Northwest Nebraska Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Northwest Nebraska Star Party clear sky chart from 2005-11-05 to 2017-09-21.

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%
16078
23%
46889
12%
16036
49%
16036
34%
27442

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
31%
900
23%
2506
11%
895
41%
895
30%
1530
January16th to endNight
28%
942
24%
2670
9%
942
43%
942
31%
1568
February1st to 15thNight
29%
699
16%
2241
7%
699
39%
699
25%
1387
February16th to endNight
28%
632
20%
1894
8%
632
39%
632
26%
1175
March1st to 15thNight
34%
720
22%
2160
9%
720
45%
720
32%
1285
March16th to endNight
37%
633
22%
2004
13%
633
48%
633
29%
1202
April1st to 15thNight
31%
539
19%
1798
11%
539
44%
539
26%
1095
April16th to endNight
33%
540
15%
1737
11%
540
40%
540
21%
1140
May1st to 15thNight
42%
540
20%
1548
14%
540
48%
540
31%
955
May16th to endNight
38%
562
15%
1498
8%
561
42%
561
29%
983
June1st to 15thNight
42%
540
14%
1440
6%
540
45%
540
34%
896
June16th to endNight
50%
540
20%
1440
9%
540
55%
540
48%
786
July1st to 15thNight
55%
510
17%
1360
9%
510
60%
510
43%
788
July16th to endNight
60%
564
27%
1416
16%
531
65%
531
50%
764
August1st to 15thNight
61%
539
25%
1540
16%
536
69%
536
45%
807
August16th to endNight
63%
573
29%
1910
27%
573
72%
573
42%
959
September1st to 15thNight
52%
540
26%
1800
23%
540
62%
540
36%
963
September16th to endNight
56%
510
33%
1869
29%
510
69%
510
44%
850
October1st to 15thNight
43%
603
25%
1923
17%
603
50%
603
31%
1121
October16th to endNight
44%
817
28%
2225
13%
817
53%
817
40%
1293
November1st to 15thNight
39%
875
28%
2275
12%
875
48%
875
43%
1307
November16th to endNight
37%
900
28%
2427
12%
900
49%
900
39%
1413
December1st to 15thNight
29%
900
18%
2520
7%
900
39%
900
31%
1551
December16th to endNight
31%
960
22%
2688
8%
960
43%
960
32%
1624

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
7%42332445%8%52%
47982
Night
6%5%2442445%7%51%
47056
Cloud CoverDay
7%5%2432445%8%51%
47992
Night
6%5%2442445%7%51%
47061
Cloud CoverDay
7%42332445%7%52%
47990
Night
7%5%2442445%7%51%
47061
TransparencyDay
29%5%14%27%17%5%
47666
Night
31%5%15%26%16%4
46889
SeeingDay
10%8%29%30%16%3
6025
Night
9%9%36%34%10%
16084

