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: Fabricating An Apo Refractor Objective

Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response To
Posted by Eric Nicely/">Eric Nicely on February 15, 1999 22:22:54 UTC

Thanks, George. I recently tried to use a 1" lap to take off a 1.75" hill on the FK02. I apparently went somewhat overboard and created a hole instead! With you suggestion though, I may try a 3" lap if the figuring continues to plague me. Ever hopeful, I am starting for the sixth time on these surfaces. Eric Nicely

: sorry about the first message. did you try a subdiameter lap? i have found that i have far more control over figuring with a small lap. it is amazing how fast it will bring an edge back, let alone pick and choose where to remove glass. : : : : : I'm in the midst of making an three-element apo objective which uses FK02 as the central element. The internal radii match. While I am confident about hitting the design radii within tolerance, and wedge is not a problem, getting the concave and convex surfaces to match has been a problem.

: : : I wonder if anyone can assist me in determining how many fringes I can tolerate. I am using the first and third elements as the concave test plates to test the convex FK02 surfaces. The diameter of the lens is 120mm, R2/R3 are +/-298mm.

: : : The closest I've been able to come is 20 fringes. Further polishing has tended to lead to the fringe pattern expanding outward from the center and inward from the edge simultaneously. I think this suggests contact at the edge and the center, meaning a depressed ring halfway across the radius of the lens. : : : Any suggestions on working with FK02 would be appreciated.

: : : I have made several mirrors and a Schmidt camera, but this triplet is a real challenge.

: : : Thanks for any help!

: : : Eric Nicely

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