BRAC Ivy Hill Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the BRAC Ivy Hill Site clear sky chart from 2005-11-06 to 2024-01-13.

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
43%
24110
21%
74727
13%
24062
52%
24062
26%
46734

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
25%
759
24%
2459
9%
757
43%
757
21%
1478
January11th to 20thNight
28%
729
23%
2367
11%
729
44%
729
20%
1510
January21st to endNight
24%
792
25%
2574
11%
792
43%
792
24%
1542
February1st to 10thNight
25%
720
19%
2340
9%
720
38%
720
23%
1438
February11th to 20thNight
16%
700
19%
2273
5%
699
33%
699
18%
1449
February21st to endNight
25%
592
26%
1677
10%
592
41%
592
23%
1111
March1st to 10thNight
31%
720
26%
1980
12%
720
45%
720
30%
1211
March11th to 20thNight
28%
720
19%
1980
8%
720
39%
720
22%
1337
March21st to endNight
32%
792
20%
2178
9%
792
41%
792
25%
1444
April1st to 10thNight
31%
720
21%
1877
8%
720
40%
720
27%
1219
April11th to 20thNight
38%
711
23%
1775
9%
711
47%
711
33%
1135
April21st to endNight
39%
667
22%
1747
9%
667
47%
667
29%
1156
May1st to 10thNight
40%
540
16%
1620
7%
540
46%
540
24%
1066
May11th to 20thNight
45%
531
14%
1592
8%
531
49%
531
22%
1103
May21st to endNight
59%
582
15%
1745
12%
582
62%
582
27%
1141
June1st to 10thNight
64%
450
18%
1530
18%
450
67%
450
29%
896
June11th to 20thNight
61%
360
16%
1440
18%
360
66%
360
24%
850
June21st to endNight
69%
535
17%
1615
14%
535
71%
535
31%
992
July1st to 10thNight
66%
525
14%
1575
12%
525
67%
525
27%
1026
July11th to 20thNight
77%
522
15%
1566
14%
522
78%
522
35%
935
July21st to endNight
72%
591
17%
1672
14%
558
73%
558
30%
1057
August1st to 10thNight
65%
537
15%
1600
12%
534
66%
534
24%
1095
August11th to 20thNight
64%
534
20%
1598
16%
534
65%
534
25%
1070
August21st to endNight
65%
785
16%
1973
11%
785
66%
785
29%
1366
September1st to 10thNight
65%
720
22%
1800
15%
720
67%
720
33%
1202
September11th to 20thNight
60%
720
23%
1944
20%
720
61%
720
29%
1287
September21st to endNight
46%
720
19%
2002
15%
720
51%
720
22%
1417
October1st to 10thNight
52%
720
23%
2160
20%
720
58%
720
31%
1317
October11th to 20thNight
47%
720
27%
2160
21%
720
57%
720
30%
1300
October21st to endNight
46%
792
31%
2376
22%
792
59%
792
34%
1361
November1st to 10thNight
43%
740
28%
2221
19%
740
54%
740
32%
1303
November11th to 20thNight
40%
760
27%
2379
16%
760
55%
760
28%
1387
November21st to endNight
40%
760
25%
2658
17%
760
53%
760
27%
1496
December1st to 10thNight
28%
760
21%
2660
10%
760
44%
760
20%
1677
December11th to 20thNight
31%
759
24%
3169
13%
758
46%
758
20%
1830
December21st to endNight
27%
825
15%
4445
10%
817
43%
817
13%
2530

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
14%5%25%5%35%5%6%8%43%
74512
Night
15%5%245%3445%7%45%
75188
TransparencyDay
38%8%13%22%16%3
74233
Night
38%6%12%22%18%4
74986
SeeingDay
19%11%24%25%16%6%
13959
Night
17%8%25%32%16%2
24128

