Shell Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shell Point clear sky chart from 2005-11-05 to

2017-09-12
.

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
60%
15549
22%
46905
18%
15511
65%
15511
31%
28478

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
39%
716
21%
2327
12%
716
52%
716
23%
1452
January16th to endNight
40%
768
24%
2346
16%
768
50%
768
26%
1499
February1st to 15thNight
44%
701
25%
2106
16%
699
54%
699
31%
1258
February16th to endNight
45%
631
25%
1893
14%
631
55%
631
30%
1156
March1st to 15thNight
52%
720
27%
2046
17%
720
59%
720
35%
1213
March16th to endNight
59%
768
27%
2112
18%
768
64%
768
40%
1209
April1st to 15thNight
58%
688
24%
1946
18%
688
63%
688
36%
1145
April16th to endNight
64%
540
31%
1764
25%
540
72%
540
40%
903
May1st to 15thNight
69%
539
27%
1619
22%
539
73%
539
41%
877
May16th to endNight
76%
561
25%
1682
22%
561
77%
561
42%
912
June1st to 15thNight
73%
540
16%
1620
15%
540
73%
540
31%
988
June16th to endNight
77%
540
15%
1620
14%
540
77%
540
30%
1006
July1st to 15thNight
79%
510
11%
1530
11%
510
79%
510
29%
971
July16th to endNight
79%
564
11%
1595
11%
531
79%
531
27%
1034
August1st to 15thNight
78%
539
8%
1760
9%
536
78%
536
22%
1160
August16th to endNight
71%
588
13%
1925
15%
588
72%
588
20%
1330
September1st to 15thNight
66%
707
10%
1944
10%
707
67%
707
21%
1405
September16th to endNight
65%
657
19%
1815
16%
657
67%
657
25%
1251
October1st to 15thNight
67%
660
31%
1815
26%
660
71%
660
40%
1059
October16th to endNight
62%
704
29%
2082
27%
704
67%
704
37%
1202
November1st to 15thNight
59%
700
30%
2182
26%
700
67%
700
36%
1204
November16th to endNight
50%
720
29%
2340
23%
720
61%
720
33%
1309
December1st to 15thNight
48%
720
26%
2340
23%
720
56%
720
30%
1378
December16th to endNight
47%
768
23%
2496
19%
768
53%
768
25%
1557

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
9%4245%35%5%6%8%42%
47736
Night
8%42443446%8%46%
47111
TransparencyDay
34%8%14%19%15%7%
47437
Night
34%7%13%19%17%8%
46914
SeeingDay
10%111%23%31%20%
5450
Night
11%316%27%30%10%
15559

