Re: [APML]: focusing

["Philip Perkins" <philip@astrocruise.com>]

> << I removed the pentaprism on my Nikon F2 and slipped in a Peak 8x loupe
>  to give me a magnified view of its focussing screen. I adjusted the
>  loupe so that it focused on the screen for my right eye (the one I use
>  to focus with). >>
> 
> Would that be the same Peak 8x loupe sold by Edmund Scientific for about $65?
> Were any modifications needed to set it on the screen?
> 
> Thanks for any information.


The actual Nikon device is called the DW2, but they are like gold dust. I
waited for more than 6 months to try to get one. In the end I made my own.
Bearing in mind that the DW2 is a 6x 'chimney' magnifier, we're after 6x,
because that allows you to see the entire FOV without moving your eye
around. I was lucky enough to find a high quality (double lens) 6x mganifier
from a local professional photographic supplier called Kenro - I can send
you one if you wish. I made the 'chimney' part out of thin plywood and this
'pseudo DW2' has since become one of my prized posessions - it's *amazing*
what you see through this device!

I then made a variant of this - a 15x magnifier - for accurate focusing,
made from an unwanted Kellner .965" 18mm eyepiece. This works amazingly
well too. So, in my very humble opinion, you may need two devices - one for
composing and one for accurate focusing. 

The upside is it's possible to make these things yourself, and achieve what
you may come to regard the 'perfect' astrophotography camera - the downside
is, it takes it takes time :-)  The key thing with these devices is to
adjust the focusing very carefully so that the frosted part of the screen
has a sharp 'grainy' appearance - don't adjust the focus on the fresnel
lines on the screen.  Oh, and don't forget, if you wear glasses, make sure 
you adjust focus in the same 'mode' as when you normally view!

Philip Perkins  --  philip@astrocruise.com
51 27'N 1 36'W  --  Wiltshire, UK
43 54'N 5 32'E  --  Luberon, France
Astrocruise     --  http://www.astrocruise.com