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According to the commonly received ration of light in a Newtonian reflector and an automatic refractor, (which I believe to be very near the truth), the illuminating power of W. Lassell's 20-foot Newtonian of 24 inches in apertune is equal to that of a refractor of about 14 inches in aperture; which is more than three times the illuminating power of your large refractor. These large refractors will therefore prove extremely efficient on nebula, and on
