Pine Mountain Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pine Mountain 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
50%
15364
18%
48835
16%
15340
54%
15340
27%
30224

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
40%
776
11%
2716
10%
776
44%
776
16%
1908
January16th to endNight
47%
832
17%
2827
17%
832
51%
832
20%
1883
February1st to 15thNight
39%
753
9%
2470
8%
753
42%
753
17%
1709
February16th to endNight
41%
632
15%
1936
13%
632
45%
632
20%
1368
March1st to 15thNight
37%
720
9%
2097
7%
720
40%
720
17%
1529
March16th to endNight
35%
768
11%
2039
7%
768
37%
768
20%
1495
April1st to 15thNight
38%
719
12%
1799
6%
719
39%
719
20%
1342
April16th to endNight
46%
701
17%
1781
9%
701
48%
701
32%
1164
May1st to 15thNight
52%
359
18%
1439
17%
359
60%
359
30%
750
May16th to endNight
52%
374
13%
1496
15%
374
58%
374
20%
925
June1st to 15thNight
53%
360
14%
1440
18%
360
60%
360
26%
813
June16th to endNight
63%
360
21%
1440
31%
360
70%
360
43%
616
July1st to 15thNight
75%
340
23%
1360
32%
340
83%
340
56%
519
July16th to endNight
68%
376
34%
1416
39%
354
79%
354
58%
518
August1st to 15thNight
81%
489
33%
1563
27%
487
88%
487
61%
664
August16th to endNight
78%
729
40%
1875
25%
729
81%
729
72%
870
September1st to 15thNight
77%
720
39%
1800
23%
720
80%
720
72%
858
September16th to endNight
65%
716
31%
1948
25%
716
68%
716
46%
1050
October1st to 15thNight
56%
720
20%
2160
19%
720
61%
720
37%
1215
October16th to endNight
52%
768
21%
2365
20%
768
56%
768
27%
1491
November1st to 15thNight
41%
760
14%
2496
13%
760
45%
760
18%
1735
November16th to endNight
41%
780
12%
2730
10%
780
45%
780
18%
1849
December1st to 15thNight
45%
780
14%
2730
13%
780
48%
780
18%
1828
December16th to endNight
36%
832
12%
2912
10%
832
39%
832
14%
2125

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%35%5%35%5%5%7%45%
49266
Night
46%35%5%35%5%6%7%46%
49003
Cloud CoverDay
6%7%35%5%3445%7%45%
49266
Night
5%7%35%5%35%5%6%7%45%
49007
TransparencyDay
37%7%11%20%16%6%
48937
Night
35%8%14%21%15%5%
48836
SeeingDay
10%16%26%25%16%4
6025
Night
7%11%24%32%21%3
15377

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
5%6%47%7%5%7%7%7%9%31%
1552
16th to endDay
48%36%6%5%6%6%6%10%35%
1749
February1st to 15thDay
39%47%5%47%6%8%10%31%
1694
16th to endDay
310%49%7%5%7%6%7%9%29%
1538
March1st to 15thDay
38%6%8%7%5%9%7%8%8%26%
1860
16th to endDay
5%11%5%9%8%5%6%6%5%6%27%
2184
April1st to 15thDay
7%12%5%10%8%45%446%28%
2149
16th to endDay
6%10%46%5%34448%40%
2178
May1st to 15thDay
8%8%35%5%34447%44%
2511
16th to endDay
13%11%36%6%25%446%33%
2615
June1st to 15thDay
10%8%35%5%34446%43%
2520
16th to endDay
6%5%24334336%57%
2520
July1st to 15thDay
2212314335%68%
2520
16th to endDay
211232333471%
2657
August1st to 15thDay
22232335%6%66%
2388
16th to endDay
11221232475%
2327
September1st to 15thDay
212213346%71%
2160
16th to endDay
6%5%14423346%55%
2010
October1st to 15thDay
8%8%26%5%3445%6%44%
1800
16th to endDay
7%7%26%5%35%45%7%45%
1857
November1st to 15thDay
6%9%36%6%47%6%7%8%33%
1693
16th to endDay
36%47%6%47%7%8%10%32%
1560
December1st to 15thDay
47%38%6%26%7%8%8%36%
1560
16th to endDay
49%5%9%8%46%6%8%9%26%
1664
January1st to 15thNight
37%37%7%47%6%8%10%32%
2716
16th to endNight
36%37%6%46%7%7%9%37%
2827
February1st to 15thNight
29%5%7%6%46%6%6%10%34%
2458
16th to endNight
48%36%5%36%6%8%9%36%
1936
March1st to 15thNight
37%46%8%47%6%9%8%33%
2097
16th to endNight
36%48%9%5%6%7%8%9%30%
2035
April1st to 15thNight
7%10%5%8%6%47%6%6%7%30%
1799
16th to endNight
49%46%42446%7%44%
1781
May1st to 15thNight
5%7%3432445%8%51%
1439
16th to endNight
8%7%26%6%37%5%46%41%
1496
June1st to 15thNight
9%6%2342445%6%49%
1440
16th to endNight
3313222226%66%
1440
July1st to 15thNight
2224435%72%
1440
16th to endNight
211211113378%
1512
August1st to 15thNight
11121335%5%72%
1571
16th to endNight
1211232479%
1875
September1st to 15thNight
1211233477%
1800
16th to endNight
45%2322335%7%60%
1948
October1st to 15thNight
47%2442345%6%54%
2160
16th to endNight
5%6%27%6%45%5%5%6%45%
2365
November1st to 15thNight
6%8%36%5%46%7%8%8%34%
2496
16th to endNight
37%36%6%46%7%7%8%38%
2730
December1st to 15thNight
37%47%5%35%5%8%9%38%
2730
16th to endNight
38%48%7%46%8%8%9%29%
2912

