This page made possible by the sponsorship of:

Friends of Beacon Field Airport
.

Beacon Field Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Beacon Field Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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
37%
23495
21%
74678
12%
23449
48%
23449
24%
46716

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
20%
757
24%
2597
8%
757
40%
757
21%
1557
January11th to 20thNight
25%
741
23%
2406
9%
741
42%
741
19%
1557
January21st to endNight
23%
792
26%
2574
10%
792
41%
792
23%
1558
February1st to 10thNight
24%
720
18%
2340
8%
720
38%
720
20%
1497
February11th to 20thNight
14%
701
20%
2213
5%
700
34%
700
19%
1417
February21st to endNight
17%
592
25%
1776
7%
592
39%
592
20%
1147
March1st to 10thNight
23%
720
25%
2019
9%
720
40%
720
26%
1260
March11th to 20thNight
22%
720
21%
1980
8%
720
35%
720
24%
1310
March21st to endNight
22%
792
21%
2140
7%
792
33%
792
24%
1436
April1st to 10thNight
22%
720
20%
1800
4%
720
33%
720
25%
1223
April11th to 20thNight
34%
711
22%
1775
7%
711
40%
711
32%
1153
April21st to endNight
32%
720
21%
1800
7%
720
38%
720
28%
1213
May1st to 10thNight
36%
613
18%
1693
8%
613
42%
613
25%
1135
May11th to 20thNight
39%
421
18%
1482
10%
421
47%
421
20%
954
May21st to endNight
52%
388
16%
1551
15%
388
57%
388
22%
943
June1st to 10thNight
53%
360
20%
1440
20%
360
61%
360
24%
834
June11th to 20thNight
53%
360
16%
1440
16%
360
60%
360
22%
874
June21st to endNight
54%
360
18%
1440
17%
360
62%
360
25%
815
July1st to 10thNight
57%
350
16%
1400
17%
350
62%
350
22%
852
July11th to 20thNight
70%
421
17%
1465
17%
421
71%
421
29%
847
July21st to endNight
63%
591
18%
1672
13%
558
68%
558
32%
1029
August1st to 10thNight
66%
537
15%
1600
11%
534
67%
534
28%
1040
August11th to 20thNight
57%
619
16%
1683
11%
619
59%
619
26%
1155
August21st to endNight
60%
792
19%
1980
11%
792
61%
792
32%
1317
September1st to 10thNight
56%
720
23%
1800
13%
720
60%
720
32%
1217
September11th to 20thNight
61%
720
29%
1800
21%
720
64%
720
39%
1141
September21st to endNight
44%
720
20%
2057
13%
720
51%
720
24%
1394
October1st to 10thNight
48%
720
20%
2160
17%
720
53%
720
28%
1364
October11th to 20thNight
41%
720
26%
2160
19%
720
52%
720
29%
1302
October21st to endNight
36%
792
28%
2376
17%
792
49%
792
28%
1442
November1st to 10thNight
38%
740
27%
2317
17%
740
53%
740
31%
1345
November11th to 20thNight
35%
760
26%
2470
15%
760
49%
760
26%
1444
November21st to endNight
34%
760
25%
2660
14%
760
50%
760
25%
1496
December1st to 10thNight
26%
760
21%
2660
7%
760
43%
760
19%
1654
December11th to 20thNight
26%
760
22%
3164
9%
759
41%
759
19%
1857
December21st to endNight
27%
825
14%
4788
11%
817
41%
817
12%
2937

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%25%5%35%5%6%8%42%
74701
Night
14%6%25%4345%5%7%44%
75090
TransparencyDay
39%6%12%23%17%3
74411
Night
39%6%11%23%17%4
74899
SeeingDay
18%12%27%25%13%5%
13881
Night
17%10%30%29%13%1
23512

