Bear Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bear Creek Observatory clear sky chart from 2005-11-05 to 2018-02-14.

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%
15125
10%
48621
10%
15096
43%
15096
15%
36107

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
32%
801
10%
2807
10%
797
34%
797
10%
2230
January16th to endNight
34%
832
10%
2886
10%
832
36%
832
11%
2241
February1st to 15thNight
33%
753
7%
2470
7%
752
34%
752
9%
2004
February16th to endNight
34%
632
10%
2008
9%
632
36%
632
12%
1555
March1st to 15thNight
30%
720
5%
2079
4%
720
31%
720
11%
1687
March16th to endNight
30%
768
5%
2058
3%
768
30%
768
11%
1715
April1st to 15thNight
35%
719
6%
1799
4%
719
35%
719
13%
1483
April16th to endNight
41%
553
7%
1633
6%
553
42%
553
14%
1271
May1st to 15thNight
49%
359
11%
1439
17%
359
50%
359
18%
935
May16th to endNight
46%
374
5%
1496
9%
374
47%
374
11%
1111
June1st to 15thNight
44%
360
3%
1358
4%
360
45%
360
12%
1000
June16th to endNight
50%
360
7%
1260
7%
360
50%
360
17%
881
July1st to 15thNight
69%
340
12%
1212
17%
340
69%
340
33%
657
July16th to endNight
72%
376
17%
1416
29%
354
74%
354
33%
710
August1st to 15thNight
78%
434
19%
1507
25%
432
78%
432
37%
773
August16th to endNight
70%
648
21%
1794
17%
648
71%
648
40%
1035
September1st to 15thNight
71%
720
21%
1800
13%
720
71%
720
43%
1084
September16th to endNight
54%
716
18%
1968
16%
716
55%
716
24%
1368
October1st to 15thNight
52%
720
11%
2160
12%
720
53%
720
21%
1513
October16th to endNight
39%
768
10%
2384
10%
768
41%
768
13%
1844
November1st to 15thNight
30%
760
5%
2627
6%
760
31%
760
9%
2158
November16th to endNight
31%
780
6%
2730
6%
780
33%
780
9%
2200
December1st to 15thNight
38%
780
9%
2730
10%
780
38%
780
12%
2104
December16th to endNight
23%
852
5%
3000
5%
852
24%
852
6%
2548

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
24%8%35%5%24445%30%
49468
Night
26%8%36%5%24345%29%
48781
Cloud CoverDay
26%8%36%5%24445%29%
49468
Night
27%8%35%5%34345%28%
48784
TransparencyDay
58%313%16%6%1
49131
Night
58%312%16%6%1
48622
SeeingDay
29%6%16%25%16%4
6305
Night
33%5%9%25%21%5%
15134

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 15thDay
39%9%35%43432418%
1457
16th to endDay
34%11%36%5%24346%18%
1687
February1st to 15thDay
32%10%47%6%35%44417%
1694
16th to endDay
29%13%46%5%2343422%
1466
March1st to 15thDay
36%13%36%42443315%
1880
16th to endDay
33%11%48%6%35%35%414%
2166
April1st to 15thDay
27%10%48%6%4445%6%17%
2149
16th to endDay
24%9%46%7%35%5%6%5%20%
2325
May1st to 15thDay
20%7%35%5%35%45%7%30%
2511
16th to endDay
26%7%46%5%35%45%7%24%
2615
June1st to 15thDay
24%8%35%5%35%446%27%
2598
16th to endDay
20%7%36%6%35%5%5%5%31%
2700
July1st to 15thDay
10%423323446%53%
2674
16th to endDay
12%423213246%55%
2657
August1st to 15thDay
11%413313247%54%
2442
16th to endDay
12%5%25%323447%48%
2408
September1st to 15thDay
11%5%25%422237%53%
2160
16th to endDay
21%5%36%5%24446%35%
1991
October1st to 15thDay
21%8%35%6%2435%7%30%
1800
16th to endDay
33%9%36%5%24446%20%
1839
November1st to 15thDay
43%9%3441343416%
1559
16th to endDay
40%9%35%43424417%
1560
December1st to 15thDay
28%12%46%6%34335%20%
1560
16th to endDay
36%12%46%5%2443316%
1570
January1st to 15thNight
38%8%25%42433422%
2807
16th to endNight
34%9%35%434446%20%
2886
February1st to 15thNight
33%10%35%5%33345%20%
2458
16th to endNight
30%10%35%5%23335%24%
2008
March1st to 15thNight
33%10%36%424445%21%
2079
16th to endNight
29%10%37%6%35%45%5%18%
2054
April1st to 15thNight
24%10%37%6%36%5%6%5%20%
1799
16th to endNight
23%7%37%5%35%45%6%25%
1633
May1st to 15thNight
18%7%36%42346%6%35%
1439
16th to endNight
20%7%46%6%35%5%46%28%
1496
June1st to 15thNight
23%5%37%6%4435%6%29%
1358
16th to endNight
17%7%46%7%3435%5%33%
1260
July1st to 15thNight
8%423423346%56%
1284
16th to endNight
9%324312346%58%
1512
August1st to 15thNight
8%312413247%60%
1515
16th to endNight
10%414422346%56%
1794
September1st to 15thNight
7%425%32334458%
1800
16th to endNight
18%7%25%434445%39%
1968
October1st to 15thNight
21%6%36%6%24445%35%
2160
16th to endNight
30%8%26%434336%25%
2384
November1st to 15thNight
37%8%36%5%2344418%
2627
16th to endNight
36%8%27%5%2433421%
2730
December1st to 15thNight
29%9%46%5%24445%24%
2730
16th to endNight
37%13%36%42333416%
3000

