Prairie Skies Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Prairie Skies Star Party clear sky chart from 2005-11-05 to 2017-09-23.

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
38%
15962
17%
46907
11%
15919
44%
15919
24%
31445

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
20%
900
13%
2506
4%
895
28%
895
18%
1841
January16th to endNight
22%
960
12%
2646
5%
960
27%
960
16%
2009
February1st to 15thNight
23%
779
13%
2190
4%
779
30%
779
19%
1577
February16th to endNight
26%
631
17%
1893
7%
631
35%
631
18%
1348
March1st to 15thNight
26%
720
13%
2160
8%
720
30%
720
17%
1535
March16th to endNight
28%
630
14%
2016
9%
630
35%
630
19%
1408
April1st to 15thNight
29%
539
15%
1797
9%
539
38%
539
21%
1196
April16th to endNight
33%
540
17%
1740
11%
540
42%
540
22%
1174
May1st to 15thNight
38%
540
15%
1620
9%
540
44%
540
23%
1118
May16th to endNight
50%
563
17%
1499
10%
561
55%
561
31%
981
June1st to 15thNight
52%
540
17%
1440
11%
540
56%
540
36%
894
June16th to endNight
53%
540
17%
1440
10%
540
58%
540
33%
918
July1st to 15thNight
65%
510
17%
1360
12%
510
67%
510
36%
844
July16th to endNight
73%
564
23%
1417
19%
531
75%
531
44%
820
August1st to 15thNight
77%
539
21%
1601
21%
536
78%
536
42%
879
August16th to endNight
68%
573
21%
1910
22%
573
72%
573
34%
1082
September1st to 15thNight
66%
549
28%
1809
29%
549
71%
549
35%
992
September16th to endNight
60%
689
27%
1903
21%
689
63%
689
36%
1161
October1st to 15thNight
50%
660
27%
1888
20%
660
57%
660
34%
1129
October16th to endNight
28%
704
19%
2236
11%
704
38%
704
22%
1449
November1st to 15thNight
32%
700
24%
2276
16%
700
43%
700
25%
1392
November16th to endNight
27%
732
16%
2352
10%
732
35%
732
18%
1587
December1st to 15thNight
22%
900
11%
2520
4%
900
27%
900
16%
1895
December16th to endNight
17%
960
10%
2688
3%
960
23%
960
11%
2216

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
14%8%36%5%3445%7%36%
48010
Night
14%8%35%5%24446%39%
47076
Cloud CoverDay
14%7%36%5%3445%7%37%
48019
Night
14%7%35%434346%40%
47081
TransparencyDay
45%6%13%20%12%1
47696
Night
44%5%12%21%13%2
46908
SeeingDay
15%6%26%25%18%7%
5969
Night
18%7%28%30%13%1
15965

