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 2018-10-08.

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%
16392
23%
51233
17%
16349
59%
16349
27%
30533

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%
780
26%
2328
13%
776
47%
776
25%
1412
January16th to endNight
35%
832
26%
2496
13%
832
46%
832
24%
1607
February1st to 15thNight
34%
763
26%
2289
12%
760
46%
760
25%
1406
February16th to endNight
34%
683
23%
2049
11%
683
44%
683
23%
1313
March1st to 15thNight
38%
770
23%
2330
12%
770
47%
770
24%
1460
March16th to endNight
45%
624
26%
2155
18%
624
56%
624
27%
1185
April1st to 15thNight
44%
584
25%
1947
19%
584
54%
584
25%
1137
April16th to endNight
52%
579
28%
1928
22%
579
64%
579
35%
973
May1st to 15thNight
58%
584
23%
1949
21%
584
64%
584
30%
1083
May16th to endNight
63%
609
20%
1902
16%
609
69%
609
28%
1091
June1st to 15thNight
64%
585
13%
1755
12%
585
66%
585
26%
1076
June16th to endNight
67%
585
14%
1755
14%
585
69%
585
29%
1076
July1st to 15thNight
72%
555
13%
1830
16%
555
73%
555
27%
1113
July16th to endNight
68%
612
10%
1932
12%
579
72%
579
26%
1203
August1st to 15thNight
76%
575
12%
1906
16%
572
76%
572
30%
1131
August16th to endNight
67%
621
12%
2070
15%
621
68%
621
22%
1353
September1st to 15thNight
65%
602
19%
1967
19%
602
68%
602
24%
1233
September16th to endNight
68%
777
27%
2145
20%
777
72%
777
32%
1320
October1st to 15thNight
66%
752
32%
2074
25%
752
70%
752
43%
1129
October16th to endNight
57%
768
35%
2304
27%
768
65%
768
38%
1247
November1st to 15thNight
54%
760
31%
2390
26%
760
61%
760
32%
1319
November16th to endNight
48%
780
32%
2535
22%
780
62%
780
30%
1366
December1st to 15thNight
40%
780
24%
2535
18%
780
49%
780
23%
1522
December16th to endNight
32%
832
20%
2662
11%
832
42%
832
17%
1778

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%425%5%35%5%6%9%41%
51861
Night
9%42442445%8%47%
51459
TransparencyDay
37%7%13%18%16%6%
51586
Night
33%6%14%19%17%8%
51239
SeeingDay
10%7%12%22%28%18%
6375
Night
10%15%14%23%25%10%
16396

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%5%245%5%7%44%
1940
16th to endDay
17%6%3442333446%
2080
February1st to 15thDay
12%6%245%33337%47%
1900
16th to endDay
12%6%24436%45%8%40%
1710
March1st to 15thDay
13%5%25%42435%8%45%
1969
16th to endDay
10%5%245%2345%7%47%
2419
April1st to 15thDay
10%4244335%6%8%45%
2331
16th to endDay
8%4233245%5%8%49%
2307
May1st to 15thDay
8%423435%7%6%8%47%
2331
16th to endDay
8%3245%35%5%7%9%44%
2559
June1st to 15thDay
7%325%6%36%8%9%12%34%
2535
16th to endDay
6%425%6%46%8%9%13%31%
2535
July1st to 15thDay
7%5%35%6%5%6%8%11%14%26%
2354
16th to endDay
6%5%36%7%47%9%10%12%26%
2468
August1st to 15thDay
6%326%5%5%8%8%10%12%27%
2295
16th to endDay
9%5%16%7%5%7%8%8%10%28%
2484
September1st to 15thDay
8%5%15%6%45%7%7%10%35%
2308
16th to endDay
7%3246%35%6%6%8%43%
2145
October1st to 15thDay
5%2134235%6%7%56%
2053
16th to endDay
6%213324346%57%
1920
November1st to 15thDay
8%313323346%57%
1797
16th to endDay
7%324423345%58%
1755
December1st to 15thDay
12%6%25%5%23346%46%
1755
16th to endDay
19%8%35%5%24446%35%
1911
January1st to 15thNight
12%6%24423347%48%
2328
16th to endNight
18%6%2442433445%
2496
February1st to 15thNight
14%5%23333447%46%
2283
16th to endNight
14%6%25%434346%45%
2049
March1st to 15thNight
12%5%25%42445%7%44%
2330
16th to endNight
10%5%23323348%51%
2155
April1st to 15thNight
10%425%425%446%50%
1947
16th to endNight
6%313313448%58%
1928
May1st to 15thNight
7%3235%35%45%9%51%
1949
16th to endNight
5%323325%5%6%11%49%
1902
June1st to 15thNight
6%3245%35%6%7%12%42%
1755
16th to endNight
6%3344346%8%12%42%
1755
July1st to 15thNight
3425%436%6%9%12%40%
1930
16th to endNight
4426%5%36%7%8%13%38%
2052
August1st to 15thNight
34244247%10%16%39%
1918
16th to endNight
8%5%25%5%36%6%7%11%36%
2070
September1st to 15thNight
6%425%5%36%6%8%11%39%
1967
16th to endNight
6%5%24335%46%8%48%
2145
October1st to 15thNight
5%213423347%60%
2074
16th to endNight
9%313313335%60%
2304
November1st to 15thNight
7%414433436%56%
2390
16th to endNight
6%324424436%57%
2535
December1st to 15thNight
12%6%245%2435%6%45%
2535
16th to endNight
17%7%36%5%35%45%6%36%
2662

