Alpenglow Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Alpenglow Observatory clear sky chart from 2005-11-06 to 2024-03-28.

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
47%
24622
22%
80576
16%
24525
54%
24525
27%
49461

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
39%
750
14%
4042
13%
736
45%
736
12%
2707
January11th to 20thNight
40%
760
13%
4097
14%
740
48%
740
11%
3023
January21st to endNight
41%
829
12%
4439
15%
814
46%
814
13%
2828
February1st to 10thNight
34%
760
14%
2470
11%
760
40%
760
19%
1709
February11th to 20thNight
35%
740
17%
2333
13%
740
42%
740
22%
1550
February21st to endNight
31%
628
19%
1884
11%
628
41%
628
21%
1290
March1st to 10thNight
33%
760
17%
2145
10%
760
41%
760
20%
1541
March11th to 20thNight
42%
760
22%
2090
14%
760
50%
760
29%
1346
March21st to endNight
35%
820
16%
2255
9%
820
42%
820
22%
1587
April1st to 10thNight
36%
702
18%
1962
11%
702
41%
702
26%
1304
April11th to 20thNight
40%
533
24%
1639
13%
533
51%
533
28%
1036
April21st to endNight
46%
540
22%
1620
15%
540
51%
540
27%
1021
May1st to 10thNight
40%
540
22%
1620
14%
540
46%
540
27%
1014
May11th to 20thNight
52%
531
23%
1595
17%
531
56%
531
34%
920
May21st to endNight
50%
582
18%
1746
14%
582
54%
582
32%
1036
June1st to 10thNight
53%
540
23%
1559
18%
540
60%
540
38%
862
June11th to 20thNight
54%
540
29%
1440
17%
540
65%
540
48%
762
June21st to endNight
60%
540
28%
1614
23%
540
69%
540
51%
775
July1st to 10thNight
58%
525
20%
1575
16%
525
63%
525
39%
850
July11th to 20thNight
58%
522
23%
1566
18%
522
64%
522
39%
865
July21st to endNight
67%
591
25%
1674
20%
558
71%
558
40%
917
August1st to 10thNight
61%
537
28%
1602
17%
534
68%
534
42%
849
August11th to 20thNight
66%
534
33%
1602
23%
534
72%
534
42%
853
August21st to endNight
63%
594
36%
1801
28%
594
70%
594
45%
928
September1st to 10thNight
66%
662
33%
1922
25%
662
72%
662
49%
971
September11th to 20thNight
62%
720
34%
1980
23%
720
71%
720
50%
1028
September21st to endNight
62%
720
37%
1980
25%
720
70%
720
51%
1035
October1st to 10thNight
51%
720
28%
2068
17%
720
60%
720
39%
1166
October11th to 20thNight
57%
720
33%
2160
24%
720
65%
720
41%
1181
October21st to endNight
51%
792
32%
2376
22%
792
59%
792
37%
1326
November1st to 10thNight
47%
740
27%
2405
19%
740
58%
740
30%
1392
November11th to 20thNight
44%
760
25%
2470
17%
760
53%
760
31%
1428
November21st to endNight
43%
868
23%
2578
16%
868
50%
868
29%
1608
December1st to 10thNight
42%
950
18%
2660
12%
950
46%
950
28%
1735
December11th to 20thNight
36%
950
17%
3143
9%
949
42%
949
19%
2145
December21st to endNight
28%
862
9%
4464
10%
851
33%
851
10%
2873

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
7%10%47%5%3445%6%44%
78856
Night
8%10%47%5%3445%6%45%
81176
TransparencyDay
39%5%8%20%19%10%
78581
Night
39%5%9%21%18%9%
80972
SeeingDay
15%16%33%26%8%1
14095
Night
13%8%24%33%18%3
24653

