Back to Home

ATM Forum Message

Forums: Atm · Astrophotography · Blackholes · Blackholes2 · CCD · Celestron · Domes · Education
Eyepieces · Meade · Misc. · God and Science · SETI · Software · UFO · XEphem
RSS Button

Home | Discussion Forums | Amateur Telescope Making | Post
Login

Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...
The Space and Astronomy Agora
Re: Donut Mirror

Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response To
Posted by Robert May on April 30, 1999 02:43:33 UTC

I've been assisting in the SDAA mirror grinding group here in San Diego and that's one of the first questions that gets asked. Don't worry about it. Use the first grit to get to about 110% of the radius and the rest of the grits to each halve that difference (10%) from the desired radius. The mirror will be hyperbolic growing towards shperical in shape due to the action of the grit until the last grit. Polishing the glass will get you all the way to spherical. Just make sure that the grit is pretty much distributed across the tool during the grinding and all will be well. The easy part is grinding as you can do any stroke and any speed and get a good mirror. The early grinding should have been at least 1/3 side overhang to get the most out of the grit. That makes the curve sharpen up fast. In other words, you don't have a problem.

Follow Ups:

    Login to Post
    Additional Information
    Google
     
    Web www.astronomy.net
    DayNightLine
    About Astronomy Net | Advertise on Astronomy Net | Contact & Comments | Privacy Policy
    Unless otherwise specified, web site content Copyright 1994-2020 John Huggins All Rights Reserved
    Forum posts are Copyright their authors as specified in the heading above the post.
    "dbHTML," "AstroGuide," "ASTRONOMY.NET" & "VA.NET"
    are trademarks of John Huggins