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 2017-08-12.

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%
15123
21%
46540
12%
15086
49%
15086
26%
29160

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%
717
22%
2398
9%
716
40%
716
20%
1518
January16th to endNight
21%
768
23%
2496
8%
768
39%
768
22%
1565
February1st to 15thNight
23%
701
20%
2287
6%
701
41%
701
22%
1399
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
45%
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
60%
360
18%
1440
20%
360
65%
360
26%
817
July1st to 15thNight
57%
349
13%
1369
14%
349
61%
349
20%
849
July16th to endNight
72%
564
17%
1595
13%
531
77%
531
38%
919
August1st to 15thNight
65%
527
18%
1575
14%
524
66%
524
31%
997
August16th to endNight
64%
687
18%
1737
11%
687
65%
687
33%
1154
September1st to 15thNight
58%
660
26%
1650
15%
660
62%
660
34%
1092
September16th to endNight
52%
657
21%
1815
17%
657
55%
657
27%
1225
October1st to 15thNight
47%
660
24%
1980
21%
660
54%
660
28%
1249
October16th to endNight
38%
704
29%
2112
17%
704
55%
704
33%
1234
November1st to 15thNight
38%
700
26%
2206
15%
700
52%
700
29%
1296
November16th to endNight
33%
720
22%
2476
12%
720
47%
720
23%
1465
December1st to 15thNight
29%
720
19%
2520
8%
720
42%
720
19%
1593
December16th to endNight
24%
768
21%
2688
8%
768
41%
768
19%
1697

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%
47423
Night
14%5%2442445%7%43%
46723
Cloud CoverDay
14%5%244345%5%7%42%
47433
Night
14%5%2442445%7%43%
46727
TransparencyDay
39%5%11%23%16%2
47125
Night
39%5%11%23%17%3
46540
SeeingDay
17%6%22%24%18%8%
5522
Night
17%8%28%30%14%1
15130

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%424424446%42%
1537
16th to endDay
16%6%345%24345%42%
1728
February1st to 15thDay
14%7%25%5%3346%6%40%
1575
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
10%5%25%6%45%7%7%8%35%
2288
16th to endDay
12%4245%345%6%8%42%
2102
September1st to 15thDay
13%32442446%8%45%
1980
16th to endDay
16%6%26%42445%6%41%
1812
October1st to 15thDay
20%423313346%46%
1650
16th to endDay
15%5%14314346%48%
1760
November1st to 15thDay
15%5%14323446%48%
1649
16th to endDay
17%42332445%6%45%
1482
December1st to 15thDay
16%5%344345%46%43%
1440
16th to endDay
19%7%2442435%7%38%
1536
January1st to 15thNight
18%5%24424347%42%
2398
16th to endNight
16%7%24424446%42%
2496
February1st to 15thNight
14%5%2442445%5%45%
2285
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%9%43%
1586
16th to endNight
10%5%35%4345%7%8%41%
1737
September1st to 15thNight
12%4244345%5%7%45%
1650
16th to endNight
14%6%26%5%34446%40%
1815
October1st to 15thNight
19%42433424446%
1980
16th to endNight
14%413323446%52%
2112
November1st to 15thNight
14%5%3342233452%
2206
16th to endNight
16%32332445%6%45%
2476
December1st to 15thNight
16%6%35%5%2445%6%39%
2520
16th to endNight
18%5%24424446%41%
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
17%434324447%42%
1537
16th to endDay
16%7%345%24345%42%
1728
February1st to 15thDay
14%7%25%5%235%5%6%40%
1575
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
10%5%26%6%36%6%7%8%35%
2288
16th to endDay
12%4246%345%6%8%42%
2102
September1st to 15thDay
12%3234245%5%8%45%
1980
16th to endDay
16%5%25%42445%6%40%
1812
October1st to 15thDay
20%424312336%46%
1650
16th to endDay
14%5%25%323346%48%
1760
November1st to 15thDay
14%5%13424346%48%
1649
16th to endDay
17%4233235%5%5%46%
1482
December1st to 15thDay
16%433425%447%43%
1440
16th to endDay
19%6%2442435%7%38%
1536
January1st to 15thNight
17%5%24423447%42%
2398
16th to endNight
16%7%2442345%6%42%
2496
February1st to 15thNight
14%5%244245%45%45%
2278
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%
1586
16th to endNight
10%5%35%4345%6%9%41%
1737
September1st to 15thNight
12%415%4345%5%8%44%
1650
16th to endNight
14%6%26%6%24446%40%
1815
October1st to 15thNight
19%42433434446%
1980
16th to endNight
14%41331345%6%52%
2112
November1st to 15thNight
14%5%24322335%52%
2206
16th to endNight
16%31332445%7%45%
2476
December1st to 15thNight
16%6%25%5%24446%39%
2520
16th to endNight
17%6%244245%46%40%
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
42%412%22%14%3
1538
16th to endDay
43%311%24%14%3
1728
February1st to 15thDay
43%311%24%14%2
1577
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
41%8%11%22%15%1
2275
16th to endDay
36%7%12%25%14%2
2102
September1st to 15thDay
34%7%13%19%21%3
1980
16th to endDay
42%48%23%19%1
1812
October1st to 15thDay
39%49%26%16%3
1650
16th to endDay
36%38%27%21%2
1760
November1st to 15thDay
36%410%23%18%5%
1649
16th to endDay
38%49%26%16%3
1482
December1st to 15thDay
40%5%13%24%13%4
1440
16th to endDay
45%410%25%12%1
1536
January1st to 15thNight
42%5%10%19%18%4
2398
16th to endNight
41%310%25%16%1
2496
February1st to 15thNight
39%411%24%17%3
2287
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%18%1
1575
16th to endNight
36%7%12%24%16%2
1737
September1st to 15thNight
36%6%11%20%21%4
1650
16th to endNight
42%6%7%20%18%3
1815
October1st to 15thNight
41%38%23%19%3
1980
16th to endNight
32%48%29%21%3
2112
November1st to 15thNight
36%27%23%21%7%
2206
16th to endNight
37%410%23%19%4
2476
December1st to 15thNight
44%411%22%15%2
2520
16th to endNight
43%5%11%24%13%2
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
31%15%35%15%11
77
16th to endDay
18%21%34%21%3
96
February1st to 15thDay
24%21%40%13%1
90
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
13%112%23%35%14%
297
16th to endDay
11%8%27%27%24%
268
September1st to 15thDay
12%313%19%24%26%
255
16th to endDay
24%114%24%19%15%
254
October1st to 15thDay
25%416%22%24%7%
255
16th to endDay
15%8%29%27%16%3
272
November1st to 15thDay
19%7%23%28%15%5%
247
16th to endDay
20%9%30%22%14%1
102
December1st to 15thDay
20%13%36%15%10%5%
60
16th to endDay
37%7%28%25%1
64
January1st to 15thNight
21%14%36%22%4
720
16th to endNight
22%12%39%23%2
768
February1st to 15thNight
18%12%39%26%2
704
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%29%3
527
16th to endNight
11%210%40%30%4
687
September1st to 15thNight
12%316%29%34%3
660
16th to endNight
17%216%32%30%1
657
October1st to 15thNight
21%5%19%29%21%2
660
16th to endNight
15%10%31%28%13%
704
November1st to 15thNight
15%10%30%28%13%1
700
16th to endNight
17%13%30%26%10%
720
December1st to 15thNight
20%10%33%26%8%
720
16th to endNight
22%10%38%25%2
768
Page generated at 2017-08-13 14:16:45. Version ac04

Copyright 2017 A. Danko


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