  We present visibility measurements of the nearby Mira-like star R Doradus
taken over a wide range of wavelengths (650-990 nm). The observations were made
using MAPPIT (Masked APerture-Plane Interference Telescope), an interferometer
operating at the 3.9-m Anglo-Australian Telescope. We used a slit to mask the
telescope aperture and prism to disperse the interference pattern in
wavelength. We observed in R Dor strong decreases in visibility within the TiO
absorption bands. The results are in general agreement with theory but differ
in detail, suggesting that further work is needed to refine the theoretical
models.
