Charlottetown
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Charlottetown clear sky chart from 2005-11-05 to 2018-02-22.

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
22%
15707
11%
48613
5%
15662
28%
15662
12%
36727

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
13%
825
9%
2716
1%
821
22%
821
8%
2089
January16th to endNight
16%
854
13%
2801
4%
854
27%
854
10%
2091
February1st to 15thNight
14%
764
10%
2481
3%
761
23%
761
9%
1868
February16th to endNight
18%
659
8%
2112
3%
659
24%
659
9%
1654
March1st to 15thNight
20%
720
12%
2025
4%
720
28%
720
11%
1577
March16th to endNight
19%
747
13%
2091
6%
747
25%
747
13%
1611
April1st to 15thNight
19%
539
11%
1796
6%
539
24%
539
10%
1360
April16th to endNight
23%
540
15%
1645
7%
540
30%
540
16%
1168
May1st to 15thNight
24%
540
11%
1464
5%
540
29%
540
14%
1128
May16th to endNight
21%
561
11%
1496
2%
560
27%
560
15%
1136
June1st to 15thNight
24%
498
5%
1398
3%
498
26%
498
14%
1094
June16th to endNight
28%
360
8%
1260
4%
360
32%
360
12%
891
July1st to 15thNight
38%
387
8%
1237
6%
387
41%
387
21%
808
July16th to endNight
32%
565
9%
1419
5%
532
38%
532
17%
1063
August1st to 15thNight
41%
539
9%
1582
6%
535
44%
535
18%
1140
August16th to endNight
44%
573
13%
1794
8%
573
49%
573
20%
1214
September1st to 15thNight
34%
540
15%
1800
11%
540
41%
540
20%
1158
September16th to endNight
32%
663
20%
1988
12%
663
40%
663
20%
1318
October1st to 15thNight
29%
720
14%
2160
7%
720
35%
720
17%
1526
October16th to endNight
18%
778
13%
2343
5%
778
25%
778
11%
1782
November1st to 15thNight
20%
805
9%
2633
5%
805
25%
805
10%
2059
November16th to endNight
14%
825
7%
2730
3%
825
20%
825
6%
2215
December1st to 15thNight
9%
825
6%
2730
0%
825
15%
825
5%
2289
December16th to endNight
6%
880
5%
2912
1%
880
12%
880
4%
2488

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
18%10%47%5%3445%6%28%
49650
Night
19%10%47%6%34446%28%
48779
TransparencyDay
55%7%12%17%7%
49334
Night
56%6%11%17%6%
48613
SeeingDay
22%20%27%19%8%1
8129
Night
22%23%25%20%6%
15707

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%15%5%8%6%35%446%25%
1552
16th to endDay
15%9%5%10%7%45%45%6%23%
1774
February1st to 15thDay
15%13%48%6%36%5%4426%
1710
16th to endDay
14%13%48%6%45%5%6%7%24%
1507
March1st to 15thDay
14%11%6%8%7%35%5%5%6%25%
1924
16th to endDay
15%12%5%10%7%3333428%
2133
April1st to 15thDay
18%12%46%5%3435%7%28%
2153
16th to endDay
21%11%35%423336%32%
2313
May1st to 15thDay
23%10%45%5%34346%28%
2487
16th to endDay
21%9%35%6%2445%7%29%
2618
June1st to 15thDay
26%8%36%6%2445%6%25%
2571
16th to endDay
21%8%26%5%2446%7%29%
2700
July1st to 15thDay
14%6%35%5%245%5%8%38%
2635
16th to endDay
17%8%36%5%245%6%8%29%
2653
August1st to 15thDay
16%7%26%5%25%5%6%8%33%
2365
16th to endDay
13%6%25%4345%6%8%39%
2408
September1st to 15thDay
18%8%35%434447%35%
2160
16th to endDay
16%8%25%5%33446%38%
1968
October1st to 15thDay
19%7%37%5%35%45%7%30%
1800
16th to endDay
20%11%47%7%35%5%45%21%
1881
November1st to 15thDay
21%14%37%5%44446%22%
1554
16th to endDay
15%14%7%8%7%46%46%7%18%
1560
December1st to 15thDay
22%15%6%7%7%35%45%7%13%
1560
16th to endDay
22%14%6%8%7%45%445%15%
1664
January1st to 15thNight
17%13%46%5%35%5%5%6%25%
2716
16th to endNight
16%10%5%8%5%3445%7%27%
2801
February1st to 15thNight
17%13%37%6%335%45%28%
2480
16th to endNight
14%13%5%9%6%46%5%5%6%21%
2112
March1st to 15thNight
17%12%5%8%7%44345%25%
2013
16th to endNight
18%12%5%8%5%2423429%
2091
April1st to 15thNight
21%11%46%6%45%445%25%
1796
16th to endNight
23%10%45%423245%33%
1645
May1st to 15thNight
25%6%35%444445%29%
1464
16th to endNight
18%10%45%6%35%338%28%
1494
June1st to 15thNight
25%9%35%5%34346%26%
1398
16th to endNight
20%7%36%5%345%6%7%30%
1260
July1st to 15thNight
12%6%25%6%246%6%9%37%
1311
16th to endNight
16%6%27%6%35%5%7%8%29%
1515
August1st to 15thNight
16%6%25%7%45%5%5%8%32%
1593
16th to endNight
14%6%25%5%25%5%5%8%38%
1794
September1st to 15thNight
16%6%25%434337%41%
1800
16th to endNight
15%6%26%433446%42%
1988
October1st to 15thNight
18%7%35%5%3445%7%34%
2160
16th to endNight
24%9%47%5%24345%27%
2343
November1st to 15thNight
21%12%47%5%35%436%25%
2633
16th to endNight
21%13%48%5%345%46%21%
2730
December1st to 15thNight
22%12%48%7%35%447%17%
2730
16th to endNight
22%15%6%9%7%35%445%15%
2912

