Oxford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oxford clear sky chart from 2005-11-06 to 2024-02-15.

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
46%
24078
24%
79713
17%
23965
54%
23965
27%
47688

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 10thNight
24%
943
22%
4198
9%
926
35%
926
15%
2625
January11th to 20thNight
23%
950
27%
3937
7%
930
33%
930
15%
2374
January21st to endNight
23%
1017
18%
4403
8%
998
36%
998
17%
2703
February1st to 10thNight
24%
760
21%
2280
8%
760
35%
760
21%
1511
February11th to 20thNight
23%
722
20%
2153
9%
718
32%
718
21%
1425
February21st to endNight
20%
592
23%
1776
9%
592
31%
592
19%
1189
March1st to 10thNight
31%
720
22%
2160
11%
720
39%
720
25%
1350
March11th to 20thNight
30%
571
18%
2011
12%
571
38%
571
18%
1340
March21st to endNight
31%
594
22%
2029
12%
594
43%
594
23%
1261
April1st to 10thNight
36%
540
27%
1800
17%
540
50%
540
28%
1038
April11th to 20thNight
37%
533
28%
1775
18%
533
53%
533
30%
1005
April21st to endNight
37%
540
26%
1800
17%
540
53%
540
29%
1056
May1st to 10thNight
47%
540
22%
1800
18%
540
55%
540
31%
1032
May11th to 20thNight
48%
531
21%
1643
18%
531
53%
531
28%
1009
May21st to endNight
63%
583
23%
1711
20%
582
66%
582
33%
1036
June1st to 10thNight
66%
540
22%
1440
19%
540
69%
540
37%
890
June11th to 20thNight
76%
540
27%
1440
23%
540
78%
540
51%
784
June21st to endNight
74%
540
25%
1440
19%
540
77%
540
46%
815
July1st to 10thNight
72%
525
19%
1400
17%
525
73%
525
35%
878
July11th to 20thNight
75%
522
22%
1492
21%
522
76%
522
40%
858
July21st to endNight
78%
591
22%
1724
24%
558
78%
558
37%
981
August1st to 10thNight
84%
537
20%
1778
24%
534
85%
534
39%
928
August11th to 20thNight
74%
534
19%
1776
22%
534
76%
534
30%
1054
August21st to endNight
73%
594
23%
1980
26%
594
75%
594
33%
1108
September1st to 10thNight
72%
540
27%
1800
30%
540
73%
540
35%
1003
September11th to 20thNight
66%
598
27%
1858
26%
598
68%
598
33%
1086
September21st to endNight
64%
720
32%
1980
24%
720
68%
720
42%
1136
October1st to 10thNight
65%
720
34%
2040
25%
720
71%
720
49%
1061
October11th to 20thNight
50%
720
31%
2160
22%
720
60%
720
36%
1219
October21st to endNight
45%
792
30%
2376
23%
792
53%
792
32%
1418
November1st to 10thNight
53%
740
31%
2365
26%
740
62%
740
37%
1268
November11th to 20thNight
41%
760
28%
2470
20%
760
54%
760
32%
1375
November21st to endNight
36%
760
26%
2470
18%
760
48%
760
26%
1488
December1st to 10thNight
31%
760
25%
2470
15%
760
44%
760
22%
1568
December11th to 20thNight
31%
867
24%
3050
12%
867
43%
867
22%
1845
December21st to endNight
26%
1042
13%
4728
9%
1026
36%
1026
14%
2971

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
13%6%35%5%35%5%5%7%43%
78523
Night
13%6%25%43445%7%47%
80590
TransparencyDay
39%6%10%22%18%4
78242
Night
37%5%10%22%21%6%
80393
SeeingDay
16%10%23%25%19%8%
14172
Night
16%9%24%29%19%4
24094

