Hi Larry,

"...can I still add places to the regular cities database the
way I did before?"

If what you mean is "can I edit geonames.dat and add in my
own cities", the answer is Yes. Some comments on the format of
the file are given at

http://www.projectpluto.com/random.htm#city_format

"...what is the current Delta-T default in the 6 June version?"

If what you're looking for is the actual value, you can
use Quick Info to see that the current value is 65.1 seconds.
If you're looking for the equation... I see that the documentation
at http://www.projectpluto.com/accuracy.htm#delta_t is a bit
outdated. (Though its basic point, that Guide assumes a
quadratic increase of 32.5 seconds/century^2, remains correct.)

The current formula works as follows: Guide has a table of
Delta-T values, the last two of which are 64.57 seconds (at the
start of 2004) and 64.85 seconds (at the start of 2006). That's
an increase of .14 seconds per year. Therefore, for dates
past 2006,

x = (year - 2006) = years since 1 Jan 2006;

Delta_T = 64.85 + .14 * x + 32.5 * x^2

Hope the above makes sense to you: it means Guide assumes
Delta-T was increasing by .14 seconds/year in 2006, but that the
rate is accelerating at 32.5 seconds/century^2.

If you really want to see the innards of this, the source code
for delta_t (and most basic astronomical functions in Guide) is
available at http://www.projectpluto.com/source.htm#astrocalc .
Some of it may make sense even if you don't "speak" C or C++. The
rest may be somewhat impenetrable, I'm afraid.

-- Bill