U-46 Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the U-46 Planetarium clear sky chart from 2005-11-05 to 2017-09-19.

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
36%
15988
17%
46863
10%
15948
43%
15948
23%
31267

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
19%
899
14%
2506
4%
895
28%
895
18%
1818
January16th to endNight
19%
960
13%
2653
4%
960
26%
960
16%
1979
February1st to 15thNight
20%
806
14%
2217
3%
806
28%
806
18%
1574
February16th to endNight
24%
631
18%
1893
7%
631
34%
631
18%
1321
March1st to 15thNight
26%
720
13%
2160
7%
720
30%
720
17%
1524
March16th to endNight
29%
618
15%
2010
11%
618
36%
618
18%
1395
April1st to 15thNight
29%
539
15%
1797
10%
539
38%
539
19%
1226
April16th to endNight
32%
540
19%
1737
11%
540
42%
540
22%
1155
May1st to 15thNight
35%
540
15%
1584
7%
540
42%
540
21%
1113
May16th to endNight
44%
561
17%
1498
9%
561
50%
561
32%
973
June1st to 15thNight
49%
540
16%
1440
10%
540
52%
540
34%
903
June16th to endNight
47%
540
16%
1440
8%
540
52%
540
30%
956
July1st to 15thNight
61%
510
17%
1360
11%
510
63%
510
40%
820
July16th to endNight
66%
564
22%
1417
15%
531
69%
531
42%
831
August1st to 15thNight
74%
539
21%
1566
20%
536
76%
536
41%
861
August16th to endNight
64%
573
21%
1910
21%
573
69%
573
35%
1053
September1st to 15thNight
59%
540
29%
1800
27%
540
66%
540
37%
962
September16th to endNight
56%
673
26%
1858
19%
673
60%
673
35%
1125
October1st to 15thNight
45%
660
25%
1906
18%
660
52%
660
31%
1154
October16th to endNight
28%
704
18%
2236
9%
704
39%
704
21%
1448
November1st to 15thNight
32%
700
23%
2276
15%
700
42%
700
24%
1399
November16th to endNight
24%
771
16%
2391
8%
771
34%
771
18%
1630
December1st to 15thNight
20%
900
13%
2520
4%
900
28%
900
17%
1866
December16th to endNight
14%
960
11%
2688
2%
960
23%
960
11%
2181

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
13%8%36%5%345%5%7%36%
47961
Night
14%7%35%424446%40%
47031
Cloud CoverDay
13%8%36%5%3445%7%36%
47970
Night
14%7%35%42445%6%40%
47036
TransparencyDay
46%6%12%21%11%1
47647
Night
43%5%12%22%13%1
46863
SeeingDay
14%10%29%26%14%5%
5990
Night
17%9%30%28%12%1
15994

