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Picketpost Mountain Trailhead
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Picketpost Mountain Trailhead clear sky chart from 2005-11-05 to 2018-01-12.

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
76%
16055
36%
48339
32%
16016
80%
16016
54%
23062

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
67%
763
30%
2471
30%
760
73%
760
44%
1227
January16th to endNight
64%
768
35%
2496
32%
768
72%
768
41%
1279
February1st to 15thNight
67%
700
35%
2205
32%
700
77%
700
50%
1045
February16th to endNight
66%
632
36%
1859
35%
632
71%
632
46%
976
March1st to 15thNight
69%
720
39%
1980
32%
720
76%
720
58%
967
March16th to endNight
76%
768
38%
2112
30%
768
82%
768
62%
1006
April1st to 15thNight
72%
689
34%
1948
25%
689
78%
689
57%
945
April16th to endNight
75%
540
45%
1740
39%
540
83%
540
70%
668
May1st to 15thNight
78%
539
40%
1619
34%
539
82%
539
68%
681
May16th to endNight
83%
561
40%
1684
34%
561
86%
561
72%
686
June1st to 15thNight
88%
540
35%
1620
31%
540
88%
540
70%
670
June16th to endNight
91%
540
34%
1620
30%
540
92%
540
72%
664
July1st to 15thNight
83%
510
23%
1530
20%
510
83%
510
44%
805
July16th to endNight
82%
564
24%
1593
21%
531
81%
531
36%
926
August1st to 15thNight
85%
539
28%
1611
25%
536
85%
536
43%
851
August16th to endNight
84%
606
32%
1857
30%
606
84%
606
40%
1013
September1st to 15thNight
80%
720
32%
1980
28%
720
81%
720
49%
1068
September16th to endNight
83%
716
44%
1980
35%
716
86%
716
66%
905
October1st to 15thNight
78%
720
39%
2082
33%
720
83%
720
65%
930
October16th to endNight
85%
768
46%
2304
41%
768
89%
768
70%
963
November1st to 15thNight
78%
760
40%
2280
35%
760
83%
760
61%
1026
November16th to endNight
75%
780
41%
2529
40%
780
80%
780
54%
1137
December1st to 15thNight
68%
780
37%
2535
37%
780
73%
780
46%
1229
December16th to endNight
69%
832
36%
2704
37%
832
73%
832
41%
1395

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
4212213346%67%
48995
Night
4212213346%66%
48535
TransparencyDay
17%35%12%24%36%
48690
Night
18%25%12%24%37%
48341
SeeingDay
5%417%35%28%8%
5785
Night
5%110%38%37%6%
16063

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
6%32321343463%
1710
16th to endDay
9%312213335%62%
1728
February1st to 15thDay
432321235%5%65%
1655
16th to endDay
9%43323347%59%
1615
March1st to 15thDay
5%212213345%66%
1980
16th to endDay
3212323235%69%
2112
April1st to 15thDay
212222246%70%
2000
16th to endDay
2111222479%
2217
May1st to 15thDay
111212235%77%
2331
16th to endDay
1111212282%
2429
June1st to 15thDay
11111222380%
2340
16th to endDay
11111222480%
2340
July1st to 15thDay
2213435%5%6%8%55%
2340
16th to endDay
42245%47%6%8%12%40%
2467
August1st to 15thDay
3313435%5%6%9%52%
2340
16th to endDay
32134345%6%8%56%
2341
September1st to 15thDay
4213323347%62%
1980
16th to endDay
31111233378%
1980
October1st to 15thDay
21121233475%
1876
16th to endDay
11221222478%
1920
November1st to 15thDay
221122236%72%
1909
16th to endDay
421321222471%
1758
December1st to 15thDay
8%312313337%61%
1755
16th to endDay
9%313312336%59%
1872
January1st to 15thNight
7%312323345%61%
2471
16th to endNight
10%313323335%60%
2496
February1st to 15thNight
5%313312335%66%
2194
16th to endNight
8%213313446%58%
1859
March1st to 15thNight
6%21222336%68%
1980
16th to endNight
3111212346%70%
2112
April1st to 15thNight
5%112223335%68%
1948
16th to endNight
21111122282%
1740
May1st to 15thNight
111212245%75%
1619
16th to endNight
2111122382%
1684
June1st to 15thNight
11111222479%
1620
16th to endNight
11112235%80%
1620
July1st to 15thNight
22125%35%5%7%10%54%
1620
16th to endNight
3324446%6%9%12%42%
1701
August1st to 15thNight
22134346%7%10%52%
1620
16th to endNight
23135%36%6%7%9%51%
1857
September1st to 15thNight
321342436%9%58%
1980
16th to endNight
21221224475%
1980
October1st to 15thNight
311121213475%
2082
16th to endNight
11111223379%
2304
November1st to 15thNight
2213212235%72%
2280
16th to endNight
5%11321233470%
2529
December1st to 15thNight
8%213212347%62%
2535
16th to endNight
9%313323345%58%
2704

