Carlos Lemmi Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carlos Lemmi 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
64%
16505
31%
48670
25%
16453
69%
16453
39%
25771

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%
776
27%
2652
24%
776
69%
776
33%
1335
January16th to endNight
57%
832
35%
2545
27%
832
68%
832
36%
1326
February1st to 15thNight
61%
756
34%
2269
32%
752
67%
752
38%
1193
February16th to endNight
51%
632
27%
1895
22%
632
61%
632
28%
1117
March1st to 15thNight
59%
720
29%
2160
25%
720
67%
720
39%
1124
March16th to endNight
59%
768
26%
1996
20%
768
64%
768
37%
1178
April1st to 15thNight
57%
719
28%
1799
17%
719
62%
719
42%
1032
April16th to endNight
59%
720
31%
1800
15%
720
63%
720
41%
1031
May1st to 15thNight
58%
641
26%
1721
15%
641
62%
641
36%
1008
May16th to endNight
62%
561
26%
1685
17%
561
67%
561
38%
924
June1st to 15thNight
63%
466
22%
1546
19%
466
65%
466
32%
866
June16th to endNight
65%
360
28%
1440
29%
360
70%
360
30%
723
July1st to 15thNight
67%
340
28%
1360
30%
340
70%
340
34%
635
July16th to endNight
66%
657
23%
1675
16%
613
72%
613
41%
947
August1st to 15thNight
71%
717
30%
1790
20%
713
71%
713
45%
1029
August16th to endNight
77%
764
34%
1910
21%
764
80%
764
49%
1046
September1st to 15thNight
77%
720
34%
1821
26%
720
79%
720
50%
987
September16th to endNight
76%
716
40%
1980
35%
716
81%
716
54%
962
October1st to 15thNight
72%
720
34%
2007
33%
720
74%
720
48%
1040
October16th to endNight
71%
768
38%
2310
36%
768
78%
768
46%
1130
November1st to 15thNight
69%
760
33%
2470
34%
760
74%
760
44%
1137
November16th to endNight
64%
780
35%
2535
33%
780
72%
780
37%
1252
December1st to 15thNight
57%
780
32%
2535
28%
780
65%
780
32%
1334
December16th to endNight
52%
832
33%
2769
27%
832
63%
832
32%
1415

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%41221235%9%60%
49369
Night
5%5%23313348%58%
48877
TransparencyDay
22%26%18%26%22%
49064
Night
25%36%16%24%22%
48682
SeeingDay
5%11%16%35%24%6%
6478
Night
7%15%6%23%34%13%
16516

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
7%414423336%58%
1614
16th to endDay
10%413212336%58%
2026
February1st to 15thDay
7%313213346%61%
1883
16th to endDay
10%5%2232335%8%52%
1579
March1st to 15thDay
422222345%8%60%
1800
16th to endDay
442332345%10%54%
2223
April1st to 15thDay
5%423222348%60%
2149
16th to endDay
3312211349%66%
2160
May1st to 15thDay
45%1331335%9%58%
2226
16th to endDay
5%5%132113410%59%
2429
June1st to 15thDay
6%7%2331135%11%52%
2409
16th to endDay
241321125%11%63%
2520
July1st to 15thDay
441321246%12%55%
2520
16th to endDay
321221236%11%61%
2369
August1st to 15thDay
231211137%11%63%
2160
16th to endDay
12111245%12%64%
2292
September1st to 15thDay
231221246%12%60%
2139
16th to endDay
231121235%9%66%
1980
October1st to 15thDay
5%312212247%65%
1951
16th to endDay
3212222446%66%
1911
November1st to 15thDay
4213222336%66%
1719
16th to endDay
4313212438%62%
1755
December1st to 15thDay
6%423313348%58%
1755
16th to endDay
9%313323347%58%
1800
January1st to 15thNight
6%41432235%7%57%
2652
16th to endNight
9%413322236%59%
2545
February1st to 15thNight
6%324313337%59%
2269
16th to endNight
11%5%33314445%50%
1895
March1st to 15thNight
5%4133223410%57%
2160
16th to endNight
5%6%2432345%8%54%
1996
April1st to 15thNight
8%5%23212236%61%
1799
16th to endNight
46%23112237%62%
1800
May1st to 15thNight
7%7%34213348%54%
1721
16th to endNight
5%6%23213347%58%
1684
June1st to 15thNight
5%8%25%5%1245%8%49%
1546
16th to endNight
38%25%313349%53%
1440
July1st to 15thNight
45%344223411%52%
1440
16th to endNight
5%6%2442335%10%49%
1793
August1st to 15thNight
46%2431236%11%52%
1800
16th to endNight
25%142135%5%11%56%
1910
September1st to 15thNight
341222345%11%57%
1821
16th to endNight
25%2312247%67%
1980
October1st to 15thNight
3323222336%65%
2007
16th to endNight
5%412213237%65%
2310
November1st to 15thNight
3422213347%64%
2470
16th to endNight
441332335%7%60%
2535
December1st to 15thNight
6%414423346%58%
2535
16th to endNight
10%313212346%59%
2769

