Hall's Harbour Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hall's Harbour Observatory clear sky chart from 2005-11-06 to 2024-02-25.

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
20%
23682
6%
80452
3%
23559
24%
23559
6%
67356

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
7%
837
5%
4687
0%
817
10%
817
1%
3779
January11th to 20thNight
10%
811
5%
4272
0%
786
13%
786
1%
3713
January21st to endNight
12%
831
3%
4516
2%
814
16%
814
3%
3778
February1st to 10thNight
9%
760
4%
2470
2%
760
12%
760
3%
2211
February11th to 20thNight
10%
743
5%
2406
1%
740
15%
740
4%
2116
February21st to endNight
15%
611
6%
1961
1%
611
20%
611
6%
1677
March1st to 10thNight
12%
720
7%
1985
2%
720
17%
720
6%
1725
March11th to 20thNight
17%
720
8%
1980
3%
720
20%
720
8%
1685
March21st to endNight
17%
792
10%
2178
2%
792
24%
792
9%
1810
April1st to 10thNight
13%
571
7%
1831
3%
571
18%
571
6%
1548
April11th to 20thNight
17%
534
11%
1666
4%
534
24%
534
9%
1333
April21st to endNight
21%
540
8%
1620
3%
540
26%
540
9%
1335
May1st to 10thNight
24%
540
8%
1589
4%
540
28%
540
8%
1336
May11th to 20thNight
26%
532
9%
1417
4%
532
31%
532
11%
1172
May21st to endNight
23%
583
8%
1551
3%
582
27%
582
12%
1282
June1st to 10thNight
26%
513
5%
1413
2%
513
29%
513
8%
1196
June11th to 20thNight
30%
360
10%
1260
5%
360
35%
360
9%
1014
June21st to endNight
29%
360
4%
1260
2%
360
30%
360
6%
1074
July1st to 10thNight
33%
350
4%
1225
1%
350
35%
350
9%
975
July11th to 20thNight
33%
451
5%
1321
3%
451
36%
451
11%
1077
July21st to endNight
37%
590
5%
1581
4%
558
38%
558
11%
1335
August1st to 10thNight
40%
538
7%
1600
5%
534
41%
534
12%
1260
August11th to 20thNight
34%
532
8%
1596
5%
532
37%
532
11%
1285
August21st to endNight
41%
594
10%
1849
6%
594
45%
594
13%
1435
September1st to 10thNight
37%
540
9%
1800
6%
540
42%
540
11%
1388
September11th to 20thNight
36%
641
13%
1901
8%
641
42%
641
14%
1452
September21st to endNight
30%
720
12%
2015
6%
720
34%
720
12%
1608
October1st to 10thNight
31%
720
12%
2160
5%
720
38%
720
13%
1648
October11th to 20thNight
24%
720
10%
2160
5%
720
29%
720
10%
1736
October21st to endNight
19%
792
9%
2376
3%
792
24%
792
6%
2007
November1st to 10thNight
18%
809
7%
2551
4%
809
21%
809
7%
2117
November11th to 20thNight
16%
850
8%
2660
4%
850
20%
850
6%
2307
November21st to endNight
14%
850
5%
2660
2%
850
18%
850
5%
2319
December1st to 10thNight
9%
850
4%
2660
0%
850
12%
850
3%
2397
December11th to 20thNight
7%
850
3%
3238
0%
849
10%
849
2%
2969
December21st to endNight
9%
927
1%
5037
0%
907
11%
907
1%
4257

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%11%48%6%3445%6%29%
78492
Night
20%13%5%9%7%34446%25%
80797
TransparencyDay
38%37%8%12%5%
78193
Night
41%36%8%11%4
80632
SeeingDay
24%19%31%19%6%1
15981
Night
25%18%30%21%5%
23709

