Keppel Henge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Keppel Henge clear sky chart from 2005-11-05 to 2018-03-21.

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
28%
15904
12%
49138
7%
15867
33%
15867
14%
36470

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
11%
971
3%
2848
1%
970
13%
970
4%
2557
January16th to endNight
13%
858
5%
2730
2%
858
16%
858
5%
2386
February1st to 15thNight
13%
761
6%
2482
2%
761
18%
761
6%
2074
February16th to endNight
20%
683
10%
2149
4%
683
26%
683
10%
1686
March1st to 15thNight
23%
780
13%
2184
6%
780
28%
780
15%
1634
March16th to endNight
30%
792
20%
2178
10%
792
37%
792
20%
1500
April1st to 15thNight
28%
671
16%
1806
7%
671
33%
671
20%
1270
April16th to endNight
30%
540
19%
1620
7%
540
40%
540
20%
1075
May1st to 15thNight
40%
522
16%
1602
11%
522
47%
522
20%
1040
May16th to endNight
41%
374
16%
1497
11%
374
54%
374
20%
856
June1st to 15thNight
41%
360
13%
1296
11%
360
50%
360
19%
790
June16th to endNight
46%
360
14%
1260
13%
360
53%
360
24%
736
July1st to 15thNight
57%
340
18%
1190
19%
340
63%
340
34%
614
July16th to endNight
50%
519
15%
1500
13%
486
59%
486
30%
882
August1st to 15thNight
54%
539
18%
1609
13%
536
58%
536
31%
946
August16th to endNight
55%
575
20%
1721
12%
575
61%
575
29%
1029
September1st to 15thNight
50%
720
17%
1865
9%
720
54%
720
32%
1202
September16th to endNight
49%
717
20%
1980
15%
717
51%
717
27%
1308
October1st to 15thNight
33%
720
14%
2148
11%
720
38%
720
18%
1523
October16th to endNight
19%
768
8%
2344
5%
768
23%
768
10%
1889
November1st to 15thNight
24%
760
12%
2575
10%
760
28%
760
11%
1963
November16th to endNight
15%
780
6%
2730
4%
780
19%
780
6%
2275
December1st to 15thNight
9%
780
3%
2730
0%
780
11%
780
3%
2437
December16th to endNight
7%
1014
4%
3094
0%
1014
10%
1014
3%
2798

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
14%9%47%6%35%45%6%31%
49713
Night
15%11%5%9%7%35%446%27%
49309
Cloud CoverDay
14%9%47%6%3445%6%31%
49723
Night
15%11%5%9%7%35%445%26%
49313
TransparencyDay
51%312%20%10%
49402
Night
58%310%17%8%
49138
SeeingDay
17%12%21%27%16%5%
6334
Night
18%21%22%23%11%2
15912

By Month

Percentage Cloud Cover NE (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%16%9%15%10%5%6%5%436%
1417
16th to endDay
12%18%9%16%11%5%5%4337%
1844
February1st to 15thDay
11%17%7%16%11%5%6%34410%
1710
16th to endDay
14%15%7%10%8%6%5%5%35%16%
1610
March1st to 15thDay
12%11%6%8%8%46%45%428%
2094
16th to endDay
12%7%47%7%3445%6%36%
2174
April1st to 15thDay
19%10%45%5%2335%6%33%
2154
16th to endDay
17%8%25%42335%7%38%
2340
May1st to 15thDay
17%6%245%23447%40%
2349
16th to endDay
11%5%25%425%45%9%44%
2618
June1st to 15thDay
12%6%244345%6%8%39%
2661
16th to endDay
11%5%344246%6%8%41%
2700
July1st to 15thDay
10%32342445%9%47%
2700
16th to endDay
10%42442446%10%45%
2559
August1st to 15thDay
10%5%14425%45%8%46%
2340
16th to endDay
11%5%25%6%3447%7%41%
2468
September1st to 15thDay
14%6%36%5%3445%7%38%
2094
16th to endDay
16%5%25%5%3445%8%37%
1980
October1st to 15thDay
19%8%37%6%44345%31%
1811
16th to endDay
29%12%5%8%5%25%345%16%
1878
November1st to 15thDay
16%15%48%7%46%5%5%5%21%
1613
16th to endDay
19%18%6%10%8%46%45%412%
1560
December1st to 15thDay
16%21%10%14%9%35%4345%
1560
16th to endDay
18%22%9%14%9%343345%
1479
January1st to 15thNight
17%17%7%15%10%5%6%4347%
2848
16th to endNight
13%15%8%15%11%5%6%445%9%
2730
February1st to 15thNight
12%15%8%15%10%5%5%35%414%
2480
16th to endNight
14%11%6%11%8%5%5%445%20%
2149
March1st to 15thNight
12%12%5%9%7%34445%28%
2172
16th to endNight
12%9%5%7%5%33445%38%
2178
April1st to 15thNight
20%7%35%5%24436%35%
1806
16th to endNight
18%6%25%5%24447%36%
1620
May1st to 15thNight
14%6%36%5%35%35%7%37%
1602
16th to endNight
11%5%25%5%35%46%6%43%
1495
June1st to 15thNight
13%425%6%36%5%48%38%
1296
16th to endNight
9%5%25%5%25%5%5%9%42%
1260
July1st to 15thNight
8%32331445%10%51%
1260
16th to endNight
7%323436%5%6%7%47%
1606
August1st to 15thNight
9%325%435%37%9%45%
1620
16th to endNight
9%5%25%33445%8%46%
1721
September1st to 15thNight
12%424425%5%6%8%42%
1865
16th to endNight
12%7%36%5%23447%41%
1980
October1st to 15thNight
19%9%36%6%3445%6%30%
2148
16th to endNight
24%13%48%6%35%345%19%
2344
November1st to 15thNight
17%12%5%8%7%46%5%45%22%
2575
16th to endNight
21%16%6%9%6%445%45%14%
2730
December1st to 15thNight
17%21%9%11%9%45%4337%
2730
16th to endNight
19%19%9%14%9%444337%
3094

