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 2017-09-14.

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%
15121
12%
46703
7%
15084
33%
15084
14%
34564

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
8%
896
3%
2628
1%
895
11%
895
4%
2364
January16th to endNight
12%
792
5%
2520
2%
792
16%
792
4%
2212
February1st to 15thNight
13%
701
5%
2287
2%
701
17%
701
6%
1927
February16th to endNight
20%
631
10%
1985
4%
631
26%
631
10%
1560
March1st to 15thNight
21%
720
13%
2016
6%
720
27%
720
15%
1523
March16th to endNight
29%
768
19%
2112
10%
768
36%
768
19%
1465
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%
716
17%
1854
8%
716
54%
716
32%
1198
September16th to endNight
47%
657
18%
1815
13%
657
49%
657
26%
1214
October1st to 15thNight
32%
660
15%
1969
11%
660
37%
660
17%
1405
October16th to endNight
18%
704
8%
2148
4%
704
22%
704
9%
1748
November1st to 15thNight
24%
700
13%
2372
11%
700
28%
700
12%
1781
November16th to endNight
15%
720
6%
2520
4%
720
19%
720
6%
2105
December1st to 15thNight
8%
720
3%
2520
0%
720
11%
720
3%
2248
December16th to endNight
7%
936
4%
2856
0%
936
10%
936
3%
2576

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%
48014
Night
15%11%5%8%7%35%446%27%
46874
Cloud CoverDay
14%9%47%6%3445%6%32%
48024
Night
15%11%5%9%7%35%445%27%
46878
TransparencyDay
51%312%20%10%
47703
Night
58%311%17%8%
46703
SeeingDay
17%12%20%27%16%5%
5773
Night
18%21%22%23%11%2
15129

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%11%45%4436%
1307
16th to endDay
12%18%10%16%12%5%5%4338%
1702
February1st to 15thDay
11%17%7%15%11%5%6%345%10%
1575
16th to endDay
14%15%7%10%8%6%6%5%35%16%
1488
March1st to 15thDay
12%10%6%8%7%46%45%428%
1932
16th to endDay
12%7%47%7%345%5%6%35%
2112
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%7%36%5%3446%7%38%
2081
16th to endDay
17%5%25%5%2446%8%36%
1815
October1st to 15thDay
20%8%37%6%44345%30%
1660
16th to endDay
30%12%5%8%5%25%345%15%
1722
November1st to 15thDay
16%14%47%7%46%5%5%5%22%
1486
16th to endDay
20%18%6%10%8%46%44411%
1440
December1st to 15thDay
18%21%9%14%9%35%4345%
1440
16th to endDay
19%22%9%14%8%343345%
1365
January1st to 15thNight
18%17%7%15%10%45%4346%
2628
16th to endNight
13%16%8%15%11%46%445%9%
2520
February1st to 15thNight
12%15%8%15%10%5%5%35%413%
2285
16th to endNight
14%12%6%11%8%5%5%445%20%
1985
March1st to 15thNight
13%12%5%10%6%34445%28%
2004
16th to endNight
13%9%5%7%5%33445%38%
2112
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%
1854
16th to endNight
13%7%46%5%24347%40%
1815
October1st to 15thNight
19%9%37%6%3445%6%29%
1969
16th to endNight
24%14%47%7%35%445%18%
2148
November1st to 15thNight
17%11%5%7%7%46%5%45%23%
2372
16th to endNight
21%16%6%9%6%45%5%45%14%
2520
December1st to 15thNight
18%21%9%11%9%45%4337%
2520
16th to endNight
20%19%9%14%9%344337%
2856

