Keeton Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Keeton Observing Site clear sky chart from 2005-11-05 to 2017-10-31.

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
66%
15435
28%
47381
25%
15398
71%
15398
41%
25377

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
56%
717
20%
2491
19%
716
61%
716
30%
1412
January16th to endNight
52%
768
25%
2496
21%
768
60%
768
28%
1527
February1st to 15thNight
53%
700
24%
2232
22%
697
60%
697
28%
1368
February16th to endNight
52%
632
24%
1895
21%
632
59%
632
28%
1193
March1st to 15thNight
51%
720
17%
2088
15%
720
55%
720
26%
1385
March16th to endNight
52%
768
19%
2037
14%
768
56%
768
28%
1351
April1st to 15thNight
54%
719
19%
1799
11%
719
57%
719
30%
1233
April16th to endNight
61%
720
23%
1800
12%
720
64%
720
41%
1092
May1st to 15thNight
67%
586
27%
1666
18%
586
71%
586
52%
823
May16th to endNight
73%
374
26%
1496
30%
374
76%
374
40%
675
June1st to 15thNight
79%
360
27%
1440
34%
360
83%
360
46%
602
June16th to endNight
88%
360
36%
1440
49%
360
89%
360
67%
470
July1st to 15thNight
94%
340
34%
1360
46%
340
95%
340
71%
434
July16th to endNight
91%
471
39%
1503
41%
441
91%
441
68%
574
August1st to 15thNight
88%
604
37%
1677
28%
601
88%
601
72%
728
August16th to endNight
91%
764
43%
1910
28%
764
92%
764
80%
869
September1st to 15thNight
91%
720
43%
1800
31%
720
92%
720
79%
817
September16th to endNight
82%
716
45%
1927
38%
716
87%
716
68%
888
October1st to 15thNight
70%
720
30%
2160
30%
720
76%
720
51%
1056
October16th to endNight
73%
768
38%
2304
39%
768
78%
768
51%
1128
November1st to 15thNight
69%
700
30%
2270
30%
700
74%
700
41%
1183
November16th to endNight
58%
720
27%
2382
27%
720
64%
720
33%
1323
December1st to 15thNight
53%
720
21%
2520
18%
720
61%
720
24%
1528
December16th to endNight
43%
768
22%
2688
18%
768
52%
768
21%
1718

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%413212335%61%
48366
Night
11%412212335%59%
47573
TransparencyDay
26%38%18%24%18%
48046
Night
27%38%19%23%18%
47392
SeeingDay
13%12%33%26%9%4
6015
Night
13%311%32%31%8%
15444

By Month

Percentage Cloud Cover SW (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
17%5%12223345%50%
1444
16th to endDay
19%9%13322335%44%
1728
February1st to 15thDay
18%7%14322336%46%
1619
16th to endDay
21%10%34312345%38%
1579
March1st to 15thDay
18%10%25%32345%6%36%
1869
16th to endDay
18%8%24324437%40%
2187
April1st to 15thDay
16%9%24423436%42%
2149
16th to endDay
14%413213235%56%
2160
May1st to 15thDay
7%312213347%62%
2282
16th to endDay
9%423413345%56%
2615
June1st to 15thDay
6%313312345%65%
2520
16th to endDay
2111113382%
2520
July1st to 15thDay
111113284%
2520
16th to endDay
1112111383%
2559
August1st to 15thDay
11111122283%
2274
16th to endDay
111222382%
2292
September1st to 15thDay
1111113382%
2160
16th to endDay
32211222377%
2031
October1st to 15thDay
6%3222235%6%64%
1800
16th to endDay
8%3232334463%
1918
November1st to 15thDay
9%5%13423447%54%
1587
16th to endDay
13%7%24323335%50%
1577
December1st to 15thDay
18%7%24323235%46%
1440
16th to endDay
21%8%23323346%39%
1536
January1st to 15thNight
16%5%12323447%48%
2491
16th to endNight
16%7%13423335%47%
2496
February1st to 15thNight
16%7%1432245%7%42%
2231
16th to endNight
19%8%23313345%45%
1895
March1st to 15thNight
19%7%24323345%42%
2088
16th to endNight
18%6%13213446%46%
2037
April1st to 15thNight
14%7%245%34436%43%
1799
16th to endNight
11%5%13213346%56%
1800
May1st to 15thNight
7%22212347%64%
1666
16th to endNight
7%412312336%62%
1496
June1st to 15thNight
421211233469%
1440
16th to endNight
11211112283%
1440
July1st to 15thNight
111222284%
1440
16th to endNight
21111112382%
1607
August1st to 15thNight
11111222380%
1686
16th to endNight
11122383%
1910
September1st to 15thNight
1111111484%
1800
16th to endNight
21111222479%
1927
October1st to 15thNight
6%212312335%68%
2160
16th to endNight
7%21212336%67%
2304
November1st to 15thNight
10%312223346%59%
2270
16th to endNight
12%5%13323346%53%
2382
December1st to 15thNight
19%5%13323346%45%
2520
16th to endNight
24%7%23312336%41%
2688