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
15%16%5%8%7%34445%24%
1432
16th to endDay
14%15%7%8%6%33346%25%
1576
February1st to 15thDay
16%13%5%7%5%25%446%27%
1672
16th to endDay
16%11%48%7%34345%32%
1580
March1st to 15thDay
17%12%47%5%25%446%27%
1790
16th to endDay
18%9%46%6%35%448%29%
2220
April1st to 15thDay
18%10%36%423346%34%
2151
16th to endDay
19%8%25%5%33447%34%
2220
May1st to 15thDay
19%8%36%5%3446%6%30%
2331
16th to endDay
13%6%25%5%3446%7%38%
2613
June1st to 15thDay
10%5%25%425%5%6%7%44%
2520
16th to endDay
9%425%5%46%6%7%9%37%
2520
July1st to 15thDay
8%425%5%35%5%6%9%43%
2520
16th to endDay
6%3245%36%5%7%10%42%
2655
August1st to 15thDay
6%425%5%36%5%6%9%44%
2346
16th to endDay
8%4346%346%6%8%43%
2292
September1st to 15thDay
12%425%344447%47%
2139
16th to endDay
9%5%244345%5%8%45%
1894
October1st to 15thDay
14%6%25%42346%5%43%
1741
16th to endDay
17%7%25%5%3445%6%35%
1635
November1st to 15thDay
15%7%2432346%5%44%
1582
16th to endDay
18%9%46%423346%35%
1605
December1st to 15thDay
18%13%48%6%35%335%26%
1440
16th to endDay
22%14%6%7%5%2434422%
1536
January1st to 15thNight
17%11%47%5%24345%33%
2506
16th to endNight
15%12%6%8%6%24446%28%
2646
February1st to 15thNight
15%12%45%5%23446%34%
2188
16th to endNight
16%10%47%5%2435%6%33%
1893
March1st to 15thNight
17%10%46%5%24346%34%
2147
16th to endNight
16%9%35%6%25%45%7%33%
2016
April1st to 15thNight
15%7%45%6%23446%39%
1797
16th to endNight
19%6%15%5%2445%6%38%
1740
May1st to 15thNight
18%6%3442446%8%34%
1620
16th to endNight
9%424425%5%6%9%44%
1498
June1st to 15thNight
10%5%25%423347%49%
1440
16th to endNight
8%5%25%5%245%5%10%43%
1440
July1st to 15thNight
8%3134345%6%9%49%
1440
16th to endNight
422443446%9%53%
1513
August1st to 15thNight
3314435%46%10%52%
1610
16th to endNight
9%32442345%8%51%
1910
September1st to 15thNight
10%323313347%55%
1809
16th to endNight
8%314425%46%7%49%
1903
October1st to 15thNight
11%5%13423346%52%
1888
16th to endNight
18%7%35%422345%41%
2236
November1st to 15thNight
13%7%34423345%46%
2276
16th to endNight
18%8%346%33336%37%
2352
December1st to 15thNight
19%12%48%5%24336%30%
2520
16th to endNight
23%14%6%8%6%35%33421%
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
15%16%5%8%7%34436%24%
1432
16th to endDay
13%16%7%8%6%24336%25%
1576
February1st to 15thDay
16%12%6%7%6%25%445%27%
1672
16th to endDay
16%10%47%6%44335%32%
1580
March1st to 15thDay
18%13%47%425%45%6%27%
1800
16th to endDay
18%9%46%5%25%45%7%29%
2219
April1st to 15thDay
19%9%36%423347%34%
2151
16th to endDay
19%7%25%5%23447%35%
2220
May1st to 15thDay
20%7%27%5%3445%7%30%
2331
16th to endDay
13%5%35%5%345%5%7%39%
2613
June1st to 15thDay
11%425%5%245%5%7%44%
2520
16th to endDay
10%425%5%46%5%7%8%37%
2520
July1st to 15thDay
8%425%5%35%6%6%9%43%
2520
16th to endDay
6%315%5%36%6%7%10%42%
2655
August1st to 15thDay
7%325%436%5%7%9%44%
2346
16th to endDay
9%425%5%345%6%7%44%
2292
September1st to 15thDay
12%42433445%7%47%
2139
16th to endDay
10%5%334345%5%8%45%
1894
October1st to 15thDay
15%6%2442445%6%43%
1741
16th to endDay
18%7%25%5%35%45%6%35%
1635
November1st to 15thDay
15%7%3442346%5%43%
1582
16th to endDay
18%9%46%424336%35%
1605
December1st to 15thDay
19%12%48%5%35%335%27%
1440
16th to endDay
23%13%6%8%5%24335%22%
1536
January1st to 15thNight
17%11%47%6%2335%5%32%
2506
16th to endNight
15%12%7%8%5%34346%28%
2646
February1st to 15thNight
15%12%46%5%33436%34%
2181
16th to endNight
16%10%47%424446%33%
1893
March1st to 15thNight
18%10%45%5%33345%33%
2160
16th to endNight
16%8%35%5%2445%7%34%
2016
April1st to 15thNight
16%7%36%5%23446%39%
1797
16th to endNight
20%5%25%5%3345%5%38%
1740
May1st to 15thNight
19%5%35%42445%8%35%
1619
16th to endNight
9%4245%35%5%6%8%45%
1498
June1st to 15thNight
11%42442335%7%49%
1440
16th to endNight
9%4344345%6%10%43%
1440
July1st to 15thNight
7%314325%5%5%10%49%
1440
16th to endNight
4224435%46%9%53%
1513
August1st to 15thNight
3324435%46%10%52%
1610
16th to endNight
10%21443345%8%51%
1910
September1st to 15thNight
11%313323347%55%
1809
16th to endNight
8%315%43446%8%49%
1903
October1st to 15thNight
12%5%23323347%51%
1888
16th to endNight
