Norris Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Norris Lake 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%
23816
20%
74568
15%
23766
52%
23766
24%
48157

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
25%
760
17%
2459
10%
757
35%
757
18%
1676
January11th to 20thNight
24%
744
16%
2417
9%
744
33%
744
15%
1731
January21st to endNight
23%
792
20%
2574
9%
792
35%
792
18%
1756
February1st to 10thNight
27%
720
18%
2180
10%
720
35%
720
19%
1522
February11th to 20thNight
19%
701
16%
2099
7%
700
28%
700
17%
1508
February21st to endNight
22%
592
19%
1776
10%
592
30%
592
16%
1287
March1st to 10thNight
31%
720
21%
2110
12%
720
39%
720
23%
1387
March11th to 20thNight
30%
720
17%
1980
9%
720
36%
720
21%
1383
March21st to endNight
34%
792
16%
2178
9%
792
39%
792
23%
1495
April1st to 10thNight
43%
666
23%
1926
13%
666
51%
666
31%
1156
April11th to 20thNight
41%
533
26%
1753
16%
533
53%
533
27%
1043
April21st to endNight
45%
540
23%
1620
15%
540
53%
540
27%
1027
May1st to 10thNight
47%
540
19%
1620
11%
540
53%
540
29%
1013
May11th to 20thNight
51%
531
15%
1593
9%
531
55%
531
26%
1036
May21st to endNight
62%
582
16%
1744
12%
582
64%
582
27%
1122
June1st to 10thNight
64%
540
16%
1620
13%
540
66%
540
28%
1022
June11th to 20thNight
74%
540
17%
1620
14%
540
76%
540
36%
946
June21st to endNight
68%
540
17%
1620
16%
540
69%
540
29%
1022
July1st to 10thNight
66%
525
12%
1575
11%
525
67%
525
24%
1050
July11th to 20thNight
75%
522
16%
1566
14%
522
75%
522
31%
962
July21st to endNight
70%
591
17%
1672
15%
558
72%
558
29%
1050
August1st to 10thNight
71%
537
16%
1600
15%
534
72%
534
27%
1023
August11th to 20thNight
67%
534
18%
1629
17%
534
68%
534
28%
1058
August21st to endNight
72%
594
19%
1980
20%
594
74%
594
28%
1207
September1st to 10thNight
67%
682
21%
1942
19%
682
68%
682
31%
1233
September11th to 20thNight
62%
720
21%
1980
18%
720
63%
720
29%
1300
September21st to endNight
58%
720
27%
1980
20%
720
63%
720
35%
1211
October1st to 10thNight
58%
720
29%
1980
25%
720
62%
720
38%
1171
October11th to 20thNight
45%
720
26%
2119
20%
720
54%
720
32%
1274
October21st to endNight
50%
792
30%
2403
25%
792
57%
792
32%
1434
November1st to 10thNight
53%
740
28%
2406
26%
740
61%
740
32%
1358
November11th to 20thNight
41%
760
26%
2470
19%
760
51%
760
27%
1465
November21st to endNight
43%
760
24%
2470
19%
760
51%
760
25%
1551
December1st to 10thNight
31%
760
17%
2470
12%
760
39%
760
16%
1745
December11th to 20thNight
34%
759
21%
2978
15%
759
43%
759
18%
1912
December21st to endNight
30%
827
11%
4459
10%
817
39%
817
9%
3021

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
12%7%36%6%35%5%6%8%39%
74910
Night
12%6%36%5%35%5%6%7%41%
74912
TransparencyDay
42%8%12%21%15%3
74633
Night
41%7%12%21%16%3
74708
SeeingDay
16%10%22%24%19%9%
13715
Night
15%9%23%31%20%3
23830

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
15%9%48%6%45%5%6%7%32%
1706
11th to 20thDay
18%10%5%9%6%34445%31%
1671
21st to endDay
14%9%46%5%3445%6%40%
1782
