Shell Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shell Point clear sky chart from 2005-11-06 to 2024-03-28.

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
59%
24242
15%
79975
12%
24147
62%
24147
15%
58172

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
36%
752
18%
3997
8%
737
45%
737
9%
2566
January11th to 20thNight
46%
750
20%
3949
12%
740
54%
740
10%
2648
January21st to endNight
34%
832
11%
4101
9%
814
41%
814
9%
2810
February1st to 10thNight
44%
760
16%
2280
11%
760
49%
760
16%
1696
February11th to 20thNight
41%
740
14%
2218
6%
739
49%
739
15%
1679
February21st to endNight
41%
628
16%
1884
10%
628
46%
628
16%
1390
March1st to 10thNight
51%
760
18%
2195
13%
760
55%
760
19%
1590
March11th to 20thNight
53%
760
20%
2090
12%
760
59%
760
21%
1503
March21st to endNight
54%
821
18%
2256
11%
821
58%
821
21%
1628
April1st to 10thNight
55%
720
16%
1980
12%
720
59%
720
20%
1437
April11th to 20thNight
53%
579
17%
1821
14%
579
58%
579
17%
1306
April21st to endNight
65%
540
21%
1746
16%
540
72%
540
20%
1184
May1st to 10thNight
70%
540
20%
1620
16%
540
73%
540
22%
1113
May11th to 20thNight
68%
531
15%
1592
13%
531
69%
531
19%
1142
May21st to endNight
78%
582
17%
1744
15%
582
78%
582
21%
1231
June1st to 10thNight
70%
540
12%
1620
11%
540
70%
540
17%
1203
June11th to 20thNight
77%
540
12%
1620
11%
540
78%
540
18%
1194
June21st to endNight
75%
540
11%
1620
10%
540
76%
540
15%
1240
July1st to 10thNight
76%
525
5%
1575
5%
525
76%
525
11%
1294
July11th to 20thNight
75%
522
5%
1566
6%
522
75%
522
13%
1250
July21st to endNight
82%
591
6%
1672
6%
558
83%
558
16%
1275
August1st to 10thNight
80%
537
6%
1735
7%
534
80%
534
16%
1282
August11th to 20thNight
77%
534
6%
1776
7%
534
77%
534
11%
1402
August21st to endNight
66%
616
7%
2002
8%
616
67%
616
9%
1660
September1st to 10thNight
68%
720
8%
1980
7%
720
68%
720
13%
1607
September11th to 20thNight
66%
720
6%
1980
5%
720
66%
720
11%
1649
September21st to endNight
68%
720
15%
1980
13%
720
70%
720
17%
1506
October1st to 10thNight
61%
720
17%
1980
13%
720
64%
720
18%
1484
October11th to 20thNight
69%
720
23%
2020
21%
720
72%
720
22%
1449
October21st to endNight
62%
792
17%
2376
16%
792
65%
792
18%
1726
November1st to 10thNight
60%
740
22%
2254
19%
740
65%
740
21%
1549
November11th to 20thNight
53%
760
19%
2470
17%
760
58%
760
16%
1774
November21st to endNight
51%
760
15%
2470
12%
760
57%
760
14%
1853
December1st to 10thNight
49%
760
17%
2470
14%
760
54%
760
15%
1818
December11th to 20thNight
46%
760
18%
2923
13%
758
50%
758
11%
2065
December21st to endNight
44%
830
13%
4413
13%
817
52%
817
10%
2969

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%6%7%9%43%
79255
Night
10%6%25%5%35%5%6%9%45%
80743
TransparencyDay
25%37%9%12%11%5%
78978
Night
25%36%9%12%13%6%
80539
SeeingDay
10%315%26%30%16%
14159
Night
11%418%28%29%10%
24275

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%4345%5%6%45%
2836
11th to 20thDay
12%5%25%5%345%6%8%44%
2876
