Buckhorn Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Buckhorn 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
30%
15325
14%
48857
8%
15293
37%
15293
18%
33891

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
14%
779
8%
2716
3%
776
21%
776
7%
2146
January16th to endNight
18%
832
12%
2749
6%
832
26%
832
10%
2105
February1st to 15thNight
15%
759
11%
2468
3%
757
25%
757
11%
1870
February16th to endNight
20%
631
14%
2015
5%
631
32%
631
14%
1461
March1st to 15thNight
18%
720
14%
2006
6%
720
27%
720
15%
1473
March16th to endNight
30%
768
21%
2100
10%
768
39%
768
24%
1404
April1st to 15thNight
24%
718
15%
1796
5%
718
29%
718
20%
1318
April16th to endNight
30%
594
20%
1674
9%
594
38%
594
25%
1116
May1st to 15thNight
37%
423
17%
1503
12%
423
46%
423
21%
941
May16th to endNight
41%
374
15%
1497
13%
374
53%
374
24%
847
June1st to 15thNight
38%
360
11%
1440
8%
360
49%
360
19%
879
June16th to endNight
47%
360
11%
1440
13%
360
53%
360
22%
862
July1st to 15thNight
52%
340
16%
1360
21%
340
59%
340
32%
695
July16th to endNight
53%
403
16%
1443
15%
379
59%
379
30%
789
August1st to 15thNight
57%
539
16%
1609
12%
536
61%
536
35%
957
August16th to endNight
54%
648
21%
1794
10%
648
60%
648
38%
1066
September1st to 15thNight
45%
720
19%
1800
8%
720
49%
720
32%
1173
September16th to endNight
50%
717
24%
1994
16%
717
55%
717
31%
1249
October1st to 15thNight
34%
720
17%
2160
10%
720
42%
720
21%
1490
October16th to endNight
20%
768
13%
2313
5%
768
29%
768
13%
1761
November1st to 15thNight
30%
760
17%
2608
14%
760
38%
760
18%
1755
November16th to endNight
21%
780
11%
2730
6%
780
28%
780
11%
2042
December1st to 15thNight
12%
780
6%
2730
2%
780
17%
780
8%
2169
December16th to endNight
11%
832
9%
2912
3%
832
18%
832
8%
2323

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
17%9%36%5%34446%31%
49228
Night
16%9%46%5%34446%33%
49030
Cloud CoverDay
17%9%37%6%3445%6%31%
49238
Night
16%9%46%5%34446%33%
49035
TransparencyDay
52%310%20%10%1
48919
Night
51%311%21%10%
48857
SeeingDay
23%11%29%20%10%4
5789
Night
22%11%29%24%10%1
15328

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
19%15%6%9%7%24335%22%
1552
16th to endDay
13%17%8%12%7%34335%20%
1826
February1st to 15thDay
14%15%7%11%10%3434319%
1695
16th to endDay
16%16%5%9%6%35%33425%
1458
March1st to 15thDay
16%12%5%7%6%4445%5%27%
1942
16th to endDay
15%10%36%5%24445%37%
2124
April1st to 15thDay
23%10%45%5%23345%31%
2152
16th to endDay
21%8%25%424336%38%
2297
May1st to 15thDay
19%8%36%5%35%445%33%
2448
16th to endDay
14%6%25%6%345%5%7%38%
2618
June1st to 15thDay
22%7%25%5%35%45%8%29%
2520
16th to endDay
17%6%25%435%46%9%32%
2520
July1st to 15thDay
13%425%5%36%5%6%9%37%
2520
16th to endDay
11%5%25%7%46%6%6%7%34%
2625
August1st to 15thDay
13%5%26%6%46%5%6%7%35%
2340
16th to endDay
13%6%26%5%25%5%5%9%37%
2396
September1st to 15thDay
17%5%245%2445%7%39%
2160
16th to endDay
16%5%26%433346%42%
1963
October1st to 15thDay
24%7%26%5%3445%5%30%
1800
16th to endDay
29%10%36%6%23445%23%
1911
November1st to 15thDay
18%9%36%5%44446%31%
1577
16th to endDay
23%15%5%7%5%345%5%5%20%
1560
December1st to 15thDay
19%20%7%10%6%3343417%
1560
16th to endDay
20%19%7%8%5%3433319%
1664
January1st to 15thNight
20%16%5%9%7%35%33419%
2716
16th to endNight
15%15%7%9%8%34445%23%
2749
February1st to 15thNight
13%15%6%10%7%35%446%22%
2466
16th to endNight
16%13%46%6%345%5%6%27%
2015
March1st to 15thNight
18%11%46%5%4434431%
1994
16th to endNight
14%7%36%5%24335%41%
2100
April1st to 15thNight
19%9%46%434445%32%
1796
16th to endNight
17%7%245%2345%6%39%
1674
May1st to 15thNight
18%6%26%4235%46%38%
1503
16th to endNight
12%5%24436%45%7%43%
1495
June1st to 15thNight
17%6%235%35%45%9%37%
1440
16th to endNight
12%6%246%25%5%5%8%39%
1440
July1st to 15thNight
8%315%43445%7%51%
1440
16th to endNight
9%4243345%5%7%48%
1541
August1st to 15thNight
9%41443445%9%47%
1620
16th to endNight
8%4235%245%5%8%49%
1794
September1st to 15thNight
14%425%42445%7%44%
1800
16th to endNight
17%414324445%47%
1994
October1st to 15thNight
20%6%36%5%24447%34%
2160
16th to endNight
23%11%36%6%34445%26%
2313
November1st to 15thNight
19%7%36%434446%34%
2608
16th to endNight
22%11%46%5%3445%6%24%
2730
December1st to 15thNight
20%18%6%9%5%24345%18%
2730
16th to endNight
20%16%7%10%6%3343418%
2912

