Lily Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lily Lake Observatory clear sky chart from 2005-11-05 to 2017-09-24.

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
37%
16006
17%
46923
10%
15965
44%
15965
24%
31329

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
19%
900
15%
2506
4%
895
29%
895
19%
1821
January16th to endNight
21%
960
12%
2643
4%
960
28%
960
16%
1962
February1st to 15thNight
21%
812
14%
2223
4%
812
29%
812
19%
1579
February16th to endNight
25%
631
18%
1893
7%
631
35%
631
18%
1319
March1st to 15thNight
27%
720
13%
2160
7%
720
32%
720
18%
1498
March16th to endNight
31%
609
15%
2007
11%
609
38%
609
18%
1413
April1st to 15thNight
30%
539
15%
1797
10%
539
39%
539
19%
1224
April16th to endNight
33%
540
19%
1746
11%
540
43%
540
22%
1165
May1st to 15thNight
36%
540
15%
1578
6%
540
44%
540
21%
1105
May16th to endNight
47%
561
17%
1498
9%
561
53%
561
31%
980
June1st to 15thNight
51%
540
16%
1440
10%
540
54%
540
35%
907
June16th to endNight
50%
540
16%
1440
8%
540
55%
540
30%
967
July1st to 15thNight
63%
510
17%
1360
11%
510
65%
510
40%
819
July16th to endNight
70%
564
21%
1417
15%
531
73%
531
42%
833
August1st to 15thNight
75%
539
21%
1573
20%
536
77%
536
41%
865
August16th to endNight
65%
573
21%
1910
21%
573
69%
573
35%
1056
September1st to 15thNight
63%
540
29%
1800
28%
540
69%
540
38%
962
September16th to endNight
58%
687
26%
1908
19%
687
62%
687
36%
1140
October1st to 15thNight
46%
660
25%
1913
18%
660
52%
660
32%
1162
October16th to endNight
29%
704
18%
2230
10%
704
39%
704
21%
1450
November1st to 15thNight
33%
700
23%
2276
16%
700
44%
700
24%
1411
November16th to endNight
26%
777
16%
2397
8%
777
35%
777
19%
1632
December1st to 15thNight
22%
900
13%
2520
4%
900
29%
900
16%
1869
December16th to endNight
16%
960
11%
2688
3%
960
24%
960
11%
2190

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
13%7%36%5%35%45%7%36%
48018
Night
14%7%35%424447%40%
47091
Cloud CoverDay
13%7%36%5%35%45%7%36%
48027
Night
14%7%35%424447%40%
47096
TransparencyDay
45%6%12%21%11%1
47704
Night
43%5%12%22%13%1
46923
SeeingDay
14%8%28%27%15%6%
6013
Night
17%8%30%29%12%1
16011

By Month

Percentage Cloud Cover NE (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
14%12%5%7%6%25%5%49%26%
1432
16th to endDay
13%14%6%8%7%35%446%26%
1578
February1st to 15thDay
14%12%5%8%6%25%445%28%
1639
16th to endDay
15%10%37%6%35%447%32%
1580
March1st to 15thDay
16%9%46%5%24448%30%
1790
16th to endDay
17%8%46%6%35%446%31%
2227
April1st to 15thDay
17%11%46%5%24446%31%
2151
16th to endDay
20%8%25%5%2445%7%34%
2214
May1st to 15thDay
18%9%36%6%345%5%8%28%
2371
16th to endDay
14%6%35%5%35%5%5%7%37%
2617
June1st to 15thDay
11%5%25%5%3445%7%43%
2520
16th to endDay
9%435%5%46%6%7%8%38%
2520
July1st to 15thDay
7%3245%36%6%6%8%44%
2520
16th to endDay
6%335%6%36%6%7%8%41%
2655
August1st to 15thDay
7%5%15%6%35%5%6%9%42%
2374
16th to endDay
10%424436%5%6%8%42%
2292
September1st to 15thDay
12%41343445%6%48%
2154
16th to endDay
9%5%25%5%25%448%45%
1905
October1st to 15thDay
14%6%25%424347%43%
1716
16th to endDay
18%8%35%424445%37%
1642
November1st to 15thDay
13%8%45%42445%6%41%
1582
16th to endDay
18%9%46%5%23345%34%
1563
December1st to 15thDay
17%12%48%5%45%335%29%
1440
16th to endDay
22%12%6%8%6%24445%22%
1536
January1st to 15thNight
16%10%47%5%23445%34%
2506
16th to endNight
12%10%6%9%6%34446%30%
2643
February1st to 15thNight
14%12%47%423346%36%
2221
16th to endNight
15%11%46%5%24347%34%
1893
March1st to 15thNight
17%8%36%5%34345%37%
2147
16th to endNight
16%8%46%6%25%5%46%33%
2007
April1st to 15thNight
17%8%35%5%25%45%6%36%
1797
16th to endNight
19%6%26%423346%40%
1746
May1st to 15thNight
17%6%25%5%245%6%7%34%
1578
16th to endNight
11%425%43447%9%43%
1496
June1st to 15thNight
11%4245%3345%6%48%
1440
16th to endNight
8%425%5%36%6%6%8%43%
1440
July1st to 15thNight
6%3135%245%6%9%51%
1440
16th to endNight
5%313325%5%6%10%50%
1513
August1st to 15thNight
4313435%46%10%53%
1582
16th to endNight
8%31342436%8%51%
1910
September1st to 15thNight
10%313322346%58%
1800
16th to endNight
9%4234245%47%51%
1908
October1st to 15thNight
12%414333347%50%
1913
16th to endNight
19%8%24423345%41%
2230
November1st to 15thNight
14%7%24423436%46%
2276
16th to endNight
17%8%46%424346%36%
2397
December1st to 15thNight
19%10%36%5%34436%31%
2520
16th to endNight
23%14%5%7%5%25%445%21%
2688

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
14%12%5%7%6%345%5%7%27%
1432
16th to endDay
13%13%6%9%7%34346%26%
1578
February1st to 15thDay
14%13%6%6%6%35%445%28%
1639
16th to endDay
15%10%47%6%24446%33%
1580
March1st to 15thDay
16%10%5%6%5%2445%7%30%
1800
16th to endDay
17%8%46%6%34446%31%
2226
April1st to 15thDay
18%11%5%6%5%34445%31%
2151
16th to endDay
20%8%25%5%2345%6%34%
2214
May1st to 15thDay
18%8%36%6%35%5%5%8%28%
2371
16th to endDay
13%6%26%436%5%5%8%37%
2617
June1st to 15thDay
11%5%25%5%345%5%7%43%
2520
16th to endDay
9%5%35%5%36%6%7%8%38%
2520
July1st to 15thDay
8%315%436%6%7%8%44%
2520
16th to endDay
6%325%6%37%6%6%9%41%
2655
August1st to 15thDay
7%5%26%6%345%7%9%42%
2374
16th to endDay
10%4245%35%5%6%8%42%
2292
September1st to 15thDay
12%413325%45%7%48%
2154
16th to endDay
9%5%25%435%45%8%45%
1905
October1st to 15thDay
13%6%25%423447%43%
1716
16th to endDay
19%8%34434446%37%
1642
November1st to 15thDay
13%9%36%324446%41%
1582
16th to endDay
18%10%46%5%33335%35%
1563
December1st to 15thDay
17%12%5%8%5%35%335%29%
1440
16th to endDay
22%12%6%8%5%24346%22%
1536
January1st to 15thNight
16%10%47%5%23345%34%
2506
16th to endNight
13%10%7%9%5%34446%30%
2643
February1st to 15thNight
14%11%5%6%423436%36%
2214
16th to endNight
15%11%36%5%24346%34%
1893
March1st to 15thNight
17%8%46%5%33345%37%
2160
16th to endNight
17%7%46%5%25%5%5%6%33%
2007
April1st to 15thNight
17%7%35%6%2445%6%36%
1797
16th to endNight
19%7%35%423436%39%
1746
May1st to 15thNight
17%5%35%435%5%5%7%34%
1577
16th to endNight
11%42443445%10%43%
1496
June1st to 15thNight
11%415%5%2345%6%49%
1440
16th to endNight
8%4245%35%6%7%9%42%
1440
July1st to 15thNight
6%2143335%5%8%52%
1440
16th to endNight
6%313325%5%6%10%51%
1513
August1st to 15thNight
3313425%5%6%9%53%
1582
16th to endNight
8%41432335%9%51%
1910
September1st to 15thNight
10%314322346%58%
1800
16th to endNight
8%4134235%48%51%
1908
October1st to 15thNight
12%424423446%50%
1913
16th to endNight
19%8%24423346%41%
2230
November1st to 15thNight
14%7%24423345%46%
2276
16th to endNight
16%9%47%433346%36%
2397
December1st to 15thNight
20%9%46%5%34436%31%
2520
16th to endNight
23%13%5%7%5%35%445%22%
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
54%7%14%14%9%
1433
16th to endDay
59%412%14%8%
1578
February1st to 15thDay
57%5%11%16%8%1
1641
16th to endDay
51%7%12%19%7%1
1580
March1st to 15thDay
52%7%13%18%7%
1800
16th to endDay
53%6%13%19%5%
2227
April1st to 15thDay
54%5%9%20%9%
2151
16th to endDay
49%6%12%17%11%2
2214
May1st to 15thDay
53%8%11%21%5%
2371
16th to endDay
44%7%12%20%13%1
2621
June1st to 15thDay
38%6%12%24%16%1
2520
16th to endDay
39%8%13%20%14%2
2520
July1st to 15thDay
34%8%14%25%13%2
2371
16th to endDay
35%8%17%21%13%3
2488
August1st to 15thDay
35%8%14%26%13%1
2359
16th to endDay
36%8%12%23%16%2
2292
September1st to 15thDay
34%6%10%25%19%3
2154
16th to endDay
35%5%12%27%16%1
1905
October1st to 15thDay
39%6%12%24%14%1
1716
16th to endDay
47%5%13%21%9%1
1642
November1st to 15thDay
43%5%12%23%13%2
1582
16th to endDay
51%413%23%6%