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
13%12%5%8%5%25%5%5%7%27%
1432
16th to endDay
13%13%7%11%7%24336%26%
1569
February1st to 15thDay
14%13%5%6%6%35%45%5%28%
1645
16th to endDay
14%11%5%7%6%33347%32%
1580
March1st to 15thDay
15%12%5%6%6%335%47%30%
1790
16th to endDay
17%8%47%6%34437%30%
2224
April1st to 15thDay
18%10%46%5%34446%30%
2151
16th to endDay
19%8%25%43345%6%34%
2222
May1st to 15thDay
18%9%37%5%35%5%5%7%29%
2364
16th to endDay
13%6%25%5%35%6%6%6%37%
2617
June1st to 15thDay
11%5%25%5%245%5%7%43%
2520
16th to endDay
9%5%35%5%36%6%7%9%38%
2520
July1st to 15thDay
7%425%5%35%6%6%9%43%
2520
16th to endDay
7%426%5%36%6%6%9%41%
2655
August1st to 15thDay
7%435%6%45%5%6%9%41%
2380
16th to endDay
10%4246%35%5%6%8%42%
2292
September1st to 15thDay
12%314334446%50%
2148
16th to endDay
9%6%345%345%6%7%43%
1848
October1st to 15thDay
13%5%26%42345%7%43%
1722
16th to endDay
18%9%25%434446%37%
1636
November1st to 15thDay
14%9%25%42345%6%40%
1582
16th to endDay
17%10%46%5%23435%36%
1568
December1st to 15thDay
16%13%48%5%35%335%29%
1440
16th to endDay
21%14%5%8%5%23446%22%
1536
January1st to 15thNight
15%11%5%6%5%23445%34%
2506
16th to endNight
13%11%7%9%5%34446%29%
2653
February1st to 15thNight
14%12%46%423436%35%
2215
16th to endNight
15%11%46%5%23347%34%
1893
March1st to 15thNight
15%8%46%5%34345%36%
2147
16th to endNight
16%7%46%5%25%46%7%33%
2010
April1st to 15thNight
17%7%36%5%345%5%5%36%
1797
16th to endNight
18%9%24424335%40%
1737
May1st to 15thNight
16%6%35%5%35%5%5%7%34%
1584
16th to endNight
11%425%3345%6%9%43%
1496
June1st to 15thNight
11%42342445%8%48%
1440
16th to endNight
8%4146%45%5%7%9%40%
1440
July1st to 15thNight
5%313335%5%6%9%51%
1440
16th to endNight
6%313425%5%7%9%50%
1513
August1st to 15thNight
3213425%47%10%53%
1575
16th to endNight
9%32432335%8%52%
1910
September1st to 15thNight
10%313322346%57%
1800
16th to endNight
8%42442435%8%50%
1858
October1st to 15thNight
12%5%14423336%50%
1906
16th to endNight
19%7%24414246%41%
2236
November1st to 15thNight
13%6%34423435%46%
2276
16th to endNight
15%9%5%6%42344437%
2391
December1st to 15thNight
20%9%46%5%34345%32%
2520
16th to endNight
23%13%5%7%6%34445%22%
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
14%12%5%7%5%25%5%6%6%27%
1432
16th to endDay
13%14%7%10%6%24436%26%
1569
February1st to 15thDay
14%13%5%7%5%35%445%28%
1645
16th to endDay
14%11%48%6%24246%32%
1580
March1st to 15thDay
15%12%46%5%345%5%6%29%
1800
16th to endDay
18%8%47%6%34447%30%
2223
April1st to 15thDay
18%10%46%6%24345%31%
2151
16th to endDay
20%8%25%5%33447%34%
2222
May1st to 15thDay
18%8%46%5%36%45%7%29%
2364
16th to endDay
13%6%246%36%6%5%6%37%
2617
June1st to 15thDay
11%5%25%5%2446%7%43%
2520
16th to endDay
10%5%35%5%35%5%7%8%38%
2520
July1st to 15thDay
8%4245%35%5%6%9%44%
2520
16th to endDay
7%5%35%6%35%5%7%9%41%
2655
August1st to 15thDay
8%5%26%5%35%6%6%9%41%
2380
16th to endDay
11%425%5%35%5%6%7%42%
2292
September1st to 15thDay
12%31442445%6%50%
2148
16th to endDay
9%6%25%4345%5%8%44%
1848
October1st to 15thDay
13%6%35%42345%6%44%
1722
16th to endDay
18%8%34424446%37%
1636
November1st to 15thDay
14%9%35%42345%6%40%
1582
16th to endDay
17%10%46%5%2334436%
1568
December1st to 15thDay
16%13%5%8%5%34345%29%
1440
16th to endDay
21%14%6%7%5%33345%23%
1536
January1st to 15thNight
16%11%46%423345%35%
2506
16th to endNight
13%12%6%9%5%24446%29%
2653
February1st to 15thNight
14%12%46%423347%35%
2208
16th to endNight
15%11%37%5%23346%34%
1893
March1st to 15thNight
16%8%5%7%5%34345%36%
2160
16th to endNight
16%7%36%5%345%5%7%33%
2010
April1st to 15thNight
17%7%36%425%45%5%36%
1797
16th to endNight
19%8%24423435%41%
1737
May1st to 15thNight
16%6%35%5%46%5%6%6%34%
1583
16th to endNight
12%425%425%46%9%43%
1496
June1st to 15thNight
11%424424447%48%
1440
16th to endNight
8%415%5%45%5%8%9%40%
1440
July1st to 15thNight
5%313425%5%6%8%52%
1440
16th to endNight
5%3134345%7%9%51%
1513
August1st to 15thNight
3213425%47%9%53%
1575
16th to endNight
10%314323349%53%
1910
September1st to 15thNight
10%314322346%57%
1800
16th to endNight
9%4145%2435%8%50%
1858
October1st to 15thNight
12%5%24423446%50%
1906
