Burland Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burland Observatory clear sky chart from 2005-11-06 to 2024-01-12.

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
38%
24542
28%
74452
12%
24481
54%
24481
38%
39110

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
28%
950
32%
2647
9%
946
50%
946
40%
1354
January11th to 20thNight
23%
838
34%
2467
10%
838
48%
838
38%
1201
January21st to endNight
22%
792
32%
2574
10%
792
49%
792
37%
1278
February1st to 10thNight
16%
720
29%
2340
6%
720
43%
720
36%
1125
February11th to 20thNight
20%
703
30%
2131
7%
700
45%
700
37%
1083
February21st to endNight
22%
592
37%
1776
6%
592
52%
592
37%
904
March1st to 10thNight
26%
720
29%
2157
7%
720
45%
720
40%
1094
March11th to 20thNight
31%
720
27%
1980
11%
720
44%
720
38%
1124
March21st to endNight
24%
675
28%
2061
6%
675
47%
675
33%
1133
April1st to 10thNight
24%
540
26%
1800
7%
540
48%
540
33%
908
April11th to 20thNight
27%
533
24%
1777
10%
533
46%
533
28%
977
April21st to endNight
31%
540
23%
1800
10%
540
49%
540
29%
1012
May1st to 10thNight
38%
540
20%
1713
10%
540
50%
540
27%
1050
May11th to 20thNight
46%
531
16%
1418
9%
531
52%
531
31%
894
May21st to endNight
47%
584
19%
1552
10%
582
56%
582
36%
908
June1st to 10thNight
63%
540
24%
1440
17%
540
68%
540
48%
779
June11th to 20thNight
51%
540
25%
1440
14%
540
59%
540
49%
772
June21st to endNight
67%
540
25%
1440
19%
540
73%
540
50%
771
July1st to 10thNight
68%
525
20%
1400
16%
525
72%
525
38%
825
July11th to 20thNight
72%
522
26%
1392
20%
522
77%
522
48%
758
July21st to endNight
74%
591
17%
1572
15%
558
76%
558
31%
956
August1st to 10thNight
69%
537
15%
1602
13%
534
71%
534
32%
924
August11th to 20thNight
69%
534
25%
1765
23%
534
75%
534
39%
912
August21st to endNight
65%
594
25%
1980
24%
594
70%
594
35%
1101
September1st to 10thNight
64%
540
29%
1800
24%
540
73%
540
39%
936
September11th to 20thNight
60%
540
34%
1804
27%
540
71%
540
44%
878
September21st to endNight
54%
544
32%
1984
24%
544
67%
544
40%
947
October1st to 10thNight
41%
720
28%
2160
13%
720
54%
720
42%
1165
October11th to 20thNight
42%
720
36%
2160
14%
720
59%
720
53%
991
October21st to endNight
36%
811
33%
2395
13%
811
52%
811
43%
1246
November1st to 10thNight
35%
925
35%
2405
10%
925
52%
925
53%
1209
November11th to 20thNight
27%
950
37%
2470
10%
950
47%
950
47%
1266
November21st to endNight
31%
950
31%
2573
9%
950
48%
950
44%
1352
December1st to 10thNight
27%
950
29%
2660
9%
950
45%
950
40%
1352
December11th to 20thNight
23%
950
29%
3119
7%
949
43%
949
34%
1590
December21st to endNight
19%
1041
19%
4698
5%
1026
41%
1026
22%
2335

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
5%6%35%5%35%5%6%8%49%
74756
Night
35%2442445%8%59%
74967
TransparencyDay
31%7%12%22%21%8%
74466
Night
23%6%13%25%24%8%
74780
SeeingDay
10%16%34%26%11%2
14384
Night
6%12%39%30%12%2
24547

