13%23%8%1
2368
April1st to 10thDay
43%6%17%23%9%3
2160
11th to 20thDay
50%7%13%19%10%2
2134
21st to endDay
47%7%15%23%8%
2277
May1st to 10thDay
46%7%15%25%7%1
2438
11th to 20thDay
43%8%17%24%8%
2482
21st to endDay
42%11%18%21%7%1
2724
June1st to 10thDay
31%9%21%26%11%2
2520
11th to 20thDay
29%9%19%27%14%3
2520
21st to endDay
22%7%15%29%22%5%
2520
July1st to 10thDay
23%6%15%31%21%4
2451
11th to 20thDay
16%6%13%29%25%11%
2445
21st to endDay
20%6%13%25%25%10%
2590
August1st to 10thDay
23%9%14%30%17%7%
2491
11th to 20thDay
22%6%13%32%21%6%
2233
21st to endDay
19%5%13%24%29%9%
2376
September1st to 10thDay
23%410%27%26%10%
2160
11th to 20thDay
24%412%28%25%7%
2102
21st to endDay
27%410%33%23%2
1980
October1st to 10thDay
34%5%11%27%19%3
1857
11th to 20thDay
34%411%29%16%5%
1782
21st to endDay
34%6%16%24%16%4
1782
November1st to 10thDay
31%8%12%24%21%3
1673
11th to 20thDay
33%6%13%26%18%4
1668
21st to endDay
30%6%16%28%16%3
1520
December1st to 10thDay
40%7%13%23%15%2
1520
11th to 20thDay
27%7%20%33%11%2
1924
21st to endDay
38%6%9%26%20%3
2794
January1st to 10thNight
38%8%16%24%13%3
2647
11th to 20thNight
40%6%16%21%13%3
2575
21st to endNight
45%6%13%21%13%2
2772
February1st to 10thNight
46%7%15%19%11%2
2354
11th to 20thNight
44%6%13%22%14%2
2164
21st to endNight
42%7%13%20%13%5%
1776
March1st to 10thNight
36%7%14%25%16%2
2160
11th to 20thNight
38%6%13%25%15%3
2100
21st to endNight
44%8%14%21%13%1
1987
April1st to 10thNight
42%7%15%22%12%3
1800
11th to 20thNight
45%6%13%23%12%2
1777
21st to endNight
42%5%14%27%11%1
1682
May1st to 10thNight
36%7%16%30%11%
1519
11th to 20thNight
39%6%16%26%12%
1418
21st to endNight
39%9%17%26%9%
1552
June1st to 10thNight
30%8%20%28%12%1
1440
11th to 20thNight
32%7%21%23%14%3
1440
21st to endNight
24%7%15%26%24%4
1440
July1st to 10thNight
24%6%13%34%19%4
1400
11th to 20thNight
21%6%11%28%24%10%
1392
21st to endNight
19%6%14%26%26%9%
1488
August1st to 10thNight
25%7%12%28%21%7%
1424
11th to 20thNight
22%5%11%28%27%8%
1663
21st to endNight
19%5%10%25%30%10%
1980
September1st to 10thNight
23%48%27%25%13%
1800
11th to 20thNight
24%6%11%26%24%9%
1857
21st to endNight
28%49%30%24%6%
1980
October1st to 10thNight
37%412%24%19%4
2100
11th to 20thNight
31%5%10%27%21%6%
2160
21st to endNight
33%6%15%25%17%5%
2574
November1st to 10thNight
34%7%14%21%19%5%
2405
11th to 20thNight
36%5%13%25%18%4
2510
21st to endNight
31%6%16%26%18%4
2660
December1st to 10thNight
41%6%12%24%14%3
2660
11th to 20thNight
30%7%14%34%13%1
3272
21st to endNight
37%7%10%28%15%3
4873

