  During detailed searches for new Galactic supernova remnants (SNRs) in the
Anglo Australian Observatory/United Kingdom Schmidt Telescope (AAO/UKST) HAlpha
survey of the southern Galactic plane, we also uncovered, for the first time,
possible associated HAlpha emission in the vicinity of about 24 known Galactic
SNRs previously known solely from radio or X-ray observations.The possible
optical counterparts to these known SNR were detected due to the 1 arcsecond
resolution and 5 Rayleigh sensitivity of this HAlpha survey.
  The newly discovered emission frequently exhibits the typical filamentary
form of other optically detected SNRs although sometimes the HAlpha emission
clouds or fragmented filaments largely inside an SNR extend over the radio
border. It is true that superposition of general diffuse and extended Galactic
emission in the region of these remnants is a complicating factor, but for many
optical candidates the HAlpha emission provides an excellent morphological and
positional match to the observed radio emission so that an association seems
clear.
  We have already published HAlpha images and confirmatory spectral
observations for several of the best optical counterparts to known SNRs but for
completeness and convenience we include them in our complete catalogue of
previously known radio detected SNRs for which we have now uncovered HAlpha
optical emission. For better visualisation of the optical emissions from these
faint supernova remnants and to enhance some low surface-brightness features we
also present quotient images of the HAlpha data divided by the accompanying
broad-band short red (SR) data. Out of 274 Galactic SNRs currently catalogued
and detected in the radio only ~20 had previous optical counterparts. We may
have now increased this by a further third by adding a further 24 candidate
optical counterparts.
