  Any future detection of the calcium monohydroxide radical (CaOH) in stellar
and exoplanetary atmospheres will rely on accurate molecular opacity data.
Here, we present the first comprehensive molecular line list of CaOH covering
the \A--\X\ rotation-vibration-electronic and \X--\X\ rotation-vibration bands.
The newly computed OYT6 line list contains over 24.2 billion transitions
between 3.2 million energy levels with rotational excitation up to $J=175.5$.
It is applicable to temperatures up to $T=3000$~K and covers the
0\,--\,35\,000~cm$^{-1}$ range (wavelengths $\lambda > 0.29$~$\mu$m) for
rotational, rotation-vibration and the \A--\X\ electronic transition. The
strong band around 16\,000~cm$^{-1}$ ($\lambda = 0.63$~$\mu$m) is likely to be
of interest in future astronomical observations, particularly in hot rocky
exoplanets where temperatures can become extremely high. The OYT6 line list has
been generated using empirically-refined \X\ and \A\ state potential energy
surfaces, high-level \textit{ab initio} transition dipole moment surfaces and a
rigorous treatment of both Renner-Teller and spin-orbit coupling effects, which
are necessary for correctly modelling the CaOH spectrum. Post-processing of the
CaOH line list has been performed so as to tailor it to high-resolution
applications, i.e.\ by replacing calculated energy levels with more accurate
empirically-derived values (where available), hence improving the accuracy of
the predicted line positions in certain regions. The OYT6 line list is
available from the ExoMol database at http://www.exomol.com and the CDS
astronomical database.