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%45%3436%
1307
16th to endDay
11%18%9%17%13%5%5%3337%
1702
February1st to 15thDay
12%15%8%16%11%45%5%3411%
1575
16th to endDay
14%15%7%11%8%5%6%5%3317%
1488
March1st to 15thDay
12%10%6%9%8%46%445%28%
1943
16th to endDay
13%7%47%6%435%5%6%35%
2111
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%38%
2081
16th to endDay
16%7%25%5%25%35%8%37%
1815
October1st to 15thDay
19%9%37%6%34446%30%
1660
16th to endDay
30%14%5%7%5%35%435%14%
1722
November1st to 15thDay
16%14%47%7%36%6%5%423%
1486
16th to endDay
20%18%7%10%7%45%45%411%
1440
December1st to 15thDay
17%21%9%16%9%344335%
1440
16th to endDay
18%24%9%14%9%443245%
1365
January1st to 15thNight
18%18%7%15%11%46%3446%
2628
16th to endNight
13%15%9%16%11%5%7%3448%
2520
February1st to 15thNight
12%15%8%15%11%45%34413%
2278
16th to endNight
14%12%7%11%10%45%5%45%20%
1985
March1st to 15thNight
14%12%6%9%6%35%5%4427%
2016
16th to endNight
13%9%47%5%2444439%
2112
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%
1854
16th to endNight
14%7%35%5%24347%41%
1815
October1st to 15thNight
20%9%46%5%3445%7%30%
1969
16th to endNight
25%15%48%6%44445%17%
2148
November1st to 15thNight
16%13%47%6%36%5%45%23%
2372
16th to endNight
22%17%6%9%6%345%4414%
2520
December1st to 15thNight
19%23%9%11%9%35%3346%
2520
16th to endNight
21%19%10%14%9%343336%
2856

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%46%5%
1308
16th to endDay
83%17%5%2
1702
February1st to 15thDay
73%47%11%2
1577
16th to endDay
70%28%12%6%
1488
March1st to 15thDay
56%312%18%8%
1943
16th to endDay
48%212%20%14%2
2112
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%26%10%
2081
16th to endDay
44%414%27%9%
1815
October1st to 15thDay
54%310%21%10%
1660
16th to endDay
70%212%10%2
1722
November1st to 15thDay
60%5%12%14%6%
1486
16th to endDay
76%210%7%2
1440
December1st to 15thDay
83%37%4
1440
16th to endDay
84%37%4
1365
January1st to 15thNight
82%27%6%1
2628
16th to endNight
80%28%6%2
2520
February1st to 15thNight
74%38%11%2
2287
16th to endNight
66%211%13%6%
1985
March1st to 15thNight
58%210%19%7%
2016
16th to endNight
48%29%20%15%2
2112
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%
1854
16th to endNight
44%314%27%9%
1815
October1st to 15thNight
53%310%22%9%
1969
16th to endNight
69%210%13%4
2148
November1st to 15thNight
61%313%15%41
2372
16th to endNight
73%312%8%1
2520
December1st to 15thNight
82%28%5%1
2520
16th to endNight
83%26%6%1
2856

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
17%10%43%23%5%
69
16th to endDay
21%8%31%31%7%
96
February1st to 15thDay
22%12%44%20%1
90
16th to endDay
20%13%33%30%1
81
March1st to 15thDay
16%18%30%26%6%1
233
16th to endDay
22%16%21%24%12%2
288
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%18%25%23%11%
310
16th to endDay
18%10%14%24%22%9%
254
October1st to 15thDay
20%13%21%27%12%4
255
16th to endDay
34%15%23%21%4
234
November1st to 15thDay
14%12%21%27%20%4
74
16th to endDay
26%11%28%31%1
60
December1st to 15thDay
20%23%31%21%3
60
16th to endDay
35%21%29%12%
64
January1st to 15thNight
21%28%29%17%3
900
16th to endNight
15%27%27%21%6%1
792
February1st to 15thNight
17%27%28%20%4
704
16th to endNight
18%21%26%25%8%
631
March1st to 15thNight
17%24%27%23%6%
720
16th to endNight
16%21%24%24%11%2
768
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%12%18%25%19%9%
716
16th to endNight
17%13%14%27%19%7%
657
October1st to 15thNight
22%14%22%23%12%3
660
16th to endNight
32%18%24%18%5%
704
November1st to 15thNight
20%23%24%20%9%1
700
16th to endNight
25%30%21%16%6%
720
December1st to 15thNight
27%31%25%12%2
720
16th to endNight
26%29%25%15%3
936
Page generated at 2017-09-15 10:29:58. Version ac04

Copyright 2017 A. Danko


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