Lynchburg College Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lynchburg College 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
46%
15917
22%
47428
14%
15879
55%
15879
28%
29502

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
29%
718
24%
2327
11%
716
45%
716
20%
1415
January16th to endNight
27%
768
24%
2496
10%
768
45%
768
24%
1502
February1st to 15thNight
25%
701
22%
2287
9%
701
42%
701
23%
1352
February16th to endNight
27%
631
26%
1884
10%
631
44%
631
24%
1160
March1st to 15thNight
37%
720
24%
1980
13%
720
47%
720
27%
1256
March16th to endNight
35%
768
20%
2112
11%
768
43%
768
27%
1386
April1st to 15thNight
34%
718
21%
1854
8%
718
43%
718
31%
1165
April16th to endNight
43%
673
21%
1753
9%
673
50%
673
31%
1145
May1st to 15thNight
45%
540
16%
1620
8%
540
51%
540
25%
1068
May16th to endNight
60%
561
16%
1684
12%
561
63%
561
29%
1067
June1st to 15thNight
68%
540
16%
1620
14%
540
70%
540
34%
970
June16th to endNight
73%
540
17%
1620
15%
540
75%
540
34%
978
July1st to 15thNight
68%
510
12%
1530
11%
510
69%
510
29%
993
July16th to endNight
72%
564
18%
1595
16%
531
75%
531
36%
959
August1st to 15thNight
67%
539
19%
1609
15%
536
68%
536
29%
1039
August16th to endNight
67%
693
20%
1839
14%
693
68%
693
30%
1224
September1st to 15thNight
65%
720
24%
1849
18%
720
66%
720
34%
1202
September16th to endNight
54%
717
21%
1988
18%
717
56%
717
25%
1354
October1st to 15thNight
52%
684
27%
2051
24%
684
59%
684
31%
1237
October16th to endNight
46%
704
32%
2112
22%
704
61%
704
35%
1188
November1st to 15thNight
47%
700
28%
2114
19%
700
58%
700
33%
1225
November16th to endNight
40%
720
25%
2436
18%
720
53%
720
27%
1384
December1st to 15thNight
31%
720
21%
2520
12%
720
43%
720
20%
1576
December16th to endNight
30%
768
23%
2548
11%
768
45%
768
19%
1657

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
14%5%25%5%35%45%7%40%
47749
Night
14%5%2442445%7%44%
47621
Cloud CoverDay
14%5%25%5%35%5%5%7%41%
47759
Night
14%42442445%7%45%
47625
TransparencyDay
40%412%22%15%3
47460
Night
38%411%23%17%3
47428
SeeingDay
18%6%18%25%19%10%
5692
Night
17%7%20%32%19%2
15924

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
15%5%3442446%6%41%
1611
16th to endDay
15%5%35%42445%5%44%
1728
February1st to 15thDay
11%6%35%435%5%46%41%
1575
16th to endDay
15%5%35%434447%41%
1587
March1st to 15thDay
15%42442435%6%46%
1969
16th to endDay
17%6%36%424447%39%
2112
April1st to 15thDay
13%41342435%7%48%
2092
16th to endDay
17%4245%24447%41%
2217
May1st to 15thDay
17%5%345%36%6%5%7%33%
2331
16th to endDay
11%5%25%6%45%5%7%8%37%
2431
June1st to 15thDay
10%3236%36%6%6%10%40%
2340
16th to endDay
8%425%6%35%6%8%9%38%
2340
July1st to 15thDay
11%6%36%7%36%6%7%9%31%
2340
16th to endDay
7%5%36%7%5%8%6%8%9%32%
2465
August1st to 15thDay
14%436%6%36%6%7%9%30%
2340
16th to endDay
11%6%26%7%45%6%6%9%32%
2351
September1st to 15thDay
11%6%245%3445%7%43%
2108
16th to endDay
21%6%145%3445%5%35%
1971
October1st to 15thDay
17%5%12323245%51%
1707
16th to endDay
15%5%23323445%50%
1760
November1st to 15thDay
12%413423336%54%
1742
16th to endDay
16%423413447%46%
1521
December1st to 15thDay
16%425%32445%6%42%
1440
16th to endDay
20%6%36%32335%5%39%
1671
January1st to 15thNight
15%4145%24346%46%
2327
16th to endNight
15%6%245%25%446%43%
2496
February1st to 15thNight
14%5%34423446%45%
2285
16th to endNight
12%6%245%335%47%44%
1884
March1st to 15thNight
15%5%1442445%6%45%
1968
16th to endNight
17%424434346%44%
2112
April1st to 15thNight
14%424424448%45%
1854
16th to endNight
15%5%234245%5%7%43%
1753
May1st to 15thNight
16%6%24434448%39%
1620
16th to endNight
12%425%4245%5%10%40%
1682
June1st to 15thNight
8%32443447%11%43%
1620
16th to endNight
7%2234345%5%10%47%
1620
July1st to 15thNight
9%5%25%5%36%5%6%8%41%
1620
16th to endNight
5%425%5%36%48%10%42%
1703
August1st to 15thNight
12%5%245%3446%8%41%
1620
16th to endNight
9%425%6%46%5%6%9%38%
1839
September1st to 15thNight
11%5%245%245%5%6%46%
1849
16th to endNight
18%5%26%5%3445%6%39%
1988
October1st to 15thNight
15%415%5%23335%49%
2051
16th to endNight
14%313323345%54%
2112
November1st to 15thNight
13%5%2432333453%
2114
16th to endNight
16%314323445%49%
2436
December1st to 15thNight
17%7%35%5%2334442%
2520
16th to endNight
18%7%3443445%6%37%
2548

