Banner Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Banner Creek Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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
41%
24522
23%
74771
13%
24461
50%
24461
31%
44816

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
33%
950
22%
2458
8%
946
43%
946
32%
1579
January11th to 20thNight
30%
915
23%
2379
9%
915
40%
915
29%
1575
January21st to endNight
28%
990
23%
2574
8%
990
38%
990
28%
1690
February1st to 10thNight
25%
900
17%
2340
5%
900
32%
900
25%
1603
February11th to 20thNight
28%
850
18%
2245
6%
846
36%
846
27%
1489
February21st to endNight
27%
587
26%
1771
8%
587
41%
587
28%
1089
March1st to 10thNight
29%
540
25%
1980
11%
540
45%
540
26%
1113
March11th to 20thNight
31%
540
19%
1980
13%
540
41%
540
20%
1221
March21st to endNight
23%
594
14%
2178
7%
594
33%
594
16%
1471
April1st to 10thNight
27%
540
20%
1928
12%
540
43%
540
27%
1071
April11th to 20thNight
30%
533
22%
1733
14%
533
44%
533
25%
1068
April21st to endNight
28%
540
21%
1620
10%
540
43%
540
26%
1039
May1st to 10thNight
39%
540
16%
1620
13%
540
46%
540
23%
1073
May11th to 20thNight
41%
531
20%
1594
16%
531
48%
531
31%
976
May21st to endNight
46%
584
16%
1745
10%
582
52%
582
29%
1090
June1st to 10thNight
63%
540
23%
1526
16%
540
67%
540
43%
837
June11th to 20thNight
58%
540
23%
1440
13%
540
62%
540
43%
831
June21st to endNight
55%
540
23%
1589
14%
540
61%
540
47%
817
July1st to 10thNight
69%
525
17%
1575
14%
525
71%
525
40%
872
July11th to 20thNight
73%
522
24%
1566
21%
522
75%
522
51%
771
July21st to endNight
69%
591
25%
1673
24%
558
72%
558
43%
900
August1st to 10thNight
70%
537
21%
1601
22%
534
75%
534
43%
866
August11th to 20thNight
71%
534
28%
1600
30%
534
75%
534
43%
872
August21st to endNight
70%
594
28%
1862
31%
594
73%
594
43%
965
September1st to 10thNight
61%
540
26%
1862
27%
540
66%
540
37%
971
September11th to 20thNight
58%
540
28%
1980
26%
540
66%
540
35%
1024
September21st to endNight
55%
540
30%
1980
25%
540
66%
540
38%
960
October1st to 10thNight
47%
666
26%
2106
19%
666
53%
666
33%
1205
October11th to 20thNight
33%
720
29%
2160
12%
720
46%
720
36%
1205
October21st to endNight
35%
792
26%
2376
13%
792
45%
792
31%
1391
November1st to 10thNight
43%
828
31%
2308
15%
828
55%
828
43%
1254
November11th to 20thNight
33%
950
28%
2470
9%
950
46%
950
38%
1462
November21st to endNight
36%
950
24%
2630
11%
950
45%
950
34%
1577
December1st to 10thNight
34%
950
22%
2660
9%
950
45%
950
31%
1642
December11th to 20thNight
29%
949
23%
3120
9%
948
39%
948
24%
1898
December21st to endNight
27%
1040
16%
4542
9%
1026
39%
1026
14%
3349

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
11%6%35%5%3445%7%46%
74564
Night
10%6%35%42445%7%50%
75182
TransparencyDay
37%7%13%25%16%3
74287
Night
34%6%12%26%18%3
74979
SeeingDay
13%10%30%29%16%3
14525
Night
13%9%33%33%11%1
24528

