Of course you must proceed to a cycloplegic refraction, otherwise you cannot be sure that the refractive error is purely astigmatic. The sign of the astigmatism may also change after cycloplegia. Moreover, be cautious about the cylinder value given by the Retinomax if the spherical ametropia is high.
(1) How accurate is the hand-held refractor Retinomax in measuring cycloplegic refraction : a further evaluation" Strabismus. 19866;3:133-142.