supernova remnant which is developing as the ejecta and their associated shocks interact with the circumstellar material.

Perhaps the most dramatic of these observations are the optical observations which show the beautiful triple-ringed structure surrounding and illuminated by the supernova (Burrows et al. 1995). The inner ring is believed to represent an equatorial density enhancement in the circumstellar gas at the interface between a dense wind emitted from an earlier red-giant phase of the supernova progenitor star, Sk$-69^{\circ}$202, and a faster wind emitted by this star in more recent times (Crotts, Kunkel & Heathcote 1995; Plait et al. 1995). In the past few years, there has been increasing evidence for interaction of the expanding ejecta or the associated shocks with the equatorial ring, with small regions of enhanced H$\alpha$ emission, or ‘hotspots’ appearing just inside the ring. The first of these was detected by Pun et al. (1997), but studies of ground-based and [*Hubble Space Telescope*]{} ([*HST*]{}) data by Lawrence et al. (2000) show that this spot was detectable as far back as March 1995 (day 2933 since the supernova[^2]). Lawrence et al. also present evidence for up to eight additional regions of enhanced emission from about day 4300 (December 