Littlebear Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Littlebear Observatory clear sky chart from 2005-11-06 to 2024-01-10.

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
42%
22424
10%
74378
11%
22378
43%
22378
15%
54981

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
24%
815
8%
2761
7%
811
26%
811
8%
2300
January11th to 20thNight
34%
720
9%
2520
9%
720
34%
720
10%
1996
January21st to endNight
35%
792
10%
2738
10%
792
37%
792
12%
2100
February1st to 10thNight
29%
720
8%
2340
7%
720
31%
720
9%
1929
February11th to 20thNight
33%
701
8%
2274
8%
700
34%
700
11%
1794
February21st to endNight
31%
592
10%
1855
10%
592
33%
592
11%
1478
March1st to 10thNight
36%
720
9%
2129
8%
720
37%
720
14%
1647
March11th to 20thNight
34%
720
10%
1980
8%
720
35%
720
14%
1565
March21st to endNight
31%
792
5%
2098
3%
792
31%
792
11%
1747
April1st to 10thNight
34%
720
7%
1800
4%
720
35%
720
13%
1476
April11th to 20thNight
38%
698
11%
1766
6%
698
40%
698
18%
1391
April21st to endNight
38%
486
8%
1566
7%
486
39%
486
12%
1212
May1st to 10thNight
46%
360
11%
1440
15%
360
48%
360
17%
952
May11th to 20thNight
51%
354
10%
1416
16%
354
52%
354
15%
958
May21st to endNight
44%
388
5%
1552
9%
388
46%
388
12%
1140
June1st to 10thNight
47%
360
4%
1414
6%
360
48%
360
13%
1005
June11th to 20thNight
41%
360
4%
1260
5%
360
41%
360
11%
973
June21st to endNight
58%
360
9%
1260
10%
360
59%
360
25%
783
July1st to 10thNight
65%
350
11%
1225
14%
350
66%
350
28%
727
July11th to 20thNight
71%
348
16%
1345
27%
348
72%
348
31%
703
July21st to endNight
76%
394
21%
1488
35%
372
78%
372
40%
682
August1st to 10thNight
76%
379
21%
1445
30%
377
76%
377
35%
725
August11th to 20thNight
76%
534
24%
1602
23%
534
77%
534
43%
849
August21st to endNight
64%
708
21%
1896
16%
708
65%
708
35%
1167
September1st to 10thNight
67%
720
20%
1800
12%
720
67%
720
39%
1122
September11th to 20thNight
57%
720
19%
1800
13%
720
58%
720
28%
1258
September21st to endNight
54%
720
17%
2047
16%
720
55%
720
25%
1407
October1st to 10thNight
52%
720
10%
2160
11%
720
53%
720
22%
1513
October11th to 20thNight
44%
720
12%
2160
13%
720
45%
720
18%
1562
October21st to endNight
39%
792
11%
2497
11%
792
41%
792
15%
1882
November1st to 10thNight
31%
740
7%
2537
7%
740
33%
740
10%
2018
November11th to 20thNight
31%
760
9%
2660
9%
760
33%
760
10%
2103
November21st to endNight
32%
760
7%
2660
7%
760
34%
760
10%
2106
December1st to 10thNight
37%
760
10%
2660
11%
760
38%
760
11%
2073
December11th to 20thNight
25%
759
7%
3223
5%
759
26%
759
6%
2611
December21st to endNight
21%
882
4%
5004
6%
865
22%
865
4%
4027

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
23%9%36%6%3445%6%30%
75010
Night
26%9%36%5%34445%29%
74658
TransparencyDay
57%313%18%7%1
74705
Night
59%313%17%7%1
74481
SeeingDay
27%8%17%26%17%5%
13895
Night
32%6%10%25%21%4
22437

