Waid Observatory (Margate)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Waid Observatory (Margate) clear sky chart from 2005-11-05 to 2017-03-22.

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
64%
15645
16%
45197
14%
15606
67%
15606
26%
30105

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
54%
716
15%
2327
12%
716
60%
716
22%
1493
January16th to endNight
56%
768
22%
2484
19%
768
63%
768
29%
1480
February1st to 15thNight
55%
703
25%
2092
21%
700
61%
700
33%
1243
February16th to endNight
62%
631
27%
1735
20%
631
68%
631
37%
1034
March1st to 15thNight
58%
720
24%
1980
16%
720
65%
720
38%
1172
March16th to endNight
63%
732
21%
2013
18%
732
65%
732
37%
1216
April1st to 15thNight
71%
658
24%
1806
21%
658
73%
658
43%
1021
April16th to endNight
65%
660
21%
1650
13%
660
68%
660
37%
1030
May1st to 15thNight
75%
659
24%
1649
16%
659
77%
659
43%
982
May16th to endNight
67%
564
11%
1590
10%
564
67%
564
24%
1125
June1st to 15thNight
66%
495
9%
1485
7%
495
66%
495
17%
1123
June16th to endNight
77%
495
7%
1485
6%
495
77%
495
20%
1062
July1st to 15thNight
69%
465
5%
1395
6%
465
69%
465
15%
1083
July16th to endNight
81%
522
8%
1469
8%
489
82%
489
24%
1009
August1st to 15thNight
78%
568
6%
1548
6%
565
78%
565
25%
1082
August16th to endNight
68%
700
5%
1830
4%
700
68%
700
17%
1398
September1st to 15thNight
66%
660
4%
1815
3%
660
66%
660
13%
1451
September16th to endNight
60%
657
5%
1815
5%
657
60%
657
12%
1504
October1st to 15thNight
66%
660
14%
1928
16%
660
67%
660
22%
1361
October16th to endNight
54%
704
16%
2112
17%
704
56%
704
22%
1476
November1st to 15thNight
62%
700
23%
2101
22%
700
66%
700
30%
1310
November16th to endNight
56%
720
20%
2160
18%
720
61%
720
25%
1449
December1st to 15thNight
58%
720
19%
2232
17%
720
61%
720
23%
1484
December16th to endNight
65%
768
21%
2496
21%
768
68%
768
28%
1517

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%6%37%7%47%7%8%9%27%
45680
Night
7%425%5%35%6%7%10%39%
45399
TransparencyDay
47%12%14%13%9%2
45381
Night
37%11%18%18%10%2
45201
SeeingDay
8%111%22%28%26%
5374
Night
8%113%30%31%13%
15653

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
12%6%37%6%35%6%7%9%31%
1611
16th to endDay
9%5%35%6%46%5%6%9%35%
1737
February1st to 15thDay
11%7%35%5%35%46%9%37%
1765
16th to endDay
7%5%26%5%36%47%9%42%
1738
March1st to 15thDay
6%426%7%37%6%7%11%37%
1980
16th to endDay
7%436%7%45%5%8%10%35%
2007
April1st to 15thDay
7%5%25%5%26%7%8%12%35%
1812
16th to endDay
7%426%5%47%7%7%10%35%
1980
May1st to 15thDay
4435%6%47%7%8%10%40%
1972
16th to endDay
11%7%38%8%5%8%7%7%8%23%
2180
June1st to 15thDay
13%7%38%10%6%8%8%7%8%16%
2145
16th to endDay
10%7%38%9%5%10%8%9%11%17%
2145
July1st to 15thDay
10%7%48%8%5%9%9%8%11%16%
2145
16th to endDay
7%6%37%8%48%9%9%13%20%
2283
August1st to 15thDay
9%6%38%8%5%7%9%9%12%18%
2060
16th to endDay
10%7%38%8%5%8%9%10%11%16%
2018
September1st to 15thDay
9%7%410%9%6%10%9%8%9%14%
1815
16th to endDay
13%10%410%10%6%8%8%7%6%12%
1815
October1st to 15thDay
9%7%47%8%5%8%7%9%10%21%
1702
16th to endDay
15%6%37%7%46%6%7%8%27%
1760
November1st to 15thDay
10%5%36%5%47%6%7%8%35%
1757
16th to endDay
12%5%36%7%47%6%6%6%34%
1800
December1st to 15thDay
12%6%47%7%45%5%5%8%32%
1725
16th to endDay
8%5%35%6%36%6%8%10%35%
1728
January1st to 15thNight
10%5%25%5%35%6%7%10%37%
2327
16th to endNight
6%324435%6%6%10%44%
2484
February1st to 15thNight
10%42442346%8%47%
2086
16th to endNight
5%225%4245%6%9%51%
1735
March1st to 15thNight
5%324425%5%6%9%50%
1980
16th to endNight
5%3235%345%5%11%48%
2013
April1st to 15thNight
32233335%6%11%53%
1806
16th to endNight
6%4244246%8%8%48%
1650
May1st to 15thNight
43133345%6%10%53%
1649
16th to endNight
8%6%35%6%47%6%8%11%32%
1589
June1st to 15thNight
11%5%26%6%5%6%8%9%11%25%
1485
16th to endNight
5%415%6%5%7%8%9%12%33%
1485
July1st to 15thNight
7%5%48%7%5%7%5%9%10%29%
1485
16th to endNight
3325%6%47%6%7%11%40%
1577
August1st to 15thNight
6%3145%36%8%8%13%38%
1559
16th to endNight
7%5%26%6%47%8%9%11%29%
1830
September1st to 15thNight
6%6%27%7%5%8%9%9%13%22%
1815
16th to endNight
10%6%28%8%6%6%9%9%9%21%
1815
October1st to 15thNight
7%5%26%7%5%7%6%9%11%31%
1928
16th to endNight
14%7%25%6%35%5%6%8%34%
2112
November1st to 15thNight
7%325%6%345%6%9%44%
2101
16th to endNight
10%5%35%5%46%46%9%37%
2160
December1st to 15thNight
9%5%25%6%35%6%7%10%38%
2232
16th to endNight
7%424436%5%7%9%45%
2496

