Here's my attempt at using SOFA to perform planetary reduction:
It performs annual aberration correction, but that's the most accurate step it stops at. It does not perform diurnal aberration, polar motion, etc. It gets to the sub arc second accuracy.
From what I understand, SOFA ...
If your friend is happy to use a tablet device while in the tub your friend could download the Heavens Above app, select the Interactive sky chart option, enter the co-ords or the name of the nearest town.
There are several apps for phones and tablets that do this.
They use the devices 3D accelerometer + compass and knowledge of location (from GPS, internet or even user entered) to determine the attitude (orientation) of the device, i.e. where it's pointing relative to the Earth.
They use its clock/calendar and an internal (or external) ephemeris to convert ...