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
19%16%48%7%2433423%
1552
16th to endDay
13%17%7%12%7%35%33420%
1826
February1st to 15thDay
14%15%6%13%9%35%44419%
1695
16th to endDay
16%14%5%9%6%45%335%24%
1458
March1st to 15thDay
16%12%5%7%7%4445%5%27%
1953
16th to endDay
15%9%46%5%34445%37%
2123
April1st to 15thDay
22%10%35%434345%31%
2152
16th to endDay
20%8%25%423346%38%
2297
May1st to 15thDay
18%8%36%5%35%345%33%
2448
16th to endDay
14%7%25%5%35%45%7%38%
2618
June1st to 15thDay
21%7%25%5%35%45%7%30%
2520
16th to endDay
16%7%25%5%36%5%6%9%32%
2520
July1st to 15thDay
11%426%6%36%5%6%8%38%
2520
16th to endDay
10%5%35%7%46%7%6%8%34%
2625
August1st to 15thDay
11%6%26%6%45%5%7%7%34%
2340
16th to endDay
12%6%26%5%35%5%6%9%37%
2396
September1st to 15thDay
16%5%35%43445%7%39%
2160
16th to endDay
15%5%35%5%24337%42%
1963
October1st to 15thDay
23%7%26%6%34446%30%
1800
16th to endDay
27%10%38%5%34345%24%
1911
November1st to 15thDay
18%9%27%5%3445%6%31%
1577
16th to endDay
23%14%5%6%5%3445%5%21%
1560
December1st to 15thDay
18%19%7%10%6%3343417%
1560
16th to endDay
19%18%8%8%6%2433319%
1664
January1st to 15thNight
20%16%5%9%7%35%33420%
2716
16th to endNight
14%14%7%9%8%34445%23%
2749
February1st to 15thNight
13%14%5%10%7%35%5%46%22%
2459
16th to endNight
16%13%46%5%45%446%27%
2015
March1st to 15thNight
18%11%46%6%34345%31%
2006
16th to endNight
14%6%37%5%34336%41%
2100
April1st to 15thNight
19%9%46%5%25%45%5%32%
1796
16th to endNight
16%7%345%3345%6%39%
1674
May1st to 15thNight
16%6%35%5%24447%38%
1503
16th to endNight
11%4335%35%5%47%43%
1495
June1st to 15thNight
16%7%24425%45%8%37%
1440
16th to endNight
11%6%245%45%5%6%8%39%
1440
July1st to 15thNight
8%3145%3435%8%51%
1440
16th to endNight
9%5%14425%46%7%48%
1541
August1st to 15thNight
8%5%245%335%5%9%46%
1620
16th to endNight
7%4245%245%5%7%49%
1794
September1st to 15thNight
13%5%26%5%2445%7%44%
1800
16th to endNight
16%414323345%47%
1994
October1st to 15thNight
19%6%26%5%3445%7%34%
2160
16th to endNight
23%9%46%6%345%45%26%
2313
November1st to 15thNight
18%7%35%5%345%46%35%
2608
16th to endNight
22%10%47%5%3445%6%24%
2730
December1st to 15thNight
20%17%7%9%6%24345%19%
2730
16th to endNight
20%16%7%10%6%3343418%
2912

