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Mountain Pines Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mountain Pines Observatory clear sky chart from 2005-11-05 to 2017-09-23.

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
71%
15711
35%
46992
29%
15672
77%
15672
51%
22772

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
64%
719
32%
2327
30%
716
72%
716
44%
1140
January16th to endNight
60%
768
35%
2496
31%
768
69%
768
40%
1289
February1st to 15thNight
64%
699
35%
2170
28%
699
75%
699
49%
1038
February16th to endNight
61%
632
34%
1895
32%
632
68%
632
43%
995
March1st to 15thNight
62%
720
36%
2001
28%
720
71%
720
51%
1015
March16th to endNight
66%
768
35%
2112
25%
768
73%
768
54%
1054
April1st to 15thNight
56%
719
30%
1978
16%
719
66%
719
50%
1029
April16th to endNight
61%
546
44%
1643
28%
546
74%
546
65%
675
May1st to 15thNight
70%
539
36%
1619
28%
539
76%
539
59%
708
May16th to endNight
71%
561
37%
1684
28%
561
77%
561
67%
697
June1st to 15thNight
76%
540
32%
1620
29%
540
78%
540
67%
681
June16th to endNight
85%
540
34%
1620
31%
540
86%
540
72%
661
July1st to 15thNight
84%
510
24%
1530
21%
510
84%
510
47%
790
July16th to endNight
81%
564
22%
1593
19%
531
83%
531
37%
914
August1st to 15thNight
88%
539
30%
1611
26%
536
88%
536
50%
800
August16th to endNight
84%
667
33%
1858
28%
667
84%
667
45%
1020
September1st to 15thNight
82%
720
30%
1980
25%
720
83%
720
50%
1065
September16th to endNight
79%
688
45%
1903
34%
688
86%
688
72%
830
October1st to 15thNight
73%
660
38%
1874
30%
660
79%
660
59%
879
October16th to endNight
77%
704
42%
2112
36%
704
83%
704
61%
948
November1st to 15thNight
73%
700
38%
2190
33%
700
80%
700
56%
992
November16th to endNight
69%
720
39%
2340
35%
720
77%
720
54%
1038
December1st to 15thNight
68%
720
34%
2340
32%
720
75%
720
43%
1160
December16th to endNight
59%
768
32%
2496
30%
768
65%
768
36%
1354

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
3313323346%62%
47916
Night
3313323345%65%
47188
TransparencyDay
22%36%14%27%25%
47611
Night
19%36%15%28%26%
46994
SeeingDay
5%10%25%32%19%6%
5510
Night
4314%33%35%8%
15720

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
35%2431234462%
1611
16th to endDay
6%5%24323346%58%
1728
February1st to 15thDay
46%33223336%59%
1691
16th to endDay
5%6%25%323348%53%
1579
March1st to 15thDay
3413323345%62%
1958
16th to endDay
3423314335%64%
2112
April1st to 15thDay
3214323445%63%
1970
16th to endDay
2213212346%69%
2315
May1st to 15thDay
3313223245%68%
2331
16th to endDay
322313235%71%
2429
June1st to 15thDay
11121223477%
2340
16th to endDay
11121222380%
2340
July1st to 15thDay
42145%26%6%5%7%53%
2340
16th to endDay
6%426%7%5%6%6%8%9%34%
2467
August1st to 15thDay
6%325%4346%6%9%46%
2340
16th to endDay
5%415%335%5%6%7%51%
2341
September1st to 15thDay
5%2145%345%5%6%54%
1980
16th to endDay
211222333473%
1893
October1st to 15thDay
221132333471%
1755
16th to endDay
3112212335%72%
1760
November1st to 15thDay
1113323336%69%
1668
16th to endDay
441221224469%
1620
December1st to 15thDay
5%7%23423337%57%
1620
16th to endDay
6%7%35%32445%5%52%
1728
January1st to 15thNight
3324313435%63%
2327
16th to endNight
5%5%2432234460%
2496
February1st to 15thNight
3413312345%66%
2159
16th to endNight
341433436%6%57%
1895
March1st to 15thNight
341331345%5%63%
2001
16th to endNight
2322213345%66%
2112
April1st to 15thNight
331432334465%
1978
16th to endNight
112112235%76%
1643
May1st to 15thNight
221212335%73%
1619
16th to endNight
22111113478%
1684
June1st to 15thNight
11121223478%
1620
16th to endNight
122212381%
1620
July1st to 15thNight
21133346%6%7%58%
1620
16th to endNight
3215%5%37%7%8%12%42%
1701
August1st to 15thNight
311325%48%9%58%
1620
16th to endNight
22134345%6%8%55%
1858
September1st to 15thNight
221343346%6%60%
1980
16th to endNight
2111112480%
1903
October1st to 15thNight
3212212345%71%
1874
16th to endNight
1212212235%74%
2112
November1st to 15thNight
221232333469%
2190
16th to endNight
3213212235%70%
2340
December1st to 15thNight
3413424445%60%
2340
16th to endNight
6%5%25%424445%54%
2496

