Hello Kevin, I make you my compliments for your good work !
I did some tests comparing your results ( first table) with those given from an old program (SUNEPH, bonus with The Compendium June 2003) : are the same. But I would like to point out two things: - EoT values normally used in gnomonic are given by (Local Civil Time - Local Solar Time) and have the opposite sign of those calculated by you (which are the values used in astronomy). - Normally in gnomonic azimuth is measured from South, positive westward, and not from North. In the *Equation** of Time Table for Year* I found some results that I did not understand. >From this table, putting Long. = 0 and TZ = 0, the values should be those of the EoT, but it’s not so. For example for March 17, the table gives the value 5m 32s while it should be -8m 21s (from first Table). In addition observing the values of March, I saw that they change in a "strange" way, while EoT in that month decreases continuously. Best wishes Gianni Ferrari 2014-06-11 18:05 GMT+02:00 Kevin Karney <[email protected]>: > Dear Friends > > I have been amusing myself with the astronomy of the Sun and have done a > very complete coding of Meeus' routines for finding EoT, altitudes, > azimuths, etc, etc. These deal with precession, nutation, aberration, > parallax and the differences between TT, UT1 and UTC time. This has > yielded routines of much greater precision than are generally required by > the gnomonist. However the speed of computers is such that lengthly > routines are hardly noticed. So I have produced a javascipt routine and > used it to prepare 4 tables for my website. They may be of interest to the > dialist. > > 1) For a given civil time and location - all the usual solar parameters > are calculated (nothing much new here - other than the precision) > 2) A table giving the noon Equation of Time and Longitude Correction over > any given year and location. > 3) A list table of civil - v - solar time, altitude, azimuth, declination > and local hour angle - for any starting date and time, covering any > increment of seconds. (Useful if you are trying to set a dial and waiting > for the Sun to shine) > 4) An EoT table of the kind used on many old sundials, where the date is > given every time the EoT changes by 1 minute. (Try changing the year from > one to the next and see the change due to the leap aye cycle) > > You can find these at > http://www.precisedirections.co.uk/Sundials/ > > Any comments, corrections, suggestions for additional tables or facilities > would be welcome. > The input of latitude, longitude is a bit basic, but it is hoped to > improve on this. Also, I plan to produce sunrise/solar noon/sunset tables. > If you use a browser that allows you to view a web-page's source (such as > Chrome or Firefox), you can see the astronomical routine that is used. > > Enjoy! > > Best wishes > Kevin > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > >
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