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
17%16%9%15%12%46%3335%
1417
16th to endDay
12%18%9%16%13%5%5%3327%
1844
February1st to 15thDay
12%15%8%16%11%45%5%3411%
1710
16th to endDay
14%15%6%11%8%5%5%5%3418%
1610
March1st to 15thDay
12%11%6%9%8%46%445%28%
2105
16th to endDay
12%7%47%6%4345%6%36%
2173
April1st to 15thDay
19%9%45%5%3335%7%33%
2154
16th to endDay
17%7%25%5%13447%39%
2340
May1st to 15thDay
17%6%24434447%41%
2349
16th to endDay
11%5%2443445%8%45%
2618
June1st to 15thDay
12%6%25%4245%6%8%39%
2661
16th to endDay
11%6%24325%5%6%8%42%
2700
July1st to 15thDay
9%3244245%5%8%48%
2700
16th to endDay
9%4244345%6%9%45%
2559
August1st to 15thDay
10%42442445%8%47%
2340
16th to endDay
11%5%245%35%46%8%41%
2468
September1st to 15thDay
14%8%26%43445%7%39%
2094
16th to endDay
16%6%25%5%25%35%8%38%
1980
October1st to 15thDay
19%9%37%6%34446%31%
1811
16th to endDay
29%13%5%7%5%35%435%16%
1878
November1st to 15thDay
16%14%48%7%36%6%45%22%
1613
16th to endDay
20%17%7%11%7%45%44411%
1560
December1st to 15thDay
16%21%9%16%10%35%4334
1560
16th to endDay
18%23%9%14%10%443245%
1479
January1st to 15thNight
17%17%7%15%11%5%6%3446%
2848
16th to endNight
13%15%8%16%11%5%6%4448%
2730
February1st to 15thNight
12%15%8%15%11%45%34414%
2473
16th to endNight
14%12%6%11%9%45%5%4420%
2149
March1st to 15thNight
13%12%6%9%6%35%5%45%28%
2184
16th to endNight
12%9%47%5%2444439%
2178
April1st to 15thNight
20%7%36%5%33445%35%
1806
16th to endNight
18%7%25%43345%7%36%
1620
May1st to 15thNight
15%6%25%6%35%35%7%37%
1601
16th to endNight
11%5%26%5%35%46%7%43%
1495
June1st to 15thNight
13%415%6%35%5%5%8%39%
1296
16th to endNight
9%5%25%5%35%5%5%9%42%
1260
July1st to 15thNight
8%42441436%8%52%
1260
16th to endNight
7%414436%5%7%7%47%
1606
August1st to 15thNight
9%414425%46%8%45%
1620
16th to endNight
9%5%25%33445%8%46%
1721
September1st to 15thNight
13%4244246%6%8%42%
1865
16th to endNight
13%7%35%5%34347%41%
1980
October1st to 15thNight
19%8%36%5%3445%7%31%
2148
16th to endNight
25%15%48%6%44445%18%
2344
November1st to 15thNight
17%14%5%8%6%46%445%21%
2575
16th to endNight
21%17%5%9%6%345%4414%
2730
December1st to 15thNight
18%22%9%12%10%35%3346%
2730
16th to endNight
20%19%10%14%10%443336%
3094

