Celestron #93640 Barlow Lens.

[Nikodn]

I have recently bought myself a 2x Barlow lens and I know that it doubles the focal length of my telescope and the magnification.

When I unscrew the lens element from the bottom of the lens and screw it onto the eyepiece what magnification do I get.

Also when I fit an eyepiece into the tube of the Barlow lens without the lens element what effect does this have on the focal length and magnification of my telescope. 
 

Thanks Niko...😜⚽️👍

[Louis D]

28 minutes ago, Nikodn said:

When I unscrew the lens element from the bottom of the lens and screw it onto the eyepiece what magnification do I get.

Generally about 1.3x.  You can figure this out for yourself with a ruler or tape measure.  Just measure the difference in width of the view without any barlow, with the barlow in the normal position, and with the barlow lens elements screwed into the eyepiece.

30 minutes ago, Nikodn said:

Also when I fit an eyepiece into the tube of the Barlow lens without the lens element what effect does this have on the focal length and magnification of my telescope. 

For refractors and Newtonians, none.  It's just acting as an extension tube.  You'll have to rack your focuser inward to compensate.  An extension tube can be handy for terrestrial usage when you want to focus closer than the stock focuser outward travel allows.

For mirror focusing telescopes like SCTs and Maks, you'll be extending your focal length slightly to reach focus further back with the extension tube.  This can also induce a bit of spherical aberration in the image because you're getting further away from the design intended focal length.