Casper
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Casper clear sky chart from 2005-11-05 to 2018-02-22.

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%
16775
22%
48934
12%
16733
49%
16733
32%
28961

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
28%
974
17%
2716
7%
970
36%
970
26%
1739
January16th to endNight
23%
913
21%
2785
8%
913
37%
913
28%
1665
February1st to 15thNight
26%
757
15%
2483
7%
757
36%
757
21%
1578
February16th to endNight
24%
660
17%
2022
5%
660
36%
660
23%
1272
March1st to 15thNight
33%
720
19%
2079
6%
720
44%
720
28%
1273
March16th to endNight
36%
708
18%
2052
8%
708
45%
708
24%
1349
April1st to 15thNight
34%
539
16%
1798
9%
539
44%
539
22%
1132
April16th to endNight
40%
540
16%
1788
13%
540
47%
540
22%
1160
May1st to 15thNight
46%
540
17%
1468
12%
540
50%
540
29%
926
May16th to endNight
49%
563
18%
1498
11%
561
53%
561
31%
950
June1st to 15thNight
50%
540
18%
1440
10%
540
54%
540
39%
838
June16th to endNight
61%
540
25%
1440
16%
540
65%
540
57%
725
July1st to 15thNight
66%
510
20%
1360
13%
510
70%
510
49%
736
July16th to endNight
75%
564
28%
1416
23%
531
77%
531
58%
713
August1st to 15thNight
71%
539
26%
1606
22%
536
76%
536
49%
794
August16th to endNight
70%
573
34%
1875
33%
573
75%
573
51%
862
September1st to 15thNight
60%
540
27%
1800
23%
540
69%
540
42%
905
September16th to endNight
60%
591
34%
1950
30%
591
67%
591
48%
920
October1st to 15thNight
42%
720
24%
2160
15%
720
50%
720
32%
1300
October16th to endNight
45%
804
31%
2340
15%
804
56%
804
38%
1317
November1st to 15thNight
34%
950
25%
2486
10%
950
44%
950
34%
1505
November16th to endNight
26%
975
24%
2730
8%
975
40%
975
35%
1568
December1st to 15thNight
20%
975
15%
2730
5%
975
29%
975
24%
1786
December16th to endNight
23%
1040
17%
2912
5%
1040
34%
1040
23%
1948

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
6%42332445%8%53%
49335
Night
6%5%2432445%7%53%
49105
TransparencyDay
30%7%15%24%16%6%
49008
Night
30%7%15%25%15%5%
48934
SeeingDay
9%13%30%27%16%2
6457
Night
8%12%33%32%11%
16783

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
35%344336%5%8%51%
1552
16th to endDay
36%24423448%53%
1801
February1st to 15thDay
410%46%5%2435%8%45%
1710
16th to endDay
48%45%42345%8%47%
1597
March1st to 15thDay
45%23324449%54%
1878
16th to endDay
7%6%245%35%5%6%9%43%
2172
April1st to 15thDay
8%7%34325%45%7%47%
2150
16th to endDay
15%9%2443445%8%37%
2169
May1st to 15thDay
13%5%144345%5%8%42%
2481
16th to endDay
12%414425%5%6%9%43%
2616
June1st to 15thDay
7%3133345%5%8%51%
2520
16th to endDay
212212447%70%
2520
July1st to 15thDay
31332445%9%60%
2520
16th to endDay
32123235%6%7%61%
2656
August1st to 15thDay
42123345%6%8%58%
2344
16th to endDay
311232446%6%64%
2325
September1st to 15thDay
6%31332335%6%60%
2160
16th to endDay
7%22213336%65%
2007
October1st to 15thDay
9%323333346%55%
1800
16th to endDay
6%5%23223448%56%
1872
November1st to 15thDay
5%423335%5%5%8%53%
1701
16th to endDay
242331346%8%57%
1560
December1st to 15thDay
37%37%5%25%5%5%7%45%
1560
16th to endDay
48%35%43445%6%50%
1664
January1st to 15thNight
37%3443446%7%48%
2716
16th to endNight
47%35%324446%53%
2785
February1st to 15thNight
48%36%425%46%9%43%
2472
16th to endNight
48%37%42445%6%47%
2022
March1st to 15thNight
47%24325%46%6%52%
2079
16th to endNight
8%6%345%245%6%8%44%
2052
April1st to 15thNight
8%8%25%42445%7%45%
1798
16th to endNight
14%7%25%42345%7%42%
1788
May1st to 15thNight
12%6%13324446%49%
1467
16th to endNight
12%3143246%5%9%46%
1497
June1st to 15thNight
7%21432445%8%56%
1440
16th to endNight
212212337%69%
1440
July1st to 15thNight
321232346%8%60%
1440
16th to endNight
3131336%6%68%
1512
August1st to 15thNight
21131447%10%61%
1614
16th to endNight
31221346%8%65%
1875
September1st to 15thNight
7%213412337%62%
1800
16th to endNight
7%212212235%68%
1950
October1st to 15thNight
11%6%22323346%53%
2160
16th to endNight
7%5%12313446%58%
2340
November1st to 15thNight
5%6%1442335%8%54%
2486
16th to endNight
46%22214448%58%
2730
December1st to 15thNight
5%7%36%6%3445%7%46%
2730
16th to endNight
38%35%5%35%5%5%7%46%
2912

