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   53035
   We propose to observe the high X-ray luminosity cluster Abell 1423
   (z=0.21). The ASCA data will be combined with ROSAT HRI data and a map
   of the Sunyaev-Zel'dovich decrement from the Ryle Telescope to
   constrain the properties of the cluster and derive an estimate of the
   Hubble Constant. The proposed target is part of a large sample for
   which we have ROSAT, ASCA and Ryle data that will permit the direct
   determination of the cluster temperature function at a redshift of 0.2
   and provide a sample of S-Z detections free from gross projection
   effects.
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