19%7%35%423245%41%
2236
November1st to 15thNight
13%7%35%423345%46%
2276
16th to endNight
18%7%35%6%33236%37%
2352
December1st to 15thNight
20%10%48%433345%30%
2520
16th to endNight
23%14%5%9%6%3433421%
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
61%412%12%8%
1433
16th to endDay
60%5%11%15%6%
1576
February1st to 15thDay
57%5%12%16%6%1
1674
16th to endDay
54%5%12%22%41
1580
March1st to 15thDay
56%414%17%6%
1800
16th to endDay
53%6%13%19%5%1
2220
April1st to 15thDay
50%411%20%12%
2151
16th to endDay
48%7%12%16%10%3
2220
May1st to 15thDay
51%6%12%20%7%
2331
16th to endDay
43%7%12%18%15%2
2617
June1st to 15thDay
36%7%12%23%17%1
2520
16th to endDay
40%9%13%19%15%1
2520
July1st to 15thDay
36%8%13%22%15%3
2371
16th to endDay
33%8%18%23%13%2
2488
August1st to 15thDay
32%8%15%24%17%1
2331
16th to endDay
35%8%13%22%16%3
2292
September1st to 15thDay
35%5%11%24%18%4
2139
16th to endDay
35%5%11%28%18%1
1894
October1st to 15thDay
40%5%12%25%15%1
1741
16th to endDay
46%5%13%22%10%1
1635
November1st to 15thDay
40%413%22%16%2
1582
16th to endDay
51%312%22%8%
1605
December1st to 15thDay
60%5%10%17%6%
1440
16th to endDay
64%5%10%12%6%
1536
January1st to 15thNight
52%5%12%17%10%
2506
16th to endNight
56%5%15%14%7%
2646
February1st to 15thNight
51%5%13%19%8%1
2190
16th to endNight
51%5%12%20%9%
1893
March1st to 15thNight
52%5%12%19%9%1
2160
16th to endNight
49%6%14%18%9%1
2016
April1st to 15thNight
45%5%12%19%14%2
1797
16th to endNight
46%6%10%19%13%4
1740
May1st to 15thNight
45%6%13%21%12%
1620
16th to endNight
34%9%14%18%18%3
1500
June1st to 15thNight
33%6%12%25%19%3
1440
16th to endNight
34%7%14%23%16%3
1440
July1st to 15thNight
31%7%13%25%18%3
1360
16th to endNight
25%6%16%28%18%4
1417
August1st to 15thNight
25%5%18%27%19%3
1601
16th to endNight
30%6%12%24%20%5%
1910
September1st to 15thNight
28%5%9%26%23%5%
1809
16th to endNight
31%6%10%26%21%3
1903
October1st to 15thNight
32%5%10%26%23%1
1888
16th to endNight
45%310%24%14%1
2236
November1st to 15thNight
40%38%25%17%4
2276
16th to endNight
48%413%22%11%
2352
December1st to 15thNight
57%411%17%8%
2520
16th to endNight
68%48%13%5%
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
32%8%32%18%6%1
90
16th to endDay
21%12%30%27%8%
96
February1st to 15thDay
21%20%44%13%1
90
16th to endDay
17%12%33%24%11%1
81
March1st to 15thDay
33%17%27%17%3
90
16th to endDay
27%10%30%19%9%1
246
April1st to 15thDay
22%11%31%22%11%1
270
16th to endDay
21%10%29%22%10%5%
270
May1st to 15thDay
22%7%29%23%12%3
288
16th to endDay
17%7%30%23%15%5%
513
June1st to 15thDay
10%327%30%22%4
495
16th to endDay
12%5%32%27%16%5%
495
July1st to 15thDay
10%325%28%21%11%
475
16th to endDay
7%120%31%25%12%
515
August1st to 15thDay
9%15%31%25%17%
382
16th to endDay
11%216%28%26%15%
332
September1st to 15thDay
12%214%29%31%9%
315
16th to endDay
11%313%27%34%10%
283
October1st to 15thDay
15%325%25%24%4
181
16th to endDay
26%5%37%27%4
96
November1st to 15thDay
10%10%21%25%24%8%
90
16th to endDay
41%8%28%12%8%
90
December1st to 15thDay
22%17%32%17%8%1
90
16th to endDay
27%20%45%24
96
January1st to 15thNight
22%14%37%20%4
900
16th to endNight
21%12%35%27%3
960
February1st to 15thNight
22%10%37%24%4
782
16th to endNight
20%12%35%25%6%
631
March1st to 15thNight
22%11%34%24%5%
720
16th to endNight
21%7%36%25%7%
630
April1st to 15thNight
19%11%36%27%5%
539
16th to endNight
22%6%33%27%9%
540
May1st to 15thNight
20%5%30%32%10%
540
16th to endNight
11%329%36%18%
563
June1st to 15thNight
13%224%44%14%
540
16th to endNight
10%227%42%17%
540
July1st to 15thNight
10%16%44%24%2
510
16th to endNight
5%114%44%31%2
564
August1st to 15thNight
5%8%48%32%3
539
16th to endNight
11%12%36%34%4
573
September1st to 15thNight
11%313%38%28%4
549
16th to endNight
10%317%33%30%3
689
October1st to 15thNight
15%6%24%32%19%1
660
16th to endNight
23%11%32%23%9%
704
November1st to 15thNight
16%10%35%26%10%1
700
16th to endNight
23%11%32%24%7%
732
December1st to 15thNight
25%12%32%23%5%
900
16th to endNight
30%10%33%22%3
960
Page generated at 2017-09-24 08:15:57. Version ac04

Copyright 2017 A. Danko


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