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Winter Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Winter Star Party clear sky chart from 2005-11-05 to 2017-09-10.

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
70%
16175
18%
46929
17%
16138
71%
16138
30%
29818

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
63%
716
18%
2327
20%
716
64%
716
26%
1460
January16th to endNight
62%
768
25%
2373
24%
768
67%
768
32%
1400
February1st to 15thNight
61%
701
27%
2108
23%
700
65%
700
34%
1252
February16th to endNight
73%
631
30%
1757
26%
631
76%
631
44%
984
March1st to 15thNight
69%
720
25%
1980
19%
720
73%
720
40%
1161
March16th to endNight
73%
768
26%
2112
24%
768
75%
768
43%
1193
April1st to 15thNight
78%
718
22%
1976
20%
718
80%
718
45%
1118
April16th to endNight
74%
720
25%
1872
19%
720
75%
720
43%
1106
May1st to 15thNight
84%
719
25%
1799
19%
719
85%
719
53%
1002
May16th to endNight
69%
583
16%
1705
14%
583
69%
583
27%
1092
June1st to 15thNight
60%
540
8%
1620
8%
540
60%
540
16%
1198
June16th to endNight
77%
540
7%
1620
6%
540
77%
540
21%
1120
July1st to 15thNight
75%
510
6%
1530
6%
510
75%
510
25%
1009
July16th to endNight
81%
564
13%
1595
13%
531
81%
531
32%
948
August1st to 15thNight
78%
584
8%
1722
7%
581
78%
581
27%
1105
August16th to endNight
71%
764
6%
2101
6%
764
71%
764
22%
1516
September1st to 15thNight
72%
700
4%
1925
4%
700
72%
700
19%
1444
September16th to endNight
64%
657
4%
1815
4%
657
64%
657
16%
1422
October1st to 15thNight
65%
660
14%
1870
15%
660
66%
660
20%
1343
October16th to endNight
58%
704
16%
2112
17%
704
60%
704
21%
1473
November1st to 15thNight
66%
700
24%
2101
24%
700
70%
700
32%
1288
November16th to endNight
68%
720
25%
2160
26%
720
70%
720
31%
1328
December1st to 15thNight
67%
720
20%
2253
22%
720
69%
720
28%
1414
December16th to endNight
70%
768
23%
2496
27%
768
72%
768
32%
1442

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%425%5%36%7%9%12%37%
47681
Night
6%425%5%36%6%7%11%39%
47132
TransparencyDay
33%11%20%22%10%2
47382
Night
35%8%19%22%11%1
46935
SeeingDay
9%17%21%33%27%
5995
Night
8%18%25%36%19%
16185

By Month

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
9%425%6%45%5%6%14%36%
1611
16th to endDay
6%424435%6%8%11%42%
1848
February1st to 15thDay
7%5%23325%5%6%8%49%
1750
16th to endDay
421322445%12%56%
1715
March1st to 15thDay
32134245%8%11%50%
1980
16th to endDay
33144245%6%10%53%
2111
April1st to 15thDay
32132245%6%13%52%
1972
16th to endDay
43331446%11%54%
2087
May1st to 15thDay
421332436%10%56%
2152
16th to endDay
7%5%25%436%7%8%11%36%
2417
June1st to 15thDay
9%8%38%7%47%7%10%10%22%
2340
16th to endDay
6%425%7%48%8%11%17%24%
2340
July1st to 15thDay
5%326%6%39%9%14%15%24%
2340
16th to endDay
33245%48%10%12%18%26%
2465
August1st to 15thDay
3425%7%5%7%9%13%14%25%
2208
16th to endDay
6%426%7%47%9%10%14%24%
2101
September1st to 15thDay
6%5%37%8%5%8%10%11%13%19%
1923
16th to endDay
9%7%38%6%5%7%8%10%13%19%
1815
October1st to 15thDay
6%438%8%49%8%10%11%25%
1757
16th to endDay
11%7%26%5%46%6%8%10%31%
1760
November1st to 15thDay
7%314435%5%5%8%47%
1757
16th to endDay
7%5%234245%7%9%45%
1800
December1st to 15thDay
7%5%25%5%335%6%10%40%
1704
16th to endDay
4324426%6%9%10%44%
1728
January1st to 15thNight
8%5%35%5%35%5%8%12%35%
2327
16th to endNight
5%425%5%36%5%8%10%43%
2373
February1st to 15thNight
7%4244245%5%7%49%
2103
16th to endNight
4313335%5%5%9%54%
1757
March1st to 15thNight
3225%5%35%5%5%9%50%
1980
16th to endNight
3315%43446%9%53%
2112
April1st to 15thNight
321343446%12%52%
1976
16th to endNight
43234245%7%11%49%
1872
May1st to 15thNight
32133235%6%9%59%
1799
16th to endNight
9%5%25%5%36%5%8%9%37%
1704
June1st to 15thNight
11%7%47%8%5%6%7%7%11%22%
1620
16th to endNight
43147%6%9%9%8%13%30%
1620
July1st to 15thNight
4426%5%45%7%10%15%33%
1620
16th to endNight
2314446%8%8%16%38%
1703
August1st to 15thNight
44145%47%7%9%15%34%
1733
16th to endNight
5%6%26%7%5%7%7%9%12%29%
2101
September1st to 15thNight
6%5%35%7%48%9%11%13%24%
1925
16th to endNight
7%7%39%7%5%8%8%9%11%22%
1815
October1st to 15thNight
8%6%37%7%47%7%8%11%27%
1870
16th to endNight
12%7%36%6%45%6%6%9%31%
2112
November1st to 15thNight
8%425%435%47%10%42%
2101
16th to endNight
8%314445%5%6%10%43%
2160
December1st to 15thNight
7%427%5%36%5%6%10%39%
2253
16th to endNight
6%424425%6%6%10%44%
2496