By Month

Percentage Cloud Cover NE (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
45%345%3445%9%48%
1432
16th to endDay
46%144335%6%8%51%
1564
February1st to 15thDay
6%9%46%4345%5%7%43%
1621
16th to endDay
5%8%344235%6%8%47%
1580
March1st to 15thDay
5%7%2341345%8%51%
1790
16th to endDay
8%6%2442345%8%47%
2217
April1st to 15thDay
10%6%25%43445%8%44%
2150
16th to endDay
16%7%2442335%7%41%
2223
May1st to 15thDay
14%5%1442445%7%44%
2400
16th to endDay
14%6%25%335%5%7%9%37%
2616
June1st to 15thDay
10%21332446%9%50%
2520
16th to endDay
32222345%7%64%
2520
July1st to 15thDay
6%2133245%6%9%54%
2520
16th to endDay
5%21232445%8%57%
2656
August1st to 15thDay
43134245%7%10%53%
2409
16th to endDay
6%21231335%6%62%
2292
September1st to 15thDay
8%212323446%59%
2160
16th to endDay
6%212212335%67%
1881
October1st to 15thDay
12%5%13324345%50%
1705
16th to endDay
6%31331235%8%59%
1636
November1st to 15thDay
5%4243145%5%8%54%
1583
16th to endDay
3434423447%56%
1531
December1st to 15thDay
5%6%344345%49%48%
1440
16th to endDay
6%7%36%324446%50%
1536
January1st to 15thNight
36%26%5%35%46%7%49%
2506
16th to endNight
35%25%5%2446%7%51%
2670
February1st to 15thNight
5%8%35%4246%6%8%44%
2238
16th to endNight
5%9%36%5%34446%46%
1894
March1st to 15thNight
5%6%245%34446%51%
2147
16th to endNight
8%6%2443445%7%47%
2004
April1st to 15thNight
10%6%243335%5%7%46%
1798
16th to endNight
16%8%25%423448%39%
1737
May1st to 15thNight
11%6%1442435%7%48%
1548
16th to endNight
15%41333446%9%43%
1497
June1st to 15thNight
10%3143245%6%10%46%
1440
16th to endNight
4223245%7%9%58%
1440
July1st to 15thNight
6%31343435%8%54%
1440
16th to endNight
121332445%9%60%
1512
August1st to 15thNight
321342447%10%54%
1548
16th to endNight
4212414447%60%
1910
September1st to 15thNight
9%323423346%56%
1800
16th to endNight
7%212212346%64%
1869
October1st to 15thNight
12%5%1432435%6%50%
1923
16th to endNight
7%41442345%7%54%
2225
November1st to 15thNight
5%31342445%6%57%
2275
16th to endNight
442442435%7%54%
2427
December1st to 15thNight
5%6%35%4345%47%48%
2520
16th to endNight
37%25%42435%7%51%
2688

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
46%35%5%3445%9%48%
1432
16th to endDay
46%144235%6%8%51%
1564
February1st to 15thDay
6%9%46%5%35%45%7%43%
1621
16th to endDay
5%8%3442446%8%46%
1580
March1st to 15thDay
5%7%2332445%7%51%
1800
16th to endDay
8%6%25%42346%7%48%
2217
April1st to 15thDay
9%6%25%43346%7%43%
2150
16th to endDay
16%7%2442335%7%41%
2223
May1st to 15thDay
13%6%2433445%7%44%
2400
16th to endDay
14%6%24435%6%6%8%37%
2616
June1st to 15thDay
9%3133245%6%9%50%
2520
16th to endDay
321221346%7%64%
2520
July1st to 15thDay
6%213425%5%6%9%54%
2520
16th to endDay
5%21232446%9%57%
2656
August1st to 15thDay
43133245%7%10%53%
2409
16th to endDay
5%21331335%7%61%
2292
September1st to 15thDay
8%312423446%59%
2160
16th to endDay
6%212212235%67%
1881
October1st to 15thDay
12%5%23325%436%50%
1705
16th to endDay
6%31421345%7%59%
1636
November1st to 15thDay
5%42422446%8%54%
1583
16th to endDay
343432445%6%56%
1531
December1st to 15thDay
5%5%345%25%449%48%
1440
16th to endDay
6%7%36%324445%49%
1536
January1st to 15thNight
35%26%5%3445%8%48%
2506
16th to endNight
35%25%5%345%5%7%50%
2670
February1st to 15thNight
5%7%36%4346%6%8%43%
2231
16th to endNight
5%8%36%5%35%446%46%
1894
March1st to 15thNight
6%6%35%5%25%446%50%
2160
16th to endNight
8%6%24435%45%7%46%
2004
April1st to 15thNight
9%6%244345%5%7%46%
1798
16th to endNight
15%7%35%42445%8%38%
1737
May1st to 15thNight
11%6%1343445%7%48%
1547
16th to endNight
14%414425%35%10%42%
1497
June1st to 15thNight
9%414335%46%10%46%
1440
16th to endNight
3223246%6%9%57%
1440
July1st to 15thNight
6%31443445%8%54%
1440
16th to endNight
221342445%8%61%
1512
August1st to 15thNight
32134245%7%10%54%
1548
16th to endNight
4313424447%60%
1910
September1st to 15thNight
8%423323346%56%
1800
16th to endNight
6%212212346%64%
1869
October1st to 15thNight
12%5%2341345%6%49%
1923
16th to endNight
7%415%323448%54%
2225
November1st to 15thNight
5%31442445%7%56%
2275
16th to endNight
442443445%8%53%
2427
December1st to 15thNight
5%6%35%4345%47%48%
2520
16th to endNight
37%25%43335%7%51%
2688