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
15%6%35%5%2445%7%43%
1564
11th to 20thDay
17%7%25%5%345%5%6%41%
1665
21st to endDay
15%6%37%6%35%445%42%
1782
February1st to 10thDay
15%7%25%6%45%5%5%7%38%
1620
11th to 20thDay
18%7%3443445%6%41%
1633
21st to endDay
19%7%36%5%33447%39%
1480
March1st to 10thDay
12%6%25%434446%50%
1938
11th to 20thDay
17%5%35%5%35%446%42%
1980
21st to endDay
18%6%36%6%35%45%6%39%
2215
April1st to 10thDay
12%6%25%5%35%5%5%7%44%
2160
11th to 20thDay
13%5%25%5%3445%6%48%
2134
21st to endDay
18%6%24435%5%5%7%41%
2160
May1st to 10thDay
14%7%26%5%35%5%6%9%38%
2281
11th to 20thDay
17%6%35%5%35%7%6%8%36%
2410
21st to endDay
14%5%25%5%35%5%6%8%41%
2725
June1st to 10thDay
11%4245%35%5%7%10%43%
2520
11th to 20thDay
11%5%25%5%35%7%7%9%41%
2520
21st to endDay
9%425%5%35%6%8%10%42%
2520
July1st to 10thDay
9%5%26%5%45%5%8%9%41%
2520
11th to 20thDay
6%3245%36%7%8%12%43%
2443
21st to endDay
9%5%27%5%47%7%8%10%36%
2547
August1st to 10thDay
9%6%36%6%5%7%6%8%9%36%
2327
11th to 20thDay
11%5%25%6%46%7%6%10%38%
2197
21st to endDay
10%425%5%45%7%8%10%40%
2376
September1st to 10thDay
14%5%25%5%4446%8%45%
2160
11th to 20thDay
10%6%3442446%9%48%
2160
21st to endDay
17%8%26%435%6%6%6%39%
1897
October1st to 10thDay
15%6%25%5%2445%7%46%
1800
11th to 20thDay
17%42432435%6%49%
1800
21st to endDay
14%6%25%42445%7%47%
1980
November1st to 10thDay
12%5%23434447%52%
1758
11th to 20thDay
14%5%2433445%8%50%
1707
21st to endDay
15%5%2443345%6%48%
1520
December1st to 10thDay
15%5%26%5%35%46%7%42%
1520
11th to 20thDay
16%7%25%334447%47%
1910
21st to endDay
17%7%35%5%35%5%6%7%37%
2772
January1st to 10thNight
16%7%24423446%47%
2597
11th to 20thNight
17%6%35%5%3445%6%41%
2406
21st to endNight
15%7%25%334447%46%
2574
February1st to 10thNight
16%7%346%35%45%7%41%
2340
11th to 20thNight
19%7%26%423446%43%
2211
21st to endNight
18%8%25%42335%7%43%
1776
March1st to 10thNight
14%425%4335%46%49%
2019
11th to 20thNight
17%6%25%5%24448%43%
1980
21st to endNight
15%6%36%5%3445%7%42%
2140
April1st to 10thNight
14%7%35%5%35%5%5%6%42%
1800
11th to 20thNight
14%5%35%4235%5%7%48%
1775
21st to endNight
18%5%25%43446%7%43%
1800
May1st to 10thNight
15%6%45%4345%6%8%39%
1693
11th to 20thNight
16%6%35%5%35%5%6%9%38%
1482
21st to endNight
12%6%25%5%246%7%10%40%
1550
June1st to 10thNight
10%425%436%5%8%9%44%
1440
11th to 20thNight
12%5%25%5%36%7%6%10%40%
1440
21st to endNight
9%5%25%6%446%8%10%43%
1440
July1st to 10thNight
8%5%36%6%36%5%8%10%40%
1440
11th to 20thNight
6%426%436%6%6%11%46%
1513
21st to endNight
8%425%5%46%5%9%11%40%
1771
August1st to 10thNight
8%426%5%47%7%7%9%41%
1611
11th to 20thNight
11%6%36%6%35%6%8%7%39%
1683
21st to endNight
9%6%36%5%45%46%9%43%
1980
September1st to 10thNight
13%5%36%435%45%8%44%
1800
11th to 20thNight
9%6%25%5%2345%8%50%
1800
21st to endNight
16%8%26%5%3446%7%39%
2057
October1st to 10thNight
17%6%34433446%46%
2160
11th to 20thNight
16%5%24433346%50%
2160
21st to endNight
15%5%244245%47%49%
2376
November1st to 10thNight
13%424424445%54%
