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Re: [APML] 35 mm Camera & Focuser
Agreed - thanks Bradley!
Stuart
----- Original Message -----
From: "Bradley Hope" <bradley@thorngarden.net>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Saturday, December 13, 2003 9:44 AM
Subject: Re: [APML] 35 mm Camera & Focuser
> Stuart;
>
> I find it easier to focus with the DW-2 using the parallax method rather
> than the loupe. I started with a Peak 8X, filed to fit down onto the
> focusing screen, but the depth of field is so great that it was a pain
> trying to figure out exactly where it was supposed to be. I also have a
> hartmann, but, to be honest, I find I can get better focus without it.
>
> In any case, for really critical focus, especially if you are going prime
> or with a focal reducer, as William and Serge has said, the best option is
> indeed knife edge or ronchi.
>
> Clear skies
>
> Bradley Hope
>
> http://astronomy.thorngarden.net
>
> No matter where ya go...there ya are.
>
> ----- Original Message -----
> From: "Stuart Heggie" <stuart.j.heggie@sympatico.ca>
> To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> Sent: Saturday, December 13, 2003 5:36 AM
> Subject: Re: [APML] 35 mm Camera & Focuser
>
>
> > Bradley, thanks for this. I actually have a DW-2 and it is GREAT for
> > composition / framing but it is not so easy to focus with (and not
> > recommended for this by experts I'd read so far). The trick with the
DW-2
> is
> > you have too many variables first of all and its focus is very dependent
> on
> > your angle of view so stuff swims in and out of focus as you move your
> > head - not so easy. I sense from what I've read that the most success
> seems
> > to come from people who are putting an eyepiece or loupe on the focus
> screen
> > directly and studying the tightness of the star's image on the matte
> portion
> > of the screen. I think!
> >
> > For my camera lenses, I put a two-hole mask over the objective and then
> took
> > a series of 30 second shots, recording the focus position at each shot
and
> > slowly stepped through the range on each side of infinity and found
> critical
> > focus for the lenses that way. With prime focus, you have no way to lock
> the
> > scope down permanently (unless you never plan to look through it I
guess).
> >
> > PS - don't be surprised if those DW-2's go for a lot more by the time
the
> > auction closes - they are fetching upwards of $200 typically.
> >
> > Stuart
> > ----- Original Message -----
> > From: "Bradley Hope" <bradley@thorngarden.net>
> > To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> > Sent: Saturday, December 13, 2003 7:28 AM
> > Subject: Re: [APML] 35 mm Camera & Focuser
> >
> >
> > > ----- Original Message -----
> > > From: "Stuart Heggie" <stuart.j.heggie@sympatico.ca>
> > > To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> > > Sent: Saturday, December 13, 2003 3:04 AM
> > > Subject: Re: [APML] 35 mm Camera & Focuser
> > >
> > >
> > > > John, for those of us with cameras with removable pentaprisms, would
> > this
> > > > thing plunked directly down onto the focus screen work? I'm still
> > shooting
> > > > piggyback so I've focussed using the the Hartmann mask technique but
> > when
> > > I
> > > > finally make the jump to prime focus, I think I'll need something
> better
> > > > than what I've got.
> > > >
> > > > Anyone else, I've got two Nikon F2's so if there is another means
that
> > > works
> > > > for sure on this camera, I'd love to know it - mostly what I read is
> > that
> > > I
> > > > buy a loupe and file it down to fit into the top of the camera and
> rest
> > on
> > > > the focus screen - if I get one that is adjustable, is that better
so
> > that
> > > I
> > > > don't have to fine tune the filing job for height?
> > > >
> > > > Stuart
> > >
> > >
> > > Stuart;
> > >
> > > I would suggest the Nikon DW-2 finder. It's 6X and has an adjustable
> > focus,
> > > full frame viewing of the focus screen. There are a couple available
on
> > > Ebay, both ending today, currently $27.50 and $99.00. There's nothing
> > wrong
> > > with the one for $27.50 except it's missing the name plate.
> > >
> > >
> >
>
http://search.ebay.com/search/search.dll?query=dw+2&catref=C3&socolumnlayout
> > =3&lotr=1&from=R2&sacategory=625&BasicSearch=
> > >
> > > Bradley
> > >
> > > _______________________________________________
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> > > http://seds.org/mailman/listinfo/astro-photo
> > >
> >
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