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Northern Prairie Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Northern Prairie Star Party clear sky chart from 2005-11-05 to 2018-03-11.

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
41%
16015
10%
49163
7%
15989
45%
15989
18%
34970

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
35%
970
7%
2910
5%
970
37%
970
13%
2222
January16th to endNight
30%
995
15%
3075
7%
995
38%
995
17%
2223
February1st to 15thNight
39%
757
9%
2608
8%
756
43%
756
15%
1875
February16th to endNight
44%
684
12%
2208
12%
684
47%
684
18%
1564
March1st to 15thNight
42%
764
13%
2225
9%
764
46%
764
18%
1631
March16th to endNight
38%
768
9%
2111
5%
767
40%
767
16%
1655
April1st to 15thNight
42%
581
12%
1667
6%
581
46%
581
20%
1200
April16th to endNight
43%
540
12%
1620
10%
540
45%
540
19%
1157
May1st to 15thNight
48%
410
9%
1318
7%
410
50%
410
20%
879
May16th to endNight
40%
374
1%
1309
1%
374
40%
374
15%
944
June1st to 15thNight
41%
360
0%
1260
0%
360
41%
360
14%
936
June16th to endNight
51%
360
0%
1260
0%
360
51%
360
17%
863
July1st to 15thNight
54%
340
0%
1190
0%
340
54%
340
23%
754
July16th to endNight
55%
376
3%
1239
3%
354
57%
354
24%
753
August1st to 15thNight
63%
396
7%
1403
8%
394
65%
394
24%
847
August16th to endNight
56%
573
13%
1719
11%
573
59%
573
28%
1109
September1st to 15thNight
57%
602
14%
1769
11%
602
59%
602
31%
1090
September16th to endNight
52%
716
20%
1980
13%
716
58%
716
35%
1215
October1st to 15thNight
42%
720
15%
2142
10%
720
47%
720
23%
1450
October16th to endNight
38%
789
15%
2517
9%
789
45%
789
19%
1725
November1st to 15thNight
32%
950
14%
2663
9%
950
37%
950
16%
2002
November16th to endNight
31%
975
9%
2925
5%
975
35%
975
14%
2251
December1st to 15thNight
31%
975
9%
2925
6%
975
34%
975
13%
2282
December16th to endNight
37%
1040
12%
3120
6%
1040
43%
1040
16%
2343

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
11%9%47%6%35%5%6%8%32%
49496
Night
9%9%48%7%45%5%6%7%31%
49321
TransparencyDay
48%8%17%18%5%
49146
Night
49%7%15%19%6%
49175
SeeingDay
15%5%23%30%19%5%
6579
Night
13%5%26%35%17%2
16029