1563
December1st to 15thDay
58%414%16%6%
1440
16th to endDay
63%6%10%11%7%
1536
January1st to 15thNight
51%5%11%19%10%
2506
16th to endNight
54%5%14%15%9%
2643
February1st to 15thNight
49%412%20%11%
2223
16th to endNight
49%5%12%21%8%2
1893
March1st to 15thNight
50%413%18%11%2
2160
16th to endNight
49%6%11%20%9%1
2007
April1st to 15thNight
48%5%10%21%13%1
1797
16th to endNight
45%5%9%22%11%4
1746
May1st to 15thNight
46%7%12%22%10%
1578
16th to endNight
35%8%14%20%18%2
1498
June1st to 15thNight
34%5%12%24%19%2
1440
16th to endNight
35%10%12%21%18%1
1440
July1st to 15thNight
28%7%12%29%19%2
1360
16th to endNight
25%8%17%26%18%3
1417
August1st to 15thNight
24%8%15%31%18%1
1573
16th to endNight
29%6%14%26%17%4
1910
September1st to 15thNight
27%5%10%27%26%2
1800
16th to endNight
31%6%11%32%16%2
1908
October1st to 15thNight
34%5%10%26%20%1
1913
16th to endNight
44%411%24%12%1
2230
November1st to 15thNight
40%49%24%17%3
2276
16th to endNight
48%413%22%11%
2397
December1st to 15thNight
54%5%11%19%8%
2520
16th to endNight
65%5%9%13%5%1
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
18%11%43%25%1
90
16th to endDay
17%9%39%23%8%1
96
February1st to 15thDay
18%22%44%12%2
90
16th to endDay
25%8%34%19%8%2
81
March1st to 15thDay
38%16%25%15%3
90
16th to endDay
28%8%34%16%9%2
234
April1st to 15thDay
22%12%30%24%8%
270
16th to endDay
20%13%25%25%10%4
270
May1st to 15thDay
23%10%29%21%10%2
328
16th to endDay
18%10%30%25%12%4
517
June1st to 15thDay
10%6%32%30%16%4
495
16th to endDay
10%8%34%28%12%5%
495
July1st to 15thDay
9%427%32%16%9%
475
16th to endDay
7%325%35%19%9%
515
August1st to 15thDay
7%219%33%23%13%
415
16th to endDay
9%317%28%28%12%
332
September1st to 15thDay
9%418%31%26%9%
315
16th to endDay
10%5%17%28%28%9%
287
October1st to 15thDay
13%8%25%29%19%3
156
16th to endDay
27%13%32%23%3
96
November1st to 15thDay
6%13%26%34%12%6%
90
16th to endDay
35%10%35%12%6%
90
December1st to 15thDay
18%17%37%20%5%
90
16th to endDay
28%23%42%32
96
January1st to 15thNight
20%13%39%20%5%
900
16th to endNight
17%13%37%27%3
960
February1st to 15thNight
21%11%37%23%4
815
16th to endNight
20%14%33%25%6%
631
March1st to 15thNight
20%11%35%24%7%
720
16th to endNight
19%9%31%29%8%
609
April1st to 15thNight
19%12%33%28%5%
539
16th to endNight
22%7%34%25%9%
540
May1st to 15thNight
21%6%31%30%10%
540
16th to endNight
12%6%28%35%17%
563
June1st to 15thNight
12%227%43%13%
540
16th to endNight
9%331%38%15%1
540
July1st to 15thNight
7%121%42%24%1
510
16th to endNight
5%117%47%25%3
564
August1st to 15thNight
410%48%31%4
539
16th to endNight
9%16%38%30%4
573
September1st to 15thNight
11%219%35%27%4
540
16th to endNight
10%5%19%33%26%3
687
October1st to 15thNight
14%7%26%31%17%2
660
16th to endNight
24%11%32%23%9%
704
November1st to 15thNight
18%10%34%24%10%1
700
16th to endNight
20%14%33%25%7%
777
December1st to 15thNight
25%12%34%22%4
900
16th to endNight
29%11%34%21%3
960
Page generated at 2017-09-25 08:02:21. Version ac04

Copyright 2017 A. Danko


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