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The amplification of the protogalaxy candidate cB58 due to gravitationallensing by the foreground cluster of galaxies MS1512.4+3647 is quantified basedon recent ROSAT and ASCA X-ray observations. It is found that the amplificationis at most 25 for any reasonable cosmological model with or withoutcosmological constant. It is also argued that the system may be used to placenew constraints on the value of the cosmological constant. The gas massfraction for this cluster is found to be about 0.2.Comment: LaTex, 9 pages, 9 figures, uses aas2pp4.sty, Accepted for publication  in Ap

Lensing Effects on the Protogalaxy Candidate cB58 and Their Implications for the Cosmological Constant