By Month

Percentage Cloud Cover NW (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
42%11%5%7%6%3333315%
1385
11th to 20thDay
33%10%36%6%345%47%18%
1440
21st to endDay
33%11%36%6%25%45%7%18%
1616
February1st to 10thDay
34%11%5%7%6%336%46%16%
1620
11th to 20thDay
30%13%48%6%35%34420%
1575
21st to endDay
29%14%5%6%6%35%44420%
1400
March1st to 10thDay
29%14%38%7%3445%5%19%
1826
11th to 20thDay
32%12%5%6%5%35%5%45%19%
1980
21st to endDay
29%13%5%8%7%45%5%5%6%14%
2258
April1st to 10thDay
28%11%48%7%46%5%6%6%17%
2160
11th to 20thDay
24%10%47%8%45%5%47%22%
2141
21st to endDay
23%9%48%7%46%5%5%6%21%
2394
May1st to 10thDay
18%10%38%7%35%5%5%6%30%
2520
11th to 20thDay
20%8%37%7%35%5%6%8%28%
2477
21st to endDay
27%9%47%6%45%45%6%24%
2723
June1st to 10thDay
24%8%47%6%46%5%5%7%26%
2542
11th to 20thDay
26%8%47%7%45%6%5%6%21%
2700
21st to endDay
14%6%37%6%345%5%7%38%
2700
July1st to 10thDay
11%6%35%43445%7%48%
2700
11th to 20thDay
11%5%244245%6%7%49%
2566
21st to endDay
9%423323346%62%
2741
August1st to 10thDay
12%6%14424446%54%
2484
11th to 20thDay
9%42342345%9%55%
2298
21st to endDay
14%6%26%433447%44%
2459
September1st to 10thDay
11%6%26%6%24347%49%
2160
11th to 20thDay
16%7%46%6%4445%6%38%
2160
21st to endDay
20%8%35%5%3445%6%37%
1910
October1st to 10thDay
19%8%47%6%446%5%7%30%
1800
11th to 20thDay
28%10%35%5%3445%7%26%
1800
21st to endDay
32%9%35%6%35%5%46%22%
1859
November1st to 10thDay
40%11%26%4345%45%17%
1538
11th to 20thDay
36%11%36%43433422%
1520
21st to endDay
36%10%46%5%3434421%
1520
December1st to 10thDay
32%10%47%5%3434423%
1520
11th to 20thDay
34%13%46%6%34446%16%
1925
21st to endDay
30%12%5%10%8%45%5%4414%
2593
January1st to 10thNight
43%10%35%5%2444416%
2761
11th to 20thNight
36%10%36%5%3444421%
2520
21st to endNight
32%10%46%5%34447%21%
2738
February1st to 10thNight
34%13%46%6%34445%18%
2340
11th to 20thNight
30%14%46%5%34345%23%
2272
21st to endNight
31%14%37%423446%21%
1855
March1st to 10thNight
29%11%36%5%34446%24%
2129
11th to 20thNight
28%11%47%5%3445%6%24%
1979
21st to endNight
29%12%48%7%35%5%46%17%
2098
April1st to 10thNight
26%11%38%7%35%6%6%7%18%
1800
11th to 20thNight
22%10%46%6%45%5%5%5%26%
1766
21st to endNight
26%10%47%6%4445%6%24%
1566
May1st to 10thNight
20%8%36%6%3436%7%35%
1440
11th to 20thNight
20%7%36%5%35%5%5%7%33%
1416
21st to endNight
22%7%48%7%45%45%5%29%
1552
June1st to 10thNight
23%6%47%7%45%5%46%30%
1414
11th to 20thNight
28%9%38%6%35%345%25%
1260
21st to endNight
13%5%36%6%345%5%7%43%
1260
July1st to 10thNight
12%5%35%43445%5%50%
1260
11th to 20thNight
9%5%3432335%6%57%
1390
21st to endNight
8%323323345%63%
1576
August1st to 10thNight
9%413424347%58%
1453
11th to 20thNight
7%413423347%61%
1602
21st to endNight
14%5%25%423345%52%
1896
September1st to 10thNight
11%5%35%424346%53%
1800
11th to 20thNight
18%7%37%5%34445%42%
1800
21st to endNight
19%8%26%5%44445%40%
2047
October1st to 10thNight
21%7%36%7%35%5%46%33%
2160
11th to 20thNight
26%8%36%5%335%46%31%
2160
21st to endNight
30%9%26%5%2335%6%28%
2497
November1st to 10thNight
36%10%36%5%34445%20%
2537
11th to 20thNight
36%9%46%6%3434423%
2660
21st to endNight
35%8%47%6%3334422%
2660
December1st to 10thNight
32%9%47%5%245%4424%
2660
11th to 20thNight
32%13%5%8%6%3445%5%15%
3280
21st to endNight
31%14%49%8%45%44414%
5054

