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 2019-06-24.

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%
18363
17%
53971
11%
18320
44%
18320
23%
36330

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
22%
1050
14%
2926
5%
1045
30%
1045
18%
2139
January16th to endNight
21%
1120
12%
3087
5%
1120
27%
1120
16%
2355
February1st to 15thNight
22%
911
13%
2562
4%
911
29%
911
17%
1879
February16th to endNight
24%
735
16%
2205
7%
735
33%
735
16%
1596
March1st to 15thNight
26%
840
15%
2520
8%
840
32%
840
18%
1761
March16th to endNight
29%
735
16%
2352
10%
735
36%
735
19%
1629
April1st to 15thNight
27%
629
15%
2097
10%
629
36%
629
20%
1410
April16th to endNight
33%
624
16%
2008
10%
624
41%
624
21%
1363
May1st to 15thNight
39%
630
15%
1890
9%
630
44%
630
23%
1310
May16th to endNight
50%
659
16%
1756
10%
657
54%
657
30%
1160
June1st to 15thNight
52%
630
18%
1680
11%
630
57%
630
35%
1057
June16th to endNight
54%
609
16%
1624
9%
609
57%
609
32%
1048
July1st to 15thNight
66%
555
18%
1480
14%
555
68%
555
38%
905
July16th to endNight
73%
612
23%
1545
19%
579
76%
579
45%
893
August1st to 15thNight
78%
575
22%
1704
22%
572
78%
572
43%
937
August16th to endNight
67%
621
20%
2070
21%
621
71%
621
34%
1172
September1st to 15thNight
65%
595
29%
1960
30%
595
70%
595
36%
1072
September16th to endNight
59%
777
27%
2145
21%
777
62%
777
37%
1303
October1st to 15thNight
47%
780
25%
2232
18%
780
53%
780
30%
1395
October16th to endNight
30%
832
20%
2642
12%
832
40%
832
23%
1692
November1st to 15thNight
31%
820
23%
2666
15%
820
42%
820
22%
1687
November16th to endNight
28%
854
17%
2744
10%
854
37%
854
19%
1837
December1st to 15thNight
22%
1050
12%
2940
5%
1050
29%
1050
17%
2182
December16th to endNight
18%
1120
10%
3136
3%
1120
24%
1120
12%
2548

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%
54857
Night
14%8%35%5%24446%39%
54140
Cloud CoverDay
14%8%36%5%3445%7%36%
54866
Night
14%8%35%5%34446%39%
54145
TransparencyDay
46%6%12%20%12%1
54543
Night
44%5%12%21%13%2
53972
SeeingDay
17%7%26%24%16%6%
8296
Night
18%7%29%30%12%1
18366

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
16%16%48%7%33445%25%
1672
16th to endDay
15%15%7%8%5%34346%25%
1839
February1st to 15thDay
18%13%5%7%6%35%446%25%
1959
16th to endDay
17%11%5%8%6%33345%30%
1840
March1st to 15thDay
17%12%47%5%25%446%27%
2090
16th to endDay
18%10%46%5%35%447%29%
2588
April1st to 15thDay
19%10%36%5%33346%32%
2511
16th to endDay
19%8%25%5%33447%35%
2557
May1st to 15thDay
19%8%26%5%3446%7%30%
2721
16th to endDay
13%6%36%5%345%6%7%38%
3060
June1st to 15thDay
10%5%25%425%5%5%7%44%
2940
16th to endDay
10%425%5%46%6%6%8%37%
2843
July1st to 15thDay
8%424435%5%6%9%44%
2730
16th to endDay
6%3245%46%6%7%10%42%
2879
August1st to 15thDay
6%425%5%36%5%7%9%45%
2496
16th to endDay
9%4246%345%6%8%43%
2484
September1st to 15thDay
12%5%25%334446%47%
2317
16th to endDay
8%5%243245%6%8%46%
2145
October1st to 15thDay
16%7%25%5%2346%5%40%
2057
16th to endDay
17%7%25%5%3335%6%37%
1932
November1st to 15thDay
16%8%2442445%5%41%
1852
16th to endDay
18%9%36%5%23346%36%
1873
December1st to 15thDay
17%12%5%8%6%35%435%27%
1680
16th to endDay
21%14%6%7%5%2445%5%22%
1792
January1st to 15thNight
16%12%47%5%24345%33%
2926
16th to endNight
14%12%6%9%6%24435%28%
3087
February1st to 15thNight
17%13%45%5%23336%32%
2560
16th to endNight
17%11%47%5%2435%5%31%
2205
March1st to 15thNight
16%10%36%5%24346%35%
2507
16th to endNight
17%9%35%5%24447%35%
2352
April1st to 15thNight
16%7%46%5%2345%6%37%
2097
16th to endNight
18%7%25%5%24446%38%
2008
May1st to 15thNight
17%6%345%25%46%8%34%
1890
16th to endNight
10%4245%35%5%6%9%43%
1755
June1st to 15thNight
10%5%25%42435%7%48%
1680
16th to endNight
9%5%25%5%245%5%10%42%
1624
July1st to 15thNight
7%3134245%6%9%50%
1560
16th to endNight
422343446%9%53%
1641
August1st to 15thNight
331343446%10%52%
1713
16th to endNight
9%22442345%8%51%
2070
September1st to 15thNight
11%313313347%55%
1960
16th to endNight
8%314425%5%6%7%49%
2145
October1st to 15thNight
12%5%24423346%48%
2232
16th to endNight
17%7%35%422345%43%
2642
November1st to 15thNight
14%7%35%423345%43%
2666
16th to endNight
18%8%346%33336%38%
2744
December1st to 15thNight
18%12%48%5%34336%31%
2940
16th to endNight
21%14%6%8%6%35%33422%
3136

