Stark Bayou Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stark Bayou Observatory clear sky chart from 2005-11-05 to 2017-03-24.

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%
14518
23%
45344
17%
14475
58%
14475
27%
27012

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%
720
26%
2148
12%
716
47%
716
24%
1307
January16th to endNight
35%
768
26%
2304
13%
768
46%
768
23%
1486
February1st to 15thNight
34%
703
28%
2109
12%
700
48%
700
27%
1248
February16th to endNight
32%
631
23%
1893
10%
631
42%
631
22%
1219
March1st to 15thNight
37%
711
23%
2151
12%
711
46%
711
22%
1367
March16th to endNight
45%
555
26%
1919
18%
555
55%
555
27%
1044
April1st to 15thNight
42%
494
26%
1647
20%
494
53%
494
23%
978
April16th to endNight
49%
495
28%
1650
21%
495
61%
495
33%
838
May1st to 15thNight
53%
494
22%
1649
18%
494
61%
494
26%
955
May16th to endNight
61%
513
21%
1602
17%
513
68%
513
30%
894
June1st to 15thNight
63%
495
14%
1485
13%
495
65%
495
27%
894
June16th to endNight
67%
495
15%
1485
15%
495
69%
495
29%
903
July1st to 15thNight
70%
465
13%
1533
15%
465
70%
465
26%
935
July16th to endNight
66%
522
10%
1632
12%
489
71%
489
25%
1022
August1st to 15thNight
76%
494
12%
1638
16%
491
76%
491
30%
969
August16th to endNight
68%
525
13%
1750
15%
525
69%
525
22%
1136
September1st to 15thNight
65%
509
19%
1664
20%
509
67%
509
23%
1056
September16th to endNight
66%
657
27%
1815
20%
657
71%
657
32%
1119
October1st to 15thNight
65%
660
33%
1820
26%
660
69%
660
44%
976
October16th to endNight
57%
704
33%
2112
26%
704
65%
704
38%
1149
November1st to 15thNight
51%
700
32%
2201
27%
700
59%
700
31%
1222
November16th to endNight
46%
720
30%
2340
20%
720
60%
720
29%
1275
December1st to 15thNight
40%
720
25%
2340
18%
720
49%
720
23%
1394
December16th to endNight
32%
768
20%
2457
11%
768
42%
768
18%
1626

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
9%4245%35%5%6%9%42%
45548
Night
9%42442445%8%47%
45570
TransparencyDay
37%7%13%18%16%6%
45273
Night
33%6%13%19%18%8%
45350
SeeingDay
10%9%11%20%29%18%
4317
Night
10%17%14%23%24%9%
14522

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
11%5%25%42445%7%45%
1790
16th to endDay
17%6%3442334445%
1920
February1st to 15thDay
12%6%24433337%50%
1750
16th to endDay
13%6%34425%447%42%
1580
March1st to 15thDay
13%5%25%5%2435%8%43%
1818
16th to endDay
9%5%245%2345%7%47%
2147
April1st to 15thDay
11%5%244345%6%7%43%
1971
16th to endDay
8%4234345%6%8%47%
1980
May1st to 15thDay
9%423435%7%6%8%43%
1971
16th to endDay
8%323435%5%6%9%46%
2156
June1st to 15thDay
6%325%6%36%8%10%12%35%
2145
16th to endDay
5%426%6%47%8%9%13%32%
2145
July1st to 15thDay
6%5%36%6%5%6%8%11%14%25%
1992
16th to endDay
6%5%36%7%47%9%10%13%24%
2108
August1st to 15thDay
6%426%5%5%8%9%10%12%28%
1980
16th to endDay
10%5%16%6%5%6%8%9%10%29%
2100
September1st to 15thDay
8%6%16%6%45%6%7%10%35%
1953
16th to endDay
8%3246%35%6%6%8%44%
1815
October1st to 15thDay
5%21342346%7%57%
1807
16th to endDay
6%214334347%57%
1760
November1st to 15thDay
8%314333336%57%
1656
16th to endDay
8%323423345%57%
1620
December1st to 15thDay
11%7%25%5%23446%46%
1620
16th to endDay
18%8%35%5%24446%35%
1764
January1st to 15thNight
12%6%24423347%48%
2148
16th to endNight
18%6%2431433445%
2304
February1st to 15thNight
12%423323447%49%
2103
16th to endNight
15%6%25%423345%45%
1893
March1st to 15thNight
13%5%25%4245%5%7%43%
2151
16th to endNight
10%5%23323347%52%
1919
April1st to 15thNight
11%415%425%446%48%
1647
16th to endNight
7%313413448%57%
1650
May1st to 15thNight
8%3235%35%5%6%9%47%
1649
16th to endNight
5%323325%5%6%11%50%
1602
June1st to 15thNight
5%2245%35%6%8%12%42%
1485
16th to endNight
4334435%6%9%13%42%
1485
July1st to 15thNight
4425%436%7%9%13%38%
1633
16th to endNight
5%325%5%36%7%8%13%37%
1752
August1st to 15thNight
2414425%7%10%16%39%
1650
16th to endNight
8%5%25%5%36%6%7%11%37%
1750
September1st to 15thNight
6%425%5%36%7%8%10%37%
1664
16th to endNight
7%5%24335%46%8%47%
1815
October1st to 15thNight
5%213423347%61%
1820
16th to endNight
9%313313345%59%
2112
November1st to 15thNight
7%414433436%55%
2201
16th to endNight
7%324424435%57%
2340
December1st to 15thNight
11%5%245%2436%6%46%
2340
16th to endNight
17%7%35%5%3445%5%37%
2457