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%5%25%5%2445%5%47%
1706
11th to 20thDay
18%7%25%435%5%47%41%
1638
21st to endDay
17%6%245%3445%5%46%
1782
February1st to 10thDay
13%7%25%6%45%5%7%7%40%
1620
11th to 20thDay
20%5%245%35%45%7%42%
1573
21st to endDay
19%7%35%5%335%46%39%
1574
March1st to 10thDay
14%5%24224446%52%
1980
11th to 20thDay
17%6%36%5%345%5%7%40%
1980
21st to endDay
18%6%36%5%3445%7%40%
2178
April1st to 10thDay
11%4244345%5%7%51%
2081
11th to 20thDay
14%5%345%245%5%7%47%
2134
21st to endDay
16%5%25%6%2445%7%43%
2227
May1st to 10thDay
14%6%245%46%6%6%9%39%
2340
11th to 20thDay
18%5%25%5%45%5%6%9%37%
2301
21st to endDay
14%426%5%35%6%6%9%39%
2531
June1st to 10thDay
10%325%5%45%6%6%10%45%
2416
11th to 20thDay
11%425%5%35%6%7%10%41%
2511
21st to endDay
8%435%6%45%6%7%11%43%
2340
July1st to 10thDay
9%5%25%5%47%6%8%12%37%
2340
11th to 20thDay
6%425%6%46%7%8%11%40%
2340
21st to endDay
9%5%37%7%46%7%8%9%35%
2547
August1st to 10thDay
12%6%25%6%45%6%7%11%36%
2327
11th to 20thDay
14%5%26%6%47%6%6%9%35%
2290
21st to endDay
11%5%26%5%35%5%6%10%41%
2376
September1st to 10thDay
13%435%5%2445%7%49%
2160
11th to 20thDay
14%5%345%25%5%5%7%46%
2012
21st to endDay
23%5%35%43445%5%39%
1958
October1st to 10thDay
16%5%24423345%52%
1800
11th to 20thDay
17%413423346%53%
1800
21st to endDay
14%5%24424346%51%
1980
November1st to 10thDay
13%423324435%57%
1857
11th to 20thDay
14%5%24424446%52%
1794
21st to endDay
15%5%1432435%8%50%
1520
December1st to 10thDay
18%6%25%4346%6%8%38%
1520
11th to 20thDay
17%423423346%54%
1910
21st to endDay
21%5%35%43446%8%38%
3069
January1st to 10thNight
15%5%35%434445%49%
2459
11th to 20thNight
15%6%345%25%5%5%6%42%
2367
21st to endNight
15%5%245%3445%7%46%
2574
February1st to 10thNight
15%6%245%245%6%8%43%
2340
11th to 20thNight
20%7%34424445%43%
2273
21st to endNight
17%6%346%235%5%6%43%
1677
March1st to 10thNight
13%42432446%6%51%
1980
11th to 20thNight
19%5%25%5%25%5%6%7%40%
1980
21st to endNight
15%6%25%5%2445%7%45%
2178
April1st to 10thNight
15%6%2442445%7%47%
1877
11th to 20thNight
13%5%15%42445%7%50%
1775
21st to endNight
15%435%435%5%5%7%44%
1747
May1st to 10thNight
14%5%25%5%35%5%6%7%42%
1620
11th to 20thNight
17%7%35%5%3445%8%38%
1592
21st to endNight
16%425%5%35%46%9%42%
1744
June1st to 10thNight
10%325%5%346%7%11%43%
1530
11th to 20thNight
10%5%36%6%35%46%8%44%
1440
21st to endNight
8%3245%45%5%6%12%45%
1615
July1st to 10thNight
9%5%36%5%345%7%10%43%
1620
11th to 20thNight
6%424436%6%8%11%46%
1620
21st to endNight
7%5%35%6%37%6%7%11%41%
1771
August1st to 10thNight
12%5%36%5%46%5%7%9%39%
1611
11th to 20thNight
12%6%35%6%46%5%7%7%40%
1598
21st to endNight
11%6%35%6%36%6%7%10%38%
1973
September1st to 10thNight
13%5%24435%5%6%7%46%
1800
11th to 20thNight
15%6%245%345%5%6%45%
1944
21st to endNight
23%7%35%5%24346%39%
2002
October1st to 10thNight
16%5%14423336%51%
2160
11th to 20thNight
16%5%24424345%51%
2160
21st to endNight
15%41332345%6%54%
2376
November1st to 10thNight
14%6%35%32333454%
2221
11th to 20thNight
14%4245%34446%51%
2379
21st to endNight
13%325%43445%8%50%
2658
December1st to 10thNight
19%6%34424446%43%
2660
11th to 20thNight
16%6%245%33446%47%
3285
21st to endNight
18%6%25%5%345%6%8%39%
4582

