Hi Romualdo,
Edit the file GUIDE.DAT and add a line such as (for examples) one of
the following:
ASTEROID_SYM=+16;
ASTEROID_SYM=d16;
ASTEROID_SYM=b16;x24;
ASTEROID_SYM=e26;e13,-11,8,8;e-13,-11,8,8;m-11,11;l0,18;l11,11;
(to convert the symbol to a "plus mark" of normal size, or a "diamond"
shape, or a box with an X inside that extends a bit past the edges of the
box, or a "happy face". Not that you'll generally want to get that fancy,
but if you do, you can.) Assorted other symbols for solar-system objects
and DSOs can be changed. For a complete list, see:
http://www.projectpluto.com/update7.htm#dso_symbols
For a complete description of how the symbols are defined:
http://www.projectpluto.com/tdf_info.htm#custom_symbols
-- Bill