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
16%16%5%8%6%34435%25%
1672
16th to endDay
14%15%6%8%6%34346%25%
1839
February1st to 15thDay
18%13%5%7%6%35%445%25%
1959
16th to endDay
17%11%5%7%6%34345%30%
1840
March1st to 15thDay
17%13%47%5%25%45%6%27%
2100
16th to endDay
18%9%36%5%25%45%7%30%
2587
April1st to 15thDay
19%10%36%5%33347%32%
2511
16th to endDay
19%7%25%5%235%46%35%
2557
May1st to 15thDay
19%8%37%5%3446%7%30%
2721
16th to endDay
13%5%35%5%345%5%7%38%
3060
June1st to 15thDay
11%4245%245%5%7%44%
2940
16th to endDay
10%5%25%5%46%5%7%8%37%
2843
July1st to 15thDay
8%4245%35%5%6%9%45%
2730
16th to endDay
7%315%5%36%6%7%9%42%
2879
August1st to 15thDay
7%325%436%5%7%9%45%
2496
16th to endDay
10%425%5%345%6%8%44%
2484
September1st to 15thDay
12%5%2433445%6%47%
2317
16th to endDay
9%5%23435%5%5%8%46%
2145
October1st to 15thDay
16%7%25%5%2345%5%40%
2057
16th to endDay
18%7%25%5%3435%6%37%
1932
November1st to 15thDay
17%7%3442345%5%40%
1852
16th to endDay
18%9%46%5%24346%36%
1873
December1st to 15thDay
17%12%49%5%45%435%27%
1680
16th to endDay
21%13%6%7%5%24346%22%
1792
January1st to 15thNight
17%11%37%5%2335%5%33%
2926
16th to endNight
14%12%6%9%6%34446%28%
3087
February1st to 15thNight
17%12%46%5%23335%32%
2553
16th to endNight
17%11%47%5%2435%5%31%
2205
March1st to 15thNight
17%10%45%5%34345%35%
2520
16th to endNight
17%9%35%5%24446%35%
2352
April1st to 15thNight
17%7%36%5%3345%6%37%
2097
16th to endNight
19%7%25%5%34445%38%
2008
May1st to 15thNight
18%6%35%43446%8%35%
1889
16th to endNight
10%4145%35%5%5%9%43%
1755
June1st to 15thNight
10%4245%2435%7%48%
1680
16th to endNight
10%435%4345%6%10%42%
1624
July1st to 15thNight
7%314325%5%5%10%51%
1560
16th to endNight
4224425%46%9%53%
1641
August1st to 15thNight
332443446%9%52%
1713
16th to endNight
10%21443345%8%51%
2070
September1st to 15thNight
11%313323347%55%
1960
16th to endNight
7%3144345%6%8%49%
2145
October1st to 15thNight
12%5%24423347%48%
2232
16th to endNight
18%7%35%423335%43%
2642
November1st to 15thNight
14%7%34433445%43%
2666
16th to endNight
18%7%35%5%33236%38%
2744
December1st to 15thNight
18%10%48%433345%31%
2940
16th to endNight
21%14%5%9%6%3433422%
3136

