Clayton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Clayton clear sky chart from 2005-11-06 to 2024-01-16.

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
46%
24622
21%
74904
14%
24573
54%
24573
27%
46841

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 10thNight
28%
757
23%
2459
11%
757
43%
757
25%
1489
January11th to 20thNight
31%
744
23%
2417
13%
744
45%
744
22%
1549
January21st to endNight
30%
792
28%
2574
14%
792
49%
792
29%
1513
February1st to 10thNight
28%
720
20%
2340
11%
720
41%
720
25%
1465
February11th to 20thNight
20%
700
19%
2233
8%
699
35%
699
21%
1434
February21st to endNight
28%
592
29%
1664
14%
592
44%
592
28%
1053
March1st to 10thNight
34%
720
26%
1980
15%
720
45%
720
32%
1203
March11th to 20thNight
30%
720
20%
1980
10%
720
39%
720
26%
1329
March21st to endNight
34%
792
21%
2178
10%
792
44%
792
28%
1426
April1st to 10thNight
33%
720
24%
1849
9%
720
43%
720
32%
1180
April11th to 20thNight
40%
711
25%
1775
10%
711
48%
711
35%
1127
April21st to endNight
43%
720
23%
1800
10%
720
49%
720
36%
1157
May1st to 10thNight
42%
622
18%
1702
8%
622
46%
622
33%
1066
May11th to 20thNight
49%
531
17%
1592
11%
531
52%
531
26%
1041
May21st to endNight
63%
582
16%
1744
13%
582
65%
582
29%
1120
June1st to 10thNight
62%
540
15%
1620
13%
540
63%
540
27%
1034
June11th to 20thNight
58%
540
14%
1620
11%
540
61%
540
27%
1051
June21st to endNight
66%
540
15%
1620
13%
540
68%
540
25%
1085
July1st to 10thNight
69%
525
13%
1575
11%
525
69%
525
26%
1051
July11th to 20thNight
73%
522
12%
1566
10%
522
73%
522
29%
1014
July21st to endNight
66%
591
16%
1672
12%
558
67%
558
26%
1090
August1st to 10thNight
66%
537
12%
1600
11%
534
66%
534
25%
1080
August11th to 20thNight
62%
613
15%
1677
11%
613
64%
613
25%
1185
August21st to endNight
64%
792
15%
1980
10%
792
65%
792
30%
1359
September1st to 10thNight
68%
720
23%
1800
17%
720
69%
720
32%
1207
September11th to 20thNight
61%
720
24%
1880
19%
720
64%
720
31%
1245
September21st to endNight
49%
720
17%
2038
13%
720
53%
720
22%
1426
October1st to 10thNight
56%
720
24%
2160
22%
720
62%
720
33%
1301
October11th to 20thNight
51%
720
29%
2160
25%
720
61%
720
33%
1273
October21st to endNight
49%
792
31%
2376
23%
792
62%
792
38%
1327
November1st to 10thNight
48%
740
27%
2221
20%
740
57%
740
33%
1320
November11th to 20thNight
45%
760
28%
2280
18%
760
56%
760
31%
1355
November21st to endNight
45%
760
26%
2596
19%
760
57%
760
31%
1447
December1st to 10thNight
34%
760
20%
2660
12%
760
46%
760
20%
1694
December11th to 20thNight
39%
760
24%
3131
18%
758
51%
758
23%
1796
December21st to endNight
35%
827
17%
4385
14%
817
48%
817
16%
2349

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
13%5%25%5%35%5%6%8%43%
74440
Night
13%6%25%5%3445%7%45%
75368
TransparencyDay
39%6%12%21%18%4
74161
Night
38%6%11%20%19%5%
75166
SeeingDay
16%8%22%25%19%9%
14224
Night
16%6%24%33%18%2
24639

