RE: Unusual sundial.
Hi Everyone, Thanks to all for the flood of info about the Campbell-Stokes recorder. About the sundial Fernando took photos of: I came across this sundial and wonder if it is our mystery sundials cousin. See this page: http://www.wengersundial.com/Picture.UniGlobe.html Food for thought. Chuck.
Re: EOT=0
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 : sundial@rrz.uni-koeln.de 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
Re: EOT=0
[EMAIL PROTECTED] wrote: Hello John and everybody on this list, I don't want to extend this discussion endlessly , but I am surprised to read that the value of EOT depends on longitude. [...] I believe John was referring to the (local civil) date (and time) of the occurrence of the zero EOT value; the date and time do depend on time zone, which is loosely coupled with longitude. I did not read his remarks as implying anything more than that. (His goal is to write a sundial manual for his customers, who may not be astronomically versed.) Of course John can correct me if I read his remarks or intent incorrectly... I agree with the rest of your remarks. Jim --- -- | Jim Cobb | 540 Arapeen Dr. #100 | [EMAIL PROTECTED] | | Parametric| Salt Lake City, UT | (801)-588-4632 | | Technology Corp. | 84108-1202 | Fax (801)-588-4650 | --- -- Hateful to me as the gates of Hades is that man who hides one thing in his heart and speaks another. -- Homer
4/15:EOT=0=Taxes
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
Unusual Sundial - Update
Dear Friends, Fernando Cabral visited the unusual sundial at Randolph Air Force Base in San Antonio Texas recently, and returned with some new photographs, including one showing the new broken part. The dial has been moved to a storage area, and it's future is questionable. The new photos can be seen at: http://www.shadow.net/~bobt/rafb/report The original (and obsolete) page can be seen at: http://www.shadow.net/~bobt/rafb Bob Terwilliger Fernando Cabral
RE: EOT=0 and longitude
Andrew James contributed: Please can someone point me to an explanation of exactly how the mean sun is derived? There is a clutch of very useful time-related definitions in the opening chapter of Whitaker's Almanack. Tony Moss
