Foxmead Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Foxmead Observatory clear sky chart from 2005-11-05 to 2017-09-21.

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
27%
14753
12%
46588
7%
14720
33%
14720
15%
33895

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
10%
718
6%
2500
2%
716
15%
716
5%
2110
January16th to endNight
18%
768
8%
2496
4%
768
23%
768
7%
2057
February1st to 15thNight
13%
701
7%
2287
2%
701
18%
701
7%
1873
February16th to endNight
18%
631
10%
2032
5%
631
26%
631
10%
1558
March1st to 15thNight
17%
720
13%
1980
4%
720
25%
720
14%
1471
March16th to endNight
27%
768
20%
2112
10%
768
35%
768
21%
1442
April1st to 15thNight
20%
718
14%
1817
5%
718
25%
718
19%
1349
April16th to endNight
30%
545
19%
1625
10%
545
37%
545
21%
1129
May1st to 15thNight
38%
468
16%
1548
12%
468
44%
468
21%
1013
May16th to endNight
36%
374
15%
1497
10%
374
49%
374
22%
866
June1st to 15thNight
37%
360
11%
1398
11%
360
44%
360
20%
855
June16th to endNight
45%
360
12%
1260
11%
360
52%
360
23%
788
July1st to 15thNight
55%
340
17%
1232
19%
340
61%
340
34%
640
July16th to endNight
49%
458
15%
1494
14%
430
53%
430
26%
878
August1st to 15thNight
54%
539
16%
1609
11%
536
58%
536
32%
951
August16th to endNight
52%
612
18%
1758
10%
612
56%
612
31%
1096
September1st to 15thNight
44%
720
16%
1809
7%
720
48%
720
30%
1219
September16th to endNight
45%
681
20%
1903
13%
681
50%
681
27%
1240
October1st to 15thNight
29%
660
15%
1980
9%
660
38%
660
17%
1436
October16th to endNight
18%
704
10%
2112
4%
704
24%
704
9%
1681
November1st to 15thNight
24%
700
15%
2411
13%
700
31%
700
14%
1735
November16th to endNight
17%
720
8%
2520
5%
720
23%
720
7%
2034
December1st to 15thNight
10%
720
4%
2520
1%
720
14%
720
4%
2159
December16th to endNight
7%
768
7%
2688
2%
768
12%
768
4%
2315

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
16%9%36%5%3445%6%32%
48274
Night
16%11%47%6%34446%30%
46758
Cloud CoverDay
16%9%36%5%34446%32%
48284
Night
16%11%47%6%34446%30%
46763
TransparencyDay
52%5%11%19%9%
47964
Night
55%411%18%9%
46588
SeeingDay
22%12%29%20%9%4
5667
Night
24%13%28%22%9%1
14759

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
19%15%6%10%7%4434418%
1435
16th to endDay
14%18%7%11%8%4444417%
1728
February1st to 15thDay
12%16%6%13%9%4444418%
1575
16th to endDay
15%16%6%11%7%3443421%
1440
March1st to 15thDay
15%11%38%6%44445%31%
1969
16th to endDay
14%8%5%5%5%34345%38%
2112
April1st to 15thDay
21%10%36%5%24345%32%
2137
16th to endDay
19%9%24423346%39%
2340
May1st to 15thDay
17%8%245%35%45%5%36%
2401
16th to endDay
13%5%244345%5%7%41%
2618
June1st to 15thDay
20%5%1442445%8%36%
2558
16th to endDay
15%6%25%5%345%5%9%36%
2700
July1st to 15thDay
12%424425%5%5%8%43%
2652
16th to endDay
11%5%26%5%35%5%6%7%39%
2570
August1st to 15thDay
13%5%25%43445%8%42%
2340
16th to endDay
11%5%26%5%35%45%9%40%
2432
September1st to 15thDay
18%6%26%5%2445%7%37%
2148
16th to endDay
16%5%25%5%35%346%40%
1850
October1st to 15thDay
21%8%37%6%3445%5%30%
1650
16th to endDay
30%11%46%6%3444419%
1760
November1st to 15thDay
20%13%46%6%24447%24%
1443
16th to endDay
20%17%5%8%6%45%5%4316%
1440
December1st to 15thDay
18%20%7%9%8%44445%13%
1440
16th to endDay
19%20%7%9%7%45%44412%
1536
January1st to 15thNight
19%17%7%10%9%35%43414%
2500
16th to endNight
14%16%6%10%9%45%45%5%16%
2496
February1st to 15thNight
11%18%7%11%9%45%44317%
2285
16th to endNight
16%12%5%10%7%35%445%24%
2032
March1st to 15thNight
17%10%47%6%35%235%32%
1968
16th to endNight
14%9%46%5%2334439%
2112
April1st to 15thNight
22%10%36%413345%33%
1817
16th to endNight
16%9%35%5%33446%36%
1625
May1st to 15thNight
17%7%35%5%2445%6%37%
1548
16th to endNight
12%415%43445%7%44%
1495
June1st to 15thNight
15%6%345%345%5%8%37%
1398
16th to endNight
11%6%35%5%25%37%8%39%
1260
July1st to 15thNight
7%225%43345%6%54%
1305
16th to endNight
10%5%244346%5%8%45%
1596
August1st to 15thNight
7%5%235%25%5%5%8%47%
1620
16th to endNight
10%5%245%34446%46%
1758
September1st to 15thNight
14%5%25%424447%42%
1809
16th to endNight
14%6%26%433346%43%
1903
October1st to 15thNight
19%8%26%6%35%446%32%
1980
16th to endNight
26%11%48%43445%5%21%
2112
November1st to 15thNight
18%12%45%5%33446%29%
2411
16th to endNight
21%14%5%8%6%345%5%5%18%
2520
December1st to 15thNight
18%20%7%10%7%34445%12%
2520
16th to endNight
21%17%8%11%8%3343312%
2688