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 10thDay
16%14%35%42333443%
2656
11th to 20thDay
22%8%25%42434442%
2850
21st to endDay
22%9%24333335%42%
3169
February1st to 10thDay
19%9%45%5%33446%39%
1900
11th to 20thDay
22%9%45%42334440%
1788
21st to endDay
22%8%35%5%24445%38%
1480
March1st to 10thDay
18%8%36%6%34345%41%
1800
11th to 20thDay
16%8%36%6%35%6%5%6%36%
1963
21st to endDay
14%7%46%5%36%46%6%39%
2326
April1st to 10thDay
13%5%25%5%345%5%8%45%
2160
11th to 20thDay
15%6%245%2445%7%45%
2134
21st to endDay
11%7%25%6%35%5%5%6%45%
2160
May1st to 10thDay
15%435%5%345%5%8%43%
2160
11th to 20thDay
10%6%36%6%35%6%5%8%42%
2247
21st to endDay
9%5%35%6%46%5%7%10%40%
2558
June1st to 10thDay
8%6%25%6%46%6%7%9%41%
2520
11th to 20thDay
5%425%6%45%6%7%10%47%
2520
21st to endDay
5%425%436%6%7%9%48%
2520
July1st to 10thDay
7%436%7%48%7%8%10%35%
2520
11th to 20thDay
8%425%5%48%8%8%12%36%
2413
21st to endDay
7%5%246%5%7%8%8%11%38%
2492
August1st to 10thDay
5%5%25%6%47%6%8%10%41%
2148
11th to 20thDay
10%5%26%6%47%6%7%9%38%
2125
21st to endDay
11%5%25%5%35%5%7%10%42%
2376
September1st to 10thDay
8%436%5%35%6%6%8%45%
2160
11th to 20thDay
11%5%36%6%45%45%7%45%
2084
21st to endDay
10%414434448%54%
1980
October1st to 10thDay
8%42442345%6%57%
1916
11th to 20thDay
10%5%25%434336%56%
1800
21st to endDay
18%6%23422345%51%
1980
November1st to 10thDay
12%5%24323335%60%
1711
11th to 20thDay
14%5%34424247%53%
1710
21st to endDay
19%8%24333445%45%
1710
December1st to 10thDay
20%9%35%434445%37%
1710
11th to 20thDay
15%8%36%5%24445%44%
1994
21st to endDay
13%10%36%6%35%5%5%7%38%
2783
January1st to 10thNight
18%10%35%42434442%
4296
11th to 20thNight
18%8%35%42333446%
4120
21st to endNight
23%10%23322335%44%
4494
February1st to 10thNight
20%8%35%5%24345%42%
2280
11th to 20thNight
19%9%35%42334443%
2153
21st to endNight
22%8%35%424346%40%
1776
March1st to 10thNight
16%6%25%5%2435%6%45%
2160
11th to 20thNight
16%8%36%5%35%45%6%39%
2011
21st to endNight
15%7%26%5%3445%6%43%
2029
April1st to 10thNight
12%5%24435%45%8%48%
1800
11th to 20thNight
14%5%3422345%7%50%
1775
21st to endNight
11%5%35%434346%51%
1800
May1st to 10thNight
12%6%3442346%8%49%
1800
11th to 20thNight
10%5%36%5%35%5%6%8%45%
1642
21st to endNight
6%436%5%45%5%8%11%44%
1711
June1st to 10thNight
6%426%6%245%7%12%46%
1440
11th to 20thNight
23224246%6%12%57%
1440
21st to endNight
44234345%6%10%55%
1440
July1st to 10thNight
3325%7%46%6%7%11%45%
1440
11th to 20thNight
7%414435%47%10%51%
1541
21st to endNight
44144347%9%12%48%
1825
August1st to 10thNight
3213435%8%7%13%50%
1790
11th to 20thNight
5%425%6%46%7%6%11%44%
1776
21st to endNight
7%4244335%7%11%49%
1980
September1st to 10thNight
8%425%4345%6%8%52%
1800
11th to 20thNight
9%5%244345%5%8%50%
1858
21st to endNight
11%41432435%6%57%
1980
October1st to 10thNight
8%21332335%8%63%
2040
11th to 20thNight
12%5%2442335%5%55%
2160
21st to endNight
16%7%25%322235%53%
2376
November1st to 10thNight
11%414323446%58%
2365
11th to 20thNight
11%5%2433445%6%53%
2470
21st to endNight
15%6%25%323445%49%
2470
December1st to 10thNight
19%9%25%5%33346%43%
2470
11th to 20thNight
16%7%345%34345%47%
3198
21st to endNight
16%8%36%5%35%5%5%7%35%
4884

