I only clean my Newtonian optics about once per season. One reason is that scrupulously clean optics are not necessary for most observations. (In fact, it's my understanding that optics are cleaned infrequently at professional observatories, also.) You are correct that cleaning is "dangerous," and that's another reason not to clean too often. I believe that the optical coatings on a SCT corrector are as soft if not softer than the aluminum coating on any mirror. I've owned Newtonians for most of my astronomy life and just haven't found it to be all that much of a hassle to clean the optics. -----Original Message----- From: Joe Bauman [mailto:bau@desnews.com] Sent: Monday, March 24, 2003 7:22 AM To: Astronomy in Utah Subject: Re: [Utah-astronomy] SCT or Newtonian? I'd like to chime in with a question that has always puzzled me. A know some prefer SCTs because they are more compact, but I am wondering about another feature: the fact that the mirrors of Newtonians are open to the air. Doesn't this allow a lot of grit and dust to cover them, for example while observing from the Wedge? And isn't it more dangerous for the optics to clean the mirror than the covering lens of an SCT? Thanks, Joe Joe Bauman science & military reporter Deseret News bau@desnews.com (801) 237-2169 _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy