RE: [Utah-astronomy] SCT or Newtonian?
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
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 <khyatt@smithlayton.com> 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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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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http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy
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How 'bout a scouring pad? Just kidding, but I think I may have damaged either my corrector plate or the mirror by cleaning with usual photo lens cleaner material, although I was extremely careful. But I think there's really something wrong with my optics now. Thanks, Joe
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:
Joe Bauman science & military reporter Deseret News bau@desnews.com (801) 237-2169
Words in caps are for emphasis, I'm not shouting. This subject is too lengthy for me to go into detail right now (at work, as usual) but the secret is PATIENCE and NOT wiping right away. Let the mirror soak in warm water for a few hours. This will loosen most of the dirt and it can be rinsed off using only the pressure from the tap. Wiping is best done judiciously, after a soak, and using only the best grade of cotton, only one wipe per cotton wad, one direction only, rotating as you wipe. All rinsing should be done with distilled water, then drip-and-air dry. If you need to use soap, you waited too long to clean, but let the mirror soak in SOAPY water if it's really filthy. This is just a quick description, many nuances remain undescribed. Cleaning requirements are a good reason to avoid mounting mirrors with silicone glue. You won't be observing the same night that you cleaned the optics if you use silicone. Of course, it goes without saying that you need to keep the mirrors COVERED when not in-use. My 6" f/8 is now 4 years old, and the mirror has hardly any dust on it. C. --- Joe Bauman <bau@desnews.com> wrote:
How 'bout a scouring pad? Just kidding, but I think I may have damaged either my corrector plate or the mirror by cleaning with usual photo lens cleaner material, although I was extremely careful. But I think there's really something wrong with my optics now. Thanks, Joe
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
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participants (4)
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Chuck Hards -
Jim Gibson -
Joe Bauman -
Kim Hyatt