Charlottetown
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Charlottetown 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
25%
23868
7%
80506
3%
23743
28%
23743
7%
66857

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
13%
836
4%
4411
1%
817
17%
817
2%
3597
January11th to 20thNight
16%
846
9%
4372
1%
820
21%
820
3%
3377
January21st to endNight
20%
853
5%
4601
4%
834
26%
834
4%
3736
February1st to 10thNight
17%
760
7%
2470
3%
760
23%
760
6%
2046
February11th to 20thNight
13%
743
7%
2406
1%
740
20%
740
5%
2051
February21st to endNight
25%
628
8%
1996
4%
628
31%
628
9%
1644
March1st to 10thNight
19%
759
8%
2161
3%
759
24%
759
7%
1860
March11th to 20thNight
24%
760
9%
2090
5%
760
28%
760
8%
1773
March21st to endNight
22%
789
9%
2224
3%
789
28%
789
9%
1877
April1st to 10thNight
20%
540
7%
1800
5%
540
23%
540
6%
1518
April11th to 20thNight
25%
534
11%
1726
6%
534
30%
534
10%
1381
April21st to endNight
23%
540
10%
1620
4%
540
27%
540
9%
1333
May1st to 10thNight
27%
540
10%
1477
5%
540
32%
540
10%
1242
May11th to 20thNight
31%
532
10%
1417
5%
532
35%
532
12%
1158
May21st to endNight
26%
583
8%
1551
3%
582
29%
582
11%
1281
June1st to 10thNight
28%
540
4%
1440
2%
540
30%
540
8%
1267
June11th to 20thNight
36%
387
9%
1287
4%
387
40%
387
10%
1012
June21st to endNight
31%
360
3%
1260
2%
360
31%
360
6%
1077
July1st to 10thNight
40%
350
6%
1225
5%
350
41%
350
10%
966
July11th to 20thNight
40%
507
6%
1377
2%
507
43%
507
12%
1132
July21st to endNight
39%
590
6%
1486
4%
558
41%
558
11%
1252
August1st to 10thNight
47%
538
7%
1559
5%
534
49%
534
12%
1245
August11th to 20thNight
43%
532
8%
1596
5%
532
46%
532
11%
1293
August21st to endNight
47%
594
10%
1893
7%
594
51%
594
13%
1462
September1st to 10thNight
40%
540
9%
1800
6%
540
44%
540
12%
1393
September11th to 20thNight
40%
549
13%
1809
12%
549
44%
549
12%
1388
September21st to endNight
33%
720
12%
2071
6%
720
37%
720
13%
1628
October1st to 10thNight
34%
720
11%
2160
5%
720
40%
720
12%
1691
October11th to 20thNight
29%
720
9%
2160
4%
720
33%
720
9%
1763
October21st to endNight
18%
821
8%
2434
3%
821
22%
821
6%
2101
November1st to 10thNight
19%
830
6%
2547
2%
830
22%
830
7%
2182
November11th to 20thNight
20%
850
8%
2660
3%
850
25%
850
6%
2283
November21st to endNight
16%
850
4%
2660
2%
850
18%
850
5%
2343
December1st to 10thNight
11%
850
3%
2660
0%
850
14%
850
3%
2408
December11th to 20thNight
9%
850
3%
3251
0%
849
11%
849
2%
2986
December21st to endNight
10%
927
1%
4849
0%
907
12%
907
1%
4111

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%11%48%6%35%5%5%7%29%
79172
Night
18%11%48%6%35%45%6%28%
80852
TransparencyDay
38%37%8%12%5%
78870
Night
40%36%8%11%5%
80689
SeeingDay
23%15%31%21%8%1
16589
Night
25%14%30%24%7%1
23901

