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 2019-06-19.

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%
18039
35%
53998
29%
18000
77%
18000
51%
26151

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%
839
34%
2717
31%
836
72%
836
43%
1363
January16th to endNight
61%
896
34%
2912
32%
896
69%
896
42%
1481
February1st to 15thNight
64%
819
35%
2540
29%
819
74%
819
46%
1250
February16th to endNight
60%
736
33%
2207
31%
736
67%
736
42%
1170
March1st to 15thNight
61%
840
35%
2335
27%
840
71%
840
50%
1197
March16th to endNight
67%
896
34%
2464
25%
896
75%
896
54%
1232
April1st to 15thNight
57%
839
32%
2308
17%
839
67%
839
50%
1190
April16th to endNight
61%
632
41%
1900
27%
632
74%
632
62%
803
May1st to 15thNight
70%
629
38%
1889
29%
629
76%
629
59%
830
May16th to endNight
71%
657
37%
1972
28%
657
76%
657
66%
824
June1st to 15thNight
78%
630
35%
1890
31%
630
80%
630
69%
781
June16th to endNight
85%
597
32%
1791
30%
597
86%
597
72%
732
July1st to 15thNight
83%
555
23%
1665
20%
555
83%
555
44%
882
July16th to endNight
81%
612
21%
1737
18%
579
83%
579
37%
991
August1st to 15thNight
88%
575
31%
1719
27%
572
88%
572
51%
847
August16th to endNight
84%
723
32%
2014
27%
723
85%
723
46%
1094
September1st to 15thNight
83%
780
32%
2145
28%
780
84%
780
52%
1133
September16th to endNight
80%
776
43%
2145
33%
776
86%
776
72%
936
October1st to 15thNight
73%
780
38%
2215
30%
780
78%
780
58%
1051
October16th to endNight
78%
832
42%
2496
36%
832
83%
832
62%
1109
November1st to 15thNight
74%
820
40%
2565
35%
820
81%
820
56%
1161
November16th to endNight
70%
840
38%
2730
36%
840
78%
840
53%
1221
December1st to 15thNight
68%
840
36%
2730
33%
840
75%
840
44%
1346
December16th to endNight
63%
896
33%
2912
31%
896
69%
896
39%
1527

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%61%
54724
Night
3313323345%65%
54194
TransparencyDay
22%36%15%27%25%
54419
Night
19%36%15%28%26%
54000
SeeingDay
6%10%24%31%20%7%
7781
Night
4314%34%35%7%
18048