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
28%36%15%21%24%
1614
16th to endDay
27%27%18%16%27%
2026
February1st to 15thDay
24%25%16%27%23%
1883
16th to endDay
31%37%22%24%10%
1579
March1st to 15thDay
22%311%20%21%19%
1800
16th to endDay
26%311%25%19%13%
2223
April1st to 15thDay
23%212%26%23%11%
2149
16th to endDay
19%210%24%26%16%
2160
May1st to 15thDay
24%39%23%24%15%
2226
16th to endDay
24%37%28%27%8%
2432
June1st to 15thDay
28%26%16%32%13%
2409
16th to endDay
20%139%30%34%
2520
July1st to 15thDay
23%3311%27%30%
2371
16th to endDay
20%37%20%31%16%
2224
August1st to 15thDay
17%2215%34%27%
2146
16th to endDay
16%3313%38%25%
2292
September1st to 15thDay
20%2412%31%28%
2139
16th to endDay
18%2115%33%28%
1980
October1st to 15thDay
21%26%19%26%24%
1951
16th to endDay
18%35%18%20%33%
1911
November1st to 15thDay
20%27%17%21%30%
1719
16th to endDay
22%27%16%20%29%
1755
December1st to 15thDay
25%39%17%19%25%
1755
16th to endDay
27%210%15%22%21%
1800
January1st to 15thNight
25%38%14%21%25%
2652
16th to endNight
26%27%16%16%29%
2545
February1st to 15thNight
26%26%17%22%24%
2280
16th to endNight
34%35%16%24%14%
1895
March1st to 15thNight
24%38%20%24%18%
2160
16th to endNight
28%410%21%21%12%
1996
April1st to 15thNight
26%29%26%23%12%
1799
16th to endNight
25%37%23%22%17%
1800
May1st to 15thNight
30%28%20%23%13%
1722
16th to endNight
26%49%24%26%9%
1685
June1st to 15thNight
31%49%14%28%11%
1546
16th to endNight
29%338%27%27%
1440
July1st to 15thNight
24%3411%26%30%
1360
16th to endNight
27%39%20%22%16%
1675
August1st to 15thNight
25%3212%34%21%
1790
16th to endNight
20%4211%36%24%
1910
September1st to 15thNight
21%349%31%29%
1821
16th to endNight
17%2115%32%30%
1980
October1st to 15thNight
21%3416%29%23%
2007
16th to endNight
20%2413%21%36%
2310
November1st to 15thNight
20%26%18%19%31%
2470
16th to endNight
23%35%16%21%29%
2535
December1st to 15thNight
29%26%14%20%25%
2535
16th to endNight
27%27%17%23%20%
2769

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
9%9%17%36%20%6%
152
16th to endDay
10%15%17%30%21%4
340
February1st to 15thDay
9%13%19%27%22%8%
320
16th to endDay
10%16%27%28%15%2
238
March1st to 15thDay
6%17%24%27%19%4
270
16th to endDay
5%18%24%34%12%5%
288
April1st to 15thDay
421%24%32%13%4
269
16th to endDay
219%32%32%7%4
270
May1st to 15thDay
415%26%35%14%3
288
16th to endDay
6%13%22%42%12%3
330
June1st to 15thDay
8%11%19%37%20%2
315
16th to endDay
19%8%42%29%7%
315
July1st to 15thDay
27%7%39%34%8%
305
16th to endDay
29%333%39%10%
327
August1st to 15thDay
36%6%43%33%6%
315
16th to endDay
15%6%34%43%8%
332
September1st to 15thDay
26%8%46%31%5%
315
16th to endDay
26%10%45%26%8%
315
October1st to 15thDay
5%6%20%38%24%4
315
16th to endDay
37%15%34%27%11%
327
November1st to 15thDay
5%29%33%33%15%
135
16th to endDay
27%8%34%34%12%
135
December1st to 15thDay
3213%32%34%12%
135
16th to endDay
7%6%18%21%35%11%
127
January1st to 15thNight
8%16%7%32%28%7%
780
16th to endNight
10%16%9%27%29%6%
832
February1st to 15thNight
6%17%7%28%30%9%
760
16th to endNight
13%17%8%28%25%6%
632
March1st to 15thNight
5%18%9%33%26%6%
720
16th to endNight
6%18%9%28%30%7%
768
April1st to 15thNight
7%19%9%29%27%5%
719
16th to endNight
6%20%9%26%30%7%
720
May1st to 15thNight
8%18%9%23%32%8%
642
16th to endNight
418%7%31%30%7%
563
June1st to 15thNight
418%5%27%35%8%
466
16th to endNight
6%16%214%43%15%
360
July1st to 15thNight
6%12%15%38%35%
340
16th to endNight
6%16%17%38%30%
657
August1st to 15thNight
7%9%112%43%25%
717
16th to endNight
5%8%17%44%32%
764
September1st to 15thNight
48%214%44%24%
720
16th to endNight
5%8%318%45%18%
716
October1st to 15thNight
5%8%6%22%43%14%
720
16th to endNight
6%9%6%19%38%19%
768
November1st to 15thNight
313%5%28%35%13%
760
16th to endNight
7%16%5%25%33%11%
780
December1st to 15thNight
8%16%8%30%27%7%
780
16th to endNight
12%18%11%27%23%6%
832
Page generated at 2018-02-15 07:58:50. Version ac04

Copyright 2018 A. Danko


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