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: Kind Of Newtonian-Cassegrain Telescope

Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response To
Posted by Jarvis Krumbein, jkrumbein@juno.com on July 3, 2000 19:19:58 UTC

What you propose is not very practical for the following reasons.
1) Use of a flat secondary, since it has no optical power, will have to be larger than 50% of the primaries diameter.
2) The secondary should contribute to the correction of spherical abberation unless a correcting lense of some sort is inserted into the optical path. A spherical primary with no other correction, unless of very long focal length will suffer severe spherical abberation.

If you want a spherical primary and a Cassegrain configuration, the Pressman-Camichel configuration is your best choice but this requires an oblate spheroid secondary which will probably be hard to figure and will have a very small useable field of view before coma becomes objectionable. A better choice would be a Dall-Kirkham which uses an ellipsoidal primary and a spherical secondary. Because of the steep curve of the secondary, it is easy to make without difficult testing.

If you need more info, contact me.

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 1994-2021 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