Stars Fell Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stars Fell Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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
47%
23558
23%
74402
16%
23503
55%
23503
28%
45401

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
22%
760
22%
2459
9%
757
38%
757
20%
1569
January11th to 20thNight
27%
732
22%
2374
10%
732
40%
732
18%
1608
January21st to endNight
24%
792
30%
2376
12%
792
40%
792
24%
1507
February1st to 10thNight
28%
720
25%
2160
11%
720
41%
720
24%
1404
February11th to 20thNight
24%
703
21%
2098
8%
699
35%
699
21%
1388
February21st to endNight
22%
592
22%
1776
9%
592
33%
592
19%
1224
March1st to 10thNight
30%
720
24%
2160
12%
720
40%
720
24%
1362
March11th to 20thNight
31%
720
19%
2029
9%
720
39%
720
25%
1332
March21st to endNight
33%
757
22%
2143
11%
757
43%
757
26%
1388
April1st to 10thNight
40%
540
27%
1800
18%
540
53%
540
29%
1017
April11th to 20thNight
37%
533
28%
1775
17%
533
52%
533
29%
1020
April21st to endNight
47%
540
28%
1772
19%
540
58%
540
32%
990
May1st to 10thNight
53%
540
25%
1620
15%
540
63%
540
37%
913
May11th to 20thNight
54%
531
20%
1592
15%
531
59%
531
31%
954
May21st to endNight
66%
582
21%
1744
19%
582
69%
582
34%
1032
June1st to 10thNight
63%
540
19%
1620
17%
540
65%
540
30%
1005
June11th to 20thNight
75%
540
20%
1620
16%
540
78%
540
46%
856
June21st to endNight
74%
540
18%
1620
16%
540
75%
540
37%
945
July1st to 10thNight
74%
525
15%
1575
14%
525
75%
525
31%
975
July11th to 20thNight
77%
522
17%
1566
17%
522
78%
522
35%
918
July21st to endNight
69%
591
17%
1672
16%
558
70%
558
27%
1088
August1st to 10thNight
77%
537
20%
1732
21%
534
78%
534
35%
975
August11th to 20thNight
69%
534
17%
1776
19%
534
70%
534
27%
1097
August21st to endNight
67%
594
21%
1980
25%
594
68%
594
26%
1245
September1st to 10thNight
68%
594
23%
1854
23%
594
69%
594
31%
1103
September11th to 20thNight
63%
720
23%
1980
19%
720
65%
720
31%
1272
September21st to endNight
62%
720
31%
1980
21%
720
69%
720
39%
1156
October1st to 10thNight
61%
720
34%
1980
26%
720
67%
720
43%
1110
October11th to 20thNight
48%
720
34%
1980
22%
720
59%
720
37%
1177
October21st to endNight
51%
792
30%
2500
26%
792
59%
792
31%
1461
November1st to 10thNight
50%
740
28%
2406
25%
740
59%
740
34%
1317
November11th to 20thNight
41%
760
31%
2470
20%
760
57%
760
32%
1375
November21st to endNight
38%
760
26%
2470
18%
760
50%
760
27%
1493
December1st to 10thNight
29%
760
23%
2470
14%
760
43%
760
20%
1633
December11th to 20thNight
31%
759
26%
2893
15%
758
43%
758
21%
1700
December21st to endNight
27%
828
14%
4380
12%
817
37%
817
11%
2792

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%6%35%5%35%5%6%8%41%
74841
Night
13%6%35%5%345%5%7%45%
74912
TransparencyDay
42%411%21%18%4
74564
Night
39%310%21%20%6%
74708
SeeingDay
18%9%22%24%19%9%
13499
Night
16%8%22%29%21%4
23569

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
18%8%35%5%2345%6%41%
1706
11th to 20thDay
