Texas A&M University Teaching Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Texas A&M University Teaching Observatory clear sky chart from 2005-11-05 to 2017-09-15.

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
52%
15427
25%
46893
19%
15381
59%
15381
33%
27414

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
38%
896
24%
2327
11%
895
45%
895
31%
1527
January16th to endNight
35%
960
28%
2496
11%
960
45%
960
32%
1598
February1st to 15thNight
35%
737
25%
2137
11%
730
45%
730
28%
1327
February16th to endNight
26%
575
27%
1837
10%
575
40%
575
26%
1099
March1st to 15thNight
31%
540
26%
1980
15%
540
45%
540
24%
1195
March16th to endNight
36%
576
24%
2112
16%
576
48%
576
27%
1202
April1st to 15thNight
36%
539
22%
1977
14%
539
50%
539
26%
1134
April16th to endNight
37%
540
24%
1800
17%
540
48%
540
28%
1071
May1st to 15thNight
36%
539
21%
1619
15%
539
46%
539
29%
985
May16th to endNight
59%
563
27%
1685
24%
561
68%
561
39%
941
June1st to 15thNight
76%
540
21%
1620
24%
540
79%
540
49%
821
June16th to endNight
77%
540
21%
1620
24%
540
79%
540
41%
895
July1st to 15thNight
80%
510
21%
1530
25%
510
82%
510
42%
832
July16th to endNight
85%
564
20%
1594
24%
531
87%
531
43%
859
August1st to 15thNight
91%
539
30%
1610
34%
536
91%
536
57%
761
August16th to endNight
77%
573
19%
1946
22%
573
78%
573
29%
1165
September1st to 15thNight
76%
540
17%
1980
20%
540
77%
540
30%
1127
September16th to endNight
73%
492
28%
1815
31%
492
75%
492
31%
994
October1st to 15thNight
73%
572
34%
1892
31%
572
75%
572
42%
956
October16th to endNight
59%
704
36%
2112
24%
704
67%
704
46%
1086
November1st to 15thNight
51%
700
29%
2100
20%
700
57%
700
35%
1227
November16th to endNight
48%
828
31%
2268
18%
828
55%
828
36%
1361
December1st to 15thNight
38%
900
26%
2340
14%
900
44%
900
28%
1568
December16th to endNight
38%
960
22%
2496
10%
960
45%
960
28%
1683

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
12%5%24435%45%7%43%
47819
Night
11%423323347%51%
47097
TransparencyDay
38%6%11%18%16%7%
47519
Night
32%5%12%20%18%10%
46902
SeeingDay
11%315%26%30%12%
5420
Night
13%5%23%35%20%2
15432

