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] Entrance · Main Index · Search · New user · Who's Online FAQ · Calendar Equipment Discussions >> ATM, Optics and DIY Forum Previous   Index   Next   Threaded   Pages: 1 NeoDinian Experienced Postmaster Reged: 10/05/05 Posts: 11997 Loc: Rockford Illinois How's my grinding doing?       #2691265 - 10/10/08 02:38 PM Edit   Reply   Quote Quick Reply   Ok, have about 3.5 hours grinding done (total time). Still working 80 grit. (I wish I had 60 grit to get this quicker!) My "Target" depth is .0833, and I'm currently at .0675. The mirror is ground out to about 3/4" from the edge (8" mirror), but my tool is only showing wear on the outter 50%, and nothing starting in the center yet. My grind has been working 40% offset cordial strokes. What should I be doing now? Continue as I am? If so, will I pass my depth? Should I change strokes now? Less of an offset? Thanks! -------------------- Neo... (Jeff) -=-=-=-=-=-=- 10" LX200-GPS/SMT UHTC "Draco" Rockford, Il. NeoDinian's Eye on the Sky! Coming soon: Post Extras:       astrosam member Reged: 05/14/08 Posts: 39 Re: How's my grinding doing? [Re: NeoDinian]       #2691360 - 10/10/08 03:39 PM Edit   Reply   Quote Quick Reply   I think you should definitely move in to a smaller offset, if not move to a centered stroke. You're .0158" off your target sagitta, less than 20% of the depth to go but 75% of the mirror is ground. The rule of thumb I was taught was you want to match your % of mirror ground with % of sagitta. So I think you're running deep and should move your stroke in. I'm concerned that you've dug a hole with the 40% overhang, at this 75% ground stage something like 20% overhang or center over center would be more appropriate I think. I'd grind center over center alternating mirror/tool on top until it's ground to the edge. Keep an eye on the sagitta and if you're getting really close then focus more ToT to keep it from going too deep. That's my 2 cents anyhow Post Extras:       Spoonsize Vendor/Clothing Reged: 08/27/04 Posts: 2150 Re: How's my grinding doing? [Re: astrosam]       #2691416 - 10/10/08 04:09 PM Edit   Reply   Quote Quick Reply   His 2 cents is the same as my 2 cents...makes 4... anybody else?? -------------------- Steve Durham www.margesmonograms.com (Marge made me do it) Post Extras:       Biff Carpal Tunnel Reged: 09/04/05 Posts: 2253 Loc: Courtice, Ontario Re: How's my grinding doing? [Re: Spoonsize]       #2691585 - 10/10/08 05:40 PM Edit   Reply   Quote Quick Reply   I'll make it 6. -------------------- Ryan Antares 200mm f/6 Dob & 130mm f/5 Travel Dob. Projects on the go... - a couple 80mm SS refractors on the back burner. - a few small mirrors awaiting polishing - 260mm f/7.15 mirror... still polishing Member of DRAA My house. DRAACO Post Extras:       Pages: 1 Previous   Index   Next   Threaded   Extra information 9 registered and 9 anonymous users are browsing this forum. Moderator:  Don W, Joe Cipriano  Print Thread Forum Permissions       You cannot start new topics       You cannot reply to topics       HTML is disabled       UBBCode is enabled Thread views: 105 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 Imaging   Film Astrophotography   DSLR & Digital Camera Astro Imaging & Processing   CCD Imaging & Processing   Solar System Imaging & Processing   Sketching   Astro Imaging/Sketching Contest *Observing* -----   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 Home

Cloudy Nights Sponsor: Astronomics