Aubright Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Aubright Observatory clear sky chart from 2005-11-05 to 2017-10-16.

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
54%
15975
21%
47250
16%
15938
60%
15938
29%
29739

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
36%
716
20%
2327
12%
716
48%
716
22%
1457
January16th to endNight
37%
768
22%
2487
14%
768
49%
768
25%
1540
February1st to 15thNight
37%
701
23%
2107
13%
700
48%
700
28%
1297
February16th to endNight
35%
631
24%
1854
13%
631
47%
631
28%
1173
March1st to 15thNight
41%
720
27%
1980
15%
720
52%
720
35%
1183
March16th to endNight
46%
768
25%
2112
15%
768
53%
768
37%
1243
April1st to 15thNight
49%
718
24%
1976
15%
718
56%
718
37%
1170
April16th to endNight
54%
695
28%
1799
17%
695
60%
695
42%
1047
May1st to 15thNight
64%
539
25%
1619
18%
539
68%
539
39%
901
May16th to endNight
69%
561
23%
1682
17%
561
71%
561
36%
978
June1st to 15thNight
66%
540
14%
1620
10%
540
67%
540
26%
1076
June16th to endNight
73%
540
11%
1620
10%
540
73%
540
27%
1097
July1st to 15thNight
73%
510
11%
1530
10%
510
74%
510
25%
1025
July16th to endNight
75%
564
10%
1595
11%
531
77%
531
24%
1112
August1st to 15thNight
74%
539
10%
1609
8%
536
75%
536
24%
1106
August16th to endNight
65%
692
11%
1974
11%
692
65%
692
20%
1411
September1st to 15thNight
64%
720
11%
1980
11%
720
64%
720
20%
1451
September16th to endNight
61%
717
16%
1980
16%
717
62%
717
22%
1405
October1st to 15thNight
61%
720
26%
2056
24%
720
65%
720
32%
1273
October16th to endNight
58%
708
30%
2123
27%
708
65%
708
34%
1236
November1st to 15thNight
54%
700
28%
2101
22%
700
63%
700
35%
1239
November16th to endNight
44%
720
27%
2283
19%
720
57%
720
31%
1334
December1st to 15thNight
45%
720
24%
2340
19%
720
53%
720
26%
1434
December16th to endNight
47%
768
23%
2496
19%
768
54%
768
25%
1551

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%36%6%35%6%6%8%37%
48156
Night
9%425%5%3446%8%44%
47455
TransparencyDay
42%8%12%16%13%6%
47857
Night
35%8%14%19%14%7%
47258
SeeingDay
11%417%22%25%19%
5834
Night
11%5%21%31%25%5%
15985

