Dun Glen
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dun Glen clear sky chart from 2005-11-06 to 2024-03-18.

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
65%
23378
24%
80648
24%
23315
69%
23315
33%
45663

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
56%
748
14%
4355
17%
736
60%
736
14%
2753
January11th to 20thNight
60%
753
14%
4412
20%
740
65%
740
14%
2964
January21st to endNight
59%
825
15%
4654
24%
814
63%
814
14%
3054
February1st to 10thNight
59%
760
23%
2372
23%
760
63%
760
31%
1417
February11th to 20thNight
60%
740
24%
2219
23%
740
66%
740
33%
1336
February21st to endNight
56%
628
23%
1884
21%
628
62%
628
31%
1161
March1st to 10thNight
53%
760
18%
2280
17%
760
59%
760
26%
1479
March11th to 20thNight
60%
752
21%
2215
19%
752
62%
752
32%
1333
March21st to endNight
53%
792
18%
1980
12%
792
56%
792
31%
1327
April1st to 10thNight
55%
720
22%
1800
13%
720
57%
720
32%
1194
April11th to 20thNight
57%
711
27%
1779
14%
711
61%
711
38%
1086
April21st to endNight
59%
637
24%
1717
15%
637
61%
637
39%
1020
May1st to 10thNight
57%
540
27%
1620
20%
540
62%
540
40%
853
May11th to 20thNight
61%
483
25%
1546
22%
483
65%
483
35%
854
May21st to endNight
62%
388
20%
1552
22%
388
67%
388
28%
836
June1st to 10thNight
65%
360
24%
1440
28%
360
72%
360
35%
700
June11th to 20thNight
68%
360
30%
1440
37%
360
77%
360
43%
613
June21st to endNight
78%
360
30%
1440
41%
360
82%
360
55%
545
July1st to 10thNight
80%
350
29%
1400
38%
350
83%
350
50%
557
July11th to 20thNight
84%
348
34%
1392
45%
348
86%
348
56%
512
July21st to endNight
83%
394
35%
1488
44%
372
84%
372
44%
627
August1st to 10thNight
76%
474
33%
1540
31%
472
77%
472
44%
756
August11th to 20thNight
83%
712
35%
1780
22%
712
85%
712
65%
890
August21st to endNight
86%
792
40%
1980
25%
792
86%
792
70%
957
September1st to 10thNight
83%
720
40%
1800
26%
720
85%
720
66%
900
September11th to 20thNight
79%
720
39%
1912
31%
720
80%
720
60%
957
September21st to endNight
80%
720
41%
1980
37%
720
83%
720
63%
925
October1st to 10thNight
72%
720
33%
1995
28%
720
76%
720
50%
1041
October11th to 20thNight
73%
720
36%
2160
35%
720
78%
720
49%
1077
October21st to endNight
74%
792
35%
2559
37%
792
79%
792
52%
1177
November1st to 10thNight
66%
740
26%
2405
28%
740
70%
740
34%
1348
November11th to 20thNight
68%
760
27%
2470
26%
760
72%
760
37%
1334
November21st to endNight
61%
760
26%
2470
25%
760
66%
760
34%
1389
December1st to 10thNight
59%
760
19%
2641
19%
760
62%
760
27%
1574
December11th to 20thNight
51%
759
17%
3179
19%
759
54%
759
17%
2087
December21st to endNight
46%
820
10%
4792
15%
817
50%
817
12%
3030

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
46%35%5%3445%7%54%
78642
Night
5%7%36%5%35%5%6%7%50%
81164
TransparencyDay
29%5%9%18%21%18%
78346
Night
32%5%10%20%19%14%
80982
SeeingDay
6%8%22%32%24%8%
13892
Night
8%415%40%28%6%
23430