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
38%6%10%22%19%5%
1707
11th to 20thDay
44%6%9%21%18%2
1638
21st to endDay
40%6%8%23%19%4
1782
February1st to 10thDay
40%7%12%23%15%3
1620
11th to 20thDay
42%5%10%21%18%4
1582
21st to endDay
46%6%12%15%17%5%
1574
March1st to 10thDay
34%5%10%24%22%5%
1980
11th to 20thDay
43%7%10%18%16%6%
1980
21st to endDay
44%7%11%20%15%4
2178
April1st to 10thDay
32%6%12%23%19%8%
2081
11th to 20thDay
35%6%12%22%20%6%
2134
21st to endDay
41%7%11%22%14%5%
2227
May1st to 10thDay
40%9%16%19%13%3
2340
11th to 20thDay
43%10%14%22%10%2
2305
21st to endDay
40%10%15%23%11%
2531
June1st to 10thDay
33%10%16%25%14%1
2416
11th to 20thDay
36%11%16%20%16%2
2511
21st to endDay
34%11%16%23%13%2
2340
July1st to 10thDay
38%12%15%19%14%3
2275
11th to 20thDay
33%12%19%20%15%1
2271
21st to endDay
40%11%15%21%12%1
2405
August1st to 10thDay
40%11%16%24%8%1
2314
11th to 20thDay
43%11%16%20%10%
2290
21st to endDay
37%9%18%20%13%2
2376
September1st to 10thDay
35%9%13%20%19%4
2160
11th to 20thDay
38%7%10%24%18%3
2012
21st to endDay
47%7%9%17%18%2
1958
October1st to 10thDay
35%5%10%26%20%4
1800
11th to 20thDay
33%5%11%25%22%4
1800
21st to endDay
35%48%26%20%7%
1980
November1st to 10thDay
31%410%23%27%5%
1857
11th to 20thDay
34%5%9%23%21%8%
1794
21st to endDay
33%5%10%23%24%4
1520
December1st to 10thDay
43%8%11%19%16%4
1520
11th to 20thDay
34%49%25%21%8%
1906
21st to endDay
42%6%12%25%13%2
3069
January1st to 10thNight
39%410%21%20%7%
2459
11th to 20thNight
41%6%10%20%18%4
2367
21st to endNight
37%5%10%24%20%4
2574
February1st to 10thNight
38%6%13%22%18%3
2340
11th to 20thNight
44%410%19%18%6%
2275
21st to endNight
41%6%9%22%15%6%
1677
March1st to 10thNight
32%6%10%25%21%5%
1980
11th to 20thNight
42%6%10%19%18%4
1980
21st to endNight
40%7%10%21%17%5%
2178
April1st to 10thNight
38%5%11%19%21%6%
1877
11th to 20thNight
33%6%11%22%22%6%
1775
21st to endNight
39%6%12%23%17%4
1747
May1st to 10thNight
40%9%14%20%14%3
1620
11th to 20thNight
44%9%12%22%11%2
1593
21st to endNight
39%8%16%25%11%1
1745
June1st to 10thNight
33%9%16%27%14%1
1530
11th to 20thNight
38%7%17%20%16%2
1440
21st to endNight
32%10%17%20%16%4
1615
July1st to 10thNight
36%11%17%17%14%5%
1575
11th to 20thNight
29%10%23%23%14%2
1566
21st to endNight
34%10%18%25%13%
1672
August1st to 10thNight
41%11%17%19%12%1
1600
11th to 20thNight
40%10%15%23%12%1
1598
21st to endNight
39%10%17%21%11%3
1973
September1st to 10thNight
36%8%15%19%18%5%
1800
11th to 20thNight
38%8%10%22%19%2
1944
21st to endNight
48%6%8%19%16%3
2002
October1st to 10thNight
37%5%10%25%20%3
2160
11th to 20thNight
36%5%8%26%21%5%
2160
21st to endNight
32%49%23%26%7%
2376
November1st to 10thNight
35%49%21%25%7%
2221
11th to 20thNight
34%5%8%21%24%8%
2379
21st to endNight
34%5%9%25%21%6%
2658
December1st to 10thNight
43%5%9%24%16%4
2660
11th to 20thNight
38%49%21%21%7%
3288
21st to endNight
41%5%12%22%18%2
4582

