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We present accurate $I$-band surface photometry of the nearby spiral galaxy M31. A $4^\circ\times3^\circ$ image of this galaxy, at $2''$ resolution, has been constructed by mosaicking together 41 $2048\times2048$ CCD frames obtained using the KPNO/CWRU Burrell Schmidt telescope. The individual CCD frames have an unvignetted, circular field of view of $\sim1^\circ$ diameter; generous overlap between the 41 CCD frames allows them to be matched to one another with a high degree of accuracy. The distinctive features of our dataset are: (1) the wide angular extent of the image makes accurate determination of the ``sky'' background possible; and (2) the relatively high angular resolution ($2''$) enables identification and removal of bright foreground stars. By measuring the total magnitude of M31, we are able to calibrate the $I$-band Tully-Fisher relation for spiral galaxies in the Coma supercluster, and thereby estimate the value of the Hubble constant ($H_0$).
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