The Shoals
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Shoals clear sky chart from 2005-11-05 to 2018-04-23.

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
53%
16261
24%
49379
19%
16217
59%
16217
31%
29756

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
31%
975
23%
2716
11%
970
42%
970
27%
1765
January16th to endNight
32%
857
26%
2521
14%
857
43%
857
26%
1642
February1st to 15thNight
31%
764
20%
2292
10%
761
40%
761
25%
1496
February16th to endNight
31%
683
22%
2049
12%
683
39%
683
23%
1351
March1st to 15thNight
33%
780
20%
2340
12%
780
40%
780
26%
1496
March16th to endNight
43%
702
22%
2187
15%
702
50%
702
30%
1327
April1st to 15thNight
46%
584
26%
1947
19%
584
57%
584
33%
1097
April16th to endNight
52%
558
25%
1858
20%
558
62%
558
34%
1029
May1st to 15thNight
57%
540
22%
1662
17%
540
62%
540
30%
1008
May16th to endNight
68%
561
21%
1682
19%
561
70%
561
35%
973
June1st to 15thNight
76%
540
21%
1554
18%
540
77%
540
40%
899
June16th to endNight
79%
540
25%
1440
20%
540
80%
540
44%
836
July1st to 15thNight
77%
510
17%
1360
16%
510
78%
510
37%
854
July16th to endNight
80%
564
20%
1607
21%
531
82%
531
40%
901
August1st to 15thNight
82%
539
20%
1788
24%
536
82%
536
36%
980
August16th to endNight
75%
573
22%
1910
27%
573
75%
573
29%
1143
September1st to 15thNight
70%
582
22%
1842
22%
582
71%
582
32%
1080
September16th to endNight
68%
717
31%
1980
26%
717
70%
717
38%
1170
October1st to 15thNight
66%
720
34%
1980
29%
720
68%
720
42%
1131
October16th to endNight
58%
768
35%
2367
30%
768
65%
768
37%
1321
November1st to 15thNight
55%
760
30%
2471
28%
760
62%
760
35%
1380
November16th to endNight
46%
780
28%
2535
23%
780
55%
780
31%
1450
December1st to 15thNight
41%
780
24%
2535
17%
780
52%
780
27%
1567
December16th to endNight
35%
884
20%
2756
14%
884
42%
884
22%
1860

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
11%5%25%5%345%5%7%42%
50121
Night
11%5%2442445%7%47%
49572
TransparencyDay
39%5%11%21%17%4
49816
Night
35%410%22%20%5%
49381
SeeingDay
13%316%23%25%17%
6218
Night
14%421%32%23%4
16263

By Month

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
19%7%36%422335%42%
1552
16th to endDay
18%5%2442335%5%44%
2047
February1st to 15thDay
18%8%36%433245%40%
1900
16th to endDay
17%6%35%5%23445%40%
1710
March1st to 15thDay
15%7%26%5%34446%39%
1950
16th to endDay
14%6%25%5%35%45%7%36%
2397
April1st to 15thDay
12%5%344235%5%7%44%
2331
16th to endDay
11%435%43445%7%45%
2216
May1st to 15thDay
13%436%5%35%5%47%41%
2289
16th to endDay
9%5%26%6%35%46%8%40%
2431
June1st to 15thDay
5%4246%36%6%7%8%43%
2401
16th to endDay
43246%46%7%7%11%41%
2520
July1st to 15thDay
8%5%25%7%48%6%8%10%33%
2520
16th to endDay
5%435%6%46%6%8%11%35%
2445
August1st to 15thDay
5%326%6%47%6%9%10%38%
2160
16th to endDay
9%6%26%6%46%5%6%10%34%
2292
September1st to 15thDay
11%6%25%6%45%5%6%7%39%
2106
16th to endDay
9%5%15%433446%50%
1980
October1st to 15thDay
10%5%14424446%50%
1980
16th to endDay
11%413322345%57%
1854
November1st to 15thDay
11%42442334453%
1717
16th to endDay
14%4144325%35%49%
1755
December1st to 15thDay
19%8%26%5%23345%38%
1755
16th to endDay
19%10%36%5%22335%37%
1813
January1st to 15thNight
16%7%25%413445%44%
2716
16th to endNight
15%7%35%5%23445%43%
2521
February1st to 15thNight
17%7%35%5%23335%42%
2283
16th to endNight
17%6%35%5%24345%40%
2049
March1st to 15thNight
15%5%35%43445%6%42%
2340
16th to endNight
13%4235%245%46%46%
2187
April1st to 15thNight
11%32432345%8%48%
1947
16th to endNight
11%32332345%7%51%
1858
May1st to 15thNight
10%425%42445%8%44%
1661
16th to endNight
5%424435%5%5%9%48%
1682
June1st to 15thNight
43136%35%46%11%49%
1554
16th to endNight
22135%26%5%7%10%51%
1440
July1st to 15thNight
5%3345%35%6%8%10%42%
1440
16th to endNight
3324325%5%8%15%44%
1718
August1st to 15thNight
32145%35%7%8%11%46%
1800
16th to endNight
6%425%6%35%5%7%9%42%
1910
September1st to 15thNight
11%4134345%5%8%47%
1842
16th to endNight
8%423424346%53%
1980
October1st to 15thNight
9%414323345%57%
1980
16th to endNight
13%6%1321222457%
2367
November1st to 15thNight
11%42441335%5%53%
2471
16th to endNight
14%5%2331333452%
2535
December1st to 15thNight
16%6%3432345%6%44%
2535
16th to endNight
18%8%25%5%235%45%38%
2756

