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 2018-02-22.

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
66%
16823
37%
48919
28%
16781
74%
16781
57%
22364

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%
777
31%
2522
28%
776
68%
776
43%
1236
January16th to endNight
55%
832
38%
2515
28%
832
68%
832
44%
1264
February1st to 15thNight
60%
760
35%
2291
28%
760
71%
760
47%
1114
February16th to endNight
47%
660
34%
1979
28%
660
58%
660
38%
1038
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
89%
717
38%
1790
24%
713
90%
713
77%
818
August16th to endNight
90%
764
44%
1910
31%
764
90%
764
72%
913
September1st to 15thNight
85%
720
39%
1893
30%
720
88%
720
72%
866
September16th to endNight
80%
716
50%
1980
41%
716
88%
716
81%
794
October1st to 15thNight
67%
720
40%
1980
30%
720
77%
720
65%
886
October16th to endNight
76%
768
46%
2282
40%
768
84%
768
69%
939
November1st to 15thNight
68%
760
35%
2470
32%
760
77%
760
55%
1053
November16th to endNight
67%
780
40%
2535
37%
780
75%
780
54%
1088
December1st to 15thNight
59%
780
34%
2535
31%
780
68%
780
45%
1198
December16th to endNight
54%
832
35%
2704
28%
832
66%
832
38%
1367

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
2112323346%68%
49323
Night
1112313336%69%
49119
TransparencyDay
16%25%13%26%35%
49022
Night
14%26%14%26%36%
48921
SeeingDay
6%13%31%30%14%3
6424
Night
47%17%30%30%9%
16832

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
422442435%7%58%
1746
16th to endDay
431442446%8%55%
2060
February1st to 15thDay
221343445%5%61%
1901
16th to endDay
2326%7%25%35%8%52%
1641
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%73%
2160
16th to endDay
2112223445%69%
2292
September1st to 15thDay
212322335%70%
2064
16th to endDay
11111112382%
1980
October1st to 15thDay
1112213335%73%
1980
16th to endDay
112222235%74%
1937
November1st to 15thDay
1213424336%67%
1719
16th to endDay
2112423445%65%
1755
December1st to 15thDay
33135%3445%7%56%
1755
16th to endDay
23245%35%5%5%7%55%
1872
January1st to 15thNight
231343445%7%58%
2522
16th to endNight
5%2125%15%438%59%
2515
February1st to 15thNight
1222435%5%48%60%
2281
16th to endNight
1225%7%35%46%6%54%
1979
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%78%
1800
16th to endNight
2111112135%78%
1910
September1st to 15thNight
1221122380%
1893
16th to endNight
1111288%
1980
October1st to 15thNight
112213335%75%
1980
16th to endNight
1111335%7%74%
2282
November1st to 15thNight
13324435%69%
2470
16th to endNight
1212323346%68%
2535
December1st to 15thNight
3214425%45%7%58%
2535
16th to endNight
33145%25%447%56%
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%17%16%27%23%
1747
16th to endDay
24%28%16%25%24%
2060
February1st to 15thDay
21%17%14%26%28%
1901
16th to endDay
27%48%17%23%18%
1641
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
13%3310%27%42%
2146
16th to endDay
16%348%26%41%
2292
September1st to 15thDay
15%25%9%24%41%
2064
16th to endDay
9%126%27%53%
1980
October1st to 15thDay
12%2413%25%41%
1980
16th to endDay
13%15%9%21%48%
1937
November1st to 15thDay
17%15%14%26%34%
1719
16th to endDay
18%26%14%24%34%
1755
December1st to 15thDay
25%17%16%20%28%
1755
16th to endDay
25%29%18%25%18%
1872
January1st to 15thNight
22%36%17%24%25%
2522
16th to endNight
22%28%15%20%30%
2515
February1st to 15thNight
19%38%13%23%31%
2292
16th to endNight
25%38%16%24%22%
1979
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%
1790
16th to endNight
10%229%26%48%
1910
September1st to 15thNight
9%2210%28%45%
1893
16th to endNight
6%17%30%54%
1980
October1st to 15thNight
11%15%13%26%41%
1980
16th to endNight
9%17%11%21%48%
2282
November1st to 15thNight
15%15%13%30%33%
2470
16th to endNight
15%16%15%26%33%
2535
December1st to 15thNight
22%18%17%23%26%
2535
16th to endNight
25%39%17%23%21%
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%15%18%29%15%1
135
16th to endDay
15%15%29%26%10%1
332
February1st to 15thDay
7%13%38%27%9%3
326
16th to endDay
11%28%31%20%6%
264
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%
315
16th to endDay
2317%47%21%8%
332
September1st to 15thDay
4433%39%13%3
315
16th to endDay
310%31%41%11%2
315
October1st to 15thDay
315%35%33%12%
315
16th to endDay
411%25%30%26%2
249
November1st to 15thDay
7%10%25%33%19%4
135
16th to endDay
10%13%25%23%22%4
135
December1st to 15thDay
6%9%22%37%22%1
135
16th to endDay
13%14%22%25%17%6%
144
January1st to 15thNight
6%8%16%32%25%9%
780
16th to endNight
11%7%18%29%26%5%
832
February1st to 15thNight
49%18%32%24%9%
764
16th to endNight
8%14%23%29%17%6%
660
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
5%29%48%15%
717
16th to endNight
2218%54%20%
764
September1st to 15thNight
17%27%49%14%
720
16th to endNight
1312%29%39%13%
716
October1st to 15thNight
28%18%31%30%8%
720
16th to endNight
1415%28%32%17%
768
November1st to 15thNight
26%17%35%27%10%
760
16th to endNight
46%16%27%30%14%
780
December1st to 15thNight
8%8%17%31%25%8%
780
16th to endNight
10%9%19%27%24%7%
832
Page generated at 2018-02-23 08:21:35. Version ac04

Copyright 2018 A. Danko


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