February1st to 10thDay
18%9%5%6%7%35%445%34%
1778
11th to 20thDay
19%8%48%5%35%346%32%
1748
21st to endDay
19%10%47%43445%5%35%
1480
March1st to 10thDay
15%8%36%5%35%5%47%40%
1849
11th to 20thDay
18%8%38%6%35%5%5%6%33%
1980
21st to endDay
16%8%47%6%35%45%6%36%
2178
April1st to 10thDay
10%7%35%5%35%5%6%8%43%
2047
11th to 20thDay
13%7%26%4345%5%6%44%
2156
21st to endDay
13%5%35%6%35%5%6%8%41%
2340
May1st to 10thDay
12%6%36%6%35%6%6%8%41%
2340
11th to 20thDay
11%7%36%7%46%5%6%8%37%
2301
21st to endDay
10%5%26%5%46%6%6%10%40%
2531
June1st to 10thDay
10%5%36%5%47%6%7%9%38%
2340
11th to 20thDay
5%425%7%46%7%8%10%39%
2340
21st to endDay
8%426%6%46%7%8%11%39%
2340
July1st to 10thDay
8%6%37%7%47%7%9%9%32%
2340
11th to 20thDay
10%5%26%7%47%7%7%11%33%
2340
21st to endDay
9%5%37%8%5%7%7%7%10%32%
2547
August1st to 10thDay
9%5%36%7%46%8%8%11%32%
2327
11th to 20thDay
9%6%26%6%5%7%7%8%10%34%
2267
21st to endDay
9%6%36%6%46%5%8%9%39%
2376
September1st to 10thDay
12%6%36%6%35%45%8%44%
1998
11th to 20thDay
13%6%25%435%5%6%9%42%
1980
21st to endDay
13%6%25%5%24447%48%
1980
October1st to 10thDay
10%5%25%434447%53%
1980
11th to 20thDay
13%5%25%434445%51%
1840
21st to endDay
15%6%15%42435%6%47%
1949
November1st to 10thDay
9%42442445%7%55%
1672
11th to 20thDay
12%6%35%4345%5%6%49%
1710
21st to endDay
14%7%446%34445%45%
1710
December1st to 10thDay
18%12%36%5%345%46%33%
1710
11th to 20thDay
12%11%36%6%36%6%6%6%34%
2153
21st to endDay
17%12%37%6%35%5%47%30%
3124
January1st to 10thNight
16%9%37%7%3445%5%37%
2459
11th to 20thNight
17%9%5%7%7%45%5%5%6%31%
2417
21st to endNight
14%7%5%7%6%35%5%45%38%
2574
February1st to 10thNight
15%9%5%6%6%45%5%6%7%34%
2180
11th to 20thNight
21%6%47%5%35%5%5%6%33%
2098
21st to endNight
21%8%45%7%35%5%5%6%31%
1776
March1st to 10thNight
14%7%36%5%4445%6%41%
2110
11th to 20thNight
15%7%47%5%35%5%6%6%38%
1980
21st to endNight
13%7%36%5%46%6%6%7%38%
2178
April1st to 10thNight
12%424435%5%6%7%49%
1926
11th to 20thNight
12%6%35%43435%7%48%
1753
21st to endNight
12%5%35%5%345%5%8%45%
1620
May1st to 10thNight
9%5%36%5%445%6%10%42%
1620
11th to 20thNight
10%5%37%5%35%6%6%9%40%
1592
21st to endNight
7%5%36%6%45%7%6%10%41%
1744
June1st to 10thNight
8%425%6%36%6%8%11%40%
1620
11th to 20thNight
3424425%7%7%12%50%
1620
21st to endNight
6%5%35%6%47%5%6%11%42%
1620
July1st to 10thNight
10%6%35%6%46%6%8%10%37%
1620
11th to 20thNight
7%4245%35%6%7%11%45%
1620
21st to endNight
6%426%6%45%7%8%12%39%
1771
August1st to 10thNight
7%5%346%36%6%8%10%41%
1611
11th to 20thNight
9%5%25%6%445%7%9%43%
1629
21st to endNight
9%4146%47%5%6%10%44%
1980
September1st to 10thNight
10%6%26%436%45%6%48%
1942
11th to 20thNight
11%6%26%5%45%5%5%8%45%
1980
21st to endNight
10%435%5%34346%52%
1980
October1st to 10thNight
10%5%245%23346%56%
1980
11th to 20thNight
13%6%2442445%6%50%
2119
21st to endNight
13%6%25%424445%51%
2403
November1st to 10thNight
11%5%34434445%53%
2406
11th to 20thNight
12%5%45%4245%5%6%48%
2470
21st to endNight
13%7%36%5%35%5%46%44%
