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Re: [APML] Nikon Cameras
Hello Eddie:
You definitely do NOT need a mark on the Nikon F2 matte (ground glass)
screen in order to get accurate focus every time. I marked one with a
Sharpie pen and it was of no help. I actually ran a test with three
astrophotographers using the knife edge technique versus visually focusing
on an unmarked Nikon F2 matte (ground glass) screen with a good magnifier (I
used a shortened 18 mm Orthoscopic eyepiece as my magnifier). There was
virtually no difference in how well the image was focused when the negatives
were checked. This was for an Astro-Physics 155 mm f/7 refractor. Schmidt
Cassegrains are more difficult to focus, so the results could vary. If you
polish the matte it might make it harder to focus. The texture of the matte
actually makes it easier to set your focus (for the magnifier). I have not
tried polishing so am not sure of its effects.
Michael Stecker
mstecker@dslextreme.com
My Web Site:
http://www.homestead.com/mstecker/index.html (INDEX)
http://www.homestead.com/mstecker/astrogallery.html (Astroimage Index)
http://www.homestead.com/mstecker/placesindex.html (Places Index)
----- Original Message -----
From: "Eddie Guscott" <eddie.guscott@blueyonder.co.uk>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Saturday, July 05, 2003 1:57 PM
Subject: Re: [APML] Nikon Cameras
> Thanks Jerry & Michael
>
> Somebody else (not on this list) suggested as another possibility:
>
> Using metal polish to make the matte screen more translucent and then just
> scribing (or drawing) a cross on the bottom side of the screen to focus
on.
> Any thoughts about this - what are the chances of ruining the screen
> comletely?
>
> Eddie Guscott
>
> ----- Original Message -----
> From: "Jerry Lodriguss" <jerry@astropix.com>
> To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> Sent: Saturday, July 05, 2003 7:24 PM
> Subject: Re: [APML] Nikon Cameras
>
>
> > Hi Eddie,
> >
> > You can just use a sharpie marking pen to put a dot on the bottom of the
> > ground glass screen and focus on that.
> >
> > You'll have to shave some of the bottom of the magnifier off (the
> thickness
> > of the focusing screen) so that it will reach focus. If the magnifier
has
> a
> > helical focuser on it, you would actually be better off shaving a bit
more
> > off, so that you can go past focus and then come back to it. If it's not
> > adjustable, you'll have to be careful to make it just the right height.
> >
> > Note that as I got older the focus of my eyes has changed considerably,
so
> > as you age you should periodically check the focus of the magnifier to
be
> > sure it has not changed.
> >
> > Jerry
> >
> > At 04:40 PM 7/5/2003 +0100, you wrote:
> > >I have managed to get hold of a second hand Nikon F2A and all appears
in
> > >working order. I've managed to remove the pentaprism Ok.
> > >
> > >My question is regarding focussing - I have a 10x watchmakers loupe
which
> > >focuses exactly at the base of the plastic holder.
> > >
> > >On what do you focus - I have read in Jerry Lodriguss's wonderful ebook
> that
> > >you focus on the bottom of the ground glass screen - would this mean
that
> I
> > >should shave the same thickness off the bottom of the loupe as the
> thickness
> > >of the ground glass screen? At the moment, the loupe obviously focuses
> > >perfectly on the top of the ground glass screen.
> >
> >
> > The book "Photoshop for Astrophotographers" is now finished!
> >
> > Go to: http://www.astropix.com/PFA/PFA.HTM
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > _______________________________________________
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> > Astro-Photo@seds.org
> > http://seds.org/mailman/listinfo/astro-photo
>
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