Berthoud Pass Trailhead
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Berthoud Pass Trailhead clear sky chart from 2005-11-05 to 2017-09-17.

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
33%
15942
21%
46877
10%
15895
44%
15895
26%
27529

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
21%
900
19%
2506
6%
895
33%
895
20%
1535
January16th to endNight
18%
780
23%
2508
9%
780
35%
780
21%
1447
February1st to 15thNight
13%
700
14%
2273
4%
696
26%
696
15%
1393
February16th to endNight
12%
632
21%
1894
3%
632
31%
632
16%
1168
March1st to 15thNight
22%
720
20%
2085
6%
720
35%
720
22%
1228
March16th to endNight
23%
699
20%
2043
7%
699
36%
699
21%
1246
April1st to 15thNight
21%
539
18%
1798
6%
539
35%
539
20%
1043
April16th to endNight
25%
540
18%
1800
10%
540
39%
540
19%
1109
May1st to 15thNight
30%
540
15%
1599
5%
540
41%
540
22%
1047
May16th to endNight
40%
563
16%
1498
8%
561
48%
561
30%
915
June1st to 15thNight
48%
540
22%
1440
11%
540
57%
540
45%
760
June16th to endNight
63%
540
26%
1440
18%
540
69%
540
51%
749
July1st to 15thNight
67%
510
17%
1360
13%
510
71%
510
34%
834
July16th to endNight
71%
564
18%
1475
16%
531
73%
531
35%
882
August1st to 15thNight
65%
539
16%
1641
14%
536
68%
536
33%
951
August16th to endNight
67%
573
25%
1910
24%
573
71%
573
32%
1087
September1st to 15thNight
57%
540
26%
1800
20%
540
67%
540
34%
977
September16th to endNight
56%
519
30%
1795
24%
519
66%
519
38%
898
October1st to 15thNight
35%
660
25%
1980
13%
660
45%
660
30%
1121
October16th to endNight
31%
709
28%
2117
10%
709
46%
709
29%
1159
November1st to 15thNight
25%
875
27%
2275
8%
875
38%
875
30%
1316
November16th to endNight
23%
900
26%
2432
8%
900
37%
900
27%
1392
December1st to 15thNight
15%
900
16%
2520
3%
900
27%
900
17%
1536
December16th to endNight
17%
960
17%
2688
5%
960
27%
960
16%
1736

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
5%7%47%7%45%45%7%40%
47913
Night
2425%5%35%46%9%50%
47054
TransparencyDay
42%6%13%19%13%3
47592
Night
29%8%18%24%15%3
46877
SeeingDay
16%23%28%18%10%2
5844
Night
8%24%28%23%12%1
15946