By Month

Percentage Cloud Cover SW (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
425%323448%65%
1518
11th to 20thDay
15%36%5%3435%7%57%
1529
21st to endDay
45%7%5%245%5%8%54%
1782
February1st to 10thDay
16%28%5%2445%8%57%
1620
11th to 20thDay
325%4345%5%8%60%
1713
21st to endDay
16%35%5%2446%6%57%
1480
March1st to 10thDay
26%36%42445%9%55%
1800
11th to 20thDay
48%45%5%345%5%8%48%
1980
21st to endDay
210%36%425%5%6%10%46%
2294
April1st to 10thDay
36%35%435%5%6%9%50%
2160
11th to 20thDay
7%10%36%6%36%5%5%8%42%
2131
21st to endDay
7%11%35%5%35%5%6%8%41%
2160
May1st to 10thDay
8%10%46%6%35%5%7%9%37%
2242
11th to 20thDay
11%10%45%6%46%6%6%9%34%
2478
21st to endDay
8%6%25%6%47%7%7%8%40%
2724
June1st to 10thDay
5%5%245%46%6%8%9%46%
2520
11th to 20thDay
6%5%24435%6%6%10%49%
2520
21st to endDay
5%425%6%47%6%8%9%43%
2520
July1st to 10thDay
7%5%25%6%5%7%7%8%9%39%
2520
11th to 20thDay
5%5%26%6%47%7%7%10%41%
2520
21st to endDay
9%6%36%7%47%8%8%9%33%
2651
August1st to 10thDay
9%7%37%8%5%7%8%8%7%32%
2328
11th to 20thDay
6%5%15%7%47%6%7%8%44%
2135
21st to endDay
8%5%26%6%46%7%6%8%42%
2376
September1st to 10thDay
6%5%35%4445%5%6%52%
2160
11th to 20thDay
7%4246%345%5%7%53%
2155
21st to endDay
5%424334447%61%
1972
October1st to 10thDay
5%5%25%435%45%7%55%
1800
11th to 20thDay
431322345%5%67%
1800
21st to endDay
46%25%324446%60%
1940
November1st to 10thDay
142331345%7%68%
1673
11th to 20thDay
143442335%7%65%
1710
21st to endDay
15%26%423448%60%
1605
December1st to 10thDay
436%5%2335%8%60%
1520
11th to 20thDay
15%2432346%10%62%
1926
21st to endDay
16%47%6%2445%9%53%
2794
January1st to 10thNight
325%42345%7%66%
2647
11th to 20thNight
142342335%8%66%
2467
21st to endNight
436%43346%6%61%
2574
February1st to 10thNight
435%323349%64%
2340
11th to 20thNight
1425%42345%7%62%
2131
21st to endNight
5%25%42446%6%62%
1776
March1st to 10thNight
142432347%9%60%
2157
11th to 20thNight
47%25%433447%58%
1980
21st to endNight
27%35%423447%58%
2061
April1st to 10thNight
26%34323348%62%
1800
11th to 20thNight
5%9%35%323437%55%
1777
21st to endNight
6%9%34424447%53%
1800
May1st to 10thNight
7%8%35%4445%6%8%46%
1713
11th to 20thNight
11%6%245%3445%8%49%
1417
21st to endNight
5%435%4245%6%7%55%
1552
June1st to 10thNight
43132235%7%10%60%
1440
11th to 20thNight
5%31232346%8%63%
1440
21st to endNight
32133345%7%10%58%
1440
July1st to 10thNight
5%324435%7%6%10%51%
1440
11th to 20thNight
2224425%5%7%9%58%
1440
21st to endNight
4424446%7%9%12%43%
1664
August1st to 10thNight
43145%45%6%8%9%50%
1611
11th to 20thNight
6%324425%5%6%8%55%
1765
21st to endNight
5%4245%25%6%6%9%53%
1980
September1st to 10thNight
6%32443447%8%55%
1800
11th to 20thNight
6%21332445%6%63%
1804
21st to endNight
45%2333435%5%63%
1984
October1st to 10thNight
6%323425%35%6%62%
2160
11th to 20thNight
2313222336%73%
2160
21st to endNight
37%2442335%6%61%
2395
November1st to 10thNight
1312324348%70%
2405
11th to 20thNight
1424323347%68%
2470
21st to endNight
15%2442435%8%62%
2573
December1st to 10thNight
13235%2335%10%63%
2660
11th to 20thNight
1425%42446%10%58%
3271
21st to endNight
17%46%6%3445%7%53%
4873

