Red Barn Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Red Barn 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
53%
24037
22%
74470
17%
23982
60%
23982
29%
45666

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
32%
759
23%
2459
11%
757
49%
757
25%
1501
January11th to 20thNight
39%
744
26%
2417
18%
744
51%
744
28%
1440
January21st to endNight
30%
792
25%
2452
12%
792
44%
792
24%
1552
February1st to 10thNight
39%
720
23%
2160
13%
720
49%
720
28%
1340
February11th to 20thNight
35%
703
24%
2098
10%
699
48%
699
28%
1310
February21st to endNight
38%
592
27%
1776
16%
592
48%
592
29%
1104
March1st to 10thNight
43%
720
29%
2052
18%
720
52%
720
36%
1211
March11th to 20thNight
41%
720
25%
1980
14%
720
51%
720
32%
1236
March21st to endNight
43%
792
25%
2178
12%
792
54%
792
35%
1295
April1st to 10thNight
46%
720
25%
1980
17%
720
53%
720
35%
1194
April11th to 20thNight
51%
617
24%
1859
18%
617
58%
617
34%
1080
April21st to endNight
59%
540
34%
1670
25%
540
68%
540
42%
877
May1st to 10thNight
59%
540
29%
1620
20%
540
67%
540
41%
879
May11th to 20thNight
63%
531
19%
1592
14%
531
66%
531
34%
955
May21st to endNight
71%
582
22%
1744
18%
582
73%
582
33%
1054
June1st to 10thNight
71%
540
15%
1620
14%
540
71%
540
28%
1060
June11th to 20thNight
75%
540
15%
1620
13%
540
76%
540
33%
993
June21st to endNight
72%
540
13%
1620
11%
540
72%
540
25%
1108
July1st to 10thNight
71%
525
11%
1575
10%
525
71%
525
23%
1093
July11th to 20thNight
74%
522
11%
1566
12%
522
74%
522
26%
1043
July21st to endNight
80%
591
14%
1672
15%
558
81%
558
32%
1058
August1st to 10thNight
71%
537
10%
1600
11%
534
71%
534
25%
1087
August11th to 20thNight
71%
534
11%
1774
13%
534
71%
534
20%
1212
August21st to endNight
65%
636
13%
2022
14%
636
65%
636
20%
1408
September1st to 10thNight
63%
720
15%
1980
14%
720
64%
720
24%
1371
September11th to 20thNight
62%
720
17%
1980
15%
720
63%
720
26%
1351
September21st to endNight
64%
720
24%
1980
21%
720
67%
720
32%
1269
October1st to 10thNight
60%
720
29%
1980
23%
720
65%
720
39%
1173
October11th to 20thNight
61%
720
35%
2082
29%
720
68%
720
41%
1154
October21st to endNight
57%
792
30%
2376
27%
792
64%
792
37%
1350
November1st to 10thNight
55%
740
30%
2247
25%
740
63%
740
38%
1234
November11th to 20thNight
46%
760
28%
2470
22%
760
58%
760
33%
1368
November21st to endNight
46%
760
26%
2470
20%
760
56%
760
31%
1420
December1st to 10thNight
41%
760
25%
2470
17%
760
53%
760
29%
1444
December11th to 20thNight
39%
759
26%
2912
17%
758
50%
758
24%
1669
December21st to endNight
38%
829
15%
4417
18%
817
47%
817
13%
2773

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
10%6%35%6%45%6%6%8%42%
74892
Night
10%6%35%5%35%5%6%8%45%
74924
TransparencyDay
39%6%13%19%17%7%
74615
Night
37%6%12%18%19%9%
74720
SeeingDay
12%418%25%24%18%
13959
Night
12%5%20%33%25%5%
24048

