Black Bear Hollow Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Black Bear Hollow Observatory clear sky chart from 2005-11-05 to 2017-09-20.

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
36%
15155
17%
46935
10%
15115
44%
15115
20%
31255

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 15thNight
18%
717
14%
2407
6%
716
29%
716
10%
1738
January16th to endNight
16%
768
13%
2496
4%
768
27%
768
13%
1787
February1st to 15thNight
18%
704
14%
2287
5%
701
29%
701
12%
1616
February16th to endNight
18%
631
16%
1958
5%
631
32%
631
13%
1369
March1st to 15thNight
23%
720
17%
1980
7%
720
34%
720
18%
1393
March16th to endNight
22%
768
18%
2112
8%
768
30%
768
20%
1432
April1st to 15thNight
24%
718
13%
1799
5%
718
29%
718
20%
1316
April16th to endNight
37%
681
18%
1761
7%
681
42%
681
26%
1190
May1st to 15thNight
39%
540
16%
1620
10%
540
44%
540
19%
1140
May16th to endNight
49%
374
17%
1497
17%
374
54%
374
19%
924
June1st to 15thNight
50%
360
16%
1440
17%
360
57%
360
23%
859
June16th to endNight
58%
360
17%
1440
19%
360
64%
360
26%
811
July1st to 15thNight
56%
340
13%
1360
15%
340
58%
340
21%
832
July16th to endNight
67%
564
16%
1595
12%
531
71%
531
35%
932
August1st to 15thNight
66%
539
18%
1609
13%
536
69%
536
34%
957
August16th to endNight
66%
702
23%
1848
16%
702
67%
702
38%
1134
September1st to 15thNight
54%
720
24%
1800
14%
720
57%
720
33%
1179
September16th to endNight
52%
677
22%
1882
18%
677
55%
677
30%
1194
October1st to 15thNight
44%
660
20%
1980
17%
660
51%
660
25%
1272
October16th to endNight
33%
704
22%
2112
12%
704
48%
704
23%
1373
November1st to 15thNight
38%
700
22%
2224
16%
700
47%
700
24%
1406
November16th to endNight
26%
720
16%
2520
10%
720
37%
720
14%
1703
December1st to 15thNight
24%
720
11%
2520
5%
720
31%
720
11%
1806
December16th to endNight
20%
768
14%
2688
5%
768
32%
768
11%
1892

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
15%7%36%5%35%5%5%7%34%
47890
Night
14%7%35%5%3445%7%38%
47118
Cloud CoverDay
15%7%36%6%35%5%5%7%34%
47900
Night
14%7%35%5%3445%7%38%
47122
TransparencyDay
48%6%12%19%11%1
47591
Night
43%6%13%21%12%1
46935
SeeingDay
20%12%23%21%14%6%
5564
Night
18%13%25%28%12%1
15159

By Month

Percentage Cloud Cover NE (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 15thDay
13%9%6%12%7%46%445%25%
1528
16th to endDay
14%13%5%8%7%45%5%45%24%
1728
February1st to 15thDay
14%13%5%10%6%45%445%26%
1575
16th to endDay
12%10%7%9%6%24446%29%
1512
March1st to 15thDay
17%9%37%6%35%445%31%
1969
16th to endDay
17%10%36%5%34447%32%
2112
April1st to 15thDay
16%9%45%5%2445%6%33%
2148
16th to endDay
19%8%35%5%24445%37%
2210
May1st to 15thDay
21%7%26%5%34447%30%
2331
16th to endDay
16%6%345%36%45%6%35%
2618
June1st to 15thDay
13%5%36%5%35%6%6%9%35%
2520
16th to endDay
12%425%6%45%5%6%9%36%
2520
July1st to 15thDay
10%6%35%6%5%5%5%6%8%35%
2517
16th to endDay
8%426%7%46%6%7%8%35%
2465
August1st to 15thDay
10%5%26%7%47%6%6%10%32%
2340
16th to endDay
13%5%245%35%5%6%9%38%
2340
September1st to 15thDay
17%5%25%42445%6%41%
2160
16th to endDay
14%7%25%5%34446%41%
1843
October1st to 15thDay
20%6%24424336%40%
1650
16th to endDay
18%7%35%43445%6%37%
1760
November1st to 15thDay
11%7%35%6%2445%6%42%
1628
16th to endDay
20%10%36%424437%32%
1440
December1st to 15thDay
17%10%49%6%345%6%6%25%
1440
16th to endDay
18%10%48%7%45%446%24%
1536
January1st to 15thNight
17%8%5%7%7%35%5%45%27%
2407
16th to endNight
13%11%46%6%46%5%46%29%
2496
February1st to 15thNight
13%10%47%6%4445%6%30%
2285
16th to endNight
11%9%48%6%35%6%5%7%32%
1958
March1st to 15thNight
16%7%36%5%3445%7%35%
1968
16th to endNight
16%7%35%423447%40%
2112
April1st to 15thNight
14%10%45%5%34446%34%
1799
16th to endNight
15%5%245%33448%41%
1761
May1st to 15thNight
19%6%25%42445%7%35%
1620
16th to endNight
12%6%244335%6%7%42%
1495
June1st to 15thNight
12%5%24325%5%6%7%45%
1440
16th to endNight
10%3144345%6%10%44%
1440
July1st to 15thNight
10%425%5%35%5%6%9%43%
1440
16th to endNight
6%335%4245%6%10%47%
1703
August1st to 15thNight
6%425%43446%10%47%
1620
16th to endNight
10%5%1432335%7%51%
1848
September1st to 15thNight
13%5%25%433347%48%
1800
16th to endNight
13%6%24423447%46%
1882
October1st to 15thNight
16%6%2342345%7%42%
1980
16th to endNight
17%5%243345%5%7%41%
2112
November1st to 15thNight
12%7%25%424336%44%
2224
16th to endNight
17%7%36%5%35%5%5%5%34%
2520
December1st to 15thNight
17%9%46%6%45%5%5%6%27%
2520
16th to endNight
16%10%37%6%35%5%5%7%28%
2688

