Lizard Hollow Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lizard Hollow Observatory clear sky chart from 2005-11-05 to 2017-10-06.

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
77%
15665
37%
47117
33%
15627
81%
15627
56%
22062

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
73%
718
33%
2327
34%
716
78%
716
51%
1074
January16th to endNight
69%
768
36%
2496
36%
768
75%
768
43%
1264
February1st to 15thNight
76%
698
37%
2197
38%
698
81%
698
53%
1010
February16th to endNight
68%
632
39%
1841
36%
632
74%
632
51%
926
March1st to 15thNight
69%
720
40%
1980
33%
720
75%
720
58%
962
March16th to endNight
76%
768
40%
2112
30%
768
83%
768
62%
998
April1st to 15thNight
71%
689
36%
1948
27%
689
78%
689
59%
920
April16th to endNight
75%
540
46%
1776
42%
540
84%
540
73%
652
May1st to 15thNight
75%
539
41%
1619
33%
539
83%
539
74%
640
May16th to endNight
78%
561
43%
1684
36%
561
82%
561
75%
654
June1st to 15thNight
83%
540
35%
1620
31%
540
84%
540
71%
665
June16th to endNight
86%
540
33%
1620
29%
540
87%
540
66%
695
July1st to 15thNight
82%
510
22%
1530
19%
510
83%
510
44%
803
July16th to endNight
84%
564
20%
1593
18%
531
83%
531
35%
931
August1st to 15thNight
86%
539
27%
1611
25%
536
86%
536
47%
827
August16th to endNight
86%
607
32%
1879
33%
607
86%
607
44%
987
September1st to 15thNight
79%
720
31%
1980
27%
720
80%
720
45%
1110
September16th to endNight
81%
716
46%
1980
35%
716
86%
716
69%
894
October1st to 15thNight
81%
684
41%
1977
34%
684
86%
684
66%
877
October16th to endNight
87%
704
45%
2112
41%
704
89%
704
70%
890
November1st to 15thNight
82%
700
44%
2100
40%
700
86%
700
68%
886
November16th to endNight
76%
720
40%
2299
38%
720
81%
720
54%
1055
December1st to 15thNight
74%
720
39%
2340
40%
720
78%
720
51%
1072
December16th to endNight
68%
768
35%
2496
36%
768
73%
768
42%
1270

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
3212323346%66%
48078
Night
3212213346%68%
47313
TransparencyDay
18%2411%24%37%
47773
Night
17%2413%25%35%
47119
SeeingDay
5%7%21%33%23%8%
5500
Night
4210%41%35%5%
15676

