Re: ATM Making a finder scope

["Bill Kocken" <wmkocken@hotmail.com>]

Vero,

Very interesting idea, using a35mm camera.  Does this result in a straight 
through image, like looking throught the viewfinder of a camera or 
binocular?  My preference is to bend the image by 90 degrees so that I can 
look through the finder without bending my head 90 degrees.

I've also been intrigued by the idea of using a camera lens as a helical 
focuser.  What size lens do you use and how do you hollow it out?  For 
example, after you take the glass out( somehow),  does a 50mm f 1.8 lens 
have a big enough opening to hold a 1.25inch eyepiece?

Summer is slowly coming to Minnesota.  Of course with the coming of summer 
we get mosquitos.  Our most comfortable observing is spring and fall, 
actually.

Thanks for any ideas,
Bill Kocken


>From: "Vero and Lisa Joseph" <thejosephs@ozemail.com.au>
>To: <atm@shore.net>,"bill kocken" <wmkocken@hotmail.com>
>Subject: Re: ATM Making a finder scope
>Date: Fri, 23 May 2003 22:13:00 +1000
>
>G'Day Bill,
>
>When I built a reflex finder, I used the mirror from an old 35mm SLR 
>camera.
>The mirror passes the image through the pentaprism for focusing and flips
>out of the way when the shutter is opened. The mirror is front surface
>silvered though I cannot vouch for it's flatness. Old 35mm camera's are 
>very
>cheap and easy to find - they also provide a wealth of other bits and 
>pieces
>for ATMers (a hollowed out lens makes a great focuser.
>
>Vero Joseph
>Goulburn, NSW Australia (winter is definitely in the air)
>
>
>----- Original Message -----
>From: "bill kocken" <wmkocken@hotmail.com>
>To: "atm list" <atm@shore.net>
>Sent: Friday, May 23, 2003 10:34 AM
>Subject: ATM Making a finder scope
>
>
> >
> > Hi all.
> > I'd like to build an 8x50 right angle correct image finder scope for use
>on
> > my dob.  I know I can buy one for $80 to $100 or so, but this is the ATM
> > forum after all!  I think I can buy a 50mm objective with a focal length
>of
> > 200mm or so, or extract one from an old pair of binoculars.  I plan to 
>use
> > an old 25mm eyepiece from my first scope. Is there a good way to put
> > crosshairs into the ep?  I expect I can assemble the pieces with PVC
> > plumbing stuff. I have access to a nice set of rings.
> > The question is, what kind of optical piece do I need to turn the 
>optical
> > train 90 degrees and present a correct image?  Does anyone know of a 
>good
> > source?  If you've got plans for one or a webpage, let me know.
> >
> > As long as I'm doing this, should I make something bigger, like 60mm?
> >
> > Thanks,
> > Bill Kocken
> >
> >
>

_________________________________________________________________
The new MSN 8: advanced junk mail protection and 2 months FREE*  
http://join.msn.com/?page=features/junkmail