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
16%18%7%11%9%5%5%35%418%
2219
11th to 20thDay
15%16%10%18%10%5%5%44411%
2657
21st to endDay
16%15%7%11%11%5%5%445%17%
3124
February1st to 10thDay
19%14%5%13%11%5%5%445%14%
1710
11th to 20thDay
17%17%412%11%5%5%44418%
1663
21st to endDay
11%12%7%10%9%45%446%28%
1389
March1st to 10thDay
15%16%7%9%9%5%5%33423%
1970
11th to 20thDay
14%10%6%10%7%36%446%30%
1980
21st to endDay
18%14%6%9%433336%31%
2178
April1st to 10thDay
22%13%47%5%35%445%28%
2128
11th to 20thDay
20%10%35%42445%7%35%
2240
21st to endDay
21%10%36%6%3445%7%30%
2340
May1st to 10thDay
23%11%46%5%35%5%5%7%27%
2371
11th to 20thDay
21%8%37%5%345%45%37%
2478
21st to endDay
19%8%36%6%3445%8%33%
2724
June1st to 10thDay
25%8%36%5%35%5%6%8%27%
2560
11th to 20thDay
22%8%35%6%3446%7%33%
2700
21st to endDay
22%10%46%6%35%5%6%6%29%
2700
July1st to 10thDay
16%6%26%5%345%6%9%38%
2700
11th to 20thDay
16%8%36%5%35%5%6%8%35%
2574
21st to endDay
19%8%37%6%35%5%6%8%31%
2641
August1st to 10thDay
15%7%35%5%36%5%5%8%39%
2327
11th to 20thDay
16%8%35%5%445%6%8%36%
2304
21st to endDay
14%7%24433447%47%
2507
September1st to 10thDay
16%6%24425%45%6%45%
2160
11th to 20thDay
18%6%35%5%24346%44%
2057
21st to endDay
17%7%35%423447%44%
1944
October1st to 10thDay
18%9%25%5%3445%6%40%
1800
11th to 20thDay
19%11%35%5%3446%8%34%
1800
21st to endDay
21%13%47%6%34447%29%
1977
November1st to 10thDay
22%13%47%5%34436%29%
1526
11th to 20thDay
18%17%6%8%8%35%35%5%23%
1520
21st to endDay
20%18%7%11%7%35%43419%
1520
December1st to 10thDay
23%19%8%12%6%3424415%
1520
11th to 20thDay
25%18%7%12%10%3432213%
1906
21st to endDay
22%18%10%13%7%3334413%
2578
January1st to 10thNight
15%16%9%15%10%345%45%16%
4715
11th to 20thNight
17%17%7%16%9%45%43414%
4308
21st to endNight
17%14%7%11%13%45%45%6%15%
4532
February1st to 10thNight
19%16%6%13%11%46%345%13%
2470
11th to 20thNight
18%14%6%11%11%5%5%445%17%
2403
21st to endNight
12%13%8%11%9%45%445%25%
1961
March1st to 10thNight
16%16%6%11%8%34335%26%
1976
11th to 20thNight
18%11%7%9%7%35%5%46%25%
1979
21st to endNight
19%13%6%8%5%33345%31%
2178
April1st to 10thNight
24%14%5%7%6%25%44426%
1831
11th to 20thNight
22%10%45%6%34446%31%
1666
21st to endNight
24%12%36%6%3445%430%
1620
May1st to 10thNight
23%12%36%6%35%45%6%28%
1589
11th to 20thNight
25%9%35%435%447%31%
1416
21st to endNight
18%11%37%5%25%5%5%7%31%
1550
June1st to 10thNight
26%7%46%7%45%5%5%6%25%
1413
11th to 20thNight
24%8%37%6%235%4434%
1260
21st to endNight
22%9%45%6%45%5%5%7%27%
1260
July1st to 10thNight
18%7%36%5%35%6%7%9%31%
1260
11th to 20thNight
15%10%37%5%37%7%7%8%28%
1364
21st to endNight
17%11%47%7%45%6%5%9%26%
1673
August1st to 10thNight
16%8%37%6%235%6%8%36%
1612
11th to 20thNight
17%10%5%6%6%45%5%7%8%28%
1596
21st to endNight
15%7%36%5%4346%7%40%
1849
September1st to 10thNight
14%7%36%5%345%6%6%41%
1800
11th to 20thNight
18%8%35%334346%42%
1901
21st to endNight
18%7%26%43445%8%38%
2015
October1st to 10thNight
18%6%25%5%445%5%7%39%
2160
11th to 20thNight
19%9%35%5%345%6%7%34%
2160
21st to endNight
26%13%36%5%33446%27%
2376
November1st to 10thNight
24%11%46%6%34445%29%
2551
11th to 20thNight
19%17%6%9%6%345%45%20%
2660
21st to endNight
22%17%6%8%5%34445%20%
2660
December1st to 10thNight
25%17%7%11%7%3444414%
2660
11th to 20thNight
23%19%6%12%9%3434414%
3293
21st to endNight
26%17%6%11%6%2333318%
5080

