Blue Ridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blue Ridge clear sky chart from 2005-11-05 to

2017-09-12
.

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
66%
15282
28%
46851
24%
15243
72%
15243
43%
24362

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
55%
719
19%
2410
17%
716
60%
716
29%
1419
January16th to endNight
55%
768
26%
2496
23%
768
62%
768
28%
1508
February1st to 15thNight
54%
697
23%
2288
21%
697
61%
697
25%
1421
February16th to endNight
55%
632
25%
1906
20%
632
63%
632
32%
1151
March1st to 15thNight
55%
720
18%
2013
16%
720
58%
720
29%
1300
March16th to endNight
50%
768
22%
2086
14%
768
56%
768
34%
1296
April1st to 15thNight
53%
719
24%
1799
11%
719
60%
719
37%
1132
April16th to endNight
61%
720
27%
1800
13%
720
65%
720
51%
990
May1st to 15thNight
71%
590
29%
1670
19%
590
75%
590
59%
780
May16th to endNight
73%
374
29%
1496
29%
374
80%
374
54%
555
June1st to 15thNight
74%
360
29%
1440
32%
360
82%
360
52%
558
June16th to endNight
84%
360
36%
1440
47%
360
88%
360
69%
471
July1st to 15thNight
90%
349
34%
1369
42%
349
95%
349
75%
425
July16th to endNight
90%
564
38%
1593
34%
531
91%
531
79%
607
August1st to 15thNight
84%
544
37%
1617
29%
541
86%
541
73%
646
August16th to endNight
90%
764
42%
1910
27%
764
91%
764
82%
855
September1st to 15thNight
88%
706
42%
1765
28%
706
91%
706
80%
788
September16th to endNight
85%
656
41%
1801
36%
656
88%
656
69%
808
October1st to 15thNight
72%
660
32%
1980
31%
660
79%
660
52%
935
October16th to endNight
70%
704
34%
2112
33%
704
76%
704
49%
1055
November1st to 15thNight
67%
700
29%
2201
26%
700
74%
700
42%
1136
November16th to endNight
61%
720
25%
2451
25%
720
66%
720
33%
1332
December1st to 15thNight
51%
720
20%
2520
16%
720
59%
720
23%
1550
December16th to endNight
45%
768
22%
2688
17%
768
54%
768
23%
1644

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
7%313313346%62%
47808
Night
8%313313347%60%
47036
TransparencyDay
23%49%20%24%17%
47493
Night
24%410%20%23%17%
46852
SeeingDay
8%6%20%31%24%7%
5945
Night
9%315%35%30%5%
15292

