Casper
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Casper clear sky chart from 2005-11-06 to 2024-03-28.

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
40%
25056
21%
80496
12%
24959
49%
24959
31%
45658

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
27%
939
18%
4363
8%
926
37%
926
18%
2490
January11th to 20thNight
21%
948
20%
4383
8%
930
33%
930
17%
2525
January21st to endNight
18%
853
14%
4397
5%
838
35%
838
22%
1993
February1st to 10thNight
20%
760
16%
2470
6%
760
33%
760
22%
1535
February11th to 20thNight
25%
740
16%
2375
6%
740
37%
740
23%
1497
February21st to endNight
21%
628
19%
1884
4%
628
36%
628
22%
1155
March1st to 10thNight
29%
760
21%
2247
7%
760
42%
760
29%
1341
March11th to 20thNight
39%
760
22%
2090
9%
760
50%
760
32%
1282
March21st to endNight
38%
729
17%
2164
7%
729
47%
729
24%
1429
April1st to 10thNight
32%
540
17%
1800
9%
540
45%
540
24%
1099
April11th to 20thNight
33%
533
15%
1777
10%
533
40%
533
20%
1187
April21st to endNight
46%
540
19%
1783
17%
540
52%
540
24%
1120
May1st to 10thNight
44%
540
16%
1483
12%
540
47%
540
28%
950
May11th to 20thNight
50%
531
19%
1418
14%
531
52%
531
29%
924
May21st to endNight
50%
584
19%
1552
11%
582
55%
582
34%
957
June1st to 10thNight
57%
540
19%
1440
12%
540
60%
540
41%
839
June11th to 20thNight
48%
540
22%
1440
12%
540
54%
540
45%
789
June21st to endNight
65%
540
26%
1440
17%
540
69%
540
54%
748
July1st to 10thNight
67%
525
20%
1400
15%
525
69%
525
47%
773
July11th to 20thNight
67%
522
28%
1392
20%
522
72%
522
61%
686
July21st to endNight
73%
591
28%
1488
22%
558
75%
558
52%
781
August1st to 10thNight
71%
537
26%
1593
22%
534
74%
534
48%
789
August11th to 20thNight
71%
534
31%
1638
27%
534
76%
534
49%
814
August21st to endNight
68%
594
32%
1980
32%
594
73%
594
49%
912
September1st to 10thNight
65%
540
30%
1800
29%
540
74%
540
48%
837
September11th to 20thNight
59%
540
34%
1800
31%
540
68%
540
44%
868
September21st to endNight
58%
621
32%
2025
26%
621
66%
621
46%
987
October1st to 10thNight
48%
720
25%
2160
16%
720
55%
720
34%
1258
October11th to 20thNight
45%
720
28%
2160
15%
720
54%
720
36%
1231
October21st to endNight
41%
845
27%
2429
12%
845
52%
845
38%
1374
November1st to 10thNight
34%
925
24%
2405
8%
925
44%
925
38%
1434
November11th to 20thNight
23%
950
24%
2588
7%
950
37%
950
29%
1602
November21st to endNight
28%
950
23%
2660
7%
950
42%
950
37%
1526
December1st to 10thNight
21%
950
19%
2660
5%
950
33%
950
27%
1642
December11th to 20thNight
20%
950
22%
3105
6%
948
32%
948
28%
1658
December21st to endNight
20%
1037
12%
4707
3%
1026
32%
1026
16%
2626

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
5%5%244345%5%8%54%
78776
Night
5%6%25%4345%6%8%53%
81285
TransparencyDay
28%8%15%25%17%6%
78479
Night
29%8%16%26%16%5%
81104
SeeingDay
9%12%31%28%17%4
14855
Night
8%12%35%33%11%1
25088

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
25%26%6%35%45%7%54%
2538
11th to 20thDay
