Exit pupil and Barlow

[bosun21]

I think that i already know the answer to this but I just need the answer to be confirmed. Say for example i am using an 18mm EP in my F6 Dobsonian. That gives me an exit pupil of 3mm. What happens to the exit pupil if i were to introduce a 2x Barlow to the arrangement? Will it be reduced to 1.5mm?. Thanks 🤔

[Pixies]

Yep. Double the magnification, half the exit pupil.

It effectively doubles the focal length of the scope

[Louis D]

The Barlow may also push the exit out a bit, increasing eye relief.  It may also induce kidney beaning (SAEP) with some eyepieces in my experience.  This is because the eyepiece is expecting a converging rather than a diverging bundle of rays.  Telecentric magnifiers solve these two issues by adding a second lens group above the magnifying lens group to reconverge the light rays.