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
38%37%17%22%10%
1791
16th to endDay
42%4418%22%8%
1920
February1st to 15thDay
35%310%16%23%10%
1752
16th to endDay
40%6%6%17%20%8%
1580
March1st to 15thDay
40%48%20%19%6%
1818
16th to endDay
35%5%11%19%20%6%
2149
April1st to 15thDay
37%6%10%20%16%8%
1971
16th to endDay
32%5%13%24%18%6%
1980
May1st to 15thDay
36%7%13%22%13%6%
1971
16th to endDay
33%7%16%23%17%1
2160
June1st to 15thDay
37%9%19%23%9%
2145
16th to endDay
37%9%21%20%9%
2145
July1st to 15thDay
44%13%22%15%3
1863
16th to endDay
45%14%21%15%2
1965
August1st to 15thDay
40%14%24%13%6%
1968
16th to endDay
44%12%19%14%6%1
2100
September1st to 15thDay
41%9%19%15%10%2
1953
16th to endDay
37%7%11%19%17%6%
1815
October1st to 15thDay
26%5%11%17%24%14%
1807
16th to endDay
27%37%15%28%18%
1760
November1st to 15thDay
29%38%18%29%10%
1656
16th to endDay
28%48%17%25%15%
1620
December1st to 15thDay
39%47%20%20%6%
1620
16th to endDay
48%48%18%15%5%
1764
January1st to 15thNight
36%48%15%24%10%
2148
16th to endNight
43%35%13%23%10%
2304
February1st to 15thNight
34%47%19%21%13%
2112
16th to endNight
41%47%14%20%11%
1893
March1st to 15thNight
39%5%9%16%22%6%
2151
16th to endNight
32%311%20%23%8%
1919
April1st to 15thNight
36%410%19%18%9%
1647
16th to endNight
25%412%27%22%7%
1650
May1st to 15thNight
32%6%13%23%18%5%
1650
16th to endNight
27%7%18%26%18%1
1604
June1st to 15thNight
30%9%23%24%10%
1485
16th to endNight
30%10%23%24%10%
1485
July1st to 15thNight
30%12%30%20%4
1533
16th to endNight
32%13%30%20%2
1632
August1st to 15thNight
25%13%35%20%4
1638
16th to endNight
37%11%25%14%6%3
1750
September1st to 15thNight
36%11%19%17%11%4
1664
16th to endNight
32%6%15%19%17%7%
1815
October1st to 15thNight
23%411%20%23%17%
1820
16th to endNight
26%46%14%25%22%
2112
November1st to 15thNight
30%35%18%29%12%
2201
16th to endNight
30%45%18%22%18%
2340
December1st to 15thNight
37%410%21%20%6%
2340
16th to endNight
46%47%19%14%6%
2457

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
16%427%31%17%2
90
16th to endDay
19%8%36%29%5%1
96
February1st to 15thDay
10%10%27%35%14%2
90
16th to endDay
7%439%35%12%
81
March1st to 15thDay
18%336%35%41
90
16th to endDay
16%16%21%23%20%1
191
April1st to 15thDay
21%17%19%24%15%1
210
16th to endDay
11%15%12%29%26%3
210
May1st to 15thDay
7%15%14%28%28%6%
228
16th to endDay
9%12%5%23%32%15%
267
June1st to 15thDay
10%11%318%29%27%
255
16th to endDay
412%39%38%31%
255
July1st to 15thDay
8%8%27%34%37%
245
16th to endDay
5%12%28%32%38%
270
August1st to 15thDay
8%7%29%33%39%
253
16th to endDay
8%6%26%39%36%
268
September1st to 15thDay
10%6%5%13%32%31%
255
16th to endDay
10%6%421%37%19%
254
October1st to 15thDay
37%12%24%39%12%
247
16th to endDay
11%2441%29%11%
96
November1st to 15thDay
15%117%30%32%3
90
16th to endDay
7%7%25%28%23%6%
90
December1st to 15thDay
16%5%22%37%16%1
90
16th to endDay
27%423%21%20%2
96
January1st to 15thNight
13%22%24%30%7%
720
16th to endNight
14%23%21%30%9%
768
February1st to 15thNight
12%20%26%27%11%
704
16th to endNight
16%20%25%28%8%
631
March1st to 15thNight
15%20%23%28%11%
711
16th to endNight
12%20%16%28%19%2
555
April1st to 15thNight
12%21%19%27%17%1
494
16th to endNight
9%19%16%27%23%3
495
May1st to 15thNight
7%19%11%31%26%2
495
16th to endNight
6%19%5%21%37%9%
515
June1st to 15thNight
6%18%115%42%15%
495
16th to endNight
418%111%36%27%
495
July1st to 15thNight
412%28%40%31%
465
16th to endNight
418%15%33%37%
522
August1st to 15thNight
410%26%38%38%
494
16th to endNight
8%9%212%37%29%
525
September1st to 15thNight
9%10%410%37%27%
509
16th to endNight
9%9%224%42%10%
657
October1st to 15thNight
6%10%10%30%34%8%
660
16th to endNight
10%11%15%26%28%6%
704
November1st to 15thNight
8%17%16%31%22%4
700
16th to endNight
9%20%19%30%19%1
720
December1st to 15thNight
12%21%20%23%20%2
720
16th to endNight
16%22%20%26%13%
768
Page generated at 2017-03-25 11:39:53. Version ac04

Copyright 2017 A. Danko


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