The paper 'The OH ground-state masers in W3(OH) - I. Results for 1665 MHz' was published in Mon. Not. R. Astron. Soc. 350, 1253-1271 (2004). The reference position of the OH ground-state masers in W3(OH) quoted in that paper (Wright, Gray & Diamond 2004a) is wrong by approximately 54 mas in RA and 175 mas in Dec. The correct value of this reference position, which should be used when working with data in Wright et al. (2004a) and Wright, Gray & Diamond (2004b), is:
 RA = 02h 27m 03.8327s, Dec. = +61 52' 25.264" (J2000).
It appears that the incorrect position quoted in Wright et al. (2004a) was derived during a conversion from B1950 to J2000 coordinates with the Starlink routine coco. The original positions in 1950 coordinates, derived from MERLIN, were assumed to be equinox 1950, with an epoch at the date of the MERLIN observations, whereas the MERLIN positions were in fact fully corrected to equinox 1950 and epoch 1950.0. The authors would like to thank R. J. Cohen and S. Etoka for bringing this mistake to their attention, and to R. J. Cohen for discovering the likely cause.