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 2017-08-12.

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
29%
14591
14%
46531
8%
14559
37%
14559
18%
32281

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
13%
719
8%
2506
2%
716
19%
716
7%
1996
January16th to endNight
18%
768
13%
2538
6%
768
26%
768
11%
1931
February1st to 15thNight
16%
703
11%
2287
3%
701
25%
701
11%
1735
February16th to endNight
20%
631
15%
2015
5%
631
32%
631
14%
1461
March1st to 15thNight
18%
720
14%
2006
6%
720
26%
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
30%
718
20%
1318
April16th to endNight
30%
594
20%
1674
9%
594
39%
594
25%
1116
May1st to 15thNight
37%
423
18%
1503
12%
423
46%
423
21%
941
May16th to endNight
41%
374
16%
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
53%
340
16%
1360
21%
340
60%
340
32%
695
July16th to endNight
52%
403
16%
1443
15%
379
59%
379
30%
789
August1st to 15thNight
57%
527
16%
1575
12%
524
61%
524
35%
934
August16th to endNight
54%
594
20%
1644
8%
594
60%
594
37%
985
September1st to 15thNight
44%
660
19%
1650
8%
660
47%
660
31%
1089
September16th to endNight
48%
657
22%
1827
14%
657
53%
657
30%
1159
October1st to 15thNight
33%
660
17%
1980
11%
660
42%
660
20%
1385
October16th to endNight
18%
704
12%
2120
4%
704
28%
704
12%
1631
November1st to 15thNight
29%
700
18%
2402
15%
700
37%
700
18%
1602
November16th to endNight
21%
720
12%
2520
6%
720
29%
720
11%
1893
December1st to 15thNight
12%
720
6%
2520
2%
720
17%
720
8%
1998
December16th to endNight
11%
768
9%
2688
3%
768
18%
768
7%
2158

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
18%9%36%5%34446%31%
47450
Night
17%9%46%5%34446%33%
46704
Cloud CoverDay
17%9%36%6%3445%6%31%
47460
Night
16%9%46%5%34446%33%
46709
TransparencyDay
52%311%20%10%1
47141
Night
51%311%21%10%
46531
SeeingDay
23%11%29%20%10%4
5225
Night
22%11%29%24%10%1
14594

