Mayborn Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mayborn Planetarium clear sky chart from 2005-11-05 to 2017-09-22.

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
51%
15497
28%
46990
19%
15449
60%
15449
37%
26119

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
36%
899
27%
2327
11%
895
46%
895
36%
1431
January16th to endNight
36%
929
31%
2465
12%
929
48%
929
36%
1483
February1st to 15thNight
36%
704
29%
2105
13%
697
48%
697
33%
1207
February16th to endNight
27%
632
30%
1894
9%
632
44%
632
33%
1074
March1st to 15thNight
36%
549
27%
1989
15%
549
51%
549
26%
1133
March16th to endNight
35%
576
25%
2112
17%
576
48%
576
30%
1123
April1st to 15thNight
30%
539
25%
1977
12%
539
48%
539
28%
1085
April16th to endNight
33%
540
26%
1740
15%
540
49%
540
32%
1006
May1st to 15thNight
35%
539
24%
1620
16%
539
47%
539
34%
954
May16th to endNight
49%
562
25%
1684
19%
561
61%
561
37%
952
June1st to 15thNight
69%
540
24%
1620
23%
540
74%
540
51%
794
June16th to endNight
72%
540
24%
1620
27%
540
74%
540
41%
886
July1st to 15thNight
79%
510
24%
1530
27%
510
82%
510
45%
812
July16th to endNight
85%
564
28%
1594
32%
531
88%
531
51%
794
August1st to 15thNight
90%
539
34%
1613
39%
536
91%
536
59%
738
August16th to endNight
75%
573
23%
1976
29%
573
76%
573
34%
1093
September1st to 15thNight
77%
540
21%
1980
25%
540
78%
540
34%
1067
September16th to endNight
75%
513
31%
1891
34%
513
77%
513
36%
981
October1st to 15thNight
68%
522
36%
1842
33%
522
74%
522
44%
876
October16th to endNight
57%
704
36%
2112
24%
704
65%
704
48%
1069
November1st to 15thNight
51%
723
31%
2123
19%
723
58%
723
41%
1165
November16th to endNight
47%
900
32%
2340
16%
900
54%
900
40%
1370
December1st to 15thNight
41%
900
30%
2340
15%
900
48%
900
35%
1460
December16th to endNight
39%
960
26%
2496
11%
960
48%
960
34%
1566

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
10%42442445%7%50%
47883
Night
9%313323347%55%
47193
Cloud CoverDay
10%42442445%6%50%
47881
Night
9%313323347%55%
47193
TransparencyDay
33%5%10%20%20%9%
47581
Night
28%411%21%21%12%
46998
SeeingDay
10%319%31%27%8%
5470
Night
11%5%26%36%17%1
15500

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
16%5%12213325%53%
1611
16th to endDay
13%312223446%53%
1770
February1st to 15thDay
14%42421223456%
1750
16th to endDay
15%6%2231333452%
1580
March1st to 15thDay
18%5%24323335%47%
1968
16th to endDay
13%5%34422345%51%
2112
April1st to 15thDay
11%5%3442345%7%47%
1971
16th to endDay
13%435%423445%47%
2216
May1st to 15thDay
14%6%25%415%45%6%42%
2331
16th to endDay
12%5%36%5%446%6%8%36%
2430
June1st to 15thDay
4313335%46%9%53%
2340
16th to endDay
8%4245%35%5%5%9%45%
2340
July1st to 15thDay
6%2245%35%6%6%9%46%
2340
16th to endDay
5%214445%5%5%9%49%
2466
August1st to 15thDay
211232445%8%61%
2334
16th to endDay
8%3146%36%6%7%8%42%
2224
September1st to 15thDay
9%4246%35%45%7%45%
1980
16th to endDay
7%335%5%33448%50%
1881
October1st to 15thDay
9%413323246%56%
1777
16th to endDay
8%31221223468%
1760
November1st to 15thDay
12%424323345%53%
1734
16th to endDay
13%42331233457%
1620
December1st to 15thDay
17%6%14322435%48%
1620
16th to endDay
14%6%24422346%47%
1728
January1st to 15thNight
16%41331223454%
2327
16th to endNight
13%423313345%55%
2465
February1st to 15thNight
12%5%1341222357%
2102
16th to endNight
12%413323346%54%
1894
March1st to 15thNight
15%324323446%49%
1989
16th to endNight
11%313313447%54%
2112
April1st to 15thNight
8%4244245%36%53%
1977
16th to endNight
12%42432325%7%51%
1740
May1st to 15thNight
9%4234235%6%9%48%
1619
16th to endNight
7%31342447%10%49%
1683
June1st to 15thNight
221231335%8%64%
1620
16th to endNight
5%2134245%5%10%55%
1620
July1st to 15thNight
42123235%5%10%59%
1620
16th to endNight
211322446%11%58%
1702
August1st to 15thNight
11122123410%69%
1623
16th to endNight
6%32442446%10%49%
1976
September1st to 15thNight
8%21343446%8%51%
1980
16th to endNight
8%32332345%7%55%
1891
October1st to 15thNight
7%212213246%63%
1842
16th to endNight
8%21321233466%
2112
November1st to 15thNight
8%413423336%59%
2123
16th to endNight
12%42331233459%
2340
December1st to 15thNight
14%5%24323346%51%
2340
16th to endNight
14%6%2332323451%
2496