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
19%15%6%9%8%4433418%
1435
16th to endDay
13%18%7%11%9%3444418%
1728
February1st to 15thDay
13%16%6%12%9%45%34418%
1575
16th to endDay
16%16%6%10%8%35%33421%
1440
March1st to 15thDay
16%11%37%6%44345%31%
1980
16th to endDay
14%8%46%5%25%345%38%
2111
April1st to 15thDay
21%10%36%434335%32%
2137
16th to endDay
19%9%24323346%39%
2340
May1st to 15thDay
18%7%25%5%345%5%5%36%
2401
16th to endDay
14%5%24435%5%5%7%41%
2618
June1st to 15thDay
19%6%2442446%8%36%
2558
16th to endDay
16%5%25%5%3445%9%36%
2700
July1st to 15thDay
11%425%43445%9%43%
2652
16th to endDay
11%5%26%5%35%5%6%7%39%
2570
August1st to 15thDay
12%6%245%2445%8%42%
2340
16th to endDay
11%5%26%5%345%5%9%40%
2432
September1st to 15thDay
17%7%26%424347%38%
2148
16th to endDay
16%435%434446%40%
1850
October1st to 15thDay
21%8%37%5%3345%5%30%
1650
16th to endDay
30%11%46%6%3444419%
1760
November1st to 15thDay
20%12%46%6%24448%24%
1443
16th to endDay
20%17%6%8%6%46%5%4417%
1440
December1st to 15thDay
18%20%7%9%7%44436%14%
1440
16th to endDay
19%19%8%8%6%45%5%3412%
1536
January1st to 15thNight
19%17%6%11%9%34435%14%
2500
16th to endNight
15%16%6%10%8%45%45%5%17%
2496
February1st to 15thNight
11%18%7%11%9%46%44317%
2278
16th to endNight
17%12%5%9%7%35%435%25%
2032
March1st to 15thNight
17%11%5%7%6%35%335%32%
1980
16th to endNight
14%9%46%5%2334439%
2112
April1st to 15thNight
22%10%35%413345%33%
1817
16th to endNight
16%9%45%5%24446%36%
1625
May1st to 15thNight
17%7%345%2445%7%37%
1548
16th to endNight
11%5%15%5%35%45%7%44%
1495
June1st to 15thNight
15%6%345%245%5%8%37%
1398
16th to endNight
11%5%35%5%35%45%9%39%
1260
July1st to 15thNight
7%325%43345%6%54%
1305
16th to endNight
10%5%24425%5%6%8%44%
1596
August1st to 15thNight
7%5%245%25%5%5%8%47%
1620
16th to endNight
10%5%345%25%347%46%
1758
September1st to 15thNight
14%425%5%2445%6%43%
1809
16th to endNight
14%6%25%434336%44%
1903
October1st to 15thNight
20%7%26%5%35%45%5%32%
1980
16th to endNight
26%11%47%5%3435%422%
2112
November1st to 15thNight
18%11%46%6%34446%29%
2411
16th to endNight
21%14%5%8%6%35%445%19%
2520
December1st to 15thNight
18%19%7%10%7%35%345%13%
2520
16th to endNight
21%17%8%11%7%4443312%
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
69%411%9%4
1436
16th to endDay
70%37%10%7%
1728
February1st to 15thDay
70%39%12%3
1577
16th to endDay
67%37%13%7%
1440
March1st to 15thDay
56%414%17%6%
1980
16th to endDay
48%49%18%16%2
2112
April1st to 15thDay
55%38%19%11%
2137
16th to endDay
47%48%23%14%1
2340
May1st to 15thDay
48%5%9%21%13%1
2401
16th to endDay
41%5%12%24%14%1
2622
June1st to 15thDay
45%5%13%24%11%
2558
16th to endDay
44%5%15%22%11%
2700
July1st to 15thDay
36%6%13%26%15%1
2497
16th to endDay
42%6%11%27%10%1
2410
August1st to 15thDay
40%5%16%22%13%
2327
16th to endDay
40%6%14%27%9%
2432
September1st to 15thDay
46%412%25%9%
2148
16th to endDay
45%412%29%8%
1850
October1st to 15thDay
55%410%19%9%
1650
16th to endDay
68%411%10%4
1760
November1st to 15thDay
59%5%12%15%6%
1443
