Lookout Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lookout 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
46%
23649
23%
74444
16%
23593
54%
23593
27%
45700

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
22%
760
22%
2459
8%
757
38%
757
20%
1574
January11th to 20thNight
25%
744
21%
2417
9%
744
39%
744
18%
1625
January21st to endNight
22%
792
29%
2430
11%
792
40%
792
23%
1528
February1st to 10thNight
28%
720
24%
2160
11%
720
41%
720
24%
1392
February11th to 20thNight
21%
703
19%
2098
7%
699
32%
699
19%
1408
February21st to endNight
21%
592
21%
1776
8%
592
33%
592
18%
1240
March1st to 10thNight
30%
720
24%
2160
13%
720
39%
720
25%
1349
March11th to 20thNight
29%
720
19%
1999
9%
720
38%
720
24%
1339
March21st to endNight
33%
792
21%
2178
11%
792
41%
792
25%
1452
April1st to 10thNight
41%
557
26%
1817
17%
557
53%
557
29%
1023
April11th to 20thNight
38%
533
28%
1775
18%
533
53%
533
30%
1012
April21st to endNight
52%
540
28%
1724
21%
540
62%
540
33%
968
May1st to 10thNight
50%
540
23%
1620
14%
540
58%
540
34%
929
May11th to 20thNight
54%
531
18%
1592
11%
531
59%
531
30%
990
May21st to endNight
63%
582
20%
1744
15%
582
66%
582
31%
1066
June1st to 10thNight
64%
540
18%
1620
15%
540
66%
540
30%
1012
June11th to 20thNight
74%
540
19%
1620
15%
540
76%
540
43%
876
June21st to endNight
72%
540
18%
1620
14%
540
73%
540
37%
941
July1st to 10thNight
71%
525
16%
1575
14%
525
72%
525
30%
990
July11th to 20thNight
72%
522
16%
1566
14%
522
73%
522
32%
946
July21st to endNight
69%
591
18%
1672
16%
558
71%
558
31%
1038
August1st to 10thNight
73%
537
17%
1658
19%
534
74%
534
32%
1002
August11th to 20thNight
66%
534
17%
1776
18%
534
67%
534
27%
1086
August21st to endNight
64%
594
20%
1980
22%
594
66%
594
25%
1265
September1st to 10thNight
67%
620
21%
1880
21%
620
69%
620
30%
1160
September11th to 20thNight
59%
720
23%
1980
19%
720
62%
720
31%
1284
September21st to endNight
59%
720
29%
1980
20%
720
65%
720
37%
1175
October1st to 10thNight
57%
720
33%
1980
25%
720
64%
720
42%
1126
October11th to 20thNight
47%
720
31%
2011
22%
720
58%
720
36%
1207
October21st to endNight
49%
792
31%
2472
27%
792
58%
792
33%
1403
November1st to 10thNight
49%
740
27%
2406
22%
740
59%
740
32%
1317
November11th to 20thNight
40%
760
30%
2470
18%
760
57%
760
32%
1385
November21st to endNight
39%
760
26%
2470
17%
760
51%
760
25%
1497
December1st to 10thNight
29%
760
23%
2470
13%
760
42%
760
19%
1638
December11th to 20thNight
32%
759
26%
2904
15%
758
44%
758
21%
1723
December21st to endNight
29%
829
14%
4385
12%
817
39%
817
11%
2734

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
14%6%35%6%35%5%6%7%40%
74886
Night
14%6%25%5%3445%7%44%
74938
TransparencyDay
42%5%11%21%17%4
74609
Night
38%5%11%22%19%5%
74734
SeeingDay
19%11%23%22%17%9%
13579
Night
17%9%21%29%20%4
23659

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
19%9%3432445%6%41%
1706
11th to 20thDay
23%9%36%424335%39%
1671
21st to endDay
