Bear Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bear Observatory clear sky chart from 2005-11-06 to 2024-02-10.

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
43%
24111
20%
79863
15%
24003
50%
24003
23%
52068

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%
945
13%
4367
8%
926
32%
926
11%
2981
January11th to 20thNight
19%
922
16%
4289
8%
903
26%
903
9%
3120
January21st to endNight
21%
831
12%
4335
8%
814
33%
814
11%
2999
February1st to 10thNight
21%
759
16%
2275
6%
759
30%
759
16%
1667
February11th to 20thNight
18%
703
17%
2099
7%
700
27%
700
17%
1488
February21st to endNight
16%
592
16%
1776
6%
592
25%
592
16%
1307
March1st to 10thNight
27%
720
19%
2160
9%
720
35%
720
21%
1452
March11th to 20thNight
25%
720
16%
2045
8%
720
32%
720
19%
1455
March21st to endNight
32%
724
16%
2110
10%
724
37%
724
20%
1473
April1st to 10thNight
38%
540
24%
1800
15%
540
50%
540
26%
1062
April11th to 20thNight
38%
533
23%
1775
17%
533
48%
533
24%
1110
April21st to endNight
38%
540
19%
1697
14%
540
44%
540
22%
1127
May1st to 10thNight
41%
540
17%
1620
11%
540
47%
540
24%
1089
May11th to 20thNight
52%
531
17%
1593
11%
531
56%
531
24%
1066
May21st to endNight
63%
582
18%
1744
13%
582
66%
582
30%
1098
June1st to 10thNight
61%
540
19%
1554
15%
540
64%
540
35%
935
June11th to 20thNight
70%
540
25%
1440
20%
540
73%
540
43%
822
June21st to endNight
70%
540
22%
1440
15%
540
73%
540
39%
861
July1st to 10thNight
69%
525
18%
1400
15%
525
70%
525
34%
896
July11th to 20thNight
74%
522
21%
1400
18%
522
76%
522
39%
851
July21st to endNight
69%
591
21%
1672
20%
558
71%
558
33%
1002
August1st to 10thNight
75%
537
24%
1601
23%
534
76%
534
37%
932
August11th to 20thNight
71%
534
20%
1776
22%
534
72%
534
31%
1043
August21st to endNight
77%
594
25%
1980
28%
594
78%
594
37%
1070
September1st to 10thNight
66%
563
24%
1823
24%
563
69%
563
30%
1092
September11th to 20thNight
65%
720
29%
1980
24%
720
67%
720
38%
1188
September21st to endNight
60%
720
31%
1980
23%
720
65%
720
39%
1153
October1st to 10thNight
61%
720
32%
1980
26%
720
66%
720
42%
1127
October11th to 20thNight
46%
720
27%
2040
19%
720
53%
720
31%
1260
October21st to endNight
38%
792
25%
2574
19%
792
48%
792
26%
1598
November1st to 10thNight
48%
740
27%
2406
23%
740
56%
740
31%
1372
November11th to 20thNight
36%
760
26%
2470
18%
760
49%
760
27%
1473
November21st to endNight
37%
760
23%
2470
18%
760
46%
760
23%
1574
December1st to 10thNight
27%
760
16%
2470
9%
760
36%
760
17%
1739
December11th to 20thNight
29%
759
19%
2977
13%
759
38%
759
16%
2012
December21st to endNight
23%
992
10%
4745
8%
978
31%
978
10%
3574

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%7%36%5%35%5%5%7%39%
78564
Night
15%8%36%5%3445%7%40%
80403
TransparencyDay
44%6%11%22%15%3
78277
Night
44%5%10%21%16%3
80210
SeeingDay
17%10%24%24%18%8%
14238
Night
18%8%25%29%18%2
24130