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
60%411%12%8%1
1673
16th to endDay
59%5%11%15%6%
1839
February1st to 15thDay
59%5%11%15%6%1
1961
16th to endDay
56%5%11%20%5%1
1840
March1st to 15thDay
56%413%17%6%
2100
16th to endDay
53%6%13%19%6%
2588
April1st to 15thDay
52%411%19%11%
2511
16th to endDay
48%7%12%15%11%4
2557
May1st to 15thDay
51%7%12%20%7%
2721
16th to endDay
43%7%12%20%14%1
3064
June1st to 15thDay
36%7%12%24%16%2
2940
16th to endDay
41%9%13%20%14%1
2843
July1st to 15thDay
34%8%13%23%15%4
2581
16th to endDay
34%8%18%23%13%1
2712
August1st to 15thDay
32%8%15%25%17%1
2481
16th to endDay
35%8%13%22%16%3
2484
September1st to 15thDay
36%5%11%23%17%5%
2317
16th to endDay
33%5%11%26%20%2
2145
October1st to 15thDay
43%6%11%23%13%2
2057
16th to endDay
45%5%13%21%12%1
1932
November1st to 15thDay
43%413%20%15%2
1852
16th to endDay
50%412%23%8%
1873
December1st to 15thDay
59%5%10%17%6%
1680
16th to endDay
62%6%12%12%6%
1792
January1st to 15thNight
52%5%12%17%11%
2926
16th to endNight
57%5%13%15%8%
3087
February1st to 15thNight
54%412%18%9%1
2562
16th to endNight
53%5%11%19%8%1
2205
March1st to 15thNight
50%5%11%20%10%1
2520
16th to endNight
48%6%12%19%11%1
2352
April1st to 15thNight
46%5%12%19%13%2
2097
16th to endNight
46%6%10%18%13%5%
2008
May1st to 15thNight
45%7%13%21%12%
1890
16th to endNight
36%9%15%19%16%3
1757
June1st to 15thNight
34%6%11%24%19%3
1680
16th to endNight
35%7%14%23%15%2
1624
July1st to 15thNight
29%7%13%25%17%4
1480
16th to endNight
25%6%16%28%18%4
1545
August1st to 15thNight
25%5%18%26%19%3
1704
16th to endNight
30%7%13%24%20%4
2070
September1st to 15thNight
28%5%10%25%23%6%
1960
16th to endNight
30%6%10%25%22%3
2145
October1st to 15thNight
35%6%10%24%20%2
2232
16th to endNight
43%310%24%16%1
2642
November1st to 15thNight
43%48%23%16%4
2666
16th to endNight
48%413%22%10%
2744
December1st to 15thNight
55%411%18%9%
2940
16th to endNight
66%48%13%6%
3136

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
31%8%29%20%8%
180
16th to endDay
23%11%34%24%5%
192
February1st to 15thDay
30%18%36%13%1
180
16th to endDay
30%10%33%19%5%
159
March1st to 15thDay
29%17%31%18%2
180
16th to endDay
27%9%30%19%10%2
366
April1st to 15thDay
24%13%29%21%10%
390
16th to endDay
21%12%28%19%12%5%
379
May1st to 15thDay
23%7%29%22%13%4
408
16th to endDay
17%8%29%22%14%7%
672
June1st to 15thDay
11%428%30%20%4
645
16th to endDay
14%5%30%28%15%5%
611
July1st to 15thDay
9%222%26%23%14%
550
16th to endDay
8%120%32%25%11%
595
August1st to 15thDay
8%14%32%26%16%
433
16th to endDay
13%215%29%25%13%
396
September1st to 15thDay
14%114%27%29%12%
375
16th to endDay
9%417%27%32%9%
374
October1st to 15thDay
21%6%25%26%17%2
287
16th to endDay
25%7%35%25%5%
192
November1st to 15thDay
23%7%24%20%16%6%
180
16th to endDay
28%6%37%17%9%
180
December1st to 15thDay
18%19%31%20%8%1
180
16th to endDay
22%18%44%9%4
192
January1st to 15thNight
23%12%36%21%6%
1050
16th to endNight
20%12%36%26%2
1120
February1st to 15thNight
25%10%35%24%4
914
16th to endNight
23%12%34%24%5%
735
March1st to 15thNight
22%11%35%24%5%
840
16th to endNight
22%7%35%25%8%
735
April1st to 15thNight
20%10%36%26%5%
629
16th to endNight
21%7%32%27%10%
624
May1st to 15thNight
20%5%30%33%10%
630
16th to endNight
11%328%36%18%
659
June1st to 15thNight
13%223%45%14%
630
16th to endNight
11%225%43%16%
609
July1st to 15thNight
10%16%42%26%3
555
16th to endNight
5%114%45%31%2
612
August1st to 15thNight
5%8%49%32%3
575
16th to endNight
11%14%35%33%4
621
September1st to 15thNight
12%313%36%29%5%
595
16th to endNight
10%318%34%29%3
777
October1st to 15thNight
16%6%25%33%17%1
780
16th to endNight
22%10%32%24%9%
832
November1st to 15thNight
18%10%35%25%9%
820
16th to endNight
22%10%33%25%7%
854
December1st to 15thNight
24%11%33%24%5%
1050
16th to endNight
29%11%33%23%3
1120
Page generated at 2019-06-24 19:41:31. Version ac04

Copyright 2019 A. Danko


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