HELP: how to include logo in LaTeX letter style

[Roberto Lionello]

Hi, I have a TeX file which allows one to write a letter with the logo
of our Department of Astronomy. If I make a PostScript file with just
the logo and no text, is it possible to use it with LaTeX letter style?
I mean is it possible to tell LaTeX to include that picture at the top
of each page and then to behave normally as if I were using a blank sheet?
How? Thank you. Please answer via e-mail.
Regards,

Roberto
--
+----------------------------------------------------------------------------+
| RRRRRR | Dipartimento di Astronomia e Scienza dello Spazio |
| R R | Universita` degli Studi di Firenze |
| L R R | Largo Enrico Fermi, 5 - 50125 Firenze ITALY |
| L RRRRRR Roberto | Tel: (+39) 55 2752 268 |
| L R R Lionello | Fax: (+39) 55 224193 |
| L R R | E-mail: lio...@arcetri.astro.it |
| L R R |----------------------------------------------------|
| L | A Elbereth Gilthoniel, |
| LLLLLLL | -J.R.R. TOLKIEN, The Fellowship of the Ring (1954) |
+----------------------------------------------------------------------------+

[Roberto Lionello]

I have been told to use bop-hook. I tried

\special{!userdict begin /bop-hook{(logodip.ps) run}def end}

where logodip.ps contains the logo.
Alas, it does not work! :-( Any suggestion? Thanks.