28%45%6%5%6%7%5%9%43%
2540
21st to endDay
25%23423447%63%
3123
February1st to 10thDay
310%47%6%35%5%48%44%
1710
11th to 20thDay
49%46%5%245%5%8%47%
1692
21st to endDay
37%35%43445%8%53%
1570
March1st to 10thDay
36%25%4335%5%8%55%
1930
11th to 20thDay
5%6%245%35%5%5%9%51%
2090
21st to endDay
8%9%35%5%35%46%9%43%
2347
April1st to 10thDay
7%8%34325%47%8%48%
2160
11th to 20thDay
10%10%35%5%45%5%6%7%40%
2131
21st to endDay
12%8%35%5%35%5%5%8%42%
2173
May1st to 10thDay
12%6%25%6%45%6%6%9%40%
2474
11th to 20thDay
14%6%245%345%7%9%41%
2478
21st to endDay
10%5%24435%6%7%10%43%
2724
June1st to 10thDay
6%4244346%5%9%54%
2520
11th to 20thDay
6%3133345%6%8%58%
2520
21st to endDay
32133245%5%8%65%
2520
July1st to 10thDay
42133245%6%10%61%
2520
11th to 20thDay
21133335%6%8%65%
2520
21st to endDay
33134245%6%8%61%
2742
August1st to 10thDay
3213435%5%6%10%58%
2335
11th to 20thDay
421333446%7%64%
2261
21st to endDay
321232446%7%66%
2376
September1st to 10thDay
5%31332245%7%64%
2160
11th to 20thDay
5%31332335%8%64%
2160
21st to endDay
7%313323345%65%
1931
October1st to 10thDay
8%5%24433447%57%
1800
11th to 20thDay
9%5%23324346%58%
1800
21st to endDay
6%7%25%32345%9%54%
1908
November1st to 10thDay
5%424335%5%5%8%54%
1673
11th to 20thDay
45%243245%6%9%56%
1590
21st to endDay
36%35%43346%6%57%
1520
December1st to 10thDay
27%38%6%2446%8%50%
1520
11th to 20thDay
35%2342445%9%59%
1926
21st to endDay
39%36%435%45%7%51%
2794
January1st to 10thNight
27%47%5%35%5%7%9%46%
4417
11th to 20thNight
27%48%6%35%5%6%9%45%
4430
21st to endNight
37%35%32345%7%58%
4571
February1st to 10thNight
38%47%5%25%46%9%45%
2470
11th to 20thNight
49%46%5%35%6%6%8%45%
2374
21st to endNight
37%37%6%345%6%8%48%
1884
March1st to 10thNight
48%345%25%46%7%53%
2247
11th to 20thNight
5%7%35%4345%6%8%51%
2090
21st to endNight
7%8%36%6%345%6%9%43%
2164
April1st to 10thNight
9%9%35%42445%8%48%
1800
11th to 20thNight
11%10%36%5%45%6%5%6%39%
1777
21st to endNight
11%8%35%4245%5%8%44%
1783
May1st to 10thNight
13%7%15%5%3445%6%47%
1483
11th to 20thNight
15%5%15%3345%5%8%46%
1417
21st to endNight
9%5%24325%6%6%10%48%
1552
June1st to 10thNight
4324436%5%7%10%53%
1440
11th to 20thNight
7%21432335%8%62%
1440
21st to endNight
421232345%8%66%
1440
July1st to 10thNight
43133345%7%8%59%
1440
11th to 20thNight
211232336%8%67%
1440
21st to endNight
31124345%6%6%64%
1576
August1st to 10thNight
22123346%8%11%58%
1601
11th to 20thNight
421232446%9%62%
1638
21st to endNight
22123235%6%9%63%
1980
September1st to 10thNight
6%312323437%66%
1800
11th to 20thNight
6%21331345%7%64%
1800
21st to endNight
8%313322235%68%
2025
October1st to 10thNight
9%7%23333347%56%
2160
11th to 20thNight
8%6%2442435%6%57%
2160
21st to endNight
7%5%2332345%7%58%
2429
November1st to 10thNight
5%7%2442346%8%55%
2405
11th to 20thNight
5%6%35%435%5%6%7%51%
2588
21st to endNight
47%2332445%8%57%
2660
December1st to 10thNight
46%36%6%3445%7%51%
2660