16%6%25%4345%45%46%
1923
February1st to 10thDay
18%9%45%5%24446%38%
1800
11th to 20thDay
23%7%25%5%34445%37%
1748
21st to endDay
23%7%35%5%3444438%
1480
March1st to 10thDay
15%6%35%5%345%5%6%42%
1800
11th to 20thDay
21%7%36%5%35%446%36%
1960
21st to endDay
15%7%36%6%35%6%6%8%36%
2178
April1st to 10thDay
13%6%35%5%35%5%6%7%44%
2157
11th to 20thDay
14%6%35%5%34446%46%
2134
21st to endDay
11%425%6%35%5%6%8%46%
2236
May1st to 10thDay
12%5%25%5%345%5%7%47%
2340
11th to 20thDay
12%6%36%7%46%5%5%7%40%
2301
21st to endDay
11%5%36%5%37%6%7%9%39%
2531
June1st to 10thDay
11%6%36%7%46%7%7%9%35%
2340
11th to 20thDay
5%436%6%46%8%8%11%41%
2340
21st to endDay
8%5%25%7%37%6%7%11%37%
2340
July1st to 10thDay
10%5%47%8%5%7%8%8%10%29%
2340
11th to 20thDay
10%5%36%7%5%7%8%9%11%29%
2340
21st to endDay
7%6%36%8%5%7%8%8%11%30%
2547
August1st to 10thDay
9%5%25%8%5%8%8%10%11%30%
2265
11th to 20thDay
11%6%36%7%46%7%8%11%31%
2125
21st to endDay
15%6%27%6%5%6%6%7%8%31%
2376
September1st to 10thDay
11%6%36%6%45%5%7%9%36%
2060
11th to 20thDay
16%5%26%6%45%5%5%7%40%
1980
21st to endDay
14%5%25%5%2445%5%49%
1980
October1st to 10thDay
13%5%24434445%52%
1980
11th to 20thDay
11%5%25%42345%5%53%
1947
21st to endDay
15%5%23334345%52%
1882
November1st to 10thDay
13%5%23423346%55%
1672
11th to 20thDay
14%4344245%5%5%50%
1710
21st to endDay
17%6%245%3435%6%45%
1710
December1st to 10thDay
22%8%25%5%25%345%37%
1710
11th to 20thDay
17%7%37%5%34445%41%
2153
21st to endDay
20%8%46%5%3445%7%34%
3124
January1st to 10thNight
20%6%26%5%34345%43%
2459
11th to 20thNight
18%7%36%6%35%5%5%6%36%
2417
21st to endNight
16%8%3443444445%
2430
February1st to 10thNight
17%6%36%434446%43%
2160
11th to 20thNight
21%6%27%5%34345%40%
2098
21st to endNight
22%7%35%5%35%45%5%35%
1776
March1st to 10thNight
15%6%35%5%24447%45%
2160
11th to 20thNight
16%7%26%5%35%45%7%40%
1999
21st to endNight
13%8%36%5%3445%6%42%
2178
April1st to 10thNight
12%4245%345%6%8%49%
1817
11th to 20thNight
14%5%24333446%51%
1775
21st to endNight
10%424425%5%6%8%51%
1724
May1st to 10thNight
10%4344345%6%7%51%
1620
11th to 20thNight
10%5%25%5%346%7%10%43%
1592
21st to endNight
9%6%25%5%35%6%5%9%44%
1744
June1st to 10thNight
7%5%36%6%45%6%7%10%41%
1620
11th to 20thNight
5%32443447%11%53%
1620
21st to endNight
5%4245%35%6%8%13%45%
1620
July1st to 10thNight
8%436%5%37%6%8%11%38%
1620
11th to 20thNight
8%5%246%36%7%7%12%40%
1620
21st to endNight
6%5%25%5%46%7%8%12%39%
1771
August1st to 10thNight
7%5%235%46%5%9%12%42%
1669
11th to 20thNight
11%5%25%446%5%7%9%42%
1776
21st to endNight
13%5%35%5%345%7%10%40%
1980
September1st to 10thNight
9%5%345%36%47%9%44%
1880
11th to 20thNight
13%5%26%5%345%5%9%43%
1980
21st to endNight
12%5%14424447%53%
1980
October1st to 10thNight
11%424323345%59%
1980
11th to 20thNight
13%5%24434345%53%
2011
21st to endNight
14%5%24423445%54%
2472
November1st to 10thNight
13%424433346%54%
2406
11th to 20thNight
13%5%2432445%6%52%
2470
21st to endNight
16%6%25%425%45%6%45%