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
76%25%11%41
1385
11th to 20thDay
67%312%10%6%2
1440
21st to endDay
66%312%14%5%
1616
February1st to 10thDay
71%411%10%31
1620
11th to 20thDay
70%310%10%7%1
1584
21st to endDay
70%311%12%5%
1400
March1st to 10thDay
69%211%14%4
1826
11th to 20thDay
71%29%14%31
1980
21st to endDay
73%411%11%1
2258
April1st to 10thDay
70%414%11%1
2160
11th to 20thDay
66%311%13%6%1
2141
21st to endDay
65%5%12%13%5%1
2394
May1st to 10thDay
57%416%17%5%
2520
11th to 20thDay
55%5%19%16%4
2480
21st to endDay
63%416%15%2
2724
June1st to 10thDay
60%417%14%5%
2542
11th to 20thDay
65%315%13%3
2700
21st to endDay
46%421%20%8%1
2700
July1st to 10thDay
40%414%27%13%2
2626
11th to 20thDay
37%412%31%15%1
2488
21st to endDay
27%214%37%17%3
2589
August1st to 10thDay
34%415%32%13%2
2467
11th to 20thDay
29%422%30%12%3
2298
21st to endDay
42%314%32%9%1
2459
September1st to 10thDay
38%215%28%12%5%
2160
11th to 20thDay
48%313%20%14%2
2160
21st to endDay
49%416%20%10%2
1910
October1st to 10thDay
54%312%24%7%1
1800
11th to 20thDay
59%315%18%5%1
1800
21st to endDay
64%310%14%9%
1859
November1st to 10thDay
71%311%11%4
1538
11th to 20thDay
69%39%11%7%2
1520
21st to endDay
68%37%12%8%2
1520
December1st to 10thDay
66%5%8%12%8%1
1520
11th to 20thDay
71%310%13%31
1928
21st to endDay
73%211%11%3
2593
January1st to 10thNight
74%37%11%41
2761
11th to 20thNight
67%410%11%6%2
2520
21st to endNight
65%211%15%6%1
2738
February1st to 10thNight
71%410%10%5%1
2340
11th to 20thNight
66%412%11%6%2
2274
21st to endNight
67%310%14%5%1
1855
March1st to 10thNight
62%313%16%5%
2129
11th to 20thNight
63%411%17%41
1980
21st to endNight
70%415%11%1
2098
April1st to 10thNight
65%5%14%13%3
1800
11th to 20thNight
61%314%14%8%1
1766
21st to endNight
63%412%15%5%1
1566
May1st to 10thNight
52%318%20%7%1
1440
11th to 20thNight
52%5%20%17%6%1
1416
21st to endNight
59%6%17%16%2
1552
June1st to 10thNight
58%316%18%5%
1414
11th to 20thNight
64%415%14%2
1260
21st to endNight
42%424%21%7%2
1260
July1st to 10thNight
39%315%25%14%4
1225
11th to 20thNight
33%314%33%16%1
1345
21st to endNight
24%311%37%21%4
1488
August1st to 10thNight
29%414%34%17%3
1445
11th to 20thNight
26%418%35%14%3
1602
21st to endNight
37%216%34%10%1
1896
September1st to 10thNight
35%216%30%13%4
1800
11th to 20thNight
47%311%21%14%4
1800
21st to endNight
47%414%22%11%2
2047
October1st to 10thNight
52%314%24%7%1
2160
11th to 20thNight
56%315%19%7%1
2160
21st to endNight
60%411%16%9%
2497
November1st to 10thNight
68%313%13%41
2537
11th to 20thNight
68%310%11%5%2
2660
21st to endNight
68%38%12%9%1
2660
December1st to 10thNight
65%410%12%8%1
2660
11th to 20thNight
72%211%11%31
3276
21st to endNight
74%210%11%3
5054