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
15%5%2432445%7%42%
1611
16th to endDay
14%5%24424445%44%
1728
February1st to 15thDay
12%6%25%5%26%447%41%
1575
16th to endDay
15%425%5%34446%41%
1587
March1st to 15thDay
14%414425%446%46%
1980
16th to endDay
18%5%25%5%14446%40%
2111
April1st to 15thDay
13%41332335%7%49%
2092
16th to endDay
17%4245%2445%7%42%
2217
May1st to 15thDay
17%6%25%446%6%5%7%33%
2331
16th to endDay
11%5%25%6%46%5%7%8%38%
2431
June1st to 15thDay
10%3135%46%6%6%9%41%
2340
16th to endDay
8%426%5%35%6%8%9%39%
2340
July1st to 15thDay
11%5%36%7%46%6%7%9%32%
2340
16th to endDay
7%5%36%6%5%8%6%7%10%32%
2465
August1st to 15thDay
14%426%5%35%6%7%9%31%
2340
16th to endDay
12%6%26%7%45%5%6%9%34%
2351
September1st to 15thDay
11%6%25%43445%7%45%
2108
16th to endDay
22%5%145%25%45%6%36%
1971
October1st to 15thDay
17%413312246%51%
1707
16th to endDay
14%5%23323435%50%
1760
November1st to 15thDay
12%413424336%54%
1742
16th to endDay
17%414413447%46%
1521
December1st to 15thDay
16%42442445%7%43%
1440
16th to endDay
21%5%35%423345%39%
1671
January1st to 15thNight
15%424433346%46%
2327
16th to endNight
15%5%3442445%6%44%
2496
February1st to 15thNight
14%425%424446%46%
2278
16th to endNight
12%6%2443445%7%44%
1884
March1st to 15thNight
15%424425%35%6%45%
1980
16th to endNight
16%424424345%45%
2112
April1st to 15thNight
14%324334448%46%
1854
16th to endNight
16%5%14415%45%6%43%
1753
May1st to 15thNight
17%5%245%3346%7%39%
1619
16th to endNight
12%425%5%245%5%10%40%
1682
June1st to 15thNight
9%32443448%11%43%
1620
16th to endNight
7%2244345%5%10%47%
1620
July1st to 15thNight
9%4245%45%5%6%8%42%
1620
16th to endNight
5%425%5%36%5%7%11%43%
1703
August1st to 15thNight
12%5%25%5%2446%8%41%
1620
16th to endNight
9%425%6%45%6%6%9%38%
1839
September1st to 15thNight
12%42443446%6%46%
1849
16th to endNight
19%5%25%5%3345%5%39%
1988
October1st to 15thNight
16%3145%23335%50%
2051
16th to endNight
14%313313445%54%
2112
November1st to 15thNight
13%5%2432333454%
2114
16th to endNight
16%413323446%49%
2436
December1st to 15thNight
18%6%3443334442%
2520
16th to endNight
19%7%2442435%6%38%
2548