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
19%6%1332333447%
1611
16th to endDay
19%5%24312245%48%
1728
February1st to 15thDay
18%7%25%312336%46%
1726
16th to endDay
19%6%2442333445%
1637
March1st to 15thDay
22%6%24323345%39%
1980
16th to endDay
17%6%24423345%44%
2110
April1st to 15thDay
13%6%35%5%3445%7%41%
1971
16th to endDay
14%5%25%435%446%42%
2158
May1st to 15thDay
13%6%35%435%5%6%9%35%
2328
16th to endDay
11%5%25%5%46%46%8%37%
2430
June1st to 15thDay
5%2236%36%6%8%9%43%
2340
16th to endDay
7%435%6%47%8%8%9%35%
2340
July1st to 15thDay
8%425%5%47%5%8%11%37%
2340
16th to endDay
6%425%6%47%6%8%11%37%
2466
August1st to 15thDay
5%113425%5%6%10%53%
2340
16th to endDay
7%4246%46%7%7%9%38%
2250
September1st to 15thDay
9%5%25%5%46%5%5%7%41%
1969
16th to endDay
7%414436%6%5%5%48%
1815
October1st to 15thDay
10%423433336%53%
1725
16th to endDay
10%21221233463%
1760
November1st to 15thDay
8%5%35%424347%48%
1758
16th to endDay
15%6%2432233451%
1689
December1st to 15thDay
19%7%35%423336%41%
1620
16th to endDay
19%7%25%42443440%
1728
January1st to 15thNight
18%6%24313335%47%
2327
16th to endNight
18%423322336%48%
2496
February1st to 15thNight
15%6%24322235%50%
2135
16th to endNight
16%42433333450%
1837
March1st to 15thNight
18%5%24322347%45%
1980
16th to endNight
12%5%23423346%52%
2112
April1st to 15thNight
9%425%435%448%47%
1977
16th to endNight
12%5%24423348%48%
1800
May1st to 15thNight
9%426%425%46%8%46%
1619
16th to endNight
421342436%11%52%
1683
June1st to 15thNight
311231347%10%59%
1620
16th to endNight
321342447%11%52%
1620
July1st to 15thNight
421442445%10%55%
1620
16th to endNight
42132245%6%14%51%
1702
August1st to 15thNight
31111236%12%64%
1620
16th to endNight
6%324435%6%7%10%45%
1946
September1st to 15thNight
7%3244335%6%8%49%
1980
16th to endNight
8%42333445%6%52%
1815
October1st to 15thNight
6%323323336%62%
1892
16th to endNight
9%212212235%65%
2112
November1st to 15thNight
10%424424346%53%
2100
16th to endNight
14%5%2331333455%
2268
December1st to 15thNight
17%7%23423246%44%
2340
16th to endNight
16%7%34323345%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
41%37%15%20%11%
1612
16th to endDay
39%36%14%22%14%
1728
February1st to 15thDay
41%35%15%20%12%
1727
16th to endDay
43%37%15%19%11%
1637
March1st to 15thDay
46%47%13%20%8%
1980
16th to endDay
43%37%16%23%6%
2112
April1st to 15thDay
42%5%7%16%16%11%
1971
16th to endDay
42%5%9%16%18%8%
2158
May1st to 15thDay
44%8%10%13%14%7%
2328
16th to endDay
42%8%12%19%15%2
2434
June1st to 15thDay
33%8%15%23%17%2
2340
16th to endDay
41%11%14%20%11%1
2340
July1st to 15thDay
37%9%19%22%9%
2201
16th to endDay
35%11%20%22%8%
2311
August1st to 15thDay
25%9%18%32%13%1
2326
16th to endDay
38%12%17%21%8%1
2250
September1st to 15thDay
40%8%12%20%12%5%
1969
16th to endDay
35%8%12%17%17%9%
1815
October1st to 15thDay
32%5%9%18%17%16%
1725
16th to endDay
25%35%15%31%18%
1760
November1st to 15thDay
34%5%10%19%19%9%
1758
16th to endDay
36%37%12%23%16%
1689
December1st to 15thDay
46%48%15%16%8%
1620
16th to endDay
46%49%14%16%8%
1728
January1st to 15thNight
40%26%15%19%14%
2327
16th to endNight
38%35%14%21%15%
2496
February1st to 15thNight
38%35%13%22%16%
2145
16th to endNight
38%36%16%18%15%
1837
March1st to 15thNight
40%48%13%21%11%
1980
16th to endNight
34%5%11%17%21%9%
2112
April1st to 15thNight
34%6%10%17%18%13%
1977
16th to endNight
36%5%9%20%17%10%
1800
May1st to 15thNight
34%7%12%19%16%8%
1620
16th to endNight
25%7%16%28%18%3
1685
June1st to 15thNight
18%7%17%30%23%3
1620
16th to endNight
25%7%20%30%15%2
1620
July1st to 15thNight
23%7%23%33%11%
1530
16th to endNight
20%10%30%29%8%
1594
August1st to 15thNight
12%7%24%39%14%1
1610
16th to endNight
30%11%22%26%7%1
1946
September1st to 15thNight
30%9%20%21%12%6%
1980
16th to endNight
29%7%12%20%19%10%
1815
October1st to 15thNight
24%410%23%19%16%
1892
16th to endNight
23%35%16%27%23%
2112
November1st to 15thNight
33%49%21%21%10%
2100
16th to endNight
32%46%13%22%20%
2268
December1st to 15thNight
42%48%18%18%8%
2340
16th to endNight
42%46%16%18%10%
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
23%5%24%33%12%1
90
16th to endDay
17%7%45%17%10%1
96
February1st to 15thDay
8%14%42%24%10%
90
16th to endDay
18%16%34%20%8%1
81
March1st to 15thDay
27%12%32%14%12%1
90
16th to endDay
11%336%30%15%3
96
April1st to 15thDay
15%8%33%26%12%3
90
16th to endDay
19%6%27%26%17%1
268
May1st to 15thDay
12%8%36%29%11%2
465
16th to endDay
13%423%33%21%3
517
June1st to 15thDay
7%17%35%37%10%
495
16th to endDay
8%18%30%36%15%
495
July1st to 15thDay
45%31%40%17%
475
16th to endDay
4321%45%24%
515
August1st to 15thDay
5%214%55%21%
493
16th to endDay
14%416%37%26%
290
September1st to 15thDay
3316%39%36%
132
16th to endDay
3212%43%38%
90
October1st to 15thDay
437%44%13%
90
16th to endDay
17%11%19%38%12%
96
November1st to 15thDay
13%5%21%35%18%5%
90
16th to endDay
23%5%24%28%10%7%
90
December1st to 15thDay
32%418%22%13%8%
90
16th to endDay
30%12%32%15%9%
96
January1st to 15thNight
21%8%26%33%9%
900
16th to endNight
20%9%30%32%7%
960
February1st to 15thNight
17%11%30%34%5%
737
16th to endNight
20%10%39%26%3
575
March1st to 15thNight
19%7%38%27%7%
540
16th to endNight
12%8%39%31%6%
576
April1st to 15thNight
10%9%40%35%4
539
16th to endNight
15%6%36%30%10%
540
May1st to 15thNight
10%7%40%32%7%1
540
16th to endNight
5%227%43%19%1
563
June1st to 15thNight
413%51%28%2
540
16th to endNight
310%46%34%4
540
July1st to 15thNight
45%44%39%5%
510
16th to endNight
3342%43%4
564
August1st to 15thNight
3141%48%4
539
16th to endNight
7%5%32%46%7%
573
September1st to 15thNight
7%5%31%46%7%
540
16th to endNight
10%7%28%44%7%
492
October1st to 15thNight
8%210%43%29%5%
572
16th to endNight
10%322%32%26%3
704
November1st to 15thNight
11%428%32%22%1
700
16th to endNight
16%5%24%33%18%1
828
December1st to 15thNight
20%7%27%31%12%
900
16th to endNight
21%9%26%31%9%
960
Page generated at 2017-09-15 23:58:32. Version ac04

Copyright 2017 A. Danko


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