2317
11th to 20thNight
14%7%34423447%50%
2470
21st to endNight
13%4245%235%5%7%49%
2660
December1st to 10thNight
17%8%35%424446%42%
2660
11th to 20thNight
17%5%25%43445%7%43%
3285
21st to endNight
16%7%35%5%35%6%6%7%37%
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
40%5%11%25%15%4
1565
11th to 20thDay
42%5%12%23%15%3
1665
21st to endDay
44%49%24%15%4
1782
February1st to 10thDay
45%5%12%24%12%2
1620
11th to 20thDay
43%48%25%17%3
1642
21st to endDay
46%5%11%18%16%4
1480
March1st to 10thDay
36%5%11%25%20%3
1938
11th to 20thDay
43%410%19%18%6%
1980
21st to endDay
46%5%9%19%17%4
2215
April1st to 10thDay
39%5%11%21%19%6%
2160
11th to 20thDay
36%6%8%22%21%7%
2134
21st to endDay
41%6%11%21%16%4
2160
May1st to 10thDay
42%6%12%21%16%3
2281
11th to 20thDay
44%7%12%21%14%2
2414
21st to endDay
40%8%13%26%12%2
2725
June1st to 10thDay
35%7%14%26%15%2
2520
11th to 20thDay
36%10%13%22%16%2
2520
21st to endDay
33%9%15%24%17%2
2520
July1st to 10thDay
37%10%12%22%16%3
2450
11th to 20thDay
31%9%16%26%16%3
2368
21st to endDay
38%9%14%20%18%1
2405
August1st to 10thDay
40%10%15%23%12%1
2314
11th to 20thDay
39%10%14%22%15%1
2197
21st to endDay
36%8%15%23%14%4
2376
September1st to 10thDay
37%7%14%19%19%4
2160
11th to 20thDay
33%6%12%25%21%4
2160
21st to endDay
44%6%10%20%18%2
1897
October1st to 10thDay
38%5%10%25%19%3
1800
11th to 20thDay
36%5%9%25%22%4
1800
21st to endDay
37%38%26%23%3
1980
November1st to 10thDay
32%411%27%21%4
1758
11th to 20thDay
33%411%25%21%5%
1707
21st to endDay
37%49%27%19%3
1520
December1st to 10thDay
42%5%13%26%12%3
1520
11th to 20thDay
38%5%8%32%13%3
1906
21st to endDay
44%7%11%25%12%1
2772
January1st to 10thNight
39%49%23%19%6%
2597
11th to 20thNight
44%5%11%22%16%2
2406
21st to endNight
39%48%26%21%2
2574
February1st to 10thNight
43%5%11%23%15%2
2340
11th to 20thNight
44%38%22%18%6%
2213
21st to endNight
43%49%22%17%5%
1776
March1st to 10thNight
37%5%10%25%20%3
2019
11th to 20thNight
41%6%11%21%18%4
1980
21st to endNight
42%6%9%21%16%6%
2140
April1st to 10thNight
42%5%9%19%21%5%
1800
11th to 20thNight
36%6%11%21%21%6%
1775
21st to endNight
40%6%10%25%14%5%
1800
May1st to 10thNight
41%7%12%22%14%4
1693
11th to 20thNight
43%7%11%19%16%3
1483
21st to endNight
37%9%17%22%13%2
1551
June1st to 10thNight
34%9%12%26%17%2
1440
11th to 20thNight
37%9%13%24%13%3
1440
21st to endNight
34%8%16%20%19%3
1440
July1st to 10thNight
38%9%16%20%13%4
1400
11th to 20thNight
31%10%15%26%16%2
1465
21st to endNight
31%10%16%26%15%1
1672
August1st to 10thNight
35%11%17%22%15%1
1600
11th to 20thNight
41%10%15%21%13%2
1683
21st to endNight
37%8%14%23%14%3
1980
September1st to 10thNight
38%7%10%22%17%5%
1800
11th to 20thNight
32%7%10%26%22%4
1800
21st to endNight
44%7%9%19%17%4
2057
October1st to 10thNight
40%5%10%23%18%4
2160
11th to 20thNight
36%5%8%26%22%3
2160
21st to endNight
36%5%9%24%22%4
2376
November1st to 10thNight
33%5%9%26%21%6%
2317
11th to 20thNight
36%49%22%22%6%
2470
21st to endNight
34%5%11%26%22%4
2660
December1st to 10thNight