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%8%47%8%46%6%7%8%30%
1552
16th to endDay
5%8%36%7%47%6%7%9%33%
1749
February1st to 15thDay
49%47%6%36%7%7%11%30%
1694
16th to endDay
310%48%7%46%6%8%9%30%
1538
March1st to 15thDay
49%5%8%6%5%8%7%7%8%25%
1860
16th to endDay
6%11%5%9%8%47%5%6%6%28%
2184
April1st to 15thDay
7%13%7%8%8%35%5%46%29%
2149
16th to endDay
7%11%47%424447%41%
2178
May1st to 15thDay
9%8%35%434446%46%
2511
16th to endDay
13%10%47%5%35%446%34%
2615
June1st to 15thDay
12%6%25%424446%44%
2520
16th to endDay
6%413424346%57%
2520
July1st to 15thDay
2212213345%69%
2520
16th to endDay
211231334471%
2657
August1st to 15thDay
212423346%66%
2388
16th to endDay
11121223475%
2327
September1st to 15thDay
212213345%72%
2160
16th to endDay
6%5%24423346%54%
2010
October1st to 15thDay
9%9%25%5%34347%44%
1800
16th to endDay
8%8%26%5%24446%45%
1857
November1st to 15thDay
8%9%36%5%36%6%7%7%34%
1693
16th to endDay
5%9%46%7%45%7%7%9%32%
1560
December1st to 15thDay
5%9%38%6%35%6%6%8%34%
1560
16th to endDay
6%9%6%8%8%5%6%5%8%9%25%
1664
January1st to 15thNight
48%46%8%5%7%6%7%9%32%
2716
16th to endNight
48%36%6%46%6%7%9%35%
2827
February1st to 15thNight
410%48%6%36%5%7%9%33%
2458
16th to endNight
5%8%47%5%46%5%7%9%35%
1936
March1st to 15thNight
49%36%8%47%5%7%9%31%
2097
16th to endNight
48%5%7%8%36%6%9%8%29%
2039
April1st to 15thNight
9%13%46%6%46%5%5%7%30%
1799
16th to endNight
5%9%35%5%2445%7%44%
1781
May1st to 15thNight
5%7%2332445%7%51%
1439
16th to endNight
9%7%26%446%5%5%6%41%
1496
June1st to 15thNight
10%6%2442445%6%49%
1440
16th to endNight
5%312323235%67%
1440
July1st to 15thNight
11122443473%
1440
16th to endNight
21111222378%
1512
August1st to 15thNight
11211345%5%72%
1571
16th to endNight
1121223380%
1875
September1st to 15thNight
1221233478%
1800
16th to endNight
5%41332335%6%59%
1948
October1st to 15thNight
6%7%23423346%54%
2160
16th to endNight
6%7%36%6%35%45%5%44%
2365
November1st to 15thNight
7%10%36%5%36%6%7%8%33%
2496
16th to endNight
5%9%35%5%46%7%7%8%37%
2730
December1st to 15thNight
49%37%6%35%6%6%8%37%
2730
16th to endNight
410%49%6%46%6%8%8%28%
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
49%11%14%14%7%1
1552
16th to endDay
44%10%16%14%9%4
1749
February1st to 15thDay
45%12%17%16%7%
1694
16th to endDay
48%12%15%17%5%
1538
March1st to 15thDay
53%11%12%14%6%1
1860
16th to endDay
55%9%13%15%5%
2184
April1st to 15thDay
54%7%13%17%6%
2149
16th to endDay
41%6%15%23%10%1
2178
May1st to 15thDay
37%5%13%27%14%1
2511
16th to endDay
50%5%10%22%9%
2619
June1st to 15thDay
41%6%9%25%14%2
2520
16th to endDay
26%49%30%24%5%
2520
July1st to 15thDay
17%38%20%29%20%
2371
16th to endDay
15%3412%33%30%
2490
August1st to 15thDay
17%46%23%29%18%
2371
16th to endDay
13%26%23%36%17%
2327
September1st to 15thDay
12%36%22%33%21%
2160
16th to endDay
29%5%9%25%22%7%
2010
October1st to 15thDay
39%5%11%19%16%7%
1800
16th to endDay
39%8%11%20%18%1
1857
November1st to 15thDay
43%11%16%18%9%
1693
16th to endDay
45%11%17%13%9%2
1560
December1st to 15thDay
45%10%14%19%8%
1560