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
14%13%6%9%7%35%45%5%30%
2527
11th to 20thDay
18%9%410%8%36%43430%
2565
21st to endDay
26%12%9%5%424346%27%
3261
February1st to 10thDay
18%12%47%5%34446%34%
1890
11th to 20thDay
20%8%47%6%3445%7%32%
1748
21st to endDay
18%10%47%6%35%446%33%
1480
March1st to 10thDay
17%9%35%5%35%446%40%
1800
11th to 20thDay
21%10%37%5%4445%5%34%
1913
21st to endDay
17%9%37%7%45%45%6%32%
2260
April1st to 10thDay
12%6%35%6%35%5%6%8%42%
2160
11th to 20thDay
15%7%36%7%24446%41%
2134
21st to endDay
17%7%36%5%4445%8%37%
2261
May1st to 10thDay
17%6%35%6%35%46%8%38%
2340
11th to 20thDay
16%8%37%5%446%5%6%37%
2301
21st to endDay
8%5%36%7%46%6%7%11%36%
2531
June1st to 10thDay
10%5%36%5%36%5%6%6%44%
2401
11th to 20thDay
5%3346%46%6%7%10%46%
2520
21st to endDay
7%434447%6%9%10%43%
2520
July1st to 10thDay
10%5%36%7%46%6%7%10%36%
2520
11th to 20thDay
8%5%25%6%46%6%7%9%41%
2507
21st to endDay
9%5%25%6%36%7%7%12%38%
2547
August1st to 10thDay
7%5%36%6%46%7%7%10%39%
2323
11th to 20thDay
9%6%36%5%46%6%6%10%40%
2125
21st to endDay
8%425%5%36%5%5%9%46%
2376
September1st to 10thDay
13%6%37%5%36%5%5%8%41%
2117
11th to 20thDay
12%6%25%5%3445%8%45%
1980
21st to endDay
13%425%33445%7%50%
1980
October1st to 10thDay
11%5%24333347%55%
1980
11th to 20thDay
13%6%24434446%49%
1915
21st to endDay
19%7%25%433445%43%
1782
November1st to 10thDay
11%5%24422346%55%
1672
11th to 20thDay
16%7%35%43345%6%46%
1710
21st to endDay
18%7%35%434446%43%
1710
December1st to 10thDay
21%10%37%5%3435%6%34%
1710
11th to 20thDay
15%11%5%8%6%34445%35%
2153
21st to endDay
18%16%46%6%345%5%6%27%
2845
January1st to 10thNight
17%14%5%6%6%3445%6%30%
4428
11th to 20thNight
17%13%6%9%7%45%33429%
4400
21st to endNight
24%14%45%423336%31%
4390
February1st to 10thNight
21%10%47%5%25%45%6%30%
2275
11th to 20thNight
20%8%47%5%35%435%36%
2098
21st to endNight
23%10%47%6%34345%31%
1776
March1st to 10thNight
17%10%35%434445%41%
2160
11th to 20thNight
19%9%37%6%34345%36%
2045
21st to endNight
17%8%46%6%35%447%36%
2110
April1st to 10thNight
11%5%246%25%5%6%7%46%
1800
11th to 20thNight
17%6%25%43445%7%43%
1775
21st to endNight
15%8%36%5%35%5%5%7%38%
1697
May1st to 10thNight
17%7%35%5%35%45%7%38%
1620
11th to 20thNight
12%6%36%6%36%5%6%8%40%
1592
21st to endNight
5%326%6%46%6%8%12%42%
1744
June1st to 10thNight
9%6%244246%6%10%47%
1554
11th to 20thNight
5%3245%35%5%7%11%52%
1440
21st to endNight
34245%35%6%8%13%48%
1440
July1st to 10thNight
9%425%5%35%5%6%10%45%
1440
11th to 20thNight
8%323435%5%6%11%49%
1448
21st to endNight
8%425%6%346%7%10%45%
1771
August1st to 10thNight
7%415%4345%6%9%51%
1612
11th to 20thNight
6%5%25%5%35%6%8%10%45%
1776
21st to endNight
6%42343346%10%54%
1980
September1st to 10thNight
11%425%5%35%45%7%49%
1823
11th to 20thNight
10%5%25%5%3345%9%50%
1980
21st to endNight
11%4243235%46%55%
1980
October1st to 10thNight
10%424323346%60%
1980
11th to 20thNight
15%5%25%42445%5%50%
2040
21st to endNight
17%7%24434446%46%
2574
November1st to 10thNight
12%6%25%42444454%
2406
11th to 20thNight
14%6%24434446%47%
2470
21st to endNight
17%8%45%434445%43%
2470
December1st to 10thNight
19%12%46%5%34445%34%
2470
11th to 20thNight
19%9%48%434446%35%
3042
21st to endNight
17%15%5%8%8%45%445%25%
4797