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
46%25%313345%59%
1881
16th to endDay
5%414323346%58%
2016
February1st to 15thDay
46%34323335%58%
1981
16th to endDay
47%25%423447%51%
1839
March1st to 15thDay
3413424446%60%
2284
16th to endDay
3424314335%63%
2464
April1st to 15thDay
231432345%6%62%
2300
16th to endDay
2212212346%68%
2662
May1st to 15thDay
2313223345%66%
2721
16th to endDay
32221323470%
2845
June1st to 15thDay
111212235%76%
2730
16th to endDay
11111212380%
2577
July1st to 15thDay
32245%36%6%5%7%52%
2535
16th to endDay
6%425%7%46%6%9%9%35%
2675
August1st to 15thDay
6%315%4346%6%9%48%
2485
16th to endDay
5%415%335%5%6%7%51%
2537
September1st to 15thDay
5%2145%345%5%5%55%
2145
16th to endDay
211222233472%
2145
October1st to 15thDay
33232333470%
2074
16th to endDay
3112312335%71%
2080
November1st to 15thDay
1113324346%68%
1952
16th to endDay
4412212245%67%
1890
December1st to 15thDay
46%13423337%56%
1890
16th to endDay
5%7%35%42345%5%53%
2016
January1st to 15thNight
4424423435%60%
2717
16th to endNight
5%5%24322345%60%
2912
February1st to 15thNight
3423312345%63%
2529
16th to endNight
35%1443445%6%57%
2207
March1st to 15thNight
341331345%6%62%
2335
16th to endNight
2322224346%66%
2464
April1st to 15thNight
331432334464%
2308
16th to endNight
1112212246%74%
1900
May1st to 15thNight
121222345%72%
1889
16th to endNight
22111123477%
1972
June1st to 15thNight
11121223479%
1890
16th to endNight
1122212282%
1791
July1st to 15thNight
2113435%6%6%7%57%
1755
16th to endNight
3215%5%36%6%8%13%42%
1845
August1st to 15thNight
31132447%9%58%
1728
16th to endNight
22134345%7%8%56%
2014
September1st to 15thNight
221343346%6%62%
2145
16th to endNight
2111112480%
2145
October1st to 15thNight
3212212345%71%
2215
16th to endNight
1112212235%74%
2496
November1st to 15thNight
221332333470%
2565
16th to endNight
3213212235%69%
2730
December1st to 15thNight
3413423445%61%
2730
16th to endNight
5%5%2442445%6%56%
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
26%25%15%31%18%
1882
16th to endDay
27%27%17%28%16%
2016
February1st to 15thDay
27%16%16%27%20%
1981
16th to endDay
30%26%16%27%16%
1839
March1st to 15thDay
24%2416%32%19%
2284
16th to endDay
23%25%17%34%16%
2464
April1st to 15thDay
21%16%18%31%20%
2300
16th to endDay
16%1315%35%27%
2662
May1st to 15thDay
18%25%15%29%26%
2721
16th to endDay
16%25%12%31%32%
2848
June1st to 15thDay
11%137%25%50%
2730
16th to endDay
10%135%19%60%
2577
July1st to 15thDay
26%7%9%13%16%26%
2396
16th to endDay
36%11%14%16%14%5%
2520
August1st to 15thDay
29%6%9%17%18%18%
2470
16th to endDay
29%5%10%16%25%12%
2537
September1st to 15thDay
26%410%14%22%21%
2145
16th to endDay
15%15%10%32%34%
2145
October1st to 15thDay
19%2413%25%33%
2074
16th to endDay
15%15%12%34%30%
2080
November1st to 15thDay
17%2418%31%25%
1952
16th to endDay
19%1417%30%26%
1890
December1st to 15thDay
27%37%20%24%16%
1890
16th to endDay
30%27%19%27%11%
2016
January1st to 15thNight
25%25%16%31%17%
2717
16th to endNight
26%2416%29%20%
2912
February1st to 15thNight
22%27%17%28%22%
2540
16th to endNight
26%25%17%29%17%
2207
March1st to 15thNight
20%36%14%33%21%
2335
16th to endNight
19%27%18%33%19%
2464
April1st to 15thNight
21%25%14%33%22%
2308
16th to endNight
12%15%13%35%32%
1900
May1st to 15thNight
14%15%17%29%30%
1890
16th to endNight
11%1312%35%34%
1973
June1st to 15thNight
11%125%25%54%
1890
16th to endNight
10%2417%64%
1791
July1st to 15thNight
22%7%11%12%17%29%
1665
16th to endNight
25%9%17%21%18%7%
1737
August1st to 15thNight
17%6%12%19%21%22%
1719
16th to endNight
21%7%10%20%25%14%
2014
September1st to 15thNight
20%5%11%17%20%24%
2145
16th to endNight
9%1311%35%38%
2145
October1st to 15thNight
16%25%15%26%33%
2215
16th to endNight
14%15%12%28%38%
2496
November1st to 15thNight
17%1416%35%24%
2565
16th to endNight
18%1415%28%30%
2730
December1st to 15thNight
24%26%18%27%20%
2730
16th to endNight
27%37%20%28%12%
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
18%321%32%18%3
180
16th to endDay
211%20%29%27%8%
192
February1st to 15thDay
9%13%26%27%15%7%
316
16th to endDay
11%22%28%23%10%2
342
March1st to 15thDay
6%21%30%25%12%3
390
16th to endDay
420%31%26%14%1
416
April1st to 15thDay
8%17%31%23%12%5%
389
16th to endDay
5%22%34%22%9%5%
378
May1st to 15thDay
6%15%32%26%14%5%
408
16th to endDay
5%15%34%29%12%2
458
June1st to 15thDay
28%33%33%15%6%
435
16th to endDay
2120%44%20%9%
388
July1st to 15thDay
417%39%27%10%
365
16th to endDay
6%9%36%28%18%
391
August1st to 15thDay
5%10%37%32%13%
359
16th to endDay
6%111%34%31%15%
396
September1st to 15thDay
5%119%39%25%8%
375
16th to endDay
5%7%22%34%23%6%
375
October1st to 15thDay
8%9%30%29%17%3
304
16th to endDay
5%317%33%29%11%
192
November1st to 15thDay
16%20%32%32%6%
180
16th to endDay
6%10%25%23%25%10%
180
December1st to 15thDay
38%17%38%30%2
180
16th to endDay
410%14%35%28%6%
192
January1st to 15thNight
5%5%16%38%24%10%
840
16th to endNight
7%419%35%27%5%
896
February1st to 15thNight
5%5%17%39%27%4
824
16th to endNight
5%6%22%40%20%3
736
March1st to 15thNight
6%6%19%37%26%3
840
16th to endNight
45%16%40%28%4
896
April1st to 15thNight
46%24%36%24%3
839
16th to endNight
17%25%35%25%4
632
May1st to 15thNight
35%16%39%32%3
630
16th to endNight
3317%41%30%4
659
June1st to 15thNight
1112%42%36%4
630
16th to endNight
18%34%48%7%
597
July1st to 15thNight
3323%58%11%
555
16th to endNight
2217%60%17%
612
August1st to 15thNight
4116%61%16%
575
16th to endNight
2316%55%22%
723
September1st to 15thNight
35%23%53%14%
780
16th to endNight
2112%28%46%9%
776
October1st to 15thNight
5%314%35%35%5%
780
16th to endNight
1211%34%36%13%
832
November1st to 15thNight
3115%40%32%7%
820
16th to endNight
4415%32%33%9%
840
December1st to 15thNight
6%414%40%30%3
840
16th to endNight
7%5%15%39%25%5%
896
Page generated at 2019-06-20 05:02:30. Version ac04

Copyright 2019 A. Danko


Mountain Pines Observatory Clear Sky Chart |Charts Home