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
14%5%245%2445%7%42%
1611
16th to endDay
12%6%246%24446%45%
1875
February1st to 15thDay
14%5%14424445%48%
1750
16th to endDay
14%5%14423335%50%
1580
March1st to 15thDay
7%4135%2446%8%52%
1913
16th to endDay
8%423424446%54%
2111
April1st to 15thDay
9%31442445%7%50%
2011
16th to endDay
6%313324347%56%
2193
May1st to 15thDay
6%31442446%8%52%
2331
16th to endDay
5%324435%6%7%10%45%
2431
June1st to 15thDay
7%415%6%37%8%11%11%31%
2340
16th to endDay
6%4246%48%7%9%13%30%
2340
July1st to 15thDay
6%436%6%47%8%9%13%29%
2340
16th to endDay
6%426%8%5%8%10%10%12%25%
2465
August1st to 15thDay
9%5%27%8%5%9%9%11%11%20%
2185
16th to endDay
9%6%36%6%47%8%8%11%27%
2264
September1st to 15thDay
9%5%36%5%5%6%8%9%10%29%
1936
16th to endDay
9%5%16%6%46%6%6%9%37%
1815
October1st to 15thDay
5%42342345%8%53%
1815
16th to endDay
7%423334435%56%
1789
November1st to 15thDay
6%31342335%6%59%
1673
16th to endDay
9%324323446%55%
1620
December1st to 15thDay
12%6%24423346%47%
1620
16th to endDay
16%6%35%43436%6%38%
1728
January1st to 15thNight
13%6%344345%46%43%
2327
16th to endNight
13%7%35%424346%43%
2346
February1st to 15thNight
13%5%2432234452%
2103
16th to endNight
13%7%235%2333449%
1893
March1st to 15thNight
8%5%2343335%8%49%
2046
16th to endNight
9%313313348%56%
2112
April1st to 15thNight
9%42442445%6%51%
1946
16th to endNight
5%313323448%58%
1764
May1st to 15thNight
6%31322445%9%56%
1619
16th to endNight
3213435%46%10%54%
1682
June1st to 15thNight
7%5%244345%7%14%41%
1620
16th to endNight
5%315%5%35%5%8%12%42%
1620
July1st to 15thNight
5%214435%7%10%14%39%
1620
16th to endNight
33235%47%7%9%15%36%
1703
August1st to 15thNight
5%5%15%5%46%7%10%16%31%
1771
16th to endNight
6%5%25%5%46%7%9%12%32%
1925
September1st to 15thNight
8%437%7%46%8%8%11%29%
1944
16th to endNight
8%5%25%6%46%7%7%8%36%
1815
October1st to 15thNight
5%32443335%7%55%
1815
16th to endNight
7%32442445%5%55%
2082
November1st to 15thNight
5%424424446%55%
2182
16th to endNight
10%5%24323435%55%
2340
December1st to 15thNight
11%5%2442445%8%47%
2340
16th to endNight
13%7%35%424346%43%
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
40%6%8%16%17%11%
1612
16th to endDay
39%48%14%21%10%
1875
February1st to 15thDay
38%46%15%21%14%
1752
16th to endDay
36%39%15%23%11%
1580
March1st to 15thDay
27%5%11%21%24%8%
1913
16th to endDay
29%412%22%19%11%
2112
April1st to 15thDay
31%5%11%19%22%10%
2011
16th to endDay
25%5%11%26%22%8%
2193
May1st to 15thDay
25%8%11%21%23%9%
2331
16th to endDay
26%9%17%26%15%3
2435
June1st to 15thDay
36%13%19%24%4
2340
16th to endDay
35%14%21%19%7%1
2340
July1st to 15thDay
37%15%26%17%1
2201
16th to endDay
40%16%24%16%2
2310
August1st to 15thDay
44%18%19%13%3
2172
16th to endDay
42%14%20%17%4
2264
September1st to 15thDay
41%14%22%13%6%1
1936
16th to endDay
39%10%13%18%13%4
1815
October1st to 15thDay
26%5%12%21%21%13%
1815
16th to endDay
29%47%14%25%17%
1789
November1st to 15thDay
25%48%21%25%15%
1673
16th to endDay
28%5%8%19%23%14%
1620
December1st to 15thDay
38%49%20%20%7%
1620
16th to endDay
43%5%9%19%14%7%
1728
January1st to 15thNight
40%5%7%14%21%10%
2327
16th to endNight
42%36%13%22%11%
2346
February1st to 15thNight
35%37%14%22%15%
2112
16th to endNight
38%37%16%20%14%
1893
March1st to 15thNight
32%5%9%22%21%9%
2046
16th to endNight
28%410%21%22%11%
2112
April1st to 15thNight
32%410%17%24%11%
1946
16th to endNight
23%6%10%28%20%10%
1764
May1st to 15thNight
25%5%13%21%23%10%
1620
16th to endNight
23%7%19%25%19%4
1684
June1st to 15thNight
32%9%23%25%9%
1620
16th to endNight
32%10%24%22%9%
1620
July1st to 15thNight
30%13%29%23%2
1530
16th to endNight
33%13%31%17%3
1595
August1st to 15thNight
35%14%30%16%2
1760
16th to endNight
40%14%21%18%4
1925
September1st to 15thNight
44%11%20%14%6%1
1944
16th to endNight
42%8%14%16%13%4
1815
October1st to 15thNight
28%6%11%18%20%13%
1815
16th to endNight
30%5%6%12%24%19%
2082
November1st to 15thNight
30%46%20%24%13%
2182
16th to endNight
32%48%16%20%17%
2340
December1st to 15thNight
35%410%23%20%6%
2340
16th to endNight
40%5%8%22%14%8%
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
11%5%31%26%15%10%
90
16th to endDay
15%13%21%37%10%1
96
February1st to 15thDay
7%336%25%23%3
90
16th to endDay
9%425%43%14%1
81
March1st to 15thDay
8%5%21%46%15%1
203
16th to endDay
11%422%30%28%3
288
April1st to 15thDay
11%226%29%26%3
270
16th to endDay
6%17%33%34%7%
270
May1st to 15thDay
8%214%34%30%10%
288
16th to endDay
9%5%24%37%21%
331
June1st to 15thDay
10%5%18%40%25%
315
16th to endDay
10%212%39%35%
315
July1st to 15thDay
7%36%36%45%
305
16th to endDay
6%412%37%39%
326
August1st to 15thDay
14%5%9%35%34%
313
16th to endDay
14%1210%31%40%
332
September1st to 15thDay
16%17%12%30%31%
299
16th to endDay
15%5%19%36%22%
254
October1st to 15thDay
10%19%29%35%14%
255
16th to endDay
6%316%34%30%8%
272
November1st to 15thDay
11%316%36%24%7%
181
16th to endDay
2318%43%21%11%
90
December1st to 15thDay
12%20%40%25%2
90
16th to endDay
23%117%31%13%12%
96
January1st to 15thNight
14%8%31%28%14%2
720
16th to endNight
17%6%28%31%15%1
768
February1st to 15thNight
16%6%26%30%17%1
704
16th to endNight
16%6%26%37%13%
631
March1st to 15thNight
10%426%36%20%1
720
16th to endNight
11%221%32%27%2
768
April1st to 15thNight
10%420%35%27%2
688
16th to endNight
8%220%27%36%5%
540
May1st to 15thNight
10%14%36%30%7%
540
16th to endNight
49%25%47%12%
563
June1st to 15thNight
12%5%20%45%16%
540
16th to endNight
7%314%47%27%
540
July1st to 15thNight
7%39%45%34%
510
16th to endNight
6%18%51%31%
564
August1st to 15thNight
9%48%45%32%
539
16th to endNight
10%316%40%28%
588
September1st to 15thNight
13%5%17%40%22%
707
16th to endNight
13%10%26%39%9%
657
October1st to 15thNight
8%115%30%36%8%
660
16th to endNight
9%317%30%33%5%
704
November1st to 15thNight
10%420%34%26%3
700
16th to endNight
12%5%25%32%21%2
720
December1st to 15thNight
14%5%24%30%22%2
720
16th to endNight
17%421%31%22%2
768
Page generated at 2017-09-13 07:39:16. Version ac04

Copyright 2017 A. Danko


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