21%9%35%42345%5%39%
1644
21st to endDay
17%7%34424446%45%
1980
February1st to 10thDay
19%9%46%5%2345%6%38%
1800
11th to 20thDay
22%8%36%5%3444437%
1748
21st to endDay
21%10%36%5%33435%37%
1480
March1st to 10thDay
15%8%35%435%446%42%
1800
11th to 20thDay
19%8%36%6%3445%6%35%
1930
21st to endDay
15%8%36%5%46%5%6%7%37%
2226
April1st to 10thDay
12%6%25%425%46%8%46%
2160
11th to 20thDay
13%7%35%5%2445%6%46%
2134
21st to endDay
10%5%25%435%6%6%7%47%
2186
May1st to 10thDay
12%5%245%3446%8%46%
2340
11th to 20thDay
11%6%36%5%36%6%5%8%41%
2301
21st to endDay
11%6%35%5%36%6%7%9%41%
2531
June1st to 10thDay
10%6%37%7%46%7%8%8%34%
2340
11th to 20thDay
5%425%5%37%7%8%11%44%
2340
21st to endDay
7%5%26%7%47%7%7%9%39%
2340
July1st to 10thDay
9%6%37%8%5%8%7%8%11%29%
2340
11th to 20thDay
9%427%7%47%7%9%12%31%
2340
21st to endDay
8%5%26%7%5%7%8%9%12%31%
2547
August1st to 10thDay
8%6%26%7%5%7%7%8%12%33%
2191
11th to 20thDay
9%7%36%7%5%7%7%8%11%31%
2125
21st to endDay
12%7%36%7%46%5%7%9%34%
2376
September1st to 10thDay
10%5%36%5%37%6%7%9%40%
2086
11th to 20thDay
14%5%345%35%6%5%8%42%
1980
21st to endDay
12%5%25%43445%6%50%
1980
October1st to 10thDay
11%5%25%5%25%445%54%
1980
11th to 20thDay
10%5%2442435%8%53%
1980
21st to endDay
14%6%24433335%53%
1851
November1st to 10thDay
13%42443433455%
1672
11th to 20thDay
12%5%26%43435%7%50%
1710
21st to endDay
16%6%25%4345%46%45%
1710
December1st to 10thDay
21%8%26%424446%37%
1710
11th to 20thDay
17%8%36%5%34445%41%
2153
21st to endDay
19%9%5%6%6%3445%6%34%
3124
January1st to 10thNight
18%7%36%434445%43%
2459
11th to 20thNight
18%9%5%6%5%245%47%36%
2374
21st to endNight
16%7%45%5%2345%5%44%
2376
February1st to 10thNight
18%8%25%5%33446%42%
2160
11th to 20thNight
21%7%36%5%2344442%
2098
21st to endNight
22%7%35%43445%6%36%
1776
March1st to 10thNight
16%6%35%5%34446%45%
2160
11th to 20thNight
17%6%25%5%3445%8%40%
2029
21st to endNight
14%7%35%5%35%445%44%
2143
April1st to 10thNight
11%4245%345%6%7%49%
1800
11th to 20thNight
14%7%35%324446%50%
1775
21st to endNight
9%5%25%5%345%47%51%
1772
May1st to 10thNight
9%42343346%8%52%
1620
11th to 20thNight
9%5%35%5%345%7%9%44%
1592
21st to endNight
8%5%35%5%35%6%7%9%47%
1744
June1st to 10thNight
6%5%27%6%5%7%6%7%10%40%
1620
11th to 20thNight
43144346%6%12%53%
1620
21st to endNight
6%3345%35%6%7%12%46%
1620
July1st to 10thNight
8%325%6%46%7%8%13%38%
1620
11th to 20thNight
6%325%5%37%6%8%11%44%
1620
21st to endNight
6%5%36%7%47%7%8%9%38%
1771
August1st to 10thNight
4426%5%45%6%8%13%43%
1743
11th to 20thNight
9%5%35%5%46%5%7%10%41%
1776
21st to endNight
11%6%26%5%45%5%6%9%41%
1980
September1st to 10thNight
8%425%6%45%6%6%7%46%
1854
11th to 20thNight
12%5%25%6%35%5%6%8%44%
1980
21st to endNight
8%5%25%42445%8%53%
1980
October1st to 10thNight
9%323423346%60%
1980
11th to 20thNight
12%5%24423446%53%
1980
21st to endNight
14%5%2442443453%
2500
November1st to 10thNight
11%425%42335%5%55%
2406
11th to 20thNight
12%6%24423446%54%
2470