43%5%10%24%15%3
2660
11th to 20thNight
40%410%24%18%4
3288
21st to endNight
44%7%13%22%11%1
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
28%18%33%16%5%
202
11th to 20thDay
28%22%32%15%3
255
21st to endDay
23%25%34%13%5%
264
February1st to 10thDay
24%25%36%11%4
240
11th to 20thDay
33%20%35%11%1
300
21st to endDay
29%21%32%16%2
346
March1st to 10thDay
20%24%31%22%2
420
11th to 20thDay
27%19%30%17%5%1
420
21st to endDay
23%16%33%23%42
462
April1st to 10thDay
20%23%30%20%6%1
420
11th to 20thDay
16%17%30%22%11%4
412
21st to endDay
26%13%31%23%6%1
420
May1st to 10thDay
24%16%26%21%11%2
423
11th to 20thDay
21%12%31%23%11%2
447
21st to endDay
18%6%23%27%21%5%
485
June1st to 10thDay
12%9%28%26%20%6%
450
11th to 20thDay
14%8%26%31%16%5%
450
21st to endDay
10%6%27%35%18%4
450
July1st to 10thDay
12%317%33%24%12%
445
11th to 20thDay
5%215%41%27%10%
444
21st to endDay
9%320%38%22%7%
488
August1st to 10thDay
10%5%20%31%25%9%
446
11th to 20thDay
11%416%32%26%11%
439
21st to endDay
9%320%31%24%13%
495
September1st to 10thDay
16%5%20%24%20%14%
450
11th to 20thDay
14%418%36%17%11%
450
21st to endDay
22%12%24%26%13%4
450
October1st to 10thDay
21%6%23%25%18%7%
450
11th to 20thDay
16%13%27%27%14%3
450
21st to endDay
18%12%34%25%8%3
495
November1st to 10thDay
16%12%30%28%11%3
408
11th to 20thDay
17%15%33%24%9%1
367
21st to endDay
22%20%28%20%9%1
180
December1st to 10thDay
18%20%38%16%6%2
180
11th to 20thDay
23%21%28%21%7%1
180
21st to endDay
25%16%32%20%7%1
198
January1st to 10thNight
20%18%39%19%4
760
11th to 20thNight
22%13%35%25%5%
741
21st to endNight
19%16%38%24%2
792
February1st to 10thNight
21%16%35%26%3
720
11th to 20thNight
25%19%38%16%2
703
21st to endNight
26%17%35%20%2
592
March1st to 10thNight
19%14%41%23%3
720
11th to 20thNight
23%13%38%19%6%1
720
21st to endNight
18%14%42%23%31
792
April1st to 10thNight
18%18%39%22%4
720
11th to 20thNight
16%14%34%29%7%
711
21st to endNight
22%8%33%27%9%
720
May1st to 10thNight
18%9%32%30%11%
613
11th to 20thNight
18%6%31%35%10%
421
21st to endNight
15%324%38%19%1
389
June1st to 10thNight
11%327%36%21%2
360
11th to 20thNight
14%5%20%41%19%1
360
21st to endNight
10%323%46%17%1
360
July1st to 10thNight
9%221%38%29%2
350
11th to 20thNight
7%212%44%31%4
421
21st to endNight
8%219%39%29%3
591
August1st to 10thNight
8%212%45%29%3
537
11th to 20thNight
13%316%39%26%2
619
21st to endNight
12%217%35%29%5%
792
September1st to 10thNight
16%317%33%27%5%
720
11th to 20thNight
11%316%38%29%4
720
21st to endNight
19%6%23%33%18%1
720
October1st to 10thNight
19%6%20%31%20%5%
720
11th to 20thNight
17%9%27%30%17%1
720
21st to endNight
18%11%32%26%13%1
792
November1st to 10thNight
14%8%34%30%12%2
740
11th to 20thNight
18%13%30%29%9%1
760
21st to endNight
17%14%32%27%10%1
760
December1st to 10thNight
20%14%34%23%8%1
760
11th to 20thNight
18%11%41%25%5%
760
21st to endNight
21%12%35%29%3
836
Page generated at 2024-01-13 01:38:11. Version ac07

Copyright 2024 Attilla Danko


Beacon Field Observatory Clear Sky Chart |Charts Home