21st to endDay
18%8%25%42445%7%40%
3476
February1st to 10thDay
17%7%245%34446%43%
1900
11th to 20thDay
16%6%24424446%48%
1848
21st to endDay
14%6%25%5%35%446%45%
1570
March1st to 10thDay
9%42442446%9%52%
1984
11th to 20thDay
8%5%245%3446%9%50%
2090
21st to endDay
11%424423447%55%
2255
April1st to 10thDay
9%5%245%35%5%6%8%47%
1980
11th to 20thDay
11%5%25%5%2445%6%50%
2100
21st to endDay
6%414335%45%8%58%
2210
May1st to 10thDay
6%31332446%8%60%
2340
11th to 20thDay
7%425%5%36%7%7%10%45%
2301
21st to endDay
6%425%5%35%7%8%10%46%
2531
June1st to 10thDay
8%5%27%8%47%8%11%11%31%
2340
11th to 20thDay
6%3246%48%9%10%14%35%
2340
21st to endDay
6%5%26%7%5%8%9%10%12%29%
2340
July1st to 10thDay
9%5%37%6%46%8%9%14%29%
2340
11th to 20thDay
7%5%37%7%5%8%9%10%12%27%
2340
21st to endDay
5%436%7%5%8%9%10%14%29%
2547
August1st to 10thDay
7%5%26%8%5%8%9%10%13%28%
2186
11th to 20thDay
10%6%36%6%5%8%9%10%12%25%
2125
21st to endDay
9%6%38%6%5%8%8%8%12%28%
2336
September1st to 10thDay
8%6%36%6%5%6%8%9%13%30%
1980
11th to 20thDay
7%5%36%7%46%8%8%11%35%
1980
21st to endDay
10%5%25%435%5%6%8%46%
1980
October1st to 10thDay
8%5%25%6%345%5%7%50%
1980
11th to 20thDay
6%41332445%7%63%
1938
21st to endDay
7%4244345%5%6%55%
1980
November1st to 10thDay
7%32342435%6%60%
1819
11th to 20thDay
9%424433446%56%
1710
21st to endDay
11%435%44445%7%50%
1710
December1st to 10thDay
13%7%25%5%3445%7%44%
1710
11th to 20thDay
15%7%36%43445%6%44%
2153
21st to endDay
20%8%35%433345%42%
3124
January1st to 10thNight
16%8%36%42445%7%42%
4109
11th to 20thNight
10%7%36%6%35%5%5%8%42%
4079
21st to endNight
18%10%45%433346%40%
4180
February1st to 10thNight
15%7%3443345%7%45%
2280
11th to 20thNight
15%7%35%5%2344449%
2218
21st to endNight
14%8%36%5%24346%45%
1884
March1st to 10thNight
11%6%3443446%8%49%
2195
11th to 20thNight
10%5%2442446%10%48%
2090
21st to endNight
10%5%2342435%8%53%
2256
April1st to 10thNight
10%4245%35%46%7%50%
1980
11th to 20thNight
8%5%26%5%345%6%7%49%
1821
21st to endNight
5%3134345%5%10%58%
1746
May1st to 10thNight
5%31232346%10%59%
1620
11th to 20thNight
5%425%5%35%47%10%52%
1592
21st to endNight
5%424435%5%7%10%52%
1744
June1st to 10thNight
7%6%35%5%36%6%7%13%40%
1620
11th to 20thNight
5%425%5%35%5%9%13%43%
1620
21st to endNight
6%425%6%36%7%8%13%41%
1620
July1st to 10thNight
5%426%6%47%7%10%14%37%
1620
11th to 20thNight
5%5%25%6%45%8%11%15%34%
1620
21st to endNight
34245%36%7%9%15%43%
1771
August1st to 10thNight
5%425%5%35%6%10%15%38%
1746
11th to 20thNight
5%425%6%5%6%8%10%16%32%
1776
21st to endNight
7%7%37%6%47%7%9%12%32%
2002
September1st to 10thNight
7%5%37%8%5%7%7%9%13%29%
1980
11th to 20thNight
9%5%36%7%47%7%8%10%33%
1980
21st to endNight
8%425%6%45%6%6%9%45%
1980
October1st to 10thNight
7%5%36%5%3445%7%50%
1980
11th to 20thNight
6%32443445%7%59%
2020
21st to endNight
8%425%5%25%5%6%6%52%
2376
November1st to 10thNight
6%425%435%5%5%7%54%
2254
11th to 20thNight
10%5%245%34446%53%
2470
21st to endNight
12%6%25%4245%46%50%
2470
