Mount Laguna Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Laguna Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
65%
16043
37%
46596
27%
16001
73%
16001
57%
21337

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
60%
717
31%
2327
28%
716
68%
716
44%
1126
January16th to endNight
54%
768
37%
2322
26%
768
68%
768
43%
1178
February1st to 15thNight
59%
700
34%
2111
27%
700
70%
700
46%
1035
February16th to endNight
46%
632
32%
1895
27%
632
57%
632
38%
1005
March1st to 15thNight
52%
720
33%
2139
27%
720
63%
720
48%
1022
March16th to endNight
56%
768
35%
2076
24%
768
66%
768
53%
1038
April1st to 15thNight
44%
719
36%
1799
15%
719
56%
719
52%
926
April16th to endNight
52%
720
40%
1800
16%
720
64%
720
65%
834
May1st to 15thNight
57%
558
39%
1638
22%
558
68%
558
65%
682
May16th to endNight
59%
562
40%
1685
24%
561
69%
561
70%
648
June1st to 15thNight
64%
540
37%
1620
25%
540
71%
540
78%
612
June16th to endNight
76%
540
39%
1620
30%
540
80%
540
81%
612
July1st to 15thNight
86%
510
30%
1530
25%
510
88%
510
66%
655
July16th to endNight
84%
600
35%
1626
27%
564
85%
564
60%
761
August1st to 15thNight
90%
701
38%
1750
24%
697
90%
697
77%
802
August16th to endNight
89%
700
41%
1750
29%
700
89%
700
70%
849
September1st to 15thNight
86%
660
41%
1735
32%
660
89%
660
73%
789
September16th to endNight
79%
656
47%
1815
39%
656
87%
656
79%
734
October1st to 15thNight
64%
660
41%
1815
30%
660
75%
660
62%
826
October16th to endNight
75%
704
43%
2092
37%
704
83%
704
68%
865
November1st to 15thNight
69%
700
36%
2275
34%
700
78%
700
58%
946
November16th to endNight
66%
720
38%
2340
36%
720
75%
720
55%
995
December1st to 15thNight
60%
720
34%
2340
31%
720
68%
720
44%
1116
December16th to endNight
52%
768
33%
2496
26%
768
64%
768
37%
1281

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
2212323346%68%
47367
Night
1112313336%69%
46796
TransparencyDay
16%25%13%26%35%
47066
Night
14%26%14%26%36%
46598
SeeingDay
6%14%32%30%12%3
5731
Night
47%18%30%29%9%
16052

