Sheerness Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sheerness Lake clear sky chart from 2005-11-05 to 2017-09-24.

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
44%
15325
12%
46851
8%
15297
48%
15297
21%
32035

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
35%
895
9%
2685
6%
895
37%
895
15%
2001
January16th to endNight
37%
892
16%
2812
9%
892
45%
892
18%
1963
February1st to 15thNight
44%
698
11%
2363
10%
696
47%
696
18%
1644
February16th to endNight
46%
632
12%
2040
12%
632
49%
632
17%
1463
March1st to 15thNight
39%
720
13%
2070
9%
720
44%
720
20%
1470
March16th to endNight
39%
768
10%
2109
4%
767
42%
767
17%
1593
April1st to 15thNight
36%
576
10%
1695
5%
576
40%
576
18%
1221
April16th to endNight
41%
540
15%
1620
13%
540
44%
540
21%
1112
May1st to 15thNight
46%
479
12%
1405
9%
479
49%
479
24%
939
May16th to endNight
44%
375
6%
1309
5%
374
45%
374
17%
923
June1st to 15thNight
43%
360
0%
1260
0%
360
43%
360
16%
872
June16th to endNight
51%
360
0%
1260
0%
360
51%
360
22%
789
July1st to 15thNight
61%
340
1%
1190
0%
340
61%
340
27%
708
July16th to endNight
63%
376
9%
1239
9%
354
67%
354
36%
647
August1st to 15thNight
66%
450
10%
1482
12%
448
68%
448
31%
877
August16th to endNight
62%
573
19%
1719
16%
573
65%
573
39%
969
September1st to 15thNight
57%
592
18%
1786
14%
592
60%
592
32%
1078
September16th to endNight
52%
692
20%
1914
14%
692
58%
692
37%
1159
October1st to 15thNight
43%
660
17%
1961
10%
660
49%
660
25%
1318
October16th to endNight
47%
712
16%
2271
10%
712
54%
712
23%
1479
November1st to 15thNight
38%
875
18%
2450
10%
875
44%
875
24%
1683
November16th to endNight
35%
900
12%
2631
8%
900
39%
900
18%
1908
December1st to 15thNight
35%
900
8%
2700
6%
900
37%
900
13%
2127
December16th to endNight
39%
960
13%
2880
7%
960
44%
960
17%
2092

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%8%37%6%35%5%6%8%34%
48116
Night
7%8%37%6%35%5%6%8%34%
47000
TransparencyDay
45%8%17%20%7%
47766
Night
44%8%16%20%8%1
46854
SeeingDay
13%5%24%30%19%5%
6106
Night
11%5%28%36%16%2
15337

By Month

Percentage Cloud Cover NW (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
7%11%47%7%48%7%7%8%24%
1253
16th to endDay
410%5%7%8%46%7%8%8%29%
1422
February1st to 15thDay
7%9%5%8%9%46%5%6%9%26%
1500
16th to endDay
5%14%5%10%8%46%6%6%8%22%
1431
March1st to 15thDay
6%9%49%10%5%7%5%5%8%26%
1889
16th to endDay
9%13%5%9%7%46%6%6%7%23%
2111
April1st to 15thDay
12%10%37%7%45%5%6%7%29%
2252
16th to endDay
14%8%46%6%4445%8%31%
2340
May1st to 15thDay
10%8%37%7%445%6%8%34%
2545
16th to endDay
17%7%36%6%35%6%6%8%27%
2802
June1st to 15thDay
17%6%37%6%35%6%6%8%28%
2700
16th to endDay
12%5%36%5%346%7%9%35%
2700
July1st to 15thDay
8%414436%47%10%42%
2700
16th to endDay
5%3134245%7%10%49%
2846
August1st to 15thDay
10%4245%3345%10%44%
2469
16th to endDay
6%424335%5%6%9%49%
2483
September1st to 15thDay
12%6%25%423345%47%
2172
16th to endDay
10%425%32346%10%46%
1904
October1st to 15thDay
8%8%48%435%5%5%6%37%
1669
16th to endDay
7%8%46%4445%6%7%38%
1590
November1st to 15thDay
7%11%5%8%6%345%5%7%32%
1408
16th to endDay
6%11%49%7%5%6%6%6%8%29%
1326
December1st to 15thDay
6%12%7%11%10%5%7%5%6%5%21%
1260
16th to endDay
5%9%7%11%8%47%5%7%9%22%
1344
January1st to 15thNight
6%9%5%9%8%5%6%7%8%9%23%
2685
16th to endNight
48%49%8%46%6%7%9%31%
2812
February1st to 15thNight
6%8%38%8%46%46%8%32%
2352
16th to endNight
5%10%5%7%8%37%6%6%8%29%
2040
March1st to 15thNight
5%7%5%7%9%47%5%8%9%29%
2070
16th to endNight
8%11%48%8%47%6%6%7%26%
2109
April1st to 15thNight
11%8%48%7%46%5%6%8%28%
1695
16th to endNight
11%9%36%7%3445%7%35%
1620
May1st to 15thNight
10%7%35%5%35%5%5%8%37%
1404
16th to endNight
17%6%35%5%35%6%6%8%30%
1309
June1st to 15thNight
15%8%35%5%45%5%6%9%30%
1260
16th to endNight
11%5%35%6%445%5%9%38%
1260
July1st to 15thNight
7%215%5%36%5%8%11%43%
1260
16th to endNight
32233245%7%11%52%
1323
August1st to 15thNight
5%315%6%35%5%7%11%44%
1489
16th to endNight
7%31442446%9%50%
1719
September1st to 15thNight
11%5%14423446%49%
1786
16th to endNight
8%42442346%7%50%
1914
October1st to 15thNight
8%8%36%5%35%5%5%7%37%
1961
16th to endNight
7%8%36%5%345%7%10%36%
2271
November1st to 15thNight
6%7%47%6%35%6%5%9%37%
2450
16th to endNight
6%11%48%6%45%6%6%8%30%
2631
December1st to 15thNight
5%10%5%13%9%5%6%5%6%7%22%
2700
16th to endNight
48%410%8%47%6%8%8%27%
2880

