Re: [APML]: "Doughnuts" in AP Scope

[Steve Bell <sb635@delphi.com>]

Ian Turner wrote:
> 
> 
> I have seen this problem with convential T ring adapters. The medium
> format gear I use uses a outside T ring adapter to help limit the
> vignetting. I wonder if a good machinest or buddy with a smitty might be
> able to make an external T ring for Nikon Cameras.
> 

Lumicon sells a T ring for the Nikon F cameras that has an internal
aperture about 3-4 mm wider than most other T rings that I've seen. It
has the Nikon bayonet attachment on one side, and a dovetail-type
attachment on the other, so you can't just screw it into a regular 2"
camera adapter like the Meade or Orion camera adapters. You wouldn't
want to anyway, because these camera adapters have an interior aperture
the same size as a usual T ring. You can, though, get a 2" extension
tube from Lumicon that you then insert the T ring's dovetail into the 2"
ID upper part and use the 2 set screws to bind down on the dovetail.
This produces a camera adapter with the T ring attached that has the
larger internal aperture.

-- 
Clear skies,
Steve Bell
email: sb635@delphi.com
Astrophoto page: http://www.mindspring.com/~sb635