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 10thDay
14%13%7%19%11%5%5%44415%
2526
11th to 20thDay
13%12%5%9%8%45%5%5%6%27%
2530
21st to endDay
12%9%5%12%8%45%46%7%28%
3039
February1st to 10thDay
17%13%5%9%7%36%45%5%27%
1710
11th to 20thDay
17%14%49%7%45%5%5%5%26%
1663
21st to endDay
11%11%5%8%7%5%5%5%6%8%29%
1457
March1st to 10thDay
15%13%7%8%6%345%5%7%27%
2015
11th to 20thDay
11%11%6%10%9%46%5%5%6%27%
2090
21st to endDay
17%15%5%10%7%4333428%
2286
April1st to 10thDay
19%12%5%8%6%3445%6%29%
2160
11th to 20thDay
20%11%35%434448%34%
2181
21st to endDay
21%12%46%5%345%46%29%
2340
May1st to 10thDay
25%12%45%5%3435%6%27%
2481
11th to 20thDay
19%10%36%6%44447%33%
2478
21st to endDay
19%10%35%5%245%5%7%34%
2724
June1st to 10thDay
25%10%37%6%35%45%7%25%
2520
11th to 20thDay
20%7%36%6%3445%6%35%
2686
21st to endDay
23%9%36%5%3445%7%30%
2700
July1st to 10thDay
16%6%36%5%346%6%8%38%
2695
11th to 20thDay
14%7%25%6%35%5%7%8%37%
2520
21st to endDay
17%9%46%6%35%5%6%9%30%
2745
August1st to 10thDay
14%7%36%5%345%7%8%37%
2365
11th to 20thDay
16%6%37%6%36%6%8%9%32%
2304
21st to endDay
13%7%25%5%35%5%6%9%40%
2462
September1st to 10thDay
16%6%35%4345%5%9%39%
2160
11th to 20thDay
18%9%37%5%34445%38%
2147
21st to endDay
16%8%36%5%3445%7%39%
1888
October1st to 10thDay
18%8%37%5%35%46%7%34%
1800
11th to 20thDay
19%10%48%7%46%6%6%7%25%
1800
21st to endDay
19%13%48%7%35%5%6%7%23%
1922
November1st to 10thDay
18%14%48%7%5%5%5%46%25%
1529
11th to 20thDay
19%17%6%7%7%45%5%48%20%
1520
21st to endDay
17%13%7%11%7%46%46%7%18%
1520
December1st to 10thDay
21%16%8%8%7%35%5%6%7%14%
1520
11th to 20thDay
21%17%7%11%8%46%445%13%
1906
21st to endDay
20%13%7%13%8%44445%19%
2783
January1st to 10thNight
13%12%5%11%8%5%7%5%6%7%21%
4429
11th to 20thNight
16%13%5%9%7%345%5%6%27%
4440
21st to endNight
14%11%5%11%9%47%45%6%23%
4619
February1st to 10thNight
17%14%48%6%345%5%5%29%
2470
11th to 20thNight
16%14%49%8%45%5%5%6%24%
2403
21st to endNight
12%13%5%8%6%36%5%5%6%31%
1996
March1st to 10thNight
16%13%5%9%7%44445%27%
2152
11th to 20thNight
17%12%5%9%8%44346%27%
2089
21st to endNight
19%13%5%8%6%35%345%29%
2224
April1st to 10thNight
21%11%48%7%46%45%6%25%
1800
11th to 20thNight
22%11%445%44345%33%
1726
21st to endNight
23%13%5%7%5%33345%29%
1620
May1st to 10thNight
26%8%46%5%45%45%5%30%
1477
11th to 20thNight
20%9%35%6%44347%35%
1416
21st to endNight
16%9%46%6%35%45%9%33%
1550
June1st to 10thNight
27%9%46%5%45%346%26%
1440
11th to 20thNight
19%8%34434446%38%
1287
21st to endNight
22%11%37%5%345%6%6%28%
1260
July1st to 10thNight
15%7%35%7%35%6%6%9%35%
1260
11th to 20thNight
14%6%36%6%347%8%8%34%
1424
21st to endNight
15%8%37%7%46%5%6%8%31%
1573
August1st to 10thNight
14%6%25%6%35%6%6%10%36%
1570
11th to 20thNight
15%9%36%6%45%6%6%8%33%
1596
21st to endNight
14%5%36%5%25%45%9%42%
1893
September1st to 10thNight
13%6%36%5%45%447%42%
1800
11th to 20thNight
18%6%26%5%2445%6%42%
1809
21st to endNight
17%7%26%43445%7%41%
2071
October1st to 10thNight
18%7%36%5%3445%6%38%
2160
11th to 20thNight
18%8%47%6%45%46%7%32%
2160
21st to endNight
24%10%48%6%3445%6%26%
2434
November1st to 10thNight
19%12%5%7%6%36%445%28%
2547
11th to 20thNight
20%12%48%6%35%5%5%8%23%
2660
21st to endNight
24%14%5%8%6%45%5%46%20%
2660
December1st to 10thNight
23%16%5%9%7%36%45%7%16%
2660
11th to 20thNight
25%16%6%9%7%34335%18%
3293
21st to endNight
25%14%6%12%6%33445%19%
4884

