Interest in the hydrogen-deficient carbon (HdC) stars, and the R Coronae Borealis (RCB) stars in particular, has been rekindled by the realisation that these stars provide the potential for testing models in a number of areas. These include: pulsation theory; grain formation; grain evolution; stellar nucleosynthesis and extended stellar atmospheres.
Observational work on these objects has increased dramatically over the last 10 years. This has included both spectroscopic and photometric projects, see Lambert & Rao (1994) and Lawson et al. (1990).
We have continued to observe a number of the cool HdC stars in the Galaxy and the LMC and now have light curves exceeding 2000 days in duration for many of these objects. In particular, we are observing the RCB stars to investigate both the low amplitude, pulsation-related variations present at maximum light and the photometric behaviour during the large amplitude declines.