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
12%7%35%6%35%5%5%6%44%
1706
11th to 20thDay
11%6%35%5%2445%8%47%
1665
21st to endDay
15%6%35%5%3445%6%45%
1899
February1st to 10thDay
15%7%26%5%335%5%7%41%
1800
11th to 20thDay
15%6%25%43445%7%46%
1748
21st to endDay
16%7%35%43445%7%44%
1480
March1st to 10thDay
10%6%34425%447%52%
1908
11th to 20thDay
11%6%26%6%45%45%8%44%
1980
21st to endDay
11%5%25%4345%5%6%48%
2178
April1st to 10thDay
10%5%26%5%35%6%5%6%46%
1980
11th to 20thDay
11%4246%345%48%48%
2063
21st to endDay
7%324435%45%7%56%
2290
May1st to 10thDay
7%32443445%8%56%
2340
11th to 20thDay
7%5%35%6%35%6%8%9%42%
2301
21st to endDay
7%425%6%46%6%7%9%43%
2531
June1st to 10thDay
9%7%37%7%46%8%7%10%32%
2340
11th to 20thDay
5%425%7%47%8%8%12%40%
2340
21st to endDay
6%6%36%7%5%8%8%9%12%29%
2340
July1st to 10thDay
7%6%36%8%5%9%9%9%11%28%
2340
11th to 20thDay
8%6%37%8%5%7%9%8%11%28%
2340
21st to endDay
7%436%7%6%8%8%9%12%30%
2547
August1st to 10thDay
8%6%37%8%5%7%7%9%13%27%
2325
11th to 20thDay
9%6%38%8%5%7%8%9%12%25%
2125
21st to endDay
10%7%48%9%48%7%7%8%27%
2314
September1st to 10thDay
9%7%36%6%5%8%6%7%11%32%
1980
11th to 20thDay
11%8%37%7%45%5%7%9%36%
1980
21st to endDay
11%4245%45%6%6%8%44%
1980
October1st to 10thDay
10%5%25%5%3445%6%50%
1980
11th to 20thDay
8%42432445%8%56%
1877
21st to endDay
9%4244345%47%54%
1980
November1st to 10thDay
9%425%5%3445%6%54%
1828
11th to 20thDay
10%6%24423445%56%
1710
21st to endDay
13%5%25%5%3345%9%47%
1710
December1st to 10thDay
14%5%25%5%345%6%7%44%
1710
11th to 20thDay
16%7%35%43445%6%43%
2153
21st to endDay
17%9%46%6%23335%41%
3124
January1st to 10thNight
12%6%35%5%35%447%45%
2459
11th to 20thNight
11%6%36%5%2445%6%47%
2417
21st to endNight
16%7%35%33445%6%43%
2452
February1st to 10thNight
14%6%35%435%45%7%45%
2160
11th to 20thNight
15%6%26%434346%48%
2098
21st to endNight
12%6%345%35%45%6%46%
1776
March1st to 10thNight
10%5%25%424347%53%
2052
11th to 20thNight
12%5%35%425%5%5%8%47%
1980
21st to endNight
8%5%245%35%447%53%
2178
April1st to 10thNight
10%5%25%4345%5%7%50%
1980
11th to 20thNight
8%5%35%435%45%8%50%
1859
21st to endNight
6%3235%3445%7%59%
1670
May1st to 10thNight
7%3245%245%5%10%55%
1620
11th to 20thNight
7%425%446%6%7%9%46%
1592
21st to endNight
6%5%25%6%45%6%7%10%46%
1744
June1st to 10thNight
8%5%35%7%47%7%10%12%33%
1620
11th to 20thNight
5%4245%46%8%10%12%40%
1620
21st to endNight
5%437%8%5%7%7%9%11%35%
1620
July1st to 10thNight
6%6%37%7%5%8%7%7%14%31%
1620
11th to 20thNight
5%5%36%7%46%7%10%14%33%
1620
21st to endNight
4325%6%37%7%10%12%39%
1771
August1st to 10thNight
6%5%27%8%47%8%9%11%34%
1611
11th to 20thNight
7%6%36%6%46%7%8%14%32%
1774
21st to endNight
7%6%47%9%47%8%9%9%32%
2022
September1st to 10thNight
8%6%38%6%45%6%8%13%32%
1980
11th to 20thNight
10%6%37%6%45%6%6%8%38%
1980
21st to endNight
8%6%26%6%35%5%6%9%42%
1980
October1st to 10thNight
8%6%2443446%8%51%
1980
11th to 20thNight
10%424423446%57%
2082
21st to endNight
8%5%245%345%46%55%
2376
November1st to 10thNight
9%5%24324446%56%
2247
11th to 20thNight
11%5%24423446%53%
2470
21st to endNight
11%6%35%42436%7%49%
2470
December1st to 10thNight
12%6%25%43446%7%46%
2470
11th to 20thNight
14%6%35%424345%49%
3042
21st to endNight
17%10%37%5%34446%37%
4532