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%5%12213325%53%
1611
16th to endDay
13%312323446%54%
1770
February1st to 15thDay
13%5%2331224456%
1750
16th to endDay
15%6%2331233453%
1580
March1st to 15thDay
18%5%24323345%47%
1968
16th to endDay
13%5%24323335%51%
2110
April1st to 15thDay
11%5%3442345%7%47%
1971
16th to endDay
13%5%245%23445%48%
2216
May1st to 15thDay
14%6%25%415%446%42%
2331
16th to endDay
12%6%36%6%345%6%8%36%
2430
June1st to 15thDay
4313435%47%9%53%
2340
16th to endDay
8%4245%35%5%5%9%45%
2340
July1st to 15thDay
6%324445%6%6%9%46%
2340
16th to endDay
5%314445%5%5%9%49%
2466
August1st to 15thDay
22123345%5%8%62%
2334
16th to endDay
8%315%5%46%7%6%8%42%
2224
September1st to 15thDay
10%4146%35%5%5%7%45%
1980
16th to endDay
7%225%5%3445%7%50%
1881
October1st to 15thDay
9%414324246%56%
1777
16th to endDay
8%31221223468%
1760
November1st to 15thDay
12%414324345%53%
1734
16th to endDay
13%42331323457%
1620
December1st to 15thDay
17%5%24323435%48%
1620
16th to endDay
14%6%25%32335%6%47%
1728
January1st to 15thNight
16%413312235%54%
2327
16th to endNight
14%323313345%55%
2465
February1st to 15thNight
12%5%1331222457%
2102
16th to endNight
13%313323346%54%
1894
March1st to 15thNight
14%324413346%49%
1989
16th to endNight
11%31331335%6%54%
2112
April1st to 15thNight
8%3243345%46%53%
1977
16th to endNight
11%423323347%51%
1740
May1st to 15thNight
10%3334235%6%8%48%
1619
16th to endNight
7%31342447%10%49%
1683
June1st to 15thNight
221231335%8%64%
1620
16th to endNight
5%21342446%10%55%
1620
July1st to 15thNight
421123345%10%58%
1620
16th to endNight
211322446%11%59%
1702
August1st to 15thNight
112212349%70%
1623
16th to endNight
6%3245%235%6%9%49%
1976
September1st to 15thNight
8%2234335%6%8%51%
1980
16th to endNight
8%31232445%8%54%
1891
October1st to 15thNight
7%312313246%63%
1842
16th to endNight
8%2321223466%
2112
November1st to 15thNight
8%413323336%59%
2123
16th to endNight
11%42331223459%
2340
December1st to 15thNight
14%5%24323246%51%
2340
16th to endNight
14%6%2332324451%
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
35%36%17%24%13%
1612
16th to endDay
32%36%15%25%15%
1770
February1st to 15thDay
33%27%15%24%16%
1751
16th to endDay
35%25%18%22%14%
1580
March1st to 15thDay
39%47%14%22%11%
1968
16th to endDay
36%49%17%23%9%
2112
April1st to 15thDay
36%48%19%16%13%
1971
16th to endDay
38%47%17%21%10%
2216
May1st to 15thDay
42%6%10%15%17%8%
2331
16th to endDay
43%7%11%17%16%3
2434
June1st to 15thDay
26%6%14%23%23%6%
2340
16th to endDay
35%6%12%23%17%4
2340
July1st to 15thDay
30%9%16%26%14%2
2201
16th to endDay
27%8%18%28%15%1
2311
August1st to 15thDay
16%6%16%35%21%1
2320
16th to endDay
35%9%14%24%13%3
2224
September1st to 15thDay
34%7%12%22%16%6%
1980
16th to endDay
31%6%10%21%21%9%
1881
October1st to 15thDay
28%49%22%17%16%
1777
16th to endDay
21%2417%33%19%
1760
November1st to 15thDay
33%39%21%21%10%
1734
16th to endDay
32%35%15%23%21%
1620
December1st to 15thDay
39%38%18%20%9%
