Re: ATM Offner compensator

["Antonio de Ugarte" <de_ugarte@terra.es>]

 Martti,
     Could you explain a bit more how they work?
 They are just used for testing and then removed
 when the telescope is finished?

 Antonio

> ----- Original Message -----
> From: "Martti Koskimo" <martti.koskimo@kolumbus.fi>
> To: <atm@shore.net>
> Sent: Wednesday, September 18, 2002 2:39 PM
> Subject: Re: ATM Offner compensator
>
>
> >
> > Antonio
> >
> > The Offner compensator is not a part of Ritchey Chretien telescope and
it
> is
> > not used at the cassegrain focus.
> >  It is a null test lens system  used  in testing the main mirror and for
> the
> > same purpose as Dall and Ross lenses. There can be field corrector
lenses
> > near cassegrain focus but not Offner compensator.
> >
> >
> > Martti Koskimo
> >
> >
> >
> > ----- Original Message -----
> > From: "Antonio de Ugarte" <de_ugarte@terra.es>
> > To: <atm@shore.net>
> > Sent: Wednesday, September 18, 2002 1:50 PM
> > Subject: ATM Offner compensator
> >
> >
> > >
> > > I've seen a design of a Richtey Chretien which uses an
> > > Offner compensator at the cassegrain focus which is made
> > > from two crown elements.
> > > Could someone explain to me whar is the purpose of
> > > these aditional optical element?
> > > Thank you very much,
> > >
> > >     Antonio
> > >
> > >
> > >
> >
> >
> >
>