Percentage Cloud Cover SW (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
41%8%3443333319%
1457
16th to endDay
37%10%25%424246%18%
1687
February1st to 15thDay
33%9%48%6%3344417%
1694
16th to endDay
30%13%45%5%3443322%
1466
March1st to 15thDay
38%13%37%5%2432413%
1880
16th to endDay
33%13%5%7%6%2444412%
2166
April1st to 15thDay
28%11%39%7%45%45%5%14%
2149
16th to endDay
26%9%48%7%46%445%17%
2325
May1st to 15thDay
21%7%46%5%25%446%29%
2511
16th to endDay
27%8%46%6%3445%6%22%
2615
June1st to 15thDay
26%8%35%6%34445%24%
2598
16th to endDay
19%7%47%7%245%5%6%28%
2700
July1st to 15thDay
11%424424445%51%
2674
16th to endDay
12%6%13313345%53%
2657
August1st to 15thDay
11%5%23323446%53%
2442
16th to endDay
13%425%42345%7%47%
2408
September1st to 15thDay
11%6%35%423245%51%
2160
16th to endDay
22%6%35%433446%35%
1991
October1st to 15thDay
23%8%345%3445%7%29%
1800
16th to endDay
35%8%26%5%3435%420%
1839
November1st to 15thDay
45%9%3443333316%
1559
16th to endDay
40%9%47%43332418%
1560
December1st to 15thDay
32%10%46%6%2433421%
1560
16th to endDay
39%11%37%5%3332316%
1570
January1st to 15thNight
40%7%2442334421%
2806
16th to endNight
36%9%25%424345%21%
2886
February1st to 15thNight
33%12%36%424335%20%
2458
16th to endNight
31%12%26%423335%24%
2008
March1st to 15thNight
36%8%36%5%34445%19%
2079
16th to endNight
30%11%5%7%6%34445%16%
2058
April1st to 15thNight
25%9%47%6%45%5%5%5%18%
1799
16th to endNight
24%8%47%5%45%5%5%6%22%
1633
May1st to 15thNight
19%7%35%33435%6%35%
1439
16th to endNight
20%7%47%7%35%5%5%5%26%
1496
June1st to 15thNight
23%8%46%6%34445%27%
1358
16th to endNight
18%8%36%6%45%44432%
1260
July1st to 15thNight
7%5%24423445%56%
1284
16th to endNight
8%5%14322245%57%
1512
August1st to 15thNight
7%413223247%59%
1515
16th to endNight
10%5%1342225%5%56%
1794
September1st to 15thNight
8%5%2442334457%
1800
16th to endNight
19%6%35%5%23345%39%
1968
October1st to 15thNight
22%5%35%5%245%45%34%
2160
16th to endNight
32%8%25%433346%24%
2384
November1st to 15thNight
39%8%35%5%3434417%
2627
16th to endNight
37%7%36%6%2423420%
2730
December1st to 15thNight
31%9%46%5%2344423%
2730
16th to endNight
39%13%46%5%2332315%
3000