21st to endNight
15%7%25%5%2445%6%46%
2470
December1st to 10thNight
19%9%35%5%2445%6%38%
2470
11th to 20thNight
16%8%35%423345%47%
3042
21st to endNight
18%7%46%5%45%5%6%8%31%
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
45%27%20%20%5%
1707
11th to 20thDay
49%25%21%20%3
1644
21st to endDay
42%25%24%22%5%
1980
February1st to 10thDay
49%26%20%21%3
1800
11th to 20thDay
51%2420%17%5%
1758
21st to endDay
52%25%14%21%6%
1480
March1st to 10thDay
44%37%16%22%8%
1800
11th to 20thDay
51%39%14%18%5%
1930
21st to endDay
46%39%23%17%2
2226
April1st to 10thDay
37%312%24%18%6%
2160
11th to 20thDay
41%26%21%24%6%
2134
21st to endDay
35%39%28%22%3
2186
May1st to 10thDay
37%311%26%19%4
2340
11th to 20thDay
41%415%24%16%
2305
21st to endDay
39%413%26%15%2
2531
June1st to 10thDay
44%5%14%21%14%1
2340
11th to 20thDay
32%5%18%28%15%2
2340
21st to endDay
39%6%16%24%12%3
2340
July1st to 10thDay
45%6%17%20%10%1
2275
11th to 20thDay
43%7%20%19%10%2
2271
21st to endDay
41%7%19%22%10%
2405
August1st to 10thDay
41%6%20%26%6%1
2178
11th to 20thDay
45%5%17%20%12%2
2125
21st to endDay
46%5%15%20%11%4
2376
September1st to 10thDay
39%5%16%19%16%6%
2086
11th to 20thDay
41%411%21%19%4
1980
21st to endDay
36%310%20%23%8%
1980
October1st to 10thDay
34%36%21%27%9%
1980
11th to 20thDay
32%27%24%26%9%
1980
21st to endDay
36%2419%31%10%
1851
November1st to 10thDay
35%25%18%29%10%
1672
11th to 20thDay
35%26%21%26%10%
1710
21st to endDay
41%35%19%26%6%
1710
December1st to 10thDay
49%37%16%20%5%
1710
11th to 20thDay
48%25%19%21%6%
2150
21st to endDay
53%17%18%18%2
3124
January1st to 10thNight
46%27%21%21%4
2459
11th to 20thNight
50%36%18%18%4
2374
21st to endNight
43%2423%23%5%
2376
February1st to 10thNight
45%25%20%22%5%
2160
11th to 20thNight
47%25%19%19%7%
2099
21st to endNight
50%35%16%19%7%
1776
March1st to 10thNight
42%26%17%21%11%
2160
11th to 20thNight
44%311%18%19%6%
2029
21st to endNight
43%37%25%18%4
2143
April1st to 10thNight
34%411%24%21%6%
1800
11th to 20thNight
37%25%22%22%12%
1775
21st to endNight
34%39%28%21%4
1772
May1st to 10thNight
31%312%24%26%4
1620
11th to 20thNight
36%418%23%17%2
1593
21st to endNight
33%6%14%26%19%3
1745
June1st to 10thNight
39%415%23%17%2
1620
11th to 20thNight
25%421%30%17%3
1620
21st to endNight
30%7%20%22%17%4
1620
July1st to 10thNight
35%7%22%22%11%3
1575
11th to 20thNight
31%7%25%22%12%3
1566
21st to endNight
40%7%20%23%10%1
1672
August1st to 10thNight
31%6%23%29%10%1
1732
11th to 20thNight
39%6%21%18%14%3
1776
21st to endNight
40%6%17%21%13%4
1980
September1st to 10thNight
35%5%18%20%16%5%
1854
11th to 20thNight
39%5%12%18%22%4
1980
21st to endNight
32%39%22%25%9%
1980
October1st to 10thNight
27%46%26%26%11%
1980
11th to 20thNight
34%26%22%25%11%
1980
21st to endNight
36%2418%29%10%
2500
November1st to 10thNight
32%37%21%24%13%
2406
11th to 20thNight
34%2420%29%12%
2470
21st to endNight
40%25%22%24%7%
2470
December1st to 10thNight
49%27%19%20%3
2470
11th to 20thNight
41%16%18%28%5%
3044