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
46%26%18%21%3
1553
16th to endDay
41%37%22%22%3
2047
February1st to 15thDay
47%27%21%17%3
1902
16th to endDay
45%29%20%17%4
1710
March1st to 15thDay
46%47%18%16%7%
1950
16th to endDay
45%413%20%14%
2398
April1st to 15thDay
37%310%23%18%6%
2331
16th to endDay
36%49%25%20%3
2216
May1st to 15thDay
42%410%22%16%4
2289
16th to endDay
40%414%25%13%2
2435
June1st to 15thDay
33%7%14%25%16%1
2401
16th to endDay
31%7%14%22%19%3
2520
July1st to 15thDay
40%7%19%19%9%3
2371
16th to endDay
37%7%18%24%10%
2293
August1st to 15thDay
36%8%16%20%14%2
2148
16th to endDay
44%6%12%23%10%2
2292
September1st to 15thDay
42%6%14%18%13%4
2106
16th to endDay
34%5%9%24%21%5%
1980
October1st to 15thDay
33%47%23%24%6%
1980
16th to endDay
29%3419%33%9%
1854
November1st to 15thDay
34%36%18%29%8%
1717
16th to endDay
36%36%21%25%5%
1755
December1st to 15thDay
47%37%20%15%5%
1755
16th to endDay
49%210%20%14%2
1813
January1st to 15thNight
42%37%21%21%3
2716
16th to endNight
43%35%21%19%5%
2521
February1st to 15thNight
45%28%20%18%4
2292
16th to endNight
45%36%20%18%4
2049
March1st to 15thNight
41%48%19%17%8%
2340
16th to endNight
37%411%25%18%2
2187
April1st to 15thNight
32%411%24%20%6%
1947
16th to endNight
32%312%22%24%5%
1858
May1st to 15thNight
36%5%12%21%20%3
1662
16th to endNight
31%5%15%26%15%4
1684
June1st to 15thNight
27%6%17%25%20%2
1554
16th to endNight
24%7%14%28%21%3
1440
July1st to 15thNight
31%7%19%25%10%4
1360
16th to endNight
25%7%22%27%15%1
1607
August1st to 15thNight
26%8%20%25%16%2
1788
16th to endNight
35%7%16%23%12%4
1910
September1st to 15thNight
33%5%16%20%17%5%
1842
16th to endNight
30%5%8%23%22%8%
1980
October1st to 15thNight
29%36%24%25%10%
1980
16th to endNight
32%2318%31%11%
2367
November1st to 15thNight
32%26%21%23%13%
2471
16th to endNight
35%26%19%27%8%
2535
December1st to 15thNight
39%49%22%19%4
2535
16th to endNight
47%310%18%16%3
2756

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
27%7%36%20%7%1
135
16th to endDay
22%8%43%15%6%4
144
February1st to 15thDay
22%5%45%19%5%
135
16th to endDay
26%8%35%21%5%1
120
March1st to 15thDay
18%11%45%19%31
135
16th to endDay
20%7%28%27%15%
322
April1st to 15thDay
16%9%25%30%15%2
330
16th to endDay
15%418%31%22%7%
289
May1st to 15thDay
14%5%16%29%21%11%
288
16th to endDay
13%312%25%22%22%
331
June1st to 15thDay
8%7%17%32%32%
376
16th to endDay
5%19%24%34%23%
495
July1st to 15thDay
8%15%27%30%26%
475
16th to endDay
5%314%29%45%
358
August1st to 15thDay
9%415%37%31%
313
16th to endDay
10%1319%37%26%
332
September1st to 15thDay
14%1416%36%26%
315
16th to endDay
11%8%19%39%20%
314
October1st to 15thDay
13%112%30%29%11%
315
16th to endDay
13%423%22%27%8%
147
November1st to 15thDay
20%324%30%16%5%
135
16th to endDay
13%328%26%20%6%
135
December1st to 15thDay
22%436%24%11%
135
16th to endDay
25%9%35%25%4
144
January1st to 15thNight
20%8%34%27%7%
975
16th to endNight
18%5%37%32%5%
857
February1st to 15thNight
21%9%33%30%5%
764
16th to endNight
20%9%35%31%3
683
March1st to 15thNight
18%8%34%33%5%
780
16th to endNight
15%5%29%31%16%
702
April1st to 15thNight
12%5%31%35%13%1
584
16th to endNight
12%325%39%16%2
558
May1st to 15thNight
10%319%38%25%2
540
16th to endNight
7%19%36%36%7%
563
June1st to 15thNight
46%37%43%7%
540
16th to endNight
315%29%48%12%
540
July1st to 15thNight
6%1427%47%13%
510
16th to endNight
4422%47%20%
564
August1st to 15thNight
4222%54%15%
539
16th to endNight
9%1123%52%10%
573
September1st to 15thNight
14%17%25%43%8%
582
16th to endNight
10%28%32%41%4
717
October1st to 15thNight
11%213%34%32%5%
720
16th to endNight
16%317%33%26%2
768
November1st to 15thNight
11%422%37%20%3
760
16th to endNight
16%7%25%33%16%1
780
December1st to 15thNight
19%6%29%34%10%
780
16th to endNight
23%7%28%34%6%
884
Page generated at 2018-04-24 09:03:01. Version ac04

Copyright 2018 A. Danko


The Shoals Clear Sky Chart |Charts Home