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 10thDay
47%25%20%22%3
2657
11th to 20thDay
46%45%23%21%2
2850
21st to endDay
46%37%19%21%4
3169
February1st to 10thDay
47%47%20%18%4
1900
11th to 20thDay
49%45%19%17%5%
1798
21st to endDay
50%46%15%17%8%
1480
March1st to 10thDay
47%46%15%18%10%
1800
11th to 20thDay
48%6%9%16%18%3
1963
21st to endDay
44%5%9%23%17%1
2326
April1st to 10thDay
37%5%10%23%20%4
2160
11th to 20thDay
39%47%23%20%6%
2134
21st to endDay
39%5%10%23%21%2
2160
May1st to 10thDay
40%6%11%21%18%4
2160
11th to 20thDay
39%7%15%23%15%2
2251
21st to endDay
39%9%14%25%12%1
2558
June1st to 10thDay
37%8%13%22%19%1
2520
11th to 20thDay
29%8%15%28%17%3
2520
21st to endDay
31%8%15%25%17%4
2520
July1st to 10thDay
38%12%17%19%11%4
2451
11th to 20thDay
35%13%19%20%9%3
2339
21st to endDay
35%11%17%28%9%1
2354
August1st to 10thDay
33%11%18%26%11%1
2136
11th to 20thDay
40%10%13%21%14%2
2125
21st to endDay
36%8%14%23%14%4
2376
September1st to 10thDay
34%8%11%24%18%5%
2160
11th to 20thDay
38%7%10%15%22%8%
2084
21st to endDay
29%5%9%24%23%9%
1980
October1st to 10thDay
28%5%9%25%23%11%
1916
11th to 20thDay
32%46%22%27%9%
1800
21st to endDay
37%45%21%26%8%
1980
November1st to 10thDay
29%29%20%30%10%
1711
11th to 20thDay
33%37%20%27%9%
1710
21st to endDay
42%36%20%23%5%
1710
December1st to 10thDay
50%5%6%17%16%6%
1710
11th to 20thDay
44%36%20%22%5%
1991
21st to endDay
45%310%20%17%3
2783
January1st to 10thNight
47%25%17%26%3
4296
11th to 20thNight
43%45%22%21%6%
4120
21st to endNight
46%25%21%21%4
4494
February1st to 10thNight
47%38%19%20%4
2280
11th to 20thNight
45%46%20%18%7%
2154
21st to endNight
48%37%16%19%7%
1776
March1st to 10thNight
40%48%16%20%12%
2160
11th to 20thNight
46%7%7%18%18%5%
2011
21st to endNight
42%5%9%22%19%4
2029
April1st to 10thNight
35%411%24%19%7%
1800
11th to 20thNight
33%47%23%25%8%
1775
21st to endNight
36%49%27%21%4
1800
May1st to 10thNight
33%5%11%23%23%5%
1800
11th to 20thNight
36%7%13%23%18%2
1643
21st to endNight
31%9%13%28%16%2
1712
June1st to 10thNight
32%7%14%24%21%2
1440
11th to 20thNight
20%6%17%30%22%5%
1440
21st to endNight
23%7%16%25%24%5%
1440
July1st to 10thNight
29%12%19%24%12%4
1400
11th to 20thNight
26%8%21%28%13%4
1492
21st to endNight
25%10%19%31%13%1
1724
August1st to 10thNight
22%10%22%33%14%
1778
11th to 20thNight
31%10%19%22%15%3
1776
21st to endNight
28%9%18%24%15%6%
1980
September1st to 10thNight
30%6%12%22%24%7%
1800
11th to 20thNight
32%7%12%17%26%6%
1858
21st to endNight
28%49%23%25%9%
1980
October1st to 10thNight
21%410%26%26%13%
2040
11th to 20thNight
31%48%19%28%11%
2160
21st to endNight
37%35%18%29%8%
2376
November1st to 10thNight
28%47%22%29%10%
2365
11th to 20thNight
32%47%19%27%11%
2470
21st to endNight
38%5%6%19%24%8%
2470
December1st to 10thNight
45%36%22%20%5%
2470
11th to 20thNight
41%27%19%26%5%
3200
21st to endNight
46%410%18%17%4
4884

