Sunset Field
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sunset Field clear sky chart from 2005-11-06 to 2024-01-10.

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
45%
24166
21%
74742
14%
24118
53%
24118
26%
46442

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
25%
759
25%
2458
9%
757
44%
757
22%
1469
January11th to 20thNight
30%
720
23%
2340
12%
720
44%
720
20%
1492
January21st to endNight
25%
792
25%
2574
10%
792
45%
792
24%
1550
February1st to 10thNight
27%
720
20%
2340
10%
720
40%
720
23%
1445
February11th to 20thNight
19%
700
19%
2269
5%
699
36%
699
18%
1448
February21st to endNight
25%
592
26%
1681
11%
592
41%
592
23%
1096
March1st to 10thNight
33%
720
27%
1980
13%
720
46%
720
30%
1213
March11th to 20thNight
30%
720
19%
1980
8%
720
41%
720
22%
1318
March21st to endNight
34%
792
20%
2178
11%
792
41%
792
26%
1434
April1st to 10thNight
32%
720
21%
1886
8%
720
41%
720
27%
1210
April11th to 20thNight
40%
711
23%
1775
10%
711
47%
711
33%
1126
April21st to endNight
43%
648
22%
1728
10%
648
49%
648
30%
1123
May1st to 10thNight
44%
540
16%
1620
8%
540
50%
540
26%
1048
May11th to 20thNight
48%
531
15%
1593
10%
531
51%
531
22%
1088
May21st to endNight
61%
582
15%
1745
12%
582
63%
582
28%
1126
June1st to 10thNight
67%
499
17%
1579
16%
499
69%
499
30%
943
June11th to 20thNight
65%
403
16%
1483
16%
403
69%
403
27%
872
June21st to endNight
71%
540
18%
1620
16%
540
73%
540
32%
980
July1st to 10thNight
68%
525
14%
1575
13%
525
69%
525
28%
1013
July11th to 20thNight
77%
522
15%
1566
15%
522
78%
522
35%
935
July21st to endNight
69%
591
19%
1672
16%
558
71%
558
32%
1046
August1st to 10thNight
63%
537
16%
1600
12%
534
65%
534
26%
1068
August11th to 20thNight
62%
534
20%
1598
17%
534
63%
534
26%
1051
August21st to endNight
65%
772
17%
1960
13%
772
65%
772
31%
1324
September1st to 10thNight
65%
720
23%
1800
16%
720
67%
720
34%
1196
September11th to 20thNight
61%
720
24%
1962
21%
720
62%
720
28%
1293
September21st to endNight
46%
720
20%
1993
15%
720
50%
720
23%
1396
October1st to 10thNight
50%
720
23%
2160
20%
720
57%
720
31%
1316
October11th to 20thNight
47%
720
27%
2160
20%
720
58%
720
31%
1281
October21st to endNight
48%
792
31%
2376
24%
792
60%
792
35%
1347
November1st to 10thNight
47%
740
29%
2221
21%
740
58%
740
32%
1299
November11th to 20thNight
41%
760
28%
2398
17%
760
55%
760
29%
1373
November21st to endNight
43%
760
25%
2638
18%
760
56%
760
28%
1484
December1st to 10thNight
28%
760
22%
2660
11%
760
44%
760
20%
1656
December11th to 20thNight
33%
759
25%
3166
13%
758
49%
758
20%
1827
December21st to endNight
30%
825
15%
4408
11%
817
43%
817
13%
2556

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%6%35%5%35%5%6%8%41%
74423
Night
14%6%25%5%3445%7%44%
75210
TransparencyDay
40%6%12%23%16%3
74144
Night
38%5%11%23%18%4
75008
SeeingDay
19%11%23%25%16%7%
13936
Night
17%8%22%33%17%2
24184

