  We investigate the possible gravitational redshift values for boson stars
with a self-interaction, studying a wide range of possible masses. We find a
limiting value of $z_{lim} \simeq 0.687$ for stable boson star configurations.
We compare theoretical expectation with the observational capabilities in
several different wavebands, concluding that direct observation of boson stars
by this means will be extremely challenging. X-ray spectroscopy is perhaps the
most interesting possibility.