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
7%18%9%11%9%34445%28%
2858
11th to 20thDay
8%21%9%12%6%33445%26%
2860
21st to endDay
6%19%7%9%5%34346%35%
3146
February1st to 10thDay
11%17%6%10%6%34335%31%
1710
11th to 20thDay
9%18%6%10%6%34446%30%
1731
21st to endDay
6%19%7%13%5%345%5%5%27%
1570
March1st to 10thDay
7%15%6%9%6%45%5%5%5%32%
2033
11th to 20thDay
7%14%5%7%6%45%5%5%8%35%
2090
21st to endDay
10%18%6%11%6%35%45%5%26%
2256
April1st to 10thDay
11%14%5%8%6%345%46%35%
1998
11th to 20thDay
10%17%5%7%6%24446%36%
2265
21st to endDay
9%15%36%5%23446%41%
2340
May1st to 10thDay
9%10%46%6%45%5%7%8%37%
2340
11th to 20thDay
8%8%36%5%35%5%7%9%40%
2301
21st to endDay
9%8%37%7%36%6%7%7%37%
2530
June1st to 10thDay
5%5%35%5%345%7%7%52%
2389
11th to 20thDay
7%5%24423446%60%
2512
21st to endDay
331332444469%
2340
July1st to 10thDay
32235%245%5%7%62%
2340
11th to 20thDay
5%325%5%35%6%5%7%56%
2340
21st to endDay
5%325%6%36%6%6%7%51%
2545
August1st to 10thDay
43245%36%5%6%6%55%
2328
11th to 20thDay
4313335%5%6%6%61%
2299
21st to endDay
5%4245%345%6%7%58%
2553
September1st to 10thDay
3313224445%67%
2034
11th to 20thDay
5%4244335%5%5%61%
1980
21st to endDay
8%413322335%65%
1980
October1st to 10thDay
9%9%35%43344452%
1890
11th to 20thDay
8%7%34423346%57%
1800
21st to endDay
7%9%34424445%53%
1978
November1st to 10thDay
11%11%35%6%24445%45%
1674
11th to 20thDay
13%11%45%434436%44%
1710
21st to endDay
8%13%6%8%5%34336%41%
1578
December1st to 10thDay
11%13%38%5%33445%40%
1520
11th to 20thDay
11%12%6%10%7%45%5%5%8%28%
1926
21st to endDay
7%13%5%11%7%35%5%5%6%33%
3112
January1st to 10thNight
7%11%8%15%6%23447%32%
4097
11th to 20thNight
8%23%7%12%5%23345%28%
4110
21st to endNight
5%16%6%9%6%35%45%6%35%
4521
February1st to 10thNight
10%14%5%9%6%35%447%33%
2470
11th to 20thNight
8%15%49%6%34445%39%
2332
21st to endNight
6%13%6%12%5%345%5%5%36%
1884
March1st to 10thNight
9%16%6%10%6%435%45%33%
2145
11th to 20thNight
7%11%5%6%5%35%5%6%7%40%
2090
21st to endNight
9%15%5%8%5%345%6%6%35%
2255
April1st to 10thNight
13%13%46%5%23346%42%
1962
11th to 20thNight
7%12%47%425%5%6%6%42%
1639
21st to endNight
10%12%36%4345%45%45%
1620
May1st to 10thNight
10%9%35%6%45%6%6%6%41%
1620
11th to 20thNight
8%6%26%5%3445%8%48%
1594
21st to endNight
9%6%26%6%45%5%8%7%43%
1746
June1st to 10thNight
7%6%25%42445%7%53%
1559
11th to 20thNight
6%423323447%63%
1440
21st to endNight
431332346%6%65%
1614
July1st to 10thNight
5%335%6%35%46%6%56%
1620
11th to 20thNight
45%36%5%35%5%6%6%53%
1620
21st to endNight
4425%5%45%5%6%10%50%
1773
August1st to 10thNight
4415%4346%6%8%55%
1611
11th to 20thNight
33245%46%45%7%57%
1602
21st to endNight
5%3144345%5%8%58%
1801
September1st to 10thNight
4324424345%66%
1922
11th to 20thNight
6%323324446%64%
1980
21st to endNight
7%42422223468%
1980
October1st to 10thNight
8%6%34425%435%56%
2068
11th to 20thNight
8%7%34422345%59%
2160
21st to endNight
7%9%33324345%56%
2376
November1st to 10thNight
10%11%3432346%7%47%
2405
11th to 20thNight
10%9%35%33345%7%47%
2470
21st to endNight
8%11%5%6%5%24446%45%
2578
December1st to 10thNight
10%12%5%6%42346%6%42%
2660
11th to 20thNight
11%12%5%7%5%35%46%7%34%
3271
21st to endNight
8%13%411%8%345%47%33%
4581