1620
16th to endDay
37%39%17%21%9%
1728
January1st to 15thNight
33%26%17%22%17%
2327
16th to endNight
32%35%14%24%18%
2465
February1st to 15thNight
32%35%14%24%20%
2112
16th to endNight
32%36%17%22%17%
1894
March1st to 15thNight
36%49%12%24%13%
1989
16th to endNight
30%5%11%18%24%9%
2112
April1st to 15thNight
33%48%18%18%16%
1977
16th to endNight
33%411%17%20%11%
1740
May1st to 15thNight
31%6%12%20%19%9%
1620
16th to endNight
27%7%16%26%18%3
1685
June1st to 15thNight
17%5%14%29%26%6%
1620
16th to endNight
23%8%14%28%20%4
1620
July1st to 15thNight
20%8%18%33%17%1
1530
16th to endNight
16%8%24%34%15%2
1594
August1st to 15thNight
12%6%16%37%23%3
1613
16th to endNight
28%7%19%27%12%4
1976
September1st to 15thNight
29%6%16%23%16%7%
1980
16th to endNight
26%6%11%24%19%11%
1891
October1st to 15thNight
23%210%25%19%17%
1842
16th to endNight
22%26%17%26%24%
2112
November1st to 15thNight
27%38%22%23%13%
2123
16th to endNight
30%26%14%23%21%
2340
December1st to 15thNight
35%38%19%20%12%
2340
16th to endNight
36%37%15%23%13%
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
20%6%31%35%42
90
16th to endDay
12%11%43%21%10%
96
February1st to 15thDay
413%34%41%6%
90
16th to endDay
16%8%43%24%7%
81
March1st to 15thDay
27%7%33%23%7%
90
16th to endDay
8%248%25%13%2
96
April1st to 15thDay
13%10%38%31%6%
90
16th to endDay
12%11%39%23%12%
326
May1st to 15thDay
16%6%37%27%10%1
468
16th to endDay
18%5%27%29%16%2
517
June1st to 15thDay
5%15%43%26%8%
495
16th to endDay
9%210%37%31%8%
495
July1st to 15thDay
48%39%36%9%
475
16th to endDay
4430%44%16%
515
August1st to 15thDay
2330%46%16%
487
16th to endDay
12%6%27%35%17%
264
September1st to 15thDay
319%48%27%
135
16th to endDay
423%53%18%
108
October1st to 15thDay
25%36%44%11%
90
16th to endDay
19%210%29%32%6%
96
November1st to 15thDay
30%422%23%15%4
90
16th to endDay
25%8%27%20%15%2
90
December1st to 15thDay
24%322%27%13%8%
90
16th to endDay
21%9%38%23%5%1
96
January1st to 15thNight
19%8%32%30%9%
900
16th to endNight
16%8%35%31%8%
929
February1st to 15thNight
17%10%33%33%5%
704
16th to endNight
15%10%43%26%3
632
March1st to 15thNight
16%9%34%33%6%
549
16th to endNight
10%9%42%32%4
576
April1st to 15thNight
8%9%46%32%2
539
16th to endNight
14%7%41%27%10%
540
May1st to 15thNight
12%6%42%30%7%
540
16th to endNight
8%234%35%17%1
563
June1st to 15thNight
221%49%23%1
540
16th to endNight
415%50%25%2
540
July1st to 15thNight
410%48%32%3
510
16th to endNight
3448%38%3
564
August1st to 15thNight
2343%44%7%
539
16th to endNight
9%439%39%6%
573
September1st to 15thNight
8%5%38%40%5%
540
16th to endNight
10%7%37%39%4
513
October1st to 15thNight
7%116%44%25%4
522
16th to endNight
10%424%34%24%2
704
November1st to 15thNight
10%431%33%18%1
723
16th to endNight
15%6%27%35%14%1
900
December1st to 15thNight
17%6%31%34%10%
900
16th to endNight
19%7%30%34%7%
960
Page generated at 2017-09-23 05:43:41. Version ac04

Copyright 2017 A. Danko


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