TAMUK Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the TAMUK Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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%
15525
24%
47885
18%
15478
61%
15478
33%
27790

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
39%
899
21%
2327
10%
895
45%
895
29%
1569
January16th to endNight
43%
831
25%
2367
14%
831
49%
831
31%
1457
February1st to 15thNight
40%
704
25%
2111
12%
699
50%
699
30%
1276
February16th to endNight
30%
617
24%
1879
9%
617
42%
617
29%
1135
March1st to 15thNight
37%
540
26%
1980
15%
540
50%
540
24%
1172
March16th to endNight
38%
576
23%
2112
15%
576
48%
576
26%
1194
April1st to 15thNight
34%
539
20%
1977
10%
539
48%
539
26%
1152
April16th to endNight
32%
540
21%
1877
14%
540
45%
540
23%
1181
May1st to 15thNight
40%
539
21%
1620
15%
539
49%
539
31%
996
May16th to endNight
50%
563
23%
1684
18%
561
60%
561
33%
1001
June1st to 15thNight
75%
540
20%
1620
22%
540
78%
540
45%
847
June16th to endNight
73%
540
18%
1620
19%
540
76%
540
42%
890
July1st to 15thNight
79%
510
18%
1530
20%
510
81%
510
43%
826
July16th to endNight
86%
564
24%
1594
27%
531
89%
531
50%
811
August1st to 15thNight
91%
539
30%
1730
35%
536
91%
536
59%
747
August16th to endNight
80%
573
20%
2015
24%
573
81%
573
33%
1100
September1st to 15thNight
77%
540
16%
1980
20%
540
77%
540
29%
1129
September16th to endNight
72%
537
22%
1980
23%
537
74%
537
28%
1137
October1st to 15thNight
80%
540
33%
1980
33%
540
81%
540
44%
911
October16th to endNight
67%
765
35%
2301
27%
765
70%
765
48%
1168
November1st to 15thNight
58%
760
26%
2280
19%
760
61%
760
34%
1346
November16th to endNight
55%
899
31%
2459
18%
899
61%
899
40%
1435
December1st to 15thNight
43%
910
24%
2366
14%
910
47%
910
28%
1607
December16th to endNight
38%
960
21%
2496
11%
960
43%
960
27%
1703

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%5%25%5%35%5%6%8%42%
48558
Night
10%42432345%7%50%
48082
TransparencyDay
37%6%12%21%15%7%
48258
Night
32%5%15%22%15%8%
47887
SeeingDay
9%320%34%24%7%
5393
Night
12%322%37%22%2
15527