December1st to 10thNight
12%5%35%5%3445%8%46%
2470
11th to 20thNight
14%7%3442345%7%47%
3042
21st to endNight
17%8%36%5%3445%5%40%
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
30%26%6%12%17%11%
2837
11th to 20thDay
30%26%7%12%12%14%
2876
21st to endDay
35%24%7%9%16%8%
3476
February1st to 10thDay
30%34%5%10%14%8%
1900
11th to 20thDay
28%36%5%7%15%11%
1858
21st to endDay
25%35%7%12%14%7%
1570
March1st to 10thDay
20%36%5%14%20%6%
1984
11th to 20thDay
20%35%12%13%13%7%
2090
21st to endDay
21%36%10%16%13%5%
2255
April1st to 10thDay
21%38%8%13%13%8%
1980
11th to 20thDay
21%37%6%15%15%7%
2100
21st to endDay
16%36%8%18%15%7%
2210
May1st to 10thDay
14%39%9%19%16%4
2340
11th to 20thDay
20%41%12%13%12%2
2305
21st to endDay
19%40%10%18%11%2
2531
June1st to 10thDay
25%42%11%18%41
2340
11th to 20thDay
20%43%15%17%5%1
2340
21st to endDay
28%42%13%11%42
2340
July1st to 10thDay
32%43%14%9%2
2275
11th to 20thDay
28%45%14%9%3
2271
21st to endDay
27%44%17%11%1
2405
August1st to 10thDay
25%44%15%13%2
2173
11th to 20thDay
31%42%14%11%3
2125
21st to endDay
34%43%11%9%3
2336
September1st to 10thDay
27%43%15%10%41
1980
11th to 20thDay
30%41%13%9%6%1
1980
21st to endDay
25%38%8%11%12%5%
1980
October1st to 10thDay
22%37%8%11%12%10%
1980
11th to 20thDay
18%36%7%14%17%8%
1938
21st to endDay
19%38%49%18%11%
1980
November1st to 10thDay
13%40%5%13%16%13%
1819
11th to 20thDay
18%40%5%11%17%9%
1710
21st to endDay
21%41%6%14%14%5%
1710
December1st to 10thDay
26%41%5%11%13%5%
1710
11th to 20thDay
30%33%6%9%16%6%
2150
21st to endDay
34%24%415%18%5%
3124
January1st to 10thNight
31%25%5%8%16%14%
4109
11th to 20thNight
33%25%5%11%18%8%
4079
21st to endNight
38%23%6%11%15%8%
4180
February1st to 10thNight
28%34%6%8%15%9%
2280
11th to 20thNight
29%35%5%7%12%12%
2219
21st to endNight
26%34%5%12%14%9%
1884
March1st to 10thNight
23%35%5%13%16%7%
2195
11th to 20thNight
21%35%8%16%13%7%
2090
21st to endNight
20%36%9%13%16%6%
2256
April1st to 10thNight
20%37%10%12%14%7%
1980
11th to 20thNight
22%36%6%12%17%6%
1821
21st to endNight
15%38%7%18%15%7%
1746
May1st to 10thNight
15%38%9%17%17%4
1620
11th to 20thNight
18%39%13%14%12%3
1593
21st to endNight
17%39%12%15%14%3
1745
June1st to 10thNight
22%39%15%16%7%
1620
11th to 20thNight
20%39%17%17%6%
1620
21st to endNight
24%40%15%13%6%1
1620
July1st to 10thNight
29%44%15%10%2
1575
11th to 20thNight
25%44%18%9%3
1566
21st to endNight
20%44%23%11%1
1672
August1st to 10thNight
19%42%21%13%4
1735
11th to 20thNight
26%44%17%11%2
1776
21st to endNight
32%44%13%8%31
2002
September1st to 10thNight
29%42%14%12%31
1980
11th to 20thNight
32%42%11%9%7%
1980
21st to endNight
25%38%10%11%12%5%
1980
October1st to 10thNight
23%38%7%9%12%11%
1980
11th to 20thNight
18%37%5%13%19%8%
2020
21st to endNight
21%38%5%8%17%11%
2376
November1st to 10thNight
13%41%5%13%15%13%
2254
11th to 20thNight
20%40%410%16%10%
2470
21st to endNight
24%40%6%11%12%7%
2470
December1st to 10thNight
22%40%6%13%14%5%
2470
11th to 20thNight