By Month

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
2310%7%48%36%11%40%
1432
16th to endDay
448%8%44449%46%
1725
February1st to 15thDay
35%11%10%46%46%8%38%
1589
16th to endDay
35%12%9%5%7%447%40%
1580
March1st to 15thDay
18%37%7%45%45%7%44%
1875
16th to endDay
29%6%8%8%35%46%7%36%
2181
April1st to 15thDay
212%5%9%6%45%46%6%36%
2150
16th to endDay
415%7%10%7%5%5%446%28%
2160
May1st to 15thDay
7%16%5%8%6%35%5%5%6%30%
2347
16th to endDay
7%11%47%7%35%6%6%7%30%
2616
June1st to 15thDay
6%6%26%6%36%45%8%43%
2520
16th to endDay
34245%35%5%5%8%50%
2520
July1st to 15thDay
9%8%37%7%36%5%5%7%36%
2520
16th to endDay
9%7%37%8%45%6%6%7%31%
2590
August1st to 15thDay
13%7%48%7%4446%6%31%
2308
16th to endDay
9%8%48%5%45%5%5%7%34%
2292
September1st to 15thDay
9%6%36%5%24445%47%
2160
16th to endDay
5%8%25%433345%51%
1868
October1st to 15thDay
6%8%35%5%5%4337%46%
1650
16th to endDay
47%26%434438%49%
1744
November1st to 15thDay
1437%5%3446%8%50%
1583
16th to endDay
435%5%3435%8%54%
1527
December1st to 15thDay
438%8%5%7%6%5%11%39%
1440
16th to endDay
448%8%7%6%47%10%38%
1536
January1st to 15thNight
115%7%48%5%7%13%44%
2506
16th to endNight
325%6%47%5%5%10%48%
2508
February1st to 15thNight
228%6%47%5%6%11%43%
2262
16th to endNight
238%6%46%46%11%44%
1894
March1st to 15thNight
335%436%46%10%50%
2085
16th to endNight
17%45%5%3445%8%50%
2043
April1st to 15thNight
6%36%5%35%5%6%9%48%
1798
16th to endNight
311%36%445%35%7%44%
1800
May1st to 15thNight
410%444346%6%9%41%
1598
16th to endNight
36%2443446%10%48%
1497
June1st to 15thNight
221232346%9%59%
1440
16th to endNight
111233346%7%62%
1440
July1st to 15thNight
4315%5%26%5%6%10%47%
1440
16th to endNight
43245%36%5%6%9%47%
1576
August1st to 15thNight
5%5%24425%5%6%8%48%
1650
16th to endNight
5%4245%25%5%5%9%49%
1910
September1st to 15thNight
5%31343445%8%53%
1800
16th to endNight
241332345%7%59%
1795
October1st to 15thNight
24134345%5%8%55%
1980
16th to endNight
25%24323347%57%
2117
November1st to 15thNight
3244345%6%8%57%
2275
16th to endNight
225%6%2445%9%56%
2432
December1st to 15thNight
3245%35%5%8%12%46%
2520
16th to endNight
238%7%46%5%8%12%41%
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
36%9%22%18%9%2
1433
16th to endDay
36%6%20%21%11%3
1725
February1st to 15thDay
42%9%20%17%8%2
1589
16th to endDay
42%6%13%22%12%2
1580
March1st to 15thDay
38%8%13%25%13%1
1875
16th to endDay
46%6%13%22%8%2
2181
April1st to 15thDay
46%5%13%18%11%4
2150
16th to endDay
56%5%11%17%7%1
2160
May1st to 15thDay
53%6%11%18%9%
2347
16th to endDay
49%8%12%18%8%2
2620
June1st to 15thDay
37%6%12%16%19%7%
2520
16th to endDay
30%5%9%22%23%8%
2520
July1st to 15thDay
47%7%10%14%14%6%
2371
16th to endDay
48%8%12%16%9%3
2428
August1st to 15thDay
51%7%11%12%12%5%
2293
16th to endDay
46%6%9%19%14%3
2292
September1st to 15thDay
40%48%17%20%8%
2160
16th to endDay
34%412%24%22%2
1868
October1st to 15thDay
38%5%10%23%20%2
1650
16th to endDay
33%5%11%27%18%3
1744
November1st to 15thDay
30%5%16%19%21%5%
1583
16th to endDay
27%6%17%28%16%4
1527
December1st to 15thDay
37%11%19%22%8%
1440
16th to endDay
41%10%16%19%9%2
1536
January1st to 15thNight
28%11%24%21%11%2
2506
16th to endNight
29%8%20%23%13%3
2508
February1st to 15thNight
33%9%23%21%10%1
2273
16th to endNight
33%7%19%22%13%3
1894
March1st to 15thNight
28%7%19%26%14%2
2085
16th to endNight
32%7%17%30%10%2
2043
April1st to 15thNight
31%8%16%25%13%4
1798
16th to endNight
38%6%17%24%12%
1800
May1st to 15thNight
38%9%16%23%11%
1599
16th to endNight
30%9%21%25%11%2
1498
June1st to 15thNight
19%6%19%24%22%7%
1440
16th to endNight
19%412%27%24%12%
1440
July1st to 15thNight
30%9%16%19%16%8%
1360
16th to endNight
29%9%21%22%12%5%
1475
August1st to 15thNight
30%7%21%19%15%6%
1641
16th to endNight
29%8%15%22%21%2
1910
September1st to 15thNight
28%6%15%20%19%9%
1800
16th to endNight
22%6%13%33%21%2
1795
October1st to 15thNight
25%7%15%27%20%4
1980
16th to endNight
25%6%14%29%21%2
2117
November1st to 15thNight
24%7%15%25%21%6%
2275
16th to endNight
25%6%16%29%18%4
2432
December1st to 15thNight
27%12%25%22%11%1
2520
16th to endNight
34%10%22%19%10%2
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
16%30%21%17%13%1
90
16th to endDay
12%39%26%18%3
96
February1st to 15thDay
25%46%20%5%2
90
16th to endDay
20%34%25%14%3
81
March1st to 15thDay
23%41%22%10%1
165
16th to endDay
18%49%23%7%
288
April1st to 15thDay
23%37%26%9%2
269
16th to endDay
24%49%15%7%2
270
May1st to 15thDay
18%26%32%14%5%1
394
16th to endDay
17%23%28%17%10%2
517
June1st to 15thDay
11%17%32%21%13%2
495
16th to endDay
6%13%34%24%17%3
495
July1st to 15thDay
14%8%27%23%21%5%
475
16th to endDay
12%5%31%22%20%8%
449
August1st to 15thDay
21%10%36%22%8%
315
16th to endDay
17%10%31%28%9%2
332
September1st to 15thDay
15%21%34%17%8%1
315
16th to endDay
11%16%37%19%11%3
156
October1st to 15thDay
12%32%21%21%10%3
90
16th to endDay
26%26%17%21%7%1
96
November1st to 15thDay
13%28%18%13%23%2
90
16th to endDay
26%33%31%8%
90
December1st to 15thDay
22%43%24%7%2
90
16th to endDay
8%58%19%10%21
96
January1st to 15thNight
15%32%27%16%6%1
900
16th to endNight
10%33%33%15%5%
780
February1st to 15thNight
10%36%33%13%5%
704
16th to endNight
11%38%31%15%3
632
March1st to 15thNight
6%36%30%18%7%
720
16th to endNight
7%33%32%22%4
699
April1st to 15thNight
8%28%38%19%4
539
16th to endNight
11%27%32%21%6%
540
May1st to 15thNight
9%16%38%24%9%1
540
16th to endNight
8%12%31%31%13%1
563
June1st to 15thNight
6%10%31%34%15%1
540
16th to endNight
35%23%41%24%1
540
July1st to 15thNight
7%113%37%36%2
510
16th to endNight
5%19%36%41%4
564
August1st to 15thNight
9%112%44%30%2
539
16th to endNight
6%314%37%31%6%
573
September1st to 15thNight
7%422%36%22%5%
540
16th to endNight
49%25%31%24%5%
519
October1st to 15thNight
7%24%30%20%13%2
660
16th to endNight
8%26%28%21%11%2
709
November1st to 15thNight
8%31%32%17%8%1
875
16th to endNight
10%32%31%20%4
900
December1st to 15thNight
8%43%30%13%3
900
16th to endNight
12%36%29%16%4
960
Page generated at 2017-09-18 06:38:28. Version ac04

Copyright 2017 A. Danko


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