16th to endNight
19%7%24423346%41%
2236
November1st to 15thNight
14%7%24422436%46%
2276
16th to endNight
16%10%5%5%423445%37%
2391
December1st to 15thNight
20%9%47%5%24336%31%
2520
16th to endNight
23%13%5%7%5%34445%22%
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
54%6%14%14%9%
1433
16th to endDay
59%412%14%8%
1569
February1st to 15thDay
57%5%11%16%8%1
1647
16th to endDay
52%6%12%19%7%1
1580
March1st to 15thDay
53%7%12%18%7%
1800
16th to endDay
54%5%13%19%5%
2224
April1st to 15thDay
54%5%9%20%9%
2151
16th to endDay
48%6%12%16%12%2
2222
May1st to 15thDay
53%8%11%20%6%
2364
16th to endDay
44%8%11%20%14%1
2621
June1st to 15thDay
38%7%10%24%17%1
2520
16th to endDay
40%9%13%20%15%2
2520
July1st to 15thDay
34%7%14%26%14%2
2371
16th to endDay
35%8%16%21%13%3
2488
August1st to 15thDay
37%7%13%26%13%1
2365
16th to endDay
37%7%12%23%16%2
2292
September1st to 15thDay
33%6%10%25%19%3
2148
16th to endDay
36%6%11%27%16%1
1848
October1st to 15thDay
40%6%11%25%14%1
1722
16th to endDay
48%5%13%21%9%2
1636
November1st to 15thDay
43%411%23%14%2
1582
16th to endDay
50%5%13%23%7%
1568
December1st to 15thDay
58%413%16%6%
1440
16th to endDay
63%5%10%11%7%
1536
January1st to 15thNight
51%5%11%19%10%1
2506
16th to endNight
55%414%15%10%
2653
February1st to 15thNight
50%412%20%11%
2217
16th to endNight
50%412%21%8%2
1893
March1st to 15thNight
50%5%12%17%11%2
2160
16th to endNight
49%6%13%20%8%1
2010
April1st to 15thNight
48%5%10%20%13%1
1797
16th to endNight
45%410%22%11%5%
1737
May1st to 15thNight
47%6%11%22%10%
1584
16th to endNight
36%7%14%21%18%2
1498
June1st to 15thNight
33%6%11%25%19%2
1440
16th to endNight
36%8%13%20%18%1
1440
July1st to 15thNight
28%7%13%28%18%2
1360
16th to endNight
25%8%16%27%18%3
1417
August1st to 15thNight
24%7%16%30%19%1
1566
16th to endNight
29%6%14%27%17%4
1910
September1st to 15thNight
28%49%27%26%2
1800
16th to endNight
31%6%10%32%16%1
1858
October1st to 15thNight
35%410%26%20%1
1906
16th to endNight
45%312%24%12%1
2236
November1st to 15thNight
40%49%23%17%3
2276
16th to endNight
48%413%22%11%
2391
December1st to 15thNight
55%410%20%8%
2520
16th to endNight
65%49%13%5%1
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
18%17%42%21%
90
16th to endDay
19%14%34%21%8%1
96
February1st to 15thDay
21%26%41%8%2
90
16th to endDay
22%18%29%18%8%2
81
March1st to 15thDay
34%22%25%15%2
90
16th to endDay
28%9%31%19%8%2
238
April1st to 15thDay
24%13%28%22%10%
270
16th to endDay
21%13%29%22%10%3
270
May1st to 15thDay
23%14%27%20%10%3
321
16th to endDay
18%13%30%22%11%3
517
June1st to 15thDay
11%8%34%28%13%3
495
16th to endDay
10%10%35%27%10%4
495
July1st to 15thDay
7%5%31%31%15%8%
475
16th to endDay
7%328%34%17%8%
515
August1st to 15thDay
8%120%34%21%12%
410
16th to endDay
8%6%18%29%25%11%
332
September1st to 15thDay
8%5%20%30%24%9%
315
16th to endDay
8%7%21%28%25%8%
266
October1st to 15thDay
10%11%26%30%16%3
162
16th to endDay
29%16%31%20%2
96
November1st to 15thDay
8%12%30%33%11%4
90
16th to endDay
34%14%33%12%41
90
December1st to 15thDay
14%31%32%16%5%
90
16th to endDay
29%30%36%22
96
January1st to 15thNight
20%15%37%20%5%
900
16th to endNight
18%15%37%25%3
960
February1st to 15thNight
21%13%36%22%4
809
16th to endNight
20%14%33%25%5%
631
March1st to 15thNight
20%13%34%23%7%
720
16th to endNight
19%8%35%25%9%
618
April1st to 15thNight
21%11%33%27%6%
539
16th to endNight
22%9%33%25%8%
540
May1st to 15thNight
20%6%32%29%10%
540
16th to endNight
12%6%30%34%15%
563
June1st to 15thNight
12%329%40%13%
540
16th to endNight
10%432%36%15%1
540
July1st to 15thNight
7%223%40%22%2
510
16th to endNight
5%21%44%25%2
564
August1st to 15thNight
412%47%30%3
539
16th to endNight
10%216%37%29%3
573
September1st to 15thNight
10%320%33%27%5%
540
16th to endNight
10%7%19%33%26%2
673
October1st to 15thNight
15%8%26%30%17%1
660
16th to endNight
24%12%31%22%8%
704
November1st to 15thNight
17%12%34%24%9%1
700
16th to endNight
20%15%33%23%6%
771
December1st to 15thNight
25%13%36%21%4
900
16th to endNight
30%13%32%20%2
960
Page generated at 2017-09-20 03:49:52. Version ac04

Copyright 2017 A. Danko


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