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
37%7%17%22%11%2
1612
16th to endDay
32%7%16%23%16%4
1848
February1st to 15thDay
30%5%11%29%17%4
1752
16th to endDay
20%5%14%35%17%6%
1715
March1st to 15thDay
25%5%16%32%18%2
1980
16th to endDay
23%6%17%31%18%3
2112
April1st to 15thDay
21%5%18%36%16%1
1972
16th to endDay
21%6%16%32%19%2
2087
May1st to 15thDay
21%6%18%32%16%4
2152
16th to endDay
35%10%19%26%7%
2421
June1st to 15thDay
48%13%21%13%2
2340
16th to endDay
38%16%35%9%
2340
July1st to 15thDay
36%18%33%10%
2201
16th to endDay
31%18%35%14%
2310
August1st to 15thDay
35%17%29%16%
2195
16th to endDay
39%18%29%12%
2101
September1st to 15thDay
44%21%25%7%
1923
16th to endDay
47%15%24%11%1
1815
October1st to 15thDay
44%12%16%17%6%2
1757
16th to endDay
43%8%13%20%11%3
1760
November1st to 15thDay
31%7%10%25%22%2
1757
16th to endDay
32%6%12%22%20%6%
1800
December1st to 15thDay
36%6%14%23%15%1
1704
16th to endDay
28%8%14%28%17%2
1728
January1st to 15thNight
38%7%18%24%8%2
2327
16th to endNight
33%6%16%25%16%2
2373
February1st to 15thNight
32%6%9%28%17%5%
2112
16th to endNight
26%415%26%20%6%
1757
March1st to 15thNight
29%5%13%28%20%2
1980
16th to endNight
26%417%28%18%4
2112
April1st to 15thNight
24%6%17%33%16%2
1976
16th to endNight
27%6%14%30%19%1
1872
May1st to 15thNight
19%6%17%34%18%3
1800
16th to endNight
38%7%16%25%10%
1706
June1st to 15thNight
52%10%22%12%3
1620
16th to endNight
38%15%33%12%
1620
July1st to 15thNight
34%14%36%13%
1530
16th to endNight
26%13%36%20%2
1595
August1st to 15thNight
32%13%31%20%1
1722
16th to endNight
41%14%29%13%
2101
September1st to 15thNight
42%18%28%10%1
1925
16th to endNight
49%15%22%10%1
1815
October1st to 15thNight
46%10%17%16%7%1
1870
16th to endNight
48%6%11%20%9%3
2112
November1st to 15thNight
35%6%12%25%18%1
2101
16th to endNight
35%6%12%21%19%4
2160
December1st to 15thNight
38%6%15%25%13%1
2253
16th to endNight
33%5%13%29%16%1
2496

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
27%313%28%26%
90
16th to endDay
14%9%20%34%18%2
96
February1st to 15thDay
2320%44%25%4
90
16th to endDay
8%112%41%31%3
216
March1st to 15thDay
7%114%44%29%4
270
16th to endDay
6%118%37%29%6%
288
April1st to 15thDay
5%18%41%37%5%
270
16th to endDay
5%18%42%40%1
270
May1st to 15thDay
35%32%46%10%
288
16th to endDay
6%1414%41%30%
331
June1st to 15thDay
15%15%13%31%32%
315
16th to endDay
5%17%26%58%
315
July1st to 15thDay
42431%56%
305
16th to endDay
7%1331%55%
326
August1st to 15thDay
6%12135%52%
313
16th to endDay
8%135%32%48%
332
September1st to 15thDay
10%2423%58%
294
16th to endDay
16%36%21%52%
254
October1st to 15thDay
5%25%16%48%20%
255
16th to endDay
17%211%26%26%14%
272
November1st to 15thDay
10%19%24%41%12%
265
16th to endDay
10%217%32%32%4
270
December1st to 15thDay
20%18%28%35%5%
174
16th to endDay
7%26%27%48%8%
96
January1st to 15thNight
10%313%32%36%3
720
16th to endNight
7%319%34%32%2
768
February1st to 15thNight
8%318%36%31%2
704
16th to endNight
5%312%38%37%3
631
March1st to 15thNight
3115%41%33%3
720
16th to endNight
4211%41%35%4
768
April1st to 15thNight
417%39%42%3
718
16th to endNight
7%19%40%38%3
720
May1st to 15thNight
4431%48%10%
720
16th to endNight
11%1423%43%16%
585
June1st to 15thNight
12%15%15%34%30%
540
16th to endNight
417%36%49%
540
July1st to 15thNight
5%15%37%49%
510
16th to endNight
31432%57%
564
August1st to 15thNight
5%1436%51%
584
16th to endNight
8%36%33%48%
764
September1st to 15thNight
7%127%29%51%
700
16th to endNight
10%26%29%49%
657
October1st to 15thNight
11%16%17%43%19%
660
16th to endNight
16%19%22%34%15%
704
November1st to 15thNight
9%310%27%39%9%
700
16th to endNight
8%213%31%38%6%
720
December1st to 15thNight
9%29%36%38%4
720
16th to endNight
10%17%33%39%6%
768
Page generated at 2017-09-11 19:35:25. Version ac04

Copyright 2017 A. Danko


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