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
5%15%7%9%7%45%6%7%9%27%
2539
11th to 20thDay
6%12%5%11%9%45%6%6%9%28%
2540
21st to endDay
6%13%5%9%8%5%6%7%7%11%23%
2894
February1st to 10thDay
47%37%6%46%47%10%41%
1805
11th to 20thDay
37%47%7%46%5%7%9%42%
1850
21st to endDay
27%46%6%46%5%7%11%43%
1570
March1st to 10thDay
410%49%7%46%6%7%8%35%
1900
11th to 20thDay
38%47%6%45%5%7%11%40%
1906
21st to endDay
48%37%6%46%6%7%8%40%
2376
April1st to 10thDay
5%8%47%6%46%5%6%8%41%
2160
11th to 20thDay
5%8%36%6%35%5%5%7%47%
2129
21st to endDay
6%7%35%5%3445%8%51%
2240
May1st to 10thDay
44145%3446%9%56%
2340
11th to 20thDay
7%6%35%4345%5%7%51%
2345
21st to endDay
6%7%27%6%46%5%6%7%44%
2723
June1st to 10thDay
44244345%5%8%57%
2520
11th to 20thDay
3323423336%68%
2520
21st to endDay
221222324475%
2520
July1st to 10thDay
1212222445%76%
2520
11th to 20thDay
2212213335%76%
2520
21st to endDay
2323323446%68%
2741
August1st to 10thDay
4323313446%67%
2388
11th to 20thDay
1112222345%78%
2122
21st to endDay
111121233481%
2376
September1st to 10thDay
111121223481%
2160
11th to 20thDay
211232335%5%71%
2048
21st to endDay
2312322346%73%
1980
October1st to 10thDay
5%42443434464%
1962
11th to 20thDay
3413423446%66%
1800
21st to endDay
332432345%8%63%
1796
November1st to 10thDay
48%36%43445%6%53%
1674
11th to 20thDay
5%5%344235%6%10%52%
1710
21st to endDay
47%46%6%3445%8%49%
1710
December1st to 10thDay
5%7%36%8%45%45%8%46%
1536
11th to 20thDay
5%9%49%8%5%7%6%9%10%29%
1928
21st to endDay
5%9%5%8%9%45%5%7%9%34%
2794
January1st to 10thNight
411%5%10%7%46%6%7%9%32%
4406
11th to 20thNight
9%11%49%8%45%6%7%7%30%
4420
21st to endNight
6%12%47%8%46%6%7%10%30%
4762
February1st to 10thNight
48%47%5%346%6%8%46%
2372
11th to 20thNight
37%37%6%46%5%6%8%45%
2218
21st to endNight
28%47%6%46%7%7%9%41%
1884
March1st to 10thNight
5%9%48%7%36%6%6%8%39%
2280
11th to 20thNight
47%36%7%45%5%7%10%42%
2215
21st to endNight
5%9%36%6%46%5%6%8%42%
1980
April1st to 10thNight
5%7%36%6%46%6%6%8%43%
1800
11th to 20thNight
6%6%35%435%45%7%52%
1779
21st to endNight
7%6%35%435%347%54%
1717
May1st to 10thNight
5%4245%245%6%7%56%
1620
11th to 20thNight
7%5%145%3446%9%50%
1545
21st to endNight
6%7%245%36%46%7%50%
1552
June1st to 10thNight
6%42433446%8%56%
1440
11th to 20thNight
4323334435%68%
1440
21st to endNight
2212323446%71%
1440
July1st to 10thNight
221333436%6%68%
1440
11th to 20thNight
2213313345%73%
1440
21st to endNight
33133336%5%8%62%
1576
August1st to 10thNight
5%31443445%7%60%
1548
11th to 20thNight
231322235%6%72%
1780
21st to endNight
2212312345%75%
1980
September1st to 10thNight
331221323476%
1800
11th to 20thNight
331332233471%
1912
21st to endNight
3212222235%74%
1980
October1st to 10thNight
5%42332433467%
1995
11th to 20thNight
332442345%5%66%
2160
21st to endNight
5%213323448%65%
2559
November1st to 10thNight
6%6%25%435%5%7%7%50%
2405
11th to 20thNight
46%25%5%245%6%8%52%
2470
21st to endNight
5%6%35%5%345%5%7%51%
2470
December1st to 10thNight
6%7%36%6%35%5%6%9%44%
2641
11th to 20thNight
6%10%49%7%46%6%7%10%31%
3276
21st to endNight
6%9%49%8%6%6%6%8%9%29%
4862