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
45%9%13%13%12%4
1612
16th to endDay
41%8%11%18%14%5%
1737
February1st to 15thDay
40%6%11%20%15%5%
1767
16th to endDay
35%7%13%22%14%6%
1738
March1st to 15thDay
37%8%15%21%14%2
1980
16th to endDay
38%9%14%18%13%5%
2008
April1st to 15thDay
36%8%17%21%13%2
1812
16th to endDay
39%8%13%18%16%3
1980
May1st to 15thDay
34%9%15%23%13%4
1972
16th to endDay
52%13%13%14%6%
2184
June1st to 15thDay
60%12%13%9%3
2145
16th to endDay
54%17%17%9%
2145
July1st to 15thDay
54%20%19%5%
2006
16th to endDay
47%20%22%8%
2128
August1st to 15thDay
48%21%22%7%
2047
16th to endDay
53%19%20%6%
2018
September1st to 15thDay
57%20%15%5%1
1815
16th to endDay
64%16%10%42
1815
October1st to 15thDay
50%13%14%12%6%1
1702
16th to endDay
50%8%10%13%11%4
1760
November1st to 15thDay
42%8%11%16%16%4
1757
16th to endDay
48%7%11%10%16%6%
1800
December1st to 15thDay
47%8%12%15%13%2
1725
16th to endDay
40%8%13%18%15%3
1728
January1st to 15thNight
40%8%17%19%11%2
2327
16th to endNight
32%8%16%22%13%5%
2484
February1st to 15thNight
33%5%11%26%16%6%
2094
16th to endNight
28%8%14%26%16%5%
1735
March1st to 15thNight
28%7%16%23%18%5%
1980
16th to endNight
30%7%18%24%14%4
2013
April1st to 15thNight
23%8%20%29%15%3
1806
16th to endNight
30%8%16%22%17%4
1650
May1st to 15thNight
25%8%15%33%14%3
1650
16th to endNight
41%11%19%21%6%
1591
June1st to 15thNight
47%15%19%13%3
1485
16th to endNight
38%18%30%11%1
1485
July1st to 15thNight
47%18%24%8%
1395
16th to endNight
33%18%31%14%2
1469
August1st to 15thNight
33%18%32%14%
1548
16th to endNight
42%20%25%10%1
1830
September1st to 15thNight
46%22%21%8%1
1815
16th to endNight
53%19%15%8%2
1815
October1st to 15thNight
42%12%18%15%9%1
1928
16th to endNight
46%7%12%17%11%4
2112
November1st to 15thNight
36%6%13%19%17%5%
2101
16th to endNight
42%7%13%14%14%7%
2160
December1st to 15thNight
40%10%14%16%15%2
2232
16th to endNight
33%9%13%22%17%3
2496

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
18%8%17%30%24%
90
16th to endDay
14%9%20%36%12%6%
96
February1st to 15thDay
11%17%40%23%5%
106
16th to endDay
8%224%39%24%1
239
March1st to 15thDay
4127%40%21%4
270
16th to endDay
6%121%40%26%4
250
April1st to 15thDay
5%117%29%33%12%
210
16th to endDay
7%11%30%36%12%
210
May1st to 15thDay
5%6%26%42%19%
228
16th to endDay
10%15%14%34%33%
267
June1st to 15thDay
9%1416%33%34%
255
16th to endDay
5%35%25%59%
255
July1st to 15thDay
6%6%26%58%
245
16th to endDay
329%27%56%
270
August1st to 15thDay
6%38%22%58%
253
16th to endDay
11%210%24%51%
268
September1st to 15thDay
8%113%20%55%
255
16th to endDay
13%1111%24%46%
254
October1st to 15thDay
7%9%24%39%18%
255
16th to endDay
13%318%27%23%13%
272
November1st to 15thDay
10%13%29%32%13%
265
16th to endDay
8%121%34%30%2
270
December1st to 15thDay
16%217%29%29%4
195
16th to endDay
11%12%28%40%7%
96
January1st to 15thNight
10%419%34%27%2
720
16th to endNight
7%424%41%21%1
768
February1st to 15thNight
10%323%41%19%
704
16th to endNight
6%222%48%20%
631
March1st to 15thNight
6%225%39%23%2
720
16th to endNight
6%121%45%23%1
732
April1st to 15thNight
4113%46%30%3
658
16th to endNight
8%15%43%29%1
660
May1st to 15thNight
4110%43%37%3
660
16th to endNight
8%18%29%39%12%
566
June1st to 15thNight
9%25%16%41%24%
495
16th to endNight
3310%43%39%
495
July1st to 15thNight
6%210%40%39%
465
16th to endNight
218%38%47%
522
August1st to 15thNight
7%17%43%39%
568
16th to endNight
9%311%35%39%
700
September1st to 15thNight
8%1412%36%36%
660
16th to endNight
13%412%36%32%
657
October1st to 15thNight
8%18%28%40%12%
660
16th to endNight
18%14%28%27%10%
704
November1st to 15thNight
9%117%34%31%5%
700
16th to endNight
12%219%34%26%3
720
December1st to 15thNight
10%319%35%28%2
720
16th to endNight
7%217%33%33%5%
768
Page generated at 2017-03-23 07:36:15. Version ac04

Copyright 2017 A. Danko


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