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
55%7%15%16%4
1253
16th to endDay
47%9%17%14%8%1
1422
February1st to 15thDay
52%7%16%17%5%
1500
16th to endDay
56%7%13%15%6%
1431
March1st to 15thDay
54%9%16%14%4
1889
16th to endDay
57%8%13%16%3
2112
April1st to 15thDay
49%7%16%17%8%
2252
16th to endDay
49%7%14%20%6%1
2340
May1st to 15thDay
45%7%14%21%10%
2545
16th to endDay
51%8%15%18%6%
2807
June1st to 15thDay
50%8%17%17%5%1
2700
16th to endDay
41%10%22%20%5%
2700
July1st to 15thDay
33%10%23%25%7%
2541
16th to endDay
27%9%22%27%10%
2667
August1st to 15thDay
33%8%24%24%7%
2451
16th to endDay
29%8%20%30%10%1
2483
September1st to 15thDay
37%5%14%24%13%4
2172
16th to endDay
32%7%15%31%10%2
1904
October1st to 15thDay
44%7%15%23%8%
1669
16th to endDay
42%6%19%23%7%
1590
November1st to 15thDay
50%6%15%19%5%1
1408
16th to endDay
52%8%15%16%7%
1326
December1st to 15thDay
62%8%11%15%1
1260
16th to endDay
55%9%15%15%4
1344
January1st to 15thNight
51%10%16%15%5%1
2685
16th to endNight
47%8%14%19%8%2
2812
February1st to 15thNight
48%7%16%18%8%
2363
16th to endNight
49%9%13%17%9%1
2040
March1st to 15thNight
46%8%19%18%5%
2070
16th to endNight
52%9%13%19%5%
2112
April1st to 15thNight
51%6%15%18%7%
1695
16th to endNight
46%7%11%23%10%2
1620
May1st to 15thNight
42%7%11%24%11%1
1405
16th to endNight
49%8%14%18%8%1
1309
June1st to 15thNight
48%8%14%18%8%1
1260
16th to endNight
40%7%20%22%8%
1260
July1st to 15thNight
32%10%21%24%9%
1190
16th to endNight
23%9%25%29%10%1
1239
August1st to 15thNight
31%8%24%26%7%1
1482
16th to endNight
27%6%16%31%14%3
1719
September1st to 15thNight
33%6%13%24%15%6%
1786
16th to endNight
30%6%16%27%15%2
1914
October1st to 15thNight
43%6%15%23%9%1
1961
16th to endNight
39%9%18%24%6%
2271
November1st to 15thNight
41%9%15%22%9%
2450
16th to endNight
49%8%17%15%7%1
2631
December1st to 15thNight
58%8%14%15%2
2700
16th to endNight
49%9%16%18%5%
2880

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
6%320%31%21%16%
60
16th to endDay
46%23%28%25%12%
64
February1st to 15thDay
12%12%16%38%15%2
77
16th to endDay
16%5%26%23%25%2
90
March1st to 15thDay
11%6%42%30%7%1
270
16th to endDay
12%9%39%26%12%1
288
April1st to 15thDay
14%13%28%28%12%1
269
16th to endDay
18%8%27%28%15%2
270
May1st to 15thDay
12%7%24%31%19%4
442
16th to endDay
17%5%22%26%20%7%
517
June1st to 15thDay
16%5%24%34%14%4
495
16th to endDay
14%323%30%20%6%
495
July1st to 15thDay
8%219%35%25%8%
475
16th to endDay
7%424%29%28%5%
515
August1st to 15thDay
12%214%31%29%8%
354
16th to endDay
8%5%19%32%27%7%
332
September1st to 15thDay
18%421%27%21%6%
315
16th to endDay
11%9%26%30%18%4
288
October1st to 15thDay
19%426%29%19%
109
16th to endDay
13%425%33%19%4
96
November1st to 15thDay
16%333%31%12%3
90
16th to endDay
8%9%33%23%12%11%
71
December1st to 15thDay
13%136%31%11%5%
60
16th to endDay
14%6%17%39%18%4
64
January1st to 15thNight
12%7%31%32%14%1
900
16th to endNight
7%8%31%37%12%2
892
February1st to 15thNight
10%7%24%37%17%3
704
16th to endNight
10%324%37%20%3
632
March1st to 15thNight
9%333%38%12%2
720
16th to endNight
13%5%28%36%14%1
768
April1st to 15thNight
13%7%30%32%12%2
576
16th to endNight
15%427%36%13%1
540
May1st to 15thNight
14%5%23%38%16%1
480
16th to endNight
20%225%26%22%1
375
June1st to 15thNight
17%426%30%17%3
360
16th to endNight
13%321%37%23%1
360
July1st to 15thNight
8%219%44%24%
340
16th to endNight
4223%45%22%1
376
August1st to 15thNight
6%316%39%30%4
450
16th to endNight
9%318%40%26%
573
September1st to 15thNight
14%319%39%21%1
592
16th to endNight
10%228%37%18%2
692
October1st to 15thNight
12%329%35%16%2
660
16th to endNight
11%5%27%40%13%1
712
November1st to 15thNight
9%6%37%34%9%2
875
16th to endNight
10%6%36%32%11%1
900
December1st to 15thNight
10%6%29%32%17%2
900
16th to endNight
7%332%37%13%4
960
Page generated at 2017-09-25 07:02:25. Version ac04

Copyright 2017 A. Danko


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