Morrison Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morrison 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
55%
15398
24%
46938
20%
15360
60%
15360
31%
27988

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
57%
718
19%
2368
17%
716
62%
716
27%
1433
January16th to endNight
54%
768
24%
2496
24%
768
57%
768
26%
1548
February1st to 15thNight
51%
700
22%
2288
20%
700
58%
700
25%
1425
February16th to endNight
45%
632
22%
1913
17%
632
53%
632
26%
1229
March1st to 15thNight
49%
720
17%
1989
15%
720
53%
720
26%
1329
March16th to endNight
44%
768
20%
2100
13%
768
50%
768
29%
1346
April1st to 15thNight
42%
719
22%
1799
10%
719
48%
719
31%
1160
April16th to endNight
49%
720
25%
1800
11%
720
55%
720
41%
1059
May1st to 15thNight
56%
592
24%
1672
14%
592
62%
592
41%
934
May16th to endNight
49%
411
21%
1534
17%
411
56%
411
28%
833
June1st to 15thNight
53%
360
21%
1440
20%
360
62%
360
27%
773
June16th to endNight
70%
360
31%
1440
38%
360
75%
360
43%
625
July1st to 15thNight
63%
401
23%
1421
24%
401
66%
401
32%
756
July16th to endNight
49%
564
20%
1593
17%
531
51%
531
22%
1069
August1st to 15thNight
52%
538
21%
1611
16%
535
54%
535
24%
1048
August16th to endNight
58%
764
25%
1910
15%
764
59%
764
34%
1260
September1st to 15thNight
69%
720
32%
1800
21%
720
71%
720
43%
1083
September16th to endNight
66%
671
34%
1847
29%
671
70%
671
46%
1008
October1st to 15thNight
63%
660
28%
1980
26%
660
71%
660
40%
1073
October16th to endNight
63%
704
30%
2112
30%
704
68%
704
37%
1196
November1st to 15thNight
62%
700
28%
2166
26%
700
67%
700
37%
1201
November16th to endNight
59%
720
24%
2451
26%
720
62%
720
31%
1366
December1st to 15thNight
51%
720
20%
2520
17%
720
58%
720
21%
1582
December16th to endNight
45%
768
21%
2688
18%
768
53%
768
22%
1652

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
8%6%24323348%51%
47872
Night
9%7%35%423347%47%
47127
TransparencyDay
31%48%19%22%13%
47561
Night
35%48%18%19%12%
46939
SeeingDay
10%13%30%31%11%2
6050
Night
12%6%15%30%28%7%
15406