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
61%28%8%31
2527
11th to 20thDay
43%28%10%12%7%
2530
21st to endDay
45%26%11%11%7%1
3039
February1st to 10thDay
43%35%9%8%5%
1710
11th to 20thDay
41%36%8%10%4
1671
21st to endDay
41%35%10%8%6%1
1457
March1st to 10thDay
42%35%8%12%4
2019
11th to 20thDay
38%36%7%13%41
2090
21st to endDay
41%35%8%10%5%1
2286
April1st to 10thDay
37%37%8%10%7%1
2160
11th to 20thDay
34%36%7%14%10%1
2181
21st to endDay
35%37%8%12%7%1
2340
May1st to 10thDay
39%37%7%10%7%1
2481
11th to 20thDay
34%39%7%15%6%
2482
21st to endDay
31%40%9%14%6%
2724
June1st to 10thDay
40%38%8%10%3
2520
11th to 20thDay
33%38%7%15%6%
2686
21st to endDay
38%39%8%10%41
2700
July1st to 10thDay
30%41%10%17%3
2620
11th to 20thDay
29%40%11%13%6%
2444
21st to endDay
34%41%9%13%3
2592
August1st to 10thDay
31%39%10%15%4
2351
11th to 20thDay
31%40%10%16%4
2304
21st to endDay
27%38%10%19%6%
2462
September1st to 10thDay
29%39%9%16%6%
2160
11th to 20thDay
31%37%8%14%8%
2147
21st to endDay
32%38%6%18%6%
1888
October1st to 10thDay
34%37%9%16%4
1800
11th to 20thDay
39%39%9%11%2
1800
21st to endDay
42%39%8%7%4
1922
November1st to 10thDay
38%42%7%10%3
1529
11th to 20thDay
39%42%9%8%2
1520
21st to endDay
41%42%10%6%2
1520
December1st to 10thDay
46%42%7%41
1520
11th to 20thDay
58%33%35%1
1905
21st to endDay
55%27%10%6%1
2783
January1st to 10thNight
49%30%12%8%1
4429
11th to 20thNight
44%28%9%12%6%
4440
21st to endNight
50%26%9%10%4
4619
February1st to 10thNight
40%35%8%9%7%1
2470
11th to 20thNight
43%36%7%8%6%1
2406
21st to endNight
39%35%8%13%5%1
1996
March1st to 10thNight
43%35%6%10%5%1
2161
11th to 20thNight
40%36%6%13%31
2090
21st to endNight
40%36%6%12%6%1
2224
April1st to 10thNight
41%37%7%7%7%1
1800
11th to 20thNight
36%35%6%13%9%1
1726
21st to endNight
37%37%7%10%9%1
1620
May1st to 10thNight
37%37%5%13%6%1
1477
11th to 20thNight
33%37%7%14%7%1
1417
21st to endNight
33%39%8%15%5%
1551
June1st to 10thNight
42%38%7%9%4
1440
11th to 20thNight
32%37%8%14%8%
1287
21st to endNight
41%39%10%5%5%
1260
July1st to 10thNight
29%41%11%15%4
1225
11th to 20thNight
31%41%11%13%5%
1377
21st to endNight
34%41%10%11%4
1486
August1st to 10thNight
30%39%9%18%5%
1559
11th to 20thNight
32%40%11%15%2
1596
21st to endNight
27%40%11%17%5%
1893
September1st to 10thNight
29%38%8%18%7%
1800
11th to 20thNight
30%36%8%17%9%1
1809
21st to endNight
29%38%8%18%7%
2071
October1st to 10thNight
30%38%9%17%6%
2160
11th to 20thNight
36%37%10%14%3
2160
21st to endNight
40%39%6%10%5%
2434
November1st to 10thNight
36%43%8%10%4
2547
11th to 20thNight
37%42%8%8%5%
2660
21st to endNight
40%42%10%6%2
2660
December1st to 10thNight
43%43%7%6%1
2660
11th to 20thNight
55%33%47%1
3295
21st to endNight
56%26%10%7%2
4884