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
30%12%24%24%7%
1553
16th to endDay
31%9%22%24%11%1
1801
February1st to 15thDay
39%8%20%23%6%1
1710
16th to endDay
37%8%20%22%8%2
1597
March1st to 15thDay
30%5%22%29%11%
1878
16th to endDay
39%8%15%26%9%1
2172
April1st to 15thDay
38%6%17%24%11%1
2150
16th to endDay
47%6%16%19%9%1
2169
May1st to 15thDay
40%7%15%24%11%
2481
16th to endDay
37%8%15%25%10%1
2620
June1st to 15thDay
30%7%14%25%16%5%
2520
16th to endDay
14%410%24%30%16%
2520
July1st to 15thDay
22%6%10%21%22%16%
2371
16th to endDay
20%410%20%23%20%
2489
August1st to 15thDay
21%7%11%23%20%15%
2328
16th to endDay
19%5%9%22%28%15%
2325
September1st to 15thDay
24%5%8%18%27%15%
2160
16th to endDay
22%310%30%27%5%
2007
October1st to 15thDay
31%5%14%28%17%2
1800
16th to endDay
27%5%15%30%16%3
1872
November1st to 15thDay
30%7%17%23%17%3
1701
16th to endDay
24%7%21%30%14%1
1560
December1st to 15thDay
37%10%21%22%7%
1560
16th to endDay
36%9%21%24%7%1
1664
January1st to 15thNight
34%9%21%23%9%1
2716
16th to endNight
33%6%20%25%12%1
2785
February1st to 15thNight
37%9%19%22%8%1
2483
16th to endNight
36%8%17%23%11%1
2022
March1st to 15thNight
32%8%18%27%10%2
2079
16th to endNight
38%8%17%25%8%1
2052
April1st to 15thNight
39%7%16%21%12%2
1798
16th to endNight
41%7%13%23%12%1
1788
May1st to 15thNight
36%6%15%25%14%1
1468
16th to endNight
34%7%17%24%15%1
1498
June1st to 15thNight
26%6%15%29%15%5%
1440
16th to endNight
16%310%23%28%16%
1440
July1st to 15thNight
21%5%12%23%23%13%
1360
16th to endNight
15%410%23%24%21%
1416
August1st to 15thNight
18%6%12%26%22%14%
1606
16th to endNight
17%47%22%30%17%
1875
September1st to 15thNight
23%410%22%25%13%
1800
16th to endNight
20%310%29%29%7%
1950
October1st to 15thNight
33%6%11%25%16%5%
2160
16th to endNight
27%5%13%30%18%4
2340
November1st to 15thNight
29%7%14%26%18%3
2486
16th to endNight
26%6%19%30%15%1
2730
December1st to 15thNight
37%8%20%23%9%
2730
16th to endNight
38%9%18%24%7%1
2912

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
414%42%27%10%
135
16th to endDay
7%14%48%20%8%
144
February1st to 15thDay
11%28%44%12%2
135
16th to endDay
14%28%34%16%8%
100
March1st to 15thDay
7%29%41%15%5%
168
16th to endDay
14%24%35%21%3
288
April1st to 15thDay
14%21%37%20%4
269
16th to endDay
25%17%30%21%41
270
May1st to 15thDay
15%12%24%27%15%3
438
16th to endDay
16%11%25%25%18%2
517
June1st to 15thDay
8%11%24%28%20%5%
495
16th to endDay
37%27%34%24%2
495
July1st to 15thDay
45%20%34%30%4
475
16th to endDay
4323%37%26%3
515
August1st to 15thDay
3428%41%19%2
319
16th to endDay
46%23%35%24%6%
332
September1st to 15thDay
7%9%33%28%17%3
315
16th to endDay
10%11%31%24%15%6%
219
October1st to 15thDay
9%14%31%31%13%
135
16th to endDay
6%16%41%21%11%2
144
November1st to 15thDay
419%40%21%11%2
135
16th to endDay
13%26%44%15%
135
December1st to 15thDay
10%20%45%17%6%
135
16th to endDay
9%18%47%18%5%
144
January1st to 15thNight
8%19%40%24%6%1
975
16th to endNight
9%17%46%22%4
913
February1st to 15thNight
8%15%41%26%7%
764
16th to endNight
7%19%41%25%5%
660
March1st to 15thNight
8%15%38%28%8%
720
16th to endNight
11%14%31%33%8%
708
April1st to 15thNight
12%11%35%33%6%
539
16th to endNight
16%11%25%34%10%
540
May1st to 15thNight
16%8%23%33%16%2
540
16th to endNight
13%9%23%34%18%
563
June1st to 15thNight
9%7%27%38%15%
540
16th to endNight
2429%46%15%
540
July1st to 15thNight
4222%43%26%
510
16th to endNight
2215%54%23%1
564
August1st to 15thNight
2318%48%24%1
539
16th to endNight
3219%44%26%2
573
September1st to 15thNight
8%324%39%22%2
540
16th to endNight
7%425%38%21%2
591
October1st to 15thNight
14%7%31%30%13%1
720
16th to endNight
9%9%32%34%11%2
804
November1st to 15thNight
8%17%36%28%8%
950
16th to endNight
7%19%45%23%4
975
December1st to 15thNight
8%19%45%21%5%
975
16th to endNight
8%21%42%23%4
1040
Page generated at 2018-02-23 09:21:33. Version ac04

Copyright 2018 A. Danko


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