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I thought about this briefly.  I had always thought that the purpose of the 
shim or wedge adjustment was to tip the dial north or south so that dial is at 
the latitude it was originally designed for.  If the original dial has a 
built-in longitude correction, that could also be factored into a wedge which 
would have both a north-south and east-west axis.  But a wedge would not work 
if it moved the gnomon out of alignment with the with the rotation of the earth 
(or the celestial sphere).  I think a longitudinal adjustment would only work 
if he original dial had a time-zone offset included by rotating the hour lines 
with respect to the origin of the gnomon.  

 

Does this make sense?  It sounds like a good project for a 3-D printer.   

 

Jack

 

From: sundial <[email protected]> On Behalf Of Steve Lelievre
Sent: Sunday, April 2, 2023 5:16 PM
To: Michael Ossipoff <[email protected]>
Cc: Sundial List <[email protected]>
Subject: Re: Adjusting dial to new location

 

Michael,

Yes, I recognize that to get Mean Time involves Equation of Time adjustment and 
that Equation of Longitude can be handled there to give Standard Time (or DST).

But anyway, my inquiry was to seek an online wedge calculator. Nobody 
identified one and  a week seemed an adequate wait for responses, so I've just 
written one.  Anyone who's interested, please see

https://sundials.org/index.php/teachers-corner/sundial-construction/367-easy-dial-adjustment-for-your-latitude

Cheers,

Steve

 

On 2023-04-02 1:41 p.m., Michael Ossipoff wrote:

I just want to mention that the shim under the north or south edge of the dial 
is only for latitude. Longitude is corrected-for by changing the constant term 
of the Sundial-Time to Clock-Time conversion.

 

But usually Sundial-Time, Local True Solar Time, is what I’d want from a 
sundial.

 

On Sun, Mar 26, 2023 at 14:30 Steve Lelievre <[email protected] 
<mailto:[email protected]> > wrote:

Hi,

Can anyone point me to an existing online calculator for making a wedge 
to adjust a horizontal dial to a new latitude and longitude?

I am not asking for an explanation of how to do the calculation; I just 
want to be able to point people to a calculator that has already been 
proved on the internet. It should use the original location (latitude 
and longitude) and the new location to calculate the angle of slope of 
the wedge and the required rotation from the meridian.

Many thanks,

Steve


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