By Month

Percentage Cloud Cover NW (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
7%12%5%9%8%6%6%5%6%7%24%
1358
16th to endDay
6%10%6%11%10%5%445%5%28%
1511
February1st to 15thDay
8%11%6%9%8%45%46%7%27%
1573
16th to endDay
6%11%7%10%8%47%6%5%7%24%
1551
March1st to 15thDay
7%13%5%9%8%35%5%6%8%24%
1971
16th to endDay
12%12%6%9%6%45%45%7%24%
2111
April1st to 15thDay
14%10%5%5%5%35%46%7%29%
2279
16th to endDay
16%12%36%6%24347%31%
2340
May1st to 15thDay
11%7%36%6%36%6%5%8%33%
2630
16th to endDay
18%7%36%436%5%6%6%31%
2802
June1st to 15thDay
16%9%37%6%46%5%6%7%25%
2700
16th to endDay
16%6%36%6%46%5%6%8%29%
2700
July1st to 15thDay
11%436%5%35%6%7%9%38%
2700
16th to endDay
10%5%23436%6%7%8%40%
2846
August1st to 15thDay
12%5%26%435%5%6%9%38%
2550
16th to endDay
8%6%25%6%245%6%9%42%
2483
September1st to 15thDay
12%6%35%43445%7%41%
2190
16th to endDay
10%6%1442345%8%45%
1980
October1st to 15thDay
13%11%46%6%34347%34%
1816
16th to endDay
10%10%46%5%36%5%7%8%32%
1695
November1st to 15thDay
8%12%7%9%6%45%5%6%7%27%
1524
16th to endDay
6%8%7%12%7%35%45%6%30%
1365
December1st to 15thDay
6%13%5%13%11%46%5%5%6%19%
1365
16th to endDay
6%11%410%8%5%7%5%6%10%22%
1456
January1st to 15thNight
6%11%5%9%10%5%7%6%6%7%24%
2910
16th to endNight
6%11%410%8%35%5%5%7%30%
3075
February1st to 15thNight
5%9%410%9%46%5%5%6%29%
2608
16th to endNight
6%11%48%7%5%5%5%6%9%29%
2208
March1st to 15thNight
7%9%48%8%38%6%6%8%29%
2225
16th to endNight
10%11%6%9%8%45%5%7%8%22%
2109
April1st to 15thNight
10%9%47%7%45%5%7%7%30%
1667
16th to endNight
15%11%46%335%5%5%6%32%
1620
May1st to 15thNight
12%7%36%6%45%6%6%6%34%
1317
16th to endNight
19%7%37%8%3435%5%31%
1309
June1st to 15thNight
15%7%38%7%5%6%5%6%8%26%
1260
16th to endNight
14%5%35%5%36%6%7%9%31%
1260
July1st to 15thNight
11%325%5%345%7%11%38%
1260
16th to endNight
9%325%6%25%5%7%9%41%
1323
August1st to 15thNight
10%3145%35%6%7%10%40%
1410
16th to endNight
8%415%5%46%6%6%8%40%
1719
September1st to 15thNight
12%42442345%7%48%
1769
16th to endNight
10%5%23323447%51%
1980
October1st to 15thNight
13%8%36%5%2445%7%36%
2142
16th to endNight
10%9%26%7%35%5%5%8%33%
2517
November1st to 15thNight
11%12%5%7%7%35%5%5%6%29%
2663
16th to endNight
7%11%5%10%8%46%5%5%6%27%
2925
December1st to 15thNight
8%11%6%11%9%45%5%5%7%23%
2925
16th to endNight
310%410%9%5%7%6%6%8%24%
3120

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
57%8%13%13%5%
1358
16th to endDay
55%6%12%16%7%1
1511
February1st to 15thDay
55%6%17%15%5%
1573
16th to endDay
57%6%14%16%5%
1551
March1st to 15thDay
55%7%17%15%3
1971
16th to endDay
58%8%12%15%4
2112
April1st to 15thDay
52%7%15%16%6%
2279
16th to endDay
53%5%16%16%6%1
2340
May1st to 15thDay
45%7%13%22%9%
2630
16th to endDay
50%7%14%17%9%
2807
June1st to 15thDay
55%8%13%16%5%
2700
16th to endDay
50%9%18%16%3
2700
July1st to 15thDay
37%10%25%23%2
2541
16th to endDay
38%10%26%22%1
2667
August1st to 15thDay
40%10%28%18%2
2532
16th to endDay
34%10%24%24%5%1
2483
September1st to 15thDay
40%7%20%22%6%1
2190
16th to endDay
34%9%19%28%6%1
1980
October1st to 15thDay
49%7%16%21%5%
1816
16th to endDay
46%9%15%23%4
1695
November1st to 15thDay
54%6%16%17%4
1524
16th to endDay
53%8%17%14%4
1365
December1st to 15thDay
64%6%11%12%4
1365
16th to endDay
56%5%14%14%8%
1456
January1st to 15thNight
56%8%16%12%41
2910
16th to endNight
51%6%14%18%7%1
3075
February1st to 15thNight
52%6%16%16%6%
2619
16th to endNight
50%7%14%19%7%
2208
March1st to 15thNight
51%7%14%19%6%
2225
16th to endNight
56%8%11%17%5%
2112
April1st to 15thNight
50%7%15%18%7%1
1667
16th to endNight
48%8%12%18%9%2
1620
May1st to 15thNight
45%7%11%22%11%1
1318
16th to endNight
54%6%10%19%7%2
1309
June1st to 15thNight
53%10%13%17%5%
1260
16th to endNight
45%10%19%19%4
1260
July1st to 15thNight
37%11%22%22%5%
1190
16th to endNight
36%9%23%26%3
1239
August1st to 15thNight
35%9%29%21%3
1403
16th to endNight
37%8%19%27%6%
1719
September1st to 15thNight
34%7%18%26%10%3
1769
16th to endNight
31%7%18%28%10%3
1980
October1st to 15thNight
45%5%16%23%8%
2142
16th to endNight
46%7%17%23%5%
2517
November1st to 15thNight
54%7%12%19%5%1
2663
16th to endNight
56%8%15%13%5%
2925
December1st to 15thNight
59%7%14%14%4
2925
16th to endNight
54%8%14%15%7%
3120

