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

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

Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response To
Posted by Robert May on October 7, 2001 19:52:37 UTC

The regular 1:10-1:6 thickness/diameter is just fine again for the secondary. Silver does have the problem of tarnishing and there's really nothing that you can do to prevent it from happening. Adding a clear coat over the silver will cause a second reflection at the surface of the coating as well as the silver so you will be getting a second image next to the main one. You will also have the problem of the coating not being even for thickness or surface shape so the second image will probably be out of focus/abberated to boot.
Silver is nice for short term work (1-6 months) but I will note that you can still get a nice image of something even if there is no coating on the glass at all as the bare glass will reflect about 4% of the light and that's enough to do a nice job of splitting the Double-Double with a 6" uncoated mirror.

Follow Ups:

    Login to Post
    Additional Information
    About Astronomy Net | Advertise on Astronomy Net | Contact & Comments | Privacy Policy
    Unless otherwise specified, web site content Copyright 1994-2024 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