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
40%10%11%16%12%10%
178
11th to 20thDay
38%8%13%17%20%4
160
21st to endDay
46%11%7%17%13%7%
208
February1st to 10thDay
46%6%17%19%9%3
340
11th to 20thDay
44%9%20%16%10%1
335
21st to endDay
37%10%21%20%10%2
311
March1st to 10thDay
38%11%20%18%10%2
420
11th to 20thDay
34%11%17%19%14%4
420
21st to endDay
40%10%21%17%11%1
462
April1st to 10thDay
36%10%20%18%12%3
420
11th to 20thDay
31%11%24%17%10%6%
412
21st to endDay
28%10%23%24%13%2
420
May1st to 10thDay
20%8%21%35%14%2
423
11th to 20thDay
29%7%16%25%17%7%
448
21st to endDay
29%7%17%25%16%5%
485
June1st to 10thDay
25%9%20%26%15%5%
472
11th to 20thDay
26%11%19%27%13%3
630
21st to endDay
14%5%19%37%21%5%
630
July1st to 10thDay
14%5%17%34%27%4
621
11th to 20thDay
10%5%18%34%28%5%
487
21st to endDay
11%212%39%28%8%
487
August1st to 10thDay
13%412%34%24%12%
447
11th to 20thDay
8%215%34%31%11%
437
21st to endDay
17%5%19%32%19%8%
495
September1st to 10thDay
15%8%20%35%18%4
450
11th to 20thDay
20%8%14%28%25%6%
450
21st to endDay
22%7%17%29%19%6%
450
October1st to 10thDay
26%7%15%25%18%8%
450
11th to 20thDay
34%8%13%23%15%7%
450
21st to endDay
37%10%13%22%13%5%
374
November1st to 10thDay
41%12%10%19%16%2
205
11th to 20thDay
42%12%10%8%19%9%
180
21st to endDay
37%8%12%19%13%11%
180
December1st to 10thDay
46%7%8%13%13%14%
180
11th to 20thDay
42%12%11%22%12%2
180
21st to endDay
41%9%11%20%16%4
198
January1st to 10thNight
48%9%10%16%13%3
815
11th to 20thNight
43%8%9%19%18%4
720
21st to endNight
40%5%10%26%16%3
792
February1st to 10thNight
44%6%11%26%12%2
720
11th to 20thNight
40%7%10%27%15%1
704
21st to endNight
41%7%11%27%12%3
592
March1st to 10thNight
37%7%13%26%16%2
720
11th to 20thNight
35%9%13%26%14%3
720
21st to endNight
38%7%13%28%11%2
792
April1st to 10thNight
35%6%15%26%16%3
720
11th to 20thNight
30%7%15%28%16%3
698
21st to endNight
32%7%12%29%16%3
486
May1st to 10thNight
23%9%11%31%23%2
360
11th to 20thNight
21%6%9%27%31%6%
354
21st to endNight
27%5%12%21%29%6%
389
June1st to 10thNight
24%5%11%31%25%3
360
11th to 20thNight
31%8%9%29%20%3
360
21st to endNight
16%412%31%32%6%
360
July1st to 10thNight
15%48%25%41%6%
350
11th to 20thNight
11%36%33%43%5%
348
21st to endNight
11%16%28%47%7%
394
August1st to 10thNight
11%25%24%46%11%
379
11th to 20thNight
10%2424%44%16%
534
21st to endNight
18%46%28%37%7%
708
September1st to 10thNight
13%47%33%36%7%
720
11th to 20thNight
20%45%23%36%10%
720
21st to endNight
23%48%28%29%7%
720
October1st to 10thNight
25%48%27%30%5%
720
11th to 20thNight
31%7%10%24%22%7%
720
21st to endNight
38%6%11%26%16%4
792
November1st to 10thNight
41%6%14%26%12%1
740
11th to 20thNight
40%8%11%23%14%3
760
21st to endNight
41%7%11%22%14%5%
760
December1st to 10thNight
38%6%10%26%18%3
760
11th to 20thNight
45%8%12%23%10%2
760
21st to endNight
50%8%11%20%10%1
890
Page generated at 2024-01-07 07:06:52. Version ac07

Copyright 2024 Attilla Danko


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