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
70%27%12%5%1
1457
16th to endDay
67%211%11%5%2
1687
February1st to 15thDay
70%410%9%31
1694
16th to endDay
68%29%14%4
1466
March1st to 15thDay
75%210%9%1
1880
16th to endDay
76%39%10%
2166
April1st to 15thDay
72%413%9%1
2149
16th to endDay
67%412%11%2
2325
May1st to 15thDay
55%415%18%5%
2511
16th to endDay
63%5%16%12%2
2619
June1st to 15thDay
62%415%11%5%
2598
16th to endDay
56%218%16%4
2700
July1st to 15thDay
36%413%28%15%1
2517
16th to endDay
33%313%31%15%2
2490
August1st to 15thDay
33%318%30%11%2
2425
16th to endDay
38%415%31%8%2
2408
September1st to 15thDay
35%213%26%17%3
2160
16th to endDay
50%316%17%8%2
1991
October1st to 15thDay
54%315%19%6%
1800
16th to endDay
65%311%12%6%
1839
November1st to 15thDay
74%39%8%21
1559
16th to endDay
72%37%9%6%
1560
December1st to 15thDay
66%5%7%13%6%
1560
16th to endDay
74%37%8%4
1570
January1st to 15thNight
67%48%13%5%1
2807
16th to endNight
65%210%12%7%2
2886
February1st to 15thNight
67%5%10%9%5%1
2470
16th to endNight
64%212%15%5%
2008
March1st to 15thNight
66%412%13%2
2079
16th to endNight
69%413%12%
2058
April1st to 15thNight
64%5%13%13%2
1799
16th to endNight
61%415%14%3
1633
May1st to 15thNight
50%218%19%8%
1440
16th to endNight
58%6%17%12%2
1496
June1st to 15thNight
60%315%15%4
1358
16th to endNight
54%219%18%31
1260
July1st to 15thNight
32%314%31%14%3
1212
16th to endNight
29%313%32%18%2
1416
August1st to 15thNight
26%5%16%33%14%3
1507
16th to endNight
31%219%33%9%2
1794
September1st to 15thNight
31%214%27%18%4
1800
16th to endNight
47%413%20%11%2
1968
October1st to 15thNight
51%315%20%7%1
2160
16th to endNight
62%412%15%6%
2384
November1st to 15thNight
70%311%9%22
2627
16th to endNight
68%39%9%8%
2730
December1st to 15thNight
63%312%12%6%
2730
16th to endNight
75%38%8%4
3000

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
30%317%26%22%
90
16th to endDay
63%9%6%7%9%4
119
February1st to 15thDay
47%314%21%9%2
276
16th to endDay
40%9%22%15%9%2
219
March1st to 15thDay
52%10%20%11%4
270
16th to endDay
50%10%19%10%9%
288
April1st to 15thDay
35%11%21%17%10%3
269
16th to endDay
32%6%27%19%10%2
270
May1st to 15thDay
29%8%18%30%10%2
288
16th to endDay
31%6%14%25%15%7%
330
June1st to 15thDay
25%7%21%24%17%3
393
16th to endDay
17%7%21%34%15%2
495
July1st to 15thDay
12%315%35%27%3
451
16th to endDay
15%213%37%24%6%
327
August1st to 15thDay
11%213%33%26%11%
315
16th to endDay
13%215%33%26%9%
332
September1st to 15thDay
17%5%17%30%22%6%
315
16th to endDay
23%7%14%29%19%5%
315
October1st to 15thDay
30%6%18%23%16%4
315
16th to endDay
43%5%9%22%14%4
255
November1st to 15thDay
61%6%11%13%5%2
97
16th to endDay
47%416%11%8%11%
90
December1st to 15thDay
43%310%13%15%14%
90
16th to endDay
41%8%8%21%13%6%
96
January1st to 15thNight
44%7%7%17%18%4
801
16th to endNight
43%410%21%16%4
832
February1st to 15thNight
41%49%27%14%2
760
16th to endNight
40%6%10%25%14%2
632
March1st to 15thNight
42%7%13%21%12%2
720
16th to endNight
39%7%12%27%11%1
768
April1st to 15thNight
33%5%15%25%17%3
719
16th to endNight
29%413%30%18%2
553
May1st to 15thNight
23%7%10%27%26%3
360
16th to endNight
25%410%22%30%6%
375
June1st to 15thNight
29%49%27%25%3
360
16th to endNight
21%5%10%32%25%5%
360
July1st to 15thNight
11%37%28%43%6%
340
16th to endNight
12%15%28%43%8%
376
August1st to 15thNight
11%220%47%17%
434
16th to endNight
14%25%26%38%12%
648
September1st to 15thNight
10%26%26%40%12%
720
16th to endNight
24%36%27%31%7%
716
October1st to 15thNight
25%49%28%27%5%
720
16th to endNight
39%48%24%18%5%
768
November1st to 15thNight
42%5%13%27%9%1
760
16th to endNight
42%7%11%20%13%5%
780
December1st to 15thNight
38%48%26%18%3
780
16th to endNight
49%6%12%20%10%
852
Page generated at 2018-02-15 07:58:49. Version ac04

Copyright 2018 A. Danko


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