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
27%26%26%16%5%1
270
11th to 20thDay
28%21%35%15%1
246
21st to endDay
31%22%32%11%4
264
February1st to 10thDay
24%24%36%12%4
240
11th to 20thDay
41%18%33%6%1
240
21st to endDay
30%20%31%16%4
306
March1st to 10thDay
25%16%33%21%4
420
11th to 20thDay
21%22%33%18%5%
420
21st to endDay
23%15%34%21%5%1
462
April1st to 10thDay
21%21%26%24%7%1
420
11th to 20thDay
20%15%25%24%12%4
412
21st to endDay
24%11%31%20%12%2
420
May1st to 10thDay
21%13%31%21%10%3
423
11th to 20thDay
19%11%24%28%15%4
447
21st to endDay
19%419%29%21%8%
485
June1st to 10thDay
12%428%31%19%7%
450
11th to 20thDay
12%6%20%34%18%10%
450
21st to endDay
10%326%31%23%7%
450
July1st to 10thDay
10%416%27%29%13%
445
11th to 20thDay
5%213%37%31%13%
444
21st to endDay
10%217%32%28%11%
488
August1st to 10thDay
14%418%25%26%13%
446
11th to 20thDay
12%316%29%26%15%
439
21st to endDay
11%311%29%26%20%
495
September1st to 10thDay
14%5%13%24%27%18%
450
11th to 20thDay
15%5%12%28%28%11%
450
21st to endDay
26%9%17%25%18%5%
450
October1st to 10thDay
21%6%19%29%19%6%
450
11th to 20thDay
16%12%22%27%19%3
450
21st to endDay
17%12%28%31%10%3
495
November1st to 10thDay
19%9%28%28%13%3
455
11th to 20thDay
20%16%26%24%11%2
354
21st to endDay
20%19%27%22%9%2
180
December1st to 10thDay
24%17%35%17%8%
180
11th to 20thDay
24%13%28%25%7%2
180
21st to endDay
28%14%32%18%6%1
283
January1st to 10thNight
21%16%34%26%4
760
11th to 20thNight
18%16%31%32%2
729
21st to endNight
19%12%41%25%3
792
February1st to 10thNight
18%14%38%27%3
720
11th to 20thNight
27%16%36%21%
703
21st to endNight
19%15%38%26%2
592
March1st to 10thNight
16%14%35%30%5%
720
11th to 20thNight
23%13%31%26%7%1
720
21st to endNight
18%12%33%30%6%
792
April1st to 10thNight
18%15%33%28%6%
720
11th to 20thNight
15%12%30%30%12%1
711
21st to endNight
18%5%30%37%9%
667
May1st to 10thNight
15%9%30%31%14%1
540
11th to 20thNight
19%6%21%36%16%2
531
21st to endNight
17%211%33%32%4
584
June1st to 10thNight
10%214%44%28%3
450
11th to 20thNight
12%215%40%28%3
360
21st to endNight
10%211%45%29%4
535
July1st to 10thNight
12%110%35%36%5%
525
11th to 20thNight
6%17%32%49%6%
522
21st to endNight
8%18%43%35%4
591
August1st to 10thNight
13%39%37%34%5%
537
11th to 20thNight
14%29%34%36%4
534
21st to endNight
12%210%34%37%5%
785
September1st to 10thNight
14%210%31%36%7%
720
11th to 20thNight
15%212%33%32%5%
720
21st to endNight
26%416%32%21%1
720
October1st to 10thNight
19%5%18%29%25%4
720
11th to 20thNight
16%8%24%34%16%2
720
21st to endNight
16%7%26%37%12%2
792
November1st to 10thNight
16%7%26%34%13%2
740
11th to 20thNight
17%10%29%32%12%1
760
21st to endNight
15%11%29%34%10%1
760
December1st to 10thNight
22%11%32%28%6%
760
11th to 20thNight
17%9%36%32%5%
760
21st to endNight
22%14%30%31%4
836
Page generated at 2024-01-10 01:25:00. Version ac07

Copyright 2024 Attilla Danko


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