Wells Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wells Observing Site clear sky chart from 2005-11-05 to 2017-09-22.

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%
15387
23%
47029
17%
15344
60%
15344
30%
28371

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
33%
720
24%
2303
12%
716
47%
716
24%
1386
January16th to endNight
32%
768
25%
2304
13%
768
44%
768
24%
1475
February1st to 15thNight
36%
703
28%
2110
13%
700
50%
700
29%
1258
February16th to endNight
34%
631
26%
1893
12%
631
45%
631
27%
1188
March1st to 15thNight
38%
720
25%
2117
13%
720
48%
720
32%
1252
March16th to endNight
44%
768
26%
2112
15%
768
52%
768
34%
1250
April1st to 15thNight
49%
551
25%
1809
20%
551
57%
551
29%
1039
April16th to endNight
55%
540
29%
1800
24%
540
64%
540
39%
928
May1st to 15thNight
58%
539
24%
1654
17%
539
66%
539
36%
947
May16th to endNight
69%
561
22%
1682
18%
561
72%
561
36%
980
June1st to 15thNight
68%
540
15%
1620
12%
540
70%
540
29%
1030
June16th to endNight
76%
540
16%
1620
14%
540
76%
540
30%
1013
July1st to 15thNight
79%
510
11%
1530
11%
510
80%
510
28%
997
July16th to endNight
76%
564
10%
1658
12%
531
77%
531
27%
1063
August1st to 15thNight
76%
539
11%
1788
12%
536
77%
536
25%
1150
August16th to endNight
67%
573
15%
1910
18%
573
68%
573
21%
1301
September1st to 15thNight
66%
663
15%
1923
15%
663
66%
663
24%
1311
September16th to endNight
59%
685
24%
1892
16%
685
64%
685
29%
1215
October1st to 15thNight
59%
660
32%
1815
23%
660
67%
660
43%
1028
October16th to endNight
55%
704
35%
2037
27%
704
64%
704
38%
1137
November1st to 15thNight
51%
700
31%
2276
27%
700
62%
700
36%
1213
November16th to endNight
45%
720
30%
2340
23%
720
59%
720
35%
1261
December1st to 15thNight
44%
720
25%
2340
20%
720
54%
720
29%
1368
December16th to endNight
36%
768
22%
2496
17%
768
46%
768
23%
1581

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
10%5%25%5%35%5%6%7%40%
47836
Night
10%42442446%8%46%
47237
TransparencyDay
40%7%11%16%16%7%
47544
Night
33%7%12%17%18%9%
47034
SeeingDay
11%5%17%22%23%18%
5309
Night
11%7%20%30%24%5%
15391

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
12%6%245%2345%6%45%
1632
16th to endDay
17%6%35%313335%46%
1920
February1st to 15thDay
12%5%25%5%23346%48%
1750
16th to endDay
16%5%23223447%46%
1580
March1st to 15thDay
10%4244245%5%8%46%
1842
16th to endDay
12%425%5%34446%47%
2111
April1st to 15thDay
12%5%25%423446%46%
2147
16th to endDay
8%4245%35%446%50%
2160
May1st to 15thDay
7%4246%45%5%6%8%45%
2295
16th to endDay
7%5%15%6%37%6%6%8%40%
2431
June1st to 15thDay
8%6%27%7%47%6%7%9%31%
2340
16th to endDay
7%5%36%8%48%7%8%10%29%
2340
July1st to 15thDay
9%5%37%6%6%9%8%9%10%23%
2340
16th to endDay
8%5%36%8%5%8%8%9%11%25%
2394
August1st to 15thDay
10%6%26%8%5%8%8%9%10%21%
2160
16th to endDay
11%8%39%7%47%7%6%8%26%
2292
September1st to 15thDay
10%6%36%7%47%6%6%7%32%
2025
16th to endDay
11%5%26%5%35%5%6%7%40%
1881
October1st to 15thDay
9%5%1443445%6%50%
1815
16th to endDay
10%31332333459%
1831
November1st to 15thDay
10%31331335%8%55%
1582
16th to endDay
10%4245%13345%53%
1620
December1st to 15thDay
13%5%24424446%47%
1620
16th to endDay
19%8%35%433436%37%
1728
January1st to 15thNight
12%5%345%24346%47%
2303
16th to endNight
17%6%34314445%44%
2304
February1st to 15thNight
13%433223345%51%
2103
16th to endNight
14%6%245%24335%47%
1893
March1st to 15thNight
11%41442435%9%47%
2117
16th to endNight
8%42442435%6%53%
2112
April1st to 15thNight
10%41443446%7%48%
1809
16th to endNight
8%31342345%8%56%
1800
May1st to 15thNight
7%32442346%7%52%
1654
16th to endNight
5%3134345%6%11%49%
1682
June1st to 15thNight
6%325%5%26%6%9%13%38%
1620
16th to endNight
5%3234346%10%13%40%
1620
July1st to 15thNight
5%325%446%7%9%12%39%
1620
16th to endNight
43236%46%7%11%14%35%
1771
August1st to 15thNight
5%425%5%36%8%10%15%33%
1800
16th to endNight
9%5%26%5%47%7%7%10%33%
1910
September1st to 15thNight
9%5%25%6%47%5%8%9%36%
1923
16th to endNight
9%5%25%5%3446%8%43%
1892
October1st to 15thNight
8%413322448%56%
1815
16th to endNight
8%42342433458%
2037
November1st to 15thNight
8%414323346%56%
2276
16th to endNight
11%314323346%56%
2340
December1st to 15thNight
12%424325%45%7%48%
2340
16th to endNight
16%6%2442445%6%41%
2496