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
64%210%14%7%
1553
16th to endDay
68%27%12%8%1
1826
February1st to 15thDay
68%28%15%4
1697
16th to endDay
63%19%13%11%
1458
March1st to 15thDay
57%313%17%6%1
1953
16th to endDay
48%36%21%15%3
2124
April1st to 15thDay
55%27%19%12%1
2152
16th to endDay
47%28%23%15%2
2297
May1st to 15thDay
52%29%20%14%1
2448
16th to endDay
44%312%23%14%1
2622
June1st to 15thDay
52%311%21%10%
2520
16th to endDay
47%411%23%11%1
2520
July1st to 15thDay
39%5%11%29%13%
2371
16th to endDay
44%5%12%25%10%
2460
August1st to 15thDay
44%5%15%22%11%1
2327
16th to endDay
41%412%28%11%1
2396
September1st to 15thDay
43%312%27%11%
2160
16th to endDay
43%312%30%10%
1963
October1st to 15thDay
54%310%20%10%
1800
16th to endDay
62%212%16%6%
1911
November1st to 15thDay
52%313%18%9%1
1577
16th to endDay
63%312%13%5%1
1560
December1st to 15thDay
70%311%11%3
1560
16th to endDay
69%27%13%6%
1664
January1st to 15thNight
67%39%12%6%1
2716
16th to endNight
63%37%16%8%
2749
February1st to 15thNight
62%211%17%6%
2468
16th to endNight
56%310%21%8%
2015
March1st to 15thNight
55%311%19%9%
2006
16th to endNight
45%39%22%17%2
2100
April1st to 15thNight
53%27%20%13%1
1796
16th to endNight
44%39%21%18%2
1674
May1st to 15thNight
45%311%21%15%3
1503
16th to endNight
38%413%26%15%2
1497
June1st to 15thNight
44%412%22%15%
1440
16th to endNight
40%5%14%25%13%
1440
July1st to 15thNight
29%411%33%19%
1360
16th to endNight
33%415%32%14%
1443
August1st to 15thNight
32%5%19%28%13%
1609
16th to endNight
31%415%32%13%1
1794
September1st to 15thNight
38%415%28%11%1
1800
16th to endNight
38%311%34%12%
1994
October1st to 15thNight
49%310%23%12%
2160
16th to endNight
59%411%16%7%
2313
November1st to 15thNight
49%313%21%9%
2608
16th to endNight
59%5%12%16%5%
2730
December1st to 15thNight
67%312%11%4
2730
16th to endNight
69%28%12%6%
2912

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%22%33%8%5%
90
16th to endDay
33%18%32%11%3
134
February1st to 15thDay
34%22%37%4
130
16th to endDay
32%14%39%11%1
117
March1st to 15thDay
27%12%35%20%5%
270
16th to endDay
25%14%32%15%9%2
288
April1st to 15thDay
28%17%25%20%7%1
270
16th to endDay
24%16%28%17%10%2
270
May1st to 15thDay
29%11%26%17%7%7%
288
16th to endDay
19%11%36%20%8%3
331
June1st to 15thDay
28%7%31%23%8%1
315
16th to endDay
18%10%33%23%11%3
315
July1st to 15thDay
14%6%29%27%14%7%
305
16th to endDay
11%9%33%24%14%6%
326
August1st to 15thDay
12%328%30%15%9%
313
16th to endDay
17%5%23%25%15%12%
332
September1st to 15thDay
14%7%26%21%17%12%
315
16th to endDay
17%8%19%24%18%11%
314
October1st to 15thDay
23%12%27%20%12%4
315
16th to endDay
35%16%22%18%5%
334
November1st to 15thDay
26%12%31%19%7%2
141
16th to endDay
36%13%34%14%1
90
December1st to 15thDay
34%18%27%15%3
90
16th to endDay
33%23%35%5%2
96
January1st to 15thNight
32%16%29%15%5%
780
16th to endNight
22%15%32%23%41
832
February1st to 15thNight
21%18%37%19%3
760
16th to endNight
24%16%32%20%5%
631
March1st to 15thNight
27%16%32%19%3
720
16th to endNight
19%12%32%23%9%1
768
April1st to 15thNight
25%13%31%22%5%
718
16th to endNight
20%12%32%22%11%1
594
May1st to 15thNight
20%7%28%26%14%2
423
16th to endNight
14%5%34%35%10%
375
June1st to 15thNight
20%8%28%30%11%
360
16th to endNight
13%427%42%12%
360
July1st to 15thNight
7%5%26%40%19%1
340
16th to endNight
10%228%37%19%1
403
August1st to 15thNight
11%319%37%24%3
539
16th to endNight
9%325%31%27%2
648
September1st to 15thNight
15%5%26%28%20%4
720
16th to endNight
19%5%19%27%22%5%
717
October1st to 15thNight
23%9%27%23%13%1
720
16th to endNight
30%12%30%20%5%
768
November1st to 15thNight
24%11%27%25%8%1
760
16th to endNight
30%13%27%20%6%
780
December1st to 15thNight
31%17%32%14%3
780
16th to endNight
31%13%32%17%31
832
Page generated at 2018-02-15 10:58:51. Version ac04

Copyright 2018 A. Danko


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