Yes, a north facing dial is useful. My latitude is the same as Ghent (51N)
and we get a lot of sunshine from the north during the summer when
daylight is over 16 hours. The disadvantages are no dark skies during
the summer and VERY short days in the winter.
The equation for sunrise / sunset times we were discussing earlier is
useful here. The time angle (t) for sunrise / sunset is:
Cos t = -Tan Dec * Tan Lat
Putting in Dec = 23.44 and Lat = 51 gives t = 122.5 degrees from noon.
Dividing by 15 gives sunrise 8 hr 9.5 min before noon (3:50:30 AM) and
sunset at 8:09:30 PM.
The Azimuth is given by solving Sin Z = Cos Dec* Sin t / Cos Alt.
Here Dec = 23.44, t = 122.5 and Alt = 0, so Z = 50.7 degrees.
In this limiting case the sun rises 50.7 derees east of north and sets
50.7 degrees west of north so it would be on the north facing dial for a
useful length of time. This is sort of academic since it would also be on
the east and west faces and who is up at these hours anyway.
Roger Bailey
Canmore Alberta Canada
On Thu, 16
Jan 1997, Rik Hill wrote:
>
> >
> >The city of Ghent (Belgium) plans to place 4 sundials on one
> >of the chimneys of the town hall. The surfaces of the dials
> >will be squares, with sides 1.5 m. They will be placed about 35 m
> >above the ground..........
>
> I am a bit confused here. (I missed the original post on this which
> admittedly may be the source of my confusion.) If there are to be
> four dials on the sides of this chimney, one would be facing north
> and, at Ghent, not see sunlight during the year, no? -Rik
>