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
322442435%7%59%
1611
16th to endDay
43145%2446%8%54%
1901
February1st to 15thDay
2213435%45%6%60%
1751
16th to endDay
2326%7%25%35%8%51%
1579
March1st to 15thDay
2223323347%64%
1820
16th to endDay
1214424346%64%
2145
April1st to 15thDay
1214424346%63%
2149
16th to endDay
11113336%73%
2160
May1st to 15thDay
12213235%74%
2310
16th to endDay
11223481%
2429
June1st to 15thDay
1111122481%
2340
16th to endDay
11211286%
2340
July1st to 15thDay
3212223346%68%
2340
16th to endDay
1212425%45%8%61%
2428
August1st to 15thDay
211223335%72%
2114
16th to endDay
3112223445%67%
2100
September1st to 15thDay
212222335%71%
1892
16th to endDay
11111122381%
1815
October1st to 15thDay
1112213435%71%
1815
16th to endDay
2223235%74%
1776
November1st to 15thDay
1212323335%69%
1584
16th to endDay
1112423445%66%
1620
December1st to 15thDay
33235%45%45%7%54%
1620
16th to endDay
23246%35%5%5%7%54%
1728
January1st to 15thNight
231343445%7%59%
2327
16th to endNight
5%2125%25%438%58%
2322
February1st to 15thNight
1222436%5%47%60%
2101
16th to endNight
1225%8%35%46%6%53%
1895
March1st to 15thNight
1212325%448%62%
2139
16th to endNight
1212325%45%8%62%
2076
April1st to 15thNight
1213413336%68%
1799
16th to endNight
111113335%76%
1800
May1st to 15thNight
1122336%76%
1638
16th to endNight
11123482%
1684
June1st to 15thNight
11112485%
1620
16th to endNight
11111288%
1620
July1st to 15thNight
12212336%74%
1620
16th to endNight
1213213347%68%
1737
August1st to 15thNight
11211236%77%
1760
16th to endNight
2111112235%76%
1750
September1st to 15thNight
1221112381%
1735
16th to endNight
11111287%
1815
October1st to 15thNight
112213326%74%
1815
16th to endNight
1111335%7%73%
2092
November1st to 15thNight
1322443472%
2275
16th to endNight
1212223347%67%
2340
December1st to 15thNight
3214425%447%58%
2340
16th to endNight
4315%5%25%447%56%
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
22%17%15%27%25%
1612
16th to endDay
25%28%14%25%23%
1901
February1st to 15thDay
21%17%14%26%27%
1751
16th to endDay
27%39%17%23%18%
1579
March1st to 15thDay
18%26%15%30%27%
1820
16th to endDay
19%28%15%32%21%
2145
April1st to 15thDay
18%26%17%36%19%
2149
16th to endDay
9%25%19%33%29%
2160
May1st to 15thDay
11%1415%29%37%
2310
16th to endDay
7%1316%36%34%
2432
June1st to 15thDay
8%38%24%53%
2340
16th to endDay
7%11411%75%
2340
July1st to 15thDay
15%339%21%46%
2201
16th to endDay
18%48%19%24%24%
2276
August1st to 15thDay
14%3310%27%41%
2100
16th to endDay
17%349%27%38%
2100
September1st to 15thDay
14%25%9%24%43%
1892
16th to endDay
10%126%27%52%
1815
October1st to 15thDay
14%2414%27%37%
1815
16th to endDay
13%15%9%22%47%
1776
November1st to 15thDay
15%15%14%26%35%
1584
16th to endDay
17%26%14%24%34%
1620
December1st to 15thDay
26%17%17%20%25%
1620
16th to endDay
26%310%19%23%17%
1728
January1st to 15thNight
21%36%16%24%27%
2327
16th to endNight
23%28%14%19%30%
2322
February1st to 15thNight
20%39%13%23%30%
2112
16th to endNight
25%39%16%23%21%
1895
March1st to 15thNight
17%38%15%26%27%
2139
16th to endNight
17%37%16%29%25%
2076
April1st to 15thNight
15%37%15%35%21%
1799
16th to endNight
8%16%17%32%32%
1800
May1st to 15thNight
8%2416%28%39%
1639
16th to endNight
6%15%15%34%37%
1685
June1st to 15thNight
5%39%23%57%
1620
16th to endNight
5%411%77%
1620
July1st to 15thNight
11%238%20%53%
1530
16th to endNight
15%36%17%28%28%
1626
August1st to 15thNight
8%1315%26%44%
1750
16th to endNight
10%3210%28%44%
1750
September1st to 15thNight
9%229%27%48%
1735
16th to endNight
6%16%30%53%
1815
October1st to 15thNight
12%16%15%27%36%
1815
16th to endNight
9%17%11%22%46%
2092
November1st to 15thNight
13%15%12%30%35%
2275
16th to endNight
15%17%16%26%32%
2340
December1st to 15thNight
22%19%18%23%24%
2340
16th to endNight
26%310%18%22%19%
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
17%20%24%31%6%
90
16th to endDay
17%17%32%24%7%
269
February1st to 15thDay
8%15%43%26%6%
266
16th to endDay
11%30%31%20%5%
238
March1st to 15thDay
9%22%31%22%11%1
270
16th to endDay
10%19%36%21%9%2
288
April1st to 15thDay
10%26%33%20%7%2
269
16th to endDay
9%22%37%20%7%2
270
May1st to 15thDay
6%19%41%22%7%2
288
16th to endDay
319%41%22%9%3
330
June1st to 15thDay
216%34%29%12%4
315
16th to endDay
2435%33%18%5%
315
July1st to 15thDay
1229%39%21%6%
305
16th to endDay
3120%40%25%9%
327
August1st to 15thDay
2227%39%19%9%
300
16th to endDay
2317%48%20%7%
268
September1st to 15thDay
35%33%41%10%4
255
16th to endDay
311%29%43%8%2
255
October1st to 15thDay
419%33%34%8%
255
16th to endDay
410%30%32%21%
192
November1st to 15thDay
7%14%17%31%22%6%
90
16th to endDay
12%17%30%23%16%
90
December1st to 15thDay
6%6%20%43%22%1
90
16th to endDay
16%17%31%25%9%
96
January1st to 15thNight
5%9%17%32%24%10%
720
16th to endNight
12%7%19%29%25%5%
768
February1st to 15thNight
5%9%19%32%24%8%
704
16th to endNight
8%14%23%28%17%6%
632
March1st to 15thNight
6%12%25%29%20%5%
720
16th to endNight
5%10%24%27%23%7%
768
April1st to 15thNight
6%15%29%25%17%5%
719
16th to endNight
413%28%26%19%7%
720
May1st to 15thNight
39%26%33%22%4
559
16th to endNight
211%25%34%22%4
563
June1st to 15thNight
5%29%37%23%4
540
16th to endNight
1218%40%30%6%
540
July1st to 15thNight
15%36%46%8%
510
16th to endNight
215%32%49%9%
600
August1st to 15thNight
429%48%15%
701
16th to endNight
3319%53%20%
700
September1st to 15thNight
17%26%48%15%
660
16th to endNight
1312%28%39%14%
656
October1st to 15thNight
39%20%31%27%8%
660
16th to endNight
1415%29%31%17%
704
November1st to 15thNight
27%17%32%28%11%
700
16th to endNight
5%6%17%27%28%14%
720
December1st to 15thNight
8%7%17%30%25%9%
720
16th to endNight
11%10%20%27%23%6%
768
Page generated at 2017-08-13 11:16:52. Version ac04

Copyright 2017 A. Danko


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