Shelter Cove
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shelter Cove clear sky chart from 2005-11-05 to 2017-09-22.

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
51%
15202
22%
46976
17%
15163
57%
15163
27%
28223

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
43%
719
13%
2369
11%
716
48%
716
15%
1668
January16th to endNight
41%
768
22%
2496
17%
768
48%
768
17%
1688
February1st to 15thNight
39%
700
16%
2288
15%
700
42%
700
14%
1645
February16th to endNight
36%
632
15%
1957
9%
632
44%
632
15%
1394
March1st to 15thNight
37%
720
10%
1980
7%
720
40%
720
16%
1509
March16th to endNight
36%
768
13%
2112
7%
768
40%
768
17%
1536
April1st to 15thNight
36%
719
15%
1826
7%
719
41%
719
20%
1315
April16th to endNight
47%
642
20%
1722
10%
642
51%
642
32%
1038
May1st to 15thNight
51%
539
25%
1619
13%
539
61%
539
36%
837
May16th to endNight
51%
422
21%
1545
17%
422
59%
422
26%
825
June1st to 15thNight
51%
360
19%
1440
17%
360
62%
360
29%
703
June16th to endNight
61%
360
32%
1440
31%
360
77%
360
44%
550
July1st to 15thNight
75%
398
30%
1418
33%
398
82%
398
63%
499
July16th to endNight
74%
564
36%
1593
29%
531
86%
531
65%
642
August1st to 15thNight
82%
538
37%
1611
30%
535
85%
535
67%
641
August16th to endNight
78%
678
41%
1824
26%
678
84%
678
66%
808
September1st to 15thNight
78%
720
40%
1809
25%
720
82%
720
71%
816
September16th to endNight
67%
683
34%
1905
24%
683
75%
683
47%
968
October1st to 15thNight
56%
660
26%
1980
26%
660
63%
660
37%
1071
October16th to endNight
56%
704
25%
2112
20%
704
65%
704
27%
1269
November1st to 15thNight
49%
700
17%
2202
14%
700
54%
700
19%
1479
November16th to endNight
42%
720
12%
2520
12%
720
45%
720
16%
1687
December1st to 15thNight
39%
720
15%
2520
13%
720
43%
720
16%
1707
December16th to endNight
36%
768
14%
2688
13%
768
41%
768
13%
1928

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%413323347%51%
47900
Night
15%413323346%50%
47165
TransparencyDay
32%5%12%21%18%9%
47589
Night
35%5%11%20%18%9%
46977
SeeingDay
15%14%18%26%19%4
6048
Night
15%16%10%23%24%8%
15209

By Month

Percentage Cloud Cover SW (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
25%6%33434445%34%
1566
16th to endDay
26%5%25%412336%39%
1728
February1st to 15thDay
26%6%2332445%7%32%
1576
16th to endDay
23%6%25%5%2445%7%31%
1513
March1st to 15thDay
28%7%35%324448%27%
1980
16th to endDay
23%6%15%33445%8%32%
2112
April1st to 15thDay
16%7%35%5%35%6%7%7%31%
2120
16th to endDay
12%5%1442325%10%46%
2235
May1st to 15thDay
6%31332445%9%57%
2331
16th to endDay
9%41432445%8%51%
2564
June1st to 15thDay
10%323323347%55%
2520
16th to endDay
422211235%72%
2520
July1st to 15thDay
111212247%72%
2454
16th to endDay
211112448%70%
2468
August1st to 15thDay
112211247%73%
2340
16th to endDay
23121245%10%66%
2378
September1st to 15thDay
23121236%8%66%
2148
16th to endDay
6%21212338%67%
1867
October1st to 15thDay
12%412323335%57%
1650
16th to endDay
15%6%2421335%7%47%
1760
November1st to 15thDay
17%43432436%8%40%
1654
16th to endDay
21%5%25%434347%38%
1440
December1st to 15thDay
25%6%23423447%33%
1440
16th to endDay
32%425%324336%29%
1536
January1st to 15thNight
23%5%24434447%35%
2369
16th to endNight
23%5%2432335%6%38%
2496
February1st to 15thNight
25%6%25%323446%35%
2276
16th to endNight
22%8%3442435%8%33%
1957
March1st to 15thNight
29%6%24424447%28%
1980
16th to endNight
25%5%23424447%34%
2112
April1st to 15thNight
20%7%24423447%38%
1826
16th to endNight
12%32231335%9%51%
1722
May1st to 15thNight
5%2122345%7%62%
1619
16th to endNight
7%5%1432345%9%53%
1544
June1st to 15thNight
7%323323348%56%
1440
16th to endNight
42121123476%
1440
July1st to 15thNight
111222480%
1503
16th to endNight
11111113382%
1701
August1st to 15thNight
11111122481%
1620
16th to endNight
11111225%79%
1824
September1st to 15thNight
1111235%80%
1809
16th to endNight
6%312211235%68%
1905
October1st to 15thNight
10%412212246%59%
1980
16th to endNight
15%324322336%52%
2112
November1st to 15thNight
18%42443446%8%39%
2202
16th to endNight
22%5%2332336%7%38%
2520
December1st to 15thNight
27%6%1431335%7%35%
2520
16th to endNight
31%424323335%33%
2688

