Re: [APML] Focus Problem with Pentax 67

["William R. Mattil" <wrmattil@ix.netcom.com>]

Roland Roberts wrote:

>Thanks to everyone whose had some suggestions.  I've put up a web page
>with some of the info on these and my comments.  I'm trying to make my
>web site a documentary of my mistakes :-)
>
>    http://www.astrofoto.org/imaging/ssp2005.html
>
>There are no links from the menus or other pages to the above (yet), so
>the direct jump is the only way to get there.
>
>roland
>  
>
Roland,

Your brief write-up on your web page with the graphic illustrating this 
problem makes me think that the method that you used to secure the 
camera is the underlying problem.


 >
I mounted the camera on a Losmandy D-compatible plate with a 125mm 
diameter ring holding the front of the lens and a normal 1/4-20 bolt 
holding the body on a small offset plate that provides a feed-through 
for a cable to the battery compartment. I attempted to have the three 
knurled-screws that held the lens front to do so snugly but without 
putting any stress on the lens. I have to wonder if I succeeded or if 
this focus is a symptom of a problem there.
<

I just can't imagine the difficulty in adjusting the 3 point ring so as 
to not put *any* unnecessary torque or stress on the lens to mounting 
flange of the camera. In your zeal to provide a stable mounting I think 
you set yourself up to introduce abberations. This assumes of course 
that the camera itself is functional and that the back isn't damged. As 
painful as it is might I suggest removing the three point DR-125 support 
and just use the mounting hole in the camera itself with a 105mm lens 
(If you have one) stopped down at least one stop.

http://www.celestial-images.com/Cygnus67.html

1 hour exposure on E200 with a 105mm lens on a Losmandy DCM on a 
Losmandy Dovetail. The only support is the tripod mounting hole in the 
camera body.


The other option that you have might be to use two DR125's and not 
secure the camera body at all. The size of the lens will dictate if this 
is needed or not.

Regards

Bill

-- 

William R. Mattil	:	http://www.celestial-images.com


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