Port Elgin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Elgin clear sky chart from 2005-11-05 to 2017-12-20.

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
22%
15354
12%
47893
5%
15309
29%
15309
14%
35060

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
14%
750
11%
2643
1%
746
26%
746
10%
1923
January16th to endNight
16%
777
14%
2547
3%
777
29%
777
14%
1776
February1st to 15thNight
15%
704
9%
2286
2%
701
24%
701
13%
1691
February16th to endNight
17%
631
9%
2048
3%
631
25%
631
10%
1583
March1st to 15thNight
18%
720
14%
1989
4%
720
27%
720
15%
1522
March16th to endNight
19%
768
14%
2112
6%
768
27%
768
16%
1596
April1st to 15thNight
19%
542
12%
1792
6%
542
26%
542
12%
1363
April16th to endNight
24%
540
14%
1620
6%
540
30%
540
17%
1173
May1st to 15thNight
26%
540
9%
1500
4%
540
31%
540
16%
1153
May16th to endNight
20%
561
10%
1496
3%
560
26%
560
18%
1127
June1st to 15thNight
24%
438
6%
1338
3%
438
27%
438
13%
1035
June16th to endNight
29%
360
7%
1260
3%
360
33%
360
14%
919
July1st to 15thNight
32%
340
10%
1190
5%
340
40%
340
20%
763
July16th to endNight
30%
560
8%
1431
5%
527
31%
527
18%
1074
August1st to 15thNight
35%
539
8%
1608
5%
535
37%
535
20%
1160
August16th to endNight
35%
573
13%
1770
7%
573
40%
573
23%
1169
September1st to 15thNight
29%
540
16%
1800
9%
540
38%
540
23%
1147
September16th to endNight
34%
702
21%
2003
12%
702
42%
702
25%
1292
October1st to 15thNight
28%
720
16%
2160
8%
720
34%
720
22%
1453
October16th to endNight
18%
770
13%
2310
5%
770
25%
770
13%
1716
November1st to 15thNight
20%
805
10%
2661
5%
805
26%
805
11%
2022
November16th to endNight
20%
825
11%
2730
4%
825
29%
825
11%
2027
December1st to 15thNight
11%
825
10%
2730
1%
825
22%
825
8%
2091
December16th to endNight
10%
824
8%
2869
1%
824
18%
824
6%
2285

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
19%9%36%5%3445%6%30%
48954
Night
19%10%36%5%34446%30%
48056
TransparencyDay
53%6%12%18%7%
48635
Night
53%6%12%18%8%
47893
SeeingDay
25%15%31%19%6%1
7607
Night
24%15%32%21%5%
15354

By Month

Percentage Cloud Cover NE (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
15%16%49%5%34325%29%
1292
16th to endDay
14%10%5%9%5%34446%30%
1674
February1st to 15thDay
15%11%48%6%35%5%35%29%
1575
16th to endDay
14%14%6%7%6%4445%6%25%
1425
March1st to 15thDay
17%12%410%5%34445%27%
1957
16th to endDay
16%13%6%8%5%3334430%
2112
April1st to 15thDay
19%11%5%6%6%35%445%27%
2156
16th to endDay
22%10%25%43445%6%30%
2340
May1st to 15thDay
25%7%36%5%34445%27%
2451
16th to endDay
25%9%36%5%2435%6%27%
2618
June1st to 15thDay
28%8%36%5%34346%25%
2631
16th to endDay
23%7%26%43445%7%28%
2700
July1st to 15thDay
14%5%25%435%5%6%9%36%
2693
16th to endDay
17%7%36%5%35%5%7%8%30%
2633
August1st to 15thDay
17%6%25%5%245%5%9%33%
2340
16th to endDay
13%5%25%43446%9%40%
2432
September1st to 15thDay
19%6%25%43345%7%37%
2160
16th to endDay
18%6%24423347%41%
1955
October1st to 15thDay
19%7%35%435%35%7%36%
1800
16th to endDay
22%9%37%5%25%446%28%
1914
November1st to 15thDay
22%13%36%5%3333429%
1525
16th to endDay
17%11%5%7%6%25%5%5%5%26%
1560
December1st to 15thDay
23%12%6%6%5%34346%22%
1560
16th to endDay
20%17%6%7%5%34236%22%
1451
January1st to 15thNight
16%11%47%6%34445%31%
2643
16th to endNight
15%11%5%6%5%34446%33%
2547
February1st to 15thNight
18%12%37%6%25%446%28%
2285
16th to endNight
16%15%48%6%45%44425%
2048
March1st to 15thNight
19%11%47%6%35%445%28%
1977
16th to endNight
19%12%5%8%42433431%
2112
April1st to 15thNight
22%12%37%6%25%34426%
1792
16th to endNight
22%12%35%423345%32%
1620
May1st to 15thNight
25%9%25%5%335%46%28%
1500
16th to endNight
19%9%45%5%25%45%7%30%
1494
June1st to 15thNight
27%8%345%4425%7%24%
1338
16th to endNight
20%9%25%5%35%5%5%7%29%
1260
July1st to 15thNight
12%6%35%5%35%5%7%10%34%
1260
16th to endNight
16%6%27%7%35%5%5%9%29%
1527
August1st to 15thNight
16%7%25%6%436%6%7%33%
1620
16th to endNight
14%6%25%4345%5%9%37%
1770
September1st to 15thNight
17%5%24414348%42%
1800
16th to endNight
14%5%25%43435%6%44%
2003
October1st to 15thNight
18%5%35%5%33446%38%
2160
16th to endNight
26%9%35%5%24345%30%
2310
November1st to 15thNight
22%11%36%5%34345%28%
2661
16th to endNight
19%11%35%5%35%5%5%7%26%
2730
December1st to 15thNight
22%12%46%6%34445%24%
2730
16th to endNight
24%14%5%7%5%24345%21%
2869

