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>George Huxtable wrote:
> This has table 10A giving delta-T for various years from 1620, for which
he
> quotes +121 sec, to 1998. Unfortunately, this table says nothing about the
> errors involved. Meeus' Table 10A differs significantly (for dates around
> 1620) from the numbers given in my 1984 Astronomical Almanac, which gives
> +98 sec for 1621. Meeus states that the Astronomical Almanac values have
> been "corrected" according to a new value for tidal acceleration of the
> Moon, given in note S055, issued by the Bureau des Longitudes, Paris, in
> 1997, by Chapront et al. The tables agree, for more recent dates.
>
> Meeus (1998) also gives equation 10.2 giving delta-T "from +948 to + 1600,
> and after the year +2000". in seconds, as-
> 102 + 102 t + 25.3 t-squared,  (Meeus eq 10.2, on page 78)
>
> where t is the time in centuries from year 2000, so for 1600, t = -4.0
>
> This is quite different from the expression Omar quoted, as
>  "DeltaT=50.6+T*(67.5+T*22.5)      (T in centuries since J2000) "
> se perhaps we have different editions. Has that equation 10.2 (1998) been
> subsequently revised in a later edition of Meeus? Otherwise, where did
Omar
> get it from?.

I have the first edition (1991), to which I have applied the "errata" by
the author (1995). The formula is to be used between years 948 and 1620
I was calcuting  dT for 1580, so I used it.

Omar

   

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