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
25%21%37%14%3
370
11th to 20thDay
27%21%30%15%6%1
370
21st to endDay
18%16%38%24%4
407
February1st to 10thDay
27%21%29%16%5%1
370
11th to 20thDay
25%23%33%16%4
366
21st to endDay
20%19%31%24%5%2
307
March1st to 10thDay
22%18%32%22%4
427
11th to 20thDay
18%22%31%22%6%2
460
21st to endDay
28%19%31%14%7%1
490
April1st to 10thDay
27%20%37%12%4
420
11th to 20thDay
24%20%33%14%7%1
412
21st to endDay
24%17%28%21%9%1
420
May1st to 10thDay
32%15%27%18%5%2
564
11th to 20thDay
22%13%30%23%10%1
624
21st to endDay
24%13%35%20%7%1
680
June1st to 10thDay
32%9%29%20%9%1
630
11th to 20thDay
23%10%33%24%10%1
630
21st to endDay
27%7%28%27%9%2
630
July1st to 10thDay
19%5%35%28%11%2
620
11th to 20thDay
18%5%33%28%16%1
618
21st to endDay
22%5%30%31%11%2
685
August1st to 10thDay
13%330%36%14%3
484
11th to 20thDay
20%7%27%27%15%4
439
21st to endDay
16%9%27%31%14%4
495
September1st to 10thDay
16%7%35%28%12%2
450
11th to 20thDay
24%13%30%20%10%2
450
21st to endDay
19%15%30%22%11%3
403
October1st to 10thDay
20%14%28%21%14%4
360
11th to 20thDay
21%18%30%19%10%3
360
21st to endDay
24%23%30%16%6%1
396
November1st to 10thDay
24%24%29%16%5%2
365
11th to 20thDay
26%26%28%15%5%1
370
21st to endDay
28%24%28%16%21
370
December1st to 10thDay
32%18%31%16%31
370
11th to 20thDay
31%26%31%12%1
370
21st to endDay
25%23%34%15%11
407
January1st to 10thNight
26%19%32%19%3
850
11th to 20thNight
26%18%32%20%4
850
21st to endNight
22%17%33%22%6%1
859
February1st to 10thNight
27%17%30%21%4
760
11th to 20thNight
26%18%35%18%4
743
21st to endNight
20%16%31%25%8%1
628
March1st to 10thNight
23%15%37%21%3
760
11th to 20thNight
22%15%29%26%8%
760
21st to endNight
27%14%29%21%8%1
789
April1st to 10thNight
28%14%30%23%5%
540
11th to 20thNight
28%11%32%19%9%
534
21st to endNight
29%11%32%21%6%1
540
May1st to 10thNight
31%8%28%23%8%1
540
11th to 20thNight
24%8%29%29%8%1
532
21st to endNight
22%13%35%26%4
583
June1st to 10thNight
30%9%27%27%6%1
540
11th to 20thNight
20%7%32%32%8%1
387
21st to endNight
26%6%30%32%6%1
360
July1st to 10thNight
19%5%31%33%12%1
350
11th to 20thNight
17%5%31%37%10%
507
21st to endNight
19%6%28%36%11%1
590
August1st to 10thNight
16%426%40%12%1
538
11th to 20thNight
18%5%26%35%16%1
532
21st to endNight
14%7%24%37%17%1
594
September1st to 10thNight
16%7%31%35%10%1
540
11th to 20thNight
21%9%22%36%11%1
549
21st to endNight
22%9%34%27%8%1
720
October1st to 10thNight
24%10%26%29%11%1
720
11th to 20thNight
23%12%31%24%9%1
720
21st to endNight
30%18%28%20%3
821
November1st to 10thNight
27%17%32%20%41
830
11th to 20thNight
27%20%29%19%42
850
21st to endNight
33%19%27%18%3
850
December1st to 10thNight
31%19%30%15%5%
850
11th to 20thNight
28%24%31%14%3
850
21st to endNight
31%19%29%16%41
935
Page generated at 2024-03-25 00:37:02. Version ac07

Copyright © 2024 Attilla Danko.


Charlottetown Clear Sky Chart |Charts Home