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   PR # 21187
       Observations of the two clusters of galaxies, A1650 and A2009, are
    proposed. These clusters are chosen from the sample of 7 X-ray select
    ed featureless well-relaxed hot clusters with high expected Sunyaev- 
    Zeldovich brightness and contrast and without bright nearby radio    
    sources. Of this set, 4 clusters have already been observed with Asca
    during the PV and AO1 phases. Clusters of this sample are good candid
    ates for reliable determination of the Hubble constant through the   
    measurement of their SZ decrements. The 2 proposed clusters are suffi
    ciently bright for Asca to be able to map the gas temperature, which,
    along with the requirement of spherical symmetry (hopefully satisfied
    in these relaxed clusters), is necessary for the Ho determination.   
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