Re: [guide-user] "Star" of Bethlehem

Laurent Zimmermann Apr 6, 2001

A quick look in "Help -> Quick Info" to see that Guide uses
delta T = 9908.6 s.
A difference of about 1/4 h with respect to SkyMap Pro.

In his book Astronomical Algorithms, Jean Meeus has mentioned several
formulae, published by several authors. They all give "slightly" different
values, but always around delta T = +2h50min (+/- 5 to 10 min) at the epoch
of the Bethleem star.



Regards,

Laurent Zimmermann
http://users.skynet.be/zmn/cab
----- Original Message -----
From: Chris Marriott <chris@...>
To: <guide-user@yahoogroups.com>
Sent: Thursday, April 05, 2001 10:20 AM
Subject: Re: [guide-user] "Star" of Bethlehem


> >
> > Perhaps the TT-UT correction used by Guide isn't accurate as
> > far back as 6 BC?
>
> Highly improbable that this would result in an error of hours. The
> uncertainty in "delta T" for 2000 years ago is a few minutes - it's
> certainly not hours!
>
> Presumably Guide can tell you what the "delta T" value is for a given map
> date. For 17th April 6BC my "SkyMap Pro" program uses a delta T value of
> +9117.5 seconds - what does "Guide" use for this date?