2470
December1st to 10thNight
21%6%46%5%33447%37%
2470
11th to 20thNight
17%7%25%423335%47%
3042
21st to endNight
21%6%36%5%35%5%7%8%32%
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
45%37%20%20%4
1707
11th to 20thDay
49%37%17%20%4
1671
21st to endDay
40%5%6%24%21%5%
1923
February1st to 10thDay
47%37%21%19%3
1800
11th to 20thDay
50%3421%17%4
1758
21st to endDay
50%37%15%19%6%
1480
March1st to 10thDay
42%48%17%23%7%
1800
11th to 20thDay
51%49%15%17%4
1960
21st to endDay
44%6%11%23%13%2
2178
April1st to 10thDay
38%5%10%23%19%5%
2157
11th to 20thDay
41%46%20%23%6%
2134
21st to endDay
35%410%30%17%3
2236
May1st to 10thDay
36%412%28%15%4
2340
11th to 20thDay
42%6%15%22%14%1
2305
21st to endDay
38%7%13%25%14%2
2531
June1st to 10thDay
43%7%15%22%13%1
2340
11th to 20thDay
33%8%18%26%13%2
2340
21st to endDay
38%8%18%22%11%3
2340
July1st to 10thDay
45%8%17%19%9%2
2275
11th to 20thDay
42%9%20%17%8%2
2271
21st to endDay
43%9%20%20%8%
2405
August1st to 10thDay
41%10%20%22%6%1
2252
11th to 20thDay
44%7%17%20%11%1
2125
21st to endDay
47%8%14%16%11%4
2376
September1st to 10thDay
42%8%15%16%14%5%
2060
11th to 20thDay
43%6%10%21%18%3
1980
21st to endDay
36%5%10%20%21%8%
1980
October1st to 10thDay
34%5%7%19%26%9%
1980
11th to 20thDay
33%38%24%23%9%
1947
21st to endDay
34%4421%28%9%
1882
November1st to 10thDay
33%35%19%30%9%
1672
11th to 20thDay
35%46%20%25%9%
1710
21st to endDay
40%45%20%25%5%
1710
December1st to 10thDay
50%36%18%19%4
1710
11th to 20thDay
45%35%18%23%5%
2150
21st to endDay
50%48%19%16%3
3124
January1st to 10thNight
45%37%20%21%4
2459
11th to 20thNight
49%48%18%17%4
2417
21st to endNight
42%35%23%23%5%
2430
February1st to 10thNight
43%37%21%21%5%
2160
11th to 20thNight
48%36%19%17%6%
2099
21st to endNight
50%46%17%17%6%
1776
March1st to 10thNight
41%37%18%22%9%
2160
11th to 20thNight
44%5%11%18%18%5%
1999
21st to endNight
43%48%25%17%2
2178
April1st to 10thNight
33%412%23%22%5%
1817
11th to 20thNight
35%36%24%21%10%
1775
21st to endNight
31%411%30%20%4
1724
May1st to 10thNight
32%5%14%22%24%3
1620
11th to 20thNight
36%7%19%23%14%1
1593
21st to endNight
35%7%14%25%16%3
1745
June1st to 10thNight
38%6%18%22%14%2
1620
11th to 20thNight
25%6%23%28%16%2
1620
21st to endNight
30%6%21%24%14%5%
1620
July1st to 10thNight
37%7%19%24%11%2
1575
11th to 20thNight
33%7%24%20%11%3
1566
21st to endNight
34%9%22%25%9%2
1672
August1st to 10thNight
32%9%24%26%9%1
1658
11th to 20thNight
37%7%22%18%14%2
1776
21st to endNight
39%9%18%19%12%3
1980
September1st to 10thNight
36%6%18%20%15%4
1880
11th to 20thNight
38%7%12%21%21%2
1980
21st to endNight
32%410%23%23%8%
1980
October1st to 10thNight
28%48%24%26%9%
1980
11th to 20thNight
34%36%23%23%10%
2011
21st to endNight
33%35%21%28%10%
2472
November1st to 10thNight
32%38%20%25%12%
2406
11th to 20thNight
33%35%21%27%11%
2470
21st to endNight
39%45%22%23%7%
2470
December1st to 10thNight
48%48%18%18%4
2470
11th to 20thNight
40%46%18%28%4
3044
