· Get a Cloudy Nights T-Shirt · Submit a Review / Article    Click here if you are having trouble logging into the forums Cloudy Nights - Official Forums of the 2009 International Year of Astronomy 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] Forum Archives · Entrance · Main Index · Search · New user · Who's Online FAQ · Calendar Equipment Discussions >> ATM, Optics and DIY Forum Previous   Index   Next   Threaded   Pages: 1 wojo sage Reged: 09/28/07 Posts: 216 How much grit       #3367604 - 10/01/09 01:21 AM Edit   Reply   Quote Quick Reply   Hello ALL I am under taking a 20" project and need some help on how much of each size grit and fine grinding material to order for a pregenerated 20" mirror I had planned to get 4 kilos of Gugolz #74 pitch for lap making and extra for smaller size laps. This will be a hand grind. YOUR help is appreciated.................WOJO Post Extras:       JohnH professor emeritus Reged: 10/04/05 Posts: 734 Loc: vancouver near the wilds of B... Re: How much grit [Re: wojo]       #3368489 - 10/03/09 01:21 PM Edit   Reply   Quote Quick Reply   If you are pregenerated, you start with 220 or 320 grits. My guess would be to take the grit quantities for a 10" and QUADRUPLE them. Four times the area. This would mean 3 lbs 220 grit, 2 lbs 25 micron, 1lb each of 15 , 9 and 5 micron and 2 lbs of CeO. And 6 lbs pitch for your lap, assuming one lap, full size. Post Extras:       wojo sage Reged: 09/28/07 Posts: 216 Re: How much grit [Re: JohnH]       #3369303 - 10/03/09 07:50 PM Edit   Reply   Quote Quick Reply   JOHNH Thanks for the reply. a little too late, as I ordered just about what you suggested plus 4 kilos of #73 gugolz. so I should be good for awhile. TOM at GotGrit was very helpfull and had a good idea of what I should need, plus I have some of every thing left over from a previous mirror. THANKS ...........................WOJO Post Extras:       Pages: 1 Previous   Index   Next   Threaded   Extra information 13 registered and 11 anonymous users are browsing this forum. Moderator:  Don W, Mike I. Jones  Print Thread Forum Permissions       You cannot start new topics       You cannot reply to topics       HTML is disabled       UBBCode is enabled Thread views: 122 Jump to *International Year of Astronomy 2009* -----   Global Coordination   Cornerstone Projects   Special Projects   Special Task Groups   Global Activities   National and Regional Activities   IYA 2009 in Africa   IYA 2009 in the USA*Announcements and News* -----   Cloudy Nights Announcements   Discussion of CN Articles, Reviews, and Reports   Beginners Forum   Celestial Events   Light Pollution*Equipment Discussions* -----   ATM, Optics and DIY Forum   Binoculars   Binoviewers   Cats & Casses   Classic Telescopes   Equipment   Eyepieces   Mounts   Observatories   Reflectors   Refractors    Celestron SkyScout and Meade mySky   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   General Observing   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*Other* -----   Science of Astronomy & Space Exploration   AstroWebsites   Space Rocks*Speciality Forums* -----   AstroArt   Astronomy Software & Computers   Stellar Media   Astro Outreach, Clubs and Star Parties*CN Feedback and Vendor Announcements* -----   Vendor and Group Announcements CN Forums Home

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