I tried the app. I used 40, -75 and 45, -70. It just said to use a 5
degree wedge and said nothing about a longitude correction.
I communicated to Steve privately last week. I said that a longitude
correction was a rotation around the gnomon. Does anybody else believe
this? One of the books, I can't remember which, calls this The Universal
Sundial Principle. It says that two dials with the same orientation in
space with respect to the sun will read the same time, regardless of
where on earth they are.
---
On 2023-04-02 19:24, Steve Lelievre wrote:
Jack,
Try out my calculator! You can specify a time zone meridian for the dial at its original location, or at its new location, or both. If there is an effective longitude change, it'll tell you how to position (twist) the dial on the wedge and how to orient the wedge itself, turning it away (rotating it ) from the meridian line.
Steve
On 2023-04-02 3:59 p.m., Jack Aubert wrote:
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 <sundial-boun...@uni-koeln.de> On Behalf Of Steve Lelievre
Sent: Sunday, April 2, 2023 5:16 PM
To: Michael Ossipoff <email9648...@gmail.com>
Cc: Sundial List <sundial@uni-koeln.de>
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 <steve.lelievre.can...@gmail.com> 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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