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
15%6%25%5%4445%6%44%
1697
11th to 20thDay
17%8%35%435%45%6%39%
1620
21st to endDay
16%7%35%5%34445%44%
1782
February1st to 10thDay
13%6%37%6%46%6%5%8%38%
1620
11th to 20thDay
18%6%35%6%34446%40%
1573
21st to endDay
19%7%46%43445%5%38%
1574
March1st to 10thDay
14%5%1432446%7%50%
1980
11th to 20thDay
17%7%36%5%45%5%5%7%38%
1980
21st to endDay
17%7%37%5%345%5%7%37%
2178
April1st to 10thDay
11%6%25%42446%8%48%
2073
11th to 20thDay
15%434435%5%5%7%45%
2134
21st to endDay
17%5%26%5%445%5%6%41%
2247
May1st to 10thDay
15%5%35%6%5%6%6%6%9%35%
2340
11th to 20thDay
17%6%36%6%36%5%6%8%34%
2301
21st to endDay
14%6%26%6%36%6%6%9%36%
2531
June1st to 10thDay
11%4245%46%6%6%10%42%
2361
11th to 20thDay
11%5%26%5%35%6%7%10%39%
2454
21st to endDay
8%426%6%35%7%7%11%40%
2340
July1st to 10thDay
10%5%35%7%47%6%8%9%36%
2340
11th to 20thDay
6%435%6%47%7%8%12%37%
2340
21st to endDay
9%5%47%7%5%7%7%7%9%32%
2547
August1st to 10thDay
13%6%26%6%45%7%7%10%33%
2327
11th to 20thDay
13%5%36%8%5%6%6%7%10%32%
2303
21st to endDay
11%6%35%5%45%6%8%9%38%
2376
September1st to 10thDay
14%4244445%5%7%45%
2160
11th to 20thDay
15%6%25%5%35%5%5%7%42%
1995
21st to endDay
22%7%25%5%3445%5%37%
1967
October1st to 10thDay
16%5%2343345%6%48%
1800
11th to 20thDay
16%5%2432335%7%50%
1800
21st to endDay
15%6%2442445%5%49%
1980
November1st to 10thDay
12%424424436%55%
1857
11th to 20thDay
15%5%1442445%7%51%
1777
21st to endDay
14%4345%23448%48%
1538
December1st to 10thDay
17%7%37%6%345%6%7%36%
1520
11th to 20thDay
16%5%24424337%52%
1910
21st to endDay
20%6%35%5%35%6%7%8%33%
3101
January1st to 10thNight
15%5%245%3445%6%47%
2458
11th to 20thNight
16%6%35%5%45%6%5%7%40%
2340
21st to endNight
14%6%245%35%5%5%6%45%
2574
February1st to 10thNight
14%7%26%5%345%6%6%42%
2340
11th to 20thNight
19%7%26%5%34446%41%
2269
21st to endNight
16%7%35%5%25%5%5%7%40%
1681
March1st to 10thNight
12%4244345%5%6%50%
1980
11th to 20thNight
19%6%25%4445%5%6%40%
1980
21st to endNight
15%6%35%6%3445%6%44%
2178
April1st to 10thNight
14%6%26%5%2436%7%45%
1886
11th to 20thNight
14%42442445%7%49%
1775
21st to endNight
16%5%25%43445%7%44%
1728
May1st to 10thNight
14%6%35%6%3446%8%41%
1620
11th to 20thNight
18%6%36%5%35%5%5%9%36%
1592
21st to endNight
15%6%26%43446%9%40%
1744
June1st to 10thNight
9%5%25%435%5%7%11%44%
1579
11th to 20thNight
10%436%4345%7%9%43%
1483
21st to endNight
9%4245%45%6%6%11%45%
1620
July1st to 10thNight
9%5%35%6%46%5%6%10%42%
1620
11th to 20thNight
6%424436%6%8%12%45%
1620
21st to endNight
6%5%36%6%45%6%7%11%41%
1771
August1st to 10thNight
12%7%26%6%45%47%10%38%
1611
11th to 20thNight
11%7%36%6%35%6%6%8%39%
1598
21st to endNight
10%6%36%6%345%7%9%40%
1960
September1st to 10thNight
11%5%35%5%35%5%5%7%47%
1800
11th to 20thNight
15%6%25%5%3445%7%43%
1962
21st to endNight
22%7%36%5%2435%5%38%
1993
October1st to 10thNight
15%6%25%43335%6%48%
2160
11th to 20thNight
14%6%23433347%49%
2160
21st to endNight
15%31432335%6%53%
2376
November1st to 10thNight
15%6%2431344454%
2221
11th to 20thNight
14%4244345%46%51%
2398
21st to endNight
14%42442445%7%49%
2638
December1st to 10thNight
18%8%35%5%3435%6%42%
2660
11th to 20thNight
14%7%35%43445%6%45%
3285
21st to endNight
17%5%25%6%36%5%7%8%37%
4550

