Making a long-distance scope to spot short-distance objects

Oct 2019
2
0
Hi everyone,

I've got a sniper scope with magnification ability of ×6-20 and can focus from 50 meters to ∞ (the scope is like an astronomical telescope).
My goal is to add a lens (or lenses) between the scope and the observed object so I could spot a focused close object (5-30 cm).

I have tried to place a convex lens between my scope and the object, so the object is placed at the focal length of the lens (15 cm). It worked fine. But I can see only a tiny part of the object. So, if the object is a credit card, I can only see one digit of the card number.

My goal is to see the whole credit card, basically performing a zoom out.
Any suggestions?

Thanks in advance!
 
Jun 2016
1,142
514
England
There is an inescapable relationship between the size of the observable region and the magnification.
This is simply down to the geometry of the problem.

If you want to observe a large area at a high magnification,
you will have to build a scope specifically for that purpose
(rather than try to adapt an existing scope)

Again the inescapable geometry of the problem will mean that,
to observe a large area at a high magnification,
your scope would have to be physically big.
 
Oct 2019
2
0
Thanks for the comment.

Unfortunately I must adapt an existing scope.

The scope FOV is 6.3° so at a distance of 25 cm will observe only around 2.75 cm of the object.
With a convex lens placed in between I can see those 2.75cm focused, But I need to see more, around 6-7 cm focused.

I hope I'm not asking for a too large area and it is possible with a simple solution.