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
41%47%18%21%9%
1707
11th to 20thDay
35%38%20%23%10%
1665
21st to endDay
42%36%17%22%10%
1899
February1st to 10thDay
43%38%16%20%9%
1800
11th to 20thDay
39%35%16%27%10%
1758
21st to endDay
40%39%19%17%12%
1480
March1st to 10thDay
33%46%20%24%12%
1908
11th to 20thDay
39%415%15%19%9%
1980
21st to endDay
35%411%22%20%8%
2178
April1st to 10thDay
37%5%9%21%17%11%
1980
11th to 20thDay
35%47%21%23%10%
2063
21st to endDay
29%39%26%26%8%
2290
May1st to 10thDay
27%411%25%25%8%
2340
11th to 20thDay
36%6%16%22%16%4
2305
21st to endDay
35%6%13%24%18%3
2531
June1st to 10thDay
44%7%16%22%10%1
2340
11th to 20thDay
34%8%19%24%14%
2340
21st to endDay
41%9%23%17%8%2
2340
July1st to 10thDay
43%11%26%15%5%1
2275
11th to 20thDay
46%9%25%15%5%
2271
21st to endDay
40%10%26%20%41
2405
August1st to 10thDay
45%10%23%19%3
2312
11th to 20thDay
46%11%24%14%5%
2125
21st to endDay
51%9%17%15%6%1
2314
September1st to 10thDay
44%8%16%17%12%3
1980
11th to 20thDay
45%7%13%17%15%3
1980
21st to endDay
36%5%12%21%19%7%
1980
October1st to 10thDay
34%49%18%23%12%
1980
11th to 20thDay
28%48%22%29%9%
1877
21st to endDay
31%45%17%27%16%
1980
November1st to 10thDay
31%47%18%24%15%
1828
11th to 20thDay
32%36%18%26%15%
1710
21st to endDay
36%38%19%24%10%
1710
December1st to 10thDay
40%412%17%18%9%
1710
11th to 20thDay
42%36%17%25%8%
2150
21st to endDay
48%2416%24%6%
3124
January1st to 10thNight
41%37%16%22%11%
2459
11th to 20thNight
38%37%16%27%9%
2417
21st to endNight
43%35%15%24%10%
2452
February1st to 10thNight
39%48%16%21%12%
2160
11th to 20thNight
39%46%14%22%15%
2099
21st to endNight
38%5%7%20%16%15%
1776
March1st to 10thNight
33%37%20%22%14%
2052
11th to 20thNight
36%411%19%18%11%
1980
21st to endNight
32%412%20%21%11%
2178
April1st to 10thNight
33%5%11%18%20%13%
1980
11th to 20thNight
33%49%20%25%10%
1859
21st to endNight
26%49%27%25%10%
1670
May1st to 10thNight
26%5%10%24%24%11%
1620
11th to 20thNight
32%7%19%18%18%6%
1593
21st to endNight
32%8%14%22%19%4
1745
June1st to 10thNight
38%9%21%20%11%1
1620
11th to 20thNight
32%9%25%23%10%1
1620
21st to endNight
39%12%21%18%7%2
1620
July1st to 10thNight
42%11%24%16%5%1
1575
11th to 20thNight
37%11%30%15%5%1
1566
21st to endNight
30%13%29%24%41
1672
August1st to 10thNight
39%12%28%16%4
1600
11th to 20thNight
39%15%24%16%5%
1774
21st to endNight
45%10%21%16%5%3
2022
September1st to 10thNight
43%10%18%16%12%2
1980
11th to 20thNight
42%8%15%16%16%3
1980
21st to endNight
37%6%14%18%17%7%
1980
October1st to 10thNight
31%5%10%21%21%13%
1980
11th to 20thNight
29%36%23%29%11%
2082
21st to endNight
31%46%15%26%18%
2376
November1st to 10thNight
30%38%18%24%17%
2247
11th to 20thNight
33%37%16%26%15%
2470
21st to endNight
35%38%21%20%12%
2470
December1st to 10thNight
37%314%16%22%7%
2470
11th to 20thNight
38%36%16%25%11%
3044
21st to endNight
49%35%16%22%4
4532