26%33%5%11%17%7%
3044
21st to endNight
33%25%414%18%5%
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
11%6%37%34%10%1
270
11th to 20thDay
7%8%28%37%17%4
270
21st to endDay
20%9%29%36%5%
297
February1st to 10thDay
17%8%28%28%18%1
270
11th to 20thDay
20%6%26%34%14%1
270
21st to endDay
12%7%31%37%13%1
225
March1st to 10thDay
10%6%27%41%14%1
354
11th to 20thDay
10%8%28%35%18%2
460
21st to endDay
12%8%27%32%20%2
490
April1st to 10thDay
11%6%26%34%20%2
420
11th to 20thDay
13%226%30%25%3
412
21st to endDay
6%319%37%29%5%
420
May1st to 10thDay
6%315%37%31%9%
423
11th to 20thDay
7%211%32%34%15%
447
21st to endDay
10%17%22%39%21%
485
June1st to 10thDay
11%6%24%41%18%
450
11th to 20thDay
8%6%20%37%28%
450
21st to endDay
8%15%14%42%30%
450
July1st to 10thDay
8%17%9%34%41%
445
11th to 20thDay
7%1411%38%39%
444
21st to endDay
5%6%11%43%35%
488
August1st to 10thDay
10%6%11%37%36%
446
11th to 20thDay
10%147%37%41%
439
21st to endDay
12%15%14%36%31%
495
September1st to 10thDay
10%17%12%37%32%
450
11th to 20thDay
12%26%18%40%23%
450
21st to endDay
11%16%18%40%23%
450
October1st to 10thDay
12%113%31%32%11%
450
11th to 20thDay
5%213%25%40%15%
450
21st to endDay
8%316%36%32%6%
495
November1st to 10thDay
10%316%34%29%8%
417
11th to 20thDay
11%321%39%21%5%
270
21st to endDay
11%423%37%20%6%
270
December1st to 10thDay
16%427%29%19%5%
270
11th to 20thDay
19%323%37%17%2
270
21st to endDay
16%6%19%34%18%7%
297
January1st to 10thNight
15%10%33%30%11%1
760
11th to 20thNight
12%8%27%34%17%2
760
21st to endNight
19%7%32%32%9%1
836
February1st to 10thNight
17%6%27%33%17%1
760
11th to 20thNight
18%8%24%35%13%1
743
21st to endNight
16%430%36%13%1
628
March1st to 10thNight
13%5%26%36%19%1
760
11th to 20thNight
12%423%35%24%2
760
21st to endNight
10%6%25%35%23%2
821
April1st to 10thNight
11%5%22%37%23%2
720
11th to 20thNight
11%423%31%27%3
579
21st to endNight
6%419%35%32%4
540
May1st to 10thNight
7%117%35%33%7%
540
11th to 20thNight
8%114%33%36%9%
531
21st to endNight
5%17%28%45%14%
584
June1st to 10thNight
11%7%23%47%11%
540
11th to 20thNight
6%15%20%43%25%
540
21st to endNight
7%2416%48%24%
540
July1st to 10thNight
5%25%12%45%32%
525
11th to 20thNight
7%126%45%39%
522
21st to endNight
448%53%32%
591
August1st to 10thNight
8%39%47%33%
537
11th to 20thNight
7%1311%45%33%
534
21st to endNight
11%25%17%38%27%
616
September1st to 10thNight
9%6%19%43%22%
720
11th to 20thNight
11%19%22%41%16%
720
21st to endNight
10%211%24%41%12%
720
October1st to 10thNight
10%218%30%32%8%
720
11th to 20thNight
6%316%32%36%8%
720
21st to endNight
10%317%35%31%4
792
November1st to 10thNight
10%421%38%25%3
740
11th to 20thNight
12%6%23%34%23%2
760
21st to endNight
12%5%24%35%21%2
760
December1st to 10thNight
15%6%24%31%21%4
760
11th to 20thNight
16%5%25%33%19%2
760
21st to endNight
18%6%23%32%19%2
836
Page generated at 2024-03-24 23:36:58. Version ac07

Copyright © 2024 Attilla Danko.


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