11th to 20thNight
36%343235%6%9%55%
3271
21st to endNight
410%35%435%5%6%8%46%
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
30%12%17%27%13%1
2539
11th to 20thDay
36%12%19%20%12%1
2540
21st to endDay
22%7%29%29%12%1
3123
February1st to 10thDay
40%8%18%26%7%1
1710
11th to 20thDay
36%10%17%23%12%3
1701
21st to endDay
31%8%19%25%14%2
1570
March1st to 10thDay
29%6%19%31%12%2
1930
11th to 20thDay
30%8%18%30%12%1
2090
21st to endDay
39%9%16%26%9%1
2347
April1st to 10thDay
35%8%20%22%12%3
2160
11th to 20thDay
42%8%14%21%12%2
2134
21st to endDay
40%8%15%25%12%
2173
May1st to 10thDay
40%9%14%24%12%1
2474
11th to 20thDay
39%9%16%24%11%1
2482
21st to endDay
34%9%17%27%11%2
2724
June1st to 10thDay
27%8%16%25%18%5%
2520
11th to 20thDay
23%7%12%23%22%13%
2520
21st to endDay
16%6%11%24%29%15%
2520
July1st to 10thDay
19%7%10%23%27%15%
2451
11th to 20thDay
18%5%10%21%24%22%
2445
21st to endDay
20%7%11%20%25%17%
2590
August1st to 10thDay
20%8%11%25%22%13%
2319
11th to 20thDay
20%6%10%24%26%13%
2261
21st to endDay
17%5%9%19%32%18%
2376
September1st to 10thDay
19%5%8%18%29%20%
2160
11th to 20thDay
20%5%9%24%27%15%
2160
21st to endDay
22%5%10%27%30%6%
1931
October1st to 10thDay
30%6%12%27%20%5%
1800
11th to 20thDay
28%6%13%30%20%4
1800
21st to endDay
28%6%17%29%17%3
1908
November1st to 10thDay
28%8%17%27%18%3
1673
11th to 20thDay
25%9%18%30%15%4
1590
21st to endDay
28%7%17%28%17%2
1520
December1st to 10thDay
33%9%21%23%13%1
1520
11th to 20thDay
25%7%25%34%9%
1924
21st to endDay
33%8%14%30%13%2
2794
January1st to 10thNight
32%12%19%26%10%1
4417
11th to 20thNight
34%11%21%19%12%3
4430
21st to endNight
26%6%30%27%10%1
4571
February1st to 10thNight
36%9%19%25%9%1
2470
11th to 20thNight
36%10%16%24%12%2
2375
21st to endNight
34%9%18%23%14%3
1884
March1st to 10thNight
31%8%17%29%14%2
2247
11th to 20thNight
31%8%17%29%12%3
2090
21st to endNight
38%10%16%25%10%1
2164
April1st to 10thNight
36%8%17%23%13%3
1800
11th to 20thNight
43%9%14%18%14%2
1777
21st to endNight
37%9%12%27%14%1
1783
May1st to 10thNight
37%7%15%25%15%1
1483
11th to 20thNight
36%9%15%27%12%2
1418
21st to endNight
30%8%17%27%16%1
1552
June1st to 10thNight
25%9%19%28%16%5%
1440
11th to 20thNight
23%5%13%24%21%14%
1440
21st to endNight
18%5%10%24%28%15%
1440
July1st to 10thNight
21%8%12%25%22%11%
1400
11th to 20thNight
14%5%12%23%26%21%
1392
21st to endNight
18%6%11%22%26%17%
1488
August1st to 10thNight
19%7%14%30%20%11%
1593
11th to 20thNight
19%6%10%25%26%14%
1638
21st to endNight
17%6%9%20%31%17%
1980
September1st to 10thNight
19%49%21%28%18%
1800
11th to 20thNight
20%6%10%24%26%14%
1800
21st to endNight
22%39%27%29%10%
2025
October1st to 10thNight
29%8%12%24%19%8%
2160
11th to 20thNight
30%5%12%28%18%7%
2160
21st to endNight
26%7%17%28%18%5%
2429
November1st to 10thNight
27%7%16%27%19%3
2405
11th to 20thNight
31%9%14%29%14%3
2588
21st to endNight
27%7%17%30%18%2
2660
December1st to 10thNight
33%8%19%25%14%1
2660
