EOT + Longitude Correction Table
Hello All, Some of you wrote me and seemed very confused with my inquiry about a way to get a EOT table that is longitude corrected. You ot understand what I wanted. So I'll try to explain it here. (thanks to everybody who sent me info on this) Sample letter: I still cannot figure out your EoT problem; EoT does not depend on longitude, it depends on an agreed absolute (GMT) and changes so little in any time zone you cannot see the difference on a dial. Maybe I am missing something, I often do these days. Yes, you are missing something. And it's so simple you will kick yourself. You're thinking too deeply! I'll try to explain... Of course you are correct in implying that EOT values are Universal and are basically the same all over the world, at any longitude or latitude and on any given date. You can use the same EOT graph with almost any sundial anywhere in the world. But you know that already. So far so good. But if somebody really wants to know clock time, then not only does he have to correct his sundial readings for EOT, but he also has to correct for his longitude (and Daylight Saving Time if applicable). This additional longitude correction is expressed as a plus or minus value in minutes and seconds. But you know this already. So far so good. Now this double correction is sometimes confusing to non-dialists (it's a triple correction if one has to correct for Daylight Savings too). So to reduce two time reading corrections into just one correction, you can add the EOT correction to the longitude correction since both expressed in minutes and seconds, and you come up with a new EOT graph or table that incorporates the longitude time correction in its values. Now do you get it? Neat huh! For my sundial customers, I usually build the longitude correction directly into my sundial faces so the customer doesn't have to do the longitude correction, just the EOT correction. This combined EOT+Longitude Correction Table is very useful if you have an antique pre-timezone sundial or any sundial that doesn't have a built-in longitude correction. The downside is that you have to make a unique customized EOT table for each sundial, depending on its particular longitude. Hope this helps -
Re: EOT + Longitude Correction Table
I combined all of the corrections for the table I prepared when helping with the faithful reconstruction of the Fredericton Soldiers Barracks sundial over a decade ago http://new-brunswick.net/new-brunswick/fredericton/page1.html. You can barely see the interpretive plaque low down on the wall. Some day I must put some better pictures of the sundial and plaque up on the Web. -- Richard Langley On Thu, 8 Jul 2004, John Carmichael wrote: Hello All, Some of you wrote me and seemed very confused with my inquiry about a way to get a EOT table that is longitude corrected. You ot understand what I wanted. So I'll try to explain it here. (thanks to everybody who sent me info on this) Sample letter: I still cannot figure out your EoT problem; EoT does not depend on longitude, it depends on an agreed absolute (GMT) and changes so little in any time zone you cannot see the difference on a dial. Maybe I am missing something, I often do these days. Yes, you are missing something. And it's so simple you will kick yourself. You're thinking too deeply! I'll try to explain... Of course you are correct in implying that EOT values are Universal and are basically the same all over the world, at any longitude or latitude and on any given date. You can use the same EOT graph with almost any sundial anywhere in the world. But you know that already. So far so good. But if somebody really wants to know clock time, then not only does he have to correct his sundial readings for EOT, but he also has to correct for his longitude (and Daylight Saving Time if applicable). This additional longitude correction is expressed as a plus or minus value in minutes and seconds. But you know this already. So far so good. Now this double correction is sometimes confusing to non-dialists (it's a triple correction if one has to correct for Daylight Savings too). So to reduce two time reading corrections into just one correction, you can add the EOT correction to the longitude correction since both expressed in minutes and seconds, and you come up with a new EOT graph or table that incorporates the longitude time correction in its values. Now do you get it? Neat huh! For my sundial customers, I usually build the longitude correction directly into my sundial faces so the customer doesn't have to do the longitude correction, just the EOT correction. This combined EOT+Longitude Correction Table is very useful if you have an antique pre-timezone sundial or any sundial that doesn't have a built-in longitude correction. The downside is that you have to make a unique customized EOT table for each sundial, depending on its particular longitude. Hope this helps === Richard B. LangleyE-mail: [EMAIL PROTECTED] Geodetic Research Laboratory Web: http://www.unb.ca/GGE/ Dept. of Geodesy and Geomatics EngineeringPhone:+1 506 453-5142 University of New Brunswick Fax: +1 506 453-4943 Fredericton, N.B., Canada E3B 5A3 Fredericton? Where's that? See: http://www.city.fredericton.nb.ca/ === -
Re: EOT + Longitude Correction Table
I might add, that you could combine all three time corrections into a single table or graph. (EOT, Longitude, and Daylight Saving Time). Then the sundial user would only have to do one single correction. But there's the minor problem that the dates for switching from Standard to Daylight Savings Time change each year (here in the US). Unfortunately, when congress passed the Daylight Savings legislation, they said that the switchover would be on the last or first Sunday of certain months instead of on certain dates. So you'd have to use the average switchover date in the table. On second thought, this might be a bad idea because the time correction would be an hour off for a few days of some years! - Original Message - From: John Carmichael [EMAIL PROTECTED] To: Sundial List sundial@rrz.uni-koeln.de Sent: Thursday, July 08, 2004 9:44 AM Subject: EOT + Longitude Correction Table Hello All, Some of you wrote me and seemed very confused with my inquiry about a way to get a EOT table that is longitude corrected. You ot understand what I wanted. So I'll try to explain it here. (thanks to everybody who sent me info on this) Sample letter: I still cannot figure out your EoT problem; EoT does not depend on longitude, it depends on an agreed absolute (GMT) and changes so