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
21%7%34424347%36%
1611
16th to endDay
14%6%35%5%2335%6%43%
1866
February1st to 15thDay
17%6%24323345%45%
1750
16th to endDay
16%7%3431234447%
1595
March1st to 15thDay
20%5%2442345%7%38%
1980
16th to endDay
12%6%245%25%347%45%
2110
April1st to 15thDay
10%42442446%7%46%
1971
16th to endDay
13%6%2442346%7%42%
2079
May1st to 15thDay
10%6%27%4345%6%7%40%
2331
16th to endDay
7%425%5%36%6%7%10%39%
2430
June1st to 15thDay
2214436%6%6%11%48%
2340
16th to endDay
5%426%6%47%6%7%11%37%
2340
July1st to 15thDay
7%436%7%37%5%6%9%38%
2340
16th to endDay
5%325%5%36%6%8%9%41%
2466
August1st to 15thDay
2212435%6%7%12%51%
2216
16th to endDay
6%425%7%46%6%7%10%37%
2186
September1st to 15thDay
9%6%27%8%5%6%6%7%9%30%
1980
16th to endDay
9%6%27%5%46%6%7%9%34%
1980
October1st to 15thDay
6%315%5%26%6%6%8%47%
1971
16th to endDay
6%314324346%59%
1920
November1st to 15thDay
11%5%37%5%35%5%5%6%40%
1908
16th to endDay
12%5%33424436%49%
1829
December1st to 15thDay
21%7%25%423437%36%
1631
16th to endDay
18%5%245%34447%39%
1728
January1st to 15thNight
20%5%24313345%44%
2327
16th to endNight
15%6%14323446%47%
2367
February1st to 15thNight
15%5%13334445%48%
2102
16th to endNight
14%5%23323335%50%
1879
March1st to 15thNight
15%7%34423347%44%
1980
16th to endNight
11%435%42335%7%48%
2112
April1st to 15thNight
12%415%435%46%9%42%
1977
16th to endNight
15%6%345%2445%7%40%
1877
May1st to 15thNight
11%4345%25%47%11%40%
1619
16th to endNight
6%425%4345%7%13%42%
1683
June1st to 15thNight
221342447%9%55%
1620
16th to endNight
33233335%7%12%50%
1620
July1st to 15thNight
432331445%12%53%
1620
16th to endNight
311231346%11%58%
1702
August1st to 15thNight
11111249%72%
1740
16th to endNight
431442345%8%55%
2015
September1st to 15thNight
6%5%25%5%345%6%10%46%
1980
16th to endNight
8%424435%45%10%45%
1980
October1st to 15thNight
4313313346%64%
1980
16th to endNight
6%223312235%66%
2301
November1st to 15thNight
9%5%24423436%53%
2280
16th to endNight
10%41431334457%
2459
December1st to 15thNight
20%6%34422326%43%
2366
16th to endNight
18%8%25%323345%41%
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
48%37%14%15%10%
1612
16th to endDay
40%38%17%16%11%
1866
February1st to 15thDay
41%36%14%18%14%
1751
16th to endDay
39%26%20%20%10%
1595
March1st to 15thDay
43%310%14%16%11%
1980
16th to endDay
38%411%17%16%11%
2112
April1st to 15thDay
34%5%11%20%18%10%
1971
16th to endDay
38%5%10%19%14%10%
2079
May1st to 15thDay
39%5%14%19%13%8%
2331
16th to endDay
35%8%10%23%19%3
2434
June1st to 15thDay
26%6%14%27%19%5%
2340
16th to endDay
35%10%16%25%11%
2340
July1st to 15thDay
37%8%16%25%10%
2201
16th to endDay
31%8%22%31%4
2311
August1st to 15thDay
23%7%21%40%7%
2202
16th to endDay
36%10%20%23%6%1
2186
September1st to 15thDay
46%9%14%16%11%1
1980
16th to endDay
41%9%13%17%13%5%
1980
October1st to 15thDay
30%7%10%21%22%7%
1971
16th to endDay
25%46%20%26%16%
1920
November1st to 15thDay
41%5%9%18%15%9%
1908
16th to endDay
36%39%14%20%15%
1829
December1st to 15thDay
47%39%15%15%8%
1631
16th to endDay
44%47%16%16%10%
1728
January1st to 15thNight
43%37%14%16%14%
2327
16th to endNight
37%39%19%17%12%
2367
February1st to 15thNight
37%310%14%16%17%
2112
16th to endNight
37%47%20%18%11%
1879
March1st to 15thNight
40%39%16%18%11%
1980
16th to endNight
36%412%18%18%10%
2112
April1st to 15thNight
37%414%18%15%9%
1977
16th to endNight
43%5%9%19%14%9%
1877
May1st to 15thNight
36%5%17%20%11%8%
1620
16th to endNight
30%8%17%24%16%2
1685
June1st to 15thNight
23%5%17%30%21%2
1620
16th to endNight
24%7%23%32%12%
1620
July1st to 15thNight
23%7%27%32%7%
1530
16th to endNight
16%8%33%34%6%
1594
August1st to 15thNight
10%6%28%46%6%
1730
16th to endNight
25%10%26%29%6%1
2015
September1st to 15thNight
32%7%23%24%8%2
1980
16th to endNight
33%7%17%24%12%4
1980
October1st to 15thNight
20%5%15%28%22%8%
1980
16th to endNight
21%47%21%26%18%
2301
November1st to 15thNight
32%5%14%20%19%7%
2280
16th to endNight
30%310%20%17%17%
2459
December1st to 15thNight
44%39%18%14%9%
2366
16th to endNight
44%38%15%16%11%
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
22%5%25%36%8%1
90
16th to endDay
14%13%38%19%13%
96
February1st to 15thDay
7%6%37%23%24%
90
16th to endDay
13%11%38%27%8%1
81
March1st to 15thDay
32%5%24%26%11%
90
16th to endDay
13%7%33%37%7%1
96
April1st to 15thDay
8%7%35%36%11%
90
16th to endDay
15%5%37%28%11%1
189
May1st to 15thDay
12%6%45%27%8%
468
16th to endDay
11%437%32%12%1
517
June1st to 15thDay
311%45%32%5%
495
16th to endDay
4113%38%31%9%
495
July1st to 15thDay
5%111%42%32%6%
475
16th to endDay
415%37%40%10%
515
August1st to 15thDay
115%45%29%16%
371
16th to endDay
7%210%40%21%16%
226
September1st to 15thDay
7%7%31%43%10%
135
16th to endDay
5%418%48%22%
135
October1st to 15thDay
5%222%40%28%
135
16th to endDay
10%118%29%31%9%
144
November1st to 15thDay
25%18%28%20%5%
135
16th to endDay
17%419%29%18%10%
135
December1st to 15thDay
36%213%21%14%11%
94
16th to endDay
27%11%29%19%8%4
96
January1st to 15thNight
23%426%33%12%
900
16th to endNight
17%6%27%39%8%
831
February1st to 15thNight
17%6%30%35%9%
704
16th to endNight
18%6%39%29%5%
617
March1st to 15thNight
19%6%33%32%8%
540
16th to endNight
12%5%38%37%5%
576
April1st to 15thNight
12%5%42%33%6%
539
16th to endNight
17%5%39%29%7%
540
May1st to 15thNight
11%439%38%6%
540
16th to endNight
8%331%43%13%
563
June1st to 15thNight
213%55%26%1
540
16th to endNight
4112%49%30%2
540
July1st to 15thNight
5%8%47%35%3
510
16th to endNight
15%43%43%4
564
August1st to 15thNight
2140%51%4
539
16th to endNight
5%431%51%6%
573
September1st to 15thNight
6%5%26%51%10%
540
16th to endNight
10%5%27%44%10%
537
October1st to 15thNight
5%17%34%45%6%
540
16th to endNight
7%118%42%27%2
765
November1st to 15thNight
12%120%39%23%2
760
16th to endNight
12%323%36%22%2
899
December1st to 15thNight
21%5%21%33%15%1
910
16th to endNight
23%5%26%32%11%
960
Page generated at 2017-12-03 10:16:40. Version ac04

Copyright 2017 A. Danko


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