Centreville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Centreville clear sky chart from 2005-11-05 to 2018-02-14.

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
39%
15866
21%
48840
12%
15829
50%
15829
26%
30535

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
23%
777
22%
2599
8%
776
41%
776
21%
1617
January16th to endNight
23%
832
24%
2704
10%
832
40%
832
22%
1689
February1st to 15thNight
23%
757
19%
2468
6%
757
40%
757
21%
1527
February16th to endNight
18%
631
24%
1925
7%
631
38%
631
22%
1213
March1st to 15thNight
25%
720
22%
1991
9%
720
38%
720
26%
1272
March16th to endNight
24%
768
21%
2097
9%
768
34%
768
24%
1416
April1st to 15thNight
28%
718
19%
1796
5%
718
37%
718
29%
1184
April16th to endNight
42%
720
20%
1800
8%
720
47%
720
32%
1192
May1st to 15thNight
39%
570
17%
1650
9%
570
46%
570
24%
1120
May16th to endNight
53%
374
17%
1497
16%
374
59%
374
24%
872
June1st to 15thNight
58%
360
19%
1440
20%
360
65%
360
26%
822
June16th to endNight
61%
360
18%
1440
20%
360
66%
360
26%
817
July1st to 15thNight
58%
349
13%
1369
14%
349
61%
349
20%
849
July16th to endNight
73%
564
18%
1595
13%
531
77%
531
38%
919
August1st to 15thNight
64%
539
18%
1609
14%
536
66%
536
31%
1022
August16th to endNight
64%
750
19%
1896
13%
750
65%
750
33%
1252
September1st to 15thNight
57%
720
24%
1800
14%
720
61%
720
33%
1201
September16th to endNight
55%
717
24%
1980
20%
717
58%
717
29%
1303
October1st to 15thNight
48%
720
23%
2160
20%
720
55%
720
28%
1363
October16th to endNight
39%
768
31%
2304
19%
768
56%
768
33%
1340
November1st to 15thNight
38%
760
25%
2395
15%
760
52%
760
29%
1421
November16th to endNight
34%
780
24%
2683
14%
780
49%
780
25%
1551
December1st to 15thNight
29%
780
18%
2730
7%
780
43%
780
19%
1738
December16th to endNight
25%
832
22%
2912
9%
832
42%
832
20%
1835

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%2442445%7%42%
49227
Night
14%5%2442445%7%44%
49023
Cloud CoverDay
14%5%244345%5%7%42%
49237
Night
14%5%2442445%7%43%
49027
TransparencyDay
39%5%11%23%16%2
48929
Night
38%5%11%23%17%3
48840
SeeingDay
17%7%23%25%18%8%
6119
Night
17%8%28%30%14%1
15873

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
17%5%24424446%42%
1666
16th to endDay
16%7%345%24345%43%
1872
February1st to 15thDay
15%7%25%43345%6%40%
1695
16th to endDay
14%7%25%434446%41%
1548
March1st to 15thDay
15%6%245%24336%45%
1957
16th to endDay
17%6%35%425%445%40%
2127
April1st to 15thDay
13%5%35%5%23347%44%
2152
16th to endDay
18%5%15%423346%44%
2160
May1st to 15thDay
17%6%25%435%45%8%36%
2311
16th to endDay
15%424435%5%7%7%40%
2616
June1st to 15thDay
11%315%425%5%6%10%42%
2520
16th to endDay
8%324435%5%7%9%44%
2520
July1st to 15thDay
9%425%5%46%6%6%9%38%
2508
16th to endDay
7%3145%36%7%8%11%39%
2465
August1st to 15thDay
11%5%25%6%45%6%7%8%35%
2340
16th to endDay
11%3245%445%7%8%42%
2294
September1st to 15thDay
13%32442446%7%45%
2160
16th to endDay
15%5%25%42445%6%43%
1977
October1st to 15thDay
20%423413346%45%
1800
16th to endDay
14%5%14323346%50%
1920
November1st to 15thDay
15%5%14323446%47%
1790
16th to endDay
16%412324445%48%
1605
December1st to 15thDay
16%5%344245%46%43%
1560
16th to endDay
18%7%2442445%6%39%
1664
January1st to 15thNight
17%5%24423347%43%
2599
16th to endNight
16%7%24423446%43%
2704
February1st to 15thNight
15%5%245%2445%5%44%
2466
16th to endNight
14%7%25%414446%44%
1925
March1st to 15thNight
16%5%2332445%7%45%
1979
16th to endNight
16%6%25%5%3435%6%41%
2097
April1st to 15thNight
13%5%345%2445%6%44%
1796
16th to endNight
15%5%143245%5%7%44%
1800
May1st to 15thNight
18%6%24425%45%7%38%
1650
16th to endNight
13%424325%5%6%9%42%
1495
June1st to 15thNight
10%314425%6%6%9%45%
1440
16th to endNight
8%4245%3446%10%44%
1440
July1st to 15thNight
8%6%35%5%36%6%7%9%39%
1449
16th to endNight
6%223336%6%7%12%44%
1703
August1st to 15thNight
8%425%6%445%7%8%42%
1620
16th to endNight
10%5%25%4345%7%9%41%
1896
September1st to 15thNight
13%4244345%47%44%
1800
16th to endNight
13%6%16%5%34447%42%
1980
October1st to 15thNight
19%324334345%45%
2160
16th to endNight
13%413323445%52%
2304
November1st to 15thNight
15%5%33422335%51%
2395
16th to endNight
15%32332445%6%47%
2683
December1st to 15thNight
16%6%35%5%2445%5%39%
2730
16th to endNight
17%5%24424446%41%
2912