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
60%7%13%10%7%
1553
16th to endDay
59%8%10%13%8%
1774
February1st to 15thDay
60%410%17%5%
1713
16th to endDay
59%6%13%12%7%1
1507
March1st to 15thDay
58%5%10%16%7%
1935
16th to endDay
59%411%15%7%
2133
April1st to 15thDay
55%410%15%11%1
2153
16th to endDay
53%5%10%17%11%
2313
May1st to 15thDay
56%6%8%19%8%
2487
16th to endDay
54%8%10%18%6%
2622
June1st to 15thDay
58%7%10%16%6%
2571
16th to endDay
51%7%12%20%6%
2700
July1st to 15thDay
40%9%15%24%8%
2481
16th to endDay
50%8%15%18%6%
2486
August1st to 15thDay
47%9%14%22%6%
2351
16th to endDay
41%9%16%25%7%
2408
September1st to 15thDay
46%7%13%23%8%
2160
16th to endDay
46%6%11%23%10%
1968
October1st to 15thDay
53%6%12%20%7%
1800
16th to endDay
63%6%11%13%5%
1881
November1st to 15thDay
62%6%12%13%4
1554
16th to endDay
66%7%14%8%2
1560
December1st to 15thDay
73%7%9%7%1
1560
16th to endDay
74%5%7%8%3
1664
January1st to 15thNight
59%7%13%12%6%
2716
16th to endNight
56%6%11%18%6%
2801
February1st to 15thNight
58%5%11%13%9%
2481
16th to endNight
62%6%10%14%5%1
2112
March1st to 15thNight
60%5%9%15%7%1
2025
16th to endNight
59%47%17%8%1
2091
April1st to 15thNight
60%48%14%9%1
1796
16th to endNight
51%49%17%14%1
1645
May1st to 15thNight
56%6%8%21%6%1
1464
16th to endNight
54%6%11%19%7%
1496
June1st to 15thNight
59%6%11%15%7%
1398
16th to endNight
51%7%12%18%8%
1260
July1st to 15thNight
40%9%18%24%7%
1237
16th to endNight
49%10%16%17%6%
1419
August1st to 15thNight
47%9%14%21%6%
1582
16th to endNight
41%11%16%24%6%
1794
September1st to 15thNight
43%6%11%28%10%
1800
16th to endNight
42%7%12%27%10%
1988
October1st to 15thNight
49%6%13%23%7%
2160
16th to endNight
58%5%10%18%6%
2343
November1st to 15thNight
60%7%13%12%5%
2633
16th to endNight
64%8%13%10%3
2730
December1st to 15thNight
67%9%10%10%2
2730
16th to endNight
72%5%8%8%3
2912

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
21%30%33%10%4
285
16th to endDay
18%23%35%19%3
304
February1st to 15thDay
22%25%28%17%5%
281
16th to endDay
23%21%26%20%5%1
232
March1st to 15thDay
17%27%25%23%6%
263
16th to endDay
22%27%27%14%6%1
288
April1st to 15thDay
25%24%31%12%5%
270
16th to endDay
18%24%25%21%8%2
270
May1st to 15thDay
29%23%21%14%8%3
443
16th to endDay
23%22%26%19%7%
519
June1st to 15thDay
30%18%23%18%9%
495
16th to endDay
24%16%24%22%9%2
495
July1st to 15thDay
17%11%28%27%13%1
475
16th to endDay
21%14%25%23%13%2
514
August1st to 15thDay
19%7%23%25%18%5%
338
16th to endDay
17%9%24%28%15%5%
332
September1st to 15thDay
19%11%31%25%11%
315
16th to endDay
19%14%26%25%11%2
298
October1st to 15thDay
17%20%28%15%12%5%
270
16th to endDay
21%27%29%12%6%1
288
November1st to 15thDay
24%26%23%15%7%3
280
16th to endDay
23%28%27%16%31
285
December1st to 15thDay
30%27%25%14%2
285
16th to endDay
26%28%32%10%
304
January1st to 15thNight
21%30%28%16%3
825
16th to endNight
20%27%30%17%4
854
February1st to 15thNight
22%27%27%18%3
764
16th to endNight
21%28%24%18%6%
659
March1st to 15thNight
19%28%24%22%4
720
16th to endNight
23%27%23%18%6%
747
April1st to 15thNight
25%26%24%18%5%
539
16th to endNight
23%23%25%20%6%
540
May1st to 15thNight
26%21%23%17%8%2
540
16th to endNight
21%25%26%20%5%
561
June1st to 15thNight
24%21%24%23%4
498
16th to endNight
20%20%24%25%8%
360
July1st to 15thNight
16%11%28%33%10%
387
16th to endNight
17%20%23%26%10%
565
August1st to 15thNight
18%11%22%29%16%
539
16th to endNight
15%12%20%37%13%
573
September1st to 15thNight
19%13%27%30%7%
540
16th to endNight
18%15%29%25%9%
663
October1st to 15thNight
21%17%27%23%10%
720
16th to endNight
28%23%25%18%4
778
November1st to 15thNight
23%24%26%18%41
805
16th to endNight
27%29%22%15%41
825
December1st to 15thNight
26%31%26%11%4
825
16th to endNight
28%28%26%11%31
880
Page generated at 2018-02-23 12:21:34. Version ac04

Copyright 2018 A. Danko


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