Lake Stars Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Stars 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
36%
15858
22%
46992
13%
15811
46%
15811
28%
28826

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
20%
900
20%
2342
6%
895
31%
895
24%
1529
January16th to endNight
20%
960
23%
2496
6%
960
32%
960
26%
1650
February1st to 15thNight
17%
880
17%
2288
4%
876
25%
876
22%
1583
February16th to endNight
18%
666
22%
1928
5%
666
31%
666
23%
1228
March1st to 15thNight
23%
540
21%
1980
10%
540
35%
540
19%
1245
March16th to endNight
23%
576
14%
2112
8%
576
33%
576
16%
1422
April1st to 15thNight
28%
539
22%
1803
12%
539
43%
539
26%
1048
April16th to endNight
26%
540
20%
1800
11%
540
40%
540
23%
1139
May1st to 15thNight
37%
540
19%
1633
13%
540
46%
540
24%
1074
May16th to endNight
41%
563
20%
1555
13%
561
47%
561
28%
1016
June1st to 15thNight
57%
540
20%
1440
12%
540
62%
540
41%
832
June16th to endNight
56%
540
25%
1440
15%
540
62%
540
48%
794
July1st to 15thNight
63%
510
18%
1437
14%
510
66%
510
41%
830
July16th to endNight
71%
564
24%
1594
24%
531
76%
531
44%
852
August1st to 15thNight
73%
539
26%
1610
29%
536
75%
536
41%
881
August16th to endNight
71%
573
26%
1884
32%
573
74%
573
40%
996
September1st to 15thNight
62%
540
27%
1800
28%
540
66%
540
34%
996
September16th to endNight
59%
557
31%
1904
23%
557
69%
557
37%
981
October1st to 15thNight
45%
660
29%
1980
19%
660
52%
660
36%
1107
October16th to endNight
32%
704
27%
2112
14%
704
44%
704
31%
1230
November1st to 15thNight
34%
700
30%
2159
15%
700
49%
700
32%
1221
November16th to endNight
26%
867
23%
2487
9%
867
37%
867
26%
1561
December1st to 15thNight
20%
900
17%
2520
5%
900
30%
900
21%
1734
December16th to endNight
20%
960
19%
2688
5%
960
31%
960
20%
1877

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
12%6%25%5%2445%7%42%
47908
Night
11%6%24423346%47%
47184
TransparencyDay
40%5%12%24%14%2
47605
Night
36%411%25%17%3
46992
SeeingDay
16%9%27%27%15%3
5893
Night
16%11%30%26%12%1
15858

By Month

Percentage Cloud Cover SE (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
13%6%36%423445%44%
1593
16th to endDay
13%7%36%423446%41%
1728
February1st to 15thDay
13%8%37%6%25%445%38%
1575
16th to endDay
13%12%45%433445%38%
1554
March1st to 15thDay
15%9%46%6%24345%37%
1980
16th to endDay
21%10%36%324445%32%
2110
April1st to 15thDay
15%8%25%5%33445%41%
2145
16th to endDay
20%7%36%5%34445%33%
2160
May1st to 15thDay
19%5%35%5%24447%36%
2316
16th to endDay
13%6%36%7%35%45%7%36%
2558
June1st to 15thDay
8%5%25%6%345%5%9%42%
2520
16th to endDay
5%2145%35%5%6%10%48%
2520
July1st to 15thDay
9%324425%6%7%10%41%
2433
16th to endDay
5%4245%37%5%8%10%42%
2466
August1st to 15thDay
6%425%5%35%5%7%10%43%
2340
16th to endDay
7%5%244345%6%7%48%
2318
September1st to 15thDay
12%5%25%4235%5%7%44%
2160
16th to endDay
9%5%245%3436%7%48%
1878
October1st to 15thDay
13%5%24323335%51%
1650
16th to endDay
13%5%2432333453%
1760
November1st to 15thDay
12%7%23213346%51%
1698
16th to endDay
17%7%24323346%43%
1470
December1st to 15thDay
14%8%46%424437%39%
1440
16th to endDay
17%10%45%423346%37%
1536
January1st to 15thNight
13%6%26%5%24335%45%
2342
16th to endNight
10%8%36%423345%45%
2496
February1st to 15thNight
12%9%47%423446%39%
2278
16th to endNight
13%8%35%423346%45%
1928
March1st to 15thNight
16%9%35%423345%42%
1980
16th to endNight
21%7%34433446%35%
2112
April1st to 15thNight
11%5%23323448%49%
1803
16th to endNight
16%7%245%33337%41%
1800
May1st to 15thNight
14%6%25%5%2435%7%42%
1632
16th to endNight
11%5%345%3345%7%43%
1553
June1st to 15thNight
43244245%8%10%49%
1440
16th to endNight
33133235%7%10%56%
1440
July1st to 15thNight
6%22442446%9%51%
1524
16th to endNight
43133245%5%10%54%
1702
August1st to 15thNight
42145%2346%8%55%
1620
16th to endNight
441433345%7%56%
1884
September1st to 15thNight
11%5%13323447%52%
1800
16th to endNight
7%31342346%8%55%
1904
October1st to 15thNight
11%413323346%55%
1980
16th to endNight
12%5%2442323454%
2112
November1st to 15thNight
12%6%13312335%55%
2159
16th to endNight
16%7%2432323449%
2487
December1st to 15thNight
17%9%45%423345%39%
2520
16th to endNight
16%11%46%423345%38%
2688