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 10thDay
16%6%25%5%3444446%
1706
11th to 20thDay
18%7%35%43435%6%43%
1665
21st to endDay
17%7%24433445%48%
1782
February1st to 10thDay
16%6%35%5%33448%43%
1620
11th to 20thDay
21%6%24323335%47%
1613
21st to endDay
18%7%45%434445%42%
1588
March1st to 10thDay
15%6%23424345%52%
1980
11th to 20thDay
16%6%26%5%2446%7%42%
1980
21st to endDay
16%7%26%5%345%5%7%40%
2178
April1st to 10thDay
11%42442445%8%54%
2110
11th to 20thDay
11%5%3442445%8%49%
2134
21st to endDay
14%5%25%5%2446%7%46%
2160
May1st to 10thDay
11%5%35%5%36%46%8%44%
2272
11th to 20thDay
13%6%46%6%35%5%6%7%39%
2301
21st to endDay
11%5%26%6%45%6%6%9%40%
2531
June1st to 10thDay
10%6%26%6%46%7%6%10%38%
2340
11th to 20thDay
9%4246%46%6%7%10%42%
2340
21st to endDay
8%435%6%47%6%8%11%37%
2340
July1st to 10thDay
8%5%37%7%45%7%8%11%34%
2340
11th to 20thDay
8%5%35%7%46%7%9%12%33%
2340
21st to endDay
7%5%36%7%48%7%8%12%34%
2547
August1st to 10thDay
10%6%37%6%46%8%7%12%30%
2327
11th to 20thDay
11%6%37%7%5%7%7%8%8%31%
2206
21st to endDay
11%6%37%6%45%5%8%10%35%
2376
September1st to 10thDay
9%425%435%6%6%9%45%
2160
11th to 20thDay
14%425%5%4446%8%42%
2076
21st to endDay
19%7%25%5%35%45%7%38%
1922
October1st to 10thDay
15%5%25%42445%6%48%
1800
11th to 20thDay
12%5%24423436%55%
1800
21st to endDay
13%424423345%56%
1980
November1st to 10thDay
14%6%24333346%54%
1857
11th to 20thDay
14%6%24323347%52%
1900
21st to endDay
14%4243235%37%51%
1574
December1st to 10thDay
18%6%35%5%3445%7%41%
1520
11th to 20thDay
16%5%24323235%56%
1951
21st to endDay
16%6%25%5%3445%7%42%
3124
January1st to 10thNight
16%7%2442345%6%47%
2459
11th to 20thNight
15%7%46%5%34446%43%
2417
21st to endNight
16%5%15%423446%49%
2574
February1st to 10thNight
18%6%245%2445%5%44%
2340
11th to 20thNight
19%7%35%434346%43%
2233
21st to endNight
16%6%2433445%5%47%
1664
March1st to 10thNight
13%5%36%333345%53%
1980
11th to 20thNight
16%7%345%25%5%5%7%41%
1980
21st to endNight
16%5%245%35%45%6%45%
2178
April1st to 10thNight
14%6%2443335%8%48%
1849
11th to 20thNight
12%5%244345%5%7%49%
1775
21st to endNight
11%5%145%35%5%6%7%48%
1800
May1st to 10thNight
9%5%26%5%345%6%9%46%
1702
11th to 20thNight
13%6%37%5%445%5%7%41%
1592
21st to endNight
12%425%5%45%5%7%8%43%
1744
June1st to 10thNight
10%425%5%46%7%7%9%40%
1620
11th to 20thNight
10%6%45%6%35%6%7%8%41%
1620
21st to endNight
7%6%35%5%47%6%9%10%37%
1620
July1st to 10thNight
6%6%37%6%37%6%10%10%36%
1620
11th to 20thNight
6%5%36%6%36%7%8%12%38%
1620
21st to endNight
6%5%36%6%46%7%8%12%36%
1771
August1st to 10thNight
9%5%36%7%5%7%7%7%10%35%
1611
11th to 20thNight
9%6%36%8%46%6%8%12%32%
1677
21st to endNight
10%6%36%6%45%6%8%11%37%
1980
September1st to 10thNight
10%5%25%5%346%5%10%44%
1800
11th to 20thNight
12%5%36%6%445%5%7%44%
1880
21st to endNight
19%7%37%5%35%5%47%37%
2038
October1st to 10thNight
14%425%43435%6%50%
2160
11th to 20thNight
12%6%24423346%53%
2160
21st to endNight
12%42432335%6%56%
2376
November1st to 10thNight
14%6%24424445%53%
2221
11th to 20thNight
14%5%2443445%6%51%
2280
21st to endNight
14%42442345%7%51%
2596
December1st to 10thNight
18%6%26%5%3445%5%42%
2660
11th to 20thNight
17%6%24324346%48%
3239
21st to endNight
16%6%2443335%6%47%
4532