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
19%5%15%31%24%6%
1519
11th to 20thDay
26%5%12%27%22%7%
1529
21st to endDay
28%413%30%19%6%
1782
February1st to 10thDay
27%415%28%19%7%
1620
11th to 20thDay
22%412%27%28%6%
1723
21st to endDay
26%411%25%25%10%
1480
March1st to 10thDay
26%5%12%27%24%5%
1800
11th to 20thDay
32%6%11%26%20%5%
1980
21st to endDay
33%7%12%26%18%4
2294
April1st to 10thDay
30%8%12%23%18%9%
2160
11th to 20thDay
40%6%12%18%18%6%
2134
21st to endDay
39%7%11%24%16%3
2160
May1st to 10thDay
42%8%12%20%15%3
2242
11th to 20thDay
44%10%14%21%9%2
2482
21st to endDay
38%9%12%19%15%6%
2724
June1st to 10thDay
30%10%15%20%17%8%
2520
11th to 20thDay
28%8%10%18%21%15%
2520
21st to endDay
32%10%12%18%19%10%
2520
July1st to 10thDay
37%11%11%15%18%8%
2451
11th to 20thDay
36%9%13%20%16%5%
2445
21st to endDay
42%12%16%17%10%3
2504
August1st to 10thDay
45%12%13%15%12%5%
2313
11th to 20thDay
34%9%12%18%18%8%
2135
21st to endDay
37%7%11%19%20%6%
2376
September1st to 10thDay
31%7%9%17%23%13%
2160
11th to 20thDay
28%6%10%19%27%10%
2155
21st to endDay
24%5%8%22%32%9%
1972
October1st to 10thDay
28%7%9%20%25%11%
1800
11th to 20thDay
19%49%24%33%11%
1800
21st to endDay
25%311%25%25%11%
1940
November1st to 10thDay
16%5%11%21%33%13%
1673
11th to 20thDay
18%49%31%28%9%
1710
21st to endDay
23%49%25%26%13%
1605
December1st to 10thDay
22%7%15%27%22%8%
1520
11th to 20thDay
18%5%14%32%24%6%
1924
21st to endDay
25%9%10%23%25%9%
2794
January1st to 10thNight
19%5%13%31%25%7%
2647
11th to 20thNight
17%5%13%28%29%8%
2467
21st to endNight
22%5%12%28%25%8%
2574
February1st to 10thNight
20%5%13%33%22%8%
2340
11th to 20thNight
21%5%10%30%27%7%
2131
21st to endNight
22%48%29%27%10%
1776
March1st to 10thNight
20%5%12%26%31%6%
2157
11th to 20thNight
27%5%10%28%25%6%
1980
21st to endNight
27%5%13%27%23%5%
2061
April1st to 10thNight
23%7%12%28%23%8%
1800
11th to 20thNight
30%6%12%27%20%6%
1777
21st to endNight
32%6%13%28%18%4
1800
May1st to 10thNight
34%10%12%24%15%5%
1713
11th to 20thNight
33%9%22%21%14%2
1418
21st to endNight
27%8%18%22%19%6%
1552
June1st to 10thNight
18%9%21%27%15%10%
1440
11th to 20thNight
18%9%14%20%23%17%
1440
21st to endNight
19%7%14%24%25%10%
1440
July1st to 10thNight
26%10%17%21%18%8%
1400
11th to 20thNight
19%9%16%29%21%6%
1392
21st to endNight
27%15%23%23%10%3
1572
August1st to 10thNight
28%11%21%21%14%5%
1602
11th to 20thNight
24%7%16%24%22%7%
1765
21st to endNight
27%9%14%24%20%6%
1980
September1st to 10thNight
25%6%12%21%23%13%
1800
11th to 20thNight
22%5%12%23%24%14%
1804
21st to endNight
22%5%9%25%30%8%
1984
October1st to 10thNight
23%6%13%21%26%11%
2160
11th to 20thNight
14%410%23%33%14%
2160
21st to endNight
24%410%25%28%9%
2395
November1st to 10thNight
15%411%25%31%14%
2405
11th to 20thNight
17%410%29%31%10%
2470
21st to endNight
21%411%24%28%12%
2573
December1st to 10thNight
19%5%16%25%26%9%
2660
11th to 20thNight
20%7%13%26%27%7%
3272
21st to endNight
25%8%11%23%23%10%
4873