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
24%25%15%32%19%
1612
16th to endDay
28%26%17%28%16%
1728
February1st to 15thDay
26%26%18%25%21%
1691
16th to endDay
29%26%17%27%16%
1579
March1st to 15thDay
23%1315%34%20%
1958
16th to endDay
22%25%16%35%17%
2112
April1st to 15thDay
21%15%18%32%20%
1970
16th to endDay
15%1315%34%28%
2315
May1st to 15thDay
17%2415%31%28%
2331
16th to endDay
16%25%11%33%31%
2432
June1st to 15thDay
10%138%25%51%
2340
16th to endDay
10%135%18%60%
2340
July1st to 15thDay
26%7%8%13%17%26%
2201
16th to endDay
38%11%13%14%14%6%
2312
August1st to 15thDay
30%6%9%16%18%18%
2325
16th to endDay
29%5%10%15%24%13%
2341
September1st to 15thDay
28%410%15%22%19%
1980
16th to endDay
14%15%10%32%35%
1893
October1st to 15thDay
17%2415%27%32%
1755
16th to endDay
15%15%12%33%31%
1760
November1st to 15thDay
17%2417%32%26%
1668
16th to endDay
19%1417%28%29%
1620
December1st to 15thDay
27%37%21%25%14%
1620
16th to endDay
31%38%19%27%10%
1728
January1st to 15thNight
23%25%16%32%19%
2327
16th to endNight
27%25%15%29%19%
2496
February1st to 15thNight
20%27%18%27%23%
2170
16th to endNight
25%25%18%28%18%
1895
March1st to 15thNight
19%26%12%35%22%
2001
16th to endNight
18%27%18%32%20%
2112
April1st to 15thNight
22%25%13%34%22%
1978
16th to endNight
10%15%14%34%33%
1643
May1st to 15thNight
14%1415%30%33%
1620
16th to endNight
11%1311%38%33%
1685
June1st to 15thNight
12%125%23%55%
1620
16th to endNight
10%2416%65%
1620
July1st to 15thNight
20%6%11%13%18%29%
1530
16th to endNight
26%9%17%19%19%7%
1593
August1st to 15thNight
18%6%12%18%21%22%
1611
16th to endNight
22%7%9%20%24%15%
1858
September1st to 15thNight
21%5%12%18%20%22%
1980
16th to endNight
9%1311%36%37%
1903
October1st to 15thNight
15%26%15%27%32%
1874
16th to endNight
14%25%11%26%39%
2112
November1st to 15thNight
17%1415%34%25%
2190
16th to endNight
17%1415%27%32%
2340
December1st to 15thNight
24%27%18%27%19%
2340
16th to endNight
30%38%19%26%11%
2496

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
18%6%28%33%10%2
90
16th to endDay
415%20%26%23%9%
96
February1st to 15thDay
5%13%29%30%14%5%
206
16th to endDay
11%23%30%22%9%2
238
March1st to 15thDay
6%18%30%25%14%5%
270
16th to endDay
425%30%25%12%1
288
April1st to 15thDay
8%20%31%23%10%5%
269
16th to endDay
427%37%18%8%3
270
May1st to 15thDay
7%17%35%25%10%3
288
16th to endDay
5%13%32%32%12%3
330
June1st to 15thDay
210%36%31%13%5%
315
16th to endDay
1121%45%21%8%
315
July1st to 15thDay
420%43%24%6%
305
16th to endDay
7%10%37%29%14%
327
August1st to 15thDay
6%11%39%31%10%
315
16th to endDay
6%11%36%31%12%
332
September1st to 15thDay
6%220%40%23%6%
315
16th to endDay
5%9%23%35%20%5%
284
October1st to 15thDay
5%10%28%30%20%5%
195
16th to endDay
7%320%34%31%3
96
November1st to 15thDay
18%14%30%33%12%
90
16th to endDay
412%37%22%21%2
90
December1st to 15thDay
36%17%38%31%2
90
16th to endDay
7%14%16%36%22%2
96
January1st to 15thNight
45%17%37%24%11%
720
16th to endNight
7%420%34%26%5%
768
February1st to 15thNight
45%17%39%28%4
704
16th to endNight
6%6%22%41%19%4
632
March1st to 15thNight
5%6%19%34%29%4
720
16th to endNight
45%18%39%27%5%
768
April1st to 15thNight
5%6%25%35%23%3
719
16th to endNight
17%27%34%24%5%
546
May1st to 15thNight
25%16%40%29%4
540
16th to endNight
3317%39%32%4
563
June1st to 15thNight
1214%43%33%4
540
16th to endNight
8%34%48%7%
540
July1st to 15thNight
2324%58%10%
510
16th to endNight
2217%61%16%
564
August1st to 15thNight
4117%60%16%
539
16th to endNight
2316%54%22%
667
September1st to 15thNight
35%24%51%14%
720
16th to endNight
2113%27%44%10%
688
October1st to 15thNight
4315%33%36%6%
660
16th to endNight
1212%33%35%13%
704
November1st to 15thNight
3116%36%33%8%
700
16th to endNight
4416%32%31%10%
720
December1st to 15thNight
6%414%39%31%4
720
16th to endNight
8%6%16%38%23%5%
768
Page generated at 2017-09-24 06:15:57. Version ac04

Copyright 2017 A. Danko


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