Original sentence: It also costs less than a Schmidt-Cassegrain telescope as the mirrors can be ground from a single piece of either pyrex or BK-12 optical glass and can use a standard focuser in place of the specialized focuser needed to obtain the correct focus.Schmidt-Newtonian telescopes suffers from less coma than a Newtonian of the same focal ratio, although it still has some (coma-correcting devices can eliminate them)
Edited sentence: It also costs less than a Schmidt-Cassegrain telescope as the mirrors can be ground from a single piece of either Pyrex or BK-12 optical glass and can use a standard focuser in place of the specialized focuser needed to obtain the correct focus.Schmidt-Newtonian telescopes suffers from less coma than a Newtonian of the same focal ratio (usually about half), although it still has some (coma-correcting devices can eliminate them)