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
11%7%46%43445%8%43%
1707
11th to 20thDay
12%9%36%5%3445%6%44%
1643
21st to endDay
10%8%5%9%5%45%45%6%40%
1782
February1st to 10thDay
11%11%47%6%3435%6%41%
1620
11th to 20thDay
10%8%47%5%3445%7%42%
1619
21st to endDay
10%8%47%5%2345%6%45%
1484
March1st to 10thDay
11%7%36%5%3445%6%45%
1980
11th to 20thDay
19%11%25%42435%6%38%
1980
21st to endDay
17%12%5%6%6%34446%32%
2178
April1st to 10thDay
13%7%26%434445%48%
2030
11th to 20thDay
13%7%36%7%35%5%5%7%40%
2172
21st to endDay
18%6%35%5%35%45%6%38%
2340
May1st to 10thDay
17%7%36%5%3445%6%38%
2340
11th to 20thDay
16%6%26%5%35%5%48%40%
2302
21st to endDay
16%5%37%5%45%6%6%7%36%
2531
June1st to 10thDay
6%325%5%35%5%6%9%51%
2425
11th to 20thDay
7%5%25%435%6%5%9%49%
2520
21st to endDay
7%424435%5%6%9%51%
2360
July1st to 10thDay
9%4245%25%6%7%10%46%
2340
11th to 20thDay
5%325%5%36%5%7%9%52%
2340
21st to endDay
8%425%4245%6%10%49%
2546
August1st to 10thDay
7%4245%35%6%7%10%46%
2328
11th to 20thDay
10%415%5%345%5%7%52%
2301
21st to endDay
8%42442445%8%55%
2493
September1st to 10thDay
11%32443445%7%53%
2094
11th to 20thDay
9%425%6%4445%7%50%
1980
21st to endDay
9%42442445%6%58%
1980
October1st to 10thDay
11%5%24424447%53%
1836
11th to 20thDay
12%423333445%57%
1800
21st to endDay
14%6%25%423435%52%
1980
November1st to 10thDay
8%5%23424447%57%
1768
11th to 20thDay
11%7%24423335%55%
1710
21st to endDay
13%7%44323346%50%
1546
December1st to 10thDay
9%6%36%5%345%5%6%47%
1520
11th to 20thDay
9%9%37%6%34446%44%
1918
21st to endDay
15%12%7%14%5%3445%6%26%
3071
January1st to 10thNight
7%8%36%5%345%47%48%
2458
11th to 20thNight
10%9%46%434446%45%
2379
21st to endNight
9%8%37%6%3445%7%46%
2574
February1st to 10thNight
10%10%47%6%35%446%41%
2340
11th to 20thNight
11%7%37%5%35%5%47%44%
2244
21st to endNight
10%8%344345%5%6%48%
1771
March1st to 10thNight
9%8%25%5%24446%51%
1980
11th to 20thNight
15%7%35%425%446%44%
1980
21st to endNight
20%11%35%5%2435%6%35%
2178
April1st to 10thNight
10%5%25%5%3435%7%52%
1928
11th to 20thNight
13%7%35%42436%5%47%
1733
21st to endNight
16%6%25%5%3445%6%44%
1620
May1st to 10thNight
15%7%35%5%345%6%7%41%
1620
11th to 20thNight
15%6%3332345%8%48%
1593
21st to endNight
10%6%36%5%3445%9%46%
1745
June1st to 10thNight
5%323335%45%10%58%
1526
11th to 20thNight
6%3144335%6%11%54%
1440
21st to endNight
5%22332435%9%62%
1589
July1st to 10thNight
7%3144245%5%9%55%
1620
11th to 20thNight
32143236%7%9%61%
1620
21st to endNight
7%32343446%11%53%
1772
August1st to 10thNight
33244246%6%10%56%
1611
11th to 20thNight
6%42443445%8%58%
1600
21st to endNight
6%31432445%6%61%
1862
September1st to 10thNight
11%313423446%58%
1862
11th to 20thNight
10%42342445%7%56%
1980
21st to endNight
9%413323446%62%
1980
October1st to 10thNight
13%5%23324347%54%
2106
11th to 20thNight
13%424323345%58%
2160
21st to endNight
14%7%23413335%55%
2376
November1st to 10thNight
7%414323346%62%
2308
11th to 20thNight
9%5%24324446%56%
2470
21st to endNight
13%5%24423346%54%
2630
December1st to 10thNight
8%7%35%5%35%45%7%50%
2660
11th to 20thNight
11%9%36%43345%6%48%
3279
21st to endNight
17%13%6%9%423345%33%
4588