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
49%8%15%23%4
2539
11th to 20thDay
50%10%17%14%7%2
2540
21st to endDay
53%8%12%18%7%2
2894
February1st to 10thDay
37%6%14%27%13%3
1805
11th to 20thDay
37%7%13%23%17%3
1860
21st to endDay
33%7%16%25%15%4
1570
March1st to 10thDay
44%6%13%20%15%2
1900
11th to 20thDay
36%5%14%26%15%3
1906
21st to endDay
38%8%15%24%12%3
2376
April1st to 10thDay
40%6%10%22%17%6%
2160
11th to 20thDay
34%5%10%22%21%7%
2132
21st to endDay
32%5%10%28%22%4
2240
May1st to 10thDay
25%5%8%25%31%7%
2340
11th to 20thDay
32%5%8%22%26%8%
2348
21st to endDay
37%6%9%20%22%6%
2724
June1st to 10thDay
25%48%19%30%14%
2520
11th to 20thDay
19%35%16%32%26%
2520
21st to endDay
14%2311%31%40%
2520
July1st to 10thDay
11%248%23%52%
2451
11th to 20thDay
12%236%20%56%
2445
21st to endDay
18%346%19%50%
2589
August1st to 10thDay
19%2310%22%44%
2371
11th to 20thDay
10%248%26%50%
2122
21st to endDay
9%129%29%49%
2376
September1st to 10thDay
9%228%27%51%
2160
11th to 20thDay
15%35%13%29%34%
2048
21st to endDay
15%25%17%31%29%
1980
October1st to 10thDay
25%36%18%28%21%
1962
11th to 20thDay
20%46%22%31%17%
1800
21st to endDay
20%39%31%25%12%
1796
November1st to 10thDay
33%5%8%23%22%8%
1674
11th to 20thDay
28%5%13%28%23%3
1710
21st to endDay
34%411%26%21%4
1710
December1st to 10thDay
38%6%13%24%15%4
1536
11th to 20thDay
45%9%15%18%12%1
1928
21st to endDay
44%7%17%21%11%
2794
January1st to 10thNight
43%10%16%23%7%1
4406
11th to 20thNight
50%7%16%13%10%3
4420
21st to endNight
46%8%11%23%9%2
4762
February1st to 10thNight
35%6%13%27%16%3
2372
11th to 20thNight
35%5%12%26%18%4
2219
21st to endNight
35%7%14%23%16%5%
1884
March1st to 10thNight
40%7%12%23%15%3
2280
11th to 20thNight
36%5%12%24%19%4
2215
21st to endNight
38%7%16%24%12%3
1980
April1st to 10thNight
37%6%11%24%16%6%
1800
11th to 20thNight
31%5%9%25%20%9%
1779
21st to endNight
32%410%26%24%5%
1717
May1st to 10thNight
26%48%24%30%8%
1620
11th to 20thNight
29%6%8%23%25%9%
1546
21st to endNight
32%6%11%24%21%6%
1552
June1st to 10thNight
26%5%6%24%26%13%
1440
11th to 20thNight
20%35%17%34%20%
1440
21st to endNight
14%35%12%29%38%
1440
July1st to 10thNight
16%35%7%24%44%
1400
11th to 20thNight
14%235%18%58%
1392
21st to endNight
19%45%9%15%48%
1488
August1st to 10thNight
24%3410%19%40%
1540
11th to 20thNight
14%247%23%49%
1780
21st to endNight
12%2310%24%50%
1980
September1st to 10thNight
15%226%26%50%
1800
11th to 20thNight
17%2412%27%37%
1912
21st to endNight
15%2415%30%35%
1980
October1st to 10thNight
23%35%18%26%25%
1995
11th to 20thNight
21%45%20%30%21%
2160
21st to endNight
19%38%28%28%13%
2559
November1st to 10thNight
31%6%10%21%22%10%
2405
11th to 20thNight
29%412%24%27%4
2470
21st to endNight
32%49%24%24%6%
2470
December1st to 10thNight
37%6%13%23%16%5%
2641
11th to 20thNight
45%7%13%21%11%4
3276
21st to endNight
47%7%15%18%12%1
4862

