Big Thicket Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Big Thicket Observatory clear sky chart from 2005-11-05 to 2017-09-18.

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
54%
15389
23%
46897
18%
15343
59%
15343
30%
28461

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
34%
900
23%
2327
11%
895
41%
895
28%
1557
January16th to endNight
34%
960
23%
2496
10%
960
41%
960
28%
1679
February1st to 15thNight
35%
846
24%
2255
10%
843
43%
843
28%
1480
February16th to endNight
31%
474
25%
1736
13%
474
44%
474
22%
1072
March1st to 15thNight
36%
540
23%
1980
17%
540
45%
540
21%
1251
March16th to endNight
44%
576
21%
2112
18%
576
51%
576
27%
1221
April1st to 15thNight
41%
539
23%
1890
17%
539
51%
539
26%
1130
April16th to endNight
43%
540
21%
1800
19%
540
51%
540
25%
1109
May1st to 15thNight
45%
539
17%
1788
16%
539
51%
539
26%
1106
May16th to endNight
63%
563
25%
1685
25%
561
68%
561
38%
965
June1st to 15thNight
81%
540
19%
1620
21%
540
82%
540
43%
871
June16th to endNight
76%
540
16%
1620
18%
540
77%
540
29%
1024
July1st to 15thNight
77%
510
16%
1530
20%
510
77%
510
36%
892
July16th to endNight
82%
564
16%
1594
20%
531
82%
531
35%
937
August1st to 15thNight
89%
539
23%
1664
27%
536
89%
536
47%
841
August16th to endNight
74%
573
14%
1910
17%
573
74%
573
25%
1223
September1st to 15thNight
75%
540
16%
1893
19%
540
75%
540
28%
1110
September16th to endNight
74%
501
27%
1848
30%
501
74%
501
30%
1028
October1st to 15thNight
72%
649
31%
1969
27%
649
73%
649
43%
1042
October16th to endNight
63%
704
35%
2112
27%
704
69%
704
45%
1100
November1st to 15thNight
56%
700
28%
2100
22%
700
59%
700
35%
1215
November16th to endNight
50%
720
32%
2160
23%
720
57%
720
35%
1251
December1st to 15thNight
40%
872
24%
2312
13%
872
46%
872
26%
1575
December16th to endNight
35%
960
19%
2496
10%
960
39%
960
23%
1782

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%5%35%5%35%5%6%7%36%
47897
Night
12%5%2442345%8%47%
47092
TransparencyDay
44%7%10%15%14%6%
47597
Night
35%6%13%19%16%8%
46897
SeeingDay
12%414%25%27%15%
5422
Night
14%420%31%24%3
15390

