Can anyone give me information on Ritchey-Chretien type telescopes? I am specifically interested in viewing quality, contrast, ease or difficulty in collimnation, mirror shift as in commercial SCT's, ease or difficulty in keeping mirrors clean as I live in an area with great skies but lots of dew, cleaning if req'd, recommended manufacturers, costs, and/or anything else you can think of to tell me about them. Any info will be appriciated. Thanks; Harry