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 15thDay
13%8%6%11%7%45%5%5%426%
1528
16th to endDay
14%12%6%9%7%45%5%45%24%
1728
February1st to 15thDay
14%13%5%9%6%45%345%26%
1575
16th to endDay
12%11%7%9%6%245%5%5%29%
1512
March1st to 15thDay
16%9%36%7%35%445%31%
1980
16th to endDay
17%9%46%5%3445%7%32%
2111
April1st to 15thDay
16%9%46%5%34446%34%
2148
16th to endDay
19%7%35%5%24435%38%
2210
May1st to 15thDay
20%7%36%5%35%5%47%30%
2331
16th to endDay
16%7%345%45%5%5%7%35%
2618
June1st to 15thDay
13%5%36%5%35%5%7%8%35%
2520
16th to endDay
12%425%6%45%6%6%9%36%
2520
July1st to 15thDay
10%6%35%6%46%5%6%9%35%
2517
16th to endDay
8%5%26%6%5%6%6%8%8%35%
2465
August1st to 15thDay
10%5%26%7%5%7%6%7%10%31%
2340
16th to endDay
13%5%245%345%6%9%38%
2340
September1st to 15thDay
17%5%2442445%6%40%
2160
16th to endDay
14%7%245%34447%40%
1843
October1st to 15thDay
20%6%14424336%40%
1650
16th to endDay
17%6%45%42445%6%37%
1760
November1st to 15thDay
10%6%36%6%2445%7%42%
1628
16th to endDay
20%10%35%425%337%32%
1440
December1st to 15thDay
17%10%39%7%445%5%6%26%
1440
16th to endDay
19%9%5%9%7%45%445%25%
1536
January1st to 15thNight
16%8%47%7%45%5%46%28%
2407
16th to endNight
13%11%46%7%36%5%47%29%
2496
February1st to 15thNight
13%9%47%5%45%5%5%7%30%
2278
16th to endNight
11%8%38%6%45%5%5%7%32%
1958
March1st to 15thNight
16%6%36%5%3445%7%35%
1980
16th to endNight
16%7%35%423447%40%
2112
April1st to 15thNight
15%9%47%435%446%34%
1799
16th to endNight
15%5%14424448%41%
1761
May1st to 15thNight
19%6%345%25%45%7%35%
1619
16th to endNight
12%7%25%4245%6%6%42%
1495
June1st to 15thNight
11%6%24335%5%6%7%45%
1440
16th to endNight
10%314425%47%10%44%
1440
July1st to 15thNight
9%5%345%346%6%8%42%
1440
16th to endNight
6%325%4245%7%10%47%
1703
August1st to 15thNight
6%5%25%5%235%6%10%46%
1620
16th to endNight
10%5%2432335%7%51%
1848
September1st to 15thNight
13%5%25%333346%48%
1800
16th to endNight
13%6%24423447%46%
1882
October1st to 15thNight
16%7%1442345%6%42%
1980
16th to endNight
17%5%244245%5%8%40%
2112
November1st to 15thNight
12%7%25%5%24346%44%
2224
16th to endNight
17%6%45%5%35%5%5%6%34%
2520
December1st to 15thNight
17%8%46%7%35%5%6%6%27%
2520
16th to endNight
16%9%46%6%35%5%6%7%28%
2688

