Thanks to all the people who answered my query. I (think) I now understand what's going on. The clearest explanation is in the Supplement to the Astronomical Almanac. Regards, Brad
On Tue, Mar 2, 2010 at 1:43 AM, <[email protected]> wrote: > Not sure if this explanation helps but I found it. > "Ephemeris Longitude is the terrestrial dynamical longitude assuming a > uniformly rotating Earth. > True Longitude is calculated by correcting the Ephemeris Longitude for > the non-uniform rotation of Earth. > (T.L. = E.L. + 1.002738*ΔT/240, where ΔT(in seconds) = TDT - UT) > (ΔT = 66.2 s =000°16'35.5") > > Because ΔT is not known in advance, the value used in the predictions is > an > extrapolation based on pre-2009 measurements. The actual value is expected > to fall within ±0.3 seconds of the estimated ΔT used here". > > Patrick > > > > -----Original Message----- > From: Brad Lufkin <[email protected]> > To: Sundial Mailing List <[email protected]> > Sent: Mon, Mar 1, 2010 7:27 pm > Subject: Ephemeris Longitude > > Can anyone explain (or point me to a resource that explains) what the > "ephemeris longitude" is and why it's related to the geodetic longitude by > the expression: > > ephemeris longitude = 1.002738 (geodetic longitude) > > Regards, Brad > > ---------------------------------------------------https://lists.uni-koeln.de/mailman/listinfo/sundial > >
--------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