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
35%39%21%19%10%
1444
16th to endDay
43%38%13%17%13%
1728
February1st to 15thDay
39%310%20%18%7%
1619
16th to endDay
48%37%24%13%2
1579
March1st to 15thDay
46%412%14%16%5%
1869
16th to endDay
44%6%13%18%13%3
2187
April1st to 15thDay
43%412%21%15%3
2149
16th to endDay
30%413%26%21%4
2160
May1st to 15thDay
21%311%30%26%5%
2282
16th to endDay
30%412%27%19%5%
2619
June1st to 15thDay
22%49%22%23%17%
2520
16th to endDay
9%1314%36%33%
2520
July1st to 15thDay
7%129%27%51%
2371
16th to endDay
9%1410%24%48%
2400
August1st to 15thDay
9%1211%30%44%
2258
16th to endDay
8%1211%40%35%
2292
September1st to 15thDay
8%1412%38%34%
2160
16th to endDay
14%15%24%34%19%
2031
October1st to 15thDay
20%38%22%25%20%
1800
16th to endDay
24%37%22%25%17%
1918
November1st to 15thDay
28%412%21%21%10%
1587
16th to endDay
36%37%18%27%6%
1577
December1st to 15thDay
42%37%20%19%6%
1440
16th to endDay
45%49%14%15%9%
1536
January1st to 15thNight
34%411%20%18%10%
2491
16th to endNight
39%37%13%17%17%
2496
February1st to 15thNight
39%48%19%18%10%
2242
16th to endNight
40%310%25%16%4
1895
March1st to 15thNight
43%5%10%16%17%6%
2088
16th to endNight
39%6%11%18%18%5%
2037
April1st to 15thNight
41%5%12%21%14%4
1799
16th to endNight
28%5%13%27%18%6%
1800
May1st to 15thNight
18%313%27%26%10%
1667
16th to endNight
22%414%30%21%7%
1496
June1st to 15thNight
16%5%11%23%23%19%
1440
16th to endNight
9%1316%34%34%
1440
July1st to 15thNight
7%128%25%54%
1360
16th to endNight
10%139%23%52%
1503
August1st to 15thNight
10%1314%26%44%
1677
16th to endNight
7%1212%34%41%
1910
September1st to 15thNight
7%2411%38%36%
1800
16th to endNight
11%2322%37%21%
1927
October1st to 15thNight
20%37%20%27%21%
2160
16th to endNight
19%36%21%28%20%
2304
November1st to 15thNight
26%310%22%22%14%
2270
16th to endNight
32%37%21%25%10%
2382
December1st to 15thNight
39%5%9%19%18%8%
2520
16th to endNight
45%38%13%18%10%
2688

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
44%227%18%42
72
16th to endDay
28%9%23%23%10%4
256
February1st to 15thDay
27%9%27%24%9%2
244
16th to endDay
31%14%25%20%8%
238
March1st to 15thDay
28%21%21%17%8%2
270
16th to endDay
25%20%29%17%6%
288
April1st to 15thDay
26%23%31%13%5%
269
16th to endDay
17%26%30%20%5%
270
May1st to 15thDay
13%18%39%18%6%2
288
16th to endDay
15%16%23%28%9%6%
330
June1st to 15thDay
9%17%36%25%5%5%
315
16th to endDay
28%39%34%5%8%
315
July1st to 15thDay
1240%39%5%9%
305
16th to endDay
1344%36%7%7%
327
August1st to 15thDay
3447%30%8%5%
315
16th to endDay
1341%34%10%7%
332
September1st to 15thDay
27%42%33%10%3
315
16th to endDay
412%35%35%10%1
315
October1st to 15thDay
6%15%35%28%9%3
315
16th to endDay
12%10%28%26%18%3
336
November1st to 15thDay
12%5%10%30%33%7%
93
16th to endDay
22%9%18%32%14%2
83
December1st to 15thDay
30%11%30%16%10%1
60
16th to endDay
25%6%20%23%14%10%
64
January1st to 15thNight
19%315%30%21%8%
720
16th to endNight
21%315%29%20%8%
768
February1st to 15thNight
21%313%33%23%4
704
16th to endNight
23%7%12%30%21%5%
632
March1st to 15thNight
21%7%13%30%22%5%
720
16th to endNight
22%6%13%29%22%4
768
April1st to 15thNight
18%5%13%37%21%3
719
16th to endNight
12%416%34%25%6%
720
May1st to 15thNight
9%316%37%29%4
587
16th to endNight
8%310%29%41%6%
375
June1st to 15thNight
5%18%37%41%5%
360
16th to endNight
15%38%47%7%
360
July1st to 15thNight
127%63%6%
340
16th to endNight
3226%52%15%
471
August1st to 15thNight
2435%47%9%
604
16th to endNight
1435%49%9%
764
September1st to 15thNight
2432%49%11%
720
16th to endNight
319%34%37%13%
716
October1st to 15thNight
8%313%33%30%10%
720
16th to endNight
9%210%28%32%15%
768
November1st to 15thNight
12%211%32%31%10%
700
16th to endNight
15%5%15%31%21%9%
720
December1st to 15thNight
23%414%32%20%6%
720
16th to endNight
28%5%16%27%17%4
768
Page generated at 2017-11-01 14:23:41. Version ac04

Copyright 2017 A. Danko


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