little in any time zone you cannot see the difference on a dial. Maybe I am missing something, I often do these days. Yes, you are missing something. And it's so simple you will kick yourself. You're thinking too deeply! I'll try to explain... Of course you are correct in implying that EOT values are Universal and are basically the same all over the world, at any longitude or latitude and on any given date. You can use the same EOT graph with almost any sundial anywhere in the world. But you know that already. So far so good. But if somebody really wants to know clock time, then not only does he have to correct his sundial readings for EOT, but he also has to correct for his longitude (and Daylight Saving Time if applicable). This additional longitude correction is expressed as a plus or minus value in minutes and seconds. But you know this already. So far so good. Now this double correction is sometimes confusing to non-dialists (it's a triple correction if one has to correct for Daylight Savings too). So to reduce two time reading corrections into just one correction, you can add the EOT correction to the longitude correction since both expressed in minutes and seconds, and you come up with a new EOT graph or table that incorporates the longitude time correction in its values. Now do you get it? Neat huh! For my sundial customers, I usually build the longitude correction directly into my sundial faces so the customer doesn't have to do the longitude correction, just the EOT correction. This combined EOT+Longitude Correction Table is very useful if you have an antique pre-timezone sundial or any sundial that doesn't have a built-in longitude correction. The downside is that you have to make a unique customized EOT table for each sundial, depending on its particular longitude. Hope this helps - -
Re: EOT + Longitude Correction Table
Hi Bob, That's a wonderful idea! A Delta Cad Macroof the EOT correction with an option for including the longitude correction. That way, one could get a graph or a table in a DC drawing format. I think it would be a very useful tool for many dialists, not just myself. So far, several people have sent me Excell spreadsheets or websites that will do the calculations and present them in tabular form, but none of them produce a graph. If I had my druthers, I'd want the graph to be of an average year (not a leap year), and for an average time of day (12 noon). It would be very helpful, from a design point of view, if the DC macro also had options for making the graph stretched out (elongated)orcompressed horizontally because sometimes, when designing a sundial face there is not a lot of extra room for the graph, so it would be nice if itcould creategraphs of different shapes. If you can't include the stretching option, I suppose one could export a PDF of your DC macro drawing to Photoshop and use its stretch tool. Great idea Bob, if you ever do this, be sure to let everybody know about it! Have fun p.s. Hope you don't mind me ccing this letter to the Sundial List. - Original Message - From: [EMAIL PROTECTED] To: John Carmichael Sent: Thursday, July 08, 2004 10:09 AM Subject: Re: EOT + Longitude Correction Table John, I understand what you are saying about a graph that combines both eot and long-correction for dials that do not have long-correction built in. In the past I have written PostScript applications that would do just exactly that.As I recall, I started to convert that process into a DeltaCad Macro a couple of years ago. It should be easy to do. Let me know if you want me to pursue that while I am kindof inactive up here in Idaho this summer. Bob Hough - ShadowMaster -- Original message -- Hello All, Some of you wrote me and seemed very confused with my inquiry about a way to get a EOT table that is longitude corrected. You ot understand what I wanted. So I'll try to explain it here. (thanks to everybody who sent me info on this) Sample letter: "I still cannot figure out your EoT problem; EoT does not depend on longitude, it depends on an agreed absolute (GMT) and changes so little in any time zone you cannot see the difference on a dial. Maybe I am missing something, I often do these days." Yes, you are missing something. And it's so simple you will kick yourself. You're thinking too deeply! I'll try to explain... Of course you are correct in implying that EOT values are "Universal" and are basically the same all over the world, at any longitude or latitude and on any given date. You can use the same EOT graph with almost any sundial anywhere in the world. But you know that already. So far so good. But if somebody really wants to know "clock" time, then not only does he have to correct his sundial readings for EOT, but he also has to correct for his longitude (and Daylight Saving Time if applicable). This additional longitude correction is expressed as a plus or minus value in minutes and seconds. But you know this already. So far so good. Now this double correction is sometimes confusing to non-dialists (it's a triple correction if one has to correct for Daylight Savings too). So to reduce two time reading corrections into just one correction, you can add the EOT correction to the longitude correction since both expressed in minutes and seconds, and you come up with a new EOT graph or table that incorporates the longitude time correction in its values. Now do you get it? Neat huh! For my sundial customers, I usually build the longitude correction directly into my sundial faces so the customer doesn't have to do the longitude correction, just the EOT correction. This combined EOT+Longitude Correction Table is very useful if you have an antique pre-timezone sundial or any sundial that doesn't have a built-in longitude correction. The downside is that you have to make a unique customized EOT table for each sundial, depending on its particular longitude. Hope this helps -
yorkshire dials
Thanks to all who responded to my request for guidance to the best Yorkshire dials. You are all too kind. To assuage your curiosity it is possibly for a possible chapter for a possible book (perhaps). Frank 55N 1W -- Frank Evans [EMAIL PROTECTED] -
Re: yorkshire dials
Frank et al, Greetings fellow dialists, Thanks to all who responded to my request for guidance to the best Yorkshire dials. You are all too kind. To assuage your curiosity it is possibly for a possible chapter for a possible book (perhaps). Frank 55N 1W Following on from my earlier comment the dial with the mining pick gnomon is in in Middleton Tyas but that may be in Durham. Tony Moss -