2470
December1st to 10thNight
16%9%37%7%35%5%6%5%33%
2470
11th to 20thNight
15%8%37%5%45%5%5%5%38%
3042
21st to endNight
17%10%37%7%5%6%6%7%7%26%
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
50%7%9%19%12%3
1707
11th to 20thDay
56%5%7%17%13%2
1671
21st to endDay
44%6%10%23%16%1
1782
February1st to 10thDay
53%5%8%18%14%2
1778
11th to 20thDay
54%5%8%20%11%2
1758
21st to endDay
51%5%9%15%15%5%
1480
March1st to 10thDay
44%5%8%21%18%4
1849
11th to 20thDay
51%6%9%17%13%3
1980
21st to endDay
49%5%11%22%11%2
2178
April1st to 10thDay
38%7%12%23%15%3
2047
11th to 20thDay
40%6%10%17%24%4
2156
21st to endDay
40%7%11%26%14%2
2340
May1st to 10thDay
40%7%13%25%12%2
2340
11th to 20thDay
45%9%14%20%11%2
2305
21st to endDay
39%8%16%23%12%2
2531
June1st to 10thDay
39%10%15%20%14%1
2340
11th to 20thDay
34%12%17%21%14%2
2340
21st to endDay
36%12%16%20%13%4
2340
July1st to 10thDay
43%12%16%16%12%2
2275
11th to 20thDay
41%11%16%16%11%4
2271
21st to endDay
42%12%14%21%10%1
2405
August1st to 10thDay
42%12%20%18%9%1
2314
11th to 20thDay
40%12%17%15%14%1
2267
21st to endDay
39%11%15%20%13%3
2376
September1st to 10thDay
39%8%13%20%14%6%
1998
11th to 20thDay
38%9%11%22%17%3
1980
21st to endDay
35%6%11%22%20%6%
1980
October1st to 10thDay
33%5%10%23%25%5%
1980
11th to 20thDay
35%410%22%22%6%
1840
21st to endDay
38%47%25%21%5%
1949
November1st to 10thDay
32%48%24%28%4
1672
11th to 20thDay
36%46%24%24%5%
1710
21st to endDay
41%5%8%23%21%2
1710
December1st to 10thDay
53%5%8%21%11%2
1710
11th to 20thDay
48%6%11%18%14%2
2150
21st to endDay
52%5%11%22%9%1
3124
January1st to 10thNight
49%5%9%19%14%3
2459
11th to 20thNight
54%5%11%15%13%2
2417
21st to endNight
49%5%8%22%15%2
2574
February1st to 10thNight
50%5%10%20%14%1
2180
11th to 20thNight
52%5%8%19%12%4
2099
21st to endNight
53%5%9%15%13%4
1776
March1st to 10thNight
43%5%9%17%21%5%
2110
11th to 20thNight
46%7%10%20%14%3
1980
21st to endNight
44%7%11%23%13%2
2178
April1st to 10thNight
33%7%13%25%20%3
1926
11th to 20thNight
37%5%9%20%21%7%
1753
21st to endNight
37%8%11%28%14%2
1620
May1st to 10thNight
37%7%15%27%13%2
1620
11th to 20thNight
40%8%18%21%12%1
1593
21st to endNight
36%10%16%25%11%1
1745
June1st to 10thNight
35%10%17%21%15%2
1620
11th to 20thNight
24%13%21%26%15%2
1620
21st to endNight
36%9%16%22%14%4
1620
July1st to 10thNight
40%10%19%17%13%2
1575
11th to 20thNight
31%11%22%18%14%5%
1566
21st to endNight
33%12%20%24%11%1
1672
August1st to 10thNight
35%11%19%23%10%1
1600
11th to 20thNight
35%12%19%18%15%1
1629
21st to endNight
36%8%16%25%13%2
1980
September1st to 10thNight
35%8%15%20%17%5%
1942
11th to 20thNight
38%8%12%20%20%2
1980
21st to endNight
34%6%11%23%23%5%
1980
October1st to 10thNight
31%410%21%27%7%
1980
11th to 20thNight
34%6%9%22%24%5%
2119
21st to endNight
35%46%23%25%7%
2403
November1st to 10thNight
34%38%22%25%8%
2406
11th to 20thNight
37%48%20%24%6%
2470
21st to endNight
41%5%7%25%20%3
2470
December1st to 10thNight
52%6%9%19%11%3
2470
11th to 20thNight