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
56%48%20%9%1
2528
11th to 20thDay
59%38%19%9%1
2565
21st to endDay
60%38%21%6%1
3261
February1st to 10thDay
52%48%21%13%2
1890
11th to 20thDay
53%48%21%11%3
1758
21st to endDay
53%5%9%16%13%5%
1480
March1st to 10thDay
47%48%21%19%2
1800
11th to 20thDay
53%410%19%11%2
1913
21st to endDay
52%6%9%21%10%2
2260
April1st to 10thDay
39%6%11%24%17%2
2160
11th to 20thDay
44%410%20%18%3
2134
21st to endDay
45%6%10%24%12%2
2261
May1st to 10thDay
45%6%13%25%11%1
2340
11th to 20thDay
47%7%10%21%13%1
2305
21st to endDay
40%10%15%21%12%2
2531
June1st to 10thDay
38%7%11%23%19%2
2401
11th to 20thDay
30%10%16%24%18%2
2520
21st to endDay
33%9%16%20%18%4
2520
July1st to 10thDay
41%10%14%20%12%3
2451
11th to 20thDay
36%10%15%21%14%4
2432
21st to endDay
35%11%16%24%11%3
2405
August1st to 10thDay
36%11%15%23%14%1
2310
11th to 20thDay
39%9%12%23%15%2
2125
21st to endDay
34%8%12%25%17%5%
2376
September1st to 10thDay
41%7%12%20%16%4
2117
11th to 20thDay
37%6%9%23%22%3
1980
21st to endDay
33%5%9%27%22%4
1980
October1st to 10thDay
30%5%9%22%30%5%
1980
11th to 20thDay
36%5%9%20%26%5%
1915
21st to endDay
44%46%23%19%4
1782
November1st to 10thDay
32%48%28%23%5%
1672
11th to 20thDay
40%39%23%21%5%
1710
21st to endDay
44%38%23%19%3
1710
December1st to 10thDay
51%411%22%10%2
1710
11th to 20thDay
53%38%19%15%2
2150
21st to endDay
57%5%11%18%9%
2845
January1st to 10thNight
54%410%20%11%1
4428
11th to 20thNight
60%46%18%11%2
4400
21st to endNight
57%38%19%12%1
4390
February1st to 10thNight
55%5%9%18%12%1
2275
11th to 20thNight
52%47%22%13%2
2099
21st to endNight
56%5%8%15%13%3
1776
March1st to 10thNight
47%5%7%18%19%5%
2160
11th to 20thNight
51%49%21%12%2
2045
21st to endNight
49%5%11%22%11%2
2110
April1st to 10thNight
35%7%11%24%21%3
1800
11th to 20thNight
41%5%9%17%22%6%
1775
21st to endNight
44%7%9%24%15%2
1697
May1st to 10thNight
45%5%10%25%11%3
1620
11th to 20thNight
41%9%13%20%15%1
1593
21st to endNight
33%11%15%23%15%2
1745
June1st to 10thNight
32%6%14%26%18%3
1554
11th to 20thNight
25%7%15%26%22%4
1440
21st to endNight
26%10%18%22%18%6%
1440
July1st to 10thNight
33%9%14%26%15%3
1400
11th to 20thNight
28%9%16%24%18%5%
1400
21st to endNight
31%9%15%28%16%1
1672
August1st to 10thNight
29%7%16%28%18%2
1601
11th to 20thNight
31%9%16%25%17%2
1776
21st to endNight
26%8%14%28%19%5%
1980
September1st to 10thNight
34%8%9%22%22%5%
1823
11th to 20thNight
32%5%10%25%23%4
1980
21st to endNight
30%5%8%25%26%6%
1980
October1st to 10thNight
27%5%8%23%30%6%
1980
11th to 20thNight
38%39%21%24%5%
2040
21st to endNight
41%47%22%21%5%
2574
November1st to 10thNight
34%48%25%25%5%
2406
11th to 20thNight
38%48%21%21%7%
2470
21st to endNight
44%48%23%18%3
2470
December1st to 10thNight
53%5%10%20%11%2
2470
11th to 20thNight
51%38%19%16%2
3044
21st to endNight
62%410%15%8%1
4797