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
39%6%12%26%15%2
1708
11th to 20thDay
42%415%25%13%1
1643
21st to endDay
43%7%15%22%11%1
1782
February1st to 10thDay
45%6%15%21%10%3
1620
11th to 20thDay
42%6%13%24%12%3
1628
21st to endDay
39%5%13%24%16%3
1484
March1st to 10thDay
39%6%11%23%17%3
1980
11th to 20thDay
48%5%9%22%14%3
1980
21st to endDay
52%6%15%17%8%2
2178
April1st to 10thDay
38%7%13%22%18%2
2030
11th to 20thDay
43%6%13%23%15%1
2172
21st to endDay
45%8%11%26%11%1
2340
May1st to 10thDay
48%6%12%20%14%1
2340
11th to 20thDay
41%9%13%23%13%
2306
21st to endDay
44%10%15%21%9%2
2531
June1st to 10thDay
29%9%16%29%16%1
2425
11th to 20thDay
30%8%15%28%17%2
2520
21st to endDay
27%8%17%28%16%4
2360
July1st to 10thDay
31%9%14%27%15%4
2276
11th to 20thDay
26%9%16%26%19%5%
2271
21st to endDay
29%7%14%32%16%2
2405
August1st to 10thDay
30%11%18%26%14%2
2314
11th to 20thDay
31%7%11%31%19%2
2301
21st to endDay
28%7%11%26%22%7%
2493
September1st to 10thDay
31%5%14%25%19%6%
2094
11th to 20thDay
33%8%11%24%21%3
1980
21st to endDay
27%6%9%31%25%2
1980
October1st to 10thDay
31%6%13%26%22%3
1836
11th to 20thDay
29%5%8%26%27%5%
1800
21st to endDay
35%5%11%23%19%6%
1980
November1st to 10thDay
27%6%14%28%20%5%
1768
11th to 20thDay
34%39%28%23%3
1710
21st to endDay
36%5%9%26%22%1
1546
December1st to 10thDay
36%5%15%29%14%1
1520
11th to 20thDay
42%5%13%26%11%1
1915
21st to endDay
59%6%10%16%8%1
3071
January1st to 10thNight
36%5%15%25%17%2
2458
11th to 20thNight
40%412%27%15%2
2379
21st to endNight
39%6%15%25%13%2
2574
February1st to 10thNight
44%5%12%21%14%3
2340
11th to 20thNight
40%6%12%23%15%4
2245
21st to endNight
36%6%10%23%19%6%
1771
March1st to 10thNight
35%5%11%26%19%4
1980
11th to 20thNight
42%6%12%21%16%4
1980
21st to endNight
50%6%12%19%11%3
2178
April1st to 10thNight
33%5%12%25%21%4
1928
11th to 20thNight
38%6%11%26%17%3
1733
21st to endNight
40%6%13%23%17%1
1620
May1st to 10thNight
42%8%14%20%15%2
1620
11th to 20thNight
35%6%16%24%18%1
1594
21st to endNight
36%7%18%24%12%2
1746
June1st to 10thNight
23%8%17%36%15%3
1526
11th to 20thNight
25%8%14%31%18%4
1440
21st to endNight
20%6%14%33%22%4
1589
July1st to 10thNight
25%8%16%30%18%4
1575
11th to 20thNight
17%7%14%34%24%4
1566
21st to endNight
25%5%14%34%20%1
1673
August1st to 10thNight
22%9%19%33%15%2
1601
11th to 20thNight
25%5%13%33%22%2
1600
21st to endNight
23%6%13%27%24%7%
1862
September1st to 10thNight
28%5%11%28%21%8%
1862
11th to 20thNight
28%5%11%27%24%4
1980
21st to endNight
24%5%10%26%31%4
1980
October1st to 10thNight
32%5%9%25%24%4
2106
11th to 20thNight
29%47%27%24%8%
2160
21st to endNight
35%310%22%26%4
2376
November1st to 10thNight
25%413%27%25%7%
2308
11th to 20thNight
29%5%11%28%23%5%
2470
21st to endNight
33%411%28%21%3
2630
December1st to 10thNight
34%6%13%27%18%1
2660
11th to 20thNight
37%5%11%31%15%1
3281
21st to endNight
56%5%9%20%9%2
4588