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 15thDay
58%6%11%15%6%
1529
16th to endDay
60%5%12%15%5%
1728
February1st to 15thDay
58%5%12%16%6%
1577
16th to endDay
54%5%13%16%7%
1512
March1st to 15thDay
53%6%12%18%8%1
1980
16th to endDay
51%5%11%20%9%1
2112
April1st to 15thDay
50%5%10%18%13%1
2148
16th to endDay
47%5%8%19%15%3
2210
May1st to 15thDay
52%6%9%18%11%
2331
16th to endDay
47%7%14%17%11%2
2622
June1st to 15thDay
43%9%12%20%13%
2520
16th to endDay
42%9%14%20%11%
2520
July1st to 15thDay
44%9%12%18%13%2
2368
16th to endDay
39%9%15%19%14%1
2310
August1st to 15thDay
45%9%13%20%10%
2327
16th to endDay
39%7%12%24%13%2
2340
September1st to 15thDay
42%5%10%22%16%1
2160
16th to endDay
43%6%9%20%18%2
1843
October1st to 15thDay
45%5%12%22%12%1
1650
16th to endDay
45%5%13%23%11%
1760
November1st to 15thDay
40%5%13%20%14%5%
1628
16th to endDay
52%411%22%8%
1440
December1st to 15thDay
57%7%14%14%5%
1440
16th to endDay
60%412%16%5%
1536
January1st to 15thNight
55%5%12%15%9%1
2407
16th to endNight
53%5%14%18%7%
2496
February1st to 15thNight
50%6%13%19%9%1
2287
16th to endNight
49%6%12%21%10%
1958
March1st to 15thNight
46%6%13%22%9%1
1980
16th to endNight
44%5%14%20%14%1
2112
April1st to 15thNight
49%5%11%18%13%1
1799
16th to endNight
40%6%10%21%15%4
1761
May1st to 15thNight
46%8%9%20%13%1
1620
16th to endNight
39%8%13%21%14%2
1497
June1st to 15thNight
36%8%11%29%13%
1440
16th to endNight
32%8%16%26%14%1
1440
July1st to 15thNight
37%10%13%21%13%3
1360
16th to endNight
28%9%18%25%16%2
1595
August1st to 15thNight
31%7%18%25%16%1
1609
16th to endNight
32%5%12%27%18%3
1848
September1st to 15thNight
37%5%10%23%20%2
1800
16th to endNight
37%5%10%26%17%2
1882
October1st to 15thNight
40%5%12%23%15%1
1980
16th to endNight
40%5%11%28%13%
2112
November1st to 15thNight
40%411%21%15%5%
2224
16th to endNight
48%5%11%19%12%1
2520
December1st to 15thNight
53%6%14%16%7%
2520
16th to endNight
52%5%16%18%6%
2688

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 15thDay
28%31%25%10%21
76
16th to endDay
38%19%30%9%2
96
February1st to 15thDay
33%32%28%5%
90
16th to endDay
24%24%34%14%1
162
March1st to 15thDay
24%22%22%25%3
270
16th to endDay
24%19%28%17%8%2
288
April1st to 15thDay
22%20%26%20%7%2
270
16th to endDay
26%12%23%13%17%6%
270
May1st to 15thDay
31%13%23%13%11%5%
288
16th to endDay
22%12%20%20%14%9%
331
June1st to 15thDay
19%11%25%22%17%3
315
16th to endDay
14%10%30%24%14%4
315
July1st to 15thDay
14%6%28%26%18%6%
305
16th to endDay
11%318%30%25%10%
326
August1st to 15thDay
12%420%24%23%13%
313
16th to endDay
13%215%29%20%18%
332
September1st to 15thDay
19%6%17%20%22%13%
315
16th to endDay
22%415%21%19%15%
270
October1st to 15thDay
25%5%20%23%20%4
255
16th to endDay
18%16%29%22%11%1
272
November1st to 15thDay
13%11%28%26%17%2
221
16th to endDay
25%16%33%15%8%1
60
December1st to 15thDay
23%35%13%15%10%3
60
16th to endDay
32%21%26%18%
64
January1st to 15thNight
24%20%30%20%3
720
16th to endNight
22%21%34%20%1
768
February1st to 15thNight
22%22%30%23%1
704
16th to endNight
19%23%32%21%2
631
March1st to 15thNight
24%17%31%22%3
720
16th to endNight
20%18%32%20%6%
768
April1st to 15thNight
21%20%31%21%5%
718
16th to endNight
18%13%26%28%12%
681
May1st to 15thNight
22%8%22%30%15%
540
16th to endNight
17%6%20%33%19%2
375
June1st to 15thNight
13%5%23%36%20%1
360
16th to endNight
11%221%47%17%
360
July1st to 15thNight
11%219%44%20%1
340
16th to endNight
7%115%40%31%3
564
August1st to 15thNight
9%115%46%24%2
539
16th to endNight
12%210%37%31%4
702
September1st to 15thNight
15%417%33%25%3
720
16th to endNight
14%5%20%22%30%5%
677
October1st to 15thNight
19%9%20%28%20%2
660
16th to endNight
21%14%27%28%7%
704
November1st to 15thNight
17%12%26%31%10%1
700
16th to endNight
24%20%23%22%7%1
720
December1st to 15thNight
25%16%27%25%5%
720
16th to endNight
22%20%29%26%1
768
Page generated at 2017-09-21 07:18:14. Version ac04

Copyright 2017 A. Danko


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