21st to endNight
52%15%20%19%2
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
26%25%34%13%2
270
11th to 20thDay
31%19%31%13%5%1
248
21st to endDay
23%23%39%11%31
264
February1st to 10thDay
25%25%34%15%11
240
11th to 20thDay
42%19%29%10%
240
21st to endDay
33%22%35%10%1
198
March1st to 10thDay
26%20%36%15%31
240
11th to 20thDay
24%18%32%18%7%1
370
21st to endDay
22%18%32%21%6%1
462
April1st to 10thDay
18%16%30%23%12%2
420
11th to 20thDay
20%16%28%22%13%1
412
21st to endDay
16%12%30%27%13%2
420
May1st to 10thDay
16%10%27%26%16%5%
423
11th to 20thDay
13%423%31%19%10%
447
21st to endDay
14%416%29%24%14%
485
June1st to 10thDay
14%217%32%24%12%
450
11th to 20thDay
8%314%24%29%21%
450
21st to endDay
12%214%28%28%17%
450
July1st to 10thDay
11%16%27%30%25%
445
11th to 20thDay
9%27%22%32%28%
444
21st to endDay
10%18%22%36%23%
488
August1st to 10thDay
12%210%21%33%23%
446
11th to 20thDay
13%17%31%32%15%
439
21st to endDay
18%17%25%32%16%
495
September1st to 10thDay
10%311%28%35%13%
450
11th to 20thDay
16%211%27%31%13%
450
21st to endDay
14%414%30%30%8%
450
October1st to 10thDay
15%322%31%20%9%
450
11th to 20thDay
14%9%27%30%18%2
450
21st to endDay
20%11%23%31%14%1
356
November1st to 10thDay
21%9%31%27%10%3
270
11th to 20thDay
17%19%37%22%5%
270
21st to endDay
18%16%39%19%8%1
270
December1st to 10thDay
31%17%30%16%5%
270
11th to 20thDay
26%18%33%17%6%
270
21st to endDay
32%15%33%16%31
297
January1st to 10thNight
23%17%33%23%4
760
11th to 20thNight
22%15%31%25%7%
732
21st to endNight
20%14%37%25%3
792
February1st to 10thNight
23%13%32%28%5%
720
11th to 20thNight
25%14%33%24%3
703
21st to endNight
27%15%34%22%3
592
March1st to 10thNight
19%15%32%30%5%
720
11th to 20thNight
21%12%32%25%10%1
720
21st to endNight
19%14%29%27%10%1
757
April1st to 10thNight
14%10%32%30%13%
540
11th to 20thNight
17%9%32%27%14%1
533
21st to endNight
13%6%28%36%16%1
540
May1st to 10thNight
12%5%24%33%23%3
540
11th to 20thNight
13%220%34%25%6%
531
21st to endNight
9%211%35%36%7%
584
June1st to 10thNight
10%111%35%35%7%
540
11th to 20thNight
4110%30%41%13%
540
21st to endNight
8%18%31%42%11%
540
July1st to 10thNight
9%15%23%46%17%
525
11th to 20thNight
7%15%23%43%20%
522
21st to endNight
8%26%25%47%13%
591
August1st to 10thNight
5%1427%48%15%
537
11th to 20thNight
11%17%27%45%10%
534
21st to endNight
13%15%30%41%10%
594
September1st to 10thNight
11%17%29%40%11%
594
11th to 20thNight
14%310%30%37%6%
720
21st to endNight
10%215%31%38%4
720
October1st to 10thNight
11%419%33%26%6%
720
11th to 20thNight
15%7%25%31%20%3
720
21st to endNight
17%8%19%35%18%3
792
November1st to 10thNight
13%7%25%33%19%3
740
11th to 20thNight
16%9%30%32%11%1
760
21st to endNight
19%9%29%30%11%1
760
December1st to 10thNight
25%12%28%26%9%
760
11th to 20thNight
22%11%31%27%9%
760
21st to endNight
26%12%27%28%6%
836
Page generated at 2024-01-10 18:35:26. Version ac07

Copyright 2024 Attilla Danko


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