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
17%434424447%42%
1666
16th to endDay
15%7%34424345%43%
1872
February1st to 15thDay
15%7%25%5%2345%6%40%
1695
16th to endDay
14%7%25%4345%36%41%
1548
March1st to 15thDay
15%6%245%34346%44%
1968
16th to endDay
16%7%35%434445%40%
2126
April1st to 15thDay
13%5%25%5%23348%44%
2152
16th to endDay
17%5%14423345%44%
2160
May1st to 15thDay
16%6%24435%45%8%36%
2311
16th to endDay
15%5%24425%5%6%8%39%
2616
June1st to 15thDay
11%3244246%6%10%41%
2520
16th to endDay
8%424435%5%7%9%43%
2520
July1st to 15thDay
9%426%5%46%6%6%9%38%
2508
16th to endDay
6%3245%35%7%9%12%38%
2465
August1st to 15thDay
11%5%26%6%46%6%7%8%35%
2340
16th to endDay
11%3246%35%5%7%8%42%
2294
September1st to 15thDay
13%3244245%5%8%45%
2160
16th to endDay
15%5%25%42445%6%42%
1977
October1st to 15thDay
20%424312436%45%
1800
16th to endDay
14%414323346%50%
1920
November1st to 15thDay
14%5%14423346%47%
1790
16th to endDay
16%412323445%48%
1605
December1st to 15thDay
16%434424446%43%
1560
16th to endDay
18%6%2442445%7%38%
1664
January1st to 15thNight
17%5%24423447%43%
2599
16th to endNight
16%7%2442345%5%43%
2704
February1st to 15thNight
15%5%245%245%45%44%
2459
16th to endNight
14%7%35%414346%44%
1925
March1st to 15thNight
16%5%33324447%44%
1991
16th to endNight
15%6%25%5%3435%6%41%
2097
April1st to 15thNight
12%6%245%2446%6%43%
1796
16th to endNight
15%5%144245%5%7%44%
1800
May1st to 15thNight
19%5%25%4345%5%7%38%
1649
16th to endNight
13%5%144345%5%10%41%
1495
June1st to 15thNight
9%324425%7%6%10%44%
1440
16th to endNight
9%325%5%3446%9%44%
1440
July1st to 15thNight
8%6%25%5%26%5%7%9%39%
1449
16th to endNight
6%224436%6%8%12%44%
1703
August1st to 15thNight
8%425%6%45%5%6%8%43%
1620
16th to endNight
9%5%35%4345%6%9%41%
1896
September1st to 15thNight
12%415%4345%5%7%44%
1800
16th to endNight
13%6%26%5%34447%42%
1980
October1st to 15thNight
19%42433434445%
2160
16th to endNight
13%413323345%52%
2304
November1st to 15thNight
14%5%24423335%51%
2395
16th to endNight
15%31332445%7%47%
2683
December1st to 15thNight
16%6%35%5%24446%39%
2730
16th to endNight
17%6%24424446%41%
2912