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
4113322346%66%
1611
16th to endDay
6%313323336%61%
1728
February1st to 15thDay
6%22212236%68%
1664
16th to endDay
7%213213336%63%
1633
March1st to 15thDay
4212213335%68%
1980
16th to endDay
21221223474%
2112
April1st to 15thDay
2111212247%72%
1998
16th to endDay
1111112482%
2181
May1st to 15thDay
1121223480%
2331
16th to endDay
111112383%
2429
June1st to 15thDay
21111135%79%
2340
16th to endDay
11221325%5%74%
2340
July1st to 15thDay
3224446%8%8%9%45%
2340
16th to endDay
5%427%7%47%6%9%11%31%
2467
August1st to 15thDay
5%226%5%35%6%7%8%45%
2340
16th to endDay
32145%46%5%7%7%50%
2319
September1st to 15thDay
5%3135%25%5%5%7%53%
1980
16th to endDay
311212235%74%
1980
October1st to 15thDay
112212235%75%
1779
16th to endDay
11111225%79%
1760
November1st to 15thDay
111111236%77%
1759
16th to endDay
322212335%71%
1659
December1st to 15thDay
7%212213247%64%
1620
16th to endDay
6%31222335%6%62%
1728
January1st to 15thNight
5%213213335%67%
2327
16th to endNight
6%314324445%60%
2496
February1st to 15thNight
423213335%68%
2186
16th to endNight
6%212214345%63%
1841
March1st to 15thNight
4112213345%69%
1980
16th to endNight
221121223474%
2112
April1st to 15thNight
3112223345%70%
1948
16th to endNight
21111286%
1776
May1st to 15thNight
112236%79%
1619
16th to endNight
12112285%
1684
June1st to 15thNight
111222381%
1620
16th to endNight
111122325%77%
1620
July1st to 15thNight
2113325%6%7%11%51%
1620
16th to endNight
3214436%7%10%15%39%
1701
August1st to 15thNight
12133246%7%9%56%
1620
16th to endNight
22234445%7%11%52%
1879
September1st to 15thNight
331443445%9%55%
1980
16th to endNight
111212235%76%
1980
October1st to 15thNight
11121223476%
1977
16th to endNight
11121122480%
2112
November1st to 15thNight
111212235%77%
2100
16th to endNight
5%211313335%68%
2299
December1st to 15thNight
6%212122336%67%
2340
16th to endNight
7%314423336%60%
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
20%2414%27%31%
1612
16th to endDay
24%3215%25%29%
1728
February1st to 15thDay
20%1213%27%34%
1664
16th to endDay
23%1213%31%27%
1633
March1st to 15thDay
18%116%31%39%
1980
16th to endDay
14%128%30%42%
2112
April1st to 15thDay
13%25%36%41%
1998
16th to endDay
9%116%23%57%
2181
May1st to 15thDay
10%17%21%58%
2331
16th to endDay
8%16%23%58%
2432
June1st to 15thDay
10%1319%65%
2340
16th to endDay
12%226%16%59%
2340
July1st to 15thDay
27%7%13%14%16%20%
2201
16th to endDay
39%7%18%20%10%2
2312
August1st to 15thDay
32%6%11%15%19%15%
2325
16th to endDay
28%6%10%18%18%17%
2319
September1st to 15thDay
28%47%19%18%21%
1980
16th to endDay
15%218%33%38%
1980
October1st to 15thDay
12%2411%25%43%
1779
16th to endDay
10%139%26%49%
1760
November1st to 15thDay
9%1111%34%41%
1759
16th to endDay
16%1210%29%39%
1659
December1st to 15thDay
21%1416%32%24%
1620
16th to endDay
21%25%20%31%17%
1728
January1st to 15thNight
20%2414%27%31%
2327
16th to endNight
25%3314%29%24%
2496
February1st to 15thNight
18%2416%24%33%
2197
16th to endNight
21%2313%32%26%
1841
March1st to 15thNight
17%1110%26%41%
1980
16th to endNight
14%2110%31%39%
2112
April1st to 15thNight
16%118%34%36%
1948
16th to endNight
8%16%25%57%
1776
May1st to 15thNight
7%138%26%53%
1620
16th to endNight
7%16%24%58%
1685
June1st to 15thNight
10%11320%63%
1620
16th to endNight
12%12417%60%
1620
July1st to 15thNight
21%7%15%17%16%20%
1530
16th to endNight
27%10%23%24%11%3
1593
August1st to 15thNight
19%7%15%21%19%16%
1611
16th to endNight
23%6%13%20%19%17%
1879
September1st to 15thNight
24%5%8%23%19%18%
1980
16th to endNight
12%1211%33%37%
1980
October1st to 15thNight
12%1215%25%41%
1977
16th to endNight
10%1211%24%49%
2112
November1st to 15thNight
11%1212%32%39%
2100
16th to endNight
18%2211%23%40%
2299
December1st to 15thNight
19%1317%31%26%
2340
16th to endNight
26%25%16%29%18%
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
13%222%42%18%1
90
16th to endDay
8%113%38%29%9%
96
February1st to 15thDay
7%8%19%35%25%2
179
16th to endDay
11%13%36%23%12%2
238
March1st to 15thDay
7%14%27%28%14%7%
270
16th to endDay
217%33%23%15%5%
288
April1st to 15thDay
6%17%30%25%14%5%
269
16th to endDay
422%31%28%11%2
270
May1st to 15thDay
415%35%27%12%4
288
16th to endDay
28%33%34%17%3
330
June1st to 15thDay
4429%38%16%6%
315
16th to endDay
2212%48%23%10%
315
July1st to 15thDay
5%17%43%31%10%
305
16th to endDay
7%26%33%28%22%
327
August1st to 15thDay
6%1435%34%17%
315
16th to endDay
325%34%37%16%
332
September1st to 15thDay
6%314%37%29%8%
315
16th to endDay
6%5%24%32%24%6%
315
October1st to 15thDay
17%25%34%19%11%
181
16th to endDay
315%30%48%11%
96
November1st to 15thDay
37%21%34%25%7%
90
16th to endDay
5%5%27%37%20%3
90
December1st to 15thDay
4110%33%45%5%
90
16th to endDay
14%5%25%35%18%1
96
January1st to 15thNight
7%12%51%24%3
720
16th to endNight
8%213%45%26%3
768
February1st to 15thNight
5%29%50%25%5%
704
16th to endNight
7%316%51%19%1
632
March1st to 15thNight
4418%42%26%4
720
16th to endNight
2312%47%29%4
768
April1st to 15thNight
3414%53%21%2
689
16th to endNight
1417%51%22%2
540
May1st to 15thNight
318%46%29%1
540
16th to endNight
1215%47%31%1
563
June1st to 15thNight
1110%48%35%1
540
16th to endNight
115%38%50%2
540
July1st to 15thNight
2422%62%7%
510
16th to endNight
3116%62%15%
564
August1st to 15thNight
2117%63%13%
539
16th to endNight
2121%60%13%
607
September1st to 15thNight
416%26%49%11%
720
16th to endNight
210%35%42%8%
716
October1st to 15thNight
211%43%36%4
684
16th to endNight
16%45%37%7%
704
November1st to 15thNight
2111%43%36%5%
700
16th to endNight
6%111%44%31%4
720
December1st to 15thNight
8%111%44%28%5%
720
16th to endNight
9%211%50%20%5%
768
Page generated at 2017-10-07 11:07:44. Version ac04

Copyright 2017 A. Danko


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