Percentage Cloud Cover SE (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
45%25%5%25%45%9%48%
1432
16th to endDay
46%2442446%9%51%
1564
February1st to 15thDay
5%9%45%43445%7%43%
1621
16th to endDay
5%8%344235%6%8%46%
1580
March1st to 15thDay
5%8%2332345%8%51%
1800
16th to endDay
8%6%245%2335%8%48%
2215
April1st to 15thDay
10%6%345%3445%8%44%
2150
16th to endDay
16%7%2442326%7%42%
2223
May1st to 15thDay
14%5%2442445%7%45%
2400
16th to endDay
14%5%24425%5%7%8%38%
2616
June1st to 15thDay
10%2133245%6%9%50%
2520
16th to endDay
32222345%7%65%
2520
July1st to 15thDay
5%2123245%6%8%55%
2520
16th to endDay
5%21232445%8%58%
2656
August1st to 15thDay
43133245%7%9%54%
2409
16th to endDay
6%213313347%62%
2292
September1st to 15thDay
8%312323346%59%
2160
16th to endDay
6%212211236%68%
1881
October1st to 15thDay
12%5%13334345%51%
1705
16th to endDay
6%313222348%59%
1636
November1st to 15thDay
5%42431446%7%54%
1583
16th to endDay
35%3432345%7%55%
1531
December1st to 15thDay
45%34435%45%9%48%
1440
16th to endDay
6%7%35%325%35%6%49%
1536
January1st to 15thNight
35%26%5%35%46%7%48%
2506
16th to endNight
36%25%425%46%7%50%
2670
February1st to 15thNight
5%7%46%3246%5%8%44%
2231
16th to endNight
5%9%36%5%34446%46%
1894
March1st to 15thNight
6%6%245%24446%50%
2160
16th to endNight
9%5%2342445%8%46%
2004
April1st to 15thNight
10%6%244245%5%6%46%
1798
16th to endNight
16%7%25%423448%39%
1737
May1st to 15thNight
12%5%1442435%7%48%
1547
16th to endNight
15%413425%36%9%43%
1497
June1st to 15thNight
10%4133245%6%8%47%
1440
16th to endNight
32122245%6%9%58%
1440
July1st to 15thNight
6%31343436%8%54%
1440
16th to endNight
211332445%8%62%
1512
August1st to 15thNight
3234345%7%9%55%
1548
16th to endNight
4213324446%61%
1910
September1st to 15thNight
9%423324346%57%
1800
16th to endNight
7%212213346%65%
1869
October1st to 15thNight
12%5%2432435%6%50%
1923
16th to endNight
7%5%14323447%54%
2225
November1st to 15thNight
6%313424447%57%
2275
16th to endNight
5%42442445%8%53%
2427
December1st to 15thNight
5%6%35%5%25%5%5%6%49%
2520
16th to endNight
37%26%42435%7%51%
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
32%6%20%29%9%1
1433
16th to endDay
29%5%19%30%12%2
1564
February1st to 15thDay
39%6%18%23%8%3
1622
16th to endDay
34%6%19%25%10%4
1580
March1st to 15thDay
29%5%17%29%16%2
1800
16th to endDay
34%7%14%28%12%2
2217
April1st to 15thDay
37%6%14%27%10%2
2150
16th to endDay
41%5%15%22%13%1
2223
May1st to 15thDay
38%416%28%11%1
2400
16th to endDay
41%6%18%21%9%1
2620
June1st to 15thDay
29%7%16%26%16%3
2520
16th to endDay
16%5%11%32%24%8%
2520
July1st to 15thDay
25%5%12%22%22%10%
2371
16th to endDay
21%5%10%25%24%12%
2489
August1st to 15thDay
24%5%15%27%17%9%
2393
16th to endDay
21%48%25%27%12%
2292
September1st to 15thDay
25%47%23%26%12%
2160
16th to endDay
19%29%33%30%4
1881
October1st to 15thDay
35%5%11%24%19%4
1705
16th to endDay
23%5%15%33%17%4
1636
November1st to 15thDay
26%5%15%25%20%6%
1583
16th to endDay
26%5%16%30%18%2
1531
December1st to 15thDay
33%5%20%26%13%