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%5%2442334443%
1611
16th to endDay
22%5%25%42323443%
1728
February1st to 15thDay
19%7%34423345%40%
1617
16th to endDay
23%7%34413245%39%
1738
March1st to 15thDay
24%6%34423335%37%
1980
16th to endDay
16%7%35%425%345%39%
2110
April1st to 15thDay
16%6%35%5%3445%6%38%
2058
16th to endDay
15%6%35%6%35%5%5%7%35%
2160
May1st to 15thDay
13%8%26%5%46%5%7%7%32%
2160
16th to endDay
9%5%36%6%47%6%7%10%32%
2430
June1st to 15thDay
7%5%36%7%5%8%8%8%9%29%
2340
16th to endDay
7%6%37%7%6%9%9%8%9%23%
2340
July1st to 15thDay
10%5%36%7%5%7%7%9%11%24%
2340
16th to endDay
9%436%8%5%9%8%8%10%24%
2466
August1st to 15thDay
4326%6%48%7%8%11%35%
2286
16th to endDay
12%5%27%6%5%9%6%7%7%27%
2292
September1st to 15thDay
11%5%36%6%47%7%6%8%33%
2064
16th to endDay
11%5%26%6%46%6%6%7%35%
1835
October1st to 15thDay
8%424445%445%50%
1650
16th to endDay
11%31432235%6%55%
1760
November1st to 15thDay
12%5%26%5%3445%5%44%
1758
16th to endDay
15%5%2442324349%
1800
December1st to 15thDay
19%7%35%5%23346%37%
1646
16th to endDay
21%9%35%423445%34%
1728
January1st to 15thNight
20%7%34312236%42%
2327
16th to endNight
20%6%24322346%43%
2496
February1st to 15thNight
17%6%34322346%45%
2245
16th to endNight
18%7%34422435%44%
1736
March1st to 15thNight
20%7%23423335%43%
1980
16th to endNight
12%6%23423347%47%
2112
April1st to 15thNight
13%424423449%44%
1890
16th to endNight
14%5%2442445%8%42%
1800
May1st to 15thNight
10%6%24425%5%6%8%41%
1787
16th to endNight
8%41332346%10%50%
1683
June1st to 15thNight
231332347%11%55%
1620
16th to endNight
6%424336%6%9%12%41%
1620
July1st to 15thNight
6%42332446%12%48%
1620
16th to endNight
4223425%5%7%13%46%
1702
August1st to 15thNight
21133347%14%55%
1674
16th to endNight
8%4145%36%6%7%12%39%
1910
September1st to 15thNight
9%3244345%5%10%45%
1893
16th to endNight
7%424434447%50%
1848
October1st to 15thNight
7%21332345%6%59%
1969
16th to endNight
10%312222225%63%
2112
November1st to 15thNight
8%41442435%7%52%
2100
16th to endNight
12%5%2442234453%
2160
December1st to 15thNight
17%8%35%424446%40%
2312
16th to endNight
20%8%245%33345%37%
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
42%46%15%20%10%
1612
16th to endDay
46%35%14%18%12%
1728
February1st to 15thDay
47%35%15%18%9%
1618
16th to endDay
47%46%13%18%9%
1738
March1st to 15thDay
49%47%11%18%7%
1980
16th to endDay
45%47%15%21%6%
2112
April1st to 15thDay
45%48%15%17%9%
2058
16th to endDay
45%7%10%14%15%6%
2160
May1st to 15thDay
48%7%10%13%13%6%
2160
16th to endDay
44%9%12%18%13%2
2434
June1st to 15thDay
44%10%12%15%15%1
2340
16th to endDay
49%12%14%14%8%
2340
July1st to 15thDay
46%12%17%16%6%
2201
16th to endDay
47%12%18%18%2
2311
August1st to 15thDay
37%11%19%23%7%
2272
16th to endDay
49%13%15%14%5%1
2292
September1st to 15thDay
45%11%13%15%11%3
2064
16th to endDay
43%7%11%16%15%5%
1835
October1st to 15thDay
34%5%10%17%17%14%
1650
16th to endDay
30%35%14%30%15%
1760
November1st to 15thDay
40%5%8%17%18%9%
1758
16th to endDay
39%36%12%23%14%
1800
December1st to 15thDay
48%47%16%15%6%
1646
16th to endDay
50%5%6%15%15%6%
1728
January1st to 15thNight
44%25%14%21%11%
2327
16th to endNight
43%36%15%17%13%
2496
February1st to 15thNight
41%46%14%21%12%
2255
16th to endNight
43%36%16%16%13%
1736
March1st to 15thNight
44%48%13%18%10%
1980
16th to endNight
36%5%13%16%20%8%
2112
April1st to 15thNight
38%5%9%19%16%10%
1890
16th to endNight
39%5%11%18%15%9%
1800
May1st to 15thNight
39%6%15%16%14%8%
1788
16th to endNight
27%8%16%28%15%3
1685
June1st to 15thNight
21%9%19%30%19%1
1620
16th to endNight
31%13%20%24%9%
1620
July1st to 15thNight
28%8%30%25%7%
1530
16th to endNight
26%11%31%26%3
1594
August1st to 15thNight
16%9%29%36%7%
1664
16th to endNight
35%12%25%18%7%1
1910
September1st to 15thNight
31%10%22%20%10%4
1893
16th to endNight
32%5%13%20%18%8%
1848
October1st to 15thNight
24%5%10%23%19%15%
1969
16th to endNight
25%26%15%29%20%
2112
November1st to 15thNight
31%5%11%19%23%8%
2100
16th to endNight
33%37%13%25%16%
2160
December1st to 15thNight
44%48%18%15%8%
2312
16th to endNight
49%45%14%16%9%
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
24%6%35%21%12%
90
16th to endDay
14%20%36%16%11%
96
February1st to 15thDay
13%18%33%28%5%
90
16th to endDay
12%13%41%25%6%
81
March1st to 15thDay
25%20%37%8%7%
90
16th to endDay
26%7%23%28%13%1
96
April1st to 15thDay
15%11%22%33%14%1
177
16th to endDay
22%7%20%26%20%2
270
May1st to 15thDay
18%6%23%29%19%2
297
16th to endDay
11%5%25%31%21%5%
517
June1st to 15thDay
9%19%33%33%11%
495
16th to endDay
10%29%25%33%18%
495
July1st to 15thDay
8%5%27%32%24%
475
16th to endDay
8%1319%36%30%
515
August1st to 15thDay
6%217%40%33%
439
16th to endDay
15%315%30%33%
332
September1st to 15thDay
6%5%18%42%27%
219
16th to endDay
9%316%45%25%
96
October1st to 15thDay
6%6%45%28%12%
90
16th to endDay
16%117%25%31%8%
96
November1st to 15thDay
13%230%32%20%2
90
16th to endDay
22%5%31%28%6%5%
90
December1st to 15thDay
27%5%21%28%11%5%
90
16th to endDay
26%15%35%17%41
96
January1st to 15thNight
22%7%30%29%9%
900
16th to endNight
21%10%29%31%7%
960
February1st to 15thNight
20%8%30%33%6%
846
16th to endNight
22%6%35%31%3
474
March1st to 15thNight
22%7%29%35%4
540
16th to endNight
17%6%29%34%12%
576
April1st to 15thNight
14%8%32%33%10%
539
16th to endNight
18%429%34%12%
540
May1st to 15thNight
13%6%27%38%12%
540
16th to endNight
8%320%39%25%2
563
June1st to 15thNight
35%44%43%3
540
16th to endNight
7%7%29%47%7%
540
July1st to 15thNight
41328%49%11%
510
16th to endNight
3221%54%17%
564
August1st to 15thNight
3123%58%14%
539
16th to endNight
8%1319%55%12%
573
September1st to 15thNight
8%5%22%50%11%
540
16th to endNight
8%5%28%48%7%
501
October1st to 15thNight
7%111%34%39%4
649
16th to endNight
11%317%34%28%3
704
November1st to 15thNight
10%422%36%23%2
700
16th to endNight
14%6%25%34%17%
720
December1st to 15thNight
20%7%26%31%13%
872
16th to endNight
24%8%26%30%9%
960
Page generated at 2017-09-19 06:32:26. Version ac04

Copyright 2017 A. Danko


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