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%9%26%26%26%5%
180
11th to 20thDay
6%425%28%27%10%
180
21st to endDay
10%319%29%27%11%
259
February1st to 10thDay
7%5%22%38%21%7%
415
11th to 20thDay
8%9%24%38%18%2
455
21st to endDay
6%7%26%38%20%3
382
March1st to 10thDay
11%9%24%33%20%3
460
11th to 20thDay
6%12%28%29%20%4
449
21st to endDay
10%14%25%33%16%3
462
April1st to 10thDay
10%13%26%25%21%6%
420
11th to 20thDay
9%14%28%28%15%6%
412
21st to endDay
10%14%23%26%21%7%
420
May1st to 10thDay
5%15%29%27%17%6%
423
11th to 20thDay
15%10%25%26%18%7%
448
21st to endDay
12%9%18%27%24%10%
485
June1st to 10thDay
411%21%31%24%10%
450
11th to 20thDay
6%14%24%33%16%6%
450
21st to endDay
37%21%34%25%9%
450
July1st to 10thDay
1322%36%28%10%
446
11th to 20thDay
2318%37%31%9%
444
21st to endDay
3216%38%27%14%
487
August1st to 10thDay
6%318%32%29%12%
447
11th to 20thDay
3416%32%29%16%
437
21st to endDay
15%17%38%30%10%
495
September1st to 10thDay
1318%31%30%16%
450
11th to 20thDay
5%7%17%35%24%12%
450
21st to endDay
46%25%29%27%9%
450
October1st to 10thDay
5%9%22%27%27%10%
450
11th to 20thDay
7%8%18%29%30%9%
450
21st to endDay
6%5%23%31%25%10%
311
November1st to 10thDay
8%8%24%28%25%7%
270
11th to 20thDay
5%420%33%29%9%
270
21st to endDay
10%7%17%34%25%7%
270
December1st to 10thDay
6%6%21%34%21%12%
187
11th to 20thDay
10%6%22%32%21%9%
180
21st to endDay
15%6%15%36%23%6%
198
January1st to 10thNight
9%5%19%37%23%8%
760
11th to 20thNight
7%418%41%24%6%
760
21st to endNight
13%313%40%25%7%
836
February1st to 10thNight
7%418%43%24%4
760
11th to 20thNight
7%419%43%23%4
744
21st to endNight
6%5%22%44%19%3
628
March1st to 10thNight
10%5%21%42%19%4
760
11th to 20thNight
7%6%17%40%26%3
752
21st to endNight
11%6%21%41%18%3
792
April1st to 10thNight
10%6%20%39%22%3
720
11th to 20thNight
10%8%18%38%20%6%
711
21st to endNight
12%419%34%25%6%
637
May1st to 10thNight
7%8%21%37%22%4
540
11th to 20thNight
8%5%18%37%26%6%
483
21st to endNight
9%5%15%32%33%6%
389
June1st to 10thNight
8%318%38%27%6%
360
11th to 20thNight
6%418%39%31%3
360
21st to endNight
2313%48%31%4
360
July1st to 10thNight
3111%49%33%3
350
11th to 20thNight
216%51%38%2
348
21st to endNight
326%41%43%6%
394
August1st to 10thNight
5%210%42%38%3
474
11th to 20thNight
327%38%42%7%
712
21st to endNight
216%41%43%7%
792
September1st to 10thNight
337%37%40%10%
720
11th to 20thNight
429%34%38%13%
720
21st to endNight
5%39%37%33%14%
720
October1st to 10thNight
8%312%38%33%7%
720
11th to 20thNight
5%412%38%33%8%
720
21st to endNight
6%312%40%28%11%
792
November1st to 10thNight
8%416%35%29%7%
740
11th to 20thNight
8%314%46%24%5%
760
21st to endNight
9%318%38%28%5%
760
December1st to 10thNight
9%417%44%20%6%
760
11th to 20thNight
15%416%38%22%5%
760
21st to endNight
14%6%20%41%16%2
836
Page generated at 2024-03-15 11:01:44. Version ac07

Copyright © 2024 Attilla Danko.


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