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 2017-04-25.

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%
15140
37%
45570
33%
15102
81%
15102
56%
21324

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
76%
525
45%
1728
42%
525
84%
525
73%
634
May1st to 15thNight
75%
494
43%
1484
34%
494
83%
494
75%
583
May16th to endNight
78%
513
40%
1540
34%
513
81%
513
74%
604
June1st to 15thNight
83%
495
37%
1485
33%
495
84%
495
71%
612
June16th to endNight
86%
495
31%
1485
27%
495
87%
495
66%
631
July1st to 15thNight
82%
465
23%
1395
19%
465
82%
465
44%
733
July16th to endNight
85%
522
21%
1467
19%
489
84%
489
38%
834
August1st to 15thNight
86%
494
29%
1476
27%
491
86%
491
47%
757
August16th to endNight
86%
556
30%
1721
31%
556
87%
556
42%
919
September1st to 15thNight
80%
660
32%
1815
28%
660
80%
660
46%
1010
September16th to endNight
81%
656
43%
1815
33%
656
86%
656
67%
828
October1st to 15thNight
81%
660
42%
1911
35%
660
86%
660
66%
852
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
3213323346%66%
46064
Night
3212213346%68%
45766
TransparencyDay
18%2411%25%36%
45759
Night
17%2413%25%35%
45572
SeeingDay
5%8%21%34%21%7%
4853
Night
4210%41%35%5%
15151

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%
2117
May1st to 15thDay
111223480%
2136
16th to endDay
111112383%
2221
June1st to 15thDay
21111135%80%
2145
16th to endDay
112212245%74%
2145
July1st to 15thDay
3225%446%8%8%9%43%
2145
16th to endDay
6%437%7%46%6%9%11%32%
2285
August1st to 15thDay
5%226%6%35%6%7%8%44%
2145
16th to endDay
32145%46%6%7%8%48%
2125
September1st to 15thDay
5%3135%25%5%5%8%52%
1815
16th to endDay
312212335%72%
1815
October1st to 15thDay
112212235%74%
1718
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%
1728
May1st to 15thNight
112236%79%
1484
16th to endNight
12112285%
1540
June1st to 15thNight
1111222381%
1485
16th to endNight
111122225%77%
1485
July1st to 15thNight
22133246%7%11%51%
1485
16th to endNight
3214436%7%10%15%40%
1575
August1st to 15thNight
12133246%8%9%57%
1485
16th to endNight
2223445%5%7%11%51%
1721
September1st to 15thNight
331443445%9%56%
1815
16th to endNight
211212235%75%
1815
October1st to 15thNight
11221223476%
1911
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%58%
2117
May1st to 15thDay
9%17%21%58%
2136
16th to endDay
8%16%24%58%
2224
June1st to 15thDay
10%1218%66%
2145
16th to endDay
12%236%16%59%
2145
July1st to 15thDay
29%7%13%14%16%19%
2006
16th to endDay
39%6%17%21%11%3
2130
August1st to 15thDay
32%6%12%15%17%15%
2130
16th to endDay
29%6%10%19%18%14%
2125
September1st to 15thDay
29%48%19%17%21%
1815
16th to endDay
16%218%33%37%
1815
October1st to 15thDay
12%2411%25%43%
1718
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%6%25%58%
1728
May1st to 15thNight
7%138%25%54%
1485
16th to endNight
8%6%24%58%
1541
June1st to 15thNight
10%11319%64%
1485
16th to endNight
12%12418%60%
1485
July1st to 15thNight
21%7%15%18%16%20%
1395
16th to endNight
25%9%22%25%12%3
1467
August1st to 15thNight
19%7%14%21%18%17%
1476
16th to endNight
24%6%14%21%18%15%
1721
September1st to 15thNight
24%5%8%23%19%18%
1815
16th to endNight
12%2212%33%37%
1815
October1st to 15thNight
13%1315%25%41%
1911
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
420%31%29%11%2
250
May1st to 15thDay
416%39%29%7%3
228
16th to endDay
37%34%36%13%3
266
June1st to 15thDay
5%5%30%39%14%5%
255
16th to endDay
2313%51%19%9%
255
July1st to 15thDay
5%28%44%30%8%
245
16th to endDay
7%27%37%26%17%
271
August1st to 15thDay
6%1440%31%15%
255
16th to endDay
225%36%36%14%
268
September1st to 15thDay
8%413%39%26%7%
255
16th to endDay
8%5%23%29%26%6%
255
October1st to 15thDay
18%23%37%17%12%
158
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
1317%51%23%2
525
May1st to 15thNight
418%48%27%1
495
16th to endNight
1215%47%31%1
515
June1st to 15thNight
2210%48%35%1
495
16th to endNight
115%39%49%2
495
July1st to 15thNight
21422%61%7%
465
16th to endNight
3117%63%13%
522
August1st to 15thNight
31116%64%13%
494
16th to endNight
2121%60%13%
556
September1st to 15thNight
416%26%49%11%
660
16th to endNight
39%35%42%8%
656
October1st to 15thNight
211%43%36%5%
660
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 2017-04-26 14:21:47. Version ac04

Copyright 2017 A. Danko


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