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
58%7%10%18%8%1
2859
11th to 20thDay
61%5%13%14%6%1
2860
21st to endDay
51%7%16%18%7%1
3146
February1st to 10thDay
56%5%12%17%9%2
1710
11th to 20thDay
54%5%11%19%11%1
1740
21st to endDay
54%6%10%19%10%1
1570
March1st to 10thDay
50%6%12%22%9%2
2033
11th to 20thDay
46%412%25%11%2
2090
21st to endDay
56%6%12%17%7%2
2256
April1st to 10thDay
49%49%20%13%5%
1998
11th to 20thDay
48%5%10%20%15%1
2268
21st to endDay
42%48%26%18%1
2340
May1st to 10thDay
40%6%7%25%18%3
2340
11th to 20thDay
36%5%7%27%21%5%
2304
21st to endDay
41%5%8%25%17%3
2530
June1st to 10thDay
28%5%6%23%29%10%
2389
11th to 20thDay
25%4420%28%18%
2512
21st to endDay
18%3113%31%33%
2340
July1st to 10thDay
20%4313%27%32%
2276
11th to 20thDay
24%5%414%25%28%
2271
21st to endDay
27%5%7%14%23%25%
2404
August1st to 10thDay
26%4418%22%25%
2313
11th to 20thDay
21%5%414%30%26%
2299
21st to endDay
24%4319%32%19%
2553
September1st to 10thDay
18%4417%29%28%
2034
11th to 20thDay
24%45%20%26%21%
1980
21st to endDay
22%3422%34%15%
1980
October1st to 10thDay
36%25%22%26%9%
1890
11th to 20thDay
29%38%31%24%6%
1800
21st to endDay
32%411%30%21%2
1978
November1st to 10thDay
40%5%10%22%19%4
1674
11th to 20thDay
41%49%29%15%1
1710
21st to endDay
45%49%26%13%2
1578
December1st to 10thDay
46%5%16%20%10%3
1520
11th to 20thDay
53%6%10%22%9%
1924
21st to endDay
48%8%11%18%15%1
3112
January1st to 10thNight
52%6%11%21%9%1
4097
11th to 20thNight
59%6%11%15%7%2
4110
21st to endNight
47%6%18%18%8%2
4521
February1st to 10thNight
49%6%13%21%10%1
2470
11th to 20thNight
47%49%22%17%2
2333
21st to endNight
47%6%9%23%13%2
1884
March1st to 10thNight
51%5%9%21%13%1
2145
11th to 20thNight
40%5%10%27%16%2
2090
21st to endNight
47%6%11%23%10%3
2255
April1st to 10thNight
43%410%20%16%7%
1962
11th to 20thNight
39%5%8%24%20%3
1639
21st to endNight
41%49%23%22%1
1620
May1st to 10thNight
39%5%8%25%21%3
1620
11th to 20thNight
33%48%28%20%7%
1595
21st to endNight
36%311%29%17%4
1746
June1st to 10thNight
28%46%23%29%9%
1559
11th to 20thNight
21%46%19%30%21%
1440
21st to endNight
19%3110%30%36%
1614
July1st to 10thNight
27%4313%20%33%
1575
11th to 20thNight
29%4415%20%28%
1566
21st to endNight
28%47%16%20%25%
1674
August1st to 10thNight
25%5%7%17%21%24%
1602
11th to 20thNight
26%4313%27%27%
1602
21st to endNight
24%4414%31%23%
1801
September1st to 10thNight
21%4415%25%32%
1922
11th to 20thNight
22%25%20%27%24%
1980
21st to endNight
23%2318%34%20%
1980
October1st to 10thNight
31%27%21%29%9%
2068
11th to 20thNight
29%35%27%28%8%
2160
21st to endNight
30%48%27%26%5%
2376
November1st to 10thNight
35%5%8%26%21%6%
2405
11th to 20thNight
35%5%12%27%19%3
2470
21st to endNight
39%48%28%16%4
2578
December1st to 10thNight
41%414%25%12%4
2660
11th to 20thNight
48%413%23%11%1
3272
21st to endNight
49%6%13%17%12%2
4581

