· Get a Cloudy Nights T-Shirt · Submit a Review / Article Click here if you are having trouble logging into the forums Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User You are not logged in. [Login] Entrance · Main Index · Search · New user · Who's Online FAQ · Calendar Equipment Discussions >> ATM, Optics and DIY Forum Previous   Index   Next   Threaded   Pages: 1 dgreyson sage Reged: 11/06/12 Loc: South Carolina Surface chips in an F8 Newtonian mirror       #5569024 - 12/13/12 11:02 AM Edit   Reply   Quote Quick Reply   Maybe someone can answer this question: I have a 10" F8 newtonian mirror that I ground back in the 70's. So it has some personal noastalgia value. Back in the day, the secondary holder failed and let the diagonal mirror fall and knick two small pits in the surface. It would have only been one pit but it bounced so two small chips. Still seems to work just fine, and a year or so ago I had it re-aluminized. My question is this: Should I leave the pits shiny or should I paint them black? and also, How signifigant a problem is this? Should I send it out to be reground? the chips are less than a wooden pencil diameter. Post Extras:       Mike I. Jones Carpal Tunnel Reged: 07/02/06 Loc: Fort Worth TX Re: Surface chips in an F8 Newtonian mirror [Re: dgreyson]       #5569283 - 12/13/12 01:33 PM Edit   Reply   Quote Quick Reply   Just blacken them with a black Sharpie and enjoy your scope. Based on your description, their area is so small relative to the primary's that they'll have essentially no effect on your image quality. The effect of your (new!) diagonal mirror shadow is hundreds of times more influential than your two little gouges. Mike Post Extras:       dgreyson sage Reged: 11/06/12 Loc: South Carolina Re: Surface chips in an F8 Newtonian mirror [Re: Mike I. Jones]       #5569349 - 12/13/12 02:09 PM Edit   Reply   Quote Quick Reply   Thanks Mike! That answers my question. Post Extras:       KenScharf member Reged: 12/16/12 Loc: South Fla Re: Surface chips in an F8 Newtonian mirror [Re: dgreyson]       #5574363 - 12/16/12 03:38 PM Edit   Reply   Quote Quick Reply   I've read that the 3 or 4 vanes that hold the secondary mirror holder are optically the same as double the number of diameter width scratches on the main mirror! Post Extras:       JohnMurphyRN sage Reged: 09/09/12 Loc: Near St Louis Re: Surface chips in an F8 Newtonian mirror [Re: KenScharf]       #5574373 - 12/16/12 03:44 PM Edit   Reply   Quote Quick Reply   It would be really helpful if the chips were in the secondary's shadow... Post Extras:       Pages: 1 Previous   Index   Next   Threaded   Extra information 19 registered and 25 anonymous users are browsing this forum. Moderator:  ausastronomer, richard7  Print Thread Forum Permissions       You cannot start new topics       You cannot reply to topics       HTML is disabled       UBBCode is enabled Thread views: 273 Jump to *Announcements and News* -----   Cloudy Nights Announcements   Discussion of CN Articles, Reviews, and Reports   Celestial Events*General Astronomy* -----   Beginners Forum   General Observing and Astronomy   Outreach   Light Pollution*Equipment Discussions* -----   ATM, Optics and DIY Forum   Binoculars   Binoviewers   Cats & Casses   Classic Telescopes   Equipment   Eyepieces   Mounts   Observatories   Reflectors   Refractors    Video and Electronically Assisted Astronomy*Astrophotography and Sketching* -----   Beginning and Intermediate Imaging   Film Astrophotography   DSLR & Digital Camera Astro Imaging & Processing   CCD Imaging & Processing   Solar System Imaging & Processing   Sketching   Astro Imaging/Sketching Contest *Observing* -----   NEO   Planetary and Solar System Observing   Lunar Observing   Deep Sky Observing   Double Star Observing   Solar   Variable Star Observing and Radio Astronomy*Telescope Specific Forums* -----   Celestron NexStar    NexStar GPS / CPC Telescopes   Questar Forum   Meade ACF/RCX / LX / GPS    Meade ETX*Speciality Forums* -----   Arizona Science and Astronomy Expo   NEAF (Northeast Astronomy Forum) and NEAIC (Northeast Astro Imaging Conference)   AstroArt   Astronomy Clubs and Star Parties   Astronomy Software & Computers   AstroWebsites   Science! Astronomy & Space Exploration, and Others   Space Rocks   Stellar Media*Swap and Shop* -----   Shop and Swap Audio Components*CN Feedback and Vendor Announcements* -----   Vendor and Group Announcements*International Year of Astronomy 2009 - Forums are now closed.* -----   IYA Archive Info CN Forums Home

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