Hello John and all, Well, I quite agree with everyone, I had read the mails a bit quickly (it was late here). EOT = 0 for a certain moment in UT, and that moment can correspond to different days according to the longitude and time zones. It is the same thing as the seasons occurence that was discussed here a few months ago. As far as I am concerned, when I explain what EOT is to people, I always say and write that EOT is, as John says, null at mid-april, mid-june, around september the 1st, and at Christmas, and it is quite enough for a casual reader and even for dialists. Any change in the exact date from year to year (as any change in the daily value from year to year) is included in the width of the line that will be drawn on the sundial's surface, and included in the penumbra of the style's shadow. To design sundials I take average values given, for instance, in tables of (good) gnomonics books. Sundials are not theoretical things designed for a given year but are designed to last long.
Regards Jean-Paul ---------- > De : Phil Pappas <[EMAIL PROTECTED]> > A : [email protected] > Objet : 4/15:EOT=0=Taxes > Date : jeudi 15 avril 1999 17:51 > > Hello yall: > > What I've been trying to do is to tell my sundial customers that there are > four "magical" days of the year when their sundial keeps perfect Standard > Mean Time. (The dials are already corrected for longitude and DLS Time). On > these four days, they don't need a copy of the EOT to tell time. These are > also the only days that a sundial can be set, without EOT corrections, using > the time method. > > >From what I've learned, with your help, is that these dates may change from > year to year mostly due to leap year adjustments. This anual variation may > be as much as 24 hrs. But the exact moment of the event, EOT=0, is absolute > and occurs at the same time everywhere. The date, however, may be different > due to longitudinal time zone differences. > > I guess what I need is the AVERAGE four dates for The United States. Do you > think that it is ok to stick with: April 15, Jun. 14, Sep 1, and Dec 25 ? > > I can accept an error of about 1 minute (EOT=0 plus or minus 1), as my dials > can only be read to about 1 min. EOT will be -1 min. tomarrow. > > Thank you all, > > John Carmichael > Tucson > >