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
82%5%6%5%
1418
16th to endDay
82%27%5%2
1844
February1st to 15thDay
74%47%11%2
1712
16th to endDay
69%29%12%6%
1610
March1st to 15thDay
56%312%18%9%
2105
16th to endDay
47%211%21%13%2
2174
April1st to 15thDay
50%38%23%12%1
2154
16th to endDay
44%311%22%15%2
2340
May1st to 15thDay
42%310%24%15%2
2349
16th to endDay
36%314%26%16%1
2622
June1st to 15thDay
39%413%27%14%
2661
16th to endDay
36%6%14%28%13%
2700
July1st to 15thDay
30%316%29%17%2
2541
16th to endDay
33%415%31%14%1
2402
August1st to 15thDay
33%417%27%15%
2327
16th to endDay
38%416%28%10%1
2468
September1st to 15thDay
43%315%27%10%
2094
16th to endDay
43%413%29%8%
1980
October1st to 15thDay
53%39%21%10%
1811
16th to endDay
68%213%11%3
1878
November1st to 15thDay
61%5%12%13%6%
1613
16th to endDay
76%310%7%1
1560
December1st to 15thDay
83%37%4
1560
16th to endDay
84%36%4
1479
January1st to 15thNight
81%27%6%1
2848
16th to endNight
79%28%6%2
2730
February1st to 15thNight
72%38%11%3
2482
16th to endNight
65%210%13%6%
2149
March1st to 15thNight
57%210%20%8%
2184
16th to endNight
48%210%21%14%2
2178
April1st to 15thNight
50%28%22%13%1
1806
16th to endNight
47%29%19%19%1
1620
May1st to 15thNight
45%29%21%18%2
1602
16th to endNight
39%312%26%16%1
1497
June1st to 15thNight
41%410%25%15%1
1296
16th to endNight
37%313%29%15%
1260
July1st to 15thNight
28%313%30%21%2
1190
16th to endNight
34%414%28%17%
1500
August1st to 15thNight
34%417%27%14%1
1609
16th to endNight
36%315%29%13%1
1721
September1st to 15thNight
37%415%30%11%
1865
16th to endNight
43%314%29%9%
1980
October1st to 15thNight
52%310%23%9%
2148
16th to endNight
68%211%13%4
2344
November1st to 15thNight
62%313%15%41
2575
16th to endNight
72%312%9%1
2730
December1st to 15thNight
82%28%5%1
2730
16th to endNight
83%26%6%1
3094

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
20%13%38%23%4
104
16th to endDay
26%8%31%28%4
144
February1st to 15thDay
22%13%43%18%2
135
16th to endDay
21%13%39%25%
120
March1st to 15thDay
17%15%30%25%10%1
290
16th to endDay
20%15%24%24%11%2
311
April1st to 15thDay
18%14%30%24%10%1
270
16th to endDay
21%14%24%22%11%4
270
May1st to 15thDay
18%13%15%29%15%5%
288
16th to endDay
14%11%18%32%19%3
331
June1st to 15thDay
12%13%20%30%18%3
456
16th to endDay
12%14%18%29%19%5%
495
July1st to 15thDay
12%9%15%32%20%9%
475
16th to endDay
13%11%17%26%24%6%
375
August1st to 15thDay
12%7%11%28%28%12%
313
16th to endDay
15%7%10%32%22%10%
332
September1st to 15thDay
13%7%17%25%24%12%
315
16th to endDay
16%9%13%22%25%12%
314
October1st to 15thDay
20%11%23%27%12%5%
315
16th to endDay
31%14%25%22%4
294
November1st to 15thDay
20%10%23%26%16%2
111
16th to endDay
25%8%34%28%11
90
December1st to 15thDay
17%25%31%21%4
90
16th to endDay
32%18%34%14%
96
January1st to 15thNight
20%27%29%18%3
975
16th to endNight
15%25%28%21%6%1
858
February1st to 15thNight
16%26%30%21%3
764
16th to endNight
18%20%28%24%7%
683
March1st to 15thNight
16%23%27%23%7%
780
16th to endNight
16%21%24%24%10%2
792
April1st to 15thNight
19%23%23%26%6%1
671
16th to endNight
18%20%22%23%12%1
540
May1st to 15thNight
18%19%12%30%16%3
522
16th to endNight
11%18%20%28%19%2
375
June1st to 15thNight
13%19%16%33%14%2
360
16th to endNight
10%18%15%29%23%2
360
July1st to 15thNight
9%13%13%33%26%4
340
16th to endNight
8%18%15%34%21%2
519
August1st to 15thNight
12%10%12%31%27%5%
539
16th to endNight
10%10%14%30%27%6%
575
September1st to 15thNight
14%11%18%25%19%10%
720
16th to endNight
17%12%13%25%21%9%
717
October1st to 15thNight
22%13%22%24%12%3
720
16th to endNight
31%18%24%19%5%
768
November1st to 15thNight
21%23%23%21%9%1
760
16th to endNight
25%30%22%15%5%
780
December1st to 15thNight
26%29%27%13%2
780
16th to endNight
25%28%26%15%3
1014
Page generated at 2018-03-22 11:34:22. Version ac04

Copyright 2018 A. Danko


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