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
10%22%30%26%9%3
270
11th to 20thDay
15%21%28%23%9%3
249
21st to endDay
23%36%24%11%5%
264
February1st to 10thDay
19%24%40%15%3
240
11th to 20thDay
17%27%37%16%3
240
21st to endDay
16%25%42%15%21
198
March1st to 10thDay
15%28%34%15%8%1
240
11th to 20thDay
13%20%38%20%7%2
298
21st to endDay
22%18%31%21%7%2
462
April1st to 10thDay
21%25%36%15%3
420
11th to 20thDay
24%27%37%9%2
412
21st to endDay
23%14%31%23%8%1
537
May1st to 10thDay
20%18%29%20%11%2
603
11th to 20thDay
22%12%26%26%12%3
625
21st to endDay
19%14%30%21%13%3
679
June1st to 10thDay
8%11%30%31%17%3
630
11th to 20thDay
12%16%37%26%9%1
630
21st to endDay
9%10%36%29%14%2
630
July1st to 10thDay
5%6%31%36%19%2
621
11th to 20thDay
49%37%35%14%1
618
21st to endDay
48%31%35%18%3
684
August1st to 10thDay
5%6%34%38%16%1
626
11th to 20thDay
7%5%35%35%14%3
486
21st to endDay
411%31%38%11%4
495
September1st to 10thDay
8%10%38%30%13%2
450
11th to 20thDay
9%8%33%32%14%4
392
21st to endDay
14%15%33%21%11%5%
270
October1st to 10thDay
17%16%27%23%14%4
270
11th to 20thDay
21%21%33%14%7%4
270
21st to endDay
14%29%29%19%8%1
297
November1st to 10thDay
17%22%32%20%7%2
270
11th to 20thDay
16%27%33%18%6%1
270
21st to endDay
12%22%36%23%7%
270
December1st to 10thDay
14%27%36%18%41
270
11th to 20thDay
14%27%33%23%3
270
21st to endDay
14%24%38%18%5%1
297
January1st to 10thNight
9%24%36%18%11%1
950
11th to 20thNight
15%27%29%20%8%1
920
21st to endNight
14%28%34%19%5%
990
February1st to 10thNight
15%25%34%19%6%1
734
11th to 20thNight
11%22%34%25%7%1
704
21st to endNight
13%17%37%26%7%1
592
March1st to 10thNight
11%20%35%24%9%1
720
11th to 20thNight
10%15%38%27%8%2
720
21st to endNight
16%12%27%34%9%1
601
April1st to 10thNight
18%10%35%30%6%
540
11th to 20thNight
21%14%31%28%6%1
533
21st to endNight
18%11%29%31%9%1
540
May1st to 10thNight
16%8%28%35%12%2
540
11th to 20thNight
17%9%25%34%13%1
531
21st to endNight
17%11%30%30%11%1
584
June1st to 10thNight
10%10%27%36%16%1
540
11th to 20thNight
10%9%41%32%7%
540
21st to endNight
7%6%33%43%11%1
540
July1st to 10thNight
6%427%42%19%1
525
11th to 20thNight
6%6%33%43%13%1
522
21st to endNight
3327%53%14%
591
August1st to 10thNight
5%329%47%16%
537
11th to 20thNight
6%325%44%19%2
534
21st to endNight
45%27%44%20%1
594
September1st to 10thNight
7%5%26%43%17%2
540
11th to 20thNight
10%8%25%38%17%2
540
21st to endNight
12%9%30%32%14%3
540
October1st to 10thNight
18%11%25%32%12%2
660
11th to 20thNight
15%14%31%28%11%1
720
21st to endNight
16%17%33%25%8%2
990
November1st to 10thNight
12%18%34%27%8%2
925
11th to 20thNight
13%21%36%22%6%2
950
21st to endNight
12%22%36%24%6%
950
December1st to 10thNight
12%25%36%21%6%1
950
11th to 20thNight
11%22%35%25%7%1
950
21st to endNight
16%22%33%22%6%
1045
Page generated at 2024-01-11 11:32:00. Version ac07

Copyright 2024 Attilla Danko


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