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 10thDay
42%38%20%20%6%
1707
11th to 20thDay
43%47%19%22%5%
1665
21st to endDay
40%36%22%23%7%
1782
February1st to 10thDay
42%410%20%19%5%
1620
11th to 20thDay
42%36%19%23%7%
1622
21st to endDay
45%48%17%19%6%
1588
March1st to 10thDay
35%48%22%23%7%
1980
11th to 20thDay
40%5%11%21%17%7%
1980
21st to endDay
43%5%11%18%18%4
2178
April1st to 10thDay
29%410%25%25%7%
2110
11th to 20thDay
34%5%10%24%21%7%
2134
21st to endDay
36%6%12%23%19%5%
2160
May1st to 10thDay
37%6%16%21%17%3
2272
11th to 20thDay
43%6%15%22%13%1
2305
21st to endDay
39%8%15%23%14%1
2531
June1st to 10thDay
39%7%15%21%16%1
2340
11th to 20thDay
34%9%17%24%14%2
2340
21st to endDay
37%11%17%20%14%2
2340
July1st to 10thDay
40%11%16%20%10%3
2275
11th to 20thDay
39%10%21%20%8%2
2271
21st to endDay
38%9%21%21%9%1
2405
August1st to 10thDay
43%10%18%19%9%
2314
11th to 20thDay
44%10%16%20%9%1
2206
21st to endDay
41%8%17%21%10%3
2376
September1st to 10thDay
35%8%16%19%17%4
2160
11th to 20thDay
40%6%9%20%21%4
2076
21st to endDay
46%6%10%19%15%4
1922
October1st to 10thDay
38%5%11%22%22%4
1800
11th to 20thDay
33%39%26%23%7%
1800
21st to endDay
33%36%23%26%9%
1980
November1st to 10thDay
34%37%22%27%7%
1857
11th to 20thDay
34%310%20%26%8%
1900
21st to endDay
34%47%24%24%7%
1574
December1st to 10thDay
43%311%21%17%4
1520
11th to 20thDay
34%27%25%24%8%
1947
21st to endDay
41%5%9%22%21%2
3124
January1st to 10thNight
40%39%19%24%6%
2459
11th to 20thNight
44%410%18%19%5%
2417
21st to endNight
37%36%22%26%6%
2574
February1st to 10thNight
42%48%19%21%6%
2340
11th to 20thNight
44%48%17%20%7%
2235
21st to endNight
38%5%9%20%21%8%
1664
March1st to 10thNight
35%49%20%24%9%
1980
11th to 20thNight
42%6%9%18%19%6%
1980
21st to endNight
39%6%10%21%18%5%
2178
April1st to 10thNight
36%49%17%25%8%
1849
11th to 20thNight
35%5%10%22%21%7%
1775
21st to endNight
34%6%12%25%19%5%
1800
May1st to 10thNight
34%7%15%23%17%4
1702
11th to 20thNight
42%6%14%21%16%1
1593
21st to endNight
37%8%16%23%15%1
1745
June1st to 10thNight
37%9%18%21%14%1
1620
11th to 20thNight
39%8%17%19%15%2
1620
21st to endNight
37%12%16%19%13%3
1620
July1st to 10thNight
38%11%19%19%10%2
1575
11th to 20thNight
34%12%24%20%9%2
1566
21st to endNight
37%11%20%22%10%
1672
August1st to 10thNight
41%10%21%21%6%1
1600
11th to 20thNight
42%11%19%20%7%1
1677
21st to endNight
39%9%19%22%9%2
1980
September1st to 10thNight
35%10%14%21%15%5%
1800
11th to 20thNight
39%7%12%20%20%3
1880
21st to endNight
48%6%11%16%16%3
2038
October1st to 10thNight
35%5%9%23%23%5%
2160
11th to 20thNight
33%5%8%22%25%7%
2160
21st to endNight
30%38%22%26%10%
2376
November1st to 10thNight
35%47%18%28%8%
2221
11th to 20thNight
35%48%16%25%11%
2280
21st to endNight
34%37%22%26%8%
2596
December1st to 10thNight
45%49%19%18%5%
2660
11th to 20thNight
38%48%19%23%8%
3242
21st to endNight
39%36%25%23%3
4532