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
39%5%10%23%19%5%
1698
11th to 20thDay
45%49%22%18%2
1620
21st to endDay
41%38%23%20%4
1782
February1st to 10thDay
43%5%12%22%15%3
1620
11th to 20thDay
44%49%22%18%4
1582
21st to endDay
48%410%17%17%5%
1574
March1st to 10thDay
33%410%25%23%5%
1980
11th to 20thDay
45%5%10%18%16%5%
1980
21st to endDay
44%6%10%21%14%4
2178
April1st to 10thDay
33%5%11%24%19%8%
2073
11th to 20thDay
38%411%23%19%6%
2134
21st to endDay
43%5%12%22%14%5%
2247
May1st to 10thDay
42%7%16%20%13%3
2340
11th to 20thDay
45%7%15%21%10%2
2305
21st to endDay
42%7%16%24%10%
2531
June1st to 10thDay
35%8%17%26%14%1
2361
11th to 20thDay
37%8%17%21%16%2
2454
21st to endDay
34%10%15%25%13%2
2340
July1st to 10thDay
39%10%15%20%13%3
2275
11th to 20thDay
35%10%19%20%15%1
2271
21st to endDay
43%9%15%22%11%1
2405
August1st to 10thDay
42%8%15%25%8%1
2314
11th to 20thDay
45%8%15%21%11%
2303
21st to endDay
39%7%19%21%13%2
2376
September1st to 10thDay
36%7%13%21%20%4
2160
11th to 20thDay
40%5%8%26%18%3
1995
21st to endDay
48%48%19%19%2
1967
October1st to 10thDay
37%39%27%18%5%
1800
11th to 20thDay
34%310%27%21%4
1800
21st to endDay
36%38%27%20%6%
1980
November1st to 10thDay
31%49%23%28%5%
1857
11th to 20thDay
34%48%24%22%8%
1777
21st to endDay
34%5%9%25%24%4
1538
December1st to 10thDay
45%5%11%20%16%4
1520
11th to 20thDay
33%5%8%25%22%7%
1906
21st to endDay
45%410%27%13%2
3101
January1st to 10thNight
38%49%22%20%6%
2458
11th to 20thNight
43%5%10%21%17%4
2340
21st to endNight
38%49%25%20%4
2574
February1st to 10thNight
40%5%12%23%18%2
2340
11th to 20thNight
45%39%19%18%6%
2271
21st to endNight
42%5%10%23%15%6%
1681
March1st to 10thNight
34%5%9%25%22%5%
1980
11th to 20thNight
43%5%10%21%19%3
1980
21st to endNight
41%5%10%22%18%5%
2178
April1st to 10thNight
38%411%20%21%5%
1886
11th to 20thNight
34%5%12%21%22%6%
1775
21st to endNight
38%6%11%24%17%4
1728
May1st to 10thNight
39%7%16%20%14%3
1620
11th to 20thNight
45%7%13%23%10%2
1593
21st to endNight
40%6%17%26%11%1
1745
June1st to 10thNight
33%9%15%28%15%1
1579
11th to 20thNight
35%8%18%21%16%2
1483
21st to endNight
31%10%17%23%16%4
1620
July1st to 10thNight
36%9%17%18%14%5%
1575
11th to 20thNight
30%9%22%24%14%2
1566
21st to endNight
36%7%17%27%13%
1672
August1st to 10thNight
40%9%17%21%12%1
1600
11th to 20thNight
40%8%14%24%12%1
1598
21st to endNight
38%8%17%22%12%3
1960
September1st to 10thNight
36%8%13%20%18%5%
1800
11th to 20thNight
40%7%8%24%19%3
1962
21st to endNight
48%5%8%20%16%3
1993
October1st to 10thNight
38%49%25%20%4
2160
11th to 20thNight
36%38%27%21%5%
2160
21st to endNight
32%38%25%26%6%
2376
November1st to 10thNight
35%38%22%25%7%
2221
11th to 20thNight
34%49%22%24%7%
2398
21st to endNight
34%49%27%21%6%
2638
December1st to 10thNight
44%38%25%16%3
2660
11th to 20thNight
39%48%22%21%6%
3288
21st to endNight
42%5%10%22%19%2
4550