21st to endNight
48%47%21%18%2
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
33%22%32%13%1
270
11th to 20thDay
36%17%32%11%32
257
21st to endDay
23%28%33%13%2
264
February1st to 10thDay
33%21%31%13%2
240
11th to 20thDay
41%26%25%8%
240
21st to endDay
40%18%38%32
198
March1st to 10thDay
28%18%38%14%21
240
11th to 20thDay
26%21%30%17%6%1
400
21st to endDay
22%18%36%17%7%
462
April1st to 10thDay
23%15%28%19%13%2
420
11th to 20thDay
19%16%31%21%11%1
412
21st to endDay
18%14%31%19%15%3
420
May1st to 10thDay
16%13%30%23%12%5%
423
11th to 20thDay
14%6%23%31%14%12%
447
21st to endDay
15%5%15%27%24%14%
485
June1st to 10thDay
16%5%17%30%18%14%
450
11th to 20thDay
7%5%14%27%25%21%
450
21st to endDay
11%418%27%23%17%
450
July1st to 10thDay
12%39%25%29%22%
445
11th to 20thDay
10%311%23%32%22%
444
21st to endDay
7%39%26%31%24%
488
August1st to 10thDay
15%311%22%28%21%
446
11th to 20thDay
14%210%33%28%13%
439
21st to endDay
18%47%26%29%15%
495
September1st to 10thDay
10%413%29%30%13%
450
11th to 20thDay
17%414%24%32%10%
450
21st to endDay
15%6%16%28%28%6%
450
October1st to 10thDay
15%5%22%26%23%8%
450
11th to 20thDay
15%10%27%28%18%2
450
21st to endDay
20%11%26%26%14%2
397
November1st to 10thDay
21%13%30%24%9%2
270
11th to 20thDay
19%20%38%21%3
270
21st to endDay
20%20%33%19%6%2
270
December1st to 10thDay
32%16%37%11%21
270
11th to 20thDay
26%20%33%16%6%
270
21st to endDay
32%15%35%13%41
297
January1st to 10thNight
25%17%31%23%4
760
11th to 20thNight
23%17%29%24%6%
744
21st to endNight
21%16%37%23%3
792
February1st to 10thNight
21%15%32%29%4
720
11th to 20thNight
24%18%33%22%2
703
21st to endNight
27%16%32%21%3
592
March1st to 10thNight
19%15%32%29%4
720
11th to 20thNight
20%15%30%25%9%1
720
21st to endNight
19%14%29%28%10%
792
April1st to 10thNight
14%15%27%32%12%1
557
11th to 20thNight
16%11%30%28%13%2
533
21st to endNight
12%9%22%38%17%1
540
May1st to 10thNight
11%6%26%33%22%2
540
11th to 20thNight
12%5%19%35%22%7%
531
21st to endNight
13%210%31%38%5%
584
June1st to 10thNight
9%211%36%36%6%
540
11th to 20thNight
5%111%33%37%13%
540
21st to endNight
7%29%31%41%10%
540
July1st to 10thNight
9%26%23%43%16%
525
11th to 20thNight
8%25%24%44%16%
522
21st to endNight
8%27%26%47%10%
591
August1st to 10thNight
8%26%22%48%14%
537
11th to 20thNight
13%46%29%39%8%
534
21st to endNight
15%36%26%41%8%
594
September1st to 10thNight
10%39%30%38%10%
620
11th to 20thNight
15%311%29%37%5%
720
21st to endNight
14%316%30%35%4
720
October1st to 10thNight
13%5%20%32%25%6%
720
11th to 20thNight
16%7%23%31%20%2
720
21st to endNight
16%9%20%36%16%3
792
November1st to 10thNight
16%8%22%33%19%3
740
11th to 20thNight
16%11%30%30%12%1
760
21st to endNight
22%9%25%32%12%1
760
December1st to 10thNight
25%13%26%28%7%1
760
11th to 20thNight
24%12%28%28%8%
760
21st to endNight
27%13%24%29%6%
836
Page generated at 2024-01-13 18:28:32. Version ac07

Copyright 2024 Attilla Danko


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