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%312%23%18%2
1612
16th to endDay
41%39%25%17%3
1728
February1st to 15thDay
40%311%23%18%2
1577
16th to endDay
42%311%23%16%2
1587
March1st to 15thDay
37%411%23%18%4
1980
16th to endDay
44%49%22%14%4
2112
April1st to 15thDay
33%312%26%16%6%
2092
16th to endDay
41%311%21%15%6%
2217
May1st to 15thDay
47%5%13%19%10%2
2331
16th to endDay
41%5%18%24%10%1
2435
June1st to 15thDay
35%6%18%25%13%
2340
16th to endDay
35%9%16%21%15%2
2340
July1st to 15thDay
45%7%14%16%13%3
2201
16th to endDay
41%7%15%21%12%1
2310
August1st to 15thDay
45%6%14%22%11%
2327
16th to endDay
44%6%15%20%11%1
2351
September1st to 15thDay
37%5%12%21%20%3
2108
16th to endDay
47%47%21%18%1
1971
October1st to 15thDay
34%39%29%17%4
1707
16th to endDay
36%29%27%19%5%
1760
November1st to 15thDay
32%29%20%26%7%
1742
16th to endDay
37%38%26%21%3
1521
December1st to 15thDay
39%312%21%17%5%
1440
16th to endDay
46%39%22%15%2
1671
January1st to 15thNight
39%410%21%17%6%
2327
16th to endNight
40%210%25%17%3
2496
February1st to 15thNight
38%29%24%19%4
2287
16th to endNight
38%49%25%18%2
1884
March1st to 15thNight
38%39%28%15%3
1980
16th to endNight
41%310%23%18%2
2112
April1st to 15thNight
36%312%23%19%5%
1854
16th to endNight
38%411%20%17%6%
1753
May1st to 15thNight
42%5%14%21%14%1
1620
16th to endNight
38%6%16%26%9%2
1684
June1st to 15thNight
32%6%19%25%14%1
1620
16th to endNight
30%8%16%21%19%3
1620
July1st to 15thNight
37%7%17%18%12%5%
1530
16th to endNight
31%6%17%28%14%1
1595
August1st to 15thNight
38%7%14%21%16%1
1609
16th to endNight
38%7%14%23%13%2
1839
September1st to 15thNight
36%6%11%21%18%5%
1849
16th to endNight
45%48%20%18%2
1988
October1st to 15thNight
37%37%27%20%3
2051
16th to endNight
32%27%28%25%4
2112
November1st to 15thNight
34%27%20%25%9%
2114
16th to endNight
36%28%25%22%4
2436
December1st to 15thNight
45%28%23%16%3
2520
16th to endNight
47%210%20%15%2
2548

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
24%17%38%13%32
90
16th to endDay
33%20%28%15%2
96
February1st to 15thDay
21%25%44%6%2
90
16th to endDay
23%15%31%25%3
144
March1st to 15thDay
23%13%25%28%8%
270
16th to endDay
23%8%26%27%11%2
288
April1st to 15thDay
16%14%22%26%16%3
270
16th to endDay
23%421%22%19%8%
270
May1st to 15thDay
25%11%23%20%11%6%
288
16th to endDay
19%318%23%21%13%
331
June1st to 15thDay
11%316%26%26%15%
315
16th to endDay
11%319%29%22%13%
315
July1st to 15thDay
16%14%33%24%10%
305
16th to endDay
7%28%25%33%22%
326
August1st to 15thDay
17%13%22%25%20%
313
16th to endDay
13%7%24%23%30%
332
September1st to 15thDay
13%411%19%28%22%
315
16th to endDay
27%310%18%25%15%
314
October1st to 15thDay
21%413%26%24%8%
278
16th to endDay
15%8%19%35%18%2
272
November1st to 15thDay
18%7%18%32%20%2
250
16th to endDay
23%12%24%20%16%2
73
December1st to 15thDay
21%13%31%20%13%
60
16th to endDay
36%12%27%20%2
87
January1st to 15thNight
20%15%28%30%4
720
16th to endNight
19%11%35%30%2
768
February1st to 15thNight
20%12%34%30%2
704
16th to endNight
17%14%36%28%3
631
March1st to 15thNight
19%11%27%35%6%
720
16th to endNight
19%8%28%32%8%1
768
April1st to 15thNight
16%14%29%28%10%
718
16th to endNight
18%6%23%33%16%1
673
May1st to 15thNight
20%5%20%34%17%2
540
16th to endNight
14%210%34%32%5%
563
June1st to 15thNight
9%110%37%36%4
540
16th to endNight
7%17%37%38%6%
540
July1st to 15thNight
10%17%33%42%4
510
16th to endNight
7%15%31%45%9%
564
August1st to 15thNight
15%1435%37%5%
539
16th to endNight
11%15%29%44%6%
693
September1st to 15thNight
14%27%30%38%6%
720
16th to endNight
21%310%29%31%4
717
October1st to 15thNight
18%5%16%31%23%4
684
16th to endNight
15%6%22%36%16%1
704
November1st to 15thNight
16%6%22%36%15%3
700
16th to endNight
20%11%22%31%14%
720
December1st to 15thNight
22%9%28%30%9%
720
16th to endNight
22%10%29%33%4
768
Page generated at 2017-10-07 14:07:47. Version ac04

Copyright 2017 A. Danko


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