Ed,
To find True North, many dialists use Hindu Circles (also known as
Indian Circles). It's worth reading up on the method if you want to
learn a bit of theory about the sun's daily path as it relates to
sundials. There's a brief description of the method at bullet point 4 at
https://www.mysundial.ca/tsp/true_north_south.html but for a full
explanation you'll need to refer to sundialing books or websites.
If you prefer to use a magnetic compass, you can do so by adjusting for
magnetic declination. There's a handy tool for figuring out your local
magnetic declination at https://www.geomag.nrcan.gc.ca/calc/mdcal-en.php.
In practice, a simple and reliable method for finding North is to use
software to tell you what the sun's azimuth is at a certain instance
during the day, and to use the shadow of a perfectly vertical rod or a
plumb line (if you are out of the wind) as a pointer. A convenient time
to do this is when the sun is due south because that is when the shadow
of the rod or line points due north (in the Northern hemisphere). At
http://www.suncalc.org there is a suitable webpage (and also an Android
app called SunCalc) for telling you the current solar position. Another
option is my SDN (for Solar Data Now) offering, suitable for a phone's
browser or a desktop browser. It is less sophisticated than SunCalc but
should also do the job. The link is https://www.gnomoni.ca/sdn
The above methods are for finding North. If your need is only to check
that a sundial is correctly aligned, use the SunCalc or SDN to tell you
the current solar time at your location, and turn your sundial to match.
Steve
On 2021-02-18 1:04 p.m., Ed wrote:
I know this is a basic question for most here but I am just trying to
figure this out I have built a few prototypes out of cardboard.
I am lat long 30.730401 north
longitude 97 degrees 41.83 west
Thanks Ed
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