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 10thDay
21%19%35%19%5%
270
11th to 20thDay
20%23%33%17%7%
255
21st to endDay
19%20%38%19%4
264
February1st to 10thDay
20%16%38%20%5%
240
11th to 20thDay
34%13%34%16%3
280
21st to endDay
24%18%30%20%7%
346
March1st to 10thDay
21%14%32%27%6%
420
11th to 20thDay
21%15%36%20%6%1
420
21st to endDay
20%12%34%25%6%2
462
April1st to 10thDay
18%15%29%25%11%2
420
11th to 20thDay
14%14%27%24%17%4
412
21st to endDay
17%10%26%24%20%2
420
May1st to 10thDay
13%12%30%25%14%7%
423
11th to 20thDay
17%6%18%29%22%9%
447
21st to endDay
19%5%13%27%22%15%
485
June1st to 10thDay
12%415%31%26%12%
450
11th to 20thDay
11%316%28%25%18%
450
21st to endDay
10%315%28%30%15%
450
July1st to 10thDay
10%26%26%33%22%
445
11th to 20thDay
7%27%23%36%25%
444
21st to endDay
9%29%28%34%17%
488
August1st to 10thDay
13%412%23%32%16%
446
11th to 20thDay
13%37%23%33%21%
439
21st to endDay
12%38%26%28%23%
495
September1st to 10thDay
12%212%24%26%23%
450
11th to 20thDay
16%210%28%29%15%
450
21st to endDay
24%418%25%20%8%
450
October1st to 10thDay
17%421%23%24%10%
450
11th to 20thDay
13%8%22%31%19%7%
450
21st to endDay
13%8%23%32%19%5%
495
November1st to 10thDay
18%7%25%29%16%4
455
11th to 20thDay
17%9%32%28%12%2
460
21st to endDay
17%9%27%28%16%3
223
December1st to 10thDay
21%11%36%26%6%2
180
11th to 20thDay
21%7%35%23%12%1
193
21st to endDay
24%11%33%20%10%2
297
January1st to 10thNight
21%11%34%27%6%1
760
11th to 20thNight
19%10%32%31%7%
744
21st to endNight
20%8%38%29%5%
792
February1st to 10thNight
21%8%38%28%4
720
11th to 20thNight
24%11%41%22%2
703
21st to endNight
19%12%36%29%4
592
March1st to 10thNight
15%12%34%33%4
720
11th to 20thNight
21%9%36%27%7%1
720
21st to endNight
18%9%35%32%6%
792
April1st to 10thNight
18%12%33%30%8%
720
11th to 20thNight
15%10%30%32%12%1
711
21st to endNight
14%5%33%38%10%
720
May1st to 10thNight
10%9%32%37%12%
622
11th to 20thNight
18%320%42%15%2
531
21st to endNight
13%213%39%31%3
584
June1st to 10thNight
13%114%43%26%2
540
11th to 20thNight
13%314%35%31%4
540
21st to endNight
8%411%40%33%4
540
July1st to 10thNight
9%28%37%40%4
525
11th to 20thNight
7%27%36%40%7%
522
21st to endNight
9%210%36%40%3
591
August1st to 10thNight
10%28%40%36%4
537
11th to 20thNight
11%28%34%38%6%
613
21st to endNight
12%38%30%38%8%
792
September1st to 10thNight
13%26%33%40%6%
720
11th to 20thNight
15%39%34%35%3
720
21st to endNight
23%414%31%26%2
720
October1st to 10thNight
16%317%32%27%5%
720
11th to 20thNight
16%6%22%33%22%2
720
21st to endNight
14%5%27%33%19%2
792
November1st to 10thNight
18%423%34%16%3
740
11th to 20thNight
16%7%26%36%14%1
760
21st to endNight
15%6%29%34%15%1
760
December1st to 10thNight
22%8%30%34%6%
760
11th to 20thNight
19%7%30%36%9%
760
21st to endNight
19%9%29%33%9%
836
Page generated at 2024-01-13 09:37:59. Version ac07

Copyright 2024 Attilla Danko


Clayton Clear Sky Chart |Charts Home