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%16%22%22%13%
270
11th to 20thDay
21%18%32%18%9%2
270
21st to endDay
18%18%30%26%8%1
297
February1st to 10thDay
27%19%34%14%6%
270
11th to 20thDay
20%22%35%17%5%1
336
21st to endDay
23%22%36%16%4
382
March1st to 10thDay
23%20%35%17%41
460
11th to 20thDay
20%18%35%22%5%
460
21st to endDay
27%21%34%16%2
491
April1st to 10thDay
25%18%31%21%41
420
11th to 20thDay
26%25%28%16%41
412
21st to endDay
27%20%25%21%7%
420
May1st to 10thDay
18%22%33%20%7%1
423
11th to 20thDay
17%19%33%21%8%2
448
21st to endDay
15%15%32%26%9%2
485
June1st to 10thDay
9%15%38%29%7%2
499
11th to 20thDay
11%16%31%27%14%1
622
21st to endDay
6%17%40%31%5%1
450
July1st to 10thDay
410%44%33%8%2
446
11th to 20thDay
5%12%42%32%7%2
444
21st to endDay
45%43%34%11%2
487
August1st to 10thDay
9%9%42%31%9%1
447
11th to 20thDay
5%8%36%39%10%3
437
21st to endDay
6%11%35%36%9%3
495
September1st to 10thDay
6%10%33%34%14%2
450
11th to 20thDay
10%15%31%34%9%2
450
21st to endDay
12%14%28%35%10%2
450
October1st to 10thDay
15%18%29%27%11%1
360
11th to 20thDay
13%14%30%27%14%1
270
21st to endDay
14%20%34%25%7%
297
November1st to 10thDay
24%17%25%25%6%2
270
11th to 20thDay
16%19%34%18%10%3
270
21st to endDay
19%13%24%31%11%2
270
December1st to 10thDay
22%11%31%24%9%2
270
11th to 20thDay
19%14%35%25%7%1
270
21st to endDay
23%17%29%25%6%
297
January1st to 10thNight
18%9%26%27%17%4
760
11th to 20thNight
18%8%27%29%14%4
760
21st to endNight
15%10%24%33%15%4
836
February1st to 10thNight
18%8%29%32%10%3
760
11th to 20thNight
14%12%29%29%14%2
744
21st to endNight
15%13%31%29%11%2
628
March1st to 10thNight
19%13%29%27%9%3
760
11th to 20thNight
13%11%27%31%15%3
760
21st to endNight
17%14%26%31%10%2
820
April1st to 10thNight
20%12%26%28%12%2
702
11th to 20thNight
14%11%29%32%11%2
533
21st to endNight
17%9%23%34%16%2
540
May1st to 10thNight
14%8%30%34%14%1
540
11th to 20thNight
12%7%21%34%22%3
531
21st to endNight
11%9%22%33%20%4
584
June1st to 10thNight
10%9%20%38%21%2
540
11th to 20thNight
8%9%25%39%16%2
540
21st to endNight
5%5%24%38%24%4
540
July1st to 10thNight
6%6%19%33%32%3
525
11th to 20thNight
6%321%43%22%4
522
21st to endNight
4315%41%36%2
591
August1st to 10thNight
6%421%40%27%2
537
11th to 20thNight
5%318%43%28%4
534
21st to endNight
5%422%43%24%3
594
September1st to 10thNight
6%5%17%43%25%5%
662
11th to 20thNight
7%6%20%36%26%6%
720
21st to endNight
9%6%19%30%27%9%
720
October1st to 10thNight
11%6%26%32%20%4
720
11th to 20thNight
12%5%21%36%22%5%
720
21st to endNight
12%8%25%31%19%4
792
November1st to 10thNight
16%11%21%30%18%4
740
11th to 20thNight
15%8%28%29%15%5%
760
21st to endNight
13%11%25%32%15%4
868
December1st to 10thNight
17%9%26%32%14%1
950
11th to 20thNight
21%9%28%30%11%2
950
21st to endNight
23%11%25%31%9%1
870
Page generated at 2024-03-24 21:37:04. Version ac07

Copyright © 2024 Attilla Danko.


Alpenglow Observatory Clear Sky Chart |Charts Home