16th to endDay
54%9%15%14%6%
1664
January1st to 15thNight
46%11%16%15%7%1
2716
16th to endNight
42%10%13%19%8%5%
2827
February1st to 15thNight
43%11%20%13%8%1
2470
16th to endNight
43%12%14%21%7%1
1936
March1st to 15thNight
46%12%15%14%7%2
2097
16th to endNight
45%11%18%19%3
2039
April1st to 15thNight
49%8%16%17%7%
1799
16th to endNight
36%7%18%25%12%
1781
May1st to 15thNight
29%7%16%32%12%2
1440
16th to endNight
39%9%15%25%8%1
1496
June1st to 15thNight
34%7%13%28%13%2
1440
16th to endNight
19%313%35%22%4
1440
July1st to 15thNight
12%49%28%28%17%
1360
16th to endNight
12%25%15%38%25%
1416
August1st to 15thNight
12%38%28%30%16%
1563
16th to endNight
9%27%25%37%17%
1875
September1st to 15thNight
9%35%26%38%17%
1800
16th to endNight
23%412%24%22%12%
1948
October1st to 15thNight
29%5%15%23%20%6%
2160
16th to endNight
38%6%15%18%19%2
2365
November1st to 15thNight
44%11%14%18%9%1
2496
16th to endNight
42%11%15%16%10%2
2730
December1st to 15thNight
42%11%14%21%8%1
2730
16th to endNight
49%12%14%15%7%
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
15%7%24%27%23%1
90
16th to endDay
9%18%30%24%15%1
181
February1st to 15thDay
10%19%29%27%12%
276
16th to endDay
9%26%28%26%8%
231
March1st to 15thDay
15%31%25%18%8%
270
16th to endDay
18%28%30%18%5%
288
April1st to 15thDay
14%22%30%18%9%4
269
16th to endDay
14%25%29%17%8%3
270
May1st to 15thDay
15%22%26%20%12%2
288
16th to endDay
16%16%20%24%16%5%
330
June1st to 15thDay
10%17%28%26%14%3
315
16th to endDay
7%12%28%27%19%5%
315
July1st to 15thDay
46%27%32%21%7%
305
16th to endDay
1433%33%17%9%
327
August1st to 15thDay
5%328%28%24%9%
315
16th to endDay
29%20%26%26%14%
332
September1st to 15thDay
36%24%29%26%9%
315
16th to endDay
7%13%18%32%25%2
315
October1st to 15thDay
15%15%24%26%16%1
315
16th to endDay
17%15%23%22%17%4
273
November1st to 15thDay
8%20%25%36%6%2
129
16th to endDay
13%26%31%18%6%3
90
December1st to 15thDay
12%22%24%23%8%8%
90
16th to endDay
9%14%30%30%13%2
96
January1st to 15thNight
8%16%26%25%20%3
780
16th to endNight
8%14%22%29%20%5%
832
February1st to 15thNight
8%13%26%31%18%1
760
16th to endNight
9%11%30%29%17%2
632
March1st to 15thNight
7%16%31%26%14%2
720
16th to endNight
7%16%33%26%15%
768
April1st to 15thNight
12%14%27%27%15%2
719
16th to endNight
7%10%30%28%18%4
701
May1st to 15thNight
8%6%28%36%19%1
360
16th to endNight
9%6%24%35%21%2
375
June1st to 15thNight
11%5%24%41%15%1
360
16th to endNight
5%325%48%17%
360
July1st to 15thNight
1118%50%26%1
340
16th to endNight
2124%50%20%
376
August1st to 15thNight
213%42%37%3
489
16th to endNight
1214%40%35%4
729
September1st to 15thNight
116%37%37%6%
720
16th to endNight
6%6%16%33%31%6%
716
October1st to 15thNight
7%7%22%34%22%5%
720
16th to endNight
7%9%23%29%22%7%
768
November1st to 15thNight
11%13%26%31%14%2
760
16th to endNight
8%20%24%23%19%4
780
December1st to 15thNight
8%15%23%26%23%2
780
16th to endNight
9%21%26%26%14%1
832
Page generated at 2018-02-15 07:58:43. Version ac04

Copyright 2018 A. Danko


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