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
50%28%13%9%1
2220
11th to 20thDay
54%30%6%8%1
2657
21st to endDay
53%25%10%8%4
3124
February1st to 10thDay
49%35%7%6%3
1710
11th to 20thDay
48%37%8%5%1
1671
21st to endDay
41%37%8%9%41
1389
March1st to 10thDay
46%36%5%9%4
1974
11th to 20thDay
35%38%8%12%6%1
1980
21st to endDay
38%36%6%13%6%1
2178
April1st to 10thDay
40%37%5%10%7%1
2128
11th to 20thDay
33%36%6%13%11%1
2240
21st to endDay
34%37%8%13%6%1
2340
May1st to 10thDay
39%37%7%9%6%1
2371
11th to 20thDay
32%38%7%15%8%
2482
21st to endDay
31%39%9%14%6%1
2724
June1st to 10thDay
39%38%8%11%4
2560
11th to 20thDay
34%38%10%11%7%1
2700
21st to endDay
40%40%7%9%31
2700
July1st to 10thDay
30%40%12%13%6%
2625
11th to 20thDay
30%40%12%12%6%
2495
21st to endDay
32%40%8%15%4
2493
August1st to 10thDay
32%39%9%13%7%
2314
11th to 20thDay
30%39%9%16%6%
2304
21st to endDay
25%37%10%20%8%
2507
September1st to 10thDay
29%37%8%17%9%1
2160
11th to 20thDay
28%37%7%16%11%2
2057
21st to endDay
29%37%6%17%10%
1944
October1st to 10thDay
28%37%9%18%7%
1800
11th to 20thDay
34%38%9%15%4
1800
21st to endDay
37%38%7%11%6%
1977
November1st to 10thDay
35%41%6%12%7%
1526
11th to 20thDay
37%41%10%9%3
1520
21st to endDay
42%43%7%7%2
1520
December1st to 10thDay
46%41%7%5%1
1520
11th to 20thDay
55%33%6%5%1
1905
21st to endDay
57%27%10%5%1
2578
January1st to 10thNight
49%29%12%9%1
4715
11th to 20thNight
55%29%7%7%3
4308
21st to endNight
53%27%9%9%2
4532
February1st to 10thNight
49%36%6%6%3
2470
11th to 20thNight
45%37%8%6%21
2406
21st to endNight
41%37%7%12%3
1961
March1st to 10thNight
42%37%7%9%4
1985
11th to 20thNight
38%38%9%10%41
1980
21st to endNight
37%37%7%12%6%1
2178
April1st to 10thNight
41%37%6%8%7%1
1831
11th to 20thNight
36%35%6%13%10%
1666
21st to endNight
36%38%8%10%7%1
1620
May1st to 10thNight
38%38%7%11%6%
1589
11th to 20thNight
34%38%7%15%5%1
1417
21st to endNight
33%39%9%13%5%1
1551
June1st to 10thNight
37%40%8%11%3
1413
11th to 20thNight
36%37%7%14%6%1
1260
21st to endNight
38%41%8%8%31
1260
July1st to 10thNight
29%42%14%10%4
1225
11th to 20thNight
32%40%11%11%6%
1321
21st to endNight
33%41%10%10%5%
1581
August1st to 10thNight
29%39%10%17%5%
1600
11th to 20thNight
32%39%12%13%3
1596
21st to endNight
28%38%11%18%5%
1849
September1st to 10thNight
28%39%8%16%7%1
1800
11th to 20thNight
27%37%9%17%9%1
1901
21st to endNight
30%38%7%15%9%1
2015
October1st to 10thNight
27%38%9%18%9%
2160
11th to 20thNight
33%38%10%15%4
2160
21st to endNight
39%38%6%10%7%1
2376
November1st to 10thNight
32%43%7%12%6%
2551
11th to 20thNight
39%42%7%8%4
2660
21st to endNight
40%41%9%8%2
2660
December1st to 10thNight
44%42%7%6%1
2660
11th to 20thNight
53%34%46%2
3295
21st to endNight
54%27%8%9%2
5080

