I recall that S&T has from time to time given directions for cleaning. Others have their own preferences but I think the best direction is to not use any kind of rubbing action - ever. Blow off loose dirt (do not brush - a brush will also grind surface particles into the mirror and scratch) and wash off any stubborn particles. It's the washing process and products (distilled water, alcohol, detergent, etc.) that so many people dispute. I know how I would do it but I'd like to hear from others. Maybe it's time for a "Spring Cleaning" lesson at the April SLAS meeting. -----Original Message----- From: Jim Gibson [mailto:xajax99@yahoo.com] Sent: Monday, March 24, 2003 9:33 AM To: Astronomy in Utah Subject: RE: [Utah-astronomy] SCT or Newtonian? The next obvious question to me is, what it the right (careful) way to clean a newtonian mirror? I have read somewhere that using a mild dish soap like Dawn is prefered. Any wiping or rubbing will grind dirt into the mirror. So how do you get the dirt off? How about using an old shaving brush (probably couldn't find one these days) or a photo air brush? Jim Gibson Chuck Hards <chuckhards@yahoo.com> wrote: I would agree for the most part with Kim, except that a proper cleaning job really isn't "dangerous" if you are very careful. Aluminum is a soft metal, and coatings are very thin, but mirrors can be cleaned without damage. It's only intimidating the first time. I only clean mine every other year, unless absolutely needed. An improperly cleaned SCT corrector or refractor objective will take damage also, it's just not as visible at a casual glance as a reflective surface. Remember, too, that SCT's do not have sealed interiors, sooner or later they will require cleaning interior surfaces also. C. --- Kim Hyatt wrote:
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
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