By Month

Percentage Cloud Cover SW (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%6%24433347%44%
1569
16th to endDay
14%6%25%435%346%43%
1728
February1st to 15thDay
17%6%34425%336%43%
1576
16th to endDay
15%7%45%42345%8%38%
1559
March1st to 15thDay
15%6%345%2445%7%38%
1968
16th to endDay
12%5%246%3445%7%43%
2124
April1st to 15thDay
12%5%35%42345%6%44%
2149
16th to endDay
6%323314249%57%
2160
May1st to 15thDay
45%23212348%59%
2277
16th to endDay
5%8%24313348%53%
2575
June1st to 15thDay
6%5%24313348%56%
2520
16th to endDay
2422212349%64%
2520
July1st to 15thDay
17%242223411%56%
2451
16th to endDay
26%2331335%12%54%
2468
August1st to 15thDay
29%2422346%11%50%
2337
16th to endDay
18%2432335%11%53%
2292
September1st to 15thDay
26%24222339%60%
2160
16th to endDay
3413223238%65%
1857
October1st to 15thDay
8%423314235%59%
1650
16th to endDay
9%5%24422327%55%
1760
November1st to 15thDay
8%5%24433446%52%
1690
16th to endDay
13%8%245%22345%47%
1506
December1st to 15thDay
17%7%35%41434441%
1440
16th to endDay
18%7%2442335%7%40%
1536
January1st to 15thNight
14%5%2442445%7%43%
2368
16th to endNight
16%6%24323345%46%
2496
February1st to 15thNight
15%5%35%424346%42%
2276
16th to endNight
14%6%34425%45%7%40%
1913
March1st to 15thNight
15%5%35%424446%41%
1989
16th to endNight
13%6%35%423247%46%
2100
April1st to 15thNight
11%5%2442335%8%46%
1799
16th to endNight
5%424423347%58%
1800
May1st to 15thNight
36%35%423246%57%
1672
16th to endNight
5%10%25%413337%51%
1533
June1st to 15thNight
45%26%6%33349%49%
1440
16th to endNight
2423313239%62%
1440
July1st to 15thNight
17%37%6%2345%10%45%
1506
16th to endNight
116%5%9%7%35%45%10%29%
1701
August1st to 15thNight
318%38%5%3435%10%33%
1620
16th to endNight
112%48%5%3445%10%39%
1910
September1st to 15thNight
27%26%32445%9%50%
1800
16th to endNight
27%34322238%59%
1847
October1st to 15thNight
6%5%35%313336%57%
1980
16th to endNight
7%42442335%6%52%
2112
November1st to 15thNight
7%5%24322237%55%
2166
16th to endNight
9%6%2342335%6%51%
2451
December1st to 15thNight
19%6%24433336%42%
2520
16th to endNight
18%5%24323446%44%
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
40%412%18%15%8%
1569
16th to endDay
42%5%10%12%18%11%
1728
February1st to 15thDay
44%39%18%20%3
1576
16th to endDay
44%49%25%12%3
1559
March1st to 15thDay
43%5%12%19%14%4
1968
16th to endDay
40%5%15%20%14%3
2124
April1st to 15thDay
39%316%19%18%2
2149
16th to endDay
26%315%26%21%6%
2160
May1st to 15thDay
24%38%29%26%7%
2277
16th to endDay
30%412%26%20%5%
2579
June1st to 15thDay
27%411%21%22%12%
2520
16th to endDay
18%4417%33%21%
2520
July1st to 15thDay
22%429%23%37%
2307
16th to endDay
23%5%38%26%32%
2313
August1st to 15thDay
26%6%110%30%23%
2321
16th to endDay
25%5%213%32%20%
2292
September1st to 15thDay
23%3213%29%26%
2160
16th to endDay
20%2325%29%18%
1857
October1st to 15thDay
27%36%20%26%14%
1650
16th to endDay
30%39%24%20%11%
1760
November1st to 15thDay
32%412%29%13%7%
1690
16th to endDay
39%49%18%22%5%
1506
December1st to 15thDay
45%410%17%17%4
1440
16th to endDay
44%5%11%18%15%5%
1536
January1st to 15thNight
39%413%20%15%8%
2368
16th to endNight
41%39%14%16%14%
2496
February1st to 15thNight
41%310%19%17%7%
2288
16th to endNight
40%5%12%24%14%2
1913
March1st to 15thNight
42%5%11%20%14%5%
1989
16th to endNight
39%413%19%18%4
2100
April1st to 15thNight
36%415%21%18%3
1799
16th to endNight
26%5%12%26%21%8%
1800
May1st to 15thNight
28%38%22%25%11%
1673
16th to endNight
34%311%23%20%6%
1534
June1st to 15thNight
32%5%8%20%20%12%
1440
16th to endNight
22%2314%33%23%
1440
July1st to 15thNight
30%5%28%20%33%
1421
16th to endNight
46%6%35%13%25%
1593
August1st to 15thNight
44%418%22%19%
1611
16th to endNight
37%5%210%23%20%
1910
September1st to 15thNight
29%4310%24%27%
1800
16th to endNight
25%3323%25%19%
1847
October1st to 15thNight
27%37%20%23%17%
1980
16th to endNight
30%47%22%21%13%
2112
November1st to 15thNight
30%411%30%16%7%
2166
16th to endNight
33%39%23%20%8%
2451
December1st to 15thNight
44%39%17%19%6%
2520
16th to endNight
40%5%12%17%17%7%
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
22%11%22%25%16%1
198
16th to endDay
15%11%27%30%14%
256
February1st to 15thDay
19%10%28%27%12%1
236
16th to endDay
18%16%29%25%9%1
235
March1st to 15thDay
22%15%27%18%11%3
270
16th to endDay
14%18%37%21%6%
288
April1st to 15thDay
19%23%31%20%5%
269
16th to endDay
9%30%29%21%6%2
270
May1st to 15thDay
8%23%35%25%6%
288
16th to endDay
11%22%26%29%7%3
330
June1st to 15thDay
8%16%42%25%6%
315
16th to endDay
27%35%39%12%1
315
July1st to 15thDay
3431%47%11%1
305
16th to endDay
2428%47%11%4
327
August1st to 15thDay
7%5%33%42%9%2
315
16th to endDay
4130%44%13%5%
332
September1st to 15thDay
5%6%27%40%14%5%
315
16th to endDay
411%26%32%18%6%
268
October1st to 15thDay
8%10%27%35%12%5%
255
16th to endDay
13%10%30%29%13%2
272
November1st to 15thDay
10%11%21%24%25%7%
196
16th to endDay
12%14%35%29%7%1
71
December1st to 15thDay
25%21%26%13%11%1
60
16th to endDay
12%26%14%37%7%1
64
January1st to 15thNight
17%5%10%31%27%6%
720
16th to endNight
19%5%12%29%26%6%
768
February1st to 15thNight
17%6%14%30%26%4
704
16th to endNight
17%7%22%28%19%5%
632
March1st to 15thNight
17%10%14%27%25%5%
720
16th to endNight
15%10%23%27%20%2
768
April1st to 15thNight
13%12%23%31%14%3
719
16th to endNight
7%11%25%27%23%5%
720
May1st to 15thNight
6%422%33%28%5%
593
16th to endNight
11%7%22%31%21%5%
412
June1st to 15thNight
5%6%21%39%22%3
360
16th to endNight
4315%42%30%4
360
July1st to 15thNight
429%38%36%8%
401
16th to endNight
12%38%25%39%11%
564
August1st to 15thNight
15%310%27%35%7%
538
16th to endNight
9%311%33%33%8%
764
September1st to 15thNight
6%19%28%40%12%
720
16th to endNight
5%312%29%36%12%
671
October1st to 15thNight
9%5%11%31%33%9%
660
16th to endNight
10%313%24%33%14%
704
November1st to 15thNight
9%314%29%35%7%
700
16th to endNight
12%6%11%31%29%8%
720
December1st to 15thNight
21%7%11%30%22%6%
720
16th to endNight
21%9%16%30%20%1
768
Page generated at 2017-09-20 01:49:53. Version ac04

Copyright 2017 A. Danko


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