  Redshift observations of galaxies outside the Local Group are fairly common
in extragalactic astrophysics. If redshifts are interpreted as arising from
radial velocities, these must be corrected by the contamination of the solar
motion. We discuss the details of such correction in the way it was performed
by the American astronomer Edwin Hubble in his 1929 seminal paper. The
investigations of spiral nebulae undertaken by the Swedish astronomer Knut
Lundmark, in 1924, are also considered in this context.