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
20%15%6%8%7%24335%23%
1432
16th to endDay
13%16%8%11%7%35%335%21%
1685
February1st to 15thDay
14%14%7%12%9%35%34419%
1575
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%
2288
16th to endDay
13%6%25%5%25%5%5%9%37%
2195
September1st to 15thDay
19%5%25%5%2445%7%37%
1980
16th to endDay
17%5%36%433347%40%
1800
October1st to 15thDay
24%6%36%6%3445%5%30%
1650
16th to endDay
30%10%36%5%2344423%
1752
November1st to 15thDay
18%9%36%5%44446%32%
1453
16th to endDay
23%15%5%7%5%3445%5%19%
1440
December1st to 15thDay
20%20%7%10%5%2343416%
1440
16th to endDay
20%19%8%8%5%2433318%
1536
January1st to 15thNight
20%16%6%8%8%25%34319%
2506
16th to endNight
14%15%6%9%8%34445%23%
2538
February1st to 15thNight
13%15%6%10%7%35%446%22%
2285
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%42443445%9%47%
1586
16th to endNight
8%4245%245%48%49%
1644
September1st to 15thNight
15%425%42445%7%42%
1650
16th to endNight
18%414324445%45%
1827
October1st to 15thNight
20%6%37%5%25%447%33%
1980
16th to endNight
24%11%36%6%3444425%
2120
November1st to 15thNight
18%7%36%434446%34%
2402
16th to endNight
23%11%46%5%3445%6%23%
2520
December1st to 15thNight
21%18%6%8%5%24445%19%
2520
16th to endNight
21%16%8%10%5%3343417%
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
19%16%48%7%2433424%
1432
16th to endDay
13%16%6%12%8%35%33421%
1685
February1st to 15thDay
14%15%6%13%9%35%44419%
1575
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%
2288
16th to endDay
12%6%25%5%35%5%6%9%37%
2195
September1st to 15thDay
17%6%35%43445%7%37%
1980
16th to endDay
16%6%35%5%24337%40%
1800
October1st to 15thDay
22%7%26%6%34446%30%
1650
16th to endDay
28%11%38%5%33345%22%
1752
November1st to 15thDay
17%9%27%5%34446%32%
1453
16th to endDay
23%14%5%7%5%345%5%5%20%
1440
December1st to 15thDay
19%19%8%10%6%3343417%
1440
16th to endDay
20%19%8%8%6%2433319%
1536
January1st to 15thNight
20%16%5%9%7%35%34419%
2506
16th to endNight
14%15%7%9%8%24445%23%
2538
February1st to 15thNight
13%14%5%10%7%35%5%46%23%
2278
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%47%
1586
16th to endNight
7%4345%245%5%7%49%
1644
September1st to 15thNight
14%5%26%5%2445%7%42%
1650
16th to endNight
17%414323446%46%
1827
October1st to 15thNight
19%6%27%6%3445%6%33%
1980
16th to endNight
24%9%46%6%345%4425%
2120
November1st to 15thNight
18%7%35%5%345%47%35%
2402
16th to endNight
22%10%46%5%3445%6%23%
2520
December1st to 15thNight
21%16%6%9%6%23445%19%
2520
16th to endNight
21%16%7%10%6%23435%17%
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
64%211%14%6%
1433
16th to endDay
66%27%12%8%1
1685
February1st to 15thDay
67%39%15%4
1577
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%21%11%1
2275
16th to endDay
42%412%28%10%1
2195
September1st to 15thDay
44%313%27%10%
1980
16th to endDay
44%312%29%9%
1800
October1st to 15thDay
54%310%19%10%
1650
16th to endDay
64%211%15%6%
1752
November1st to 15thDay
52%314%19%9%1
1453
16th to endDay
64%311%13%5%1
1440
December1st to 15thDay
71%311%10%3
1440
16th to endDay
70%28%13%5%
1536
January1st to 15thNight
68%39%12%5%
2506
16th to endNight
62%37%16%8%
2538
February1st to 15thNight
62%211%16%6%
2287
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%27%13%
1575
16th to endNight
32%415%32%13%1
1644
September1st to 15thNight
40%415%28%10%
1650
16th to endNight
39%312%33%11%
1827
October1st to 15thNight
50%310%23%11%
1980
16th to endNight
60%411%15%7%
2120
November1st to 15thNight
48%314%21%10%1
2402
16th to endNight
59%5%12%16%5%
2520
December1st to 15thNight
67%313%12%3
2520
16th to endNight
69%28%12%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
31%20%31%10%6%
60
16th to endDay
32%15%34%13%3
89
February1st to 15thDay
34%22%37%5%
90
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%327%30%15%9%
297
16th to endDay
16%5%23%25%16%12%
268
September1st to 15thDay
17%7%25%20%16%13%
255
16th to endDay
20%8%21%24%15%9%
254
October1st to 15thDay
20%13%27%21%12%4
255
16th to endDay
37%14%23%18%5%
271
November1st to 15thDay
22%10%32%22%9%2
107
16th to endDay
41%8%26%21%1
60
December1st to 15thDay
31%20%28%16%3
60
16th to endDay
39%28%28%31
64
January1st to 15thNight
32%16%28%15%5%
720
16th to endNight
22%14%33%23%5%1
768
February1st to 15thNight
21%17%37%19%3
704
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%320%37%23%3
527
16th to endNight
10%325%31%27%2
594
September1st to 15thNight
16%5%27%27%20%3
660
16th to endNight
20%5%20%28%21%3
657
October1st to 15thNight
23%9%28%23%13%1
660
16th to endNight
30%12%30%20%5%
704
November1st to 15thNight
23%11%28%25%9%1
700
16th to endNight
31%12%27%20%6%
720
December1st to 15thNight
32%17%31%14%4
720
16th to endNight
32%13%32%17%31
768
Page generated at 2017-08-13 14:16:37. Version ac04

Copyright 2017 A. Danko


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