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
28%18%30%18%6%1
270
11th to 20thDay
28%28%25%14%5%
270
21st to endDay
24%22%39%12%4
297
February1st to 10thDay
24%22%37%13%3
267
11th to 20thDay
34%20%35%9%3
240
21st to endDay
30%20%35%12%3
198
March1st to 10thDay
23%23%40%13%2
240
11th to 20thDay
26%17%35%14%7%1
353
21st to endDay
24%20%32%16%7%1
462
April1st to 10thDay
19%17%26%26%10%1
420
11th to 20thDay
19%17%25%22%13%3
412
21st to endDay
21%15%31%20%9%3
420
May1st to 10thDay
19%14%30%23%8%5%
423
11th to 20thDay
17%8%29%27%12%7%
447
21st to endDay
11%5%19%30%22%13%
485
June1st to 10thDay
11%5%21%25%26%12%
511
11th to 20thDay
6%419%33%27%11%
630
21st to endDay
8%422%30%24%13%
630
July1st to 10thDay
9%314%27%27%20%
621
11th to 20thDay
9%415%28%27%17%
605
21st to endDay
10%311%31%27%18%
488
August1st to 10thDay
11%113%26%31%17%
446
11th to 20thDay
12%5%11%33%29%10%
439
21st to endDay
11%310%24%32%20%
495
September1st to 10thDay
14%313%23%32%15%
450
11th to 20thDay
12%214%24%33%15%
450
21st to endDay
15%6%19%25%23%12%
450
October1st to 10thDay
12%420%32%24%8%
450
11th to 20thDay
15%13%30%26%12%5%
425
21st to endDay
25%13%29%25%8%1
297
November1st to 10thDay
17%9%31%29%11%4
270
11th to 20thDay
20%15%34%24%7%
270
21st to endDay
25%12%32%21%9%1
270
December1st to 10thDay
22%19%30%19%9%1
270
11th to 20thDay
21%17%33%23%6%
270
21st to endDay
28%19%33%15%4
297
January1st to 10thNight
24%15%31%26%4
950
11th to 20thNight
28%16%31%21%4
923
21st to endNight
24%13%39%23%1
836
February1st to 10thNight
27%13%35%23%3
759
11th to 20thNight
25%16%37%20%2
703
21st to endNight
29%13%38%18%2
592
March1st to 10thNight
21%15%33%27%4
720
11th to 20thNight
23%13%34%23%6%1
720
21st to endNight
22%11%30%30%6%
724
April1st to 10thNight
14%12%33%31%9%1
540
11th to 20thNight
22%9%28%27%13%1
533
21st to endNight
19%8%31%31%11%1
540
May1st to 10thNight
21%6%28%31%13%2
540
11th to 20thNight
15%421%39%19%3
531
21st to endNight
6%218%38%31%6%
584
June1st to 10thNight
12%117%35%31%3
540
11th to 20thNight
6%214%41%33%4
540
21st to endNight
4216%39%34%5%
540
July1st to 10thNight
11%19%28%43%8%
525
11th to 20thNight
9%27%31%45%6%
522
21st to endNight
9%210%36%36%7%
591
August1st to 10thNight
8%27%32%45%6%
537
11th to 20thNight
7%111%35%40%6%
534
21st to endNight
7%17%32%44%8%
594
September1st to 10thNight
12%211%31%39%5%
563
11th to 20thNight
12%212%31%39%5%
720
21st to endNight
12%318%31%30%4
720
October1st to 10thNight
12%318%33%28%5%
720
11th to 20thNight
18%7%24%33%16%3
720
21st to endNight
20%7%32%27%14%1
792
November1st to 10thNight
13%9%27%33%17%1
740
11th to 20thNight
16%11%32%29%11%
760
21st to endNight
22%13%24%29%12%
760
December1st to 10thNight
27%11%29%27%6%
760
11th to 20thNight
25%8%34%27%6%
760
21st to endNight
28%13%29%26%3
997
Page generated at 2024-02-07 05:11:55. Version ac07

Copyright 2024 Attilla Danko


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