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
16%5%345%24346%44%
1525
16th to endDay
15%5%24434445%44%
1728
February1st to 15thDay
16%5%25%33435%5%43%
1576
16th to endDay
16%5%25%5%3445%6%40%
1566
March1st to 15thDay
14%6%25%6%35%46%8%38%
1945
16th to endDay
12%5%24425%5%6%7%43%
2137
April1st to 15thDay
13%5%344246%5%8%42%
2149
16th to endDay
5%312323447%62%
2160
May1st to 15thDay
321121235%7%68%
2275
16th to endDay
411322335%7%64%
2615
June1st to 15thDay
3212213346%67%
2520
16th to endDay
1111235%81%
2520
July1st to 15thDay
112484%
2508
16th to endDay
1125%85%
2468
August1st to 15thDay
1111222481%
2334
16th to endDay
111125%84%
2292
September1st to 15thDay
1111225%81%
2114
16th to endDay
211211235%76%
1827
October1st to 15thDay
4312213236%67%
1650
16th to endDay
7%423322245%61%
1760
November1st to 15thDay
7%42332446%7%54%
1657
16th to endDay
12%5%24433335%50%
1506
December1st to 15thDay
17%7%35%41345%443%
1440
16th to endDay
18%7%24423347%41%
1536
January1st to 15thNight
13%5%24323448%46%
2410
16th to endNight
16%5%23323336%48%
2496
February1st to 15thNight
14%425%4245%46%43%
2276
16th to endNight
14%3244225%5%6%47%
1906
March1st to 15thNight
13%4245%3445%6%44%
2013
16th to endNight
12%5%14323346%50%
2086
April1st to 15thNight
9%3234345%47%51%
1799
16th to endNight
6%212222337%64%
1800
May1st to 15thNight
212212248%70%
1670
16th to endNight
211111235%8%69%
1496
June1st to 15thNight
2112212337%71%
1440
16th to endNight
112235%81%
1440
July1st to 15thNight
11112485%
1449
16th to endNight
11139%78%
1701
August1st to 15thNight
11111248%75%
1626
16th to endNight
111249%76%
1910
September1st to 15thNight
111237%80%
1765
16th to endNight
11112336%76%
1801
October1st to 15thNight
421231335%6%66%
1980
16th to endNight
5%213323347%62%
2112
November1st to 15thNight
6%22332345%8%57%
2201
16th to endNight
9%413324346%55%
2451
December1st to 15thNight
17%424423347%43%
2520
16th to endNight
17%6%24323346%45%
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%15%18%6%
1525
16th to endDay
41%5%8%13%20%10%
1728
February1st to 15thDay
41%6%8%20%18%4
1576
16th to endDay
41%412%25%11%4
1566
March1st to 15thDay
42%5%12%19%14%4
1945
16th to endDay
37%8%14%17%18%3
2137
April1st to 15thDay
37%7%13%18%18%3
2149
16th to endDay
21%5%14%25%24%8%
2160
May1st to 15thDay
14%411%27%30%11%
2275
16th to endDay
19%5%15%28%22%9%
2619
June1st to 15thDay
17%5%13%23%24%15%
2520
16th to endDay
6%16%18%36%29%
2520
July1st to 15thDay
6%1412%26%48%
2360
16th to endDay
5%16%13%23%49%
2313
August1st to 15thDay
7%16%16%31%36%
2318
16th to endDay
6%6%17%36%32%
2292
September1st to 15thDay
8%16%13%35%34%
2114
16th to endDay
12%25%22%34%21%
1827
October1st to 15thDay
18%5%8%21%28%17%
1650
16th to endDay
26%38%23%26%11%
1760
November1st to 15thDay
26%5%14%29%16%8%
1657
16th to endDay
37%49%20%22%5%
1506
December1st to 15thDay
43%48%19%18%3
1440
16th to endDay
43%6%9%18%16%6%
1536
January1st to 15thNight
35%5%13%20%16%8%
2410
16th to endNight
37%5%8%16%18%14%
2496
February1st to 15thNight
40%410%19%17%8%
2288
16th to endNight
35%5%12%25%18%3
1906
March1st to 15thNight
38%5%13%18%16%6%
2013
16th to endNight
35%411%21%19%7%
2086
April1st to 15thNight
31%6%14%22%18%7%
1799
16th to endNight
20%413%25%25%10%
1800
May1st to 15thNight
13%412%20%33%15%
1671
16th to endNight
12%317%32%22%12%
1496
June1st to 15thNight
13%410%24%27%18%
1440
16th to endNight
7%35%16%32%35%
1440
July1st to 15thNight
6%1312%24%51%
1369
16th to endNight
6%15%18%19%48%
1593
August1st to 15thNight
8%16%17%27%38%
1617
16th to endNight
6%16%18%29%37%
1910
September1st to 15thNight
7%16%12%32%40%
1765
16th to endNight
9%37%19%33%26%
1801
October1st to 15thNight
17%310%20%27%21%
1980
16th to endNight
21%310%21%25%17%
2112
November1st to 15thNight
24%413%28%18%9%
2201
16th to endNight
30%49%21%24%9%
2451
December1st to 15thNight
40%410%17%19%6%
2520
16th to endNight
40%5%10%15%21%7%
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
26%5%20%28%15%4
153
16th to endDay
16%8%19%22%26%6%
256
February1st to 15thDay
21%10%17%22%22%5%
236
16th to endDay
21%7%19%25%18%7%
236
March1st to 15thDay
19%10%23%22%15%8%
270
16th to endDay
14%13%25%24%17%4
288
April1st to 15thDay
15%13%29%21%15%4
269
16th to endDay
7%16%27%23%21%3
270
May1st to 15thDay
49%30%32%20%2
288
16th to endDay
37%23%33%24%6%
330
June1st to 15thDay
6%7%26%36%20%2
315
16th to endDay
320%36%34%4
315
July1st to 15thDay
12%46%32%7%
305
16th to endDay
114%42%29%11%
327
August1st to 15thDay
1213%41%33%8%
315
16th to endDay
12%37%34%13%
332
September1st to 15thDay
2111%38%33%13%
300
16th to endDay
35%16%29%24%20%
255
October1st to 15thDay
7%8%17%31%21%14%
255
16th to endDay
12%420%31%20%10%
272
November1st to 15thDay
8%418%22%34%11%
163
16th to endDay
16%8%21%22%30%
71
December1st to 15thDay
26%16%20%21%15%
60
16th to endDay
12%332%21%26%3
64
January1st to 15thNight
15%416%32%25%6%
720
16th to endNight
16%317%30%24%6%
768
February1st to 15thNight
15%416%33%25%4
704
16th to endNight
16%417%35%21%5%
632
March1st to 15thNight
15%417%30%28%3
720
16th to endNight
15%5%21%33%22%1
768
April1st to 15thNight
10%5%24%35%21%2
719
16th to endNight
7%5%21%35%25%4
720
May1st to 15thNight
3219%40%29%3
591
16th to endNight
4118%41%32%1
375
June1st to 15thNight
2118%47%28%1
360
16th to endNight
111%51%35%
360
July1st to 15thNight
16%50%40%1
349
16th to endNight
16%43%44%5%
564
August1st to 15thNight
19%38%44%4
544
16th to endNight
6%41%45%5%
764
September1st to 15thNight
17%35%48%6%
706
16th to endNight
219%35%41%9%
656
October1st to 15thNight
5%312%37%32%8%
660
16th to endNight
6%215%31%32%10%
704
November1st to 15thNight
7%316%31%35%6%
700
16th to endNight
11%5%15%34%25%8%
720
December1st to 15thNight
18%5%16%31%21%6%
720
16th to endNight
20%5%20%29%22%1
768
Page generated at 2017-09-13 04:39:26. Version ac04

Copyright 2017 A. Danko


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