Will A 2x Doubler Change The Fiels Of View?

[UtopiaTexasG19]

My neighbor down the road has let me borrow his Gen.1-2.5X50 NV scope that I am playing around with at short range for armadillos in my yard at night.
He has moved on to Gen 3 scopes.
I ran into another friend the other day who has a 50mm Doubler that he says will thread into the lens of the scope and make it into a 5X50.
What can I expect from adding the doubler as far as "field of view" width compared to the 2.5 X 50 lens?
I have to admit to being uneducated on this subject and any replies are welcome.

 

[wogpotter]

It will halve exactly.
Think of the doubler as a magnifying glass that expands the center of the image & spreads it out over the whole viewing area. It will reduce light output by 75% (2-stops or 50% plus a half of 50%) as compared to the original because its removing 1/2 the radius of the imaging (objective) lens by only "seeing" the center 50%.

 

[UtopiaTexasG19]

Can I assume that the lines of the reticle will appear twice as thick also?

 

[wogpotter]

if it goes behind the reticule then yes. Everything is magnified 2X.

 

[Double Naught Spy]

wogpotter is right. That is how it will work.