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
11%14%43%24%7%1
270
11th to 20thDay
11%11%31%31%12%4
255
21st to endDay
22%13%43%17%41
264
February1st to 10thDay
21%13%33%23%10%
240
11th to 20thDay
21%10%35%26%8%
240
21st to endDay
16%11%37%29%6%1
198
March1st to 10thDay
12%6%32%31%17%1
348
11th to 20thDay
15%6%34%30%12%2
420
21st to endDay
13%6%34%32%13%1
462
April1st to 10thDay
15%11%25%26%20%3
420
11th to 20thDay
14%7%26%29%19%5%
412
21st to endDay
9%321%35%22%9%
420
May1st to 10thDay
6%6%23%29%25%12%
423
11th to 20thDay
9%311%28%29%21%
447
21st to endDay
10%17%23%32%26%
485
June1st to 10thDay
11%17%23%33%26%
450
11th to 20thDay
7%18%21%29%34%
450
21st to endDay
9%1419%35%32%
450
July1st to 10thDay
8%1413%32%43%
445
11th to 20thDay
9%28%30%50%
444
21st to endDay
7%2410%36%41%
488
August1st to 10thDay
11%2214%30%40%
446
11th to 20thDay
8%2111%31%47%
439
21st to endDay
12%2417%35%31%
495
September1st to 10thDay
13%2321%31%30%
450
11th to 20thDay
14%2429%36%16%
450
21st to endDay
12%18%25%32%23%
450
October1st to 10thDay
12%218%35%24%8%
450
11th to 20thDay
8%218%31%27%13%
450
21st to endDay
11%6%20%34%24%6%
495
November1st to 10thDay
13%323%31%22%8%
426
11th to 20thDay
15%5%34%30%11%4
270
21st to endDay
11%9%31%30%17%3
270
December1st to 10thDay
17%7%30%28%14%4
270
11th to 20thDay
24%6%32%26%10%2
270
21st to endDay
21%6%30%27%15%1
297
January1st to 10thNight
16%11%35%33%6%1
760
11th to 20thNight
14%9%31%33%13%1
744
21st to endNight
19%8%37%31%5%
792
February1st to 10thNight
16%9%30%36%8%
720
11th to 20thNight
17%8%33%34%7%
703
21st to endNight
15%8%35%37%5%
592
March1st to 10thNight
14%7%30%40%9%
720
11th to 20thNight
13%7%33%33%14%1
720
21st to endNight
10%9%33%34%14%
792
April1st to 10thNight
13%7%29%37%14%1
720
11th to 20thNight
10%6%28%41%14%2
617
21st to endNight
7%326%40%22%2
540
May1st to 10thNight
8%423%40%23%2
540
11th to 20thNight
8%219%39%27%5%
531
21st to endNight
9%19%37%36%8%
584
June1st to 10thNight
10%1438%38%8%
540
11th to 20thNight
7%25%31%42%13%
540
21st to endNight
6%1332%47%11%
540
July1st to 10thNight
9%2224%44%19%
525
11th to 20thNight
8%1115%52%23%
522
21st to endNight
5%1221%57%14%
591
August1st to 10thNight
9%1124%51%14%
537
11th to 20thNight
9%2218%51%18%
534
21st to endNight
9%2327%41%17%
636
September1st to 10thNight
11%25%25%45%13%
720
11th to 20thNight
14%15%36%39%6%
720
21st to endNight
11%211%30%41%5%
720
October1st to 10thNight
11%217%38%29%3
720
11th to 20thNight
12%217%37%28%3
720
21st to endNight
11%422%37%25%1
792
November1st to 10thNight
12%421%38%22%3
740
11th to 20thNight
13%7%27%36%16%2
760
21st to endNight
13%429%35%17%1
760
December1st to 10thNight
14%6%32%32%15%1
760
11th to 20thNight
16%5%31%31%16%1
760
21st to endNight
22%8%25%32%13%
836
Page generated at 2024-01-13 09:37:57. Version ac07

Copyright 2024 Attilla Danko


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