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
9%15%42%24%9%1
270
11th to 20thDay
5%23%47%22%3
243
21st to endDay
222%54%18%41
264
February1st to 10thDay
9%36%42%10%11
240
11th to 20thDay
10%31%45%12%3
240
21st to endDay
11%24%47%17%2
198
March1st to 10thDay
11%23%39%21%6%
240
11th to 20thDay
15%21%41%20%4
420
21st to endDay
17%30%34%16%3
462
April1st to 10thDay
17%26%32%20%4
420
11th to 20thDay
25%30%28%14%31
412
21st to endDay
19%25%35%16%41
420
May1st to 10thDay
14%22%38%21%5%1
501
11th to 20thDay
18%13%32%27%8%1
625
21st to endDay
12%15%29%28%14%2
679
June1st to 10thDay
7%11%30%32%16%3
630
11th to 20thDay
7%12%36%29%13%3
630
21st to endDay
5%10%38%28%15%4
630
July1st to 10thDay
7%5%22%40%21%5%
621
11th to 20thDay
6%423%37%24%6%
618
21st to endDay
10%5%19%36%24%6%
593
August1st to 10thDay
11%6%29%33%17%4
447
11th to 20thDay
7%6%31%38%15%3
437
21st to endDay
8%8%30%37%14%3
495
September1st to 10thDay
9%10%33%32%15%2
450
11th to 20thDay
8%12%35%31%12%2
445
21st to endDay
8%13%31%29%13%5%
270
October1st to 10thDay
8%18%30%26%14%5%
270
11th to 20thDay
5%21%40%24%8%1
270
21st to endDay
9%19%40%25%6%1
297
November1st to 10thDay
9%21%43%17%9%1
270
11th to 20thDay
11%20%39%24%6%1
270
21st to endDay
8%20%44%22%6%
270
December1st to 10thDay
12%23%39%19%6%1
270
11th to 20thDay
8%17%52%18%5%
270
21st to endDay
12%25%41%15%7%1
297
January1st to 10thNight
419%42%26%7%2
950
11th to 20thNight
6%22%45%20%6%2
838
21st to endNight
415%53%22%5%
792
February1st to 10thNight
5%19%57%15%4
720
11th to 20thNight
418%51%21%5%
704
21st to endNight
420%49%25%2
592
March1st to 10thNight
417%49%25%5%1
720
11th to 20thNight
6%13%46%27%8%1
720
21st to endNight
6%15%49%24%5%
675
April1st to 10thNight
8%15%49%24%3
540
11th to 20thNight
11%17%40%25%7%1
533
21st to endNight
10%16%39%27%7%1
540
May1st to 10thNight
11%8%38%31%11%1
540
11th to 20thNight
14%5%30%38%11%2
531
21st to endNight
6%9%30%37%15%2
584
June1st to 10thNight
5%424%47%18%3
540
11th to 20thNight
6%5%34%40%12%2
540
21st to endNight
3224%46%24%2
540
July1st to 10thNight
8%214%43%31%2
525
11th to 20thNight
2116%40%38%3
522
21st to endNight
7%38%45%34%4
591
August1st to 10thNight
6%114%45%31%3
537
11th to 20thNight
7%218%45%26%3
534
21st to endNight
5%319%43%26%4
594
September1st to 10thNight
6%221%43%24%5%
540
11th to 20thNight
7%225%42%19%4
540
21st to endNight
6%6%29%39%17%3
544
October1st to 10thNight
6%9%41%30%12%3
720
11th to 20thNight
410%41%33%9%3
720
21st to endNight
7%10%43%27%11%1
811
November1st to 10thNight
313%46%28%9%1
925
11th to 20thNight
6%17%47%23%7%1
950
21st to endNight
415%46%27%7%1
950
December1st to 10thNight
6%19%44%27%4
950
11th to 20thNight
417%51%21%6%1
950
21st to endNight
7%20%46%21%5%1
1045
Page generated at 2024-01-08 20:31:27. Version ac07

Copyright 2024 Attilla Danko


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