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 2005-11-05 to 2017-10-06.

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
54%
15692
23%
47155
17%
15649
61%
15649
30%
28830

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 15thNight
35%
719
23%
2327
12%
716
50%
716
25%
1424
January16th to endNight
35%
768
25%
2415
15%
768
47%
768
25%
1493
February1st to 15thNight
40%
704
25%
2108
14%
700
52%
700
29%
1282
February16th to endNight
37%
631
27%
1893
14%
631
50%
631
30%
1157
March1st to 15thNight
43%
720
28%
2028
15%
720
53%
720
36%
1203
March16th to endNight
46%
768
24%
2112
14%
768
54%
768
35%
1262
April1st to 15thNight
50%
713
25%
1971
17%
713
57%
713
38%
1163
April16th to endNight
57%
540
30%
1713
23%
540
66%
540
38%
921
May1st to 15thNight
58%
539
26%
1619
18%
539
65%
539
38%
917
May16th to endNight
70%
561
22%
1682
18%
561
72%
561
35%
996
June1st to 15thNight
72%
540
13%
1620
12%
540
72%
540
28%
1046
June16th to endNight
71%
540
14%
1620
13%
540
71%
540
26%
1090
July1st to 15thNight
74%
510
13%
1530
13%
510
74%
510
27%
1007
July16th to endNight
76%
564
12%
1595
12%
531
76%
531
27%
1054
August1st to 15thNight
70%
539
12%
1668
13%
536
70%
536
23%
1141
August16th to endNight
66%
603
15%
1940
16%
603
66%
603
19%
1346
September1st to 15thNight
61%
720
15%
1980
13%
720
62%
720
23%
1393
September16th to endNight
62%
717
21%
1980
19%
717
64%
717
28%
1310
October1st to 15thNight
61%
684
31%
1889
26%
684
66%
684
40%
1097
October16th to endNight
58%
704
32%
2112
29%
704
65%
704
38%
1165
November1st to 15thNight
56%
700
32%
2177
28%
700
65%
700
41%
1147
November16th to endNight
46%
720
28%
2340
21%
720
58%
720
35%
1276
December1st to 15thNight
44%
720
25%
2340
19%
720
53%
720
30%
1355
December16th to endNight
41%
768
23%
2496
20%
768
49%
768
24%
1585

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%5%25%5%35%5%5%8%41%
48033
Night
9%5%25%43445%8%45%
47359
TransparencyDay
39%5%12%18%16%7%
47734
Night
35%5%12%18%18%9%
47162
SeeingDay
11%313%23%25%21%
5574
Night
11%419%32%26%5%
15696

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 15thDay
12%6%345%34447%43%
1611
16th to endDay
14%5%34424446%47%
1806
February1st to 15thDay
13%5%245%23446%45%
1750
16th to endDay
14%6%24322346%48%
1580
March1st to 15thDay
9%5%24424447%49%
1932
16th to endDay
11%5%25%434445%48%
2111
April1st to 15thDay
11%4145%246%46%47%
1985
16th to endDay
7%324425%447%53%
2247
May1st to 15thDay
8%3245%35%45%8%49%
2331
16th to endDay
7%425%5%35%6%6%9%42%
2431
June1st to 15thDay
8%5%25%6%46%8%7%9%34%
2340
16th to endDay
5%5%36%7%47%7%8%11%32%
2340
July1st to 15thDay
7%6%35%8%5%8%8%8%9%29%
2340
16th to endDay
8%436%7%5%8%8%8%11%25%
2465
August1st to 15thDay
10%6%38%9%6%7%7%8%11%21%
2278
16th to endDay
11%7%36%8%47%7%7%9%26%
2250
September1st to 15thDay
10%7%26%6%5%6%6%6%9%31%
1980
16th to endDay
12%6%26%5%345%6%7%39%
1980
October1st to 15thDay
11%5%24323345%52%
1869
16th to endDay
8%424333335%58%
1760
November1st to 15thDay
7%32443335%6%55%
1679
16th to endDay
12%423322446%52%
1620
December1st to 15thDay
14%5%25%43445%6%44%
1620
16th to endDay
18%7%35%5%34346%37%
1728
January1st to 15thNight
12%5%35%435%446%44%
2327
16th to endNight
14%6%35%323346%45%
2415
February1st to 15thNight
13%434424336%49%
2103
16th to endNight
12%6%24434346%48%
1893
March1st to 15thNight
9%425%424447%50%
2028
16th to endNight
10%423424435%54%
2112
April1st to 15thNight
9%42433335%6%52%
1971
16th to endNight
5%32342445%8%54%
1713
May1st to 15thNight
7%3245%2345%8%52%
1619
16th to endNight
5%314435%6%7%9%47%
1682
June1st to 15thNight
7%4246%36%7%9%12%33%
1620
16th to endNight
5%437%6%46%7%9%10%34%
1620
July1st to 15thNight
6%5%25%6%47%7%7%14%33%
1620
16th to endNight
5%326%7%37%7%9%12%33%
1703
August1st to 15thNight
7%5%26%6%37%9%9%11%31%
1679
16th to endNight
8%6%36%7%46%6%8%10%31%
1940
September1st to 15thNight
9%6%37%6%35%5%5%10%33%
1980
16th to endNight
9%5%26%6%35%6%6%8%38%
1980
October1st to 15thNight
10%423323347%53%
1889
16th to endNight
9%413423345%56%
2112
November1st to 15thNight
8%413313347%57%
2177
16th to endNight
10%423323346%54%
2340
December1st to 15thNight
12%5%2432345%7%46%
2340
16th to endNight
14%6%36%5%24347%41%
2496