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
38%5%7%13%24%10%
1633
16th to endDay
41%25%15%23%11%
1920
February1st to 15thDay
37%37%16%24%11%
1752
16th to endDay
38%46%15%23%10%
1580
March1st to 15thDay
34%5%9%18%22%8%
1842
16th to endDay
37%410%18%19%10%
2112
April1st to 15thDay
38%47%16%21%11%
2147
16th to endDay
32%5%10%22%19%9%
2160
May1st to 15thDay
36%6%10%16%20%9%
2295
16th to endDay
38%8%14%19%15%3
2435
June1st to 15thDay
45%10%13%21%8%1
2340
16th to endDay
45%11%16%16%9%1
2340
July1st to 15thDay
48%15%19%12%3
2201
16th to endDay
46%13%21%13%4
2245
August1st to 15thDay
49%13%18%13%4
2148
16th to endDay
53%9%15%13%6%1
2292
September1st to 15thDay
47%10%14%12%11%4
2025
16th to endDay
40%7%11%18%15%7%
1881
October1st to 15thDay
32%49%18%21%13%
1815
16th to endDay
28%3413%28%20%
1831
November1st to 15thDay
27%47%19%26%14%
1582
16th to endDay
32%36%18%21%16%
1620
December1st to 15thDay
37%5%8%18%22%7%
1620
16th to endDay
48%37%18%14%7%
1728
January1st to 15thNight
37%47%13%25%11%
2303
16th to endNight
42%36%12%24%10%
2304
February1st to 15thNight
35%36%17%23%14%
2112
16th to endNight
40%35%13%20%15%
1893
March1st to 15thNight
33%410%19%22%8%
2117
16th to endNight
31%49%20%21%11%
2112
April1st to 15thNight
33%5%8%16%23%12%
1809
16th to endNight
26%411%27%20%10%
1800
May1st to 15thNight
30%5%14%16%21%11%
1655
16th to endNight
27%9%17%22%15%7%
1684
June1st to 15thNight
31%12%20%22%10%1
1620
16th to endNight
29%14%23%21%9%1
1620
July1st to 15thNight
30%15%29%20%2
1530
16th to endNight
31%15%30%17%5%
1658
August1st to 15thNight
33%14%31%16%21
1788
16th to endNight
41%12%20%14%9%2
1910
September1st to 15thNight
40%11%17%16%11%3
1923
16th to endNight
36%7%14%16%18%6%
1892
October1st to 15thNight
27%410%20%22%15%
1815
16th to endNight
29%25%13%27%21%
2037
November1st to 15thNight
28%3418%27%17%
2276
16th to endNight
29%37%16%22%19%
2340
December1st to 15thNight
34%5%10%17%24%7%
2340
16th to endNight
42%48%21%15%7%
2496

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
15%13%40%17%10%3
90
16th to endDay
16%28%35%12%7%
96
February1st to 15thDay
432%34%17%11%
90
16th to endDay
17%28%27%23%3
81
March1st to 15thDay
10%21%43%15%7%
132
16th to endDay
13%11%24%27%21%2
288
April1st to 15thDay
13%14%24%22%21%3
270
16th to endDay
9%5%22%28%24%9%
270
May1st to 15thDay
8%7%24%24%23%11%
288
16th to endDay
11%114%28%19%24%
331
June1st to 15thDay
14%10%22%25%26%
315
16th to endDay
11%5%24%23%33%
315
July1st to 15thDay
5%316%33%40%
305
16th to endDay
7%419%31%36%
326
August1st to 15thDay
10%6%18%30%33%
313
16th to endDay
9%17%20%30%30%
332
September1st to 15thDay
16%29%21%29%20%
315
16th to endDay
14%110%27%30%16%
278
October1st to 15thDay
9%219%31%29%7%
255
16th to endDay
10%5%27%22%25%9%
253
November1st to 15thDay
24%227%27%14%3
90
16th to endDay
10%10%44%21%8%5%
90
December1st to 15thDay
20%16%33%22%7%
90
16th to endDay
31%11%19%22%12%2
96
January1st to 15thNight
15%16%29%29%8%1
720
16th to endNight
19%15%28%28%7%
768
February1st to 15thNight
15%12%30%31%9%
704
16th to endNight
16%14%31%31%5%
631
March1st to 15thNight
13%12%32%32%9%
720
16th to endNight
11%11%27%34%14%
768
April1st to 15thNight
13%8%22%37%16%
551
16th to endNight
10%5%23%35%23%1
540
May1st to 15thNight
10%322%35%25%3
540
16th to endNight
6%211%35%38%4
563
June1st to 15thNight
7%19%32%40%9%
540
16th to endNight
7%6%27%43%15%
540
July1st to 15thNight
6%423%45%19%
510
16th to endNight
5%424%46%19%
564
August1st to 15thNight
6%216%49%24%
539
16th to endNight
11%16%18%45%17%
573
September1st to 15thNight
11%18%25%41%11%
663
16th to endNight
12%214%30%32%7%
685
October1st to 15thNight
10%221%33%28%3
660
16th to endNight
9%8%21%29%28%2
704
November1st to 15thNight
9%7%26%32%20%3
700
16th to endNight
11%9%29%30%16%1
720
December1st to 15thNight
15%8%26%33%14%2
720
16th to endNight
19%10%27%28%13%
768
Page generated at 2017-09-23 06:43:39. Version ac04

Copyright 2017 A. Danko


Wells Observing Site Clear Sky Chart | Charts Home