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
27%27%25%18%31
267
11th to 20thDay
34%16%32%18%
240
21st to endDay
31%22%29%13%4
264
February1st to 10thDay
26%23%37%10%4
240
11th to 20thDay
40%18%34%7%2
240
21st to endDay
30%22%27%18%3
292
March1st to 10thDay
25%18%28%25%4
420
11th to 20thDay
23%21%28%22%5%1
420
21st to endDay
24%16%30%23%7%
462
April1st to 10thDay
22%21%25%22%10%1
420
11th to 20thDay
21%13%28%22%12%4
412
21st to endDay
25%12%27%21%11%3
420
May1st to 10thDay
19%15%33%21%9%3
423
11th to 20thDay
20%10%24%26%15%5%
447
21st to endDay
19%5%18%28%20%10%
485
June1st to 10thDay
11%5%26%30%19%8%
450
11th to 20thDay
12%6%19%31%21%11%
450
21st to endDay
11%6%23%32%21%8%
450
July1st to 10thDay
12%214%27%30%15%
445
11th to 20thDay
5%214%33%32%14%
444
21st to endDay
12%118%29%25%15%
488
August1st to 10thDay
17%315%24%26%15%
446
11th to 20thDay
13%415%28%25%15%
439
21st to endDay
11%311%28%27%21%
495
September1st to 10thDay
14%213%24%28%18%
450
11th to 20thDay
18%313%25%30%12%
450
21st to endDay
24%9%18%25%19%5%
450
October1st to 10thDay
22%5%18%28%21%5%
450
11th to 20thDay
15%13%21%28%19%3
450
21st to endDay
18%13%26%28%12%2
495
November1st to 10thDay
17%9%26%31%13%4
455
11th to 20thDay
22%17%23%24%12%1
337
21st to endDay
22%16%27%23%10%2
188
December1st to 10thDay
24%19%32%19%6%
180
11th to 20thDay
24%16%28%19%10%2
180
21st to endDay
28%15%28%20%9%1
292
January1st to 10thNight
21%16%33%27%3
760
11th to 20thNight
20%14%30%33%3
720
21st to endNight
19%13%38%27%3
792
February1st to 10thNight
18%13%36%30%3
720
11th to 20thNight
27%16%32%23%
703
21st to endNight
21%15%35%27%2
592
March1st to 10thNight
16%15%32%33%4
720
11th to 20thNight
24%12%29%26%8%1
720
21st to endNight
18%11%30%33%7%1
792
April1st to 10thNight
17%17%30%30%7%
720
11th to 20thNight
16%13%27%31%13%1
711
21st to endNight
19%5%27%37%11%
648
May1st to 10thNight
16%7%26%36%14%1
540
11th to 20thNight
18%5%19%38%17%2
531
21st to endNight
17%29%33%33%5%
584
June1st to 10thNight
11%111%43%32%2
499
11th to 20thNight
10%214%39%34%2
403
21st to endNight
9%29%45%31%4
540
July1st to 10thNight
11%18%32%42%6%
525
11th to 20thNight
7%16%31%49%7%
522
21st to endNight
8%18%39%39%5%
591
August1st to 10thNight
13%19%35%38%4
537
11th to 20thNight
13%28%34%39%4
534
21st to endNight
13%19%33%37%7%
772
September1st to 10thNight
14%210%31%37%7%
720
11th to 20thNight
17%210%31%34%5%
720
21st to endNight
23%417%32%22%2
720
October1st to 10thNight
17%7%17%28%27%4
720
11th to 20thNight
16%8%23%34%18%2
720
21st to endNight
17%7%20%41%13%2
792
November1st to 10thNight
18%7%21%37%14%2
740
11th to 20thNight
17%11%24%35%12%1
760
21st to endNight
16%11%25%37%11%1
760
December1st to 10thNight
23%12%29%29%6%
760
11th to 20thNight
18%10%31%36%5%
760
21st to endNight
20%13%28%35%3
836
Page generated at 2024-01-07 10:06:54. Version ac07

Copyright 2024 Attilla Danko


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