At 10:13 AM 6/2/01 +0200, you wrote:

>Hi,
>Just trying to compute the contact times for the
>upcoming total solar eclipse. Guide seems to
>predict Delta_T (TD-UT) by an internal formula.

Hi, Hartwig,

I believe all astronomy programs use variously tweaked algorithms
internally. They're just "This works" curve fits from various sources as
far as I know, but they're all we have at this point.

[snipped]

>Is there any way to manually enter a value for
>Delta_T (TD-UT) in Guide ?

Yes, you can manually change individual coeffecients in the dT equation. Go
to http://www.projectpluto.com/update7.htm and click on
"(8 Aug 2000) Ability to re-define Delta-T" It works fine, I've been doing
it ever since Bill opened Guide for user dT input. I don't know how well it
will work for modern eclipses, though. I'm only using it for historic
eclipses between 1300 B.C. and 1620 A.D.

dT has been my passion (and my nemesis) for years. When (if?) I can get
something calculated that isn't just an algorithm, I'll post it.

Laren
--
http://www.got.net/~ldart
photography, short stories