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%7%36%5%33347%41%
1611
16th to endDay
12%6%35%424445%45%
1734
February1st to 15thDay
15%6%245%2344446%
1750
16th to endDay
11%6%24423446%48%
1619
March1st to 15thDay
9%42442345%6%52%
1980
16th to endDay
9%5%25%5%245%46%48%
2111
April1st to 15thDay
9%5%35%424448%46%
1972
16th to endDay
6%425%5%35%5%6%8%47%
2169
May1st to 15thDay
7%3245%35%5%6%9%47%
2331
16th to endDay
9%326%5%46%7%6%10%38%
2431
June1st to 15thDay
10%5%27%7%5%7%7%6%8%29%
2340
16th to endDay
8%5%47%7%5%7%6%8%10%28%
2340
July1st to 15thDay
8%5%36%8%5%8%8%8%10%26%
2340
16th to endDay
8%5%38%9%5%8%9%7%9%23%
2465
August1st to 15thDay
10%7%38%9%5%8%8%8%10%19%
2340
16th to endDay
13%6%27%8%5%7%8%7%8%22%
2212
September1st to 15thDay
13%6%37%8%6%7%8%8%7%23%
1980
16th to endDay
16%7%38%8%46%6%5%6%25%
1980
October1st to 15thDay
10%6%37%6%445%5%8%37%
1902
16th to endDay
10%5%245%24446%49%
1770
November1st to 15thDay
8%425%5%235%5%8%47%
1757
16th to endDay
10%4246%2435%7%47%
1674
December1st to 15thDay
13%6%25%5%2446%8%40%
1620
16th to endDay
10%6%25%5%35%5%6%8%41%
1728
January1st to 15thNight
12%6%35%5%3445%6%44%
2327
16th to endNight
14%6%3442335%6%45%
2487
February1st to 15thNight
13%5%25%5%23335%50%
2103
16th to endNight
11%6%25%5%34336%47%
1854
March1st to 15thNight
7%425%5%23447%52%
1980
16th to endNight
7%324424445%55%
2112
April1st to 15thNight
7%42333445%8%52%
1976
16th to endNight
6%32342346%9%54%
1799
May1st to 15thNight
5%1134245%6%8%55%
1619
16th to endNight
6%413425%5%7%10%47%
1682
June1st to 15thNight
10%3245%446%8%12%35%
1620
16th to endNight
7%315%6%5%6%6%7%12%37%
1620
July1st to 15thNight
5%325%5%36%6%9%13%37%
1620
16th to endNight
4327%6%47%7%10%10%34%
1703
August1st to 15thNight
4315%6%47%6%10%15%32%
1620
16th to endNight
9%5%26%7%45%6%9%11%31%
1974
September1st to 15thNight
10%5%26%7%5%6%7%7%10%30%
1980
16th to endNight
10%6%26%6%46%5%6%10%32%
1980
October1st to 15thNight
9%425%5%2445%7%48%
2056
16th to endNight
8%42443445%6%51%
2123
November1st to 15thNight
8%42442445%7%50%
2101
16th to endNight
9%434425%347%50%
2283
December1st to 15thNight
12%6%245%2345%7%45%
2340
16th to endNight
10%5%26%5%2446%7%44%
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
43%48%16%17%10%
1612
16th to endDay
40%46%17%19%10%
1734
February1st to 15thDay
41%37%11%20%15%
1752
16th to endDay
37%49%14%21%12%
1619
March1st to 15thDay
31%410%22%21%9%
1980
16th to endDay
36%5%10%16%20%9%
2112
April1st to 15thDay
35%6%8%17%21%9%
1972
16th to endDay
32%7%11%19%19%9%
2169
May1st to 15thDay
31%9%11%20%18%8%
2331
16th to endDay
38%9%14%17%15%4
2435
June1st to 15thDay
47%11%17%16%7%
2340
16th to endDay
46%13%18%15%5%
2340
July1st to 15thDay
45%15%21%14%1
2201
16th to endDay
49%15%18%12%3
2310
August1st to 15thDay
53%15%19%10%1
2327
16th to endDay
53%14%16%11%2
2212
September1st to 15thDay
53%14%13%11%6%
1980
16th to endDay
56%9%10%13%7%2
1980
October1st to 15thDay
44%6%9%15%15%8%
1902
16th to endDay
35%48%15%22%13%
1770
November1st to 15thDay
33%5%9%20%20%9%
1757
16th to endDay
36%5%10%15%20%12%
1674
December1st to 15thDay
41%5%10%21%14%6%
1620
16th to endDay
39%7%10%22%12%8%
1728
January1st to 15thNight
40%6%9%17%17%9%
2327
16th to endNight
39%48%15%20%11%
2487
February1st to 15thNight
37%47%15%19%15%
2112
16th to endNight
38%48%16%19%11%
1854
March1st to 15thNight
31%5%11%23%18%9%
1980
16th to endNight
29%5%12%21%19%10%
2112
April1st to 15thNight
30%5%10%21%21%10%
1976
16th to endNight
25%6%15%23%21%7%
1799
May1st to 15thNight
25%7%15%26%18%7%
1620
16th to endNight
29%7%17%27%15%2
1684
June1st to 15thNight
36%12%20%23%6%
1620
16th to endNight
37%12%23%20%6%
1620
July1st to 15thNight
33%15%27%20%2
1530
16th to endNight
35%16%26%17%3
1595
August1st to 15thNight
35%16%29%15%2
1609
16th to endNight
41%14%24%15%3
1974
September1st to 15thNight
44%13%19%14%6%
1980
16th to endNight
44%10%14%19%7%2
1980
October1st to 15thNight
34%6%11%18%19%8%
2056
16th to endNight
32%48%18%22%13%
2123
November1st to 15thNight
31%5%10%20%20%10%
2101
16th to endNight
33%6%9%18%18%13%
2283
December1st to 15thNight
38%5%12%22%15%6%
2340
16th to endNight
39%5%12%20%13%8%
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
13%15%41%20%45%
90
16th to endDay
9%21%37%22%8%
96
February1st to 15thDay
8%23%33%22%12%
90
16th to endDay
10%10%37%33%7%
120
March1st to 15thDay
12%7%30%31%15%1
270
16th to endDay
13%5%30%22%22%5%
288
April1st to 15thDay
14%12%21%23%21%6%
270
16th to endDay
5%424%25%21%18%
270
May1st to 15thDay
5%423%30%21%14%
288
16th to endDay
7%112%22%32%22%
331
June1st to 15thDay
12%10%19%29%27%
315
16th to endDay
8%6%15%33%35%
315
July1st to 15thDay
3215%31%45%
305
16th to endDay
7%7%15%33%34%
326
August1st to 15thDay
12%15%15%30%34%
313
16th to endDay
12%25%14%28%36%
332
September1st to 15thDay
17%25%16%29%28%
315
16th to endDay
17%17%19%30%22%
314
October1st to 15thDay
14%216%30%26%9%
315
16th to endDay
11%420%28%28%6%
276
November1st to 15thDay
10%426%27%23%6%
265
16th to endDay
7%9%38%18%20%4
144
December1st to 15thDay
6%11%38%28%13%1
90
16th to endDay
16%6%22%37%12%4
96
January1st to 15thNight
14%13%28%30%10%1
720
16th to endNight
16%10%31%30%9%
768
February1st to 15thNight
15%9%31%32%9%
704
16th to endNight
14%11%32%34%7%
631
March1st to 15thNight
9%11%33%35%10%
720
16th to endNight
9%8%31%36%14%
768
April1st to 15thNight
9%7%28%39%14%
718
16th to endNight
7%6%27%38%18%
695
May1st to 15thNight
5%322%43%23%1
540
16th to endNight
8%110%32%39%6%
563
June1st to 15thNight
10%10%31%37%9%
540
16th to endNight
7%7%24%44%15%
540
July1st to 15thNight
7%6%22%43%19%
510
16th to endNight
4324%52%15%
564
August1st to 15thNight
5%420%52%16%
539
16th to endNight
10%18%21%39%17%
692
September1st to 15thNight
13%17%23%42%11%
720
16th to endNight
14%110%26%37%9%
717
October1st to 15thNight
12%117%31%34%3
720
16th to endNight
10%419%34%28%2
708
November1st to 15thNight
11%424%36%22%1
700
16th to endNight
11%6%32%28%19%1
720
December1st to 15thNight
14%8%26%30%19%1
720
16th to endNight
12%8%25%35%16%
768
Page generated at 2017-10-17 16:35:28. Version ac04

Copyright 2017 A. Danko


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