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
24%30%34%11%1
192
11th to 20thDay
29%27%30%11%2
370
21st to endDay
21%26%38%13%2
407
February1st to 10thDay
26%27%31%12%31
370
11th to 20thDay
27%34%27%11%1
366
21st to endDay
19%26%37%14%4
302
March1st to 10thDay
25%26%35%11%3
420
11th to 20thDay
23%27%35%12%31
420
21st to endDay
27%25%30%13%5%
462
April1st to 10thDay
35%26%27%10%3
420
11th to 20thDay
25%28%30%13%4
412
21st to endDay
25%20%29%16%10%
420
May1st to 10thDay
29%24%26%16%41
454
11th to 20thDay
25%17%28%23%7%
624
21st to endDay
25%16%34%20%5%1
680
June1st to 10thDay
31%11%30%21%7%1
630
11th to 20thDay
23%14%32%23%7%1
630
21st to endDay
26%11%30%25%7%2
630
July1st to 10thDay
20%7%37%25%10%1
620
11th to 20thDay
19%6%32%29%13%1
618
21st to endDay
22%7%33%28%10%1
581
August1st to 10thDay
13%7%35%33%12%1
446
11th to 20thDay
18%11%31%25%13%2
439
21st to endDay
16%13%27%28%14%2
495
September1st to 10thDay
18%9%34%27%10%1
450
11th to 20thDay
22%14%28%24%10%2
450
21st to endDay
20%15%32%19%12%2
432
October1st to 10thDay
21%16%27%24%9%3
360
11th to 20thDay
23%23%25%19%8%1
360
21st to endDay
25%22%31%16%5%1
396
November1st to 10thDay
26%22%32%16%31
365
11th to 20thDay
32%26%25%12%5%
370
21st to endDay
28%28%33%10%21
370
December1st to 10thDay
32%25%28%13%2
370
11th to 20thDay
36%34%20%11%
370
21st to endDay
29%27%33%6%41
280
January1st to 10thNight
27%27%31%13%2
850
11th to 20thNight
26%28%29%14%3
812
21st to endNight
21%28%33%15%3
836
February1st to 10thNight
28%27%28%15%2
760
11th to 20thNight
27%29%28%13%2
743
21st to endNight
19%25%34%18%2
611
March1st to 10thNight
25%25%32%15%3
720
11th to 20thNight
21%23%32%18%5%
720
21st to endNight
25%20%34%17%5%
792
April1st to 10thNight
32%20%29%16%3
571
11th to 20thNight
26%20%32%17%4
534
21st to endNight
29%15%30%21%41
540
May1st to 10thNight
29%11%31%21%6%1
540
11th to 20thNight
26%11%32%26%5%
532
21st to endNight
21%12%38%23%6%
583
June1st to 10thNight
27%10%31%25%7%
513
11th to 20thNight
26%6%31%31%6%1
360
21st to endNight
24%8%29%31%8%
360
July1st to 10thNight
18%5%34%35%7%
350
11th to 20thNight
15%7%35%32%11%
451
21st to endNight
19%5%28%39%9%
590
August1st to 10thNight
18%5%27%40%9%
538
11th to 20thNight
17%8%28%31%15%1
532
21st to endNight
16%7%28%33%15%1
594
September1st to 10thNight
16%9%31%34%10%1
540
11th to 20thNight
19%10%29%29%11%1
641
21st to endNight
19%12%34%23%11%1
720
October1st to 10thNight
20%11%34%24%10%1
720
11th to 20thNight
23%15%33%20%8%1
720
21st to endNight
32%22%24%17%4
792
November1st to 10thNight
29%19%30%17%41
809
11th to 20thNight
28%24%27%15%41
850
21st to endNight
30%23%28%17%2
850
December1st to 10thNight
31%24%31%12%2
850
11th to 20thNight
31%28%28%11%2
850
21st to endNight
31%25%26%14%3
935
Page generated at 2024-02-22 07:05:48. Version ac07

Copyright 2024 Attilla Danko


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