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
23%25%13%27%27%
1711
16th to endDay
23%3416%23%29%
1728
February1st to 15thDay
19%35%17%24%29%
1655
16th to endDay
25%2414%28%24%
1615
March1st to 15thDay
19%136%31%36%
1980
16th to endDay
18%228%32%35%
2112
April1st to 15thDay
14%139%36%35%
2000
16th to endDay
9%128%24%52%
2217
May1st to 15thDay
10%138%25%50%
2331
16th to endDay
10%117%24%54%
2432
June1st to 15thDay
10%11417%65%
2340
16th to endDay
9%125%14%65%
2340
July1st to 15thDay
23%5%10%15%18%26%
2201
16th to endDay
31%9%17%21%14%5%
2312
August1st to 15thDay
25%5%10%18%16%23%
2325
16th to endDay
23%5%9%17%24%19%
2341
September1st to 15thDay
20%38%16%24%25%
1980
16th to endDay
11%127%29%46%
1980
October1st to 15thDay
13%239%25%45%
1876
16th to endDay
11%148%26%48%
1920
November1st to 15thDay
13%2212%32%36%
1909
16th to endDay
17%239%24%42%
1758
December1st to 15thDay
23%35%15%27%24%
1755
16th to endDay
25%3419%29%17%
1872
January1st to 15thNight
24%2411%27%29%
2471
16th to endNight
26%2412%25%27%
2496
February1st to 15thNight
20%25%14%24%32%
2205
16th to endNight
24%3414%26%26%
1859
March1st to 15thNight
17%238%26%41%
1980
16th to endNight
15%2311%32%35%
2112
April1st to 15thNight
18%128%32%35%
1948
16th to endNight
9%127%24%55%
1740
May1st to 15thNight
10%128%28%47%
1620
16th to endNight
9%128%18%60%
1685
June1st to 15thNight
10%11414%67%
1620
16th to endNight
9%13412%68%
1620
July1st to 15thNight
22%6%11%16%15%27%
1530
16th to endNight
29%7%16%20%19%6%
1593
August1st to 15thNight
22%7%12%18%14%25%
1611
16th to endNight
25%6%9%16%22%19%
1857
September1st to 15thNight
22%49%19%21%22%
1980
16th to endNight
12%237%26%47%
1980
October1st to 15thNight
13%1410%21%48%
2082
16th to endNight
10%239%22%52%
2304
November1st to 15thNight
15%1312%29%38%
2280
16th to endNight
18%139%23%43%
2529
December1st to 15thNight
23%2414%27%27%
2535
16th to endNight
26%25%16%27%20%
2704

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
19%116%38%23%
123
16th to endDay
10%5%16%36%21%9%
96
February1st to 15thDay
6%222%41%24%1
170
16th to endDay
12%7%26%34%16%
238
March1st to 15thDay
5%11%27%32%19%4
270
16th to endDay
311%31%30%19%3
288
April1st to 15thDay
413%28%33%13%7%
269
16th to endDay
315%35%30%11%3
270
May1st to 15thDay
313%28%31%19%3
288
16th to endDay
25%28%38%21%3
330
June1st to 15thDay
4223%37%25%5%
315
16th to endDay
217%45%32%10%
315
July1st to 15thDay
38%41%33%12%
305
16th to endDay
5%1329%37%23%
327
August1st to 15thDay
3228%47%18%
315
16th to endDay
2331%43%18%
332
September1st to 15thDay
8%16%38%33%11%
315
16th to endDay
5%217%40%28%5%
315
October1st to 15thDay
4315%35%34%6%
211
16th to endDay
4431%45%13%
144
November1st to 15thDay
5%413%41%29%5%
135
16th to endDay
7%314%40%28%4
135
December1st to 15thDay
9%14%39%31%4
135
16th to endDay
13%414%31%29%7%
144
January1st to 15thNight
9%115%46%22%4
764
16th to endNight
11%216%39%24%5%
768
February1st to 15thNight
7%215%43%28%3
704
16th to endNight
9%117%46%22%2
632
March1st to 15thNight
5%218%42%26%5%
720
16th to endNight
3212%42%33%5%
768
April1st to 15thNight
4314%48%26%2
689
16th to endNight
2217%45%27%4
540
May1st to 15thNight
1215%45%30%5%
540
16th to endNight
2110%41%37%5%
563
June1st to 15thNight
115%45%42%3
540
16th to endNight
432%56%5%
540
July1st to 15thNight
2423%59%8%
510
16th to endNight
4114%62%15%
564
August1st to 15thNight
2214%65%14%
539
16th to endNight
4118%62%12%
606
September1st to 15thNight
46%26%50%11%
720
16th to endNight
217%40%37%10%
716
October1st to 15thNight
4111%41%36%5%
720
16th to endNight
28%38%40%9%
768
November1st to 15thNight
4110%44%33%6%
760
16th to endNight
5%113%40%33%5%
780
December1st to 15thNight
10%212%40%32%2
780
16th to endNight
10%110%47%25%4
832
Page generated at 2018-01-12 20:01:35. Version ac04

Copyright 2018 A. Danko


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