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
59%5%12%12%8%1
1293
16th to endDay
55%5%10%15%13%
1674
February1st to 15thDay
57%412%17%7%
1578
16th to endDay
59%6%10%14%7%1
1425
March1st to 15thDay
59%410%17%7%1
1968
16th to endDay
57%5%10%17%7%1
2112
April1st to 15thDay
59%48%14%10%1
2156
16th to endDay
53%5%10%18%10%1
2340
May1st to 15thDay
58%5%9%17%8%
2451
16th to endDay
57%7%11%16%5%
2622
June1st to 15thDay
59%6%11%15%5%
2631
16th to endDay
54%7%12%18%5%
2700
July1st to 15thDay
42%8%16%23%9%
2534
16th to endDay
51%7%16%18%5%
2467
August1st to 15thDay
46%8%14%22%7%
2327
16th to endDay
40%8%19%23%7%
2432
September1st to 15thDay
47%415%21%10%
2160
16th to endDay
40%5%12%27%12%1
1955
October1st to 15thDay
46%414%25%8%
1800
16th to endDay
55%6%12%19%7%
1914
November1st to 15thDay
57%6%13%14%8%
1525
16th to endDay
57%7%15%13%5%
1560
December1st to 15thDay
61%7%13%14%3
1560
16th to endDay
63%5%12%11%6%
1451
January1st to 15thNight
55%6%13%16%8%
2643
16th to endNight
50%5%14%20%8%
2547
February1st to 15thNight
56%5%12%14%10%
2286
16th to endNight
60%6%10%13%8%1
2048
March1st to 15thNight
57%5%9%17%8%1
1989
16th to endNight
57%48%19%9%1
2112
April1st to 15thNight
59%5%7%13%11%2
1792
16th to endNight
54%410%16%12%1
1620
May1st to 15thNight
57%6%11%17%6%1
1500
16th to endNight
53%6%14%19%6%
1496
June1st to 15thNight
59%6%11%15%6%
1338
16th to endNight
53%8%13%17%6%
1260
July1st to 15thNight
41%9%18%23%7%
1190
16th to endNight
50%9%16%15%7%
1431
August1st to 15thNight
48%9%16%19%6%
1608
16th to endNight
41%8%19%24%6%
1770
September1st to 15thNight
41%6%13%29%10%
1800
16th to endNight
39%6%14%28%11%
2003
October1st to 15thNight
45%5%14%25%9%
2160
16th to endNight
55%5%11%18%7%
2310
November1st to 15thNight
58%7%13%13%7%
2661
16th to endNight
55%7%14%16%5%
2730
December1st to 15thNight
59%6%13%15%4
2730
16th to endNight
65%6%10%12%5%
2869

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
24%26%38%9%2
99
16th to endDay
19%16%43%17%2
256
February1st to 15thDay
20%20%35%15%6%
236
16th to endDay
25%17%33%18%4
212
March1st to 15thDay
22%24%33%14%41
268
16th to endDay
24%22%31%15%32
288
April1st to 15thDay
28%22%30%14%2
270
16th to endDay
23%22%30%16%5%1
270
May1st to 15thDay
34%14%24%17%7%1
407
16th to endDay
30%16%29%19%3
519
June1st to 15thDay
34%12%28%17%6%
495
16th to endDay
28%9%31%23%5%1
495
July1st to 15thDay
20%8%38%22%9%1
475
16th to endDay
22%6%31%29%9%
494
August1st to 15thDay
20%9%28%30%10%
313
16th to endDay
16%8%33%27%11%2
332
September1st to 15thDay
21%8%40%22%6%
315
16th to endDay
21%10%31%25%9%2
304
October1st to 15thDay
21%15%31%18%10%2
270
16th to endDay
23%28%24%16%41
288
November1st to 15thDay
27%20%25%15%9%1
280
16th to endDay
24%23%29%15%5%
285
December1st to 15thDay
27%25%33%11%2
285
16th to endDay
22%23%35%15%2
151
January1st to 15thNight
22%21%32%18%4
750
16th to endNight
22%19%37%15%4
777
February1st to 15thNight
24%14%39%17%2
704
16th to endNight
25%18%32%17%41
631
March1st to 15thNight
25%18%32%20%3
720
16th to endNight
24%17%30%19%7%
768
April1st to 15thNight
28%16%30%19%4
542
16th to endNight
31%10%30%21%5%
540
May1st to 15thNight
29%11%28%22%7%
540
16th to endNight
24%11%36%23%3
561
June1st to 15thNight
32%6%32%24%3
438
16th to endNight
21%6%35%27%8%
360
July1st to 15thNight
14%244%28%9%
340
16th to endNight
19%7%35%30%7%
560
August1st to 15thNight
18%5%33%30%11%
539
16th to endNight
16%7%35%30%9%
573
September1st to 15thNight
20%9%37%26%6%
540
16th to endNight
17%12%32%29%7%
702
October1st to 15thNight
20%13%34%22%10%
720
16th to endNight
28%21%29%15%4
770
November1st to 15thNight
26%17%30%18%6%1
805
16th to endNight
24%22%27%19%5%
825
December1st to 15thNight
28%23%31%13%2
825
16th to endNight
31%22%28%14%2
824
Page generated at 2017-12-21 08:04:42. Version ac04

Copyright 2017 A. Danko


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