RE: [APML] Focal Reducers with Newtonian Reflectors

["Chris Schur" <cschur@cybertrails.com>]

Eddie, The problem is not so much the secondary shadow, but backfocus and vignetting.  you will need to move your mirror forward in its cell several inches to make the focal reducer work right.  Then you dont want to exceed faster than about f/4 for 35mm work. Youll still get enhanced coma and vignetting with such a setup which makes off axis guiding very difficult. 

 

Chris Schur

 

Astrophotography: http://www.psiaz.com/schur/astro/index.html

-----Original Message-----
From: owner-astro-photo@seds.org [mailto:owner-astro-photo@seds.org]On Behalf Of Eddie Guscott
Sent: Friday, July 26, 2002 12:09 AM
To: APML
Subject: [APML] Focal Reducers with Newtonian Reflectors

Hello All

 

Does anybody have any experience with using focal reducers with Newtonian refelctors for photography?

 

I've read that secondary shadow can become a problem - anyone any ideas or experience??

 

Eddie Guscott