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
40%411%25%17%
1594
16th to endDay
42%314%26%10%1
1728
February1st to 15thDay
48%414%21%10%
1576
16th to endDay
48%410%22%13%1
1554
March1st to 15thDay
49%310%20%12%2
1980
16th to endDay
53%412%18%8%
2112
April1st to 15thDay
45%411%21%15%2
2145
16th to endDay
52%411%17%12%1
2160
May1st to 15thDay
47%5%12%21%12%
2316
16th to endDay
46%7%12%20%12%1
2562
June1st to 15thDay
37%7%12%25%15%1
2520
16th to endDay
28%6%17%29%14%2
2520
July1st to 15thDay
34%8%15%25%12%2
2291
16th to endDay
31%9%14%29%13%1
2311
August1st to 15thDay
33%8%16%24%15%
2326
16th to endDay
32%7%11%23%19%5%
2318
September1st to 15thDay
36%6%10%23%18%4
2160
16th to endDay
34%5%9%30%16%3
1878
October1st to 15thDay
36%38%26%21%4
1650
16th to endDay
34%38%28%19%5%
1760
November1st to 15thDay
33%313%23%20%5%
1698
16th to endDay
42%48%25%17%1
1470
December1st to 15thDay
45%412%24%12%
1440
16th to endDay
48%313%21%10%2
1536
January1st to 15thNight
41%313%24%16%
2342
16th to endNight
40%414%24%15%1
2496
February1st to 15thNight
45%411%23%12%1
2288
16th to endNight
40%312%23%17%2
1928
March1st to 15thNight
44%39%23%15%2
1980
16th to endNight
49%5%11%21%10%1
2112
April1st to 15thNight
33%5%10%27%19%3
1803
16th to endNight
43%411%24%14%1
1800
May1st to 15thNight
41%6%10%21%18%
1633
16th to endNight
39%6%15%24%12%2
1555
June1st to 15thNight
26%7%17%28%18%2
1440
16th to endNight
20%7%16%28%22%3
1440
July1st to 15thNight
28%5%14%30%16%3
1437
16th to endNight
23%6%13%36%18%1
1594
August1st to 15thNight
24%7%12%34%19%2
1610
16th to endNight
26%5%11%26%23%6%
1884
September1st to 15thNight
31%49%24%23%5%
1800
16th to endNight
26%5%10%32%22%3
1904
October1st to 15thNight
30%310%24%23%6%
1980
16th to endNight
34%38%27%20%5%
2112
November1st to 15thNight
32%39%25%21%7%
2159
16th to endNight
39%38%28%17%2
2487
December1st to 15thNight
46%413%21%13%
2520
16th to endNight
49%311%19%12%3
2688

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
33%17%36%12%
90
16th to endDay
21%27%37%10%3
96
February1st to 15thDay
20%27%41%11%
90
16th to endDay
29%22%32%9%6%
81
March1st to 15thDay
32%20%36%8%2
90
16th to endDay
33%19%28%16%2
96
April1st to 15thDay
25%12%30%25%5%
264
16th to endDay
27%11%32%19%7%
270
May1st to 15thDay
21%15%33%20%5%2
453
16th to endDay
18%11%37%21%9%1
517
June1st to 15thDay
11%5%30%31%18%3
495
16th to endDay
7%7%35%34%12%3
495
July1st to 15thDay
14%320%36%21%3
475
16th to endDay
5%216%35%35%4
515
August1st to 15thDay
9%117%38%27%5%
493
16th to endDay
12%314%36%25%7%
358
September1st to 15thDay
14%5%14%33%25%6%
315
16th to endDay
6%8%29%32%17%6%
148
October1st to 15thDay
7%20%28%30%10%3
90
16th to endDay
19%8%44%19%5%2
96
November1st to 15thDay
18%7%30%25%16%1
90
16th to endDay
43%21%16%13%5%
90
December1st to 15thDay
21%23%33%15%42
90
16th to endDay
31%26%33%8%1
96
January1st to 15thNight
21%19%35%18%4
900
16th to endNight
16%22%38%19%3
960
February1st to 15thNight
20%18%38%19%2
880
16th to endNight
21%18%38%17%2
666
March1st to 15thNight
22%16%35%22%3
540
16th to endNight
26%11%34%22%4
576
April1st to 15thNight
17%17%34%25%5%
539
16th to endNight
20%10%38%22%7%
540
May1st to 15thNight
17%8%30%32%10%
540
16th to endNight
13%8%30%32%12%2
563
June1st to 15thNight
7%226%40%22%
540
16th to endNight
4332%36%19%3
540
July1st to 15thNight
9%119%43%22%4
510
16th to endNight
5%113%37%38%3
564
August1st to 15thNight
414%42%34%3
539
16th to endNight
6%115%38%33%4
573
September1st to 15thNight
13%316%32%30%3
540
16th to endNight
8%322%32%26%5%
557
October1st to 15thNight
13%7%29%27%18%3
660
16th to endNight
18%11%35%25%9%
704
November1st to 15thNight
15%14%32%25%11%
700
16th to endNight
22%16%33%21%6%
867
December1st to 15thNight
24%16%34%19%4
900
16th to endNight
25%16%33%20%3
960
Page generated at 2017-09-24 08:15:56. Version ac04

Copyright 2017 A. Danko


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