45%5%9%22%16%2
3044
21st to endNight
52%8%12%16%11%1
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
24%24%32%17%31
270
11th to 20thDay
28%25%26%16%41
257
21st to endDay
19%25%40%12%4
264
February1st to 10thDay
25%25%33%13%41
240
11th to 20thDay
35%25%28%10%2
240
21st to endDay
37%17%36%8%21
198
March1st to 10thDay
21%17%37%20%4
289
11th to 20thDay
22%21%29%21%6%1
420
21st to endDay
22%18%29%22%9%1
462
April1st to 10thDay
17%17%25%25%14%2
420
11th to 20thDay
17%13%30%26%12%2
412
21st to endDay
19%13%27%25%14%2
420
May1st to 10thDay
15%11%33%24%12%5%
423
11th to 20thDay
12%8%26%27%19%8%
447
21st to endDay
14%5%15%27%22%16%
485
June1st to 10thDay
14%416%26%26%15%
450
11th to 20thDay
5%417%26%31%18%
450
21st to endDay
8%222%30%23%15%
450
July1st to 10thDay
11%411%22%28%24%
445
11th to 20thDay
10%412%25%29%20%
444
21st to endDay
11%211%25%33%18%
488
August1st to 10thDay
11%313%22%32%19%
446
11th to 20thDay
10%313%33%28%13%
439
21st to endDay
11%37%25%31%22%
495
September1st to 10thDay
11%310%28%28%20%
450
11th to 20thDay
15%49%21%32%20%
450
21st to endDay
14%6%18%26%25%11%
450
October1st to 10thDay
12%6%18%25%27%11%
450
11th to 20thDay
13%11%24%29%20%3
450
21st to endDay
20%9%22%29%17%3
464
November1st to 10thDay
14%10%32%23%17%4
270
11th to 20thDay
14%14%33%29%8%2
270
21st to endDay
14%12%35%26%11%2
270
December1st to 10thDay
26%17%31%18%7%1
270
11th to 20thDay
20%17%29%24%9%1
270
21st to endDay
22%17%32%20%9%
297
January1st to 10thNight
21%17%31%26%4
760
11th to 20thNight
23%17%31%25%5%
744
21st to endNight
18%15%39%26%3
792
February1st to 10thNight
21%13%34%28%4
720
11th to 20thNight
24%17%36%22%1
703
21st to endNight
25%18%32%23%2
592
March1st to 10thNight
18%15%31%32%4
720
11th to 20thNight
19%13%32%28%8%1
720
21st to endNight
17%12%31%32%8%
792
April1st to 10thNight
15%12%27%36%10%
666
11th to 20thNight
15%9%31%31%14%1
533
21st to endNight
14%8%28%38%12%1
540
May1st to 10thNight
12%7%26%36%18%2
540
11th to 20thNight
12%323%32%26%3
531
21st to endNight
8%214%34%35%7%
584
June1st to 10thNight
9%213%37%33%5%
540
11th to 20thNight
4213%36%37%9%
540
21st to endNight
7%111%36%38%7%
540
July1st to 10thNight
12%38%26%40%12%
525
11th to 20thNight
8%17%27%44%12%
522
21st to endNight
6%29%28%44%12%
591
August1st to 10thNight
8%36%28%45%9%
537
11th to 20thNight
12%27%31%42%5%
534
21st to endNight
10%27%28%44%9%
594
September1st to 10thNight
10%310%27%43%6%
682
11th to 20thNight
12%311%28%39%7%
720
21st to endNight
11%319%32%31%4
720
October1st to 10thNight
13%6%16%27%31%8%
720
11th to 20thNight
16%7%26%31%18%3
720
21st to endNight
17%8%21%36%17%2
792
November1st to 10thNight
14%9%19%35%20%3
740
11th to 20thNight
13%13%27%34%12%1
760
21st to endNight
16%12%25%35%12%
760
December1st to 10thNight
22%15%27%29%7%
760
11th to 20thNight
20%12%29%31%8%1
760
21st to endNight
22%15%25%32%6%
836
Page generated at 2024-01-13 19:28:28. Version ac07

Copyright 2024 Attilla Danko


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