Is it possible in theory or practice to construct a contact lens which
could provide telescopic vision? I presume it would require two or
more lenses in a single unit, which might be too bulky?

This isn't precisely what you're asking about, but you may find it interesting:

http://www.albinism.org/webboard/driving/messages/426.html

pinkfreud-ga: Anytime you comment is a delight. Yes, that reference is
not directly related, but is interesting. Thanks.
monroe22

A telescope works by having an objective lens form a real image which
is magnified by a second lens, the eyepiece.

|               
|            |      | 
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Objective  Image   Eyepiece
 
The magnification is the focal length of the objective divided by the
focal length of the eyepiece - for a telescope, this needs to be
greater than 1.

The simplest system would use the lens in your eye as the eyepiece -
problem is, with normal vision, the virtual image would have to be
several inches away otherwise you couldn't focus it, so no way of
using a contact lens.

If you try using 2 lenses, you run into the problem that the focal
lengths of those lenses have to be extremely short, and that means the
lenses have to be very thick, especialy when you consider that the
eyepiece has to be concave on one side in order to fit the eye.

Ian G.

iang-ga: Your comment confirms what I suspected: a telescope is too
large to be contained in a contact lens. If it were easy, it would
have already been done.
What prompted the question was a GA question I posted once: How do
birds find prey at a great distance, such as hawks and buzzards? Do
they have telescopic vision? The answer was: No, they do not have
telescopic vision, but thet have great visual acuity which permits
them to see extremely small movements.
Thanks,
monroe22