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
11%218%47%16%3
90
16th to endDay
5%421%39%21%7%
96
February1st to 15thDay
13%330%35%13%2
104
16th to endDay
10%423%37%18%6%
132
March1st to 15thDay
13%5%32%32%14%1
312
16th to endDay
15%5%32%26%17%1
288
April1st to 15thDay
17%10%28%28%12%1
269
16th to endDay
26%8%18%30%12%3
270
May1st to 15thDay
13%7%19%35%17%6%
460
16th to endDay
18%5%21%26%21%6%
517
June1st to 15thDay
18%6%27%26%15%5%
495
16th to endDay
13%5%24%29%19%7%
495
July1st to 15thDay
12%115%34%28%7%
475
16th to endDay
12%421%30%25%6%
515
August1st to 15thDay
14%113%29%26%14%
381
16th to endDay
9%7%22%30%25%3
332
September1st to 15thDay
16%5%25%29%17%6%
315
16th to endDay
16%9%24%29%16%4
315
October1st to 15thDay
27%5%22%26%15%3
165
16th to endDay
19%9%25%27%14%3
144
November1st to 15thDay
21%328%35%9%3
133
16th to endDay
11%7%38%25%8%7%
90
December1st to 15thDay
12%6%26%30%20%4
90
16th to endDay
8%230%33%19%6%
96
January1st to 15thNight
11%7%28%36%13%2
975
16th to endNight
12%7%33%33%11%2
995
February1st to 15thNight
8%7%26%35%20%1
764
16th to endNight
10%323%37%20%4
684
March1st to 15thNight
10%328%39%14%3
764
16th to endNight
14%425%34%17%3
768
April1st to 15thNight
12%7%27%32%17%2
581
16th to endNight
19%5%20%38%14%1
540
May1st to 15thNight
14%6%21%34%21%2
411
16th to endNight
20%5%19%30%22%1
375
June1st to 15thNight
18%421%34%18%3
360
16th to endNight
13%322%30%26%2
360
July1st to 15thNight
12%117%40%27%
340
16th to endNight
10%319%41%22%3
376
August1st to 15thNight
12%213%33%33%5%
396
16th to endNight
10%121%37%27%1
573
September1st to 15thNight
14%118%36%27%1
602
16th to endNight
13%425%38%17%1
716
October1st to 15thNight
18%225%33%18%1
720
16th to endNight
15%430%36%12%
789
November1st to 15thNight
17%5%32%31%10%2
950
16th to endNight
12%7%32%33%11%2
975
December1st to 15thNight
13%7%30%30%14%2
975
16th to endNight
9%429%37%16%3
1040
Page generated at 2018-03-12 11:28:14. Version ac04

Copyright 2018 A. Danko


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