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%21%9%
1941
16th to endDay
42%3317%22%9%
2080
February1st to 15thDay
38%310%15%21%9%
1902
16th to endDay
40%7%8%17%19%7%
1710
March1st to 15thDay
38%48%19%21%7%
1969
16th to endDay
36%6%11%18%20%6%
2421
April1st to 15thDay
34%6%10%21%19%7%
2331
16th to endDay
30%5%13%24%19%6%
2307
May1st to 15thDay
33%6%12%22%18%7%
2331
16th to endDay
34%7%17%21%15%2
2563
June1st to 15thDay
38%9%18%22%10%
2535
16th to endDay
39%9%22%20%8%
2535
July1st to 15thDay
43%14%22%15%3
2225
16th to endDay
44%14%21%17%2
2325
August1st to 15thDay
42%14%24%13%5%
2283
16th to endDay
45%12%18%14%6%1
2484
September1st to 15thDay
40%10%18%15%10%4
2308
16th to endDay
36%7%12%20%16%5%
2145
October1st to 15thDay
25%6%13%18%22%12%
2053
16th to endDay
26%37%15%27%19%
1920
November1st to 15thDay
28%39%20%28%10%
1797
16th to endDay
27%48%17%25%15%
1755
December1st to 15thDay
39%47%20%20%7%
1755
16th to endDay
49%47%18%14%4
1911
January1st to 15thNight
36%48%16%24%9%
2328
16th to endNight
43%35%13%23%10%
2496
February1st to 15thNight
37%46%18%19%12%
2292
16th to endNight
41%48%15%19%10%
2049
March1st to 15thNight
38%5%9%15%22%7%
2330
16th to endNight
32%412%20%22%7%
2155
April1st to 15thNight
35%49%19%20%10%
1947
16th to endNight
24%412%26%24%7%
1928
May1st to 15thNight
29%6%12%23%21%6%
1950
16th to endNight
29%8%18%24%18%1
1904
June1st to 15thNight
31%9%23%22%11%
1755
16th to endNight
31%10%23%24%9%
1755
July1st to 15thNight
30%13%29%21%5%
1830
16th to endNight
32%12%30%21%1
1932
August1st to 15thNight
27%12%35%20%4
1906
16th to endNight
38%11%25%15%5%3
2070
September1st to 15thNight
35%10%18%18%11%4
1967
16th to endNight
32%6%16%20%16%6%
2145
October1st to 15thNight
23%412%22%21%15%
2074
16th to endNight
26%45%14%26%21%
2304
November1st to 15thNight
30%36%18%28%11%
2390
16th to endNight
28%45%19%23%18%
2535
December1st to 15thNight
37%410%20%19%7%
2535
16th to endNight
47%47%19%14%6%
2662

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%6%31%27%16%1
135
16th to endDay
19%6%37%29%6%
144
February1st to 15thDay
15%6%29%33%13%1
135
16th to endDay
7%433%45%9%
120
March1st to 15thDay
14%337%37%6%
135
16th to endDay
15%13%24%27%17%1
277
April1st to 15thDay
16%13%20%29%17%2
330
16th to endDay
11%10%15%31%25%5%
319
May1st to 15thDay
6%11%13%30%28%10%
348
16th to endDay
8%8%6%29%31%15%
395
June1st to 15thDay
12%8%218%33%24%
375
16th to endDay
8%8%412%38%27%
375
July1st to 15thDay
9%6%37%32%41%
365
16th to endDay
5%8%49%33%37%
390
August1st to 15thDay
10%5%28%36%37%
358
16th to endDay
8%5%46%38%36%
396
September1st to 15thDay
9%47%16%33%28%
375
16th to endDay
9%5%419%38%22%
374
October1st to 15thDay
45%10%24%37%16%
336
16th to endDay
11%29%40%27%9%
144
November1st to 15thDay
12%16%32%34%3
135
16th to endDay
5%5%22%29%28%8%
135
December1st to 15thDay
20%322%33%17%2
135
16th to endDay
27%324%27%15%1
144
January1st to 15thNight
14%21%25%31%7%
780
16th to endNight
14%21%22%30%9%
832
February1st to 15thNight
15%19%25%28%10%
764
16th to endNight
15%19%25%29%9%
683
March1st to 15thNight
14%20%24%29%11%
770
16th to endNight
11%18%18%30%18%1
624
April1st to 15thNight
12%19%19%27%19%2
584
16th to endNight
8%17%16%28%24%4
579
May1st to 15thNight
7%16%11%32%27%3
585
16th to endNight
7%16%5%23%36%11%
611
June1st to 15thNight
7%15%116%41%17%
585
16th to endNight
6%15%211%38%25%
585
July1st to 15thNight
410%17%38%37%
555
16th to endNight
415%16%34%37%
612
August1st to 15thNight
49%26%38%38%
575
16th to endNight
8%8%311%36%32%
621
September1st to 15thNight
9%8%6%12%35%28%
602
16th to endNight
9%8%222%45%12%
777
October1st to 15thNight
7%8%9%29%33%11%
752
16th to endNight
9%11%16%27%28%6%
768
November1st to 15thNight
8%16%15%31%24%4
760
16th to endNight
8%18%19%29%21%2
780
December1st to 15thNight
13%19%20%23%20%2
780
16th to endNight
16%20%21%27%13%
832
Page generated at 2018-10-09 09:39:15. Version ac04

Copyright 2018 A. Danko


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