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
50%6%9%14%10%8%
1566
16th to endDay
48%47%13%15%10%
1728
February1st to 15thDay
51%5%9%15%15%2
1576
16th to endDay
52%7%13%18%6%1
1513
March1st to 15thDay
57%6%9%11%12%2
1980
16th to endDay
52%7%13%17%7%2
2112
April1st to 15thDay
50%8%13%19%8%
2120
16th to endDay
35%6%16%23%13%3
2235
May1st to 15thDay
24%7%15%30%15%6%
2331
16th to endDay
31%7%15%30%12%2
2568
June1st to 15thDay
28%5%17%20%20%6%
2520
16th to endDay
14%310%26%33%10%
2520
July1st to 15thDay
9%310%23%32%20%
2310
16th to endDay
10%29%18%27%31%
2313
August1st to 15thDay
8%210%28%32%17%
2324
16th to endDay
11%315%22%28%17%
2378
September1st to 15thDay
14%212%21%30%18%
2148
16th to endDay
16%413%26%24%15%
1867
October1st to 15thDay
29%49%25%21%9%
1650
16th to endDay
36%5%12%20%17%6%
1760
November1st to 15thDay
42%8%16%17%8%6%
1654
16th to endDay
47%6%11%14%13%6%
1440
December1st to 15thDay
50%5%10%18%11%3
1440
16th to endDay
56%6%7%11%12%4
1536
January1st to 15thNight
49%8%11%13%11%6%
2369
16th to endNight
47%5%8%14%13%9%
2496
February1st to 15thNight
51%7%10%13%14%2
2288
16th to endNight
49%7%12%18%8%2
1957
March1st to 15thNight
55%7%11%12%11%1
1980
16th to endNight
50%6%16%17%7%1
2112
April1st to 15thNight
46%7%15%19%9%
1826
16th to endNight
31%5%17%29%13%1
1722
May1st to 15thNight
20%7%13%34%19%5%
1620
16th to endNight
28%7%15%31%14%2
1545
June1st to 15thNight
26%5%18%24%19%6%
1440
16th to endNight
13%36%28%35%11%
1440
July1st to 15thNight
8%15%21%39%23%
1418
16th to endNight
8%26%14%31%36%
1593
August1st to 15thNight
7%27%25%32%23%
1611
16th to endNight
9%211%21%33%22%
1824
September1st to 15thNight
6%28%24%33%24%
1809
16th to endNight
18%49%28%23%15%
1905
October1st to 15thNight
26%410%24%24%10%
1980
16th to endNight
34%5%10%25%17%6%
2112
November1st to 15thNight
43%9%16%16%9%5%
2202
16th to endNight
45%8%12%16%12%5%
2520
December1st to 15thNight
48%5%11%16%14%3
2520
16th to endNight
53%6%10%13%11%4
2688

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
32%13%15%21%14%2
195
16th to endDay
30%16%14%17%14%7%
256
February1st to 15thDay
28%19%14%21%15%
236
16th to endDay
26%19%18%21%10%3
221
March1st to 15thDay
35%15%18%16%9%4
270
16th to endDay
26%20%25%19%6%2
288
April1st to 15thDay
20%25%19%21%10%2
269
16th to endDay
20%23%24%18%10%1
270
May1st to 15thDay
9%18%33%21%14%2
288
16th to endDay
9%19%19%23%21%6%
330
June1st to 15thDay
11%17%20%29%17%2
315
16th to endDay
6%11%24%39%14%2
315
July1st to 15thDay
38%14%34%33%5%
305
16th to endDay
211%16%33%27%9%
327
August1st to 15thDay
5%6%15%34%31%6%
315
16th to endDay
46%15%33%34%6%
332
September1st to 15thDay
5%7%15%32%28%10%
315
16th to endDay
7%13%13%30%26%7%
280
October1st to 15thDay
15%12%17%21%21%11%
255
16th to endDay
21%11%19%25%17%4
272
November1st to 15thDay
14%14%20%23%21%6%
210
16th to endDay
16%10%26%30%16%
60
December1st to 15thDay
53%8%15%20%3
60
16th to endDay
25%317%31%21%1
64
January1st to 15thNight
23%18%8%23%19%7%
720
16th to endNight
25%18%8%18%21%7%
768
February1st to 15thNight
24%19%10%24%18%3
704
16th to endNight
23%18%14%24%14%4
632
March1st to 15thNight
28%19%9%20%16%6%
720
16th to endNight
26%20%11%24%15%2
768
April1st to 15thNight
18%21%15%21%15%6%
719
16th to endNight
14%20%14%25%18%6%
642
May1st to 15thNight
6%19%17%29%21%4
540
16th to endNight
9%19%13%26%21%9%
423
June1st to 15thNight
7%19%15%29%23%4
360
16th to endNight
6%17%11%35%27%1
360
July1st to 15thNight
211%8%24%37%16%
398
16th to endNight
116%423%32%20%
564
August1st to 15thNight
19%328%40%16%
538
16th to endNight
28%6%22%43%15%
678
September1st to 15thNight
19%7%21%39%20%
720
16th to endNight
9%10%9%19%36%14%
683
October1st to 15thNight
13%12%11%23%26%13%
660
16th to endNight
17%11%7%24%27%12%
704
November1st to 15thNight
16%15%11%24%24%7%
700
16th to endNight
22%19%9%22%20%5%
720
December1st to 15thNight
25%19%11%24%13%5%
720
16th to endNight
26%20%11%22%14%3
768
Page generated at 2017-09-23 03:43:34. Version ac04

Copyright 2017 A. Danko


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