16th to endDay
71%5%10%9%2
1440
December1st to 15thDay
73%5%10%8%1
1440
16th to endDay
75%48%8%2
1536
January1st to 15thNight
74%48%8%3
2500
16th to endNight
69%5%8%10%5%
2496
February1st to 15thNight
70%49%12%3
2287
16th to endNight
62%311%15%6%
2032
March1st to 15thNight
56%312%18%8%
1980
16th to endNight
47%29%21%16%1
2112
April1st to 15thNight
54%38%19%12%1
1817
16th to endNight
48%47%18%18%2
1625
May1st to 15thNight
46%311%18%17%2
1548
16th to endNight
39%413%25%15%1
1497
June1st to 15thNight
43%312%25%13%
1398
16th to endNight
41%5%14%23%14%
1260
July1st to 15thNight
28%413%30%20%1
1232
16th to endNight
36%5%12%29%14%
1494
August1st to 15thNight
33%5%18%27%14%
1609
16th to endNight
36%5%15%26%15%1
1758
September1st to 15thNight
40%5%15%24%11%1
1809
16th to endNight
42%313%29%10%
1903
October1st to 15thNight
52%5%10%20%10%
1980
16th to endNight
64%5%9%14%5%
2112
November1st to 15thNight
56%413%16%8%1
2411
16th to endNight
66%6%11%11%2
2520
December1st to 15thNight
74%5%11%6%2
2520
16th to endNight
76%37%8%2
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
22%29%32%11%3
61
16th to endDay
41%10%34%9%4
96
February1st to 15thDay
31%34%33%1
90
16th to endDay
32%27%33%7%
81
March1st to 15thDay
26%17%35%15%4
270
16th to endDay
25%17%30%15%10%1
288
April1st to 15thDay
29%15%31%13%8%1
270
16th to endDay
25%17%29%12%10%4
270
May1st to 15thDay
29%9%27%18%9%4
288
16th to endDay
18%13%35%20%7%4
331
June1st to 15thDay
25%11%26%25%9%1
353
16th to endDay
18%10%35%25%8%1
495
July1st to 15thDay
14%9%30%28%11%5%
431
16th to endDay
11%8%31%28%12%6%
326
August1st to 15thDay
16%426%28%12%12%
313
16th to endDay
15%7%24%27%13%11%
332
September1st to 15thDay
16%7%24%23%17%9%
315
16th to endDay
19%9%22%24%15%9%
275
October1st to 15thDay
25%14%29%16%10%3
255
16th to endDay
38%15%27%14%4
272
November1st to 15thDay
25%14%29%25%5%
71
16th to endDay
33%21%33%11%
60
December1st to 15thDay
31%26%26%6%8%
60
16th to endDay
37%42%18%1
64
January1st to 15thNight
32%22%25%14%3
720
16th to endNight
26%15%31%20%5%1
768
February1st to 15thNight
22%22%32%18%4
704
16th to endNight
25%19%29%20%5%
631
March1st to 15thNight
27%19%30%19%3
720
16th to endNight
23%14%29%22%8%
768
April1st to 15thNight
31%13%29%19%5%
718
16th to endNight
22%12%31%22%10%
545
May1st to 15thNight
21%8%25%29%12%2
468
16th to endNight
13%7%34%28%14%
375
June1st to 15thNight
17%9%27%34%11%
360
16th to endNight
14%431%35%13%
360
July1st to 15thNight
7%326%41%18%1
340
16th to endNight
12%426%35%21%
458
August1st to 15thNight
10%5%23%34%23%2
539
16th to endNight
13%424%29%25%2
612
September1st to 15thNight
17%6%26%25%18%5%
720
16th to endNight
18%6%23%30%17%3
681
October1st to 15thNight
25%11%28%22%10%1
660
16th to endNight
35%18%24%17%4
704
November1st to 15thNight
28%14%27%20%8%1
700
16th to endNight
32%15%27%18%4
720
December1st to 15thNight
35%21%27%11%2
720
16th to endNight
33%19%32%11%2
768
Page generated at 2017-09-22 07:35:32. Version ac04

Copyright 2017 A. Danko


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