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 15thDay
41%37%16%19%10%
1612
16th to endDay
38%26%18%22%11%
1806
February1st to 15thDay
40%26%15%23%11%
1752
16th to endDay
38%26%16%24%11%
1580
March1st to 15thDay
34%37%20%23%9%
1932
16th to endDay
37%310%18%22%7%
2112
April1st to 15thDay
35%47%20%21%9%
1985
16th to endDay
30%39%24%23%8%
2247
May1st to 15thDay
32%410%22%21%8%
2331
16th to endDay
35%5%15%24%14%4
2435
June1st to 15thDay
40%7%18%22%9%1
2340
16th to endDay
39%8%18%20%11%1
2340
July1st to 15thDay
44%9%23%16%5%
2201
16th to endDay
45%10%21%17%4
2310
August1st to 15thDay
52%8%20%14%3
2265
16th to endDay
49%9%17%14%7%1
2250
September1st to 15thDay
47%8%15%14%12%2
1980
16th to endDay
41%412%19%17%4
1980
October1st to 15thDay
33%38%19%22%12%
1869
16th to endDay
29%2417%29%16%
1760
November1st to 15thDay
28%27%19%25%16%
1679
16th to endDay
32%37%17%24%14%
1620
December1st to 15thDay
40%39%18%18%9%
1620
16th to endDay
48%28%18%13%8%
1728
January1st to 15thNight
40%37%16%22%10%
2327
16th to endNight
41%25%14%24%11%
2415
February1st to 15thNight
37%35%14%23%16%
2112
16th to endNight
37%35%16%20%16%
1893
March1st to 15thNight
33%38%21%21%11%
2028
16th to endNight
33%39%18%23%11%
2112
April1st to 15thNight
32%38%19%23%12%
1971
16th to endNight
27%410%23%22%10%
1713
May1st to 15thNight
28%5%13%20%21%10%
1620
16th to endNight
31%6%15%24%16%5%
1684
June1st to 15thNight
37%8%23%19%10%1
1620
16th to endNight
39%9%18%19%9%2
1620
July1st to 15thNight
36%11%25%20%5%1
1530
16th to endNight
36%11%26%19%5%
1595
August1st to 15thNight
38%14%26%16%4
1668
16th to endNight
44%11%19%16%6%2
1940
September1st to 15thNight
44%9%16%13%14%2
1980
16th to endNight
40%6%14%16%15%6%
1980
October1st to 15thNight
30%38%21%21%13%
1889
16th to endNight
29%35%15%26%19%
2112
November1st to 15thNight
27%27%19%26%17%
2177
16th to endNight
31%37%17%22%17%
2340
December1st to 15thNight
36%312%19%20%8%
2340
16th to endNight
43%37%21%14%9%
2496

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 15thDay
14%10%37%18%10%8%
90
16th to endDay
17%15%37%19%6%3
96
February1st to 15thDay
11%22%33%22%11%
90
16th to endDay
16%6%35%35%6%
81
March1st to 15thDay
11%6%31%34%15%
222
16th to endDay
12%425%35%20%2
288
April1st to 15thDay
12%9%21%29%23%3
270
16th to endDay
10%316%33%22%13%
270
May1st to 15thDay
7%5%19%33%20%13%
288
16th to endDay
9%26%23%31%25%
331
June1st to 15thDay
11%16%15%32%32%
315
16th to endDay
9%114%34%38%
315
July1st to 15thDay
7%211%29%48%
305
16th to endDay
6%139%28%50%
326
August1st to 15thDay
13%2112%33%36%
313
16th to endDay
10%1313%27%43%
332
September1st to 15thDay
16%2419%30%26%
315
16th to endDay
14%6%21%35%21%
314
October1st to 15thDay
14%216%33%27%6%
278
16th to endDay
8%318%33%27%7%
272
November1st to 15thDay
11%227%29%21%8%
187
16th to endDay
38%34%27%15%10%
90
December1st to 15thDay
21%6%26%25%11%8%
90
16th to endDay
27%7%21%29%11%3
96
January1st to 15thNight
14%10%31%31%9%1
720
16th to endNight
17%9%32%31%8%
768
February1st to 15thNight
15%9%29%35%9%
704
16th to endNight
13%8%34%36%6%
631
March1st to 15thNight
11%7%31%36%11%
720
16th to endNight
11%7%29%32%18%
768
April1st to 15thNight
11%6%26%38%15%1
713
16th to endNight
7%426%35%23%2
540
May1st to 15thNight
8%223%36%25%3
540
16th to endNight
6%112%36%35%7%
563
June1st to 15thNight
9%2433%40%10%
540
16th to endNight
7%1229%46%13%
540
July1st to 15thNight
7%1125%43%20%
510
16th to endNight
7%120%54%15%
564
August1st to 15thNight
9%121%54%11%
539
16th to endNight
10%1322%42%19%
603
September1st to 15thNight
12%25%26%40%12%
720
16th to endNight
12%27%32%40%4
717
October1st to 15thNight
12%216%36%30%2
684
16th to endNight
11%321%33%27%2
704
November1st to 15thNight
11%422%37%22%3
700
16th to endNight
10%5%30%31%19%1
720
December1st to 15thNight
13%6%29%32%16%1
720
16th to endNight
17%7%25%33%15%
768
Page generated at 2017-10-07 14:07:46. Version ac04

Copyright 2017 A. Danko


Red Barn Observatory Clear Sky Chart | Charts Home