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 10thDay
29%21%34%13%3
270
11th to 20thDay
32%18%33%13%21
270
21st to endDay
26%26%35%9%3
297
February1st to 10thDay
27%19%33%13%7%
270
11th to 20thDay
40%19%30%9%2
252
21st to endDay
38%24%28%7%3
198
March1st to 10thDay
24%27%33%13%4
240
11th to 20thDay
24%27%37%12%
240
21st to endDay
24%19%34%17%7%
412
April1st to 10thDay
20%19%30%25%5%
420
11th to 20thDay
22%16%30%21%9%2
412
21st to endDay
20%15%29%25%10%1
420
May1st to 10thDay
17%13%29%27%12%2
423
11th to 20thDay
13%8%29%29%16%6%
447
21st to endDay
11%425%30%21%9%
512
June1st to 10thDay
10%418%31%26%11%
630
11th to 20thDay
5%319%34%26%13%
630
21st to endDay
8%219%36%26%10%
630
July1st to 10thDay
5%313%33%31%15%
621
11th to 20thDay
8%210%27%33%19%
618
21st to endDay
7%210%28%34%19%
630
August1st to 10thDay
7%38%29%38%14%
446
11th to 20thDay
14%210%28%33%13%
439
21st to endDay
14%210%22%35%18%
495
September1st to 10thDay
9%111%31%36%12%
450
11th to 20thDay
10%314%26%32%16%
450
21st to endDay
12%317%32%24%12%
450
October1st to 10thDay
10%324%28%25%9%
386
11th to 20thDay
11%12%34%34%7%1
270
21st to endDay
24%13%31%23%8%1
297
November1st to 10thDay
20%10%25%29%15%2
270
11th to 20thDay
13%18%40%25%41
270
21st to endDay
26%14%33%14%11%2
270
December1st to 10thDay
28%20%33%15%4
270
11th to 20thDay
22%20%34%17%6%1
270
21st to endDay
24%21%37%14%31
297
January1st to 10thNight
24%17%31%23%4
950
11th to 20thNight
25%18%30%21%5%
950
21st to endNight
22%16%37%23%2
1020
February1st to 10thNight
26%14%33%23%4
760
11th to 20thNight
24%19%31%23%2
722
21st to endNight
26%20%31%21%2
592
March1st to 10thNight
21%14%30%30%5%
720
11th to 20thNight
22%12%32%27%7%1
571
21st to endNight
20%12%34%25%9%1
594
April1st to 10thNight
16%11%34%28%11%
540
11th to 20thNight
16%11%33%27%13%1
533
21st to endNight
13%11%35%26%13%1
540
May1st to 10thNight
15%6%26%36%13%3
540
11th to 20thNight
11%5%27%32%21%4
531
21st to endNight
8%218%37%27%7%
584
June1st to 10thNight
7%312%39%32%7%
540
11th to 20thNight
4211%37%39%7%
540
21st to endNight
5%211%35%39%8%
540
July1st to 10thNight
4110%30%44%12%
525
11th to 20thNight
8%18%28%38%17%
522
21st to endNight
5%18%28%46%12%
591
August1st to 10thNight
41426%50%14%
537
11th to 20thNight
6%18%37%37%11%
534
21st to endNight
8%28%28%43%11%
594
September1st to 10thNight
10%27%34%41%7%
540
11th to 20thNight
11%213%31%36%8%
598
21st to endNight
13%215%33%33%4
720
October1st to 10thNight
8%419%32%32%6%
720
11th to 20thNight
15%7%23%35%18%2
720
21st to endNight
20%8%23%29%18%2
792
November1st to 10thNight
12%8%23%35%19%3
740
11th to 20thNight
14%11%30%33%12%1
760
21st to endNight
21%10%30%27%11%1
760
December1st to 10thNight
25%12%27%28%8%
760
11th to 20thNight
21%14%29%29%7%
869
21st to endNight
27%15%27%26%4
1045
Page generated at 2024-02-12 05:35:34. Version ac07

Copyright 2024 Attilla Danko


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