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 2017-08-12.

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%
15955
21%
46507
12%
15913
49%
15913
32%
27570

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
27%
899
18%
2506
8%
895
36%
895
26%
1602
January16th to endNight
23%
843
21%
2571
8%
843
37%
843
28%
1547
February1st to 15thNight
27%
697
14%
2288
8%
697
36%
697
21%
1447
February16th to endNight
23%
632
17%
1935
5%
632
36%
632
23%
1214
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%
527
27%
1570
22%
524
76%
524
49%
776
August16th to endNight
68%
525
32%
1718
30%
525
74%
525
50%
799
September1st to 15thNight
57%
495
28%
1650
23%
495
68%
495
40%
852
September16th to endNight
61%
541
33%
1787
30%
541
67%
541
50%
828
October1st to 15thNight
43%
660
24%
1980
16%
660
50%
660
30%
1211
October16th to endNight
45%
737
29%
2145
14%
737
56%
737
37%
1222
November1st to 15thNight
34%
875
25%
2290
10%
875
44%
875
36%
1367
November16th to endNight
26%
900
24%
2520
8%
900
39%
900
35%
1449
December1st to 15thNight
20%
900
14%
2520
4%
900
29%
900
23%
1665
December16th to endNight
24%
960
17%
2688
5%
960
35%
960
23%
1789

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%
47483
Night
6%5%2432445%7%53%
46678
TransparencyDay
30%6%15%24%16%6%
47156
Night
30%7%15%25%15%5%
46507
SeeingDay
9%12%29%28%16%2
5833
Night
8%12%33%32%11%1
15963

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
36%344335%5%8%52%
1432
16th to endDay
36%24433447%53%
1662
February1st to 15thDay
410%46%5%2435%8%45%
1575
16th to endDay
48%45%42345%8%47%
1538
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
42123245%6%8%58%
2294
16th to endDay
311232446%6%62%
2130
September1st to 15thDay
7%31332235%6%59%
1980
16th to endDay
6%22212335%68%
1840
October1st to 15thDay
9%323333346%54%
1650
16th to endDay
7%5%23223448%55%
1716
November1st to 15thDay
5%423335%45%7%54%
1568
16th to endDay
242431347%7%57%
1440
December1st to 15thDay
47%37%5%35%5%5%7%44%
1440
16th to endDay
38%35%43445%6%50%
1536
January1st to 15thNight
37%3443446%7%49%
2506
16th to endNight
48%35%324346%52%
2571
February1st to 15thNight
48%36%425%46%9%44%
2277
16th to endNight
38%37%42445%7%48%
1935
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%
1578
16th to endNight
311121346%8%64%
1718
September1st to 15thNight
7%313413337%60%
1650
16th to endNight
6%112212235%69%
1787
October1st to 15thNight
12%6%22323346%51%
1980
16th to endNight
7%5%13313446%57%
2145
November1st to 15thNight
5%5%1431335%7%55%
2290
16th to endNight
46%22214447%58%
2520
December1st to 15thNight
5%7%36%6%3445%7%45%
2520
16th to endNight
38%445%35%5%5%7%46%
2688

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%23%24%7%
1433
16th to endDay
31%9%22%24%10%1
1662
February1st to 15thDay
39%8%20%24%6%1
1575
16th to endDay
37%8%21%22%8%2
1538
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%10%23%21%16%
2278
16th to endDay
20%5%9%21%26%15%
2130
September1st to 15thDay
25%5%8%17%27%15%
1980
16th to endDay
20%310%30%29%6%
1840
October1st to 15thDay
32%5%14%28%15%2
1650
16th to endDay
28%6%16%30%15%2
1716
November1st to 15thDay
29%6%17%24%17%3
1568
16th to endDay
25%7%22%29%14%1
1440
December1st to 15thDay
38%10%22%21%6%
1440
16th to endDay
36%9%21%25%6%1
1536
January1st to 15thNight
34%9%20%24%9%1
2506
16th to endNight
34%6%20%26%10%1
2571
February1st to 15thNight
37%10%19%23%8%1
2288
16th to endNight
36%8%18%24%10%1
1935
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%11%26%22%14%
1570
16th to endNight
17%47%22%30%16%
1718
September1st to 15thNight
25%410%20%24%13%
1650
16th to endNight
19%210%29%30%7%
1787
October1st to 15thNight
34%6%12%25%15%5%
1980
16th to endNight
28%5%14%30%16%4
2145
November1st to 15thNight
28%6%15%26%18%3
2290
16th to endNight
26%6%19%30%15%1
2520
December1st to 15thNight
38%8%21%23%7%
2520
16th to endNight
37%9%18%25%7%1
2688

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
416%35%33%8%1
90
16th to endDay
7%12%46%23%8%1
96
February1st to 15thDay
8%33%40%15%2
90
16th to endDay
13%23%35%17%9%
81
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%40%18%2
304
16th to endDay
5%7%25%33%22%4
268
September1st to 15thDay
7%12%38%27%12%1
255
16th to endDay
7%9%29%27%17%8%
167
October1st to 15thDay
412%27%36%18%
90
16th to endDay
5%13%38%22%16%3
96
November1st to 15thDay
213%36%26%16%4
90
16th to endDay
14%23%46%15%
90
December1st to 15thDay
12%24%40%16%6%
90
16th to endDay
7%17%44%21%8%
96
January1st to 15thNight
7%20%40%23%6%1
900
16th to endNight
9%17%46%21%4
843
February1st to 15thNight
8%14%40%27%8%
704
16th to endNight
7%18%42%24%5%
632
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
2319%48%24%1
527
16th to endNight
3321%46%22%2
525
September1st to 15thNight
9%325%39%19%2
495
16th to endNight
6%425%39%21%2
541
October1st to 15thNight
15%7%29%31%14%1
660
16th to endNight
9%8%32%34%12%2
737
November1st to 15thNight
7%17%37%27%9%
875
16th to endNight
6%19%45%23%4
900
December1st to 15thNight
8%21%43%20%5%
900
16th to endNight
7%22%40%24%5%
960
Page generated at 2017-08-13 12:16:27. Version ac04

Copyright 2017 A. Danko


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