Re: ATM field stop / spare in travel

["Bob May" <bobmay@nethere.com>]

On most EPs that's the ring inside the tube that doesn't have any glass in
it.  Short FL EPs generally have the ring as the end of the holder for the
field lens and some longer FL EPs don't have one as the focus point may be
outside the length of the EP.
As a reference, the Field Stop is the point at which the EP focuses and is
that hard black edge to the FOV of the EP.  You can put a pen up inside and
see the tip of the pen at the field stop.
Bob May
http://nav.to/bobmay
bobmay@nethere.com