11th to 20thNight
25%8%22%35%9%1
3272
21st to endNight
34%8%16%25%14%2
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
9%21%38%23%9%1
270
11th to 20thDay
8%21%47%20%4
270
21st to endDay
7%15%51%20%6%1
297
February1st to 10thDay
8%25%50%13%41
270
11th to 20thDay
9%23%53%11%5%
270
21st to endDay
12%20%42%21%5%
225
March1st to 10thDay
8%25%41%20%7%
300
11th to 20thDay
10%18%37%28%6%1
460
21st to endDay
14%19%34%24%8%1
491
April1st to 10thDay
14%19%41%22%4
420
11th to 20thDay
15%17%40%23%5%
412
21st to endDay
16%14%32%25%11%3
420
May1st to 10thDay
13%14%28%28%13%4
557
11th to 20thDay
16%7%25%28%20%4
625
21st to endDay
14%11%25%26%21%4
679
June1st to 10thDay
5%9%23%28%27%8%
630
11th to 20thDay
7%10%31%33%17%2
630
21st to endDay
45%26%34%26%5%
630
July1st to 10thDay
4419%33%34%6%
621
11th to 20thDay
3420%38%30%6%
618
21st to endDay
3217%37%36%6%
684
August1st to 10thDay
3423%34%30%6%
454
11th to 20thDay
35%19%37%27%10%
437
21st to endDay
26%24%35%25%8%
495
September1st to 10thDay
6%6%24%32%23%8%
450
11th to 20thDay
5%9%29%31%20%6%
450
21st to endDay
8%9%28%29%17%8%
306
October1st to 10thDay
10%9%26%29%20%6%
270
11th to 20thDay
11%13%37%26%10%2
270
21st to endDay
8%18%41%22%9%1
297
November1st to 10thDay
9%16%46%21%6%2
270
11th to 20thDay
9%23%41%22%6%
270
21st to endDay
10%20%45%21%3
270
December1st to 10thDay
10%23%41%19%7%
270
11th to 20thDay
11%29%39%19%3
270
21st to endDay
14%20%40%22%41
297
January1st to 10thNight
6%18%42%26%6%1
950
11th to 20thNight
7%21%47%20%5%
950
21st to endNight
9%13%53%20%4
860
February1st to 10thNight
7%16%49%22%6%
760
11th to 20thNight
7%16%43%27%7%
744
21st to endNight
7%21%43%23%6%
628
March1st to 10thNight
8%15%42%28%6%
760
11th to 20thNight
9%12%34%36%9%
760
21st to endNight
11%13%33%35%8%1
729
April1st to 10thNight
15%11%36%34%4
540
11th to 20thNight
14%11%34%33%7%
533
21st to endNight
13%9%26%38%13%
540
May1st to 10thNight
15%8%27%34%15%2
540
11th to 20thNight
16%8%22%34%20%1
531
21st to endNight
10%9%25%38%17%1
584
June1st to 10thNight
6%5%24%42%21%1
540
11th to 20thNight
8%7%34%41%9%
540
21st to endNight
5%323%50%19%
540
July1st to 10thNight
4421%44%26%1
525
11th to 20thNight
2225%50%21%
522
21st to endNight
3217%54%24%1
591
August1st to 10thNight
3318%52%23%
537
11th to 20thNight
4318%49%25%1
534
21st to endNight
3322%47%23%2
594
September1st to 10thNight
7%320%48%20%1
540
11th to 20thNight
6%6%26%42%19%1
540
21st to endNight
10%5%24%41%18%2
621
October1st to 10thNight
13%9%27%33%17%1
720
11th to 20thNight
10%8%32%39%10%1
720
21st to endNight
10%8%38%32%10%2
845
November1st to 10thNight
8%12%43%28%8%
925
11th to 20thNight
7%20%45%23%4
950
21st to endNight
7%14%47%26%5%
950
December1st to 10thNight
8%20%44%23%5%
950
11th to 20thNight
7%20%47%22%4
950
21st to endNight
9%24%41%21%4
1045
Page generated at 2024-03-24 21:36:59. Version ac07

Copyright © 2024 Attilla Danko.


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