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
18%16%35%21%9%
270
11th to 20thDay
22%15%40%21%2
248
21st to endDay
14%13%48%23%2
264
February1st to 10thDay
20%18%45%14%3
240
11th to 20thDay
18%18%46%11%7%
240
21st to endDay
16%21%44%15%4
198
March1st to 10thDay
16%18%43%20%3
240
11th to 20thDay
27%15%33%18%6%
240
21st to endDay
30%22%35%11%11
264
April1st to 10thDay
21%16%37%21%6%
290
11th to 20thDay
18%14%40%22%5%1
450
21st to endDay
21%17%33%18%10%1
600
May1st to 10thDay
20%13%35%23%8%1
603
11th to 20thDay
20%9%29%28%12%2
625
21st to endDay
18%9%29%27%14%3
679
June1st to 10thDay
5%5%23%32%28%7%
630
11th to 20thDay
6%330%38%17%5%
630
21st to endDay
6%6%34%37%14%2
630
July1st to 10thDay
9%413%34%31%9%
621
11th to 20thDay
5%318%41%26%7%
618
21st to endDay
7%218%39%29%5%
684
August1st to 10thDay
7%317%40%30%4
626
11th to 20thDay
8%317%42%26%4
615
21st to endDay
9%315%34%32%8%
612
September1st to 10thDay
11%220%34%28%4
384
11th to 20thDay
6%422%37%26%6%
270
21st to endDay
13%7%30%33%14%3
270
October1st to 10thDay
18%6%28%29%14%5%
270
11th to 20thDay
9%17%43%23%6%2
270
21st to endDay
18%16%37%20%8%2
297
November1st to 10thDay
12%13%34%30%10%1
270
11th to 20thDay
15%17%38%23%7%1
270
21st to endDay
20%11%37%21%10%
270
December1st to 10thDay
8%16%40%28%7%2
270
11th to 20thDay
17%14%39%22%7%
270
21st to endDay
20%19%42%18%2
297
January1st to 10thNight
11%12%39%31%7%
950
11th to 20thNight
15%13%34%30%6%
915
21st to endNight
13%11%43%29%4
990
February1st to 10thNight
15%13%42%26%3
900
11th to 20thNight
15%13%40%29%4
850
21st to endNight
17%13%41%25%5%1
587
March1st to 10thNight
13%13%42%27%5%
540
11th to 20thNight
19%10%37%27%7%
540
21st to endNight
25%11%38%21%5%
594
April1st to 10thNight
13%12%45%25%5%
540
11th to 20thNight
17%13%36%29%5%
533
21st to endNight
17%11%41%25%6%1
540
May1st to 10thNight
14%11%32%34%7%1
540
11th to 20thNight
17%8%30%34%11%
531
21st to endNight
11%7%32%35%15%1
584
June1st to 10thNight
6%324%44%24%
540
11th to 20thNight
7%328%45%16%
540
21st to endNight
5%432%45%13%
540
July1st to 10thNight
7%216%44%30%1
525
11th to 20thNight
2117%52%25%2
522
21st to endNight
6%116%49%27%
591
August1st to 10thNight
4118%49%27%1
537
11th to 20thNight
5%214%49%26%3
534
21st to endNight
6%217%41%32%3
594
September1st to 10thNight
13%221%42%19%3
540
11th to 20thNight
11%322%39%23%2
540
21st to endNight
10%428%40%17%1
540
October1st to 10thNight
15%6%29%33%16%1
666
11th to 20thNight
14%8%41%27%9%
720
21st to endNight
18%12%31%30%8%
792
November1st to 10thNight
8%11%35%36%10%
828
11th to 20thNight
13%11%40%29%7%
950
21st to endNight
15%11%35%30%8%
950
December1st to 10thNight
13%12%37%31%6%1
950
11th to 20thNight
17%10%38%30%5%
950
21st to endNight
18%14%37%26%5%
1045
Page generated at 2024-01-10 18:35:19. Version ac07

Copyright 2024 Attilla Danko


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