1440
16th to endDay
35%6%16%27%12%1
1536
January1st to 15thNight
33%6%17%26%14%2
2506
16th to endNight
30%5%17%29%14%2
2670
February1st to 15thNight
36%7%18%25%9%2
2241
16th to endNight
37%5%15%24%12%5%
1894
March1st to 15thNight
34%413%26%16%3
2160
16th to endNight
35%5%15%27%14%1
2004
April1st to 15thNight
36%7%14%26%12%3
1798
16th to endNight
44%5%12%22%13%1
1737
May1st to 15thNight
35%5%16%27%14%1
1548
16th to endNight
37%7%20%21%11%1
1498
June1st to 15thNight
32%7%21%23%11%3
1440
16th to endNight
19%8%14%32%18%7%
1440
July1st to 15thNight
28%413%26%18%8%
1360
16th to endNight
21%5%11%27%21%12%
1416
August1st to 15thNight
21%6%16%30%18%6%
1540
16th to endNight
23%5%8%23%27%11%
1910
September1st to 15thNight
28%5%8%23%24%10%
1800
16th to endNight
20%38%33%24%8%
1869
October1st to 15thNight
34%414%22%18%5%
1923
16th to endNight
28%5%12%28%19%6%
2225
November1st to 15thNight
26%414%25%22%6%
2275
16th to endNight
28%413%30%17%4
2427
December1st to 15thNight
33%5%19%26%11%2
2520
16th to endNight
31%6%19%27%12%2
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
7%12%32%27%16%3
90
16th to endDay
5%15%40%21%12%4
96
February1st to 15thDay
12%20%45%21%1
90
16th to endDay
11%22%38%14%13%
81
March1st to 15thDay
6%12%40%32%8%
90
16th to endDay
15%17%34%23%8%
258
April1st to 15thDay
13%20%38%19%7%
269
16th to endDay
26%11%30%20%8%2
333
May1st to 15thDay
15%11%30%24%14%3
468
16th to endDay
19%8%27%25%15%2
517
June1st to 15thDay
9%7%29%30%17%5%
495
16th to endDay
5%5%33%36%15%2
495
July1st to 15thDay
8%324%36%22%4
475
16th to endDay
5%323%40%25%2
515
August1st to 15thDay
6%223%42%22%2
439
16th to endDay
6%325%31%25%6%
332
September1st to 15thDay
9%6%24%34%20%5%
315
16th to endDay
12%10%20%35%14%6%
115
October1st to 15thDay
8%10%27%30%21%2
90
16th to endDay
49%28%29%21%7%
96
November1st to 15thDay
337%28%21%8%
90
16th to endDay
20%16%31%24%7%
90
December1st to 15thDay
10%17%43%21%7%
90
16th to endDay
6%8%54%28%3
96
January1st to 15thNight
6%16%40%27%8%1
900
16th to endNight
7%18%41%26%6%
942
February1st to 15thNight
8%12%42%29%7%
704
16th to endNight
11%12%40%28%6%
632
March1st to 15thNight
10%9%40%32%5%
720
16th to endNight
12%9%37%33%6%
633
April1st to 15thNight
13%10%40%30%5%
539
16th to endNight
18%12%30%30%8%
540
May1st to 15thNight
14%8%30%32%13%
540
16th to endNight
16%6%34%32%9%
563
June1st to 15thNight
11%6%37%32%11%1
540
16th to endNight
4338%42%9%
540
July1st to 15thNight
6%323%45%18%1
510
16th to endNight
2228%46%19%
564
August1st to 15thNight
3226%47%17%1
539
16th to endNight
5%322%50%18%
573
September1st to 15thNight
10%427%35%20%1
540
16th to endNight
7%5%28%40%16%1
510
October1st to 15thNight
16%7%28%33%12%
603
16th to endNight
9%7%34%36%11%1
817
November1st to 15thNight
8%8%39%32%9%1
875
16th to endNight
6%12%40%33%6%
900
December1st to 15thNight
8%12%44%27%5%
900
16th to endNight
7%13%43%29%5%
960
Page generated at 2017-09-22 05:35:36. Version ac04

Copyright 2017 A. Danko


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