RE: [APML] Proper Use of Varimagni Finder

["Patrick Freeman" <pfreeman@woh.rr.com>]

Actually, I've had decent luck with my own VariMagniFinder, on numerous
focusing screens including the Beattie.  There IS a trick to making the
VMF work well, though.  You have to first focus the VMF to the SCREEN,
using the diopter adjustment barrel on the VMF.  This is easiest at
night by shining a moderately dim red light into the camera body and
focus the VMF to the matte finish of the screen.  On my Beattie screens,
there is a pattern of concentric rings around the center that are pretty
easy to focus the VMF to.  Once you've done this, DON'T MOVE THE DIOPTER
CORRECTION AGAIN.  I have a friend who's even taped his diopter to the
proper position.  

I've also found that a good Hartmann mask in combination with the
properly-adjusted VMF works virtually flawlessly for me.  Without the
mask, it's still not too bad, but the mask makes it that much more
positive for me.

While it's true that the 2.5x setting isn't as powerful as, say, a Nikon
with an eyepiece attached to the pentaprism, I've been quite successful
with the VMF as described above.

-- Pat Freeman


-----Original Message-----
From: owner-astro-photo@seds.org [mailto:owner-astro-photo@seds.org] On
Behalf Of Matt BenDaniel
Sent: Saturday, June 15, 2002 16:57 PM
To: astro-photo@seds.org
Cc: APML Discussion List
Subject: Re: [APML] Proper Use of Varimagni Finder

I agree. I tried the Varimagni. Its magnification is only 2.5x, whereas
you probably want 20x. Plus, if you examine the unit you'll see that its
aperture is quite restricted, which makes stars very dim. I sold mine. 

I've been using knife edge focusing for two years for telescopic
astrophotography, and I believe it is the best possible method. 

Almost all of my Olympus and Pentax 67 lenses seems to be well focused
at the infinity stop. 

I agree with Torsten's focus test approach.

Matt

At 01:03 PM 6/15/2002 -0700, R Torsten Clay wrote:
>I have found that the varimagni finder is pretty much useless for 
>astrophoto focusing- not enough magnification. For focusing piggyback 
>shots, I just set the lenses at infinity. 
>
>You can determine if the infinity mark is accurate by attaching tape
with
>many small marks (ie a ruler scale) to the lens and making a series of
>test exposures with a stationary tripod, each time moving the focus
>slightly. Then just use the mark that gives the thinnest line on the
test
>shot.
>
>Torsten
>
>On Sat, 15 Jun 2002, Kevin Wigell wrote:
>
>> I just received a Varimagni finder for my Olympus OM-1. I bought it
to
>> improve my ability to focus when I have the OM-1 mounted piggyback on
my
>> scope and using a 50 mm or telephoto lens (I use a KEF for focusing
through
>> the scope). I've been having great trouble getting good, consistent
focus
>> with lenses on the camera.
>> 
>> I'd appreciate any advice for using the Varimagni to focus the lens.
I've
>> practiced with it during the day on terrestrial objects, but focusing
on
>> stars is completely different, as we all know. BTW, I have a Beattie
screen
>> in the camera. Do I just focus with the Varimagni at its highest
>> magnification setting (2.5x) until the stars look the sharpest, or is
there
>> more to it than that? Normally I photograph one f/stop higher than
the
>> lens's wide open setting.
>> 
>> Thanks,
>> Kevin Wigell
>> 
>> 
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--
Matt BenDaniel
matt@starmatt.com
http://starmatt.com


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