ATM GEM Tangent arm

Hello all,

I am building a German Equatorial Mount for a 12" Newtonian. I want to install

a tangent arm on the Dec. axis. I've been looking around the web and I have seen

the Schaefer mount used by Tony Hallas and others. I would like to know if any of

you has seen this mount and can describe and/or send pictures of the tangent

arm.

I would also appreciate if anyone could send me ideas for a minimum

backlash and strong tangent arm.

Thanks a lot,

Antonio de Ugarte Postigo

Boadilla del Monte (Madrid)

Spain