I believe you are talking about 2 different kinds of focusers. JMI
makes a focuser that fits over the focus knob (motofocus), and they also
make the NGF-S.

The NGF-S is the one you want to reduce mirror shift, since it attaches
to the rear cell of the scope, and focuses like a crayford. You may
also have to lock down the mirror to reduce flop, but I don't know if
you have this problem. You would use the scope's focuser to do a rough
focus, and then do the fine focusing with the NGF-S

Mike Gerszewski
Univ. of North Dakota
Space Studies


>
> In a message dated 02/10/01 12:23:59 Greenwich Standard Time,
>
> > Subj: Re: [M]: JMI focuser helps for shift?
> > Date: 02/10/01 12:23:59 Greenwich Standard Time
> >
> > In a message dated Tue, 2 Oct 2001 2:32:12 AM Eastern Daylight Time, "
> >
> > > One simple question:I am considering to buy an electric focuser (the JMI
> > or
> > > the Meade) for my LX200 12",this to focus in an easyer way.Does it work
> > also
> > > to reduce the shift of the mirror?
> > > thank you everybody
> > >
> > > Stefano Padovan Photographer
> >
> >
> > HI Stefano:
> >
> > No. A motofocus unit that attaches to the normal focus control does
> nothing
> > for focus shift. All it does is provide a remote focusing arrangement.
> >
> > Peace,
> > Rod
> >
> Hello Stefano
>
> The set-up we have here is using the JMI unit and lock the mirror after
> course focusing. The JMI will then give you an excellent fine focus. We use
> the RoboFocus attachment to remote the operation.
>
> John
>
> Dr. John Linse
> Headley Observatory
> Hampshire, England

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