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
42%411%22%15%4
1667
16th to endDay
43%211%23%14%3
1872
February1st to 15thDay
44%311%24%13%3
1697
16th to endDay
42%311%26%14%1
1548
March1st to 15thDay
41%410%24%15%3
1968
16th to endDay
45%411%18%17%2
2127
April1st to 15thDay
39%310%23%18%3
2152
16th to endDay
41%49%18%19%6%
2160
May1st to 15thDay
43%6%11%20%15%1
2311
16th to endDay
39%7%14%25%11%1
2620
June1st to 15thDay
35%8%13%27%13%1
2520
16th to endDay
34%7%15%23%16%2
2520
July1st to 15thDay
39%8%14%20%15%3
2360
16th to endDay
31%9%15%26%14%1
2310
August1st to 15thDay
42%7%11%22%15%
2327
16th to endDay
36%7%13%25%14%2
2294
September1st to 15thDay
35%7%12%20%20%3
2160
16th to endDay
40%5%7%25%19%2
1977
October1st to 15thDay
39%410%26%16%3
1800
16th to endDay
35%37%28%22%2
1920
November1st to 15thDay
38%411%23%17%5%
1790
16th to endDay
36%49%27%17%3
1605
December1st to 15thDay
40%5%12%24%13%3
1560
16th to endDay
44%410%26%12%1
1664
January1st to 15thNight
41%410%19%18%5%
2599
16th to endNight
41%39%25%17%1
2704
February1st to 15thNight
40%411%23%16%2
2468
16th to endNight
40%49%25%18%1
1925
March1st to 15thNight
38%412%27%13%2
1991
16th to endNight
43%49%22%16%3
2097
April1st to 15thNight
39%49%20%21%3
1796
16th to endNight
38%5%11%20%17%7%
1800
May1st to 15thNight
43%7%11%20%14%3
1650
16th to endNight
36%7%17%21%15%2
1497
June1st to 15thNight
33%8%12%27%15%1
1440
16th to endNight
34%7%15%22%18%2
1440
July1st to 15thNight
40%9%15%18%12%4
1369
16th to endNight
26%8%17%26%18%1
1595
August1st to 15thNight
36%7%13%23%17%1
1609
16th to endNight
36%7%13%24%16%2
1896
September1st to 15thNight
37%6%10%21%20%4
1800
16th to endNight
40%6%7%22%19%3
1980
October1st to 15thNight
41%39%23%19%3
2160
16th to endNight
32%48%29%21%3
2304
November1st to 15thNight
37%37%23%20%7%
2395
16th to endNight
35%410%24%20%4
2683
December1st to 15thNight
44%411%22%14%2
2730
16th to endNight
43%5%11%24%12%2
2912

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
25%13%38%18%21
116
16th to endDay
17%22%33%22%4
144
February1st to 15thDay
26%19%40%13%
130
16th to endDay
18%16%38%23%2
207
March1st to 15thDay
17%15%33%26%7%
270
16th to endDay
19%13%34%21%7%3
288
April1st to 15thDay
16%14%27%25%14%2
270
16th to endDay
22%425%23%18%5%
270
May1st to 15thDay
23%10%29%15%15%5%
288
16th to endDay
21%319%25%21%8%
331
June1st to 15thDay
14%324%23%22%11%
315
16th to endDay
10%121%37%19%9%
315
July1st to 15thDay
13%316%30%26%10%
305
16th to endDay
9%10%28%34%15%
326
August1st to 15thDay
15%12%23%34%14%
313
16th to endDay
10%9%30%27%21%
332
September1st to 15thDay
14%316%21%21%22%
315
16th to endDay
19%214%25%21%16%
314
October1st to 15thDay
25%414%21%26%8%
315
16th to endDay
14%7%30%25%17%4
336
November1st to 15thDay
20%7%22%29%16%4
298
16th to endDay
16%11%33%23%13%2
135
December1st to 15thDay
17%12%34%20%11%4
90
16th to endDay
30%8%35%22%3
96
January1st to 15thNight
21%14%37%22%4
780
16th to endNight
22%12%38%25%2
832
February1st to 15thNight
18%12%39%26%2
760
16th to endNight
20%18%36%22%1
631
March1st to 15thNight
21%12%37%25%3
720
16th to endNight
19%12%37%23%5%1
768
April1st to 15thNight
15%14%38%25%5%
718
16th to endNight
18%6%27%34%12%
720
May1st to 15thNight
22%5%26%31%12%
570
16th to endNight
14%318%39%22%1
375
June1st to 15thNight
9%123%38%25%1
360
16th to endNight
8%117%51%20%
360
July1st to 15thNight
9%119%42%25%2
349
16th to endNight
5%110%41%34%5%
564
August1st to 15thNight
11%110%44%28%3
539
16th to endNight
11%210%40%31%3
750
September1st to 15thNight
14%316%30%32%3
720
16th to endNight
15%215%32%31%2
717
October1st to 15thNight
21%418%29%22%3
720
16th to endNight
15%9%31%27%14%
768
November1st to 15thNight
16%9%30%29%13%1
760
16th to endNight
17%12%31%27%10%
780
December1st to 15thNight
20%10%32%27%8%
780
16th to endNight
21%10%38%27%2
832
Page generated at 2018-02-15 10:58:44. Version ac04

Copyright 2018 A. Danko


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