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 2017-04-02.

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%
14757
28%
45369
25%
14720
70%
14720
40%
24476

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
55%
666
20%
1667
12%
666
58%
666
31%
1129
April16th to endNight
61%
660
23%
1650
12%
660
64%
660
43%
987
May1st to 15thNight
65%
538
28%
1528
19%
538
69%
538
51%
760
May16th to endNight
72%
342
22%
1368
26%
342
74%
342
39%
628
June1st to 15thNight
80%
330
29%
1320
36%
330
84%
330
45%
555
June16th to endNight
87%
330
34%
1320
46%
330
89%
330
66%
436
July1st to 15thNight
93%
310
36%
1240
48%
310
94%
310
69%
403
July16th to endNight
90%
435
37%
1383
39%
405
91%
405
67%
532
August1st to 15thNight
90%
553
39%
1536
30%
550
90%
550
75%
657
August16th to endNight
92%
700
42%
1750
27%
700
92%
700
80%
794
September1st to 15thNight
92%
660
45%
1650
32%
660
93%
660
80%
743
September16th to endNight
83%
656
43%
1766
38%
656
87%
656
68%
816
October1st to 15thNight
69%
660
30%
1980
30%
660
74%
660
48%
996
October16th to endNight
71%
704
35%
2112
36%
704
76%
704
49%
1052
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%
45748
Night
11%412212335%59%
45561
TransparencyDay
26%38%18%24%18%
45428
Night
27%38%18%23%17%
45380
SeeingDay
14%12%34%26%8%3
5172
Night
13%311%32%30%8%
14766

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
15%9%24423446%43%
1983
16th to endDay
13%413213235%57%
1980
May1st to 15thDay
7%313213346%62%
2090
16th to endDay
10%5%23423445%54%
2391
June1st to 15thDay
5%313312345%65%
2310
16th to endDay
2111213380%
2310
July1st to 15thDay
111113383%
2310
16th to endDay
1111112383%
2371
August1st to 15thDay
1111122284%
2085
16th to endDay
111122383%
2100
September1st to 15thDay
1111112384%
1980
16th to endDay
32111222377%
1862
October1st to 15thDay
7%3222335%6%63%
1650
16th to endDay
8%31232333462%
1760
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
13%7%245%24446%43%
1667
16th to endNight
10%5%13212346%57%
1650
May1st to 15thNight
7%22212347%64%
1528
16th to endNight
7%412312446%60%
1368
June1st to 15thNight
4212113335%69%
1320
16th to endNight
11211122283%
1320
July1st to 15thNight
111222283%
1320
16th to endNight
11111212381%
1487
August1st to 15thNight
1111222381%
1545
16th to endNight
11112384%
1750
September1st to 15thNight
111111386%
1650
16th to endNight
21111222478%
1766
October1st to 15thNight
7%222312335%65%
1980
16th to endNight
7%22212336%65%
2112
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
42%412%21%15%3
1983
16th to endDay
29%313%26%21%4
1980
May1st to 15thDay
22%310%30%26%6%
2090
16th to endDay
30%413%27%18%5%
2395
June1st to 15thDay
21%410%21%22%19%
2310
16th to endDay
10%1414%39%30%
2310
July1st to 15thDay
8%129%29%48%
2161
16th to endDay
9%15%10%26%46%
2212
August1st to 15thDay
8%1210%31%45%
2069
16th to endDay
8%1210%41%36%
2100
September1st to 15thDay
7%1410%40%35%
1980
16th to endDay
13%16%23%34%21%
1862
October1st to 15thDay
21%38%23%26%16%
1650
16th to endDay
24%37%23%26%14%
1760
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
40%5%13%20%14%4
1667
16th to endNight
27%413%27%19%7%
1650
May1st to 15thNight
19%313%26%26%10%
1529
16th to endNight
23%415%29%19%7%
1368
June1st to 15thNight
16%5%11%22%22%20%
1320
16th to endNight
9%1416%35%32%
1320
July1st to 15thNight
8%139%26%51%
1240
16th to endNight
10%1310%24%49%
1383
August1st to 15thNight
8%1313%27%43%
1536
16th to endNight
6%1211%36%41%
1750
September1st to 15thNight
6%239%40%37%
1650
16th to endNight
12%2321%36%23%
1766
October1st to 15thNight
21%37%22%28%16%
1980
16th to endNight
20%36%22%29%16%
2112
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
24%22%34%11%5%
214
16th to endDay
13%28%31%21%3
210
May1st to 15thDay
15%20%41%17%31
228
16th to endDay
17%17%24%28%6%5%
266
June1st to 15thDay
8%18%38%26%44
255
16th to endDay
310%41%34%37%
255
July1st to 15thDay
1343%39%5%6%
245
16th to endDay
1245%36%7%5%
271
August1st to 15thDay
25%49%31%6%4
255
16th to endDay
1445%34%7%5%
268
September1st to 15thDay
28%43%33%8%3
255
16th to endDay
411%34%36%11%1
255
October1st to 15thDay
8%14%37%29%8%3
255
16th to endDay
15%12%32%26%13%
272
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%14%37%21%3
666
16th to endNight
12%415%34%25%6%
660
May1st to 15thNight
9%317%36%28%4
539
16th to endNight
8%311%29%41%6%
343
June1st to 15thNight
5%17%37%42%4
330
16th to endNight
15%39%46%6%
330
July1st to 15thNight
127%63%6%
310
16th to endNight
2226%51%14%
435
August1st to 15thNight
1436%47%9%
553
16th to endNight
1437%48%8%
700
September1st to 15thNight
2332%49%11%
660
16th to endNight
318%34%37%14%
656
October1st to 15thNight
9%313%31%31%11%
660
16th to endNight
9%211%30%30%14%
704
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 2017-04-02 22:35:06. Version ac04

Copyright 2017 A. Danko


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